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Sample records for cation channels inhibit

  1. SLO2 Channels Are Inhibited by All Divalent Cations That Activate SLO1 K+ Channels.

    Science.gov (United States)

    Budelli, Gonzalo; Sun, Qi; Ferreira, Juan; Butler, Alice; Santi, Celia M; Salkoff, Lawrence

    2016-04-01

    Two members of the family of high conductance K(+)channels SLO1 and SLO2 are both activated by intracellular cations. However, SLO1 is activated by Ca(2+)and other divalent cations, while SLO2 (Slack or SLO2.2 from rat) is activated by Na(+) Curiously though, we found that SLO2.2 is inhibited by all divalent cations that activate SLO1, with Zn(2+)being the most effective inhibitor with an IC50of ∼8 μmin contrast to Mg(2+), the least effective, with an IC50of ∼ 1.5 mm Our results suggest that divalent cations are not SLO2 pore blockers, but rather inhibit channel activity by an allosteric modification of channel gating. By site-directed mutagenesis we show that a histidine residue (His-347) downstream of S6 reduces inhibition by divalent cations. An analogous His residue present in some CNG channels is an inhibitory cation binding site. To investigate whether inhibition by divalent cations is conserved in an invertebrate SLO2 channel we cloned the SLO2 channel fromDrosophila(dSLO2) and compared its properties to those of rat SLO2.2. We found that, like rat SLO2.2, dSLO2 was also activated by Na(+)and inhibited by divalent cations. Inhibition of SLO2 channels in mammals andDrosophilaby divalent cations that have second messenger functions may reflect the physiological regulation of these channels by one or more of these ions. PMID:26823461

  2. Aluminium and hydrogen ions inhibit a mechanosensory calcium-selective cation channel

    Science.gov (United States)

    Ding, J. P.; Pickard, B. G.

    1993-01-01

    The tension-dependent activity of mechanosensory calcium-selective cation channels in excised plasmalemmal patches from onion bulb scale epidermis is modulated by pH in the physiologically meaningful range between 4.5 and 7.2. It is rapidly lowered by lowering pH and rapidly raised by raising pH. Channel activity is effectively inhibited by low levels of aluminium ions and activity can be partially restored by washing for a few minutes. We suggest that under normal conditions the sensitivity of the mechanosensory channels to pH of the wall free space plays important roles in regulation of plant activities such as growth. We further suggest that, when levels of acid and aluminium ions in the soil solution are high, they might inhibit similar sensory channels in cells of the root tip, thus contributing critically to the acid soil syndrome.

  3. Englerin A Agonizes the TRPC4/C5 Cation Channels to Inhibit Tumor Cell Line Proliferation.

    Directory of Open Access Journals (Sweden)

    Cheryl Carson

    Full Text Available Englerin A is a structurally unique natural product reported to selectively inhibit growth of renal cell carcinoma cell lines. A large scale phenotypic cell profiling experiment (CLiP of englerin A on ¬over 500 well characterized cancer cell lines showed that englerin A inhibits growth of a subset of tumor cell lines from many lineages, not just renal cell carcinomas. Expression of the TRPC4 cation channel was the cell line feature that best correlated with sensitivity to englerin A, suggesting the hypothesis that TRPC4 is the efficacy target for englerin A. Genetic experiments demonstrate that TRPC4 expression is both necessary and sufficient for englerin A induced growth inhibition. Englerin A induces calcium influx and membrane depolarization in cells expressing high levels of TRPC4 or its close ortholog TRPC5. Electrophysiology experiments confirmed that englerin A is a TRPC4 agonist. Both the englerin A induced current and the englerin A induced growth inhibition can be blocked by the TRPC4/C5 inhibitor ML204. These experiments confirm that activation of TRPC4/C5 channels inhibits tumor cell line proliferation and confirms the TRPC4 target hypothesis generated by the cell line profiling. In selectivity assays englerin A weakly inhibits TRPA1, TRPV3/V4, and TRPM8 which suggests that englerin A may bind a common feature of TRP ion channels. In vivo experiments show that englerin A is lethal in rodents near doses needed to activate the TRPC4 channel. This toxicity suggests that englerin A itself is probably unsuitable for further drug development. However, since englerin A can be synthesized in the laboratory, it may be a useful chemical starting point to identify novel modulators of other TRP family channels.

  4. Mechanosensory calcium-selective cation channels in epidermal cells

    Science.gov (United States)

    Ding, J. P.; Pickard, B. G.

    1993-01-01

    This paper explores the properties and likely functions of an epidermal Ca(2+)-selective cation channel complex activated by tension. As many as eight or nine linked or linkable equivalent conductance units or co-channels can open together. Open time for co-channel quadruplets and quintuplets tends to be relatively long with millimolar Mg2+ (but not millimolar Ca2+) at the cytosolic face of excised plasma membrane. Sensitivity to tension is regulated by transmembrane voltage and temperature. Under some circumstances channel activity is sychronized in rhythmic pulses. Certain lanthanides and a cytoskeleton-disturbing herbicide that inhibit gravitropic reception act on the channel system at low concentrations. Specifically, ethyl-N-phenylcarbamate promotes tension-dependent activity at micromolar levels. With moderate suction, Gd3+ provided at about 0.5 micromole at the extracellular face of the membrane promotes for several seconds but may then become inhibitory. Provision at 1-2 micromoles promotes and subsequently inhibits more vigorously (often abruptly and totally), and at high levels inhibits immediately. La3+, a poor gravitropic inhibitor, acts similarly but much more gradually and only at much higher concentrations. These properties, particularly these susceptibilities to modulation, indicate that in vivo the mechanosensitive channel must be mechanosensory and mechanoregulatory. It could serve to transduce the shear forces generated in the integrated wall-membrane-cytoskeleton system during turgor changes and cell expansion as well as transducing the stresses induced by gravity, touch and flexure. In so far as such transduction is modulated by voltage and temperature, the channels would also be sensors for these modalities as long as the wall-membrane-cytoskeleton system experiences mechanical stress.

  5. Cation Selectivity in Biological Cation Channels Using Experimental Structural Information and Statistical Mechanical Simulation.

    Directory of Open Access Journals (Sweden)

    Justin John Finnerty

    Full Text Available Cation selective channels constitute the gate for ion currents through the cell membrane. Here we present an improved statistical mechanical model based on atomistic structural information, cation hydration state and without tuned parameters that reproduces the selectivity of biological Na+ and Ca2+ ion channels. The importance of the inclusion of step-wise cation hydration in these results confirms the essential role partial dehydration plays in the bacterial Na+ channels. The model, proven reliable against experimental data, could be straightforwardly used for designing Na+ and Ca2+ selective nanopores.

  6. Pharmacology of the human cell voltage-dependent cation channel. Part II: inactivation and blocking

    DEFF Research Database (Denmark)

    Bennekou, Poul; Barksmann, Trine L.; Kristensen, Berit I.;

    2004-01-01

    Human red cells; Nonselective voltage-dependent cation channel; NSVDC channel; Thiol group reagents......Human red cells; Nonselective voltage-dependent cation channel; NSVDC channel; Thiol group reagents...

  7. Pharmacology of the human red cell voltage-dependent cation channel Part I. Activation by clotrimazole and analogues

    DEFF Research Database (Denmark)

    Barksmann, Trine Lyberth; Kristensen, Berit I.; Christophersen, Palle.;

    2004-01-01

    Human red cells, Nonselective voltage dependent cation channel, NSVDC channel, Gárdos channel blockers, NSVDC channel activators......Human red cells, Nonselective voltage dependent cation channel, NSVDC channel, Gárdos channel blockers, NSVDC channel activators...

  8. Modulation of fast synaptic transmission by presynaptic ligand-gated cation channels.

    Science.gov (United States)

    Khakh, B S; Henderson, G

    2000-07-01

    There is now considerable evidence demonstrating that ligand-gated cation channels (i.e., P2X, nicotinic, kainate, NMDA, AMPA and 5-HT(3) receptors), in addition to mediating fast excitatory neurotransmission, may be located presynaptically on nerve terminals in the peripheral and central nervous systems where they function to modulate neurotransmitter release. This modulation can be facilitation, inhibition or both. In this article, we first outline the multiple mechanisms by which activation of presynaptic ligand-gated cation channels can modulate spontaneous and evoked neurotransmitter release, before reviewing in detail published electrophysiological studies of presynaptic P2X, nicotinic, kainate, NMDA, AMPA and 5-HT(3) receptors.

  9. Cloning and first functional characterization of a plant cyclic nucleotide-gated cation channel

    Energy Technology Data Exchange (ETDEWEB)

    Leng, Q.; Mercier, R.W.; Yao, W.; Berkowitz, G.A.

    1999-11-01

    Cyclic nucleotide-gated (cng) non-selective cation channels have been cloned from a number of animal systems. These channels are characterized by direct gating upon cAMO or cGMO binding to the intracellular portion of the channel protein, which leads to an increase in channel conductance. Animal cng channels are involved in signal transduction systems; they translate stimulus-induced changes in cytosolic cyclic nucleotide into altered cell membrane potential and/or cation flux as part of a signal cascade pathway. Putative plant homologs of animal cng channels have been identified. However, functional characterization (i.e., demonstration of cyclic-nucleotide-dependent ion currents) of a plant cng channel has not yet been accomplished. The authors report the cloning and first functional characterization of a plant member of this family of ion channels. The Arabidopsis cDNA AtCNGC2 encodes a polypeptide with deduced homology to the {alpha}-subunit of animal channels, and facilitates cyclic nucleotide-dependent cation currents upon expression in a number of heterologous systems. AtCNGC2 expression in a yeast mutant lacking a low-affinity K{sup +} uptake system complements growth inhibition only when lipophilic nucleotides are present in the culture medium. Voltage clamp analysis indicates that Xenopus lawvis oocytes injected with AtCNGC2 cRNA demonstrate cyclic-nucleotide-dependent, inward-rectifying K{sup +} currents. Human embryonic kidney cells (HEK293) transfected with AtCNGC2 cDNA demonstrate increased permeability to Ca{sup 2+} only in the presence of lipophilic cyclic nucleotides. The evidence presented here supports the functional classification of AtCNGC2 as a cyclic-nucleotide-gated cation channel, and presents the first direct evidence identifying a plant member of this ion channel family.

  10. Modulation of mechanosensitive calcium-selective cation channels by temperature

    Science.gov (United States)

    Ding, J. P.; Pickard, B. G.

    1993-01-01

    Gating of associations of mechanosensitive Ca(2+)-selective cation co-channels in the plasmalemma of onion epidermis has a strong and unusual temperature dependence. Tension-dependent activity rises steeply as temperature is lowered from 25 degrees C to about 6 degrees C, but drops to a low level at about 5 degrees C. Under the conditions tested (with Mg2+ and K+ at the cytosolic face of outside-out membrane patches), promotion results both from more bursting at all observed linkage levels and from longer duration of bursts of co-channels linked as quadruplets and quintuplets. Co-channel conductance decreases linearly, but only modestly, with declining temperature. It is proposed that these and related mechanosensitive channels may participate in a variety of responses to temperature, including thermonasty, thermotropism, hydrotropism, and both cold damage and cold acclimation.

  11. Stretch-activated cation channel from larval bullfrog skin

    OpenAIRE

    Hillyard, Stanley D.; Willumsen, Niels J.; Marrero, Mario B.

    2010-01-01

    Cell-attached patches from isolated epithelial cells from larval bullfrog skin revealed a cation channel that was activated by applying suction (−1 kPa to −4.5 kPa) to the pipette. Activation was characterized by an initial large current spike that rapidly attenuated to a stable value and showed a variable pattern of opening and closing with continuing suction. Current–voltage plots demonstrated linear or inward rectification and single channel conductances of 44–56 pS with NaCl or KCl Ringer...

  12. Crystal structure of channelrhodopsin, a light-gated cation channel - all cations lead through the monomer.

    Science.gov (United States)

    Kato, Hideaki E; Nureki, Osamu

    2013-01-01

    Channelrhodopsin (ChR) is a light-gated cation channel derived from green algae. Since the inward flow of cations triggers the neuron firing, neurons expressing ChRs can be optically controlled even within freely moving mammals. Although ChR has been broadly applied to neuro-science research, little is known about its molecular mechanisms. We determined the crystal structure of chimeric ChR at 2.3 Å resolution and revealed its molecular architecture. The integration of structural, electrophysio-logical, and computational analyses provided insight into the molecular basis for the channel function of ChR, and paved the way for the principled design of ChR variants with novel properties. PMID:27493541

  13. Diphtheria toxin-induced channels in Vero cells selective for monovalent cations

    Energy Technology Data Exchange (ETDEWEB)

    Sandvig, K.; Olsnes, S.

    1988-09-05

    Ion fluxes associated with translocation of diphtheria toxin across the surface membrane of Vero cells were studied. When cells with surface-bound toxin were exposed to low pH to induce toxin entry, the cells became permeable to Na+, K+, H+, choline+, and glucosamine+. There was no increased permeability to Cl-, SO4(-2), glucose, or sucrose, whereas the uptake of /sup 45/Ca2+ was slightly increased. The influx of Ca2+, which appears to be different from that of monovalent cations, was reduced by several inhibitors of anion transport and by verapamil, Mn2+, Co2+, and Ca2+, but not by Mg2+. The toxin-induced fluxes of N+, K+, and protons were inhibited by Cd2+. Cd2+ also protected the cells against intoxication by diphtheria toxin, suggesting that the open cation-selective channel is required for toxin translocation. The involvement of the toxin receptor is discussed.

  14. Sodium Channel Inhibiting Marine Toxins

    Science.gov (United States)

    Llewellyn, Lyndon E.

    Saxitoxin (STX), tetrodotoxin (TTX) and their many chemical relatives are part of our daily lives. From killing people who eat seafood containing these toxins, to being valuable research tools unveiling the invisible structures of their pharmacological receptor, their global impact is beyond measure. The pharmacological receptor for these toxins is the voltage-gated sodium channel which transports Na ions between the exterior to the interior of cells. The two structurally divergent families of STX and TTX analogues bind at the same location on these Na channels to stop the flow of ions. This can affect nerves, muscles and biological senses of most animals. It is through these and other toxins that we have developed much of our fundamental understanding of the Na channel and its part in generating action potentials in excitable cells.

  15. Role of thromboxane A₂-activated nonselective cation channels in hypoxic pulmonary vasoconstriction of rat.

    Science.gov (United States)

    Yoo, Hae Young; Park, Su Jung; Seo, Eun-Young; Park, Kyung Sun; Han, Jung-A; Kim, Kyung Soo; Shin, Dong Hoon; Earm, Yung E; Zhang, Yin-Hua; Kim, Sung Joon

    2012-01-01

    Hypoxia-induced pulmonary vasoconstriction (HPV) is critical for matching of ventilation/perfusion in lungs. Although hypoxic inhibition of K(+) channels has been a leading hypothesis for depolarization of pulmonary arterial smooth muscle cells (PASMCs) under hypoxia, pharmacological inhibition of K(+) channels does not induce significant contraction in rat pulmonary arteries. Because a partial contraction by thromboxane A(2) (TXA(2)) is required for induction of HPV, we hypothesize that TXA(2) receptor (TP) stimulation might activate depolarizing nonselective cation channels (NSCs). Consistently, we found that 5-10 nM U46619, a stable agonist for TP, was indispensible for contraction of rat pulmonary arteries by 4-aminopyridine, a blocker of voltage-gated K(+) channel (K(v)). Whole cell voltage clamp with rat PASMC revealed that U46619 induced a NSC current (I(NSC,TXA2)) with weakly outward rectifying current-voltage relation. I(NSC,TXA2) was blocked by ruthenium red (RR), an antagonist of the transient receptor potential vanilloid-related channel (TRPV) subfamily. 2-Aminoethoxydiphenyl borate, an agonist for TRPV1-3, consistently activated NSC channels in PASMCs. In contrast, agonists for TRPV1 (capsaicin), TRPV3 (camphor), or TRPV4 (α-PDD) rarely induced an increase in the membrane conductance of PASMCs. RT-PCR analysis showed the expression of transcripts for TRPV2 and -4 in rat PASMCs. Finally, it was confirmed that pretreatment with RR largely inhibited HPV in the presence of U46619. The pretreatment with agonists for TRPV1 (capsaicin) and TRPV4 (α-PDD) was ineffective as pretone agents for HPV. Taken together, it is suggested that the concerted effects of I(NSC,TXA2) activation and K(v) inhibition under hypoxia induce membrane depolarization sufficient for HPV. TRPV2 is carefully suggested as the TXA(2)-activated NSC in rat PASMC. PMID:21998141

  16. Transient receptor potential (TRP gene superfamily encoding cation channels

    Directory of Open Access Journals (Sweden)

    Pan Zan

    2011-01-01

    Full Text Available Abstract Transient receptor potential (TRP non-selective cation channels constitute a superfamily, which contains 28 different genes. In mammals, this superfamily is divided into six subfamilies based on differences in amino acid sequence homology between the different gene products. Proteins within a subfamily aggregate to form heteromeric or homomeric tetrameric configurations. These different groupings have very variable permeability ratios for calcium versus sodium ions. TRP expression is widely distributed in neuronal tissues, as well as a host of other tissues, including epithelial and endothelial cells. They are activated by environmental stresses that include tissue injury, changes in temperature, pH and osmolarity, as well as volatile chemicals, cytokines and plant compounds. Their activation induces, via intracellular calcium signalling, a host of responses, including stimulation of cell proliferation, migration, regulatory volume behaviour and the release of a host of cytokines. Their activation is greatly potentiated by phospholipase C (PLC activation mediated by coupled GTP-binding proteins and tyrosine receptors. In addition to their importance in maintaining tissue homeostasis, some of these responses may involve various underlying diseases. Given the wealth of literature describing the multiple roles of TRP in physiology in a very wide range of different mammalian tissues, this review limits itself to the literature describing the multiple roles of TRP channels in different ocular tissues. Accordingly, their importance to the corneal, trabecular meshwork, lens, ciliary muscle, retinal, microglial and retinal pigment epithelial physiology and pathology is reviewed.

  17. Inhibiting bacterial toxins by channel blockage.

    Science.gov (United States)

    Bezrukov, Sergey M; Nestorovich, Ekaterina M

    2016-03-01

    Emergent rational drug design techniques explore individual properties of target biomolecules, small and macromolecule drug candidates, and the physical forces governing their interactions. In this minireview, we focus on the single-molecule biophysical studies of channel-forming bacterial toxins that suggest new approaches for their inhibition. We discuss several examples of blockage of bacterial pore-forming and AB-type toxins by the tailor-made compounds. In the concluding remarks, the most effective rationally designed pore-blocking antitoxins are compared with the small-molecule inhibitors of ion-selective channels of neurophysiology.

  18. The non-selective voltage-activated cation channel in the human red blood cell membrane: reconciliation between two conflicting reports and further characterisation

    DEFF Research Database (Denmark)

    Kaestner, Lars; Christophersen, Palle; Bernhardt, Ingolf;

    2000-01-01

    Erythrocyte; Patch-clamp; Non-specific; cation channel; Voltage dependence; Acetylcholin receptor......Erythrocyte; Patch-clamp; Non-specific; cation channel; Voltage dependence; Acetylcholin receptor...

  19. GPR119 Agonist AS1269574 Activates TRPA1 Cation Channels to Stimulate GLP-1 Secretion.

    Science.gov (United States)

    Chepurny, Oleg G; Holz, George G; Roe, Michael W; Leech, Colin A

    2016-06-01

    GPR119 is a G protein-coupled receptor expressed on intestinal L cells that synthesize and secrete the blood glucose-lowering hormone glucagon-like peptide-1 (GLP-1). GPR119 agonists stimulate the release of GLP-1 from L cells, and for this reason there is interest in their potential use as a new treatment for type 2 diabetes mellitus. AS1269574 is one such GPR119 agonist, and it is the prototype of a series of 2,4,6 trisubstituted pyrimidines that exert positive glucoregulatory actions in mice. Here we report the unexpected finding that AS1269574 stimulates GLP-1 release from the STC-1 intestinal cell line by directly promoting Ca(2+) influx through transient receptor potential ankyrin 1 (TRPA1) cation channels. These GPR119-independent actions of AS1269574 are inhibited by TRPA1 channel blockers (AP-18, A967079, HC030031) and are not secondary to intracellular Ca(2+) release or cAMP production. Patch clamp studies reveal that AS1269574 activates an outwardly rectifying membrane current with properties expected of TRPA1 channels. However, the TRPA1 channel-mediated action of AS1269574 to increase intracellular free calcium concentration is not replicated by GPR119 agonists (AR231453, oleoylethanolamide) unrelated in structure to AS1269574. Using human embryonic kidney-293 cells expressing recombinant rat TRPA1 channels but not GPR119, direct TRPA1 channel activating properties of AS1269574 are validated. Because we find that AS1269574 also acts in a conventional GPR119-mediated manner to stimulate proglucagon gene promoter activity in the GLUTag intestinal L cell line, new findings reported here reveal the surprising capacity of AS1269574 to act as a dual agonist at two molecular targets (GPR119/TRPA1) important to the control of L-cell function and type 2 diabetes mellitus drug discovery research. PMID:27082897

  20. Crystal structure of channelrhodopsin, a light-gated cation channel – all cations lead through the monomer –

    OpenAIRE

    Kato, Hideaki E.; Nureki, Osamu

    2013-01-01

    Channelrhodopsin (ChR) is a light-gated cation channel derived from green algae. Since the inward flow of cations triggers the neuron firing, neurons expressing ChRs can be optically controlled even within freely moving mammals. Although ChR has been broadly applied to neuro-science research, little is known about its molecular mechanisms. We determined the crystal structure of chimeric ChR at 2.3 Å resolution and revealed its molecular architecture. The integration of structural, electrophys...

  1. Crystal structure of channelrhodopsin, a light-gated cation channel – all cations lead through the monomer –

    Science.gov (United States)

    Kato, Hideaki E.; Nureki, Osamu

    2013-01-01

    Channelrhodopsin (ChR) is a light-gated cation channel derived from green algae. Since the inward flow of cations triggers the neuron firing, neurons expressing ChRs can be optically controlled even within freely moving mammals. Although ChR has been broadly applied to neuro-science research, little is known about its molecular mechanisms. We determined the crystal structure of chimeric ChR at 2.3 Å resolution and revealed its molecular architecture. The integration of structural, electrophysio-logical, and computational analyses provided insight into the molecular basis for the channel function of ChR, and paved the way for the principled design of ChR variants with novel properties. PMID:27493541

  2. 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 ...

  3. Evolutionary and structural perspectives of plant cyclic nucleotide-gated cation channels

    KAUST Repository

    Zelman, Alice K.

    2012-05-29

    Ligand-gated cation channels are a frequent component of signaling cascades in eukaryotes. Eukaryotes contain numerous diverse gene families encoding ion channels, some of which are shared and some of which are unique to particular kingdoms. Among the many different types are cyclic nucleotide-gated channels (CNGCs). CNGCs are cation channels with varying degrees of ion conduction selectivity. They are implicated in numerous signaling pathways and permit diffusion of divalent and monovalent cations, including Ca2+ and K+. CNGCs are present in both plant and animal cells, typically in the plasma membrane; recent studies have also documented their presence in prokaryotes. All eukaryote CNGC polypeptides have a cyclic nucleotide-binding domain and a calmodulin binding domain as well as a six transmembrane/one pore tertiary structure. This review summarizes existing knowledge about the functional domains present in these cation-conducting channels, and considers the evidence indicating that plant and animal CNGCs evolved separately. Additionally, an amino acid motif that is only found in the phosphate binding cassette and hinge regions of plant CNGCs, and is present in all experimentally confirmed CNGCs but no other channels was identified. This CNGC-specific amino acid motif provides an additional diagnostic tool to identify plant CNGCs, and can increase confidence in the annotation of open reading frames in newly sequenced genomes as putative CNGCs. Conversely, the absence of the motif in some plant sequences currently identified as probable CNGCs may suggest that they are misannotated or protein fragments. 2012 Zelman, Dawe, Gehring and Berkowitz.

  4. Concerted action of two cation filters in the aquaporin water channel

    DEFF Research Database (Denmark)

    Wu, Binghua; Steinbronn, Christina; Alsterfjord, Magnus;

    2009-01-01

    Aquaporin (AQP) facilitated water transport is common to virtually all cell membranes and is marked by almost perfect specificity and high flux rates. Simultaneously, protons and cations are strictly excluded to maintain ionic transmembrane gradients. Yet, the AQP cation filters have not been...... identified experimentally. We report that three point mutations turned the water-specific AQP1 into a proton/alkali cation channel with reduced water permeability and the permeability sequence: H(+) >>K(+) >Rb(+) >Na(+) >Cs(+) >Li(+). Contrary to theoretical models, we found that electrostatic repulsion...

  5. Stretch-activated cation channel from larval bullfrog skin

    DEFF Research Database (Denmark)

    Hillyard, Stanley D; Willumsen, Niels J; Marrero, Mario B

    2010-01-01

    a variable pattern of opening and closing with continuing suction. Current-voltage plots demonstrated linear or inward rectification and single channel conductances of 44-56 pS with NaCl or KCl Ringer's solution as the pipette solution, and a reversal potential (-V(p)) of 20-40 mV. The conductance...

  6. Tuning the ion selectivity of tetrameric cation channels by changing the number of ion binding sites

    Energy Technology Data Exchange (ETDEWEB)

    Derebe, Mehabaw G.; Sauer, David B.; Zeng, Weizhong; Alam, Amer; Shi, Ning; Jiang, Youxing (UTSMC); (ETH Zurich)

    2015-11-30

    Selective ion conduction across ion channel pores is central to cellular physiology. To understand the underlying principles of ion selectivity in tetrameric cation channels, we engineered a set of cation channel pores based on the nonselective NaK channel and determined their structures to high resolution. These structures showcase an ensemble of selectivity filters with a various number of contiguous ion binding sites ranging from 2 to 4, with each individual site maintaining a geometry and ligand environment virtually identical to that of equivalent sites in K{sup +} channel selectivity filters. Combined with single channel electrophysiology, we show that only the channel with four ion binding sites is K{sup +} selective, whereas those with two or three are nonselective and permeate Na{sup +} and K{sup +} equally well. These observations strongly suggest that the number of contiguous ion binding sites in a single file is the key determinant of the channel's selectivity properties and the presence of four sites in K{sup +} channels is essential for highly selective and efficient permeation of K{sup +} ions.

  7. Structural Insights into Divalent Cation Modulations of ATP-Gated P2X Receptor Channels.

    Science.gov (United States)

    Kasuya, Go; Fujiwara, Yuichiro; Takemoto, Mizuki; Dohmae, Naoshi; Nakada-Nakura, Yoshiko; Ishitani, Ryuichiro; Hattori, Motoyuki; Nureki, Osamu

    2016-02-01

    P2X receptors are trimeric ATP-gated cation channels involved in physiological processes ranging widely from neurotransmission to pain and taste signal transduction. The modulation of the channel gating, including that by divalent cations, contributes to these diverse physiological functions of P2X receptors. Here, we report the crystal structure of an invertebrate P2X receptor from the Gulf Coast tick Amblyomma maculatum in the presence of ATP and Zn(2+) ion, together with electrophysiological and computational analyses. The structure revealed two distinct metal binding sites, M1 and M2, in the extracellular region. The M1 site, located at the trimer interface, is responsible for Zn(2+) potentiation by facilitating the structural change of the extracellular domain for pore opening. In contrast, the M2 site, coupled with the ATP binding site, might contribute to regulation by Mg(2+). Overall, our work provides structural insights into the divalent cation modulations of P2X receptors. PMID:26804916

  8. A cationic tetrapyrrole inhibits toxic activities of the cellular prion protein.

    Science.gov (United States)

    Massignan, Tania; Cimini, Sara; Stincardini, Claudia; Cerovic, Milica; Vanni, Ilaria; Elezgarai, Saioa R; Moreno, Jorge; Stravalaci, Matteo; Negro, Alessandro; Sangiovanni, Valeria; Restelli, Elena; Riccardi, Geraldina; Gobbi, Marco; Castilla, Joaquín; Borsello, Tiziana; Nonno, Romolo; Biasini, Emiliano

    2016-01-01

    Prion diseases are rare neurodegenerative conditions associated with the conformational conversion of the cellular prion protein (PrP(C)) into PrP(Sc), a self-replicating isoform (prion) that accumulates in the central nervous system of affected individuals. The structure of PrP(Sc) is poorly defined, and likely to be heterogeneous, as suggested by the existence of different prion strains. The latter represents a relevant problem for therapy in prion diseases, as some potent anti-prion compounds have shown strain-specificity. Designing therapeutics that target PrP(C) may provide an opportunity to overcome these problems. PrP(C) ligands may theoretically inhibit the replication of multiple prion strains, by acting on the common substrate of any prion replication reaction. Here, we characterized the properties of a cationic tetrapyrrole [Fe(III)-TMPyP], which was previously shown to bind PrP(C), and inhibit the replication of a mouse prion strain. We report that the compound is active against multiple prion strains in vitro and in cells. Interestingly, we also find that Fe(III)-TMPyP inhibits several PrP(C)-related toxic activities, including the channel-forming ability of a PrP mutant, and the PrP(C)-dependent synaptotoxicity of amyloid-β (Aβ) oligomers, which are associated with Alzheimer's Disease. These results demonstrate that molecules binding to PrP(C) may produce a dual effect of blocking prion replication and inhibiting PrP(C)-mediated toxicity. PMID:26976106

  9. Antiarrhythmic Mechanisms of SK Channel Inhibition in the Rat Atrium

    DEFF Research Database (Denmark)

    Skibsbye, Lasse; Wang, Xiaodong; Axelsen, Lene Nygaard;

    2015-01-01

    period (ERP) and slowing the conduction velocity. We therefore aimed at elucidating these properties of SK channel inhibition and the underlying antiarrhythmic mechanisms by using; microelectrode action potential recordings and conduction velocity measurements in isolated rat atrium. Automated patch-clamping...... and two-electrode voltage-clamp was used to access INa and IK,ACh respectively. RESULTS: The SK channel inhibitor N-(pyridin-2-yl)-4-(pyridin-2-yl)thiazol-2-amine (ICA) exhibited antiarrhythmic effects. ICA prevented electrically induced runs of atrial fibrillation in the isolated right atrium and...... channel inhibition by ICA (10-30 µM) demonstrated prominent depression of other sodium channel-dependent parameters. ICA did not inhibit IK,ACh, but at concentrations above 10 µM ICA use-dependently inhibited INa. CONCLUSION: SK channel inhibition modulates multiple parameters of the action potential. It...

  10. Spontaneous and CRH-Induced Excitability and Calcium Signaling in Mice Corticotrophs Involves Sodium, Calcium, and Cation-Conducting Channels.

    Science.gov (United States)

    Zemkova, Hana; Tomić, Melanija; Kucka, Marek; Aguilera, Greti; Stojilkovic, Stanko S

    2016-04-01

    Transgenic mice expressing the tdimer2(12) form of Discosoma red fluorescent protein under control of the proopiomelanocortin gene's regulatory elements are a useful model for studying corticotrophs. Using these mice, we studied the ion channels and mechanisms controlling corticotroph excitability. Corticotrophs were either quiescent or electrically active, with a 22-mV difference in the resting membrane potential (RMP) between the 2 groups. In quiescent cells, CRH depolarized the membrane, leading to initial single spiking and sustained bursting; in active cells, CRH further facilitated or inhibited electrical activity and calcium spiking, depending on the initial activity pattern and CRH concentration. The stimulatory but not inhibitory action of CRH on electrical activity was mimicked by cAMP independently of the presence or absence of arachidonic acid. Removal of bath sodium silenced spiking and hyperpolarized the majority of cells; in contrast, the removal of bath calcium did not affect RMP but reduced CRH-induced depolarization, which abolished bursting electrical activity and decreased the spiking frequency but not the amplitude of single spikes. Corticotrophs with inhibited voltage-gated sodium channels fired calcium-dependent action potentials, whereas cells with inhibited L-type calcium channels fired sodium-dependent spikes; blockade of both channels abolished spiking without affecting the RMP. These results indicate that the background voltage-insensitive sodium conductance influences RMP, the CRH-depolarization current is driven by a cationic conductance, and the interplay between voltage-gated sodium and calcium channels plays a critical role in determining the status and pattern of electrical activity and calcium signaling.

  11. Cationic Pillararenes Potently Inhibit Biofilm Formation without Affecting Bacterial Growth and Viability.

    Science.gov (United States)

    Joseph, Roymon; Naugolny, Alissa; Feldman, Mark; Herzog, Ido M; Fridman, Micha; Cohen, Yoram

    2016-01-27

    It is estimated that up to 80% of bacterial infections are accompanied by biofilm formation. Since bacteria in biofilms are less susceptible to antibiotics than are bacteria in the planktonic state, biofilm-associated infections pose a major health threat, and there is a pressing need for antibiofilm agents. Here we report that water-soluble cationic pillararenes differing in the quaternary ammonium groups efficiently inhibited the formation of biofilms by clinically important Gram-positive pathogens. Biofilm inhibition did not result from antimicrobial activity; thus, the compounds should not inhibit growth of natural bacterial flora. Moreover, none of the cationic pillararenes caused detectable membrane damage to red blood cells or toxicity to human cells in culture. The results indicate that cationic pillararenes have potential for use in medical applications in which biofilm formation is a problem. PMID:26745311

  12. Increase in cytosolic Ca2+ produced by hypoxia and other depolarizing stimuli activates a non-selective cation channel in chemoreceptor cells of rat carotid body.

    Science.gov (United States)

    Kang, Dawon; Wang, Jiaju; Hogan, James O; Vennekens, Rudi; Freichel, Marc; White, Carl; Kim, Donghee

    2014-05-01

    The current model of O2 sensing by carotid body chemoreceptor (glomus) cells is that hypoxia inhibits the outward K(+) current and causes cell depolarization, Ca(2+) influx via voltage-dependent Ca(2+) channels and a rise in intracellular [Ca(2+)] ([Ca(2+)]i). Here we show that hypoxia (<5% O2), in addition to inhibiting the two-pore domain K(+) channels TASK-1/3 (TASK), indirectly activates an ∼20 pS channel in isolated glomus cells. The 20 pS channel was permeable to K(+), Na(+) and Cs(+) but not to Cl(-) or Ca(2+). The 20 pS channel was not sensitive to voltage. Inhibition of TASK by external acid, depolarization of glomus cells with high external KCl (20 mm) or opening of the Ca(2+) channel with FPL64176 activated the 20 pS channel when 1 mm Ca(2+) was present in the external solution. Ca(2+) (10 μm) applied to the cytosolic side of inside-out patches activated the 20 pS channel. The threshold [Ca(2+)]i for activation of the 20 pS channel in cell-attached patches was ∼200 nm. The reversal potential of the 20 pS channel was estimated to be -28 mV. Our results reveal a sequential mechanism in which hypoxia (<5% O2) first inhibits the K(+) conductance and then activates a Na(+)-permeable, non-selective cation channel via depolarization-induced rise in [Ca(2+)]i. Our results suggest that inhibition of K(+) efflux and stimulation of Na(+) influx both contribute to the depolarization of glomus cells during moderate to severe hypoxia.

  13. Adsorption and Uptake of Cadmium by Azolla pinnata:Kinetics of Inhibition by Cations

    Institute of Scientific and Technical Information of China (English)

    J.P.GAUR; N.NORAHO

    1995-01-01

    A.pinnata showed a remarkable ability of taking up Cd from the external medium.Of the total Cd taken up by the test plant,surface adsorption was about 90%.Cd adsorption did not occur at a constant rate,however,an equilibrium was reached in 2h.The uptake of Cd occurred at a constant rate.Test cations.Including heavy metals(Ca,Mg,K,Na,Ni,F,Cu and Zn),inhibited adsorption as well as uptake of Cd.Cd adsorption was competitively inhibited by Cu,Fe and Zn,whereas Ca,Mg,K,Na and Ni caused non-competitive inhibition,Similarly,Cd uptake was competitively(Ca,Mg,Fe)or non-competitively(Na,K,Ni,Zn) inhibited by cations.Inhibition of Cd uptake by Cu was not wholly competitive.

