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Sample records for channel density regulates

  1. Ion channel density regulates switches between regular and fast spiking in soma but not in axons.

    Directory of Open Access Journals (Sweden)

    Hugo Zeberg

    2010-04-01

    Full Text Available The threshold firing frequency of a neuron is a characterizing feature of its dynamical behaviour, in turn determining its role in the oscillatory activity of the brain. Two main types of dynamics have been identified in brain neurons. Type 1 dynamics (regular spiking shows a continuous relationship between frequency and stimulation current (f-I(stim and, thus, an arbitrarily low frequency at threshold current; Type 2 (fast spiking shows a discontinuous f-I(stim relationship and a minimum threshold frequency. In a previous study of a hippocampal neuron model, we demonstrated that its dynamics could be of both Type 1 and Type 2, depending on ion channel density. In the present study we analyse the effect of varying channel density on threshold firing frequency on two well-studied axon membranes, namely the frog myelinated axon and the squid giant axon. Moreover, we analyse the hippocampal neuron model in more detail. The models are all based on voltage-clamp studies, thus comprising experimentally measurable parameters. The choice of analysing effects of channel density modifications is due to their physiological and pharmacological relevance. We show, using bifurcation analysis, that both axon models display exclusively Type 2 dynamics, independently of ion channel density. Nevertheless, both models have a region in the channel-density plane characterized by an N-shaped steady-state current-voltage relationship (a prerequisite for Type 1 dynamics and associated with this type of dynamics in the hippocampal model. In summary, our results suggest that the hippocampal soma and the two axon membranes represent two distinct kinds of membranes; membranes with a channel-density dependent switching between Type 1 and 2 dynamics, and membranes with a channel-density independent dynamics. The difference between the two membrane types suggests functional differences, compatible with a more flexible role of the soma membrane than that of the axon membrane.

  2. Lipid Regulation of Sodium Channels.

    Science.gov (United States)

    D'Avanzo, N

    2016-01-01

    The lipid landscapes of cellular membranes are complex and dynamic, are tissue dependent, and can change with the age and the development of a variety of diseases. Researchers are now gaining new appreciation for the regulation of ion channel proteins by the membrane lipids in which they are embedded. Thus, as membrane lipids change, for example, during the development of disease, it is likely that the ionic currents that conduct through the ion channels embedded in these membranes will also be altered. This chapter provides an overview of the complex regulation of prokaryotic and eukaryotic voltage-dependent sodium (Nav) channels by fatty acids, sterols, glycerophospholipids, sphingolipids, and cannabinoids. The impact of lipid regulation on channel gating kinetics, voltage-dependence, trafficking, toxin binding, and structure are explored for Nav channels that have been examined in heterologous expression systems, native tissue, and reconstituted into artificial membranes. Putative mechanisms for Nav regulation by lipids are also discussed. PMID:27586290

  3. Volume Regulated Channels

    DEFF Research Database (Denmark)

    Klausen, Thomas Kjær

    expressed ICl, swell will decrease proliferation in several cell types, including Ehrlich cells. A differentiated expression of ICl, swell in the cell cycle has been described in different cell types indicating a regulating role. In Ehrlich Lettré ascites (ELA) cells we suggest the differentiated expression...

  4. Regulated trafficking of the CFTR chloride channel

    NARCIS (Netherlands)

    Braakman, L.J.; Kleizen, B.; Jonge, H.R. de

    2000-01-01

    The cystic fibrosis transmembrane conductance regulator (CFTR), the ABC transporter encoded by the cystic fibrosis gene, is localized in the apical membrane of epithelial cells where it functions as a cyclic AMP-regulated chloride channel and as a regulator of other ion channels and transporters. Wh

  5. Ion Channels Involved in Cell Volume Regulation

    DEFF Research Database (Denmark)

    Hoffmann, Else Kay

    2011-01-01

    regulatory ion channels involved, and the mechanisms (cellular signalling pathways) that regulate these channels. Finally, I shall also briefly review current investigations in these two cell lines that focuses on how changes in cell volume can regulate cell functions such as cell migration, proliferation...

  6. Pilot study on navigation channel regulation works in the North Channel, Yangtze estuary

    NARCIS (Netherlands)

    Gao, M.; Roelvink, J.A.

    2011-01-01

    It is estimated that the waterway in North Passage would not be able to meet the demand of shipping development soon and it is necessary to open a new deep navigation channel with a depth of 10 m in North Channel in the near future. A pilot study on the regulation of North Channel was proposed by Ya

  7. Regulation of sodium channel function by bilayer elasticity

    DEFF Research Database (Denmark)

    Lundbaek, Jens A; Birn, Pia; Hansen, Anker J;

    2004-01-01

    kinetics of the protein conformational changes therefore will be regulated by the bilayer elasticity, which is determined by the lipid composition. This hydrophobic coupling mechanism has been studied extensively in gramicidin channels, where the channel-bilayer hydrophobic interactions link a...... "conformational" change (the monomerdimer transition) to an elastic bilayer deformation. Gramicidin channels thus are regulated by the lipid bilayer elastic properties (thickness, monolayer equilibrium curvature, and compression and bending moduli). To investigate whether this hydrophobic coupling mechanism could...... be a general mechanism regulating membrane protein function, we examined whether voltage-dependent skeletal-muscle sodium channels, expressed in HEK293 cells, are regulated by bilayer elasticity, as monitored using gramicidin A (gA) channels. Nonphysiological amphiphiles (beta...

  8. Numerical Simulation of Density Current Evolution in a Diverging Channel

    Directory of Open Access Journals (Sweden)

    Mitra Javan

    2012-01-01

    Full Text Available When a buoyant inflow of higher density enters a reservoir, it sinks below the ambient water and forms an underflow. Downstream of the plunge point, the flow becomes progressively diluted due to the fluid entrainment. This study seeks to explore the ability of 2D width-averaged unsteady Reynolds-averaged Navier-Stokes (RANS simulation approach for resolving density currents in an inclined diverging channel. 2D width-averaged unsteady RANS equations closed by a buoyancy-modified − turbulence model are integrated in time with a second-order fractional step approach coupled with a direct implicit method and discretized in space on a staggered mesh using a second-order accurate finite volume approach incorporating a high-resolution semi-Lagrangian technique for the convective terms. A series of 2D width-averaged unsteady simulations is carried out for density currents. Comparisons with the experimental measurements and the other numerical simulations show that the predictions of velocity and density field are with reasonable accuracy.

  9. VEGF regulates TRPC6 channels in podocytes

    DEFF Research Database (Denmark)

    Thilo, Florian; Liu, Ying; Loddenkemper, Christoph;

    2012-01-01

    BACKGROUND: Both, increased plasma concentrations of vascular endothelial growth factor (VEGF) and increased expression of transient receptor potential canonical type 6 (TRPC6) channels in podocytes have been associated with proteinuric kidney diseases. Now, we investigated the hypothesis that VE...

  10. Roles and Regulation of Renal K Channels.

    Science.gov (United States)

    Welling, Paul A

    2016-01-01

    More than two dozen types of potassium channels, with different biophysical and regulatory properties, are expressed in the kidney, influencing renal function in many important ways. Recently, a confluence of discoveries in areas from human genetics to physiology, cell biology, and biophysics has cast light on the special function of five different potassium channels in the distal nephron, encoded by the genes KCNJ1, KCNJ10, KCNJ16, KCNMA1, and KCNN3. Research aimed at understanding how these channels work in health and go awry in disease has transformed our understanding of potassium balance and provided new insights into mechanisms of renal sodium handling and the maintenance of blood pressure. This review focuses on recent advances in this rapidly evolving field. PMID:26654186

  11. Nutritional Regulation of IGFs in Channel Catfish

    Science.gov (United States)

    We examined changes in hepatic IGF-I and IGF-II mRNA, insulin like growth factor binding proteins (IGFBP-1 and IGFBP-2) mRNA, muscle IGF-I and IGF-II mRNA in fed (fed daily for 45 days) and restricted (not fed for 30 days followed by feeding for 15 days) channel catfish. By day 30, liver IGF-I mRNA...

  12. Factors influencing the density profiles of granular flux in a two-dimensional inclined channel

    Institute of Scientific and Technical Information of China (English)

    BAO DeSong; ZHOU Ying; ZHANG XunSheng; TANG XiaoWei

    2009-01-01

    The two-dimensional dilute granular flow on a smooth incline bounded by rough sidewalls is investigated experimentally, and the transverse density profiles of granular flux (ξ=pv) across the channel are measured. The results show that the transverse density profiles of granular flux are symmetric about the channel center and that the density of granular flux near the boundary is clearly lower than that of the center. There is a critical width of channel Wc for the transition of the density of granular flux. The density of granular flux near the boundary decays with the increasing of inclination (sinθ) of the channel.

  13. Factors influencing the density profiles of granular flux in a two-dimensional inclined channel

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The two-dimensional dilute granular flow on a smooth incline bounded by rough sidewalls is investigated experimentally, and the transverse density profiles of granular flux (ξ = ρ v) across the channel are measured. The results show that the transverse density profiles of granular flux are symmetric about the channel center and that the density of granular flux near the boundary is clearly lower than that of the center. There is a critical width of channel Wc for the transition of the density of granular flux. The density of granular flux near the boundary decays with the increasing of inclination (sinθ ) of the channel.

  14. Regulation of Intestinal Glucose Absorption by Ion Channels and Transporters.

    Science.gov (United States)

    Chen, Lihong; Tuo, Biguang; Dong, Hui

    2016-01-14

    The absorption of glucose is electrogenic in the small intestinal epithelium. The major route for the transport of dietary glucose from intestinal lumen into enterocytes is the Na⁺/glucose cotransporter (SGLT1), although glucose transporter type 2 (GLUT2) may also play a role. The membrane potential of small intestinal epithelial cells (IEC) is important to regulate the activity of SGLT1. The maintenance of membrane potential mainly depends on the activities of cation channels and transporters. While the importance of SGLT1 in glucose absorption has been systemically studied in detail, little is currently known about the regulation of SGLT1 activity by cation channels and transporters. A growing line of evidence suggests that cytosolic calcium ([Ca(2+)]cyt) can regulate the absorption of glucose by adjusting GLUT2 and SGLT1. Moreover, the absorption of glucose and homeostasis of Ca(2+) in IEC are regulated by cation channels and transporters, such as Ca(2+) channels, K⁺ channels, Na⁺/Ca(2+) exchangers, and Na⁺/H⁺ exchangers. In this review, we consider the involvement of these cation channels and transporters in the regulation of glucose uptake in the small intestine. Modulation of them may be a potential strategy for the management of obesity and diabetes.

  15. Regulation of Intestinal Glucose Absorption by Ion Channels and Transporters

    Directory of Open Access Journals (Sweden)

    Lihong Chen

    2016-01-01

    Full Text Available The absorption of glucose is electrogenic in the small intestinal epithelium. The major route for the transport of dietary glucose from intestinal lumen into enterocytes is the Na+/glucose cotransporter (SGLT1, although glucose transporter type 2 (GLUT2 may also play a role. The membrane potential of small intestinal epithelial cells (IEC is important to regulate the activity of SGLT1. The maintenance of membrane potential mainly depends on the activities of cation channels and transporters. While the importance of SGLT1 in glucose absorption has been systemically studied in detail, little is currently known about the regulation of SGLT1 activity by cation channels and transporters. A growing line of evidence suggests that cytosolic calcium ([Ca2+]cyt can regulate the absorption of glucose by adjusting GLUT2 and SGLT1. Moreover, the absorption of glucose and homeostasis of Ca2+ in IEC are regulated by cation channels and transporters, such as Ca2+ channels, K+ channels, Na+/Ca2+ exchangers, and Na+/H+ exchangers. In this review, we consider the involvement of these cation channels and transporters in the regulation of glucose uptake in the small intestine. Modulation of them may be a potential strategy for the management of obesity and diabetes.

  16. Physiology and Regulation of Calcium Channels in Stomatal Guard Cells

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Julian I.

    2007-05-02

    Stomatal pores in the epidermis of leaves regulate the diffusion of CO2 into leaves for photosynthetic carbon fixation and control water loss of plants during drought periods. Guard cells sense CO2, water status, light and other environmental conditions to regulate stomatal apertures for optimization of CO2 intake and plant growth under drought stress. The cytosolic second messenger calcium contributes to stomatal movements by transducing signals and regulating ion channels in guard cells. Studies suggest that both plasma membrane Ca2+ influx channels and vacuolar/organellar Ca2+ release channels contribute to ABA-induced Ca2+ elevations in guard cells. Recent research in the P.I.'s laboratory has led to identification of a novel major cation-selective Ca2+-permeable influx channel (Ica) in the plasma membrane of Arabidopsis guard cells. These advances will allow detailed characterization of Ica plasma membrane Ca2+ influx channels in guard cells. The long term goal of this research project is to gain a first detailed characterization of these novel plasma membrane Ca2+-permeable channel currents in Arabidopsis guard cells. The proposed research will investigate the hypothesis that Ica represents an important Ca2+ influx pathway for ABA and CO2 signal transduction in Arabidopsis guard cells. These studies will lead to elucidation of key signal transduction mechanisms by which plants balance CO2 influx into leaves and transpirational water loss and may contribute to future strategies for manipulating gas exchange for improved growth of crop plants and for biomass production.

  17. Charge density dependent two-channel conduction in organic electric double layer transistors (EDLTs).

    Science.gov (United States)

    Xie, Wei; Liu, Feilong; Shi, Sha; Ruden, P Paul; Frisbie, C Daniel

    2014-04-23

    A transport model based on hole-density-dependent trapping is proposed to explain the two unusual conductivity peaks at surface hole densities above 10(13) cm(-2) in rubrene electric double layer transistors (EDLTs). Hole transport in rubrene is described to occur via multiple percolation pathways, where conduction is dominated by transport in the free-site channel at low hole density, and in the trap-site channel at larger hole density. PMID:24496822

  18. Prolactin receptor in regulation of neuronal excitability and channels.

    Science.gov (United States)

    Patil, Mayur J; Henry, Michael A; Akopian, Armen N

    2014-01-01

    Prolactin (PRL) activates PRL receptor isoforms to exert regulation of specific neuronal circuitries, and to control numerous physiological and clinically-relevant functions including; maternal behavior, energy balance and food intake, stress and trauma responses, anxiety, neurogenesis, migraine and pain. PRL controls these critical functions by regulating receptor potential thresholds, neuronal excitability and/or neurotransmission efficiency. PRL also influences neuronal functions via activation of certain neurons, resulting in Ca(2+) influx and/or electrical firing with subsequent release of neurotransmitters. Although PRL was identified almost a century ago, very little specific information is known about how PRL regulates neuronal functions. Nevertheless, important initial steps have recently been made including the identification of PRL-induced transient signaling pathways in neurons and the modulation of neuronal transient receptor potential (TRP) and Ca(2+) -dependent K(+) channels by PRL. In this review, we summarize current knowledge and recent progress in understanding the regulation of neuronal excitability and channels by PRL.

  19. Searching for the physiological mechanism of density dependence: Does corticosterone regulate tadpole responses to density?

    OpenAIRE

    Belden, L. K.; Rubbo, M. J.; Wingfield, J. C.; Kiesecker, J M

    2007-01-01

    Density-dependent population regulation is important in many natural populations, and in those populations, high population density is a likely stressor. In amphibians, previous laboratory studies with tadpoles suggest that corticosterone, the main glucocorticoid stress hormone, is one of the key regulators of density-dependent growth. To test this relationship in natural settings, we manipulated wood frog (Rana sylvatica) tadpole density at three levels in outdoor mesocosms and used a captur...

  20. Density-functional theory study of gramicidin A ion channel geometry and electronic properties

    OpenAIRE

    Todorović, Milica; Bowler, David R.; Gillan, Michael J.; Miyazaki, Tsuyoshi

    2013-01-01

    Understanding the mechanisms underlying ion channel function from the atomic-scale requires accurate ab initio modelling as well as careful experiments. Here, we present a density functional theory (DFT) study of the ion channel gramicidin A, whose inner pore conducts only monovalent cations and whose conductance has been shown to depend on the side chains of the amino acids in the channel. We investigate the ground-state geometry and electronic properties of the channel in vacuum, focusing o...

  1. Physiological regulation of epithelial sodium channel by proteolysis

    DEFF Research Database (Denmark)

    Svenningsen, Per; Friis, Ulla G; Bistrup, Claus;

    2011-01-01

    PURPOSE OF REVIEW: Activation of epithelial sodium channel (ENaC) by proteolysis appears to be relevant for day-to-day physiological regulation of channel activity in kidney and other epithelial tissues. Pathophysiogical, proteolytic activation of ENaC in kidney has been demonstrated in proteinuric...... disease. RECENT FINDINGS: A variation in sodium and potassium intake or plasma aldosterone changes the number of cleaved α and γ-ENaC subunits and is associated with changes in ENaC currents. The protease furin mediates intracellular cleavage, whereas the channel-activating protease prostasin (CAP-1...... is formed from filtered plasminogen via urokinase-type plasminogen activator. Plasmin activates ENaC directly at high concentrations and through prostasin at lower concentrations. SUMMARY: The discovery of serine protease-mediated activation of renal ENaC in physiological and pathophysiological conditions...

  2. Regulation of heartbeat by G protein-coupled ion channels.

    Science.gov (United States)

    Brown, A M

    1990-12-01

    The coupling of ion channels to receptors by G proteins is the subject of this American Physiological Society Walter B. Cannon Memorial "Physiology in Perspective" Lecture. This subject is particularly appropriate because it includes a molecular explanation of a homeostatic mechanism involving the autonomic nervous system and the latter subject preoccupied Dr. Cannon during most of his career. With the use of reconstitution methods, we and others have shown that heterotrimeric guanine nucleotide-binding (G) proteins couple receptors to ion channels by both membrane-delimited, direct pathways and cytoplasmic second messenger pathways. Furthermore, one set of receptors may be coupled to as many as three different sets of ion channels to form networks. Dual G protein pathways lead to the prediction of biphasic ion current responses in cell signaling, and this prediction was confirmed. In sinoatrial pacemaker cells, the pacemaking hyperpolarization-activated inward current (If) is directly regulated by the G proteins Gs and Go, and the two can act simultaneously. This could explain the classical observation that vagal inhibition of heart rate is greater during sympathetic stimulation. Because deactivation of the muscarinic response occurs much faster than the G protein alpha-subunit hydrolyzes guanosine 5'-triphosphate, we looked for accessory cellular factors. A surprising result was that the small monomeric ras G protein blocked the muscarinic pathway. The significance of this observation is unknown, but it appears that small and large G proteins may interact in ion channel signaling pathways.

  3. Dynamic regulation of aquaporin-4 water channels in neurological disorders.

    Science.gov (United States)

    Hsu, Ying; Tran, Minh; Linninger, Andreas A

    2015-10-01

    Aquaporin-4 water channels play a central role in brain water regulation in neurological disorders. Aquaporin-4 is abundantly expressed at the astroglial endfeet facing the cerebral vasculature and the pial membrane, and both its expression level and subcellular localization significantly influence brain water transport. However, measurements of aquaporin-4 levels in animal models of brain injury often report opposite trends of change at the injury core and the penumbra. Furthermore, aquaporin-4 channels play a beneficial role in brain water clearance in vasogenic edema, but a detrimental role in cytotoxic edema and exacerbate cell swelling. In light of current evidence, we still do not have a complete understanding of the role of aquaporin-4 in brain water transport. In this review, we propose that the regulatory mechanisms of aquaporin-4 at the transcriptional, translational, and post-translational levels jointly regulate water permeability in the short and long time scale after injury. Furthermore, in order to understand why aquaporin-4 channels play opposing roles in cytotoxic and vasogenic edema, we discuss experimental evidence on the dynamically changing osmotic gradients between blood, extracellular space, and the cytosol during the formation of cytotoxic and vasogenic edema. We conclude with an emerging picture of the distinct osmotic environments in cytotoxic and vasogenic edema, and propose that the directions of aquaporin-4-mediated water clearance in these two types of edema are distinct. The difference in water clearance pathways may provide an explanation for the conflicting observations of the roles of aquaporin-4 in edema resolution. PMID:26526878

  4. Joint Delay Doppler Probability Density Functions for Air-to-Air Channels

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    Michael Walter

    2014-01-01

    Full Text Available Recent channel measurements indicate that the wide sense stationary uncorrelated scattering assumption is not valid for air-to-air channels. Therefore, purely stochastic channel models cannot be used. In order to cope with the nonstationarity a geometric component is included. In this paper we extend a previously presented two-dimensional geometric stochastic model originally developed for vehicle-to-vehicle communication to a three-dimensional air-to-air channel model. Novel joint time-variant delay Doppler probability density functions are presented. The probability density functions are derived by using vector calculus and parametric equations of the delay ellipses. This allows us to obtain closed form mathematical expressions for the probability density functions, which can then be calculated for any delay and Doppler frequency at arbitrary times numerically.

  5. [Polymethoxylated flavonoids activate cystic fibrosis transmembrane conductance regulator chloride channel].

    Science.gov (United States)

    Cao, Huan-Huan; Fang, Fang; Yu, Bo; Luan, Jian; Jiang, Yu; Yang, Hong

    2015-04-25

    Cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-dependent chloride channel, plays key roles in fluid secretion in serous epithelial cells. Previously, we identified two polymethoxylated flavonoids, 3',4',5,5',6,7-hexamethoxyflavone (HMF) and 5-hydroxy-6,7,3',4'-tetramethoxyflavone (HTF) which could potentiate CFTR chloride channel activities. The present study was aimed to investigate the potentiation effects of HMF and HTF on CFTR Cl(-) channel activities by using a cell-based fluorescence assay and the short circuit Ussing chamber assay. The results of cell-based fluorescence assay showed that both HMF and HTF could dose-dependently potentiate CFTR Cl(-) channel activities in rapid and reversible ways, and the activations could be reversed by the CFTR blocker CFTRinh-172. Notably, HMF showed the highest affinity (EC50 = 2 μmol/L) to CFTR protein among the flavonoid CFTR activators identified so far. The activation of CFTR by HMF or HTF was forskolin (FSK) dependent. Both compounds showed additive effect with FSK and 3-Isobutyl-1-methylx (IBMX) in the activation of CFTR, while had no additive effect with genistein (GEN). In ex vivo studies, HMF and HTF could stimulate transepithelial Cl(-) secretion in rat colonic mucosa and enhance fluid secretion in mouse trachea submucosal glands. These results suggest that HMF and HTF may potentiate CFTR Cl(-) channel activities through both elevation of cAMP level and binding to CFTR protein pathways. The results provide new clues in elucidating structure and activity relationship of flavonoid CFTR activators. HMF might be developed as a new drug in the therapy of CFTR-related diseases such as bronchiectasis and habitual constipation. PMID:25896054

  6. DISCONTINUOUS FLOW OF TURBID DENSITY CURRENTS I. CHANNEL EXPANSION AND CONTRACTION

    Institute of Scientific and Technical Information of China (English)

    Jiahua FAN

    2005-01-01

    Laboratory experiments on turbid density currents were conducted to observe the flow features of these currents with abrupt contracted and expanded reaches. Experimental data were used to determine water entrainment coefficients for both channel expansion and contraction. Expressions for turbid density currents with water entrainment coefficients in abrupt contracted and expanded reaches were derived,and compared with experimental data.

  7. Isovector coupling channel and central properties of the charge density distribution in heavy spherical nuclei

    Indian Academy of Sciences (India)

    S Haddad

    2010-09-01

    The influence of the isovector coupling channel on the central depression parameter and the central value of the charge density distribution in heavy spherical nuclei was studied. The isovector coupling channel leads to about 50% increase of the central depression parameter, and weakens the dependency of both central depression parameter and central density on the asymmetry, impressively contributing to the semibubble form of the charge density distribution in heavy nuclei, and increasing the probability of larger nuclei with higher proton numbers and higher neutron-to-proton ratios stable.

  8. Role of Density Profiles for the Nonlinear Propagation of Intense Laser Beam through Plasma Channel

    OpenAIRE

    Sonu Sen; Meenu Asthana Varshney; Dinesh Varshney

    2014-01-01

    In this work role of density profiles for the nonlinear propagation of intense laser beam through plasma channel is analyzed. By employing the expression for the dielectric function of different density profile plasma, a differential equation for beamwidth parameter is derived under WKB and paraxial approximation. The laser induces modifications of the dielectric function through nonlinearities. It is found that density profiles play vital role in laser-plasma interaction studies. To have num...

  9. A melanosomal two-pore sodium channel regulates pigmentation.

    Science.gov (United States)

    Bellono, Nicholas W; Escobar, Iliana E; Oancea, Elena

    2016-01-01

    Intracellular organelles mediate complex cellular functions that often require ion transport across their membranes. Melanosomes are organelles responsible for the synthesis of the major mammalian pigment melanin. Defects in melanin synthesis result in pigmentation defects, visual deficits, and increased susceptibility to skin and eye cancers. Although genes encoding putative melanosomal ion transporters have been identified as key regulators of melanin synthesis, melanosome ion transport and its contribution to pigmentation remain poorly understood. Here we identify two-pore channel 2 (TPC2) as the first reported melanosomal cation conductance by directly patch-clamping skin and eye melanosomes. TPC2 has been implicated in human pigmentation and melanoma, but the molecular mechanism mediating this function was entirely unknown. We demonstrate that the vesicular signaling lipid phosphatidylinositol bisphosphate PI(3,5)P2 modulates TPC2 activity to control melanosomal membrane potential, pH, and regulate pigmentation. PMID:27231233

  10. Evaluating the impact of a wide range of vegetation densities on river channel pattern

    Science.gov (United States)

    Pattison, Ian; Roucou, Ron

    2016-04-01

    Braided rivers are very dynamic systems which have complex controls over their planform and flow dynamics. Vegetation is one variable which influences channel geometry and pattern, through its effect on local flow hydraulics and the process continuum of sediment erosion-transport-deposition. Furthermore, where in the braided floodplain stable vegetation develops depends on the temporal sequencing of the river discharge i.e. floods. Understanding the effect of vegetation in these highly dynamic systems has multiple consequences for human activity and floodplain management. This paper focusses on the specific role of vegetation density in controlling braided river form and processes. Previous research in this field has been contradictory; with Gran and Paola (2001) finding that increasing vegetation density decreased the number of active channels. In contrast, Coulthard (2005] observed that as vegetation become denser there was an increase in the number of channels. This was hypothesized to be caused by flow separation around vegetation and the development of bars immediately downstream of the plant. This paper reports the results from a set of experiments in a 4m by 1m flume, where discharge, slope and sediment size were kept constant. Artificial grass was used to represent vegetation with a density ranging from 50 plants/m2 to 400 plants/m2. Digital photographs, using a GoPro camera with a fish eye lens, were taken from ~1m above the flume at an interval of 30 seconds during the 3 hour experiment. The experiments showed that as the vegetation density increased from 50 to 150 plants/m2, the number of channel bars developing doubled from 12 to 24. At vegetation densities greater than 150 plants/m2 there was a decline in the number of bars created to a minimum of 8 bars for a density of 400 plants/m2. We attribute these patterns to the effect that the vegetation has on flow hydraulics, sediment transport processes and the spatial patterns of erosion and deposition. We

  11. The effect of cell size and channel density on neuronal information encoding and energy efficiency.

    Science.gov (United States)

    Sengupta, Biswa; Faisal, A Aldo; Laughlin, Simon B; Niven, Jeremy E

    2013-09-01

    Identifying the determinants of neuronal energy consumption and their relationship to information coding is critical to understanding neuronal function and evolution. Three of the main determinants are cell size, ion channel density, and stimulus statistics. Here we investigate their impact on neuronal energy consumption and information coding by comparing single-compartment spiking neuron models of different sizes with different densities of stochastic voltage-gated Na(+) and K(+) channels and different statistics of synaptic inputs. The largest compartments have the highest information rates but the lowest energy efficiency for a given voltage-gated ion channel density, and the highest signaling efficiency (bits spike(-1)) for a given firing rate. For a given cell size, our models revealed that the ion channel density that maximizes energy efficiency is lower than that maximizing information rate. Low rates of small synaptic inputs improve energy efficiency but the highest information rates occur with higher rates and larger inputs. These relationships produce a Law of Diminishing Returns that penalizes costly excess information coding capacity, promoting the reduction of cell size, channel density, and input stimuli to the minimum possible, suggesting that the trade-off between energy and information has influenced all aspects of neuronal anatomy and physiology.

  12. KCNQ channels regulate age-related memory impairment.

    Directory of Open Access Journals (Sweden)

    Sonia Cavaliere

    Full Text Available In humans KCNQ2/3 heteromeric channels form an M-current that acts as a brake on neuronal excitability, with mutations causing a form of epilepsy. The M-current has been shown to be a key regulator of neuronal plasticity underlying associative memory and ethanol response in mammals. Previous work has shown that many of the molecules and plasticity mechanisms underlying changes in alcohol behaviour and addiction are shared with those of memory. We show that the single KCNQ channel in Drosophila (dKCNQ when mutated show decrements in associative short- and long-term memory, with KCNQ function in the mushroom body α/βneurons being required for short-term memory. Ethanol disrupts memory in wildtype flies, but not in a KCNQ null mutant background suggesting KCNQ maybe a direct target of ethanol, the blockade of which interferes with the plasticity machinery required for memory formation. We show that as in humans, Drosophila display age-related memory impairment with the KCNQ mutant memory defect mimicking the effect of age on memory. Expression of KCNQ normally decreases in aging brains and KCNQ overexpression in the mushroom body neurons of KCNQ mutants restores age-related memory impairment. Therefore KCNQ is a central plasticity molecule that regulates age dependent memory impairment.

  13. Experimental study of the velocity of density currents in convergent and divergent channels

    Institute of Scientific and Technical Information of China (English)

    Hasan Torabi POUDEH; Samad EMAMGHOLIZADEH; Manoocher Fathi-MOGHADAM

    2014-01-01

    The head velocity of the density current in the convergent and divergent channel is a key parameter for evaluating the extent to which suspended material travels, and for determining the type and distribution of sediment in the water body. This study experimentally evaluated the effects of the reach degree of convergence and divergence on the head velocity of the density current. Experiments were conducted in the flume with 6.0 m long, 0.72 m width and 0.6 m height. The head velocity was measured at three convergent degrees (-8o;-12o;-26o), at three divergent degrees (8o; 12o; 26o) and two slopes (0.009, 0.016) for various discharges. The measured head velocity of the density current is compared with the head velocity of the density current in the constant cross section channel. Based on non-dimensional and statistical analysis, relations as linear multiple regression are offered for predicting head velocity of the density current in the convergent, divergent and constant cross section channel. Also the results of this research show that for the same slope and discharge, the head velocity of the density current in the convergent and divergent channel are greater and less than the head velocity of the constant cross section, respectively.

  14. Aquaporins: highly regulated channels controlling plant water relations.

    Science.gov (United States)

    Chaumont, François; Tyerman, Stephen D

    2014-04-01

    Plant growth and development are dependent on tight regulation of water movement. Water diffusion across cell membranes is facilitated by aquaporins that provide plants with the means to rapidly and reversibly modify water permeability. This is done by changing aquaporin density and activity in the membrane, including posttranslational modifications and protein interaction that act on their trafficking and gating. At the whole organ level aquaporins modify water conductance and gradients at key "gatekeeper" cell layers that impact on whole plant water flow and plant water potential. In this way they may act in concert with stomatal regulation to determine the degree of isohydry/anisohydry. Molecular, physiological, and biophysical approaches have demonstrated that variations in root and leaf hydraulic conductivity can be accounted for by aquaporins but this must be integrated with anatomical considerations. This Update integrates these data and emphasizes the central role played by aquaporins in regulating plant water relations.

  15. Breach channel morphology in the unsatured zone and under various compaction densities

    Energy Technology Data Exchange (ETDEWEB)

    Al-Riffai, Mahmoud; Nistor, Ioan [University of Ottawa, Ottawa, (Canada)

    2010-07-01

    Dam failure analysis is a major issue for emergency planning and disaster mitigation agencies. The study of the breaching mechanics of homogeneous non-cohesive earth dams and dikes is important for drafting effective emergency plans. Models are used to predict information on the outflow hydrograph occurring with a dam breach. This paper investigated the breach channel morphology in the unsaturated zones and under various compaction densities. The purpose of this study was to investigate the influence of the dam material's dry unit weight, of unsaturated soil on the downstream slope of the dam on the initiation, the morphology of the breach channel and the breach outflow hydrograph. Small-scale homogeneous and non-cohesive dam models were used under different drainage conditions and under different compaction densities. The experimental results showed that the drainage conditions and the compaction densities had a clear influence on the breach channel morphology.

  16. Intense laser beam propagating in a plasma channel with flat-bottom leaky density profile

    International Nuclear Information System (INIS)

    The propagation characteristics of an intense laser beam in a preformed plasma channel with the flat-bottom leaky density profile are investigated in detail. The evolution equation of the laser spot size is derived by employing variational technique. Seven propagation modes of the laser spot size are identified and some numerical results are presented. By comparison, we find that the results in this Letter may be more realistic since the flat-bottom leaky plasma channel comes closer to the practical plasma channel.

  17. Channel Gating Regulation by the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) First Cytosolic Loop.

    Science.gov (United States)

    Ehrhardt, Annette; Chung, W Joon; Pyle, Louise C; Wang, Wei; Nowotarski, Krzysztof; Mulvihill, Cory M; Ramjeesingh, Mohabir; Hong, Jeong; Velu, Sadanandan E; Lewis, Hal A; Atwell, Shane; Aller, Steve; Bear, Christine E; Lukacs, Gergely L; Kirk, Kevin L; Sorscher, Eric J

    2016-01-22

    In this study, we present data indicating a robust and specific domain interaction between the cystic fibrosis transmembrane conductance regulator (CFTR) first cytosolic loop (CL1) and nucleotide binding domain 1 (NBD1) that allows ion transport to proceed in a regulated fashion. We used co-precipitation and ELISA to establish the molecular contact and showed that binding kinetics were not altered by the common clinical mutation F508del. Both intrinsic ATPase activity and CFTR channel gating were inhibited severely by CL1 peptide, suggesting that NBD1/CL1 binding is a crucial requirement for ATP hydrolysis and channel function. In addition to cystic fibrosis, CFTR dysregulation has been implicated in the pathogenesis of prevalent diseases such as chronic obstructive pulmonary disease, acquired rhinosinusitis, pancreatitis, and lethal secretory diarrhea (e.g. cholera). On the basis of clinical relevance of the CFTR as a therapeutic target, a cell-free drug screen was established to identify modulators of NBD1/CL1 channel activity independent of F508del CFTR and pharmacologic rescue. Our findings support a targetable mechanism of CFTR regulation in which conformational changes in the NBDs cause reorientation of transmembrane domains via interactions with CL1 and result in channel gating.

  18. Calcium binding protein-mediated regulation of voltage-gated calcium channels linked to human diseases

    Institute of Scientific and Technical Information of China (English)

    Nasrin NFJATBAKHSH; Zhong-ping FENG

    2011-01-01

    Calcium ion entry through voltage-gated calcium channels is essential for cellular signalling in a wide variety of cells and multiple physiological processes. Perturbations of voltage-gated calcium channel function can lead to pathophysiological consequences. Calcium binding proteins serve as calcium sensors and regulate the calcium channel properties via feedback mechanisms. This review highlights the current evidences of calcium binding protein-mediated channel regulation in human diseases.

  19. Dislocation density of pure copper processed by accumulative roll bonding and equal-channel angular pressing

    Energy Technology Data Exchange (ETDEWEB)

    Miyajima, Yoji, E-mail: miyajima.y.ab@m.titech.ac.jp [Department of Materials Science and Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259-J2-63, Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Okubo, Satoshi; Abe, Hiroki; Okumura, Hiroki [Department of Materials Science and Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259-J2-63, Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Fujii, Toshiyuki [Department of Metallurgy and Ceramics Science, Graduate School of Engineering, Tokyo Institute of Technology, 2-12-1-S8-7, Ookayama, Meguro-ku, Tokyo 152-8552 (Japan); Onaka, Susumu; Kato, Masaharu [Department of Materials Science and Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology, 4259-J2-63, Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan)

    2015-06-15

    The dislocation density of pure copper fabricated by two severe plastic deformation (SPD) processes, i.e., accumulative roll bonding and equal-channel angular pressing, was evaluated using scanning transmission electron microscopy/transmission electron microscopy observations. The dislocation density drastically increased from ~ 10{sup 13} m{sup −} {sup 2} to about 5 × 10{sup 14} m{sup −} {sup 2}, and then saturated, for both SPD processes.

  20. Distributed Joint Source and Channel Coding with Low-Density Parity-Check Codes

    OpenAIRE

    Cen, Feng

    2014-01-01

    Low-density parity-check (LDPC) codes with the parity-based approach for distributed joint source channel coding (DJSCC) with decoder side information is described in this paper. The parity-based approach is theoretical limit achievable. Different edge degree distributions are used for source variable nodes and parity variable nodes. Particularly, the codeword-averaged density evolution (CADE) is presented for asymmetrically correlated nonuniform sources over the asymmetric memoryless transmi...

  1. Regulation of Na+ channels in frog lung epithelium: a target tissue for aldosterone action.

    Science.gov (United States)

    Fischer, H; Clauss, W

    1990-04-01

    Sodium transport across isolated lung tissue of the frog Xenopus laevis was measured in Ussing chambers under voltage-clamp conditions. Perfusing the lungs with NaCl-Ringer's solutions on both sides, a basal distinct amiloride-blockable Na+ current was present. Incubating the lungs with 1 mumol/l aldosterone from the pleural side raised the short circuit current after a 1-h latent period. Maximal values were reached after 4-5 h of aldosterone treatment, at which time the transepithelial Na+ current was more than doubled compared to the control. The stimulatory effect was totally inhibited when the aldosterone treatment was preceded by incubation of the lung tissues with spironolactone in 2000-fold excess. In the presence of amiloride (0.5-8 mumol/l) in the alveolar compartment, a Lorentzian noise component appeared in the power spectrum of the fluctuations in the short circuit current. This enabled the calculation of single Na+ channel current and Na+ channel density under both experimental conditions. Aldosterone stimulation did not change single Na+ channel current. On the other hand, the number of conducting Na+ channels increased in parallel with the transepithelial Na+ transport. This suggests that the alveolar epithelium may be a physiological target tissue for aldosterone. Since fluid absorption in the lung is secondary to active Na+ transport, aldosterone may be a potent regulator for maintaining the relatively fluid-free state of the lumen of the lung in some cases of fluid accumulation. PMID:2162035

  2. Causes and effects of morphological changes of the regulated channel of the river Toplica

    Directory of Open Access Journals (Sweden)

    Đeković Vojislav

    2005-01-01

    Full Text Available The regulation of small torrential watercourses outside the urbanized areas is often based on the so-called field type of regulation. In the selection of this concept, after the regulation works, the new channel is left to the natural process of the morphological formation of the water cross-section taking care not to disturb the general stability of the regulated channel. We present the process of morphological development of the regulated channel of the river Toplica, tributary of the river Kolubara, in the period 1982-2004 i.e. from immediately after the regulation works to the present day.

  3. 76 FR 11679 - Drawbridge Operation Regulation; Shark River (South Channel), Belmar, NJ

    Science.gov (United States)

    2011-03-03

    ... SECURITY Coast Guard 33 CFR Part 117 Drawbridge Operation Regulation; Shark River (South Channel), Belmar... operation of the S71 Bridge across Shark River (South Channel), mile 0.8, at Belmar, NJ. The deviation is... INFORMATION: The S71 Bridge, a bascule lift drawbridge, across Shark River (South Channel), at mile 0.8,...

  4. Atrial natriuretic peptide regulates Ca channel in early developmental cardiomyocytes.

    Directory of Open Access Journals (Sweden)

    Lin Miao

    Full Text Available BACKGROUND: Cardiomyocytes derived from murine embryonic stem (ES cells possess various membrane currents and signaling cascades link to that of embryonic hearts. The role of atrial natriuretic peptide (ANP in regulation of membrane potentials and Ca(2+ currents has not been investigated in developmental cardiomyocytes. METHODOLOGY/PRINCIPAL FINDINGS: We investigated the role of ANP in regulating L-type Ca(2+ channel current (I(CaL in different developmental stages of cardiomyocytes derived from ES cells. ANP decreased the frequency of action potentials (APs in early developmental stage (EDS cardiomyocytes, embryonic bodies (EB as well as whole embryo hearts. ANP exerted an inhibitory effect on basal I(CaL in about 70% EDS cardiomyocytes tested but only in about 30% late developmental stage (LDS cells. However, after stimulation of I(CaL by isoproterenol (ISO in LDS cells, ANP inhibited the response in about 70% cells. The depression of I(CaL induced by ANP was not affected by either Nomega, Nitro-L-Arginine methyl ester (L-NAME, a nitric oxide synthetase (NOS inhibitor, or KT5823, a cGMP-dependent protein kinase (PKG selective inhibitor, in either EDS and LDS cells; whereas depression of I(CaL by ANP was entirely abolished by erythro-9-(2-Hydroxy-3-nonyl adenine (EHNA, a selective inhibitor of type 2 phosphodiesterase(PDE2 in most cells tested. CONCLUSION/SIGNIFICANCES: Taken together, these results indicate that ANP induced depression of action potentials and I(CaL is due to activation of particulate guanylyl cyclase (GC, cGMP production and cGMP-activation of PDE2 mediated depression of adenosine 3', 5'-cyclic monophophate (cAMP-cAMP-dependent protein kinase (PKA in early cardiomyogenesis.

  5. Coupled-channels quantum theory of electronic flux density in electronically adiabatic processes: fundamentals.

    Science.gov (United States)

    Diestler, D J

    2012-03-22

    The Born-Oppenheimer (BO) description of electronically adiabatic molecular processes predicts a vanishing electronic flux density (j(e)), =1/2∫dR[Δ(b) (x;R) - Δ(a) (x;R)] even though the electrons certainly move in response to the movement of the nuclei. This article, the first of a pair, proposes a quantum-mechanical "coupled-channels" (CC) theory that allows the approximate extraction of j(e) from the electronically adiabatic BO wave function . The CC theory is detailed for H(2)(+), in which case j(e) can be resolved into components associated with two channels α (=a,b), each of which corresponds to the "collision" of an "internal" atom α (proton a or b plus electron) with the other nucleus β (proton b or a). The dynamical role of the electron, which accommodates itself instantaneously to the motion of the nuclei, is submerged in effective electronic probability (population) densities, Δ(α), associated with each channel (α). The Δ(α) densities are determined by the (time-independent) BO electronic energy eigenfunction, which depends parametrically on the configuration of the nuclei, the motion of which is governed by the usual BO nuclear Schrödinger equation. Intuitively appealing formal expressions for the electronic flux density are derived for H(2)(+).

  6. Regulation of Shaker-type potassium channels by hypoxia. Oxygen-sensitive K+ channels in PC12 cells.

    Science.gov (United States)

    Conforti, L; Millhorn, D E

    2000-01-01

    Little is known about the molecular composition of the O2-sensitive K+ (Ko2) channels. The possibility that these channels belong to the Shaker subfamily (Kv1) of voltage-dependent K+ (Kv) channels has been raised in pulmonary artery (PA) smooth muscle cells. Numerous findings suggest that the Ko2 channel in PC12 cells is a Kv1 channel, formed by the Kv1.2 alpha subunit. The Ko2 channel in PC12 cells is a slow-inactivating voltage-dependent K+ channel of 20 pS conductance. Other Kv channels, also expressed in PC12 cells, are not inhibited by hypoxia. Selective up-regulation by chronic hypoxia of the Kv1.2 alpha subunit expression correlates with an increase O2-sensitivity of the K+ current. Other Kv1 alpha subunit genes encoding slow-inactivating Kv channels, such as Kv1.3, Kv2.1, Kv3.1 and Kv3.2 are not modulated by chronic hypoxia. The Ko2 current in PC12 cells is blocked by 5 mM externally applied tetraethylammonium chloride (TEA) and by charydbotoxin (CTX). The responses of the Kv1.2 K+ channel to hypoxia have been studied in the Xenopus oocytes and compared to those of Kv2.1, also proposed as Ko2 channel in PA smooth muscle cells. Two-electrode voltage clamp experiments show that hypoxia induces inhibition of K+ current amplitude only in oocytes injected with Kv1.2 cRNA. These data indicate that Kv1.2 K+ channels are inhibited by hypoxia. PMID:10849667

  7. Phosphorylation of K[superscript +] Channels at Single Residues Regulates Memory Formation

    Science.gov (United States)

    Vernon, Jeffrey; Irvine, Elaine E.; Peters, Marco; Jeyabalan, Jeshmi; Giese, K. Peter

    2016-01-01

    Phosphorylation is a ubiquitous post-translational modification of proteins, and a known physiological regulator of K[superscript +] channel function. Phosphorylation of K[superscript +] channels by kinases has long been presumed to regulate neuronal processing and behavior. Although circumstantial evidence has accumulated from behavioral studies…

  8. Hollow density channels and transport in a laser irradiated plasma slab

    CERN Document Server

    Ruhl, H

    2001-01-01

    A three dimensional Particle-In-Cell simulation describing the interaction of an intense laser beam with a plasma slab is presented. It is observed that the laser generated electron current decays into magnetically isolated filaments. The filaments grow in scale and magnitude by a merging process in the course of which the field topology changes. The opposite process also takes place occasionally. The laser driven charge and energy flows and the reconnecting magnetic field mutually interact. At the end of the merging process flows and fields are confined close to the laser irradiated surface of the plasma slab. Both decay rapidly in the bulk plasma. Due to the magnetic pressure in the filaments hollow density channels in the electron and ion densities are formed. The simulation reveals that charge flows in these channels can exceed the Alfven current.

  9. Novel vertical channel double gate structures for high density and low power flash memory applications

    Institute of Scientific and Technical Information of China (English)

    HUANG Ru; ZHOU FaLong; CAI YiMao; WU DaKe; ZHANG Xing

    2008-01-01

    The flash memory technology meets physical and technical obstacles in further caling. New structures and new materials are implemented as possible solutions. This paper focuses on two kinds of new flash cells for high density and low power memory applications based on the vertical channel double gate structure. The proposed VD-NROM with dual-nitride-trapping-layer and vertical structure can achieve four-bit-per-cell storage capability. And the proposed VSAS-FG cell bene-fits the high programming efficiency, low power and high density capability, which can be realized without any additional mask and can achieve the self-alignment of the split-gate channel and the floating-gate. The two novel flash cell structures can be considered as potential candidates for different flash memory applications.

  10. Bubble density variations in narrow channel under inclination and rolling motions

    International Nuclear Information System (INIS)

    Visual experiments on bubble density were carried out at subcooled flow boiling in a narrow channel under rolling and inclination conditions. Image analysis based results show that the bubble density fluctuates periodically under rolling condition. It is found by data comparison that the bubble density fluctuation amplitude increases with the decrease of rolling period, while the fluctuation form doesn't vary considerably. The increase of rolling angle for a given rolling period reduces the bubble density, but results in an almost invariable fluctuation form. In regard to inclination conditions, when the heating plate of the test section lies at lower side (positive angle inclination), the bubble density decreases with the increase of inclination angle. When the heating plate is at upper side (negative angle inclination), the bubble density first decreases then increases with the increase of inclination angle. Comparison of bubble densities shows that the bubble density at the maximum angle during rolling is close to that under the corresponding inclination. (authors)

  11. Upper Bounds on the Rate of Low Density Stabilizer Codes for the Quantum Erasure Channel

    CERN Document Server

    Delfosse, Nicolas

    2012-01-01

    Using combinatorial arguments, we determine an upper bound on achievable rates of stabilizer codes used over the quantum erasure channel. This allows us to recover the no-cloning bound on the capacity of the quantum erasure channel, R is below 1-2p, for stabilizer codes: we also derive an improved upper bound of the form : R is below 1-2p-D(p) with a function D(p) that stays positive for 0 < p < 1/2 and for any family of stabilizer codes whose generators have weights bounded from above by a constant - low density stabilizer codes. We obtain an application to percolation theory for a family of self-dual tilings of the hyperbolic plane. We associate a family of low density stabilizer codes with appropriate finite quotients of these tilings. We then relate the probability of percolation to the probability of a decoding error for these codes on the quantum erasure channel. The application of our upper bound on achievable rates of low density stabilizer codes gives rise to an upper bound on the critical prob...

  12. Transient receptor potential channels in mechanosensing and cell volume regulation

    DEFF Research Database (Denmark)

    Pedersen, Stine Falsig; Nilius, Bernd

    2007-01-01

    Transient receptor potential (TRP) channels are unique cellular sensors responding to a wide variety of extra- and intracellular signals, including mechanical and osmotic stress. In recent years, TRP channels from multiple subfamilies have been added to the list of mechano- and/or osmosensitive c...

  13. Oxidized Low-density Lipoprotein (ox-LDL) Cholesterol Induces the Expression of miRNA-223 and L-type Calcium Channel Protein in Atrial Fibrillation

    Science.gov (United States)

    He, Fengping; Xu, Xin; Yuan, Shuguo; Tan, Liangqiu; Gao, Lingjun; Ma, Shaochun; Zhang, Shebin; Ma, Zhanzhong; Jiang, Wei; Liu, Fenglian; Chen, Baofeng; Zhang, Beibei; Pang, Jungang; Huang, Xiuyan; Weng, Jiaqiang

    2016-08-01

    Atrial fibrillation (AF) is the most common sustained arrhythmia causing high morbidity and mortality. While changing of the cellular calcium homeostasis plays a critical role in AF, the L-type calcium channel α1c protein has suggested as an important regulator of reentrant spiral dynamics and is a major component of AF-related electrical remodeling. Our computational modeling predicted that miRNA-223 may regulate the CACNA1C gene which encodes the cardiac L-type calcium channel α1c subunit. We found that oxidized low-density lipoprotein (ox-LDL) cholesterol significantly up-regulates both the expression of miRNA-223 and L-type calcium channel protein. In contrast, knockdown of miRNA-223 reduced L-type calcium channel protein expression, while genetic knockdown of endogenous miRNA-223 dampened AF vulnerability. Transfection of miRNA-223 by adenovirus-mediated expression enhanced L-type calcium currents and promoted AF in mice while co-injection of a CACNA1C-specific miR-mimic counteracted the effect. Taken together, ox-LDL, as a known factor in AF-associated remodeling, positively regulates miRNA-223 transcription and L-type calcium channel protein expression. Our results implicate a new molecular mechanism for AF in which miRNA-223 can be used as an biomarker of AF rheumatic heart disease.

  14. Oxidized Low-density Lipoprotein (ox-LDL) Cholesterol Induces the Expression of miRNA-223 and L-type Calcium Channel Protein in Atrial Fibrillation.

    Science.gov (United States)

    He, Fengping; Xu, Xin; Yuan, Shuguo; Tan, Liangqiu; Gao, Lingjun; Ma, Shaochun; Zhang, Shebin; Ma, Zhanzhong; Jiang, Wei; Liu, Fenglian; Chen, Baofeng; Zhang, Beibei; Pang, Jungang; Huang, Xiuyan; Weng, Jiaqiang

    2016-01-01

    Atrial fibrillation (AF) is the most common sustained arrhythmia causing high morbidity and mortality. While changing of the cellular calcium homeostasis plays a critical role in AF, the L-type calcium channel α1c protein has suggested as an important regulator of reentrant spiral dynamics and is a major component of AF-related electrical remodeling. Our computational modeling predicted that miRNA-223 may regulate the CACNA1C gene which encodes the cardiac L-type calcium channel α1c subunit. We found that oxidized low-density lipoprotein (ox-LDL) cholesterol significantly up-regulates both the expression of miRNA-223 and L-type calcium channel protein. In contrast, knockdown of miRNA-223 reduced L-type calcium channel protein expression, while genetic knockdown of endogenous miRNA-223 dampened AF vulnerability. Transfection of miRNA-223 by adenovirus-mediated expression enhanced L-type calcium currents and promoted AF in mice while co-injection of a CACNA1C-specific miR-mimic counteracted the effect. Taken together, ox-LDL, as a known factor in AF-associated remodeling, positively regulates miRNA-223 transcription and L-type calcium channel protein expression. Our results implicate a new molecular mechanism for AF in which miRNA-223 can be used as an biomarker of AF rheumatic heart disease. PMID:27488468

  15. GATE REGULATION SPEED AND TRANSITION PROCESS OF UNSTEADY FLOW IN CHANNEL

    Institute of Scientific and Technical Information of China (English)

    TAN Guang-ming; DING Zhi-liang; WANG Chang-de; YAO Xiong

    2008-01-01

    The operation methods of channel and the speed of gate regulation have great influence on the transformation of flow in water conveyance channels. Based on characteristics method, a 1-D unsteady flow numerical model for gate regulation was established in this study. The process of water flow was simulated under different boundary conditions. The influence of gate regulation speed and channel operation methods on flow transition process was analyzed. The numerical results show that under the same conditions, with increasing regulation speed of the gate, the change rates of discharge and water level increase, while the response time of channel becomes shorter, and ultimately the discharge and water level will transit to the same equilibrium states. Moreover, the flow is easier to reach stable state, if the water level in front of the sluice is kept constant, instead of behind the sluice. This study will be important to the scheme design of automatic operation control in water conveyance channels.

  16. The mucolipidosis IV Ca2+ channel TRPML1 (MCOLN1) is regulated by the TOR kinase.

    Science.gov (United States)

    Onyenwoke, Rob U; Sexton, Jonathan Z; Yan, Feng; Díaz, María Cristina Huertas; Forsberg, Lawrence J; Major, Michael B; Brenman, Jay E

    2015-09-15

    Autophagy is a complex pathway regulated by numerous signalling events that recycles macromolecules and may be perturbed in lysosomal storage disorders (LSDs). During autophagy, aberrant regulation of the lysosomal Ca(2+) efflux channel TRPML1 [transient receptor potential mucolipin 1 (MCOLN1)], also known as MCOLN1, is solely responsible for the human LSD mucolipidosis type IV (MLIV); however, the exact mechanisms involved in the development of the pathology of this LSD are unknown. In the present study, we provide evidence that the target of rapamycin (TOR), a nutrient-sensitive protein kinase that negatively regulates autophagy, directly targets and inactivates the TRPML1 channel and thereby functional autophagy, through phosphorylation. Further, mutating these phosphorylation sites to unphosphorylatable residues proved to block TOR regulation of the TRPML1 channel. These findings suggest a mechanism for how TOR activity may regulate the TRPML1 channel.

  17. Impact of Flow Regulation on Channel Morphology Around Tributary Junctions, West and White Rivers, Vermont

    Science.gov (United States)

    Renshaw, C.; Curtis, K.; Magilligan, F.; Dade, W.

    2008-12-01

    By resupplying the mainstem with water and sediment, tributaries are a primary mechanism for mitigating the impacts of flow regulation. As a result, morphological and ecological adjustments associated with flow regulation may be particularly pronounced at tributary junctions. Despite the extensive literature on how dams alter channel morphology, few studies have focused specifically on the relationship between flow regulation and consequent changes in bedload sediment transport at tributary junctions. Using historical aerial photographs, modern channel surveys, and flow modeling, we compare temporal changes between regulated and unregulated tributary junction morphology and sediment transport dynamics. In contrast to what has been observed along the Colorado River, where flow regulation has led to a reduction in the number and size of channel bars, we observe significant bar growth post-regulation along the West River in southern Vermont. In some cases exposed bar area increased more than 50 percent in the first three decades after regulation and coincides with a corresponding reduction in channel width. Revegetation of former floodplain surfaces has begun to reduce the exposed bar area. However, flow modeling indicates that the channel remains underfit with respect to the new flow regime, with the current 2- and 50-yr floods lacking sufficient competence to transport the bedload sediment discharged by tributaries. Thus even 50 years post regulation, additional morphological changes are still required for the mainstem channel to fully adjust to the new flow regime.

  18. Swelling-Activated Anion Channels Are Essential for Volume Regulation of Mouse Thymocytes

    Directory of Open Access Journals (Sweden)

    Ravshan Z. Sabirov

    2011-12-01

    Full Text Available Channel-mediated trans-membrane chloride movement is a key process in the active cell volume regulation under osmotic stress in most cells. However, thymocytes were hypothesized to regulate their volume by activating a coupled K-Cl cotransport mechanism. Under the patch-clamp, we found that osmotic swelling activates two types of macroscopic anion conductance with different voltage-dependence and pharmacology. At the single-channel level, we identified two types of events: one corresponded to the maxi-anion channel, and the other one had characteristics of the volume-sensitive outwardly rectifying (VSOR chloride channel of intermediate conductance. A VSOR inhibitor, phloretin, significantly suppressed both macroscopic VSOR-type conductance and single-channel activity of intermediate amplitude. The maxi-anion channel activity was largely suppressed by Gd3+ ions but not by phloretin. Surprisingly, [(dihydroindenyloxy] alkanoic acid (DIOA, a known antagonist of K-Cl cotransporter, was found to significantly suppress the activity of the VSOR-type single-channel events with no effect on the maxi-anion channels at 10 μM. The regulatory volume decrease (RVD phase of cellular response to hypotonicity was mildly suppressed by Gd3+ ions and was completely abolished by phloretin suggesting a major impact of the VSOR chloride channel and modulatory role of the maxi-anion channel. The inhibitory effect of DIOA was also strong, and, most likely, it occurred via blocking the VSOR Cl− channels.

  19. A role for BK channels in heart rate regulation in rodents.

    Directory of Open Access Journals (Sweden)

    Wendy L Imlach

    Full Text Available The heart generates and propagates action potentials through synchronized activation of ion channels allowing inward Na(+ and Ca(2+ and outward K(+ currents. There are a number of K(+ channel types expressed in the heart that play key roles in regulating the cardiac cycle. Large conductance calcium-activated potassium (BK ion channels are not thought to be directly involved in heart function. Here we present evidence that heart rate can be significantly reduced by inhibiting the activity of BK channels. Agents that specifically inhibit BK channel activity, including paxilline and lolitrem B, slowed heart rate in conscious wild-type mice by 30% and 42%, respectively. Heart rate of BK channel knock-out mice (Kcnma1(-/- was not affected by these BK channel inhibitors, suggesting that the changes to heart rate were specifically mediated through BK channels. The possibility that these effects were mediated through BK channels peripheral to the heart was ruled out with experiments using isolated, perfused rat hearts, which showed a significant reduction in heart rate when treated with the BK channel inhibitors paxilline (1 microM, lolitrem B (1 microM, and iberiotoxin (0.23 microM, of 34%, 60%, and 42%, respectively. Furthermore, paxilline was shown to decrease heart rate in a dose-dependent manner. These results implicate BK channels located in the heart to be directly involved in the regulation of heart rate.

  20. Pressure, density, temperature and entropy fluctuations in compressible turbulent plane channel flow

    CERN Document Server

    Gerolymos, G A

    2013-01-01

    We investigate the fluctuations of thermodynamic state-variables in compressible aerodynamic wall-turbulence, using results of direct numerical simulation (DNS) of compressible turbulent plane channel flow. The basic transport equations governing the behaviour of thermodynamic variables (density, pressure, temperature and entropy) are reviewed and used to derive the exact transport equations for the variances and fluxes (transport by the fluctuating velocity field) of the thermodynamic fluctuations. The scaling with Reynolds and Mach number of compressible turbulent plane channel flow is discussed. Correlation coefficients and higher-order statistics of the thermodynamic fluctuations are examined. Finally, detailed budgets of the transport equations for the variances and fluxes of the thermodynamic variables from a well-resolved DNS are analysed. Implications of these results both to the understanding of the thermodynamic interactions in compressible wall-turbulence and to possible improvements in statistical...

  1. Quinidine-sensitive K+ channels in the basolateral membrane of embryonic coprodeum epithelium: regulation by aldosterone and thyroxine.

    Science.gov (United States)

    Illek, B; Fischer, H; Clauss, W

    1993-01-01

    Basolateral K+ channels and their regulation during aldosterone- and thyroxine-stimulated Na+ transport were studied in the lower intestinal epithelium (coprodeum) of embryonic chicken in vitro. Isolated tissues of the coprodeum were mounted in Ussing chambers and investigated under voltage-clamped conditions. Simultaneous stimulation with aldosterone (1 mumol.l-1) and thyroxine (1 mumol.l-1) raised short-circuit current after a 1- to 2-h latent period. Maximal values were reached after 6-7 h of hormonal treatment, at which time transepithelial Na+ absorption was more than tripled (77 +/- 11 microA.cm-2) compared to control (24 +/- 8 microA.cm-2). K+ currents across the basolateral membrane were investigated after permeabilizing the apical membrane with the pore-forming antibiotic amphotericin B and application of a mucosal-to-serosal K+ gradient. This K+ current could be dose dependently depressed by the K+ channel blocker quinidine. Fluctuation analysis of the short-circuit current revealed a spontaneous and a blocker-induced Lorentzian noise component in the power density spectra. The Lorentzian corner frequencies increased linearly with the applied blocker concentration. This enabled the calculation of single K+ channel current and K+ channel density. Single K+ channel current was not affected by stimulation, whereas the number of quinidine-sensitive K+ channels in the basolateral membrane increased from 11 to 26.10(6).cm-2 in parallel to the hormonal stimulation transepithelial Na+ transport. This suggests that the basolateral membrane is a physiological target during synergistic aldosterone and thyroxine regulation of transepithelial Na+ transport for maintaining intracellular K+ homeostasis. PMID:8151014

  2. A heme-binding domain controls regulation of ATP-dependent potassium channels.

    Science.gov (United States)

    Burton, Mark J; Kapetanaki, Sofia M; Chernova, Tatyana; Jamieson, Andrew G; Dorlet, Pierre; Santolini, Jérôme; Moody, Peter C E; Mitcheson, John S; Davies, Noel W; Schmid, Ralf; Raven, Emma L; Storey, Nina M

    2016-04-01

    Heme iron has many and varied roles in biology. Most commonly it binds as a prosthetic group to proteins, and it has been widely supposed and amply demonstrated that subtle variations in the protein structure around the heme, including the heme ligands, are used to control the reactivity of the metal ion. However, the role of heme in biology now appears to also include a regulatory responsibility in the cell; this includes regulation of ion channel function. In this work, we show that cardiac KATP channels are regulated by heme. We identify a cytoplasmic heme-binding CXXHX16H motif on the sulphonylurea receptor subunit of the channel, and mutagenesis together with quantitative and spectroscopic analyses of heme-binding and single channel experiments identified Cys628 and His648 as important for heme binding. We discuss the wider implications of these findings and we use the information to present hypotheses for mechanisms of heme-dependent regulation across other ion channels.

  3. Mechanical properties of lipid bilayers and regulation of mechanosensitive function: from biological to biomimetic channels.

    Science.gov (United States)

    Balleza, Daniel

    2012-01-01

    Material properties of lipid bilayers, including thickness, intrinsic curvature and compressibility regulate the function of mechanosensitive (MS) channels. This regulation is dependent on phospholipid composition, lateral packing and organization within the membrane. Therefore, a more complete framework to understand the functioning of MS channels requires insights into bilayer structure, thermodynamics and phospholipid structure, as well as lipid-protein interactions. Phospholipids and MS channels interact with each other mainly through electrostatic forces and hydrophobic matching, which are also crucial for antimicrobial peptides. They are excellent models for studying the formation and stabilization of membrane pores. Importantly, they perform equivalent responses as MS channels: (1) tilting in response to tension and (2) dissipation of osmotic gradients. Lessons learned from pore forming peptides could enrich our knowledge of mechanisms of action and evolution of these channels. Here, the current state of the art is presented and general principles of membrane regulation of mechanosensitive function are discussed. PMID:22790280

  4. Newly expressed SUR1-regulated NCCa-ATP channel mediates cerebral edema after ischemic stroke

    OpenAIRE

    Simard, J. Marc; Chen, Mingkui; Tarasov, Kirill V.; Bhatta, Sergei; Ivanova, Svetlana; Melnitchenko, Ludmila; Tsymbalyuk, Natalya; West, G. Alexander; Gerzanich, Volodymyr

    2006-01-01

    Pathological conditions in the central nervous system, including stroke and trauma, are often exacerbated by cerebral edema. We recently identified a nonselective cation channel, the NCCa-ATP channel, in ischemic astrocytes that is regulated by sulfonylurea receptor 1 (SUR1), is opened by depletion of ATP and, when opened, causes cytotoxic edema. Here, we evaluated involvement of this channel in rodent models of stroke. SUR1 protein and mRNA were newly expressed in ischemic neurons, astrocyte...

  5. Structural analysis of calmodulin binding to ion channels demonstrates the role of its plasticity in regulation.

    NARCIS (Netherlands)

    Kovalevskaya, N.V.; Waterbeemd, M. van de; Bokhovchuk, F.M.; Bate, N.; Bindels, R.J.M.; Hoenderop, J.G.J.; Vuister, G.W.

    2013-01-01

    The Ca2+-binding protein calmodulin (CaM) is a well-known regulator of ion-channel activity. Consequently, the Protein Data Bank contains many structures of CaM in complex with different fragments of ion channels that together display a variety of binding modes. In addition to the canonical interact

  6. An adenylate kinase is involved in KATP channel regulation of mouse pancreatic beta cells.

    NARCIS (Netherlands)

    Schulze, D.U.; Dufer, M.; Wieringa, B.; Krippeit-Drews, P.; Drews, G.

    2007-01-01

    AIMS/HYPOTHESIS: In a previous study, we demonstrated that a creatine kinase (CK) modulates K(ATP) channel activity in pancreatic beta cells. To explore phosphotransfer signalling pathways in more detail, we examined whether K(ATP) channel regulation in beta cells is determined by a metabolic intera

  7. Store-operated channels regulate intracellular calcium in mammalian rods.

    Science.gov (United States)

    Molnar, Tünde; Barabas, Peter; Birnbaumer, Lutz; Punzo, Claudio; Kefalov, Vladimir; Križaj, David

    2012-08-01

    Exposure to daylight closes cyclic nucleotide-gated (CNG) and voltage-operated Ca(2+) -permeable channels in mammalian rods. The consequent lowering of the cytosolic calcium concentration ([Ca(2+)](i)), if protracted, can contribute to light-induced damage and apoptosis in these cells. We here report that mouse rods are protected against prolonged lowering of [Ca(2+)](i) by store-operated Ca(2+) entry (SOCE). Ca(2+) stores were depleted in Ca(2+)-free saline supplemented with the endoplasmic reticulum (ER) sequestration blocker cyclopiazonic acid. Store depletion elicited [Ca(2+)](i) signals that exceeded baseline [Ca(2+)](i) by 5.9 ± 0.7-fold and were antagonized by an inhibitory cocktail containing 2-APB, SKF 96365 and Gd(3+). Cation influx through SOCE channels was sufficient to elicit a secondary activation of L-type voltage-operated Ca2+ entry. We also found that TRPC1, the type 1 canonical mammalian homologue of the Drosophila photoreceptor TRP channel, is predominantly expressed within the outer nuclear layer of the retina. Rod loss in Pde6b(rdl) (rd1), Chx10/Kip1(-/-rdl) and Elovl4(TG2) dystrophic models was associated with ∼70% reduction in Trpc1 mRNA content whereas Trpc1 mRNA levels in rodless cone-full Nrl(-/-) retinas were decreased by ∼50%. Genetic ablation of TRPC1 channels, however, had no effect on SOCE, the sensitivity of the rod phototransduction cascade or synaptic transmission at rod and cone synapses. Thus, we localized two new mechanisms, SOCE and TRPC1, to mammalian rods and characterized the contribution of SOCE to Ca(2+) homeostasis. By preventing the cytosolic [Ca(2+)](i) from dropping too low under sustained saturating light conditions, these signalling pathways may protect Ca(2+)-dependent mechanisms within the ER and the cytosol without affecting normal rod function. PMID:22674725

  8. Regulation of voltage-gated sodium channel expression in cancer:hormones, growth factors and auto-regulation

    OpenAIRE

    Fraser, Scott P.; Ozerlat-Gunduz, Iley; Brackenbury, William J; Fitzgerald, Elizabeth M.; Campbell, Thomas M.; Coombes, R. Charles; Djamgoz, Mustafa B. A.

    2014-01-01

    Although ion channels are increasingly being discovered in cancer cells in vitro and in vivo, and shown to contribute to different aspects and stages of the cancer process, much less is known about the mechanisms controlling their expression. Here, we focus on voltage-gated Na(+) channels (VGSCs) which are upregulated in many types of carcinomas where their activity potentiates cell behaviours integral to the metastatic cascade. Regulation of VGSCs occurs at a hierarchy of levels from transcr...

  9. IKK regulates the deubiquitinase CYLD at the postsynaptic density

    Energy Technology Data Exchange (ETDEWEB)

    Thein, Soe; Pham, Anna [Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892 (United States); Bayer, K. Ulrich [Department of Pharmacology, University of Colorado Denver School of Medicine, Aurora, CO 80045 (United States); Tao-Cheng, Jung-Hwa [EM Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892 (United States); Dosemeci, Ayse, E-mail: dosemeca@mail.nih.gov [Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892 (United States)

    2014-07-18

    Highlights: • CYLD is phosphorylated by IKK in isolated PSDs in the absence of Ca{sup 2+}. • CYLD is phosphorylated by IKK at the PSDs of intact neurons in basal conditions. • Phosphorylation of CYLD by IKK increases its deubiquitinase activity. • The process is likely to influence protein trafficking at the PSD in basal conditions. - Abstract: K63-linked polyubiquitination of proteins regulates their trafficking into specific cellular pathways such as endocytosis and autophagy. CYLD, a deubiquitinase specific for K63-linked polyubiquitins, is present in high quantities at the postsynaptic density (PSD). It was previously shown that, under excitatory conditions, CaMKII activates CYLD in a Ca{sup 2+}-dependent manner. The observation that CYLD can also be phosphorylated in the absence of Ca{sup 2+} in isolated PSDs led us to further explore the regulation of CYLD under basal conditions. A possible involvement of the autonomous form of CaMKII and IKK, both kinases known to be localized at the PSD, was examined. A CaMKII inhibitor CN21 had no effect on CYLD phosphorylation in the absence of Ca{sup 2+}, but two different IKK inhibitors, IKK16 and tatNEMO, inhibited its phosphorylation. Immuno-electron microscopy on hippocampal cultures, using an antibody for CYLD phosphorylated at S-418, revealed that the phosphorylated form of CYLD is present at the PSD under basal conditions. Phosphorylation of CYLD under basal conditions was inhibited by IKK16. NMDA treatment further promoted phosphorylation of CYLD at the PSD, but IKK16 failed to block the NMDA-induced effect. In vitro experiments using purified proteins demonstrated direct phosphorylation and activation of CYLD by the beta catalytic subunit of IKK. Activation of IKK in isolated PSDs also promoted phosphorylation of CYLD and an increase in endogenous deubiquitinase activity for K63-linked polyubiquitins. Altogether, the results suggest that in the absence of excitatory conditions, constitutive IKK activity

  10. 77 FR 45247 - Drawbridge Operation Regulations; Gallants Channel, Beaufort, NC

    Science.gov (United States)

    2012-07-31

    ... Foundation Sprint Triathlon. DATES: This deviation is effective 12:30 p.m. until 3 p.m. on Saturday... accommodate the Neuse River Keeper Foundation Sprint Triathlon. Under the current operating regulations...

  11. 77 FR 56115 - Drawbridge Operation Regulations; Fort Point Channel, Boston, MA

    Science.gov (United States)

    2012-09-12

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF HOMELAND SECURITY Coast Guard 33 CFR Part 117 Drawbridge Operation Regulations; Fort Point Channel, Boston, MA AGENCY: Coast Guard, DHS. ACTION: Notice of temporary deviation from regulations. SUMMARY: The...

  12. Lipid Bilayer – mediated Regulation of Ion Channel Function by Amphiphilic Drugs

    DEFF Research Database (Denmark)

    Lundbæk, Jens August

    2008-01-01

    Drugs that at pico- to nanomolar concentration regulate ion channel function by high-affi nity binding to their cognate receptor often have a “ secondary pharmacology, ” in which the same molecule at low micromolar concentrations regulates a diversity of membrane proteins in an apparently...

  13. 77 FR 70372 - Drawbridge Operation Regulation; Shark River (South Channel), Avon Township, NJ

    Science.gov (United States)

    2012-11-26

    ... FR Federal Register NPRM Notice of Proposed Rulemaking Sec. Section Symbol U.S.C. United States Code... SECURITY Coast Guard 33 CFR Part 117 RIN 1625-AA09 Drawbridge Operation Regulation; Shark River (South..., across Shark River (South Channel) at Avon Township, NJ. The existing regulation contains a...

  14. The influence of near-wall density and viscosity gradients on turbulence in channel flows

    CERN Document Server

    Patel, Ashish; Pecnik, Rene

    2016-01-01

    The influence of near-wall density and viscosity gradients on near-wall turbulence in a channel are studied by means of Direct Numerical Simulation (DNS) of the low-Mach number approximation of the Navier--Stokes equations. Different constitutive relations for density and viscosity as a function of temperature are used in order to mimic a wide range of fluid behaviours and to develop a generalised framework for studying turbulence modulations in variable property flows. Instead of scaling the velocity solely based on local density, as done for the van Driest transformation, we derive an extension of the scaling that is based on gradients of the semi-local Reynolds number $Re_\\tau^*$. This extension of the van Driest transformation is able to collapse velocity profiles for flows with near-wall property gradients as a function of the semi-local wall coordinate. However, flow quantities like mixing length, turbulence anisotropy and turbulent vorticity fluctuations do not show a universal scaling very close to th...

  15. Role of Density Profiles for the Nonlinear Propagation of Intense Laser Beam through Plasma Channel

    Directory of Open Access Journals (Sweden)

    Sonu Sen

    2014-01-01

    Full Text Available In this work role of density profiles for the nonlinear propagation of intense laser beam through plasma channel is analyzed. By employing the expression for the dielectric function of different density profile plasma, a differential equation for beamwidth parameter is derived under WKB and paraxial approximation. The laser induces modifications of the dielectric function through nonlinearities. It is found that density profiles play vital role in laser-plasma interaction studies. To have numerical appreciation of the results the propagation equation for plasma is solved using the fourth order Runge-Kutta method for the initial plane wave front of the beam, using boundary conditions. The spot size of the laser beam decreases as the beam penetrates into the plasma and significantly adds self-focusing in plasma. This causes the laser beam to become more focused by reduction of diffraction effect, which is an important phenomenon in inertial confinement fusion and also for the understanding of self-focusing of laser pulses. Numerical computations are presented and discussed in the form of graphs for typical parameters of laser-plasma interaction.

  16. Control of Energy Density inside a Disordered Medium by Coupling to Open or Closed Channels.

    Science.gov (United States)

    Sarma, Raktim; Yamilov, Alexey G; Petrenko, Sasha; Bromberg, Yaron; Cao, Hui

    2016-08-19

    We demonstrate experimentally the efficient control of light intensity distribution inside a random scattering system. The adaptive wave front shaping technique is applied to a silicon waveguide containing scattering nanostructures, and the on-chip coupling scheme enables access to all input spatial modes. By selectively coupling the incident light to the open or closed channels of the disordered system, we not only vary the total energy stored inside the system by a factor of 7.4, but also change the energy density distribution from an exponential decay to a linear decay and to a profile peaked near the center. This work provides an on-chip platform for controlling light-matter interactions in turbid media. PMID:27588875

  17. Control of Energy Density inside a Disordered Medium by Coupling to Open or Closed Channels

    Science.gov (United States)

    Sarma, Raktim; Yamilov, Alexey G.; Petrenko, Sasha; Bromberg, Yaron; Cao, Hui

    2016-08-01

    We demonstrate experimentally the efficient control of light intensity distribution inside a random scattering system. The adaptive wave front shaping technique is applied to a silicon waveguide containing scattering nanostructures, and the on-chip coupling scheme enables access to all input spatial modes. By selectively coupling the incident light to the open or closed channels of the disordered system, we not only vary the total energy stored inside the system by a factor of 7.4, but also change the energy density distribution from an exponential decay to a linear decay and to a profile peaked near the center. This work provides an on-chip platform for controlling light-matter interactions in turbid media.

  18. Control of energy density inside disordered medium by coupling to open or closed channels

    CERN Document Server

    Sarma, Raktim; Petrenko, Sasha; Bromberg, Yaron; Cao, Hui

    2016-01-01

    We demonstrate experimentally an efficient control of light intensity distribution inside a random scattering system. The adaptive wavefront shaping technique is applied to a silicon waveguide containing scattering nanostructures, and the on-chip coupling scheme enables access to all input spatial modes. By selectively coupling the incident light to open or closed channels of the disordered system, we not only vary the total energy stored inside the system by 7.4 times, but also change the energy density distribution from an exponential decay to a linear decay and to a profile peaked near the center. This work provides an on-chip platform for controlling light-matter interactions in turbid media.

  19. KV7 Channels Regulate Firing during Synaptic Integration in GABAergic Striatal Neurons

    Directory of Open Access Journals (Sweden)

    M. Belén Pérez-Ramírez

    2015-01-01

    Full Text Available Striatal projection neurons (SPNs process motor and cognitive information. Their activity is affected by Parkinson’s disease, in which dopamine concentration is decreased and acetylcholine concentration is increased. Acetylcholine activates muscarinic receptors in SPNs. Its main source is the cholinergic interneuron that responds with a briefer latency than SPNs during a cortical command. Therefore, an important question is whether muscarinic G-protein coupled receptors and their signaling cascades are fast enough to intervene during synaptic responses to regulate synaptic integration and firing. One of the most known voltage dependent channels regulated by muscarinic receptors is the KV7/KCNQ channel. It is not known whether these channels regulate the integration of suprathreshold corticostriatal responses. Here, we study the impact of cholinergic muscarinic modulation on the synaptic response of SPNs by regulating KV7 channels. We found that KV7 channels regulate corticostriatal synaptic integration and that this modulation occurs in the dendritic/spines compartment. In contrast, it is negligible in the somatic compartment. This modulation occurs on sub- and suprathreshold responses and lasts during the whole duration of the responses, hundreds of milliseconds, greatly altering SPNs firing properties. This modulation affected the behavior of the striatal microcircuit.

  20. T-type voltage-gated calcium channels regulate the tone of mouse efferent arterioles

    DEFF Research Database (Denmark)

    Poulsen, Christian B; Al-Mashhadi, Rozh H; Cribbs, Leanne L;

    2011-01-01

    Voltage-gated calcium channels are important for the regulation of renal blood flow and the glomerular filtration rate. Excitation-contraction coupling in afferent arterioles is known to require activation of these channels and we studied their role in the regulation of cortical efferent arteriolar...... tone. We used microdissected perfused mouse efferent arterioles and found a transient vasoconstriction in response to depolarization with potassium; an effect abolished by removal of extracellular calcium. The T-type voltage-gated calcium channel antagonists mibefradil and nickel blocked this potassium....... Low concentrations of nickel, an agent that blocks Ca(v)3.2, had a similar effect. Thus, T-type voltage-gated calcium channels are functionally important for depolarization-induced vasoconstriction and subsequent dilatation in mouse cortical efferent arterioles.Kidney International advance online...

  1. Regulation of voltage-gated sodium channel expression in cancer: hormones, growth factors and auto-regulation.

    Science.gov (United States)

    Fraser, Scott P; Ozerlat-Gunduz, Iley; Brackenbury, William J; Fitzgerald, Elizabeth M; Campbell, Thomas M; Coombes, R Charles; Djamgoz, Mustafa B A

    2014-03-19

    Although ion channels are increasingly being discovered in cancer cells in vitro and in vivo, and shown to contribute to different aspects and stages of the cancer process, much less is known about the mechanisms controlling their expression. Here, we focus on voltage-gated Na(+) channels (VGSCs) which are upregulated in many types of carcinomas where their activity potentiates cell behaviours integral to the metastatic cascade. Regulation of VGSCs occurs at a hierarchy of levels from transcription to post-translation. Importantly, mainstream cancer mechanisms, especially hormones and growth factors, play a significant role in the regulation. On the whole, in major hormone-sensitive cancers, such as breast and prostate cancer, there is a negative association between genomic steroid hormone sensitivity and functional VGSC expression. Activity-dependent regulation by positive feedback has been demonstrated in strongly metastatic cells whereby the VGSC is self-sustaining, with its activity promoting further functional channel expression. Such auto-regulation is unlike normal cells in which activity-dependent regulation occurs mostly via negative feedback. Throughout, we highlight the possible clinical implications of functional VGSC expression and regulation in cancer. PMID:24493753

  2. Gasotransmitter regulation of ion channels: a key step in O2 sensing by the carotid body.

    Science.gov (United States)

    Prabhakar, Nanduri R; Peers, Chris

    2014-01-01

    Carotid bodies detect hypoxia in arterial blood, translating this stimulus into physiological responses via the CNS. It is long established that ion channels are critical to this process. More recent evidence indicates that gasotransmitters exert powerful influences on O2 sensing by the carotid body. Here, we review current understanding of hypoxia-dependent production of gasotransmitters, how they regulate ion channels in the carotid body, and how this impacts carotid body function.