  14. Effects of Octylphenol and Bisphenol A on the Metal Cation Transporter Channels of Mouse Placentas

    Science.gov (United States)

    Lee, Jae-Hwan; Ahn, Changhwan; Kang, Hee Young; Hong, Eui-Ju; Hyun, Sang-Hwan; Choi, Kyung-Chul; Jeung, Eui-Bae

    2016-01-01

    Octylphenol (OP) and bisphenol A (BPA) are known as endocrine-disrupting chemicals (EDCs). During pregnancy, the expression of steroid hormone receptors is controlled by maternal and fetal nutrition. To evaluate the impact of EDCs during pregnancy, ethinyl estradiol (EE, 0.2 mg/kg/day), OP (50 mg/kg/day), and BPA (50 mg/kg/day) were administered to pregnant mice. The mRNA levels of TRPV6 (transient receptor potential cation channels in subfamily V, member 6) decreased significantly by EE and OP. The PMCA1 (ATPase, Ca++ transporting, plasma membrane 1) mRNA and protein levels decreased significantly by EE, OP, and BPA. CTR1 (solute carrier family 31, member 1) and ATP7A (ATPase, Cu++ transporting, alpha polypeptide) expression decreased significantly by EE, OP, and BPA. The mRNA levels of IREG1 (iron-regulated transporter, member 1) decreased significantly by EE. Hephaestin (HEPH) mRNA levels decreased significantly by EE, OP, and BPA, and protein levels decreased significantly by BPA. As a result of immunohistochemistry analysis, all cation transporter proteins were found in labyrinth of placenta. To confirm the cytosolic level of cations, levels of cation level in fetal serum were measured. EE, OP, and BPA significantly reduced serum calcium and copper levels, and iron levels were reduced by BPA. Taken together, some EDCs, such as OP and BPA, could modulate the calcium, copper, and iron ion-transporting channels during pregnancy. The fetus relies on the mother for ionic transportation, and, therefore, pregnant women should avoid exposure to cation-channel-disrupting chemicals. PMID:27690074

  15. Effects of Octylphenol and Bisphenol A on the Metal Cation Transporter Channels of Mouse Placentas

    Directory of Open Access Journals (Sweden)

    Jae-Hwan Lee

    2016-09-01

    Full Text Available Octylphenol (OP and bisphenol A (BPA are known as endocrine-disrupting chemicals (EDCs. During pregnancy, the expression of steroid hormone receptors is controlled by maternal and fetal nutrition. To evaluate the impact of EDCs during pregnancy, ethinyl estradiol (EE, 0.2 mg/kg/day, OP (50 mg/kg/day, and BPA (50 mg/kg/day were administered to pregnant mice. The mRNA levels of TRPV6 (transient receptor potential cation channels in subfamily V, member 6 decreased significantly by EE and OP. The PMCA1 (ATPase, Ca++ transporting, plasma membrane 1 mRNA and protein levels decreased significantly by EE, OP, and BPA. CTR1 (solute carrier family 31, member 1 and ATP7A (ATPase, Cu++ transporting, alpha polypeptide expression decreased significantly by EE, OP, and BPA. The mRNA levels of IREG1 (iron-regulated transporter, member 1 decreased significantly by EE. Hephaestin (HEPH mRNA levels decreased significantly by EE, OP, and BPA, and protein levels decreased significantly by BPA. As a result of immunohistochemistry analysis, all cation transporter proteins were found in labyrinth of placenta. To confirm the cytosolic level of cations, levels of cation level in fetal serum were measured. EE, OP, and BPA significantly reduced serum calcium and copper levels, and iron levels were reduced by BPA. Taken together, some EDCs, such as OP and BPA, could modulate the calcium, copper, and iron ion-transporting channels during pregnancy. The fetus relies on the mother for ionic transportation, and, therefore, pregnant women should avoid exposure to cation-channel-disrupting chemicals.

  16. Block of endplate channels by permeant cations in frog skeletal muscle

    OpenAIRE

    1981-01-01

    Motor endplates of frog semitendinosus muscles were studied under voltage clamp. Current fluctuations induced by iontophoretic application of acetylcholine were analyzed to give the elementary conductance, gamma , and mean open time, tau , of endplate channels. Total replacement of the external Na+ ion by several other metal ions and by many permeant organic cations changed both gamma and tau . Except with NH4+ ions, the gamma values with foreign test ions were all smaller than expected from ...

  17. Identification and analysis of cation channel homologues in human pathogenic fungi.

    Directory of Open Access Journals (Sweden)

    David L Prole

    Full Text Available Fungi are major causes of human, animal and plant disease. Human fungal infections can be fatal, but there are limited options for therapy, and resistance to commonly used anti-fungal drugs is widespread. The genomes of many fungi have recently been sequenced, allowing identification of proteins that may become targets for novel therapies. We examined the genomes of human fungal pathogens for genes encoding homologues of cation channels, which are prominent drug targets. Many of the fungal genomes examined contain genes encoding homologues of potassium (K(+, calcium (Ca(2+ and transient receptor potential (Trp channels, but not sodium (Na(+ channels or ligand-gated channels. Some fungal genomes contain multiple genes encoding homologues of K(+ and Trp channel subunits, and genes encoding novel homologues of voltage-gated K(v channel subunits are found in Cryptococcus spp. Only a single gene encoding a homologue of a plasma membrane Ca(2+ channel was identified in the genome of each pathogenic fungus examined. These homologues are similar to the Cch1 Ca(2+ channel of Saccharomyces cerevisiae. The genomes of Aspergillus spp. and Cryptococcus spp., but not those of S. cerevisiae or the other pathogenic fungi examined, also encode homologues of the mitochondrial Ca(2+ uniporter (MCU. In contrast to humans, which express many K(+, Ca(2+ and Trp channels, the genomes of pathogenic fungi encode only very small numbers of K(+, Ca(2+ and Trp channel homologues. Furthermore, the sequences of fungal K(+, Ca(2+, Trp and MCU channels differ from those of human channels in regions that suggest differences in regulation and susceptibility to drugs.

  18. Structural Insights into Divalent Cation Modulations of ATP-Gated P2X Receptor Channels

    Directory of Open Access Journals (Sweden)

    Go Kasuya

    2016-02-01

    Full Text Available P2X receptors are trimeric ATP-gated cation channels involved in physiological processes ranging widely from neurotransmission to pain and taste signal transduction. The modulation of the channel gating, including that by divalent cations, contributes to these diverse physiological functions of P2X receptors. Here, we report the crystal structure of an invertebrate P2X receptor from the Gulf Coast tick Amblyomma maculatum in the presence of ATP and Zn2+ ion, together with electrophysiological and computational analyses. The structure revealed two distinct metal binding sites, M1 and M2, in the extracellular region. The M1 site, located at the trimer interface, is responsible for Zn2+ potentiation by facilitating the structural change of the extracellular domain for pore opening. In contrast, the M2 site, coupled with the ATP binding site, might contribute to regulation by Mg2+. Overall, our work provides structural insights into the divalent cation modulations of P2X receptors.

  19. Hyperpolarization-activated, cyclic nucleotide-gated cation channels in Aplysia: Contribution to classical conditioning

    Science.gov (United States)

    Yang, Qizong; Kuzyk, Pavlo; Antonov, Igor; Bostwick, Caleb J.; Kohn, Andrea B.; Moroz, Leonid L.; Hawkins, Robert D.

    2015-01-01

    Hyperpolarization-activated, cyclic nucleotide-gated cation (HCN) channels are critical regulators of neuronal excitability, but less is known about their possible roles in synaptic plasticity and memory circuits. Here, we characterized the HCN gene organization, channel properties, distribution, and involvement in associative and nonassociative forms of learning in Aplysia californica. Aplysia has only one HCN gene, which codes for a channel that has many similarities to the mammalian HCN channel. The cloned acHCN gene was expressed in Xenopus oocytes, which displayed a hyperpolarization-induced inward current that was enhanced by cGMP as well as cAMP. Similarly to its homologs in other animals, acHCN is permeable to K+ and Na+ ions, and is selectively blocked by Cs+ and ZD7288. We found that acHCN is predominantly expressed in inter- and motor neurons, including LFS siphon motor neurons, and therefore tested whether HCN channels are involved in simple forms of learning of the siphon-withdrawal reflex in a semiintact preparation. ZD7288 (100 μM) significantly reduced an associative form of learning (classical conditioning) but had no effect on two nonassociative forms of learning (intermediate-term sensitization and unpaired training) or baseline responses. The HCN current is enhanced by nitric oxide (NO), which may explain the postsynaptic role of NO during conditioning. HCN current in turn enhances the NMDA-like current in the motor neurons, suggesting that HCN channels contribute to conditioning through this pathway. PMID:26668355

  20. Hyperpolarization-activated, cyclic nucleotide-gated cation channels in Aplysia: Contribution to classical conditioning.

    Science.gov (United States)

    Yang, Qizong; Kuzyk, Pavlo; Antonov, Igor; Bostwick, Caleb J; Kohn, Andrea B; Moroz, Leonid L; Hawkins, Robert D

    2015-12-29

    Hyperpolarization-activated, cyclic nucleotide-gated cation (HCN) channels are critical regulators of neuronal excitability, but less is known about their possible roles in synaptic plasticity and memory circuits. Here, we characterized the HCN gene organization, channel properties, distribution, and involvement in associative and nonassociative forms of learning in Aplysia californica. Aplysia has only one HCN gene, which codes for a channel that has many similarities to the mammalian HCN channel. The cloned acHCN gene was expressed in Xenopus oocytes, which displayed a hyperpolarization-induced inward current that was enhanced by cGMP as well as cAMP. Similarly to its homologs in other animals, acHCN is permeable to K(+) and Na(+) ions, and is selectively blocked by Cs(+) and ZD7288. We found that acHCN is predominantly expressed in inter- and motor neurons, including LFS siphon motor neurons, and therefore tested whether HCN channels are involved in simple forms of learning of the siphon-withdrawal reflex in a semiintact preparation. ZD7288 (100 μM) significantly reduced an associative form of learning (classical conditioning) but had no effect on two nonassociative forms of learning (intermediate-term sensitization and unpaired training) or baseline responses. The HCN current is enhanced by nitric oxide (NO), which may explain the postsynaptic role of NO during conditioning. HCN current in turn enhances the NMDA-like current in the motor neurons, suggesting that HCN channels contribute to conditioning through this pathway.

  1. Activation of TRPV1 channels inhibits mechanosensitive Piezo channel activity by depleting membrane phosphoinositides.

    Science.gov (United States)

    Borbiro, Istvan; Badheka, Doreen; Rohacs, Tibor

    2015-02-10

    Capsaicin is an activator of the heat-sensitive TRPV1 (transient receptor potential vanilloid 1) ion channels and has been used as a local analgesic. We found that activation of TRPV1 channels with capsaicin either in dorsal root ganglion neurons or in a heterologous expression system inhibited the mechanosensitive Piezo1 and Piezo2 channels by depleting phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and its precursor phosphatidylinositol 4-phosphate [PI(4)P] from the plasma membrane through Ca(2+)-induced phospholipase Cδ (PLCδ) activation. Experiments with chemically inducible phosphoinositide phosphatases and receptor-induced activation of PLCβ indicated that inhibition of Piezo channels required depletion of both PI(4)P and PI(4,5)P2. The mechanically activated current amplitudes decreased substantially in the excised inside-out configuration, where the membrane patch containing Piezo1 channels is removed from the cell. PI(4,5)P2 and PI(4)P applied to these excised patches inhibited this decrease. Thus, we concluded that Piezo channel activity requires the presence of phosphoinositides, and the combined depletion of PI(4,5)P2 and PI(4)P reduces channel activity. In addition to revealing a role for distinct membrane lipids in mechanosensitive ion channel regulation, these data suggest that inhibition of Piezo2 channels may contribute to the analgesic effect of capsaicin.

  2. Modeling hysteresis observed in the human erythrocyte voltage-dependent cation channel

    DEFF Research Database (Denmark)

    Flyvbjerg, Henrik; Gudowska-Nowak, Ewa; Christophersen, Palle;

    2012-01-01

    The non-selective voltage-activated cation channel from human red cells, which is activated at depolarizing potentials, has been shown to exhibit counter-clockwise gating hysteresis. Here, we analyze this phenomenon with the simplest possible phenomenological models. Specifically, the hysteresis...... cycle, including its direction, is reproduced by a model with 2×2 discrete states: the normal open/closed states and two different states of "gate tension". Rates of transitions between the two branches of the hysteresis curve are modeled with single-barrier kinetics by introducing a real...

  3. The broad-spectrum cation channel blocker pinokalant (LOE 908 MS) reduces brain infarct volume in rats

    DEFF Research Database (Denmark)

    Christensen, Thomas; Wienrich, Marion; Ensinger, Helmut A;

    2005-01-01

    Activation of cation channels conducting Ca2+, Na+ and K+ is involved in the pathogenesis of infarction in experimental focal cerebral ischaemia. Pinokalant (LOE 908 MS) is a novel broad-spectrum inhibitor of several subtypes of such channels and has previously been shown to improve the metabolic...

  4. Cationic oligonucleotides can mediate specific inhibition of gene expression in Xenopus oocytes.

    OpenAIRE

    Bailey, C P; Dagle, J M; Weeks, D L

    1998-01-01

    Base-specific hydrogen bonding between an oligonucleotide and the purines in the major groove of a DNA duplex provide an approach to selective inhibition of gene expression. Oligonucleotide-mediated triplex formation in vivo may be enhanced by a number of different chemical modifications. We have previously described an in vitro analysis of triplex formation using oligonucleotides containing internucleoside phosphate linkages modified with the cation N , N -diethyl-ethylenediamine (DEED). Whe...

  5. Divalent cation ionophores stimulate resorption and inhibit DNA synthesis in cultured fetal rat bone

    Energy Technology Data Exchange (ETDEWEB)

    Lorenzo, J.A.; Raisz, L.G.

    1981-06-01

    Two divalent cation ionophores, A23187 and Ionomycin, which are selective for calcium, stimulated the resorption of fetal rat long bones in organ culture at 0.1 to 1 micromolar but not at higher concentrations. Both agents inhibited DNA synthesis at concentrations that stimulated resorption. These results might explain the differences in ionophore effects on bone previously reported, and they imply that cell replication is not required for osteoclast formation in fetal rat long bone cultures.

  6. Inhibition of Voltage-Gated Calcium Channels by RGK Proteins.

    Science.gov (United States)

    Buraei, Zafir; Yang, Jian

    2015-01-01

    Due to their essential biological roles, voltage-gated calcium channels (VGCCs) are regulated by a myriad of molecules and mechanisms. Fifteen years ago, RGK proteins were discovered to bind the VGCC β subunit (Cavβ) and potently inhibit high-voltage activated Ca(2+) channels. RGKs (Rad, Rem, Rem2 and Gem/Kir) are a family of monomeric small GTPases belonging to the superfamily of Ras GTPases. They exert dual inhibitory effects on VGCCs, decreasing surface expression and suppressing surface channels through immobilization of the voltage sensor or reduction of channel open probability. While Cavβ is required for all forms of RGK inhibition, not all inhibition is mediated by the RGK-Cavβ interaction. Some RGK proteins also interact directly with the pore-forming α1 subunit of some types of VGCCs (Cavα1). Importantly, RGK proteins tonically inhibit VGCCs in native cells, regulating cardiac and neural functions. This minireview summarizes the mechanisms, molecular determinants, and physiological impact of RGK inhibition of VGCCs. PMID:25966691

  7. Inhibition of voltage-gated sodium channels by sumatriptan bioisosteres

    Directory of Open Access Journals (Sweden)

    Roberta eCarbonara

    2015-07-01

    Full Text Available Voltage-gated sodium channels are known to play a pivotal role in perception and transmission of pain sensations. Gain-of-function mutations in the genes encoding the peripheral neuronal sodium channels, hNav1.7-1.9, cause human painful diseases. Thus while treatment of chronic pain remains an unmet clinical need, sodium channel blockers are considered as promising druggable targets. In a previous study, we evaluated the analgesic activity of sumatriptan, an agonist of serotonin 5HT1B/D receptors, and some new chiral bioisosteres, using the hot plate test in the mouse. Interestingly, we observed that the analgesic effectiveness was not necessarily correlated to serotonin agonism. In this study, we evaluated whether sumatriptan and its congeners may inhibit heterologously-expressed hNav1.7 sodium channels using the patch-clamp method. We show that sumatriptan blocks hNav1.7 channels only at very high, supratherapeutic concentrations. In contrast, its three analogues, namely 20b, (R-31b, and (S-22b, exert a dose and use-dependent sodium channel block. At 0.1 and 10 Hz stimulation frequencies, the most potent compound, (S-22b, was 4.4 and 1.7 fold more potent than the well-known sodium channel blocker mexiletine. The compound induces a negative shift of voltage dependence of fast inactivation, suggesting higher affinity to the inactivated channel. Accordingly, we show that (S-22b likely binds the conserved local anesthetic receptor within voltage-gated sodium channels. Combining these results with the previous ones, we hypothesize that use-dependent sodium channel blockade contributes to the analgesic activity of (R-31b and (S-22b. These later compounds represent promising lead compounds for the development of efficient analgesics, the mechanism of action of which may include a dual action on sodium channels and 5HT1D receptors.

  8. Inhibition of TRPV1 channels enables long-term potentiation in the entorhinal cortex.

    Science.gov (United States)

    Banke, Tue G

    2016-04-01

    The transient receptor potential vanilloid 1 (TRPV1) channel is a non-selective cation channel that is mainly found in nociceptive neurons of the peripheral nervous system; however, these channels have also been located within the CNS, including the entorhinal cortex. Whole-cell patch-clamp recordings of principal entorhinal cortex (EC) layers II/III neurons revealed that evoked inhibitory postsynaptic currents were depressed by application of the TRPV1 agonist capsaicin (CAP), accompanied by a change in the pair-pulse ratio (PPR). In addition, recordings of miniature inhibitory postsynaptic currents (mIPSCs) revealed that inter-event intervals but not amplitude were decreased in wild-type (WT) after application of CAP. This suggests that TRPV1 channels are functional in the entorhinal cortex and are located on inhibitory neurons with their axonal arborization within layers II/III. In order to study TRPV1 channels and their involvement in long-term potentiation (LTP) induction in a more intact circuit, extracellular field potential recordings were performed in EC layers II/III. It was found that activated TRPV1 channels preclude induction of long-term potentiation. In sharp contrast, clear LTP was observed when antagonizing TRPV1 channels or recording from TRPV1 knock-out mice. Thus, these results suggests that signaling through activating inhibitory presynaptic TRPV1 channels represents a novel mechanism by which a shift in feed-forward inhibition of layers II/III cortical principal neurons prompt changes in synaptic strength and thereby contribute to a change of information storage within the brain. PMID:26729265

  9. Disulphide cross linked pullulan based cationic polymer for improved gene delivery and efflux pump inhibition.

    Science.gov (United States)

    S, Priya S; R, Rekha M

    2016-10-01

    Multidrug resistance is a hurdle to successful cancer chemotherapy. Over expression of P-glycoprotein (P-gp) is a prime contributing factor for drug resistance. In this study, a disulphide cross-linked pullulan-based cationic polymer (PPSS) was synthesized to act simultaneously as gene delivery vehicle and efflux pump inhibitor. The PPSS nanoplexes were of size p53/PPSS/DOX nanoplexes was attributed to the synergistic effect of P-gp inhibition and p53 transfection efficiency. Therefore, this multifunctional polymeric system may have significant promise for therapeutic application against cancer drug resistance. PMID:27459414

  10. OmpW of Caulobacter crescentus Functions as an Outer Membrane Channel for Cations.

    Directory of Open Access Journals (Sweden)

    Roland Benz

    Full Text Available Caulobacter crescentus is an oligotrophic bacterium that lives in dilute organic environments such as soil and freshwater. This bacterium represents an interesting model for cellular differentiation and regulation because daughter cells after division have different forms: one is motile while the other is non-motile and can adhere to surfaces. Interestingly, the known genome of C. crescentus does not contain genes predicted to code for outer membrane porins of the OmpF/C general diffusion type present in enteric bacteria or those coding for specific porins selective for classes of substrates. Instead, genes coding for 67 TonB-dependent outer membrane receptors have been identified, suggesting that active transport of specific nutrients may be the norm. Here, we report that high channel-forming activity was observed with crude outer membrane extracts of C. crescentus in lipid bilayer experiments, indicating that the outer membrane of C. crescentus contained an ion-permeable channel with a single-channel conductance of about 120 pS in 1M KCl. The channel-forming protein with an apparent molecular mass of about 20 kDa was purified to homogeneity. Partial protein sequencing of the protein indicated it was a member of the OmpW family of outer membrane proteins from Gram-negative bacteria. This channel was not observed in reconstitution experiments with crude outer membrane extracts of an OmpW deficient C. crescentus mutant. Biophysical analysis of the C. crescentus OmpW suggested that it has features that are special for general diffusion porins of Gram-negative outer membranes because it was not a wide aqueous channel. Furthermore, OmpW of C. crescentus seems to be different to known OmpW porins and has a preference for ions, in particular cations. A putative model for OmpW of C. crescentus was built on the basis of the known 3D-structures of OmpW of Escherichia coli and OprG of Pseudomonas aeruginosa using homology modeling. A comparison of the two

  11. OmpW of Caulobacter crescentus Functions as an Outer Membrane Channel for Cations.

    Science.gov (United States)

    Benz, Roland; Jones, Michael D; Younas, Farhan; Maier, Elke; Modi, Niraj; Mentele, Reinhard; Lottspeich, Friedrich; Kleinekathöfer, Ulrich; Smit, John

    2015-01-01

    Caulobacter crescentus is an oligotrophic bacterium that lives in dilute organic environments such as soil and freshwater. This bacterium represents an interesting model for cellular differentiation and regulation because daughter cells after division have different forms: one is motile while the other is non-motile and can adhere to surfaces. Interestingly, the known genome of C. crescentus does not contain genes predicted to code for outer membrane porins of the OmpF/C general diffusion type present in enteric bacteria or those coding for specific porins selective for classes of substrates. Instead, genes coding for 67 TonB-dependent outer membrane receptors have been identified, suggesting that active transport of specific nutrients may be the norm. Here, we report that high channel-forming activity was observed with crude outer membrane extracts of C. crescentus in lipid bilayer experiments, indicating that the outer membrane of C. crescentus contained an ion-permeable channel with a single-channel conductance of about 120 pS in 1M KCl. The channel-forming protein with an apparent molecular mass of about 20 kDa was purified to homogeneity. Partial protein sequencing of the protein indicated it was a member of the OmpW family of outer membrane proteins from Gram-negative bacteria. This channel was not observed in reconstitution experiments with crude outer membrane extracts of an OmpW deficient C. crescentus mutant. Biophysical analysis of the C. crescentus OmpW suggested that it has features that are special for general diffusion porins of Gram-negative outer membranes because it was not a wide aqueous channel. Furthermore, OmpW of C. crescentus seems to be different to known OmpW porins and has a preference for ions, in particular cations. A putative model for OmpW of C. crescentus was built on the basis of the known 3D-structures of OmpW of Escherichia coli and OprG of Pseudomonas aeruginosa using homology modeling. A comparison of the two known structures

  12. Extracellular quaternary ammonium blockade of transient receptor potential vanilloid subtype 1 channels expressed in Xenopus laevis oocytes

    DEFF Research Database (Denmark)

    Rivera-Acevedo, Ricardo E; Pless, Stephan Alexander; Schwarz, Stephan K W;

    2012-01-01

    Transient receptor potential vanilloid subtype 1 (TRPV1) channels are essential nociceptive integrators in primary afferent neurons. These nonselective cation channels are inhibited by local anesthetic compounds through an undefined mechanism. Here, we show that lidocaine inhibits TRPV1 channels ...

  13. Transient Receptor Potential Melastatin 7 Cation Channel Kinase: New Player in Angiotensin II-Induced Hypertension.

    Science.gov (United States)

    Antunes, Tayze T; Callera, Glaucia E; He, Ying; Yogi, Alvaro; Ryazanov, Alexey G; Ryazanova, Lillia V; Zhai, Alexander; Stewart, Duncan J; Shrier, Alvin; Touyz, Rhian M

    2016-04-01

    Transient receptor potential melastatin 7 (TRPM7) is a bifunctional protein comprising a magnesium (Mg(2+))/cation channel and a kinase domain. We previously demonstrated that vasoactive agents regulate vascular TRPM7. Whether TRPM7 plays a role in the pathophysiology of hypertension and associated cardiovascular dysfunction is unknown. We studied TRPM7 kinase-deficient mice (TRPM7Δkinase; heterozygous for TRPM7 kinase) and wild-type (WT) mice infused with angiotensin II (Ang II; 400 ng/kg per minute, 4 weeks). TRPM7 kinase expression was lower in heart and aorta from TRPM7Δkinase versus WT mice, effects that were further reduced by Ang II infusion. Plasma Mg(2+) was lower in TRPM7Δkinase versus WT mice in basal and stimulated conditions. Ang II increased blood pressure in both strains with exaggerated responses in TRPM7Δkinase versus WT groups (Phypertension is exaggerated, cardiac remodeling and left ventricular dysfunction are amplified, and endothelial function is impaired. These processes are associated with hypomagnesemia, blunted TRPM7 kinase expression/signaling, endothelial nitric oxide synthase downregulation, and proinflammatory vascular responses. Our findings identify TRPM7 kinase as a novel player in Ang II-induced hypertension and associated vascular and target organ damage.

  14. The cation channel TRPA1 tunes mosquito thermotaxis to host temperatures.

    Science.gov (United States)

    Corfas, Román A; Vosshall, Leslie B

    2015-01-01

    While most animals thermotax only to regulate their temperature, female mosquitoes are attracted to human body heat during pursuit of a blood meal. Here we elucidate the basic rules of Aedes aegypti thermotaxis and test the function of candidate thermoreceptors in this important behavior. We show that host-seeking mosquitoes are maximally attracted to thermal stimuli approximating host body temperatures, seeking relative warmth while avoiding both relative cool and stimuli exceeding host body temperature. We found that the cation channel TRPA1, in addition to playing a conserved role in thermoregulation and chemosensation, is required for this specialized host-selective thermotaxis in mosquitoes. During host-seeking, AaegTRPA1(-/-) mutants failed to avoid stimuli exceeding host temperature, and were unable to discriminate between host-temperature and high-temperature stimuli. TRPA1-dependent tuning of thermotaxis is likely critical for mosquitoes host-seeking in a complex thermal environment in which humans are warmer than ambient air, but cooler than surrounding sun-warmed surfaces. PMID:26670734

  15. Involvement of Transient Receptor Potential Cation Channel Vanilloid 1 (TRPV1) in Myoblast Fusion.

    Science.gov (United States)

    Kurosaka, Mitsutoshi; Ogura, Yuji; Funabashi, Toshiya; Akema, Tatsuo

    2016-10-01

    The mechanisms that underlie the complex process of muscle regeneration after injury remain unknown. Transient receptor potential cation channel vanilloid 1 (TRPV1) is expressed in several cell types, including skeletal muscle, and is activated by high temperature and by certain molecules secreted during tissue inflammation. Severe inflammation and local temperature perturbations are induced during muscle regeneration, which suggests that TRPV1 might be activated and involved in the process. The aim of this study, was to clarify the role of TRPV1 in the myogenic potential of satellite cells responsible for muscle regeneration. We found that mRNA and protein levels of TRPV1 increased during regeneration after cardiotoxin (CTX)-induced muscle injury in mice. Using isolated mouse satellite cells (i.e., myoblasts), we observed that activation of TRPV1 by its agonist capsaicin (CAP) augmented myogenin protein levels. Whereas CAP did not alter myoblast proliferation, it facilitated myoblast fusion (evaluated using myonucleii number per myotube and fusion index). In contrast, suppression of TRPV1 by siRNA impaired myoblast fusion. Using mice, we also demonstrated that intramuscular injection of CAP facilitated muscle repair after CTX-induced muscle injury. Moreover, we showed that these roles of TRPV1 might be mediated by interleukin-4 and calcium signaling during myoblast fusion. Collectively, these results suggest that TRPV1 underlies normal myogenesis through promotion of myoblast fusion. J. Cell. Physiol. 231: 2275-2285, 2016. © 2016 Wiley Periodicals, Inc. PMID:26892397

  16. Curcumin inhibits activation of TRPM2 channels in rat hepatocytes

    Directory of Open Access Journals (Sweden)

    E. Kheradpezhouh

    2016-04-01

    Full Text Available Oxidative stress is a hallmark of many liver diseases including viral and drug-induced hepatitis, ischemia-reperfusion injury, and non-alcoholic steatohepatitis. One of the consequences of oxidative stress in the liver is deregulation of Ca2+ homeostasis, resulting in a sustained elevation of the free cytosolic Ca2+ concentration ([Ca2+]c in hepatocytes, which leads to irreversible cellular damage. Recently it has been shown that liver damage induced by paracetamol and subsequent oxidative stress is, in large part, mediated by Ca2+ entry through Transient Receptor Potential Melastatin 2 (TRPM2 channels. Involvement of TRPM2 channels in hepatocellular damage induced by oxidative stress makes TRPM2 a potential therapeutic target for treatment of a range of oxidative stress-related liver diseases. We report here the identification of curcumin ((1E,6E-1,7-bis(4-hydroxy-3-methoxyphenyl-1,6-heptadiene-3,5-dione, a natural plant-derived polyphenol in turmeric spice, as a novel inhibitor of TRPM2 channel. Presence of 5 µM curcumin in the incubation medium prevented the H2O2- and paracetamol-induced [Ca2+]c rise in rat hepatocytes. Furthermore, in patch clamping experiments incubation of hepatocytes with curcumin inhibited activation of TRPM2 current by intracellular ADPR with IC50 of approximately 50 nM. These findings enhance understanding of the actions of curcumin and suggest that the known hepatoprotective properties of curcumin are, at least in part, mediated through inhibition of TRPM2 channels.

  17. Inhibition of biofouling by modification of forward osmosis membrane using quaternary ammonium cation.

    Science.gov (United States)

    Park, Kang-Hee; Yu, Sang-Hyun; Kim, Han-Shin; Park, Hee-Deung

    2015-01-01

    In the operation of the forward osmosis (FO) process, biofouling of the membrane is a potentially serious problem. Development of an FO membrane with antibacterial properties could contribute to a reduction in biofouling. In this study, quaternary ammonium cation (QAC), a widely used biocidal material, was conjugated with a silane coupling agent (3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride) and used to modify an FO membrane to confer antibacterial properties. Fourier transform infrared spectroscopy (FT-IR) demonstrated that the conjugated QAC was successfully immobilized on the FO membrane via covalent bonding. Bacterial viability on the QAC-modified membrane was confirmed via colony count method and visualized via bacterial viability assay. The QAC membrane decreased the viability of Escherichia coli to 62% and Staphylococcus aureus to 77% versus the control membrane. Inhibition of biofilm formation on the QAC modified membrane was confirmed via anti-biofilm tests using the drip-flow reactor and FO unit, resulting in 64% and 68% inhibition in the QAC-modified membrane against the control membrane, respectively. The results demonstrate the effectiveness of the modified membrane in reducing bacterial viability and inhibiting biofilm formation, indicating the potential of QAC-modified membranes to decrease operation costs incurred by biofouling.

  18. Inhibition of human organic cation transporters by the alkaloids matrine and oxymatrine.

    Science.gov (United States)

    Pan, Xiaolei; Wang, Li; Gründemann, Dirk; Sweet, Douglas H

    2014-01-01

    Human organic cation transporters (hOCTs; SLC22) are expressed in many organs, including intestine, liver, kidney, heart and brain, where they contribute to the absorption, distribution, and elimination of endogenous and exogenous substances. The alkaloids matrine and oxymatrine are widely used in herbal medicine for the treatment of cancer, as well as viral, and cardiac diseases. Their physicochemical properties indicated that they are potential inhibitors for hOCTs, leading to drug-drug interactions in vivo. Therefore, we assessed the inhibitory effects of matrine and oxymatrine on the function of hOCT1 (SLC22A1), hOCT2 (SLC22A2) and hOCT3 (SLC22A3) using stably transfected transporter-expressing cells. At 100-fold excess, oxymatrine exhibited marked inhibition of hOCT1-mediated substrate uptake (pmatrine failed to produce significant inhibition on hOCT1. The IC50 value for oxymatrine on hOCT1 was estimated as 513±132 μM. While there was no significant inhibition of hOCT2 or hOCT3 at 100-fold excess, oxymatrine and matrine showed 42% and 88% inhibition of hOCT3-mediated substrate uptake at 3 and 6mM, respectively. Considering the potential intestinal lumen and reported plasma concentrations of matrine and oxymatrine, these data suggest that drug-drug interactions may occur during hOCT1-mediated hepatic and renal uptake and during hOCT3-mediated intestinal absorption.

  19. Influence of dexamethasone on the expression and distribution of transient receptor potential cation channel 6 in glomerular podocytes

    Institute of Scientific and Technical Information of China (English)

    王辉阳

    2014-01-01

    Objective To observe the changes of foot processes,expression and distribution of transient receptor potential cation channel 6(TRPC6)in podocytes by puromycin aminonucleoside(PAN)and dexamethasone(DEX)intervention,then to investigate the function of TRPC6 in podocytes and its relation to proteinuria in kidney diseases.Methods Podocytes cultured in vitro were divided into three group:control group,PAN stimulation group and DEX intervention group.Mouse podocyte cell line

  20. The human red cell voltage-dependent cation channel. Part III: Distribution homogeneity and pH dependence

    DEFF Research Database (Denmark)

    Bennekou, P.; Barksmann, T. L.; Christophersen, P.;

    2006-01-01

    The homogeneity of the distribution of the non-selective voltage-dependent cation channel (the NSVDC channel) in the human erythrocyte, and the pH dependence was investigated. Activation of this channel caused a uniform cellular dehydration, which was characterized by the changes in the erythrocyte...... osmotic resistance profiles: After 1/2 h of activation, the osmolarity at 50% hemolysis changed from 73 mM (control) to 34 mM NaCl, corresponding to 0.48% and 0.21% NaCl respectively. Unchanging standard deviations show participation of the entire erythrocyte population, which implies an even distribution...... - but not the extracellular - pH. The apparent pKA value for the effect was estimated to be 6.5, and the specific histidine reagent 2.4'-dibromoacetophenone (DBAB) inactivated the NSVDC channel....

  1. Influence of some growth regulators and cations on inhibition of chlorophyll biosynthesis by lead in maize

    Energy Technology Data Exchange (ETDEWEB)

    Sinha, S.K. (Council of Science Technology, Lucknow (India)); Srivastava, H.S. (Rohilkhand Univ., Bareilly (India)); Tripathi, R.D. (National Botanical Research Institute, Lucknow (India))

    1993-08-01

    Phytotoxic effects of Pb pollution are well established. In order to analyse the physiological basis of toxic symptoms and of reduced plant productivity, its effect on chlorophyll content has been examined in some plants. Thus, a decrease in total chlorophyll content during Pb supply has been observed in oats, mung beam, pea, etc. The activity of delta aminolevulinic acid dehydratase, an important enzyme in the biosynthesis of heme pigments, is inhibited by Pb in mung bean and several other species. This observation may perhaps indicate that a reduction in chlorophyll content in the presence of lead is due to an inhibition of pigment synthesis. The effect of Pb on greening maize leaf segments in the presence of various precursors of chlorophyll has been studied in the present investigation to evaluate this hypothesis. The effect of some growth regulators and cations, which could otherwise modify chlorophyll biosynthesis, has been examined to see whether the toxic effects of Pb on photosynthetic pigments could also be modified by these effectors. 16 refs., 4 tabs.

  2. Gap-junction channels inhibit transverse propagation in cardiac muscle

    Directory of Open Access Journals (Sweden)

    Ramasamy Lakshminarayanan

    2005-01-01

    Full Text Available Abstract The effect of adding many gap-junctions (g-j channels between contiguous cells in a linear chain on transverse propagation between parallel chains was examined in a 5 × 5 model (5 parallel chains of 5 cells each for cardiac muscle. The action potential upstrokes were simulated using the PSpice program for circuit analysis. Either a single cell was stimulated (cell A1 or the entire chain was stimulated simultaneously (A-chain. Transverse velocity was calculated from the total propagation time (TPT from when the first AP crossed a Vm of -20 mV and the last AP crossed -20 mV. The number of g-j channels per junction was varied from zero to 100, 1,000 and 10,000 (Rgj of ∞, 100 MΩ, 10 MΩ, 1.0 MΩ, respectively. The longitudinal resistance of the interstitial fluid (ISF space between the parallel chains (Rol2 was varied between 200 KΩ (standard value and 1.0, 5.0, and 10 MΩ. The higher the Rol2 value, the tighter the packing of the chains. It was found that adding many g-j channels inhibited transverse propagation by blocking activation of all 5 chains, unless Rol2 was greatly increased above the standard value of 200 KΩ. This was true for either method of stimulation. This was explained by, when there is strong longitudinal coupling between all 5 cells of a chain awaiting excitation, there must be more transfer energy (i.e., more current to simultaneously excite all 5 cells of a chain.

  3. Structure of gramicidin D-RbCl complex at atomic resolution from low-temperature synchrotron data: interactions of double-stranded gramicidin channel contents and cations with channel wall

    Energy Technology Data Exchange (ETDEWEB)

    Glówka, M.L.; Olczak, A.; Bojarska, J.; Szczesio, M.; Duax, W.L.; Burkhart, B.M.; Pangborn, W.A.; Langs, D.A.; Wawrzak, Z. (Poland); (NWU); (Hauptman)

    2010-03-05

    Gramicidin D (gD) is a naturally occurring ionophoric antibiotic that forms membrane channels specific for monovalent cations. The crystal structure of the RbCl complex of gD has been determined at 1.14 {angstrom} resolution from low-temperature (100 K) synchrotron-radiation data with a final R of 16%. The structure was refined with anisotropic temperature factors for all non-H atoms and with partial occupancies for many of them. The asymmetric unit in the crystal contains four crystallographically independent molecules that form two right-handed antiparallel double-stranded dimers. There are seven distinct rubidium-binding sites in each dimeric channel. The occupancy factors of Rb cations are between 0.11 and 0.35 and the total ion contents of the two crystallographically independent channels are 1.59 and 1.22 ions, respectively. Although each channel is 'chemically symmetrical', the side-chain conformations, the distributions of rubidium cations and their binding sites in the two independent channels are not. Cations are 'coordinated' by delocalized {pi}-electrons of three to five carbonyl groups that together with peptide backbone chains form the gramicidin channel walls. The water:cation ratio in the channel interior is four or five:one, and five or six waters separate Rb cations during their passage through the channel.

  4. A genome-wide study of panic disorder suggests the amiloride-sensitive cation channel 1 as a candidate gene

    DEFF Research Database (Denmark)

    Gregersen, Noomi; Dahl, Hans A.; Buttenschön, Henriette N.;

    2012-01-01

    Panic disorder (PD) is a mental disorder with recurrent panic attacks that occur spontaneously and are not associated to any particular object or situation. There is no consensus on what causes PD. However, it is recognized that PD is influenced by environmental factors, as well as genetic factors...... of the Faroe Islands. Subsequently, we conducted a fine mapping, which revealed the amiloride-sensitive cation channel 1 (ACCN1) located on chromosome 17q11.2-q12 as a potential candidate gene for PD. The further analyses of the ACCN1 gene using single-nucleotide polymorphisms (SNPs) revealed significant...

  5. Triple-channel portable capillary electrophoresis instrument with individual background electrolytes for the concurrent separations of anionic and cationic species.

    Science.gov (United States)

    Mai, Thanh Duc; Le, Minh Duc; Sáiz, Jorge; Duong, Hong Anh; Koenka, Israel Joel; Pham, Hung Viet; Hauser, Peter C

    2016-03-10

    The portable capillary electrophoresis instrument is automated and features three independent channels with different background electrolytes to allow the concurrent optimized determination of three different categories of charged analytes. The fluidic system is based on a miniature manifold which is based on mechanically milled channels for injection of samples and buffers. The planar manifold pattern was designed to minimize the number of electronic valves required for each channel. The system utilizes pneumatic pressurization to transport solutions at the grounded as well as the high voltage side of the separation capillaries. The instrument has a compact design, with all components arranged in a briefcase with dimensions of 45 (w) × 35 (d) × 15 cm (h) and a weight of about 15 kg. It can operate continuously for 8 h in the battery-powered mode if only one electrophoresis channel is in use, or for about 2.5 h in the case of simultaneous employment of all three channels. The different operations, i.e. capillary flushing, rinsing of the interfaces at both capillary ends, sample injection and electrophoretic separation, are activated automatically with a control program featuring a graphical user interface. For demonstration, the system was employed successfully for the concurrent separation of different inorganic cations and anions, organic preservatives, additives and artificial sweeteners in various beverage and food matrices. PMID:26893094

  6. Cation gating and selectivity in a purified, reconstituted, voltage-dependent sodium channel

    International Nuclear Information System (INIS)

    In excitable membranes, the voltage-dependent sodium channel controls the primary membrane conductance change necessary for the generation of an action potential. Over the past four decades, the time- and voltage-dependent sodium currents gated by this channel have been thoroughly documented with increasingly sophisticated voltage-clamp techniques. Recent advances in the biochemistry of membrane proteins have led to the solubilization and purification of this channel protein from nerve (6) and from muscle (4) or muscle-derived (1) membranes, and have provided an approach to the correlation of the channel's molecular structure with its functional properties. Each of these sodium channel preparations appears to contain a large glycoprotein either as its sole component (2) or in association with several small subunits (6, 3). Evidence that these purified proteins represent the excitable membrane sodium channel is presented. 8 refs., 1 fig., 1 tab

  7. Involvement of Potassium and Cation Channels in Hippocampal Abnormalities of Embryonic Ts65Dn and Tc1 Trisomic Mice

    Directory of Open Access Journals (Sweden)

    Shani Stern

    2015-09-01

    Numerical simulations reproduced the DS measured phenotype by variations in the conductance of the delayed rectifier and A-type, but necessitated also changes in inward rectifying and M-type potassium channels and in the hyperpolarization-activated cyclic nucleotide-gated (HCN channels. We therefore conducted whole cell patch clamp measurements of M-type potassium currents, which showed a ~90% decrease in Ts65Dn neurons, while HCN measurements displayed an increase of ~65% in Ts65Dn cells. Quantitative real-time PCR analysis indicates overexpression of 40% of KCNJ15, an inward rectifying potassium channel, contributing to the increased inhibition. We thus find that changes in several types of potassium channels dominate the observed DS model phenotype.

  8. Hyperpolarization-activated cation and T-type calcium ion channel expression in porcine and human renal pacemaker tissues.

    Science.gov (United States)

    Hurtado, Romulo; Smith, Carl S

    2016-05-01

    Renal pacemaker activity triggers peristaltic upper urinary tract contractions that propel waste from the kidney to the bladder, a process prone to congenital defects that are the leading cause of pediatric kidney failure. Recently, studies have discovered that hyperpolarization-activated cation (HCN) and T-type calcium (TTC) channel conductances underlie murine renal pacemaker activity, setting the origin and frequency and coordinating upper urinary tract peristalsis. Here, we determined whether this ion channel expression is conserved in the porcine and human urinary tracts, which share a distinct multicalyceal anatomy with multiple pacemaker sites. Double chromagenic immunohistochemistry revealed that HCN isoform 3 is highly expressed at the porcine minor calyces, the renal pacemaker tissues, whereas the kidney and urinary tract smooth muscle lacked this HCN expression. Immunofluorescent staining demonstrated that HCN(+) cells are integrated within the porcine calyx smooth muscle, and that they co-express TTC channel isoform Cav3.2. In humans, the anatomic structure of the minor calyx pacemaker was assayed via hematoxylin and eosin analyses, and enabled the visualization of the calyx smooth muscle surrounding adjacent papillae. Strikingly, immunofluorescence revealed that HCN3(+) /Cav3.2(+) cells are also localized to the human minor calyx smooth muscle. Collectively, these data have elucidated a conserved molecular signature of HCN and TTC channel expression in porcine and human calyx pacemaker tissues. These findings provide evidence for the mechanisms that can drive renal pacemaker activity in the multi-calyceal urinary tract, and potential causes of obstructive uropathies. PMID:26805464

  9. Divalent cation tolerance protein binds to β-secretase and inhibits the processing of amyloid precursor protein

    Institute of Scientific and Technical Information of China (English)

    Runzhong Liu; Haibo Hou; Xuelian Yi; Shanwen Wu; Huan Zeng

    2013-01-01

    The deposition of amyloid-beta is a pathological hallmark of Alzheimer's disease. Amyloid-beta is derived from amyloid precursor protein through sequential proteolytic cleavages by β-secretase (beta-site amyloid precursor protein-cleaving enzyme 1) and γ-secretase. To further elucidate the roles of beta-site amyloid precursor protein-cleaving enzyme 1 in the development of Alzheimer's disease, a yeast two-hybrid system was used to screen a human embryonic brain cDNA library for proteins directly interacting with the intracellular domain of beta-site amyloid precursor protein-cleaving enzyme 1. A potential beta-site amyloid precursor protein-cleaving enzyme 1- interacting protein identified from the positive clones was divalent cation tolerance protein. Immunoprecipitation studies in the neuroblastoma cell line N2a showed that exogenous divalent cation tolerance protein interacts with endogenous beta-site amyloid precursor protein-cleaving enzyme 1. The overexpression of divalent cation tolerance protein did not affect beta-site amyloid precursor protein-cleaving enzyme 1 protein levels, but led to increased amyloid precursor protein levels in N2a/APP695 cells, with a concomitant reduction in the processing product amyloid precursor protein C-terminal fragment, indicating that divalent cation tolerance protein inhibits the processing of amyloid precursor protein. Our experimental findings suggest that divalent cation tolerance protein negatively regulates the function of beta-site amyloid precursor protein-cleaving enzyme 1. Thus, divalent cation tolerance protein could play a protective role in Alzheimer's disease.

  10. Ancient association between cation leak channels and Mid1 proteins is conserved in fungi and animals

    Directory of Open Access Journals (Sweden)

    Alfredo eGhezzi

    2014-03-01

    Full Text Available Neuronal resting potential can tune the excitability of neural networks, affecting downstream behavior. Sodium leak channels (NALCN play a key role in rhythmic behaviors by helping set, or subtly changing neuronal resting potential. The full complexity of these newly described channels is just beginning to be appreciated, however. NALCN channels can associate with numerous subunits in different tissues and can be activated by several different peptides and second messengers. We recently showed that NALCN channels are closely related to fungal calcium channels, which they functionally resemble. Here, we use this relationship to predict a family of NALCN-associated proteins in animals on the basis of homology with the yeast protein Mid1, the subunit of the yeast calcium channel. These proteins all share a cysteine-rich region that is necessary for Mid1 function in yeast. We validate this predicted association by showing that the Mid1 homolog in Drosophila, encoded by the CG33988 gene, is coordinately expressed with NALCN, and that knockdown of either protein creates identical phenotypes in several behaviors associated with NALCN function. The relationship between Mid1 and leak channels has therefore persisted over a billion years of evolution, despite drastic changes to both proteins and the organisms in which they exist.

  11. Inhibition of Escherichia coli chemotaxis by omega-conotoxin, a calcium ion channel blocker.

    OpenAIRE

    Tisa, L S; Olivera, B M; Adler, J

    1993-01-01

    Escherichia coli chemotaxis was inhibited by omega-conotoxin, a calcium ion channel blocker. With Tris-EDTA-permeabilized cells, nanomolar levels of omega-conotoxin inhibited chemotaxis without loss of motility. Cells treated with omega-conotoxin swam with a smooth bias, i.e., tumbling was inhibited.

  12. Mechanism of HERG potassium channel inhibition by tetra-n-octylammonium bromide and benzethonium chloride

    Energy Technology Data Exchange (ETDEWEB)

    Long, Yan; Lin, Zuoxian [Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530 (China); Xia, Menghang; Zheng, Wei [National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892 (United States); Li, Zhiyuan, E-mail: li_zhiyuan@gibh.ac.cn [Key Laboratory of Regenerative Biology, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530 (China)

    2013-03-01

    Tetra-n-octylammonium bromide and benzethonium chloride are synthetic quaternary ammonium salts that are widely used in hospitals and industries for the disinfection and surface treatment and as the preservative agent. Recently, the activities of HERG channel inhibition by these compounds have been found to have potential risks to induce the long QT syndrome and cardiac arrhythmia, although the mechanism of action is still elusive. This study was conducted to investigate the mechanism of HERG channel inhibition by these compounds by using whole-cell patch clamp experiments in a CHO cell line stably expressing HERG channels. Tetra-n-octylammonium bromide and benzethonium chloride exhibited concentration-dependent inhibitions of HERG channel currents with IC{sub 50} values of 4 nM and 17 nM, respectively, which were also voltage-dependent and use-dependent. Both compounds shifted the channel activation I–V curves in a hyperpolarized direction for 10–15 mV and accelerated channel activation and inactivation processes by 2-fold. In addition, tetra-n-octylammonium bromide shifted the inactivation I–V curve in a hyperpolarized direction for 24.4 mV and slowed the rate of channel deactivation by 2-fold, whereas benzethonium chloride did not. The results indicate that tetra-n-octylammonium bromide and benzethonium chloride are open-channel blockers that inhibit HERG channels in the voltage-dependent, use-dependent and state-dependent manners. - Highlights: ► Tetra-n-octylammonium and benzethonium are potent HERG channel inhibitors. ► Channel activation and inactivation processes are accelerated by the two compounds. ► Both compounds are the open-channel blockers to HERG channels. ► HERG channel inhibition by both compounds is use-, voltage- and state dependent. ► The in vivo risk of QT prolongation needs to be studied for the two compounds.

  13. Inhibition of parathyroid hormone release by maitotoxin, a calcium channel activator

    International Nuclear Information System (INIS)

    Maitotoxin, a toxin derived from a marine dinoflagellate, is a potent activator of voltage-sensitive calcium channels. To further test the hypothesis that inhibition of PTH secretion by calcium is mediated via a calcium channel we studied the effect of maitotoxin on dispersed bovine parathyroid cells. Maitotoxin inhibited PTH release in a dose-dependent fashion, and inhibition was maximal at 1 ng/ml. Chelation of extracellular calcium by EGTA blocked the inhibition of PTH by maitotoxin. Maitotoxin enhanced the effects of the dihydropyridine calcium channel agonist (+)202-791 and increased the rate of radiocalcium uptake in parathyroid cells. Pertussis toxin, which ADP-ribosylates and inactivates a guanine nucleotide regulatory protein that interacts with calcium channels in the parathyroid cell, did not affect the inhibition of PTH secretion by maitotoxin. Maitotoxin, by its action on calcium channels allows entry of extracellular calcium and inhibits PTH release. Our results suggest that calcium channels are involved in the release of PTH. Inhibition of PTH release by maitotoxin is not sensitive to pertussis toxin, suggesting that maitotoxin may act distal to the site interacting with a guanine nucleotide regulatory protein, or maitotoxin could interact with other ions or second messengers to inhibit PTH release

  14. Data in support of the negative influence of divalent cations on (−)-epigallocatechin-3-gallate (EGCG)-mediated inhibition of matrix metalloproteinase-2 (MMP-2)

    OpenAIRE

    Gauri Deb; Sahil Batra; Anil M. Limaye

    2016-01-01

    In this data article we have provided evidence for the negative influence of divalent cations on (−)‐epigallocatechin-3-gallate (EGCG)-mediated inhibition of matrix metalloproteinase-2 (MMP-2) activity in cell-free experiments. Chelating agents, such as EDTA and sodium citrate alone, did not affect MMP-2 activity. While EDTA enhanced, excess of divalent cations interfered with EGCG-mediated inhibition of MMP-2.

  15. The DEG/ENaC cation channel protein UNC-8 drives activity-dependent synapse removal in remodeling GABAergic neurons

    Science.gov (United States)

    Miller-Fleming, Tyne W; Petersen, Sarah C; Manning, Laura; Matthewman, Cristina; Gornet, Megan; Beers, Allison; Hori, Sayaka; Mitani, Shohei; Bianchi, Laura; Richmond, Janet; Miller, David M

    2016-01-01

    Genetic programming and neural activity drive synaptic remodeling in developing neural circuits, but the molecular components that link these pathways are poorly understood. Here we show that the C. elegans Degenerin/Epithelial Sodium Channel (DEG/ENaC) protein, UNC-8, is transcriptionally controlled to function as a trigger in an activity-dependent mechanism that removes synapses in remodeling GABAergic neurons. UNC-8 cation channel activity promotes disassembly of presynaptic domains in DD type GABA neurons, but not in VD class GABA neurons where unc-8 expression is blocked by the COUP/TF transcription factor, UNC-55. We propose that the depolarizing effect of UNC-8-dependent sodium import elevates intracellular calcium in a positive feedback loop involving the voltage-gated calcium channel UNC-2 and the calcium-activated phosphatase TAX-6/calcineurin to initiate a caspase-dependent mechanism that disassembles the presynaptic apparatus. Thus, UNC-8 serves as a link between genetic and activity-dependent pathways that function together to promote the elimination of GABA synapses in remodeling neurons. DOI: http://dx.doi.org/10.7554/eLife.14599.001 PMID:27403890

  16. Molecular Dynamics Simulations of Voltage Gated Cation Channels: Insights on Voltage-Sensor Domain Function and Modulation

    Directory of Open Access Journals (Sweden)

    Lucie eDelemotte

    2012-05-01

    Full Text Available Since their discovery in the 1950s, the structure and function of voltage gated cation channels (VGCC has been largely understood thanks to results stemming from electrophysiology, pharmacology, spectroscopy and structural biology. Over the past decade, computational methods such as molecular dynamics (MD simulations have also contributed, providing molecular level information that can be tested against experimental results, thereby allowing the validation of the models and protocols. Importantly, MD can shed light on elements of VGCC function that cannot be easily accessed through classical experiments. Here, we review the results of recent MD simulations addressing key questions that pertain to the function and modulation of the VGCC’s voltage sensor domain (VSD highlighting: 1 the movement of the S4-helix basic residues during channel activation, articulating how the electrical driving force acts upon them; 2 the nature of the VSD intermediate states on transitioning between open and closed states of the VGCC; and 3 the molecular level effects on the VSD arising from mutations of specific S4 positively charged residues involved in certain genetic diseases.

  17. Autophagic flux inhibition and lysosomogenesis ensuing cellular capture and retention of the cationic drug quinacrine in murine models.

    Science.gov (United States)

    Parks, Alexandre; Charest-Morin, Xavier; Boivin-Welch, Michael; Bouthillier, Johanne; Marceau, Francois

    2015-01-01

    The proton pump vacuolar (V)-ATPase is the driving force that mediates the concentration of cationic drugs (weak bases) in the late endosome-lysosome continuum; secondary cell reactions include the protracted transformation of enlarged vacuoles into autophagosomes. We used the inherently fluorescent tertiary amine quinacrine in murine models to further assess the accumulation and signaling associated with cation trapping. Primary fibroblasts concentrate quinacrine ∼5,000-fold from their culture medium (KM 9.8 µM; transport studies). The drug is present in perinuclear granules that are mostly positive for Rab7 and LAMP1 (microscopy). Both drug uptake and retention are extensively inhibited by treatments with the V-ATPase inhibitor bafilomycin A1. The H(+) ionophore monensin also prevented quinacrine concentration by fibroblasts. However, inhibition of plasma membrane transporters or of the autophagic process with spautin-1 did not alter quinacrine transport parameters. Ancillary experiments did not support that low micromolar concentrations of quinacrine are substrates for organic cation transporters-1 to -3 or P-glycoprotein. The secondary autophagy induced by quinacrine in cells may derive from the accumulation of incompetent autophagolysosomes, as judged from the accumulation of p62/SQSTM1 and LC3 II (immunoblots). Accordingly, protracted lysosomogenesis is evidenced by increased expression of LAMP1 and LAMP2 in quinacrine-treated fibroblasts (48 h, immunoblots), a response that follows the nuclear translocation of the lysosomal genesis transcription factor TFEB and upregulation of LAMP1 and -2 mRNAs (24 h). Quinacrine administration to live mice evidenced variable distribution to various organs and heterogeneous accumulation within the lung (stereo-microscopy, extraction). Dose-dependent in vivo autophagic and lysosomal accumulation was observed in the lung (immunoblots). No evidence has been found for transport or extrusion mechanisms modulating the cellular

  18. Sigma-1 receptor agonists directly inhibit Nav1.2/1.4 channels.

    Directory of Open Access Journals (Sweden)

    Xiao-Fei Gao

    Full Text Available (+-SKF 10047 (N-allyl-normetazocine is a prototypic and specific sigma-1 receptor agonist that has been used extensively to study the function of sigma-1 receptors. (+-SKF 10047 inhibits K(+, Na(+ and Ca2+ channels via sigma-1 receptor activation. We found that (+-SKF 10047 inhibited Na(V1.2 and Na(V1.4 channels independently of sigma-1 receptor activation. (+-SKF 10047 equally inhibited Na(V1.2/1.4 channel currents in HEK293T cells with abundant sigma-1 receptor expression and in COS-7 cells, which barely express sigma-1 receptors. The sigma-1 receptor antagonists BD 1063,BD 1047 and NE-100 did not block the inhibitory effects of (+-SKF-10047. Blocking of the PKA, PKC and G-protein pathways did not affect (+-SKF 10047 inhibition of Na(V1.2 channel currents. The sigma-1 receptor agonists Dextromethorphan (DM and 1,3-di-o-tolyl-guanidine (DTG also inhibited Na(V1.2 currents through a sigma-1 receptor-independent pathway. The (+-SKF 10047 inhibition of Na(V1.2 currents was use- and frequency-dependent. Point mutations demonstrated the importance of Phe(1764 and Tyr(1771 in the IV-segment 6 domain of the Na(V1.2 channel and Phe(1579 in the Na(V1.4 channel for (+-SKF 10047 inhibition. In conclusion, our results suggest that sigma-1 receptor agonists directly inhibit Na(V1.2/1.4 channels and that these interactions should be given special attention for future sigma-1 receptor function studies.

  19. Cpt-cAMP activates human epithelial sodium channels via relieving self-inhibition

    OpenAIRE

    Molina, Raul; Han, Dong-Yun; Su, Xue-Feng; Zhao, Run-Zhen; Zhao, Meimi; Sharp, Gretta M.; Chang, Yongchang; Ji, Hong-Long

    2011-01-01

    External Na+ self-inhibition is an intrinsic feature of epithelial sodium channels (ENaC). Cpt-cAMP regulates heterologous guinea pig but not rat αβγ ENaC in a ligand-gated manner. We hypothesized that cpt-cAMP may eliminate the self-inhibition of human ENaC thereby open channels. Regulation of self-inhibition by this compound in oocytes was analyzed using the two-electrode voltage clamp and Ussing chamber setups. External cpt-cAMP stimulated human but not rat and murine αβγ ENaC in a dose- a...

  20. Inhibition of the Cardiac Na+ Channel Nav1.5 by Carbon Monoxide*

    OpenAIRE

    Elies, J; Dallas, M.; Boyle, JP; Scragg, JL; Duke, A; Steele, DS; Peers, C

    2014-01-01

    Sublethal carbon monoxide (CO) exposure is frequently associated with myocardial arrhythmias, and our recent studies have demonstrated that these may be attributable to modulation of cardiac Na(+) channels, causing an increase in the late current and an inhibition of the peak current. Using a recombinant expression system, we demonstrate that CO inhibits peak human Nav1.5 current amplitude without activation of the late Na(+) current observed in native tissue. Inhibition was associated with a...

  1. Biochemical requirements for inhibition of Connexin26-containing channels by natural and synthetic taurine analogs.

    Science.gov (United States)

    Tao, Liang; Harris, Andrew L

    2004-09-10

    Previous work has shown that protonated taurine and aminosulfonate pH buffers, including HEPES, can directly and reversibly inhibit connexin channels that contain connexin26 (Cx26) (Bevans, C. G., and Harris, A. L. (1999) J. Biol. Chem. 274, 3711-3719). The structural requirements for this inhibition were explored by studies of the effects of structural analogs of taurine on the activity of Cx26-containing reconstituted hemichannels from native tissue. Several analogs inhibited the channels, with a range of relative affinities and efficacies. Each active compound contains a protonated amine separated from an ionized sulfonate or sulfinate moiety by several methylene groups. The inhibition is eliminated if the sulfonate/sulfinate moiety or the amine is not present. Compounds that contain a protonated amine but lack a sulfonate/sulfinate moiety do not inhibit but do competitively block the effect of the active compounds. Compounds that lack the protonated amine do not significantly inhibit or antagonize inhibition. The results suggest involvement of the protonated amine in binding and of the ionized sulfur-containing moiety in effecting the inhibition. The maximal effect of the inhibitory compounds is enhanced when a carboxyl group is linked to the alpha-carbon. Inhibition but not binding is stereospecific, with l-isomers being inhibitory and the corresponding d-isomers being inactive but able to antagonize inhibition by the l-isomers. Whereas not all connexins are sensitive to aminosulfonates, the well defined structural requirements described here argue strongly for a highly specific regulatory interaction with some connexins. The finding that cytoplasmic aminosulfonates inhibit connexin channels whereas other cytoplasmic compounds antagonize the inhibition suggests that gap junction channels are regulated by a complex interplay of cytoplasmic ligands.

  2. Corrosion inhibition efficiency and surface activity of benzothiazol-3-ium cationic Schiff base derivatives in hydrochloric acid

    Energy Technology Data Exchange (ETDEWEB)

    Negm, N.A., E-mail: nabelnegm@hotmail.co [Petrochemicals Department, Egyptian Petroleum Research Institute, Nasr City, Cairo (Egypt); Elkholy, Y.M.; Zahran, M.K. [Chemistry Department, Faculty of Science, Helwan University, Helwan (Egypt); Tawfik, S.M. [Petrochemicals Department, Egyptian Petroleum Research Institute, Nasr City, Cairo (Egypt)

    2010-10-15

    Research highlights: {yields} Benzothiazolium inhibitors show high corrosion inhibition for carbon steel. {yields} Weight loss and corrosion rates decrease by increasing inhibitor dose. {yields} Inhibition mechanism suggested as physisorption mechanism supported by adsorption free energy values. {yields} The adsorption of the inhibitors obeys Langmuir isotherm. {yields} Side chains have ascending order on the corrosion inhibition of the different inhibitors. - Abstract: Two series of cationic Schiff base surfactants namely: 2-(benzylideneamino)-3-(2-oxo-2-alkoxyethyl)-1,3-benzothiazol-3-ium bromide and 2-[(4-methoxybenzylidene)amino]-3-(2-oxo-2-alkoxyethyl)-1, 3-benzothiazol-3-ium bromide were prepared and confirmed using elemental analysis, FTIR, and {sup 1}H NMR spectra. The surface activity of the synthesized Schiff bases showed their tendency towards adsorption at the interfaces. The prepared compounds were evaluated as corrosion inhibitors for carbon steel in 0.5 M HCl solution using gravimetric and polarization measurements. By fitting the gravimetric data, some thermodynamic and kinetic parameters were estimated. The adsorption of the inhibitors on the carbon steel surface obeyed Langmuir adsorption isotherm and had a physical mechanism. Polarization measurements showed that the synthesized inhibitors act as mixed inhibitors for carbon steel in the acidic media. The results of the corrosion inhibition using two different methods showed narrow differences in the obtained values between the two methods within 5%.

  3. Irreversible inhibition of epithelial sodium channels by ultraviolet irradiation.

    OpenAIRE

    Cuthbert, A W; Fanestil, D. D.; Herrera, F. C.; Pryn, S. J.

    1982-01-01

    1 The effects of u.v. irradiation at 254 nm and 350 nm on sodium transport across frog skin epithelium have been investigated. 2 Irradiation at 254 nm but not at 350 nm produces a dose-dependent, functionally selective blockade of sodium transport. The effect is apparently due to the irreversible closure of apical sodium channels. 3 The amiloride-sensitive conductance was directly related to sodium transport as measured by short circuit current (SCC) both in normal and irradiated tissues, alt...

  4. Breathing Stimulant Compounds Inhibit TASK-3 Potassium Channel Function Likely by Binding at a Common Site in the Channel Pore.

    Science.gov (United States)

    Chokshi, Rikki H; Larsen, Aaron T; Bhayana, Brijesh; Cotten, Joseph F

    2015-11-01

    Compounds PKTHPP (1-{1-[6-(biphenyl-4-ylcarbonyl)-5,6,7,8-tetrahydropyrido[4,3-d]-pyrimidin-4-yl]piperidin-4-yl}propan-1-one), A1899 (2''-[(4-methoxybenzoylamino)methyl]biphenyl-2-carboxylic acid 2,4-difluorobenzylamide), and doxapram inhibit TASK-1 (KCNK3) and TASK-3 (KCNK9) tandem pore (K2P) potassium channel function and stimulate breathing. To better understand the molecular mechanism(s) of action of these drugs, we undertook studies to identify amino acid residues in the TASK-3 protein that mediate this inhibition. Guided by homology modeling and molecular docking, we hypothesized that PKTHPP and A1899 bind in the TASK-3 intracellular pore. To test our hypothesis, we mutated each residue in or near the predicted PKTHPP and A1899 binding site (residues 118-128 and 228-248), individually, to a negatively charged aspartate. We quantified each mutation's effect on TASK-3 potassium channel concentration response to PKTHPP. Studies were conducted on TASK-3 transiently expressed in Fischer rat thyroid epithelial monolayers; channel function was measured in an Ussing chamber. TASK-3 pore mutations at residues 122 (L122D, E, or K) and 236 (G236D) caused the IC50 of PKTHPP to increase more than 1000-fold. TASK-3 mutants L122D, G236D, L239D, and V242D were resistant to block by PKTHPP, A1899, and doxapram. Our data are consistent with a model in which breathing stimulant compounds PKTHPP, A1899, and doxapram inhibit TASK-3 function by binding at a common site within the channel intracellular pore region, although binding outside the channel pore cannot yet be excluded. PMID:26268529

  5. Characterization of a ligand-gated cation channel based on an inositol receptor in the silkworm, Bombyx mori.

    Science.gov (United States)

    Kikuta, Shingo; Endo, Haruka; Tomita, Natsuo; Takada, Tomoyuki; Morita, Chiharu; Asaoka, Kiyoshi; Sato, Ryoichi

    2016-07-01

    Insect herbivores recognize non-volatile compounds in plants to direct their feeding behavior. Gustatory receptors (Gr) appear to be required for nutrient recognition by gustatory organs in the mouthparts of insects. Gr10 is expressed in Bombyx mori (BmGr10) mouthparts such as maxillary galea, maxillary palp, and labrum. BmGr10 is predicted to function in sugar recognition; however, the precise biochemical function remains obscure. Larvae of B. mori are monophagous feeders able to find and feed on mulberry leaves. Soluble mulberry leaf extract contains sucrose, glucose, fructose, and myo-inositol. In this study, we identified BmGr10 as an inositol receptor using electrophysiological analysis with the Xenopus oocyte expression system and Ca(2+) imaging techniques using mammalian cells. These results demonstrated that Xenopus oocytes or HEK293T cells expressing BmGr10 specifically respond to myo-inositol and epi-inositol but do not respond to any mono-, di-, or tri-saccharides or to some sugar alcohols. These inositols caused Ca(2+) and Na(+) influxes into the cytoplasm independently of a G protein-mediated signaling cascade, indicating that BmGr10 is a ligand-gated cation channel. Overall, BmGr10 plays an important role in the myo-inositol recognition required for B. mori larval feeding behavior. PMID:27132146

  6. Magnesium Sensitizes Slow Vacuolar Channels to Physiological Cytosolic Calcium and Inhibits Fast Vacuolar Channels in Fava Bean Guard Cell Vacuoles.

    Science.gov (United States)

    Pei; Ward; Schroeder

    1999-11-01

    Vacuolar ion channels in guard cells play important roles during stomatal movement and are regulated by many factors including Ca(2+), calmodulin, protein kinases, and phosphatases. We report that physiological cytosolic and luminal Mg(2+) levels strongly regulate vacuolar ion channels in fava bean (Vicia faba) guard cells. Luminal Mg(2+) inhibited fast vacuolar (FV) currents with a K(i) of approximately 0.23 mM in a voltage-dependent manner at positive potentials on the cytoplasmic side. Cytosolic Mg(2+) at 1 mM also inhibited FV currents. Furthermore, in the absence of cytosolic Mg(2+), cytosolic Ca(2+) at less than 10 µM did not activate slow vacuolar (SV) currents. However, when cytosolic Mg(2+) was present, submicromolar concentrations of cytosolic Ca(2+) activated SV currents with a K(d) of approximately 227 nM, suggesting a synergistic Mg(2+)-Ca(2+) effect. The activation potential of SV currents was shifted toward physiological potentials in the presence of cytosolic Mg(2+) concentrations. The direction of SV currents could also be changed from outward to both outward and inward currents. Our data predict a model for SV channel regulation, including a cytosolic binding site for Ca(2+) with an affinity in the submicromolar range and a cytosolic low-affinity Mg(2+)-Ca(2+) binding site. SV channels are predicted to contain a third binding site on the vacuolar luminal side, which binds Ca(2+) and is inhibitory. In conclusion, cytosolic Mg(2+) sensitizes SV channels to physiological cytosolic Ca(2+) elevations. Furthermore, we propose that cytosolic and vacuolar Mg(2+) concentrations ensure that FV channels do not function as a continuous vacuolar K(+) leak, which would prohibit stomatal opening. PMID:10557247

  7. Lipid nanocapsules containing the non-ionic surfactant Solutol HS15 inhibit the transport of calcium through hyperforin-activated channels in neuronal cells.

    Science.gov (United States)

    Chauvet, Sylvain; Barras, Alexandre; Boukherroub, Rabah; Bouron, Alexandre

    2015-12-01

    Hyperforin is described as a natural antidepressant inhibiting the reuptake of neurotransmitters and also activating cation channels. However the blood-brain barrier limits the access to the brain of this biomolecule. To circumvent this problem it was envisaged to encapsulate hyperforin into biomimetic lipid nano-carriers like lipid nanocapsules (LNCs). When testing the safety of 25 nm LNCs it appeared that they strongly blocked hyperforin-activated Ca2+ channels of cultured cortical neurons. This inhibition was due to one of their main component: solutol HS15 (polyoxyethylene-660-12-hydroxy stearate), a non-ionic soluble surfactant. Solutol HS15 rapidly depresses in a concentration-dependent manner the entry of Ca2+ through hyperforin-activated channels without influencing store-operated channels. This effect is mimicked by Brij58 but not by PEG600, indicating that the lipid chain of Solutol HS15 is important in determining its effects on the channels. The inhibition of the Ca2+ fluxes depends on the cellular cholesterol content; it is stronger after depleting cholesterol with methyl-β-cyclodextrin and is nearly absent on cells cultured in a cholesterol-rich medium. When chronically applied for 24 h, Solutol HS15 slightly up-regulates the entry of Ca2+ through hyperforin-activated channels. Similar observations were made when testing 25 nm lipid nanocapsules containing the surfactant Solutol HS15. Altogether, this study shows that Solutol HS15 perturbs in a cholesterol-dependent manner the activity of some neuronal channels. This is the first demonstration that LNCs containing this surfactant can influence cellular calcium signaling in the brain, a finding that can have important clinical implications.

  8. A membrane-access mechanism of ion channel inhibition by voltage sensor toxins from spider venom

    Science.gov (United States)

    Lee, Seok-Yong; MacKinnon, Roderick

    2004-07-01

    Venomous animals produce small protein toxins that inhibit ion channels with high affinity. In several well-studied cases the inhibitory proteins are water-soluble and bind at a channel's aqueous-exposed extracellular surface. Here we show that a voltage-sensor toxin (VSTX1) from the Chilean Rose Tarantula (Grammostola spatulata) reaches its target by partitioning into the lipid membrane. Lipid membrane partitioning serves two purposes: to localize the toxin in the membrane where the voltage sensor resides and to exploit the free energy of partitioning to achieve apparent high-affinity inhibition. VSTX1, small hydrophobic poisons and anaesthetic molecules reveal a common theme of voltage sensor inhibition through lipid membrane access. The apparent requirement for such access is consistent with the recent proposal that the sensor in voltage-dependent K+ channels is located at the membrane-protein interface.