  3. A melanosomal two-pore sodium channel regulates pigmentation

    OpenAIRE

    Bellono, Nicholas W.; Escobar, Iliana E.; Elena Oancea

    2016-01-01

    Intracellular organelles mediate complex cellular functions that often require ion transport across their membranes. Melanosomes are organelles responsible for the synthesis of the major mammalian pigment melanin. Defects in melanin synthesis result in pigmentation defects, visual deficits, and increased susceptibility to skin and eye cancers. Although genes encoding putative melanosomal ion transporters have been identified as key regulators of melanin synthesis, melanosome ion transport and...

  4. Plant guard cell anion channel SLAC1 regulates stomatal closure

    OpenAIRE

    Vahisalu, Triin

    2010-01-01

    Plants are rooted to their growth place; therefore it is important that they react adequately to changes in environmental conditions. Stomatal pores, which are formed of a pair of guard cells in leaf epidermis, regulate plant gas-exchange. Importantly, guard cells protect the plant from desiccation in drought conditions by reducing the aperture of the stomatal pore. They serve also as the first barrier against the major air pollutant ozone, but the behaviour of guard cells during ozone expo...

  5. Novel role of KCNQ2/3 channels in regulating neuronal cell viability.

    Science.gov (United States)

    Zhou, X; Wei, J; Song, M; Francis, K; Yu, S P

    2011-03-01

    Overactivation of certain K(+) channels can mediate excessive K(+) efflux and intracellular K(+) depletion, which are early ionic events in apoptotic cascade. The present investigation examined a possible role of the KCNQ2/3 channel or M-channel (also named Kv7.2/7.3 channels) in the pro-apoptotic process. Whole-cell recordings detected much larger M-currents (212 ± 31 pA or 10.5 ± 1.5 pA/pF) in cultured hippocampal neurons than that in cultured cortical neurons (47 ± 21 pA or 2.4 ± 0.8 pA/pF). KCNQ2/3 channel openers N-ethylmaleimide (NEM) and flupirtine caused dose-dependent K(+) efflux, intracellular K(+) depletion, and cell death in hippocampal cultures, whereas little cell death was induced by NEM in cortical cultures. The NEM-induced cell death was antagonized by co-applied KCNQ channel inhibitor XE991 (10 μM), or by elevated extracellular K(+) concentration. Supporting a mediating role of KCNQ2/3 channels in apoptosis, expression of KCNQ2 or KCNQ2/3 channels in Chinese hamster ovary (CHO) cells initiated caspase-3 activation. Consistently, application of NEM (20 μM, 8 h) in hippocampal cultures similarly caused caspase-3 activation assessed by immunocytochemical staining and western blotting. NEM increased the expression of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2), induced mitochondria membrane depolarization, cytochrome c release, formation of apoptosome complex, and apoptosis-inducing factor (AIF) translocation into nuclear. All these events were attenuated by blocking KCNQ2/3 channels. These findings provide novel evidence that KCNQ2/3 channels could be an important regulator in neuronal apoptosis. PMID:20885443

  6. Functional coupling of TRPV4 channels and BK channels in regulating spontaneous contractions of the guinea pig urinary bladder.

    Science.gov (United States)

    Isogai, Ayu; Lee, Ken; Mitsui, Retsu; Hashitani, Hikaru

    2016-09-01

    We investigated the role of TRPV4 channels (TRPV4) in regulating the contractility of detrusor smooth muscle (DSM) and muscularis mucosae (MM) of the urinary bladder. Distribution of TRPV4 in DSM and MM of guinea-pig bladders was examined by fluorescence immunohistochemistry. Changes in the contractility of DSM and MM bundles were measured using isometric tension recording. Intracellular Ca(2+) dynamics were visualized by Cal-520 fluorescent Ca(2+) imaging, while membrane potential changes were recorded using intracellular microelectrode technique. DSM and MM expressed TRPV4 immunoreactivity. GSK1016790A (GSK, 1 nM), a TRPV4 agonist, evoked a sustained contraction in both DSM and MM associated with a cessation of spontaneous phasic contractions in a manner sensitive to HC-067047 (10 μM), a TRPV4 antagonist. Iberiotoxin (100 nM) and paxilline (1 μM), large conductance Ca(2+)-activated K(+) (BK) channel blockers restored the spontaneous contractions in GSK. The sustained contractions in DSM and MM were reduced by nifedipine (10 μM), a blocker of L-type voltage-dependent Ca(2+) channels (LVDCCs) by about 40 % and by nominally Ca(2+)-free solution by some 90 %. GSK (1 nM) abolished spontaneous Ca(2+) transients, increased basal Ca(2+) levels and also prevented spontaneous action potential discharge associated with DSM membrane hyperpolarization. In conclusion, Ca(2+) influx through TRPV4 appears to activate BK channels to suppress spontaneous contractions and thus a functional coupling of TRPV4 with BK channels may act as a self-limiting mechanism for bladder contractility during its storage phase. Despite the membrane hyperpolarization in GSK, Ca(2+) entry mainly through TRPV4 develops the tonic contraction. PMID:27497848

  7. Correlation of apical fluid-regulating channel proteins with lung function in human COPD lungs.

    Directory of Open Access Journals (Sweden)

    Runzhen Zhao

    Full Text Available Links between epithelial ion channels and chronic obstructive pulmonary diseases (COPD are emerging through animal model and in vitro studies. However, clinical correlations between fluid-regulating channel proteins and lung function in COPD remain to be elucidated. To quantitatively measure epithelial sodium channels (ENaC, cystic fibrosis transmembrane conductance regulator (CFTR, and aquaporin 5 (AQP5 proteins in human COPD lungs and to analyze the correlation with declining lung function, quantitative western blots were used. Spearman tests were performed to identify correlations between channel proteins and lung function. The expression of α and β ENaC subunits was augmented and inversely associated with lung function. In contrast, both total and alveolar type I (ATI and II (ATII-specific CFTR proteins were reduced. The expression level of CFTR proteins was associated with FEV1 positively. Abundance of AQP5 proteins and extracellular superoxide dismutase (SOD3 was decreased and correlated with spirometry test results and gas exchange positively. Furthermore, these channel proteins were significantly associated with severity of disease. Our study demonstrates that expression of ENaC, AQP5, and CFTR proteins in human COPD lungs is quantitatively associated with lung function and severity of COPD. These apically located fluid-regulating channels may thereby serve as biomarkers and potent druggable targets of COPD.

  8. Transmembrane channel-like (tmc) gene regulates Drosophila larval locomotion.

    Science.gov (United States)

    Guo, Yanmeng; Wang, Yuping; Zhang, Wei; Meltzer, Shan; Zanini, Damiano; Yu, Yue; Li, Jiefu; Cheng, Tong; Guo, Zhenhao; Wang, Qingxiu; Jacobs, Julie S; Sharma, Yashoda; Eberl, Daniel F; Göpfert, Martin C; Jan, Lily Yeh; Jan, Yuh Nung; Wang, Zuoren

    2016-06-28

    Drosophila larval locomotion, which entails rhythmic body contractions, is controlled by sensory feedback from proprioceptors. The molecular mechanisms mediating this feedback are little understood. By using genetic knock-in and immunostaining, we found that the Drosophila melanogaster transmembrane channel-like (tmc) gene is expressed in the larval class I and class II dendritic arborization (da) neurons and bipolar dendrite (bd) neurons, both of which are known to provide sensory feedback for larval locomotion. Larvae with knockdown or loss of tmc function displayed reduced crawling speeds, increased head cast frequencies, and enhanced backward locomotion. Expressing Drosophila TMC or mammalian TMC1 and/or TMC2 in the tmc-positive neurons rescued these mutant phenotypes. Bending of the larval body activated the tmc-positive neurons, and in tmc mutants this bending response was impaired. This implicates TMC's roles in Drosophila proprioception and the sensory control of larval locomotion. It also provides evidence for a functional conservation between Drosophila and mammalian TMCs. PMID:27298354

  9. The Proteoglycan Syndecan 4 Regulates Transient Receptor Potential Canonical 6 Channels via RhoA/ROCK Signaling

    DEFF Research Database (Denmark)

    Liu, Ying; Echtermeyer, Frank; Thilo, Florian;

    2012-01-01

    OBJECTIVE: Syndecan 4 (Sdc4) modulates signal transduction and regulates activity of protein channels. Sdc4 is essential for the regulation of cellular permeability. We hypothesized that Sdc4 may regulate transient receptor potential canonical 6 (TRPC6) channels, a determinant of glomerular perme...

  10. Forms of density regulation and (quasi-) stationary distributions of population sizes in birds

    DEFF Research Database (Denmark)

    Sæther, Bernt-Erik; Engen, Steinar; Grøtan, Vidar;

    2008-01-01

    The theta-logistic model of density regulation is an especially flexible class of density regulation models where different forms of non-linear density regulation can be expressed by only one parameter, u. Estimating the parameters of the thetalogistic model is, however, challenging. This is mainly...... due to the need for information concerning population growth at low densities as well as data on fluctuations around the carrying capacity K in order to estimate the strength of density regulation. Here we estimate parameters of the theta-logistic model for 28 populations of three species of birds...... that have grown from very small population sizes followed by a period of fluctuations around K. We then use these parameters to estimate the quasi-stationary distribution of population size. There were often large uncertainties in these parameters specifying the form of density regulation that were...

  11. The KCNQ1 potassium channel is down-regulated by ubiquitylating enzymes of the Nedd4/Nedd4-like family

    DEFF Research Database (Denmark)

    Jespersen, Thomas; Membrez, Mathieu; Nicolas, Céline S;

    2007-01-01

    participate in controlling body electrolyte homeostasis. Several regulatory mechanisms of the KCNQ1 channel complexes have been reported, including protein kinase A (PKA)-phosphorylation and beta-subunit interactions. However, the mechanisms controlling the membrane density of KCNQ1 channels have attracted...... less attention. METHODS AND RESULTS: Here we demonstrate that KCNQ1 proteins expressed in HEK293 cells are down-regulated by Nedd4/Nedd4-like ubiquitin-protein ligases. KCNQ1 and KCNQ1/KCNE1 currents were reduced upon co-expression of Nedd4-2, the isoform among the nine members of the Nedd4/Nedd4-like...... by Nedd4-2, an increased ubiquitylation as well as a decreased total level of KCNQ1 proteins were observed in HEK293 cells. Pull-down and co-immunoprecipitation experiments showed that Nedd4-2 interacts with the C-terminal part of KCNQ1. The Nedd4/Nedd4-like-mediated regulation of the KCNQ1 channel...

  12. VRACs and other ion channels and transporters in the regulation of cell volume and beyond.

    Science.gov (United States)

    Jentsch, Thomas J

    2016-05-01

    Cells need to regulate their volume to counteract osmotic swelling or shrinkage, as well as during cell division, growth, migration and cell death. Mammalian cells adjust their volume by transporting potassium, sodium, chloride and small organic osmolytes using plasma membrane channels and transporters. This generates osmotic gradients, which drive water in and out of cells. Key players in this process are volume-regulated anion channels (VRACs), the composition of which has recently been identified and shown to encompass LRRC8 heteromers. VRACs also transport metabolites and drugs and function in extracellular signal transduction, apoptosis and anticancer drug resistance. PMID:27033257

  13. Cell volume changes regulate slick (Slo2.1, but not slack (Slo2.2 K+ channels.

    Directory of Open Access Journals (Sweden)

    Maria A Tejada

    Full Text Available Slick (Slo2.1 and Slack (Slo2.2 channels belong to the family of high-conductance K+ channels and have been found widely distributed in the CNS. Both channels are activated by Na+ and Cl- and, in addition, Slick channels are regulated by ATP. Therefore, the roles of these channels in regulation of cell excitability as well as ion transport processes, like regulation of cell volume, have been hypothesized. It is the aim of this work to evaluate the sensitivity of Slick and Slack channels to small, fast changes in cell volume and to explore mechanisms, which may explain this type of regulation. For this purpose Slick and Slack channels were co-expressed with aquaporin 1 in Xenopus laevis oocytes and cell volume changes of around 5% were induced by exposure to hypotonic or hypertonic media. Whole-cell currents were measured by two electrode voltage clamp. Our results show that Slick channels are dramatically stimulated (196% of control by cell swelling and inhibited (57% of control by a decrease in cell volume. In contrast, Slack channels are totally insensitive to similar cell volume changes. The mechanism underlining the strong volume sensitivity of Slick channels needs to be further explored, however we were able to show that it does not depend on an intact actin cytoskeleton, ATP release or vesicle fusion. In conclusion, Slick channels, in contrast to the similar Slack channels, are the only high-conductance K+ channels strongly sensitive to small changes in cell volume.

  14. The unc-8 and sup-40 genes regulate ion channel function in Caenorhabditis elegans motorneurons

    Energy Technology Data Exchange (ETDEWEB)

    Shreffler, W.; Magardino, T.; Shekdar, K.; Wolinsky, E. [New York Univ. Medical School, NY (United States)

    1995-03-01

    Two Caenorhabditis elegans genes, unc-8 and sup-40, have been newly identified, by genetic criteria, as regulating ion channel function in motorneurons. Two dominant unc-8 alleles cause motorneuron swelling similar to that of other neuronal types in dominant mutants of the deg-1 gene family, which is homologous to a mammalian gene family encoding amiloride-sensitive sodium channel subunits. As for previously identified deg-1 family members, unc-8 dominant mutations are recessively suppressed by mutations in the mec-6 gene, which probably encodes a second type of channel component. An unusual dominant mutation, sup-41 (lb125), also co-suppresses unc-8 and deg-1, suggesting the existence of yet another common component of ion channels containing unc-8 or deg-1 subunits. Dominant, transacting, intragenic suppressor mutations have been isolated for both unc-8 and deg-1, consistent with the idea that, like their mammalian homologues, the two gene products function as multimers. The sup-40 (lb130) mutation dominantly suppresses unc-8 motorneuron swelling and produces a novel swelling phenotype in hypodermal nuclei. sup-40 may encode an ion channel component or regulator that can correct the osmotic defect caused by abnormal unc-8 channels. 37 refs., 6 figs., 3 tabs.

  15. Regulation of photosynthesis by ion channels in cyanobacteria and higher plants.

    Science.gov (United States)

    Checchetto, Vanessa; Teardo, Enrico; Carraretto, Luca; Formentin, Elide; Bergantino, Elisabetta; Giacometti, Giorgio Mario; Szabo, Ildiko

    2013-12-01

    Photosynthesis converts light energy into chemical energy, and supplies ATP and NADPH for CO2 fixation into carbohydrates and for the synthesis of several compounds which are essential for autotrophic growth. Oxygenic photosynthesis takes place in thylakoid membranes of chloroplasts and photosynthetic prokaryote cyanobacteria. An ancestral photoautotrophic prokaryote related to cyanobacteria has been proposed to give rise to chloroplasts of plants and algae through an endosymbiotic event. Indeed, photosynthetic complexes involved in the electron transport coupled to H(+) translocation and ATP synthesis are similar in higher plants and cyanobacteria. Furthermore, some of the protein and solute/ion conducting machineries also share common structure and function. Electrophysiological and biochemical evidence support the existence of ion channels in the thylakoid membrane in both types of organisms. By allowing specific ion fluxes across thylakoid membranes, ion channels have been hypothesized to either directly or indirectly regulate photosynthesis, by modulating the proton motive force. Recent molecular identification of some of the thylakoid-located channels allowed to obtain genetic proof in favor of such hypothesis. Furthermore, some ion channels of the envelope membrane in chloroplasts have also been shown to impact on this light-driven process. Here we give an overview of thylakoid/chloroplast located ion channels of higher plants and of cyanobacterium Synechocystis sp. PCC 6803. We focus on channels shown to be implicated in the regulation of photosynthesis and discuss the possible mechanisms of action.

  16. Regulation of CFTR Cl− channel gating by ATP binding and hydrolysis

    OpenAIRE

    Ikuma, Mutsuhiro; Welsh, Michael J.

    2000-01-01

    Opening and closing of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel is regulated by the interaction of ATP with its two cytoplasmic nucleotide-binding domains (NBD). Although ATP hydrolysis by the NBDs is required for normal gating, the influence of ATP binding versus hydrolysis on specific steps in the gating cycle remains uncertain. Earlier work showed that the absence of Mg2+ prevents hydrolysis. We found that even in the absence of Mg2+, ATP could support cha...

  17. Lipid bilayer regulation of membrane protein function: gramicidin channels as molecular force probes

    DEFF Research Database (Denmark)

    Lundbæk, Jens August; Collingwood, S.A.; Ingolfsson, H.I.;

    2010-01-01

    Membrane protein function is regulated by the host lipid bilayer composition. This regulation may depend on specific chemical interactions between proteins and individual molecules in the bilayer, as well as on non-specific interactions between proteins and the bilayer behaving as a physical enti...... use of gramicidin channels as molecular force probes for studying this mechanism, with a unique ability to discriminate between consequences of changes in monolayer curvature and bilayer elastic moduli....

  18. High-density channel model and detection method for signal readout from super-resolution near-field structure discs

    Science.gov (United States)

    Hosogai, Shota; Ansai, Tsutomu; Yoshinari, Takehisa; Tanabe, Takaya

    2016-09-01

    Although a readout method using the super-resolution near-field structure (super-RENS) effect can overcome diffraction limits, readout characteristics for greatly surpassed high-density conditions do not become clear, because a high-density channel function having a differential response property is superimposed on a normal readout function. We propose a high-density channel model to indicate the properties of the super-RENS effect directly. This model can be expressed as a differential response function using the finite impulse response (FIR) filter model. It expresses the super-RENS readout process, which is divided on the basis of recording densities such as high and normal Blu-ray Disc™ densities. We estimated the properties of super-RENS readout signals by comparison between theoretical expressions and experiments. Results show that good signal quality require readout signals having sharp peaks and smaller offsets. We also evaluated the channel model by adding an adaptive FIR filter and a Viterbi decoder by simulations. Results show that the super-RENS disc can achieve a fourfold higher recording density if the signal-to-noise ratio (S/N) is improved to 6 dB in the case of partial response (PR) (1 + D + D 2).

  19. Do cysteine residues regulate transient receptor potential canonical type 6 (TRPC6) channel protein expression?

    DEFF Research Database (Denmark)

    Thilo, Florian; Liu, Ying; Krueger, Katharina;

    2012-01-01

    The regulation of calcium influx through transient receptor potential canonical type 6 channel is mandatory for the activity of human monocytes. We submit the first evidence that cysteine residues of homocysteine or acetylcysteine affect TRPC6 expression in human monocytes. We observed that patie......The regulation of calcium influx through transient receptor potential canonical type 6 channel is mandatory for the activity of human monocytes. We submit the first evidence that cysteine residues of homocysteine or acetylcysteine affect TRPC6 expression in human monocytes. We observed...... that patients with chronic renal failure had significantly elevated homocysteine levels and TRPC6 mRNA expression levels in monocytes compared to control subjects. We further observed that administration of homocysteine or acetylcysteine significantly increased TRPC6 channel protein expression compared...

  20. PKC and AMPK regulation of Kv1.5 potassium channels.

    Science.gov (United States)

    Andersen, Martin Nybo; Skibsbye, Lasse; Tang, Chuyi; Petersen, Frederic; MacAulay, Nanna; Rasmussen, Hanne Borger; Jespersen, Thomas

    2015-01-01

    The voltage-gated Kv1.5 potassium channel, conducting the ultra-rapid rectifier K(+) current (IKur), is regulated through several pathways. Here we investigate if Kv1.5 surface expression is controlled by the 2 kinases PKC and AMPK, using Xenopus oocytes, MDCK cells and atrial derived HL-1 cells. By confocal microscopy combined with electrophysiology we demonstrate that PKC activation reduces Kv1.5 current, through a decrease in membrane expressed channels. AMPK activation was found to decrease the membrane expression in MDCK cells, but not in HL-1 cells and was furthermore shown to be dependent on co-expression of Nedd4-2 in Xenopus oocytes. These results indicate that Kv1.5 channels are regulated by both kinases, although through different molecular mechanisms in different cell systems. PMID:26043299

  1. Apamin-Sensitive Small Conductance Calcium-Activated Potassium Channels were Negatively Regulated by Captopril in Volume-Overload Heart Failure Rats.

    Science.gov (United States)

    Hongyuan, Bai; Xin, Dong; Jingwen, Zhang; Li, Gao; Yajuan, Ni

    2016-08-01

    In heart failure (HF), the malignant arrhythmias occur frequently; a study demonstrated that upregulation of I KAS resulted in recurrent spontaneous ventricular fibrillation in HF. However, the regulation of SK channels was poorly understood. The activation of SK channels depended on [Ca(2+)]i and PP2A; studies suggested that angiotensin II can regulate them. So, we hypothesized that in HF, the excess of angiotensin may regulate the SK channels and result in the remodeling of SK channels. To test the hypothesis, we used volume-overload-induced HF rat model, treated with captopril, performed whole-cell patch clamp to record apamin-sensitive currents (I KAS), and I-V curve was studied. The sensitivity of I KAS to [Ca(2+)]i was also explored by setting various [Ca(2+)]i (10, 100, 500, 900, 1000, and 10,000 nM), and the steady-state Ca(2+) response of I KAS was attained and performed Hill fitting with the equation (y = 1/[1 + (EC50/x) (n) ]). Immunofluorescent staining, real-time PCR, Western blot were also carried out to furtherly investigate the underlying molecular mechanisms of the regulation. Captopril significantly decreased the mean density of I KAS when [Ca(2+)]i was 500, 900, 1000, and 10000 nM. The Hill fitting showed significantly different EC50 values and the Hill coefficients and showed captopril significantly shifted rightward the steady-state Ca(2+) response of I KAS. The results of real-time PCR and Western blot demonstrated captopril decreased the mRNA and protein expression of SK3 channels. Captopril significantly downregulated the sensitivity of SK channels to [Ca(2+)]i and the SK3 channels expression in HF, and reversed the SK channels remodeling. PMID:26924798

  2. SLOB, a SLOWPOKE channel binding protein, regulates insulin pathway signaling and metabolism in Drosophila.

    Directory of Open Access Journals (Sweden)

    Amanda L Sheldon

    Full Text Available There is ample evidence that ion channel modulation by accessory proteins within a macromolecular complex can regulate channel activity and thereby impact neuronal excitability. However, the downstream consequences of ion channel modulation remain largely undetermined. The Drosophila melanogaster large conductance calcium-activated potassium channel SLOWPOKE (SLO undergoes modulation via its binding partner SLO-binding protein (SLOB. Regulation of SLO by SLOB influences the voltage dependence of SLO activation and modulates synaptic transmission. SLO and SLOB are expressed especially prominently in median neurosecretory cells (mNSCs in the pars intercerebralis (PI region of the brain; these cells also express and secrete Drosophila insulin like peptides (dILPs. Previously, we found that flies lacking SLOB exhibit increased resistance to starvation, and we reasoned that SLOB may regulate aspects of insulin signaling and metabolism. Here we investigate the role of SLOB in metabolism and find that slob null flies exhibit changes in energy storage and insulin pathway signaling. In addition, slob null flies have decreased levels of dilp3 and increased levels of takeout, a gene known to be involved in feeding and metabolism. Targeted expression of SLOB to mNSCs rescues these alterations in gene expression, as well as the metabolic phenotypes. Analysis of fly lines mutant for both slob and slo indicate that the effect of SLOB on metabolism and gene expression is via SLO. We propose that modulation of SLO by SLOB regulates neurotransmission in mNSCs, influencing downstream insulin pathway signaling and metabolism.

  3. 78 FR 33219 - Special Local Regulations; Swim Across the Potomac, Potomac River; National Harbor Access Channel...

    Science.gov (United States)

    2013-06-04

    ... INFORMATION: Table of Acronyms DHS Department of Homeland Security FR Federal Register NPRM Notice of Proposed... Access Channel, MD'' in the Federal Register (78 FR 67). We received no comments on the proposed rule. No... SECURITY Coast Guard 33 CFR Part 100 RIN 1625-AA08 Special Local Regulations; Swim Across the...

  4. Regulation of the epithelial calcium channel TRPV5 by extracellular factors.

    NARCIS (Netherlands)

    Topala, C.N.; Bindels, R.J.M.; Hoenderop, J.G.J.

    2007-01-01

    PURPOSE OF REVIEW: Recent studies have greatly increased our knowledge concerning the regulation of renal calcium handling. This review focuses on newly identified calciotropic factors present in the pro-urine and the mechanisms by which they control the transient receptor potential channel vanilloi

  5. 78 FR 34881 - Special Local Regulations; Marine Events, Wrightsville Channel; Wrightsville Beach, NC

    Science.gov (United States)

    2013-06-11

    ... INFORMATION: Table of Acronyms DHS Department of Homeland Security FR Federal Register NPRM Notice of Proposed... Rulemaking for this event in the Federal Register (78 FR 19155). We received no comments on the proposed rule... Guard is establishing a Special Local Regulation for the ``Swim the Loop/Motts Channel Sprint''...

  6. PKC and AMPK regulation of Kv1.5 potassium channels

    DEFF Research Database (Denmark)

    Andersen, Martin Nybo; Skibsbye, Lasse; Tang, Chuyi;

    2015-01-01

    The voltage-gated Kv1.5 potassium channel, conducting the ultra-rapid rectifier K(+) current (IKur), is regulated through several pathways. Here we investigate if Kv1.5 surface expression is controlled by the 2 kinases PKC and AMPK, using Xenopus oocytes, MDCK cells and atrial derived HL-1 cells...

  7. Involvement of Ca2+-activated K+ Channels in Receptor-Regulated Sperm Motility in Rats

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Previous voltage-clamp studies have demonstrated the modulation of sperm Ca2+-activated K+ (KCa) channels expressed in Xenopus oocytes by angiotensin Ⅱ (Ang Ⅱ)and extracellular ATP via AT1 receptor and P2U receptor, respectively. In the presentstudy, we investigated the involvement of KCa channels in receptor-regulated spermmotility of the rat using a computer-aided sperm analysis system, HTM-IVOS, in con-junction with Ca2+-mobilizing agents, receptor agonists/antagonists and KCa channelsblockers.The percentage of motile sperm was increased by ionomycin (0. 5 μmol/L), whichcould be inhibited by K+ channel blockers, tetraethylammonium (TEA 1 μmol/L ) orcharybdotoxin (ChTX, 300 nmol/L) indicating the presence of KCa channels. AngⅡ, at low concentration, 10 nmol/L, was found to increase motility, however, athigher concentration, 1 μmol/L, percentage of motility was found to be suppressed.Both stimulatory and inhibitory effects of Ang Ⅱ could be reversed by losartan, aspecific antagonist of AT 1 receptors, but not AT 2 antagonist PD123177, indicating theinvolvement of AT1 but not AT2 receptor in mediating both effects. ChTX also abol-ished both stimulatory and inhibitory effects of Ang H, suggesting the involvement ofKCa channels. The percentage of motility was also enhanced by extracellular ATP, afactor known to be involved in sperm activation. The ATP-enhanced sperm motilitywas mimicked by UTP , and inhibited by ChTX and reactive blue, an antagonist of P2receptor, indicating the involvement of both P2U and KCa channels. RT-PCR studywas also conducted to confirm the expression of KCa channels, AT1 receptors and P2Ureceptor, but not AT2 receptor, in rat caudal epididymal sperm. The present findingssuggest an important role of KCa channels in the regulation of sperm motility by AT1and P 2U receptors.

  8. Redox and trace metal regulation of ion channels in the pain pathway.

    Science.gov (United States)

    Evans, J Grayson; Todorovic, Slobodan M

    2015-09-15

    Given the clinical significance of pain disorders and the relative ineffectiveness of current therapeutics, it is important to identify alternative means of modulating nociception. The most obvious pharmacological targets are the ion channels that facilitate nervous transmission from pain sensors in the periphery to the processing regions within the brain and spinal cord. In order to design effective pharmacological tools for this purpose, however, it is first necessary to understand how these channels are regulated. A growing area of research involves the investigation of the role that trace metals and endogenous redox agents play in modulating the activity of a diverse group of ion channels within the pain pathway. In the present review, the most recent literature concerning trace metal and redox regulation of T-type calcium channels, NMDA (N-methyl-D-aspartate) receptors, GABAA (γ-aminobutyric acid A) receptors and TRP (transient receptor potential) channels are described to gain a comprehensive understanding of the current state of the field as well as to provide a basis for future thought and experimentation.

  9. STIM1 and STIM2 proteins differently regulate endogenous store-operated channels in HEK293 cells.

    Science.gov (United States)

    Shalygin, Alexey; Skopin, Anton; Kalinina, Vera; Zimina, Olga; Glushankova, Lyuba; Mozhayeva, Galina N; Kaznacheyeva, Elena

    2015-02-20

    The endoplasmic reticulum calcium sensors stromal interaction molecules 1 and 2 (STIM1 and STIM2) are key modulators of store-operated calcium entry. Both these sensors play a major role in physiological functions in normal tissue and in pathology, but available data on native STIM2-regulated plasma membrane channels are scarce. Only a few studies have recorded STIM2-induced CRAC (calcium release-activated calcium) currents. On the other hand, many cell types display store-operated currents different from CRAC. The STIM1 protein regulates not only CRAC but also transient receptor potential canonical (TRPC) channels, but it has remained unclear whether STIM2 is capable of regulating store-operated non-CRAC channels. Here we present for the first time experimental evidence for the existence of endogenous non-CRAC STIM2-regulated channels. As shown in single-channel patch clamp experiments on HEK293 cells, selective activation of native STIM2 proteins or STIM2 overexpression results in store-operated activation of Imin channels, whereas STIM1 activation blocks this process. Changes in the ratio between active STIM2 and STIM1 proteins can switch the regulation of Imin channels between store-operated and store-independent modes. We have previously characterized electrophysiological properties of different Ca(2+) influx channels coexisting in HEK293 cells. The results of this study show that STIM1 and STIM2 differ in the ability to activate these store-operated channels; Imin channels are regulated by STIM2, TRPC3-containing INS channels are induced by STIM1, and TRPC1-composed Imax channels are activated by both STIM1 and STIM2. These new data about cross-talk between STIM1 and STIM2 and their different roles in store-operated channel activation are indicative of an additional level in the regulation of store-operated calcium entry pathways.

  10. KCNQ Modulators Reveal a Key Role for KCNQ Potassium Channels in Regulating the Tone of Rat Pulmonary Artery Smooth Muscle

    OpenAIRE

    Joshi, Shreena; Sedivy, Vojtech; Hodyc, Daniel; Herget, Jan; Gurney, Alison M

    2009-01-01

    Potassium channels are central to the regulation of pulmonary vascular tone. The smooth muscle cells of pulmonary artery display a background K+ conductance with biophysical properties resembling those of KCNQ (KV7) potassium channels. Therefore, we investigated the expression and functional role of KCNQ channels in pulmonary artery. The effects of selective KCNQ channel modulators were investigated on K+ current and membrane potential in isolated pulmonary artery smoo...

  11. Trafficking and intracellular regulation of Kv7.1 potassium channels in the heart

    DEFF Research Database (Denmark)

    Nielsen, Nathalie Hélix

    abnormalities induced by “loss of function” Kv7.1 mutations increase the risk of polymorphic ventricular arrhythmias. These cardiac arrhythmias, typically in the form of torsades de pointes, may underlie ventricular fibrillation, recurrent syncope, and sudden death. To date, nearly 300 Kv7.1 mutations have been...... to the regulation of the Kv7.1 channel, which displays a consensus site in the N-terminus for this kinase. Our study, with the support of others, tends to demonstrate that the Kv7.1 channel forms a macromolecular signaling complex with its interactions partners in order to allow a fast response to external signals....

  12. An experimental investigation of the dynamics of submarine leveed channel initiation as sediment-laden density currents experience sudden unconfinement

    Energy Technology Data Exchange (ETDEWEB)

    Rowland, Joel C [Los Alamos National Laboratory; Hilley, George E [STANFORD UNIV; Fildani, Andrea [CHEVRON ETC

    2009-01-01

    Leveed submarine channels play a critical role in the transfer of sediment from the upper continental slopes to interslope basins and ultimately deepwater settings. Despite a reasonable understanding of how these channels grow once established, how such channels initiate on previously unchannelized portions of the seafloor remains poorly understood. We conducted a series of experiments that elucidate the influence of excess density relative to flow velocity on the dynamics of, and depositional morphologies arising from, density currents undergoing sudden unconfinement across a sloped bed. Experimental currents transported only suspended sediment across a non-erodible substrate. Under flow conditions ranging from supercritical to subcritical (bulk Richardson numbers of 0.02 to 1.2) our experiments failed to produce deposits resembling or exhibiting the potential to evolve into self-formed leveed channels. In the absence of excess density, a submerged sediment-laden flow produced sharp crested lateral deposits bounding the margins of the flow for approximately a distance of two outlet widths down basin. These lateral deposits terminated in a centerline deposit that greatly exceeded marginal deposits in thickness. As excess density increased relative to the outlet velocity, the rate of lateral spreading of the flow increased relative to the downstream propagation of the density current, transitioning from a narrow flow aligned with the channel outlet to a broad radially expanding flow. Coincident with these changes in flow dynamics, the bounding lateral deposits extended for shorter distances, had lower, more poorly defined crests that were increasingly wider in separation than the initial outlet, and progressively became more oblong rather than linear. Based on our results, we conclude that leveed channels cannot initiate from sediment-laden density currents under strictly depositional conditions. Partial confinement of these currents appears to be necessary to

  13. Protein kinase CK2 is coassembled with small conductance Ca(2+)-activated K+ channels and regulates channel gating

    DEFF Research Database (Denmark)

    Bildl, Wolfgang; Strassmaier, Tim; Thurm, Henrike;

    2004-01-01

    Small conductance Ca(2+)-activated K+ channels (SK channels) couple the membrane potential to fluctuations in intracellular Ca2+ concentration in many types of cells. SK channels are gated by Ca2+ ions via calmodulin that is constitutively bound to the intracellular C terminus of the channels and...

  14. Cystic fibrosis transmembrane conductance regulator chloride channel blockers: Pharmacological, biophysical and physiological relevance

    Institute of Scientific and Technical Information of China (English)

    Paul; Linsdell

    2014-01-01

    Dysfunction of the cystic fibrosis transmembrane con-ductance regulator(CFTR) chloride channel causes cys-tic fibrosis, while inappropriate activity of this channeloccurs in secretory diarrhea and polycystic kidney dis-ease. Drugs that interact directly with CFTR are there-fore of interest in the treatment of a number of diseasestates. This review focuses on one class of small mol-ecules that interacts directly with CFTR, namely inhibi-tors that act by directly blocking chloride movementthrough the open channel pore. In theory such com-pounds could be of use in the treatment of diarrheaand polycystic kidney disease, however in practice allknown substances acting by this mechanism to inhibitCFTR function lack either the potency or specificity forin vivo use. Nevertheless, this theoretical pharmaco-logical usefulness set the scene for the developmentof more potent, specific CFTR inhibitors. Biophysically,open channel blockers have proven most useful as ex-perimental probes of the structure and function of theCFTR chloride channel pore. Most importantly, the useof these blockers has been fundamental in developing afunctional model of the pore that includes a wide innervestibule that uses positively charged amino acid sidechains to attract both permeant and blocking anionsfrom the cell cytoplasm. CFTR channels are also subjectto this kind of blocking action by endogenous anionspresent in the cell cytoplasm, and recently this blocking effect has been suggested to play a role in the physio-logical control of CFTR channel function, in particular as a novel mechanism linking CFTR function dynamically to the composition of epithelial cell secretions. It has also been suggested that future drugs could target this same pathway as a way of pharmacologically increasing CFTR activity in cystic fibrosis. Studying open channel blockers and their mechanisms of action has resulted in significant advances in our understanding of CFTR as a pharmacological target in disease states, of

  15. Purinergic regulation of CFTR and Ca2+ -activated Cl- channels and K+ channels in human pancreatic duct epithelium

    DEFF Research Database (Denmark)

    Wang, Jing; Haanes, Kristian A; Novak, Ivana

    2013-01-01

    dependent on intracellular Ca(2+). Apically applied ATP/UTP stimulated CF transmembrane conductance regulator (CFTR) and Ca(2+)-activated Cl(-) (CaCC) channels, which were inhibited by CFTRinh-172 and niflumic acid, respectively. The basolaterally applied ATP stimulated CFTR. In CFPAC-1 cells, which have...... mutated CFTR, basolateral ATP and UTP had negligible effects. In addition to Cl(-) transport in Capan-1 cells, the effects of 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one (DC-EBIO) and clotrimazole indicated functional expression of the intermediate conductance K(+) channels (IK, KCa3.1). The...... receptors both Cl(-) channels (TMEM16A/ANO1 and CFTR) and K(+) channels (IK). The K(+) channels provide the driving force for Cl(-)-channel-dependent secretion, and luminal ATP provided locally or secreted from acini may potentiate secretory processes. Future strategies in augmenting pancreatic duct...

  16. Identification of positive regulators of the yeast fps1 glycerol channel.

    Directory of Open Access Journals (Sweden)

    Sara E Beese

    2009-11-01

    Full Text Available The yeast Fps1 protein is an aquaglyceroporin that functions as the major facilitator of glycerol transport in response to changes in extracellular osmolarity. Although the High Osmolarity Glycerol pathway is thought to have a function in at least basal control of Fps1 activity, its mode of regulation is not understood. We describe the identification of a pair of positive regulators of the Fps1 glycerol channel, Rgc1 (Ypr115w and Rgc2 (Ask10. An rgc1/2Delta mutant experiences cell wall stress that results from osmotic pressure associated with hyper-accumulation of glycerol. Accumulation of glycerol in the rgc1/2Delta mutant results from a defect in Fps1 activity as evidenced by suppression of the defect through Fps1 overexpression, failure to release glycerol upon hypo-osmotic shock, and resistance to arsenite, a toxic metalloid that enters the cell through Fps1. Regulation of Fps1 by Rgc1/2 appears to be indirect; however, evidence is presented supporting the view that Rgc1/2 regulate Fps1 channel activity, rather than its expression, folding, or localization. Rgc2 was phosphorylated in response to stresses that lead to regulation of Fps1. This stress-induced phosphorylation was partially dependent on the Hog1 MAPK. Hog1 was also required for basal phosphorylation of Rgc2, suggesting a mechanism by which Hog1 may regulate Fps1 indirectly.

  17. Isovector channel of relativistic and non-relativistic energy density functionals and its sensitive influence on the density dependence of symmetry energy

    CERN Document Server

    Wang, X B; Xu, F R

    2010-01-01

    The non-relativistic approximations of relativistic energy density functionals (such as the Relativistic Mean-Field and the Quark-Meson-Coupling models) have been deduced. The formulae are compared with the non-relativistic Skyrme-Hartree-Fock model. These models give quite different descriptions of nuclear matter as well as finite nuclei in the extreme cases of high isospin and high density. In the non-relativistic approximations, it is found that the difference is traced back to the isovector channel of the models and leads to significant effect on the density-dependent behavior of the nuclear symmetry energy. A new Skyrme effective interaction is obtained from the Quark-Meson-Coupling model.

  18. Life-history evolution in guppies VIII: the demographics of density regulation in guppies (Poecilia reticulata).

    Science.gov (United States)

    Reznick, David N; Bassar, Ronald D; Travis, Joseph; Helen Rodd, F

    2012-09-01

    In prior research, we found the way guppy life histories evolve in response to living in environments with a high or low risk of predation is consistent with life-history theory that assumes no density dependence. We later found that guppies from high-predation environments experience higher mortality rates than those from low-predation environments, but the increased risk was evenly distributed across all age/size classes. Life-history theory that assumes density-independent population growth predicts that life histories will not evolve under such circumstances, yet we have shown with field introduction experiments that they do evolve. However, theory that incorporates density regulation predicts this pattern of mortality can result in the patterns of life-history evolution we had observed. Here we report on density manipulation experiments performed in populations of guppies from low-predation environments to ask whether natural populations normally experience density regulation and, if so, to characterize the short-term demographic changes that underlie density regulation. Our experiments reveal that these populations are density regulated. Decreased density resulted in higher juvenile growth, decreased juvenile mortality rates, and increased reproductive investment by adult females. Increased density causes reduced offspring size, decreased fat storage by adult females, and increased adult mortality.

  19. Proteolytic fragmentation of inositol 1,4,5-trisphosphate receptors: a novel mechanism regulating channel activity?

    Science.gov (United States)

    Wang, Liwei; Alzayady, Kamil J; Yule, David I

    2016-06-01

    Inositol 1,4,5-trisphosphate receptors (IP3 Rs) are a family of ubiquitously expressed intracellular Ca(2+) release channels. Regulation of channel activity by Ca(2+) , nucleotides, phosphorylation, protein binding partners and other cellular factors is thought to play a major role in defining the specific spatiotemporal characteristics of intracellular Ca(2+) signals. These properties are, in turn, believed pivotal for the selective and specific physiological activation of Ca(2+) -dependent effectors. IP3 Rs are also substrates for the intracellular cysteine proteases, calpain and caspase. Cleavage of the IP3 R has been proposed to play a role in apoptotic cell death by uncoupling regions important for IP3 binding from the channel domain, leaving an unregulated leaky Ca(2+) pore. Contrary to this hypothesis, we demonstrate following proteolysis that N- and C-termini of IP3 R1 remain associated, presumably through non-covalent interactions. Further, we show that complementary fragments of IP3 R1 assemble into tetrameric structures and retain their ability to be regulated robustly by IP3 . While peptide continuity is clearly not necessary for IP3 -gating of the channel, we propose that cleavage of the IP3 R peptide chain may alter other important regulatory events to modulate channel activity. In this scenario, stimulation of the cleaved IP3 R may support distinct spatiotemporal Ca(2+) signals and activation of specific effectors. Notably, in many adaptive physiological events, the non-apoptotic activities of caspase and calpain are demonstrated to be important, but the substrates of the proteases are poorly defined. We speculate that proteolytic fragmentation may represent a novel form of IP3 R regulation, which plays a role in varied adaptive physiological processes.

  20. The G. L. Brown Prize Lecture. Hypoxic regulation of ion channel function and expression.

    Science.gov (United States)

    Peers, Chris

    2002-07-01

    Acute hypoxia regulates the activity of specific ion channels in a rapid and reversible manner. Such effects underlie appropriate cellular responses to hypoxia which are designed to initiate cardiorespiratory reflexes and contribute importantly to other tissue responses, all of which are designed to improve tissue O2 supply. These responses include excitation of chemoreceptors as well as pulmonary vasoconstriction and systemic vasodilatation. However, such responses may also contribute to the adverse responses to hypoxia, such as excitotoxicity in the central nervous system. Whilst numerous ion channel types are known to be modulated by acute hypoxia, the nature of the O2 sensor in most tissues remains to be identified. Prolonged (chronic) hypoxia regulates functional expression of ion channels, and so remodels excitability of various cell types. Whilst this may contribute to adaptive responses such as high-altitude acclimatization, such altered channel expression may also contribute to the onset of pathological disorders, including Alzheimer's disease. Indeed, evidence is emerging that production of pathological peptides associated with Alzheimer's disease is increased during prolonged hypoxia. Such effects may account for the known increased incidence of this disease in patients who have previously endured hypoxic episodes, such as congestive heart failure and stroke. Identification of the mechanisms coupling hypoxia to the increased production of these peptides is likely to be of therapeutic benefit. PMID:12392105

  1. The G. L. Brown Prize Lecture. Hypoxic regulation of ion channel function and expression.

    Science.gov (United States)

    Peers, Chris

    2002-07-01

    Acute hypoxia regulates the activity of specific ion channels in a rapid and reversible manner. Such effects underlie appropriate cellular responses to hypoxia which are designed to initiate cardiorespiratory reflexes and contribute importantly to other tissue responses, all of which are designed to improve tissue O2 supply. These responses include excitation of chemoreceptors as well as pulmonary vasoconstriction and systemic vasodilatation. However, such responses may also contribute to the adverse responses to hypoxia, such as excitotoxicity in the central nervous system. Whilst numerous ion channel types are known to be modulated by acute hypoxia, the nature of the O2 sensor in most tissues remains to be identified. Prolonged (chronic) hypoxia regulates functional expression of ion channels, and so remodels excitability of various cell types. Whilst this may contribute to adaptive responses such as high-altitude acclimatization, such altered channel expression may also contribute to the onset of pathological disorders, including Alzheimer's disease. Indeed, evidence is emerging that production of pathological peptides associated with Alzheimer's disease is increased during prolonged hypoxia. Such effects may account for the known increased incidence of this disease in patients who have previously endured hypoxic episodes, such as congestive heart failure and stroke. Identification of the mechanisms coupling hypoxia to the increased production of these peptides is likely to be of therapeutic benefit.

  2. Atypical calcium regulation of the PKD2-L1 polycystin ion channel.

    Science.gov (United States)

    DeCaen, Paul G; Liu, Xiaowen; Abiria, Sunday; Clapham, David E

    2016-01-01

    Native PKD2-L1 channel subunits are present in primary cilia and other restricted cellular spaces. Here we investigate the mechanism for the channel's unusual regulation by external calcium, and rationalize this behavior to its specialized function. We report that the human PKD2-L1 selectivity filter is partially selective to calcium ions (Ca(2+)) moving into the cell, but blocked by high internal Ca(2+)concentrations, a unique feature of this transient receptor potential (TRP) channel family member. Surprisingly, we find that the C-terminal EF-hands and coiled-coil domains do not contribute to PKD2-L1 Ca(2+)-induced potentiation and inactivation. We propose a model in which prolonged channel activity results in calcium accumulation, triggering outward-moving Ca(2+) ions to block PKD2-L1 in a high-affinity interaction with the innermost acidic residue (D523) of the selectivity filter and subsequent long-term channel inactivation. This response rectifies Ca(2+) flow, enabling Ca(2+) to enter but not leave small compartments such as the cilium. PMID:27348301

  3. Emerging role of cystic fibrosis transmembrane conductance regulator - an epithelial chloride channel in gastrointestinal cancers

    OpenAIRE

    Hou, Yuning; Guan, Xiaoqing; Yang, Zhe; Li, Chunying

    2016-01-01

    Cystic fibrosis transmembrane conductance regulator (CFTR), a glycoprotein with 1480 amino acids, has been well established as a chloride channel mainly expressed in the epithelial cells of various tissues and organs such as lungs, sweat glands, gastrointestinal system, and reproductive organs. Although defective CFTR leads to cystic fibrosis, a common genetic disorder in the Caucasian population, there is accumulating evidence that suggests a novel role of CFTR in various cancers, especially...

  4. PIP2 regulation of KCNQ channels: biophysical and molecular mechanisms for lipid modulation of voltage-dependent gating

    Directory of Open Access Journals (Sweden)

    Mark Alan Zaydman

    2014-05-01

    Full Text Available Voltage-gated potassium (Kv channels contain voltage-sensing (VSD and pore-gate (PGD structural domains. During voltage-dependent gating, conformational changes in the two domains are coupled giving rise to voltage-dependent opening of the channel. In addition to membrane voltage, KCNQ (Kv7 channel opening requires the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2. Recent studies suggest that PIP2 serves as a cofactor to mediate VSD-PGD coupling in KCNQ1 channels. In this review, we put these findings in the context of the current understanding of voltage-dependent gating, lipid modulation of Kv channel activation, and PIP2-regulation of KCNQ channels. We suggest that lipid-mediated coupling of functional domains is a common mechanism among KCNQ channels that may be applicable to other Kv channels and membrane proteins.

  5. Simulation-based validation for four- dimensional multi-channel ultrasound current source density imaging.

    Science.gov (United States)

    Wang, Zhaohui; Witte, Russell S

    2014-03-01

    Ultrasound current source density imaging (UCSDI), which has application to the heart and brain, exploits the acoustoelectric (AE) effect and Ohm's law to detect and map an electrical current distribution. In this study, we describe 4-D UCSDI simulations of a dipole field for comparison and validation with bench-top experiments. The simulations consider the properties of the ultrasound pulse as it passes through a conductive medium, the electric field of the injected dipole, and the lead field of the detectors. In the simulation, the lead fields of detectors and electric field of the dipole were calculated by the finite element (FE) method, and the convolution and correlation in the computation of the detected AE voltage signal were accelerated using 3-D fast Fourier transforms. In the bench-top experiment, an electric dipole was produced in a bath of 0.9% NaCl solution containing two electrodes, which injected an ac pulse (200 Hz, 3 cycles) ranging from 0 to 140 mA. Stimulating and recording electrodes were placed in a custom electrode chamber made on a rapid prototype printer. Each electrode could be positioned anywhere on an x-y grid (5 mm spacing) and individually adjusted in the depth direction for precise control of the geometry of the current sources and detecting electrodes. A 1-MHz ultrasound beam was pulsed and focused through a plastic film to modulate the current distribution inside the saline-filled tank. AE signals were simultaneously detected at a sampling frequency of 15 MHz on multiple recording electrodes. A single recording electrode is sufficient to form volume images of the current flow and electric potentials. The AE potential is sensitive to the distance from the dipole, but is less sensitive to the angle between the detector and the dipole. Multi-channel UCSDI potentially improves 4-D mapping of bioelectric sources in the body at high spatial resolution, which is especially important for diagnosing and guiding treatment of cardiac and

  6. The Role of Riparian Vegetation Density, Channel Orientation and Water Velocity in Determining River Water Temperature Dynamics

    Science.gov (United States)

    Garner, G.; Malcolm, I.; Sadler, J. P.; Hannah, D. M.

    2015-12-01

    There is substantial scientific and practical interest in the potential of riparian shading to mitigate climate change impacts on river temperature extremes. However, there is limited process-based evidence to determine the density and spatial extent of riparian tree planting required to obtain temperature targets under differing environmental conditions. A simulation experiment was used to understand the importance of riparian vegetation density, channel orientation and flow velocity for stream energy budgets and river temperature dynamics. Water temperature and meteorological observations were obtained in addition to hemispherical photographs along a ~1 km reach of the Girnock Burn, a tributary of the Aberdeenshire Dee, Scotland. Nine hemispherical images (representing different uniform canopy density scenarios) were used to parameterise a deterministic net radiation model and simulate radiative fluxes. For each vegetation scenario, the effects of eight channel orientations were investigated by changing the position of north at 45° intervals in each hemispheric image. Simulated radiative fluxes and observed turbulent fluxes drove a high-resolution water temperature model for the reach. Simulations were performed under low and high water velocity scenarios. Both velocity scenarios yielded decreases in mean (≥ 1.7 °C) and maximum (≥ 3.0 °C) temperature as canopy density increased. Slow-flowing water resided longer within the reach, which enhanced heat accumulation and dissipation and drove higher maximum and lower minimum temperatures. Intermediate levels of shade produced highly variable energy flux and water temperature dynamics depending on the channel orientation and thus the time of day when the channel was shaded. We demonstrate that in many reaches relatively sparse but strategically located vegetation could produce substantial reductions in maximum temperature and suggest that these criteria are used to inform future river management.

  7. Large-scale, high-density (up to 512 channels) recording of local circuits in behaving animals

    OpenAIRE

    Berényi, Antal; Somogyvári, Zoltán; Nagy, Anett J.; Roux, Lisa; Long, John D.; Fujisawa, Shigeyoshi; Stark, Eran; Leonardo, Anthony; Harris, Timothy D.; Buzsáki, György

    2013-01-01

    Monitoring representative fractions of neurons from multiple brain circuits in behaving animals is necessary for understanding neuronal computation. Here, we describe a system that allows high-channel-count recordings from a small volume of neuronal tissue using a lightweight signal multiplexing headstage that permits free behavior of small rodents. The system integrates multishank, high-density recording silicon probes, ultraflexible interconnects, and a miniaturized microdrive. These improv...

  8. Explaining density-dependent regulation in earthworm populations using life-history analysis

    NARCIS (Netherlands)

    Kammenga, J.E.; Spurgeon, D.J.; Svendsen, C.; Weeks, J.M.

    2003-01-01

    At present there is little knowledge about how density regulates population growth rate and to what extent this is determined by life-history patterns. We compared density dependent population consequences in the Nicholsonian sense based oil experimental observations and life-history modeling for th

  9. Effects of ethanol on voltage-sensitive Na-channels in cultured skeletal muscle: Up-regulation as a result of chronic treatment

    International Nuclear Information System (INIS)

    The effects of acute and chronic treatment with ethanol were studied on the number and activity of tetrodotoxin-sensitive Na-channels in cultured rat skeletal muscle. The number of channels was determined by measurements of specific binding of [3H] saxitoxin (STX) in whole cell preparations. Measurements were also made of the frequency and rate of rise of spontaneously occurring action potentials, which are the physiologic expression of Na-channel density. Acute ethanol (37.5-150 mM), while causing depolarization of membrane potential and blockade of electrical activity, was without effect on specific STX binding. Neither methanol, acetaldehyde nor ethylene glycol had significant effects on these properties when given acutely in the same concentrations as ethanol. Chronic ethanol caused dose-related increases in STX binding and action potential properties with maximal levels being attained after 3 days of treatment at a concentration of 150 mM. On removal of ethanol from the culture medium all properties returned to control levels after 48 hr. Both increased external K+ and tetrodotoxin, which up-regulate Na-channels by reducing cytosolic Ca++, potentiated the ethanol-induced increase in Na-channel density. The increase in STX binding was not associated with changes in affinity of the binding sites for the ligand but was completely prevented by treatment with cycloheximide and actinomycin D. The results demonstrate that ethanol interacts with the cell membrane to induce synthesis of STX-binding sites

  10. Actin Dynamics Regulates Voltage-Dependent Calcium-Permeable Channels of the Vicia faba Guard Cell Plasma Membrane

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Liu-Min Fan

    2009-01-01

    Free cytosolic Ca~(2+) ([Ca~(2+)]_(cyt)) is an ubiquitous second messenger in plant cell signaling, and [Ca~(2+)]_(cyt) elevation is associated with Ca~(2+)-permeable channels in the plasma membrane and endomembranes regulated by a wide range of stimuli. However, knowledge regarding Ca~(2+) channels and their regulation remains limited in planta. A type of voltage-dependent Ca~(2+)-permeable channel was identified and characterized for the Vicia faba L. guard cell plasma membrane by using patch-clamp techniques. These channels are permeable to both Ba~(2+) and Ca~(2+), and their activities can be inhibited by micromolar Gd~(3+). The unitary conductance and the reversal potential of the channels depend on the Ca~(2+) or Ba~(2+) gradients across the plasma membrane. The inward whole-cell Ca~(2+) (Ba~(2+)) current, as well as the unitary current amplitude and NP. of the single Ca~(2+) channel, increase along with the membrane hyperpolarization. Pharmacological experiments suggest that actin dynamics may serve as an upstream regulator of this type of calcium channel of the guard cell plasma membrane. Cytochalasin D, an actin polymerization blocker, activated the NP_o of these channels at the single channel level and increased the current amplitude at the whole-cell level. But these channel activations and current increments could be restrained by pretreatment with an F-actin stabilizer, phalloidin. The potential physiological significance of this regulatory mechanism is also discussed.

  11. Calcium-regulated anion channels in the plasma membrane of Lilium longiflorum pollen protoplasts.

    Science.gov (United States)

    Tavares, Bárbara; Dias, Pedro Nuno; Domingos, Patrícia; Moura, Teresa Fonseca; Feijó, José Alberto; Bicho, Ana

    2011-10-01

    • Currents through anion channels in the plasma membrane of Lilium longiflorum pollen grain protoplasts were studied under conditions of symmetrical anionic concentrations by means of patch-clamp whole-cell configuration. • With Cl(-) -based intra- and extracellular solutions, three outward-rectifying anion conductances, I(Cl1) , I(Cl2) and I(Cl3) , were identified. These three activities were discriminated by differential rundown behaviour and sensitivity to 5-nitro-2-(phenylpropylamino)-benzoate (NPPB), which could not be attributed to one or more channel types. All shared strong outward rectification, activated instantaneously and displayed a slow time-dependent activation for positive potentials. All showed modulation by intracellular calcium ([Ca(2+) ](in) ), increasing intensity from 6.04 nM up to 0.5 mM (I(Cl1) ), or reaching a maximum value with 8.50 μM (I(Cl2) and I(Cl3) ). • After rundown, the anionic currents measured using NO(3) (-) -based solutions were indistinguishable, indicating that the permeabilities of the channels for Cl(-) and NO(3) (-) are similar. Additionally, unitary anionic currents were measured from outside-out excised patches, confirming the presence of individual anionic channels. • This study shows for the first time the presence of a large anionic conductance across the membrane of pollen protoplasts, resulting from the presence of Ca(2+) -regulated channels. A similar conductance was also found in germinated pollen. We hypothesize that these putative channels may be responsible for the large anionic fluxes previously detected by means of self-referencing vibrating probes. PMID:21668885

  12. Post-translational regulation of P2X receptor channels: modulation by phospholipids

    Directory of Open Access Journals (Sweden)

    Louis-Philippe eBernier

    2013-11-01

    Full Text Available P2X receptor channels mediate fast excitatory signaling by ATP and play major roles in sensory transduction, neuro-immune communication and inflammatory response. P2X receptors constitute a gene family of calcium-permeable ATP-gated cation channels therefore the regulation of P2X signaling is critical for both membrane potential and intracellular calcium homeostasis. Phosphoinositides (PIPn are anionic signaling phospholipids that act as functional regulators of many types of ion channels. Direct PIPn binding was demonstrated for several ligand- or voltage-gated ion channels, however no generic motif emerged to accurately predict lipid-protein binding sites. This review presents what is currently known about the modulation of the different P2X subtypes by phospholipids and about critical determinants underlying their sensitivity to PIPn levels in the plasma membrane.All functional mammalian P2X subtypes tested, with the notable exception of P2X5, have been shown to be positively modulated by PIPn, i.e. homomeric P2X1, P2X2, P2X3, P2X4, and P2X7, as well as heteromeric P2X1/5 and P2X2/3 receptors. Based on various results reported on the aforementioned subtypes including mutagenesis of the prototypical PIPn-sensitive P2X4 and PIPn-insensitive P2X5 receptor subtypes, an increasing amount of functional, biochemical and structural evidence converges on the modulatory role of a short polybasic domain located in the proximal C-terminus of P2X subunits. This linear motif, semi-conserved in the P2X family, seems necessary and sufficient for encoding direct modulation of ATP-gated channels by PIPn. Furthermore, the physiological impact of the regulation of ionotropic purinergic responses by phospholipids on pain pathways was recently revealed in the context of native crosstalks between phospholipase C-linked metabotropic receptors and P2X receptor channels in DRG sensory neurons and microglia.

  13. The Eag domain regulates the voltage-dependent inactivation of rat Eag1 K+ channels.

    Directory of Open Access Journals (Sweden)

    Ting-Feng Lin

    Full Text Available Eag (Kv10 and Erg (Kv11 belong to two distinct subfamilies of the ether-à-go-go K+ channel family (KCNH. While Erg channels are characterized by an inward-rectifying current-voltage relationship that results from a C-type inactivation, mammalian Eag channels display little or no voltage-dependent inactivation. Although the amino (N-terminal region such as the eag domain is not required for the C-type inactivation of Erg channels, an N-terminal deletion in mouse Eag1 has been shown to produce a voltage-dependent inactivation. To further discern the role of the eag domain in the inactivation of Eag1 channels, we generated N-terminal chimeras between rat Eag (rEag1 and human Erg (hERG1 channels that involved swapping the eag domain alone or the complete cytoplasmic N-terminal region. Functional analyses indicated that introduction of the homologous hERG1 eag domain led to both a fast phase and a slow phase of channel inactivation in the rEag1 chimeras. By contrast, the inactivation features were retained in the reverse hERG1 chimeras. Furthermore, an eag domain-lacking rEag1 deletion mutant also showed the fast phase of inactivation that was notably attenuated upon co-expression with the rEag1 eag domain fragment, but not with the hERG1 eag domain fragment. Additionally, we have identified a point mutation in the S4-S5 linker region of rEag1 that resulted in a similar inactivation phenotype. Biophysical analyses of these mutant constructs suggested that the inactivation gating of rEag1 was distinctly different from that of hERG1. Overall, our findings are consistent with the notion that the eag domain plays a critical role in regulating the inactivation gating of rEag1. We propose that the eag domain may destabilize or mask an inherent voltage-dependent inactivation of rEag1 K+ channels.

  14. Linear Modeling and Regulation Quality Analysis for Hydro-Turbine Governing System with an Open Tailrace Channel

    Directory of Open Access Journals (Sweden)

    Jiandong Yang

    2015-10-01

    Full Text Available On the basis of the state–space method (SSM, a novel linear mathematical model of the unsteady flow for the tailrace system with an open channel is proposed. This novel model is an elastic linearized model of water hammer. The validity of the model has been verified by several examples of numerical simulation, which are based on a finite difference technique. Then, the complete mathematical model for the hydro-turbine governing system of hydropower station with an open tailrace channel, which is used for simulating the transient process of the hydro-turbine governing system under load disturbance, is established by combining the models of hydro-turbine, generator, governor and open tailrace channel. Finally, according to the complete model, the regulation quality for hydro-turbine governing system with an open tailrace channel under load disturbance is studied, and the effects of open tailrace channel and tailrace surge tank on regulation quality are analyzed. The results indicate that: The open tailrace channel has a strong influence on the regulation quality by observing the water level fluctuations in tailrace surge tank. The surge shows a piecewise periodical change along with the variation in the length of an open channel. The open tailrace channel can be used to improve the regulation quality of hydro-turbine governing system.

  15. Intrinsic limits of channel transport hysteresis in graphene-SiO2 interface and its dependence on graphene defect density

    Science.gov (United States)

    Krishna Bharadwaj, B.; Chandrasekar, Hareesh; Nath, Digbijoy; Pratap, Rudra; Raghavan, Srinivasan

    2016-07-01

    Hysteresis in channel conductance is commonly observed on graphene field effect transistors. Although consistent and repeatable hysteresis could possibly be attractive for memory based applications, it is detrimental to the deployment of graphene in high speed electronic switches. While the origin of such hysteresis has been variously attributed to graphene-insulator interface traps, adsorbed molecules and bulk charges in the dielectric, its dependence on the quality of the graphene has been largely unexplored. Since, CVD is the most promising synthesis route for large area graphene and defects in such a growth process are inevitable, it is important to understand the influence of the quality of graphene on hysteresis. Here we demonstrate, for the first time, the effect of graphene growth defect density on device hysteresis. By intentionally tailoring the defect densities in the growth phase, we demonstrate a linear correlation between the film defect density and conductance hysteresis. The trap charge density calculated from the observed hysteresis in the electrical transfer characteristics was found to both follow the same qualitative trend, and give reasonable quantitative agreement with the defect density as extracted from Raman spectroscopy. Most importantly, by extrapolation from the observed behavior, we identify the intrinsic limits of hysteresis in graphene-SiO2 system, demonstrating that the defects in graphene contribute to traps over and above the baseline set by the SiO2 surface trap charge density.

  16. Coupled-channels calculations of nonelastic cross sections using a density-functional structure model

    CERN Document Server

    Nobre, G P A; Escher, J E; Thompson, I J; Dupuis, M; Terasaki, J; Engel, J

    2010-01-01

    A microscopic calculation of the reaction cross-section for nucleon-nucleus scattering has been performed by explicitly coupling the elastic channel to all particle-hole (p-h) excitation states in the target and to all one-nucleon pickup channels. The p-h states may be regarded as doorway states through which the flux flows to more complicated configurations, and subsequently to long-lived compound nucleus resonances. Target excitations for 40,48Ca, 58Ni, 90Zr and 144Sm were described in a QRPA framework using a Skyrme functional. Reaction cross sections calculated in this approach were compared to predictions of a fitted optical potential and to experimental data, reaching very good agreement. Couplings between inelastic states were found to be negligible, while the couplings to pickup channels contribute significantly. For the first time observed reaction cross-sections are completely accounted for by explicit channel coupling, for incident energies between 10 and 40 MeV.

  17. AMP kinase regulates ligand-gated K-ATP channels in substantia nigra dopamine neurons.

    Science.gov (United States)

    Shen, Ke-Zhong; Wu, Yan-Na; Munhall, Adam C; Johnson, Steven W

    2016-08-25

    AMP-activated protein kinase (AMPK) is a master enzyme that regulates ATP-sensitive K(+) (K-ATP) channels in pancreatic beta-cells and cardiac myocytes. We used patch pipettes to record currents and potentials to investigate effects of AMPK on K-ATP currents in substantia nigra compacta (SNC) dopamine neurons in slices of rat midbrain. When slices were superfused repeatedly with the K-ATP channel opener diazoxide, we were surprised to find that diazoxide currents gradually increased in magnitude, reaching 300% of the control value 60min after starting whole-cell recording. However, diazoxide current increased significantly more, to 472% of control, when recorded in the presence of the AMPK activator A769662. Moreover, superfusing the slice with the AMPK blocking agent dorsomorphin significantly reduced diazoxide current to 38% of control. Control experiments showed that outward currents evoked by the K-ATP channel opener NN-414 also increased over time, but not currents evoked by the GABAB agonist baclofen. Delaying the application of diazoxide after starting whole-cell recording correlated with augmentation of current. Loose-patch recording showed that diazoxide produced a 34% slowing of spontaneous firing rate that did not intensify with repeated applications of diazoxide. However, superfusion with A769662 significantly augmented the inhibitory effect of diazoxide on firing rate. We conclude that K-ATP channel function is augmented by AMPK, which is activated during the process of making whole-cell recordings. Our results suggest that AMPK and K-ATP interactions may play an important role in regulating dopamine neuronal excitability. PMID:27267246

  18. AMP kinase regulates ligand-gated K-ATP channels in substantia nigra dopamine neurons.

    Science.gov (United States)

    Shen, Ke-Zhong; Wu, Yan-Na; Munhall, Adam C; Johnson, Steven W

    2016-08-25

    AMP-activated protein kinase (AMPK) is a master enzyme that regulates ATP-sensitive K(+) (K-ATP) channels in pancreatic beta-cells and cardiac myocytes. We used patch pipettes to record currents and potentials to investigate effects of AMPK on K-ATP currents in substantia nigra compacta (SNC) dopamine neurons in slices of rat midbrain. When slices were superfused repeatedly with the K-ATP channel opener diazoxide, we were surprised to find that diazoxide currents gradually increased in magnitude, reaching 300% of the control value 60min after starting whole-cell recording. However, diazoxide current increased significantly more, to 472% of control, when recorded in the presence of the AMPK activator A769662. Moreover, superfusing the slice with the AMPK blocking agent dorsomorphin significantly reduced diazoxide current to 38% of control. Control experiments showed that outward currents evoked by the K-ATP channel opener NN-414 also increased over time, but not currents evoked by the GABAB agonist baclofen. Delaying the application of diazoxide after starting whole-cell recording correlated with augmentation of current. Loose-patch recording showed that diazoxide produced a 34% slowing of spontaneous firing rate that did not intensify with repeated applications of diazoxide. However, superfusion with A769662 significantly augmented the inhibitory effect of diazoxide on firing rate. We conclude that K-ATP channel function is augmented by AMPK, which is activated during the process of making whole-cell recordings. Our results suggest that AMPK and K-ATP interactions may play an important role in regulating dopamine neuronal excitability.

  19. BK channels regulate spontaneous action potential rhythmicity in the suprachiasmatic nucleus.

    Directory of Open Access Journals (Sweden)

    Jack Kent

    Full Text Available BACKGROUND: Circadian ( approximately 24 hr rhythms are generated by the central pacemaker localized to the suprachiasmatic nucleus (SCN of the hypothalamus. Although the basis for intrinsic rhythmicity is generally understood to rely on transcription factors encoded by "clock genes", less is known about the daily regulation of SCN neuronal activity patterns that communicate a circadian time signal to downstream behaviors and physiological systems. Action potentials in the SCN are necessary for the circadian timing of behavior, and individual SCN neurons modulate their spontaneous firing rate (SFR over the daily cycle, suggesting that the circadian patterning of neuronal activity is necessary for normal behavioral rhythm expression. The BK K(+ channel plays an important role in suppressing spontaneous firing at night in SCN neurons. Deletion of the Kcnma1 gene, encoding the BK channel, causes degradation of circadian behavioral and physiological rhythms. METHODOLOGY/PRINCIPAL FINDINGS: To test the hypothesis that loss of robust behavioral rhythmicity in Kcnma1(-/- mice is due to the disruption of SFR rhythms in the SCN, we used multi-electrode arrays to record extracellular action potentials from acute wild-type (WT and Kcnma1(-/- slices. Patterns of activity in the SCN were tracked simultaneously for up to 3 days, and the phase, period, and synchronization of SFR rhythms were examined. Loss of BK channels increased arrhythmicity but also altered the amplitude and period of rhythmic activity. Unexpectedly, Kcnma1(-/- SCNs showed increased variability in the timing of the daily SFR peak. CONCLUSIONS/SIGNIFICANCE: These results suggest that BK channels regulate multiple aspects of the circadian patterning of neuronal activity in the SCN. In addition, these data illustrate the characteristics of a disrupted SCN rhythm downstream of clock gene-mediated timekeeping and its relationship to behavioral rhythms.

  20. Molecular determinants for cardiovascular TRPC6 channel regulation by Ca2+/calmodulin-dependent kinase II

    DEFF Research Database (Denmark)

    Shi, Juan; Geshi, Naomi; Takahashi, Shinichi;

    2013-01-01

    The molecular mechanism underlying Ca2+/calmodulin (CaM)-dependent kinase II (CaMKII)-mediated regulation of the mouse transient receptor potential channel TRPC6 was explored by chimera, deletion and site-directed mutagenesis approaches. Induction of currents (ICCh) in TRPC6-expressing HEK293 cel...... essential for CaMKII-mediated regulation of TRPC6 channels. This mechanism may be of physiological significance in a native environment such as in vascular smooth muscle cells....

  1. The N-terminal domain allosterically regulates cleavage and activation of the epithelial sodium channel.

    Science.gov (United States)

    Kota, Pradeep; Buchner, Ginka; Chakraborty, Hirak; Dang, Yan L; He, Hong; Garcia, Guilherme J M; Kubelka, Jan; Gentzsch, Martina; Stutts, M Jackson; Dokholyan, Nikolay V

    2014-08-15

    The epithelial sodium channel (ENaC) is activated upon endoproteolytic cleavage of specific segments in the extracellular domains of the α- and γ-subunits. Cleavage is accomplished by intracellular proteases prior to membrane insertion and by surface-expressed or extracellular soluble proteases once ENaC resides at the cell surface. These cleavage events are partially regulated by intracellular signaling through an unknown allosteric mechanism. Here, using a combination of computational and experimental techniques, we show that the intracellular N terminus of γ-ENaC undergoes secondary structural transitions upon interaction with phosphoinositides. From ab initio folding simulations of the N termini in the presence and absence of phosphatidylinositol 4,5-bisphosphate (PIP2), we found that PIP2 increases α-helical propensity in the N terminus of γ-ENaC. Electrophysiology and mutation experiments revealed that a highly conserved cluster of lysines in the γ-ENaC N terminus regulates accessibility of extracellular cleavage sites in γ-ENaC. We also show that conditions that decrease PIP2 or enhance ubiquitination sharply limit access of the γ-ENaC extracellular domain to proteases. Further, the efficiency of allosteric control of ENaC proteolysis is dependent on Tyr(370) in γ-ENaC. Our findings provide an allosteric mechanism for ENaC activation regulated by the N termini and sheds light on a potential general mechanism of channel and receptor activation.

  2. The N-terminal Domain Allosterically Regulates Cleavage and Activation of the Epithelial Sodium Channel*

    Science.gov (United States)

    Kota, Pradeep; Buchner, Ginka; Chakraborty, Hirak; Dang, Yan L.; He, Hong; Garcia, Guilherme J. M.; Kubelka, Jan; Gentzsch, Martina; Stutts, M. Jackson; Dokholyan, Nikolay V.

    2014-01-01

    The epithelial sodium channel (ENaC) is activated upon endoproteolytic cleavage of specific segments in the extracellular domains of the α- and γ-subunits. Cleavage is accomplished by intracellular proteases prior to membrane insertion and by surface-expressed or extracellular soluble proteases once ENaC resides at the cell surface. These cleavage events are partially regulated by intracellular signaling through an unknown allosteric mechanism. Here, using a combination of computational and experimental techniques, we show that the intracellular N terminus of γ-ENaC undergoes secondary structural transitions upon interaction with phosphoinositides. From ab initio folding simulations of the N termini in the presence and absence of phosphatidylinositol 4,5-bisphosphate (PIP2), we found that PIP2 increases α-helical propensity in the N terminus of γ-ENaC. Electrophysiology and mutation experiments revealed that a highly conserved cluster of lysines in the γ-ENaC N terminus regulates accessibility of extracellular cleavage sites in γ-ENaC. We also show that conditions that decrease PIP2 or enhance ubiquitination sharply limit access of the γ-ENaC extracellular domain to proteases. Further, the efficiency of allosteric control of ENaC proteolysis is dependent on Tyr370 in γ-ENaC. Our findings provide an allosteric mechanism for ENaC activation regulated by the N termini and sheds light on a potential general mechanism of channel and receptor activation. PMID:24973914

  3. SNX27 regulation of GIRK channels in VTA dopamine neurons attenuates in vivo cocaine response

    Science.gov (United States)

    Munoz, Michaelanne B.; Slesinger, Paul A.

    2014-01-01

    The subcellular pathways that regulate G protein-gated inwardly rectifying potassium (GIRK or Kir3) channels are important for controlling the excitability of neurons. Sorting nexin 27 (SNX27) is a PDZ-containing protein known to bind GIRK2c/3 channels but its function in vivo is poorly understood. Here, we investigated the role of SNX27 in regulating GIRK currents in dopamine (DA) neurons of the ventral tegmental area (VTA). Mice lacking SNX27 in DA neurons exhibited reduced GABABR-activated GIRK currents but had normal Ih currents and dopamine D2R-activated GIRK currents. Expression of GIRK2a, a SNX27-insensitive splice-variant, restored GABABR-activated GIRK currents in SNX27-deficient DA neurons. Remarkably, mice with significantly reduced GABABR-activated GIRK currents in only DA neurons were hypersensitive to cocaine, and could be restored to a normal locomotor response with GIRK2a expression. These results identify a novel pathway for regulating excitability of VTA DA neurons, highlighting SNX27 as a promising target for treating addiction. PMID:24811384

  4. Queuing Theory Based Co-Channel Interference Analysis Approach for High-Density Wireless Local Area Networks

    Science.gov (United States)

    Zhang, Jie; Han, Guangjie; Qian, Yujie

    2016-01-01

    Increased co-channel interference (CCI) in wireless local area networks (WLANs) is bringing serious resource constraints to today’s high-density wireless environments. CCI in IEEE 802.11-based networks is inevitable due to the nature of the carrier sensing mechanism however can be reduced by resource optimization approaches. That means the CCI analysis is basic, but also crucial for an efficient resource management. In this article, we present a novel CCI analysis approach based on the queuing theory, which considers the randomness of end users’ behavior and the irregularity and complexity of network traffic in high-density WLANs that adopts the M/M/c queuing model for CCI analysis. Most of the CCIs occur when multiple networks overlap and trigger channel contentions; therefore, we use the ratio of signal-overlapped areas to signal coverage as a probabilistic factor to the queuing model to analyze the CCI impacts in highly overlapped WLANs. With the queuing model, we perform simulations to see how the CCI influences the quality of service (QoS) in high-density WLANs. PMID:27563896

  5. Queuing Theory Based Co-Channel Interference Analysis Approach for High-Density Wireless Local Area Networks.

    Science.gov (United States)

    Zhang, Jie; Han, Guangjie; Qian, Yujie

    2016-08-23

    Increased co-channel interference (CCI) in wireless local area networks (WLANs) is bringing serious resource constraints to today's high-density wireless environments. CCI in IEEE 802.11-based networks is inevitable due to the nature of the carrier sensing mechanism however can be reduced by resource optimization approaches. That means the CCI analysis is basic, but also crucial for an efficient resource management. In this article, we present a novel CCI analysis approach based on the queuing theory, which considers the randomness of end users' behavior and the irregularity and complexity of network traffic in high-density WLANs that adopts the M/M/c queuing model for CCI analysis. Most of the CCIs occur when multiple networks overlap and trigger channel contentions; therefore, we use the ratio of signal-overlapped areas to signal coverage as a probabilistic factor to the queuing model to analyze the CCI impacts in highly overlapped WLANs. With the queuing model, we perform simulations to see how the CCI influences the quality of service (QoS) in high-density WLANs.

  6. Queuing Theory Based Co-Channel Interference Analysis Approach for High-Density Wireless Local Area Networks.

    Science.gov (United States)

    Zhang, Jie; Han, Guangjie; Qian, Yujie

    2016-01-01

    Increased co-channel interference (CCI) in wireless local area networks (WLANs) is bringing serious resource constraints to today's high-density wireless environments. CCI in IEEE 802.11-based networks is inevitable due to the nature of the carrier sensing mechanism however can be reduced by resource optimization approaches. That means the CCI analysis is basic, but also crucial for an efficient resource management. In this article, we present a novel CCI analysis approach based on the queuing theory, which considers the randomness of end users' behavior and the irregularity and complexity of network traffic in high-density WLANs that adopts the M/M/c queuing model for CCI analysis. Most of the CCIs occur when multiple networks overlap and trigger channel contentions; therefore, we use the ratio of signal-overlapped areas to signal coverage as a probabilistic factor to the queuing model to analyze the CCI impacts in highly overlapped WLANs. With the queuing model, we perform simulations to see how the CCI influences the quality of service (QoS) in high-density WLANs. PMID:27563896

  7. Interacting influence of diuretics and diet on BK channel-regulated K homeostasis

    OpenAIRE

    Wen, Donghai; Cornelius, Ryan J.; Sansom, Steven C.

    2013-01-01

    Large conductance, Ca-activated K channels are abundantly located in cells of vasculature, glomerulus and distal nephron, where they are involved in maintaining blood volume, blood pressure and K homeostasis. In mesangial cells and smooth muscle cells of vessels, the BK-α pore associates with BK-β1 subunits and regulates contraction in a Ca-mediated feedback manner. The BK-β1 also resides in connecting tubule cells of the nephron. BK-β1 knockout mice (β1KO) exhibit fluid retention, hypertensi...

  8. Muscarinic cholinergic regulation of L-type calcium channel in heart of embryonic mice at different developmental stages

    Institute of Scientific and Technical Information of China (English)

    Hua-minLIANG; MingTANG; Chang-jinLIU; Hong-yanLUO; Yuan-longSONG; Xin-wuHU; Jiao-yaXI; Lin-linGAO; BinNIE; Su-yunLI; Ling-lingLAI; JuergenHESCHELER

    2004-01-01

    AIM: To investigate the muscarinic regulation of L-type calcium current (ICa-L) during development. METHODS:The whole cell patch-clamp technique was used to record ICa-L in mice embryonic cardiomyocytes at different stages (the early developmental stage, EDS; the intermediate developmental stage, IDS; and the late developmental stage, LDS). Carbachol (CCh) was used to stimulate M-receptor in the embryonic cardiomyocytes of mice.RESULTS: The expression of lCa.L density did not change in different developmental stages (P>0.05). There was no difference in the sensitivity of ICa-L to CCh during development (P>0.05). This inhibitory action of CCh was mediated by inhibition of cyclic AMP since 8-bromo-cAMP completely reversed the muscarinic inhibitory action. IBMX, a non-selective inhibitor of phosphodiesterase (PDE), reversed the inhibitory action of M-receptor on ICa-L current by 71.2 %±9.2% (n=8) and 11.3%±2.5% (n=9) in EDS and LDS respectively. However forskolin, an agonist of adenylyl cyclase (AC), reversed the action of CCh by 14.5%±3.5% (n=5) and 82.7%± 10.4% (n=7) in EDS and LDS respectively. CONCLUSION: The inhibitory action of CCh on lca.L current was mediated in different pathways: in EDS, the inhibitory action of M-receptor on ICa-L channel mainly depended on the stimulation of PDE. However, in LDS, the regulation by M-receptor on lCa.L channel mainly depended on the inactivation of AC.

  9. External Zn(2+) binding to cysteine-substituted cystic fibrosis transmembrane conductance regulator constructs regulates channel gating and curcumin potentiation.

    Science.gov (United States)

    Wang, Guangyu; Linsley, Rheeann; Norimatsu, Yohei

    2016-07-01

    The cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel is activated by ATP binding-induced dimerization of nucleotide-binding domains, the interaction between the phosphorylated regulatory (R) domain and the curcumin-sensitive interface between intracellular loop (ICL) 1 and ICL4, and the resultant inward-to-'outward' reorientation of transmembrane domains. Although transmembrane helices (TM) 2 and TM11 link the ICL1-ICL4 interface with the interface between extracellular loop (ECL) 1 and ECL6, it is unknown whether both interfaces are gating-coupled during the reorientation. Herein, R334C and T1122C mutations were used to engineer two Zn(2+) bridges near and at the ECL1-ECL6 interface, respectively, and the gating effects of a Zn(2+) disturbance at the ECL1-ECL6 interface on the stimulatory ICL1/ICL4-R interaction were determined. The results showed that both Zn(2+) bridges inhibited channel activity in a dose- and Cl(-) -dependent manner, and the inhibition was reversed by a washout or suppressed by thiol-specific modification. Interestingly, their Cl(-) -dependent Zn(2+) inhibition was weakened at higher Zn(2+) concentrations, their Zn(2+) affinity was stronger in the resting state than in the activated state, and their activation current noises were decreased by external Zn(2+) binding. More importantly, the external Zn(2+) inhibition was reversed by internal curcumin in the R334C construct but not in the T1122C mutant. Therefore, although both Zn(2+) bridges may promote channel closure, external Zn(2+) may disturb the ECL1-ECL6 interface and thus prevent the stimulatory ICL1/ICL4-R interaction and curcumin potentiation via a gating coupling between these two interfaces. PMID:27175795

  10. Experimental investigation on a polymer electrolyte membrane fuel cell (PEMFC) parallel flow field design with external two-valve regulation on cathode channels

    Science.gov (United States)

    Tong, Shijie; Bachman, John C.; Santamaria, Anthony; Park, Jae Wan

    2013-11-01

    Parallel/interdigitated/serpentine flow field PEM fuel cells have similar performance under low overvoltage operation. At higher overvoltage, interdigitated/serpentine flow field performance may exceed parallel flow field designs due to better water removal and more uniform reactant distribution by convective reactant flow in the GDL under land area, i.e. cross flow. However, serpentine flow field design suffers from high pumping losses and the risk of local flooding at channel U-bends. Additionally, interdigitated flow field designs may have higher local flooding risk in the inlet channels and relatively large pumping requirement at low current densities. In this study, a novel parallel flow field design with external two-valve regulation on the cathode was presented. Two valves introduced continuous pressure differences to two separate manifolds in the cathode that induce cross flow across the land areas. Moreover, both valves remained partially open to maintain a good water removal from flow channels. Comparative test results showed the proposed design surpasses performance of both parallel and interdigitated flow field design at operation current density of 0.7 A cm-2 or higher. The performance enhancement is 10.9% at peak power density point (0.387 W cm-2 @ 0.99 A cm-2) compared to parallel flow field taking into account pumping losses.

  11. Effects of roughness on density-weighted particle statistics in turbulent channel flows

    Science.gov (United States)

    Milici, Barbara

    2015-12-01

    The distribution of inertial particles in turbulent flows is strongly influenced by the characteristics of the coherent turbulent structures which develop in the carrier flow field. In wall-bounded flows, these turbulent structures, which control the turbulent regeneration cycles, are strongly affected by the roughness of the wall, nevertheless its effects on the particle transport in two-phase turbulent flows has been still poorly investigated. The issue is discussed here by addressing DNS combined with LPT to obtain statistics of velocity and preferential accumulation of a dilute dispersion of heavy particles in a turbulent channel flow, bounded by irregular two-dimensional rough surfaces, in the one-way coupling regime.

  12. Effects of roughness on density-weighted particle statistics in turbulent channel flows

    Energy Technology Data Exchange (ETDEWEB)

    Milici, Barbara [Faculty of Engineering and Architecture, Cittadella Universitaria - 94100 - Enna (Italy)

    2015-12-31

    The distribution of inertial particles in turbulent flows is strongly influenced by the characteristics of the coherent turbulent structures which develop in the carrier flow field. In wall-bounded flows, these turbulent structures, which control the turbulent regeneration cycles, are strongly affected by the roughness of the wall, nevertheless its effects on the particle transport in two-phase turbulent flows has been still poorly investigated. The issue is discussed here by addressing DNS combined with LPT to obtain statistics of velocity and preferential accumulation of a dilute dispersion of heavy particles in a turbulent channel flow, bounded by irregular two-dimensional rough surfaces, in the one-way coupling regime.

  13. Role of volume-regulated and calcium-activated anion channels in cell volume homeostasis, cancer and drug resistance

    DEFF Research Database (Denmark)

    Hoffmann, Else Kay; Sørensen, Belinda Halling; Sauter, Daniel Rafael Peter;

    2015-01-01

    Volume-regulated channels for anions (VRAC) / organic osmolytes (VSOAC) play essential roles in cell volume regulation and other cellular functions, e.g. proliferation, cell migration and apoptosis. LRRC8A, which belongs to the leucine rich-repeat containing protein family, was recently shown to ...

  14. TRPV4 and AQP4 Channels Synergistically Regulate Cell Volume and Calcium Homeostasis in Retinal Müller Glia

    DEFF Research Database (Denmark)

    Jo, Andrew O; Ryskamp, Daniel A; Phuong, Tam T T;

    2015-01-01

    through TRPV4 channels reciprocally modulates volume regulation, swelling, and Aqp4 gene expression. Therefore, TRPV4-AQP4 interactions constitute a molecular system that fine-tunes astroglial volume regulation by integrating osmosensing, calcium signaling, and water transport and, when overactivated...

  15. Characterization of the first honeybee Ca²⁺ channel subunit reveals two novel species- and splicing-specific modes of regulation of channel inactivation.

    Science.gov (United States)

    Cens, Thierry; Rousset, Matthieu; Collet, Claude; Raymond, Valérie; Démares, Fabien; Quintavalle, Annabelle; Bellis, Michel; Le Conte, Yves; Chahine, Mohamed; Charnet, Pierre

    2013-07-01

    The honeybee is a model system to study learning and memory, and Ca(2+) signals play a key role in these processes. We have cloned, expressed, and characterized the first honeybee Ca(2+) channel subunit. We identified two splice variants of the Apis CaVβ Ca(2+) channel subunit (Am-CaVβ) and demonstrated expression in muscle and neurons. Although AmCaVβ shares with vertebrate CaVβ subunits the SH3 and GK domains, it beholds a unique N terminus that is alternatively spliced in the first exon to produce a long (a) and short (b) variant. When expressed with the CaV2 channels both, AmCaVβa and AmCaVβb, increase current amplitude, shift the voltage-sensitivity of the channel, and slow channel inactivation as the vertebrate CaVβ2a subunit does. However, as opposed to CaVβ2a, slow inactivation induced by Am-CaVβa was insensitive to palmitoylation but displayed a unique PI3K sensitivity. Inactivation produced by the b variant was PI3K-insensitive but staurosporine/H89-sensitive. Deletion of the first exon suppressed the sensitivity to PI3K inhibitors, staurosporine, or H89. Recording of Ba(2+) currents in Apis neurons or muscle cells evidenced a sensitivity to PI3K inhibitors and H89, suggesting that both AmCaVβ variants may be important to couple cell signaling to Ca(2+) entry in vivo. Functional interactions with phospho-inositide and identification of phosphorylation sites in AmCaVβa and AmCaVβb N termini, respectively, suggest that AmCaVβ splicing promoted two novel and alternative modes of regulation of channel activity with specific signaling pathways. This is the first description of a splicing-dependent kinase switch in the regulation of Ca(2+) channel activity by CaVβ subunit. PMID:23588376

  16. Regulation of substantia nigra pars reticulata GABAergic neuron activity by hydrogen peroxide via flufenamic acid-sensitive channels and KATP channels

    Directory of Open Access Journals (Sweden)

    Christian R Lee

    2011-04-01

    Full Text Available Substantia nigra pars reticulata (SNr GABAergic neurons are key output neurons of the basal ganglia. Given the role of these neurons in motor control, it is important to understand factors that regulate their firing rate and pattern. One potential regulator is hydrogen peroxide (H2O2, a reactive oxygen species that is increasingly recognized as a neuromodulator. We used whole-cell current clamp recordings of SNr GABAergic neurons in guinea-pig midbrain slices to determine how H2O2 affects the activity of these neurons and to explore the classes of ion channels underlying those effects. Elevation of H2O2 levels caused an increase in the spontaneous firing rate of SNr GABAergic neurons, whether by application of exogenous H2O2 or amplification of endogenous H2O2 through inhibition of glutathione peroxidase with mercaptosuccinate. This effect was reversed by flufenamic acid, implicating transient receptor potential (TRP channels. Conversely, depletion of endogenous H2O2 by catalase, a peroxidase enzyme, decreased spontaneous firing rate and firing precision of SNr neurons, demonstrating tonic control of firing rate by H2O2. Elevation of H2O2 in the presence of flufenamic acid revealed an inhibition of tonic firing that was prevented by blockade of ATP-sensitive K+ (KATP channels with glibenclamide. In contrast to guinea-pig SNr neurons, the dominant effect of H2O2 elevation in mouse SNr GABAergic neurons was hyperpolarization, indicating a species difference in H2O2-dependent regulation. Thus, H2O2 is an endogenous modulator of SNr GABAergic neurons, acting primarily through presumed TRP channels in guinea pig, with additional modulation via KATP channels to regulate SNr output.

  17. Magnetic topology and current channels in plasmas with toroidal current density inversions

    Science.gov (United States)

    Ciro, D.; Caldas, I. L.

    2013-10-01

    The equilibrium magnetic field inside axisymmetric plasmas with inversions on the toroidal current density is considered. Previous works have shown that internal regions with negative current density lead to non-nested magnetic surfaces inside the plasma. Following these results, we derive a general expression relating the positive and negative currents inside the non-nested surfaces. This is done in terms of an anisotropy parameter that is model-independent and is based in very general properties of the magnetic field. We demonstrate that the positive currents in axisymmetric islands screen the negative one in the plasma center by reaching about twice its magnitude. Further, we illustrate these results by developing a family of analytical local solutions for the poloidal magnetic field in a region of interest that contains the inverted current. These local solutions exhibit non-nested magnetic surfaces with a combined current of at least twice the magnitude of the negative one, as prescribed from the topological arguments, and allow to study topological transitions driven by geometrical changes in the current profile. To conclude, we discuss the signatures of internal current density inversions in a confinement device and show that magnetic pitch measurements may be inappropriate to differentiate current reversals and small current holes in plasmas.

  18. Cystic fibrosis transmembrane conductance regulator and the outwardly rectifying chloride channel: a relationship between two chloride channels expressed in epithelial cells.

    Science.gov (United States)

    Hryciw, D H; Guggino, W B

    2000-11-01

    1. Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) result in the primary defect observed in patients with cystic fibrosis. 2. The CFTR is a member of the ATPase-binding cassette (ABC) transporter family but, unlike other members of this group, CFTR conducts a chloride current that is activated by cAMP. 3. In epithelial cells, the cAMP-stimulated chloride current is conducted by both CFTR and the outwardly rectifying chloride channel (ORCC). 4. The present review summarizes the current knowledge of the properties of the two channels, as well as their relationship. Because the gene encoding the ORCC has not been identified, a discussion as to possible candidates for this chloride channel is included. PMID:11071305

  19. SPAK Sensitive Regulation of the Epithelial Na+ Channel ENaC

    Directory of Open Access Journals (Sweden)

    Musaab Ahmed

    2015-06-01

    Full Text Available Background/Aims: The WNK-dependent STE20/SPS1-related proline/alanine-rich kinase SPAK participates in the regulation of NaCl and Na+,K+,2Cl- cotransport and thus renal salt excretion. The present study explored whether SPAK has similarly the potential to regulate the epithelial Na+ channel (ENaC. Methods: ENaC was expressed in Xenopus oocytes with or without additional expression of wild type SPAK, constitutively active T233ESPAK, WNK insensitive T233ASPAK or catalytically inactive D212ASPAK, and ENaC activity estimated from amiloride (50 µM sensitive current (Iamil in dual electrode voltage clamp experiments. Moreover, Ussing chamber was employed to determine Iamil in colonic tissue from wild type mice (spakwt/wt and from gene targeted mice carrying WNK insensitive SPAK (spaktg/tg. Results: Iamil was observed in ENaC-expressing oocytes, but not in water-injected oocytes. In ENaC expressing oocytes Iamil was significantly increased following coexpression of wild-type SPAK and T233ESPAK, but not following coexpression of T233ASPAK or D212ASPAK. Colonic Iamil was significantly higher in spakwt/wt than in spaktg/tg mice. Conclusion: SPAK has the potential to up-regulate ENaC.

  20. The function and regulation of acid-sensing ion channels (ASICs) and the epithelial Na(+) channel (ENaC): IUPHAR Review 19.

    Science.gov (United States)

    Boscardin, Emilie; Alijevic, Omar; Hummler, Edith; Frateschi, Simona; Kellenberger, Stephan

    2016-09-01

    Acid-sensing ion channels (ASICs) and the epithelial Na(+) channel (ENaC) are both members of the ENaC/degenerin family of amiloride-sensitive Na(+) channels. ASICs act as proton sensors in the nervous system where they contribute, besides other roles, to fear behaviour, learning and pain sensation. ENaC mediates Na(+) reabsorption across epithelia of the distal kidney and colon and of the airways. ENaC is a clinically used drug target in the context of hypertension and cystic fibrosis, while ASIC is an interesting potential target. Following a brief introduction, here we will review selected aspects of ASIC and ENaC function. We discuss the origin and nature of pH changes in the brain and the involvement of ASICs in synaptic signalling. We expose how in the peripheral nervous system, ASICs cover together with other ion channels a wide pH range as proton sensors. We introduce the mechanisms of aldosterone-dependent ENaC regulation and the evidence for an aldosterone-independent control of ENaC activity, such as regulation by dietary K(+) . We then provide an overview of the regulation of ENaC by proteases, a topic of increasing interest over the past few years. In spite of the profound differences in the physiological and pathological roles of ASICs and ENaC, these channels share many basic functional and structural properties. It is likely that further research will identify physiological contexts in which ASICs and ENaC have similar or overlapping roles. PMID:27278329

  1. Interacting influence of diuretics and diet on BK channel-regulated K homeostasis.

    Science.gov (United States)

    Wen, Donghai; Cornelius, Ryan J; Sansom, Steven C

    2014-04-01

    Large conductance, Ca-activated K channels (BK) are abundantly located in cells of vasculature, glomerulus, and distal nephron, where they are involved in maintaining blood volume, blood pressure, and K homeostasis. In mesangial cells and smooth muscle cells of vessels, the BK-α pore associates with BK-β1 subunits and regulates contraction in a Ca-mediated feedback manner. The BK-β1 also resides in connecting tubule cells of the nephron. BK-β1 knockout mice (β1KO) exhibit fluid retention, hypertension, and compromised K handling. The BK-α/β4 resides in acid/base transporting intercalated cells (IC) of the distal nephron, where they mediate K secretion in mammals on a high K, alkaline diet. BK-α expression in IC is increased by a high K diet via aldosterone. The BK-β4 subunit and alkaline urine are necessary for the luminal expression and function of BK-α in mouse IC. In distal nephron cells, membrane BK-α expression is inhibited by WNK4 in in vitro expression systems, indicating a role in the hyperkalemic phenotype in patients with familial hyperkalemic hypertension type 2 (FHHt2). β1KO and BK-β4 knockout mice (β4KO) are hypertensive because of exaggerated epithelial Na channels (ENaC) mediated Na retention in an effort to secrete K via only renal outer medullary K channels (ROMK). BK hypertension is resistant to thiazides and furosemide, and would be more amenable to ENaC and aldosterone inhibiting drugs. Activators of BK-α/β1 or BK-α/β4 might be effective blood pressure lowering agents for a subset of hypertensive patients. Inhibitors of renal BK would effectively spare K in patients with Bartter Syndrome, a renal K wasting disease. PMID:24721651

  2. The cardiac L-type calcium channel distal carboxy terminus autoinhibition is regulated by calcium.

    Science.gov (United States)

    Crump, Shawn M; Andres, Douglas A; Sievert, Gail; Satin, Jonathan

    2013-02-01

    The L-type calcium channel (LTCC) provides trigger Ca(2+) for sarcoplasmic reticulum Ca-release, and LTCC function is influenced by interacting proteins including the LTCC distal COOH terminus (DCT) and calmodulin. DCT is proteolytically cleaved and reassociates with the LTCC complex to regulate calcium channel function. DCT reduces LTCC barium current (I(Ba,L)) in reconstituted channel complexes, yet the contribution of DCT to LTCC Ca(2+) current (I(Ca,L)) in cardiomyocyte systems is unexplored. This study tests the hypothesis that DCT attenuates cardiomyocyte I(Ca,L). We measured LTCC current and Ca(2+) transients with DCT coexpressed in murine cardiomyocytes. We also heterologously coexpressed DCT and Ca(V)1.2 constructs with truncations corresponding to the predicted proteolytic cleavage site, Ca(V)1.2Δ1801, and a shorter deletion corresponding to well-studied construct, Ca(V)1.2Δ1733. DCT inhibited I(Ba,L) in cardiomyocytes, and in human embryonic kidney (HEK) 293 cells expressing Ca(V)1.2Δ1801 and Ca(V)1.2Δ1733. Ca(2+)-CaM relieved DCT block in cardiomyocytes and HEK cells. The selective block of I(Ba,L) combined with Ca(2+)-CaM effects suggested that DCT-mediated blockade may be relieved under conditions of elevated Ca(2+). We therefore tested the hypothesis that DCT block is dynamic, increasing under relatively low Ca(2+), and show that DCT reduced diastolic Ca(2+) at low stimulation frequencies but spared high frequency Ca(2+) entry. DCT reduction of diastolic Ca(2+) and relief of block at high pacing frequencies and under conditions of supraphysiological bath Ca(2+) suggests that a physiological function of DCT is to increase the dynamic range of Ca(2+) transients in response to elevated pacing frequencies. Our data motivate the new hypothesis that DCT is a native reverse use-dependent inhibitor of LTCC current.

  3. Coupled-channels quantum theory of electronic flux density in electronically adiabatic processes: application to the hydrogen molecule ion.

    Science.gov (United States)

    Diestler, D J; Kenfack, A; Manz, J; Paulus, B

    2012-03-22

    This article presents the results of the first quantum simulations of the electronic flux density (j(e)) by the "coupled-channels" (CC) theory, the fundamentals of which are presented in the previous article [Diestler, D. J. J. Phys. Chem. A 2012, DOI: 10.1021/jp207843z]. The principal advantage of the CC scheme is that it employs exclusively standard methods of quantum chemistry and quantum dynamics within the framework of the Born-Oppenheimer approximation (BOA). The CC theory goes beyond the BOA in that it yields a nonzero j(e) for electronically adiabatic processes, in contradistinction to the BOA itself, which always gives j(e) = 0. The CC is applied to oriented H(2)(+) vibrating in the electronic ground state ((2)Σ(g)(+)), for which the nuclear and electronic flux densities evolve on a common time scale of about 22 fs per vibrational period. The system is chosen as a touchstone for the CC theory, because it is the only one for which highly accurate flux densities have been calculated numerically without invoking the BOA [Barth et al, Chem. Phys. Lett. 2009, 481, 118]. Good agreement between CC and accurate results supports the CC approach, another advantage of which is that it allows a transparent interpretation of the temporal and spatial properties of j(e).

  4. Noncanonical binding of calmodulin to aquaporin-0: implications for channel regulation.

    Science.gov (United States)

    Reichow, Steve L; Gonen, Tamir

    2008-09-10

    Aquaporins (AQPs) are a family of ubiquitous membrane channels that conduct water across cell membranes. AQPs form homotetramers containing four functional and independent water pores. Aquaporin-0 (AQP0) is expressed in the eye lens, where its water permeability is regulated by calmodulin (CaM). Here we use a combination of biochemical methods and NMR spectroscopy to probe the interaction between AQP0 and CaM. We show that CaM binds the AQP0 C-terminal domain in a calcium-dependent manner. We demonstrate that only two CaM molecules bind a single AQP0 tetramer in a noncanonical fashion, suggesting a form of cooperativity between AQP0 monomers. Based on these results, we derive a structural model of the AQP0/CaM complex, which suggests CaM may be inhibitory to channel permeability by capping the vestibules of two monomers within the AQP0 tetramer. Finally, phosphorylation within AQP0's CaM binding domain inhibits the AQP0/CaM interaction, suggesting a temporal regulatory mechanism for complex formation. PMID:18786401

  5. VAMP7 regulates constitutive membrane incorporation of the cold-activated channel TRPM8.

    Science.gov (United States)

    Ghosh, Debapriya; Pinto, Silvia; Danglot, Lydia; Vandewauw, Ine; Segal, Andrei; Van Ranst, Nele; Benoit, Melissa; Janssens, Annelies; Vennekens, Rudi; Vanden Berghe, Pieter; Galli, Thierry; Vriens, Joris; Voets, Thomas

    2016-01-01

    The cation channel TRPM8 plays a central role in the somatosensory system, as a key sensor of innocuously cold temperatures and cooling agents. Although increased functional expression of TRPM8 has been implicated in various forms of pathological cold hypersensitivity, little is known about the cellular and molecular mechanisms that determine TRPM8 abundance at the plasma membrane. Here we demonstrate constitutive transport of TRPM8 towards the plasma membrane in atypical, non-acidic transport vesicles that contain lysosomal-associated membrane protein 1 (LAMP1), and provide evidence that vesicle-associated membrane protein 7 (VAMP7) mediates fusion of these vesicles with the plasma membrane. In line herewith, VAMP7-deficient mice exhibit reduced functional expression of TRPM8 in sensory neurons and concomitant deficits in cold avoidance and icilin-induced cold hypersensitivity. Our results uncover a cellular pathway that controls functional plasma membrane incorporation of a temperature-sensitive TRP channel, and thus regulates thermosensitivity in vivo. PMID:26843440

  6. Regulation of Mitochondrial Function by Voltage Dependent Anion Channels in Ethanol Metabolism and the Warburg Effect

    Science.gov (United States)

    Lemasters, John J.; Holmuhamedov, Ekhson L.; Czerny, Christoph; Zhong, Zhi; Maldonado, Eduardo N.

    2012-01-01

    Voltage dependent anion channels (VDAC) are highly conserved proteins that are responsible for permeability of the mitochondrial outer membrane to hydrophilic metabolites like ATP, ADP and respiratory substrates. Although previously assumed to remain open, VDAC closure is emerging as an important mechanism for regulation of global mitochondrial metabolism in apoptotic cells and also in cells that are not dying. During hepatic ethanol oxidation to acetaldehyde, VDAC closure suppresses exchange of mitochondrial metabolites, resulting in inhibition of ureagenesis. In vivo, VDAC closure after ethanol occurs coordinately with mitochondrial uncoupling. Since acetaldehyde passes through membranes independently of channels and transporters, VDAC closure and uncoupling together foster selective and more rapid oxidative metabolism of toxic acetaldehyde to nontoxic acetate by mitochondrial aldehyde dehydrogenase. In single reconstituted VDAC, tubulin decreases VDAC conductance, and in HepG2 hepatoma cells, free tubulin negatively modulates mitochondrial membrane potential, an effect enhanced by protein kinase A. Tubulin-dependent closure of VDAC in cancer cells contributes to suppression of mitochondrial metabolism and may underlie the Warburg phenomenon of aerobic glycolysis. PMID:22172804

  7. Emerging role of cystic fibrosis transmembrane conductance regulator - an epithelial chloride channel in gastrointestinal cancers.

    Science.gov (United States)

    Hou, Yuning; Guan, Xiaoqing; Yang, Zhe; Li, Chunying

    2016-03-15

    Cystic fibrosis transmembrane conductance regulator (CFTR), a glycoprotein with 1480 amino acids, has been well established as a chloride channel mainly expressed in the epithelial cells of various tissues and organs such as lungs, sweat glands, gastrointestinal system, and reproductive organs. Although defective CFTR leads to cystic fibrosis, a common genetic disorder in the Caucasian population, there is accumulating evidence that suggests a novel role of CFTR in various cancers, especially in gastroenterological cancers, such as pancreatic cancer and colon cancer. In this review, we summarize the emerging findings that link CFTR with various cancers, with focus on the association between CFTR defects and gastrointestinal cancers as well as the underlying mechanisms. Further study of CFTR in cancer biology may help pave a new way for the diagnosis and treatment of gastrointestinal cancers. PMID:26989463

  8. Spurious finite-size instabilities in nuclear energy density functionals: Spin channel

    Science.gov (United States)

    Pastore, A.; Tarpanov, D.; Davesne, D.; Navarro, J.

    2015-08-01

    Background: It has been recently shown that some Skyrme functionals can lead to nonconverging results in the calculation of some properties of atomic nuclei. A previous study has pointed out a possible link between these convergence problems and the appearance of finite-size instabilities in symmetric nuclear matter (SNM) around saturation density. Purpose: We show that the finite-size instabilities not only affect the ground-state properties of atomic nuclei, but they can also influence the calculations of vibrational excited states in finite nuclei. Method: We perform systematic fully-self consistent random phase approximation (RPA) calculations in spherical doubly magic nuclei. We employ several Skyrme functionals and vary the isoscalar and isovector coupling constants of the time-odd term s .Δ s . We determine critical values of these coupling constants beyond which the RPA calculations do not converge because the RPA stability matrix becomes nonpositive. Results: By comparing the RPA calculations of atomic nuclei with those performed for SNM we establish a correspondence between the critical densities in the infinite system and the critical coupling constants for which the RPA calculations do not converge. Conclusions: We find a quantitative stability criterion to detect finite-size instabilities related to the spin s .Δ s term of a functional. This criterion could be easily implemented in the standard fitting protocols to fix the coupling constants of the Skyrme functional.

  9. The demography of climate-driven and density-regulated population dynamics in a perennial plant.

    Science.gov (United States)

    Dahlgren, Johan P; Bengtsson, Karin; Ehrlén, Johan

    2016-04-01

    Identifying the internal and external drivers of population dynamics is a key objective in ecology, currently accentuated by the need to forecast the effects of climate change on species distributions and abundances. The interplay between environmental and density effects is one particularly important aspect of such forecasts. We examined the simultaneous impact of climate and intraspecific density on vital rates of the dwarf shrub Fumana procumbens over 20 yr, using generalized additive mixed models. We then analyzed effects on population dynamics using integral projection models. The population projection models accurately captured observed fluctuations in population size. Our analyses suggested the population was intrinsically regulated but with annual fluctuations in response to variation in weather. Simulations showed that implicitly assuming variation in demographic rates to be driven solely by the environment can overestimate extinction risks if there is density dependence. We conclude that density regulation can dampen effects of climate change on Fumana population size, and discuss the need to quantify density dependence in predictions of population responses to environmental changes. PMID:27220206

  10. The Fleming-Viot limit of an interacting spatial population with fast density regulation

    CERN Document Server

    Gupta, Ankit

    2012-01-01

    We consider population models in which the individuals reproduce, die and also migrate in space. The population size scales according to some parameter $N$, which can have different interpretations depending on the context. Each individual is assigned a mass of 1/N and the total mass in the system is called population density. The dynamics has an intrinsic density regulation mechanism that drives the population density towards an equilibrium. We show that under a timescale separation between the slow migration mechanism and the fast density regulation mechanism, the population dynamics converges to a Fleming-Viot process as the scaling parameter $N \\to \\infty$. We first prove this result for a basic model in which the birth and death rates can only depend on the population density. In this case we obtain a neutral Fleming-Viot process. We then extend this model by including position-dependence in the birth and death rates, as well as, offspring dispersal and immigration mechanisms. We show how these extension...

  11. CFTR channel in oocytes from Xenopus laevis and its regulation by xShroom1 protein.

    Science.gov (United States)

    Palma, Alejandra G; Galizia, Luciano; Kotsias, Basilio A; Marino, Gabriela I

    2016-05-01

    Shroom is a family of related proteins linked to the actin cytoskeleton. xShroom1 is constitutively expressed in Xenopus laevis oocytes, and it is required for the expression of the epithelial sodium channel (ENaC). As there is a close relationship between ENaC and the cystic fibrosis transmembrane regulator (CFTR), we examined the action of xShroom1 on CFTR expression and activity. Biotinylation was used to measure CFTR surface expression, and currents were registered with voltage clamp when stimulated with forskolin and 3-isobutyl-1-methylxanthine. Oocytes were coinjected with CFTR complementary RNAs (cRNAs) and xShroom1 sense or antisense oligonucleotides. We observed an increment in CFTR currents and CFTR surface expression in oocytes coinjected with CFTR and xShroom1 antisense oligonucleotides. MG-132, a proteasome inhibitor, did not prevent the increment in currents when xShroom1 was suppressed by antisense oligonucleotides. In addition, we inhibited the delivery of newly synthesized proteins to the plasma membrane with BFA and we found that the half-life of plasma membrane CFTR was prolonged when coinjected with the xShroom1 antisense oligonucleotides. Chloroquine, an inhibitor of the late endosome/lysosome, did not significantly increase CFTR currents when xShroom1 expression was inhibited. The higher expression of CFTR when xShroom1 is suppressed is in concordance with the functional studies suggesting that the suppression of the xShroom1 protein resulted in an increment in CFTR currents by promoting the increase of the half-life of CFTR in the plasma membrane. The role of xShroom1 in regulating CFTR expression could be relevant in the understanding of the channel malfunction in several diseases.

  12. The Caenorhabditis elegans iodotyrosine deiodinase ortholog SUP-18 functions through a conserved channel SC-box to regulate the muscle two-pore domain potassium channel SUP-9.

    Directory of Open Access Journals (Sweden)

    Ignacio Perez de la Cruz

    2014-02-01

    Full Text Available Loss-of-function mutations in the Caenorhabditis elegans gene sup-18 suppress the defects in muscle contraction conferred by a gain-of-function mutation in SUP-10, a presumptive regulatory subunit of the SUP-9 two-pore domain K(+ channel associated with muscle membranes. We cloned sup-18 and found that it encodes the C. elegans ortholog of mammalian iodotyrosine deiodinase (IYD, an NADH oxidase/flavin reductase that functions in iodine recycling and is important for the biosynthesis of thyroid hormones that regulate metabolism. The FMN-binding site of mammalian IYD is conserved in SUP-18, which appears to require catalytic activity to function. Genetic analyses suggest that SUP-10 can function with SUP-18 to activate SUP-9 through a pathway that is independent of the presumptive SUP-9 regulatory subunit UNC-93. We identified a novel evolutionarily conserved serine-cysteine-rich region in the C-terminal cytoplasmic domain of SUP-9 required for its specific activation by SUP-10 and SUP-18 but not by UNC-93. Since two-pore domain K(+ channels regulate the resting membrane potentials of numerous cell types, we suggest that the SUP-18 IYD regulates the activity of the SUP-9 channel using NADH as a coenzyme and thus couples the metabolic state of muscle cells to muscle membrane excitability.

  13. High-Rate Short-Block LDPC Codes for Iterative Decoding with Applications to High-Density Magnetic Recording Channels

    CERN Document Server

    Morero, Damian A; Rodriguez, Carmen; Hueda, Mario R

    2011-01-01

    This paper investigates the Triangle Single Parity Check (T/SPC) code, a novel class of high-rate low-complexity LDPC codes. T/SPC is a regular, soft decodable, linear-time encodable/decodable code. Compared to previous high-rate and low-complexity LDPC codes, such as the well-known Turbo Product Code / Single Parity Check (TPC/SPC), T/SPC provides higher code rates, shorter code words, and lower complexity. This makes T/SPC very attractive for practical implementation on integrated circuits. In addition, we analyze the performance of iterative decoders based on a soft-input soft-output (SISO) equalizer using T/SPC over high-density perpendicular magnetic recording channels. Computer simulations show that the proposed scheme is able to achieve a gain of up to 0.3 dB over TPC/SPC codes with a significant reduction of implementation complexity.

  14. Expression and Function of CLC and Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channels in Renal Epithelial Tubule Cells: Pathophysiological Implications

    OpenAIRE

    Alain Vandewalle

    2007-01-01

    Cl- channels play important roles in the regulation of a variety of functions, includingelectrical excitability, cell volume regulation, transepithelial transport and acidification ofcellular organelles. They are expressed in plasma membranes or reside in intracellularorganelles. A large number of Cl- channels with different functions have been identified.Some of them are highly expressed in the kidney. They include members of the CLC Clchannelfamily: ClC-K1 (or ClC-Ka), ClC-K2 (or ClC-Kb) an...

  15. TRESK background K(+ channel is inhibited by PAR-1/MARK microtubule affinity-regulating kinases in Xenopus oocytes.

    Directory of Open Access Journals (Sweden)

    Gabriella Braun

    Full Text Available TRESK (TWIK-related spinal cord K(+ channel, KCNK18 is a major background K(+ channel of sensory neurons. Dominant-negative mutation of TRESK is linked to familial migraine. This important two-pore domain K(+ channel is uniquely activated by calcineurin. The calcium/calmodulin-dependent protein phosphatase directly binds to the channel and activates TRESK current several-fold in Xenopus oocytes and HEK293 cells. We have recently shown that the kinase, which is responsible for the basal inhibition of the K(+ current, is sensitive to the adaptor protein 14-3-3. Therefore we have examined the effect of the 14-3-3-inhibited PAR-1/MARK, microtubule-associated-protein/microtubule affinity-regulating kinase on TRESK in the Xenopus oocyte expression system. MARK1, MARK2 and MARK3 accelerated the return of TRESK current to the resting state after the calcium-dependent activation. Several other serine-threonine kinase types, generally involved in the modulation of other ion channels, failed to influence TRESK current recovery. MARK2 phosphorylated the primary determinant of regulation, the cluster of three adjacent serine residues (S274, 276 and 279 in the intracellular loop of mouse TRESK. In contrast, serine 264, the 14-3-3-binding site of TRESK, was not phosphorylated by the kinase. Thus MARK2 selectively inhibits TRESK activity via the S274/276/279 cluster, but does not affect the direct recruitment of 14-3-3 to the channel. TRESK is the first example of an ion channel phosphorylated by the dynamically membrane-localized MARK kinases, also known as general determinants of cellular polarity. These results raise the possibility that microtubule dynamics is coupled to the regulation of excitability in the neurons, which express TRESK background potassium channel.

  16. UBE3A Regulates Synaptic Plasticity and Learning and Memory by Controlling SK2 Channel Endocytosis

    Directory of Open Access Journals (Sweden)

    Jiandong Sun

    2015-07-01

    Full Text Available Gated solely by activity-induced changes in intracellular calcium, small-conductance potassium channels (SKs are critical for a variety of functions in the CNS, from learning and memory to rhythmic activity and sleep. While there is a wealth of information on SK2 gating, kinetics, and Ca2+ sensitivity, little is known regarding the regulation of SK2 subcellular localization. We report here that synaptic SK2 levels are regulated by the E3 ubiquitin ligase UBE3A, whose deficiency results in Angelman syndrome and overexpression in increased risk of autistic spectrum disorder. UBE3A directly ubiquitinates SK2 in the C-terminal domain, which facilitates endocytosis. In UBE3A-deficient mice, increased postsynaptic SK2 levels result in decreased NMDA receptor activation, thereby impairing hippocampal long-term synaptic plasticity. Impairments in both synaptic plasticity and fear conditioning memory in UBE3A-deficient mice are significantly ameliorated by blocking SK2. These results elucidate a mechanism by which UBE3A directly influences cognitive function.

  17. Spurious finite-size instabilities in nuclear energy density functionals: spin channel

    CERN Document Server

    Pastore, A; Davesne, D; Navarro, J

    2015-01-01

    It has been recently shown, that some Skyrme functionals can lead to non-converging results in the calculation of some properties of atomic nuclei. A previous study has pointed out a possible link between these convergence problems and the appearance of finite-size instabilities in symmetric nuclear matter (SNM) around saturation density. We show that the finite-size instabilities not only affect the ground state properties of atomic nuclei, but they can also influence the calculations of vibrational excited states in finite nuclei. We perform systematic fully-self consistent Random Phase Approximation (RPA) calculations in spherical doubly-magic nuclei. We employ several Skyrme functionals and vary the isoscalar and isovector coupling constants of the time-odd term $\\mathbf{s}\\cdot \\Delta \\mathbf{s}$ . We determine critical values of these coupling constants beyond which the RPA calculations do not converge because RPA the stability matrix becomes non-positive.By comparing the RPA calculations of atomic nucl...

  18. Spatial synchrony in population dynamics: The effects of demographic stochasticity and density regulation with a spatial scale.

    Science.gov (United States)

    Engen, Steinar; Sæther, Bernt-Erik

    2016-04-01

    We generalize a previous simple result by Lande et al. (1999) on how spatial autocorrelated noise, dispersal rate and distance as well as strength of density regulation determine the spatial scale of synchrony in population density. It is shown how demographic noise can be incorporated, what effect it has on variance and spatial scale of synchrony, and how it interacts with the point process for locations of individuals under random sampling. Although the effect of demographic noise is a rather complex interaction with environmental noise, migration and density regulation, its effect on population fluctuations and scale of synchrony can be presented in a transparent way. This is achieved by defining a characteristic area dependent on demographic and environmental variances as well as population density, and subsequently using this area to define a spatial demographic coefficient. The demographic noise acts through this coefficient on the spatial synchrony, which may increase or decrease with increasing demographic noise depending on other parameters. A second generalization yields the modeling of density regulation taking into account that regulation at a given location does not only depend on the density at that site but also on densities in the whole territory or home range of individuals. It is shown that such density regulation with a spatial scale reduces the scale of synchrony in population fluctuations relative to the simpler model with density regulation at each location determined only by the local point density, and may even generate negative spatial autocorrelations. PMID:26852669

  19. Voltage dependent anion channel-1 regulates death receptor mediated apoptosis by enabling cleavage of caspase-8

    International Nuclear Information System (INIS)

    Activation of the extrinsic apoptosis pathway by tumour necrosis factor related apoptosis inducing ligand (TRAIL) is a novel therapeutic strategy for treating cancer that is currently under clinical evaluation. Identification of molecular biomarkers of resistance is likely to play an important role in predicting clinical anti tumour activity. The involvement of the mitochondrial type 1 voltage dependent anion channel (VDAC1) in regulating apoptosis has been highly debated. To date, a functional role in regulating the extrinsic apoptosis pathway has not been formally excluded. We carried out stable and transient RNAi knockdowns of VDAC1 in non-small cell lung cancer cells, and stimulated the extrinsic apoptotic pathway principally by incubating cells with the death ligand TRAIL. We used in-vitro apoptotic and cell viability assays, as well as western blot for markers of apoptosis, to demonstrate that TRAIL-induced toxicity is VDAC1 dependant. Confocal microscopy and mitochondrial fractionation were used to determine the importance of mitochondria for caspase-8 activation. Here we show that either stable or transient knockdown of VDAC1 is sufficient to antagonize TRAIL mediated apoptosis in non-small cell lung cancer (NSCLC) cells. Specifically, VDAC1 is required for processing of procaspase-8 to its fully active p18 form at the mitochondria. Loss of VDAC1 does not alter mitochondrial sensitivity to exogenous caspase-8-cleaved BID induced mitochondrial depolarization, even though VDAC1 expression is essential for TRAIL dependent activation of the intrinsic apoptosis pathway. Furthermore, expression of exogenous VDAC1 restores the apoptotic response to TRAIL in cells in which endogenous VDAC1 has been selectively silenced. Expression of VDAC1 is required for full processing and activation of caspase-8 and supports a role for mitochondria in regulating apoptosis signaling via the death receptor pathway

  20. Regulation of Calcium Channels and Exocytosis in Mouse Adrenal Chromaffin Cells by Prostaglandin EP3 Receptors

    Science.gov (United States)

    Jewell, Mark L.; Breyer, Richard M.

    2011-01-01

    Prostaglandin (PG) E2 controls numerous physiological functions through a family of cognate G protein-coupled receptors (EP1–EP4). Targeting specific EP receptors might be therapeutically useful and reduce side effects associated with nonsteroidal anti-inflammatory drugs and selective cyclooxygenase-2 inhibitors that block prostanoid synthesis. Systemic immune challenge and inflammatory cytokines have been shown to increase expression of the synthetic enzymes for PGE2 in the adrenal gland. Catecholamines and other hormones, released from adrenal chromaffin cells in response to Ca2+ influx through voltage-gated Ca2+ channels, play central roles in homeostatic function and the coordinated stress response. However, long-term elevation of circulating catecholamines contributes to the pathogenesis of hypertension and heart failure. Here, we investigated the EP receptor(s) and cellular mechanisms by which PGE2 might modulate chromaffin cell function. PGE2 did not alter resting intracellular [Ca2+] or the peak amplitude of nicotinic acetylcholine receptor currents, but it did inhibit CaV2 voltage-gated Ca2+ channel currents (ICa). This inhibition was voltage-dependent and mediated by pertussis toxin-sensitive G proteins, consistent with a direct Gβγ subunit-mediated mechanism common to other Gi/o-coupled receptors. mRNA for all four EP receptors was detected, but using selective pharmacological tools and EP receptor knockout mice, we demonstrated that EP3 receptors mediate the inhibition of ICa. Finally, changes in membrane capacitance showed that Ca2+-dependent exocytosis was reduced in parallel with ICa. To our knowledge, this is the first study of EP receptor signaling in mouse chromaffin cells and identifies a molecular mechanism for paracrine regulation of neuroendocrine function by PGE2. PMID:21383044

  1. Regulation of adenosine triphosphate-sensitive potassium channels suppresses the toxic effects of amyloid-beta peptide (25-35)

    Institute of Scientific and Technical Information of China (English)

    Min Kong; Maowen Ba; Hui Liang; Peng Shao; Tianxia Yu; Ying Wang

    2013-01-01

    In this study, we treated PC12 cells with 0-20 μM amyloid-β peptide (25-35) for 24 hours to induce cytotoxicity, and found that 5-20 μM amyloid-β peptide (25-35) decreased PC12 cell viability, but adenosine triphosphate-sensitive potassium channel activator diazoxide suppressed the decrease reactive oxygen species levels. These protective effects were reversed by the selective mitochondrial adenosine triphosphate-sensitive potassium channel blocker 5-hydroxydecanoate. An inducible nitric oxide synthase inhibitor, Nω-nitro-L-arginine, also protected PC12 cells from intracellular reactive oxygen species levels. However, the H2O2-degrading enzyme catalase could that the increases in both mitochondrial membrane potential and reactive oxygen species levels adenosine triphosphate-sensitive potassium channels and nitric oxide. Regulation of adenosine triphosphate-sensitive potassium channels suppresses PC12 cell cytotoxicity induced by amyloid-β

  2. Influence of Thromboxane A2 on the Regulation of Adenosine Triphosphate-Sensitive Potassium Channels in Mouse Ventricular Myocytes

    Science.gov (United States)

    Jeong, In Seok; Cho, Hwa Jin; Cho, Jeong Gwan; Kim, Sang Hyung; Na, Kook Joo

    2016-01-01

    Background and Objectives Adenosine triphosphate (ATP)-sensitive potassium (KATP) channels play an important role in myocardial protection. We examined the effects of thromboxane A2 on the regulation of KATP channel activity in single ventricular myocytes. Subjects and Methods Single ventricular myocytes were isolated from the hearts of adult Institute of Cancer Research (ICR) mice by enzymatic digestion. Single channel activity was recorded by excised inside-out and cell-attached patch clamp configurations at −60 mV holding potential during the perfusion of an ATP-free K-5 solution. Results In the excised inside-out patches, the thromboxane A2 analog, U46619, decreased the KATP channel activity in a dose-dependent manner; however, the thromboxane A2 receptor antagonist, SQ29548, did not significantly attenuate the inhibitory effect of U46619. In the cell-attached patches, U46619 inhibited dinitrophenol (DNP)-induced KATP channel activity in a dose-dependent manner, and SQ29548 attenuated the inhibitory effects of U46619 on DNP-induced KATP channel activity. Conclusion Thromboxane A2 may inhibit KATP channel activity, and may have a harmful effect on ischemic myocardium. PMID:27482267

  3. H{sub 2}S does not regulate proliferation via T-type Ca{sup 2+} channels

    Energy Technology Data Exchange (ETDEWEB)

    Elies, Jacobo; Johnson, Emily; Boyle, John P.; Scragg, Jason L.; Peers, Chris, E-mail: c.s.peers@leeds.ac.uk

    2015-06-12

    T-type Ca{sup 2+} channels (Cav3.1, 3.2 and 3.3) strongly influence proliferation of various cell types, including vascular smooth muscle cells (VSMCs) and certain cancers. We have recently shown that the gasotransmitter carbon monoxide (CO) inhibits T-type Ca{sup 2+} channels and, in so doing, attenuates proliferation of VSMC. We have also shown that the T-type Ca{sup 2+} channel Cav3.2 is selectively inhibited by hydrogen sulfide (H{sub 2}S) whilst the other channel isoforms (Cav3.1 and Cav3.3) are unaffected. Here, we explored whether inhibition of Cav3.2 by H{sub 2}S could account for the anti-proliferative effects of this gasotransmitter. H{sub 2}S suppressed proliferation in HEK293 cells expressing Cav3.2, as predicted by our previous observations. However, H{sub 2}S was similarly effective in suppressing proliferation in wild type (non-transfected) HEK293 cells and those expressing the H{sub 2}S insensitive channel, Cav3.1. Further studies demonstrated that T-type Ca{sup 2+} channels in the smooth muscle cell line A7r5 and in human coronary VSMCs strongly influenced proliferation. In both cell types, H{sub 2}S caused a concentration-dependent inhibition of proliferation, yet by far the dominant T-type Ca{sup 2+} channel isoform was the H{sub 2}S-insensitive channel, Cav3.1. Our data indicate that inhibition of T-type Ca{sup 2+} channel-mediated proliferation by H{sub 2}S is independent of the channels’ sensitivity to H{sub 2}S. - Highlights: • T-type Ca{sup 2+} channels regulate proliferation and are sensitive to the gasotransmitters CO and H{sub 2}S. • H{sub 2}S reduced proliferation in HEK293 cells expressing the H{sub 2}S sensitive Cav3.2 channel. • H{sub 2}S also inhibited proliferation in non-transfected cells and HEK293 cells expressing Cav3.1. • Native smooth muscle cells primarily express Cav3.1. Their proliferation was also inhibited by H{sub 2}S. • Unlike CO, H{sub 2}S does not regulate smooth muscle proliferation via T-type Ca{sup 2

  4. dTULP, the Drosophila melanogaster homolog of tubby, regulates transient receptor potential channel localization in cilia.

    Directory of Open Access Journals (Sweden)

    Jina Park

    Full Text Available Mechanically gated ion channels convert sound into an electrical signal for the sense of hearing. In Drosophila melanogaster, several transient receptor potential (TRP channels have been implicated to be involved in this process. TRPN (NompC and TRPV (Inactive channels are localized in the distal and proximal ciliary zones of auditory receptor neurons, respectively. This segregated ciliary localization suggests distinct roles in auditory transduction. However, the regulation of this localization is not fully understood. Here we show that the Drosophila Tubby homolog, King tubby (hereafter called dTULP regulates ciliary localization of TRPs. dTULP-deficient flies show uncoordinated movement and complete loss of sound-evoked action potentials. Inactive and NompC are mislocalized in the cilia of auditory receptor neurons in the dTulp mutants, indicating that dTULP is required for proper cilia membrane protein localization. This is the first demonstration that dTULP regulates TRP channel localization in cilia, and suggests that dTULP is a protein that regulates ciliary neurosensory functions.

  5. TRP channel-associated factors are a novel protein family that regulates TRPM8 trafficking and activity.

    NARCIS (Netherlands)

    Gkika, D.; Lemonnier, L.; Shapovalov, G.; Gordienko, D.; Poux, C.; Bernardini, M.; Bokhobza, A.; Bidaux, G.; Degerny, C.; Verreman, K.; Guarmit, B.; Benahmed, M.; Launoit, Y. de; Bindels, R.J.M.; Fiorio Pla, A.; Prevarskaya, N.

    2015-01-01

    TRPM8 is a cold sensor that is highly expressed in the prostate as well as in other non-temperature-sensing organs, and is regulated by downstream receptor-activated signaling pathways. However, little is known about the intracellular proteins necessary for channel function. Here, we identify two pr

  6. Hutchinson revisited: patterns of density regulation and the coexistence of strong competitors.

    Science.gov (United States)

    Münkemüller, Tamara; Bugmann, Harald; Johst, Karin

    2009-07-01

    Ecologists have long been searching for mechanisms of species coexistence, particularly since G.E. Hutchinson raised the 'paradox of the plankton'. A promising approach to solve this paradox and to explain the coexistence of many species with strong niche overlap is to consider over-compensatory density regulation with its ability to generate endogenous population fluctuations. Previous work has analysed the role of over-compensation in coexistence based on analytical approaches. Using a spatially explicit time-discrete simulation model, we systematically explore the dynamics and conditions for coexistence of two species. We go beyond the analytically accessible range of models by studying the whole range of density regulation from under- to very strong over-compensation and consider the impact of spatial structure and temporal disturbances. In particular, we investigate how coexistence can emerge in different types of population growth models. We show that two strong competitors are able to coexist if at least one species exhibits over-compensation. Analysing the time series of population dynamics reveals how the differential responses to density fluctuations of the two competitors lead to coexistence: The over-compensator generates density fluctuations but is the inferior competitor at strong amplitudes of those fluctuations; the competitor, therefore, becomes frequent and dampens the over-compensator's amplitudes, but it becomes inferior under dampened fluctuations. These species interactions cause a dynamic alternation of community states with long-term persistence of both species. We show that a variety of population growth models is able to reproduce this coexistence although the particular parameter ranges differ among the models. Spatial structure influences the probability of coexistence but coexistence is maintained for a broad range of dispersal parameters. The flexibility and robustness of coexistence through over-compensation emphasize the importance

  7. Yield components in wheat affected by sowing density and growth regulators

    Directory of Open Access Journals (Sweden)

    Samuel Luiz Fioreze

    2014-02-01

    Full Text Available Improvement on yield potential of plants by crop management is the main research challenge due to the growing of food demand worldwide. The objective of this work was to study physiological and morphological traits and its relationship with yield components and yield of wheat as affected by sowing densities and plant growth regulators. The experimental design was a split-plot design with four replications. The plots were consisted by four sowing densities (30, 50 70 and 90 plants m-1 and the subplots were consisted by plant growth regulators [control, (IBA+GA+KT, Trinexapac-Ethyl e (IBA+GA+KT + Trinexapac-Ethyl]. Dry matter accumulation, plant height, source-sink distance, gas exchange and yield were determined. Trinexapac-Ethyl application resulted in decreasing of plant height, source-sink distance and flag leaf length; however, the grain yield was not affected. The number of plants per unit area affected dry matter accumulation. Higher dry matter accumulation showed direct relationship with yield and yield components in lower plant densities.

  8. Hippo signaling regulates microprocessor and links cell-density-dependent miRNA biogenesis to cancer.

    Science.gov (United States)

    Mori, Masaki; Triboulet, Robinson; Mohseni, Morvarid; Schlegelmilch, Karin; Shrestha, Kriti; Camargo, Fernando D; Gregory, Richard I

    2014-02-27

    Global downregulation of microRNAs (miRNAs) is commonly observed in human cancers and can have a causative role in tumorigenesis. The mechanisms responsible for this phenomenon remain poorly understood. Here, we show that YAP, the downstream target of the tumor-suppressive Hippo-signaling pathway regulates miRNA biogenesis in a cell-density-dependent manner. At low cell density, nuclear YAP binds and sequesters p72 (DDX17), a regulatory component of the miRNA-processing machinery. At high cell density, Hippo-mediated cytoplasmic retention of YAP facilitates p72 association with Microprocessor and binding to a specific sequence motif in pri-miRNAs. Inactivation of the Hippo pathway or expression of constitutively active YAP causes widespread miRNA suppression in cells and tumors and a corresponding posttranscriptional induction of MYC expression. Thus, the Hippo pathway links contact-inhibition regulation to miRNA biogenesis and may be responsible for the widespread miRNA repression observed in cancer.

  9. Loop diuretics are open-channel blockers of the cystic fibrosis transmembrane conductance regulator with distinct kinetics

    Science.gov (United States)

    Ju, Min; Scott-Ward, Toby S; Liu, Jia; Khuituan, Pissared; Li, Hongyu; Cai, Zhiwei; Husbands, Stephen M; Sheppard, David N

    2014-01-01

    BACKGROUND AND PURPOSE Loop diuretics are widely used to inhibit the Na+, K+, 2Cl− co-transporter, but they also inhibit the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel. Here, we investigated the mechanism of CFTR inhibition by loop diuretics and explored the effects of chemical structure on channel blockade. EXPERIMENTAL APPROACH Using the patch-clamp technique, we tested the effects of bumetanide, furosemide, piretanide and xipamide on recombinant wild-type human CFTR. KEY RESULTS When added to the intracellular solution, loop diuretics inhibited CFTR Cl− currents with potency approaching that of glibenclamide, a widely used CFTR blocker with some structural similarity to loop diuretics. To begin to study the kinetics of channel blockade, we examined the time dependence of macroscopic current inhibition following a hyperpolarizing voltage step. Like glibenclamide, piretanide blockade of CFTR was time and voltage dependent. By contrast, furosemide blockade was voltage dependent, but time independent. Consistent with these data, furosemide blocked individual CFTR Cl− channels with ‘very fast’ speed and drug-induced blocking events overlapped brief channel closures, whereas piretanide inhibited individual channels with ‘intermediate’ speed and drug-induced blocking events were distinct from channel closures. CONCLUSIONS AND IMPLICATIONS Structure–activity analysis of the loop diuretics suggests that the phenoxy group present in bumetanide and piretanide, but absent in furosemide and xipamide, might account for the different kinetics of channel block by locking loop diuretics within the intracellular vestibule of the CFTR pore. We conclude that loop diuretics are open-channel blockers of CFTR with distinct kinetics, affected by molecular dimensions and lipophilicity. PMID:24117047

  10. Keeping active channels in their place: membrane phosphoinositides regulate TRPM channel activity in a compartment-selective manner.

    Science.gov (United States)

    Braun, Andrew P

    2012-01-01

    We have long appreciated that the controlled movement of ions and solutes across the cell surface or plasma membrane affects every aspect of cell function, ranging from membrane excitability to metabolism to secretion, and is also critical for the long-term maintenance of cell viability. Studies examining these physiological transport processes have revealed a vast array of ion channels, transporters and ATPase-driven pumps that underlie these transmembrane ionic movements and how acquired or genetic disruption of these processes are linked to disease. More recently, it has become evident that the ongoing function of intracellular organelles and subcellular compartments also depends heavily on the controlled movement of ions to establish distinct pH or ionic environments. However, limited experimental access to these subcellular domains/structures has hampered scientific progress in this area, due in large part to the difficulty of applying proven functional assays, such as patch clamp and radiotracer methodologies, to these specialized membrane locations. Using both functional and immune-labeling assays, we now know that the types and complement of channels, transporters and pumps located within intracellular membranes and organelles often differ from those present on the plasma membrane. Moreover, it appears that this differential distribution is due to the presence of discrete tags/signals present within these transport proteins that dictate their sorting/trafficking to spatially discrete membrane compartments, where they may also interact with scaffolding proteins that help maintain their localization. Such targeting signals may thus operate in a manner analogous to the way a postal code is used to direct the delivery of a letter. PMID:23151432

  11. Down-regulation of the cardiac sarcoplasmic reticulum ryanodine channel in severely food-restricted rats

    Directory of Open Access Journals (Sweden)

    V.A. Vizotto

    2007-01-01

    Full Text Available We have shown that myocardial dysfunction induced by food restriction is related to calcium handling. Although cardiac function is depressed in food-restricted animals, there is limited information about the molecular mechanisms that lead to this abnormality. The present study evaluated the effects of food restriction on calcium cycling, focusing on sarcoplasmic Ca2+-ATPase (SERCA2, phospholamban (PLB, and ryanodine channel (RYR2 mRNA expressions in rat myocardium. Male Wistar-Kyoto rats, 60 days old, were submitted to ad libitum feeding (control rats or 50% diet restriction for 90 days. The levels of left ventricle SERCA2, PLB, and RYR2 were measured using semi-quantitative RT-PCR. Body and ventricular weights were reduced in 50% food-restricted animals. RYR2 mRNA was significantly decreased in the left ventricle of the food-restricted group (control = 5.92 ± 0.48 vs food-restricted group = 4.84 ± 0.33, P < 0.01. The levels of SERCA2 and PLB mRNA were similar between groups (control = 8.38 ± 0.44 vs food-restricted group = 7.96 ± 0.45, and control = 1.52 ± 0.06 vs food-restricted group = 1.53 ± 0.10, respectively. Down-regulation of RYR2 mRNA expressions suggests that chronic food restriction promotes abnormalities in sarcoplasmic reticulum Ca2+ release.

  12. KV7 channels contribute to paracrine, but not metabolic or ischemic, regulation of coronary vascular reactivity in swine.

    Science.gov (United States)

    Goodwill, Adam G; Fu, Lijuan; Noblet, Jillian N; Casalini, Eli D; Sassoon, Daniel; Berwick, Zachary C; Kassab, Ghassan S; Tune, Johnathan D; Dick, Gregory M

    2016-03-15

    Hydrogen peroxide (H2O2) and voltage-dependent K(+) (KV) channels play key roles in regulating coronary blood flow in response to metabolic, ischemic, and paracrine stimuli. The KV channels responsible have not been identified, but KV7 channels are possible candidates. Existing data regarding KV7 channel function in the coronary circulation (limited to ex vivo assessments) are mixed. Thus we examined the hypothesis that KV7 channels are present in cells of the coronary vascular wall and regulate vasodilation in swine. We performed a variety of molecular, biochemical, and functional (in vivo and ex vivo) studies. Coronary arteries expressed KCNQ genes (quantitative PCR) and KV7.4 protein (Western blot). Immunostaining demonstrated KV7.4 expression in conduit and resistance vessels, perhaps most prominently in the endothelial and adventitial layers. Flupirtine, a KV7 opener, relaxed coronary artery rings, and this was attenuated by linopirdine, a KV7 blocker. Endothelial denudation inhibited the flupirtine-induced and linopirdine-sensitive relaxation of coronary artery rings. Moreover, linopirdine diminished bradykinin-induced endothelial-dependent relaxation of coronary artery rings. There was no effect of intracoronary flupirtine or linopirdine on coronary blood flow at the resting heart rate in vivo. Linopirdine had no effect on coronary vasodilation in vivo elicited by ischemia, H2O2, or tachycardia. However, bradykinin increased coronary blood flow in vivo, and this was attenuated by linopirdine. These data indicate that KV7 channels are expressed in some coronary cell type(s) and influence endothelial function. Other physiological functions of coronary vascular KV7 channels remain unclear, but they do appear to contribute to endothelium-dependent responses to paracrine stimuli. PMID:26825518

  13. Low Density Lipoprotein Receptor Related Proteins as Regulators of Neural Stem and Progenitor Cell Function

    Directory of Open Access Journals (Sweden)

    Loic Auderset

    2016-01-01

    Full Text Available The central nervous system (CNS is a highly organised structure. Many signalling systems work in concert to ensure that neural stem cells are appropriately directed to generate progenitor cells, which in turn mature into functional cell types including projection neurons, interneurons, astrocytes, and oligodendrocytes. Herein we explore the role of the low density lipoprotein (LDL receptor family, in particular family members LRP1 and LRP2, in regulating the behaviour of neural stem and progenitor cells during development and adulthood. The ability of LRP1 and LRP2 to bind a diverse and extensive range of ligands, regulate ligand endocytosis, recruit nonreceptor tyrosine kinases for direct signal transduction and signal in conjunction with other receptors, enables them to modulate many crucial neural cell functions.

  14. Photosynthetic photon flux density and phytochrome B interact to regulate branching in Arabidopsis.

    Science.gov (United States)

    Su, Hongwen; Abernathy, Scott D; White, Richard H; Finlayson, Scott A

    2011-11-01

    Branching is regulated by environmental signals including phytochrome B (phyB)-mediated responses to the ratio of red to far red light. While the mechanisms associated with phytochrome regulation of branching are beginning to be elucidated, there is little information regarding other light signals, including photosynthetic photon flux density (PPFD) and how it influences phytochrome-mediated responses. This study shows that Arabidopsis (Arabidopsis thaliana) branching is modified by both varying PPFD and phyB status and that significant interactions occur between these variables. While phyB deficiency decreased branching when the PPFD was low, the effect was suppressed by high PPFD and some branching aspects were actually promoted. Photosynthesis measurements showed that PPFD may influence branching in phyB-deficient plants at least partially through a specific signalling pathway rather than directly through energy effects on the shoot. The expression of various genes in unelongated buds of phyB-deficient and phyB-sufficient plants grown under high and low PPFD demonstrated potential roles for several hormones, including auxin, cytokinins and ABA, and also showed imperfect correlation between expression of the branching regulators BRC1 and BRC2 and bud fate. These results may implicate additional undiscovered bud autonomous mechanisms and/or components contributing to bud outgrowth regulation by environmental signals.

  15. Evidence for functional interaction of plasma membrane electron transport, voltage-dependent anion channel and volume-regulated anion channel in frog aorta

    Indian Academy of Sciences (India)

    Rashmi P Rao; J Prakasa Rao

    2010-12-01

    Frog aortic tissue exhibits plasma membrane electron transport (PMET) owing to its ability to reduce ferricyanide even in the presence of mitochondrial poisons, such as cyanide and azide. Exposure to hypotonic solution (108 mOsmol/kg H2O) enhanced the reduction of ferricyanide in excised aortic tissue of frog. Increment in ferricyanide reductase activity was also brought about by the presence of homocysteine (100 M dissolved in isotonic frog Ringer solution), a redox active compound and a potent modulator of PMET. Two plasma-membrane-bound channels, the volume regulated anion channel (VRAC) and the voltage-dependent anion channel (VDAC), are involved in the response to hypotonic stress. The presence of VRAC and VDAC antagonists–tamoxifen, glibenclamide, fluoxetine and verapamil, and 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS), respectively–inhibited this enhanced activity brought about by either hypotonic stress or homocysteine. The blockers do not affect the ferricyanide reductase activity under isotonic conditions. Taken together, these findings indicate a functional interaction of the three plasma membrane proteins, namely, ferricyanide reductase (PMET), VDAC and VRAC.

  16. KV7 channels regulate muscle tone and nonadrenergic noncholinergic relaxation of the rat gastric fundus

    OpenAIRE

    Ipavec, V.; Martire, M; Barrese, V.; Taglialatela, M; Currò, D.

    2011-01-01

    Voltage-dependent type 7 K+ (KV7) channels play important physiological roles in neurons and muscle cells. The aims of the present study were to investigate the motor effects of KV7 channel modulators in the rat gastric fundus and the expression of KV7 channels in this tissue. Muscle tone and electrical field stimulation (EFS)-evoked relaxations of precontracted longitudinal muscle strips of the rat gastric fundus were investigated under nonadrenergic noncholinergic conditions by organ bath s...

  17. Protein kinase C is involved in regulation of Ca2+ channels in plasmalemma of Nitella syncarpa.

    Science.gov (United States)

    Zherelova, O M

    1989-01-01

    Ca2+ current recordings have been made on Nitella syncarpa cells using the intracellular perfusion and the voltage-clamp technique. TPA (12-O-tetradecanoylphorbol-13-acetate), a substance capable of activating protein kinase C from plasmalemma of Nitella cells, modulates voltage-dependent Ca2+ channels. Polymixin B, inhibitor of protein kinase C, blocks the Nitella plasmalemma Ca2+ channels; the rate of channel blockage depends on the concentration and exposure time of the substance. PMID:2536617

  18. Trypanosoma cruzi Proline Transport Presents a Cell Density-dependent Regulation.

    Science.gov (United States)

    Sayé, Melisa; Miranda, Mariana R; Reigada, Chantal; Pereira, Claudio A

    2016-07-01

    Trypanosoma cruzi, the etiological agent of Chagas disease, uses proline as its main carbon source, essential for parasite growth and stage differentiation in epimastigotes and amastigotes. Since proline is mainly obtained from extracellular medium by transport proteins, in this work we studied the regulation of the T. cruzi proline transporter TcAAAP069. Proline uptake and intracellular concentration presented oscillations during epimastigote growth phases, increasing during the early exponential phase (322 pmol/min) and decreasing to undetectable levels during the late exponential phase. Transporter expression rate correlated with proline uptake, and its subcellular localization alternated from both, the plasma membrane and close to the flagellar pocket, when the transport is higher, to only the flagellar pocket region, when the transport decreased until proline uptake and TcAAAP069 protein became undetectable at the end of the growth curve. Interestingly, when parasites were treated with conditioned medium or were concentrated to artificially increase the culture density, the proline transport was completely abolished resembling the effects observed in late exponential phase. These data highlight for the first time the existence of a density-associated regulation of relevant physiological processes such as proline metabolism. PMID:26750517

  19. Interacting influence of diuretics and diet on BK channel-regulated K homeostasis

    Science.gov (United States)

    Wen, Donghai; Cornelius, Ryan J.; Sansom, Steven C.

    2014-01-01

    Large conductance, Ca-activated K channels are abundantly located in cells of vasculature, glomerulus and distal nephron, where they are involved in maintaining blood volume, blood pressure and K homeostasis. In mesangial cells and smooth muscle cells of vessels, the BK-α pore associates with BK-β1 subunits and regulates contraction in a Ca-mediated feedback manner. The BK-β1 also resides in connecting tubule cells of the nephron. BK-β1 knockout mice (β1KO) exhibit fluid retention, hypertension, and compromised K handling. The BK-α/β4resides in acid/base transporting intercalated cells (IC) of the distal nephron, where they mediate K secretion in mammals on a high K, alkaline diet. BK-α expression in IC is increased by a high K diet via aldosterone. The BK-β4 subunit and alkaline urine are necessary for the luminal expression and function of BK-α in mouse IC. In distal nephron cells, membrane BK-α expression is inhibited by WNK4 in in vitro expression systems, indicating a role in the hyperkalemic phenotype in patients with familial hyperkalemic hypertension type 2 (FHHt2). β1KO and BK-β4 knockout mice (β4KO) are hypertensive because of exaggerated ENaC-mediated Na retention in an effort to secrete K via only ROMK. BK hypertension is resistant to thiazides and furosemide, and would be more amenable to ENaC and aldosterone inhibiting drugs. Activators of BK-α/β1 or BK-α/β4 might be effective blood pressure lowering agents for a subset of hypertensive patients. Inhibitors of renal BK would effectively spare K in patients with Bartter Syndrome, a renal K wasting disease. PMID:24721651

  20. Neuroprotective effects of volume-regulated anion channel blocker DCPIB on neonatal hypoxic-ischemic injury

    Institute of Scientific and Technical Information of China (English)

    Ammar ALIBRAHIM; Li-yan ZHAO; Christine You-jin BAE; Andrew BARSZCZYK; Christopher LF SUN; Guan-lei WANG; Hong-shuo SUN

    2013-01-01

    Aim:To evaluate the role of swelling-induced activation of volume-regulated anion channels (VRACs) in a neonatal hypoxic-ischemic injury model using the selective VRAC blocker 4-(2-butyl-6,7-dichloro-2-cyclopentyl-indan-1-on5-yl) oxobutyric acid (DCPIB).Methods:Cerebral hypoxic-ischemic injury was induced in 7-day-old mouse pups with Rice-Vannucci method.Prior to the onset of ischemia,the animals were ip administered DCPIB (10 mg/kg).The animals were sacrificed 24 h afterwards,coronal sections of the brains were cut and the areas of infarct were examined using TTC staining and an image-analysis system.Cultured PC12 cells were subjected to oxygen-glucose deprivation (OGD) for 4 h.The cellular viability was assessed using Cell Counting Kit 8.Intracellular chloride concentration [Clˉ]i was measured using 6-methoxy-N-ethylquinolinium iodide.Results:DCPIB-treated mice showed a significant reduction in hemispheric corrected infarct volume (26.65%+2.23%) compared to that in vehicle-treated mice (45.52%+1.45%,P<O.O01).DCPIB-treated mice also showed better functional recovery as they were more active than vehicle-treated mice at 4 and 24 h post injury.In cultured PC12 cells,DCPIB (10 μmol/L) significantly reduced OGD-induced cell death.Moreover,DCPIB (20 μmol/L) blocked hypotonic-induced decrease in [Clˉ]i in PC12 cells of both control and OGD groups.Conclusion:The results further support the pathophysiological role of VRACs in ischemic brain injury,and suggest DCPIB as a potential,easily administrable agent targeting VRACs in the context of perinatal and neonatal hypoxic-ischemic brain injury.

  1. The vacuolar Ca2+-activated channel TPC1 regulates germination and stomatal movement.

    Science.gov (United States)

    Peiter, Edgar; Maathuis, Frans J M; Mills, Lewis N; Knight, Heather; Pelloux, Jérôme; Hetherington, Alistair M; Sanders, Dale

    2005-03-17

    Cytosolic free calcium ([Ca2+]cyt) is a ubiquitous signalling component in plant cells. Numerous stimuli trigger sustained or transient elevations of [Ca2+]cyt that evoke downstream stimulus-specific responses. Generation of [Ca2+]cyt signals is effected through stimulus-induced opening of Ca2+-permeable ion channels that catalyse a flux of Ca2+ into the cytosol from extracellular or intracellular stores. Many classes of Ca2+ current have been characterized electrophysiologically in plant membranes. However, the identity of the ion channels that underlie these currents has until now remained obscure. Here we show that the TPC1 ('two-pore channel 1') gene of Arabidopsis thaliana encodes a class of Ca2+-dependent Ca2+-release channel that is known from numerous electrophysiological studies as the slow vacuolar channel. Slow vacuolar channels are ubiquitous in plant vacuoles, where they form the dominant conductance at micromolar [Ca2+]cyt. We show that a tpc1 knockout mutant lacks functional slow vacuolar channel activity and is defective in both abscisic acid-induced repression of germination and in the response of stomata to extracellular calcium. These studies unequivocally demonstrate a critical role of intracellular Ca2+-release channels in the physiological processes of plants. PMID:15772667

  2. UCP3 Regulates Single-Channel Activity of the Cardiac mCa1.

    Science.gov (United States)

    Motloch, Lukas J; Gebing, Tina; Reda, Sara; Schwaiger, Astrid; Wolny, Martin; Hoppe, Uta C

    2016-08-01

    Mitochondrial Ca(2+) uptake (mCa(2+) uptake) is thought to be mediated by the mitochondrial Ca(2+) uniporter (MCU). UCP2 and UCP3 belong to a superfamily of mitochondrial ion transporters. Both proteins are expressed in the inner mitochondrial membrane of the heart. Recently, UCP2 was reported to modulate the function of the cardiac MCU related channel mCa1. However, the possible role of UCP3 in modulating cardiac mCa(2+) uptake via the MCU remains inconclusive. To understand the role of UCP3, we analyzed cardiac mCa1 single-channel activity in mitoplast-attached single-channel recordings from isolated murine cardiac mitoplasts, from adult wild-type controls (WT), and from UCP3 knockout mice (UCP3(-/-)). Single-channel registrations in UCP3(-/-) confirmed a murine voltage-gated Ca(2+) channel, i.e., mCa1, which was inhibited by Ru360. Compared to WT, mCa1 in UCP3(-/-) revealed similar single-channel characteristics. However, in UCP3(-/-) the channel exhibited decreased single-channel activity, which was insensitive to adenosine triphosphate (ATP) inhibition. Our results suggest that beyond UCP2, UCP3 also exhibits regulatory effects on cardiac mCa1/MCU function. Furthermore, we speculate that UCP3 might modulate previously described inhibitory effects of ATP on mCa1/MCU activity as well.

  3. The Epithelial Calcium Channel TRPV5 Is Regulated Differentially by Klotho and Sialidase.

    NARCIS (Netherlands)

    Leunissen, E.H.P.; Nair, A.V.; Büll, C.; Lefeber, D.J.; Delft, F.L. van; Bindels, R.J.M.; Hoenderop, J.G.J.

    2013-01-01

    The transient receptor potential vanilloid type 5 (TRPV5) Ca(2+) channel facilitates transcellular Ca(2+) transport in the distal convoluted tubule (DCT) of the kidney. The channel is glycosylated with a complex type N-glycan and it has been postulated that hydrolysis of the terminal sialic acid(s)

  4. The sigma receptor as a ligand-regulated auxiliary potassium channel subunit.

    Science.gov (United States)

    Aydar, Ebru; Palmer, Christopher P; Klyachko, Vitaly A; Jackson, Meyer B

    2002-04-25

    The sigma receptor is a novel protein that mediates the modulation of ion channels by psychotropic drugs through a unique transduction mechanism depending neither on G proteins nor protein phosphorylation. The present study investigated sigma receptor signal transduction by reconstituting responses in Xenopus oocytes. Sigma receptors modulated voltage-gated K+ channels (Kv1.4 or Kv1.5) in different ways in the presence and absence of ligands. Association between Kv1.4 channels and sigma receptors was demonstrated by coimmunoprecipitation. These results indicate a novel mechanism of signal transduction dependent on protein-protein interactions. Domain accessibility experiments suggested a structure for the sigma receptor with two cytoplasmic termini and two membrane-spanning segments. The ligand-independent effects on channels suggest that sigma receptors serve as auxiliary subunits to voltage-gated K+ channels with distinct functional interactions, depending on the presence or absence of ligand.

  5. Nav1.5 cardiac sodium channels, regulation and clinical implications

    Directory of Open Access Journals (Sweden)

    Henry Humberto León-Ariza

    2014-10-01

    Full Text Available Voltage-gated sodium channels constitute a group of membrane proteins widely distributed thought the body. In the heart, there are at least six different isoforms, being the Nav1.5 the most abundant. The channel is composed of an α subunit that is formed by four domains of six segments each, and four much smaller β subunits that provide stability and integrate other channels into the α subunit. The function of the Nav1.5 channel is modulated by intracellular cytoskeleton proteins, extracellular proteins, calcium concentration, free radicals, and medications, among other things. The study of the channel and its alterations has grown thanks to its association with pathogenic conditions such as Long QT syndrome, Brugada syndrome, atrial fibrillation, arrhythmogenic ventricular dysplasia and complications during ischemic processes.

  6. Role of vascular potassium channels in the regulation of renal hemodynamics

    DEFF Research Database (Denmark)

    Sørensen, Charlotte Mehlin; Braunstein, Thomas Hartig; von Holstein-Rathlou, Niels-Henrik;

    2012-01-01

    of one or more classes of K+ channels will lead to a change in hemodynamic resistance and therefore of renal blood flow and glomerular filtration pressure. Through these effects, the activity of renal vascular K+ channels influences renal salt and water excretion, fluid homeostasis, and ultimately blood......K+ conductance is a major determinant of membrane potential (Vm) in vascular smooth muscle (VSMC) and endothelial cells (EC). The vascular tone is controlled by Vm through the action of voltage-operated Ca2+ channels (VOCC) in VSMC. Increased K+ conductance leads to hyperpolarization...... in K+ channel function, the role of renal vascular K+ channels in the control of salt and water excretion deserves attention....

  7. Regulation of the membrane insertion and conductance activity of the metamorphic chloride intracellular channel protein CLIC1 by cholesterol.

    Directory of Open Access Journals (Sweden)

    Stella M Valenzuela

    Full Text Available The Chloride Intracellular ion channel protein CLIC1 has the ability to spontaneously insert into lipid membranes from a soluble, globular state. The precise mechanism of how this occurs and what regulates this insertion is still largely unknown, although factors such as pH and redox environment are known contributors. In the current study, we demonstrate that the presence and concentration of cholesterol in the membrane regulates the spontaneous insertion of CLIC1 into the membrane as well as its ion channel activity. The study employed pressure versus area change measurements of Langmuir lipid monolayer films; and impedance spectroscopy measurements using tethered bilayer membranes to monitor membrane conductance during and following the addition of CLIC1 protein. The observed cholesterol dependent behaviour of CLIC1 is highly reminiscent of the cholesterol-dependent-cytolysin family of bacterial pore-forming proteins, suggesting common regulatory mechanisms for spontaneous protein insertion into the membrane bilayer.

  8. Ischemic postconditioning protects against ischemic brain injury by up-regulation of acid-sensing ion channel 2a

    Institute of Scientific and Technical Information of China (English)

    Wang-sheng Duanmu; Liu Cao; Jing-yu Chen; Hong-fei Ge; Rong Hu; Hua Feng

    2016-01-01

    Ischemic postconditioning renders brain tissue tolerant to brain ischemia, thereby alleviating ischemic brain injury. However, the exact mechanism of action is still unclear. In this study, a rat model of global brain ischemia was subjected to ischemic postconditioning treat-ment using the vessel occlusion method. After 2 hours of ischemia, the bilateral common carotid arteries were blocked immediately for 10 seconds and then perfused for 10 seconds. This procedure was repeated six times. Ischemic postconditioning was found to mitigate hippocampal CA1 neuronal damage in rats with brain ischemia, and up-regulate acid-sensing ion channel 2a expression at the mRNA and protein level. These ifndings suggest that ischemic postconditioning up-regulates acid-sensing ion channel 2a expression in the rat hippo-campus after global brain ischemia, which promotes neuronal tolerance to ischemic brain injury.

  9. S1-S3 counter charges in the voltage sensor module of a mammalian sodium channel regulate fast inactivation.

    Science.gov (United States)

    Groome, James R; Winston, Vern

    2013-05-01

    The movement of positively charged S4 segments through the electric field drives the voltage-dependent gating of ion channels. Studies of prokaryotic sodium channels provide a mechanistic view of activation facilitated by electrostatic interactions of negatively charged residues in S1 and S2 segments, with positive counterparts in the S4 segment. In mammalian sodium channels, S4 segments promote domain-specific functions that include activation and several forms of inactivation. We tested the idea that S1-S3 countercharges regulate eukaryotic sodium channel functions, including fast inactivation. Using structural data provided by bacterial channels, we constructed homology models of the S1-S4 voltage sensor module (VSM) for each domain of the mammalian skeletal muscle sodium channel hNaV1.4. These show that side chains of putative countercharges in hNaV1.4 are oriented toward the positive charge complement of S4. We used mutagenesis to define the roles of conserved residues in the extracellular negative charge cluster (ENC), hydrophobic charge region (HCR), and intracellular negative charge cluster (INC). Activation was inhibited with charge-reversing VSM mutations in domains I-III. Charge reversal of ENC residues in domains III (E1051R, D1069K) and IV (E1373K, N1389K) destabilized fast inactivation by decreasing its probability, slowing entry, and accelerating recovery. Several INC mutations increased inactivation from closed states and slowed recovery. Our results extend the functional characterization of VSM countercharges to fast inactivation, and support the premise that these residues play a critical role in domain-specific gating transitions for a mammalian sodium channel.