  9. Nitric oxide suppresses stomatal opening by inhibiting inward-rectifying Kin channels in Arabidopsis guard cells

    Institute of Scientific and Technical Information of China (English)

    XUE ShaoWu; YANG Pin; HE YiKun

    2008-01-01

    We explore nitric oxide (NO) effect on K+in channels in Arabidopsis guard cells. We observed NO inhib-ited K+in currents when Ca2+ chelator EGTA (Ethylene glycol-bis(2-aminoethylether)-N,N,N',N'tetraacetic acid) was not added in the pipette solution; K+in currents were not sensitive to NO when cytosolic Ca2+ was chelated by EGTA. NO inhibited the Arabidopsis stomatal opening, but when EGTA was added in the bath solution, inhibition effect of NO on stomatal opening vanished. Thus, it implies that NO ele-vates cytosolic Ca2+ by activating plasma membrane Ca2+ channels firstly, then inactivates K+in chan-nels, resulting in stomatal opening suppressed subsequently.

  10. SLO BK Potassium Channels Couple Gap Junctions to Inhibition of Calcium Signaling in Olfactory Neuron Diversification.

    Science.gov (United States)

    Alqadah, Amel; Hsieh, Yi-Wen; Schumacher, Jennifer A; Wang, Xiaohong; Merrill, Sean A; Millington, Grethel; Bayne, Brittany; Jorgensen, Erik M; Chuang, Chiou-Fen

    2016-01-01

    The C. elegans AWC olfactory neuron pair communicates to specify asymmetric subtypes AWCOFF and AWCON in a stochastic manner. Intercellular communication between AWC and other neurons in a transient NSY-5 gap junction network antagonizes voltage-activated calcium channels, UNC-2 (CaV2) and EGL-19 (CaV1), in the AWCON cell, but how calcium signaling is downregulated by NSY-5 is only partly understood. Here, we show that voltage- and calcium-activated SLO BK potassium channels mediate gap junction signaling to inhibit calcium pathways for asymmetric AWC differentiation. Activation of vertebrate SLO-1 channels causes transient membrane hyperpolarization, which makes it an important negative feedback system for calcium entry through voltage-activated calcium channels. Consistent with the physiological roles of SLO-1, our genetic results suggest that slo-1 BK channels act downstream of NSY-5 gap junctions to inhibit calcium channel-mediated signaling in the specification of AWCON. We also show for the first time that slo-2 BK channels are important for AWC asymmetry and act redundantly with slo-1 to inhibit calcium signaling. In addition, nsy-5-dependent asymmetric expression of slo-1 and slo-2 in the AWCON neuron is necessary and sufficient for AWC asymmetry. SLO-1 and SLO-2 localize close to UNC-2 and EGL-19 in AWC, suggesting a role of possible functional coupling between SLO BK channels and voltage-activated calcium channels in AWC asymmetry. Furthermore, slo-1 and slo-2 regulate the localization of synaptic markers, UNC-2 and RAB-3, in AWC neurons to control AWC asymmetry. We also identify the requirement of bkip-1, which encodes a previously identified auxiliary subunit of SLO-1, for slo-1 and slo-2 function in AWC asymmetry. Together, these results provide an unprecedented molecular link between gap junctions and calcium pathways for terminal differentiation of olfactory neurons.

  11. Membrane coordination of receptors and channels mediating the inhibition of neuronal ion currents by ADP.

    Science.gov (United States)

    Gafar, Hend; Dominguez Rodriguez, Manuel; Chandaka, Giri K; Salzer, Isabella; Boehm, Stefan; Schicker, Klaus

    2016-09-01

    ADP and other nucleotides control ion currents in the nervous system via various P2Y receptors. In this respect, Cav2 and Kv7 channels have been investigated most frequently. The fine tuning of neuronal ion channel gating via G protein coupled receptors frequently relies on the formation of higher order protein complexes that are organized by scaffolding proteins and harbor receptors and channels together with interposed signaling components. However, ion channel complexes containing P2Y receptors have not been described. Therefore, the regulation of Cav2.2 and Kv7.2/7.3 channels via P2Y1 and P2Y12 receptors and the coordination of these ion channels and receptors in the plasma membranes of tsA 201 cells have been investigated here. ADP inhibited currents through Cav2.2 channels via both P2Y1 and P2Y12 receptors with phospholipase C and pertussis toxin-sensitive G proteins being involved, respectively. The nucleotide controlled the gating of Kv7 channels only via P2Y1 and phospholipase C. In fluorescence energy transfer assays using conventional as well as total internal reflection (TIRF) microscopy, both P2Y1 and P2Y12 receptors were found juxtaposed to Cav2.2 channels, but only P2Y1, and not P2Y12, was in close proximity to Kv7 channels. Using fluorescence recovery after photobleaching in TIRF microscopy, evidence for a physical interaction was obtained for the pair P2Y12/Cav2.2, but not for any other receptor/channel combination. These results reveal a membrane juxtaposition of P2Y receptors and ion channels in parallel with the control of neuronal ion currents by ADP. This juxtaposition may even result in apparent physical interactions between receptors and channels.

  12. Pinostrobin from Cajanus cajan (L.) Millsp. inhibits sodium channel-activated depolarization of mouse brain synaptoneurosomes.

    Science.gov (United States)

    Nicholson, Russell A; David, Laurence S; Pan, Rui Le; Liu, Xin Min

    2010-10-01

    This investigation focuses on the in vitro neuroactive properties of pinostrobin, a substituted flavanone from Cajanus cajan (L.) Millsp. of the Fabaceae family. We demonstrate that pinostrobin inhibits voltage-gated sodium channels of mammalian brain (IC(50)=23 µM) based on the ability of this substance to suppress the depolarizing effects of the sodium channel-selective activator veratridine in a synaptoneurosomal preparation from mouse brain. The resting membrane potential of synaptoneurosomes was unaffected by pinostrobin. The pharmacological profile of pinostrobin resembles that of depressant drugs that block sodium channels. PMID:20472040

  13. Transient receptor potential cation channel subfamily V member 1 expressing corneal sensory neurons can be subdivided into at least three subpopulations

    OpenAIRE

    Abdulhakeem eAlamri; Romke eBron; James Alexander Brock; Jason eIvanusic

    2015-01-01

    The cornea is innervated by three main functional classes of sensory neurons: polymodal nociceptors, pure mechano-nociceptors and cold-sensing neurons. Here we explored transient receptor potential cation channel subfamily V member 1 (TRPV1) expression in guinea pig corneal sensory neurons, a widely used molecular marker of polymodal nociceptors. We used retrograde tracing to identify corneal afferent neurons in the trigeminal ganglion (TG) and double label in situ hybridization and/or immuno...

  14. Synergistic effect between cationic gemini surfactant and chloride ion for the corrosion inhibition of steel in sulphuric acid

    Energy Technology Data Exchange (ETDEWEB)

    Qiu Lingguang [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China)], E-mail: lgqiu@ahu.edu.cn; Wu Yun; Wang Yimin; Jiang Xia [School of Chemistry and Chemical Engineering, Anhui University, Hefei 230039 (China)

    2008-02-15

    Corrosion inhibition of cold rolled steel in 0.5 mol L{sup -1} sulphuric acid by a quaternary ammonium gemini surfactant, l,3-propane-bis(dimethyl dodecylammonium bromide) (designated as 12-3-12), in the absence and presence of chloride ions was investigated at different temperatures. The results revealed significant synergistic effect between gemini 12-3-12 and chloride ions for the corrosion protection of cold rolled steel in sulphuric acid, and that the novel composite inhibitor system containing cationic gemini surfactant and chloride ions was efficient and low-cost for steel corrosion inhibition in sulphuric acid medium, even when concentration of 12-3-12 was as low as 1 x 10{sup -6} mol L{sup -1}. By fitting the obtained experimental data with Langmuir adsorption model and Arrhenius equation, some thermodynamic and kinetic parameters such as adsorption free energy, the apparent activation energy, and the pre-exponential factor were estimated. The adsorption mechanism of the gemini surfactant onto steel surface in acid medium in the absence and presence of chloride ions was also discussed, respectively.

  15. Latent Ice Recrystallization Inhibition Activity in Nonantifreeze Proteins: Ca2+-Activated Plant Lectins and Cation-Activated Antimicrobial Peptides.

    Science.gov (United States)

    Mitchell, Daniel E; Gibson, Matthew I

    2015-10-12

    Organisms living in polar regions have evolved a series of antifreeze (glyco) proteins (AFGPs) to enable them to survive by modulating the structure of ice. These proteins have huge potential for use in cellular cryopreservation, ice-resistant surfaces, frozen food, and cryosurgery, but they are limited by their relatively low availability and questions regarding their mode of action. This has triggered the search for biomimetic materials capable of reproducing this function. The identification of new structures and sequences capable of inhibiting ice growth is crucial to aid our understanding of these proteins. Here, we show that plant c-type lectins, which have similar biological function to human c-type lectins (glycan recognition) but no sequence homology to AFPs, display calcium-dependent ice recrystallization inhibition (IRI) activity. This IRI activity can be switched on/off by changing the Ca2+ concentration. To show that more (nonantifreeze) proteins may exist with the potential to display IRI, a second motif was considered, amphipathicity. All known AFPs have defined hydrophobic/hydrophilic domains, rationalizing this choice. The cheap, and widely used, antimicrobial Nisin was found to have cation-dependent IRI activity, controlled by either acid or addition of histidine-binding ions such as zinc or nickel, which promote its amphipathic structure. These results demonstrate a new approach in the identification of antifreeze protein mimetic macromolecules and may help in the development of synthetic mimics of AFPs.

  16. Open State Destabilization by Atp Occupancy Is Mechanism Speeding Burst Exit Underlying KATP Channel Inhibition by Atp

    OpenAIRE

    Li, Lehong; Geng, Xuehui; Drain, Peter

    2002-01-01

    The ATP-sensitive potassium (KATP) channel is named after its characteristic inhibition by intracellular ATP. The inhibition is a centerpiece of how the KATP channel sets electrical signaling to the energy state of the cell. In the β cell of the endocrine pancreas, for example, ATP inhibition results from high blood glucose levels and turns on electrical activity leading to insulin release. The underlying gating mechanism (ATP inhibition gating) includes ATP stabilization of closed states, bu...

  17. Selective inhibition of a slow-inactivating voltage-dependent K+ channel in rat PC12 cells by hypoxia.

    Science.gov (United States)

    Conforti, L; Millhorn, D E

    1997-07-15

    1. Electrophysiological (single-channel patch clamp) and molecular biological experiments (reverse transcriptase-polymerase chain reaction) were performed to attempt to identify the O2-sensitive K+ channel in rat phaeochromocytoma (PC12) cells. 2. Four types of K+ channels were recorded in PC12 cells: a small-conductance K+ channel (14 pS), a calcium-activated K+ channel (KCa; 102 pS) and two K+ channels with similar conductance (20 pS). These last two channels differed in their time-dependent inactivation: one was a slow-inactivating channel, while the other belonged to the family of fast transient K+ channels. 3. The slow-inactivating 20 pS K+ channel was inhibited by hypoxia. Exposure to hypoxia produced a 50% reduction in channel activity (number of active channels in the patch x open probability). Hypoxia had no effect on the 20 pS transient K+ channels, whereas reduced O2 stimulated the KCa channels. 4. The genes encoding the alpha-subunits of slow-inactivating K+ channels for two members of the Shaker subfamily of K+ channels (Kv1.2 and Kv1.3) together with the Kv2.1, Kv3.1 and Kv3.2 channel genes were identified in PC12 cells. 5. The expression of the Shaker Kv1.2, but none of the other K+ channel genes, increased in cells exposed to prolonged hypoxia (18 h). The same cells were more responsive to a subsequent exposure to hypoxia (35% inhibition of K+ current measured in whole-cell voltage clamp) compared with the cells maintained in normoxia (19% inhibition). 6. These results indicate that the O2-sensitive K+ channel in PC12 cells is a 20 pS slow-inactivating K+ channel that is upregulated by hypoxia. This channel appears to belong to the Shaker subfamily of voltage-gated K+ channels. PMID:9263911

  18. Shikonin Inhibits Intestinal Calcium-Activated Chloride Channels and Prevents Rotaviral Diarrhea.

    Science.gov (United States)

    Jiang, Yu; Yu, Bo; Yang, Hong; Ma, Tonghui

    2016-01-01

    Secretory diarrhea remains a global health burden and causes major mortality in children. There have been some focuses on antidiarrheal therapies that may reduce fluid losses and intestinal motility in diarrheal diseases. In the present study, we identified shikonin as an inhibitor of TMEM16A chloride channel activity using cell-based fluorescent-quenching assay. The IC50 value of shikonin was 6.5 μM. Short-circuit current measurements demonstrated that shikonin inhibited Eact-induced Cl(-) current in a dose-dependent manner, with IC50 value of 1.5 μM. Short-circuit current measurement showed that shikonin exhibited inhibitory effect against CCh-induced Cl(-) currents in mouse colonic epithelia but did not affect cytoplasmic Ca(2+) concentration as well as the other major enterocyte chloride channel conductance regulator. Characterization study found that shikonin inhibited basolateral K(+) channel activity without affecting Na(+)/K(+)-ATPase activities. In vivo studies revealed that shikonin significantly delayed intestinal motility in mice and reduced stool water content in a neonatal mice model of rotaviral diarrhea without affecting the viral infection process in vivo. Taken together, the results suggested that shikonin inhibited enterocyte calcium-activated chloride channels, the inhibitory effect was partially through inhbition of basolateral K(+) channel activity, and shikonin could be a lead compound in the treatment of rotaviral secretory diarrhea. PMID:27601995

  19. State-Dependent Inhibition of Sodium Channels by Local Anesthetics: A 40-Year Evolution.

    Science.gov (United States)

    Wang, G-K; Strichartz, G R

    2012-04-01

    Knowledge about the mechanism of impulse blockade by local anesthetics has evolved over the past four decades, from the realization that Na(+) channels were inhibited to affect the impulse blockade to an identification of the amino acid residues within the Na(+) channel that bind the local anesthetic molecule. Within this period appreciation has grown of the state-dependent nature of channel inhibition, with rapid binding and unbinding at relatively high affinity to the open state, and weaker binding to the closed resting state. Slow binding of high affinity for the inactivated state accounts for the salutary therapeutic as well as the toxic actions of diverse class I anti-arrhythmic agents, but may have little importance for impulse blockade, which requires concentrations high enough to block the resting state. At the molecular level, residues on the S6 transmembrane segments in three of the homologous domains of the channel appear to contribute to the binding of local anesthetics, with some contribution also from parts of the selectivity filter. Binding to the inactivated state, and perhaps the open state, involves some residues that are not identical to those that bind these drugs in the resting state, suggesting spatial flexibility in the "binding site". Questions remaining include the mechanism that links local anesthetic binding with the inhibition of gating charge movements, and the molecular nature of the theoretical "hydrophobic pathway" that may be critical for determining the recovery rates from blockade of closed channels, and thus account for both therapeutic and cardiotoxic actions. PMID:23710324

  20. Effects on atrial fibrillation in aged hypertensive rats by Ca(2+)-activated K(+) channel inhibition

    DEFF Research Database (Denmark)

    Diness, Jonas Goldin; Skibsbye, Lasse; Jespersen, Thomas;

    2011-01-01

    in both the normotensive and hypertensive strains with no decline in efficacy as age increased. In conclusion, SK channel inhibition with NS8593 and UCL1684 possesses antiarrhythmic properties in a rat in vivo model of paroxysmal AF with hypertension-induced atrial remodeling. The present results support...

  1. Polyamine triggering of exocytosis in Paramecium involves an extracellular Ca(2+)/(polyvalent cation)-sensing receptor, subplasmalemmal Ca-store mobilization and store-operated Ca(2+)-influx via unspecific cation channels.

    Science.gov (United States)

    Klauke, N; Blanchard, M; Plattner, H

    2000-03-15

    The polyamine secretagogue, aminoethyldextran (AED), causes a cortical [Ca(2+)] transient in Paramecium cells, as analyzed by fluorochrome imaging. Our most essential findings are: (i) Cortical Ca(2+) signals also occur when AED is applied in presence of the fast Ca(2+) chelator, BAPTA. (ii) Extracellular La(3+) application causes within seconds a rapid, reversible fluorescence signal whose reversibility can be attributed to a physiological [Ca(2+)](i) transient (while injected La(3+) causes a sustained fluorescence signal). (iii) Simply increasing [Ca(2+)](o) causes a similar rapid, short-lived [Ca(2+)](i) transient. All these phenomena, (i-iii), are compatible with activation of an extracellular "Ca(2+)/(polyvalent cation)-sensing receptor" known from some higher eukaryotic systems, where this sensor (responding to Ca(2+), La(3+) and some multiply charged cations) is linked to cortical calcium stores which, thus, are activated. In Paramecium, such subplasmalemmal stores ("alveolar sacs") are physically linked to the cell membrane and they can also be activated by the Ca(2+) releasing agent, 4-chloro-m-cresol, just like in Sarcoplasmic Reticulum. Since this drug causes a cortical Ca(2+) signal also in absence of Ca(2+)(o) we largely exclude a "Ca(2+)-induced Ca(2+) release" (CICR) mechanism. Our finding of increased cortical Ca(2+) signals after store depletion and re-addition of extracellular Ca(2+) can be explained by a "store-operated Ca(2+) influx" (SOC), i.e., a Ca(2+) influx superimposing store activation. AED stimulation in presence of Mn(2+)(o) causes fluorescence quenching in Fura-2 loaded cells, indicating involvement of unspecific cation channels. Such channels, known to occur in Paramecium, share some general characteristics of SOC-type Ca(2+) influx channels. In conclusion, we assume the following sequence of events during AED stimulated exocytosis: (i) activation of an extracellular Ca(2+)/polyamine-sensing receptor, (ii) release of Ca(2+) from

  2. Suppressing effect of C a2 + blips on puff amplitudes by inhibiting channels to prevent recovery

    Science.gov (United States)

    Chen, Yuan; Qi, Hong; Li, Xiang; Cai, Meichun; Chen, Xingqiang; Liu, Wen; Shuai, Jianwei

    2016-08-01

    As local signals, calcium puffs arise from the concerted opening of a few nearby inositol 1,4,5-trisphospate receptor channels to release C a2 + ions from the endoplasmic reticulum. Although C a2 + puffs have been well studied, little is known about the modulation of cytosolic basal C a2 + concentration ([Ca2 +] Basal) on puff dynamics. In this paper we consider a puff model to study how the statistical properties of puffs are modulated by [Ca2 +] Basal. The puff frequency and lifetime trivially increase with the increasing [Ca2 +] Basal, but an unexpected result is that the puff amplitude and the maximum open-channel number of the puff show decreasing relationship with the increasing [Ca2 +] Basal. The underlying dynamics is related not only to the increasing puff frequency which gives a shorter recovery time, but also to the increasing frequency of blips with only one channel open. We indicate that C a2 + blips cause the channels to be inhibited and prevent their recovery during interpuff intervals, resulting in the suppressing effect on puff amplitudes. With increasing [Ca2 +] Basal, more blips occur to cause more channels to be inhibited, leaving fewer channels available for puff events. This study shows that the blips may play relevant functions in global C a2 + waves through modulating puff dynamics.

  3. Inhibition of G protein-activated inwardly rectifying K+ channels by different classes of antidepressants.

    Directory of Open Access Journals (Sweden)

    Toru Kobayashi

    Full Text Available Various antidepressants are commonly used for the treatment of depression and several other neuropsychiatric disorders. In addition to their primary effects on serotonergic or noradrenergic neurotransmitter systems, antidepressants have been shown to interact with several receptors and ion channels. However, the molecular mechanisms that underlie the effects of antidepressants have not yet been sufficiently clarified. G protein-activated inwardly rectifying K(+ (GIRK, Kir3 channels play an important role in regulating neuronal excitability and heart rate, and GIRK channel modulation has been suggested to have therapeutic potential for several neuropsychiatric disorders and cardiac arrhythmias. In the present study, we investigated the effects of various classes of antidepressants on GIRK channels using the Xenopus oocyte expression assay. In oocytes injected with mRNA for GIRK1/GIRK2 or GIRK1/GIRK4 subunits, extracellular application of sertraline, duloxetine, and amoxapine effectively reduced GIRK currents, whereas nefazodone, venlafaxine, mianserin, and mirtazapine weakly inhibited GIRK currents even at toxic levels. The inhibitory effects were concentration-dependent, with various degrees of potency and effectiveness. Furthermore, the effects of sertraline were voltage-independent and time-independent during each voltage pulse, whereas the effects of duloxetine were voltage-dependent with weaker inhibition with negative membrane potentials and time-dependent with a gradual decrease in each voltage pulse. However, Kir2.1 channels were insensitive to all of the drugs. Moreover, the GIRK currents induced by ethanol were inhibited by sertraline but not by intracellularly applied sertraline. The present results suggest that GIRK channel inhibition may reveal a novel characteristic of the commonly used antidepressants, particularly sertraline, and contributes to some of the therapeutic effects and adverse effects.

  4. Specific inhibition of long-lasting, L-type calcium channels by synthetic parathyroid hormone

    International Nuclear Information System (INIS)

    The effect of an active synthetic N-terminal fragment of bovine parathyroid hormone (bPTH), bPTH-(1-34), on Ca2+ channels was studied in mouse neuroblastoma cells (N1E-115). With the whole-cell variation of the patch-clamp technique, T (transient) and L (long-lasting) types of Ca2+ currents were identified. Pharmacological characterization showed that the L current was amplified by the Ca2+ channel stimulator BAY K-8644, but the T current was unaffected. The administration of bPTH-(1-34) produced dose-related inhibition of the L current, which could be reversed by BAY K-8644. The peptide had no effect on the T current. In addition, use of the fluorescent indicator fura-2 showed that bPTH-(1-34) inhibited the KCl-stimulated increase in intracellular free Ca2+ in neuroblastoma cells with L channels but not in cells with T channels. An inactivated (oxidized) preparation of bPTH-(1-34) failed to affect the L current. High-affinity binding of labeled PTH analog to these neuroblastoma cells was also demonstrated. In addition, bPTH-(1-34) inhibited the L current in cultured vascular smooth muscle cells from rat tail artery. These data indicate that, in some tissues PTH can act as an endogenous blocker of Ca2+ entry

  5. Immunization with cationized BSA inhibits progression of disease in ApoBec-1/LDL receptor deficient mice with manifest atherosclerosis.

    Science.gov (United States)

    Kolbus, Daniel; Wigren, Maria; Ljungcrantz, Irena; Söderberg, Ingrid; Alm, Ragnar; Björkbacka, Harry; Nilsson, Jan; Fredrikson, Gunilla N

    2011-06-01

    Immune responses against modified self-antigens generated by hypercholesterolemia play an important role in atherosclerosis identifying the immune system as a possible novel target for prevention and treatment of cardiovascular disease. It has recently been shown that these immune responses can be modulated by subcutaneous injection of adjuvant. In the present study we immunized 25-week old ApoBec-1/LDL receptor deficient mice with manifest atherosclerosis with adjuvant and two different concentrations of the carrier molecule cationized BSA (cBSA). Plasma levels of Th2-induced apolipoprotein B (apoB)/IgG1 immune complexes were increased in the cBSA immunized groups verifying induction of immunity against a self-antigen. Mice were sacrificed at 36 weeks of age and atherosclerosis was monitored by en face Oil red O staining of the aorta. Immunization with 100 μg cBSA inhibited plaque progression, whereas the lower dose (50 μg) did not. In addition, the higher dose induced a more stable plaque phenotype, indicated by a higher content of collagen and less macrophages and T cells in the plaques. Moreover, there was an increased ratio of Foxp3+/Foxp3⁻ T cells in the circulation suggesting activation of a regulatory T cell response. In conclusion, we show that immunization with cBSA induces an immune response against apoB as well as an activation of Treg cells. This was associated with development of a more stable plaque phenotype and reduced atherosclerosis progression.

  6. Inhibition of Na(+) -K+ pump activity by divalent cations in intact peritoneal mast cells of the rat

    DEFF Research Database (Denmark)

    Knudsen, T; Berthelsen, Carsten; Johansen, Torben

    1990-01-01

    1. The inhibition by the divalent cations magnesium, barium and strontium and the trivalent ion lanthanum of the Na(+) -K+ pump in the plasma membrane of rat peritoneal mast cells was studied in pure mast cell populations by measurement of the ouabain-sensitive uptake of the radioactive potassium......-resistant uptake was not changed. Half maximum decrease in the ouabain-sensitive K+(86Rb+)-uptake was observed with 1.8 mM magnesium, 1.2mM barium and 0.7 mM strontium. 4. The trivalent ion lanthanum blocked almost completely the ouabain-sensitive K+(86Rb+)-uptake at a concentration of 1 microM as does 1 m......M calcium. Combining either of these ions with magnesium had no further inhibitory effect on the ouabain-sensitive uptake. 5. In conclusion, in addition to the previously suggested modulation by calcium of the activity of the Na+ (-)K+ pump, evidence is provided in this investigation that the modulation may...

  7. Cell-penetrating peptide derived from human eosinophil cationic protein inhibits mite allergen Der p 2 induced inflammasome activation.

    Directory of Open Access Journals (Sweden)

    Sheng-Jie Yu

    Full Text Available Newly discovered cell penetration peptides derived from human eosinophil cationic proteins (CPPecp have the characteristic of cell internalization, but the effect of CPPecp on immunomodulation has not been clarified. House dust mite (HDM major allergen, Der p 2, can induce proinflammatory cytokine production which contributes to airway inflammation and allergic asthma. However, the mechanism of Der p 2 on NLRP3 inflammasome activation remains unclear. The aim of this study was to investigate the immunomodulatory effect of CPPecp on inhibition of Der p 2 induced inflammasome activation. We showed that proinflammatory cytokines IL-1β, IL-6 and IL-8 were significantly upregulated in peripheral blood mononuclear cells (PBMCs derived from HDM allergic patients after Der p 2 stimulation. Expression of NLRP3, ASC, Caspase-1, IL-1β and Caspase-1 activity was upregulated in THP-1 cells after Der p 2 stimulation. Proinflammatory cytokine production, NLRP3 inflammasome activation and caspase-1 activity were downregulated in THP-1 cells and CD14+ cells co-cultured with Der p 2 and CPPecp. The immunomodulatory effect of CPPecp was through upregulation of IFN-α production but not induction of autophagy. These results suggested Der p 2 plays an important role in NLRP3 inflammasome activation and CPPecp has the potential to be a novel anti-inflammatory agent for allergic inflammation treatment in the future.

  8. Calpeptin, not calpain, directly inhibits an ion channel of the inner mitochondrial membrane.

    Science.gov (United States)

    Derksen, Maria; Vorwerk, Christian; Siemen, Detlef

    2016-05-01

    The permeability transition pore (PTP) of inner mitochondrial membranes is a large conductance pathway for ions up to 1500 Da which opening is responsible for ion equilibration and loss of membrane potential in apoptosis and thus in several neurodegenerative diseases. The PTP can be regulated by the Ca(2+)-activated mitochondrial K channel (BK). Calpains are Ca(2+)-activated cystein proteases; calpeptin is an inhibitor of calpains. We wondered whether calpain or calpeptin can modulate activity of PTP or BK. Patch clamp experiments were performed on mitoplasts of rat liver (PTP) and of an astrocytoma cell line (BK). Channel-independent open probability (P o) was determined (PTP) and, taking into account the number of open levels, NPo by single channel analysis (BK). We find that PTP in the presence of Ca(2+) (200 μM) is uninfluenced by calpain (13 nM) and shows insignificant decrease by the calpain inhibitor calpeptin (1 μM). The NPo of the BK is insensitive to calpain (54 nM), too. However, it is significantly and reversibly inhibited by the calpain inhibitor calpeptin (IC50 = 42 μM). The results agree with calpeptin-induced activation of the PTP via inhibition of the BK. Screening experiments with respirometry show calpeptin effects, fitting to inhibition of the BK by calpeptin, and strong inhibition of state 3 respiration. PMID:26108743

  9. Mechanism of inhibition of calcium channels in rat nucleus tractus solitarius by neurotransmitters.

    OpenAIRE

    Rhim, H; Toth, P. T.; Miller, R. J.

    1996-01-01

    1. High-threshold Ca2+ channel currents were measured every 15 s following a 200 ms voltage step from -80 mV to 0 mV in order to study the coupling mechanism between neurotransmitter receptors and Ca2+ channels in neurones acutely isolated from the nucleus tractus solitarius (NTS) of the rat. 2. Application of 30 microM baclofen (GABAB receptor agonist) caused 38.9 +/- 1.2% inhibition of the peak inward Ba2+ current (IBa2+) in most NTS cells tested (n = 85 of 88). Somatostatin, 300 nM, also r...

  10. An RNA aptamer possessing a novel monovalent cation-mediated fold inhibits lysozyme catalysis by inhibiting the binding of long natural substrates.

    Science.gov (United States)

    Padlan, Camille S; Malashkevich, Vladimir N; Almo, Steve C; Levy, Matthew; Brenowitz, Michael; Girvin, Mark E

    2014-04-01

    RNA aptamers are being developed as inhibitors of macromolecular and cellular function, diagnostic tools, and potential therapeutics. Our understanding of the physical nature of this emerging class of nucleic acid-protein complexes is limited; few atomic resolution structures have been reported for aptamers bound to their protein target. Guided by chemical mapping, we systematically minimized an RNA aptamer (Lys1) selected against hen egg white lysozyme. The resultant 59-nucleotide compact aptamer (Lys1.2minE) retains nanomolar binding affinity and the ability to inhibit lysozyme's catalytic activity. Our 2.0-Å crystal structure of the aptamer-protein complex reveals a helical stem stabilizing two loops to form a protein binding platform that binds lysozyme distal to the catalytic cleft. This structure along with complementary solution analyses illuminate a novel protein-nucleic acid interface; (1) only 410 Å(2) of solvent accessible surface are buried by aptamer binding; (2) an unusually small fraction (∼18%) of the RNA-protein interaction is electrostatic, consistent with the limited protein phosphate backbone contacts observed in the structure; (3) a single Na(+) stabilizes the loops that constitute the protein-binding platform, and consistent with this observation, Lys1.2minE-lysozyme complex formation takes up rather than displaces cations at low ionic strength; (4) Lys1.2minE inhibits catalysis of large cell wall substrates but not catalysis of small model substrates; and (5) the helical stem of Lys1.2minE can be shortened to four base pairs (Lys1.2minF) without compromising binding affinity, yielding a 45-nucleotide aptamer whose structure may be an adaptable protein binding platform.

  11. Gating of the two-pore cation channel AtTPC1 in the plant vacuole is based on a single voltage-sensing domain.

    Science.gov (United States)

    Jaślan, D; Mueller, T D; Becker, D; Schultz, J; Cuin, T A; Marten, I; Dreyer, I; Schönknecht, G; Hedrich, R

    2016-09-01

    The two-pore cation channel TPC1 operates as a dimeric channel in animal and plant endomembranes. Each subunit consists of two homologous Shaker-like halves, with 12 transmembrane domains in total (S1-S6, S7-S12). In plants, TPC1 channels reside in the vacuolar membrane, and upon voltage stimulation, give rise to the well-known slow-activating SV currents. Here, we combined bioinformatics, structure modelling, site-directed mutagenesis, and in planta patch clamp studies to elucidate the molecular mechanisms of voltage-dependent channel gating in TPC1 in its native plant background. Structure-function analysis of the Arabidopsis TPC1 channel in planta confirmed that helix S10 operates as the major voltage-sensing site, with Glu450 and Glu478 identified as possible ion-pair partners for voltage-sensing Arg537. The contribution of helix S4 to voltage sensing was found to be negligible. Several conserved negative residues on the luminal site contribute to calcium binding, stabilizing the closed channel. During evolution of plant TPC1s from two separate Shaker-like domains, the voltage-sensing function in the N-terminal Shaker-unit (S1-S4) vanished.

  12. Gating of the two-pore cation channel AtTPC1 in the plant vacuole is based on a single voltage-sensing domain.

    Science.gov (United States)

    Jaślan, D; Mueller, T D; Becker, D; Schultz, J; Cuin, T A; Marten, I; Dreyer, I; Schönknecht, G; Hedrich, R

    2016-09-01

    The two-pore cation channel TPC1 operates as a dimeric channel in animal and plant endomembranes. Each subunit consists of two homologous Shaker-like halves, with 12 transmembrane domains in total (S1-S6, S7-S12). In plants, TPC1 channels reside in the vacuolar membrane, and upon voltage stimulation, give rise to the well-known slow-activating SV currents. Here, we combined bioinformatics, structure modelling, site-directed mutagenesis, and in planta patch clamp studies to elucidate the molecular mechanisms of voltage-dependent channel gating in TPC1 in its native plant background. Structure-function analysis of the Arabidopsis TPC1 channel in planta confirmed that helix S10 operates as the major voltage-sensing site, with Glu450 and Glu478 identified as possible ion-pair partners for voltage-sensing Arg537. The contribution of helix S4 to voltage sensing was found to be negligible. Several conserved negative residues on the luminal site contribute to calcium binding, stabilizing the closed channel. During evolution of plant TPC1s from two separate Shaker-like domains, the voltage-sensing function in the N-terminal Shaker-unit (S1-S4) vanished. PMID:27270880

  13. K+ channel openers restore verapamil-inhibited lung fluid resolution and transepithelial ion transport

    Directory of Open Access Journals (Sweden)

    Su Xue-Feng

    2010-05-01

    Full Text Available Abstract Background Lung epithelial Na+ channels (ENaC are regulated by cell Ca2+ signal, which may contribute to calcium antagonist-induced noncardiogenic lung edema. Although K+ channel modulators regulate ENaC activity in normal lungs, the therapeutical relevance and the underlying mechanisms have not been completely explored. We hypothesized that K+ channel openers may restore calcium channel blocker-inhibited alveolar fluid clearance (AFC by up-regulating both apical and basolateral ion transport. Methods Verapamil-induced depression of heterologously expressed human αβγ ENaC in Xenopus oocytes, apical and basolateral ion transport in monolayers of human lung epithelial cells (H441, and in vivo alveolar fluid clearance were measured, respectively, using the two-electrode voltage clamp, Ussing chamber, and BSA protein assays. Ca2+ signal in H441 cells was analyzed using Fluo 4AM. Results The rate of in vivo AFC was reduced significantly (40.6 ± 6.3% of control, P Ca3.1 (1-EBIO and KATP (minoxidil channel openers significantly recovered AFC. In addition to short-circuit current (Isc in intact H441 monolayers, both apical and basolateral Isc levels were reduced by verapamil in permeabilized monolayers. Moreover, verapamil significantly altered Ca2+ signal evoked by ionomycin in H441 cells. Depletion of cytosolic Ca2+ in αβγ ENaC-expressing oocytes completely abolished verapamil-induced inhibition. Intriguingly, KV (pyrithione-Na, K Ca3.1 (1-EBIO, and KATP (minoxidil channel openers almost completely restored the verapamil-induced decrease in Isc levels by diversely up-regulating apical and basolateral Na+ and K+ transport pathways. Conclusions Our observations demonstrate that K+ channel openers are capable of rescuing reduced vectorial Na+ transport across lung epithelial cells with impaired Ca2+ signal.