  10. Regulation of sodium channel function by bilayer elasticity: the importance of hydrophobic coupling. Effects of Micelle-forming amphiphiles and cholesterol

    DEFF Research Database (Denmark)

    Lundbæk, Jens August; Birn, Pia; Hansen, Anker J;

    2004-01-01

    kinetics of the protein conformational changes therefore will be regulated by the bilayer elasticity, which is determined by the lipid composition. This hydrophobic coupling mechanism has been studied extensively in gramicidin channels, where the channel-bilayer hydrophobic interactions link a...... "conformational" change (the monomerdimer transition) to an elastic bilayer deformation. Gramicidin channels thus are regulated by the lipid bilayer elastic properties (thickness, monolayer equilibrium curvature, and compression and bending moduli). To investigate whether this hydrophobic coupling mechanism could...... be a general mechanism regulating membrane protein function, we examined whether voltage-dependent skeletal-muscle sodium channels, expressed in HEK293 cells, are regulated by bilayer elasticity, as monitored using gramicidin A (gA) channels. Nonphysiological amphiphiles (beta...

  11. Regulation of KV channel voltage-dependent activation by transmembrane β subunits

    Directory of Open Access Journals (Sweden)

    Xiaohui eSun

    2012-04-01

    Full Text Available Voltage-activated K+ (KV channels are important for shaping action potentials and maintaining resting membrane potential in excitable cells. KV channels contain a central pore-gate domain (PGD surrounded by four voltage-sensing domains (VSD. The VSDs will change conformation in response to alterations of the membrane potential thereby inducing the opening of the PGD. Many KV channels are heteromeric protein complexes containing auxiliary β subunits. These β subunits modulate channel expression and activity to increase functional diversity and render tissue specific phenotypes. This review focuses on the KV β subunits that contain transmembrane (TM segments including the KCNE family and the β subunits of large conductance, Ca2+- and voltage-activated K+ (BK channels. These TM β subunits affect the voltage-dependent activation of KV α subunits. Experimental and computational studies have described the structural location of these β subunits in the channel complexes and the biophysical effects on VSD activation, PGD opening and VSD-PGD coupling. These results reveal some common characteristics and mechanistic insights into KV channel modulation by TM β subunits.

  12. High-density interspecific genetic linkage mapping provides insights into genomic incompatibility between channel catfish and blue catfish.

    Science.gov (United States)

    Liu, S; Li, Y; Qin, Z; Geng, X; Bao, L; Kaltenboeck, L; Kucuktas, H; Dunham, R; Liu, Z

    2016-02-01

    Catfish is the leading aquaculture species in the United States. The interspecific hybrid catfish produced by mating female channel catfish with male blue catfish outperform both of their parent species in a number of traits. However, mass production of the hybrids has been difficult because of reproductive isolation. Investigations of genome structure and organization of the hybrids provide insights into the genetic basis for maintenance of species divergence in the face of gene flow, thereby helping develop strategies for introgression and efficient production of the hybrids for aquaculture. In this study, we constructed a high-density genetic linkage map using the hybrid catfish system with the catfish 250K SNP array. A total of 26,238 SNPs were mapped to 29 linkage groups, with 12,776 unique marker positions. The linkage map spans approximately 3240 cM with an average intermarker distance of 0.25 cM. A fraction of markers (986 of 12,776) exhibited significant deviation from the expected Mendelian ratio of segregation, and they were clustered in major genomic blocks across 15 LGs, most notably LG9 and LG15. The distorted markers exhibited significant bias for maternal alleles among the backcross progenies, suggesting strong selection against the blue catfish alleles. The clustering of distorted markers within genomic blocks should lend insights into speciation as marked by incompatibilities between the two species. Such findings should also have profound implications for understanding the genomic evolution of closely related species as well as the introgression of hybrid production programs in aquaculture.

  13. BK channels regulate sinoatrial node firing rate and cardiac pacing in vivo.

    Science.gov (United States)

    Lai, Michael H; Wu, Yuejin; Gao, Zhan; Anderson, Mark E; Dalziel, Julie E; Meredith, Andrea L

    2014-11-01

    Large-conductance Ca(2+)- and voltage-activated K(+) (BK) channels play prominent roles in shaping muscle and neuronal excitability. In the cardiovascular system, BK channels promote vascular relaxation and protect against ischemic injury. Recently, inhibition of BK channels has been shown to lower heart rate in intact rodents and isolated hearts, suggesting a novel role in heart function. However, the underlying mechanism is unclear. In the present study, we recorded ECGs from mice injected with paxilline (PAX), a membrane-permeable BK channel antagonist, and examined changes in cardiac conduction. ECGs revealed a 19 ± 4% PAX-induced reduction in heart rate in wild-type but not BK channel knockout (Kcnma1(-/-)) mice. The heart rate decrease was associated with slowed cardiac pacing due to elongation of the sinus interval. Action potential firing recorded from isolated sinoatrial node cells (SANCs) was reduced by 55 ± 15% and 28 ± 9% by application of PAX (3 μM) and iberiotoxin (230 nM), respectively. Furthermore, baseline firing rates from Kcnma1(-/-) SANCs were 33% lower than wild-type SANCs. The slowed firing upon BK current inhibition or genetic deletion was due to lengthening of the diastolic depolarization phase of the SANC action potential. Finally, BK channel immunoreactivity and PAX-sensitive currents were identified in SANCs with HCN4 expression and pacemaker current, respectively, and BK channels cloned from SANCs recapitulated similar activation as the PAX-sensitive current. Together, these data localize BK channels to SANCs and demonstrate that loss of BK current decreases SANC automaticity, consistent with slowed sinus pacing after PAX injection in vivo. Furthermore, these findings suggest BK channels are potential therapeutic targets for disorders of heart rate.

  14. 75 FR 61096 - Regulated Navigation Area; Reserved Channel, Boston Harbor, Boston, MA

    Science.gov (United States)

    2010-10-04

    ... Harbor, Boston, MA AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is... Navigation Areas: Reserved Channel, Boston Harbor, Boston, MA (a) Location. The following areas are...

  15. Novel role of KCNQ2/3 channels in regulating neuronal cell viability

    OpenAIRE

    Zhou, X.; Wei, J; Song, M; Francis, K.; Yu, S. P.

    2010-01-01

    Overactivation of certain K+ channels can mediate excessive K+ efflux and intracellular K+ depletion, which are early ionic events in apoptotic cascade. The present investigation examined a possible role of the KCNQ2/3 channel or M-channel (also named Kv7.2/7.3 channels) in the pro-apoptotic process. Whole-cell recordings detected much larger M-currents (212±31 pA or 10.5±1.5 pA/pF) in cultured hippocampal neurons than that in cultured cortical neurons (47±21 pA or 2.4±0.8 pA/pF). KCNQ2/3 cha...

  16. Primers on molecular pathways - ion channels: key regulators of pancreatic physiology

    OpenAIRE

    Banales, J.M. (Jesús M.); Gradilone, S.A. (Sergio A.)

    2009-01-01

    Ion transport across the cellular plasma membrane is important in almost every physiological process. This phenomenon is driven by the coordinated action of carriers, pumps and channels, which move ions in and out the cells and between different organelles. Ion channels are transmembrane proteins that provide a continuous aqueous pore through which ions can selectively move. The interest in these molecules has increased due to the recognition of diverse pathologies related with mutations in g...

  17. Cardiac ATP-sensitive K+ channels. Evidence for preferential regulation by glycolysis

    OpenAIRE

    1989-01-01

    The ability of glycolysis, oxidative phosphorylation, the creatine kinase system, and exogenous ATP to suppress ATP-sensitive K+ channels and prevent cell shortening were compared in patch-clamped single guinea pig ventricular myocytes. In cell-attached patches on myocytes permeabilized at one end with saponin, ATP-sensitive K+ channels were activated by removing ATP from the bath, and could be closed equally well by exogenous ATP or substrates for endogenous ATP production by glycolysis (wit...

  18. The Sarcoglycan complex is expressed in the cerebrovascular system and is specifically regulated by astroglial Cx30 channels

    Directory of Open Access Journals (Sweden)

    Anne-Cécile eBoulay

    2015-02-01

    Full Text Available Astrocytes, the most prominent glial cell type in the brain, send specialized processes called endfeet, around blood vessels and express a large molecular repertoire regulating the cerebrovascular system physiology. One of the most striking properties of astrocyte endfeet is their enrichment in gap junction protein Connexin 43 and 30 (Cx43 and Cx30 allowing in particular for direct intercellular trafficking of ions and small signaling molecules through perivascular astroglial networks. In this study, we addressed the specific role of Cx30 at the gliovascular interface. Using an inactivation mouse model for Cx30 (Cx30Δ/Δ, we showed that absence of Cx30 does not affect blood-brain barrier (BBB organization and permeability. However, it results in the cerebrovascular fraction, in a strong upregulation of Sgcg encoding γ-Sarcoglycan (SG, a member of the Dystrophin-associated protein complex (DAPC connecting cytoskeleton and the extracellular matrix. The same molecular event occurs in Cx30T5M/T5M mutated mice, where Cx30 channels are closed, demonstrating that Sgcg regulation relied on Cx30 channel functions. We further characterized the expression of other Sarcoglycan complex (SGC molecules in the cerebrovascular system and showed the presence of α-, β-, δ-, γ-, ε- and ζ- SG, as well as Sarcospan. Their expression was however not modified in Cx30Δ/Δ. These results suggest that a full SGC might be present in the cerebrovascular system, and that expression of one of its member, γ-Sarcoglycan, depends on Cx30 channels. As described in skeletal muscles, the SGC may contribute to membrane stabilization and signal transduction in the cerebrovascular system, which may therefore be regulated by Cx30 channel-mediated functions.

  19. KV7 channels regulate muscle tone and nonadrenergic noncholinergic relaxation of the rat gastric fundus.

    Science.gov (United States)

    Ipavec, V; Martire, M; Barrese, V; Taglialatela, M; Currò, D

    2011-10-01

    Voltage-dependent type 7 K+ (KV7) channels play important physiological roles in neurons and muscle cells. The aims of the present study were to investigate the motor effects of KV7 channel modulators in the rat gastric fundus and the expression of KV7 channels in this tissue. Muscle tone and electrical field stimulation (EFS)-evoked relaxations of precontracted longitudinal muscle strips of the rat gastric fundus were investigated under nonadrenergic noncholinergic conditions by organ bath studies. Gene expression was studied by real-time PCR and tissue localization of channels was investigated by immunohistochemistry. The KV7 channel blocker XE-991 induced concentration-dependent contractions, with mean pD2 and Emax of 5.4 and 48% of the maximal U46619-induced contraction, respectively. The KV7 channel activators retigabine and flupirtine concentration-dependently relaxed U46619-precontracted strips, with pD2s of 4.7 and 4.4 and Emax of 93% and 91% of the maximal relaxation induced by papaverine, respectively. XE-991 concentration-dependently inhibited retigabine-induced relaxation with a pIC50 of 6.2. XE-991 and DMP-543, another KV7 channel blocker, increased by 13-25% or reduced by 11-21% the relaxations evoked by low- or high-frequency EFS, respectively. XE-991 also reduced the relaxation induced by vasoactive intestinal polypeptide (VIP) by 33% of controls. Transcripts encoded by all KV7 genes were detected in the fundus, with 7.4 and 7.5 showing the highest expression levels. KV7.4 and 7.5 channels were visualized by confocal immunofluorescence in both circular and longitudinal muscle layers. In conclusion, in the rat proximal stomach, KV7 channels appear to contribute to the resting muscle tone and to VIP- and high-frequency EFS-induced relaxation. KV7 channel activators could be useful relaxant agents of the gastric smooth muscle. PMID:21740972

  20. Power lateral pnp transistor operating with high current density in irradiated voltage regulator

    Directory of Open Access Journals (Sweden)

    Vukić Vladimir Đ.

    2013-01-01

    Full Text Available The operation of power lateral pnp transistors in gamma radiation field was examined by detection of the minimum dropout voltage on heavily loaded low-dropout voltage regulators LM2940CT5, clearly demonstrating their low radiation hardness, with unacceptably low values of output voltage and collector-emitter voltage volatility. In conjunction with previous results on base current and forward emitter current gain of serial transistors, it was possible to determine the positive influence of high load current on a slight improvement of voltage regulator LM2940CT5 radiation hardness. The high-current flow through the wide emitter aluminum contact of the serial transistor above the isolation oxide caused intensive annealing of the positive oxide-trapped charge, leading to decrease of the lateral pnp transistor's current gain, but also a more intensive recovery of the small-signal npn transistors in the control circuit. The high current density in the base area of the lateral pnp transistor immediately below the isolation oxide decreased the concentration of negative interface traps. Consequently, the positive influence of the reduced concentration of the oxide-trapped charge on the negative feedback reaction circuit, together with the favourable effect of reduced interface traps concentration, exceeded negative influence of the annealed oxide-trapped charge on the serial pnp transistor's forward emitter current gain.

  1. Sildenafil prevents the up-regulation of transient receptor potential canonical channels in the development of cardiomyocyte hypertrophy

    Energy Technology Data Exchange (ETDEWEB)

    Kiso, Hironori [Department of Internal Medicine, Division of Cardiovascular and Respiratory Medicine, Akita University Graduate School of Medicine (Japan); Ohba, Takayoshi [Department of Cell Physiology, Akita University Graduate School of Medicine (Japan); Iino, Kenji; Sato, Kazuhiro; Terata, Yutaka [Department of Internal Medicine, Division of Cardiovascular and Respiratory Medicine, Akita University Graduate School of Medicine (Japan); Murakami, Manabu [Department of Pharmacology, Hirosaki University Graduate School of Medicine (Japan); Ono, Kyoichi [Department of Cell Physiology, Akita University Graduate School of Medicine (Japan); Watanabe, Hiroyuki, E-mail: hirow@doc.med.akita-u.ac.jp [Department of Internal Medicine, Division of Cardiovascular and Respiratory Medicine, Akita University Graduate School of Medicine (Japan); Ito, Hiroshi [Department of Internal Medicine, Division of Cardiovascular and Respiratory Medicine, Akita University Graduate School of Medicine (Japan)

    2013-07-05

    Highlights: •Transient receptor potential canonical (TRPC1, 3 and 6) are up-regulated by ET-1. •Sildenafil inhibited hypertrophic responses (BNP, Ca entry, NFAT activation). •Sildenafil suppressed TRPC1, 3 and 6 expression. -- Abstract: Background: Transient receptor potential canonical (TRPCs) channels are up-regulated in the development of cardiac hypertrophy. Sildenafil inhibits TRPC6 activation and expression, leading to the prevention of cardiac hypertrophy. However, the effects of sildenafil on the expression of other TRPCs remain unknown. We hypothesized that in addition to its effects of TRPC6, sildenafil blocks the up-regulation of other TRPC channels to suppress cardiomyocyte hypertrophy. Methods and results: In cultured neonatal rat cardiomyocytes, a 48 h treatment with 10 nM endothelin (ET)-1 induced hypertrophic responses characterized by nuclear factor of activated T cells activation and enhancement of brain natriuretic peptide expression and cell surface area. Co-treatment with sildenafil (1 μM, 48 h) inhibited these ET-1-induced hypertrophic responses. Although ET-1 enhanced the gene expression of TRPCs, sildenafil inhibited the enhanced gene expression of TRPC1, C3 and C6. Moreover, co-treatment with sildenafil abolished the augmentation of SOCE in the hypertrophied cardiomyocytes. Conclusions: These results suggest that sildenafil inhibits cardiomyocyte hypertrophy by suppressing the up-regulation of TRPC expression.

  2. PLC-mediated PI(4,5)P2 hydrolysis regulates activation and inactivation of TRPC6/7 channels.

    Science.gov (United States)

    Itsuki, Kyohei; Imai, Yuko; Hase, Hideharu; Okamura, Yasushi; Inoue, Ryuji; Mori, Masayuki X

    2014-02-01

    Transient receptor potential classical (or canonical) (TRPC)3, TRPC6, and TRPC7 are a subfamily of TRPC channels activated by diacylglycerol (DAG) produced through the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) by phospholipase C (PLC). PI(4,5)P2 depletion by a heterologously expressed phosphatase inhibits TRPC3, TRPC6, and TRPC7 activity independently of DAG; however, the physiological role of PI(4,5)P2 reduction on channel activity remains unclear. We used Förster resonance energy transfer (FRET) to measure PI(4,5)P2 or DAG dynamics concurrently with TRPC6 or TRPC7 currents after agonist stimulation of receptors that couple to Gq and thereby activate PLC. Measurements made at different levels of receptor activation revealed a correlation between the kinetics of PI(4,5)P2 reduction and those of receptor-operated TRPC6 and TRPC7 current activation and inactivation. In contrast, DAG production correlated with channel activation but not inactivation; moreover, the time course of channel inactivation was unchanged in protein kinase C-insensitive mutants. These results suggest that inactivation of receptor-operated TRPC currents is primarily mediated by the dissociation of PI(4,5)P2. We determined the functional dissociation constant of PI(4,5)P2 to TRPC channels using FRET of the PLCδ Pleckstrin homology domain (PHd), which binds PI(4,5)P2, and used this constant to fit our experimental data to a model in which channel gating is controlled by PI(4,5)P2 and DAG. This model predicted similar FRET dynamics of the PHd to measured FRET in either human embryonic kidney cells or smooth muscle cells, whereas a model lacking PI(4,5)P2 regulation failed to reproduce the experimental data, confirming the inhibitory role of PI(4,5)P2 depletion on TRPC currents. Our model also explains various PLC-dependent characteristics of channel activity, including limitation of maximum open probability, shortening of the peak time, and the bell-shaped response of total

  3. Effects of hatchery fish density on emigration, growth, survival, and predation risk of natural steelhead parr in an experimental stream channel

    Science.gov (United States)

    Tatara, Christopher P.; Riley, Stephen C.; Berejikian, Barry A.

    2011-01-01

    Hatchery supplementation of steelhead Oncorhynchus mykiss raises concerns about the impacts on natural populations, including reduced growth and survival, displacement, and increased predation. The potential risks may be density dependent.We examined how hatchery stocking density and the opportunity to emigrate affect the responses of natural steelhead parr in an experimental stream channel and after 15 d found no density-dependent effects on growth, emigration, or survival at densities ranging from 1-6 hatchery parr/m2. The opportunity for steelhead parr to emigrate reduced predation by coastal cutthroat trout O. clarkii clarkii on both hatchery and natural steelhead parr. The cutthroat trout exhibited a type-I functional response (constant predation rate with increased prey density) for the hatchery and composite populations. In contrast, the predation rate on natural parr decreased as hatchery stocking density increased. Supplementation with hatchery parr at any experimental stocking density reduced the final natural parr density. This decline was explained by increased emigration fromthe supplemented groups. Natural parr had higher mean instantaneous growth rates than hatchery parr. The proportion of parr emigrating decreased as parr size increased over successive experimental trials. Smaller parr had lower survival and suffered higher predation. The final density of the composite population, a measure of supplementation effectiveness, increased with the hatchery steelhead stocking rate. Our results indicate that stocking larger hatchery parr (over 50 d postemergence) at densities within the carrying capacity would have low short-term impact on the growth, survival, and emigration of natural parr while increasing the density of the composite population; in addition, a stocking density greater than 3 fish/m2 might be a good starting point for the evaluation of parr stocking in natural streams.

  4. Definitive Endoderm Formation from Plucked Human Hair-Derived Induced Pluripotent Stem Cells and SK Channel Regulation

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    Anett Illing

    2013-01-01

    Full Text Available Pluripotent stem cells present an extraordinary powerful tool to investigate embryonic development in humans. Essentially, they provide a unique platform for dissecting the distinct mechanisms underlying pluripotency and subsequent lineage commitment. Modest information currently exists about the expression and the role of ion channels during human embryogenesis, organ development, and cell fate determination. Of note, small and intermediate conductance, calcium-activated potassium channels have been reported to modify stem cell behaviour and differentiation. These channels are broadly expressed throughout human tissues and are involved in various cellular processes, such as the after-hyperpolarization in excitable cells, and also in differentiation processes. To this end, human induced pluripotent stem cells (hiPSCs generated from plucked human hair keratinocytes have been exploited in vitro to recapitulate endoderm formation and, concomitantly, used to map the expression of the SK channel (SKCa subtypes over time. Thus, we report the successful generation of definitive endoderm from hiPSCs of ectodermal origin using a highly reproducible and robust differentiation system. Furthermore, we provide the first evidence that SKCas subtypes are dynamically regulated in the transition from a pluripotent stem cell to a more lineage restricted, endodermal progeny.

  5. Analysis of the impact of coolant density variations in the high efficiency channel of a pressure tube super critical water reactor

    International Nuclear Information System (INIS)

    The Pressure Tube (PT) Supercritical Water Reactor (SCWR) is based on a light water coolant operating at pressures above the thermodynamic critical pressure; a separate low temperature and low pressure moderator. The coolant density changes by an order of magnitude depending on its local enthalpy in the porous ceramic insulator tube. This causes significant changes in the neutron transport characteristics, axially and radially, in the fuel channel. This work performs lattice physics calculations for a 78-element Pu-Th fuel at zero burnup and examines the effect of assumptions related to coolant density in the radial direction of a HEC, using the neutron transport code WIMS-AECL. (author)

  6. Estrogens and human papilloma virus oncogenes regulate human ether-à-go-go-1 potassium channel expression.

    Science.gov (United States)

    Díaz, Lorenza; Ceja-Ochoa, Irais; Restrepo-Angulo, Iván; Larrea, Fernando; Avila-Chávez, Euclides; García-Becerra, Rocío; Borja-Cacho, Elizabeth; Barrera, David; Ahumada, Elías; Gariglio, Patricio; Alvarez-Rios, Elizabeth; Ocadiz-Delgado, Rodolfo; Garcia-Villa, Enrique; Hernández-Gallegos, Elizabeth; Camacho-Arroyo, Ignacio; Morales, Angélica; Ordaz-Rosado, David; García-Latorre, Ethel; Escamilla, Juan; Sánchez-Peña, Luz Carmen; Saqui-Salces, Milena; Gamboa-Dominguez, Armando; Vera, Eunice; Uribe-Ramírez, Marisela; Murbartián, Janet; Ortiz, Cindy Sharon; Rivera-Guevara, Claudia; De Vizcaya-Ruiz, Andrea; Camacho, Javier

    2009-04-15

    Ether-à-go-go-1 (Eag1) potassium channels are potential tools for detection and therapy of numerous cancers. Here, we show human Eag1 (hEag1) regulation by cancer-associated factors. We studied hEag1 gene expression and its regulation by estradiol, antiestrogens, and human papillomavirus (HPV) oncogenes (E6/E7). Primary cultures from normal placentas and cervical cancer tissues; tumor cell lines from cervix, choriocarcinoma, keratinocytes, and lung; and normal cell lines from vascular endothelium, keratinocytes, and lung were used. Reverse transcription-PCR (RT-PCR) experiments and Southern blot analysis showed Eag1 expression in all of the cancer cell types, normal trophoblasts, and vascular endothelium, in contrast to normal keratinocytes and lung cells. Estradiol and antiestrogens regulated Eag1 in a cell type-dependent manner. Real-time RT-PCR experiments in HeLa cells showed that Eag1 estrogenic regulation was strongly associated with the expression of estrogen receptor-alpha. Eag1 protein was detected by monoclonal antibodies in normal placenta and placental blood vessels. Patch-clamp recordings in normal trophoblasts treated with estradiol exhibited potassium currents resembling Eag1 channel activity. Eag1 gene expression in keratinocytes depended either on cellular immortalization or the presence of HPV oncogenes. Eag1 protein was found in keratinocytes transfected with E6/E7 HPV oncogenes. Cell proliferation of E6/E7 keratinocytes was decreased by Eag1 antibodies inhibiting channel activity and by the nonspecific Eag1 inhibitors imipramine and astemizole; the latter also increased apoptosis. Our results propose novel oncogenic mechanisms of estrogen/antiestrogen use and HPV infection. We also suggest Eag1 as an early indicator of cell proliferation leading to malignancies and a therapeutic target at early stages of cellular hyperproliferation. PMID:19351862

  7. Hydrogen Sulfide Regulates Inward-Rectifying K+ Channels in Conjunction with Stomatal Closure1[OPEN

    Science.gov (United States)

    Papanatsiou, Maria; Scuffi, Denisse; Blatt, Michael R.; García-Mata, Carlos

    2015-01-01

    Hydrogen sulfide (H2S) is the third biological gasotransmitter, and in animals, it affects many physiological processes by modulating ion channels. H2S has been reported to protect plants from oxidative stress in diverse physiological responses. H2S closes stomata, but the underlying mechanism remains elusive. Here, we report the selective inactivation of current carried by inward-rectifying K+ channels of tobacco (Nicotiana tabacum) guard cells and show its close parallel with stomatal closure evoked by submicromolar concentrations of H2S. Experiments to scavenge H2S suggested an effect that is separable from that of abscisic acid, which is associated with water stress. Thus, H2S seems to define a unique and unresolved signaling pathway that selectively targets inward-rectifying K+ channels. PMID:25770153

  8. Regulation of gap junction channels by infectious agents and inflammation in the CNS

    Directory of Open Access Journals (Sweden)

    Paul eCastellano

    2014-05-01

    Full Text Available Gap junctions are conglomerates of intercellular channels that connect the cytoplasm of two or more cells, and facilitate the transfer of second messengers, small peptides and RNA resulting in metabolic and electrical coordination. In general, loss of gap junctional communication (GJC has been associated with cellular damage and inflammation resulting in compromise of physiological functions. Recently, it has become evident that gap junction channels also play a critical role in the pathogenesis of infectious diseases and associated inflammation. Several pathogens use the transfer of intracellular signals through GJ channels to spread infection and toxic signals that amplify inflammation to neighboring cells. Thus, identification of the mechanisms by which several infectious agents alter GJC could result in new potential therapeutic approaches to reduce inflammation and their pathogenesis.

  9. SPAK and OSR1 Dependent Down-Regulation of Murine Renal Outer Medullary K+ Channel ROMK1

    Directory of Open Access Journals (Sweden)

    Bernat Elvira

    2014-09-01

    Full Text Available Background/Aims: The kinases SPAK (SPS1-related proline/alanine-rich kinase and OSR1 (oxidative stress-responsive kinase 1 participate in the regulation of the NaCl cotransporter NCC and the Na+,K+,2Cl- cotransporter NKCC2. The kinases are regulated by WNK (with-no-K[Lys] kinases. Mutations of genes encoding WNK kinases underly Gordon's syndrome, a monogenic disease leading to hypertension and hyperkalemia. WNK kinases further regulate the renal outer medullary K+ channel ROMK1. The present study explored, whether SPAK and/or OSR1 have similarly the potential to modify the activity of ROMK1. Methods: ROMK1 was expressed in Xenopus oocytes with or without additional expression of wild-type SPAK, constitutively active T233ESPAK, catalytically inactive D212ASPAK, wild-type OSR1, constitutively active T185EOSR1 and catalytically inactive D164AOSR1. Channel activity was determined utilizing dual electrode voltage clamp and ROMK1 protein abundance in the cell membrane utilizing chemiluminescence of ROMK1 containing an extracellular hemagglutinin epitope (ROMK1-HA. Results: ROMK1 activity and ROMK1-HA protein abundance were significantly down-regulated by wild-type SPAK and T233ESPAK, but not by D212ASPAK. Similarly, ROMK1 activity and ROMK1-HA protein abundance were significantly down-regulated by wild-type OSR1 and T185EOSR1, but not by D164AOSR1. Conclusion: ROMK1 protein abundance and activity are down-regulated by SPAK and OSR1.

  10. Distribution of Water Channel Protein RWC3 and Its Regulation by GA and Sucrose in Rice (Oryza sativa)

    Institute of Scientific and Technical Information of China (English)

    SUNMei-Hao; ZHANGMin-Hua; LIUHong-Yan; LILe-Gong; YUXin; SUWei-Ai; TANGZhang-Cheng

    2004-01-01

    Water channel proteins facilitate water flux across cell membranes and play important roles in plant growth and development. By GUS histochemical assay in RWC3 promoter-GUS transgenic rice (Oryza sativa L. cv. Shenxiangjin 4), one of the members of water channel proteins in rice, RWC3, was found to distribute widely in variety of organs, from vegetative and reproductive organs. Further studies showed that gibberellin (GA) enhanced the GUS activity in the transgenic calli, suspension cells and leaves, whereas ancymidol (anc), an inhibitor of GA synthesis, reduced the GUS activity. Sucrose was found to inhibit the effects induced by addition of GA, suggesting a possible cross-talk between GA and sucrose signaling on regulation of the RWC3 gene expression.

  11. Calcium homeostasis and cone signaling are regulated by interactions between calcium stores and plasma membrane ion channels.

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    Tamas Szikra

    Full Text Available Calcium is a messenger ion that controls all aspects of cone photoreceptor function, including synaptic release. The dynamic range of the cone output extends beyond the activation threshold for voltage-operated calcium entry, suggesting another calcium influx mechanism operates in cones hyperpolarized by light. We have used optical imaging and whole-cell voltage clamp to measure the contribution of store-operated Ca(2+ entry (SOCE to Ca(2+ homeostasis and its role in regulation of neurotransmission at cone synapses. Mn(2+ quenching of Fura-2 revealed sustained divalent cation entry in hyperpolarized cones. Ca(2+ influx into cone inner segments was potentiated by hyperpolarization, facilitated by depletion of intracellular Ca(2+ stores, unaffected by pharmacological manipulation of voltage-operated or cyclic nucleotide-gated Ca(2+ channels and suppressed by lanthanides, 2-APB, MRS 1845 and SKF 96365. However, cation influx through store-operated channels crossed the threshold for activation of voltage-operated Ca(2+ entry in a subset of cones, indicating that the operating range of inner segment signals is set by interactions between store- and voltage-operated Ca(2+ channels. Exposure to MRS 1845 resulted in approximately 40% reduction of light-evoked postsynaptic currents in photopic horizontal cells without affecting the light responses or voltage-operated Ca(2+ currents in simultaneously recorded cones. The spatial pattern of store-operated calcium entry in cones matched immunolocalization of the store-operated sensor STIM1. These findings show that store-operated channels regulate spatial and temporal properties of Ca(2+ homeostasis in vertebrate cones and demonstrate their role in generation of sustained excitatory signals across the first retinal synapse.

  12. Insight into the molecular regulation of the epithelial magnesium channel TRPM6.

    NARCIS (Netherlands)

    Cao, G.; Hoenderop, J.G.J.; Bindels, R.J.M.

    2008-01-01

    PURPOSE OF REVIEW: Recent studies have greatly increased our knowledge concerning the molecular mechanisms of renal magnesium handling. This review highlights the functional features of the newly identified transient receptor potential channel melastatin subtype 6 (TRPM6), which forms the gatekeeper

  13. Role of KATP channels in the regulation of rat dura and pia artery diameter

    DEFF Research Database (Denmark)

    Gozalov, A.; Petersen, K.A.; Mortensen, C.;

    2005-01-01

    The aim of the present study was to examine the effect of K(ATP) channel openers pinacidil and levcromakalim on rat dural and pial arteries as well as their inhibition by glibenclamide. We used an in-vivo genuine closed cranial window model and an in-vitro organ bath. Glibenclamide alone reduced ...

  14. Critical contribution of KV1 channels to the regulation of coronary blood flow.

    Science.gov (United States)

    Goodwill, Adam G; Noblet, Jillian N; Sassoon, Daniel; Fu, Lijuan; Kassab, Ghassan S; Schepers, Luke; Herring, B Paul; Rottgen, Trey S; Tune, Johnathan D; Dick, Gregory M

    2016-09-01

    Ion channels in smooth muscle control coronary vascular tone, but the identity of the potassium channels involved requires further investigation. The purpose of this study was to evaluate the functional role of KV1 channels on porcine coronary blood flow using the selective antagonist correolide. KV1 channel gene transcripts were found in porcine coronary arteries, with KCNA5 (encoding KV1.5) being most abundant (P muscle layer of both porcine and human coronary arteries, including microvessels. Whole-cell patch-clamp experiments demonstrated significant correolide-sensitive (1-10 µM) current in coronary smooth muscle. In vivo studies included direct intracoronary infusion of vehicle or correolide into a pressure-clamped left anterior descending artery of healthy swine (n = 5 in each group) with simultaneous measurement of coronary blood flow. Intracoronary correolide (~0.3-3 µM targeted plasma concentration) had no effect on heart rate or systemic pressure, but reduced coronary blood flow in a dose-dependent manner (P metabolic vasodilation and intracoronary correolide (3 µM) significantly reduced coronary blood flow at any given level of myocardial oxygen consumption (P metabolism and transient ischemia. PMID:27496159

  15. Expression of inwardly rectifying potassium channels (GIRKs and beta-adrenergic regulation of breast cancer cell lines

    Directory of Open Access Journals (Sweden)

    Cakir Yavuz

    2004-12-01

    Full Text Available Abstract Background Previous research has indicated that at various organ sites there is a subset of adenocarcinomas that is regulated by beta-adrenergic and arachidonic acid-mediated signal transduction pathways. We wished to determine if this regulation exists in breast adenocarcinomas. Expression of mRNA that encodes a G-protein coupled inwardly rectifying potassium channel (GIRK1 has been shown in tissue samples from approximately 40% of primary human breast cancers. Previously, GIRK channels have been associated with beta-adrenergic signaling. Methods Breast cancer cell lines were screened for GIRK channels by RT-PCR. Cell cultures of breast cancer cells were treated with beta-adrenergic agonists and antagonists, and changes in gene expression were determined by both relative competitive and real time PCR. Potassium flux was determined by flow cytometry and cell signaling was determined by western blotting. Results Breast cancer cell lines MCF-7, MDA-MB-361 MDA-MB 453, and ZR-75-1 expressed mRNA for the GIRK1 channel, while MDA-MB-468 and MDA-MB-435S did not. GIRK4 was expressed in all six breast cancer cell lines, and GIRK2 was expressed in all but ZR-75-1 and MDA-MB-435. Exposure of MDA-MB-453 cells for 6 days to the beta-blocker propranolol (1 μM increased the GIRK1 mRNA levels and decreased beta2-adrenergic mRNA levels, while treatment for 30 minutes daily for 7 days had no effect. Exposure to a beta-adrenergic agonist and antagonist for 24 hours had no effect on gene expression. The beta adrenergic agonist, formoterol hemifumarate, led to increases in K+ flux into MDA-MB-453 cells, and this increase was inhibited by the GIRK channel inhibitor clozapine. The tobacco carcinogen 4-(methylnitrosamino-1-(3-pyridyl-1-butanone (NNK, a high affinity agonist for beta-adrenergic receptors stimulated activation of Erk 1/2 in MDA-MB-453 cells. Conclusions Our data suggests β-adrenergic receptors and GIRK channels may play a role in breast cancer.

  16. Dynamic regulation of mechanosensitive channels: capacitance used to monitor patch tension in real time

    Science.gov (United States)

    Suchyna, Thomas M.; Besch, Steven R.; Sachs, Frederick

    2004-03-01

    All cells, from bacteria to human, are mechanically sensitive. The most rapid of these membrane protein transducers are mechanosensitive ion channels, ionic pores in the membrane that open and close in response to membrane tension. In specific sensory organs, these channels serve the senses of touch and hearing, and inform the central nervous system about the filling of hollow organs such as the bladder. Non-specialized cells use these channels to report on changes in cell volume and local strain. To preserve dynamic sensitivity, sensory receptors adapt to steady-state stimuli. Here we show that in rat astrocytes, the most abundant cells in the brain, this apparent adaptation to the stimulus is actually an inactivation. We have been able to track the time course of local strain by measuring attofarad changes in membrane capacitance and show that it is not correlated with loss of channel activity. The reduction in current with time is caused by an increased occupancy of low conductance states, and a reduction in the probability of opening, not a relaxation of local stress. The occupancy of these substates depends on the integrity of the cell's cytoplasm. However, while disruption of the cytoskeleton leads to a loss of inactivation, it leaves activation unaffected. The activation process is voltage-insensitive, closely correlated with changes in capacitance, and seems to arise solely from stress in the bilayer. The inactivation rate decreases with depolarization, and kinetic analysis suggests that the process involves multiple cytoplasmic ligands. Surprisingly, multivalent ions such as Gd+3 and Ca+2 that bind to the lipids and affect channel gating, do not affect the strain-induced increase in membrane capacitance; contrary to expectations, membrane elasticity is unchanged.

  17. TRPC1 regulates calcium-activated chloride channels in salivary gland cells.

    Science.gov (United States)

    Sun, Yuyang; Birnbaumer, Lutz; Singh, Brij B

    2015-11-01

    Calcium-activated chloride channel (CaCC) plays an important role in modulating epithelial secretion. It has been suggested that in salivary tissues, sustained fluid secretion is dependent on Ca(2+) influx that activates ion channels such as CaCC to initiate Cl(-) efflux. However direct evidence as well as the molecular identity of the Ca(2+) channel responsible for activating CaCC in salivary tissues is not yet identified. Here we provide evidence that in human salivary cells, an outward rectifying Cl(-) current was activated by increasing [Ca(2+)]i, which was inhibited by the addition of pharmacological agents niflumic acid (NFA), an antagonist of CaCC, or T16Ainh-A01, a specific TMEM16a inhibitor. Addition of thapsigargin (Tg), that induces store-depletion and activates TRPC1-mediated Ca(2+) entry, potentiated the Cl(-) current, which was inhibited by the addition of a non-specific TRPC channel blocker SKF96365 or removal of external Ca(2+). Stimulation with Tg also increased plasma membrane expression of TMEM16a protein, which was also dependent on Ca(2+) entry. Importantly, in salivary cells, TRPC1 silencing, but not that of TRPC3, inhibited CaCC especially upon store depletion. Moreover, primary acinar cells isolated from submandibular gland also showed outward rectifying Cl(-) currents upon increasing [Ca(2+)]i. These Cl(-) currents were again potentiated with the addition of Tg, but inhibited in the presence of T16Ainh-A01. Finally, acinar cells isolated from the submandibular glands of TRPC1 knockout mice showed significant inhibition of the outward Cl(-) currents without decreasing TMEM16a expression. Together the data suggests that Ca(2+) entry via the TRPC1 channels is essential for the activation of CaCC.

  18. Swelling-activated ion channels: functional regulation in cell-swelling, proliferation and apoptosis

    DEFF Research Database (Denmark)

    Stutzin, A; Hoffmann, E K

    2006-01-01

    Cell volume regulation is one of the most fundamental homeostatic mechanisms and essential for normal cellular function. At the same time, however, many physiological mechanisms are associated with regulatory changes in cell size meaning that the set point for cell volume regulation is under phys...... as key players in the maintenance of normal steady-state cell volume, with particular emphasis on the intracellular signalling pathways responsible for their regulation during hypotonic stress, cell proliferation and apoptosis....

  19. Src family protein tyrosine kinase regulates the basolateral K channel in the distal convoluted tubule (DCT) by phosphorylation of KCNJ10 protein.

    Science.gov (United States)

    Zhang, Chengbiao; Wang, Lijun; Thomas, Sherin; Wang, Kemeng; Lin, Dao-Hong; Rinehart, Jesse; Wang, Wen-Hui

    2013-09-01

    The loss of function of the basolateral K channels in the distal nephron causes electrolyte imbalance. The aim of this study is to examine the role of Src family protein tyrosine kinase (SFK) in regulating K channels in the basolateral membrane of the mouse initial distal convoluted tubule (DCT1). Single-channel recordings confirmed that the 40-picosiemen (pS) K channel was the only type of K channel in the basolateral membrane of DCT1. The suppression of SFK reversibly inhibited the basolateral 40-pS K channel activity in cell-attached patches and decreased the Ba(2+)-sensitive whole-cell K currents in DCT1. Inhibition of SFK also shifted the K reversal potential from -65 to -43 mV, suggesting a role of SFK in determining the membrane potential in DCT1. Western blot analysis showed that KCNJ10 (Kir4.1), a key component of the basolateral 40-pS K channel in DCT1, was a tyrosine-phosphorylated protein. LC/MS analysis further confirmed that SFK phosphorylated KCNJ10 at Tyr(8) and Tyr(9). The single-channel recording detected the activity of a 19-pS K channel in KCNJ10-transfected HEK293T cells and a 40-pS K channel in the cells transfected with KCNJ10+KCNJ16 (Kir.5.1) that form a heterotetramer in the basolateral membrane of the DCT. Mutation of Tyr(9) did not alter the channel conductance of the homotetramer and heterotetramer. However, it decreased the whole-cell K currents, the probability of finding K channels, and surface expression of KCNJ10 in comparison to WT KCNJ10. We conclude that SFK stimulates the basolateral K channel activity in DCT1, at least partially, by phosphorylating Tyr(9) on KCNJ10. We speculate that the modulation of tyrosine phosphorylation of KCNJ10 should play a role in regulating membrane transport function in DCT1.

  20. Amphiphile regulation of ion channel function by changes in the bilayer spring constant

    DEFF Research Database (Denmark)

    Lundbæk, Jens August; Koeppe, R.E.; Andersen, Oluf Sten

    2010-01-01

    effect of amphiphiles, at concentrations often used in biological research, on the bilayer elastic response to a change in the hydrophobic length of an embedded protein. The effects of structurally diverse amphiphiles can be described by changes in a phenomenological bilayer spring constant (H......Many drugs are amphiphiles that, in addition to binding to a particular target protein, adsorb to cell membrane lipid bilayers and alter intrinsic bilayer physical properties (e. g., bilayer thickness, monolayer curvature, and elastic moduli). Such changes can modulate membrane protein function......-B) that summarizes the bilayer elastic properties, as sensed by a bilayer-spanning protein. Amphiphile-induced changes in H-B, measured using gA channels of a particular length, quantitatively predict changes in lifetime for channels of a different length-as well as changes in the inactivation of voltage...

  1. Inside the black box: incentive regulation and incentive channeling on energy markets

    NARCIS (Netherlands)

    K. Heine (Klaus)

    2011-01-01

    textabstractThis paper aims to achieve more insight into the complex interplay between the "external" market regulations and "internal" regulations (corporate governance) of energy firms. In recent years, many countries have deregulated the incumbent energy monopolies and have introduced new modes o

  2. Functional analysis of metabolic channeling and regulation in lignin biosynthesis: a computational approach.

    Science.gov (United States)

    Lee, Yun; Escamilla-Treviño, Luis; Dixon, Richard A; Voit, Eberhard O

    2012-01-01

    Lignin is a polymer in secondary cell walls of plants that is known to have negative impacts on forage digestibility, pulping efficiency, and sugar release from cellulosic biomass. While targeted modifications of different lignin biosynthetic enzymes have permitted the generation of transgenic plants with desirable traits, such as improved digestibility or reduced recalcitrance to saccharification, some of the engineered plants exhibit monomer compositions that are clearly at odds with the expected outcomes when the biosynthetic pathway is perturbed. In Medicago, such discrepancies were partly reconciled by the recent finding that certain biosynthetic enzymes may be spatially organized into two independent channels for the synthesis of guaiacyl (G) and syringyl (S) lignin monomers. Nevertheless, the mechanistic details, as well as the biological function of these interactions, remain unclear. To decipher the working principles of this and similar control mechanisms, we propose and employ here a novel computational approach that permits an expedient and exhaustive assessment of hundreds of minimal designs that could arise in vivo. Interestingly, this comparative analysis not only helps distinguish two most parsimonious mechanisms of crosstalk between the two channels by formulating a targeted and readily testable hypothesis, but also suggests that the G lignin-specific channel is more important for proper functioning than the S lignin-specific channel. While the proposed strategy of analysis in this article is tightly focused on lignin synthesis, it is likely to be of similar utility in extracting unbiased information in a variety of situations, where the spatial organization of molecular components is critical for coordinating the flow of cellular information, and where initially various control designs seem equally valid. PMID:23144605

  3. Functional analysis of metabolic channeling and regulation in lignin biosynthesis: a computational approach.

    Directory of Open Access Journals (Sweden)

    Yun Lee

    Full Text Available Lignin is a polymer in secondary cell walls of plants that is known to have negative impacts on forage digestibility, pulping efficiency, and sugar release from cellulosic biomass. While targeted modifications of different lignin biosynthetic enzymes have permitted the generation of transgenic plants with desirable traits, such as improved digestibility or reduced recalcitrance to saccharification, some of the engineered plants exhibit monomer compositions that are clearly at odds with the expected outcomes when the biosynthetic pathway is perturbed. In Medicago, such discrepancies were partly reconciled by the recent finding that certain biosynthetic enzymes may be spatially organized into two independent channels for the synthesis of guaiacyl (G and syringyl (S lignin monomers. Nevertheless, the mechanistic details, as well as the biological function of these interactions, remain unclear. To decipher the working principles of this and similar control mechanisms, we propose and employ here a novel computational approach that permits an expedient and exhaustive assessment of hundreds of minimal designs that could arise in vivo. Interestingly, this comparative analysis not only helps distinguish two most parsimonious mechanisms of crosstalk between the two channels by formulating a targeted and readily testable hypothesis, but also suggests that the G lignin-specific channel is more important for proper functioning than the S lignin-specific channel. While the proposed strategy of analysis in this article is tightly focused on lignin synthesis, it is likely to be of similar utility in extracting unbiased information in a variety of situations, where the spatial organization of molecular components is critical for coordinating the flow of cellular information, and where initially various control designs seem equally valid.

  4. Hydrodynamic Effect of the Regulation Project of Yangtze River Deepwater Channel Downstream of Nanjing

    Institute of Scientific and Technical Information of China (English)

    杨东利; 窦希萍; 张新周; 罗小峰

    2013-01-01

    A two-dimensional flow numerical model of the tidal reaches, which total length is more than 700 km, is established from Datong to the Yangtze River estuary. The tidal levels, velocities, diversion ratios and dynamic axes before and after the separate regulation of each reach and combined regulation of all reaches are obtained. The comparative analysis shows that the regulation project of a separate reach basically has no impact on velocity distributions and variations of diversion ratios of upper and lower reaches, the variations of dynamic axes are only within the local scope of the project. The regulation project of a separate reach also has less impact on the water level in the lower adjacent reaches, but will make the water levels in the upper reaches rise. After the implementation of the regulation projects for all reaches, the rise of water level in the upstream reaches will have a cumulative impact.

  5. The Role of Ion Channels to Regulate Airway Ciliary Beat Frequency During Allergic Inflammation.

    Science.gov (United States)

    Joskova, M; Sutovska, M; Durdik, P; Koniar, D; Hargas, L; Banovcin, P; Hrianka, M; Khazaei, V; Pappova, L; Franova, S

    2016-01-01

    Overproduction of mucus is a hallmark of asthma. The aim of this study was to identify potentially effective therapies for removing excess mucus. The role of voltage-gated (Kir 6.1, KCa 1.1) and store-operated ion channels (SOC, CRAC) in respiratory cilia, relating to the tracheal ciliary beat frequency (CBF), was compared under the physiological and allergic airway conditions. Ex vivo experiments were designed to test the local effects of Kir 6.1, KCa 1.1 and CRAC ion channel modulators in a concentration-dependent manner on the CBF. Cilia, obtained with the brushing method, were monitored by a high-speed video camera and analyzed with ciliary analysis software. In natural conditions, a Kir 6.1 opener accelerated CBF, while CRAC blocker slowed it in a concentration-dependent manner. In allergic inflammation, the effect of Kir 6.1 opener was insignificant, with a tendency to decrease CBF. A cilio-inhibitory effect of a CRAC blocker, while gently reduced by allergic inflammation, remained significant. A KCa 1.1 opener turned out to significantly enhance the CBF under the allergic OVA-sensitized conditions. We conclude that optimally attuned concentration of KCa 1.1 openers or special types of bimodal SOC channel blockers, potentially given by inhalation, might benefit asthma. PMID:27369295

  6. Role of physiological ClC-1 Cl- ion channel regulation for the excitability and function of working skeletal muscle

    DEFF Research Database (Denmark)

    Pedersen, Thomas Holm; Riisager, Anders; de Paoli, Frank Vincenzo;

    2016-01-01

    gene. However, given that ClC-1 must be drastically inhibited (∼80%) before myotonia develops, more recent studies have explored whether acute and more subtle ClC-1 regulation contributes to controlling the excitability of working muscle. Methods were developed to measure ClC-1 function with subsecond...... ions. This inhibition is important for preserving excitability of working muscle in the face of activity-induced elevation of extracellular K+ and accumulating inactivation of voltage-gated sodium channels. Furthermore, during prolonged activity, a marked ClC-1 activation can develop that compromises...... muscle excitability. Data from ClC-1 expression systems suggest that this ClC-1 activation may arise from loss of regulation by adenosine nucleotides and/or oxidation. The present review summarizes the current knowledge of the physiological factors that control ClC-1 function in active muscle....

  7. Fluoride Induces a Volume Reduction in CA1 Hippocampal Slices Via MAP Kinase Pathway Through Volume Regulated Anion Channels.

    Science.gov (United States)

    Lee, Jaekwang; Han, Young-Eun; Favorov, Oleg; Tommerdahl, Mark; Whitsel, Barry; Lee, C Justin

    2016-04-01

    Regulation of cell volume is an important aspect of cellular homeostasis during neural activity. This volume regulation is thought to be mediated by activation of specific transporters, aquaporin, and volume regulated anion channels (VRAC). In cultured astrocytes, it was reported that swelling-induced mitogen-activated protein (MAP) kinase activation is required to open VRAC, which are thought to be important in regulatory volume decrease and in the response of CNS to trauma and excitotoxicity. It has been also described that sodium fluoride (NaF), a recognized G-protein activator and protein phosphatase inhibitor, leads to a significant MAP kinase activation in endothelial cells. However, NaF's effect in volume regulation in the brain is not known yet. Here, we investigated the mechanism of NaF-induced volume change in rat and mouse hippocampal slices using intrinsic optical signal (IOS) recording, in which we measured relative changes in intracellular and extracellular volume as changes in light transmittance through brain slices. We found that NaF (1~5 mM) application induced a reduction in light transmittance (decreased volume) in CA1 hippocampus, which was completely reversed by MAP kinase inhibitor U0126 (10 µM). We also observed that NaF-induced volume reduction was blocked by anion channel blockers, suggesting that NaF-induced volume reduction could be mediated by VRAC. Overall, our results propose a novel molecular mechanism of NaF-induced volume reduction via MAP kinase signaling pathway by activation of VRAC. PMID:27122993

  8. Fluoride Induces a Volume Reduction in CA1 Hippocampal Slices Via MAP Kinase Pathway Through Volume Regulated Anion Channels

    Science.gov (United States)

    Lee, Jaekwang; Han, Young-Eun; Favorov, Oleg; Tommerdahl, Mark; Whitsel, Barry

    2016-01-01

    Regulation of cell volume is an important aspect of cellular homeostasis during neural activity. This volume regulation is thought to be mediated by activation of specific transporters, aquaporin, and volume regulated anion channels (VRAC). In cultured astrocytes, it was reported that swelling-induced mitogen-activated protein (MAP) kinase activation is required to open VRAC, which are thought to be important in regulatory volume decrease and in the response of CNS to trauma and excitotoxicity. It has been also described that sodium fluoride (NaF), a recognized G-protein activator and protein phosphatase inhibitor, leads to a significant MAP kinase activation in endothelial cells. However, NaF's effect in volume regulation in the brain is not known yet. Here, we investigated the mechanism of NaF-induced volume change in rat and mouse hippocampal slices using intrinsic optical signal (IOS) recording, in which we measured relative changes in intracellular and extracellular volume as changes in light transmittance through brain slices. We found that NaF (1~5 mM) application induced a reduction in light transmittance (decreased volume) in CA1 hippocampus, which was completely reversed by MAP kinase inhibitor U0126 (10 µM). We also observed that NaF-induced volume reduction was blocked by anion channel blockers, suggesting that NaF-induced volume reduction could be mediated by VRAC. Overall, our results propose a novel molecular mechanism of NaF-induced volume reduction via MAP kinase signaling pathway by activation of VRAC. PMID:27122993

  9. Genome-wide identification of Hsp70 genes in channel catfish and their regulated expression after bacterial infection.

    Science.gov (United States)

    Song, Lin; Li, Chao; Xie, Yangjie; Liu, Shikai; Zhang, Jiaren; Yao, Jun; Jiang, Chen; Li, Yun; Liu, Zhanjiang

    2016-02-01

    Heat shock proteins 70/110 (Hsp70/110) are a family of conserved ubiquitously expressed heat shock proteins which are produced by cells in response to exposure to stressful conditions. Besides the chaperone and housekeeping functions, they are also known to be involved in immune response during infection. In this study, we identified 16 Hsp70/110 geness in channel catfish (Ictalurus punctatus) through in silico analysis using RNA-Seq and genome databases. Among them 12 members of Hsp70 (Hspa) family and 4 members of Hsp110 (Hsph) family were identified. Phylogenetic and syntenic analyses provided strong evidence in supporting the orthologies of these HSPs. In addition, we also determined the expression patterns of Hsp70/110 genes after Flavobacterium columnare and Edwardsiella ictaluri infections by meta-analyses, for the first time in channel catfish. Ten out of sixteen genes were significantly up/down-regulated after bacterial challenges. Specifically, nine genes were found significantly expressed in gill after F. columnare infection. Two genes were found significantly expressed in intestine after E. ictaluri infection. Pathogen-specific pattern and tissue-specific pattern were found in the two infections. The significantly regulated expressions of catfish Hsp70 genes after bacterial infections suggested their involvement in immune response in catfish. PMID:26693666

  10. A Putative Calcium-Permeable Cyclic Nucleotide-Gated Channel, CNGC18, Regulates Polarized Pollen Tube Growth

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A tip-focused Ca2+ gradient is tightly coupled to polarized pollen tube growth, and tip-localized influxes of extracellular Ca2+ are required for this process. However the molecular identity and regulation of the potential Ca2+ channels remains elusive.The present study has implicated CNGC18 (cyclic nucleotide-gated channel 18) in polarized pollen tube growth, because its overexpression induced wider and shorter pollen tubes. Moreover, CNGC18 overexpression induced depolarization of pollen tube growth was suppressed by lower extracellular calcium ([Ca2+]ex). CNGC18-yellow fluorescence protein (YFP)was preferentially localized to the apparent post-Golgi vesicles and the plasma membrane (PM) in the apex of pollen tubes.The PM localization was affected by tip-localized ROP1 signaling. Expression of wild type ROP1 or an active form of ROP1enhanced CNGC18-YFP localization to the apical region of the PM, whereas expression of RopGAP1 (a ROP1 deactivator)blocked the PM localization. These results support a role for PM-localized CNGC18 in the regulation of polarized pollen tube growth through Its potential function in the modulation of calcium influxes.

  11. Regulating role of acetylcholine and its antagonists in inward rectified K+ channels from guard cell protoplasts of Vicia faba

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The inward rectified potassium current of Vicia faba guard cell protoplasts treated with acetylcholine (ACh) or the antagonists of its receptors were recorded by employing the patch clamp technique. The results show that ACh at lower concentrations increases the inward K+ current, in contrast, ACh at higher concentrations inhibits it. Treated with d-Tubocurarine (d-Tub), an antagonist of the nicotine ACh receptor (nAChR) inhibits the inward K+ current by 30%. Treated with atropine (Atr), an antagonist of the muscarine (Mus) ACh receptor (mAChR) also inhibits it by 36%.However,if guard cell protoplasts are treated with d-Tub and Atr together, the inward K+ current is inhibited by 60%-75%. Tetraethylammonium chloride (TEA), a strong inhibitor of K+ channels has no effect on the inward K+ current regulated by ACh, suggesting that there are inward K+ channels modulated by AChRs on the membrane of the guard cell protoplasts. These data demonstrate an ACh-regulated mechanism for stomatal movement.

  12. Regulating role of acetylcholine and its antagonists in inward rectified K~+ channels from guard cell protoplasts of Vicia faba

    Institute of Scientific and Technical Information of China (English)

    冷强; 花宝光; 郭玉海; 娄成后

    2000-01-01

    The inward rectified potassium current of Vicia faba guard cell protoplasts treated with acetylcholine (ACh) or the antagonists of its receptors were recorded by employing the patch clamp technique. The results show that ACh at lower concentrations increases the inward K+ current, in contrast, ACh at higher concentrations inhibits it. Treated with d-Tubocurarine (d-Tub), an antagonist of the nicotine ACh receptor (nAChR) inhibits the inward K+ current by 30%. Treated with atropine (Atr), an antagonist of the muscarine (Mus) ACh receptor (mAChR) also inhibits it by 36%. However, if guard cell protoplasts are treated with d-Tub and Atr together, the inward K+ current is inhibited by 60%-75%. Tetraethylammonium chloride (TEA), a strong inhibitor of K+ channels has no effect on the inward K+ current regulated by ACh, suggesting that there are inward K+ channels modulated by AChRs on the membrane of the guard cell protoplasts. These data demonstrate an ACh-regulated mechanism for stomatal movement.

  13. Regulation by L channels of Ca(2+)-evoked secretory responses in ouabain-treated chromaffin cells.

    Science.gov (United States)

    De Pascual, Ricardo; Colmena, Inés; Ruiz-Pascual, Lucía; Baraibar, Andrés Mateo; Egea, Javier; Gandía, Luis; García, Antonio G

    2016-10-01

    It is known that the sustained depolarisation of adrenal medullary bovine chromaffin cells (BCCs) with high K(+) concentrations produces an initial sharp catecholamine release that subsequently fades off in spite depolarisation persists. Here, we have recreated a sustained depolarisation condition of BCCs by treating them with the Na(+)/K(+) ATPase blocker ouabain; in doing so, we searched experimental conditions that permitted the development of a sustained long-term catecholamine release response that could be relevant during prolonged stress. BCCs were perifused with nominal 0Ca(2+) solution, and secretion responses were elicited by intermittent application of short 2Ca(2+) pulses (Krebs-HEPES containing 2 mM Ca(2+)). These pulses elicited a biphasic secretory pattern with an initial 30-min period with secretory responses of increasing amplitude and a second 30-min period with steady-state, non-inactivating responses. The initial phase was not due to gradual depolarisation neither to gradual increases of the cytosolic calcium transients ([Ca(2+)]c) elicited by 2Ca(2+) pulses in BBCs exposed to ouabain; both parameters increased soon after ouabain addition. Νifedipine blocked these responses, and FPL64176 potentiated them, suggesting that they were triggered by Ca(2+) entry through non-inactivating L-type calcium channels. This was corroborated by nifedipine-evoked blockade of the L-type Ca(2+) channel current and the [Ca(2+)]c transients elicited by 2Ca(2+) pulses. Furthermore, the plasmalemmal Na(+)/Ca(2+) exchanger (NCX) blocker SEA0400 caused a mild inhibition followed by a large rebound increase of the steady-state secretory responses. We conclude that these two phases of secretion are mostly contributed by Ca(2+) entry through L calcium channels, with a minor contribution of Ca(2+) entry through the reverse mode of the NCX.

  14. Calmodulin and calcium differentially regulate the neuronal Nav1.1 voltage-dependent sodium channel

    International Nuclear Information System (INIS)

    Highlights: → Both Ca++-Calmodulin (CaM) and Ca++-free CaM bind to the C-terminal region of Nav1.1. → Ca++ and CaM have both opposite and convergent effects on INav1.1. → Ca++-CaM modulates INav1.1 amplitude. → CaM hyperpolarizes the voltage-dependence of activation, and increases the inactivation rate. → Ca++ alone antagonizes CaM for both effects, and depolarizes the voltage-dependence of inactivation. -- Abstract: Mutations in the neuronal Nav1.1 voltage-gated sodium channel are responsible for mild to severe epileptic syndromes. The ubiquitous calcium sensor calmodulin (CaM) bound to rat brain Nav1.1 and to the human Nav1.1 channel expressed by a stably transfected HEK-293 cell line. The C-terminal region of the channel, as a fusion protein or in the yeast two-hybrid system, interacted with CaM via a consensus C-terminal motif, the IQ domain. Patch clamp experiments on HEK1.1 cells showed that CaM overexpression increased peak current in a calcium-dependent way. CaM had no effect on the voltage-dependence of fast inactivation, and accelerated the inactivation kinetics. Elevating Ca++ depolarized the voltage-dependence of fast inactivation and slowed down the fast inactivation kinetics, and for high concentrations this effect competed with the acceleration induced by CaM alone. Similarly, the depolarizing action of calcium antagonized the hyperpolarizing shift of the voltage-dependence of activation due to CaM overexpression. Fluorescence spectroscopy measurements suggested that Ca++ could bind the Nav1.1 C-terminal region with micromolar affinity.

  15. Tyrosine phosphatases epsilon and alpha perform specific and overlapping functions in regulation of voltage-gated potassium channels in Schwann cells

    DEFF Research Database (Denmark)

    Tiran, Zohar; Peretz, Asher; Sines, Tal;

    2006-01-01

    Tyrosine phosphatases (PTPs) epsilon and alpha are closely related and share several molecular functions, such as regulation of Src family kinases and voltage-gated potassium (Kv) channels. Functional interrelationships between PTPepsilon and PTPalpha and the mechanisms by which they regulate K+ ...

  16. Ion channels involved in cell volume regulation: effects on migration, proliferation, and programmed cell death in non adherent EAT cells and adherent ELA cells.

    Science.gov (United States)

    Hoffmann, Else Kay

    2011-01-01

    This mini review outlines studies of cell volume regulation in two closely related mammalian cell lines: nonadherent Ehrlich ascites tumour cells (EATC) and adherent Ehrlich Lettre ascites (ELA) cells. Focus is on the regulatory volume decrease (RVD) that occurs after cell swelling, the volume regulatory ion channels involved, and the mechanisms (cellular signalling pathways) that regulate these channels. Finally, I shall also briefly review current investigations in these two cell lines that focuses on how changes in cell volume can regulate cell functions such as cell migration, proliferation, and programmed cell death.

  17. Interactions among forest age, valley and channel morphology, and log jams regulate animal production in mountain streams

    Science.gov (United States)

    Walters, D. M.; Venarsky, M. P.; Hall, R. O., Jr.; Herdrich, A.; Livers, B.; Winkelman, D.; Wohl, E.

    2014-12-01

    Forest age and local valley morphometry strongly influence the form and function of mountain streams in Colorado. Streams in valleys with old growth forest (>350 years) have extensive log jam complexes that create multi-thread channel reaches with extensive pool habitat and large depositional areas. Streams in younger unmanaged forests (e.g., 120 years old) and intensively managed forests have much fewer log jams and lower wood loads. These are single-thread streams dominated by riffles and with little depositional habitat. We hypothesized that log jam streams would retain more organic matter and have higher metabolism, leading to greater production of stream macroinvertebrates and trout. Log jam reaches should also have greater emergence of adult aquatic insects, and consequently have higher densities of riparian spiders taking advantage of these prey. Surficial organic matter was 3-fold higher in old-growth streams, and these streams had much higher ecosystem respiration. Insect production (g m2 y-1) was similar among forest types, but fish density was four times higher in old-growth streams with copious log jams. However, at the valley scale, insect production (g m-1 valley-1) and trout density (number m-1 valley-1) was 2-fold and 10-fold higher, respectively, in old growth streams. This finding is because multi-thread reaches created by log jams have much greater stream area and stream length per meter of valley than single-thread channels. The more limited response of macroinvertebrates may be related to fish predation. Trout in old growth streams had similar growth rates and higher fat content than fish in other streams in spite of occurring at higher densities and higher elevation/colder temperatures. This suggests that the positive fish effect observed in old growth streams is related to greater availability of invertebrate prey, which is consistent with our original hypothesis. Preliminary analyses suggest that spider densities do not respond strongly to

  18. Role of tumour necrosis factor-a in the regulation of T-type calcium channel current in HL-1 cells.

    Science.gov (United States)

    Rao, Fang; Xue, Yu-Mei; Wei, Wei; Yang, Hui; Liu, Fang-Zhou; Chen, Shao-Xian; Kuang, Su-Juan; Zhu, Jie-Ning; Wu, Shu-Lin; Deng, Chun-Yu

    2016-07-01

    Increasing evidence indicates that inflammation contributes to the initiation and perpetuation of atrial fibrillation (AF). Although tumour necrosis factor (TNF)-α levels are increased in patients with AF, the role of TNF-α in the pathogenesis of AF remains unclear. Besides L-type Ca(2+) currents (IC a,L ), T-type Ca(2+) currents (IC a,T ) also plays an important role in the pathogenesis of AF. This study was designed to use the whole-cell voltage-clamp technique and biochemical assays to explore if TNF-α is involved in the pathogenesis of AF through regulating IC a,T in atrial myocytes. It was found that compared with sinus rhythm (SR) controls, T-type calcium channel (TCC) subunit mRNA levels were decreased, while TNF-α expression levels were increased, in human atrial tissue from patients with AF. In murine atrial myocyte HL-1 cells, after culturing for 24 h, 12.5, 25 and 50 ng/mL TNF-α significantly reduced the protein expression levels of the TCC α1G subunit in a concentration-dependent manner. The peak current was reduced by the application of 12.5 or 25 ng/mL TNF-α in a concentration-dependent manner (from -15.08 ± 1.11 pA/pF in controls to -11.89 ± 0.83 pA/pF and -8.54 ± 1.55 pA/pF in 12.5 or 25 ng/mL TNF-α group respectively). TNF-α application also inhibited voltage-dependent inactivation of IC a,T, shifted the inactivation curve to the left. These results suggest that TNF-α is involved in the pathogenesis of AF, probably via decreasing IC a,T current density in atrium-derived myocytes through impaired channel function and down-regulation of channel protein expression. This pathway thus represents a potential pathogenic mechanism in AF. PMID:27119319

  19. Cross-layer Framework for Fine-grained Channel Access in Next Generation High-density WiFi Networks

    OpenAIRE

    ZHAO, HAITAO; Zhang, Shaojie; Garcia-Palacios, Francisco

    2016-01-01

    Densely deployed WiFi networks will play a crucial role in providing the capacity for next generation mobile internet. However, due to increasing interference, overlapped channels in WiFi networks and throughput efficiency degradation, densely deployed WiFi networks is not a guarantee to obtain higher throughput. An emergent challenge is how to efficiently utilize scarce spectrum resources, by matching physical layer resources to traffic demand. In this aspect, access control allocation strat...

  20. Large-conductance voltage- and Ca2+-activated K+ channel regulation by protein kinase C in guinea pig urinary bladder smooth muscle.

    Science.gov (United States)

    Hristov, Kiril L; Smith, Amy C; Parajuli, Shankar P; Malysz, John; Petkov, Georgi V

    2014-03-01

    Large-conductance voltage- and Ca(2+)-activated K(+) (BK) channels are critical regulators of detrusor smooth muscle (DSM) excitability and contractility. PKC modulates the contraction of DSM and BK channel activity in non-DSM cells; however, the cellular mechanism regulating the PKC-BK channel interaction in DSM remains unknown. We provide a novel mechanistic insight into BK channel regulation by PKC in DSM. We used patch-clamp electrophysiology, live-cell Ca(2+) imaging, and functional studies of DSM contractility to elucidate BK channel regulation by PKC at cellular and tissue levels. Voltage-clamp experiments showed that pharmacological activation of PKC with PMA inhibited the spontaneous transient BK currents in native freshly isolated guinea pig DSM cells. Current-clamp recordings revealed that PMA significantly depolarized DSM membrane potential and inhibited the spontaneous transient hyperpolarizations in DSM cells. The PMA inhibitory effects on DSM membrane potential were completely abolished by the selective BK channel inhibitor paxilline. Activation of PKC with PMA did not affect the amplitude of the voltage-step-induced whole cell steady-state BK current or the single BK channel open probability (recorded in cell-attached mode) upon inhibition of all major Ca(2+) sources for BK channel activation with thapsigargin, ryanodine, and nifedipine. PKC activation with PMA elevated intracellular Ca(2+) levels in DSM cells and increased spontaneous phasic and nerve-evoked contractions of DSM isolated strips. Our results support the concept that PKC activation leads to a reduction of BK channel activity in DSM via a Ca(2+)-dependent mechanism, thus increasing DSM contractility.

  1. β-Arrestin-Dependent Dopaminergic Regulation of Calcium Channel Activity in the Axon Initial Segment.

    Science.gov (United States)

    Yang, Sungchil; Ben-Shalom, Roy; Ahn, Misol; Liptak, Alayna T; van Rijn, Richard M; Whistler, Jennifer L; Bender, Kevin J

    2016-08-01

    G-protein-coupled receptors (GPCRs) initiate a variety of signaling cascades, depending on effector coupling. β-arrestins, which were initially characterized by their ability to "arrest" GPCR signaling by uncoupling receptor and G protein, have recently emerged as important signaling effectors for GPCRs. β-arrestins engage signaling pathways that are distinct from those mediated by G protein. As such, arrestin-dependent signaling can play a unique role in regulating cell function, but whether neuromodulatory GPCRs utilize β-arrestin-dependent signaling to regulate neuronal excitability remains unclear. Here, we find that D3 dopamine receptors (D3R) regulate axon initial segment (AIS) excitability through β-arrestin-dependent signaling, modifying CaV3 voltage dependence to suppress high-frequency action potential generation. This non-canonical D3R signaling thereby gates AIS excitability via pathways distinct from classical GPCR signaling pathways.

  2. Splice variants of the CaV1.3 L-type calcium channel regulate dendritic spine morphology

    Science.gov (United States)

    Stanika, Ruslan; Campiglio, Marta; Pinggera, Alexandra; Lee, Amy; Striessnig, Jörg; Flucher, Bernhard E.; Obermair, Gerald J.

    2016-01-01

    Dendritic spines are the postsynaptic compartments of glutamatergic synapses in the brain. Their number and shape are subject to change in synaptic plasticity and neurological disorders including autism spectrum disorders and Parkinson’s disease. The L-type calcium channel CaV1.3 constitutes an important calcium entry pathway implicated in the regulation of spine morphology. Here we investigated the importance of full-length CaV1.3L and two C-terminally truncated splice variants (CaV1.342A and CaV1.343S) and their modulation by densin-180 and shank1b for the morphology of dendritic spines of cultured hippocampal neurons. Live-cell immunofluorescence and super-resolution microscopy of epitope-tagged CaV1.3L revealed its localization at the base-, neck-, and head-region of dendritic spines. Expression of the short splice variants or deletion of the C-terminal PDZ-binding motif in CaV1.3L induced aberrant dendritic spine elongation. Similar morphological alterations were induced by co-expression of densin-180 or shank1b with CaV1.3L and correlated with increased CaV1.3 currents and dendritic calcium signals in transfected neurons. Together, our findings suggest a key role of CaV1.3 in regulating dendritic spine structure. Under physiological conditions it may contribute to the structural plasticity of glutamatergic synapses. Conversely, altered regulation of CaV1.3 channels may provide an important mechanism in the development of postsynaptic aberrations associated with neurodegenerative disorders. PMID:27708393

  3. Cooperative regulation by G proteins and Na+ of neuronal GIRK2 K+ channels

    Science.gov (United States)

    Wang, Weiwei; Touhara, Kouki K; Weir, Keiko; Bean, Bruce P; MacKinnon, Roderick

    2016-01-01

    G protein gated inward rectifier K+ (GIRK) channels open and thereby silence cellular electrical activity when inhibitory G protein coupled receptors (GPCRs) are stimulated. Here we describe an assay to measure neuronal GIRK2 activity as a function of membrane-anchored G protein concentration. Using this assay we show that four Gβγ subunits bind cooperatively to open GIRK2, and that intracellular Na+ – which enters neurons during action potentials – further amplifies opening mostly by increasing Gβγ affinity. A Na+ amplification function is characterized and used to estimate the concentration of Gβγ subunits that appear in the membrane of mouse dopamine neurons when GABAB receptors are stimulated. We conclude that GIRK2, through its dual responsiveness to Gβγ and Na+, mediates a form of neuronal inhibition that is amplifiable in the setting of excess electrical activity. DOI: http://dx.doi.org/10.7554/eLife.15751.001 PMID:27074662

  4. Molecular structure and regulation of the epithelial calcium channels TRPV5 and TRPV6

    NARCIS (Netherlands)

    Chang, Q.

    2007-01-01

    Ca2+ homeostasis is of utmost importance for the normal development and function of the body. Active transcellular Ca2+ transport involves a chain of Ca2+ transport proteins mediating apical Ca2+ influx, transport to the basolateral membrane and extrusion into the bloodstream. Regulation of the two

  5. 78 FR 20451 - Drawbridge Operation Regulations; Pelican Island Causeway, Galveston, Channel, TX

    Science.gov (United States)

    2013-04-05

    ... CFR Code of Federal Regulations DHS Department of Homeland Security FR Federal Register NPRM Notice of... discretionary regulatory actions. In particular, the Act addresses actions that may result in the expenditure by a State, local, or tribal government, in the aggregate, or by the private sector of...

  6. 77 FR 25073 - Special Local Regulation; Hebda Cup Rowing Regatta, Trenton Channel; Detroit River, Wyandotte, MI

    Science.gov (United States)

    2012-04-27

    ... SECURITY Coast Guard 33 CFR Part 100 RIN 1625-AA08 Special Local Regulation; Hebda Cup Rowing Regatta... on the navigable waters immediately prior to, during, and immediately after the Hebda Cup Rowing... Purpose On April 28, 2012, the Wyandotte Boat Club is holding a rowing race that will require...

  7. 78 FR 24063 - Special Local Regulation; Hebda Cup Rowing Regatta, Trenton Channel; Detroit River, Wyandotte, MI

    Science.gov (United States)

    2013-04-24

    ... INFORMATION: Table of Acronyms DHS Department of Homeland Security FR Federal Register NPRM Notice of Proposed... SECURITY Coast Guard 33 CFR Part 100 RIN 1625-AA08 Special Local Regulation; Hebda Cup Rowing Regatta... on the navigable waters immediately prior to, during, and immediately after the Hebda Cup...

  8. Interactions between β-catenin and the HSlo potassium channel regulates HSlo surface expression.

    Directory of Open Access Journals (Sweden)

    Shumin Bian

    Full Text Available BACKGROUND: The large conductance calcium-activated potassium channel alpha-subunit (Slo is widely distributed throughout the body and plays an important role in a number of diseases. Prior work has shown that Slo, through its S10 region, interacts with β-catenin, a key component of the cytoskeleton framework and the Wnt signaling pathway. However, the physiological significance of this interaction was not clear. METHODOLOGY/PRINCIPAL FINDINGS: Using a combination of proteomic and cell biology tools we show the existence of additional multiple binding sites in Slo, and explore in detail β-catenin interactions with the S10 region. We demonstrate that deletion of this region reduces Slo surface expression in HEK cells, which indicates that interaction with beta-catenin is important for Slo surface expression. This is confirmed by reduced expression of Slo in HEK cells and chicken (Gallus gallus domesticus leghorn white hair cells treated with siRNA to β-catenin. HSlo reciprocally co-immunoprecipitates with β-catenin, indicating a stable binding between these two proteins, with the S10 deletion mutant having reduced binding with β-catenin. We also observed that mutations of the two putative GSK phosphorylation sites within the S10 region affect both the surface expression of Slo and the channel's voltage and calcium sensitivities. Interestingly, expression of exogenous Slo in HEK cells inhibits β-catenin-dependent canonical Wnt signaling. CONCLUSIONS AND SIGNIFICANCE: These studies identify for the first time a central role for β-catenin in mediating Slo surface expression. Additionally we show that Slo overexpression can lead to downregulation of Wnt signaling.

  9. Drosophila SLC5A11 Mediates Hunger by Regulating K(+) Channel Activity.

    Science.gov (United States)

    Park, Jin-Yong; Dus, Monica; Kim, Seonil; Abu, Farhan; Kanai, Makoto I; Rudy, Bernardo; Suh, Greg S B

    2016-08-01

    Hunger is a powerful drive that stimulates food intake. Yet, the mechanism that determines how the energy deficits that result in hunger are represented in the brain and promote feeding is not well understood. We previously described SLC5A11-a sodium/solute co-transporter-like-(or cupcake) in Drosophila melanogaster, which is required for the fly to select a nutritive sugar over a sweeter nonnutritive sugar after periods of food deprivation. SLC5A11 acts on approximately 12 pairs of ellipsoid body (EB) R4 neurons to trigger the selection of nutritive sugars, but the underlying mechanism is not understood. Here, we report that the excitability of SLC5A11-expressing EB R4 neurons increases dramatically during starvation and that this increase is abolished in the SLC5A11 mutation. Artificial activation of SLC5A11-expresssing neurons is sufficient to promote feeding and hunger-driven behaviors; silencing these neurons has the opposite effect. Notably, SLC5A11 transcript levels in the brain increase significantly when flies are starved and decrease shortly after starved flies are refed. Furthermore, expression of SLC5A11 is sufficient for promoting hunger-driven behaviors and enhancing the excitability of SLC5A11-expressing neurons. SLC5A11 inhibits the function of the Drosophila KCNQ potassium channel in a heterologous expression system. Accordingly, a knockdown of dKCNQ expression in SLC5A11-expressing neurons produces hunger-driven behaviors even in fed flies, mimicking the overexpression of SLC5A11. We propose that starvation increases SLC5A11 expression, which enhances the excitability of SLC5A11-expressing neurons by suppressing dKCNQ channels, thereby conferring the hunger state. PMID:27397890

  10. Deubiquitylating enzyme USP2 counteracts Nedd4-2-mediated downregulation of KCNQ1 potassium channels

    DEFF Research Database (Denmark)

    Krzystanek, Katarzyna; Rasmussen, Hanne Borger; Grunnet, Morten;

    2012-01-01

    with the KCNQ1 potassium channel through a PY motif located in the C terminus of KCNQ1. This interaction induces ubiquitylation of KCNQ1, resulting in a reduced surface density of the channel. It was reported recently that the epithelial sodium channel is regulated by the reverse process...

  11. Entropy generation in a channel resembling gas turbine cooling passage: Effect of rotation number and density ratio on entropy generation

    Indian Academy of Sciences (India)

    M Basha; M Al-Qahtani; B S Yilbas

    2009-06-01

    Flow into a passage resembling a gas turbine blade cooling passage is considered and entropy generation rate in the passage is examined for unique rotation number and density ratios. In the simulations, leading and trailing walls of the passage are assumed to be at constant temperature. A control volume approach is introduced to discretize the governing equations of flow, heat transfer, and entropy generation. Reynolds stress turbulence model is accommodated in the simulation to account for the turbulence. The study is extended to include two rotational speeds and three density ratios. The passage aspect ratio is kept 10:1. It is found that volumetric entropy generation rate attains high values at passage inlet due to attainment of high temperature gradient in this region. Increasing rotation number and density ratio enhances volumetric entropy generation rate in the passage.

  12. Sexual dimorphism and oestrogen regulation of KCNE3 expression modulates the functional properties of KCNQ1 K channels.

    LENUS (Irish Health Repository)

    Alzamora, Rodrigo

    2012-02-01

    The KCNQ1 potassium channel associates with various KCNE ancillary subunits that drastically affect channel gating and pharmacology. Co-assembly with KCNE3 produces a current with nearly instantaneous activation, some time-dependent activation at very positive potentials, a linear current-voltage relationship and a 10-fold higher sensitivity to chromanol 293B. KCNQ1:KCNE3 channels are expressed in colonic crypts and mediate basolateral K(+) recycling required for Cl(-) secretion. We have previously reported the female-specific anti-secretory effects of oestrogen via KCNQ1:KCNE3 channel inhibition in colonic crypts. This study was designed to determine whether sex and oestrogen regulate the expression and function of KCNQ1 and KCNE3 in rat distal colon. Colonic crypts were isolated from Sprague-Dawley rats and used for whole-cell patch-clamp and to extract total RNA and protein. Sheets of epithelium were used for short-circuit current recordings. KCNE1 and KCNE3 mRNA and protein abundance were significantly higher in male than female crypts. No expression of KCNE2 was found and no difference was observed in KCNQ1 expression between male and female (at oestrus) colonic crypts. Male crypts showed a 2.2-fold higher level of association of KCNQ1 and KCNE3 compared to female cells. In female colonic crypts, KCNQ1 and KCNE3 protein expression fluctuated throughout the oestrous cycle and 17beta-oestradiol (E2 10 nM) produced a rapid (<15 min) dissociation of KCNQ1 and KCNE3 in female crypts only. Whole-cell K(+) currents showed a linear current-voltage relationship in male crypts, while K(+) currents in colonic crypts isolated from females displayed voltage-dependent outward rectification. Currents in isolated male crypts and epithelial sheets were 10-fold more sensitive to specific KCNQ1 inhibitors, such as chromanol 293B and HMR-1556, than in female. The effect of E2 on K(+) currents mediated by KCNQ1 with or without different beta-subunits was assayed from current

  13. Irresponsiveness of two retinoblastoma cases to conservative therapy correlates with up- regulation of hERG1 channels and of the VEGF-A pathway

    International Nuclear Information System (INIS)

    Treatment strategies for Retinoblastoma (RB), the most common primary intraocular tumor in children, have evolved over the past few decades and chemoreduction is currently the most popular treatment strategy. Despite success, systemic chemotherapeutic treatment has relevant toxicity, especially in the pediatric population. Antiangiogenic therapy has thus been proposed as a valuable alternative for pediatric malignancies, in particolar RB. Indeed, it has been shown that vessel density correlates with both local invasive growth and presence of metastases in RB, suggesting that angiogenesis could play a pivotal role for both local and systemic invasive growth in RB. We present here two cases of sporadic, bilateral RB that did not benefit from the conservative treatment and we provide evidence that the VEGF-A pathway is significantly up-regulated in both RB cases along with an over expression of hERG1 K+ channels. Two patients showed a sporadic, bilateral RB, classified at Stage II of the Reese-Elsworth Classification. Neither of them got benefits from conservative treatment, and the two eyes were enucleated. In samples from both RB cases we studied the VEGF-A pathway: VEGF-A showed high levels in the vitreous, the vegf-a, flt-1, kdr, and hif1-α transcripts were over-expressed. Moreover, both the transcripts and proteins of the hERG1 K+ channels turned out to be up-regulated in the two RB cases compared to the non cancerous retinal tissue. We provide evidence that the VEGF-A pathway is up-regulated in two particular aggressive cases of bilateral RB, which did not experience any benefit from conservative treatment, showing the overexpression of the vegf-a, flt-1, kdr and hif1-α transcripts and the high secretion of VEGF-A. Moreover we also show for the first time that the herg1 gene transcripts and protein are over expressed in RB, as occurs in several aggressive tumors. These results further stress the relevance of the VEGF-A pathway in RB and the correlation with h

  14. Irresponsiveness of two retinoblastoma cases to conservative therapy correlates with up- regulation of hERG1 channels and of the VEGF-A pathway

    Directory of Open Access Journals (Sweden)

    La Torre Agostino

    2010-09-01

    Full Text Available Abstract Background Treatment strategies for Retinoblastoma (RB, the most common primary intraocular tumor in children, have evolved over the past few decades and chemoreduction is currently the most popular treatment strategy. Despite success, systemic chemotherapeutic treatment has relevant toxicity, especially in the pediatric population. Antiangiogenic therapy has thus been proposed as a valuable alternative for pediatric malignancies, in particolar RB. Indeed, it has been shown that vessel density correlates with both local invasive growth and presence of metastases in RB, suggesting that angiogenesis could play a pivotal role for both local and systemic invasive growth in RB. We present here two cases of sporadic, bilateral RB that did not benefit from the conservative treatment and we provide evidence that the VEGF-A pathway is significantly up-regulated in both RB cases along with an over expression of hERG1 K+ channels. Case presentation Two patients showed a sporadic, bilateral RB, classified at Stage II of the Reese-Elsworth Classification. Neither of them got benefits from conservative treatment, and the two eyes were enucleated. In samples from both RB cases we studied the VEGF-A pathway: VEGF-A showed high levels in the vitreous, the vegf-a, flt-1, kdr, and hif1-α transcripts were over-expressed. Moreover, both the transcripts and proteins of the hERG1 K+ channels turned out to be up-regulated in the two RB cases compared to the non cancerous retinal tissue. Conclusions We provide evidence that the VEGF-A pathway is up-regulated in two particular aggressive cases of bilateral RB, which did not experience any benefit from conservative treatment, showing the overexpression of the vegf-a, flt-1, kdr and hif1-α transcripts and the high secretion of VEGF-A. Moreover we also show for the first time that the herg1 gene transcripts and protein are over expressed in RB, as occurs in several aggressive tumors. These results further stress

  15. PECAM-1 (CD31) regulates a hydrogen peroxide–activated nonselective cation channel in endothelial cells

    OpenAIRE

    Ji, Guangju; O'Brien, Christopher D.; Feldman, Morris; Manevich, Yefim; Lim, Poay; Sun, Jing; Albelda, Steven M.; Kotlikoff, Michael I.

    2002-01-01

    Hydrogen peroxide (H2O2) released by neutrophils is an important mediator of endothelial cell (EC) injury and vascular inflammation via its effect on EC-free Ca2+, [Ca2+]i. Although the underlying mechanisms are not well understood, platelet endothelial cell adhesion molecule (PECAM)-1/CD-31 is a critical modulator of neutrophil–EC transmigration. PECAM-1 is also known to regulate EC calcium signals and to undergo selective tyrosine phosphorylation. Here, we report that PECAM-1 molecules tran...

  16. Generalized quasi-one-dimensional model of non-homogeneous two-phase flow and criterion for density wave oscillation in parallel channels with riser

    International Nuclear Information System (INIS)

    A one-dimensional analytical model (with quasi-1D (or q1D) corrections to the homogeneous flow representation) estimated in a lumped parameter fashion has been developed to describe the threshold of density wave oscillations (DWO) in a parallel heated channel with riser. The heated channel consists of a single-phase part occurring up to the point of bubble detachment and a two-phase part comprising the riser. The two-phase region is described by the drift-flux model that accounts for drift velocity and subcooled boiling. In the proposed model, corresponding pressure drops include friction, acceleration, drift, and local pressure drops linked with the inlet and the outlet of the system, respectively. Using perturbation theory, we have linearized conservation law equations around the steady-state operating conditions. The result is a set of two ordinary differential equations with coefficients representing physical properties and model parameters. Using the theory of linear attenuating oscillator, generalized expression (criterion) is obtained for the stability thresholds of DWO for wide range regime and geometric conditions. The current study shows that this generalized criterion is a function of not only traditional homogeneous parameters represented in the classical studies (e.g., Morozov- Gerliga, Ishii-Zuber, Guido et al.), but also new parameters, such as q1D corrections, riser effect, and density, enthalpy, and pressure drop, which are described with drift effects and phase-shift of the model parameters. It is show. (author)

  17. Towards optimal multi-channel EMG electrode configurations in muscle force estimation: a high density EMG study.

    NARCIS (Netherlands)

    Staudenmann, D.; Kingma, I.; Stegeman, D.F.; Dieen, J.H. van

    2005-01-01

    Surface EMG is an important tool in biomechanics, kinesiology and neurophysiology. In neurophysiology the concept of high-density EMG (HD-EMG), using two dimensional electrode grids, was developed for the measurement of spatiotemporal activation patterns of the underlying muscle and its motor units

  18. RhoA exerts a permissive effect on volume-regulated anion channels in vascular endothelial cells

    DEFF Research Database (Denmark)

    Carton, Iris; Trouet, Dominique; Hermans, Diane;

    2002-01-01

    pathway reduces the swelling-dependent activation of I(Cl,swell). However, these experiments did not allow us to discriminate between a direct activator role or a permissive effect. We now show that the Rho pathway did not affect VRAC activity if this pathway was activated by transfecting CPAE cells......'-O-(3-thiotriphosphate) or C3 exoenzyme had no effect on VRACs in caveolin-1-expressing Caco-2 cells. We conclude that the Rho pathway exerts a permissive effect on VRACs in CPAE cells, i.e., swelling-induced opening of VRACs requires a functional Rho pathway, but not an activation of the Rho pathway.......Cell swelling triggers in most cell types an outwardly rectifying anion current, I(Cl,swell), via volume-regulated anion channels (VRACs). We have previously demonstrated in calf pulmonary artery endothelial (CPAE) cells that inhibition of the Rho/Rho kinase/myosin light chain phosphorylation...

  19. The H-loop in the Second Nucleotide-binding Domain of the Cystic Fibrosis Transmembrane Conductance Regulator is Required for Efficient Chloride Channel Closing

    OpenAIRE

    Kloch, Monika; Milewski, Michał; Nurowska, Ewa; Dworakowska, Beata; Cutting, Garry R; Dołowy, Krzysztof

    2010-01-01

    The cystic fibrosis transmembrane conductance regulator (CFTR) is an ATP-binding cassette (ABC) transporter that functions as a cAMP-activated chloride channel. The recent model of CFTR gating predicts that the ATP binding to both nucleotide-binding domains (NBD1 and NBD2) of CFTR is required for the opening of the channel, while the ATP hydrolysis at NBD2 induces subsequent channel closing. In most ABC proteins, efficient hydrolysis of ATP requires the presence of the invariant histidine res...

  20. BKCa and hEag1 channels regulate cell proliferation and differentiation in human bone marrow-derived mesenchymal stem cells.

    Science.gov (United States)

    Zhang, Ying-Ying; Yue, Jianbo; Che, Hui; Sun, Hai-Ying; Tse, Hung-Fat; Li, Gui-Rong

    2014-02-01

    Human bone marrow-derived mesenchymal stem cells (MSCs) serve as a reservoir for the continuous renewal of various mesenchymal tissues; however, cellular physiology of ion channels is not fully understood. The present study investigated potential roles of large-conductance Ca(2+) -activated potassium (BKCa ) channels and ether-à-go-go potassium (hEag1 or Kv10.1) channels in regulating cell proliferation and differentiation in human MSCs. We found that inhibition of BKCa with paxilline or hEag1 with astemizole, or knockdown of BKCa with shRNAs targeting KCa1.1 or hEag1 channels with shRNAs targeting KCNH1 arrested the cells at G0/G1 phase. In addition, silencing BKCa or hEag1 channels significantly reduced adipogenic differentiation with decrease of lipid accumulation and expression of the adipocyte marker PPARγ, and decreased osteogenic differentiation with reduction of mineral precipitation and osteocalcin. These effects were accompanied with a reduced cyclin D1, cyclin E, p-ERK1/2, and p-Akt. Our results demonstrate that BKCa and hEag1 channels not only regulate cell proliferation, but also participate in the adipogenic and osteogenic differentiations in human MSCs, which indicates that BKCa and hEag1 channels may be essential in maintaining bone marrow physiological function and bone regeneration. PMID:23881642

  1. T-type Calcium Channel Regulation of Neural Tube Closure and EphrinA/EPHA Expression

    Directory of Open Access Journals (Sweden)

    Sarah Abdul-Wajid

    2015-10-01

    Full Text Available A major class of human birth defects arise from aberrations during neural tube closure (NTC. We report on a NTC signaling pathway requiring T-type calcium channels (TTCCs that is conserved between primitive chordates (Ciona and Xenopus. With loss of TTCCs, there is a failure to seal the anterior neural folds. Accompanying loss of TTCCs is an upregulation of EphrinA effectors. Ephrin signaling is known to be important in NTC, and ephrins can affect both cell adhesion and repulsion. In Ciona, ephrinA-d expression is downregulated at the end of neurulation, whereas, with loss of TTCC, ephrinA-d remains elevated. Accordingly, overexpression of ephrinA-d phenocopied TTCC loss of function, while overexpression of a dominant-negative Ephrin receptor was able to rescue NTC in a Ciona TTCC mutant. We hypothesize that signaling through TTCCs is necessary for proper anterior NTC through downregulation of ephrins, and possibly elimination of a repulsive signal.

  2. Regulation of CLC-1 chloride channel biosynthesis by FKBP8 and Hsp90β

    Science.gov (United States)

    Peng, Yi-Jheng; Huang, Jing-Jia; Wu, Hao-Han; Hsieh, Hsin-Ying; Wu, Chia-Ying; Chen, Shu-Ching; Chen, Tsung-Yu; Tang, Chih-Yung

    2016-01-01

    Mutations in human CLC-1 chloride channel are associated with the skeletal muscle disorder myotonia congenita. The disease-causing mutant A531V manifests enhanced proteasomal degradation of CLC-1. We recently found that CLC-1 degradation is mediated by cullin 4 ubiquitin ligase complex. It is currently unclear how quality control and protein degradation systems coordinate with each other to process the biosynthesis of CLC-1. Herein we aim to ascertain the molecular nature of the protein quality control system for CLC-1. We identified three CLC-1-interacting proteins that are well-known heat shock protein 90 (Hsp90)-associated co-chaperones: FK506-binding protein 8 (FKBP8), activator of Hsp90 ATPase homolog 1 (Aha1), and Hsp70/Hsp90 organizing protein (HOP). These co-chaperones promote both the protein level and the functional expression of CLC-1 wild-type and A531V mutant. CLC-1 biosynthesis is also facilitated by the molecular chaperones Hsc70 and Hsp90β. The protein stability of CLC-1 is notably increased by FKBP8 and the Hsp90β inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) that substantially suppresses cullin 4 expression. We further confirmed that cullin 4 may interact with Hsp90β and FKBP8. Our data are consistent with the idea that FKBP8 and Hsp90β play an essential role in the late phase of CLC-1 quality control by dynamically coordinating protein folding and degradation. PMID:27580824

  3. Acid-sensing ion channels regulate spontaneous inhibitory activity in the hippocampus: possible implications for epilepsy.

    Science.gov (United States)

    Ievglevskyi, O; Isaev, D; Netsyk, O; Romanov, A; Fedoriuk, M; Maximyuk, O; Isaeva, E; Akaike, N; Krishtal, O

    2016-08-01

    Acid-sensing ion channels (ASICs) play an important role in numerous functions in the central and peripheral nervous systems ranging from memory and emotions to pain. The data correspond to a recent notion that each neuron and many glial cells of the mammalian brain express at least one member of the ASIC family. However, the mechanisms underlying the involvement of ASICs in neuronal activity are poorly understood. However, there are two exceptions, namely, the straightforward role of ASICs in proton-based synaptic transmission in certain brain areas and the role of the Ca(2+)-permeable ASIC1a subtype in ischaemic cell death. Using a novel orthosteric ASIC antagonist, we have found that ASICs specifically control the frequency of spontaneous inhibitory synaptic activity in the hippocampus. Inhibition of ASICs leads to a strong increase in the frequency of spontaneous inhibitory postsynaptic currents. This effect is presynaptic because it is fully reproducible in single synaptic boutons attached to isolated hippocampal neurons. In concert with this observation, inhibition of the ASIC current diminishes epileptic discharges in a low Mg(2+) model of epilepsy in hippocampal slices and significantly reduces kainate-induced discharges in the hippocampus in vivo Our results reveal a significant novel role for ASICs.This article is part of the themed issue 'Evolution brings Ca(2+) and ATP together to control life and death'. PMID:27377725

  4. Identification of KCa3.1 channel as a novel regulator of Oxidative phosphorylation in a subset of pancreatic carcinoma cell lines

    DEFF Research Database (Denmark)

    Kovalenko, Ilya; Glasauer, Andrea; Schöckel, Laura;

    2016-01-01

    -of-function mutations in p53. Both mutations have severe impacts on the metabolism of tumor cells. Many of these metabolic changes are mediated by transporters or channels that regulate the exchange of metabolites and ions between the intracellular compartment and the tumor microenvironment. In the study presented here......, our goal was to identify novel transporters or channels that regulate oxidative phosphorylation (OxPhos) in PDAC in order to characterize novel potential drug targets for the treatment of these cancers. We set up a Seahorse Analyzer XF based siRNA screen and identified previously described as well...... of a small molecule inhibitor confirmed its role in regulating oxygen consumption, ATP production and cellular proliferation. Furthermore, PDAC cell lines sensitive to KCa3.1 inhibition were shown to express the channel protein in the plasma membrane as well as in the mitochondria. These differences...

  5. TRPM7 channel regulates PDGF-BB-induced proliferation of hepatic stellate cells via PI3K and ERK pathways

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Ling, E-mail: fangling_1984@126.com; Zhan, Shuxiang; Huang, Cheng; Cheng, Xi; Lv, Xiongwen; Si, Hongfang; Li, Jun, E-mail: lj@ahmu.edu.cn

    2013-11-01

    TRPM7, a non-selective cation channel of the TRP channel superfamily, is implicated in diverse physiological and pathological processes including cell proliferation. Recently, TRPM7 has been reported in hepatic stellate cells (HSCs). Here, we investigated the contribution role of TRPM7 in activated HSC-T6 cell (a rat hepatic stellate cell line) proliferation. TRPM7 mRNA and protein were measured by RT-PCR and Western blot in rat model of liver fibrosis in vivo and PDGF-BB-activated HSC-T6 cells in vitro. Both mRNA and protein of TRPM7 were dramatically increased in CCl{sub 4}-treated rat livers. Stimulation of HSC-T6 cells with PDGF-BB resulted in a time-dependent increase of TRPM7 mRNA and protein. However, PDGF-BB-induced HSC-T6 cell proliferation was inhibited by non-specific TRPM7 blocker 2-aminoethoxydiphenyl borate (2-APB) or synthetic siRNA targeting TRPM7, and this was accompanied by downregulation of cell cycle proteins, cyclin D1, PCNA and CDK4. Blockade of TRPM7 channels also attenuated PDGF-BB induced expression of myofibroblast markers as measured by the induction of α-SMA and Col1α1. Furthermore, the phosphorylation of ERK and AKT, associated with cell proliferation, decreased in TRPM7 deficient HSC-T6 cells. These observations suggested that TRPM7 channels contribute to perpetuated fibroblast activation and proliferation of PDGF-BB induced HSC-T6 cells via the activation of ERK and PI3K pathways. Therefore, TRPM7 may constitute a useful target for the treatment of liver fibrosis. - Highlights: • Upregulation of TRPM7 mRNA and protein in the fibrotic livers from CCl{sub 4}-treated rats. • Increasing expression of TRPM7 mRNA and protein during HSC activation. • Blockade of TRPM7 inhibited the PDGF-BB induced proliferation of HSC-T6 cells. • Blockade of TRPM7 decreased α-SMA and Col1α1 expressions in activated HSC-T6 cells. • TRPM7 up-regulation contributes to the activation of ERK and AKT pathways.

  6. Multiple intracellular signallings involved in regulation of on channels by GH releasing or inhibitory hormones in pituitary somatotropes

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Influx of Ca2- via Ca2+ channels is the major step triggering exocytosis of pituitary somatotropes to release growth hormone (GH). Voltage-gated Ca2+ and K+ channels, the primary determinants of the influx of Ca2+ in somatotropes, are regulated by GH-releasing hornone (GHRH) and somatostatin (SRIF) through G protein-coupled signalling systems. Using whole-cell patch-clamp techniques, the changes of the Ca2+ and K+ currents in primary cultured somatotropes were recorded and signalling systems were studied using pharmacological reagents and intracellular dialysis of non-permeable molecules including antibodies and antisense oligonucleotides. GHRH increased both L-and T-types Ca2+ currents and decreased transient (I4) and delayed rectified (Ik) K+ currents. The increase in Ca2+ currents by GHRH was mediated by cAMP/protein kinase A system but the decrease in K+ currents required normal function of protein kinase C system. The GHRH-induced alteration of Ca2+ and K+ currents augments the influx of Ca2+ , leading to an increase in the [ Ca2+ ]i and the GH secretion. In contrary, a significant reduction in Ca2+ currents and increase in K currents were obtained in response to SRIF. The ion channel response to SRIF was demonstrated as a membrane delimited pathway and can be recorded by classic whole-cell configuration, Intracellular dialysis of anti-αi3 antibodies attenuated the increase in K + currents by SRIF whereas anti-αo antibodies blocked the reduction in the Ca2+ current by SRIF. Dialysis of antisense oligonucleotides specific for αo2 sub-units also attenuated the inhibition of SRIF on the Ca2+current. The Gi3 protein mediated the increase in K + currents and the Go2 protein mediated the reduction in the Ca2 +current by SRIF. The SRIF-induced alteration of Ca2 + and K + currents diminished the influx of Ca2+ , leading to a decrease in the [ Ca2+ ]i and the GH secretion. It is therefore concluded that multiple signalling systems are employed in the ion channel

  7. Association between tetrodotoxin resistant channels and lipid rafts regulates sensory neuron excitability.

    Directory of Open Access Journals (Sweden)

    Alessandro Pristerà

    Full Text Available Voltage-gated sodium channels (VGSCs play a key role in the initiation and propagation of action potentials in neurons. Na(V1.8 is a tetrodotoxin (TTX resistant VGSC expressed in nociceptors, peripheral small-diameter neurons able to detect noxious stimuli. Na(V1.8 underlies the vast majority of sodium currents during action potentials. Many studies have highlighted a key role for Na(V1.8 in inflammatory and chronic pain models. Lipid rafts are microdomains of the plasma membrane highly enriched in cholesterol and sphingolipids. Lipid rafts tune the spatial and temporal organisation of proteins and lipids on the plasma membrane. They are thought to act as platforms on the membrane where proteins and lipids can be trafficked, compartmentalised and functionally clustered. In the present study we investigated Na(V1.8 sub-cellular localisation and explored the idea that it is associated with lipid rafts in nociceptors. We found that Na(V1.8 is distributed in clusters along the axons of DRG neurons in vitro and ex vivo. We also demonstrated, by biochemical and imaging studies, that Na(V1.8 is associated with lipid rafts along the sciatic nerve ex vivo and in DRG neurons in vitro. Moreover, treatments with methyl-β-cyclodextrin (MβCD and 7-ketocholesterol (7KC led to the dissociation between rafts and Na(V1.8. By calcium imaging we demonstrated that the lack of association between rafts and Na(V1.8 correlated with impaired neuronal excitability, highlighted by a reduction in the number of neurons able to conduct mechanically- and chemically-evoked depolarisations. These findings reveal the sub-cellular localisation of Na(V1.8 in nociceptors and highlight the importance of the association between Na(V1.8 and lipid rafts in the control of nociceptor excitability.

  8. TRPV3 Channel Negatively Regulates Cell Cycle Progression and Safeguards the Pluripotency of Embryonic Stem Cells.

    Science.gov (United States)

    Lo, Iek Chi; Chan, Hing Chung; Qi, Zenghua; Ng, Kwun Lam; So, Chun; Tsang, Suk Ying

    2016-02-01

    Embryonic stem cells (ESCs) have tremendous potential for research and future therapeutic purposes. However, the calcium handling mechanism in ESCs is not fully elucidated. Aims of this study are (1) to investigate if transient receptor potential vanilloid-3 (TRPV3) channels are present in mouse ESCs (mESCs) and their subcellular localization; (2) to investigate the role of TRPV3 in maintaining the characteristics of mESCs. Western blot and immunocytochemistry showed that TRPV3 was present at the endoplasmic reticulum (ER) of mESCs. Calcium imaging showed that, in the absence of extracellular calcium, TRPV3 activators camphor and 6-tert-butyl-m-cresol increased the cytosolic calcium. However, depleting the ER store in advance of activator addition abolished the calcium increase, suggesting that TRPV3 released calcium from the ER. To dissect the functional role of TRPV3, TRPV3 was activated and mESC proliferation was measured by trypan blue exclusion and MTT assays. The results showed that TRPV3 activation led to a decrease in mESC proliferation. Cell cycle analysis revealed that TRPV3 activation increased the percentage of cells in G2 /M phase; consistently, Western blot also revealed a concomitant increase in the expression of inactive form of cyclin-dependent kinase 1, suggesting that TRPV3 activation arrested mESCs at G2 /M phase. TRPV3 activation did not alter the expression of pluripotency markers Oct-4, Klf4 and c-Myc, suggesting that the pluripotency was preserved. Our study is the first study to show the presence of TRPV3 at ER. Our study also reveals the novel role of TRPV3 in controlling the cell cycle and preserving the pluripotency of ESCs.

  9. Sites of pH regulation of the urea channel of Helicobacter pylori.

    Science.gov (United States)

    Weeks, D L; Sachs, G

    2001-06-01

    Helicobacter pylori (Hp) and Streptococcus salivarius (Ss) require intrabacterial urease for acid resistance and express a urea channel, UreI. The presence of UreI was shown to increase urea permeability approximately 300-fold over that of a non-polar ureI deletion mutant. Expression of SsUreI in Xenopus oocytes increased urea uptake pH independently, whereas HpUreI shows an acidic pH dependence, half-maximal at pH 6.0. Mutagenesis of all histidines, aspartates, glutamates and the lysine in the periplasmic domain of HpUreI showed that His-123, His-131, Asp-129, Asp-140, Glu-138 and Lys-132 in the second periplasmic loop (PL2) and His-193 in the C-terminus (Ct) were important for activation of transport. With the exception of a lysine that was shown to substitute for His-193 in HpUreI, these charged amino acids are absent in SsUreI. A chimera in which PL1 of HpUreI was replaced by PL1 of SsUreI retained activity at acidic pH and gained partial activity at neutral pH. Exchange of PL2 inactivated transport, whereas exchange of Ct had no effect. Chimeras, in which either PL1 or PL2 of HpUreI replaced those of SsUreI, retained wild-type transport, but replacement of the Ct or both loops inactivated transport. PL1 appears to be important for restricting transport through HpUreI at neutral pH, whereas protonation of three histidines in PL2 and Ct and the presence of three dicarboxylic amino acids in PL2 appears to be necessary to activate HpUreI at acidic pH.

  10. Cell-Autonomous Regulation of Dendritic Spine Density by PirB

    Science.gov (United States)

    2016-01-01

    Synapse density on cortical pyramidal neurons is modulated by experience. This process is highest during developmental critical periods, when mechanisms of synaptic plasticity are fully engaged. In mouse visual cortex, the critical period for ocular dominance (OD) plasticity coincides with the developmental pruning of synapses. At this time, mice lacking paired Ig-like receptor B (PirB) have excess numbers of dendritic spines on L5 neurons; these spines persist and are thought to underlie the juvenile-like OD plasticity observed in adulthood. Here we examine whether PirB is required specifically in excitatory neurons to exert its effect on dendritic spine and synapse density during the critical period. In mice with a conditional allele of PirB (PirBfl/fl), PirB was deleted only from L2/3 cortical pyramidal neurons in vivo by timed in utero electroporation of Cre recombinase. Sparse mosaic expression of Cre produced neurons lacking PirB in a sea of wild-type neurons and glia. These neurons had significantly elevated dendritic spine density, as well as increased frequency of miniature EPSCs, suggesting that they receive a greater number of synaptic inputs relative to Cre– neighbors. The effect of cell-specific PirB deletion on dendritic spine density was not accompanied by changes in dendritic branching complexity or axonal bouton density. Together, results imply a neuron-specific, cell-autonomous action of PirB on synaptic density in L2/3 pyramidal cells of visual cortex. Moreover, they are consistent with the idea that PirB functions normally to corepress spine density and synaptic plasticity, thereby maintaining headroom for cells to encode ongoing experience-dependent structural change throughout life.

  11. Regulation of excitability in tonic firing substantia gelatinosa neurons of the spinal cord by small-conductance Ca(2+)-activated K(+) channels.

    Science.gov (United States)

    Yang, Kun

    2016-06-01

    The excitability of substantia gelatinosa (SG) neurons in the spinal dorsal horn determines the processing of nociceptive information from the periphery to the central nervous system. Small conductance Ca(2+)-activated K(+) (SK) channels on neurons supply strong negative feedback control on neuronal excitability by affecting afterhyperpolarization (AHP). However, the role of SK channels in regulating tonic-firing SG neuron excitability remains elusive. In the present study, whole-cell recordings were conducted in SG neurons from acute spinal cord slices of adult rats. The SK channel opener 1-ethyl-2-benzimidazolinone (1-EBIO) attenuated spike discharges and increased AHP amplitudes; this effect was mimicked by a high Ca(2+) external solution. Systemic administration of 1-EBIO attenuated the thermal-induced nociception behavior. Conversely, the inhibition of SK channels with apamin, a specific SK channel inhibitor, increased neuronal excitability and decreased the AHP amplitudes; this effect was mimicked by a Ca(2+)-free external solution. Apamin increased excitatory synaptic transmission by increasing the amplitudes of evoked excitatory postsynaptic potentials (eEPSPs). This facilitation depended on N-methyl-d-aspartate (NMDA) receptors, extracellular Mg(2+) and intracellular Ca(2+). Voltage-gated Ca(2+) channels (VGCCs) were also involved in the apamin-induced effects. Strikingly, 1-EBIO action on decreasing excitability persisted in the presence of apamin, indicating that 1-EBIO manipulates SK channels via a pathway rather than via apamin-sensitive SK channels. The data reveal a previously uncharacterized mechanism for manipulating SG neuronal excitability by Ca(2+) conductances via both apamin-sensitive and apamin-insensitive pathways. Because SG neurons in the dorsal horn are involved in regulating nociception, manipulating neuronal excitability via SK channels indicates a potential therapeutic target. PMID:26777279

  12. Dual regulation of the native ClC-K2 chloride channel in the distal nephron by voltage and pH.

    Science.gov (United States)

    Pinelli, Laurent; Nissant, Antoine; Edwards, Aurélie; Lourdel, Stéphane; Teulon, Jacques; Paulais, Marc

    2016-09-01

    ClC-K2, a member of the ClC family of Cl(-) channels and transporters, forms the major basolateral Cl(-) conductance in distal nephron epithelial cells and therefore plays a central role in renal Cl(-) absorption. However, its regulation remains largely unknown because of the fact that recombinant ClC-K2 has not yet been studied at the single-channel level. In the present study, we investigate the effects of voltage, pH, Cl(-), and Ca(2+) on native ClC-K2 in the basolateral membrane of intercalated cells from the mouse connecting tubule. The ∼10-pS channel shows a steep voltage dependence such that channel activity increases with membrane depolarization. Intracellular pH (pHi) and extracellular pH (pHo) differentially modulate the voltage dependence curve: alkaline pHi flattens the curve by causing an increase in activity at negative voltages, whereas alkaline pHo shifts the curve toward negative voltages. In addition, pHi, pHo, and extracellular Ca(2+) strongly increase activity, mainly because of an increase in the number of active channels with a comparatively minor effect on channel open probability. Furthermore, voltage alters both the number of active channels and their open probability, whereas intracellular Cl(-) has little influence. We propose that changes in the number of active channels correspond to them entering or leaving an inactivated state, whereas modulation of open probability corresponds to common gating by these channels. We suggest that pH, through the combined effects of pHi and pHo on ClC-K2, might be a key regulator of NaCl absorption and Cl(-)/HCO3 (-) exchange in type B intercalated cells. PMID:27574292

  13. A novel conditional mouse model for Nkx2-5 reveals transcriptional regulation of cardiac ion channels.

    Science.gov (United States)

    Furtado, Milena B; Wilmanns, Julia C; Chandran, Anjana; Tonta, Mary; Biben, Christine; Eichenlaub, Michael; Coleman, Harold A; Berger, Silke; Bouveret, Romaric; Singh, Reena; Harvey, Richard P; Ramialison, Mirana; Pearson, James T; Parkington, Helena C; Rosenthal, Nadia A; Costa, Mauro W

    2016-01-01

    Nkx2-5 is one of the master regulators of cardiac development, homeostasis and disease. This transcription factor has been previously associated with a suite of cardiac congenital malformations and impairment of electrical activity. When disease causative mutations in transcription factors are considered, NKX2-5 gene dysfunction is the most common abnormality found in patients. Here we describe a novel mouse model and subsequent implications of Nkx2-5 loss for aspects of myocardial electrical activity. In this work we have engineered a new Nkx2-5 conditional knockout mouse in which flox sites flank the entire Nkx2-5 locus, and validated this line for the study of heart development, differentiation and disease using a full deletion strategy. While our homozygous knockout mice show typical embryonic malformations previously described for the lack of the Nkx2-5 gene, hearts of heterozygous adult mice show moderate morphological and functional abnormalities that are sufficient to sustain blood supply demands under homeostatic conditions. This study further reveals intriguing aspects of Nkx2-5 function in the control of cardiac electrical activity. Using a combination of mouse genetics, biochemistry, molecular and cell biology, we demonstrate that Nkx2-5 regulates the gene encoding Kcnh2 channel and others, shedding light on potential mechanisms generating electrical abnormalities observed in patients bearing NKX2-5 dysfunction and opening opportunities to the study of novel therapeutic targets for anti-arrhythmogenic therapies. PMID:26897459

  14. Smooth muscle myosin regulation by serum and cell density in cultured rat lung connective tissue cells.

    Science.gov (United States)

    Babij, P; Zhao, J; White, S; Woodcock-Mitchell, J; Mitchell, J; Absher, M; Baldor, L; Periasamy, M; Low, R B

    1993-08-01

    RNA and protein analyses were used to detect expression of SM1 and SM2 smooth muscle myosin heavy chain (MHC) in cultured adult rat lung connective tissue cells (RL-90). Smooth muscle MHC mRNA expression in confluent cells grown in 10% serum was approximately 50% of the level in adult stomach. Similar results were obtained in cells cultured at low density (25% confluency) in 1% serum. However, in low-density cultures transferred to 10% serum for 24 h, the level of MHC mRNA decreased to approximately 20% of that in adult stomach. Smooth muscle alpha-actin showed a pattern of expression similar to that for smooth muscle MHC. Expression of nonmuscle MHC-A mRNA was higher in all culture conditions compared to stomach. MHC-A mRNA expression was less in low-density cultures in low serum and increased when low-density cultures were transferred to 10% serum for 24 h. MHC-B mRNA expression was less in low- vs. high-density cultures. In contrast to MHC-A, however, MHC-B mRNA expression in low-density cultures was higher in low serum. Immunofluorescence and immunoblotting with SM1-specific antibody demonstrated the presence of the SM1 protein isoform as well as reactivity to a protein band migrating slightly faster than SM2. These results demonstrate that cultured rat lung connective tissue cells express smooth muscle MHC and that expression is modulated by culture conditions.

  15. Stochastic seasonality and nonlinear density-dependent factors regulate population size in an African rodent

    DEFF Research Database (Denmark)

    Leirs, Herwig; Steneth, Nils Chr.; Nichols, James D.;

    1997-01-01

    , but clear examples of both processes acting in the same population are rare(7,8). Key-factor analysis (regression of population changes on possible causal factors) and time-series analysis are often used to investigate the presence of density dependence, but such approaches may be biased and provide...... demonstrate that they do not affect all demographic rates in the same way. We have incorporated the obtained estimates of demographic rates in a population dynamics model and show that the observed dynamics are affected by stabilizing nonlinear density-dependent components coupled with strong deterministic...

  16. Regulation of IGF-1-dependent cyclin D1 and E expression by hEag1 channels in MCF-7 cells: the critical role of hEag1 channels in G1 phase progression.

    Science.gov (United States)

    Borowiec, Anne-Sophie; Hague, Frédéric; Gouilleux-Gruart, Valérie; Lassoued, Kaiss; Ouadid-Ahidouch, Halima

    2011-05-01

    Insulin-like Growth Factor-1 (IGF-1) plays a key role in breast cancer development and cell cycle regulation. It has been demonstrated that IGF-1 stimulates cyclin expression, thus regulating the G1 to S phase transition of the cell cycle. Potassium (K(+)) channels are involved in the G1 phase progression of the cell cycle induced by growth factors. However, mechanisms that allow growth factors to cooperate with K(+) channels in order to modulate the G1 phase progression and cyclin expression remain unknown. Here, we focused on hEag1 K(+) channels which are over-expressed in breast cancer and are involved in the G1 phase progression of breast cancer cells (MCF-7). As expected, IGF-1 increased cyclin D1 and E expression of MCF-7 cells in a cyclic manner, whereas the increase of CDK4 and 2 levels was sustained. IGF-1 stimulated p21(WAF1/Cip1) expression with a kinetic similar to that of cyclin D1, however p27(Kip1) expression was insensitive to IGF-1. Interestingly, astemizole, a blocker of hEag1 channels, but not E4031, a blocker of HERG channels, inhibited the expression of both cyclins after 6-8h of co-stimulation with IGF-1. However, astemizole failed to modulate CDK4, CDK2, p21(WAF1/Cip1) and p27(Kip1) expression. The down-regulation of hEag1 by siRNA provoked a decrease in cyclin expression. This study is the first to demonstrate that K(+) channels such as hEag1 are directly involved in the IGF-1-induced up-regulation of cyclin D1 and E expression in MCF-7 cells. By identifying more specifically the temporal position of the arrest site induced by the inhibition of hEag1 channels, we confirmed that hEag1 activity is predominantly upstream of the arrest site induced by serum-deprivation, prior to the up-regulation of both cyclins D1 and E. This article is part of a Special Issue entitled: 11th European Symposium on Calcium. PMID:21315112

  17. Troponin T3 regulates nuclear localization of the calcium channel Cavβ1a subunit in skeletal muscle

    International Nuclear Information System (INIS)

    The voltage-gated calcium channel (Cav) β1a subunit (Cavβ1a) plays an important role in excitation–contraction coupling (ECC), a process in the myoplasm that leads to muscle-force generation. Recently, we discovered that the Cavβ1a subunit travels to the nucleus of skeletal muscle cells where it helps to regulate gene transcription. To determine how it travels to the nucleus, we performed a yeast two-hybrid screening of the mouse fast skeletal muscle cDNA library and identified an interaction with troponin T3 (TnT3), which we subsequently confirmed by co-immunoprecipitation and co-localization assays in mouse skeletal muscle in vivo and in cultured C2C12 muscle cells. Interacting domains were mapped to the leucine zipper domain in TnT3 COOH-terminus (160–244 aa) and Cavβ1a NH2-terminus (1–99 aa), respectively. The double fluorescence assay in C2C12 cells co-expressing TnT3/DsRed and Cavβ1a/YFP shows that TnT3 facilitates Cavβ1a nuclear recruitment, suggesting that the two proteins play a heretofore unknown role during early muscle differentiation in addition to their classical role in ECC regulation. - Highlights: • Previously, we demonstrated that Cavβ1a is a gene transcription regulator. • Here, we show that TnT3 interacts with Cavβ1a. • We mapped TnT3 and Cavβ1a interaction domain. • TnT3 facilitates Cavβ1a nuclear enrichment. • The two proteins play a heretofore unknown role during early muscle differentiation

  18. Osteoclast cytosolic calcium, regulated by voltage-gated calcium channels and extracellular calcium, controls podosome assembly and bone resorption

    Science.gov (United States)

    Miyauchi, A.; Hruska, K. A.; Greenfield, E. M.; Duncan, R.; Alvarez, J.; Barattolo, R.; Colucci, S.; Zambonin-Zallone, A.; Teitelbaum, S. L.; Teti, A.

    1990-01-01

    The mechanisms of Ca2+ entry and their effects on cell function were investigated in cultured chicken osteoclasts and putative osteoclasts produced by fusion of mononuclear cell precursors. Voltage-gated Ca2+ channels (VGCC) were detected by the effects of membrane depolarization with K+, BAY K 8644, and dihydropyridine antagonists. K+ produced dose-dependent increases of cytosolic calcium ([Ca2+]i) in osteoclasts on glass coverslips. Half-maximal effects were achieved at 70 mM K+. The effects of K+ were completely inhibited by dihydropyridine derivative Ca2+ channel blocking agents. BAY K 8644 (5 X 10(-6) M), a VGCC agonist, stimulated Ca2+ entry which was inhibited by nicardipine. VGCCs were inactivated by the attachment of osteoclasts to bone, indicating a rapid phenotypic change in Ca2+ entry mechanisms associated with adhesion of osteoclasts to their resorption substrate. Increasing extracellular Ca2+ ([Ca2+]e) induced Ca2+ release from intracellular stores and Ca2+ influx. The Ca2+ release was blocked by dantrolene (10(-5) M), and the influx by La3+. The effects of [Ca2+]e on [Ca2+]i suggests the presence of a Ca2+ receptor on the osteoclast cell membrane that could be coupled to mechanisms regulating cell function. Expression of the [Ca2+]e effect on [Ca2+]i was similar in the presence or absence of bone matrix substrate. Each of the mechanisms producing increases in [Ca2+]i, (membrane depolarization, BAY K 8644, and [Ca2+]e) reduced expression of the osteoclast-specific adhesion structure, the podosome. The decrease in podosome expression was mirrored by a 50% decrease in bone resorptive activity. Thus, stimulated increases of osteoclast [Ca2+]i lead to cytoskeletal changes affecting cell adhesion and decreasing bone resorptive activity.

  19. Differential regulation of human Eag1 channel expression by serum and epidermal growth factor in lung and breast cancer cells

    Directory of Open Access Journals (Sweden)

    Acuña-Macías I

    2015-10-01

    Full Text Available Isabel Acuña-Macías,1 Eunice Vera,1 Alma Yolanda Vázquez-Sánchez,1 María Eugenia Mendoza-Garrido,2 Javier Camacho1 1Department of Pharmacology, 2Department of Physiology, Biophysics and Neurosciences, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Mexico City, Mexico Abstract: Oncogenic ether à-go-go-1 (Eag1 potassium channels are overexpressed in most primary human solid tumors. Low oxygen and nutrient/growth factor concentrations play critical roles in tumorigenesis. However, the mechanisms by which tumor cells survive and proliferate under growth factor-depleted conditions remain elusive. Here, we investigated whether serum-deprived conditions and epidermal growth factor (EGF regulate Eag1 expression in human lung and breast cancer cells. The human cancer cell lines A549 and MCF-7 (from the lungs and breast, respectively were obtained from the American Type Culture Collection and cultured following the manufacturer’s recommendations. Eag1 gene and protein expression were studied by real-time PCR and immunocytochemistry, respectively. Cell proliferation was evaluated using the 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide assay, and ERK1/2 phosphorylation was investigated by Western blot. Serum-deprived conditions increased Eag1 mRNA and protein expression in both cell lines. This Eag1 upregulation was prevented by EGF and the ERK1/2 inhibitor U0126 in only lung cancer cells; vascular endothelial growth factor did not prevent Eag1 upregulation. Our results suggest that Eag1 may act as a survival and mitogenic factor under low-serum and nutrient conditions and may be a clinical target during the early stages of tumor development. Keywords: lung cancer, serum deprivation, ether à-go-go, potassium channels, EGF, epidermal growth factor, ERK 1/2

  20. The GTP- and Phospholipid-Binding Protein TTD14 Regulates Trafficking of the TRPL Ion Channel in Drosophila Photoreceptor Cells

    Science.gov (United States)

    Cerny, Alexander C.; Altendorfer, André; Schopf, Krystina; Baltner, Karla; Maag, Nathalie; Sehn, Elisabeth; Wolfrum, Uwe; Huber, Armin

    2015-01-01

    Recycling of signaling proteins is a common phenomenon in diverse signaling pathways. In photoreceptors of Drosophila, light absorption by rhodopsin triggers a phospholipase Cβ-mediated opening of the ion channels transient receptor potential (TRP) and TRP-like (TRPL) and generates the visual response. The signaling proteins are located in a plasma membrane compartment called rhabdomere. The major rhodopsin (Rh1) and TRP are predominantly localized in the rhabdomere in light and darkness. In contrast, TRPL translocates between the rhabdomeral plasma membrane in the dark and a storage compartment in the cell body in the light, from where it can be recycled to the plasma membrane upon subsequent dark adaptation. Here, we identified the gene mutated in trpl translocation defective 14 (ttd14), which is required for both TRPL internalization from the rhabdomere in the light and recycling of TRPL back to the rhabdomere in the dark. TTD14 is highly conserved in invertebrates and binds GTP in vitro. The ttd14 mutation alters a conserved proline residue (P75L) in the GTP-binding domain and abolishes binding to GTP. This indicates that GTP binding is essential for TTD14 function. TTD14 is a cytosolic protein and binds to PtdIns(3)P, a lipid enriched in early endosome membranes, and to phosphatidic acid. In contrast to TRPL, rhabdomeral localization of the membrane proteins Rh1 and TRP is not affected in the ttd14 P75L mutant. The ttd14 P75L mutation results in Rh1-independent photoreceptor degeneration and larval lethality suggesting that other processes are also affected by the ttd14 P75L mutation. In conclusion, TTD14 is a novel regulator of TRPL trafficking, involved in internalization and subsequent sorting of TRPL into the recycling pathway that enables this ion channel to return to the plasma membrane. PMID:26509977

  1. Lack of Kinase Regulation of Canonical Transient Receptor Potential 3 (TRPC3) Channel-dependent Currents in Cerebellar Purkinje Cells

    OpenAIRE

    Nelson, Charmaine; Glitsch, Maike D.

    2011-01-01

    Background: TRPC3 channels are inhibited by PKC and PKG, which also induce cerebellar LTD. We investigate if PKC- and PKG-mediated modulation of cerebellar TRPC3 channels contributes to cerebellar LTD.

  2. VDNROM: A novel four-physical-bits/cell vertical channel dual-nitride-trapping-layers ROM for high density flash memory applications

    Science.gov (United States)

    Zhou, Falong; Cai, Yimao; Huang, Ru; Li, Yan; Shan, Xiaonan; Liu, Jia; Guo, Ao; Zhang, Xing; Wang, Yangyuan

    2007-11-01

    A novel vertical channel dual-nitride-trapping-layer ROM (VDNROM) flash memory with oxide-nitride-oxide-nitride-oxide (ONONO) dielectrics stack is proposed and experimentally demonstrated. Compared with the conventional planar NROM cell, since the cell area of the proposed vertical structure is independent of the gate length, the VDNROM structure can relax the limitation of the gate length scaling, and can have high capability of cell area shrinking. The fabrication process of this VDNROM device is basically compatible with planar CMOS technology. The VDNROM cell can be programmed and erased by the hot carrier injection to the localized trapping dual-nitride layers, so it can achieve a four-physical-bits storage capability each cell. The reliability behaviors including the cycling endurance and the bake retention at 150 °C have also been investigated and show the acceptable characteristics. The experiment results verify the VDNROM cell as a good candidate for high density applications.

  3. The Phospholipid-binding Protein SESTD1 Is a Novel Regulator of the Transient Receptor Potential Channels TRPC4 and TRPC5

    Science.gov (United States)

    Miehe, Susanne; Bieberstein, Andrea; Arnould, Isabelle; Ihdene, Orhia; Rütten, Hartmut; Strübing, Carsten

    2010-01-01

    TRPC4 and TRPC5 are two closely related members of the mammalian transient receptor potential cation channel family that have been implicated in important physiological functions, such as growth cone guidance and smooth muscle contraction. To further unravel the role of TRPC4 and TRPC5 in these processes in vivo, detailed information about the molecular composition of native channel complexes and their association with cellular signaling networks is needed. We therefore searched a human aortic cDNA library for novel TRPC4-interacting proteins using a modified yeast two-hybrid assay. This screen identified SESTD1, a previously uncharacterized protein containing a lipid-binding SEC14-like domain as well as spectrin-type cytoskeleton interaction domains. SESTD1 was found to associate with TRPC4 and TRPC5 via the channel's calmodulin- and inositol 1,4,5-trisphosphate receptor-binding domain. In functional studies, we demonstrate that SESTD1 binds several phospholipid species in vitro and is essential for efficient receptor-mediated activation of TRPC5. Notably, phospholipid binding to SESTD1 was Ca2+-dependent. Because TRPC4 and -5 conduct Ca2+, SESTD1-channel signaling may be bidirectional and also couple TRPC activity to lipid signaling through SESTD1. The modulation of TRPC channel function by specific lipid-binding proteins, such as SESTD1, adds another facet to the complex regulation of these channels complementary to the previously described effects of direct channel-phospholipid interaction. PMID:20164195

  4. cGMP stimulation of cystic fibrosis transmembrane conductance regulator Cl- channels co-expressed with cGMP-dependent protein kinase type II but not type Ibeta

    NARCIS (Netherlands)

    A.B. Vaandrager (Arie); S.M. Lohmann (Suzanne); H.R. de Jonge (Hugo); W.C. Poller; B.C. Tilly (Bernard); A. Smolenski; S. Schneider-Rasp; A.G. Bot (Alice); M.J. Edixhoven (Marcel); B.J. Scholte (Bob); T. Jarchau; U. Walter

    1997-01-01

    textabstractIn order to investigate the involvement of cGMP-dependent protein kinase (cGK) type II in cGMP-provoked intestinal Cl- secretion, cGMP-dependent activation and phosphorylation of cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels was ana

  5. Isotype-specific activation of cystic fibrosis transmembrane conductance regulator-chloride channels by cGMP-dependent protein kinase II

    NARCIS (Netherlands)

    P.J. French (Pim); J. Bijman (Jan); M.J. Edixhoven (Marcel); A.B. Vaandrager (Arie); B.J. Scholte (Bob); S.M. Lohmann (Suzanne); A.C. Nairn; H.R. de Jonge (Hugo)

    1995-01-01

    textabstractType II cGMP-dependent protein kinase (cGKII) isolated from pig intestinal brush borders and type I alpha cGK (cGKI) purified from bovine lung were compared for their ability to activate the cystic fibrosis transmembrane conductance regulator (CFTR)-Cl- channel in excis

  6. Heteromeric Kv7.2/7.3 channels differentially regulate action potential initiation and conduction in neocortical myelinated axons

    NARCIS (Netherlands)

    Battefeld, A.; Tran, B.T.; Gavrilis, J.; Cooper, E.C.; Kole, Maarten

    2014-01-01

    Rapid energy-efficient signaling along vertebrate axons is achieved through intricate subcellular arrangements of voltage-gated ion channels and myelination. One recently appreciated example is the tight colocalization of Kv7 potassium channels and voltage-gated sodium (Nav ) channels in the axonal

  7. Osteoprotegerin: a novel secreted protein involved in the regulation of bone density.

    Science.gov (United States)

    Simonet, W S; Lacey, D L; Dunstan, C R; Kelley, M; Chang, M S; Lüthy, R; Nguyen, H Q; Wooden, S; Bennett, L; Boone, T; Shimamoto, G; DeRose, M; Elliott, R; Colombero, A; Tan, H L; Trail, G; Sullivan, J; Davy, E; Bucay, N; Renshaw-Gegg, L; Hughes, T M; Hill, D; Pattison, W; Campbell, P; Sander, S; Van, G; Tarpley, J; Derby, P; Lee, R; Boyle, W J

    1997-04-18

    A novel secreted glycoprotein that regulates bone resorption has been identified. The protein, termed Osteoprotegerin (OPG), is a novel member of the TNF receptor superfamily. In vivo, hepatic expression of OPG in transgenic mice results in a profound yet nonlethal osteopetrosis, coincident with a decrease in later stages of osteoclast differentiation. These same effects are observed upon administration of recombinant OPG into normal mice. In vitro, osteoclast differentiation from precursor cells is blocked in a dose-dependent manner by recombinant OPG. Furthermore, OPG blocks ovariectomy-associated bone loss in rats. These data show that OPG can act as a soluble factor in the regulation of bone mass and imply a utility for OPG in the treatment of osteoporosis associated with increased osteoclast activity. PMID:9108485

  8. Regulation of spine density and morphology by IQGAP1 protein domains.

    Directory of Open Access Journals (Sweden)

    Ignacio Jausoro

    Full Text Available IQGAP1 is a scaffolding protein that regulates spine number. We now show a differential role for IQGAP1 domains in spine morphogenesis, in which a region of the N-terminus that promotes Arp2/3-mediated actin polymerization and branching stimulates spine head formation while a region that binds to Cdc42 and Rac is required for stalk extension. Conversely, IQGAP1 rescues spine deficiency induced by expression of dominant negative Cdc42 by stimulating formation of stubby spines. Together, our observations place IQGAP1 as a crucial regulator of spine number and shape acting through the N-Wasp Arp2/3 complex, as well as upstream and downstream of Cdc42.

  9. High-Density and Very-Low-Density Lipoprotein Have Opposing Roles in Regulating Tumor-Initiating Cells and Sensitivity to Radiation in Inflammatory Breast Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Wolfe, Adam R. [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Atkinson, Rachel L. [Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Reddy, Jay P. [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Debeb, Bisrat G.; Larson, Richard; Li, Li [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Department of Clinical Cancer Prevention, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Masuda, Hiroko; Brewer, Takae [Department of Clinical Cancer Prevention, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Atkinson, Bradley J. [Department of Clinical Pharmacy Services, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Brewster, Abeena [Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Ueno, Naoto T. [Department of Clinical Cancer Prevention, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Woodward, Wendy A., E-mail: wwoodward@mdanderson.org [Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Department of Clinical Cancer Prevention, University of Texas MD Anderson Cancer Center, Houston, Texas (United States)

    2015-04-01

    Purpose: We previously demonstrated that cholesterol-lowering agents regulate radiation sensitivity of inflammatory breast cancer (IBC) cell lines in vitro and are associated with less radiation resistance among IBC patients who undergo postmastectomy radiation. We hypothesized that decreasing IBC cellular cholesterol induced by treatment with lipoproteins would increase radiation sensitivity. Here, we examined the impact of specific transporters of cholesterol (ie lipoproteins) on the responses of IBC cells to self-renewal and to radiation in vitro and on clinical outcomes in IBC patients. Methods and Materials: Two patient-derived IBC cell lines, SUM 149 and KPL4, were incubated with low-density lipoproteins (LDL), very-low-density lipoproteins (VLDL), or high-density lipoproteins (HDL) for 24 hours prior to irradiation (0-6 Gy) and mammosphere formation assay. Cholesterol panels were examined in a cohort of patients with primary IBC diagnosed between 1995 and 2011 at MD Anderson Cancer Center. Lipoprotein levels were then correlated to patient outcome, using the log rank statistical model, and examined in multivariate analysis using Cox regression. Results: VLDL increased and HDL decreased mammosphere formation compared to untreated SUM 149 and KPL4 cells. Survival curves showed enhancement of survival in both of the IBC cell lines when pretreated with VLDL and, conversely, radiation sensitization in all cell lines when pretreated with HDL. In IBC patients, higher VLDL values (>30 mg/dL) predicted a lower 5-year overall survival rate than normal values (hazard ratio [HR] = 1.9 [95% confidence interval [CI]: 1.05-3.45], P=.035). Lower-than-normal patient HDL values (<60 mg/dL) predicted a lower 5-year overall survival rate than values higher than 60 mg/dL (HR = 3.21 [95% CI: 1.25-8.27], P=.015). Conclusions: This study discovered a relationship among the plasma levels of lipoproteins, overall patient response, and radiation resistance in IBC patients

  10. High-Density and Very-Low-Density Lipoprotein Have Opposing Roles in Regulating Tumor-Initiating Cells and Sensitivity to Radiation in Inflammatory Breast Cancer

    International Nuclear Information System (INIS)

    Purpose: We previously demonstrated that cholesterol-lowering agents regulate radiation sensitivity of inflammatory breast cancer (IBC) cell lines in vitro and are associated with less radiation resistance among IBC patients who undergo postmastectomy radiation. We hypothesized that decreasing IBC cellular cholesterol induced by treatment with lipoproteins would increase radiation sensitivity. Here, we examined the impact of specific transporters of cholesterol (ie lipoproteins) on the responses of IBC cells to self-renewal and to radiation in vitro and on clinical outcomes in IBC patients. Methods and Materials: Two patient-derived IBC cell lines, SUM 149 and KPL4, were incubated with low-density lipoproteins (LDL), very-low-density lipoproteins (VLDL), or high-density lipoproteins (HDL) for 24 hours prior to irradiation (0-6 Gy) and mammosphere formation assay. Cholesterol panels were examined in a cohort of patients with primary IBC diagnosed between 1995 and 2011 at MD Anderson Cancer Center. Lipoprotein levels were then correlated to patient outcome, using the log rank statistical model, and examined in multivariate analysis using Cox regression. Results: VLDL increased and HDL decreased mammosphere formation compared to untreated SUM 149 and KPL4 cells. Survival curves showed enhancement of survival in both of the IBC cell lines when pretreated with VLDL and, conversely, radiation sensitization in all cell lines when pretreated with HDL. In IBC patients, higher VLDL values (>30 mg/dL) predicted a lower 5-year overall survival rate than normal values (hazard ratio [HR] = 1.9 [95% confidence interval [CI]: 1.05-3.45], P=.035). Lower-than-normal patient HDL values (<60 mg/dL) predicted a lower 5-year overall survival rate than values higher than 60 mg/dL (HR = 3.21 [95% CI: 1.25-8.27], P=.015). Conclusions: This study discovered a relationship among the plasma levels of lipoproteins, overall patient response, and radiation resistance in IBC patients

  11. A cell model study of calcium influx mechanism regulated by calcium-dependent potassium channels in Purkinje cell dendrites.

    Science.gov (United States)

    Chono, Koji; Takagi, Hiroshi; Koyama, Shozo; Suzuki, Hideo; Ito, Etsuro

    2003-10-30

    The present study was designed to elucidate the roles of dendritic voltage-gated K+ channels in Ca2+ influx mechanism of a rat Purkinje cell using a computer simulation program. First, we improved the channel descriptions and the maximum conductance in the Purkinje cell model to mimic both the kinetics of ion channels and the Ca2+ spikes, which had failed in previous studies. Our cell model is, therefore, much more authentic than those in previous studies. Second, synaptic inputs that mimic stimulation of parallel fibers and induce sub-threshold excitability were simultaneously applied to the spiny dendrites. As a result, transient Ca2+ responses were observed in the stimulation points and they decreased with the faster decay rate in the cell model including high-threshold Ca2+-dependent K+ channels than in those excluding these channels. Third, when a single synaptic input was applied into a spiny dendrite, Ca2+-dependent K+ channels suppressed Ca2+ increases at stimulation and recording points. Finally, Ca2+-dependent K+ channels were also found to suppress the time to peak Ca2+ values in the recording points. These results suggest that the opening of Ca2+-dependent K+ channels by Ca2+ influx through voltage-gated Ca2+ channels hyperpolarizes the membrane potentials and deactivates these Ca2+ channels in a negative feedback manner, resulting in local, weak Ca2+ responses in spiny dendrites of Purkinje cells.

  12. Dendritic Kv3.3 potassium channels in cerebellar purkinje cells regulate generation and spatial dynamics of dendritic Ca2+ spikes.

    Science.gov (United States)

    Zagha, Edward; Manita, Satoshi; Ross, William N; Rudy, Bernardo

    2010-06-01

    Purkinje cell dendrites are excitable structures with intrinsic and synaptic conductances contributing to the generation and propagation of electrical activity. Voltage-gated potassium channel subunit Kv3.3 is expressed in the distal dendrites of Purkinje cells. However, the functional relevance of this dendritic distribution is not understood. Moreover, mutations in Kv3.3 cause movement disorders in mice and cerebellar atrophy and ataxia in humans, emphasizing the importance of understanding the role of these channels. In this study, we explore functional implications of this dendritic channel expression and compare Purkinje cell dendritic excitability in wild-type and Kv3.3 knockout mice. We demonstrate enhanced excitability of Purkinje cell dendrites in Kv3.3 knockout mice, despite normal resting membrane properties. Combined data from local application pharmacology, voltage clamp analysis of ionic currents, and assessment of dendritic Ca(2+) spike threshold in Purkinje cells suggest a role for Kv3.3 channels in opposing Ca(2+) spike initiation. To study the physiological relevance of altered dendritic excitability, we measured [Ca(2+)](i) changes throughout the dendritic tree in response to climbing fiber activation. Ca(2+) signals were specifically enhanced in distal dendrites of Kv3.3 knockout Purkinje cells, suggesting a role for dendritic Kv3.3 channels in regulating propagation of electrical activity and Ca(2+) influx in distal dendrites. These findings characterize unique roles of Kv3.3 channels in dendrites, with implications for synaptic integration, plasticity, and human disease. PMID:20357073

  13. Adenosine regulates a chloride channel via protein kinase C and a G protein in a rabbit cortical collecting duct cell line.

    OpenAIRE

    Schwiebert, E. M.; Karlson, K H; Friedman, P A; Dietl, P.; Spielman, W S; Stanton, B.A.

    1992-01-01

    We examined the regulation by adenosine of a 305-pS chloride (Cl-) channel in the apical membrane of a continuous cell line derived from rabbit cortical collecting duct (RCCT-28A) using the patch clamp technique. Stimulation of A1 adenosine receptors by N6-cyclohexyladenosine (CHA) activated the channel in cell-attached patches. Phorbol 12,13-didecanoate and 1-oleoyl 2-acetylglycerol, activators of protein kinase C (PKC), mimicked the effect of CHA, whereas the PKC inhibitor H7 blocked the ac...

  14. A conserved threonine in the S1-S2 loop of KV7.2 and K V7.3 channels regulates voltage-dependent activation.

    Science.gov (United States)

    Füll, Yvonne; Seebohm, Guiscard; Lerche, Holger; Maljevic, Snezana

    2013-06-01

    The voltage-gated potassium channels KV7.2 and KV7.3 (KCNQ2/3 genes) play an important role in regulating neuronal excitability. More than 50 KCNQ2/3 mutations have been identified to cause an inherited form of epilepsy in newborns. For two of those (E119G and S122L) found in the S1-S2 region of KV7.2, we previously showed a decreased channel availability mainly at action potential subthreshold voltages caused by a slight depolarizing shift of the activation curve. Interestingly, recent studies revealed that a threonine residue within the S1-S2 loop, highly conserved among different classes of KV channels, is crucial for both their function and surface expression. To investigate the functional role of the homologous threonine residues in KV7.2 (T114) and KV7.3 (T144) channels, we replaced them with alanine and examined the electrophysiological properties using heterologous expression in CHO cells and whole cell patch clamping. Channels comprising mutant subunits yielded decreased potassium currents with slowed activation and accelerated deactivation kinetics. However, the most striking effect was a depolarizing shift in the voltage dependence of activation reaching +30 mV upon co-expression of both mutant subunits. Potential interactions of T114 within the channel were analyzed by creating a 3D homology model of KV7.2 in an open state suggesting that this residue plays a central role in the formation of a stable interface between the S1-S2 and the S5 segment helices. This could be the explanation why substitution of the conserved threonine in KV7.2 and KV7.3 channels destabilizes the open and favors the closed state of these channels.

  15. Camkii-mediated phosphorylation regulates distributions of Syngap-α1 and -α2 at the postsynaptic density.

    Directory of Open Access Journals (Sweden)

    Yijung Yang

    Full Text Available SynGAP, a protein abundant at the postsynaptic density (PSD of glutamatergic neurons, is known to modulate synaptic strength by regulating the incorporation of AMPA receptors at the synapse. Two isoforms of SynGAP, α1 and α2, which differ in their C-termini, have opposing effects on synaptic strength. In the present study, antibodies specific for SynGAP-α1 and SynGAP-α2 are used to compare the distribution patterns of the two isoforms at the postsynaptic density (PSD under basal and excitatory conditions. Western immunoblotting shows enrichment of both isoforms in PSD fractions isolated from adult rat brain. Immunogold electron microscopy of rat hippocampal neuronal cultures shows similar distribution of both isoforms at the PSD, with a high density of immunolabel within the PSD core under basal conditions. Application of NMDA promotes movement of SynGAP-α1 as well as SynGAP-α2 out of the PSD core. In isolated PSDs both isoforms of SynGAP can be phosphorylated upon activation of the endogenous CaMKII. Application of tatCN21, a cell-penetrating inhibitor of CaMKII, to hippocampal neuronal cultures blocks NMDA-induced redistribution of SynGAP-α1 and SynGAP-α2. Thus CaMKII activation promotes the removal of two distinct C-terminal SynGAP variants from the PSD.

  16. Effect of Porphyromonas gingivalis infection on post-transcriptional regulation of the low-density lipoprotein receptor in mice

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    Miyazawa Haruna

    2012-09-01

    Full Text Available Abstract Background Periodontal disease is suggested to increase the risk of atherothrombotic disease by inducing dyslipidemia. Recently, we demonstrated that proprotein convertase subtilisin/kexin type 9 (PCSK9, which is known to play a critical role in the regulation of circulating low-density lipoprotein (LDL cholesterol levels, is elevated in periodontitis patients. However, the underlying mechanisms of elevation of PCSK9 in periodontitis patients are largely unknown. Here, we explored whether Porphyromonas gingivalis, a representative periodontopathic bacterium, -induced inflammatory response regulates serum PCSK9 and cholesterol levels using animal models. Methods We infected C57BL/6 mice intraperitoneally with Porphyromonas gingivalis, a representative strain of periodontopathic bacteria, and evaluated serum PCSK9 levels and the serum lipid profile. PCSK9 and LDL receptor (LDLR gene and protein expression, as well as liver X receptors (Lxrs, inducible degrader of the LDLR (Idol, and sterol regulatory element binding transcription factor (Srebf2 gene expression, were examined in the liver. Results P. gingivalis infection induced a significant elevation of serum PCSK9 levels and a concomitant elevation of total and LDL cholesterol compared with sham-infected mice. The LDL cholesterol levels were significantly correlated with PCSK9 levels. Expression of the Pcsk9, Ldlr, and Srebf2 genes was upregulated in the livers of the P. gingivalis-infected mice compared with the sham-infected mice. Although Pcsk9 gene expression is known to be positively regulated by sterol regulatory element binding protein (SREBP2 (human homologue of Srebf2, whereas Srebf2 is negatively regulated by cholesterol, the elevated expression of Srebf2 found in the infected mice is thought to be mediated by P. gingivalis infection. Conclusions P. gingivalis infection upregulates PCSK9 production via upregulation of Srebf2, independent of cholesterol levels. Further studies

  17. Regulation of ATP-sensitive K+ channels in insulinoma cells: Activation by somatostatin and protein kinase C and the role of cAMP

    International Nuclear Information System (INIS)

    The actions of somatostatin and of the phorbol ester 4β-phorbol 12-myristate 13-acetate (PMA) were studied in rat insulinoma (RINm5F) cells by electrophysiological and 86Rb+ flux techniques. Both PMA and somatostatin hyperpolarize insulinoma cells by activating ATP-sensitive K+ channels. The presence of intracellular GTP is required for the somatostatin effects. PMA- and somatostatin-induced hyperpolarization and channel activity are inhibited by the sulfonylurea glibenclamide. Glibenclamide-sensitive 86Rb+ efflux from insulinoma cells is stimulated by somatostatin in a dose-dependent manner (half maximal effect at 0.7 nM) and abolished by pertussis toxin pretreatment. Mutual roles of a GTP-binding protein, of protein kinase C, and of cAMP in the regulation of ATP-sensitive K+ channels are discussed

  18. Potassium Channel Interacting Protein 2 (KChIP2) is not a transcriptional regulator of cardiac electrical remodeling.

    Science.gov (United States)

    Winther, Sine V; Tuomainen, Tomi; Borup, Rehannah; Tavi, Pasi; Antoons, Gudrun; Thomsen, Morten B

    2016-01-01

    The heart-failure relevant Potassium Channel Interacting Protein 2 (KChIP2) augments CaV1.2 and KV4.3. KChIP3 represses CaV1.2 transcription in cardiomyocytes via interaction with regulatory DNA elements. Hence, we tested nuclear presence of KChIP2 and if KChIP2 translocates into the nucleus in a Ca(2+) dependent manner. Cardiac biopsies from human heart-failure patients and healthy donor controls showed that nuclear KChIP2 abundance was significantly increased in heart failure; however, this was secondary to a large variation of total KChIP2 content. Administration of ouabain did not increase KChIP2 content in nuclear protein fractions in anesthetized mice. KChIP2 was expressed in cell lines, and Ca(2+) ionophores were applied in a concentration- and time-dependent manner. The cell lines had KChIP2-immunoreactive protein in the nucleus in the absence of treatments to modulate intracellular Ca(2+) concentration. Neither increasing nor decreasing intracellular Ca(2+) concentrations caused translocation of KChIP2. Microarray analysis did not identify relief of transcriptional repression in murine KChIP2(-/-) heart samples. We conclude that although there is a baseline presence of KChIP2 in the nucleus both in vivo and in vitro, KChIP2 does not directly regulate transcriptional activity. Moreover, the nuclear transport of KChIP2 is not dependent on Ca(2+). Thus, KChIP2 does not function as a conventional transcription factor in the heart. PMID:27349185

  19. MiR-130a regulates neurite outgrowth and dendritic spine density by targeting MeCP2.

    Science.gov (United States)

    Zhang, Yunjia; Chen, Mengmeng; Qiu, Zilong; Hu, Keping; McGee, Warren; Chen, Xiaoping; Liu, Jianghong; Zhu, Li; Wu, Jane Y

    2016-07-01

    MicroRNAs (miRNAs) are critical for both development and function of the central nervous system. Significant evidence suggests that abnormal expression of miRNAs is associated with neurodevelopmental disorders. MeCP2 protein is an epigenetic regulator repressing or activating gene transcription by binding to methylated DNA. Both loss-of-function and gain-of-function mutations in the MECP2 gene lead to neurodevelopmental disorders such as Rett syndrome, autism and MECP2 duplication syndrome. In this study, we demonstrate that miR-130a inhibits neurite outgrowth and reduces dendritic spine density as well as dendritic complexity. Bioinformatics analyses, cell cultures and biochemical experiments indicate that miR-130a targets MECP2 and down-regulates MeCP2 protein expression. Furthermore, expression of the wild-type MeCP2, but not a loss-of-function mutant, rescues the miR-130a-induced phenotype. Our study uncovers the MECP2 gene as a previous unknown target for miR-130a, supporting that miR-130a may play a role in neurodevelopment by regulating MeCP2. Together with data from other groups, our work suggests that a feedback regulatory mechanism involving both miR-130a and MeCP2 may serve to ensure their appropriate expression and function in neural development. PMID:27245166

  20. Emerging role of calcium-activated potassium channel in the regulation of cell viability following potassium ions challenge in HEK293 cells and pharmacological modulation.

    Directory of Open Access Journals (Sweden)

    Domenico Tricarico

    Full Text Available Emerging evidences suggest that Ca(2+activated-K(+-(BK channel is involved in the regulation of cell viability. The changes of the cell viability observed under hyperkalemia (15 mEq/L or hypokalemia (0.55 mEq/L conditions were investigated in HEK293 cells expressing the hslo subunit (hslo-HEK293 in the presence or absence of BK channel modulators. The BK channel openers(10(-11-10(-3M were: acetazolamide(ACTZ, Dichlorphenamide(DCP, methazolamide(MTZ, bendroflumethiazide(BFT, ethoxzolamide(ETX, hydrochlorthiazide(HCT, quercetin(QUERC, resveratrol(RESV and NS1619; and the BK channel blockers(2 x 10(-7M-5 x 10(-3M were: tetraethylammonium(TEA, iberiotoxin(IbTx and charybdotoxin(ChTX. Experiments on cell viability and channel currents were performed using cell counting kit-8 and patch-clamp techniques, respectively. Hslo whole-cell current was potentiated by BK channel openers with different potency and efficacy in hslo-HEK293. The efficacy ranking of the openers at -60 mV(Vm was BFT> ACTZ >DCP ≥RESV≥ ETX> NS1619> MTZ≥ QUERC; HCT was not effective. Cell viability after 24 h of incubation under hyperkalemia was enhanced by 82+6% and 33+7% in hslo-HEK293 cells and HEK293 cells, respectively. IbTx, ChTX and TEA enhanced cell viability in hslo-HEK293. BK openers prevented the enhancement of the cell viability induced by hyperkalemia or IbTx in hslo-HEK293 showing an efficacy which was comparable with that observed as BK openers. BK channel modulators failed to affect cell currents and viability under hyperkalemia conditions in the absence of hslo subunit. In contrast, under hypokalemia cell viability was reduced by -22+4% and -23+6% in hslo-HEK293 and HEK293 cells, respectively; the BK channel modulators failed to affect this parameter in these cells. In conclusion, BK channel regulates cell viability under hyperkalemia but not hypokalemia conditions. BFT and ACTZ were the most potent drugs either in activating the BK current and in preventing the

  1. Emerging role of calcium-activated potassium channel in the regulation of cell viability following potassium ions challenge in HEK293 cells and pharmacological modulation.

    Science.gov (United States)

    Tricarico, Domenico; Mele, Antonietta; Calzolaro, Sara; Cannone, Gianluigi; Camerino, Giulia Maria; Dinardo, Maria Maddalena; Latorre, Ramon; Conte Camerino, Diana

    2013-01-01

    Emerging evidences suggest that Ca(2+)activated-K(+)-(BK) channel is involved in the regulation of cell viability. The changes of the cell viability observed under hyperkalemia (15 mEq/L) or hypokalemia (0.55 mEq/L) conditions were investigated in HEK293 cells expressing the hslo subunit (hslo-HEK293) in the presence or absence of BK channel modulators. The BK channel openers(10(-11)-10(-3)M) were: acetazolamide(ACTZ), Dichlorphenamide(DCP), methazolamide(MTZ), bendroflumethiazide(BFT), ethoxzolamide(ETX), hydrochlorthiazide(HCT), quercetin(QUERC), resveratrol(RESV) and NS1619; and the BK channel blockers(2 x 10(-7)M-5 x 10(-3)M) were: tetraethylammonium(TEA), iberiotoxin(IbTx) and charybdotoxin(ChTX). Experiments on cell viability and channel currents were performed using cell counting kit-8 and patch-clamp techniques, respectively. Hslo whole-cell current was potentiated by BK channel openers with different potency and efficacy in hslo-HEK293. The efficacy ranking of the openers at -60 mV(Vm) was BFT> ACTZ >DCP ≥RESV≥ ETX> NS1619> MTZ≥ QUERC; HCT was not effective. Cell viability after 24 h of incubation under hyperkalemia was enhanced by 82+6% and 33+7% in hslo-HEK293 cells and HEK293 cells, respectively. IbTx, ChTX and TEA enhanced cell viability in hslo-HEK293. BK openers prevented the enhancement of the cell viability induced by hyperkalemia or IbTx in hslo-HEK293 showing an efficacy which was comparable with that observed as BK openers. BK channel modulators failed to affect cell currents and viability under hyperkalemia conditions in the absence of hslo subunit. In contrast, under hypokalemia cell viability was reduced by -22+4% and -23+6% in hslo-HEK293 and HEK293 cells, respectively; the BK channel modulators failed to affect this parameter in these cells. In conclusion, BK channel regulates cell viability under hyperkalemia but not hypokalemia conditions. BFT and ACTZ were the most potent drugs either in activating the BK current and in preventing

  2. HERG K+ channels expression in gastric cancers and analysis of its regulation in tumor cell proliferation and apoptosis

    Institute of Scientific and Technical Information of China (English)

    Qing Lü; Huiyu Li; Xiaoming Lu; Guobin Wang

    2009-01-01

    Objective: To investigate the expression of herg 1 gene in tumor tissues from gastric carcinomas and gastric carcinoma cell lines, and study the relationship between HERG K+ channel expressions and tumor cell proliferation and apoptosis. Methods: RT-PCR and PCR assays were used to detect the expression of herg 1 gene in 64 gastric carcinomas and the gastric cancer cell line SGC-7901. Blocking the HERG K+ channels was used to evaluate their effects on tumor cell proliferation and apoptosis. Results:The statistically significant expression of herg 1 gene was detected in all the gastric cancers and SGC-7901 cells, but not in normal tissues. The HERG K+ channel blocker, E-4031, increased the cell population in G0/G1 (P<0.05) and the number of apoptotic tumor cells(P<0.05). Conclusion: HERG K+ channels were expressed in all gastric carcinomas tested and these channels appear to modulate tumor cell proliferation and apoptosis.

  3. Investigation of Density and Velocity of Abrikosov Vortices in YBa2Cu3O7–x Superconducting Thin Films with a Laser-Written Channel for Easy Vortex Motion

    Directory of Open Access Journals (Sweden)

    Lina STEPONAVICIENE

    2011-07-01

    Full Text Available The 0.3-mm-thick, 50-mm-wide and 100-mm-long YBa2Cu3O7-x superconducting bridges with a laser-written, single, Π-shaped channel have been investigated by means of electronic transport measurements at temperatures below the onset of the bridge's superconducting transition temperature. Our results demonstrate that the coherent vortex motion confined in the P-shaped channel can be used for determination of both the density and velocity of Abrikosov magnetic vortices in the channel. The coherent motion of Abrikosov vortices expresses itself as Josephson-like voltage steps, observed on the current-voltage characteristics of our microbridges, measured at zero external magnetic field, in a limited range of temperatures and bias currents. The steps' amplitude corresponds to the entrance of an additional vortex-antivortex pair into the channel's area and change in the vortex velocity. This amplitude also affects the increase of the Lorentz force for energy dissipative drift of the magnetic flux in the channel, but it does not increase, however, with the increase of the biasing current. We present and discuss the results of experimentally measured and calculated energy dissipation, which originated from variations in the vortex density and velocity when the vortices are moving along the channel of the superconducting bridge.http://dx.doi.org/10.5755/j01.ms.17.2.489

  4. Spermidine oxidase-derived H₂O₂ regulates pollen plasma membrane hyperpolarization-activated Ca(2+) -permeable channels and pollen tube growth.

    Science.gov (United States)

    Wu, Juyou; Shang, Zhonglin; Wu, Jun; Jiang, Xueting; Moschou, Panagiotis N; Sun, Wending; Roubelakis-Angelakis, Kalliopi A; Zhang, Shaoling

    2010-09-01

    Spermidine (Spd) has been correlated with various physiological and developmental processes in plants, including pollen tube growth. In this work, we show that Spd induces an increase in the cytosolic Ca(2+) concentration that accompanies pollen tube growth. Using the whole-cell patch clamp and outside-out single-channel patch clamp configurations, we show that exogenous Spd induces a hyperpolarization-activated Ca(2+) current: the addition of Spd cannot induce the channel open probability increase in excised outside-out patches, indicating that the effect of Spd in the induction of Ca(2+) currents is exerted via a second messenger. This messenger is hydrogen peroxide (H₂O₂), and is generated during Spd oxidation, a reaction mediated by polyamine oxidase (PAO). These reactive oxygen species trigger the opening of the hyperpolarization-activated Ca(2+) -permeable channels in pollen. To provide further evidence that PAO is in fact responsible for the effect of Spd on the Ca(2+) -permeable channels, two Arabidopsis mutants lacking expression of the peroxisomal-encoding AtPAO3 gene, were isolated and characterized. Pollen from these mutants was unable to induce the opening of the Ca(2+) -permeable channels in the presence of Spd, resulting in reduced pollen tube growth and seed number. However, a high Spd concentration triggers a Ca(2+) influx beyond the optimal, which has a deleterious effect. These findings strongly suggest that the Spd-derived H₂O₂ signals Ca(2+) influx, thereby regulating pollen tube growth.

  5. The hydrometeorological implications of zoning laws: Can land use regulations of urban density and sprawl improve a city's resilience?

    Science.gov (United States)

    Bou-Zeid, E.; Ryu, Y. H.; Smith, J. A.; Newburn, D. A.