  14. Inhibition of KV7 Channels Protects the Rat Heart against Myocardial Ischemia and Reperfusion Injury.

    Science.gov (United States)

    Hedegaard, Elise R; Johnsen, Jacob; Povlsen, Jonas A; Jespersen, Nichlas R; Shanmuganathan, Jeffrey A; Laursen, Mia R; Kristiansen, Steen B; Simonsen, Ulf; Bøtker, Hans Erik

    2016-04-01

    The voltage-gated KV7 (KCNQ) potassium channels are activated by ischemia and involved in hypoxic vasodilatation. We investigated the effect of KV7 channel modulation on cardiac ischemia and reperfusion injury and its interaction with cardioprotection by ischemic preconditioning (IPC). Reverse-transcription polymerase chain reaction revealed expression of KV7.1, KV7.4, and KV7.5 in the left anterior descending rat coronary artery and all KV7 subtypes (KV7.1-KV7.5) in the left and right ventricles of the heart. Isolated hearts were subjected to no-flow global ischemia and reperfusion with and without IPC. Infarct size was quantified by 2,3,5-triphenyltetrazolium chloride staining. Two blockers of KV7 channels, XE991 [10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone] (10 µM) and linopirdine (10 µM), reduced infarct size and exerted additive infarct reduction to IPC. An opener of KV7 channels, flupirtine (10 µM) abolished infarct size reduction by IPC. Hemodynamics were measured using a catheter inserted in the left ventricle and postischemic left ventricular recovery improved in accordance with reduction of infarct size and deteriorated with increased infarct size. XE991 (10 µM) reduced coronary flow in the reperfusion phase and inhibited vasodilatation in isolated small branches of the left anterior descending coronary artery during both simulated ischemia and reoxygenation. KV7 channels are expressed in rat coronary arteries and myocardium. Inhibition of KV7 channels exerts cardioprotection and opening of KV7 channels abrogates cardioprotection by IPC. Although safety issues should be further addressed, our findings suggest a potential role for KV7 blockers in the treatment of ischemia-reperfusion injury. PMID:26869667

  15. Transient Receptor Potential Channel and Interleukin-17A Involvement in LTTL Gel Inhibition of Bone Cancer Pain in a Rat Model.

    Science.gov (United States)

    Wang, Juyong; Zhang, Ruixin; Dong, Changsheng; Jiao, Lijing; Xu, Ling; Liu, Jiyong; Wang, Zhengtao; Lao, Lixing

    2015-07-01

    Cancer pain management is a challenge for which Chinese herbal medicine might be useful. To study the spinal mechanisms of the Chinese medicated gel Long-Teng-Tong-Luo (LTTL), a 7-herb compound, on bone cancer pain, a bone cancer pain model was made by inoculating the tibias of female rats with Walker 256 cells. LTTL gel or inert gel, 0.5 g/cm(2)/d, was applied to the skin of tumor-bearing tibias for 21 days beginning a day after the inoculation. Mechanical threshold and paw withdrawal latency to thermal stimulation was measured. Transient receptor potential (TRP) cation channels in lumbar dorsal root ganglia (DRG) were immunostained and counted, and lumbar spinal cord interleukin-17A (IL-17A) was measured with real-time polymerase chain reaction and enzyme-linked immunosorbent assay. TRP antagonists and interleukin (IL)-17A antibodies were intrathecally administered to determine their effects on bone cancer pain. The gel significantly (P cancer-induced mechanical allodynia and thermal hyperalgesia and inhibited cancer-enhanced expression of IL-17A in spinal astrocytes and the TRP subfamily members V1, A1, and V4 in lumbar DRG. Intrathecal TRP antagonists at 10 µg significantly (P cancer pain. IL-17A antibodies inhibited cancer pain, suggesting that IL-17A promotes such pain. The data show that LTTL gel inhibits cancer pain, and this might be accounted for by the decrease in expression of DRG TRP channels and spinal astrocyte IL-17A. PMID:26100378

  16. Extracellular potassium inhibits Kv7.1 potassium channels by stabilizing an inactivated state

    DEFF Research Database (Denmark)

    Larsen, Anders Peter; Steffensen, Annette Buur; Grunnet, Morten;

    2011-01-01

    Kv7.1 (KCNQ1) channels are regulators of several physiological processes including vasodilatation, repolarization of cardiomyocytes, and control of secretory processes. A number of Kv7.1 pore mutants are sensitive to extracellular potassium. We hypothesized that extracellular potassium also...... modulates wild-type Kv7.1 channels. The Kv7.1 currents were measured in Xenopus laevis oocytes at different concentrations of extracellular potassium (1-50 mM). As extracellular potassium was elevated, Kv7.1 currents were reduced significantly more than expected from theoretical calculations based...... on the Goldman-Hodgkin-Katz flux equation. Potassium inhibited the steady-state current with an IC(50) of 6.0 ± 0.2 mM. Analysis of tail-currents showed that potassium increased the fraction of channels in the inactivated state. Similarly, the recovery from inactivation was slowed by potassium, suggesting...

  17. Structure and inhibition of the SARS coronavirus envelope protein ion channel.

    Directory of Open Access Journals (Sweden)

    Konstantin Pervushin

    2009-07-01

    Full Text Available The envelope (E protein from coronaviruses is a small polypeptide that contains at least one alpha-helical transmembrane domain. Absence, or inactivation, of E protein results in attenuated viruses, due to alterations in either virion morphology or tropism. Apart from its morphogenetic properties, protein E has been reported to have membrane permeabilizing activity. Further, the drug hexamethylene amiloride (HMA, but not amiloride, inhibited in vitro ion channel activity of some synthetic coronavirus E proteins, and also viral replication. We have previously shown for the coronavirus species responsible for severe acute respiratory syndrome (SARS-CoV that the transmembrane domain of E protein (ETM forms pentameric alpha-helical bundles that are likely responsible for the observed channel activity. Herein, using solution NMR in dodecylphosphatidylcholine micelles and energy minimization, we have obtained a model of this channel which features regular alpha-helices that form a pentameric left-handed parallel bundle. The drug HMA was found to bind inside the lumen of the channel, at both the C-terminal and the N-terminal openings, and, in contrast to amiloride, induced additional chemical shifts in ETM. Full length SARS-CoV E displayed channel activity when transiently expressed in human embryonic kidney 293 (HEK-293 cells in a whole-cell patch clamp set-up. This activity was significantly reduced by hexamethylene amiloride (HMA, but not by amiloride. The channel structure presented herein provides a possible rationale for inhibition, and a platform for future structure-based drug design of this potential pharmacological target.

  18. Fluoxetine-induced inhibition of synaptosomal ( sup 3 H)5-HT release: Possible Ca sup 2+ -channel inhibition

    Energy Technology Data Exchange (ETDEWEB)

    Stauderman, K.A. (Marion Merrell Dow Research Inst., Cincinnati, OH (United States)); Gandhi, V.C.; Jones, D.J. (Univ. of Texas Health Science Center, San Antonio, TX (United States))

    1992-01-01

    Fluoxetine, a selective 5-Ht uptake inhibitor, inhibited 15 mM K{sup +}-induced ({sup 3}H)5-HT release from rat spinal cord and cortical synaptosomes at concentrations > 0.5 uM. This effect reflected a property shared by another selective 5-HT uptake inhibitor paroxetine but not by less selective uptake inhibitors such as amitriptyline, desipramine, imipramine or nortriptyline. Inhibition of release by fluoxetine was inversely related to both the concentration of K{sup +} used to depolarize the synaptosomes and the concentration of external Ca{sup 2+}. Experiments aimed at determining a mechanism of action revealed that fluoxetine did not inhibit voltage-independent release of ({sup 3}H)5-HT release induced by the Ca{sup 2+}-ionophore A 23187 or Ca{sup 2+}-independent release induced by fenfluramine. Moreover the 5-HT autoreceptor antagonist methiothepin did not reverse the inhibitory actions of fluoxetine on K{sup +}-induced release. Further studies examined the effects of fluoxetine on voltage-dependent Ca{sup 2+} channels and Ca{sup 2+} entry.

  19. Histidine phosphorylation relieves copper inhibition in the mammalian potassium channel KCa3.1.

    Science.gov (United States)

    Srivastava, Shekhar; Panda, Saswati; Li, Zhai; Fuhs, Stephen R; Hunter, Tony; Thiele, Dennis J; Hubbard, Stevan R; Skolnik, Edward Y

    2016-01-01

    KCa2.1, KCa2.2, KCa2.3 and KCa3.1 constitute a family of mammalian small- to intermediate-conductance potassium channels that are activated by calcium-calmodulin. KCa3.1 is unique among these four channels in that activation requires, in addition to calcium, phosphorylation of a single histidine residue (His358) in the cytoplasmic region, by nucleoside diphosphate kinase-B (NDPK-B). The mechanism by which KCa3.1 is activated by histidine phosphorylation is unknown. Histidine phosphorylation is well characterized in prokaryotes but poorly understood in eukaryotes. Here, we demonstrate that phosphorylation of His358 activates KCa3.1 by antagonizing copper-mediated inhibition of the channel. Furthermore, we show that activated CD4(+) T cells deficient in intracellular copper exhibit increased KCa3.1 histidine phosphorylation and channel activity, leading to increased calcium flux and cytokine production. These findings reveal a novel regulatory mechanism for a mammalian potassium channel and for T-cell activation, and highlight a unique feature of histidine versus serine/threonine and tyrosine as a regulatory phosphorylation site. PMID:27542194

  20. Cell swelling activates K+ and Cl- channels as well as nonselective, stretch-activated cation channels in ehrlich ascites tumor cells

    DEFF Research Database (Denmark)

    Christensen, Ove; Hoffmann, Else Kay

    1992-01-01

    external K+ is estimated at about 7 pS. A K+ channel with similar properties can be activated in the cellattached mode by addition of Ca2+ plus ionophore A23187. The channel is also activated by cell swelling, within 1 min following hypotonic exposure. No evidence was found of channel activation...... by membrane stretch (suction). The time-averaged number of open K+ channels during regulatory volume decrease (RVD) can be estimated at 40 per cell. The number of open K+ channels following addition of Ca2+ plus ionophore A23187 was estimated at 250 per cell. Concurrent activation in cell-attached patches...... in the cell-attached mode could be activated by addition of Ca2+ plus ionophore A23187. The channel is also activated by hypotonic exposure with a single-channel conductance at 7 pS (or less) and with a time delay at about 1 min. The number of open channels during RVD is estimated at 80 per cell. Two other...

  1. CRAC channel is inhibited by neomycin in a Ptdlns(4,5)P2-independent manner.

    Science.gov (United States)

    Huang, Kun; Wang, Xuemei; Liu, Yanjun; Zhao, Yi

    2015-03-01

    Depletion of intracellular Ca(2+) stores evokes store-operated Ca(2+) entry through the Ca(2+) release-activated Ca(2+) (CRAC) channels. In this study, we found that the store-operated Ca(2+) entry was inhibited by neomycin, an aminoglycoside that strongly binds phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). Patch clamp recordings revealed that neomycin blocked the CRAC currents reconstituted by co-expression of Orai1 and Stim1 in HEK293 cells. Using a rapamycin-inducible PtdIns(4,5)P2-specific phosphatase (Inp54p) system to manipulate the PtdIns(4,5)P2 in the plasma membrane, we found that the CRAC current was not altered by PtdIns(4,5)P2 depletion. This result suggests that PtdIns(4,5)P2 is not required for CRAC channel activity, and thereby, neomycin inhibits CRAC channels in a manner that is independent of neomycin-PtdIns(4,5)P2 binding.

  2. Anti-proliferative actions of T-type calcium channel inhibition in Thy1 nephritis.

    Science.gov (United States)

    Cove-Smith, Andrea; Mulgrew, Christopher J; Rudyk, Olena; Dutt, Neelanjana; McLatchie, Linda M; Shattock, Michael J; Hendry, Bruce M

    2013-08-01

    Aberrant proliferation of mesangial cells (MCs) is a key finding in progressive glomerular disease. TH1177 is a small molecule that has been shown to inhibit low-voltage activated T-type Ca(2+) channels (TCCs). The current study investigates the effect of TH1177 on MC proliferation in vitro and in vivo. The effect of Ca(2+) channel inhibition on primary rat MC proliferation in vitro was studied using the microculture tetrazolium assay and by measuring bromodeoxyuridine incorporation. In vivo, rats with Thy1 nephritis were treated with TH1177 or vehicle. Glomerular injury and average glomerular cell number were determined in a blinded fashion. Immunostaining for Ki-67 and phosphorylated ERK were also performed. The expression of TCC isoforms in healthy and diseased tissue was investigated using quantitative real-time PCR. TCC blockade caused a significant reduction in rat MC proliferation in vitro, whereas L-type inhibition had no effect. Treatment of Thy1 nephritis with TH1177 significantly reduced glomerular injury (P < 0.005) and caused a 49% reduction in glomerular cell number (P < 0.005) compared to the placebo. TH1177 also reduced Ki-67-positive and pERK-positive cells per glomerulus by 52% (P < 0.01 and P < 0.005, respectively). These results demonstrate that TH1177 inhibits MC proliferation in vitro and in vivo, supporting the hypothesis that TCC inhibition may be a useful strategy for studying and modifying MC proliferative responses to injury. PMID:23746655

  3. [Inhibition of oxygen free radicals in potassium channels of cardiac myocytes and the action of salvianolic acid A].

    Science.gov (United States)

    Bao, G

    1993-10-01

    By using the patch clamp technique, the effect of oxygen free radicals on the single potassium channels of cardiac papillary muscle cells were studied, as well as the action of salvianolic acid A. It was found that xanthane-xanthane oxidase generated oxygen free radicals could apparently inhibited the unitary currents of the single potassium channel activity. This inhibition was reversed by salvianolic acid A, which is an effective component extracted from Salvia miltiorrhiza. PMID:8168213

  4. Identification of large channels in cationic PEGylated cubosome nanoparticles by synchrotron radiation SAXS and Cryo-TEM imaging.

    Science.gov (United States)

    Angelov, Borislav; Angelova, Angelina; Drechsler, Markus; Garamus, Vasil M; Mutafchieva, Rada; Lesieur, Sylviane

    2015-05-14

    Extra-large nanochannel formation in the internal structure of cationic cubosome nanoparticles results from the interplay between charge repulsion and steric stabilization of the lipid membrane interfaces and is evidenced by cryogenic transmission electron microscopy (Cryo-TEM) and synchrotron radiation small-angle X-ray scattering (SAXS). The swollen cubic symmetry of the lipid nanoparticles emerges through a shaping transition of onion bilayer vesicle intermediates containing a fusogenic nonlamellar lipid. Cationic amphiphile cubosome particles, thanks to the advantages of their liquid crystalline soft porous nanoarchitecture and capability for multi-drug nanoencapsulation, appear to be of interest for the design of mitochondrial targeting devices in anti-cancer therapies and as siRNA nanocarriers for gene silencing. PMID:25820228

  5. Clofazimine inhibits human Kv1.3 potassium channel by perturbing calcium oscillation in T lymphocytes.

    Directory of Open Access Journals (Sweden)

    Yunzhao R Ren

    Full Text Available The Kv1.3 potassium channel plays an essential role in effector memory T cells and has been implicated in several important autoimmune diseases including multiple sclerosis, psoriasis and type 1 diabetes. A number of potent small molecule inhibitors of Kv1.3 channel have been reported, some of which were found to be effective in various animal models of autoimmune diseases. We report herein the identification of clofazimine, a known anti-mycobacterial drug, as a novel inhibitor of human Kv1.3. Clofazimine was initially identified as an inhibitor of intracellular T cell receptor-mediated signaling leading to the transcriptional activation of human interleukin-2 gene in T cells from a screen of the Johns Hopkins Drug Library. A systematic mechanistic deconvolution revealed that clofazimine selectively blocked the Kv1.3 channel activity, perturbing the oscillation frequency of the calcium-release activated calcium channel, which in turn led to the inhibition of the calcineurin-NFAT signaling pathway. These effects of clofazimine provide the first line of experimental evidence in support of a causal relationship between Kv1.3 and calcium oscillation in human T cells. Furthermore, clofazimine was found to be effective in blocking human T cell-mediated skin graft rejection in an animal model in vivo. Together, these results suggest that clofazimine is a promising immunomodulatory drug candidate for treating a variety of autoimmune disorders.

  6. The cyclic nucleotide gated cation channel AtCNGC10 traffics from the ER via Golgi vesicles to the plasma membrane of Arabidopsis root and leaf cells

    Directory of Open Access Journals (Sweden)

    Andres Marilou A

    2007-09-01

    Full Text Available Abstract Background The cyclic nucleotide-gated ion channels (CNGCs maintain cation homeostasis essential for a wide range of physiological processes in plant cells. However, the precise subcellular locations and trafficking of these membrane proteins are poorly understood. This is further complicated by a general deficiency of information about targeting pathways of membrane proteins in plants. To investigate CNGC trafficking and localization, we have measured Atcngc5 and Atcngc10 expression in roots and leaves, analyzed AtCNGC10-GFP fusions transiently expressed in protoplasts, and conducted immunofluorescence labeling of protoplasts and immunoelectron microscopic analysis of high pressure frozen leaves and roots. Results AtCNGC10 mRNA and protein levels were 2.5-fold higher in roots than leaves, while AtCNGC5 mRNA and protein levels were nearly equal in these tissues. The AtCNGC10-EGFP fusion was targeted to the plasma membrane in leaf protoplasts, and lightly labeled several intracellular structures. Immunofluorescence microscopy with affinity purified CNGC-specific antisera indicated that AtCNGC5 and AtCNGC10 are present in the plasma membrane of protoplasts. Immunoelectron microscopy demonstrated that AtCNGC10 was associated with the plasma membrane of mesophyll, palisade parenchyma and epidermal cells of leaves, and the meristem, columella and cap cells of roots. AtCNCG10 was also observed in the endoplasmic reticulum and Golgi cisternae and vesicles of 50–150 nm in size. Patch clamp assays of an AtCNGC10-GFP fusion expressed in HEK293 cells measured significant cation currents. Conclusion AtCNGC5 and AtCNGC10 are plasma membrane proteins. We postulate that AtCNGC10 traffics from the endoplasmic reticulum via the Golgi apparatus and associated vesicles to the plasma membrane. The presence of the cation channel, AtCNGC10, in root cap meristem cells, cell plate, and gravity-sensing columella cells, combined with the previously reported

  7. Inhibition of hepatic fibrosis with artificial microRNA using ultrasound and cationic liposome-bearing microbubbles.

    Science.gov (United States)

    Yang, D; Gao, Y-H; Tan, K-B; Zuo, Z-X; Yang, W-X; Hua, X; Li, P-J; Zhang, Y; Wang, G

    2013-12-01

    We sought to investigate the antifibrotic effects of an artificial microRNA (miRNA) targeting connective tissue growth factor (CTGF) using the ultrasound-targeted cationic liposome-bearing microbubble destruction gene delivery system. Cationic liposomes were conjugated with microbubbles using a biotin-avidin system. Plasmids carrying the most effective artificial miRNA sequences were delivered by ultrasound-targeted cationic liposome-bearing microbubble destruction gene delivery system to rats with hepatic fibrosis. The results show that this method of gene delivery effectively transported the plasmids to the rat liver. The artificial miRNA reduced hepatic fibrosis pathological alterations as well as the protein and mRNA expressions of CTGF and transforming growth factor β1. Furthermore, the CTGF gene silencing decreased the levels of type I collagen and α-smooth muscle actin (Pliposome-bearing microbubble destruction may be an efficacious therapeutic method to ameliorate hepatic fibrosis.

  8. Kinetics and thermodynamics of binding reactions as exemplified by anthrax toxin channel blockage with a cationic cyclodextrin derivative.

    Science.gov (United States)

    Nestorovich, Ekaterina M; Karginov, Vladimir A; Berezhkovskii, Alexander M; Parsegian, V Adrian; Bezrukov, Sergey M

    2012-11-01

    The thermodynamics of binding reactions is usually studied in the framework of the linear van't Hoff analysis of the temperature dependence of the equilibrium constant. The logarithm of the equilibrium constant is plotted versus inverse temperature to discriminate between two terms: an enthalpic contribution that is linear in the inverse temperature, and a temperature-independent entropic contribution. When we apply this approach to a particular case-blockage of the anthrax PA(63) channel by a multicharged cyclodextrin derivative-we obtain a nearly linear behavior with a slope that is characterized by enthalpy of about 1 kcal/mol. In contrast, from blocker partitioning between the channel and the bulk, we estimate the depth of the potential well for the blocker in the channel to be at least 8 kcal/mol. To understand this apparent discrepancy, we use a simple model of particle interaction with the channel and show that this significant difference between the two estimates is due to the temperature dependence of the physical forces between the blocker and the channel. In particular, we demonstrate that if the major component of blocker-channel interaction is van der Waals interactions and/or Coulomb forces in water, the van't Hoff enthalpy of the binding reaction may be close to zero or even negative, including cases of relatively strong binding. The results are quite general and, therefore, of importance for studies of enzymatic reactions, rational drug design, small-molecule binding to proteins, protein-protein interactions, and protein folding, among others.

  9. Stereoselective inhibition of thromboxane-induced coronary vasoconstriction by 1,4-dihydropyridine calcium channel antagonists

    International Nuclear Information System (INIS)

    The biological activity of the (+)-S- and (-)-R-enantiomers of niguldipine, of the (-)-S- and (+)-R-enantiomers of felodipine and nitrendipine, and of rac-nisoldipine and rac-nimodipine was investigated in vitro and in vivo. Inhibition of coronary vasoconstriction due to the thromboxane A2 (TxA2)-mimetic U-46619 in guinea pig Langendorff hearts, displacement of (+)-[3H]isradipine from calcium channel binding sites of guinea pig skeletal muscle T-tubule membranes, and blood pressure reduction in spontaneously hypertensive rats were determined. The enantiomers were obtained by stereoselective synthesis. Cross-contamination was less than 0.5% for both S- and R-enantiomers of niguldipine and nitrendipine and less than 1% for those of felodipine. From the doses necessary for a 50% inhibition of coronary vasoconstriction, stereoselectivity ratios for (+)-(S)-/(-)-(R)-niguldipine, (-)-(S)-/(+)-(R)-felodipine, and (-)-(S)-/(+)-(R)-nitrendipine of 28, 13, and 7, respectively, were calculated. The potency ratio rac-nisoldipine/rac-nimodipine was 3.5. Ratios obtained from binding experiments and antihypertensive activity were (+)-(S)-/(-)-(R)-niguldipine = 45 and 35, (-)-(S)-/(+)-(R)-felodipine = 12 and 13, (-)-(S)-/(+)-(R)-nitrendipine = 8 and 8, and rac-nisoldipine/rac-nimodipine = 8 and 7, respectively. Highly significant correlations were found between the in vitro potency of the substances to prevent U-46619-induced coronary vasoconstriction and their affinity for calcium channel binding sites as well as their antihypertensive activity

  10. Mutant connexin 50 (S276F) inhibits channel and hemichannel functions inducing cataract

    Indian Academy of Sciences (India)

    Yuanyuan Liu; Chen Qiao; Tanwei Wei; Fang Zheng; Shuren Guo; Qiang Chen; Ming Yan; Xin Zhou

    2015-06-01

    This study was designed to detect the expression, detergent resistance, subcellular localization, and channel and hemichannel functions of mutant Cx50 to understand the forming mechanism for inducing congenital cataract by a novel mutation p.S276F in connexin 50 (Cx50) reported previously by us. HeLa and human lens epithelial (HLE) cells were transfected with wild-type Cx50 and mutant Cx50 (S276F). We examined the functional characteristics of mutant Cx50 (S276F) in comparison with those of wild-type Cx50 using immunoblot, confocal fluorescence microscopy, dye transfer analysis and dye uptake assay. The mutant and wild-type Cx50 were expressed in equal levels and could efficiently localize to the plasma membrane without transportation and assembly problems. Scrape loading dye transfer was significantly evident in cells transfected with wild-type Cx50 compared to those in cells transfected with mutant Cx50 and cotransfected with wild-type and mutant Cx50. The dye uptake was found to be significantly lower in cells transfected with mutant Cx50 than in cells transfected with wild-type Cx50 and cells cotransfected with wild-type and mutant Cx50. The transfected HeLa and HLE cell lines showed similar performance in all the experiments. These results indicated that the mutant Cx50 (S276F) might inhibit the function of gap junction channel in a dominant negative manner, but inhibit the hemichannel function in a recessive negative manner.

  11. Myricetin inhibits Kv1.5 channels in HEK293 cells.

    Science.gov (United States)

    Ou, Xianhong; Bin, Xiaohong; Wang, Luzhen; Li, Miaoling; Yang, Yan; Fan, Xinrong; Zeng, Xiaorong

    2016-02-01

    Myricetin (Myr) is a flavonoid that exerts anti-arrhythmic effects. However, its potential effects on ion channels have remained elusive. The aim of the present study was to investigate the effects of Myr on Kv1.5 channels in HEK293 cells. The current of Kv1.5 channels (Ikur) in HEK293 cells was recorded using the whole-cell patch-clamp technique and the expression of the Kv1.5 protein was measured using western blot analysis 24 h after treatment with Myr. The results showed that 5 µM Myr significantly reduced Ikur from 215.04 ± 40.59 to 77.72 ± 17.94 pA/pF (PHEK293 cells treated with 10 µM Myr for 5 min. Furthermore, Myr reduced hKv1.5 protein expression in a dose-dependent manner. These results demonstrated that Myr inhibited Ikur and the expression of hKv1.5 in HEK293 cells in a dose-, time- and frequency-dependent manner. These observations partly explained the mechanisms by which Myr exerts anti-arrhythmic effect.

  12. Inhibition of herpes simplex virus type 1 entry by chloride channel inhibitors tamoxifen and NPPB

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Kai [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China); College of Life Science and Technology, Jinan University, Guangzhou (China); Chen, Maoyun [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China); College of pharmacy, Jinan University, Guangzhou (China); Xiang, Yangfei; Ma, Kaiqi [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China); Jin, Fujun [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China); College of pharmacy, Jinan University, Guangzhou (China); Wang, Xiao [School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006 (China); Wang, Xiaoyan; Wang, Shaoxiang [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China); Wang, Yifei, E-mail: twang-yf@163.com [Guangzhou Jinan Biomedicine Research and Development Center, National Engineering Research Center of Genetic Medicine, Jinan University, Guangzhou (China)

    2014-04-18

    Highlights: • We analyze the anti-HSV potential of chloride channel inhibitors. • Tamoxifen and NPPB show anti-HSV-1 and anti-ACV-resistant HSV-1 activities. • HSV-1 infection induces intracellular chloride concentration increasing. • Tamoxifen and NPPB inhibit HSV-1 early infection. • Tamoxifen and NPPB prevent the fusion process of HSV-1. - Abstract: Herpes simplex virus type 1 (HSV-1) infection is very common worldwide and can cause significant health problems from periodic skin and corneal lesions to encephalitis. Appearance of drug-resistant viruses in clinical therapy has made exploring novel antiviral agents emergent. Here we show that chloride channel inhibitors, including tamoxifen and 5-nitro-2-(3-phenyl-propylamino) benzoic acid (NPPB), exhibited extensive antiviral activities toward HSV-1 and ACV-resistant HSV viruses. HSV-1 infection induced chloride ion influx while treatment with inhibitors reduced the increase of intracellular chloride ion concentration. Pretreatment or treatment of inhibitors at different time points during HSV-1 infection all suppressed viral RNA synthesis, protein expression and virus production. More detailed studies demonstrated that tamoxifen and NPPB acted as potent inhibitors of HSV-1 early entry step by preventing viral binding, penetration and nuclear translocation. Specifically the compounds appeared to affect viral fusion process by inhibiting virus binding to lipid rafts and interrupting calcium homeostasis. Taken together, the observation that tamoxifen and NPPB can block viral entry suggests a stronger potential for these compounds as well as other ion channel inhibitors in antiviral therapy against HSV-1, especially the compound tamoxifen is an immediately actionable drug that can be reused for treatment of HSV-1 infections.

  13. Inhibition of herpes simplex virus type 1 entry by chloride channel inhibitors tamoxifen and NPPB

    International Nuclear Information System (INIS)

    Highlights: • We analyze the anti-HSV potential of chloride channel inhibitors. • Tamoxifen and NPPB show anti-HSV-1 and anti-ACV-resistant HSV-1 activities. • HSV-1 infection induces intracellular chloride concentration increasing. • Tamoxifen and NPPB inhibit HSV-1 early infection. • Tamoxifen and NPPB prevent the fusion process of HSV-1. - Abstract: Herpes simplex virus type 1 (HSV-1) infection is very common worldwide and can cause significant health problems from periodic skin and corneal lesions to encephalitis. Appearance of drug-resistant viruses in clinical therapy has made exploring novel antiviral agents emergent. Here we show that chloride channel inhibitors, including tamoxifen and 5-nitro-2-(3-phenyl-propylamino) benzoic acid (NPPB), exhibited extensive antiviral activities toward HSV-1 and ACV-resistant HSV viruses. HSV-1 infection induced chloride ion influx while treatment with inhibitors reduced the increase of intracellular chloride ion concentration. Pretreatment or treatment of inhibitors at different time points during HSV-1 infection all suppressed viral RNA synthesis, protein expression and virus production. More detailed studies demonstrated that tamoxifen and NPPB acted as potent inhibitors of HSV-1 early entry step by preventing viral binding, penetration and nuclear translocation. Specifically the compounds appeared to affect viral fusion process by inhibiting virus binding to lipid rafts and interrupting calcium homeostasis. Taken together, the observation that tamoxifen and NPPB can block viral entry suggests a stronger potential for these compounds as well as other ion channel inhibitors in antiviral therapy against HSV-1, especially the compound tamoxifen is an immediately actionable drug that can be reused for treatment of HSV-1 infections

  14. Inhibition of B16BL6 tumor progression by coadministration of recombinant angiostatin K1-3 and endostatin genes with cationic liposomes.

    Science.gov (United States)

    Kim, Keun Sik; Kim, Hong Sung; Park, Jin Seu; Kwon, Young Guen; Park, Yong Serk

    2004-06-01

    Transfection of the antiangiogenic angiostatin and endostatin genes was shown to be an alternative to high-dose administration of angiostatin or endostatin proteins for cancer therapy. We have systematically investigated whether coadministration of the mouse angiostatin kringle 1-3 gene (pFLAG-AngioK1/3) and the endostatin gene (pFLAG-Endo) complexed with cationic liposomes exhibits enhanced therapeutic efficacy. In vitro, the coexpressed mixture of angiostatin K1-3 and endostatin more effectively reduced angiogenesis in chorioallantoic membranes than either angiostatin K1-3 or endostatin alone. In vivo, subcutaneous co-administration of pFLAG-AngioK1/3 and pFLAG-Endo lipoplexes more effectively inhibited vascularization in Matrigel plugs implanted in mice than either one alone. Additionally, subcutaneous administration of these genes inhibited the growth and formation of pulmonary metastases of B16BL6 melanoma cells in mice. Compared to treatment with an empty vector, treatment with pFLAG-AngioK1/3 plus pFLAG-Endo inhibited 81% of tumor growth, while treatment with pFLAG-AngioK1/3 or pFLAG-Endo inhibited tumor growth 70 and 69%, respectively. Cotreatment with the two plasmids after primary tumor excision induced a 90% inhibition of pulmonary metastases versus 79% for pFLAG-AngioK1/3 or 80% for pFLAG-Endo individually. These results suggest that combined administration of angiostatin K1-3 and endostatin genes complexed with cationic liposomes may be an innovated antiangiogenic strategy for cancer therapy. PMID:15118757

  15. Xanthurenic acid binds to neuronal G-protein-coupled receptors that secondarily activate cationic channels in the cell line NCB-20.

    Science.gov (United States)

    Taleb, Omar; Maammar, Mohammed; Brumaru, Daniel; Bourguignon, Jean-Jacques; Schmitt, Martine; Klein, Christian; Kemmel, Véronique; Maitre, Michel; Mensah-Nyagan, Ayikoe Guy

    2012-01-01

    Xanthurenic acid (XA) is a metabolite of the tryptophan oxidation pathway through kynurenine and 3-hydroxykynurenine. XA was until now considered as a detoxification compound and dead-end product reducing accumulation of reactive radical species. Apart from a specific role for XA in the signaling cascade resulting in gamete maturation in mosquitoes, nothing was known about its functions in other species including mammals. Based upon XA distribution, transport, accumulation and release in the rat brain, we have recently suggested that XA may potentially be involved in neurotransmission/neuromodulation, assuming that neurons presumably express specific XA receptors. Recently, it has been shown that XA could act as a positive allosteric ligand for class II metabotropic glutamate receptors. This finding reinforces the proposed signaling role of XA in brain. Our present results provide several lines of evidence in favor of the existence of specific receptors for XA in the brain. First, binding experiments combined with autoradiography and time-course analysis led to the characterization of XA binding sites in the rat brain. Second, specific kinetic and pharmacological properties exhibited by these binding sites are in favor of G-protein-coupled receptors (GPCR). Finally, in patch-clamp and calcium imaging experiments using NCB-20 cells that do not express glutamate-induced calcium signals, XA elicited specific responses involving activation of cationic channels and increases in intracellular Ca(2+) concentration. Altogether, these results suggest that XA, acting through a GPCR-induced cationic channel modulatory mechanism, may exert excitatory functions in various brain neuronal pathways. PMID:23139790

  16. Xanthurenic acid binds to neuronal G-protein-coupled receptors that secondarily activate cationic channels in the cell line NCB-20.

    Directory of Open Access Journals (Sweden)

    Omar Taleb

    Full Text Available Xanthurenic acid (XA is a metabolite of the tryptophan oxidation pathway through kynurenine and 3-hydroxykynurenine. XA was until now considered as a detoxification compound and dead-end product reducing accumulation of reactive radical species. Apart from a specific role for XA in the signaling cascade resulting in gamete maturation in mosquitoes, nothing was known about its functions in other species including mammals. Based upon XA distribution, transport, accumulation and release in the rat brain, we have recently suggested that XA may potentially be involved in neurotransmission/neuromodulation, assuming that neurons presumably express specific XA receptors. Recently, it has been shown that XA could act as a positive allosteric ligand for class II metabotropic glutamate receptors. This finding reinforces the proposed signaling role of XA in brain. Our present results provide several lines of evidence in favor of the existence of specific receptors for XA in the brain. First, binding experiments combined with autoradiography and time-course analysis led to the characterization of XA binding sites in the rat brain. Second, specific kinetic and pharmacological properties exhibited by these binding sites are in favor of G-protein-coupled receptors (GPCR. Finally, in patch-clamp and calcium imaging experiments using NCB-20 cells that do not express glutamate-induced calcium signals, XA elicited specific responses involving activation of cationic channels and increases in intracellular Ca(2+ concentration. Altogether, these results suggest that XA, acting through a GPCR-induced cationic channel modulatory mechanism, may exert excitatory functions in various brain neuronal pathways.

  17. Eugenol dilates rat cerebral arteries by inhibiting smooth muscle cell voltage-dependent calcium channels.

    Science.gov (United States)

    Peixoto-Neves, Dieniffer; Leal-Cardoso, Jose Henrique; Jaggar, Jonathan H

    2014-11-01

    Plants high in eugenol, a phenylpropanoid compound, are used as folk medicines to alleviate diseases including hypertension. Eugenol has been demonstrated to relax conduit and ear arteries and reduce systemic blood pressure, but mechanisms involved are unclear. Here, we studied eugenol regulation of resistance-size cerebral arteries that control regional brain blood pressure and flow and investigated mechanisms involved. We demonstrate that eugenol dilates arteries constricted by either pressure or membrane depolarization (60 mM K) in a concentration-dependent manner. Experiments performed using patch-clamp electrophysiology demonstrated that eugenol inhibited voltage-dependent calcium (Ca) currents, when using Ba as a charge carrier, in isolated cerebral artery smooth muscle cells. Eugenol inhibition of voltage-dependent Ca currents involved pore block, a hyperpolarizing shift (∼-10 mV) in voltage-dependent inactivation, an increase in the proportion of steady-state inactivating current, and acceleration of inactivation rate. In summary, our data indicate that eugenol dilates cerebral arteries by means of multimodal inhibition of voltage-dependent Ca channels.