    2015-12-01

    The intensification of heat waves and of the hydrological cycle due to global climate change pose particularly high risks to urban residents. Cities are already hotter than their surroundings due to the urban heat island effect and are known to result in local intensification of rainfall and flooding due to their coupled impacts on the surface and the lower atmosphere. These interacting local and global changes can adversely affect the health and well being of urban residents, and city administrators are increasing efforts to mitigate and adapt to the potential disruptions though various infrastructure and preparedness programs. However, as cities worldwide continue to expand, a key decision is how to manage that urban sprawl and regulate its spatial features to aid in the mitigation and adaptation effort. This study assesses whether alternative zoning regulations that modify the density and extent of a metropolitan region, but have a minimal impact on total population and demographic growth, have an appreciable impact on its response to extreme weather events, and as such, whether they can be used to increase urban resilience. We consider Baltimore (the city and its surrounding suburbs), which in 1967 adopted one of the first urban growth boundaries (UGBs) in the United States, as our test case. Departing from the urban extent circa 1900, we create alternative land use patterns that, compared to the actual current land use baseline, would have resulted from drastically different policy scenarios and approaches to zoning that the city would have undertaken. We consider various alternatives where the city is smaller and denser, due to stricter regulation, versus larger and less dense than the actual baseline, while maintaining the same total population. Our findings indicate that lower densities have significant benefits: compared to the current landscape and to denser patterns, they reduce both extreme temperatures during heat waves and spatio-temporal rainfall

  6. Ion channel regulation by phosphoinositides analyzed with VSPs – PI(4,5P2 affinity, phosphoinositide selectivity, and PI(4,5P2 pool accessibility

    Directory of Open Access Journals (Sweden)

    Alexandra eRjasanow

    2015-06-01

    Full Text Available The activity of many proteins depends on the phosphoinositide (PI content of the membrane. E.g., dynamic changes of the concentration of PI(4,5P2 are cellular signals that regulate ion channels. The susceptibility of a channel to such dynamics depends on its affinity for PI(4,5P2. Yet, measuring affinities for endogenous PIs has not been possible directly, but has relied largely on the response to soluble analogs, which may not quantitatively reflect binding to native lipids.Voltage-sensitive phosphatases (VSPs turn over PI(4,5P2 to PI(4P when activated by depolarization. In combination with voltage-clamp electrophysiology VSPs are useful tools for rapid and reversible depletion of PI(4,5P2. Because cellular PI(4,5P2 is resynthesized rapidly, steady state PI(4,5P2 changes with the degree of VSP activation and thus depends on membrane potential.Here we show that titration of endogenous PI(4,5P2 with Ci-VSP allows for the quantification of relative PI(4,5P2 affinities of ion channels. The sensitivity of inward rectifier and voltage-gated K+ channels to Ci-VSP allowed for comparison of PI(4,5P2 affinities within and across channel subfamilies and detected changes of affinity in mutant channels. The results also reveal that VSPs are useful only for PI effectors with high binding specificity among PI isoforms, because PI(4,5P2 depletion occurs at constant overall PI level. Thus, Kir6.2, a channel activated by PI(4,5P2 and PI(4P was insensitive to VSP.Surprisingly, despite comparable PI(4,5P2 affinity as determined by Ci-VSP, the Kv7 and Kir channel families strongly differed in their sensitivity to receptor-mediated depletion of PI(4,5P2. While Kv7 members were highly sensitive to activation of PLC by Gq-coupled receptors, Kir channels were insensitive even when PI(4,5P2 affinity was lowered by mutation. We hypothesize that different channels may be associated with distinct pools of PI(4,5P2 that differ in their accessibility to PLC and VSPs.

  7. The Combined Effect of Hydrophobic Mismatch and Bilayer Local Bending on the Regulation of Mechanosensitive Ion Channels.

    Science.gov (United States)

    Bavi, Omid; Vossoughi, Manouchehr; Naghdabadi, Reza; Jamali, Yousef

    2016-01-01

    The hydrophobic mismatch between the lipid bilayer and integral membrane proteins has well-defined effect on mechanosensitive (MS) ion channels. Also, membrane local bending is suggested to modulate MS channel activity. Although a number of studies have already shown the significance of each individual factor, the combined effect of these physical factors on MS channel activity have not been investigated. Here using finite element simulation, we study the combined effect of hydrophobic mismatch and local bending on the archetypal mechanosensitive channel MscL. First we show how the local curvature direction impacts on MS channel modulation. In the case of MscL, we show inward (cytoplasmic) bending can more effectively gate the channel compared to outward bending. Then we indicate that in response to a specific local curvature, MscL inserted in a bilayer with the same hydrophobic length is more expanded in the constriction pore region compared to when there is a protein-lipid hydrophobic mismatch. Interestingly in the presence of a negative mismatch (thicker lipids), MscL constriction pore is more expanded than in the presence of positive mismatch (thinner lipids) in response to an identical membrane curvature. These results were confirmed by a parametric energetic calculation provided for MscL gating. These findings have several biophysical consequences for understanding the function of MS channels in response to two major physical stimuli in mechanobiology, namely hydrophobic mismatch and local membrane curvature. PMID:26958847

  8. Quantum Binary Symmetric Channels

    Institute of Scientific and Technical Information of China (English)

    陈小余; 仇佩亮

    2001-01-01

    Quantum binary symmetric channels are defined via the invariance of fidelity under unitary transformations ofthe input density operators. In this definition, they not only include the most studied case of the depolarizingchannel but also other channels. We investigate the character of the latter and find the maximum of the coherentinformation to estimate the capacities of the channels.

  9. The Earliest Ion Channels

    Science.gov (United States)

    Pohorille, A.; Wilson, M. A.; Wei, C.

    2009-12-01

    Supplying protocells with ions required assistance from channels spanning their membrane walls. The earliest channels were most likely short proteins that formed transmembrane helical bundles surrounding a water-filled pore. These simple aggregates were capable of transporting ions with efficiencies comparable to those of complex, contemporary ion channels. Channels with wide pores exhibited little ion selectivity but also imposed only modest constraints on amino acid sequences of channel-forming proteins. Channels with small pores could have been selective but also might have required a more precisely defined sequence of amino acids. In contrast to modern channels, their protocellular ancestors had only limited capabilities to regulate ion flux. It is postulated that subsequent evolution of ion channels progressed primarily to acquire precise regulation, and not high efficiency or selectivity. It is further proposed that channels and the surrounding membranes co-evolved.

  10. Mutating the Conserved Q-loop Glutamine 1291 Selectively Disrupts Adenylate Kinase-dependent Channel Gating of the ATP-binding Cassette (ABC) Adenylate Kinase Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) and Reduces Channel Function in Primary Human Airway Epithelia.

    Science.gov (United States)

    Dong, Qian; Ernst, Sarah E; Ostedgaard, Lynda S; Shah, Viral S; Ver Heul, Amanda R; Welsh, Michael J; Randak, Christoph O

    2015-05-29

    The ATP-binding cassette (ABC) transporter cystic fibrosis transmembrane conductance regulator (CFTR) and two other non-membrane-bound ABC proteins, Rad50 and a structural maintenance of chromosome (SMC) protein, exhibit adenylate kinase activity in the presence of physiologic concentrations of ATP and AMP or ADP (ATP + AMP ⇆ 2 ADP). The crystal structure of the nucleotide-binding domain of an SMC protein in complex with the adenylate kinase bisubstrate inhibitor P(1),P(5)-di(adenosine-5') pentaphosphate (Ap5A) suggests that AMP binds to the conserved Q-loop glutamine during the adenylate kinase reaction. Therefore, we hypothesized that mutating the corresponding residue in CFTR, Gln-1291, selectively disrupts adenylate kinase-dependent channel gating at physiologic nucleotide concentrations. We found that substituting Gln-1291 with bulky side-chain amino acids abolished the effects of Ap5A, AMP, and adenosine 5'-monophosphoramidate on CFTR channel function. 8-Azidoadenosine 5'-monophosphate photolabeling of the AMP-binding site and adenylate kinase activity were disrupted in Q1291F CFTR. The Gln-1291 mutations did not alter the potency of ATP at stimulating current or ATP-dependent gating when ATP was the only nucleotide present. However, when physiologic concentrations of ADP and AMP were added, adenylate kinase-deficient Q1291F channels opened significantly less than wild type. Consistent with this result, we found that Q1291F CFTR displayed significantly reduced Cl(-) channel function in well differentiated primary human airway epithelia. These results indicate that a highly conserved residue of an ABC transporter plays an important role in adenylate kinase-dependent CFTR gating. Furthermore, the results suggest that adenylate kinase activity is important for normal CFTR channel function in airway epithelia.

  11. Expulsion of symbiotic algae during feeding by the green hydra--a mechanism for regulating symbiont density?

    Directory of Open Access Journals (Sweden)

    Yelena Fishman

    Full Text Available BACKGROUND: Algal-cnidarian symbiosis is one of the main factors contributing to the success of cnidarians, and is crucial for the maintenance of coral reefs. While loss of the symbionts (such as in coral bleaching may cause the death of the cnidarian host, over-proliferation of the algae may also harm the host. Thus, there is a need for the host to regulate the population density of its symbionts. In the green hydra, Chlorohydra viridissima, the density of symbiotic algae may be controlled through host modulation of the algal cell cycle. Alternatively, Chlorohydra may actively expel their endosymbionts, although this phenomenon has only been observed under experimentally contrived stress conditions. PRINCIPAL FINDINGS: We show, using light and electron microscopy, that Chlorohydra actively expel endosymbiotic algal cells during predatory feeding on Artemia. This expulsion occurs as part of the apocrine mode of secretion from the endodermal digestive cells, but may also occur via an independent exocytotic mechanism. SIGNIFICANCE: Our results demonstrate, for the first time, active expulsion of endosymbiotic algae from cnidarians under natural conditions. We suggest this phenomenon may represent a mechanism whereby cnidarians can expel excess symbiotic algae when an alternative form of nutrition is available in the form of prey.

  12. Human α-endosulfine, a possible regulator of sulfonylurea-sensitive KATP channel: Molecular cloning, expression and biological properties

    OpenAIRE

    Heron, Lisa; Virsolvy, Anne; Peyrollier, Karine; Gribble, Fiona M.; Le Cam, Alphonse; Ashcroft, Frances M.; Bataille, Dominique

    1998-01-01

    Sulfonylureas are a class of drugs commonly used in the management of non-insulin-dependent diabetes mellitus. Their therapeutic action results primarily from their ability to inhibit ATP-sensitive potassium (KATP) channels in the plasma membrane of pancreatic β cells and thereby stimulate insulin release. A key question is whether an endogenous ligand for the KATP channel exists that is able to mimic the inhibitory effects of sulfonylureas. We describe here the cloning of the cDNA encoding h...

  13. Regulation and function of the two-pore-domain (K2P) potassium channel Trek-1 in alveolar epithelial cells

    OpenAIRE

    Schwingshackl, Andreas; Teng, Bin; Ghosh, Manik; West, Alina Nico; Makena, Patrudu; Gorantla, Vijay; Sinclair, Scott E.; Waters, Christopher M.

    2011-01-01

    Hyperoxia can lead to a myriad of deleterious effects in the lung including epithelial damage and diffuse inflammation. The specific mechanisms by which hyperoxia promotes these pathological changes are not completely understood. Activation of ion channels has been proposed as one of the mechanisms required for cell activation and mediator secretion. The two-pore-domain K+ channel (K2P) Trek-1 has recently been described in lung epithelial cells, but its function remains elusive. In this stud...

  14. ATP敏感钾通道调节血管张力的分子机制%KATP channel action in vascular tone regulation: from genetics to diseases

    Institute of Scientific and Technical Information of China (English)

    施巍巍; 杨洋; 石云; 姜淳

    2012-01-01

    ATP敏感钾通道(ATP-sensitive potassium channel,KATP通道)广泛分布在血管系统,并在血管张力调节中发挥重要作用.KATp通道由4个孔道形成的内向整流钾离子通道(inward rectifier K+ channels,Kir)亚基和4个磺脲受体调节亚基(sulfonylurea receptor,SUR)组成.尽管其它一些亚基在血管中也存在,Kir6.1/SUR2B是主要的血管亚型KATP通道.KATP通道转基因小鼠的研究以及人群中KATP通道基因突变的发现,都强烈支持KATP通道对于心血管系统的动态平衡调控是不可缺少的.大量的血管活性物质通过调节KATP通道活性来改变血管平滑肌细胞的膜电位,从而调节血管张力.多数内源性血管收缩物质,例如血管加压素,激活蛋白激酶C (protein kinase C,PKC),磷酸化KAP通道并抑制其活性;而血管扩张物质,如血管活性肠肽,通过增加cAMP的形成和提高蛋白激酶A(protein kinase A,PKA)的活性来增加KATP通道的活性.PKC作用于Kir6.1亚基C-末端,磷酸化4个保守的丝氨酸,而PKA磷酸化SUR2B亚基第2核苷酸结合域的Ser1387位点.血管KATP通道也受活性氧的调节,其中Kir6.1的Cys176是一个重要的过氧化物调节位点.此外,KATP通道功能可被一些慢性的病理生理条件上调,如感染性休克.核因子-κB依赖的基因转录是脂多糖诱导的血管KATP通道激活的一个机制.本综述将概括性描述血管KATP通道在生理和病理情况下受到的调节,以期阐明血管KATP通道在治疗和预防心血管疾病方面可能是一个有用的靶点.%ATP-sensitive potassium (KATP) channels are widely distributed in vasculatures,and play an important role in the vascular tone regulation.The KATP channels consist of 4 pore-forming inward rectifier K+ channel (Kir) subunits and 4 regulatory sulfonylurea receptors (SUR).The major vascular isoform of KATP channels is composed of Kir6.1/SUR2B,although low levels of other subunits are also present in vascular beds

  15. Differential neuronal targeting of a new and two known calcium channel β4 subunit splice variants correlates with their regulation of gene expression.

    Science.gov (United States)

    Etemad, Solmaz; Obermair, Gerald J; Bindreither, Daniel; Benedetti, Ariane; Stanika, Ruslan; Di Biase, Valentina; Burtscher, Verena; Koschak, Alexandra; Kofler, Reinhard; Geley, Stephan; Wille, Alexandra; Lusser, Alexandra; Flockerzi, Veit; Flucher, Bernhard E

    2014-01-22

    The β subunits of voltage-gated calcium channels regulate surface expression and gating of CaV1 and CaV2 α1 subunits and thus contribute to neuronal excitability, neurotransmitter release, and calcium-induced gene regulation. In addition, certain β subunits are targeted into the nucleus, where they interact directly with the epigenetic machinery. Whereas their involvement in this multitude of functions is reflected by a great molecular heterogeneity of β isoforms derived from four genes and abundant alternative splicing, little is known about the roles of individual β variants in specific neuronal functions. In the present study, an alternatively spliced β4 subunit lacking the variable N terminus (β4e) is identified. It is highly expressed in mouse cerebellum and cultured cerebellar granule cells (CGCs) and modulates P/Q-type calcium currents in tsA201 cells and CaV2.1 surface expression in neurons. Compared with the other two known full-length β4 variants (β4a and β4b), β4e is most abundantly expressed in the distal axon, but lacks nuclear-targeting properties. To determine the importance of nuclear targeting of β4 subunits for transcriptional regulation, we performed whole-genome expression profiling of CGCs from lethargic (β4-null) mice individually reconstituted with β4a, β4b, and β4e. Notably, the number of genes regulated by each β4 splice variant correlated with the rank order of their nuclear-targeting properties (β4b > β4a > β4e). Together, these findings support isoform-specific functions of β4 splice variants in neurons, with β4b playing a dual role in channel modulation and gene regulation, whereas the newly detected β4e variant serves exclusively in calcium-channel-dependent functions. PMID:24453333

  16. Mouse genome-wide association and systems genetics identify Asxl2 as a regulator of bone mineral density and osteoclastogenesis.

    Directory of Open Access Journals (Sweden)

    Charles R Farber

    2011-04-01

    Full Text Available Significant advances have been made in the discovery of genes affecting bone mineral density (BMD; however, our understanding of its genetic basis remains incomplete. In the current study, genome-wide association (GWA and co-expression network analysis were used in the recently described Hybrid Mouse Diversity Panel (HMDP to identify and functionally characterize novel BMD genes. In the HMDP, a GWA of total body, spinal, and femoral BMD revealed four significant associations (-log10P>5.39 affecting at least one BMD trait on chromosomes (Chrs. 7, 11, 12, and 17. The associations implicated a total of 163 genes with each association harboring between 14 and 112 genes. This list was reduced to 26 functional candidates by identifying those genes that were regulated by local eQTL in bone or harbored potentially functional non-synonymous (NS SNPs. This analysis revealed that the most significant BMD SNP on Chr. 12 was a NS SNP in the additional sex combs like-2 (Asxl2 gene that was predicted to be functional. The involvement of Asxl2 in the regulation of bone mass was confirmed by the observation that Asxl2 knockout mice had reduced BMD. To begin to unravel the mechanism through which Asxl2 influenced BMD, a gene co-expression network was created using cortical bone gene expression microarray data from the HMDP strains. Asxl2 was identified as a member of a co-expression module enriched for genes involved in the differentiation of myeloid cells. In bone, osteoclasts are bone-resorbing cells of myeloid origin, suggesting that Asxl2 may play a role in osteoclast differentiation. In agreement, the knockdown of Asxl2 in bone marrow macrophages impaired their ability to form osteoclasts. This study identifies a new regulator of BMD and osteoclastogenesis and highlights the power of GWA and systems genetics in the mouse for dissecting complex genetic traits.

  17. Reconstitution of CO2 Regulation of SLAC1 Anion Channel and Function of CO2-Permeable PIP2;1 Aquaporin as CARBONIC ANHYDRASE4 Interactor.

    Science.gov (United States)

    Wang, Cun; Hu, Honghong; Qin, Xue; Zeise, Brian; Xu, Danyun; Rappel, Wouter-Jan; Boron, Walter F; Schroeder, Julian I

    2016-02-01

    Dark respiration causes an increase in leaf CO2 concentration (Ci), and the continuing increases in atmospheric [CO2] further increases Ci. Elevated leaf CO2 concentration causes stomatal pores to close. Here, we demonstrate that high intracellular CO2/HCO3 (-) enhances currents mediated by the Arabidopsis thaliana guard cell S-type anion channel SLAC1 upon coexpression of any one of the Arabidopsis protein kinases OST1, CPK6, or CPK23 in Xenopus laevis oocytes. Split-ubiquitin screening identified the PIP2;1 aquaporin as an interactor of the βCA4 carbonic anhydrase, which was confirmed in split luciferase, bimolecular fluorescence complementation, and coimmunoprecipitation experiments. PIP2;1 exhibited CO2 permeability. Mutation of PIP2;1 in planta alone was insufficient to impair CO2- and abscisic acid-induced stomatal closing, likely due to redundancy. Interestingly, coexpression of βCA4 and PIP2;1 with OST1-SLAC1 or CPK6/23-SLAC1 in oocytes enabled extracellular CO2 enhancement of SLAC1 anion channel activity. An inactive PIP2;1 point mutation was identified that abrogated water and CO2 permeability and extracellular CO2 regulation of SLAC1 activity. These findings identify the CO2-permeable PIP2;1 as key interactor of βCA4 and demonstrate functional reconstitution of extracellular CO2 signaling to ion channel regulation upon coexpression of PIP2;1, βCA4, SLAC1, and protein kinases. These data further implicate SLAC1 as a bicarbonate-responsive protein contributing to CO2 regulation of S-type anion channels. PMID:26764375

  18. KV7 potassium channels

    DEFF Research Database (Denmark)

    Stott, Jennifer B; Jepps, Thomas Andrew; Greenwood, Iain A

    2014-01-01

    Potassium channels are key regulators of smooth muscle tone, with increases in activity resulting in hyperpolarisation of the cell membrane, which acts to oppose vasoconstriction. Several potassium channels exist within smooth muscle, but the KV7 family of voltage-gated potassium channels have been...

  19. Computing rates of Markov models of voltage-gated ion channels by inverting partial differential equations governing the probability density functions of the conducting and non-conducting states.

    Science.gov (United States)

    Tveito, Aslak; Lines, Glenn T; Edwards, Andrew G; McCulloch, Andrew

    2016-07-01

    Markov models are ubiquitously used to represent the function of single ion channels. However, solving the inverse problem to construct a Markov model of single channel dynamics from bilayer or patch-clamp recordings remains challenging, particularly for channels involving complex gating processes. Methods for solving the inverse problem are generally based on data from voltage clamp measurements. Here, we describe an alternative approach to this problem based on measurements of voltage traces. The voltage traces define probability density functions of the functional states of an ion channel. These probability density functions can also be computed by solving a deterministic system of partial differential equations. The inversion is based on tuning the rates of the Markov models used in the deterministic system of partial differential equations such that the solution mimics the properties of the probability density function gathered from (pseudo) experimental data as well as possible. The optimization is done by defining a cost function to measure the difference between the deterministic solution and the solution based on experimental data. By evoking the properties of this function, it is possible to infer whether the rates of the Markov model are identifiable by our method. We present applications to Markov model well-known from the literature. PMID:27154008

  20. Store-Operated Ca2+ Release-Activated Ca2+ Channels Regulate PAR2-Activated Ca2+ Signaling and Cytokine Production in Airway Epithelial Cells.

    Science.gov (United States)

    Jairaman, Amit; Yamashita, Megumi; Schleimer, Robert P; Prakriya, Murali

    2015-09-01

    The G-protein-coupled protease-activated receptor 2 (PAR2) plays an important role in the pathogenesis of various inflammatory and auto-immune disorders. In airway epithelial cells (AECs), stimulation of PAR2 by allergens and proteases triggers the release of a host of inflammatory mediators to regulate bronchomotor tone and immune cell recruitment. Activation of PAR2 turns on several cell signaling pathways of which the mobilization of cytosolic Ca(2+) is likely a critical but poorly understood event. In this study, we show that Ca(2+) release-activated Ca(2+) (CRAC) channels encoded by stromal interaction molecule 1 and Orai1 are a major route of Ca(2+) entry in primary human AECs and drive the Ca(2+) elevations seen in response to PAR2 activation. Activation of CRAC channels induces the production of several key inflammatory mediators from AECs including thymic stromal lymphopoietin, IL-6, and PGE2, in part through stimulation of gene expression via nuclear factor of activated T cells (NFAT). Furthermore, PAR2 stimulation induces the production of many key inflammatory mediators including PGE2, IL-6, IL-8, and GM-CSF in a CRAC channel-dependent manner. These findings indicate that CRAC channels are the primary mechanism for Ca(2+) influx in AECs and a vital checkpoint for the induction of PAR2-induced proinflammatory cytokines. PMID:26238490

  1. Differential regulation of the InsP₃ receptor type-1 and -2 single channel properties by InsP₃, Ca²⁺ and ATP.

    Science.gov (United States)

    Wagner, Larry E; Yule, David I

    2012-07-15

    An elevation of intracellular Ca2+ levels as a result of InsP3 receptor (InsP3R) activity represents a ubiquitous signalling pathway controlling a wide variety of cellular events. InsP3R activity is tightly controlled by the levels of the primary ligands, InsP3, Ca2+ and ATP. Importantly, InsP3Rs are regulated by Ca2+ i in a biphasic manner. Ca2+ release through all InsP3R family members is also modulated dramatically by ATP, albeit with sub-type-specific properties. To ascertain if a common mechanism can account for ATP and Ca2+ regulation of these InsP3R family members, we examined the effects of [ATP] on the Ca2+ dependency of rat InsP3R-1 (rInsP3R-1) and mouse InsP3R-2 (mInsP3R-2) activity expressed in DT40-3KO cells. We used the on-nucleus patch clamp recording technique with various [ATP], [InsP3] and [Ca2+] in the patch pipette and measured single InsP3R channel activity in stably transfected DT40 cells. Under identical conditions, at saturating [InsP3] and [ATP], the activity of rInsP3R-1 and mInsP3R-2 was essentially identical in terms of single channel conductance, maximal achievable open probability (Po) and the [Ca2+] required for activation and inhibition of activity. However, in contrast to rInsP3R-1 at saturating [InsP3], the activity of mInsP3R-2 was unaffected by [ATP]. At lower [InsP3], ATP had dramatic effects on mInsP3R-2 Po, but unlike the rInsP3R-1, this did not occur by altering the relative Ca2+ dependency, but by simply increasing the maximally achievable Po at a particular [InsP3] and [Ca2+]. [InsP3] did not alter the biphasic regulation of activity by Ca2+ in either rInsP3R-1 or mInsP3R-2. Analysis of the single channel kinetics indicated that Ca2+ and ATP modulate the Po predominately by facilitating extended bursting activity of the channel but the underlying biophysical mechanism appears to be distinct for each receptor. Subtype-specific regulation of InsP3R channel activity probably contributes to the fidelity of Ca2+ signalling in

  2. Molecular determinants of voltage-gated sodium channel regulation by the Nedd4/Nedd4-like proteins

    DEFF Research Database (Denmark)

    Rougier, Jean-Sébastien; van Bemmelen, Miguel X; Bruce, M Christine;

    2004-01-01

    The voltage-gated Na(+) channels (Na(v)) form a family composed of 10 genes. The COOH termini of Na(v) contain a cluster of amino acids that are nearly identical among 7 of the 10 members. This COOH-terminal sequence, PPSYDSV, is a PY motif known to bind to WW domains of E3 protein...

  3. Is there a role for T-type Ca2+ channels in regulation of vasomotor tone in mesenteric arterioles?

    DEFF Research Database (Denmark)

    Jensen, Lars Jørn; Holstein-Rathlou, Niels-Henrik

    2009-01-01

    The largest peripheral blood pressure drop occurs in terminal arterioles (<40 microm lumen diameter). L-type voltage-dependent Ca2+ channels (VDCCs) are considered the primary pathway for Ca2+ influx during physiologic activation of vascular smooth muscle cells (VSMC). Recent evidence suggests th...

  4. Human ether à-gogo K(+) channel 1 (hEag1) regulates MDA-MB-231 breast cancer cell migration through Orai1-dependent calcium entry.

    Science.gov (United States)

    Hammadi, Mehdi; Chopin, Valérie; Matifat, Fabrice; Dhennin-Duthille, Isabelle; Chasseraud, Maud; Sevestre, Henri; Ouadid-Ahidouch, Halima

    2012-12-01

    Breast cancer (BC) has a poor prognosis due to its strong metastatic ability. Accumulating data present ether à go-go (hEag1) K(+) channels as relevant player in controlling cell cycle and proliferation of non-invasive BC cells. However, the role of hEag1 in invasive BC cells migration is still unknown. In this study, we studied both the functional expression and the involvement in cell migration of hEag1 in the highly metastatic MDA-MB-231 human BC cells. We showed that hEag1 mRNA and proteins were expressed in human invasive ductal carcinoma tissues and BC cell lines. Functional activity of hEag1 channels in MDA-MB-231 cells was confirmed using astemizole, a hEag1 blocker, or siRNA. Blocking or silencing hEag1 depolarized the membrane potential and reduced both Ca(2+) entry and MDA-MB-231 cell migration without affecting cell proliferation. Recent studies have reported that Ca(2+) entry through Orai1 channels is required for MDA-MB-231 cell migration. Down-regulation of hEag1 or Orai1 reduced Ca(2+) influx and cell migration with similar efficiency. Interestingly, no additive effects on Ca(2+) influx or cell migration were observed in cells co-transfected with sihEag1 and siOrai1. Finally, both Orai1 and hEag1 are expressed in invasive breast adenocarcinoma tissues and invaded metastatic lymph node samples (LNM(+)). In conclusion, this study is the first to demonstrate that hEag1 channels are involved in the serum-induced migration of BC cells by controlling the Ca(2+) entry through Orai1 channels. hEag1 may therefore represent a potential target for the suppression of BC cell migration, and thus prevention of metastasis development.

  5. Conserved allosteric hot spots in the transmembrane domains of cystic fibrosis transmembrane conductance regulator (CFTR) channels and multidrug resistance protein (MRP) pumps.

    Science.gov (United States)

    Wei, Shipeng; Roessler, Bryan C; Chauvet, Sylvain; Guo, Jingyu; Hartman, John L; Kirk, Kevin L

    2014-07-18

    ATP-binding cassette (ABC) transporters are an ancient family of transmembrane proteins that utilize ATPase activity to move substrates across cell membranes. The ABCC subfamily of the ABC transporters includes active drug exporters (the multidrug resistance proteins (MRPs)) and a unique ATP-gated ion channel (cystic fibrosis transmembrane conductance regulator (CFTR)). The CFTR channel shares gating principles with conventional ligand-gated ion channels, but the allosteric network that couples ATP binding at its nucleotide binding domains (NBDs) with conformational changes in its transmembrane helices (TMs) is poorly defined. It is also unclear whether the mechanisms that govern CFTR gating are conserved with the thermodynamically distinct MRPs. Here we report a new class of gain of function (GOF) mutation of a conserved proline at the base of the pore-lining TM6. Multiple substitutions of this proline promoted ATP-free CFTR activity and activation by the weak agonist, 5'-adenylyl-β,γ-imidodiphosphate (AMP-PNP). TM6 proline mutations exhibited additive GOF effects when combined with a previously reported GOF mutation located in an outer collar of TMs that surrounds the pore-lining TMs. Each TM substitution allosterically rescued the ATP sensitivity of CFTR gating when introduced into an NBD mutant with defective ATP binding. Both classes of GOF mutations also rescued defective drug export by a yeast MRP (Yor1p) with ATP binding defects in its NBDs. We conclude that the conserved TM6 proline helps set the energy barrier to both CFTR channel opening and MRP-mediated drug efflux and that CFTR channels and MRP pumps utilize similar allosteric mechanisms for coupling conformational changes in their translocation pathways to ATP binding at their NBDs.

  6. Human ether à-gogo K(+) channel 1 (hEag1) regulates MDA-MB-231 breast cancer cell migration through Orai1-dependent calcium entry.

    Science.gov (United States)

    Hammadi, Mehdi; Chopin, Valérie; Matifat, Fabrice; Dhennin-Duthille, Isabelle; Chasseraud, Maud; Sevestre, Henri; Ouadid-Ahidouch, Halima

    2012-12-01

    Breast cancer (BC) has a poor prognosis due to its strong metastatic ability. Accumulating data present ether à go-go (hEag1) K(+) channels as relevant player in controlling cell cycle and proliferation of non-invasive BC cells. However, the role of hEag1 in invasive BC cells migration is still unknown. In this study, we studied both the functional expression and the involvement in cell migration of hEag1 in the highly metastatic MDA-MB-231 human BC cells. We showed that hEag1 mRNA and proteins were expressed in human invasive ductal carcinoma tissues and BC cell lines. Functional activity of hEag1 channels in MDA-MB-231 cells was confirmed using astemizole, a hEag1 blocker, or siRNA. Blocking or silencing hEag1 depolarized the membrane potential and reduced both Ca(2+) entry and MDA-MB-231 cell migration without affecting cell proliferation. Recent studies have reported that Ca(2+) entry through Orai1 channels is required for MDA-MB-231 cell migration. Down-regulation of hEag1 or Orai1 reduced Ca(2+) influx and cell migration with similar efficiency. Interestingly, no additive effects on Ca(2+) influx or cell migration were observed in cells co-transfected with sihEag1 and siOrai1. Finally, both Orai1 and hEag1 are expressed in invasive breast adenocarcinoma tissues and invaded metastatic lymph node samples (LNM(+)). In conclusion, this study is the first to demonstrate that hEag1 channels are involved in the serum-induced migration of BC cells by controlling the Ca(2+) entry through Orai1 channels. hEag1 may therefore represent a potential target for the suppression of BC cell migration, and thus prevention of metastasis development. PMID:22495877

  7. Regional flexibility in the S4-S5 linker regulates hERG channel closed-state stabilization.

    Science.gov (United States)

    Hull, Christina M; Sokolov, Stanislav; Van Slyke, Aaron C; Claydon, Tom W

    2014-10-01

    hERG K(+) channel function is vital for normal cardiac rhythm, yet the mechanisms underlying the unique biophysical characteristics of the channel, such as slow activation and deactivation gating, are incompletely understood. The S4-S5 linker is thought to transduce voltage sensor movement to opening of the pore gate, but may also integrate signals from cytoplasmic domains. Previously, we showed that substitutions of G546 within the S4-S5 linker destabilize the closed state of the channel. Here, we present results of a glycine-scan in the background of 546L. We demonstrate site-specific restoration of WT-like activation which suggests that flexibility in the N-terminal portion of the S4-S5 linker is critical for the voltage dependence of hERG channel activation. In addition, we show that the voltage dependence of deactivation, which was recently shown to be left-shifted from that of activation due to voltage sensor mode-shift, is also modulated by the S4-S5 linker. The G546L mutation greatly attenuated the coupling of voltage sensor mode-shift to the pore gate without altering the mode-shift itself. Indeed, all of the S4-S5 linker mutations tested similarly reduced coupling of the mode-shift to the pore gate. These data demonstrate a key role for S4-S5 linker in the unique activation and deactivation gating of hERG channels. Furthermore, uncoupling of the mode-shift to the pore by S4-S5 linker mutations parallels the effects of mutations in the N-terminus suggestive of functional interactions between the two regions.

  8. Voltage-gated potassium channel Kvl.3 in rabbit ciliary epithelium regulates the membrane potential via coupling intracellular calcium

    Institute of Scientific and Technical Information of China (English)

    LI Yan-feng; ZHUO Ye-hong; BI Wei-na; BAI Yu-jing; LI Yan-na; WANG Zhi-jian

    2008-01-01

    Background The cell layer of the ciliary epithelium is responsible for aqueous humor secretion and maintenance.Ion channels play an important role in these processes.The main aim of this study was to determine whether the well-characterized members of the Kvl family (Kv1.3) contribute to the Kv currents in ciliary epithelium.Methods New Zealand White rabbits were maintained in a 12 hours light/dark cycle.Ciliary epithelium samples were isolated from the rabbits.We used Western blotting and immunocytochemistry to identify the expression and location of a voltage-gated potassium channel Kvl.3 in ciliary body epithelium.Membrane potential change after adding of Kv1.3 inhibitor margatoxin (MgTX) was observed with a fluorescence method.Results Western blotting and immunocytochemical studies showed that the Kv1.3 protein expressed in pigment ciliary epithelium and nonpigment ciliary epithelium,however it seemed to express more in the apical membrane of the nonpigmented epithelial cells.One nmol/L margatoxin,a specific inhibitor of Kv1.3 channels caused depolarization of the cultured nonpigmented epithelium (NPE) membrane potential.The cytosotic calcium increased after NPE cell depolarization,this increase of cytosolic calcium was partially blocked by 12.5 μmol/L dantrolene and 10 μmol/L nifedipine.These observations suggest that Kv1.3 channels modulate ciliary epithelium potential and effect calcium dependent mechanisms.Conclusion Kv1.3 channels contribute to K+ efflux at the membrane of rabbit ciliary epithelium.

  9. Regulación por proteasas del canal de sodio sensible al amiloride (ENaC Amiloride sensitive sodium channels (ENaC and their regulation by proteases

    Directory of Open Access Journals (Sweden)

    Luciano Galizia

    2011-04-01

    Full Text Available El ENaC es un canal que permite el movimiento de Na+ desde el líquido luminal hacia las células en numerosos epitelios reabsortivos y también en otros tejidos como la placenta. ENaC juega un papel crucial en la homeostasis de los electrolitos y volumen de líquido extracelular. Es regulado por numerosas hormonas, incluyendo la aldosterona y bloqueado por el diurético amiloride. El ENaC está formado por tres subunidades homólogas α, β y γ que forman el poro por el cual se mueven los iones Na+. Dos factores regulan la actividad del ENaC. 1 el número de canales insertos en la membrana celular y 2 la probabilidad de apertura o tiempo en que se encuentra abierto el canal. El número de canales es el resultado de un balance entre su síntesis y degradación. La probabilidad de apertura depende de la proteólisis de zonas específicas de las subunidades α y γ por múltiples proteasas dentro de la célula y en el espacio extracelular. Entre las proteasas más estudiadas se encuentran la furina, prostasina, elastasa, plasmina y tripsina. Existen sustancias endógenas que bloquean la actividad de estas proteasas como la aprotinina, la bikunina y la nexina-1 y la expresión de las proteasas y sus inhibidores es regulada a su vez por la aldosterona, la tasa de movimiento de Na y el TFGβ. En este trabajo presentamos algunos ejemplos de esta regulación y su potencial papel en condiciones normales y en ciertas enfermedades como la fibrosis quística, renales e hipertensión.ENaC is a channel that mediates entry of Na+ from the luminal fluid into the cells in many reabsorbing epithelia and it is also expressed in human placenta. ENaC is crucial in the control of electrolyte and extracellular volume homeostasis. ENaC is regulated by several hormones, including aldosterone and blocked by amiloride and its analogs. ENaC channels are composed by three homologous subunits, α, β and γ that form the pore where Na ions are transported. Two factors

  10. Characterization of an Oct1 orthologue in the channel catfish, Ictalurus punctatus: A negative regulator of immunoglobulin gene transcription?

    OpenAIRE

    Miller Norman W; Wilson Melanie R; Kruiswijk Corine P; Ross David A; Hikima Jun-ichi; Lennard Mara L; Warr Gregory W

    2007-01-01

    Abstract Background The enhancer (Eμ3') of the immunoglobulin heavy chain locus (IGH) of the channel catfish (Ictalurus punctatus) has been well characterized. The functional core region consists of two variant Oct transcription factor binding octamer motifs and one E-protein binding μE5 site. An orthologue to the Oct2 transcription factor has previously been cloned in catfish and is a functionally active transcription factor. This study was undertaken to clone and characterize the Oct1 trans...

  11. Hydrogen sulfide-mediated regulation of contractility in the mouse ileum with electrical stimulation: roles of L-cysteine, cystathionine β-synthase, and K+ channels.

    Science.gov (United States)

    Yamane, Satoshi; Kanno, Toshio; Nakamura, Hiroyuki; Fujino, Hiromichi; Murayama, Toshihiko

    2014-10-01

    Hydrogen sulfide (H2S) is considered to be a signaling molecule. The precise mechanisms underlying H2S-related events, including the producing enzymes and target molecules in gastrointestinal tissues, have not been elucidated in detail. We herein examined the involvement of H2S in contractions induced by repeated electrical stimulations (ES). ES-induced contractions were neurotoxin-sensitive and increased by aminooxyacetic acid, an inhibitor of cystathionine β-synthase (CBS) and cystathionine γ-lyase, but not by D,L-propargylglycine, a selective inhibitor of cystathionine γ-lyase, in an ES trial-dependent manner. ES-induced contractions were markedly decreased in the presence of L-cysteine. This response was inhibited by aminooxyacetic acid and an antioxidant, and accelerated by L-methionine, an activator of CBS. The existence of CBS was confirmed. NaHS transiently inhibited ES- and acetylcholine-induced contractions, and sustainably decreased basal tone for at least 20 min after its addition. The treatment with glibenclamide, an ATP-sensitive K+ channel blocker, reduced both the L-cysteine response and NaHS-induced inhibition of contractions. The NaHS-induced decrease in basal tone was inhibited by apamin, a small conductance Ca2+-activated K+ channel blocker. These results suggest that H2S may be endogenously produced via CBS in ES-activated enteric neurons, and regulates contractility via multiple K+ channels in the ileum.

  12. Serum Starvation-Induced Voltage-Gated Potassium Channel Kv7.5 Expression and Its Regulation by Sp1 in Canine Osteosarcoma Cells

    Directory of Open Access Journals (Sweden)

    Bo Hyung Lee

    2014-01-01

    Full Text Available The KCNQ gene family, whose members encode Kv7 channels, belongs to the voltage-gated potassium (Kv channel group. The roles of this gene family have been widely investigated in nerve and muscle cells. In the present study, we investigated several characteristics of Kv7.5, which is strongly expressed in the canine osteosarcoma cell line, CCL-183. Serum starvation upregulated Kv7.5 expression, and the Kv7 channel opener, flupirtine, attenuated cell proliferation by arresting cells in the G0/G1 phase. We also showed that Kv7.5 knockdown helps CCL-183 cells to proliferate. In an effort to find an endogenous regulator of Kv7.5, we used mithramycin A to reduce the level of the transcription factor Sp1, and it strongly inhibited the induction of Kv7.5 in CCL-183 cells. These results suggest that the activation of Kv7.5 by flupirtine may exert an anti-proliferative effect in canine osteosarcoma. Therefore, Kv7.5 is a possible molecular target for canine osteosarcoma therapy.

  13. Serum starvation-induced voltage-gated potassium channel Kv7.5 expression and its regulation by Sp1 in canine osteosarcoma cells.

    Science.gov (United States)

    Lee, Bo Hyung; Ryu, Pan Dong; Lee, So Yeong

    2014-01-01

    The KCNQ gene family, whose members encode Kv7 channels, belongs to the voltage-gated potassium (Kv) channel group. The roles of this gene family have been widely investigated in nerve and muscle cells. In the present study, we investigated several characteristics of Kv7.5, which is strongly expressed in the canine osteosarcoma cell line, CCL-183. Serum starvation upregulated Kv7.5 expression, and the Kv7 channel opener, flupirtine, attenuated cell proliferation by arresting cells in the G0/G1 phase. We also showed that Kv7.5 knockdown helps CCL-183 cells to proliferate. In an effort to find an endogenous regulator of Kv7.5, we used mithramycin A to reduce the level of the transcription factor Sp1, and it strongly inhibited the induction of Kv7.5 in CCL-183 cells. These results suggest that the activation of Kv7.5 by flupirtine may exert an anti-proliferative effect in canine osteosarcoma. Therefore, Kv7.5 is a possible molecular target for canine osteosarcoma therapy. PMID:24434641

  14. Design, Synthesis and Biological Evaluation of Hydroxamic Acid Derivatives as Potential High Density Lipoprotein (HDL) Receptor CLA-1 Up-Regulating Agents

    OpenAIRE

    Yu Du; Yanbin Wu; Bin Hong; Yuan Yang; Xiaojian Jia; Li Wang; Xiaofang Chen

    2011-01-01

    Trichostatin A (TSA) and suberoylanilide hydroxamic acid (SAHA) were reported in our recent publication as novel human high density lipoprotein (HDL) receptor CD36 and Lysosomal integral membrane protein-II Analogous-1 (CLA-1) up-regulators. As part of a broader effort to more fully explore the structure-activity relationships (SAR) of CLA-1 up-regulators, we synthesized a series of hydroxamic acid derivatives and evaluated their CLA-1 up-regulating activities in HepG2 cells. Some compounds e...

  15. 尾矿库明渠排洪系统调洪演算方法%Flood Regulating Calculation Algorithm of Open Channel Drainage System of Tailing Ponds

    Institute of Scientific and Technical Information of China (English)

    闫鹏

    2015-01-01

    在尾矿库闭库治理、截洪型新建尾矿库工程中,明渠作为排洪系统应用较为广泛。排洪系统是尾矿库的重要构筑物,直接关系到尾矿库工程的经济与安全。目前,明渠应用存在的问题:设计流量直接按洪峰流量计算,造成明渠设计断面偏大;明渠缓流状态时未考虑淹没系数对流量的影响,存在防洪安全隐患;明渠急流状态未设置过渡段,致使断面设计偏大。针对以上问题,利用临界底坡将明渠进口的流态分为自由出流、淹没出流,给出了矩形断面进口自由出流状态下的临界水深、临界流速、临界底坡的计算公式;根据明渠进口的流态,分别给出了明渠缓流、急流泄流关系的计算步骤;根据区域洪水过程线、调蓄库容曲线及泄流关系曲线,进行了尾矿库调洪验算。%In the closed treatment of tailing ponds and the intercepting flood type new tailing pond project,open channel has been widely applied as drainage system.Drainage system is an important struc-ture of tailing pond,it is directly related to economic and security engineering of tailing pond.At pres-ent,there are several problems of the application of open channel are existed:flood regulating calculation is not conducted,design of open channel flow is directly calculated by peak flow,resulting in open chan-nel cross -section design is too large;the influence of the submerged coefficient flow is not considered in channel slow state,so,flood control safety hazards are existed;the transition section is not set in channel rapids state,resulting in the design of cross section is too large.In view of the above problems,the flow of imports of open channel is divided into free flow submerged discharge flow by using the critical bottom slope.The calculation formulas of critical depth,critical flow velocity and critical bottom slope are given under the state of rectangular import free flow.According to the

  16. Increased dendritic spine density and tau expression are associated with individual differences in steroidal regulation of male sexual behavior.

    Directory of Open Access Journals (Sweden)

    Pranay Bharadwaj

    Full Text Available Male sexual behavior (MSB is modulated by gonadal steroids, yet this relationship is highly variable across species and between individuals. A significant percentage (~30% of B6D2F1 hybrid male mice demonstrate MSB after long-term orchidectomy (herein after referred to as "maters", providing an opportunity to examine the mechanisms that underlie individual differences in steroidal regulation of MSB. Use of gene expression arrays comparing maters and non-maters has provided a first pass look at the genetic underpinnings of steroid-independent MSB. Surprisingly, of the ~500 genes in the medial preoptic area (MPOA that differed between maters and non-maters, no steroid hormone or receptor genes were differentially expressed between the two groups. Interestingly, best known for their association with Alzheimer's disease, amyloid precursor protein (APP and the microtubule-associated protein tau (MAPT were elevated in maters. Increased levels of their protein products (APP and tau in their non-pathological states have been implicated in cell survival, neuroprotection, and supporting synaptic integrity. Here we tested transgenic mice that overexpress tau and found facilitated mounting and intromission behavior after long-term orchidectomy relative to littermate controls. In addition, levels of synaptophysin and spinophilin, proteins generally enriched in synapses and dendritic spines respectively, were elevated in the MPOA of maters. Dendritic morphology was also assessed in Golgi-impregnated brains of orchidectomized B6D2F1 males, and hybrid maters exhibited greater dendritic spine density in MPOA neurons. In sum, we show for the first time that retention of MSB in the absence of steroids is correlated with morphological differences in neurons.

  17. The volume-regulated anion channel is formed by LRRC8 heteromers – molecular identification and roles in membrane transport and physiology.

    Science.gov (United States)

    Stauber, Tobias

    2015-09-01

    Cellular volume regulation is fundamental for numerous physiological processes. The volume-regulated anion channel, VRAC, plays a crucial role in regulatory volume decrease. This channel, which is ubiquitously expressed in vertebrates, has been vastly characterized by electrophysiological means. It opens upon cell swelling and conducts chloride and arguably organic osmolytes. VRAC has been proposed to be critically involved in various cellular and organismal functions, including cell proliferation and migration, apoptosis, transepithelial transport, swelling-induced exocytosis and intercellular communication. It may also play a role in pathological states like cancer and ischemia. Despite many efforts, the molecular identity of VRAC had remained elusive for decades, until the recent discovery of heteromers of LRRC8A with other LRRC8 family members as an essential VRAC component. This identification marks a starting point for studies on the structure-function relation, for molecular biological investigations of its cell biology and for re-evaluating the physiological roles of VRAC. This review recapitulates the identification of LRRC8 heteromers as VRAC components, depicts the similarities between LRRC8 proteins and pannexins, and discussed whether VRAC conducts larger osmolytes. Furthermore, proposed physiological functions of VRAC and the present knowledge about the physiological significance of LRRC8 proteins are summarized and collated. PMID:25868000

  18. Eps15 Homology Domain-containing Protein 3 Regulates Cardiac T-type Ca2+ Channel Targeting and Function in the Atria*

    Science.gov (United States)

    Curran, Jerry; Musa, Hassan; Kline, Crystal F.; Makara, Michael A.; Little, Sean C.; Higgins, John D.; Hund, Thomas J.; Band, Hamid; Mohler, Peter J.

    2015-01-01

    Proper trafficking of membrane-bound ion channels and transporters is requisite for normal cardiac function. Endosome-based protein trafficking of membrane-bound ion channels and transporters in the heart is poorly understood, particularly in vivo. In fact, for select cardiac cell types such as atrial myocytes, virtually nothing is known regarding endosomal transport. We previously linked the C-terminal Eps15 homology domain-containing protein 3 (EHD3) with endosome-based protein trafficking in ventricular cardiomyocytes. Here we sought to define the roles and membrane protein targets for EHD3 in atria. We identify the voltage-gated T-type Ca2+ channels (CaV3.1, CaV3.2) as substrates for EHD3-dependent trafficking in atria. Mice selectively lacking EHD3 in heart display reduced expression and targeting of both Cav3.1 and CaV3.2 in the atria. Furthermore, functional experiments identify a significant loss of T-type-mediated Ca2+ current in EHD3-deficient atrial myocytes. Moreover, EHD3 associates with both CaV3.1 and CaV3.2 in co-immunoprecipitation experiments. T-type Ca2+ channel function is critical for proper electrical conduction through the atria. Consistent with these roles, EHD3-deficient mice demonstrate heart rate variability, sinus pause, and atrioventricular conduction block. In summary, our findings identify CaV3.1 and CaV3.2 as substrates for EHD3-dependent protein trafficking in heart, provide in vivo data on endosome-based trafficking pathways in atria, and implicate EHD3 as a key player in the regulation of atrial myocyte excitability and cardiac conduction. PMID:25825486

  19. Regulation of transient receptor potential channels of melastatin type 8 (TRPM8): effect of cAMP, cannabinoid CB(1) receptors and endovanilloids.

    Science.gov (United States)

    De Petrocellis, Luciano; Starowicz, Katarzyna; Moriello, Aniello Schiano; Vivese, Marta; Orlando, Pierangelo; Di Marzo, Vincenzo

    2007-05-15

    The transient receptor potential channel of melastatin type 8 (TRPM8), which is gated by low (<25 degrees C) temperature and chemical compounds, is regulated by protein kinase C-mediated phosphorylation in a way opposite to that observed with the transient receptor potential channel of vanilloid type 1 (TRPV1), i.e. by being desensitized and not sensitized. As TRPV1 is sensitized also by protein kinase A (PKA)-mediated phosphorylation, we investigated the effect of two activators of the PKA pathway, 8-Br-cAMP and forskolin, on the activity of menthol and icilin at TRPM8 in HEK-293 cells stably overexpressing the channel (TRPM8-HEK-293 cells). We also studied the effect on TRPM8 of: (1) a series of compounds previously shown to activate or antagonize TRPV1, and (2) co-stimulation of transiently co-expressed cannabinoid CB(1) receptors. Both 8-Br-cAMP (100 microM) and forskolin (10 microM) right-shifted the dose-response curves for the TRPM8-mediated effect of icilin and menthol on intracellular Ca(2+). The inhibitory effects of 8-Br-cAMP and forskolin were attenuated by the selective PKA inhibitor Rp-cAMP-S. Stimulation of human CB(1) receptors transiently co-expressed in TRPM8-HEK-293 cells also inhibited TRPM8 response to icilin. Finally, some TRPV1 agonists and antagonists, but not iodinated antagonists, antagonized icilin- and much less so menthol-, induced TRPM8 activation. Importantly, the endovanilloids/endocannabinoids, anandamide and NADA, also antagonized TRPM8 at submicromolar concentrations. Although these findings need to be confirmed by experiments directly measuring TRPM8 activity in natively TRPM8-expressing cells, they support the notion that the same regulatory events have opposing actions on TRPM8 and TRPV1 receptors and identify anandamide and NADA as the first potential endogenous functional antagonists of TRPM8 channels.

  20. L-type calcium channels play a critical role in maintaining lens transparency by regulating phosphorylation of aquaporin-0 and myosin light chain and expression of connexins.

    Science.gov (United States)

    Maddala, Rupalatha; Nagendran, Tharkika; de Ridder, Gustaaf G; Schey, Kevin L; Rao, Ponugoti Vasantha

    2013-01-01

    Homeostasis of intracellular calcium is crucial for lens cytoarchitecture and transparency, however, the identity of specific channel proteins regulating calcium influx within the lens is not completely understood. Here we examined the expression and distribution profiles of L-type calcium channels (LTCCs) and explored their role in morphological integrity and transparency of the mouse lens, using cDNA microarray, RT-PCR, immunoblot, pharmacological inhibitors and immunofluorescence analyses. The results revealed that Ca (V) 1.2 and 1.3 channels are expressed and distributed in both the epithelium and cortical fiber cells in mouse lens. Inhibition of LTCCs with felodipine or nifedipine induces progressive cortical cataract formation with time, in association with decreased lens weight in ex-vivo mouse lenses. Histological analyses of felodipine treated lenses revealed extensive disorganization and swelling of cortical fiber cells resembling the phenotype reported for altered aquaporin-0 activity without detectable cytotoxic effects. Analysis of both soluble and membrane rich fractions from felodipine treated lenses by SDS-PAGE in conjunction with mass spectrometry and immunoblot analyses revealed decreases in β-B1-crystallin, Hsp-90, spectrin and filensin. Significantly, loss of transparency in the felodipine treated lenses was preceded by an increase in aquaporin-0 serine-235 phosphorylation and levels of connexin-50, together with decreases in myosin light chain phosphorylation and the levels of 14-3-3ε, a phosphoprotein-binding regulatory protein. Felodipine treatment led to a significant increase in gene expression of connexin-50 and 46 in the mouse lens. Additionally, felodipine inhibition of LTCCs in primary cultures of mouse lens epithelial cells resulted in decreased intracellular calcium, and decreased actin stress fibers and myosin light chain phosphorylation, without detectable cytotoxic response. Taken together, these observations reveal a crucial

  1. L-type calcium channels play a critical role in maintaining lens transparency by regulating phosphorylation of aquaporin-0 and myosin light chain and expression of connexins.

    Directory of Open Access Journals (Sweden)

    Rupalatha Maddala

    Full Text Available Homeostasis of intracellular calcium is crucial for lens cytoarchitecture and transparency, however, the identity of specific channel proteins regulating calcium influx within the lens is not completely understood. Here we examined the expression and distribution profiles of L-type calcium channels (LTCCs and explored their role in morphological integrity and transparency of the mouse lens, using cDNA microarray, RT-PCR, immunoblot, pharmacological inhibitors and immunofluorescence analyses. The results revealed that Ca (V 1.2 and 1.3 channels are expressed and distributed in both the epithelium and cortical fiber cells in mouse lens. Inhibition of LTCCs with felodipine or nifedipine induces progressive cortical cataract formation with time, in association with decreased lens weight in ex-vivo mouse lenses. Histological analyses of felodipine treated lenses revealed extensive disorganization and swelling of cortical fiber cells resembling the phenotype reported for altered aquaporin-0 activity without detectable cytotoxic effects. Analysis of both soluble and membrane rich fractions from felodipine treated lenses by SDS-PAGE in conjunction with mass spectrometry and immunoblot analyses revealed decreases in β-B1-crystallin, Hsp-90, spectrin and filensin. Significantly, loss of transparency in the felodipine treated lenses was preceded by an increase in aquaporin-0 serine-235 phosphorylation and levels of connexin-50, together with decreases in myosin light chain phosphorylation and the levels of 14-3-3ε, a phosphoprotein-binding regulatory protein. Felodipine treatment led to a significant increase in gene expression of connexin-50 and 46 in the mouse lens. Additionally, felodipine inhibition of LTCCs in primary cultures of mouse lens epithelial cells resulted in decreased intracellular calcium, and decreased actin stress fibers and myosin light chain phosphorylation, without detectable cytotoxic response. Taken together, these observations

  2. Tubulin tail sequences and post-translational modifications regulate closure of mitochondrial voltage-dependent anion channel (VDAC).

    Science.gov (United States)

    Sheldon, Kely L; Gurnev, Philip A; Bezrukov, Sergey M; Sackett, Dan L

    2015-10-30

    It was previously shown that tubulin dimer interaction with the mitochondrial outer membrane protein voltage-dependent anion channel (VDAC) blocks traffic through the channel and reduces oxidative metabolism and that this requires the unstructured anionic C-terminal tail peptides found on both α- and β-tubulin subunits. It was unclear whether the α- and β-tubulin tails contribute equally to VDAC blockade and what effects might be due to sequence variations in these tail peptides or to tubulin post-translational modifications, which mostly occur on the tails. The nature of the contribution of the tubulin body beyond acting as an anchor for the tails had not been clarified either. Here we present peptide-protein chimeras to address these questions. These constructs allow us to easily combine a tail peptide with different proteins or combine different tail peptides with a particular protein. The results show that a single tail grafted to an inert protein is sufficient to produce channel closure similar to that observed with tubulin. We show that the β-tail is more than an order of magnitude more potent than the α-tail and that the lower α-tail activity is largely due to the presence of a terminal tyrosine. Detyrosination activates the α-tail, and activation is reversed by the removal of the glutamic acid penultimate to the tyrosine. Nitration of tyrosine reverses the tyrosine inhibition of binding and even induces prolonged VDAC closures. Our results demonstrate that small changes in sequence or post-translational modification of the unstructured tails of tubulin result in substantial changes in VDAC closure. PMID:26306046

  3. PKA and cAMP/CNG Channels Independently Regulate the Cholinergic Ca2+-Response of Drosophila Mushroom Body Neurons1,2,3

    Science.gov (United States)

    Pavot, Pierre; Carbognin, Elena

    2015-01-01

    Abstract The mushroom bodies (MBs), one of the main structures in the adult insect brain, play a critical role in olfactory learning and memory. Though historical genes such as dunce and rutabaga, which regulate the level of cAMP, were identified more than 30 years ago, their in vivo effects on cellular and physiological mechanisms and particularly on the Ca2+-responses still remain largely unknown. In this work, performed in Drosophila, we took advantage of in vivo bioluminescence imaging, which allowed real-time monitoring of the entire MBs (both the calyx/cell-bodies and the lobes) simultaneously. We imaged neuronal Ca2+-activity continuously, over a long time period, and characterized the nicotine-evoked Ca2+-response. Using both genetics and pharmacological approaches to interfere with different components of the cAMP signaling pathway, we first show that the Ca2+-response is proportional to the levels of cAMP. Second, we reveal that an acute change in cAMP levels is sufficient to trigger a Ca2+-response. Third, genetic manipulation of protein kinase A (PKA), a direct effector of cAMP, suggests that cAMP also has PKA-independent effects through the cyclic nucleotide-gated Ca2+-channel (CNG). Finally, the disruption of calmodulin, one of the main regulators of the rutabaga adenylate cyclase (AC), yields different effects in the calyx/cell-bodies and in the lobes, suggesting a differential and regionalized regulation of AC. Our results provide insights into the complex Ca2+-response in the MBs, leading to the conclusion that cAMP modulates the Ca2+-responses through both PKA-dependent and -independent mechanisms, the latter through CNG-channels. PMID:26464971

  4. 77 FR 25077 - Special Local Regulation; Wy-Hi Rowing Regatta, Trenton Channel; Detroit River, Wyandotte, MI

    Science.gov (United States)

    2012-04-27

    ... SECURITY Coast Guard 33 CFR Part 100 RIN 1625-AA08 Special Local Regulation; Wy-Hi Rowing Regatta, Trenton... navigable waters immediately prior to, during, and immediately after the Wy-Hi Rowing Regatta. This special..., the Wyandotte Boat Club is holding a rowing race that will require the immediate area to be clear...

  5. 78 FR 25572 - Special Local Regulation; Wy-Hi Rowing Regatta, Trenton Channel; Detroit River, Wyandotte, MI

    Science.gov (United States)

    2013-05-02

    ... Security FR Federal Register NPRM Notice of Proposed Rulemaking A. Regulatory History and Information The... SECURITY Coast Guard 33 CFR Part 100 RIN 1625-AA08 Special Local Regulation; Wy-Hi Rowing Regatta, Trenton... navigable waters immediately prior to, during, and immediately after the Wy-Hi Rowing Regatta. This...

  6. Density-dependent regulation of brook trout population dynamics along a core-periphery distribution gradient in a central Appalachian watershed.

    Directory of Open Access Journals (Sweden)

    Brock M Huntsman

    Full Text Available Spatial population models predict strong density-dependence and relatively stable population dynamics near the core of a species' distribution with increasing variance and importance of density-independent processes operating towards the population periphery. Using a 10-year data set and an information-theoretic approach, we tested a series of candidate models considering density-dependent and density-independent controls on brook trout population dynamics across a core-periphery distribution gradient within a central Appalachian watershed. We sampled seven sub-populations with study sites ranging in drainage area from 1.3-60 km(2 and long-term average densities ranging from 0.335-0.006 trout/m. Modeled response variables included per capita population growth rate of young-of-the-year, adult, and total brook trout. We also quantified a stock-recruitment relationship for the headwater population and coefficients of variability in mean trout density for all sub-populations over time. Density-dependent regulation was prevalent throughout the study area regardless of stream size. However, density-independent temperature models carried substantial weight and likely reflect the effect of year-to-year variability in water temperature on trout dispersal between cold tributaries and warm main stems. Estimated adult carrying capacities decreased exponentially with increasing stream size from 0.24 trout/m in headwaters to 0.005 trout/m in the main stem. Finally, temporal variance in brook trout population size was lowest in the high-density headwater population, tended to peak in mid-sized streams and declined slightly in the largest streams with the lowest densities. Our results provide support for the hypothesis that local density-dependent processes have a strong control on brook trout dynamics across the entire distribution gradient. However, the mechanisms of regulation likely shift from competition for limited food and space in headwater streams to

  7. Density-dependent regulation of brook trout population dynamics along a core-periphery distribution gradient in a central Appalachian watershed.

    Science.gov (United States)

    Huntsman, Brock M; Petty, J Todd

    2014-01-01

    Spatial population models predict strong density-dependence and relatively stable population dynamics near the core of a species' distribution with increasing variance and importance of density-independent processes operating towards the population periphery. Using a 10-year data set and an information-theoretic approach, we tested a series of candidate models considering density-dependent and density-independent controls on brook trout population dynamics across a core-periphery distribution gradient within a central Appalachian watershed. We sampled seven sub-populations with study sites ranging in drainage area from 1.3-60 km(2) and long-term average densities ranging from 0.335-0.006 trout/m. Modeled response variables included per capita population growth rate of young-of-the-year, adult, and total brook trout. We also quantified a stock-recruitment relationship for the headwater population and coefficients of variability in mean trout density for all sub-populations over time. Density-dependent regulation was prevalent throughout the study area regardless of stream size. However, density-independent temperature models carried substantial weight and likely reflect the effect of year-to-year variability in water temperature on trout dispersal between cold tributaries and warm main stems. Estimated adult carrying capacities decreased exponentially with increasing stream size from 0.24 trout/m in headwaters to 0.005 trout/m in the main stem. Finally, temporal variance in brook trout population size was lowest in the high-density headwater population, tended to peak in mid-sized streams and declined slightly in the largest streams with the lowest densities. Our results provide support for the hypothesis that local density-dependent processes have a strong control on brook trout dynamics across the entire distribution gradient. However, the mechanisms of regulation likely shift from competition for limited food and space in headwater streams to competition for

  8. The tarantula toxin jingzhaotoxin-XI (κ-theraphotoxin-Cj1a) regulates the activation and inactivation of the voltage-gated sodium channel Nav1.5.

    Science.gov (United States)

    Tang, Cheng; Zhou, Xi; Huang, Yin; Zhang, Yunxiao; Hu, Zhaotun; Wang, Meichi; Chen, Ping; Liu, Zhonghua; Liang, Songping

    2014-12-15

    Specific peptide toxins interact with voltage-gated sodium channels by regulating the activation or inactivation of targeted channels. However, few toxins possessing dual effects have been identified. In the present study, we showed that jingzhaotoxin-XI/κ-theraphotoxin-Cj1a (JZTX-XI), a 34-residue peptide from the venom of the Chinese spider Chilobrachys jingzhao, inhibits the sodium conductance (IC50 = 124 ± 26 nM) and slows the fast inactivation (EC50 = 1.18 ± 0.2 μM) of Nav1.5 expressed in Chinese hamster ovary (CHO-K1) cells. JZTX-XI significantly shifted the activation to more depolarized voltages and decreased the deactivation of Nav1.5 currents upon extreme depolarization, but only slightly affected voltage-dependence of steady-state inactivation. In addition, JZTX-XI caused an approximately five-fold decrease in the rate of recovery from inactivation and an approximately 1.9-fold reduction in the closed-state inactivation rate. Our data suggest that JZTX-XI integrates the functions of site 3 toxins (α-scorpion toxins) with site 4 toxins (β-scorpion and spider toxins) by targeting multiple sites on Nav1.5. The unique properties displayed by JZTX-XI in its inhibitory activity on Nav1.5 suggest that its mechanism of action is distinct from those of site 3 and site 4 toxins, making JZTX-XI a useful probe for investigating the gating mechanism of Nav1.5 and toxin-channel interactions. PMID:25240294

  9. M-Type Potassium Channels Modulate the Intrinsic Excitability of Infralimbic Neurons and Regulate Fear Expression and Extinction

    OpenAIRE

    Santini, Edwin; James T. Porter

    2010-01-01

    Growing evidence indicates that the activity of infralimbic prefrontal cortex (IL) is critical for inhibiting inappropriate fear responses following extinction learning. Recently, we showed that fear conditioning and extinction alter the intrinsic excitability and bursting of IL pyramidal neurons in brain slices. IL neurons from Sprague Dawley rats expressing high fear had lower intrinsic excitability and bursting than those from rats expressing low fear, suggesting that regulating the intrin...

  10. C. elegans TRP channels.

    Science.gov (United States)

    Xiao, Rui; Xu, X Z Shawn

    2011-01-01

    Transient receptor potential (TRP) channels represent a superfamily of cation channels found in all eukaryotes. The C. elegans genome encodes seventeen TRP channels covering all of the seven TRP subfamilies. Genetic analyses in C. elegans have implicated TRP channels in a wide spectrum of behavioral and physiological processes, ranging from sensory transduction (e.g. chemosensation, touch sensation, proprioception and osmosensation) to fertilization, drug dependence, organelle biogenesis, apoptosis, gene expression, and neurotransmitter/hormone release. Many C. elegans TRP channels share similar activation and regulatory mechanisms with their vertebrate counterparts. Studies in C. elegans have also revealed some previously unrecognized functions and regulatory mechanisms of TRP channels. C. elegans represents an excellent genetic model organism for the study of function and regulation of TRP channels in vivo. PMID:21290304

  11. The orphan pentameric ligand-gated ion channel pHCl-2 is gated by pH and regulates fluid secretion in Drosophila Malpighian tubules.

    Science.gov (United States)

    Feingold, Daniel; Starc, Tanja; O'Donnell, Michael J; Nilson, Laura; Dent, Joseph A

    2016-09-01

    Pentameric ligand-gated ion channels (pLGICs) constitute a large protein superfamily in metazoa whose role as neurotransmitter receptors mediating rapid, ionotropic synaptic transmission has been extensively studied. Although the vast majority of pLGICs appear to be neurotransmitter receptors, the identification of pLGICs in non-neuronal tissues and homologous pLGIC-like proteins in prokaryotes points to biological functions, possibly ancestral, that are independent of neuronal signalling. Here, we report the molecular and physiological characterization of a highly divergent, orphan pLGIC subunit encoded by the pHCl-2 (CG11340) gene, in Drosophila melanogaster We show that pHCl-2 forms a channel that is insensitive to a wide array of neurotransmitters, but is instead gated by changes in extracellular pH. pHCl-2 is expressed in the Malpighian tubules, which are non-innervated renal-type secretory tissues. We demonstrate that pHCl-2 is localized to the apical membrane of the epithelial principal cells of the tubules and that loss of pHCl-2 reduces urine production during diuresis. Our data implicate pHCl-2 as an important source of chloride conductance required for proper urine production, highlighting a novel role for pLGICs in epithelial tissues regulating fluid secretion and osmotic homeostasis. PMID:27358471

  12. Natural Compound Curcumin-a Channel Potentiator Rather Than a Corrector of the Defective Intracellular Processing of △F508 Mutant Cystic Fibrosis Transmembrane Conductance Regulator

    Institute of Scientific and Technical Information of China (English)

    LIU Xin; GUAN Li; HE Cheng-yan; ZHANG Xiao-jing; XU Li-na; SHANG De-jing; MA Tong-hui; YANG Hong

    2008-01-01

    Cystic fibrosis(CF)is a severe genetic disease caused by the gene mutation of the cystic fibrosis transmembrane conductance regulator(CFTR)chloride channel.The most common point mutation △F508,which leads to impaired intracellular processing and channel gating of CFTR, appears in about 90%CF patients.The natural compound curcumin was reported to correct the processing defect of △F508-CFTR and proposed as a potential therapeutic drug to cure CF.In the present study.we analyzed the efrect of curcumin on △F508-CFTR and demonstrated that curcumin can restore the impaired chloride conductance of △F508 mutant CFTR.The activity is rapid,reversible and cAMP-dependent.However,we couldn't reproduce the previously reported correction of the defective membrane trafficking of △F508-CFTR by curcumin.Therefore,curcumin may not be a superior lead compound for developing anti-CF drugs.

  13. A functional assay to measure postsynaptic gamma-aminobutyric acidB responses in cultured spinal cord neurons: Heterologous regulation of the same K+ channel

    Energy Technology Data Exchange (ETDEWEB)

    Kamatchi, G.L.; Ticku, M.K. (Univ. of Texas Health Science Center, San Antonio (USA))

    1991-02-01

    The stimulation of postsynaptic gamma-aminobutyric acid (GABA)B receptors leads to slow inhibitory postsynaptic potentials due to the influx of K(+)-ions. This was studied biochemically, in vitro in mammalian cultured spinal cord neurons by using 86Rb as a substitute for K+. (-)-Baclofen, a GABAB receptor agonist, produced a concentration-dependent increase in the 86Rb-influx. This effect was stereospecific and blocked by GABAB receptor antagonists like CGP 35 348 (3-aminopropyl-diethoxymethyl-phosphonic acid) and phaclofen. Apart from the GABAB receptors, both adenosine via adenosine1 receptors and 5-hydroxytryptamine (5-HT) via 5-HT1 alpha agonists also increased the 86Rb-influx. These agonists failed to show any additivity between them when they were combined in their maximal concentration. In addition, their effect was antagonized specifically by their respective antagonists without influencing the others. These findings suggest the presence of GABAB, adenosine1 and 5-HT1 alpha receptors in the cultured spinal cord neurons, which exhibit a heterologous regulation of the same K(+)-channel. The effect of these agonists were antagonized by phorbol 12,13-didecanoate, an activator of protein kinase C, and pretreatment with pertussis toxin. This suggests that these agonists by acting on their own receptors converge on the same K(+)-channel through the Gi/Go proteins. In summary, we have developed a biochemical functional assay for studying and characterizing GABAB synaptic pharmacology in vitro, using spinal cord neurons.

  14. A functional assay to measure postsynaptic gamma-aminobutyric acidB responses in cultured spinal cord neurons: Heterologous regulation of the same K+ channel

    International Nuclear Information System (INIS)

    The stimulation of postsynaptic gamma-aminobutyric acid (GABA)B receptors leads to slow inhibitory postsynaptic potentials due to the influx of K(+)-ions. This was studied biochemically, in vitro in mammalian cultured spinal cord neurons by using 86Rb as a substitute for K+. (-)-Baclofen, a GABAB receptor agonist, produced a concentration-dependent increase in the 86Rb-influx. This effect was stereospecific and blocked by GABAB receptor antagonists like CGP 35 348 (3-aminopropyl-diethoxymethyl-phosphonic acid) and phaclofen. Apart from the GABAB receptors, both adenosine via adenosine1 receptors and 5-hydroxytryptamine (5-HT) via 5-HT1 alpha agonists also increased the 86Rb-influx. These agonists failed to show any additivity between them when they were combined in their maximal concentration. In addition, their effect was antagonized specifically by their respective antagonists without influencing the others. These findings suggest the presence of GABAB, adenosine1 and 5-HT1 alpha receptors in the cultured spinal cord neurons, which exhibit a heterologous regulation of the same K(+)-channel. The effect of these agonists were antagonized by phorbol 12,13-didecanoate, an activator of protein kinase C, and pretreatment with pertussis toxin. This suggests that these agonists by acting on their own receptors converge on the same K(+)-channel through the Gi/Go proteins. In summary, we have developed a biochemical functional assay for studying and characterizing GABAB synaptic pharmacology in vitro, using spinal cord neurons

  15. Neuroprotective effect of interleukin-6 regulation of voltage-gated Na+ channels of cortical neurons is time- and dose-dependent

    Directory of Open Access Journals (Sweden)

    Wei Xia

    2015-01-01

    Full Text Available Interleukin-6 has been shown to be involved in nerve injury and nerve regeneration, but the effects of long-term administration of high concentrations of interleukin-6 on neurons in the central nervous system is poorly understood. This study investigated the effects of 24 hour exposure of interleukin-6 on cortical neurons at various concentrations (0.1, 1, 5 and 10 ng/mL and the effects of 10 ng/mL interleukin-6 exposure to cortical neurons for various durations (2, 4, 8, 24 and 48 hours by studying voltage-gated Na + channels using a patch-clamp technique. Voltage-clamp recording results demonstrated that interleukin-6 suppressed Na + currents through its receptor in a time- and dose-dependent manner, but did not alter voltage-dependent activation and inactivation. Current-clamp recording results were consistent with voltage-clamp recording results. Interleukin-6 reduced the action potential amplitude of cortical neurons, but did not change the action potential threshold. The regulation of voltage-gated Na + channels in rat cortical neurons by interleukin-6 is time- and dose-dependent.

  16. Preserved regulation of renal perfusion pressure by small and intermediate conductance K-Ca channels in hypertensive mice with or without renal failure

    DEFF Research Database (Denmark)

    Waeckel, L.; Bertin, F.; Clavreul, N.;

    2015-01-01

    The purpose of this study was to assess, in the murine kidney, the mechanisms underlying the endothelium-dependent control of vascular tone and whether or not, in a severe model of hypertension and renal failure, K-Ca channels contribute to its regulation. Wild-type (BL) and double...... hypertensive without kidney disease while ARSL developed severe hypertension and renal failure. In the four groups, methacholine induced biphasic endothelium-dependent responses, a transient decrease in RPP followed by a cyclooxygenase-dependent increase in RPP. In the presence or not of indomethacin......-transgenic female mice expressing human angiotensinogen and renin (AR) genes received either control or a high-salt diet associated to a nitric oxide (NO) synthase inhibitor treatment (BLSL and ARSL). Changes in renal perfusion pressure (RPP) were measured in isolated perfused kidneys. BLSL and AR were moderately...

  17. Regulation of store-operated and voltage-operated Ca2+ channels in the proliferation and death of oligodendrocyte precursor cells by golli proteins

    Directory of Open Access Journals (Sweden)

    Pablo M Paez

    2009-04-01

    Full Text Available OPCs (oligodendrocyte precursor cells) express golli proteins which, through regulation of Ca2+ influx, appear to be important in OPC process extension/retraction and migration. The aim of the present study was to examine further the role of golli in regulating OPC development. The effects of golli ablation and overexpression were examined in primary cultures of OPCs prepared from golli-KO (knockout) and JOE (golli J37-overexpressing) mice. In OPCs lacking golli, or overexpressing golli, differentiation induced by growth factor withdrawal was impaired. Proliferation analysis in the presence of PDGF (platelet-derived growth factor), revealed that golli enhanced the mitogen-stimulated proliferation of OPCs through activation of SOCCs (store-operated Ca2+ channels). PDGF treatment induced a biphasic increase in OPC intracellular Ca2+, and golli specifically increased Ca2+ influx during the second SOCC-dependent phase that followed the initial release of Ca2+ from intracellular stores. This store-operated Ca2+ uptake appeared to be essential for cell division, since specific SOCC antagonists completely blocked the effects of PDGF and golli on OPC proliferation. Additionally, in OPCs overexpressing golli, increased cell death was observed after mitogen withdrawal. This phenomenon could be prevented by exposure to VOCC (voltage-operated Ca2+ channel) blockers, indicating that the effect of golli on cell death involved increased Ca2+ influx through VOCCs. The results showed a clear effect of golli on OPC development and support a role for golli in modulating multiple Ca2+-regulatory events through VOCCs and SOCCs. Our results also suggest that PDGF engagement of its receptor resulting in OPC proliferation proceeds through activation of SOCCs.

  18. Volume regulated anion channel currents of rat hippocampal neurons and their contribution to oxygen-and-glucose deprivation induced neuronal death.

    Directory of Open Access Journals (Sweden)

    Huaqiu Zhang

    Full Text Available Volume-regulated anion channels (VRAC are widely expressed chloride channels that are critical for the cell volume regulation. In the mammalian central nervous system, the physiological expression of neuronal VRAC and its role in cerebral ischemia are issues largely unknown. We show that hypoosmotic medium induce an outwardly rectifying chloride conductance in CA1 pyramidal neurons in rat hippocampal slices. The induced chloride conductance was sensitive to some of the VRAC inhibitors, namely, IAA-94 (300 µM and NPPB (100 µM, but not to tamoxifen (10 µM. Using oxygen-and-glucose deprivation (OGD to simulate ischemic conditions in slices, VRAC activation appeared after OGD induced anoxic depolarization (AD that showed a progressive increase in current amplitude over the period of post-OGD reperfusion. The OGD induced VRAC currents were significantly inhibited by inhibitors for glutamate AMPA (30 µM NBQX and NMDA (40 µM AP-5 receptors in the OGD solution, supporting the view that induction of AD requires an excessive Na(+-loading via these receptors that in turn to activate neuronal VRAC. In the presence of NPPB and DCPIB in the post-OGD reperfusion solution, the OGD induced CA1 pyramidal neuron death, as measured by TO-PRO-3-I staining, was significantly reduced, although DCPIB did not appear to be an effective neuronal VRAC blocker. Altogether, we show that rat hippocampal pyramidal neurons express functional VRAC, and ischemic conditions can initial neuronal VRAC activation that may contribute to ischemic neuronal damage.

  19. Arctigenin, a Potential Anti-Arrhythmic Agent, Inhibits Aconitine-Induced Arrhythmia by Regulating Multi-Ion Channels

    Directory of Open Access Journals (Sweden)

    Zhenying Zhao

    2013-11-01

    Full Text Available Background/Aims: Arctigenin possesses biological activities, but its underlying mechanisms at the cellular and ion channel levels are not completely understood. Therefore, the present study was designed to identify the anti-arrhythmia effect of arctigenin in vivo, as well as its cellular targets and mechanisms. Methods: A rat arrhythmia model was established via continuous aconitine infusion, and the onset times of ventricular premature contraction, ventricular tachycardia and death were recorded. The Action Potential Duration (APD, sodium current (INa, L-type calcium current (ICa, L and transient outward potassium current (Ito were measured and analysed using a patch-clamp recording technique in normal rat cardiomyocytes and myocytes of arrhythmia aconitine-induced by. Results: Arctigenin significantly delayed the arrhythmia onset in the aconitine-induced rat model. The 50% and 90% repolarisations (APD50 and APD90 were shortened by 100 µM arctigenin; the arctigenin dose also inhibited the prolongation of APD50 and APD90 caused by 1 µM aconitine. Arctigenin inhibited INa and ICa,L and attenuated the aconitine-increased INa and ICa,L by accelerating the activation process and delaying the inactivation process. Arctigenin enhanced Ito by facilitating the activation process and delaying the inactivation process, and recoverd the decreased Ito induced by aconitine. Conclusions: Arctigenin has displayed anti-arrhythmia effects, both in vivo and in vitro. In the context of electrophysiology, INa, ICa, L, and Ito may be multiple targets of arctigenin, leading to its antiarrhythmic effect.

  20. Regulator of G-protein signalling and GoLoco proteins suppress TRPC4 channel function via acting at Gαi/o.

    Science.gov (United States)

    Jeon, Jae-Pyo; Thakur, Dhananjay P; Tian, Jin-Bin; So, Insuk; Zhu, Michael X

    2016-05-15

    Transient receptor potential canonical 4 (TRPC4) forms non-selective cation channels implicated in the regulation of diverse physiological functions. Previously, TRPC4 was shown to be activated by the Gi/o subgroup of heterotrimeric G-proteins involving Gαi/o, rather than Gβγ, subunits. Because the lifetime and availability of Gα-GTP are regulated by regulators of G-protein signalling (RGS) and Gαi/o-Loco (GoLoco) domain-containing proteins via their GTPase-activating protein (GAP) and guanine-nucleotide-dissociation inhibitor (GDI) functions respectively, we tested how RGS and GoLoco domain proteins affect TRPC4 currents activated via Gi/o-coupled receptors. Using whole-cell patch-clamp recordings, we show that both RGS and GoLoco proteins [RGS4, RGS6, RGS12, RGS14, LGN or activator of G-protein signalling 3 (AGS3)] suppress receptor-mediated TRPC4 activation without causing detectable basal current or altering surface expression of the channel protein. The inhibitory effects are dependent on the GAP and GoLoco domains and facilitated by enhancing membrane targeting of the GoLoco protein AGS3. In addition, RGS, but not GoLoco, proteins accelerate desensitization of receptor-activation evoked TRPC4 currents. The inhibitory effects of RGS and GoLoco domains are additive and are most prominent with RGS12 and RGS14, which contain both RGS and GoLoco domains. Our data support the notion that the Gα, but not Gβγ, arm of the Gi/o signalling is involved in TRPC4 activation and unveil new roles for RGS and GoLoco domain proteins in fine-tuning TRPC4 activities. The versatile and diverse functions of RGS and GoLoco proteins in regulating G-protein signalling may underlie the complexity of receptor-operated TRPC4 activation in various cell types under different conditions. PMID:26987813

  1. Time-dependent effects of electroacupuncture at the Ren channel on extracellular signal-regulated kinases 1/2 expression in focal cerebral ischemia rats

    Institute of Scientific and Technical Information of China (English)

    Zhuoxin Yang; Lihong Diao; Haibo Yu; Wenshu Luo; Ling Wang; Min Pi; Xiaodan Rao; Junhua Peng

    2008-01-01

    BACKGROUND: The onset of focal cerebral ischemia activates extracellular signal-regulated kinases 1 and 2, regulates cell cycle, promotes cell proliferation and differentiation, and affects the normal stage and function of brain cells.OBJECTIVE: To observe the effects of electroacupuncture at the Ren channel on extracellular signal-regulated kinases 1/2 expression in the lateral cerebral ventricle wall of rats with focal cerebral ischemia. The effects were analyzed at different time points after intervention.DESIGN: Randomized controlled study.SETTING: Department of Anatomy, Sun Yat-Sen University. MATERIALS: A total of 60 healthy adult male Wistar rats weighing (250±10) g were provided by the Experimental Animal Center, Medical College of Sun Yat-Sen University. The animal experiment was conducted with confirmed consent by the local ethics committee. The GB6805-Ⅱ electric acupuncture apparatus was provided by Shanghai Medical Equipment High-techno Company. METHODS: The experiment was performed at the Laboratory of Anatomy, Sun Yat-Sen University, from February to July 2007. All experimental animals were randomly divided into the following groups: normal group (n = 6), sham operation group (n = 18), model group (n = 18), and electroacupuncture group (n = 18). Middle cerebral artery occlusion (MCAO) was performed in the model group and electroacupuncture group. Zea Longa's grading standard was used to assess neurological impairment after reperfusion; animals whose grades were between 1 and 4 were included in this study. The normal control group was not exposed to MCAO. In sham operation animals, the right common carotid artery (CCA) was isolated, and the external carotid artery (ECA) was damaged, but no embolism was induced. The electroacupuncture group was given acupuncture on the second day after surgery. The acupoint locations were chosen according to Experimental Acupuncture (People's Publishing House; 1997; First Edition). The Chengjiang, Qihai, and Guanyuan

  2. Regulation of epithelial sodium channel a-subunit expression by adenosine receptor A2a in alveolar epithelial cells

    Institute of Scientific and Technical Information of China (English)

    DENG Wang; WANG Dao-xin; ZHANG Wei; LI Chang-yi

    2011-01-01

    Background The amiloride-sensitive epithelial sodium channel a-subunit (a-ENaC) is an important factor for alveolar fluid clearance during acute lung injury. The relationship between adenosine receptor A2a (A2aAR) expressed in alveolar epithelial cells and aα-ENaC is poorly understood. We targeted the A2aAR in this study to investigate its role in the expression of αa-ENaC and in acute lung injury.Methods A549 cells were incubated with different concentrations of A2aAR agonist CGS-21680 and with 100 μmol/L CGS-21680 for various times. Rats were treated with lipopolysaccharide (LPS) after CGS-21680 was injected. Animals were sacrificed and tissue was harvested for evaluation of lung injury by analysis of the lung wet-to-dry weight ratio, lung permeability and myeloperoxidase activity. RT-PCR and Western blotting were used to determine the mRNA and protein expression levels of α-ENaC in A549 cells and alveolar type II epithelial cells.Results Both mRNA and protein levels of α-ENaC were markedly higher from 4 hours to 24 hours after exposure to 100μmol/L CGS-21680. There were significant changes from 0.1 umol/L to 100 μmol/L CGS-21680, with a positive correlation between increased concentrations of CGS-21680 and expression of α-ENaC. Treatment with CGS-21680during LPS induced lung injury protected the lung and promoted α-ENaC expression in the alveolar epithelial cells.Conclusion Activation of A2aAR has a protective effect during the lung injury, which may be beneficial to the prognosis of acute lung injury.

  3. Density But Not Kinship Regulates the Growth and Developmental Traits of Chinese Tiger Frog (Hoplobatrachus chinensis) Tadpoles

    Institute of Scientific and Technical Information of China (English)

    Li WEI; Weiwei SHAO; Guohua DING; Xiaoli FAN; Zhihua LIN

    2014-01-01

    Kinship and density are believed to affect important ecological processes such as intraspeciifc competition, predation, growth, development, cannibalism, habitat selection and mate choice. In this work, we used Chinese tiger frog Hoplobatrachus chinensis tadpoles as an experimental model to investigate the effects of kinship and density on growth and development of this species over a 73 day period. The results showed that density can affect the growth and developmental traits (survival rate, larval period, size at the limb bud protrusion/metamorphic climax and body mass at different life stages) of H. chinensis tadpoles, while kinship does not. Tadpoles took longer to develop and potential metamorphosis was greater in high density groups of both sibling and non-siblings. The interaction of kinship and density did not signiifcantly inlfuenced growth traits of H. chinensis tadpoles during the experimental period. For coefifcient variations of each growth trait, no differences were detected between sibling and non-sibling groups. These ifndings provide valuable information on the basic ecology of H. chinensis which will be helpful in future studies of other anuran species.

  4. MiR-223-3p as a Novel MicroRNA Regulator of Expression of Voltage-Gated K+ Channel Kv4.2 in Acute Myocardial Infarction

    Directory of Open Access Journals (Sweden)

    Xue Liu

    2016-06-01

    Full Text Available Background/Aims: Acute myocardial infarction (AMI is a devastating cardiovascular disease with a high rate of morbidity and mortality, partly due to enhanced arrhythmogenicity. MicroRNAs (miRNAs have been shown to participate in the regulation of cardiac ion channels and the associated arrhythmias. The purpose of this study was to test our hypothesis that miR-223-3p contributes to the electrical disorders in AMI via modulating KCND2, the gene encoding voltage-gated channel Kv4.2 that carries transient outward K+ current Ito. Methods: AMI model was established in male Sprague-Dawley (SD rats by left anterior descending artery (LAD ligation. Evans blue and TTC staining was used to measure infarct area. Ito was recorded in isolated ventricular cardiomyocytes or cultured neonatal rat ventricular cells (NRVCs by whole-cell patch-clamp techniques. Western blot analysis was employed to detect the protein level of Kv4.2 and real-time RT-PCR to determine the transcript level of miR-223-3p. Luciferase assay was used to examine the interaction between miR-223-3p and KCND2 in cultured NRVCs. Results: Expression of miR-223-3p was remarkably upregulated in AMI relative to sham control rats. On the contrary, the protein level of Kv4.2 and Ito density were significantly decreased in AMI. Consistently, transfection of miR-223-3p mimic markedly reduced Kv4.2 protein level and Ito current in cultured NRVCs. Co-transfection of AMO-223-3p (an antisense inhibitor of miR-223-3p reversed the repressive effect of miR-223-3p. Luciferase assay showed that miR-223-3p, but not the negative control, substantially suppressed the luciferase activity, confirming the direct binding of miR-223-3p to the seed site within the KCND2 sequence. Finally, direct intramuscular injection of AMO-223-3p into the ischemic myocardium to knockdown endogenous miR-223-3p decreased the propensity of ischemic arrhythmias. Conclusions: Upregulation of miR-223-3p in AMI repressed the expression of

  5. Up-Regulation of Interleukin-9 and the Interleukin-9-Associated Calcium-Activated Chloride Channel hCLCA1 in Nasal Mucosa Following In Vivo Allergen Challenge

    Directory of Open Access Journals (Sweden)

    Hauber Hans-Peter

    2007-03-01

    Full Text Available Interleukin (IL-9 is a pleiotropic T helper 2-type cytokine that has been shown to be up-regulated in allergic airway disease, including asthma. IL-9 has been demonstrated to be a potent stimulus for the production and secretion of mucus from airway epithelial cells via induction of a calcium-activated chloride channel, hCLCA1. The objective of this study was to investigate the expression of IL-9 and hCLCA1 following allergen challenge in the nasal mucosa of allergic rhinitis patients. Nasal biopsies were obtained from allergic rhinitis patients out of allergen season both before (baseline and after local antigen challenge with either ragweed or diluent (control. Immunohistochemistry and in situ hybridization were used to assess IL-9 protein and hCLCA1 messenger ribonucleic acid. Eosinophils and T cells were detected using immunohistochemistry. IL-9 and hCLCA1 were very low at baseline, and expression was significantly up-regulated following ragweed challenge. Whereas the number of eosinophils increased after allergen challenge, T-cell counts did not change significantly. The results of this study demonstrate the relationship between specific allergen challenge and expression of both IL-9 and hCLCA1, suggesting a possible mechanism for the increased production of mucus from airway epithelial cells in allergic rhinitis.

  6. Analysis of the breakdown mechanism for an ultra high voltage high-side thin layer silicon-on-insulator p-channel low-density metal-oxide semiconductor

    Institute of Scientific and Technical Information of China (English)

    Zhuang Xiang; Qiao Ming; Zhang Bo; Li Zhao-Ji

    2012-01-01

    This paper discusses the breakdown mechanism and proposes a new simulation and test method of breakdown voltage (BV) for an ultra-high-voltage (UHV) high-side thin layer silicon-on-insulator (SOI) p-channel low-density metaloxide semiconductor (LDMOS).Compared with the conventional simulation method,the new one is more accordant with the actual conditions of a device that can be used in the high voltage circuit.The BV of the SOI p-channel LDMOS can be properly represented and the effect of reduced bulk field can be revealed by employing the new simulation method.Simulation results show that the off-state (on-state) BV of the SOI p-channel LDMOS can reach 741 (620) V in the 3-μm-thick buried oxide layer,50-un-length drift region,and at -400 V back-gate voltage,enabling the device to be used in a 400 V UHV integrated circuit.

  7. Nuclear translocation of the cardiac L-type calcium channel C-terminus is regulated by sex and 17β-estradiol.

    Science.gov (United States)

    Mahmoodzadeh, S; Haase, H; Sporbert, A; Rharass, T; Panáková, D; Morano, I

    2016-08-01

    The cardiac voltage gated l-type Ca(2+) channel (Cav1.2) constitutes the main entrance gate for Ca(2+) that triggers cardiac contraction. Several studies showed that the distal C-terminus fragment of Cav1.2 α1C subunit (α1C-dCT) is proteolytically cleaved and shuttles between the plasma membrane and the nucleus, which is regulated both developmentally and by Ca(2+). However, the effects of sex and sex hormone 17β-estradiol (E2, estrogen) on α1C-dCT nuclear translocation are still unexplored. To investigate the sexual disparity in the α1C-dCT nuclear translocation, we first generated an antibody directed against a synthetic peptide (GRRASFHLE) located in α1C-dCT, and used it to probe ventricular myocytes from adult female and male mice. Immunocytochemistry of isolated mouse primary adult ventricular myocytes revealed both nuclear staining and cytosolic punctuate staining around the T-tubules. The ratio of nuclear to cytosolic intensity (Inuc/Icyt) was significantly higher in isolated female cardiomyocytes (1.42±0.05) compared to male cardiomyocytes (1.05±0.02). Western blot analysis of nuclear fraction confirmed these data. Furthermore, we found a significant decrease in nuclear staining intensity of α1C-dCT in both female and male cardiomyocytes upon serum withdrawal for 18h (Inuc/Icyt 1.05±0.02 and 0.89±0.02, respectively). Interestingly, subsequent E2 treatment (10(-8)M) for 8h normalized the intracellular distribution of α1C-dCT in male cardiomyocytes (Inuc/Icyt 1.04±0.02), but not in female cardiomyocytes. Acute treatment of male cardiomyocytes with E2 for 45min revealed a similar effect. This effect of E2 was revised by ICI indicating the involvement of ER in this signaling pathway. Taken together, our results showed that the shuttling of α1C-CT in cardiomyocytes is regulated in a sex-dependent manner, and E2-activated ER may play a role in the nuclear shuttling of α1C-dCT in male cardiomyocytes. This may explain, at least partly, the observed

  8. Low-density microarray analysis of TGFβ1-dependent cell cycle regulation in human breast adenocarcinoma MCF7 cell line

    Directory of Open Access Journals (Sweden)

    Dubrovska A. M.

    2014-03-01

    Full Text Available Transforming growth factor β1 (TGFβ1 is a growth regulator that has antiproliferative effects on a range of epithelial cells at the early stages and promoting tumorigenesis at the later stages of cancer progression. The molecular mechanisms of a duel role of TGFβ1 in tumor growth regulation remain poorly understood. Aim. To analyze the TGFβ1-dependent cell cycle regulation of tumorigenic breast epithelial cells. Methods. Our present study was designed to examine the regulatory effect of TGFβ1 on the expression of a panel of 96 genes which are known to be critically involved in cell cycle regulation. GEArray Q series Human Cell Cycle Gene Array was applied to profile the gene expression changes in MCF7 human breast adenocarcinoma cell line treated with TGFβ1. Results. The gene expression array data enabled us to reveal the molecular regulators that might connect TGFβ1 signaling to the promoting of the tumor growth, e. g. retinoblastoma protein (pRB1, check-point kinase 2 (Chk2, breast cancer 1, early onset (BRCA1, DNA damage checkpoint protein RAD9, cyclin-dependent kinase 2 (CDK2, cyclin D1 (CCND1. Conclusions. The uncovering of the key signaling modules involved in TGFβ1- dependent signaling might provide an insight into the mechanisms of TGFβ1-dependent tumor growth and can be beneficial for the development of novel therapeutic approaches.

  9. Culture density regulates both the cholinergic phenotype and the expression of the CNTF receptor in P19 neurons.

    Science.gov (United States)

    Parnas, D; Linial, M

    1997-04-01

    The P19 embryonal carcinoma cells differentiate into neurons, astrocytes, and fibroblast-like cells following induction with retinoic acid. The cells mature into functional neurons, as determined by their ability to release neurotransmitters in a Ca(2+)- and depolarization-dependent manner. P19 neurons in culture represent a mixed population in terms of their neurotransmitter phenotype. The cholinergic phenotype of these neurons is modulated by culture density. Cholinergic markers, such as the vesicular acetylcholine transporter, acetyl cholinesterase, and choline acetyltransferase, are expressed in about 85% of the cells in sparse cultures and are largely suppressed at high cell densities. In contrast, glutamate release is enhanced in dense P19 neuronal cultures. The factor mediating the density effect is concentrated exclusively on the cell membrane of P19 neurons and not on the nonneuronal cells, which also differentiate from P19 embryonal carcinoma cells. This membrane-associated component retains its functionality, even after membrane fixation. The downregulation of the cholinergic properties in dense cultures is paralleled by a downregulation of the alpha subunit of the ciliary neurotrophic factor (CNTF) receptor. Thus, it is suggested that the membrane-associated factor, which mediates the density effect, downregulates the cholinergic phenotype by inhibiting the responsiveness of these neurons to CNTF. We further suggest that the P19 cell line can serve as a model system for the study of neurotransmitter phenotype acquisition and plasticity throughout neuronal differentiation. PMID:9188041

  10. Use of complex hydraulic variables to predict the distribution and density of unionids in a side channel of the Upper Mississippi River

    Science.gov (United States)

    Steuer, J.J.; Newton, T.J.; Zigler, S.J.

    2008-01-01

    Previous attempts to predict the importance of abiotic and biotic factors to unionids in large rivers have been largely unsuccessful. Many simple physical habitat descriptors (e.g., current velocity, substrate particle size, and water depth) have limited ability to predict unionid density. However, more recent studies have found that complex hydraulic variables (e.g., shear velocity, boundary shear stress, and Reynolds number) may be more useful predictors of unionid density. We performed a retrospective analysis with unionid density, current velocity, and substrate particle size data from 1987 to 1988 in a 6-km reach of the Upper Mississippi River near Prairie du Chien, Wisconsin. We used these data to model simple and complex hydraulic variables under low and high flow conditions. We then used classification and regression tree analysis to examine the relationships between hydraulic variables and unionid density. We found that boundary Reynolds number, Froude number, boundary shear stress, and grain size were the best predictors of density. Models with complex hydraulic variables were a substantial improvement over previously published discriminant models and correctly classified 65-88% of the observations for the total mussel fauna and six species. These data suggest that unionid beds may be constrained by threshold limits at both ends of the flow regime. Under low flow, mussels may require a minimum hydraulic variable (Rez.ast;, Fr) to transport nutrients, oxygen, and waste products. Under high flow, areas with relatively low boundary shear stress may provide a hydraulic refuge for mussels. Data on hydraulic preferences and identification of other conditions that constitute unionid habitat are needed to help restore and enhance habitats for unionids in rivers. ?? 2008 Springer Science+Business Media B.V.

  11. Neuritin Up-regulates Kv4.2 α-Subunit of Potassium Channel Expression and Affects Neuronal Excitability by Regulating the Calcium-Calcineurin-NFATc4 Signaling Pathway*

    Science.gov (United States)

    Yao, Jin-jing; Zhao, Qian-Ru; Liu, Dong-Dong; Chow, Chi-Wing; Mei, Yan-Ai

    2016-01-01

    Neuritin is an important neurotrophin that regulates neural development, synaptic plasticity, and neuronal survival. Elucidating the downstream molecular signaling is important for potential therapeutic applications of neuritin in neuronal dysfunctions. We previously showed that neuritin up-regulates transient potassium outward current (IA) subunit Kv4.2 expression and increases IA densities, in part by activating the insulin receptor signaling pathway. Molecular mechanisms of neuritin-induced Kv4.2 expression remain elusive. Here, we report that the Ca2+/calcineurin (CaN)/nuclear factor of activated T-cells (NFAT) c4 axis is required for neuritin-induced Kv4.2 transcriptional expression and potentiation of IA densities in cerebellum granule neurons. We found that neuritin elevates intracellular Ca2+ and increases Kv4.2 expression and IA densities; this effect was sensitive to CaN inhibition and was eliminated in Nfatc4−/− mice but not in Nfatc2−/− mice. Stimulation with neuritin significantly increased nuclear accumulation of NFATc4 in cerebellum granule cells and HeLa cells, which expressed IR. Furthermore, NFATc4 was recruited to the Kv4.2 gene promoter loci detected by luciferase reporter and chromatin immunoprecipitation assays. More importantly, data obtained from cortical neurons following adeno-associated virus-mediated overexpression of neuritin indicated that reduced neuronal excitability and increased formation of dendritic spines were abrogated in the Nfatc4−/− mice. Together, these data demonstrate an indispensable role for the CaN/NFATc4 signaling pathway in neuritin-regulated neuronal functions. PMID:27307045

  12. Neuritin Up-regulates Kv4.2 α-Subunit of Potassium Channel Expression and Affects Neuronal Excitability by Regulating the Calcium-Calcineurin-NFATc4 Signaling Pathway.

    Science.gov (United States)

    Yao, Jin-Jing; Zhao, Qian-Ru; Liu, Dong-Dong; Chow, Chi-Wing; Mei, Yan-Ai

    2016-08-12

    Neuritin is an important neurotrophin that regulates neural development, synaptic plasticity, and neuronal survival. Elucidating the downstream molecular signaling is important for potential therapeutic applications of neuritin in neuronal dysfunctions. We previously showed that neuritin up-regulates transient potassium outward current (IA) subunit Kv4.2 expression and increases IA densities, in part by activating the insulin receptor signaling pathway. Molecular mechanisms of neuritin-induced Kv4.2 expression remain elusive. Here, we report that the Ca(2+)/calcineurin (CaN)/nuclear factor of activated T-cells (NFAT) c4 axis is required for neuritin-induced Kv4.2 transcriptional expression and potentiation of IA densities in cerebellum granule neurons. We found that neuritin elevates intracellular Ca(2+) and increases Kv4.2 expression and IA densities; this effect was sensitive to CaN inhibition and was eliminated in Nfatc4(-/-) mice but not in Nfatc2(-/-) mice. Stimulation with neuritin significantly increased nuclear accumulation of NFATc4 in cerebellum granule cells and HeLa cells, which expressed IR. Furthermore, NFATc4 was recruited to the Kv4.2 gene promoter loci detected by luciferase reporter and chromatin immunoprecipitation assays. More importantly, data obtained from cortical neurons following adeno-associated virus-mediated overexpression of neuritin indicated that reduced neuronal excitability and increased formation of dendritic spines were abrogated in the Nfatc4(-/-) mice. Together, these data demonstrate an indispensable role for the CaN/NFATc4 signaling pathway in neuritin-regulated neuronal functions. PMID:27307045

  13. Localization and regulation of the human very low density lipoprotein/apolipoprotein-E receptor: trophoblast expression predicts a role for the receptor in placental lipid transport.

    Science.gov (United States)

    Wittmaack, F M; Gåfvels, M E; Bronner, M; Matsuo, H; McCrae, K R; Tomaszewski, J E; Robinson, S L; Strickland, D K; Strauss, J F

    1995-01-01

    The very low density lipoprotein/apolipoprotein-E receptor (VLDLR) is the newest member of the low density lipoprotein receptor (LDLR) family. Very little is known about VLDLR localization and regulation. Immunohistochemical analysis of human placenta with a specific polyclonal antibody detected VLDLR in syncytiotrophoblast and intermediate trophoblast cells. VLDLR transcripts were also localized in these cells by in situ hybridization histochemistry. In addition, VLDLR messenger RNA (mRNA) was detected in villous core endothelial cells and cells appearing to be Hofbauer cells. Northern blot analysis of placenta revealed a 2.6-fold increase in VLDLR mRNA at term compared to that in the first trimester. The regulation of VLDLR expression was studied in JEG-3 and BeWo choriocarcinoma cells, two trophoblast-derived cell lines. Treatment of these cells with 8-bromo-cAMP caused a profound suppression of VLDLR message, whereas LDLR transcripts were increased. Incubation of JEG-3 cells with 25-hydroxycholesterol did not lead to sterol negative feedback on VLDLR gene expression, unlike LDLR mRNA, which declined markedly. Insulin (200 mg/L) up-regulated VLDLR message in JEG-3 cells 2-fold, as did the fibrate hypolipidemic drug, clofibric acid. We conclude that 1) VLDLR is expressed in human placental trophoblast cells in a pattern consistent with a role in placental lipid transport; 2) VLDLR expression is high at term relative to that in the first trimester; and 3) the trophoblast VLDLR is subject to down-regulation by cAMP and up-regulation by insulin and fibrate hypolipidemic drugs. PMID:7828550

  14. Regulation of action potential delays via voltage-gated potassium Kv1.1 channels in dentate granule cells during hippocampal epilepsy

    Directory of Open Access Journals (Sweden)

    Florian eKirchheim

    2013-12-01

    Full Text Available Action potential (AP responses of dentate gyrus granule (DG cells have to be tightly regulated to maintain hippocampal function. However, which ion channels control the response delay of DG cells is not known. In some neuron types, spike latency is influenced by a dendrotoxin (DTX-sensitive delay current (ID mediated by unidentified combinations of voltage-gated K+ (Kv channels of the Kv1 family Kv1.1-6. In DG cells, the ID has not been characterized and its molecular basis is unknown. The response phenotype of mature DG cells is usually considered homogenous but intrinsic adaptations likely occur in particular in conditions of hyperexcitability, for example during temporal lobe epilepsy (TLE. In this study, we examined response delays of DG cells and underlying ion channel molecules by employing a new combination of gramicidin-perforated patch-clamp recordings in acute brain slices and single-cell reverse transcriptase quantitative polymerase chain reaction (SC RT-qPCR experiments. An in vivo mouse model of TLE consisting of intrahippocampal kainate (KA injection was used to examine epilepsy-related plasticity. Response delays of DG cells were DTX-sensitive and strongly increased in KA-injected hippocampi; Kv1.1 mRNA was elevated 10-fold, and the response delays correlated with Kv1.1 mRNA abundance on the single cell level. Other Kv1 subunits did not show overt changes in mRNA levels. Kv1.1 immunolabeling was enhanced in KA DG cells. The biophysical properties of ID and the delay heterogeneity between inner and outer DG cell layer were characterized. Using organotypic hippocampal slice cultures (OHCs, where KA incubation also induced ID upregulation, reversibility and neuroprotective potential for DG cells were tested. In summary, the AP timing of DG cells is effectively controlled via scaling of Kv1.1 subunit transcription. With this antiepileptic mechanism, DG cells delay their

  15. Transient receptor potential (TRP and Cch1-Yam8 channels play key roles in the regulation of cytoplasmic Ca2+ in fission yeast.

    Directory of Open Access Journals (Sweden)

    Yan Ma

    Full Text Available The regulation of cytoplasmic Ca(2+ is crucial for various cellular processes. Here, we examined the cytoplasmic Ca(2+ levels in living fission yeast cells by a highly sensitive bioluminescence resonance energy transfer-based assay using GFP-aequorin fusion protein linked by 19 amino acid. We monitored the cytoplasmic Ca(2+ level and its change caused by extracellular stimulants such as CaCl(2 or NaCl plus FK506 (calcineurin inhibitor. We found that the extracellularly added Ca(2+ caused a dose-dependent increase in the cytoplasmic Ca(2+ level and resulted in a burst-like peak. The overexpression of two transient receptor potential (TRP channel homologues, Trp1322 or Pkd2, markedly enhanced this response. Interestingly, the burst-like peak upon TRP overexpression was completely abolished by gene deletion of calcineurin and was dramatically decreased by gene deletion of Prz1, a downstream transcription factor activated by calcineurin. Furthermore, 1 hour treatment with FK506 failed to suppress the burst-like peak. These results suggest that the burst-like Ca(2+ peak is dependent on the transcriptional activity of Prz1, but not on the direct TRP dephosphorylation. We also found that extracellularly added NaCl plus FK506 caused a synergistic cytosolic Ca(2+ increase that is dependent on the inhibition of calcineurin activity, but not on the inhibition of Prz1. The synergistic Ca(2+ increase is abolished by the addition of the Ca(2+ chelator BAPTA into the media, and is also abolished by deletion of the gene encoding a subunit of the Cch1-Yam8 Ca(2+ channel complex, indicating that the synergistic increase is caused by the Ca(2+ influx from the extracellular medium via the Cch1-Yam8 complex. Furthermore, deletion of Pmk1 MAPK abolished the Ca(2+ influx, and overexpression of the constitutively active Pek1 MAPKK enhanced the influx. These results suggest that Pmk1 MAPK and calcineurin positively and negatively regulate the Cch1-Yam8 complex

  16. RFI channels

    Science.gov (United States)

    Mceliece, R. J.

    1980-01-01

    A class of channel models is presented which exhibit varying burst error severity much like channels encountered in practice. An information-theoretic analysis of these channel models is made, and conclusions are drawn that may aid in the design of coded communication systems for realistic noisy channels.

  17. K(v)7 channels: function, pharmacology and channel modulators.

    Science.gov (United States)

    Dalby-Brown, William; Hansen, Henrik H; Korsgaard, Mads P G; Mirza, Naheed; Olesen, Søren-P

    2006-01-01

    K(v)7 channels are unique among K(+) channels, since four out of the five channel subtypes have well-documented roles in the development of human diseases. They have distinct physiological functions in the heart and in the nervous system, which can be ascribed to their voltage-gating properties. The K(v)7 channels also lend themselves to pharmacological modulation, and synthetic openers as well as blockers of the channels, regulating neuronal excitability, have existed even before the K(v)7 channels were identified by cloning. In the present review we give an account on the focused efforts to develop selective modulators, openers as well as blockers, of the K(v)7 channel subtypes, which have been undertaken during recent years, along with a discussion of the K(v)7 ion channel physiology and therapeutic indications for modulators of the neuronal K(v)7 channels.

  18. Search for t bar t production in the e+jets channel using the probability density estimation (PDE) method at D0

    International Nuclear Information System (INIS)

    The authors construct probability density functions for signal and background events in multi-dimensional space, using Monte Carlo samples. A variant of the Bayes' discriminant function is then applied to classify signal and background events. The effect of some kinematic quantities on the performance of the discriminant has been studied and the results of applying the PDE method to search for the top quark in D0 data (p bar p collisions at √s = 1.8 TeV) will be presented

  19. Regulation of structural and functional synapse density by L-threonate through modulation of intraneuronal magnesium concentration.

    Science.gov (United States)

    Sun, Qifeng; Weinger, Jason G; Mao, Fei; Liu, Guosong

    2016-09-01

    Oral administration of the combination of L-threonate (threonate) and magnesium (Mg(2+)) in the form of L-Threonic acid Magnesium salt (L-TAMS) can enhance learning and memory in young rats and prevent memory decline in aging rats and in Alzheimer's disease model mice. Recent results from a human clinical trial demonstrate the efficacy of L-TAMS in restoring global cognitive abilities of older adults. Previously, we reported that neuronal intracellular Mg(2+) serves as a critical signaling molecule for controlling synapse density, a key factor that determines cognitive ability. The elevation of brain Mg(2+) by oral administration of L-TAMS in intact animals plays a significant role in mediating the therapeutic effects of L-TAMS. The current study sought to elucidate the unique role of threonate. We aimed to understand if threonate acts directly to elevate intraneuronal Mg(2+), and why Mg(2+) given without threonate is ineffective for enhancing learning and memory ability. We discovered that threonate is naturally present in cerebrospinal fluid (CSF) and oral treatment with L-TAMS elevated CSF threonate. In cultured hippocampal neurons, threonate treatment directly induced an increase in intracellular Mg(2+) concentration. Functionally, elevating threonate upregulated expression of NR2B-containing NMDAR, boosted mitochondrial membrane potential (ΔΨm), and increased functional synapse density in neuronal cultures. These effects are unique to threonate, as other common Mg(2+) anions failed to have the same results. Mechanistically, threonate's effects were specifically mediated through glucose transporters (GLUTs). We also evaluated the effects of threonate in human neural stem cell-derived neurons, and found it was equally effective at upregulating synapse density. The current study provides an explanation for why threonate is an essential component of L-TAMS and supports the use of L-TAMS to promote cognitive abilities in human. PMID:27178134

  20. Optimal sterile insect release for area-wide integrated pest management in a density regulated pest population.

    Science.gov (United States)

    Gordillo, Luis F

    2014-06-01

    To determine optimal sterile insect release policies in area-wide integrated pest management is a challenge that users of this pest control method inevitably confront. In this note we provide approximations to best policies of release through the use of simulated annealing. The discrete time model for the population dynamics includes the effects of sterile insect release and density dependence in the pest population. Spatial movement is introduced through integrodifference equations, which allow the use of the stochastic search in cases where movement is described through arbitrary dispersal kernels. As a byproduct of the computations, an assessment of appropriate control zone sizes is possible. PMID:24506557

  1. High-density SNP screen of sodium channel genes by haplotype tagging and DNA pooling for association with idiopathic generalized epilepsy.

    Science.gov (United States)

    Makoff, Andrew; Lai, Teck; Barratt, Catherine; Valentin, Antonio; Moran, Nick; Asherson, Philip; Nashef, Lina

    2010-04-01

    We have investigated seven voltage-gated sodium channel genes for association with idiopathic generalized epilepsy (IGE). Probands and control DNA were grouped into pools and used to screen 85 single-nucleotide polymorphisms (SNPs), mostly HapMap SNPs tagging the common variation in these genes. Twelve SNPs exhibiting an allele frequency difference between pools were genotyped individually in our sample of 232 probands, 313 controls, and 95 parent-proband trios. Two SNPs, in SCN1A and SCN8A, were associated by allele and genotype at nominal level of significance, but were not significant after Bonferroni correction. Two SCN2A SNPs (rs3943809 and rs16850331) were associated by case-control with a subgroup with IGE and history of febrile seizures and also by transmission disequilibrium test (TDT) in parent-proband trios. Both SNPs are part of a linkage disequilibrium (LD) cluster of 38 SNPs, but none are obvious functional variants. The association of rs3943809 with the febrile seizure subgroup (p = 0.0004) remains significant after the conservative Bonferroni correction for multiple testing.

  2. The amine-containing cutaneous irritant heptylamine inhibits the volume-regulated anion channel and mobilizes intracellular calcium in normal human epidermal keratinocytes.

    Science.gov (United States)

    Raoux, Matthieu; Colomban, Cécile; Delmas, Patrick; Crest, Marcel

    2007-06-01

    Many amines are skin irritants and cause contact dermatitis. However, little is known about their mechanisms of action in keratinocytes except that they induce the release of the inflammatory mediators cytokines and ATP. Here, we tested whether volume-regulated anion channels (VRACs) in primary cultures of normal human epidermal keratinocytes are modulated by the referenced amine-containing cutaneous irritant heptylamine. Under isotonic conditions, we isolated the VRAC current (I(VRAC)) from other conductances using a high Ca(2+)-buffering internal solution. I(VRAC) ran up after patch rupturing and reached a plateau within 15 min. It was reversibly and dose-dependently inhibited by heptylamine with an IC(50) value of 260 microM. Cell-swelling caused by the application of a hypotonic solution increased 2.7-fold I(VRAC) and reduced the inhibition of VRAC by heptylamine with a dose-response curve shifted approximately 10-fold to the right. In addition, we showed, using cell-attached patch recordings, that adding heptylamine to the bath inhibited VRAC activity. This suggests that heptylamine diffuses into the membrane to inhibit VRAC. Finally, we demonstrated that heptylamine induced Ca(2+)-store depletion and that VRAC inhibition was not caused by the increase in cytosolic Ca(2+). Taken together, these results identify heptylamine as a blocker of VRAC and suggest that Ca(2+)-store depletion may be involved in mechanisms of irritant contact dermatitis caused by heptylamine. PMID:17384225

  3. Troponin T3 regulates nuclear localization of the calcium channel Ca{sub v}β{sub 1a} subunit in skeletal muscle

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tan; Taylor, Jackson; Jiang, Yang [Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States); Pereyra, Andrea S. [Department of Histology, National University of La Plata, 1900 La Plata (Argentina); Messi, Maria Laura; Wang, Zhong-Min [Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States); Hereñú, Claudia [Department of Histology, National University of La Plata, 1900 La Plata (Argentina); Delbono, Osvaldo, E-mail: odelbono@wakehealth.edu [Department of Internal Medicine-Gerontology, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States); Neuroscience Program, Wake Forest School of Medicine, Winston-Salem, NC 27157 (United States)

    2015-08-15

    The voltage-gated calcium channel (Ca{sub v}) β{sub 1a} subunit (Ca{sub v}β{sub 1a}) plays an important role in excitation–contraction coupling (ECC), a process in the myoplasm that leads to muscle-force generation. Recently, we discovered that the Ca{sub v}β{sub 1a} subunit travels to the nucleus of skeletal muscle cells where it helps to regulate gene transcription. To determine how it travels to the nucleus, we performed a yeast two-hybrid screening of the mouse fast skeletal muscle cDNA library and identified an interaction with troponin T3 (TnT3), which we subsequently confirmed by co-immunoprecipitation and co-localization assays in mouse skeletal muscle in vivo and in cultured C2C12 muscle cells. Interacting domains were mapped to the leucine zipper domain in TnT3 COOH-terminus (160–244 aa) and Ca{sub v}β{sub 1a} NH{sub 2}-terminus (1–99 aa), respectively. The double fluorescence assay in C2C12 cells co-expressing TnT3/DsRed and Ca{sub v}β{sub 1a}/YFP shows that TnT3 facilitates Ca{sub v}β{sub 1a} nuclear recruitment, suggesting that the two proteins play a heretofore unknown role during early muscle differentiation in addition to their classical role in ECC regulation. - Highlights: • Previously, we demonstrated that Ca{sub v}β{sub 1a} is a gene transcription regulator. • Here, we show that TnT3 interacts with Ca{sub v}β{sub 1a}. • We mapped TnT3 and Ca{sub v}β{sub 1a} interaction domain. • TnT3 facilitates Ca{sub v}β{sub 1a} nuclear enrichment. • The two proteins play a heretofore unknown role during early muscle differentiation.

  4. Activation of Yes-Associated Protein in Low-Grade Meningiomas Is Regulated by Merlin, Cell Density, and Extracellular Matrix Stiffness.

    Science.gov (United States)

    Tanahashi, Kuniaki; Natsume, Atsushi; Ohka, Fumiharu; Motomura, Kazuya; Alim, Adiljan; Tanaka, Ichidai; Senga, Takeshi; Harada, Ichiro; Fukuyama, Ryuichi; Sumiyoshi, Naoyuki; Sekido, Yoshitaka; Wakabayashi, Toshihiko

    2015-07-01

    The NF2 gene product Merlin is a protein containing ezrin, radixin, and moesin domains; it is a member of the 4.1 protein superfamily associated with the membrane cytoskeleton and also interacts with cell surface molecules. The mammalian Hippo cascade, a downstream signaling cascade of merlin, inactivates the Yes-associated protein (YAP). Yes-associated protein is activated by loss of the NF2 gene and functions as an oncogene in meningioma cells; however, the factors controlling YAP expression, phosphorylation, and subcellular localization in meningiomas have not been fully elucidated. Here, we demonstrate that merlin expression is heterogeneous in 1 NF2 gene-negative and 3 NF2 gene-positive World Health Organization grade I meningiomas. In the NF2 gene-positive meningiomas, regions with low levels of merlin (tumor rims) had greater numbers of cells with nuclear YAP versus regions with high merlin levels (tumor cores). Merlin expression and YAP phosphorylation were also affected by cell density in the IOMM-Lee and HKBMM human meningioma cell lines; nuclear localization of YAP was regulated by cell density and extracellular matrix (ECM) stiffness in IOMM-Lee cells. These results suggest that cell density and ECM stiffness may contribute to the heterogeneous loss of merlin and increased nuclear YAP expression in human meningiomas.

  5. Light-induced systemic regulation of photosynthesis in primary and trifoliate leaves of Phaseolus vulgaris: effects of photosynthetic photon flux density (PPFD) versus spectrum.

    Science.gov (United States)

    Murakami, K; Matsuda, R; Fujiwara, K

    2014-01-01

    The objectives of this work using Phaseolus vulgaris were to examine whether the light spectrum incident on mature primary leaves (PLs) is related to leaf-to-leaf systemic regulation of developing trifoliate leaves (TLs) in photosynthetic characteristics, and to investigate the relative importance of spectrum and photosynthetic photon flux density (PPFD) in light-induced systemic regulation. Systemic regulation was induced by altering PPFD and the spectrum of light incident on PLs using a shading treatment and lighting treatments including either white, blue, green or red light-emitting diodes (LEDs). Photosynthetic characteristics were evaluated by measuring the light-limited and light-saturated net photosynthetic rates and the amounts of nitrogen (N), chlorophyll (Chl) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39). Shading treatment on PLs decreased the amounts of N, Chl and Rubisco of TLs and tended to decrease the photosynthetic rates. However, we observed no systemic effects induced by the light spectrum on PLs in this study, except that a higher amount of Rubisco of TLs was observed when the PLs were irradiated with blue LEDs. Our results imply that photoreceptors in mature leaves have little influence on photosynthetic rates and amounts of N and Chl of developing leaves through systemic regulation, although the possibility of the action of blue light irradiation on the amount of Rubisco cannot be ruled out. Based on these results, we concluded that the light spectrum incident on mature leaves has little systemic effect on developing leaves in terms of photosynthetic characteristics and that the light-induced systemic regulation was largely accounted for by PPFD.

  6. Regulation of free radical generation in a sample irradiated by heavy-ion beam. Density of hydroxyl radical

    International Nuclear Information System (INIS)

    Density of hydroxyl radical (·OH) in gelatin samples caused by irradiation of carbon ion beam was investigated. ·OH was detected by EPR spin trapping technique using DMPO as a spin trapping agent. Gelatin samples containing several concentrations (7.7 to 1650 mM) of DMPO were irradiated by 290 MeV carbon mono beam using Heavy Ion Medical Accelerator in Chiba (HIMAC), applying several linear energy transfer (LET) (20 to 180 keV/μm) at the surface of the gelatin. The dose at the surface of the gelatin sample was 32 Gy. DMPO-OH (spin trapped ·OH) in irradiated samples were detected by X-band EPR spectrometer. The experiments were repeated using X-ray. Amount of DMPO-OH generated by carbon-ion beam was markedly lower than that by X-ray. For carbon-ion beam, amount of DMPO-OH decreased with increasing LET. The EPR signal intensity of DMPO-OH in X-ray-irradiated sample reached plateau around 30 mM DMPO; however, amount of DMPO-OH in carbon-beam-irradiated sample increased with concentration of DMPO added in the sample. This result suggests that ·OH generation around the truck of carbon ion beam was much dense compared with X-ray. (author)

  7. The Ca{sup 2+} channel TRPML3 specifically interacts with the mammalian ATG8 homologue GATE16 to regulate autophagy

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Suzy; Kim, Hyun Jin, E-mail: kimhyunjin@skku.edu

    2014-01-03

    Highlights: •Split-ubiquitin MY2H screen identified GATE16 as an interacting protein of TRPML3. •TRPML3 specifically binds to a mammalian ATG8 homologue GATE16, not to LC3B. •The interaction of TRPML3 with GATE16 facilitates autophagosome formation. •GATE16 is expressed in both autophagosome and extra-autophagosomal compartments. -- Abstract: TRPML3 is a Ca{sup 2+} permeable cation channel expressed in multiple intracellular compartments. Although TRPML3 is implicated in autophagy, how TRPML3 can regulate autophagy is not understood. To search interacting proteins with TRPML3 in autophagy, we performed split-ubiquitin membrane yeast two-hybrid (MY2H) screening with TRPML3-loop as a bait and identified GATE16, a mammalian ATG8 homologue. GST pull-down assay revealed that TRPML3 and TRPML3-loop specifically bind to GATE16, not to LC3B. Co-immunoprecipitation (co-IP) experiments showed that TRPML3 and TRPML3-loop pull down only the lipidated form of GATE16, indicating that the interaction occurs exclusively at the organellar membrane. The interaction of TRPML3 with GATE16 and GATE16-positive vesicle formation were increased in starvation induced autophagy, suggesting that the interaction facilitates the function of GATE16 in autophagosome formation. However, GATE16 was not required for TRPML3 trafficking to autophagosomes. Experiments using dominant-negative (DN) TRPML3(D458K) showed that GATE16 is localized not only in autophagosomes but also in extra-autophagosomal compartments, by contrast with LC3B. Since GATE16 acts at a later stage of the autophagosome biogenesis, our results suggest that TRPML3 plays a role in autophagosome maturation through the interaction with GATE16, by providing Ca{sup 2+} in the fusion process.

  8. Cardiac sodium channel Na(v)1.5 interacts with and is regulated by the protein tyrosine phosphatase PTPH1

    DEFF Research Database (Denmark)

    Jespersen, Thomas; Gavillet, Bruno; van Bemmelen, Miguel X;

    2006-01-01

    In order to identify proteins interacting with the cardiac voltage-gated sodium channel Na(v)1.5, we used the last 66 amino acids of the C-terminus of the channel as bait to screen a human cardiac cDNA library. We identified the protein tyrosine phosphatase PTPH1 as an interacting protein. Pull...

  9. Patch clamp studies on root cell vacuoles of a salt-tolerant and a salt-sensitive plantago species : regulation of channel activity by salt stress.

    Science.gov (United States)

    Maathuis, F J; Prins, H B

    1990-01-01

    Plantago media L. and Plantago maritima L. differ in their strategy toward salt stress, a major difference being the uptake and distribution of ions. Patch clamp techniques were applied to root cell vacuoles to study the tonoplast channel characteristics. In both species the major channel found was a 60 to 70 picosiemens channel with a low ion selectivity. The conductance of this channel for Na(+) was the same as for K(+), P(K) (+)/P(Na) (+) = 1, whereas the cation/anion selectivity (P(K) (+)/P(c1) (-)) was about 5. Gating characteristics were voltage and calcium dependent. An additional smaller channel of 25 picosiemens was present in P. maritima. In the whole vacuole configuration, the summation of the single channel currents resulted in slowly activated inward currents (t((1/2)) = 1.2 second). Inwardly directed, ATP-dependent currents could be measured against a DeltapH gradient of 1.5 units over the tonoplast. This observation strongly indicated the physiological intactness of the used vacuoles. The open probability of the tonoplast channels dramatically decreased when plants were grown on NaCl, although single channel conductance and selectivity were not altered.

  10. Positive Feedback Regulation of Agonist-Stimulated Endothelial Ca2+ Dynamics by KCa3.1 Channels in Mouse Mesenteric Arteries

    DEFF Research Database (Denmark)

    Qian, Xun; Francis, Michael; Köhler, Ralf;

    2014-01-01

    Intermediate and small conductance KCa channels IK1 (KCa3.1) and SK3 (KCa2.3) are primary targets of endothelial Ca(2+) signals in the arterial vasculature, and their ablation results in increased arterial tone and hypertension. Activation of IK1 channels by local Ca(2+) transients from internal ...

  11. Flow management and fish density regulate salmonid recruitment and adult size in tailwaters across western North America.

    Science.gov (United States)

    Dibble, Kimberly L; Yackulic, Charles B; Kennedy, Theodore A; Budy, Phaedra

    2015-12-01

    Rainbow and brown trout have been intentionally introduced into tailwaters downriver of dams globally and provide billions of dollars in economic benefits. At the same time, recruitment and maximum length of trout populations in tailwaters often fluctuate erratically, which negatively affects the value of fisheries. Large recruitment events may increase dispersal downriver where other fish species may be a priority (e.g., endangered species). There is an urgent need to understand the drivers of trout population dynamics in tailwaters, in particular the role of flow management. Here, we evaluate how flow, fish density, and other physical factors of the river influence recruitment and mean adult length in tailwaters across western North America, using data from 29 dams spanning 1-19 years. Rainbow trout recruitment was negatively correlated with high annual, summer, and spring flow and dam latitude, and positively correlated with high winter flow, subadult brown trout catch, and reservoir storage capacity. Brown trout recruitment was negatively correlated with high water velocity and daily fluctuations in flow (i.e., hydropeaking) and positively correlated with adult rainbow trout catch. Among these many drivers, rainbow trout recruitment was primarily correlated with high winter flow combined with low spring flow, whereas brown trout recruitment was most related to high water velocity. The mean lengths of adult rainbow and brown trout were influenced by similar flow and catch metrics. Length in both species was positively correlated with high annual flow but declined in tailwaters with high daily fluctuations in flow, high catch rates of conspecifics, and when large cohorts recruited to adult size. Whereas brown trout did not respond to the proportion of water allocated between seasons, rainbow trout length increased in rivers that released more water during winter than in spring. Rainbow trout length was primarily related to high catch rates of conspecifics

  12. Brain-derived neurotrophic factor (BDNF) induces sustained intracellular Ca2+ elevation through the up-regulation of surface transient receptor potential 3 (TRPC3) channels in rodent microglia.

    Science.gov (United States)

    Mizoguchi, Yoshito; Kato, Takahiro A; Seki, Yoshihiro; Ohgidani, Masahiro; Sagata, Noriaki; Horikawa, Hideki; Yamauchi, Yusuke; Sato-Kasai, Mina; Hayakawa, Kohei; Inoue, Ryuji; Kanba, Shigenobu; Monji, Akira

    2014-06-27

    Microglia are immune cells that release factors, including proinflammatory cytokines, nitric oxide (NO), and neurotrophins, following activation after disturbance in the brain. Elevation of intracellular Ca(2+) concentration ([Ca(2+)]i) is important for microglial functions such as the release of cytokines and NO from activated microglia. There is increasing evidence suggesting that pathophysiology of neuropsychiatric disorders is related to the inflammatory responses mediated by microglia. Brain-derived neurotrophic factor (BDNF) is a neurotrophin well known for its roles in the activation of microglia as well as in pathophysiology and/or treatment of neuropsychiatric disorders. In this study, we sought to examine the underlying mechanism of BDNF-induced sustained increase in [Ca(2+)]i in rodent microglial cells. We observed that canonical transient receptor potential 3 (TRPC3) channels contribute to the maintenance of BDNF-induced sustained intracellular Ca(2+) elevation. Immunocytochemical technique and flow cytometry also revealed that BDNF rapidly up-regulated the surface expression of TRPC3 channels in rodent microglial cells. In addition, pretreatment with BDNF suppressed the production of NO induced by tumor necrosis factor α (TNFα), which was prevented by co-adiministration of a selective TRPC3 inhibitor. These suggest that BDNF induces sustained intracellular Ca(2+) elevation through the up-regulation of surface TRPC3 channels and TRPC3 channels could be important for the BDNF-induced suppression of the NO production in activated microglia. We show that TRPC3 channels could also play important roles in microglial functions, which might be important for the regulation of inflammatory responses and may also be involved in the pathophysiology and/or the treatment of neuropsychiatric disorders.

  13. Serum Starvation-Induced Voltage-Gated Potassium Channel Kv7.5 Expression and Its Regulation by Sp1 in Canine Osteosarcoma Cells

    OpenAIRE

    Bo Hyung Lee; Pan Dong Ryu; So Yeong Lee

    2014-01-01

    The KCNQ gene family, whose members encode Kv7 channels, belongs to the voltage-gated potassium (Kv) channel group. The roles of this gene family have been widely investigated in nerve and muscle cells. In the present study, we investigated several characteristics of Kv7.5, which is strongly expressed in the canine osteosarcoma cell line, CCL-183. Serum starvation upregulated Kv7.5 expression, and the Kv7 channel opener, flupirtine, attenuated cell proliferation by arresting cells in the G0/G...

  14. Differential regulation of acid sphingomyelinase in macrophages stimulated with oxidized low-density lipoprotein (LDL) and oxidized LDL immune complexes: role in phagocytosis and cytokine release.

    Science.gov (United States)

    Truman, Jean-Philip; Al Gadban, Mohammed M; Smith, Kent J; Jenkins, Russell W; Mayroo, Nalini; Virella, Gabriel; Lopes-Virella, Maria F; Bielawska, Alicja; Hannun, Yusuf A; Hammad, Samar M

    2012-05-01

    Oxidized low-density lipoprotein (oxLDL) and oxLDL-containing immune complexes (oxLDL-IC) contribute to the formation of lipid-laden macrophages (foam cells). Fcγ receptors mediate uptake of oxLDL-IC, whereas scavenger receptors internalize oxLDL. We have previously reported that oxLDL-IC, but not free oxLDL, activate macrophages and prolong their survival. Sphingomyelin is a major constituent of cell membranes and lipoprotein particles and acid sphingomyelinase (ASMase) hydrolyses sphingomyelin to generate the bioactive lipid ceramide. ASMase exists in two forms: lysosomal (L-ASMase) and secretory (S-ASMase). In this study we examined whether oxLDL and oxLDL-IC regulate ASMase differently, and whether ASMase mediates monocyte/macrophage activation and cytokine release. The oxLDL-IC, but not oxLDL, induced early and consistent release of catalytically active S-ASMase. The oxLDL-IC also consistently stimulated L-ASMase activity, whereas oxLDL induced a rapid transient increase in L-ASMase activity before it steadily declined below baseline. Prolonged exposure to oxLDL increased L-ASMase activity; however, activity remained significantly lower than that induced by oxLDL-IC. Further studies were aimed at defining the function of the activated ASMase. In response to oxLDL-IC, heat-shock protein 70B' (HSP70B') was up-regulated and localized with redistributed ASMase in the endosomal compartment outside the lysosome. Treatment with oxLDL-IC induced the formation and release of HSP70-containing and IL-1β-containing exosomes via an ASMase-dependent mechanism. Taken together, the results suggest that oxLDL and oxLDL-IC differentially regulate ASMase activity, and the pro-inflammatory responses to oxLDL-IC are mediated by prolonged activation of ASMase. These findings may contribute to increased understanding of mechanisms mediating macrophage involvement in atherosclerosis.

  15. Cytoplasmic cAMP-sensing domain of hyperpolarization-activated cation (HCN) channels uses two structurally distinct mechanisms to regulate voltage gating

    OpenAIRE

    Wicks, Nadine L.; Wong, Tammy; Sun, Jinyi; Madden, Zarina; Young, Edgar C.

    2010-01-01

    Voltage gating of hyperpolarization-activated cation (HCN) channels is potentiated by direct binding of cAMP to a cytoplasmic cAMP-sensing domain (CSD). When unliganded, the CSD inhibits hyperpolarization-dependent opening of the HCN channel gate; cAMP binding relieves this autoinhibition so that opening becomes more favorable thermodynamically. This autoinhibition-relief mechanism is conserved with that of several other cyclic nucleotide receptors using the same ligand-binding fold. Besides ...

  16. Molecular basis of potassium channels in pancreatic duct epithelial cells

    DEFF Research Database (Denmark)

    Hayashi, M.; Novak, Ivana

    2013-01-01

    Potassium channels regulate excitability, epithelial ion transport, proliferation, and apoptosis. In pancreatic ducts, K channels hyperpolarize the membrane potential and provide the driving force for anion secretion. This review focuses on the molecular candidates of functional K channels...

  17. Mass spectrometric analysis and mutagenesis predict involvement of multiple cysteines in redox regulation of the skeletal muscle ryanodine receptor ion channel complex

    Directory of Open Access Journals (Sweden)

    Evgeniy V Petrotchenko

    2011-01-01

    Full Text Available Evgeniy V Petrotchenko1,2,4, Naohiro Yamaguchi1,3,4, Daniel A Pasek1, Christoph H Borchers1,2, Gerhard Meissner11Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC, USA; 2University of Victoria, Genome BC Proteomics Centre, Victoria, British Columbia, Canada; 3Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, USA 4Contributed equally to the workAbstract: The tetrameric skeletal muscle ryanodine receptor ion channel complex (RyR1 contains a large number of free cysteines that are potential targets for redox-active molecules. Here, we report the mass spectrometric analysis of free thiols in RyR1 using the lipophilic, thiol-specific probe monobromobimane (MBB. In the presence of reduced glutathione, MBB labeled 14 cysteines per RyR1 subunit in tryptic peptides in five of five experiments. Forty-six additional MBB-labeled cysteines per RyR1 subunit were detected with lower frequency in tryptic peptides, bringing the total number of MBB-labeled cysteines to 60 per RyR1 subunit. A combination of fluorescence detection and mass spectrometry of RyR1, labeled in the presence of reduced and oxidized glutathione, identified two redox-sensitive cysteines (C1040 and C1303. Regulation of RyR activity by reduced and oxidized glutathione was investigated in skeletal muscle mutant RyR1s in which 18 cysteines were substituted with serine or alanine, using a [3H]ryanodine ligand binding assay. Three single-site RyR1 mutants (C1781S, C2436S, and C2606S and two multisite mutants with five and seven substituted cysteines exhibited a reduced redox response compared with wild-type RyR1. The results suggest that multiple cysteines determine the redox state and activity of RyR1.Keywords: mass spectrometry, mutagenesis, ryanodine receptor, redox modification of cysteines

  18. TRP channels: an overview

    DEFF Research Database (Denmark)

    Pedersen, Stine Falsig; Owsianik, Grzegorz; Nilius, Bernd

    2005-01-01

    to a plethora of data on the roles of TRPs in a variety of tissues and species, including mammals, insects, and yeast. The present review summarizes the most pertinent recent evidence regarding the structural and functional properties of TRP channels, focusing on the regulation and physiology of mammalian TRPs....

  19. Chloride channels in stroke

    Institute of Scientific and Technical Information of China (English)

    Ya-ping ZHANG; Hao ZHANG; Dayue Darrel DUAN

    2013-01-01

    Vascular remodeling of cerebral arterioles,including proliferation,migration,and apoptosis of vascular smooth muscle cells (VSMCs),is the major cause of changes in the cross-sectional area and diameter of the arteries and sudden interruption of blood flow or hemorrhage in the brain,ie,stroke.Accumulating evidence strongly supports an important role for chloride (Clˉ) channels in vascular remodeling and stroke.At least three Clˉ channel genes are expressed in VSMCs:1) the TMEM16A (or Ano1),which may encode the calcium-activated Clˉ channels (CACCs); 2) the CLC-3 Clˉ channel and Clˉ/H+ antiporter,which is closely related to the volume-regulated Clˉ channels (VRCCs); and 3) the cystic fibrosis transmembrane conductance regulator (CFTR),which encodes the PKA-and PKC-activated Clˉ channels.Activation of the CACCs by agonist-induced increase in intracellular Ca2+ causes membrane depolarization,vasoconstriction,and inhibition of VSMC proliferation.Activation of VRCCs by cell volume increase or membrane stretch promotes the production of reactive oxygen species,induces proliferation and inhibits apoptosis of VSMCs.Activation of CFTR inhibits oxidative stress and may prevent the development of hypertension.In addition,Clˉ current mediated by gammaaminobutyric acid (GABA) receptor has also been implicated a role in ischemic neuron death.This review focuses on the functional roles of Clˉ channels in the development of stroke and provides a perspective on the future directions for research and the potential to develop Clˉ channels as new targets for the prevention and treatment of stroke.

  20. Model studies of dense water overflows in the Faroese Channels

    Science.gov (United States)

    Cuthbertson, Alan; Davies, Peter; Stashchuk, Nataliya; Vlasenko, Vasiliy

    2014-01-01

    The overflow of dense water from the Nordic Seas through the Faroese Channel system was investigated through combined laboratory experiments and numerical simulations using the Massachusetts Institute of Technology General Circulation Model. In the experimental study, a scaled, topographic representation of the Faroe-Shetland Channel, Wyville-Thomson Basin and Ridge and Faroe Bank Channel seabed bathymetry was constructed and mounted in a rotating tank. A series of parametric experiments was conducted using dye-tracing and drogue-tracking techniques to investigate deep-water overflow pathways and circulation patterns within the modelled region. In addition, the structure of the outflowing dense bottom water was investigated through density profiling along three cross-channel transects located in the Wyville-Thomson Basin and the converging, up-sloping approach to the Faroe Bank Channel. Results from the dye-tracing studies demonstrate a range of parametric conditions under which dense water overflow across the Wyville-Thomson Ridge is shown to occur, as defined by the Burger number, a non-dimensional length ratio and a dimensionless dense water volume flux parameter specified at the Faroe-Shetland Channel inlet boundary. Drogue-tracking measurements reveal the complex nature of flow paths and circulations generated in the modelled topography, particularly the development of a large anti-cyclonic gyre in the Wyville-Thompson Basin and up-sloping approach to the Faroe Bank Channel, which diverts the dense water outflow from the Faroese shelf towards the Wyville-Thomson Ridge, potentially promoting dense water spillage across the ridge itself. The presence of this circulation is also indicated by associated undulations in density isopycnals across the Wyville-Thomson Basin. Numerical simulations of parametric test cases for the main outflow pathways and density structure in a similarly-scaled Faroese Channels model domain indicate excellent qualitative agreement with

  1. Lysine 362 in cytochrome c oxidase regulates opening of the K-channel via changes in pKA and conformation.

    Science.gov (United States)

    Woelke, Anna Lena; Galstyan, Gegham; Knapp, Ernst-Walter

    2014-12-01

    The metabolism of aerobic life uses the conversion of molecular oxygen to water as an energy source. This reaction is catalyzed by cytochrome e oxidase (CeO) consuming four electrons and four protons, which move along specific routes. While all four electrons are transferred via the same cofactors to the binuclear reaction center (BNC), the protons take two different routes in the A-type CeO, i.e., two of the four chemical protons consumed in the reaction arrive via the D-channel in the oxidative first half starting after oxygen binding. The other two chemical protons enter via the K-channel in the reductive second half of the reaction cycle. To date, the mechanism behind these separate proton transport pathways has not been understood. In this study, we propose a model that can explain the reaction-step specific opening and closing of the K-channel by conformational and pKA changes of its central lysine 362. Molecular dynamics simulations reveal an upward movement of Lys362 towards the BNC, which had already been supposed by several experimental studies. Redox state-dependent pKA calculations provide evidence that Lys362 may protonate transiently, thereby opening the K-channel only in the reductive second half of the reaction cycle. From our results, we develop a model that assigns a key role to Lys362 in the proton gating between the two proton input channels of the A-type CeO. PMID:25149865

  2. Exogenous γ-aminobutyric acid (GABA) affects pollen tube growth via modulating putative Ca2+-permeable membrane channels and is coupled to negative regulation on glutamate decarboxylase.

    Science.gov (United States)

    Yu, Guang-Hui; Zou, Jie; Feng, Jing; Peng, Xiong-Bo; Wu, Ju-You; Wu, Ying-Liang; Palanivelu, Ravishankar; Sun, Meng-Xiang

    2014-07-01

    γ-Aminobutyric acid (GABA) is implicated in pollen tube growth, but the molecular and cellular mechanisms that it mediates are largely unknown. Here, it is shown that exogenous GABA modulates putative Ca(2+)-permeable channels on the plasma membranes of tobacco pollen grains and pollen tubes. Whole-cell voltage-clamp experiments and non-invasive micromeasurement technology (NMT) revealed that the influx of Ca(2+) increases in pollen tubes in response to exogenous GABA. It is also demonstrated that glutamate decarboxylase (GAD), the rate-limiting enzyme of GABA biosynthesis, is involved in feedback controls of Ca(2+)-permeable channels to fluctuate intracellular GABA levels and thus modulate pollen tube growth. The findings suggest that GAD activity linked with Ca(2+)-permeable channels relays an extracellular GABA signal and integrates multiple signal pathways to modulate tobacco pollen tube growth. Thus, the data explain how GABA mediates the communication between the style and the growing pollen tubes.

  3. The low density lipoprotein receptor-related protein/alpha2-macroglobulin receptor regulates cell surface plasminogen activator activity on human trophoblast cells.

    Science.gov (United States)

    Zhang, J C; Sakthivel, R; Kniss, D; Graham, C H; Strickland, D K; McCrae, K R

    1998-11-27

    The low density lipoprotein receptor-related protein/alpha2-macroglobulin receptor (LRP/alpha2MR) mediates the internalization of numerous ligands, including prourokinase (pro-UK) and complexes between two-chain urokinase (tc-u-PA) and plasminogen activator inhibitor type-1 (PAI-1). It has been suggested that through its ability to internalize these ligands, LRP/alpha2MR may regulate the expression of plasminogen activator activity on cell surfaces; this hypothesis, however, has not been experimentally confirmed. To address this issue, we assessed the ability of LRP/alpha2MR to regulate plasminogen activator activity on human trophoblast cells, which express both LRP/alpha2MR and the urokinase receptor (uPAR). Trophoblasts internalized and degraded exogenous 125I-pro-UK (primarily following its conversion to tc-u-PA and incorporation into tc-u-PA.PAI complexes) in an LRP/alpha2MR-dependent manner, which was inhibited by the LRP/alpha2MR receptor-associated protein. Receptor-associated protein also caused a approximately 50% reduction in cell surface plasminogen activator activity and delayed the regeneration of unoccupied uPAR by cells on which uPAR were initially saturated with pro-UK. Identical effects were caused by anti-LRP/alpha2MR antibodies. These results demonstrate that LRP/alpha2MR promotes the expression of cell surface plasminogen activator activity on trophoblasts by facilitating the clearance of tc-u-PA.PAI complexes and regeneration of unoccupied cell surface uPAR. PMID:9822706

  4. Phosphatidylinositol 4,5-biphosphate (PIP2) modulates syntaxin-1A binding to sulfonylurea receptor 2A to regulate cardiac ATP-sensitive potassium (KATP) channels.

    Science.gov (United States)

    Xie, Li; Liang, Tao; Kang, Youhou; Lin, Xianguang; Sobbi, Roozbeh; Xie, Huanli; Chao, Christin; Backx, Peter; Feng, Zhong-Ping; Shyng, Show-Ling; Gaisano, Herbert Y

    2014-10-01

    Cardiac sarcolemmal syntaxin (Syn)-1A interacts with sulfonylurea receptor (SUR) 2A to inhibit ATP-sensitive potassium (KATP) channels. Phosphatidylinositol 4,5-bisphosphate (PIP2), a ubiquitous endogenous inositol phospholipid, known to bind Kir6.2 subunit to open KATP channels, has recently been shown to directly bind Syn-1A in plasma membrane to form Syn-1A clusters. Here, we sought to determine whether the interaction between Syn-1A and PIP2 interferes with the ability of Syn-1A to bind SUR2A and inhibit KATP channel activity. We found that PIP2 dose-dependently reduced SUR2A binding to GST-Syn-1A by in vitro pulldown assays. FRET studies in intact cells using TIRFM revealed that increasing endogenous PIP2 levels led to increased Syn-1A (-EGFP) cluster formation and a severe reduction in availability of Syn-1A molecules to interact with SUR2A (-mCherry) molecules outside the Syn-1A clusters. Correspondingly, electrophysiological studies employing SUR2A/Kir6.2-expressing HEK cells showed that increasing endogenous or exogenous PIP2 diminished the inhibitory effect of Syn-1A on KATP currents. The physiological relevance of these findings was confirmed by ability of exogenous PIP2 to block exogenous Syn-1A inhibition of cardiac KATP currents in inside-out patches of mouse ventricular myocytes. The effect of PIP2 on physical and functional interactions between Syn-1A and KATP channels is specific and not observed with physiologic concentrations of other phospholipids. To unequivocally demonstrate the specificity of PIP2 interaction with Syn-1A and its impact on KATP channel modulation by Syn-1A, we employed a PIP2-insensitive Syn-1A-5RK/A mutant. The Syn-1A-5RK/A mutant retains the ability to interact with SUR2A in both in vitro binding and in vivo FRET assays, although as expected the interaction is no longer disrupted by PIP2. Interestingly, at physiological PIP2 concentrations, Syn-1A-5RK/A inhibited KATP currents to a greater extent than Syn-1A-WT, indicating

  5. Demystifying Mechanosensitive Piezo Ion Channels.

    Science.gov (United States)

    Xu, X Z Shawn

    2016-06-01

    Mechanosensitive channels mediate touch, hearing, proprioception, and blood pressure regulation. Piezo proteins, including Piezo1 and Piezo2, represent a new class of mechanosensitive channels that have been reported to play key roles in most, if not all, of these modalities. The structural architecture and molecular mechanisms by which Piezos act as mechanosensitive channels, however, remain mysterious. Two new studies have now provided critical insights into the atomic structure and molecular basis of the ion permeation and mechano-gating properties of the Piezo1 channel.

  6. Demystifying Mechanosensitive Piezo Ion Channels.

    Science.gov (United States)

    Xu, X Z Shawn

    2016-06-01

    Mechanosensitive channels mediate touch, hearing, proprioception, and blood pressure regulation. Piezo proteins, including Piezo1 and Piezo2, represent a new class of mechanosensitive channels that have been reported to play key roles in most, if not all, of these modalities. The structural architecture and molecular mechanisms by which Piezos act as mechanosensitive channels, however, remain mysterious. Two new studies have now provided critical insights into the atomic structure and molecular basis of the ion permeation and mechano-gating properties of the Piezo1 channel. PMID:27164907

  7. The roles and relations of calpastatin, calmodulin and an undefined cytoplasmic factor in the regulation of cardiac L-type Ca2+ channels

    Institute of Scientific and Technical Information of China (English)

    HAO Li-ying; ZHU Tong; HU Hui-yuan; ZHAO Mei-mi; RUI Feng; LIU Yan; ZHAO Jin-sheng; tsuko Minobe; Masaki Kameyama

    2008-01-01

    Objective To explore the mechanism that cytoplasmic factors could recover L-type Ca2+ channel activity after "run-down'. The factors include ATP, calpastatin and H fraction (a high molecular fraction of bovine cardiac cytoplasm). Methods Single Ca2+ channel activities were recorded with patch clamp technique in guinea-pig cardiac myocytes. Run-down was induced by the inside-out patch formation. Calpastatin (CS), calmodulin(CaM) and three GST-fusion fragment peptides derived from the C-terminal tail of guineapig Car1.2, CT-1 (amino acids number 1509-1791), CTo2 (1777-2003) and CT-3 (1944-2169) were produced as GST fusion proteins. Results (1)CaM + ATP or CS + ATP restored the channels after rundown;however, the CaM or CS's effects became smaller with the longer run-down time. (2)After run down, CaM-dependent protein kinase (CaMKII) produced Ca2+ channel activity to only 2-10% of the basal activity, however, in the presence of CaMKII, the time-dependent nature of the CaM effect was abolished. (3) In pull-down assay, CT-1 treated with CaMKII showed a higher affinity for CaM than that treated with phosphatase. (4)CaMKII was detected in the H fraction of bovine cardiac cytoplasm. Conclusions The results show that CS, CaM and CaMKII are all involved in the maintenance of the basal activity of L-type Ca2+ channels, and that there might be cross talks among the four factors (CS, CaM, CaMKII and the undefined cytoplasmic factor). This work was supported by the grants from the Japan Society for the Promotion of Science and the National Natural Science Foundation of China (No. 30670761, No. 30671726).

  8. Methods of albedo electron densimetry. 2. Two-channel methods

    Energy Technology Data Exchange (ETDEWEB)

    Sorokin, V.B. (Tomskij Politekhnicheskij Inst. (USSR). Nauchno-Issledovatel' skij Inst. Ehlektronnoj Introskopii)

    1981-12-01

    Two-channel methods of densimetry permitting to realize control over density of materials with fluctuating composition which have been developed on the basis of one-channel albedo electron methods are considered. The two-channel methods permits to decrease the errors as compared with one-channel ones and when central-peripheral method is applied - also to increase the sensitivity to density variation. The methods are intended for control density of porous materials, especially in powder metallurgy, ceramics production, etc.

  9. DYRK1A-mediated phosphorylation of GluN2A at Ser1048 regulates the surface expression and channel activity of GluN1/GluN2A receptors

    Directory of Open Access Journals (Sweden)

    Cristina eGrau

    2014-10-01

    Full Text Available N-methyl-D-aspartate glutamate receptors (NMDARs play a pivotal role in neural development and synaptic plasticity, as well as in neurological disease. Since NMDARs exert their function at the cell surface, their density in the plasma membrane is finely tuned by a plethora of molecules that regulate their production, trafficking, docking and internalization in response to external stimuli. In addition to transcriptional regulation, the density of NMDARs is also influenced by post-translational mechanisms like phosphorylation, a modification that also affects their biophysical properties. We previously described the increased surface expression of GluN1/GluN2A receptors in transgenic mice overexpressing the Dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A, suggesting that DYRK1A regulates NMDARs. Here we have further investigated whether the density and activity of NMDARs was modulated by DYRK1A phosphorylation. Accordingly, we show that endogenous DYRK1A is recruited to GluN2A-containing NMDARs in the adult mouse brain, and we identify a DYRK1A phosphorylation site at Ser1048 of GluN2A, within its intracellular C-terminal domain. Mechanistically, the DYRK1A-dependent phosphorylation of GluN2A at Ser1048 hinders the internalization of GluN1/GluN2A, causing an increase of surface GluN1/GluN2A in heterologous systems, as well as in primary cortical neurons. Furthermore, GluN2A phosphorylation at Ser1048 increases the current density and potentiates the gating of GluN1/GluN2A receptors. We conclude that DYRK1A is a direct regulator of NMDA receptors and we propose a novel mechanism for the control of NMDAR activity in neurons.

  10. DYRK1A-mediated phosphorylation of GluN2A at Ser(1048) regulates the surface expression and channel activity of GluN1/GluN2A receptors.

    Science.gov (United States)

    Grau, Cristina; Arató, Krisztina; Fernández-Fernández, José M; Valderrama, Aitana; Sindreu, Carlos; Fillat, Cristina; Ferrer, Isidre; de la Luna, Susana; Altafaj, Xavier

    2014-01-01

    N-methyl-D-aspartate glutamate receptors (NMDARs) play a pivotal role in neural development and synaptic plasticity, as well as in neurological disease. Since NMDARs exert their function at the cell surface, their density in the plasma membrane is finely tuned by a plethora of molecules that regulate their production, trafficking, docking and internalization in response to external stimuli. In addition to transcriptional regulation, the density of NMDARs is also influenced by post-translational mechanisms like phosphorylation, a modification that also affects their biophysical properties. We previously described the increased surface expression of GluN1/GluN2A receptors in transgenic mice overexpressing the Dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A), suggesting that DYRK1A regulates NMDARs. Here we have further investigated whether the density and activity of NMDARs were modulated by DYRK1A phosphorylation. Accordingly, we show that endogenous DYRK1A is recruited to GluN2A-containing NMDARs in the adult mouse brain, and we identify a DYRK1A phosphorylation site at Ser(1048) of GluN2A, within its intracellular C-terminal domain. Mechanistically, the DYRK1A-dependent phosphorylation of GluN2A at Ser(1048) hinders the internalization of GluN1/GluN2A, causing an increase of surface GluN1/GluN2A in heterologous systems, as well as in primary cortical neurons. Furthermore, GluN2A phosphorylation at Ser(1048) increases the current density and potentiates the gating of GluN1/GluN2A receptors. We conclude that DYRK1A is a direct regulator of NMDA receptors and we propose a novel mechanism for the control of NMDAR activity in neurons. PMID:25368549

  11. Desempenho de um regulador automático de vazão para canais de irrigação Performance of an automatic discharge regulator for irrigation channels

    Directory of Open Access Journals (Sweden)

    Luís G. H. do Amaral

    2010-12-01

    Full Text Available As estruturas de controle comumente utilizadas nas tomadas de água dos canais de irrigação não permitem a distribuição da quantidade correta de água, favorecendo o desperdício e, consequentemente, reduzindo a eficiência no uso da água. O objetivo deste trabalho foi determinar o desempenho de um regulador automático de vazão no controle da vazão derivada. Para tanto, um exemplar do equipamento, construído em fibra de vidro, foi instalado na lateral de um canal de concreto do Laboratório de Hidráulica da Universidade Federal de Viçosa, em Viçosa-MG. O equipamento foi avaliado em toda a sua faixa de operação, sendo que, em cada regulagem prefixada, determinou-se a vazão derivada com o nível da água a montante variando de 0,30 a 0,45 m. A variação média na vazão do regulador, considerando toda a sua faixa de operação, foi de ± 2,3% em relação às vazões médias fornecidas pelo equipamento em cada regulagem. A amplitude de variação na vazão fornecida foi pequena em relação aos equipamentos usualmente empregados no controle de vazão, em canais de irrigação, demonstrando que o regulador automático de vazão é um equipamento apropriado para a distribuição de água em redes de canais.The control structures commonly used in irrigation channels water intakes are inefficient in delivering the correct water volume to crops, collaborating to water waste and, hence, reducing the water use efficiency. The objective of this work was to determine the performance of an automatic discharge regulator in the control of the supplied discharge. The regulator was made of fiberglass and its evaluation was accomplished in a concrete channel belonging to the Hydraulic Laboratory of the Federal University of Viçosa, in Viçosa, state of Minas Gerais, Brazil. The evaluation was performed for all equipment discharge regulation options. In each regulation, the supplied discharge was determined for the upstream water level changing

  12. Density-Dependent Regulation of Brook Trout Population Dynamics along a Core-Periphery Distribution Gradient in a Central Appalachian Watershed

    OpenAIRE

    Huntsman, Brock M.; Petty, J. Todd

    2014-01-01

    Spatial population models predict strong density-dependence and relatively stable population dynamics near the core of a species' distribution with increasing variance and importance of density-independent processes operating towards the population periphery. Using a 10-year data set and an information-theoretic approach, we tested a series of candidate models considering density-dependent and density-independent controls on brook trout population dynamics across a core-periphery distribution...

  13. Microarray analysis of ox-LDL (oxidized low-density lipoprotein)-regulated genes in human coronary artery smooth muscle cells.

    Science.gov (United States)

    Minta, Joe; Jungwon Yun, James; St Bernard, Rosanne

    2010-01-01

    Recent studies suggest that circulating LDL (low-density lipoproteins) play a central role in the pathogenesis of atherosclerosis, and the oxidized form (ox-LDL) is highly atherogenic. Deposits of ox-LDL have been found in atherosclerotic plaques, and ox-LDL has been shown to promote monocyte recruitment, foam cell formation and the transition of quiescent and contractile vascular SMCs (smooth muscle cells) to the migratory and proliferative phenotype. SMC phenotype transition and hyperplasia are the pivotal events in the pathogenesis of atherosclerosis. To comprehend the complex molecular mechanisms involved in ox-LDL-mediated SMC phenotype transition, we have compared the differential gene expression profiles of cultured quiescent human coronary artery SMCs with cells induced with ox-LDL for 3 and 21 h using Affymetrix HG-133UA cDNA microarray chips. Assignment of the regulated genes into functional groups indicated that several genes involved in metabolism, membrane transport, cell-cell interactions, signal transduction, transcription, translation, cell migration, proliferation and apoptosis were differentially expressed. Our data suggests that the interaction of ox-LDL with its cognate receptors on SMCs modulates the induction of several growth factors and cytokines, which activate a variety of intracellular signalling mechanisms (including PI3K, MAPK, Jak/STAT, sphingosine, Rho kinase pathways) that contribute to SMC transition from the quiescent and contractile phenotype to the proliferative and migratory phenotype. Our study has also identified several genes (including CDC27, cyclin A1, cyclin G2, glypican 1, MINOR, p15 and apolipoprotein) not previously implicated in ox-LDL-induced SMC phenotype transition and substantially extends the list of potential candidate genes involved in atherogenesis.

  14. Regulation of cell proliferation of human induced pluripotent stem cell-derived mesenchymal stem cells via ether-à-go-go 1 (hEAG1) potassium channel.

    Science.gov (United States)

    Zhang, Jiao; Chan, Yau-Chi; Ho, Jenny Chung-Yee; Siu, Chung-Wah; Lian, Qizhou; Tse, Hung-Fat

    2012-07-15

    The successful generation of a high yield of mesenchymal stem cells (MSCs) from human induced pluripotent stem cells (iPSCs) may represent an unlimited cell source with superior therapeutic benefits for tissue regeneration to bone marrow (BM)-derived MSCs. We investigated whether the differential expression of ion channels in iPSC-MSCs was responsible for their higher proliferation capacity than BM-MSCs. The expression of ion channels for K(+), Na(+), Ca(2+), and Cl(-) was examined by RT-PCR. The electrophysiological properties of iPSC-MSCs and BM-MSCs were then compared by patch-clamp experiments to verify their functional roles. Significant mRNA expression of ion channel genes including KCa1.1, KCa3.1, KCNH1, Kir2.1, SCN9A, CACNA1C, and Clcn3 was observed in both human iPSC-MSCs and BM-MSCs, whereas Kir2.2 and Kir2.3 were only detected in human iPSC-MSCs. Five types of currents [big-conductance Ca(2+)-activated K(+) current (BK(Ca)), delayed rectifier K(+) current (IK(DR)), inwardly rectifying K(+) current (I(Kir)), Ca(2+)-activated K(+) current (IK(Ca)), and chloride current (I(Cl))] were found in iPSC-MSCs (83%, 47%, 11%, 5%, and 4%, respectively) but only four of them (BK(Ca), IK(DR), I(Kir), and IK(Ca)) were identified in BM-MSCs (76%, 25%, 22%, and 11%, respectively). Cell proliferation was examined with MTT or bromodeoxyuridine assay, and doubling times were 2.66 and 3.72 days for iPSC-MSCs and BM-MSCs, respectively, showing a 1.4-fold discrepancy. Blockade of IK(DR) with short hairpin RNA or human ether-à-go-go 1 (hEAG1) channel blockers, 4-AP and astemizole, significantly reduced the rate of proliferation of human iPSC-MSCs. These treatments also decreased the rate of proliferation of human BM-MSCs albeit to a lesser extent. These findings demonstrate that the hEAG1 channel plays a crucial role in controlling the proliferation rate of human iPSC-MSCs and to a lesser extent in BM-MSCs. PMID:22357737

  15. 从微信收费之争看瓶颈垄断的反垄断法规制%Discussing the Bottleneck Monopoly Antitrust Regulation Viewing from the Dispute of the Micro-channel Charge

    Institute of Scientific and Technical Information of China (English)

    张积储

    2013-01-01

    Recently , the "micro-channel charge dispute"between three major telecom operators and Tencent set off a wave of the Internet economy monopoly .In the network economy era , the bottleneck monopoly of the economy is becoming more and more , China's "anti-monopoly law"should make corresponding regulations aganist the bottle-neck monopoly , standardize the market behavior of dominant companies .This study takes the dispute of micro-channel charge as clues to introduce the concept of monopoly bottlenecks , analyzes the regulation against the bottle-neck monopoly , highlights the necessity of regulation .Finally, some legislation recommandations are proposed for regulating the bottleneck monopoly .%日前,电信三大运营商与腾讯的“微信收费之争”掀起了网络经济的垄断浪潮。在网络经济的时代下,瓶颈垄断经济越来越多,我国《反垄断法》应该对这种瓶颈垄断行为作出相应的规定,规范优势企业的市场行为。将以微信收费的争端为线索,引出瓶颈垄断的概念,浅析我国垄断法对瓶颈垄断的规制,突出瓶颈垄断行为应受规制的必要性,并提出瓶颈垄断反垄断法规制的立法建议。

  16. Proton channel models

    OpenAIRE

    Pupo, Amaury; Baez-Nieto, David; Martínez, Agustín; Latorre, Ramón; González, Carlos

    2014-01-01

    Voltage-gated proton channels are integral membrane proteins with the capacity to permeate elementary particles in a voltage and pH dependent manner. These proteins have been found in several species and are involved in various physiological processes. Although their primary topology is known, lack of details regarding their structures in the open conformation has limited analyses toward a deeper understanding of the molecular determinants of their function and regulation. Consequently, the f...