  18. K-channels inhibited by hydrogen peroxide mediate abscisic acid signaling in Vicia guard cells

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A number of studies show that environmental stress conditions increase abscisic acid (ABA) and hydrogen peroxide (H2O2) levels in plant cells. Despite this central role of ABA in altering stomatal aperture by regulating guard cell ion transport, little is known concerning the relationship between ABA and H2O2 in signal transduction leading to stomatal movement. Epidermal strip bioassay illustrated that ABA-inhibited stomatal opening and ABA-induced stomatal closure were abolished partly by externally added catalase (CAT) or diphenylene iodonium (DPI), which are a H2O2 scavenger and a NADPH oxidase inhibitor respectively. In contrast, internally added CAT or DPI nearly completely or partly reversed ABA-induced closure in half-stoma. Consistent with these results, whole-cell patch-clamp analysis showed that intracellular application of CAT or DPI partly abolished ABA-inhibited inward K+ current across the plasma membrane of guard cells. H2O2 mimicked ABA to inhibit inward K+ current, an effect which was reversed by the addition of ascorbic acid (Vc) in patch clamping micropipettes. These results suggested that H2O2 mediated ABA-induced stomatal movement by targeting inward K+ channels at plasma membrane.

  19. Prostaglandin metabolite induces inhibition of TRPA1 and channel-dependent nociception

    Directory of Open Access Journals (Sweden)

    Weng Yingqi

    2012-09-01

    Full Text Available Abstract Background The Transient Receptor Potential (TRP ion channel TRPA1 is a key player in pain pathways. Irritant chemicals activate ion channel TRPA1 via covalent modification of N-terminal cysteines. We and others have shown that 15-Deoxy-Δ12, 14-prostaglandin J2 (15d-PGJ2 similarly activates TRPA1 and causes channel-dependent nociception. Paradoxically, 15d-PGJ2 can also be anti-nociceptive in several pain models. Here we hypothesized that activation and subsequent desensitization of TRPA1 in dorsal root ganglion (DRG neurons underlies the anti-nociceptive property of 15d-PGJ2. To investigate this, we utilized a battery of behavioral assays and intracellular Ca2+ imaging in DRG neurons to test if pre-treatment with 15d-PGJ2 inhibited TRPA1 to subsequent stimulation. Results Intraplantar pre-injection of 15d-PGJ2, in contrast to mustard oil (AITC, attenuated acute nocifensive responses to subsequent injections of 15d-PGJ2 and AITC, but not capsaicin (CAP. Intraplantar 15d-PGJ2—administered after the induction of inflammation—reduced mechanical hypersensitivity in the Complete Freund’s Adjuvant (CFA model for up to 2 h post-injection. The 15d-PGJ2-mediated reduction in mechanical hypersensitivity is dependent on TRPA1, as this effect was absent in TRPA1 knockout mice. Ca2+ imaging studies of DRG neurons demonstrated that 15d-PGJ2 pre-exposure reduced the magnitude and number of neuronal responses to AITC, but not CAP. AITC responses were not reduced when neurons were pre-exposed to 15d-PGJ2 combined with HC-030031 (TRPA1 antagonist, demonstrating that inhibitory effects of 15d-PGJ2 depend on TRPA1 activation. Single daily doses of 15d-PGJ2, administered during the course of 4 days in the CFA model, effectively reversed mechanical hypersensitivity without apparent tolerance or toxicity. Conclusions Taken together, our data support the hypothesis that 15d-PGJ2 induces activation followed by persistent inhibition of TRPA1 channels

  20. The open-close mechanism of M2 channel protein in influenza A virus:A computational study on the hydrogen bonds and cation-π interactions among His37 and Trp41

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The M2 protein from influenza A virus is a tetrameric ion channel. It was reported that the permeation of the ion channel is correlated with the hydrogen bond network among His37 residues and the cation-π interactions between His37 and Trp41. In the present study,the hydrogen bonding network of 4-methyl-imidazoles was built to mimic the hydrogen bonds between His37 residues,and the cation-π interactions between 4-methyl-imidazolium and indole systems were selected to represent the interac-tions between His37 and Trp41. Then,quantum chemistry calculations at the MP2/6-311G level were carried out to explore the properties of the hydrogen bonds and the cation-π interactions. The calcula-tion results indicate that the binding strength of the N-H···N hydrogen bond between imidazole rings is up to -6.22 kcal·mol-1,and the binding strength of the strongest cation-π interaction is up to -18.8 kcal·mol-1(T-shaped interaction) or -12.3 kcal·mol-1(parallel stacking interaction). Thus,the calcu-lated binding energies indicate that it is possible to control the permeation of the M2 ion channel through the hydrogen bond network and the cation-π interactions by altering the pH values.

  1. The open-close mechanism of M2 channel protein in influenza A virus: A computational study on the hydrogen bonds and cation-π interactions among His37 and Trp41

    Institute of Scientific and Technical Information of China (English)

    CHENG JiaGao; ZHU WeiLiang; WANG YanLi; YAN XiuHua; LI Zhong; TANG Yun; JIANG HuaLiang

    2008-01-01

    The M2 protein from influenza A virus is a tetrameric ion channel. It was reported that the permeation of the ion channel is correlated with the hydrogen bond network among His37 residues and the cation-π interactions between His37 and Trp41. In the present study, the hydrogen bonding network of 4-methyl-imidazoles was built to mimic the hydrogen bonds between His37 residues, and the cation-π interactions between 4-methyl-imidazolium and indole systems were selected to represent the interac-tions between His37 and Trp41. Then, quantum chemistry calculations at the MP2/6-311G** level were carried out to explore the properties of the hydrogen bonds and the cation-π interactions. The calculation results indicate that the binding strength of the N--H…N hydrogen bond between imidazole rings is up to -6.22 kcal·mol-1, and the binding strength of the strongest cation-π interaction is up to -18.8 kcal·mol-1 (T-shaped interaction) or -12.3 kcal·mol-1 (parallel stacking interaction). Thus, the calculated binding energies indicate that it is possible to control the permeation of the M2 ion channel through the hydrogen bond network and the cation-π interactions by altering the pH values.

  2. Like Extinction, Latent Inhibition of Conditioned Fear in Mice Is Blocked by Systemic Inhibition of L-Type Voltage-Gated Calcium Channels

    Science.gov (United States)

    Blouin, Ashley M.; Cain, Chris K.; Barad, Mike

    2004-01-01

    Having recently shown that extinction of conditioned fear depends on L-type voltage-gated calcium channels (LVGCCs), we have been seeking other protocols that require this unusual induction mechanism. We tested latent inhibition (LI) of fear, because LI resembles extinction except that cue exposures precede, rather than follow, cue-shock pairing.…

  3. K channel activation by nucleotide diphosphates and its inhibition by glibenclamide in vascular smooth muscle cells.

    Science.gov (United States)

    Beech, D J; Zhang, H; Nakao, K; Bolton, T B

    1993-10-01

    1. Whole-cell and inside-out patch recordings were made from single smooth muscle cells that had been isolated enzymatically and mechanically from the rabbit portal vein. 2. In whole-cells the inclusion in the recording pipette solution of nucleotide diphosphates (NDPs), but not tri- or monophosphates, induced a K-current that developed gradually over 5 to 15 min. Intracellular 1 mM guanosine 5'-diphosphate (GDP) induced a slowly developing outward K-current at -37 mV that reached a maximum on average of 72 +/- 4 pA (n = 40). Half maximal effect was estimated to occur with about 0.2 mM GDP. Except for ADP, other NDPs had comparable effects. At 0.1 mM, ADP was equivalent to GDP but at higher concentration ADP was less effective. ADP induced its maximum effect at 1 mM but had almost no effect at 10 mM. 3. In 14% of inside-out patches exposed to 1 mM GDP at the intracellular surface, characteristic K channel activity was observed which showed long (> 1 s) bursts of openings separated by longer closed periods. The current-voltage relationship for the channel was linear in a 60 mM:130 mM K-gradient and the unitary conductance was 24 pS. 4. Glibenclamide applied via the extracellular solution was found to be a potent inhibitor of GDP-induced K-current (IK(GDP)) in the whole-cell. The Kd was 25 nM and the inhibition was fully reversible on wash-out. 5. IK(GDP) was not evoked if Mg ions were absent from the pipette solution. In contrast the omission of extracellular Mg ions had no effect on outward or inward IK(GDP). 6. Inclusion of 1 mM ATP in the recording pipette solution reduced IK(GDP) and also attenuated its decline during long (25 min) recordings. 7. When perforated-patch whole-cell recording was used, metabolic poisoning with cyanide and 2-deoxy-D-glucose induced a glibenclamide-sensitive K-current. This current was not observed when conventional whole-cell recording was used. Possible reasons for this difference are discussed. 8. These K channels appear similar to

  4. Cardamonin, a Novel Antagonist of hTRPA1 Cation Channel, Reveals Therapeutic Mechanism of Pathological Pain

    Directory of Open Access Journals (Sweden)

    Shifeng Wang

    2016-08-01

    Full Text Available The increasing demand for safe and effective treatments of chronic pain has promoted the investigation of novel analgesic drugs. Some herbals have been known to be able to relieve pain, while the chemical basis and target involved in this process remained to be clarified. The current study aimed to find anti-nociceptive candidates targeting transient receptor potential ankyrin 1 (TRPA1, a receptor that implicates in hyperalgesia and neurogenic inflammation. In the current study, 156 chemicals were tested for blocking HEK293/TRPA1 ion channel by calcium-influx assay. Docking study was conducted to predict the binding modes of hit compound with TRPA1 using Discovery Studio. Cytotoxicity in HEK293 was conducted by Cell Titer-Glo assay. Additionally, cardiotoxicity was assessed via xCELLigence RTCA system. We uncovered that cardamonin selectively blocked TRPA1 activation while did not interact with TRPV1 nor TRPV4 channel. A concentration-dependent inhibitory effect was observed with IC50 of 454 nM. Docking analysis of cardamonin demonstrated a compatible interaction with A-967079-binding site of TRPA1. Meanwhile, cardamonin did not significantly reduce HEK293 cell viability, nor did it impair cardiomyocyte constriction. Our data suggest that cardamonin is a selective TRPA1 antagonist, providing novel insight into the target of its anti-nociceptive activity.

  5. A monoclonal antibody against KCNK9 K+ channel extracellular domain inhibits tumour growth and metastasis

    Science.gov (United States)

    Sun, Han; Luo, Liqun; Lal, Bachchu; Ma, Xinrong; Chen, Lieping; Hann, Christine L.; Fulton, Amy M.; Leahy, Daniel J.; Laterra, John

    2016-01-01

    Two-pore domain potassium (K2P) channels act to maintain cell resting membrane potential—a prerequisite for many biological processes. KCNK9, a member of K2P family, is implicated in cancer, owing to its overexpression in human tumours and its ability to promote neoplastic cell survival and growth. However, KCNK9's underlying contributions to malignancy remain elusive due to the absence of specific modulators. Here we describe the development of monoclonal antibodies against the KCNK9 extracellular domain and their functional effects. We show that one antibody (Y4) with the highest affinity binding induces channel internalization. The addition of Y4 to KCNK9-expressing carcinoma cells reduces cell viability and increases cell death. Systemic administration of Y4 effectively inhibits growth of human lung cancer xenografts and murine breast cancer metastasis in mice. Evidence for Y4-mediated carcinoma cell autonomous and immune-dependent cytotoxicity is presented. Our study reveals that antibody-based KCNK9 targeting is a promising therapeutic strategy in KCNK9-expressing malignancies. PMID:26842342

  6. Inhibition of nitrite-induced toxicity in channel catfish by calcium chloride and sodium chloride

    Science.gov (United States)

    Tommasso J.R., Wright; Simco, B.A.; Davis, K.B.

    1980-01-01

    Environmental chloride has been shown to inhibit methemoglobin formation in fish, thereby offering a protective effect against nitrite toxicity. Channel catfish (Ictalurus punctatus) were simultaneously exposed to various environmental nitrite and chloride levels (as either CaCl2 or NaCl) in dechlorinated tap water (40 mg/L total hardness, 47 mg/L alkalinity, 4 mg/L chloride, pH = 6.9-7.1, and temperature 21-24°C). Methemoglobin levels in fish simultaneously exposed to 2.5 mg/L nitrite and up to 30 mg/L chloride as either CaCl2 or NaCl were similar but significantly lower than in unprotected fish. Exposure to 10 mg/L nitrite and 60 mg/L chloride resulted in methemoglobin levels similar to those of the controls; most unprotected fish died. Fish exposed to 10 mg/L nitrite had significantly lower methemoglobin levels when protected with 15.0 mg/L chloride as CaCl2 than with NaCl. Fish exposed to nitrite in the presence of 60 mg/L chloride (as either CaCl2 or NaCl) had similar 24-h LC50 values that were significantly elevated above those obtained in the absence of chloride. Calcium had little effect on tolerance to nitrite toxicity in channel catfish in contrast to its large effect reported in steelhead trout (Salmo gairdneri).

  7. 1,3-propanediol binds deep inside the channel to inhibit water permeation through aquaporins.

    Science.gov (United States)

    Yu, Lili; Rodriguez, Roberto A; Chen, L Laurie; Chen, Liao Y; Perry, George; McHardy, Stanton F; Yeh, Chih-Ko

    2016-02-01

    Aquaporins and aquaglyceroporins (AQPs) are membrane channel proteins responsible for transport of water and for transport of glycerol in addition to water across the cell membrane, respectively. They are expressed throughout the human body and also in other forms of life. Inhibitors of human AQPs have been sought for therapeutic treatment for various medical conditions including hypertension, refractory edema, neurotoxic brain edema, and so forth. Conducting all-atom molecular dynamics simulations, we computed the binding affinity of acetazolamide to human AQP4 that agrees closely with in vitro experiments. Using this validated computational method, we found that 1,3-propanediol (PDO) binds deep inside the AQP4 channel to inhibit that particular aquaporin efficaciously. Furthermore, we used the same method to compute the affinities of PDO binding to four other AQPs and one aquaglyceroporin whose atomic coordinates are available from the protein data bank (PDB). For bovine AQP1, human AQP2, AQP4, AQP5, and Plasmodium falciparum PfAQP whose structures were resolved with high resolution, we obtained definitive predictions on the PDO dissociation constant. For human AQP1 whose PDB coordinates are less accurate, we estimated the dissociation constant with a rather large error bar. Taking into account the fact that PDO is generally recognized as safe by the US FDA, we predict that PDO can be an effective diuretic which directly modulates water flow through the protein channels. It should be free from the serious side effects associated with other diuretics that change the hydro-homeostasis indirectly by altering the osmotic gradients.

  8. Inhibition of the human two-pore domain potassium channel, TREK-1, by fluoxetine and its metabolite norfluoxetine

    OpenAIRE

    Kennard, Louise E; Chumbley, Justin R.; Ranatunga, Kishani M.; Armstrong, Stephanie J; Veale, Emma L.; Mathie, Alistair

    2005-01-01

    Block of the human two-pore domain potassium (2-PK) channel TREK-1 by fluoxetine (ProzacR) and its active metabolite, norfluoxetine, was investigated using whole-cell patch-clamp recording of currents through recombinant channels in tsA 201 cells.Fluoxetine produced a concentration-dependent inhibition of TREK-1 current that was reversible on wash. The IC50 for block was 19 μM. Block by fluoxetine was voltage-independent. Fluoxetine (100 μM) produced an 84% inhibition of TREK-1 currents, but ...

  9. Stimulation of beta-adrenoceptors inhibits calcium-dependent potassium-channels in mouse macrophages

    Energy Technology Data Exchange (ETDEWEB)

    Rosati, C.; Hannaert, P.; Dausse, J.P.; Braquet, P.; Garay, R.

    1986-12-01

    K/sup +/ efflux in mouse macrophages exhibited a rate constant (k/sub k/) of 0.67 +/- 0.04 (h)/sup -1/. This was strongly stimulated by increasing concentrations of the Ca/sup 2 +/ ionophore A23187 up to a maximal value of 4.01 +/- 0.25 (h)/sup -1/ with an IC/sub 50/ of 7.6 +/- 1.9 ..mu..M. Similar results were obtained with the Ca/sup 2 +/ ionophore ionomycin. Binding experiments with /sup 3/H-dihydroalprenolol revealed a high density of beta-adrenergic receptors with apparent dissociation constant of 2.03 +/- 0.06 nM. Isoproterenol at a concentration of 10/sup -6/ -10/sup -5/ M induced a two- to threefold stimulation of endogenous levels of cyclic AMP (cAMP). A23187-stimulated K/sup +/ efflux was partially inhibited by (i) stimulation of adenylate cyclase with isoproterenol, forskolin or, PGE/sub 1/; (ii) exogenous cAMP; and (iii) inhibition of phosphodiesterase with MIX (1-methyl-3-isobutylxanthine). Maximal inhibition of K/sup +/ efflux was obtained by simultaneous addition of isoproterenol and MIX. In dose-response curves, the isoproterenol-sensitive K/sup +/ efflux was half-maximally inhibited (IC/sub 50/) with 2-5 x 10/sup -10/ M of isoproterenol concentration. Propranolol was able to completely block the effect of isoproterenol, with an IC/sub 50/ of about 1-2 x 10/sup -7/ M. Isoproterenol and MIX did not inhibit A23187-stimulated K/sup +/ efflux in an incubation medium where NaCl was replaced by sucrose (or choline), suggesting the involvement of an Na/sup +/:Ca/sup 2 +/ exchange mechanism. The results show that stimulation of beta-adrenoceptors in mouse macrophages counter balances the opening of K/sup +/ channels induced by the calcium ionophore A23187. This likely reflects a decrease in cytoslic free calcium content via a cAMP-mediated stimulation of Na/sup +/:Ca/sup 2 +/ exchange.

  10. Endostatin is protective against monocrotaline-induced right heart disease through the inhibition of T-type Ca(2+) channel.

    Science.gov (United States)

    Imoto, Keisuke; Kumatani, Sayaka; Okada, Muneyoshi; Yamawaki, Hideyuki

    2016-07-01

    Endostatin (ES), a C-terminal fragment of collagen XVIIIα1, has a potent anti-angiogenic effect. ES prevents tumor proliferation through inhibiting T-type Ca(2+) channel. T-type Ca(2+) channel is re-expressed during heart diseases including monocrotaline (MCT)-induced right heart failure. The present study aimed to clarify the effects of ES on T-type Ca(2+) channel and pathogenesis of MCT-induced right ventricular disease. MCT or saline was injected intraperitoneally to rats. After cardiomyocytes were isolated from right ventricles (RVs), T-type Ca(2+) channel current (I CaT) was measured by a patch-clamp method. After ES small interfering RNA (siRNA) or control siRNA (20 μg) was administrated for 1 week via the right jugular vein 1 week after MCT injection, echocardiography and histological analysis were done. I CaT was significantly increased in RV from MCT-injected rats, and ES significantly inhibited it. The survival rate of ES siRNA-administrated MCT rats (MCT ES si group) was decreased. In echocardiography, although ES siRNA did not affect pulmonary arterial pressure, RV systolic function was impaired in MCT ES si group compared with control siRNA-administrated MCT rats (MCT cont si group). In the histological analysis of RV, ES expression was increased in MCT cont si group, and ES siRNA inhibited it. Furthermore, although MCT cont si group showed only cardiomyocyte hypertrophy, MCT ES si group showed notable enlargement of intercellular spaces. The present study for the first time revealed that ES inhibits T-type Ca(2+) channel activity in RV from MCT-injected rats. ES gene knockdown deteriorates MCT-induced right heart disease. ES is thus cardioprotective possibly through inhibiting T-type Ca(2+) channel activity.

  11. Changes in cationic selectivity of the nicotinic channel at the rat ganglionic synapse: a role for chloride ions?

    Directory of Open Access Journals (Sweden)

    Oscar Sacchi

    Full Text Available The permeability of the nicotinic channel (nAChR at the ganglionic synapse has been examined, in the intact rat superior cervical ganglion in vitro, by fitting the Goldman current equation to the synaptic current (EPSC I-V relationship. Subsynaptic nAChRs, activated by neurally-released acetylcholine (ACh, were thus analyzed in an intact environment as natively expressed by the mature sympathetic neuron. Postsynaptic neuron hyperpolarization (from -40 to -90 mV resulted in a change of the synaptic potassium/sodium permeability ratio (P(K/P(Na from 1.40 to 0.92, corresponding to a reversible shift of the apparent acetylcholine equilibrium potential, E(ACh, by about +10 mV. The effect was accompanied by a decrease of the peak synaptic conductance (g(syn and of the EPSC decay time constant. Reduction of [Cl(-](o to 18 mM resulted in a change of P(K/P(Na from 1.57 (control to 2.26, associated with a reversible shift of E(ACh by about -10 mV. Application of 200 nM αBgTx evoked P(K/P(Na and g(syn modifications similar to those observed in reduced [Cl(-](o. The two treatments were overlapping and complementary, as if the same site/mechanism were involved. The difference current before and after chloride reduction or toxin application exhibited a strongly positive equilibrium potential, which could not be explained by the block of a calcium component of the EPSC. Observations under current-clamp conditions suggest that the driving force modification of the EPSC due to P(K/P(Na changes represent an additional powerful integrative mechanism of neuron behavior. A possible role for chloride ions is suggested: the nAChR selectivity was actually reduced by increased chloride gradient (membrane hyperpolarization, while it was increased, moving towards a channel preferentially permeable for potassium, when the chloride gradient was reduced.

  12. 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.

  13. Drug-induced Inhibition and Trafficking Disruption of ion Channels: Pathogenesis of QT Abnormalities and Drug-induced Fatal Arrhythmias.

    Science.gov (United States)

    Cubeddu, Luigi X

    2016-01-01

    Risk of severe and fatal ventricular arrhythmias, presenting as Torsade de Pointes (TdP), is increased in congenital and acquired forms of long QT syndromes (LQTS). Drug-induced inhibition of K+ currents, IKs, IKr, IK1, and/or Ito, delay repolarization, prolong QT, and increase the risk of TdP. Drug-induced interference with IKr is the most common cause of acquired LQTS/TdP. Multiple drugs bind to KNCH2-hERG-K+ channels affecting IKr, including antiarrythmics, antibiotics, antivirals, azole-antifungals, antimalarials, anticancer, antiemetics, prokinetics, antipsychotics, and antidepressants. Azithromycin has been recently added to this list. In addition to direct channel inhibition, some drugs interfere with the traffic of channels from the endoplasmic reticulum to the cell membrane, decreasing mature channel membrane density; e.g., pentamidine, geldalamicin, arsenic trioxide, digoxin, and probucol. Other drugs, such as ketoconazole, fluoxetine, norfluoxetine, citalopram, escitalopram, donepezil, tamoxifen, endoxifen, atazanavir, and roxitromycin, induce both direct channel inhibition and impaired channel trafficking. Although many drugs prolong the QT interval, TdP is a rare event. The following conditions increase the risk of drug-induced TdP: a) Disease states/electrolyte levels (heart failure, structural cardiac disease, bradycardia, hypokalemia); b) Pharmacogenomic variables (presence of congenital LQTS, subclinical ion-channel mutations, history of or having a relative with history of drug-induced long QT/TdP); c) Pharmacodynamic and kinetic factors (high doses, women, elderly, metabolism inhibitors, combining two or more QT prolonging drugs, drugs that prolong the QT and increase QT dispersion, and drugs with multiple actions on ion channels). Because most of these conditions are preventable, careful evaluation of risk factors and increased knowledge of drug use associated with repolarization abnormalities are strongly recommended. PMID:26926294

  14. 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

  15. Inhibition of mitochondrial permeability transition pore contributes to the neuroprotection induced by activation of mitochondrial ATP-sensitive potassium channel

    Institute of Scientific and Technical Information of China (English)

    Li-pingWU; FangSHEN; QiangXIA

    2004-01-01

    AIM: To investigate whether the neuroprotection via activating mitochondrial ATP-sensitive potassium channel (mitoKTP) is mediated by the inhibition of mitochondrial permeability transition pore (MPTP). METHODS: Adult male Sprague-Dawleyrats were undergoing 90 min of middle cerebral artery occlusion(MCAO) by introducing a nylon monofilament through the external

  16. Autoantibody against transient receptor potential M1 cation channels of retinal ON bipolar cells in paraneoplastic vitelliform retinopathy

    Directory of Open Access Journals (Sweden)

    Wang Yujuan

    2012-11-01

    degenerated and replaced with empty vacuoles and disintegrated organelles. Conclusion This case provides a convincing histological evidence of melanoma-associated autoantibodies directly against transient receptor potential M1 channels that target the ON bipolar cell structures in the inner nuclear and outer plexiform layers in paraneoplastic vitelliform retinopathy.

  17. Class I antiarrhythmic drugs inhibit human cardiac two-pore-domain K(+) (K2 ₂p) channels.

    Science.gov (United States)

    Schmidt, Constanze; Wiedmann, Felix; Schweizer, Patrick A; Becker, Rüdiger; Katus, Hugo A; Thomas, Dierk

    2013-12-01

    Class IC antiarrhythmic drugs are commonly used for rhythm control in atrial fibrillation. In addition, class I drugs are administered to suppress ventricular tachyarrhythmia in selected cases. The multichannel blocking profile of class I compounds includes reduction of cardiac potassium currents in addition to their primary mechanism of action, sodium channel inhibition. Blockade of two-pore-domain potassium (K2P) channels in the heart causes action potential prolongation and may provide antiarrhythmic action in atrial fibrillation. This study was designed to elucidate inhibitory effects of class I antiarrhythmic drugs on K2P channels. Human K2P2.1 (TREK1) and hK2P3.1 (TASK1) channels were systematically tested for their sensitivity to clinically relevant class IA (ajmaline), class IB (mexiletine), and class IC (propafenone) antiarrhythmic compounds using whole-cell patch clamp and two-electrode voltage clamp electrophysiology in Chinese hamster ovary cells and in Xenopus oocytes. Mexiletine and propafenone inhibited hK2P2.1 (IC50,mexiletine=173µM; IC50,propafenone=7.6µM) and hK2P3.1 channels (IC50,mexiletine=97.3µM; IC50,propafenone=5.1µM) in mammalian cells. Ajmaline did not significantly reduce current amplitudes. K2P channels were blocked in open and closed states, resulting in resting membrane potential depolarization. Open rectification properties of the channels were not affected by class I drugs. In summary, class I antiarrhythmic drugs target cardiac K2P K(+) channels. Blockade of hK2P2.1 and hK2P3.1 potassium currents provides mechanistic evidence to establish cardiac K2P channels as antiarrhythmic drug targets. PMID:24070813

  18. Calcium influx through L-type channels attenuates skeletal muscle contraction via inhibition of adenylyl cyclases.

    Science.gov (United States)

    Menezes-Rodrigues, Francisco Sandro; Pires-Oliveira, Marcelo; Duarte, Thiago; Paredes-Gamero, Edgar Julian; Chiavegatti, Tiago; Godinho, Rosely Oliveira

    2013-11-15

    Skeletal muscle contraction is triggered by acetylcholine induced release of Ca(2+) from sarcoplasmic reticulum. Although this signaling pathway is independent of extracellular Ca(2+), L-type voltage-gated calcium channel (Cav) blockers have inotropic effects on frog skeletal muscles which occur by an unknown mechanism. Taking into account that skeletal muscle fiber expresses Ca(+2)-sensitive adenylyl cyclase (AC) isoforms and that cAMP is able to increase skeletal muscle contraction force, we investigated the role of Ca(2+) influx on mouse skeletal muscle contraction and the putative crosstalk between extracellular Ca(2+) and intracellular cAMP signaling pathways. The effects of Cav blockers (verapamil and nifedipine) and extracellular Ca(2+) chelator EGTA were evaluated on isometric contractility of mouse diaphragm muscle under direct electrical stimulus (supramaximal voltage, 2 ms, 0.1 Hz). Production of cAMP was evaluated by radiometric assay while Ca(2+) transients were assessed by confocal microscopy using L6 cells loaded with fluo-4/AM. Ca(2+) channel blockers verapamil and nifedipine had positive inotropic effect, which was mimicked by removal of extracellular Ca(+2) with EGTA or Ca(2+)-free Tyrode. While phosphodiesterase inhibitor IBMX potentiates verapamil positive inotropic effect, it was abolished by AC inhibitors SQ22536 and NYK80. Finally, the inotropic effect of verapamil was associated with increased intracellular cAMP content and mobilization of intracellular Ca(2+), indicating that positive inotropic effects of Ca(2+) blockers depend on cAMP formation. Together, our results show that extracellular Ca(2+) modulates skeletal muscle contraction, through inhibition of Ca(2+)-sensitive AC. The cross-talk between extracellular calcium and cAMP-dependent signaling pathways appears to regulate the extent of skeletal muscle contraction responses.

  19. Inhibition of T cell proliferation by selective block of Ca(2+)-activated K(+) channels

    DEFF Research Database (Denmark)

    Jensen, B S; Odum, Niels; Jorgensen, N K;

    1999-01-01

    T lymphocytes express a plethora of distinct ion channels that participate in the control of calcium homeostasis and signal transduction. Potassium channels play a critical role in the modulation of T cell calcium signaling, and the significance of the voltage-dependent K channel, Kv1.3, is well...... established. The recent cloning of the Ca(2+)-activated, intermediate-conductance K(+) channel (IK channel) has enabled a detailed investigation of the role of this highly Ca(2+)-sensitive K(+) channel in the calcium signaling and subsequent regulation of T cell proliferation. The role IK channels play in T...

  20. A mitochondria-K+ channel axis is suppressed in cancer and its normalization promotes apoptosis and inhibits cancer growth.

    Science.gov (United States)

    Bonnet, Sébastien; Archer, Stephen L; Allalunis-Turner, Joan; Haromy, Alois; Beaulieu, Christian; Thompson, Richard; Lee, Christopher T; Lopaschuk, Gary D; Puttagunta, Lakshmi; Bonnet, Sandra; Harry, Gwyneth; Hashimoto, Kyoko; Porter, Christopher J; Andrade, Miguel A; Thebaud, Bernard; Michelakis, Evangelos D

    2007-01-01

    The unique metabolic profile of cancer (aerobic glycolysis) might confer apoptosis resistance and be therapeutically targeted. Compared to normal cells, several human cancers have high mitochondrial membrane potential (DeltaPsim) and low expression of the K+ channel Kv1.5, both contributing to apoptosis resistance. Dichloroacetate (DCA) inhibits mitochondrial pyruvate dehydrogenase kinase (PDK), shifts metabolism from glycolysis to glucose oxidation, decreases DeltaPsim, increases mitochondrial H2O2, and activates Kv channels in all cancer, but not normal, cells; DCA upregulates Kv1.5 by an NFAT1-dependent mechanism. DCA induces apoptosis, decreases proliferation, and inhibits tumor growth, without apparent toxicity. Molecular inhibition of PDK2 by siRNA mimics DCA. The mitochondria-NFAT-Kv axis and PDK are important therapeutic targets in cancer; the orally available DCA is a promising selective anticancer agent. PMID:17222789

  1. The non-selective cation-permeable channel TRPC3 is a tetrahedron with a cap on the large cytoplasmic end.

    Science.gov (United States)

    Mio, Kazuhiro; Ogura, Toshihiko; Hara, Yuji; Mori, Yasuo; Sato, Chikara

    2005-08-01

    TRPC3 plays important roles in neuronal differentiation and immune cell maturation by mediating the cationic current in response to phospholipase C activation, Ca2+ depletion, and diacylglycerol stimulation. Here, we purified the TRPC3 channel using a glycosylated tetramer and observed the structure using electron microscopy. Negatively stained specimens demonstrate homogeneous protein particles containing an internal cavity-like structure. These particle images were picked up by automated pick-up programs, aligned, and classified by the growing neural gas network method. Similarly oriented projections were averaged to decrease the signal-to-noise ratio. The averaged images progress from the top view to the side views, which are representative of their raw images. The top view confirmed the hypothesis of a four-domain structure, and the side view demonstrates a large cytoplasmic domain with a capped structure at the bottom, which is near a predicted locus of ion release. The total image of the protein is a blunt-edged trapezoid of 200 x 200 x 235 A. This large dimension of TRPC3 is also supported by the Stokes radius (92 A) obtained from gel filtration chromatography. PMID:15964551

  2. A tale of switched functions: from cyclooxygenase inhibition to M-channel modulation in new diphenylamine derivatives.

    Directory of Open Access Journals (Sweden)

    Asher Peretz

    Full Text Available Cyclooxygenase (COX enzymes are molecular targets of nonsteroidal anti-inflammatory drugs (NSAIDs, the most used medication worldwide. However, the COX enzymes are not the sole molecular targets of NSAIDs. Recently, we showed that two NSAIDs, diclofenac and meclofenamate, also act as openers of Kv7.2/3 K(+ channels underlying the neuronal M-current. Here we designed new derivatives of diphenylamine carboxylate to dissociate the M-channel opener property from COX inhibition. The carboxylate moiety was derivatized into amides or esters and linked to various alkyl and ether chains. Powerful M-channel openers were generated, provided that the diphenylamine moiety and a terminal hydroxyl group are preserved. In transfected CHO cells, they activated recombinant Kv7.2/3 K(+ channels, causing a hyperpolarizing shift of current activation as measured by whole-cell patch-clamp recording. In sensory dorsal root ganglion and hippocampal neurons, the openers hyperpolarized the membrane potential and robustly depressed evoked spike discharges. They also decreased hippocampal glutamate and GABA release by reducing the frequency of spontaneous excitatory and inhibitory post-synaptic currents. In vivo, the openers exhibited anti-convulsant activity, as measured in mice by the maximal electroshock seizure model. Conversion of the carboxylate function into amide abolished COX inhibition but preserved M-channel modulation. Remarkably, the very same template let us generating potent M-channel blockers. Our results reveal a new and crucial determinant of NSAID-mediated COX inhibition. They also provide a structural framework for designing novel M-channel modulators, including openers and blockers.

  3. Pungent agents from Szechuan peppers excite sensory neurons by inhibiting two-pore potassium channels.

    Science.gov (United States)

    Bautista, Diana M; Sigal, Yaron M; Milstein, Aaron D; Garrison, Jennifer L; Zorn, Julie A; Tsuruda, Pamela R; Nicoll, Roger A; Julius, David

    2008-07-01

    In traditional folk medicine, Xanthoxylum plants are referred to as 'toothache trees' because their anesthetic or counter-irritant properties render them useful in the treatment of pain. Psychophysical studies have identified hydroxy-alpha-sanshool as the compound most responsible for the unique tingling and buzzing sensations produced by Szechuan peppercorns or other Xanthoxylum preparations. Although it is generally agreed that sanshool elicits its effects by activating somatosensory neurons, the underlying cellular and molecular mechanisms remain a matter of debate. Here we show that hydroxy-alpha-sanshool excites two types of sensory neurons, including small-diameter unmyelinated cells that respond to capsaicin (but not mustard oil) as well as large-diameter myelinated neurons that express the neurotrophin receptor TrkC. We found that hydroxy-alpha-sanshool excites neurons through a unique mechanism involving inhibition of pH- and anesthetic-sensitive two-pore potassium channels (KCNK3, KCNK9 and KCNK18), providing a framework for understanding the unique and complex psychophysical sensations associated with the Szechuan pepper experience.

  4. Benzopyrimido-pyrrolo-oxazine-dione (R)-BPO-27 Inhibits CFTR Chloride Channel Gating by Competition with ATP.

    Science.gov (United States)

    Kim, Yonjung; Anderson, Marc O; Park, Jinhong; Lee, Min Goo; Namkung, Wan; Verkman, A S

    2015-10-01

    We previously reported that benzopyrimido-pyrrolo-oxazinedione BPO-27 [6-(5-bromofuran-2-yl)-7,9-dimethyl-8,10-dioxo-11-phenyl-7,8,9,10-tetrahydro-6H-benzo[b]pyrimido [4',5':3,4]pyrrolo [1,2-d][1,4]oxazine-2-carboxylic acid] inhibits the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel with low nanomolar potency and reduces cystogenesis in a model of polycystic kidney disease. We used computational chemistry and patch-clamp to show that enantiomerically pure (R)-BPO-27 inhibits CFTR by competition with ATP, whereas (S)-BPO-27 is inactive. Docking computations using a homology model of CFTR structure suggested that (R)-BPO-27 binds near the canonical ATP binding site, and these findings were supported by molecular dynamics simulations showing a lower binding energy for the (R) versus (S) stereoisomers. Three additional lower-potency BPO-27 analogs were modeled in a similar fashion, with the binding energies predicted in the correct order. Whole-cell patch-clamp studies showed linear CFTR currents with a voltage-independent (R)-BPO-27 block mechanism. Single-channel recordings in inside-out patches showed reduced CFTR channel open probability and increased channel closed time by (R)-BPO-27 without altered unitary channel conductance. At a concentration of (R)-BPO-27 that inhibited CFTR chloride current by ∼50%, the EC50 for ATP activation of CFTR increased from 0.27 to 1.77 mM but was not changed by CFTRinh-172 [4-[[4-oxo-2-thioxo-3-[3-trifluoromethyl)phenyl]-5-thiazolidinylidene]methyl]benzoic acid], a thiazolidinone CFTR inhibitor that acts at a site distinct from the ATP binding site. Our results suggest that (R)-BPO-27 inhibition of CFTR involves competition with ATP.

  5. GABA/sub B/ receptor activation inhibits Ca2+-activated potassium channels in synaptosomes: involvement of G-proteins

    International Nuclear Information System (INIS)

    86Rb-efflux assay from preloaded synaptosomes of rat cerebral cortex was developed to study the effect of GABA/sub B/ receptor agonist baclofen on Ca2+-activated K+-channels. Depolarization of 86Rb-loaded synaptosomes in physiological buffer increased Ca2+-activated 86Rb-efflux by 400%. The 86Rb-efflux was blocked by quinine sulfate, tetraethylammonium, and La3+ indicating the involvement of Ca2+-activated K+-channels. (-)Baclofen inhibited Ca2+-activated 86Rb-efflux in a stereospecific manner. The inhibitory effect of (-)baclofen was mediated by GABA/sub B/ receptor activation, since it was blocked by GABA/sub B/ antagonist phaclofen, but not by bicuculline. Further, pertussis toxin also blocked the ability of baclofen or depolarizing action to affect Ca2+-activated K+-channels. These results suggest that baclofen inhibits Ca2+-activated K+-channels in synaptosomes and these channels are regulated by G-proteins. This assay may provide an ideal in vitro model to study GABA/sub B/ receptor pharmacology

  6. Activation, Permeability, and Inhibition of Astrocytic and Neuronal Large Pore (Hemi)channels

    DEFF Research Database (Denmark)

    Hansen, Daniel Bloch; Ye, Zu-Cheng; Calloe, Kirstine;

    2014-01-01

    overlapping sensitivity to the inhibitors Brilliant Blue, gadolinium, and carbenoxolone. These results demonstrated isoform-specific characteristics among the large pore membrane channels; an open (hemi)channel is not a nonselective channel. With these isoform-specific properties in mind, we characterized...

  7. Gynura procumbens Merr. decreases blood pressure in rats by vasodilatation via inhibition of calcium channels

    Directory of Open Access Journals (Sweden)

    See-Ziau Hoe

    2011-01-01

    Full Text Available INTRODUCTION: Gynura procumbens has been shown to decrease blood pressure via inhibition of the angiotensinconverting enzyme. However, other mechanisms that may contribute to the hypotensive effect have not been studied. OBJECTIVES: To investigate the cardiovascular effects of a butanolic fraction of Gynura procumbens in rats. METHODS: Anaesthetized rats were given intravenous bolus injections of butanolic fraction at doses of 2.5-20 mg/kg in vivo. The effect of butanolic fraction on vascular reactivity was recorded in isolated rat aortic rings in vitro. RESULTS: Intravenous administrations of butanolic fraction elicited significant (p<0.001 and dose-dependent decreases in the mean arterial pressure. However, a significant (p<0.05 decrease in the heart rate was observed only at the higher doses (10 and 20 mg/kg. In isolated preparations of rat aortic rings, phenylephrine (1×10-6 M- or potassium chloride (8×10-2 M-precontracted endothelium-intact and -denuded tissue; butanolic fraction (1×10-6-1×10-1 g/ml induced similar concentration-dependent relaxation of the vessels. In the presence of 2.5×10-3 and 5.0×10-3 g/ml butanolic fraction, the contractions induced by phenylephrine (1×10-9-3×10-5 M and potassium chloride (1×10-2-8×10-2 M were significantly antagonized. The calcium-induced vasocontractions (1×10-4-1×10-2 M were antagonized by butanolic fraction concentration-dependently in calcium-free and high potassium (6×10-2 M medium, as well as in calcium- and potassium-free medium containing 1×10-6 M phenylephrine. However, the contractions induced by noradrenaline (1×10-6 M and caffeine (4.5×10-2 M were not affected by butanolic fraction. CONCLUSION: Butanolic fraction contains putative hypotensive compounds that appear to inhibit calcium influx via receptor-operated and/or voltage-dependent calcium channels to cause vasodilation and a consequent fall in blood pressure.

  8. Atrial-selective prolongation of refractory period with AVE0118 is due principally to inhibition of sodium channel activity

    OpenAIRE

    Burashnikov, Alexander; Barajas-Martinez, Hector; Hu, Dan; Nof, Eyal; Blazek, Jonathan; Antzelevitch, Charles

    2012-01-01

    AVE0118’s action to prolong effective refractory period (ERP) in atria but not ventricles is thought to be due to its inhibition of IKur. However, in non-remodeled atria, AVE0118 prolongs ERP but not action potential duration (APD70-90), which can be explained with inhibition of sodium, but not potassium channel current. ERP, APD, and the maximum rate of rise of the AP upstroke (Vmax) were measured in canine isolated coronary-perfused right atrial and in superfused ventricular tissue preparat...

  9. A novel Schiff base-based cationic gemini surfactants: Synthesis and effect on corrosion inhibition of carbon steel in hydrochloric acid solution

    Energy Technology Data Exchange (ETDEWEB)

    Hegazy, M.A. [Petrochemicals Department, Egyptian Petroleum Research Institute (EPRI), Nasr City, Cairo (Egypt)], E-mail: mohamed_hgazy@yahoo.com

    2009-11-15

    The corrosion inhibition characteristics of the synthesized cationic gemini surfactants, namely bis(p-(N,N,N-decyldimethylammonium bromide)benzylidene thiourea (10-S-10), bis(p-(N,N,N-dodecyldimethylammonium bromide)benzylidene thiourea (12-S-12) and bis(p-(N,N,N-tetradecyldimethylammonium bromide)benzylidene thiourea (14-S-14) on the carbon steel corrosion in 1 M hydrochloric acid have been investigated at 25 deg. C by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The inhibition efficiencies obtained from all methods employed are in good agreement with each other. The obtained results show that compound 14-S-14 is the best inhibitor with an efficiency of 97.75% at 5 x 10{sup -3} M additive concentration. Generally, the inhibition efficiency increased with increase of the inhibitor concentration. Changes in impedance parameters (charge transfer resistance, R{sub ct}, and double-layer capacitance, C{sub dl}) were indicative of adsorption of 14-S-14 on the metal surface, leading to the formation of a protective film. The potentiodynamic polarization measurements indicated that the inhibitors are of mixed type. The adsorption of the inhibitors on the carbon steel surface in the acid solution was found to obey Langmuir's adsorption isotherm. The free energy of adsorption processes were calculated and discussed. The surface parameters of each synthesized surfactant were calculated from its surface tension including the critical micelle concentration (CMC), maximum surface excess ({gamma}{sub max}) and the minimum surface area (A{sub min}). The free energies of micellization ({delta}G{sup o}{sub mic}) were calculated. The surface morphology of carbon steel sample was investigated by scanning electron microscopy (SEM)

  10. Squalamine, a novel cationic steroid, specifically inhibits the brush-border Na+/H+ exchanger isoform NHE3.

    Science.gov (United States)

    Akhter, S; Nath, S K; Tse, C M; Williams, J; Zasloff, M; Donowitz, M

    1999-01-01

    Squalamine, an endogenous molecule found in the liver and other tissues of Squalus acanthias, has antibiotic properties and causes changes in endothelial cell shape. The latter suggested that its potential targets might include transport proteins that control cell volume or cell shape. The effect of purified squalamine was examined on cloned Na+/H+ exchanger isoforms NHE1, NHE2, and NHE3 stably transfected in PS120 fibroblasts. Squalamine (1-h pretreatment) decreased the maximal velocity of rabbit NHE3 in a concentration-dependent manner (13, 47, and 57% inhibition with 3, 5, and 7 micrograms/ml, respectively) and also increased K'[H+]i. Squalamine did not affect rabbit NHE1 or NHE2 function. The inhibitory effect of squalamine was 1) time dependent, with no effect of immediate addition and maximum effect with 1 h of exposure, and 2) fully reversible. Squalamine pretreatment of the ileum for 60 min inhibited brush-border membrane vesicle Na+/H+ activity by 51%. Further investigation into the mechanism of squalamine's effects showed that squalamine required the COOH-terminal 76 amino acids of NHE3. Squalamine had no cytotoxic effect at the concentrations studied, as indicated by monitoring lactate dehydrogenase release. These results indicate that squalamine 1) is a specific inhibitor of the brush-border NHE isoform NHE3 and not NHE1 or NHE2, 2) acts in a nontoxic and fully reversible manner, and 3) has a delayed effect, indicating that it may influence brush-border Na+/H+ exchanger function indirectly, through an intracellular signaling pathway or by acting as an intracellular modulator. PMID:9886929

  11. Absence of the ER Cation Channel TMEM38B/TRIC-B Disrupts Intracellular Calcium Homeostasis and Dysregulates Collagen Synthesis in Recessive Osteogenesis Imperfecta.

    Directory of Open Access Journals (Sweden)

    Wayne A Cabral

    2016-07-01

    Full Text Available Recessive osteogenesis imperfecta (OI is caused by defects in proteins involved in post-translational interactions with type I collagen. Recently, a novel form of moderately severe OI caused by null mutations in TMEM38B was identified. TMEM38B encodes the ER membrane monovalent cation channel, TRIC-B, proposed to counterbalance IP3R-mediated Ca2+ release from intracellular stores. The molecular mechanisms by which TMEM38B mutations cause OI are unknown. We identified 3 probands with recessive defects in TMEM38B. TRIC-B protein is undetectable in proband fibroblasts and osteoblasts, although reduced TMEM38B transcripts are present. TRIC-B deficiency causes impaired release of ER luminal Ca2+, associated with deficient store-operated calcium entry, although SERCA and IP3R have normal stability. Notably, steady state ER Ca2+ is unchanged in TRIC-B deficiency, supporting a role for TRIC-B in the kinetics of ER calcium depletion and recovery. The disturbed Ca2+ flux causes ER stress and increased BiP, and dysregulates synthesis of proband type I collagen at multiple steps. Collagen helical lysine hydroxylation is reduced, while telopeptide hydroxylation is increased, despite increased LH1 and decreased Ca2+-dependent FKBP65, respectively. Although PDI levels are maintained, procollagen chain assembly is delayed in proband cells. The resulting misfolded collagen is substantially retained in TRIC-B null cells, consistent with a 50-70% reduction in secreted collagen. Lower-stability forms of collagen that elude proteasomal degradation are not incorporated into extracellular matrix, which contains only normal stability collagen, resulting in matrix insufficiency. These data support a role for TRIC-B in intracellular Ca2+ homeostasis, and demonstrate that absence of TMEM38B causes OI by dysregulation of calcium flux kinetics in the ER, impacting multiple collagen-specific chaperones and modifying enzymes.

  12. Conjugation to polymeric chains of influenza drugs targeting M2 ion channels partially restores inhibition of drug-resistant mutants

    OpenAIRE

    Larson, Alyssa M.; Chen, Jianzhu; Klibanov, Alexander M.

    2013-01-01

    By attaching multiple copies of the influenza M2 ion channel inhibitors amantadine (1) and rimantadine (2) to polymeric chains, we endeavored to recover their potency in inhibiting drug-resistant influenza viruses. Depending on loading densities, as well as the nature of the drug, the polymer, and the spacer arm, polymer-conjugated drugs were up to 30-fold more potent inhibitors of drug-resistant strains than their monomeric parents. In particular, a 20% loading density and a short linker gro...

  13. Inhibition of KV7 channels protects against myocardial ischemia and reperfusion injury

    DEFF Research Database (Denmark)

    Hedegaard, Elise Røge; Johnsen, Jacob; Povlsen, Jonas Agerlund;

    2015-01-01

    the expression of the KV7 channels in rat hearts by reverse transcriptse PCR. The effect of the KV7 channel inhibitors, XE991 and linopirdine, and the KV7 channel opener, flupirtine on myocardial IR injury in isolated hearts and coronary arteries from Wistar rats was examined. Hearts were subjected to no-flow......Aims: KV7 channel are activated by ischemia and mediate hypoxic vasodilatation. We investigated the effect of KV7 channel modulation on cardiac ischemia and reperfusion (IR) injury and the interaction with cardioprotection by ischemic preconditioning (IPC). Methods and Results: We investigated.......1, KV7.4 and KV7.5 were expressed in rat coronary arteries and all KV7 subtypes (KV7.1-5) in the left and right ventricles of the heart. KV7 channel blockade by XE991 and linopirdine reduced infarct size additive to infarct reduction by IPC. Flupirtine abolished infarct size reduction by IPC...

  14. L—type calcium channel blockers inhibit the development but not the expression of sensitization to morphine in mice

    Institute of Scientific and Technical Information of China (English)

    ZhanQ; ZhenJW

    2002-01-01

    The relationship between opioid actions and L-type calcium channel blockers has been well documented.However,there is no report relevant to L-type calcium channel blockers and morphinesensitization,which is suggested to be an analog of behaviors that are the characteristics of drug addiction.Here the effects of three L-type calcium channel blockers,nimodipine,nifedipine and verapamil,on morphine-induced locomotor activity,the development and the expression of sensitization to morphine were studied systematically.The results showed that both nimodipine and verapamil attenuated,while nifedipine had only a tendency to decrease morphine-induced locomotor activity.All the three drugs inhibited the development of sensitization to morphine.However,none of them showed any effects on the expression of morphine sensitization.These results indicate that blocking L-tpye calcium channel attenuates the locomotor stimulating effects of morphine and inhibits the development but not the expression of morphine-sensitization.

  15. Inhibition of the corrosion process of alloy AA5083 (Al-Mg) in seawater by cerium cations. An EIS study

    Energy Technology Data Exchange (ETDEWEB)

    Aballe, A.; Bethencourt, M.; Botana, F.J.; Cano, M.J. [Cadiz Univ. (Spain). Dept. de Ciencia de los Materiales e Ingenieria Metalurgica y Quimica Inorganica; Marcos, M. [Cadiz Univ. (Spain). Dept. de Ingenieria Mecanica y Diseno Industrial

    2001-05-01

    The principal corrosion process of the alloy AA5083 in aerated NaCl solutions mainly affects the zones occupied by Al(Mn,Fe,Cr) cathodic precipitates, over which the oxygen reduction reaction takes place. Thus, the design of an effective protection system could be based on the use of cathodic inhibitors. In previous papers, the inhibition efficiency of various lanthanide chlorides, particularly CeCl{sub 3}, has been proved. These compounds act as cathodic inhibitors, blocking these cathodic sites by means of the precipitation of a lanthanide oxide or hydroxide film. In this paper, EIS has been used to detect the blocking effect of the cathodic sites. This fact is reflected in the electrical response of the system through the minimisation of the values of those elements of the electrical loop that are related to the response of the cathodic intermetallics. In addition, the dielectric properties of the anodic film have been evaluated by measuring the value of the associated capacitance. From these values, it can be concluded that the thickness of the film produced over the matrix when the inhibitor is added is much lower than that produced in the bare solution. This finding is in good agreement with the results obtained with other techniques and may be related to the minimisation of the anodic reaction as a consequence of the decrease in the intensity of the cathodic process by the action of CeCl{sub 3}. (orig.)

  16. Sex differences in neuroprotection provided by inhibition of TRPM2 channels following experimental stroke

    OpenAIRE

    Jia, Jia; Verma, Saurabh; Nakayama, Shin; Quillinan, Nidia; Grafe, Marjorie R; Hurn, Patricia D.; Herson, Paco S.

    2011-01-01

    The calcium-permeable transient receptor potential M2 (TRPM2) ion channel is activated following oxidative stress and has been implicated in ischemic damage; however, little experimental evidence exists linking TRPM2 channel activation to damage following cerebral ischemia. We directly assessed the involvement of TRPM2 channels in ischemic brain injury using pharmacological inhibitors and short-hairpin RNA (shRNA)-mediated knockdown of TRPM2 expression. Each of the four TRPM2 inhibitors teste...

  17. Inhibition of small-conductance Ca2+-activated K+ channels terminates and protects against atrial fibrillation

    DEFF Research Database (Denmark)

    Diness, Jonas Goldin; Sørensen, Ulrik S; Nissen, Jakob Dahl;

    2010-01-01

    Recently, evidence has emerged that small-conductance Ca(2+)-activated K(+) (SK) channels are predominantly expressed in the atria in a number of species including human. In rat, guinea pig, and rabbit ex vivo and in vivo models of atrial fibrillation (AF), we used 3 different SK channel inhibitors...

  18. Steviol reduces MDCK Cyst formation and growth by inhibiting CFTR channel activity and promoting proteasome-mediated CFTR degradation.

    Directory of Open Access Journals (Sweden)

    Chaowalit Yuajit

    Full Text Available Cyst enlargement in polycystic kidney disease (PKD involves cAMP-activated proliferation of cyst-lining epithelial cells and transepithelial fluid secretion into the cyst lumen via cystic fibrosis transmembrane conductance regulator (CFTR chloride channel. This study aimed to investigate an inhibitory effect and detailed mechanisms of steviol and its derivatives on cyst growth using a cyst model in Madin-Darby canine kidney (MDCK cells. Among 4 steviol-related compounds tested, steviol was found to be the most potent at inhibiting MDCK cyst growth. Steviol inhibition of cyst growth was dose-dependent; steviol (100 microM reversibly inhibited cyst formation and cyst growth by 72.53.6% and 38.2±8.5%, respectively. Steviol at doses up to 200 microM had no effect on MDCK cell viability, proliferation and apoptosis. However, steviol acutely inhibited forskolin-stimulated apical chloride current in MDCK epithelia, measured with the Ussing chamber technique, in a dose-dependent manner. Prolonged treatment (24 h with steviol (100 microM also strongly inhibited forskolin-stimulated apical chloride current, in part by reducing CFTR protein expression in MDCK cells. Interestingly, proteasome inhibitor, MG-132, abolished the effect of steviol on CFTR protein expression. Immunofluorescence studies demonstrated that prolonged treatment (24 h with steviol (100 microM markedly reduced CFTR expression at the plasma membrane. Taken together, the data suggest that steviol retards MDCK cyst progression in two ways: first by directly inhibiting CFTR chloride channel activity and second by reducing CFTR expression, in part, by promoting proteasomal degradation of CFTR. Steviol and related compounds therefore represent drug candidates for treatment of polycystic kidney disease.

  19. Inhibition of hERG potassium channel by the antiarrhythmic agent mexiletine and its metabolite m-hydroxymexiletine.

    Science.gov (United States)

    Gualdani, Roberta; Tadini-Buoninsegni, Francesco; Roselli, Mariagrazia; Defrenza, Ivana; Contino, Marialessandra; Colabufo, Nicola Antonio; Lentini, Giovanni

    2015-10-01

    Mexiletine is a sodium channel blocker, primarily used in the treatment of ventricular arrhythmias. Moreover, recent studies have demonstrated its therapeutic value to treat myotonic syndromes and to relieve neuropathic pain. The present study aims at investigating the direct blockade of hERG potassium channel by mexiletine and its metabolite m-hydroxymexiletine (MHM). Our data show that mexiletine inhibits hERG in a time- and voltage-dependent manner, with an IC50 of 3.7 ± 0.7 μmol/L. Analysis of the initial onset of current inhibition during a depolarizing test pulse indicates mexiletine binds preferentially to the open state of the hERG channel. Looking for a possible mexiletine alternative, we show that m-hydroxymexiletine (MHM), a minor mexiletine metabolite recently reported to be as active as the parent compound in an arrhythmia animal model, is a weaker hERG channel blocker, compared to mexiletine (IC50 = 22.4 ± 1.2 μmol/L). The hERG aromatic residues located in the S6 helix (Tyr652 and Phe656) are crucial in the binding of mexiletine and the different affinities of mexiletine and MHM with hERG channel are interpreted by modeling their corresponding binding interactions through ab initio calculations. The simulations demonstrate that the introduction of a hydroxyl group on the meta-position of the aromatic portion of mexiletine weakens the interaction of the drug xylyloxy moiety with Tyr652. These results provide further insights into the molecular basis of drug/hERG interactions and, in agreement with previously reported results on clofilium and ibutilide analogs, support the possibility of reducing hERG potency and related toxicity by modifying the aromatic pattern of substitution of clinically relevant compounds. PMID:26516576

  20. High glucose inhibits ClC-2 chloride channels and attenuates cell migration of rat keratinocytes

    Directory of Open Access Journals (Sweden)

    Pan F

    2015-08-01

    Full Text Available Fuqiang Pan, Rui Guo, Wenguang Cheng, Linlin Chai, Wenping Wang, Chuan Cao, Shirong LiDepartment of Plastic and Reconstructive Surgery, Southwestern Hospital, Third Military Medical University, Chongqing, People’s Republic of China Background: Accumulating evidence has demonstrated that migration of keratinocytes is critical to wound epithelialization, and defects of this function result in chronic delayed-healing wounds in diabetes mellitus patients, and the migration has been proved to be associated with volume-activated chloride channels. The aim of the study is to investigate the effects of high glucose (HG, 25 mM on ClC-2 chloride channels and cell migration of keratinocytes.Methods: Newborn Sprague Dawley rats were used to isolate and culture the keratinocyte in this study. Immunofluorescence assay, real-time polymerase chain reaction, and Western blot assay were used to examine the expression of ClC-2 protein or mRNA. Scratch wound assay was used to measure the migratory ability of keratinocytes. Transwell cell migration assay was used to measure the invasion and migration of keratinocytes. Recombinant lentivirus vectors were established and transducted to keratinocytes. Whole-cell patch clamp was used to perform the electrophysiological studies.Results: We found that the expression of ClC-2 was significantly inhibited when keratinocytes were exposed to a HG (25 mM medium, accompanied by the decline of volume-activated Cl- current (ICl,vol, migration potential, and phosphorylated PI3K as compared to control group. When knockdown of ClC-2 by RNAi or pretreatment with wortmannin, similar results were observed, including ICl,vol and migration keratinocytes were inhibited.Conclusion: Our study proved that HG inhibited ClC-2 chloride channels and attenuated cell migration of rat keratinocytes via inhibiting PI3K signaling.Keywords: high glucose, keratinocytes, ClC-2, cell migration, PI3K

  1. Voltage-independent inhibition of Cav2.2 channels is delimited to a specific region of the membrane potential in rat SCG neurons

    Institute of Scientific and Technical Information of China (English)

    Oscar Vivas; Isabel Arenas; David E.García

    2012-01-01

    Neurotransmitters and hormones regulate Cav2.2 channels through a voltage-independent pathway which is not well understood.It has been suggested that this voltageindependent inhibition is constant at all membrane voltages.However,changes in the percent of voltageindependent inhibition of Cav2.2 have not been tested within a physiological voltage range.Here,we used a double-pulse protocol to isolate the voltage-independent inhibition of Cav2.2 channels induced by noradrenaline in rat superior cervical ganglion neurons.To assess changes in the percent of the voltage-independent inhibition,the activation voltage of the channels was tested between -40 and +40 mV.We found that the percent of voltage-independent inhibition induced by noradrenaline changed with the activation voltage used.In addition,voltage-independent inhibition induced by oxo-M,a muscarinic agonist,exhibited thesame dependence on activation voltage,which supports that this pattern is not exclusive for adrenergic activation.Our results suggested that voltage-independent inhibition of Cav2.2 channels depends on the activation voltage of the channel in a physiological voltage range.This may have relevant implications in the understanding of the mechanism involved in voltage-independent inhibition.

  2. INVESTIGATION OF SEIZURE ACTIVITY AFTER CYCLIC NUCLEOTIDE PHOSPHODIESTERASE INHIBITION WITH SECOND MESSENGER AND CALCIUM ION CHANNEL INHIBITION IN MICE

    Directory of Open Access Journals (Sweden)

    J Nandhakumar

    2012-03-01

    Full Text Available The role of PDE-4 inhibitor etazolate, was evaluated in the presence of PDE-7 inhibitor, BRL-50481, in animal models of epilepsy. Seizures were induced in the animals by subjecting them to injection of chemical convulsants, Pilocarpine, Kainic acid (KA and maximal electroshock (MES. The combination of etazolate and BRL50481 treated mice showed a significant (P<0.001 quick onset of action, jerky movements and convulsion when compared to gabapentin. The combination of etazolate and sGC inhibitor, methylene blue (MB treated mice showed a significant (P<0.001 delay in onset of action, jerky movements and convulsion when compare to gabapentin as well as against the combination of etazolate with BRL 50481.The present study mainly highlights the individual effects of etazolate and combination with BRL-50481 potentiates (P<0.001 the onset of seizure activity against all models of convulsion. The study mainly comprises the onset of seizures, mortality/recovery, percentage of prevention of seizures (anticonvulsant and total duration of convulsive time. The total convulsive time was prolonged significantly (P<0.05 and P<0.01 in combination of methylene blue with etazolate treated (28.59% and 35.15 % groups, compared to DMSO received group (100% in the MES model. In the same way, the combination of calcium channel modulator (CCM and calcium channel blocker (CCB amiodarone and nifedipine respectively, with etazolate showed a significant (P<0.001 delay in onset of seizures, compared to DMSO and etazolate treated groups in all models of epilepsy. This confirms that both CCM and CCB possess anticonvulsant activity. Finally, the study reveals that identification of new cAMP mediated phosphodiesterases family members offers a potential new therapy for epilepsy management in future.

  3. The T-type calcium channel antagonist Z944 disrupts prepulse inhibition in both epileptic and non-epileptic rats.

    Science.gov (United States)

    Marks, Wendie N; Greba, Quentin; Cain, Stuart M; Snutch, Terrance P; Howland, John G

    2016-09-22

    The role of T-type calcium channels in brain diseases such as absence epilepsy and neuropathic pain has been studied extensively. However, less is known regarding the involvement of T-type channels in cognition and behavior. Prepulse inhibition (PPI) is a measure of sensorimotor gating which is a basic process whereby the brain filters incoming stimuli to enable appropriate responding in sensory rich environments. The regulation of PPI involves a network of limbic, cortical, striatal, pallidal and pontine brain areas, many of which show high levels of T-type calcium channel expression. Therefore, we tested the effects of blocking T-type calcium channels on PPI with the potent and selective T-type antagonist Z944 (0.3, 1, 3, 10mg/kg; i.p.) in adult Wistar rats and two related strains, the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) and Non-Epileptic Control (NEC). PPI was tested using a protocol that varied prepulse intensity (3, 6, and 12dB above background) and prepulse-pulse interval (30, 50, 80, 140ms). Z944 decreased startle in the Wistar strain at the highest dose relative to lower doses. Z944 dose-dependently disrupted PPI in the Wistar and GAERS strains with the most potent effect observed with the higher doses. These findings suggest that T-type calcium channels contribute to normal patterns of brain activity that regulate PPI. Given that PPI is disrupted in psychiatric disorders, future experiments that test the specific brain regions involved in the regulation of PPI by T-type calcium channels may help inform therapeutic development for those suffering from sensorimotor gating impairments. PMID:27365170

  4. Mice with deficient BK channel function show impaired prepulse inhibition and spatial learning, but normal working and spatial reference memory.

    Directory of Open Access Journals (Sweden)

    Marei Typlt

    Full Text Available Genetic variations in the large-conductance, voltage- and calcium activated potassium channels (BK channels have been recently implicated in mental retardation, autism and schizophrenia which all come along with severe cognitive impairments. In the present study we investigate the effects of functional BK channel deletion on cognition using a genetic mouse model with a knock-out of the gene for the pore forming α-subunit of the channel. We tested the F1 generation of a hybrid SV129/C57BL6 mouse line in which the slo1 gene was deleted in both parent strains. We first evaluated hearing and motor function to establish the suitability of this model for cognitive testing. Auditory brain stem responses to click stimuli showed no threshold differences between knockout mice and their wild-type littermates. Despite of muscular tremor, reduced grip force, and impaired gait, knockout mice exhibited normal locomotion. These findings allowed for testing of sensorimotor gating using the acoustic startle reflex, as well as of working memory, spatial learning and memory in the Y-maze and the Morris water maze, respectively. Prepulse inhibition on the first day of testing was normal, but the knockout mice did not improve over the days of testing as their wild-type littermates did. Spontaneous alternation in the y-maze was normal as well, suggesting that the BK channel knock-out does not impair working memory. In the Morris water maze knock-out mice showed significantly slower acquisition of the task, but normal memory once the task was learned. Thus, we propose a crucial role of the BK channels in learning, but not in memory storage or recollection.

  5. Downregulation of transient receptor potential cation channel, subfamily C, member 1 (TRPC1 is associated with drug resistance and high histologic grade in ovarian cancer

    Directory of Open Access Journals (Sweden)

    Xia Liu

    2015-12-01

    Full Text Available Purpose: Ovarian cancer (OC drug resistance, believed to result in treatment failure and death in more than 90% of patients with metastatic OC, is due to a myriad of contributing factors. However, no matter what mechanisms, dysregulation of critical genes essentially play important roles. Transient receptor potential cation channel, subfamily C, member 1 (TRPC1 contributes to various physiological functions, and is involved in the regulation of cancer development. However, the overall studies of TRPC1 with cancer are limited, the study with drug resistance or OC is rare, and the research on TRPC1 with drug resistance in OC has never been reported. In this study, we aimed to explain the associations of TRPC1 with drug resistance in OC.Methods: The expression of TRPC1 was determined by the microarrays retrieved from Oncomine (https://www.oncomine.org/resource/login.html and GEO Profiles (http://www.ncbi.nlm.nih.gov/geoprofiles/, and further confirmed by RT-qPCR. The clinical data of 341 OC patients with TRPC1 mRNA expression data in TCGA cohort was retrieved from cBioPortal (http://cbioportal.org. Comprehensive bioinformatics analyses including protein/gene interaction, protein-small molecule/chemical interaction, biological process annotation, microRNA-mRNA interaction and pathway enrichment analysis of microRNAs were performed to clarify the drug resistant-related functions of TRPC1. The data was analyzed by SPSS 20.0 software. P-values of <0.05 were considered to indicate statistically significant differences.Results: The mRNA expressions of TRPC1 were downregulated by 3.955-fold, 3.681-fold and 3.260-fold in ovarian cancers according to the Welsh Ovarian covering 28 cases of ovarian serous surface papillary carcinoma and 4 cases of ovaries, the Bonome Ovarian covering 185 cases of ovarian carcinomas and 10 cases of ovarian surface epitheliums, and the Yoshihara Ovarian covering 38 cases of ovarian serous adenocarcinomas and 10 cases of

  6. The stress protein heat shock cognate 70 (Hsc70) inhibits the Transient Receptor Potential Vanilloid type 1 (TRPV1) channel

    Science.gov (United States)

    Iftinca, Mircea; Flynn, Robyn; Basso, Lilian; Melo, Helvira; Aboushousha, Reem; Taylor, Lauren

    2016-01-01

    Background Specialized cellular defense mechanisms prevent damage from chemical, biological, and physical hazards. The heat shock proteins have been recognized as key chaperones that maintain cell survival against a variety of exogenous and endogenous stress signals including noxious temperature. However, the role of heat shock proteins in nociception remains poorly understood. We carried out an expression analysis of the constitutively expressed 70 kDa heat-shock cognate protein, a member of the stress-induced HSP70 family in lumbar dorsal root ganglia from a mouse model of Complete Freund’s Adjuvant-induced chronic inflammatory pain. We used immunolabeling of dorsal root ganglion neurons, behavioral analysis and patch clamp electrophysiology in both dorsal root ganglion neurons and HEK cells transfected with Hsc70 and Transient Receptor Potential Channels to examine their functional interaction in heat shock stress condition. Results We report an increase in protein levels of Hsc70 in mouse dorsal root ganglia, 3 days post Complete Freund’s Adjuvant injection in the hind paw. Immunostaining of Hsc70 was observed in most of the dorsal root ganglion neurons, including the small size nociceptors immunoreactive to the TRPV1 channel. Standard whole-cell patch-clamp technique was used to record Transient Receptor Potential Vanilloid type 1 current after exposure to heat shock. We found that capsaicin-evoked currents are inhibited by heat shock in dorsal root ganglion neurons and transfected HEK cells expressing Hsc70 and TRPV1. Blocking Hsc70 with matrine or spergualin compounds prevented heat shock-induced inhibition of the channel. We also found that, in contrast to TRPV1, both the cold sensor channels TRPA1 and TRPM8 were unresponsive to heat shock stress. Finally, we show that inhibition of TRPV1 depends on the ATPase activity of Hsc70 and involves the rho-associated protein kinase. Conclusions Our work identified Hsc70 and its ATPase activity as a central

  7. Filter gate closure inhibits ion but not water transport through potassium channels.

    Science.gov (United States)

    Hoomann, Torben; Jahnke, Nadin; Horner, Andreas; Keller, Sandro; Pohl, Peter

    2013-06-25

    The selectivity filter of K(+) channels is conserved throughout all kingdoms of life. Carbonyl groups of highly conserved amino acids point toward the lumen to act as surrogates for the water molecules of K(+) hydration. Ion conductivity is abrogated if some of these carbonyl groups flip out of the lumen, which happens (i) in the process of C-type inactivation or (ii) during filter collapse in the absence of K(+). Here, we show that K(+) channels remain permeable to water, even after entering such an electrically silent conformation. We reconstituted fluorescently labeled and constitutively open mutants of the bacterial K(+) channel KcsA into lipid vesicles that were either C-type inactivating or noninactivating. Fluorescence correlation spectroscopy allowed us to count both the number of proteoliposomes and the number of protein-containing micelles after solubilization, providing the number of reconstituted channels per proteoliposome. Quantification of the per-channel increment in proteoliposome water permeability with the aid of stopped-flow experiments yielded a unitary water permeability pf of (6.9 ± 0.6) × 10(-13) cm(3)⋅s(-1) for both mutants. "Collapse" of the selectivity filter upon K(+) removal did not alter pf and was fully reversible, as demonstrated by current measurements through planar bilayers in a K(+)-containing medium to which K(+)-free proteoliposomes were fused. Water flow through KcsA is halved by 200 mM K(+) in the aqueous solution, which indicates an effective K(+) dissociation constant in that range for a singly occupied channel. This questions the widely accepted hypothesis that multiple K(+) ions in the selectivity filter act to mutually destabilize binding.

  8. Pharmacological Inhibition of Voltage-gated Ca2+ Channels for Chronic Pain Relief

    OpenAIRE

    Lee, Seungkyu

    2013-01-01

    Chronic pain is a major therapeutic problem as the current treatment options are unsatisfactory with low efficacy and deleterious side effects. Voltage-gated Ca2+ channels (VGCCs), which are multi-complex proteins consisting of α1, β, γ, and α2δ subunits, play an important role in pain signaling. These channels are involved in neurogenic inflammation, excitability, and neurotransmitter release in nociceptors. It has been previously shown that N-type VGCCs (Cav2.2) are a major pain target. U.S...

  9. Substrate channeling: alpha-ketobutyrate inhibition of acetohydroxy acid synthase in Salmonella typhimurium.

    OpenAIRE

    Shaw, K J; Berg, C M

    1980-01-01

    Excess alpha-ketobutyrate inhibited the growth of Salmonella typhimurium LT2 by inhibiting the acetohydroxy acid synthase-catalyzed synthesis of alpha-acetolactate (a valine precursor). As a result, cells were starved for valine, and both ilvB (encoding acetohydroxy acid synthase I) and ilvGEDA (ilvG encodes acetohydroxy acid synthase II) were derepressed. The addition of valine reversed the effects of alpha-ketobutyrate.