  17. How Does the Reductase Help To Regulate the Catalytic Cycle of Cytochrome P450 3A4 Using the Conserved Water Channel?

    OpenAIRE

    Fishelovitch, Dan; Shaik, Sason; Wolfson, Haim J.; Nussinov, Ruth

    2010-01-01

    Water molecules play a major role in the P450 catalytic cycle. Here, we locate the preferred water pathways and their gating mechanisms for the human cytochrome P450 3A4 (CYP3A4) and elucidate the role of the cytochrome P450 reductase (CPR) in turning on and activating these water channels. We perform explicit solvent molecular dynamic simulations of CYP3A4, unbound and bound to two substrates, and with and without the flavin mononucleotide (FMN)-binding domain of CPR. We observe in/out passa...

  18. Brands & Channels

    Institute of Scientific and Technical Information of China (English)

    Alice Yang

    2009-01-01

    @@ "Brands" and "Channels" are the two most important things in Ku-Hai Chen's eyes when doing business with Main-land China. Ku-Hai Chen, Executive Director of the International Trade Institute of Taiwan External Trade Development Council (TAITRA), flies frequently between Chinese Taipei and Mainland China, and was in Beijing earlier this month for his seminar.

  19. INDUCTION OF LOW-DENSITY AND UP-REGULATION OF CD11B EXPRESSION OF NEUTROPHILS AND EOSINOPHILS BY DEXTRAN SEDIMENTATION AND CENTRIFUGATION

    NARCIS (Netherlands)

    DIJKHUIZEN, B; DEMONCHY, JGR; GERRITSEN, J; KAUFFMAN, HF

    1994-01-01

    Neutrophils and eosinophils circulating in an activated state are of low density. However, purification procedures such as dextran sedimentation and centrifugation may influence the density and function of cells. In the present study we have evaluated the effect of dextran sedimentation and subseque

  20. Cystic Fibrosis Gene Encodes a cAMP-Dependent Chloride Channel in Heart

    Science.gov (United States)

    Hart, Padraig; Warth, John D.; Levesque, Paul C.; Collier, Mei Lin; Geary, Yvonne; Horowitz, Burton; Hume, Joseph R.

    1996-06-01

    cAMP-dependent chloride channels in heart contribute to autonomic regulation of action potential duration and membrane potential and have been inferred to be due to cardiac expression of the epithelial cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. In this report, a cDNA from rabbit ventricle was isolated and sequenced, which encodes an exon 5 splice variant (exon 5-) of CFTR, with >90% identity to human CFTR cDNA present in epithelial cells. Expression of this cDNA in Xenopus oocytes gave rise to robust cAMP-activated chloride currents that were absent in control water-injected oocytes. Antisense oligodeoxynucleotides directed against CFTR significnatly reduced the density of cAMP-dependent chloride currents in acutely cultured myocytes, thereby establishing a direct functional link between cardiac expression of CFTR protein and an endogenous chloride channel in native cardiac myocytes.

  1. Maternal effects and population regulation: maternal density-induced reproduction suppression impairs offspring capacity in response to immediate environment in root voles Microtus oeconomus.

    Science.gov (United States)

    Bian, Jiang-Hui; Du, Shou-Yang; Wu, Yan; Cao, Yi-Fan; Nie, Xu-Heng; He, Hui; You, Zhi-Bing

    2015-03-01

    The hypothesis that maternal effects act as an adaptive bridge in translating maternal environments into offspring phenotypes, and thereby affecting population dynamics has not been studied in the well-controlled fields. In this study, the effects of maternal population density on offspring stress axis, reproduction and population dynamics were studied in root voles (Microtus oeconomus). Parental enclosures for breeding offspring were established by introducing six adults per sex into each of 4 (low density) and 30 adults per sex into each of another 4 (high density) enclosures. Live-trapping started 2 weeks after. Offspring captured at age of 20-30 days were removed to the laboratory, housed under laboratory conditions until puberty, and subsequently used to establish offspring populations in these same enclosures, after parental populations had been removed. [Correction added on 8 January 2015 after first online publication: '10-20 days' has been changed to '20-30 days.'] Offspring from each of the two parental sources were assigned into four enclosures with two for each of the two density treatments used in establishing parental populations (referred to as LL and LH for maternally unstressed offspring, assigned in low and high density, and HL and HH for maternally stressed offspring, assigned in low and high density). Faecal corticosterone metabolites (FCM) levels, offspring reproduction traits and population dynamics were tested following repeated live-trapping over two seasons. Differential fluctuations in population size were observed between maternally density-stressed and density-unstressed offspring. Populations in LL and LH groups changed significantly in responding to initial density and reached the similar levels at beginning of the second trapping season. Populations in HL and HH groups, however, were remained relatively steady, and in HL group, the low population size was sustained until end of experiment. Maternal density stress was associated with

  2. The influence of ambient salinity and temperature on lipid metabolism in toad (Bufo bufo) skin. Is phosphatidylethanolamine an endogenous regulator of ion channels?

    DEFF Research Database (Denmark)

    Hansen, H.J.M.; Olsen, Allan Gylling; Willumsen, Niels J.

    1994-01-01

    ) were found in vivo, when toads adapted to Ringer solution were transferred to tap water containing tracer amounts of (32P) phosphate and (14C) acetate. PE could play a role in the formation of a "hydrophilic" environment and thereby, e.g. stabilise the integral membrane proteins that regulate...

  3. Channel Power in Multi-Channel Environments

    NARCIS (Netherlands)

    M.G. Dekimpe (Marnik); B. Skiera (Bernd)

    2004-01-01

    textabstractIn the literature, little attention has been paid to instances where companies add an Internet channel to their direct channel portfolio. However, actively managing multiple sales channels requires knowing the customers’ channel preferences and the resulting channel power. Two key compon

  4. Up-Regulatory Effects of Curcumin on Large Conductance Ca2+-Activated K+ Channels.

    Directory of Open Access Journals (Sweden)

    Qijing Chen

    Full Text Available Large conductance Ca2+-activated potassium channels (BK are targets for research that explores therapeutic means to various diseases, owing to the roles of the channels in mediating multiple physiological processes in various cells and tissues. We investigated the pharmacological effects of curcumin, a compound isolated from the herb Curcuma longa, on BK channels. As recorded by whole-cell patch-clamp, curcumin increased BK (α and BK (α+β1 currents in transfected HEK293 cells as well as the current density of BK in A7r5 smooth muscle cells in a dose-dependent manner. By incubating with curcumin for 24 hours, the current density of exogenous BK (α in HEK293 cells and the endogenous BK in A7r5 cells were both enhanced notably, though the steady-state activation of the channels did not shift significantly, except for BK (α+β1. Curcumin up-regulated the BK protein expression without changing its mRNA level in A7r5 cells. The surface expression and the half-life of BK channels were also increased by curcumin in HEK293 cells. These effects of curcumin were abolished by MG-132, a proteasome inhibitor. Curcumin also increased ERK 1/2 phosphorylation, while inhibiting ERK by U0126 attenuated the curcumin-induced up-regulation of BK protein expression. We also observed that the curcumin-induced relaxation in the isolated rat aortic rings was significantly attenuated by paxilline, a BK channel specific blocker. These results show that curcumin enhances the activity of the BK channels by interacting with BK directly as well as enhancing BK protein expression through inhibiting proteasomal degradation and activating ERK signaling pathway. The findings suggest that curcumin is a potential BK channel activator and provide novel insight into its complicated pharmacological effects and the underlying mechanisms.

  5. Cyclic 3'-5'-adenosine monophosphate binds to annexin I and regulates calcium-dependent membrane aggregation and ion channel activity.

    Science.gov (United States)

    Cohen, B E; Lee, G; Arispe, N; Pollard, H B

    1995-12-27

    The annexin (Anx) gene family comprises a set of calcium-dependent membrane binding proteins, which have been implicated in a wide variety of cellular processes including membrane fusion and calcium channel activity. We report here that cAMP activates Ca(2+)-dependent aggregation of both phosphatidylserine (PS) liposomes and bovine chromaffin granules driven by [des 1-12]annexin I (lipocortin I, Anx1). The mechanism of cAMP action involves an increase in AnxI-dependent cooperativity on the rate of such a reaction without affecting the corresponding k1/2 values. Cyclic AMP causes the values of the Hill coefficient (nH) for AnxI to change from 3 to 6 in both PS liposomes and chromaffin granules. By contrast, ATP inhibits the rate of aggregation activity without affecting the cooperativity or the extent of aggregation process. We were also able to photolabel Anx1 specifically with an 8-azido analogue of cAMP by a calcium-independent process. Such a process is saturable, yielding a Kd = 0.8 microM by Scatchard analysis. Specific displacement occurs in the presence of cAMP and ATP. Finally, we found that cAMP alters the conductance of calcium channels formed by AnxI in planar lipid bilayers. We interpret these data to indicate that AnxI binds both calcium and cAMP independently, and that both actions have functional consequences. This is the first report of a nucleotide binding function for a member of the annexin gene family.

  6. Neural KCNQ (Kv7) channels

    OpenAIRE

    Brown, David A.; Passmore, Gayle M.

    2009-01-01

    KCNQ genes encode five Kv7 K+ channel subunits (Kv7.1–Kv7.5). Four of these (Kv7.2–Kv7.5) are expressed in the nervous system. Kv7.2 and Kv7.3 are the principal molecular components of the slow voltage-gated M-channel, which widely regulates neuronal excitability, although other subunits may contribute to M-like currents in some locations. M-channels are closed by receptors coupled to Gq such as M1 and M3 muscarinic receptors; this increases neuronal excitability and underlies some forms of c...

  7. KCa3.1/IK1 Channel Regulation by cGMP-Dependent Protein Kinase (PKG) via Reactive Oxygen Species and CaMKII in Microglia: An Immune Modulating Feedback System?

    Science.gov (United States)

    Ferreira, Roger; Wong, Raymond; Schlichter, Lyanne C

    2015-01-01

    The intermediate conductance Ca(2+)-activated K(+) channel, KCa3.1 (IK1/SK4/KCNN4) is widely expressed in the innate and adaptive immune system. KCa3.1 contributes to proliferation of activated T lymphocytes, and in CNS-resident microglia, it contributes to Ca(2+) signaling, migration, and production of pro-inflammatory mediators (e.g., reactive oxygen species, ROS). KCa3.1 is under investigation as a therapeutic target for CNS disorders that involve microglial activation and T cells. However, KCa3.1 is post-translationally regulated, and this will determine when and how much it can contribute to cell functions. We previously found that KCa3.1 trafficking and gating require calmodulin (CaM) binding, and this is inhibited by cAMP kinase (PKA) acting at a single phosphorylation site. The same site is potentially phosphorylated by cGMP kinase (PKG), and in some cells, PKG can increase Ca(2+), CaM activation, and ROS. Here, we addressed KCa3.1 regulation through PKG-dependent pathways in primary rat microglia and the MLS-9 microglia cell line, using perforated-patch recordings to preserve intracellular signaling. Elevating cGMP increased both the KCa3.1 current and intracellular ROS production, and both were prevented by the selective PKG inhibitor, KT5823. The cGMP/PKG-evoked increase in KCa3.1 current in intact MLS-9 microglia was mediated by ROS, mimicked by applying hydrogen peroxide (H2O2), inhibited by a ROS scavenger (MGP), and prevented by a selective CaMKII inhibitor (mAIP). Similar results were seen in alternative-activated primary rat microglia; their KCa3.1 current required PKG, ROS, and CaMKII, and they had increased ROS production that required KCa3.1 activity. The increase in current apparently did not result from direct effects on the channel open probability (P o) or Ca(2+) dependence because, in inside-out patches from transfected HEK293 cells, single-channel activity was not affected by cGMP, PKG, H2O2 at normal or elevated intracellular Ca(2+). The

  8. LDPC Code Design for Nonuniform Power-Line Channels

    Directory of Open Access Journals (Sweden)

    Sanaei Ali

    2007-01-01

    Full Text Available We investigate low-density parity-check code design for discrete multitone channels over power lines. Discrete multitone channels are well modeled as nonuniform channels, that is, different bits experience various channel parameters. We propose a coding system for discrete multitone channels that allows for using a single code over a nonuniform channel. The number of code parameters for the proposed system is much greater than the number of code parameters in conventional channel. Therefore, search-based optimization methods are impractical. We first formulate the problem of optimizing the rate of an irregular low-density parity-check code, with guaranteed convergence over a general nonuniform channel, as an iterative linear programming which is significantly more efficient than search-based methods. Then we use this technique for a typical power-line channel. The methodology of this paper is directly applicable to all decoding algorithms for which a density evolution analysis is possible.

  9. Na(+) -Activated K(+) Channels in Rat Supraoptic Neurones.

    Science.gov (United States)

    Bansal, V; Fisher, T E

    2016-06-01

    The magnocellular neurosecretory cells (MNCs) of the hypothalamus secrete the neurohormones vasopressin and oxytocin. The systemic release of these hormones depends on the rate and pattern of MNC firing and it is therefore important to identify the ion channels that contribute to the electrical behaviour of MNCs. In the present study, we report evidence for the presence of Na(+) -activated K(+) (KN a ) channels in rat MNCs. KN a channels mediate outwardly rectifying K(+) currents activated by the increases in intracellular Na(+) that occur during electrical activity. Although the molecular identity of native KN a channels is unclear, their biophysical properties are consistent with those of expressed Slick (slo 2.1) and Slack (slo 2.2) proteins. Using immunocytochemistry and Western blot experiments, we found that both Slick and Slack proteins are expressed in rat MNCs. Using whole cell voltage clamp techniques on acutely isolated rat MNCs, we found that inhibiting Na(+) influx by the addition of the Na(+) channel blocker tetrodotoxin or the replacement of Na(+) in the external solution with Li(+) caused a significant decrease in sustained outward currents. Furthermore, the evoked outward current density was significantly higher in rat MNCs using patch pipettes containing 60 mm Na(+) than it was when patch pipettes containing 0 mm Na(+) were used. Our data show that functional KN a channels are expressed in rat MNCs. These channels could contribute to the activity-dependent afterhyperpolarisations that have been identified in the MNCs and thereby play a role in the regulation of their electrical behaviour. PMID:27091544

  10. Laparoscopic real-time en-face differential optical topography of near-surface heterogeneity by using an applicator probe with the maximum-density radially alternating illumination and detection fiber-channels

    CERN Document Server

    Piao, Daqing; Holyoak, G Reed; Patel, Sanjay

    2016-01-01

    We demonstrate a laparoscopic applicator probe and a method thereof for real-time en-face topographic mapping of near-surface heterogeneity for potential use in intraoperative margin assessment during minimally invasive oncological procedures. The probe fits in a 12mm port and houses at its maximum 128 copper-coated 750um fibers that form radially alternating illumination (70 fibers) and detection (58 fibers) channels. By simultaneously illuminating the 70 source channels of the probe that is in contact with a scattering medium and concurrently measuring the light diffusely propagated to the 58 detector channels, the presence of near-surface optical heterogeneities can be resolved in an en-face 9.5mm field-of-view in real-time. Visualization of a subsurface margin of strong attenuation contrast at a depth up to 3mm is demonstrated at one wavelength at a frame rate of 1.25Hz.

  11. Enhanced expression of extracellular calcium sensing receptor in monocyte-differentiated versus undifferentiated HL-60 cells: potential role in regulation of a nonselective cation channel

    Science.gov (United States)

    Yamaguchi, T.; Ye, C.; Chattopadhyay, N.; Sanders, J. L.; Vassilev, P. M.; Brown, E. M.; O'Malley, B. W. (Principal Investigator)

    2000-01-01

    Human promyelocytic leukemia cells (HL-60) have been used widely as a model for studying the differentiation of hematopoietic progenitor cells in vitro. After treatment with phorbol-12-myristate-13-acetate (PMA) or 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], HL-60 cells differentiate into cells with the phenotype of monocytes/macrophages. We previously showed that peripheral blood monocytes and the murine J774 monocytic cell line express the CaR, and myeloid progenitors in the bone marrow and myeloid cells in peripheral blood other than monocytes express lower levels of the CaR. Therefore, we investigated whether undifferentiated HL-60 cells express a functional G protein-coupled, extracellular calcium (Ca(2+)(o))-sensing receptor (CaR) and if the expression of the CaR increases as these cells differentiate along the monocytic lineage. The use of reverse transcription-polymerase chain reaction (RT-PCR) with CaR-specific primers, followed by sequencing of the amplified products, identified an authentic CaR transcript in undifferentiated HL-60 cells. Both immunocytochemistry and Western blot analysis using a CaR-specific antiserum detected low levels of CaR protein expression in undifferentiated HL-60 cells. The levels of CaR protein increased considerably following treatment of the cells with PMA (50 nM) or 1,25(OH)(2)D(3) (100 nM) for 5 days. Northern analysis using a CaR-specific riboprobe identified CaR transcripts in undifferentiated HL-60 cells, but CaR mRNA levels did not change appreciably after treatment with either agent, suggesting that upregulation of CaR protein occurs at a translational level. PMA-treated HL-60 cells expressed a nonselective cation channel (NCC), and the calcimimetic CaR activator, NPS R-467, but not its less active stereoisomer, NPS S-467, as well as the polycationic CaR agonist, neomycin, activated this NCC, demonstrating that the CaR expressed in these cells is functionally active. Therefore, HL-60 cells exhibit an increase in Ca

  12. TGF-β1-elevated TRPM7 channel regulates collagen expression in hepatic stellate cells via TGF-β1/Smad pathway

    International Nuclear Information System (INIS)

    Transdifferentiation of hepatic stellate cells (HSCs) into myofibroblasts plays a critical role in the development of liver fibrosis, since myofibroblasts are the key cells responsible for excessive deposition of ECM proteins. Transient receptor potential melastatin 7 (TRPM7), a non-selective cation channel with protein serine/threonine kinase activity, has been demonstrated to function in the proliferation of activated HSCs. Here, we investigated the functional role of TRPM7 in collagen deposition in activated HSC-T6 cells (a rat hepatic stellate cell line). TRPM7 mRNA and protein were measured by Real-time PCR and Western blot in TGF-β1-activated HSC-T6 cells in vitro. Results demonstrated that TRPM7 protein was dramatically increased in fibrotic human livers. Stimulation of HSC-T6 cells with TGF-β1 increased TRPM7 mRNA and protein level in a time-dependent manner. Nevertheless, TGF-β1-elicited upregulation of TRPM7 in HSC-T6 cells was abrogated by SB431542 (TGF-β1 receptor blocker) or SIS3 (inhibitor of Smad3 phosphorylation). Additionally, blockade of TRPM7 channels with non-specific TRPM7 blocker 2-APB or synthetic siRNA targeting TRPM7 attenuated TGF-β1-induced expression of myofibroblast markers, as measured by the induction of α-SMA and Col1α1. Silencing TRPM7 also increased the ratio of MMPs/TIMPs by increasing MMP-13 expression and decreasing TIMP-1 and TIMP-2 levels. Strikingly, phosphorylation of p-Smad2 and p-Smad3, associated with collagen production, was decreased in TRPM7 deficient HSC-T6 cells. These observations suggested that TGF-β1 elevates TRPM7 expression in HSCs via Smad3-dependant mechanisms, which in turn contributes Smad protein phosphorylation, and subsequently increases fibrous collagen expression. Therefore, TRPM7 may constitute a useful target for the treatment of liver fibrosis. - Highlights: • Upregulation of TRPM7 protein in human fibrotic livers • Upregulation of TRPM7 by TGF-β1 elicited Smad signaling in HSC-T6 cells

  13. TGF-β1-elevated TRPM7 channel regulates collagen expression in hepatic stellate cells via TGF-β1/Smad pathway

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Ling, E-mail: fangling_1984@126.com [School of Pharmacy, Anhui Medical University, Mei Shan Road, Hefei, Anhui Province 230032 (China); Institute for Liver Diseases of Anhui Medical University, Mei Shan Road, Hefei, Anhui Province 230032 (China); Key Laboratory of Anti-inflammatory and Immune Medicine, Anhui Medical University, Ministry of Education, Mei Shan Road, Hefei, Anhui Province 230032 (China); The First Affiliated Hospital of Anhui Medical University, Mei Shan Road, Hefei, Anhui Province 230032 (China); Huang, Cheng; Meng, Xiaoming; Wu, Baoming; Ma, Taotao; Liu, Xuejiao; Zhu, Qian [School of Pharmacy, Anhui Medical University, Mei Shan Road, Hefei, Anhui Province 230032 (China); Institute for Liver Diseases of Anhui Medical University, Mei Shan Road, Hefei, Anhui Province 230032 (China); Key Laboratory of Anti-inflammatory and Immune Medicine, Anhui Medical University, Ministry of Education, Mei Shan Road, Hefei, Anhui Province 230032 (China); Zhan, Shuxiang [School of Pharmacy, Anhui Medical University, Mei Shan Road, Hefei, Anhui Province 230032 (China); Institute for Liver Diseases of Anhui Medical University, Mei Shan Road, Hefei, Anhui Province 230032 (China); Key Laboratory of Anti-inflammatory and Immune Medicine, Anhui Medical University, Ministry of Education, Mei Shan Road, Hefei, Anhui Province 230032 (China); The First Affiliated Hospital of Anhui Medical University, Mei Shan Road, Hefei, Anhui Province 230032 (China); Li, Jun, E-mail: lj@ahmu.edu.cn [School of Pharmacy, Anhui Medical University, Mei Shan Road, Hefei, Anhui Province 230032 (China); Institute for Liver Diseases of Anhui Medical University, Mei Shan Road, Hefei, Anhui Province 230032 (China); Key Laboratory of Anti-inflammatory and Immune Medicine, Anhui Medical University, Ministry of Education, Mei Shan Road, Hefei, Anhui Province 230032 (China)

    2014-10-15

    Transdifferentiation of hepatic stellate cells (HSCs) into myofibroblasts plays a critical role in the development of liver fibrosis, since myofibroblasts are the key cells responsible for excessive deposition of ECM proteins. Transient receptor potential melastatin 7 (TRPM7), a non-selective cation channel with protein serine/threonine kinase activity, has been demonstrated to function in the proliferation of activated HSCs. Here, we investigated the functional role of TRPM7 in collagen deposition in activated HSC-T6 cells (a rat hepatic stellate cell line). TRPM7 mRNA and protein were measured by Real-time PCR and Western blot in TGF-β1-activated HSC-T6 cells in vitro. Results demonstrated that TRPM7 protein was dramatically increased in fibrotic human livers. Stimulation of HSC-T6 cells with TGF-β1 increased TRPM7 mRNA and protein level in a time-dependent manner. Nevertheless, TGF-β1-elicited upregulation of TRPM7 in HSC-T6 cells was abrogated by SB431542 (TGF-β1 receptor blocker) or SIS3 (inhibitor of Smad3 phosphorylation). Additionally, blockade of TRPM7 channels with non-specific TRPM7 blocker 2-APB or synthetic siRNA targeting TRPM7 attenuated TGF-β1-induced expression of myofibroblast markers, as measured by the induction of α-SMA and Col1α1. Silencing TRPM7 also increased the ratio of MMPs/TIMPs by increasing MMP-13 expression and decreasing TIMP-1 and TIMP-2 levels. Strikingly, phosphorylation of p-Smad2 and p-Smad3, associated with collagen production, was decreased in TRPM7 deficient HSC-T6 cells. These observations suggested that TGF-β1 elevates TRPM7 expression in HSCs via Smad3-dependant mechanisms, which in turn contributes Smad protein phosphorylation, and subsequently increases fibrous collagen expression. Therefore, TRPM7 may constitute a useful target for the treatment of liver fibrosis. - Highlights: • Upregulation of TRPM7 protein in human fibrotic livers • Upregulation of TRPM7 by TGF-β1 elicited Smad signaling in HSC-T6 cells

  14. The molecular physiology of CRAC channels

    OpenAIRE

    Prakriya, Murali

    2009-01-01

    The Ca2+release-activated Ca2+ (CRAC) channel is a highly Ca2+-selective store-operated channel expressed in T cells, mast cells, and various other tissues. CRAC channels regulate critical cellular processes such as gene expression, motility, and the secretion of inflammatory mediators. The identification of Orai1, a key subunit of the CRAC channel pore, and STIM1, the endoplasmic reticulum (ER) Ca2+ sensor, have provided the tools to illuminate the mechanisms of regulation and the pore prope...

  15. Acoustic Diagnostics of Plasma Channels Induced by Intense Femtosecond Laser Pulses in Air

    Institute of Scientific and Technical Information of China (English)

    HAO Zuo-Qiang; WEI Zhi-Yi; YU Jin; ZHANG Jie; LI Yu-Tong; YUAN Xiao-Hui; ZHENG Zhi-Yuan; WANG Peng; WANG Zhao-Hua; LING Wei-Jun

    2005-01-01

    @@ Long plasma channels induced by femtosecond laser pulses in air are diagnosed using the sonographic method. By detecting the sound signals along the channels, the length and the electron density of the channels are measured.

  16. Chloride Channels: Often enigmatic, rarely predictable

    Science.gov (United States)

    Duran, Charity; Thompson, Christopher H.; Xiao, Qinghuan; Hartzell, Criss

    2010-01-01

    Until recently, anion (Cl−) channels have received considerably less attention than cation channels. One reason for this may be that many Cl− channels perform functions that might be considered cell biological, like fluid secretion and cell volume regulation, whereas cation channels have historically been associated with cellular excitability that typically happens more rapidly. In this review, we discuss the recent explosion of interest in Cl− channels with special emphasis on new and often surprising developments over the last 5 years. This is exemplified by the findings that more than half of the ClC family members are antiporters, and not channels as was previously thought, and that bestrophins, previously prime candidates for Ca2+-activated Cl− channels, have been supplanted by the newly discovered anoctamins and now hold a tenuous position in the Cl− channel world. PMID:19827947

  17. Effects of Different Fertilizer Rates, Planting Density and Plant Growth Regulators on Yield of Soybean Cultivar Tiedou 68%肥密化控对铁豆68号产量的影响

    Institute of Scientific and Technical Information of China (English)

    董友魁; 刘德恒; 韩艳红

    2015-01-01

    采用正交试验对影响铁豆68号产量的密度、施肥量、叶面喷肥、化控次数4因素进行研究,结果表明,对大豆新品种铁豆68号产量影响的顺序是:施肥量、密度、叶面喷肥、化控次数;铁豆68号最理想的栽培技术模式是密度1.1万株/667m2,施肥量为20 kg/667m2,叶面喷肥1次,化控次数1次。%In order to examine the effects of planting density, fertilization rates, foliar application and times of plant growth regulator application during the growing period of soybean cultivar Tiedou 68, the orthogonal experimental design was used to carry out data analysis. The result indicated that the order of cultivation practices on soybean new variety Tiedou 68 was: fertilization rate, planting density, foliar application and times of plant growth regulator application. The ideal cultural pattern of cultivar Tiedou 68 was planting density of 11 000/667m2, fertilization rate of 20 kg/667m2, and one time of foliar and plant growth regulator application.

  18. Boiling Heat Transfer on Porous Surfaces with Vapor Channels

    Institute of Scientific and Technical Information of China (English)

    吴伟; 杜建华; 王补宣

    2002-01-01

    Boiling heat transfer on porous coated surfaces with vapor channels was investigated experimentally to determine the effects of the size and density of the vapor channels on the boiling heat transfer. Observations showed that bubbles escaping from the channels enhanced the heat transfer. Three regimes were identified: liquid flooding, bubbles in the channel and the bottom drying out region. The maximum heat transfer occurred for an optimum vapor channel density and the boiling heat transfer performance was increased if the channels were open to the bottom of the porous coating.

  19. Channel Networks

    Science.gov (United States)

    Rinaldo, Andrea; Rodriguez-Iturbe, Ignacio; Rigon, Riccardo

    This review proceeds from Luna Leopold's and Ronald Shreve's lasting accomplishments dealing with the study of random-walk and topologically random channel networks. According to the random perspective, which has had a profound influence on the interpretation of natural landforms, nature's resiliency in producing recurrent networks and landforms was interpreted to be the consequence of chance. In fact, central to models of topologically random networks is the assumption of equal likelihood of any tree-like configuration. However, a general framework of analysis exists that argues that all possible network configurations draining a fixed area are not necessarily equally likely. Rather, a probability P(s) is assigned to a particular spanning tree configuration, say s, which can be generally assumed to obey a Boltzmann distribution: P(s) % e^-H(s)/T, where T is a parameter and H(s) is a global property of the network configuration s related to energetic characters, i.e. its Hamiltonian. One extreme case is the random topology model where all trees are equally likely, i.e. the limit case for T6 4 . The other extreme case is T 6 0, and this corresponds to network configurations that tend to minimize their total energy dissipation to improve their likelihood. Networks obtained in this manner are termed optimal channel networks (OCNs). Observational evidence suggests that the characters of real river networks are reproduced extremely well by OCNs. Scaling properties of energy and entropy of OCNs suggest that large network development is likely to effectively occur at zero temperature (i.e. minimizing its Hamiltonian). We suggest a corollary of dynamic accessibility of a network configuration and speculate towards a thermodynamics of critical self-organization. We thus conclude that both chance and necessity are equally important ingredients for the dynamic origin of channel networks---and perhaps of the geometry of nature.

  20. Glucose- and interleukin-1beta-induced beta-cell apoptosis requires Ca2+ influx and extracellular signal-regulated kinase (ERK) 1/2 activation and is prevented by a sulfonylurea receptor 1/inwardly rectifying K+ channel 6.2 (SUR/Kir6.2) selective potassium channel opener in human islets

    DEFF Research Database (Denmark)

    Maedler, Kathrin; Størling, Joachim; Sturis, Jeppe;

    2004-01-01

    -regulated kinase (ERK) 1/2, an effect that was abrogated by 3 micromol/l NN414. Similarly, 1 micromol/l of the mitogen-activated protein kinase/ERK kinase 1/2 inhibitor PD098059 or 1 micromol/l of the l-type Ca(2+) channel blocker nimodipine prevented glucose- and IL-1beta-induced ERK activation, beta......-cell apoptosis, and impaired function. Finally, islet release of IL-1beta in response to high glucose could be abrogated by nimodipine, NN414, or PD098059. Thus, in human islets, glucose- and IL-1beta-induced beta-cell secretory dysfunction and apoptosis are Ca(2+) influx and ERK dependent and can be prevented...

  1. KCa3.1/IK1 channel regulation by cGMP-dependent protein kinase (PKG via reactive oxygen species and CaMKII in microglia: An immune modulating feedback system?

    Directory of Open Access Journals (Sweden)

    Roger eFerreira

    2015-04-01

    Full Text Available The intermediate conductance Ca2+-activated K+ channel, KCa3.1 (IK1/SK4/KCNN4 is widely expressed in the innate and adaptive immune system. KCa3.1 contributes to proliferation of activated T lymphocytes and, in CNS-resident microglia, it contributes to Ca2+ signaling, migration and production of pro-inflammatory mediators (e.g., reactive oxygen species; ROS. KCa3.1 is under investigation as a therapeutic target for CNS disorders that involve microglial activation and T cells. However, KCa3.1 is post-translationally regulated, and this will determine when and how much it can contribute to cell functions. We previously found that KCa3.1 trafficking and gating require calmodulin (CaM binding, and this is inhibited by cAMP kinase (PKA acting at a single phosphorylation site. The same site is potentially phosphorylated by cGMP kinase (PKG and, in some cells; PKG can increase Ca2+, CaM activation and ROS. Here, we addressed KCa3.1 regulation through PKG-dependent pathways in primary rat microglia and the MLS-9 microglia cell line, using perforated-patch recordings to preserve intracellular signaling. Elevating cGMP increased both the KCa3.1 current and intracellular ROS production, and both were prevented by the selective PKG inhibitor, KT5823. The cGMP/PKG-evoked increase in KCa3.1 current in intact MLS-9 microglia was mediated by ROS, mimicked by applying hydrogen peroxide (H2O2, inhibited by a ROS scavenger (MGP, and prevented by a selective CaMKII inhibitor (mAIP. Similar results were seen in alternative-activated primary rat microglia; their KCa3.1 current required PKG, ROS and CaMKII, and they had increased ROS production that required KCa3.1 activity. The increase in current apparently did not result from direct effects on the channel open probability (Po or Ca2+ dependence because, in inside-out patches from transfected HEK293 cells, single-channel activity was not affected by cGMP, PKG, H2O2 at normal or elevated intracellular Ca2+.

  2. The activation effect of nobiletin on cystic fibrosis transmembrane conductance regulator chloride channel%川陈皮素对囊性纤维化跨膜传导调节因子的激活作用

    Institute of Scientific and Technical Information of China (English)

    杨爽; 于波; 张耀方; 王雪; 杨红

    2013-01-01

    Aim of the present study is to investigate activation effect of nobiletin on cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel activity.CFTR-mediated iodide influx assay and patch-clamp tests were done on FRT cells stably co-transfected with human CFTR and EYFP/H148Q.Nobiletin potently activated CFTR chloride channel activity in a dose-and time-dependent manner.The CFTR blocker CFTRinh-172 could completely reverse the effect.Preliminary mechanism study indicated that nobiletin activated CFTR chloride channel through a direct binding way.In addition,ex vivo tests done on mice trachea showed that nobiletin time-dependently stimulated submucosal gland fluid secretion.Nobiletin may be a therapeutic lead compound in treating CFTR-related diseases including disseminated bronchiectasis.%本实验利用荧光淬灭实验和膜片钳技术在稳定表达人CFTR和荧光绿蛋白突变体EYFP/H148Q的Fischer大鼠甲状腺上皮细胞(Fischer rat thyroid,FRT)上,测定川陈皮素(nobiletin)对囊性纤维化跨膜传导因子(cystic fibrosis transmembrane conductance regulator,CFTR)氯离子通道的激活作用.结果发现,川陈皮素以剂量依赖的方式激活CFTR氯离子通道的C1-转运活性,且这种活性是快速、可逆的,并能够被CFTR特异性抑制剂CFTRinh-172完全抑制.初步的分子机制研究表明,川陈皮素是以与CFTR直接作用来激活通道活性的.进一步的研究结果显示,川陈皮素能够有效刺激小鼠气管黏膜下腺液体分泌速度.因此,川陈皮素可能发展成为治疗包括支气管扩张在内的CFTR相关疾病的先导药物.

  3. Cardiac calcium release channel (ryanodine receptor) in control and cardiomyopathic human hearts: mRNA and protein contents are differentially regulated.

    Science.gov (United States)

    Sainte Beuve, C; Allen, P D; Dambrin, G; Rannou, F; Marty, I; Trouvé, P; Bors, V; Pavie, A; Gandgjbakch, I; Charlemagne, D

    1997-04-01

    Abnormal intracellular calcium handling in cardiomyopathic human hearts has been associated with an impaired function of the sarcoplasmic reticulum, but previous reports on the gene expression of the ryanodine receptors (Ry2) are contradictory. We measured the mRNA levels, the protein levels and the number of high affinity [3H]ryanodine binding sites in the left ventricle of non-failing (n = 9) and failing human hearts [idiopathic dilated (IDCM n = 16), ischemic (ICM n = 7) or mixed (MCM n = 8) cardiomyopathies]. Ry2 mRNA levels were significantly reduced in IDCM (-30%) and unchanged in MCM and ICM and Ry2 protein levels were similar. In contrast, we observed a two-fold increase in the number of high affinity Ry2 (B(max) = 0.43 +/- 0.11 v 0.22 +/- 0.13 pmol/mg protein, respectively; P<0.01) and an unchanged K(d). Furthermore, levels of myosin heavy chain mRNA and protein per g of tissue were similar in failing and non-failing hearts, suggesting that the observed differences in Ry2 are not caused by the increase in fibrosis in failing heart. Therefore, the dissociation between the two-fold increase in the number of high affinity ryanodine receptors observed in all failing hearts and the slightly decreased mRNA level or unchanged protein level suggests that the ryanodine binding properties are affected in failing myocardium and that such modifications rather than a change in gene expression alter the channel activity and could contribute to abnormalities in intracellular Ca2+ handling. PMID:9160875

  4. Structure of conducting channel of lightning

    NARCIS (Netherlands)

    Alanakyan, Yu. R.

    2013-01-01

    The spatial distribution of the plasma density in a lightning channel is studied theoretically. It is shown that the electric-field double layer is formed at the channel boundary. In this case, the electron temperature changes abruptly and ions are accelerated by the electric field of the double lay

  5. Road density

    Data.gov (United States)

    U.S. Environmental Protection Agency — Road density is generally highly correlated with amount of developed land cover. High road densities usually indicate high levels of ecological disturbance. More...

  6. Voltage-gated proton channels.

    Science.gov (United States)

    Decoursey, Thomas E

    2012-04-01

    Voltage-gated proton channels, HV1, have vaulted from the realm of the esoteric into the forefront of a central question facing ion channel biophysicists, namely, the mechanism by which voltage-dependent gating occurs. This transformation is the result of several factors. Identification of the gene in 2006 revealed that proton channels are homologues of the voltage-sensing domain of most other voltage-gated ion channels. Unique, or at least eccentric, properties of proton channels include dimeric architecture with dual conduction pathways, perfect proton selectivity, a single-channel conductance approximately 10(3) times smaller than most ion channels, voltage-dependent gating that is strongly modulated by the pH gradient, ΔpH, and potent inhibition by Zn(2+) (in many species) but an absence of other potent inhibitors. The recent identification of HV1 in three unicellular marine plankton species has dramatically expanded the phylogenetic family tree. Interest in proton channels in their own right has increased as important physiological roles have been identified in many cells. Proton channels trigger the bioluminescent flash of dinoflagellates, facilitate calcification by coccolithophores, regulate pH-dependent processes in eggs and sperm during fertilization, secrete acid to control the pH of airway fluids, facilitate histamine secretion by basophils, and play a signaling role in facilitating B-cell receptor mediated responses in B-lymphocytes. The most elaborate and best-established functions occur in phagocytes, where proton channels optimize the activity of NADPH oxidase, an important producer of reactive oxygen species. Proton efflux mediated by HV1 balances the charge translocated across the membrane by electrons through NADPH oxidase, minimizes changes in cytoplasmic and phagosomal pH, limits osmotic swelling of the phagosome, and provides substrate H(+) for the production of H2O2 and HOCl, reactive oxygen species crucial to killing pathogens.

  7. Reduction of Skin pH during Treatment for Palmoplantar Hyperhidrosis: A Conjecture on the Role of pH-Regulated Water Channel, i.e. Aquaporin

    Directory of Open Access Journals (Sweden)

    Kyoko Nakahigashi

    2013-04-01

    Full Text Available Primary palmoplantar hyperhidrosis (PPH is a disorder that involves excessive sweating on the palms and soles. Although the pathophysiology of PPH remains unknown, some treatments, including topical aluminum chloride (AC and tap water iontophoresis (TWI, are effective at suppressing the perspiration. Herein, we report the kinetics of the skin pH of two cases of PPH treated with AC and TWI. We found that the skin pH decreased in accordance with the reduction in sweating. This finding indicates that the reduction in sweating may be attributed to the reduction of skin pH in AC and TWI. Whether or not the pH-regulated function of aquaporin can explain this finding remains unknown.

  8. Central nervous system neuropeptide Y regulates mediators of hepatic phospholipid remodeling and very low-density lipoprotein triglyceride secretion via sympathetic innervation

    NARCIS (Netherlands)

    Rojas, Jennifer M; Bruinstroop, E.; Printz, Richard L; Alijagic-Boers, Aldijana; Foppen, E.; Turney, Maxine K; George, Leena; Beck-Sickinger, Annette G; Kalsbeek, A.; Niswender, Kevin D

    2015-01-01

    OBJECTIVE: Elevated very low-density lipoprotein (VLDL)-triglyceride (TG) secretion from the liver contributes to an atherogenic dyslipidemia that is associated with obesity, diabetes and the metabolic syndrome. Numerous models of obesity and diabetes are characterized by increased central nervous s

  9. Ion Channels in Brain Metastasis.

    Science.gov (United States)

    Klumpp, Lukas; Sezgin, Efe C; Eckert, Franziska; Huber, Stephan M

    2016-01-01

    Breast cancer, lung cancer and melanoma exhibit a high metastatic tropism to the brain. Development of brain metastases severely worsens the prognosis of cancer patients and constrains curative treatment options. Metastasizing to the brain by cancer cells can be dissected in consecutive processes including epithelial-mesenchymal transition, evasion from the primary tumor, intravasation and circulation in the blood, extravasation across the blood-brain barrier, formation of metastatic niches, and colonization in the brain. Ion channels have been demonstrated to be aberrantly expressed in tumor cells where they regulate neoplastic transformation, malignant progression or therapy resistance. Moreover, many ion channel modulators are FDA-approved drugs and in clinical use proposing ion channels as druggable targets for future anti-cancer therapy. The present review article aims to summarize the current knowledge on the function of ion channels in the different processes of brain metastasis. The data suggest that certain channel types involving voltage-gated sodium channels, ATP-release channels, ionotropic neurotransmitter receptors and gap junction-generating connexins interfere with distinct processes of brain metastazation. PMID:27618016

  10. Channeling experiment

    International Nuclear Information System (INIS)

    Channeling of water flow and tracer transport in real fractures in a granite body at Stripa have been investigated experimentally. The experimental site was located 360 m below the ground level. Two kinds of experiments were performed. In the single hole experiments, 20 cm diameter holes were drilled about 2.5 m into the rock in the plane of the fracture. Specially designed packers were used to inject water into the fracture in 5 cm intervals all along the fracture trace in the hole. The variation of the injection flowrates along the fracture were used to determine the transmissivity variations in the fracture plane. Detailed photographs were taken from inside the hole and the visual fracture aperture was compared with the injection flowrates in the same locations. Geostatistical methods were used to evaluate the results. Five holes were measured in great detail. In addition 7 holes were drilled and scanned by simpler packer systems. A double hole experiment was performed where two parallel holes were drilled in the same fracture plane at nearly 2 m distance. Pressure pulse tests were made between the holes in both directions. Tracers were injected in 5 locations in one hole and monitored for in many locations in the other hole. The single hole experiment and the double hole experiment show that most of the fracture planes are tight but that there are open sections which form connected channels over distances of at least 2 meters. It was also found in the double hole experiment that the investigated fracture was intersected by at least one fracture between the two holes which diverted a large amount of the injected tracers to several distant locations at the tunnel wall. (authours)

  11. Phosphodiesterase 4B in the cardiac L-type Ca²⁺ channel complex regulates Ca²⁺ current and protects against ventricular arrhythmias in mice.

    Science.gov (United States)

    Leroy, Jérôme; Richter, Wito; Mika, Delphine; Castro, Liliana R V; Abi-Gerges, Aniella; Xie, Moses; Scheitrum, Colleen; Lefebvre, Florence; Schittl, Julia; Mateo, Philippe; Westenbroek, Ruth; Catterall, William A; Charpentier, Flavien; Conti, Marco; Fischmeister, Rodolphe; Vandecasteele, Grégoire

    2011-07-01

    β-Adrenergic receptors (β-ARs) enhance cardiac contractility by increasing cAMP levels and activating PKA. PKA increases Ca²⁺-induced Ca²⁺ release via phosphorylation of L-type Ca²⁺ channels (LTCCs) and ryanodine receptor 2. Multiple cyclic nucleotide phosphodiesterases (PDEs) regulate local cAMP concentration in cardiomyocytes, with PDE4 being predominant for the control of β-AR-dependent cAMP signals. Three genes encoding PDE4 are expressed in mouse heart: Pde4a, Pde4b, and Pde4d. Here we show that both PDE4B and PDE4D are tethered to the LTCC in the mouse heart but that β-AR stimulation of the L-type Ca²⁺ current (ICa,L) is increased only in Pde4b-/- mice. A fraction of PDE4B colocalized with the LTCC along T-tubules in the mouse heart. Under β-AR stimulation, Ca²⁺ transients, cell contraction, and spontaneous Ca²⁺ release events were increased in Pde4b-/- and Pde4d-/- myocytes compared with those in WT myocytes. In vivo, after intraperitoneal injection of isoprenaline, catheter-mediated burst pacing triggered ventricular tachycardia in Pde4b-/- mice but not in WT mice. These results identify PDE4B in the CaV1.2 complex as a critical regulator of ICa,L during β-AR stimulation and suggest that distinct PDE4 subtypes are important for normal regulation of Ca²⁺-induced Ca²⁺ release in cardiomyocytes.

  12. Effect of down-regulation of voltage-gated sodium channel Nav1.7 on activation of astrocytes and microglia in DRG in rats with cancer pain

    Institute of Scientific and Technical Information of China (English)

    Jun Pan; Xiang-Jin Lin; Zhi-Heng Ling; You-Zhi Cai

    2015-01-01

    Objective:To evaluate the effect of down-regulation of Nav1.7 on the activation of astrocytes and microglia in DRG of rats with cancer pain, and explore the transmission of the nociceptive information.Methods:Lentiviral vector harboring RNAi sequence targeting theNav1.7gene was constructed, and Walker 256 breast cancer cell and morphine was injected to build the bone cancer pain model and morphine tolerance model in rats. Lentiviral vector was injected. Rats in each model were divided into 4 groups: model group, PBS group, vehicle group and LV-Nav1.7 group. The expression levels of GFAP and OX42 in dorsal root ganglia (DRG) were measured.Results: After the animal model was built,the level of Nav1.7, GFAP and OX42 was improved obviously with the time prolonged, which was statistically significant (P<0.05). The expression level of GFAP and OX42 in the DRG in the LV-Nav1.7 group declined obviously compared to the model group, PBS group and vehicle group (P<0.05).Conclusions:Intrathecal injection of Navl.7 shRNA lentiviral vector can reduce the expression of Nav1.7 and inhibit the activation of astrocytes and microglia in DRG. The effort is also effective in morphine tolerance bone cancer pain model rats.

  13. Effect of down-regulation of voltage-gated sodium channel Nav1.7 on activation of astrocytes and microglia in DRG in rats with cancer pain

    Institute of Scientific and Technical Information of China (English)

    Jun; Pan; Xiang-Jin; Lin; Zhi-Heng; Ling; You-Zhi; Cai

    2015-01-01

    Objective:To evaluate the effect of down-regulation of Nav1.7 on the activation of astrocytes and microglia in DRG of rats with cancer pain,and explore the transmission of the nociceptive information.Methods:Lentiviral vector harboring RNAi sequence targeting the Navl.7 gene was constructed,and Walker 256 breast cancer cell and morphine was injected to build the bone cancer pain model and morphine tolerance model in rats.Lentiviral vector was injected.Rats in each model were divided into 4 groups:model group,PBS group,vehicle group and LV-Nav1.7 group.The expression levels of GFAP and OX42 in dorsal root ganglia(DRG) were measured.Results:After the animal model was built,the level of Navl.7,GFAP and OX42 was improved obviously with the time prolonged,which was statistically significant(P<0.05).The expression level of GFAP and OX42 in the DRG in the LV-Navl.7 group declined obviously compared to the model group,PBS group and vehicle group(P<0.05).Conclusions:Intrathecal injection of Navl.7 shRNA lentiviral vector can reduce the expression of Nav1.7and inhibit the activation of astrocytes and microglia in DRG.The effort is also effective in morphine tolerance bone cancer pain model rats.

  14. Channel of Monetary Policy in Regulating the Real Estate Market in China%我国货币政策调控房地产市场的渠道研究

    Institute of Scientific and Technical Information of China (English)

    熊劼

    2014-01-01

    从货币政策传导机制的信贷渠道与汇率渠道方面入手,构建我国货币政策影响房地产市场的政策因素模型,以探讨货币政策调控工具对我国房地产市场的具体影响途径与效果。实证研究表明,我国2005年之后房价的持续上升与货币供应量、个人按揭贷款额度和汇率三者有一定关系。从长期来看,我国房地产市场景气程度与货币供应量、个人按揭贷款额和汇率长期存在稳定关系且呈正向变动。%Starting with the credit channel of monetary policy transmission mechanism and exchange rate channels, this paper builds a factor model of our country monetary policy influencing the real estate market policy, to discuss the specific impact of monetary policy regulation tools on the way and effect of the real estate market in China. Empirical study shows that after 2005, the sustained growth of the house price in our country has a certain relationship with the money supply, personal mortgage loan a-mount and exchange rate. In the long run, the prosperity degree of the real estate market of our country with the money supply, personal mortgage loan amount and exchange rate has a longstanding and positive relationship.

  15. The Influenza M2 Ectodomain Regulates the Conformational Equilibria of the Transmembrane Proton Channel: Insights from Solid-State Nuclear Magnetic Resonance.

    Science.gov (United States)

    Kwon, Byungsu; Hong, Mei

    2016-09-27

    The influenza M2 protein is the target of the amantadine family of antiviral drugs, and its transmembrane (TM) domain structure and dynamics have been extensively studied. However, little is known about the structure of the highly conserved N-terminal ectodomain, which contains epitopes targeted by influenza vaccines. In this study, we synthesized an M2 construct containing the N-terminal ectodomain and the TM domain, to understand the site-specific conformation and dynamics of the ectodomain and to investigate the effect of the ectodomain on the TM structure. We incorporated (13)C- and (15)N-labeled residues into both domains and measured their chemical shifts and line widths using solid-state nuclear magnetic resonance. The data indicate that the entire ectodomain is unstructured and dynamic, but the motion is slower for residues closer to the TM domain. (13)C line shapes indicate that this ecto-TM construct undergoes fast uniaxial rotational diffusion, like the isolated TM peptide, but drug binding increases the motional rates of the TM helix while slowing the local motion of the ectodomain residues that are close to the TM domain. Moreover, (13)C and (15)N chemical shifts indicate that the ectodomain shifts the conformational equilibria of the TM residues toward the drug-bound state even in the absence of amantadine, thus providing a molecular structural basis for the lower inhibitory concentration of full-length M2 compared to that of the ectodomain-truncated M2. We propose that this conformational selection may result from electrostatic repulsion between negatively charged ectodomain residues in the tetrameric protein. Together with the recent study of the M2 cytoplasmic domain, these results show that intrinsically disordered extramembrane domains in membrane proteins can regulate the functionally relevant conformation and dynamics of the structurally ordered TM domains.

  16. Lung density

    DEFF Research Database (Denmark)

    Garnett, E S; Webber, C E; Coates, G;

    1977-01-01

    The density of a defined volume of the human lung can be measured in vivo by a new noninvasive technique. A beam of gamma-rays is directed at the lung and, by measuring the scattered gamma-rays, lung density is calculated. The density in the lower lobe of the right lung in normal man during quiet...... breathing in the sitting position ranged from 0.25 to 0.37 g.cm-3. Subnormal values were found in patients with emphsema. In patients with pulmonary congestion and edema, lung density values ranged from 0.33 to 0.93 g.cm-3. The lung density measurement correlated well with the findings in chest radiographs...... but the lung density values were more sensitive indices. This was particularly evident in serial observations of individual patients....

  17. Mobile Radio Channels Modeling in MATLAB

    Directory of Open Access Journals (Sweden)

    N. Kostov

    2003-12-01

    Full Text Available In this paper, a MATLAB based approach for mobile radio channelsmodeling is presented. Specifically, the paper introduces the basicconcepts for modeling flat fading channels in MATLAB by means ofuser-defined m-files. Typical small-scale fading channel models arederived such as uncorrelated Rician fading channel and Rayleigh fadingchannel with Doppler shift. Further, simple and useful MATLABconstructions for approximation of cumulative distribution functions(CDFs and probability density functions (PDFs are also given.Finally, a MATLAB based Monte Carlo simulation example is presented,which comprises performance estimation of phase shift keying (PSKsignaling over a Rician fading channel.

  18. The molecular physiology of CRAC channels

    Science.gov (United States)

    Prakriya, Murali

    2011-01-01

    Summary The Ca2+release-activated Ca2+ (CRAC) channel is a highly Ca2+-selective store-operated channel expressed in T cells, mast cells, and various other tissues. CRAC channels regulate critical cellular processes such as gene expression, motility, and the secretion of inflammatory mediators. The identification of Orai1, a key subunit of the CRAC channel pore, and STIM1, the endoplasmic reticulum (ER) Ca2+ sensor, have provided the tools to illuminate the mechanisms of regulation and the pore properties of CRAC channels. Recent evidence indicates that the activation of CRAC channels by store depletion involves a coordinated series of steps, which include the redistributions of STIM1 and Orai1, direct physical interactions between these proteins, and conformational changes in Orai1, culminating in channel activation. Additional studies have revealed that the high Ca2+ selectivity of CRAC channels arises from the presence of an intrapore Ca2+ binding site, the properties of which are finely honed to occlude the permeation of the much more prevalent Na+. Structure-function studies have led to the identification of the potential pore-binding sites for Ca2+, providing a firm framework for understanding the mechanisms of selectivity and gating of the CRAC channel. This review summarizes recent progress in understanding the mechanisms of CRAC channel activation, pore properties, and modulation. PMID:19754891

  19. Hypernormal Densities

    OpenAIRE

    Giacomini, Raffaella; Gottschling, Andreas; Haefke, Christian; White, Halbert

    2002-01-01

    We derive a new family of probability densities that have the property of closed-form integrability. This flexible family finds a variety of applications, of which we illustrate density forecasting from models of the AR-ARCH class for U.S. inflation. We find that the hypernormal distribution for the model's disturbances leads to better density forecasts than the ones produced under the assumption that the disturbances are Normal or Student's t.

  20. Regulating effect of density and top-dressing time of nitrogen fertilizer on 14C-assimilation and distribution of assimilate of large-spike cultivar of wheat

    International Nuclear Information System (INIS)

    The results of present study indicated that laminas, especially first and second lamina from top, were the most important assimilating organs of large-spike cultivar of wheat at flag leaf stage. More than ninety percent of assimilate of a single stem was made by laminas, while the assimilate amount of sheathes only accounted for less than 10%. Not only assimilating rate but also transport and distribution efficiency was declined when the density was too high. Deferring top-dressing time of nitrogen fertilizer could increase both assimilate amount and transport and distribution efficiency

  1. Scaling Vegetation on Experimental Channel Patterns

    Science.gov (United States)

    van Breemen, D. M.; van de Lageweg, W. I.; van Dijk, W. M.; Kleinhans, M. G.

    2010-12-01

    There are strong feedbacks between river channels, floodplains and riparian and floodplain vegetation. We study the effect of experimental vegetation on channel pattern. Through linear bar theory it is known that channel width-depth ratio affects bar pattern and relatively narrow channels with strong banks are required for meandering. Riparian vegetation is able to alter the channel width-depth ratio and therefore the channel pattern through strengthening of the banks. Floodplain vegetation adds hydraulic resistance so the flow is more focused into the channels. However, determination of the underlying mechanisms and processes has remained scarce and qualitative and hence these effects are not yet fully understood. The objectives of this study are 1) to develop a controllable and scalable method to reproduce vegetation effect in experimental self-formed channels, and 2) to experimentally determine the effects of riparian vegetation on bank strength, channel pattern and meandering dynamics. Sprouts of three plant species were systematically subjected to different seeding densities and to various growing conditions, including light intensity, submergence and nutrient starvation. Denser seeding reduced sprout growth after about a week. Stronger light increased plant growth and plant strength. Nutrient starvation caused different branching intensity of the root system. Tens of small-scale bank erosion experiments and bank failure experiments (see Kleinhans et al., this conference) were performed to quantify the strength of banks reinforced by plant roots at the experimental scale, demonstrating that bank strength is strongly determined by seeding density, rooting density and depth relative to channel depth. To study pattern evolution and morphodynamics we used a 1.25x7.5 m flume with a constant discharge and sediment feed. The introduction of vegetation in experiments results in narrower and deeper channels. Higher vegetation density leads to static channels with

  2. Effects of Bulk Density on Root Growth of High Yield Maize and Their Regulation%土壤容重对高产玉米根系生长的影响及调控研究

    Institute of Scientific and Technical Information of China (English)

    郑存德; 依艳丽; 张大庚; 徐龙超

    2012-01-01

    不同土壤容重不同,其稳定性也不同.土壤容重的变化会引起土壤调节水、气、热能力的变化,提高土壤的自动调节能力可以使土壤肥力水平得以提高并满足植物对生长因子的持续需求.为研究土壤物理性质对玉米高产稳产的影响机理,以耕地棕壤为试验材料,采用盆栽方法,研究不同容重对玉米根系生长指标的影响,并进一步研究了施用不同有机肥量及模拟不同耕作深度对玉米根系生长的调控效果.结果表明:在设计容重范围内,容重增加,根系生长指标都表现为下降,容重大于1.2g/m3时,不同处理根系生长指标差异显著;当容重大于1.3g/cm3时,不同处理根系活力差异显著.施用有机肥对高容重土壤调控效果更好,有机质含量为4%与5%的处理差异减小,低容重土壤在所设计的有机质水平内调控效果也都较好.耕层厚度增加可以提高根系生长参数,但与对照相比,差异不显著.所以,对于紧实结构性较差的土壤,改善其调节能力应该通过增施有机肥的方法,紧实结构较好的土壤考虑使用耕翻的办法.%Soil bulk density is one of the important soil physical properties. Different soil with different soil bulk density and stability, at the same time , soil regulation ability of soil-water, soil-gas, soil-heat capacity changed with unstability of soil bulk density. It can improve soil fertility degree and the continuing demand factors of plant growth if the soil's automatically adaptational ability was enhanced, therefore, it is necessary to research how soil bulk density vary and how to regulate and control it. In order to study the mechanism of the impact of soil physical properties on high and stable yield of maize, this paper, with cultivated brown soil and pot experiment, studied the effect of soil bulk density on maize root growth parameters( root length,root area,root volume) ,furthermore,it studied the result of regulation by

  3. Densities, Spectral Densities and Modality

    OpenAIRE

    Davies, PL Laurie; Kovac, A.

    2002-01-01

    This paper considers the problem of specifying a simple approximating density function for a given data set (x1,…,xn). Simplicity is measured by the number of modes but several different definitions of approximation are introduced. The taut string method is used to control the numbers of modes and to produce candidate approximating densities. Refinements are introduced that improve the local adaptivity of the procedures and the method is extended to spectral densities.

  4. Cystic fibrosis transmembrane conductance regulator: a chloride channel gated by ATP binding and hydrolysis%囊性纤维化跨膜电导调节体:ATP结合和水解门控Cl-通道

    Institute of Scientific and Technical Information of China (English)

    BOMPADRE; Silvia; G; HWANG; Tzyh-Chang

    2007-01-01

    囊性纤维化跨膜电导调节体(cystic fibrosis transmembrane conductance regulator,CFTR)是一种Cl-通道,属于ATP结合(ATP-binding cassette,ABC)转运体超家族.CFTR功能缺陷是高加索人种中普遍存在的致死性常染色体隐性遗传疾病囊性纤维化(cystic fibrosis,CF)发生的主要原因.这种疾病患者各组织上皮细胞内Cl-转运失调.目前,与CF相关的不同突变超过1 400种.CFTR调节(regulatory,R)域负责调控,核苷酸结合域(nucleotide-binding domains,NBDs)NBD1和NBD2负责ATP结合和水解门控.近期研究发现CFTR的NBDs与其它ABC蛋白一样可以二聚化.二聚化过程中,NBD1和NBD2首-尾相连,一个NBD上的WalkerA和B模块与另一个NBD提供的标签序列(signature sequence)形成ATP结合袋(ATP-binding pockets,ABPs)ABP1和ABP2.ABPs中与ATP结合相关的氨基酸突变实验揭示,ABP1和ABP2在CFTR的ATP依赖门控中发挥不同作用.ABP2由NBD2上的Walk A和B模块与NBD1提供的标签序列形成,它与ATP结合催化通道开放,而ABP1单独与ATP结合不能促进通道开放,只能稳定通道构象.有一些CFTR突变相关疾病的特征就是门控失调,进一步深入研究CFTR的NBD1和NBD2如何通过相互作用而达到通道门控,将为药理学研究提供更多所需的机制信息,有利于为CF治疗的药物设计铺平道路.%The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel that belongs to the ATP-binding cassette (ABC) transporter superfamily. Defective function of CFTR is responsible for cystic fibrosis (CF), the most common lethal autosomal recessive disorder in Caucasian populations. The disease is manifested in defective chloride transport across the epithelial cells in various tissues. To date, more than 1400 different mutations have been identified as CF-associated. CFTR is regulated by phosphorylation in its regulatory (R) domain, and gated by ATP binding and hydrolysis at its two nucleotide-binding domains (NBD1

  5. Anion Channel Inhibitor NPPB-Inhibited Fluoride Accumulation in Tea Plant (Camellia sinensis Is Related to the Regulation of Ca2+, CaM and Depolarization of Plasma Membrane Potential

    Directory of Open Access Journals (Sweden)

    Xian-Chen Zhang

    2016-01-01

    Full Text Available Tea plant is known to be a hyper-accumulator of fluoride (F. Over-intake of F has been shown to have adverse effects on human health, e.g., dental fluorosis. Thus, understanding the mechanisms fluoride accumulation and developing potential approaches to decrease F uptake in tea plants might be beneficial for human health. In the present study, we found that pretreatment with the anion channel inhibitor NPPB reduced F accumulation in tea plants. Simultaneously, we observed that NPPB triggered Ca2+ efflux from mature zone of tea root and significantly increased relative CaM in tea roots. Besides, pretreatment with the Ca2+ chelator (EGTA and CaM antagonists (CPZ and TFP suppressed NPPB-elevated cytosolic Ca2+ fluorescence intensity and CaM concentration in tea roots, respectively. Interestingly, NPPB-inhibited F accumulation was found to be significantly alleviated in tea plants pretreated with either Ca2+ chelator (EGTA or CaM antagonists (CPZ and TFP. In addition, NPPB significantly depolarized membrane potential transiently and we argue that the net Ca2+ and H+ efflux across the plasma membrane contributed to the restoration of membrane potential. Overall, our results suggest that regulation of Ca2+-CaM and plasma membrane potential depolarization are involved in NPPB-inhibited F accumulation in tea plants.

  6. Anion Channel Inhibitor NPPB-Inhibited Fluoride Accumulation in Tea Plant (Camellia sinensis) Is Related to the Regulation of Ca²⁺, CaM and Depolarization of Plasma Membrane Potential.

    Science.gov (United States)

    Zhang, Xian-Chen; Gao, Hong-Jian; Yang, Tian-Yuan; Wu, Hong-Hong; Wang, Yu-Mei; Zhang, Zheng-Zhu; Wan, Xiao-Chun

    2016-01-01

    Tea plant is known to be a hyper-accumulator of fluoride (F). Over-intake of F has been shown to have adverse effects on human health, e.g., dental fluorosis. Thus, understanding the mechanisms fluoride accumulation and developing potential approaches to decrease F uptake in tea plants might be beneficial for human health. In the present study, we found that pretreatment with the anion channel inhibitor NPPB reduced F accumulation in tea plants. Simultaneously, we observed that NPPB triggered Ca(2+) efflux from mature zone of tea root and significantly increased relative CaM in tea roots. Besides, pretreatment with the Ca(2+) chelator (EGTA) and CaM antagonists (CPZ and TFP) suppressed NPPB-elevated cytosolic Ca(2+) fluorescence intensity and CaM concentration in tea roots, respectively. Interestingly, NPPB-inhibited F accumulation was found to be significantly alleviated in tea plants pretreated with either Ca(2+) chelator (EGTA) or CaM antagonists (CPZ and TFP). In addition, NPPB significantly depolarized membrane potential transiently and we argue that the net Ca(2+) and H⁺ efflux across the plasma membrane contributed to the restoration of membrane potential. Overall, our results suggest that regulation of Ca(2+)-CaM and plasma membrane potential depolarization are involved in NPPB-inhibited F accumulation in tea plants. PMID:26742036

  7. Anion Channel Inhibitor NPPB-Inhibited Fluoride Accumulation in Tea Plant (Camellia sinensis) Is Related to the Regulation of Ca2+, CaM and Depolarization of Plasma Membrane Potential

    Science.gov (United States)

    Zhang, Xian-Chen; Gao, Hong-Jian; Yang, Tian-Yuan; Wu, Hong-Hong; Wang, Yu-Mei; Zhang, Zheng-Zhu; Wan, Xiao-Chun

    2016-01-01

    Tea plant is known to be a hyper-accumulator of fluoride (F). Over-intake of F has been shown to have adverse effects on human health, e.g., dental fluorosis. Thus, understanding the mechanisms fluoride accumulation and developing potential approaches to decrease F uptake in tea plants might be beneficial for human health. In the present study, we found that pretreatment with the anion channel inhibitor NPPB reduced F accumulation in tea plants. Simultaneously, we observed that NPPB triggered Ca2+ efflux from mature zone of tea root and significantly increased relative CaM in tea roots. Besides, pretreatment with the Ca2+ chelator (EGTA) and CaM antagonists (CPZ and TFP) suppressed NPPB-elevated cytosolic Ca2+ fluorescence intensity and CaM concentration in tea roots, respectively. Interestingly, NPPB-inhibited F accumulation was found to be significantly alleviated in tea plants pretreated with either Ca2+ chelator (EGTA) or CaM antagonists (CPZ and TFP). In addition, NPPB significantly depolarized membrane potential transiently and we argue that the net Ca2+ and H+ efflux across the plasma membrane contributed to the restoration of membrane potential. Overall, our results suggest that regulation of Ca2+-CaM and plasma membrane potential depolarization are involved in NPPB-inhibited F accumulation in tea plants. PMID:26742036

  8. Anion Channel Inhibitor NPPB-Inhibited Fluoride Accumulation in Tea Plant (Camellia sinensis) Is Related to the Regulation of Ca²⁺, CaM and Depolarization of Plasma Membrane Potential.

    Science.gov (United States)

    Zhang, Xian-Chen; Gao, Hong-Jian; Yang, Tian-Yuan; Wu, Hong-Hong; Wang, Yu-Mei; Zhang, Zheng-Zhu; Wan, Xiao-Chun

    2016-01-05

    Tea plant is known to be a hyper-accumulator of fluoride (F). Over-intake of F has been shown to have adverse effects on human health, e.g., dental fluorosis. Thus, understanding the mechanisms fluoride accumulation and developing potential approaches to decrease F uptake in tea plants might be beneficial for human health. In the present study, we found that pretreatment with the anion channel inhibitor NPPB reduced F accumulation in tea plants. Simultaneously, we observed that NPPB triggered Ca(2+) efflux from mature zone of tea root and significantly increased relative CaM in tea roots. Besides, pretreatment with the Ca(2+) chelator (EGTA) and CaM antagonists (CPZ and TFP) suppressed NPPB-elevated cytosolic Ca(2+) fluorescence intensity and CaM concentration in tea roots, respectively. Interestingly, NPPB-inhibited F accumulation was found to be significantly alleviated in tea plants pretreated with either Ca(2+) chelator (EGTA) or CaM antagonists (CPZ and TFP). In addition, NPPB significantly depolarized membrane potential transiently and we argue that the net Ca(2+) and H⁺ efflux across the plasma membrane contributed to the restoration of membrane potential. Overall, our results suggest that regulation of Ca(2+)-CaM and plasma membrane potential depolarization are involved in NPPB-inhibited F accumulation in tea plants.

  9. Understanding autoimmunity: The ion channel perspective.

    Science.gov (United States)

    RamaKrishnan, Anantha Maharasi; Sankaranarayanan, Kavitha

    2016-07-01

    Ion channels are integral membrane proteins that orchestrate the passage of ions across the cell membrane and thus regulate various key physiological processes of the living system. The stringently regulated expression and function of these channels hold a pivotal role in the development and execution of various cellular functions. Malfunction of these channels results in debilitating diseases collectively termed channelopathies. In this review, we highlight the role of these proteins in the immune system with special emphasis on the development of autoimmunity. The role of ion channels in various autoimmune diseases is also listed out. This comprehensive review summarizes the ion channels that could be used as molecular targets in the development of new therapeutics against autoimmune disorders.

  10. Channel strategy adaptation

    OpenAIRE

    Rangan, V. Kasturi; Nueno, Jose L

    1999-01-01

    Using transaction cost theory, considerable research in marketing has focused on the conditions under which firms would use direct or vertically integrated versus indirect or arms length channels of distribution. Data from the field, however, indicate that channel configurations are more varied and complex, with multiple channels and composite channels being just as common as direct and indirect channels. In an attempt to explain this variety, this paper revisits the influence on channel stru...

  11. Arithmetic density

    CERN Document Server

    Garay, Mauricio

    2012-01-01

    Arithmetic class are closed subsets of the euclidean space which generalise arithmetical conditions encoutered in dynamical systems, such as diophantine conditions or Bruno type conditions. I prove density estimates for such sets using Dani-Kleinbock-Margulis techniques.

  12. Coordinated regulation of nitrogen supply mode and initial cell density for energy storage compounds production with economized nitrogen utilization in a marine microalga Isochrysis zhangjiangensis.

    Science.gov (United States)

    Chi, Lei; Yao, Changhong; Cao, Xupeng; Xue, Song

    2016-01-01

    Lipids and carbohydrates are main energy storage compounds (ESC) of microalgae under stressed conditions and they are potential feedstock for biofuel production. Yet, the sustainable and commercially successful production of ESC in microalgae needs to consider nitrogen utilization efficiency. Here the impact of different initial cell densities (ICDs) on ESC accumulation in Isochrysis zhangjiangensis under two nitrogen supply modes (an initially equal concentration of nitrogen per-cell in the medium (N1) and an equal total concentration of nitrogen in the culture system (N2)) were investigated. The results demonstrated that the highest ESC yield (1.36gL(-1)) at N1, which included a maximal nitrogen supply in the cultivation system, and the highest ESC content (66.5%) and ESC productivity per mass of nitrogen (3.28gg(-1) (N) day(-1)) at N2, were all obtained under a high ICD of 8.0×10(6)cellsmL(-1). Therefore I. zhangjiangensis qualifies for ESC-enriched biomass production with economized nitrogen utilization.

  13. Olfactory receptor signaling is regulated by the post-synaptic density 95, Drosophila discs large, zona-occludens 1 (PDZ) scaffold multi-PDZ domain protein 1.

    LENUS (Irish Health Repository)

    Dooley, Ruth

    2009-12-01

    The unique ability of mammals to detect and discriminate between thousands of different odorant molecules is governed by the diverse array of olfactory receptors expressed by olfactory sensory neurons in the nasal epithelium. Olfactory receptors consist of seven transmembrane domain G protein-coupled receptors and comprise the largest gene superfamily in the mammalian genome. We found that approximately 30% of olfactory receptors possess a classical post-synaptic density 95, Drosophila discs large, zona-occludens 1 (PDZ) domain binding motif in their C-termini. PDZ domains have been established as sites for protein-protein interaction and play a central role in organizing diverse cell signaling assemblies. In the present study, we show that multi-PDZ domain protein 1 (MUPP1) is expressed in the apical compartment of olfactory sensory neurons. Furthermore, on heterologous co-expression with olfactory sensory neurons, MUPP1 was shown to translocate to the plasma membrane. We found direct interaction of PDZ domains 1 + 2 of MUPP1 with the C-terminus of olfactory receptors in vitro. Moreover, the odorant-elicited calcium response of OR2AG1 showed a prolonged decay in MUPP1 small interfering RNA-treated cells. We have therefore elucidated the first building blocks of the putative \\'olfactosome\\

  14. Quercetin Alleviates High-Fat Diet-Induced Oxidized Low-Density Lipoprotein Accumulation in the Liver: Implication for Autophagy Regulation

    Directory of Open Access Journals (Sweden)

    Liang Liu

    2015-01-01

    Full Text Available A growing body of evidence has indicated that high-fat diet-induced nonalcoholic fatty liver disease is usually accompanied by oxidized low-density lipoprotein (ox-LDL deposited in the liver. The current study aimed to investigate the effect of quercetin on high-fat diet-induced ox-LDL accumulation in the liver and to explore the potential underlying mechanisms. The results demonstrate that quercetin supplementation for 24 weeks significantly alleviated high-fat diet-induced liver damage and reduced hepatic cholesterol and ox-LDL level. Quercetin notably inhibited both mRNA and protein expression of CD36 (reduced by 53% and 71%, resp. and MSR1 (reduced by 25% and 45%, resp., which were upregulated by high-fat diet. The expression of LC3II was upregulated by 2.4 times whereas that of p62 and mTOR was downregulated by 57% and 63% by quercetin treatment. Therefore, the significantly improved autophagy lysosomal degradation capacity for ox-LDL may be implicated in the hepatoprotective effect of quercetin; scavenger receptors mediated ox-LDL uptake might also be involved.

  15. The low-density lipoprotein receptor-related protein 10 is a negative regulator of the canonical Wnt/{beta}-catenin signaling pathway

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Young-Hee; Sekiya, Manami; Hirata, Michiko; Ye, Mingjuan; Yamagishi, Azumi [Department of Molecular and Biochemical Nutrition, Graduate School of Human Life Science, Osaka City University, Osaka 558-8585 (Japan); Lee, Sang-Mi; Kang, Man-Jong [Department of Animal Science, College of Agriculture and Life Science, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Hosoda, Akemi; Fukumura, Tomoe; Kim, Dong-Ho [Department of Molecular and Biochemical Nutrition, Graduate School of Human Life Science, Osaka City University, Osaka 558-8585 (Japan); Saeki, Shigeru, E-mail: saeki@life.osaka-cu.ac.jp [Department of Molecular and Biochemical Nutrition, Graduate School of Human Life Science, Osaka City University, Osaka 558-8585 (Japan)

    2010-02-19

    Wnt signaling pathways play fundamental roles in the differentiation, proliferation and functions of many cells as well as developmental, growth, and homeostatic processes in animals. Low-density lipoprotein receptor (LDLR)-related protein (LRP) 5 and LRP6 serve as coreceptors of Wnt proteins together with Frizzled receptors, triggering activation of canonical Wnt/{beta}-catenin signaling. Here, we found that LRP10, a new member of the LDLR gene family, inhibits the canonical Wnt/{beta}-catenin signaling pathway. The {beta}-catenin/T cell factor (TCF) transcriptional activity in HEK293 cells was activated by transfection with Wnt3a or LRP6, which was then inhibited by co-transfection with LRP10. Deletion of the extracellular domain of LRP10 negated its inhibitory effect. The inhibitory effect of LRP10 was consistently conserved in HEK293 cells even when GSK3{beta} phosphorylation was inhibited by incubation with lithium chloride and co-transfection with constitutively active S33Y-mutated {beta}-catenin. Nuclear {beta}-catenin accumulation was unaffected by LRP10. The present studies suggest that LRP10 may interfere with the formation of the {beta}-catenin/TCF complex and/or its binding to target DNA in the nucleus, and that the extracellular domain of LRP10 is critical for inhibition of the canonical Wnt/{beta}-catenin signaling pathway.

  16. Low Bone Density

    Science.gov (United States)

    ... Density Exam/Testing › Low Bone Density Low Bone Density Low bone density is when your bone density ... people with normal bone density. Detecting Low Bone Density A bone density test will determine whether you ...

  17. VKCDB: Voltage-gated potassium channel database

    Directory of Open Access Journals (Sweden)

    Gallin Warren J

    2004-01-01

    Full Text Available Abstract Background The family of voltage-gated potassium channels comprises a functionally diverse group of membrane proteins. They help maintain and regulate the potassium ion-based component of the membrane potential and are thus central to many critical physiological processes. VKCDB (Voltage-gated potassium [K] Channel DataBase is a database of structural and functional data on these channels. It is designed as a resource for research on the molecular basis of voltage-gated potassium channel function. Description Voltage-gated potassium channel sequences were identified by using BLASTP to search GENBANK and SWISSPROT. Annotations for all voltage-gated potassium channels were selectively parsed and integrated into VKCDB. Electrophysiological and pharmacological data for the channels were collected from published journal articles. Transmembrane domain predictions by TMHMM and PHD are included for each VKCDB entry. Multiple sequence alignments of conserved domains of channels of the four Kv families and the KCNQ family are also included. Currently VKCDB contains 346 channel entries. It can be browsed and searched using a set of functionally relevant categories. Protein sequences can also be searched using a local BLAST engine. Conclusions VKCDB is a resource for comparative studies of voltage-gated potassium channels. The methods used to construct VKCDB are general; they can be used to create specialized databases for other protein families. VKCDB is accessible at http://vkcdb.biology.ualberta.ca.

  18. Mobile radio channels

    CERN Document Server

    Pätzold, Matthias

    2011-01-01

    Providing a comprehensive overview of the modelling, analysis and simulation of mobile radio channels, this book gives a detailed understanding of fundamental issues and examines state-of-the-art techniques in mobile radio channel modelling. It analyses several mobile fading channels, including terrestrial and satellite flat-fading channels, various types of wideband channels and advanced MIMO channels, providing a fundamental understanding of the issues currently being investigated in the field. Important classes of narrowband, wideband, and space-time wireless channels are explored in deta

  19. The complex channel networks of bone structure

    CERN Document Server

    Costa, Luciano da Fontoura; Beletti, Marcelo E

    2006-01-01

    Bone structure in mammals involves a complex network of channels (Havers and Volkmann channels) required to nourish the bone marrow cells. This work describes how three-dimensional reconstructions of such systems can be obtained and represented in terms of complex networks. Three important findings are reported: (i) the fact that the channel branching density resembles a power law implies the existence of distribution hubs; (ii) the conditional node degree density indicates a clear tendency of connection between nodes with degrees 2 and 4; and (iii) the application of the recently introduced concept of hierarchical clustering coefficient allows the identification of typical scales of channel redistribution. A series of important biological insights is drawn and discussed

  20. Biological function and exercise regulation of high-density lipoprotein%高密度脂蛋白生物学功能及运动调节的研究与进展

    Institute of Scientific and Technical Information of China (English)

    苏中军; 张肃; 姜军

    2015-01-01

    BACKGROUND:High-density lipoprotein is related to lipid metabolism, but its function cannot be restricted to the scope of lipid metabolism. Simultaneously, exercise regulation has effects on the activity and amount of high-density lipoprotein, but the optimal movement pattern needs to be studied. OBJECTIVE:To offer the theoretical support for formulating fitness training and prospect the possible direction and reference in fol ow-up studying the biological function and exercise regulation of high-density lipoprotein. METHODS:PubMed database was searched for relevant articles published from 1990 to 2015 using the keywords of“HDL and exercise, HDL and biological function”in English. Final y, 44 articles were included in result analysis. RESULTS AND CONCLUSION:The biological functions of high-density lipoprotein mainly include high-density lipoprotein-mediated metabolism of glucose, protein and fat, anti-inflammation, antioxidation and insulin secretion, and at the same time, we summarize the effects of exercise on the concentration, numbers of molecular and components of high-density lipoprotein. The results indicate that the combination of resistance and endurance training is the best way for raising the concentration and functional effects of high-density lipoprotein.%背景:高密度脂蛋白是指与脂代谢有关的高密度脂蛋白,但研究表明其功能不仅局限于脂代谢范畴;同时运动调节高密度脂蛋白的活性和数量,但最佳的运动方式有待于研究。  目的:总结高密度脂蛋白的生物学功能及运动调节高密度脂蛋白研究进展,展望了高密度脂蛋白研究的可能方向,旨在为健身训练方案的制定提供理论支持,为后续研究提供参考;  方法:以关键词“HDL and exercise,HDL and biological function”搜索PubMed数据库,筛选到1990至2015年间文章98篇;按纳入、排除标准最后纳入文献44篇。  结果与结论:高密度脂