  10. The ryanodine receptor pore blocker neomycin also inhibits channel activity via a previously undescribed high-affinity Ca(2+) binding site.

    Science.gov (United States)

    Laver, Derek R; Hamada, Tomoyo; Fessenden, James D; Ikemoto, Noriaki

    2007-12-01

    In this study, we present evidence for the mechanism of neomycin inhibition of skeletal ryanodine receptors (RyRs). In single-channel recordings, neomycin produced monophasic inhibition of RyR open probability and biphasic inhibition of [(3)H]ryanodine binding. The half-maximal inhibitory concentration (IC(50)) for channel blockade by neomycin was dependent on membrane potential and cytoplasmic [Ca(2+)], suggesting that neomycin acts both as a pore plug and as a competitive antagonist at a cytoplasmic Ca(2+) binding site that causes allosteric inhibition. This novel Ca(2+)/neomycin binding site had a neomycin affinity of 100 nM: and a Ca(2+) affinity of 35 nM,: which is 30-fold higher than that of the well-described cytoplasmic Ca(2+) activation site. Therefore, a new high-affinity class of Ca(2+) binding site(s) on the RyR exists that mediates neomycin inhibition. Neomycin plugging of the channel pore induced brief (1-2 ms) conductance substates at 30% of the fully open conductance, whereas allosteric inhibition caused complete channel closure with durations that depended on the neomycin concentration. We quantitatively account for these results using a dual inhibition model for neomycin that incorporates voltage-dependent pore plugging and Ca(2+)-dependent allosteric inhibition.

  11. Sodium channel-inhibiting drugs and cancer survival: protocol for a cohort study using the CPRD primary care database

    Science.gov (United States)

    Fairhurst, Caroline; Martin, Fabiola; Watt, Ian; Doran, Tim; Bland, Martin

    2016-01-01

    Introduction Voltage-gated sodium channel (VGSC)-inhibiting drugs are commonly used to treat epilepsy and cardiac arrhythmia. VGSCs are also widely expressed in various cancers, including those of the breast, bowel and prostate. A number of VGSC-inhibiting drugs have been shown to inhibit cancer cell proliferation, invasion, tumour growth and metastasis in preclinical models, suggesting that VGSCs may be novel molecular targets for cancer treatment. Surprisingly, we previously found that prior exposure to VGSC-inhibiting drugs may be associated with reduced overall survival in patients with cancer, but we were unable to control for the cause of death or indication for prescription. The purpose of the present study is to interrogate a different database to further investigate the relationship between VGSC-inhibiting drugs and cancer-specific survival. Methods and analysis A cohort study using primary care data from the Clinical Practice Research Datalink database will include patients with diagnosis of breast, bowel and prostate cancer (13 000). The primary outcome will be cancer-specific survival from the date of cancer diagnosis. Cox proportional hazards regression will be used to compare survival of patients taking VGSC-inhibiting drugs (including antiepileptic drugs and class I antiarrhythmic agents) with patients with cancer not taking these drugs, adjusting for cancer type, age and sex. Drug exposure will be treated as a time-varying covariate to account for potential immortal time bias. Various sensitivity and secondary analyses will be performed. Ethics and dissemination The project has been reviewed and approved by the University of York Ethical Review Process. Results will be presented at an international conference and published in open access peer-reviewed journals according to the STROBE and RECORD guidelines. PMID:27601493

  12. Inhibition of collagen synthesis by select calcium and sodium channel blockers can be mitigated by ascorbic acid and ascorbyl palmitate.

    Science.gov (United States)

    Ivanov, Vadim; Ivanova, Svetlana; Kalinovsky, Tatiana; Niedzwiecki, Aleksandra; Rath, Matthias

    2016-01-01

    muscle cells, assayed by measuring intracellular collagen content. We observed increased intracellular levels of ascorbate under supplementation with elevated doses of ascorbic acid, as well as its lipid soluble derivative ascorbyl palmitate. Nifedipine reduced ascorbic acid intracellular influx in cultured aortic smooth muscle cells with nifedipine (50 µM) compared to control. Adverse effects of nifedipine were neutralized either by an increased level of cell supplementation with ascorbic acid or by substituting it with ascorbyl palmitate. These studies suggest that adverse effects of channel blockers could be caused by their weakening the arterial wall integrity by interfering with proper extracellular matrix formation. In conclusion, these studies confirm the adverse effects of channel blockers on collagen type l and lV deposition, the key ECM components essential for maintaining optimal structural integrity of the arterial walls. Ascorbate supplementation reversed channel blocker inhibition of these collagen types synthesis and deposition. The results of this study imply the benefits of ascorbate and ascorbate palmitate supplementation in medical management of cardiovascular disease in order to compensate for adverse effects of channel blockers. PMID:27335688

  13. An improved ivermectin-activated chloride channel receptor for inhibiting electrical activity in defined neuronal populations

    DEFF Research Database (Denmark)

    Lynagh, Timothy Peter; Lynch, Joseph W

    2010-01-01

    for surgically implanted stimulus delivery methods and their use of nonhuman receptors. A third silencing method, an invertebrate glutamate-gated chloride channel receptor (GluClR) activated by ivermectin, solves the stimulus delivery problem as ivermectin is a safe, well tolerated drug that reaches the brain...

  14. Blockade of microglial KATP -channel abrogates suppression of inflammatory-mediated inhibition of neural precursor cells.

    Science.gov (United States)

    Ortega, Francisco J; Vukovic, Jana; Rodríguez, Manuel J; Bartlett, Perry F

    2014-02-01

    Microglia positively affect neural progenitor cell physiology through the release of inflammatory mediators or trophic factors. We demonstrated previously that reactive microglia foster K(ATP) -channel expression and that blocking this channel using glibenclamide administration enhances striatal neurogenesis after stroke. In this study, we investigated whether the microglial K(ATP) -channel directly influences the activation of neural precursor cells (NPCs) from the subventricular zone using transgenic Csf1r-GFP mice. In vitro exposure of NPCs to lipopolysaccharide and interferon-gamma resulted in a significant decrease in precursor cell number. The complete removal of microglia from the culture or exposure to enriched microglia culture also decreased the precursor cell number. The addition of glibenclamide rescued the negative effects of enriched microglia on neurosphere formation and promoted a ∼20% improvement in precursor cell number. Similar results were found using microglial-conditioned media from isolated microglia. Using primary mixed glial and pure microglial cultures, glibenclamide specifically targeted reactive microglia to restore neurogenesis and increased the microglial production of the chemokine monocyte chemoattractant protein-1 (MCP-1). These findings provide the first direct evidence that the microglial K(ATP) -channel is a regulator of the proliferation of NPCs under inflammatory conditions.

  15. 5,6-EET potently inhibits T-type calcium channels

    DEFF Research Database (Denmark)

    Cazade, M.; Bidaud, I.; Hansen, Pernille B. Lærkegaard;

    2014-01-01

    T-type calcium channels (T-channels) are important actors in neuronal pacemaking, in heart rhythm, and in the control of the vascular tone. T-channels are regulated by several endogenous lipids including the primary eicosanoid arachidonic acid (AA), which display an important role in vasodilation...... via its metabolism leading to prostanoids, leukotrienes, and epoxyeicosatrienoic acids (EETs). However, the effects of these latter molecules on T-currents have not been investigated. Here, we describe the effects of the major cyclooxygenase, lipoxygenase, and cytochrome P450 epoxygenase products...... on the three human recombinant T-channels (Ca(v)3.1, Ca(v)3.2, and Ca(v)3.3), as compared to those of AA. We identified the P450 epoxygenase product, 5,6-EET, as a potent physiological inhibitor of Ca(v)3 currents. The effects of 5,6-EET were observed at sub-micromolar concentrations (IC50 = 0.54 mu M...

  16. The Inhibition by Oxaliplatin, a Platinum-Based Anti-Neoplastic Agent, of the Activity of Intermediate-Conductance Ca2+-Activated K+ Channels in Human Glioma Cells

    Directory of Open Access Journals (Sweden)

    Mei-Han Huang

    2015-10-01

    Full Text Available Oxaliplatin (OXAL is a third-generation organoplatinum which is effective against advanced cancer cells including glioma cells. How this agent and other related compounds interacts with ion channels in glioma cells is poorly understood. OXAL (100 µM suppressed the amplitude of whole-cell K+ currents (IK; and, either DCEBIO or ionomycin significantly reversed OXAL-mediated inhibition of IK in human 13-06-MG glioma cells. In OXAL-treated cells, TRAM-34 did not suppress IK amplitude in these cells. The intermediate-conductance Ca2+-activated K+ (IKCa channels subject to activation by DCEBIO and to inhibition by TRAM-34 or clotrimazole were functionally expressed in these cells. Unlike cisplatin, OXAL decreased the probability of IKCa-channel openings in a concentration-dependent manner with an IC50 value of 67 µM. No significant change in single-channel conductance of IKCa channels in the presence of OXAL was demonstrated. Neither large-conductance Ca2+-activated K+ channels nor inwardly rectifying K+ currents in these cells were affected in the presence of OXAL. OXAL also suppressed the proliferation and migration of 13-06-MG cells in a concentration- and time-dependent manner. OXAL reduced IKCa-channel activity in LoVo colorectal cancer cells. Taken together, the inhibition by OXAL of IKCa channels would conceivably be an important mechanism through which it acts on the functional activities of glioma cells occurring in vivo.

  17. ZD7288, a selective hyperpolarization-activated cyclic nucleotide-gated channel blocker, inhibits hippocampal synaptic plasticity

    Institute of Scientific and Technical Information of China (English)

    Xiao-xue Zhang; Xiao-chun Min; Xu-lin Xu; Min Zheng; Lian-jun Guo

    2016-01-01

    The selective hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker 4-(N-ethyl-N-phenylamino)-1,2-dimeth-yl-6-(methylamino) pyrimidinium chloride (ZD7288) blocks the induction of long-term potentiation in the perforant path–CA3 region in rat hippocampusin vivo. To explore the mechanisms underlying the action of ZD7288, we recorded excitatory postsynaptic potentials in perforant path–CA3 synapses in male Sprague-Dawley rats. We measured glutamate content in the hippocampus and in cultured hip-pocampal neurons using high performance liquid chromatography, and determined intracellular Ca2+ concentration ([Ca2+]i) using Fura-2. ZD7288 inhibited the induction and maintenance of long-term potentiation, and these effects were mirrored by the nonspeciifc HCN channel blocker cesium. ZD7288 also decreased glutamate release in hippocampal tissue and in cultured hippocampal neurons. Further-more, ZD7288 attenuated glutamate-induced rises in [Ca2+]i in a concentration-dependent manner and reversed 8-Br-cAMP-mediated facilitation of these glutamate-induced [Ca2+]i rises. Our results suggest that ZD7288 inhibits hippocampal synaptic plasticity both gluta-mate release and resultant [Ca2+]i increases in rat hippocampal neurons.

  18. Neurotensinergic Excitation of Dentate Gyrus Granule Cells via Gαq-Coupled Inhibition of TASK-3 Channels.

    Science.gov (United States)

    Zhang, Haopeng; Dong, Hailong; Cilz, Nicholas I; Kurada, Lalitha; Hu, Binqi; Wada, Etsuko; Bayliss, Douglas A; Porter, James E; Lei, Saobo

    2016-03-01

    Neurotensin (NT) is a 13-amino acid peptide and serves as a neuromodulator in the brain. Whereas NT has been implicated in learning and memory, the underlying cellular and molecular mechanisms are ill-defined. Because the dentate gyrus receives profound innervation of fibers containing NT and expresses high density of NT receptors, we examined the effects of NT on the excitability of dentate gyrus granule cells (GCs). Our results showed that NT concentration dependently increased action potential (AP) firing frequency of the GCs by the activation of NTS1 receptors resulting in the depolarization of the GCs. NT-induced enhancement of AP firing frequency was not caused indirectly by releasing glutamate, GABA, acetylcholine, or dopamine, but due to the inhibition of TASK-3 K(+) channels. NT-mediated excitation of the GCs was G protein dependent, but independent of phospholipase C, intracellular Ca(2+) release, and protein kinase C. Immunoprecipitation experiment demonstrates that the activation of NTS1 receptors induced the association of Gαq/11 and TASK-3 channels suggesting a direct coupling of Gαq/11 to TASK-3 channels. Endogenously released NT facilitated the excitability of the GCs contributing to the induction of long-term potentiation at the perforant path-GC synapses. Our results provide a cellular mechanism that helps to explain the roles of NT in learning and memory. PMID:25405940

  19. Mitochondrial KATP channel inhibition blunts arrhythmia protection in ischemic exercised hearts

    OpenAIRE

    Quindry, John C.; Schreiber, Lindsey; Hosick, Peter; Wrieden, Jenna; Irwin, J. Megan; Hoyt, Emily

    2010-01-01

    The mechanisms responsible for anti-arrhythmic protection during ischemia-reperfusion (IR) in exercised hearts are not fully understood. The purpose of this investigation was to examine whether the ATP-sensitive potassium channels in the mitochondria (mito KATP) and sarcolemma (sarc KATP) provide anti-arrhythmic protection in exercised hearts during IR. Male Sprague-Dawley rats were randomly assigned to cardioprotective treadmill exercise or sedentary conditions before IR (I = 20 min, R = 30 ...

  20. Inhibition of Recombinant Human T-type Calcium Channels by Δ9-Tetrahydrocannabinol and Cannabidiol*

    OpenAIRE

    Ross, Hamish Redmond; Napier, Ian; Connor, Mark

    2008-01-01

    Δ9-Tetrahydrocannabinol (THC) and cannabidiol (CBD) are the most prevalent biologically active constituents of Cannabis sativa. THC is the prototypic cannabinoid CB1 receptor agonist and is psychoactive and analgesic. CBD is also analgesic, but it is not a CB1 receptor agonist. Low voltage-activated T-type calcium channels, encoded by the CaV3 gene family, regulate the excitability of many cells, including neurons involved in nociceptive processing. We examined the eff...

  1. Pharmacological Inhibition of Voltage-gated Ca(2+) Channels for Chronic Pain Relief.

    Science.gov (United States)

    Lee, Seungkyu

    2013-12-01

    Chronic pain is a major therapeutic problem as the current treatment options are unsatisfactory with low efficacy and deleterious side effects. Voltage-gated Ca2+ channels (VGCCs), which are multi-complex proteins consisting of α1, β, γ, and α2δ subunits, play an important role in pain signaling. These channels are involved in neurogenic inflammation, excitability, and neurotransmitter release in nociceptors. It has been previously shown that N-type VGCCs (Cav2.2) are a major pain target. U.S. FDA approval of three Cav2.2 antagonists, gabapentin, pregabalin, and ziconotide, for chronic pain underlies the importance of this channel subtype. Also, there has been increasing evidence that L-type (Cav1.2) or T-type (Cav3.2) VGCCs may be involved in pain signaling and chronic pain. In order to develop novel pain therapeutics and to understand the role of VGCC subtypes, discovering subtype selective VGCC inhibitors or methods that selectively target the inhibitor into nociceptors would be essential. This review describes the various VGCC subtype inhibitors and the potential of utilizing VGCC subtypes as targets of chronic pain. Development of VGCC subtype inhibitors and targeting them into nociceptors will contribute to a better understanding of the roles of VGCC subtypes in pain at a spinal level as well as development of a novel class of analgesics for chronic pain. PMID:24396337

  2. Deltamethrin Inhibits the Human T-type Voltage-Sensitive Calcium Channel (Cav3.2

    Directory of Open Access Journals (Sweden)

    Steven B. Symington

    2009-01-01

    Full Text Available The goal of this study was to determine the effect of deltamethrin, a pyrethroid insecticide, on CaV3.2, a human T-type voltage-sensitive calcium channel expressed in Xenopus laevis (X.laevis oocytes. Cav3.2 cDNA was transcribed into cRNA; the cRNA was then injected into X.laevis oocytes and electrophysiologically characterized using the two-electrode voltage clamp technique with Ba2+ as a charge carrier. Deltamethrin (10-7 M reduced peak current in a nonreversible manner compared to the untreated control, but had no effect on the voltagedependent activation and inactivation kinetics. These findings confirm that human CaV3.2 is a target for deltamethrin and quite possibly other pyrethroid insecticides. These studies provide insight into the molecular mechanisms of the effect that pyrethroids have on voltage-sensitive calcium channels in general. This information will allow a more complete understanding of the molecular and cellular nature of pyrethroid-induced toxicity and expand our knowledge of the structure-activity relationships of pyrethroids with regard to their action on voltage-sensitive calcium channels.

  3. Structural Basis for the Function and Inhibition of an Influenze Virus Proton Channel

    Energy Technology Data Exchange (ETDEWEB)

    Stouffer,A.; Acharya, R.; Salom, D.; Levine, A.; Di Costanzo, L.; Soto, C.; Tershko, V.; Nanda, V.; Stayrook, S.; DeGrado, W.

    2008-01-01

    The M2 protein from influenza A virus is a pH-activated proton channel that mediates acidification of the interior of viral particles entrapped in endosomes. M2 is the target of the anti-influenza drugs amantadine and rimantadine; recently, resistance to these drugs in humans, birds and pigs has reached more than 90% (ref. 1). Here we describe the crystal structure of the transmembrane-spanning region of the homotetrameric protein in the presence and absence of the channel-blocking drug amantadine. pH-dependent structural changes occur near a set of conserved His and Trp residues that are involved in proton gating2. The drug-binding site is lined by residues that are mutated in amantadine-resistant viruses3, 4. Binding of amantadine physically occludes the pore, and might also perturb the pKa of the critical His residue. The structure provides a starting point for solving the problem of resistance to M2-channel blockers.

  4. Strong Inhibition of O-Atom Transfer Reactivity for Mn(IV)(O)(π-Radical-Cation)(Lewis Acid) versus Mn(V)(O) Porphyrinoid Complexes.

    Science.gov (United States)

    Zaragoza, Jan Paulo T; Baglia, Regina A; Siegler, Maxime A; Goldberg, David P

    2015-05-27

    The oxygen atom transfer (OAT) reactivity of two valence tautomers of a Mn(V)(O) porphyrinoid complex was compared. The OAT kinetics of Mn(V)(O)(TBP8Cz) (TBP8Cz = octakis(p-tert-butylphenyl)corrolazinato(3-)) reacting with a series of triarylphosphine (PAr3) substrates were monitored by stopped-flow UV-vis spectroscopy, and revealed second-order rate constants ranging from 16(1) to 1.43(6) × 10(4) M(-1) s(-1). Characterization of the OAT transition state analogues Mn(III)(OPPh3)(TBP8Cz) and Mn(III)(OP(o-tolyl)3)(TBP8Cz) was carried out by single-crystal X-ray diffraction (XRD). A valence tautomer of the closed-shell Mn(V)(O)(TBP8Cz) can be stabilized by the addition of Lewis and Brønsted acids, resulting in the open-shell Mn(IV)(O)(TBP8Cz(•+)):LA (LA = Zn(II), B(C6F5)3, H(+)) complexes. These Mn(IV)(O)(π-radical-cation) derivatives exhibit dramatically inhibited rates of OAT with the PAr3 substrates (k = 8.5(2) × 10(-3) - 8.7 M(-1) s(-1)), contrasting the previously observed rate increase of H-atom transfer (HAT) for Mn(IV)(O)(TBP8Cz(•+)):LA with phenols. A Hammett analysis showed that the OAT reactivity for Mn(IV)(O)(TBP8Cz(•+)):LA is influenced by the Lewis acid strength. Spectral redox titration of Mn(IV)(O)(TBP8Cz(•+)):Zn(II) gives Ered = 0.69 V vs SCE, which is nearly +700 mV above its valence tautomer Mn(V)(O)(TBP8Cz) (Ered = -0.05 V). These data suggest that the two-electron electrophilicity of the Mn(O) valence tautomers dominate OAT reactivity and do not follow the trend in one-electron redox potentials, which appear to dominate HAT reactivity. This study provides new fundamental insights regarding the relative OAT and HAT reactivity of valence tautomers such as M(V)(O)(porph) versus M(IV)(O)(porph(•+)) (M = Mn or Fe) found in heme enzymes.

  5. Blockade of chloride channels by DIDS stimulates renin release and inhibits contraction of afferent arterioles

    DEFF Research Database (Denmark)

    Jensen, B L; Skøtt, O

    1996-01-01

    or without ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] and DIDS were not additive. In the absence of chloride, basal renin release was suppressed and the stimulatory effect of DIDS was abolished. The DIDS-induced enhancement of renin release was not dependent on bicarbonate...... arterioles with the chloride channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). Renin secretion was equally enhanced by omission of extracellular calcium and by addition of 0.5 mM DIDS. The inhibitory effect of calcium was blocked by DIDS. The stimulatory effects of low calcium [with...

  6. Spicing up the sensation of stretch: TRPV1 controls mechanosensitive Piezo channels.

    Science.gov (United States)

    Altier, Christophe

    2015-02-10

    Piezo proteins--a family of mammalian cation-selective ion channels that respond to mechanical stretch--are molecular mediators of biological processes, including vascular tone, hearing, touch, and pain. In this issue of Science Signaling, Rohacs and colleagues demonstrate that activation of the heat-sensitive transient receptor potential vanilloid 1 (TRPV1), another cation channel, inhibits Piezo channels through a calcium-induced depletion of phosphoinositides. This regulation could contribute to the cellular mechanisms by which the TRPV1 activator capsaicin mitigates mechanical hypersensitivity.

  7. Lipopolysaccharide Inhibits the Channel Activity of the P2X7 Receptor

    Directory of Open Access Journals (Sweden)

    Elias Leiva-Salcedo

    2011-01-01

    Full Text Available The purinergic P2X7 receptor (P2X7R plays an important role during the immune response, participating in several events such as cytokine release, apoptosis, and necrosis. The bacterial endotoxin lipopolysaccharide (LPS is one of the strongest stimuli of the immune response, and it has been shown that P2X7R activation can modulate LPS-induced responses. Moreover, a C-terminal binding site for LPS has been proposed. In order to evaluate if LPS can directly modulate the activity of the P2X7R, we tested several signaling pathways associated with P2X7R activation in HEK293 cells that do not express the TLR-4 receptor. We found that LPS alone was unable to induce any P2X7R-related activity, suggesting that the P2X7R is not directly activated by the endotoxin. On the other hand, preapplication of LPS inhibited ATP-induced currents, intracellular calcium increase, and ethidium bromide uptake and had no effect on ERK activation in HEK293 cells. In splenocytes-derived T-regulatory cells, in which ATP-induced apoptosis is driven by the P2X7R, LPS inhibited ATP-induced apoptosis. Altogether, these results demonstrate that LPS modulates the activity of the P2X7R and suggest that this effect could be of physiological relevance.

  8. Lipopolysaccharide Inhibits the Channel Activity of the P2X7 Receptor

    Science.gov (United States)

    Leiva-Salcedo, Elias; Coddou, Claudio; Rodríguez, Felipe E.; Penna, Antonello; Lopez, Ximena; Neira, Tanya; Fernández, Ricardo; Imarai, Mónica; Rios, Miguel; Escobar, Jorge; Montoya, Margarita; Huidobro-Toro, J. Pablo; Escobar, Alejandro; Acuña-Castillo, Claudio

    2011-01-01

    The purinergic P2X7 receptor (P2X7R) plays an important role during the immune response, participating in several events such as cytokine release, apoptosis, and necrosis. The bacterial endotoxin lipopolysaccharide (LPS) is one of the strongest stimuli of the immune response, and it has been shown that P2X7R activation can modulate LPS-induced responses. Moreover, a C-terminal binding site for LPS has been proposed. In order to evaluate if LPS can directly modulate the activity of the P2X7R, we tested several signaling pathways associated with P2X7R activation in HEK293 cells that do not express the TLR-4 receptor. We found that LPS alone was unable to induce any P2X7R-related activity, suggesting that the P2X7R is not directly activated by the endotoxin. On the other hand, preapplication of LPS inhibited ATP-induced currents, intracellular calcium increase, and ethidium bromide uptake and had no effect on ERK activation in HEK293 cells. In splenocytes-derived T-regulatory cells, in which ATP-induced apoptosis is driven by the P2X7R, LPS inhibited ATP-induced apoptosis. Altogether, these results demonstrate that LPS modulates the activity of the P2X7R and suggest that this effect could be of physiological relevance. PMID:21941410

  9. Selective inhibition of caspases in skeletal muscle reverses the apoptotic synaptic degeneration in slow-channel myasthenic syndrome.

    Science.gov (United States)

    Zhu, Haipeng; Pytel, Peter; Gomez, Christopher M

    2014-01-01

    Slow-channel syndrome (SCS) is a congenital myasthenic disorder caused by point mutations in subunits of skeletal muscle acetylcholine receptor leading to Ca(2+) overload and degeneration of the postsynaptic membrane, nuclei and mitochondria of the neuromuscular junction (NMJ). In both SCS muscle biopsies and transgenic mouse models for SCS (mSCS), the endplate regions are shrunken, and there is evidence of DNA damage in the subsynaptic region. Activated caspase-9, -3 and -7 are intensely co-localized at the NMJ, and the Ca(2+)-activated protease, calpain, and the atypical cyclin-dependent kinase (Cdk5) are overactivated in mSCS. Thus, the true mediator(s) of the disease process is not clear. Here, we demonstrate that selective inhibition of effector caspases, caspase-3 and -7, or initiator caspase, caspase-9, in limb muscle in vivo by localized expression of recombinant inhibitor proteins dramatically decreases subsynaptic DNA damage, increases endplate area and improves ultrastructural abnormalities in SCS transgenic mice. Calpain and Cdk5 are not affected by this treatment. On the other hand, inhibition of Cdk5 by expression of a dominant-negative form of Cdk5 has no effect on the degeneration. Together with previous studies, these results indicate that focal activation of caspase activity at the NMJ is the principal pathological process responsible for the synaptic apoptosis in SCS. Thus, treatments that reduce muscle caspase activity are likely to be of benefit for SCS patients.

  10. 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.

  11. Sulfonation of 17β-estradiol and inhibition of sulfotransferase activity by polychlorobiphenylols and celecoxib in channel catfish, Ictalurus punctatus

    International Nuclear Information System (INIS)

    The sulfonation of 17β-estradiol (E2) by human liver and recombinant sulfotransferases is influenced by environmental contaminants such as hydroxylated metabolites of polychlorinated biphenyls (OH-PCBs), which are potent inhibitors, and the therapeutic drug, celecoxib, which affects positional sulfonation of E2. In some locations, the aquatic environment is contaminated by PCBs, OH-PCBs and widely used therapeutic drugs. The objectives of this study were to investigate the sulfonation kinetics of E2 in liver cytosol from channel catfish (Ictalurus punctatus); to examine the effect of OH-PCBs on E2 sulfonation; and to determine if celecoxib altered the position of E2 sulfonation, as it does with human liver cytosol. E2 was converted to both 3- and 17-sulfates by catfish liver cytosol. At E2 concentrations below 1μM, formation of E2-3-sulfate (E2-3-S) predominated, but substrate inhibition was observed at higher concentrations. Rates of E2-3-S formation at different E2 concentrations were fit to a substrate inhibition model, with K'm and V'max values of 0.40+/-0.10μM and 91.0+/-4.7pmol/min/mg protein, respectively and Ki of 1.08+/-0.09μM. The formation of E2-17-S fit Michaelis-Menten kinetics over the concentration range 25nM to 2.5μM, with Km and Vmax values of 1.07+/-0.23μM and 25.7+/-4.43pmol/min/mg protein, respectively. The efficiency (Vmax/Km) of formation of E2-3-S was 9.8-fold higher than that of E2-17-S. Several OH-PCBs inhibited E2 3-sulfonation, measured at an E2 concentration of 1nM. Of those tested, the most potent inhibitor was 4'-OH-CB79, with two chlorine atoms flanking the OH group (IC50: 94nM). The inhibition of estrogen sulfonation by OH-PCBs may disrupt the endocrine system and thus contribute to the known toxic effects of these compounds. Celecoxib did not stimulate E2-17-S formation, as is the case with human liver cytosol, but did inhibit the formation of E2-3-S (IC50: 44μM) and to a lesser extent, E2-17-S (IC50: >160μM), suggesting the

  12. FM1-43 is a permeant blocker of mechanosensitive ion channels in sensory neurons and inhibits behavioural responses to mechanical stimuli

    Directory of Open Access Journals (Sweden)

    Drew Liam J

    2007-01-01

    Full Text Available Abstract The molecular identity and pharmacological properties of mechanically gated ion channels in sensory neurons are poorly understood. We show that FM1-43, a styryl dye used to fluorescently label cell membranes, permeates mechanosensitive ion channels in cultured dorsal root ganglion neurons, resulting in blockade of three previously defined subtypes of mechanically activated currents. Blockade and dye uptake is voltage dependent and regulated by external Ca2+. The structurally related larger dye FM3-25 inhibited mechanically activated currents to a lesser degree and did not permeate the channels. In vivo, FMI-43 decreases pain sensitivity in the Randall-Selitto test and increases the withdrawal threshold from von Frey hairs, together suggesting that the channels expressed at the cell body in culture mediate mechanosensation in the intact animal. These data give further insight into the mechanosensitive ion channels expressed by somatosensory neurons and suggest FM dyes are an interesting tool for studying them.

  13. Inhibition of voltage-gated calcium channels as common mode of action for (mixtures of) distinct classes of insecticides.

    Science.gov (United States)

    Meijer, Marieke; Dingemans, Milou M L; van den Berg, Martin; Westerink, Remco H S

    2014-09-01

    Humans are exposed to distinct structural classes of insecticides with different neurotoxic modes of action. Because calcium homeostasis is essential for proper neuronal function and development, we investigated the effects of insecticides from different classes (pyrethroid: (α-)cypermethrin; organophosphate: chlorpyrifos; organochlorine: endosulfan; neonicotinoid: imidacloprid) and mixtures thereof on the intracellular calcium concentration ([Ca(2+)]i). Effects of acute (20 min) exposure to (mixtures of) insecticides on basal and depolarization-evoked [Ca(2+)]i were studied in vitro with Fura-2-loaded PC12 cells and high resolution single-cell fluorescence microscopy. The data demonstrate that cypermethrin, α-cypermethrin, endosulfan, and chlorpyrifos concentration-dependently decreased depolarization-evoked [Ca(2+)]i, with 50% (IC50) at 78nM, 239nM, 250nM, and 899nM, respectively. Additionally, acute exposure to chlorpyrifos or endosulfan (10μM) induced a modest increase in basal [Ca(2+)]i, amounting to 68 ± 8nM and 53 ± 8nM, respectively. Imidacloprid did not disturb basal or depolarization-evoked [Ca(2+)]i at 10μM. Following exposure to binary mixtures, effects on depolarization-evoked [Ca(2+)]i were within the expected effect additivity range, whereas the effect of the tertiary mixture was less than this expected additivity effect range. These results demonstrate that different types of insecticides inhibit depolarization-evoked [Ca(2+)]i in PC12 cells by inhibiting voltage-gated calcium channels (VGCCs) in vitro at concentrations comparable with human occupational exposure levels. Moreover, the effective concentrations in this study are below those for earlier described modes of action. Because inhibition of VGCCs appears to be a common and potentially additive mode of action of several classes of insecticides, this target should be considered in neurotoxicity risk assessment studies.

  14. The calmodulin inhibitor CGS 9343B inhibits voltage-dependent K{sup +} channels in rabbit coronary arterial smooth muscle cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hongliang; Hong, Da Hye; Kim, Han Sol; Kim, Hye Won [Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 200-701 (Korea, Republic of); Jung, Won-Kyo [Department of Biomedical Engineering, Center for Marine-Integrated Biomedical Technology (BK21 Plus), Pukyong National University, Busan 608-737 (Korea, Republic of); Na, Sung Hun [Institute of Medical Sciences, Department of Obstetrics and Gynecology, Kangwon National University Hospital, School of Medicine, Kangwon National University, Chuncheon, 200-701 (Korea, Republic of); Jung, In Duk; Park, Yeong-Min [Department of Immunology, Lab of Dendritic Cell Differentiation and Regulation, College of Medicine, Konkuk University, Chungju 380-701 (Korea, Republic of); Choi, Il-Whan, E-mail: cihima@inje.ac.kr [Department of Microbiology, Inje University College of Medicine, Busan, 614-735 (Korea, Republic of); Park, Won Sun, E-mail: parkws@kangwon.ac.kr [Institute of Medical Sciences, Department of Physiology, Kangwon National University School of Medicine, Chuncheon, 200-701 (Korea, Republic of)

    2015-06-15

    We investigated the effects of the calmodulin inhibitor CGS 9343B on voltage-dependent K{sup +} (Kv) channels using whole-cell patch clamp technique in freshly isolated rabbit coronary arterial smooth muscle cells. CGS 9343B inhibited Kv currents in a concentration-dependent manner, with a half-maximal inhibitory concentration (IC{sub 50}) value of 0.81 μM. The decay rate of Kv channel inactivation was accelerated by CGS 9343B. The rate constants of association and dissociation for CGS 9343B were 2.77 ± 0.04 μM{sup −1} s{sup −1} and 2.55 ± 1.50 s{sup −1}, respectively. CGS 9343B did not affect the steady-state activation curve, but shifted the inactivation curve toward to a more negative potential. Train pulses (1 or 2 Hz) application progressively increased the CGS 9343B-induced Kv channel inhibition. In addition, the inactivation recovery time constant was increased in the presence of CGS 9343B, suggesting that CGS 9343B-induced inhibition of Kv channel was use-dependent. Another calmodulin inhibitor, W-13, did not affect Kv currents, and did not change the inhibitory effect of CGS 9343B on Kv current. Our results demonstrated that CGS 9343B inhibited Kv currents in a state-, time-, and use-dependent manner, independent of calmodulin inhibition. - Highlights: • We investigated the effects of CGS 9394B on Kv channels. • CGS 9394B inhibited Kv current in a state-, time-, and use-dependent manner. • Caution is required when using CGS 9394B in vascular function studies.

  15. A ROS-Assisted Calcium Wave Dependent on the AtRBOHD NADPH Oxidase and TPC1 Cation Channel Propagates the Systemic Response to Salt Stress.

    Science.gov (United States)

    Evans, Matthew J; Choi, Won-Gyu; Gilroy, Simon; Morris, Richard J

    2016-07-01

    Plants exhibit rapid, systemic signaling systems that allow them to coordinate physiological and developmental responses throughout the plant body, even to highly localized and quickly changing environmental stresses. The propagation of these signals is thought to include processes ranging from electrical and hydraulic networks to waves of reactive oxygen species (ROS) and cytoplasmic Ca(2+) traveling throughout the plant. For the Ca(2+) wave system, the involvement of the vacuolar ion channel TWO PORE CHANNEL1 (TPC1) has been reported. However, the precise role of this channel and the mechanism of cell-to-cell propagation of the wave have remained largely undefined. Here, we use the fire-diffuse-fire model to analyze the behavior of a Ca(2+) wave originating from Ca(2+) release involving the TPC1 channel in Arabidopsis (Arabidopsis thaliana). We conclude that a Ca(2+) diffusion-dominated calcium-induced calcium-release mechanism is insufficient to explain the observed wave transmission speeds. The addition of a ROS-triggered element, however, is able to quantitatively reproduce the observed transmission characteristics. The treatment of roots with the ROS scavenger ascorbate and the NADPH oxidase inhibitor diphenyliodonium and analysis of Ca(2+) wave propagation in the Arabidopsis respiratory burst oxidase homolog D (AtrbohD) knockout background all led to reductions in Ca(2+) wave transmission speeds consistent with this model. Furthermore, imaging of extracellular ROS production revealed a systemic spread of ROS release that is dependent on both AtRBOHD and TPC1 These results suggest that, in the root, plant systemic signaling is supported by a ROS-assisted calcium-induced calcium-release mechanism intimately involving ROS production by AtRBOHD and Ca(2+) release dependent on the vacuolar channel TPC1. PMID:27261066

  16. A ROS-Assisted Calcium Wave Dependent on the AtRBOHD NADPH Oxidase and TPC1 Cation Channel Propagates the Systemic Response to Salt Stress1[OPEN

    Science.gov (United States)

    Evans, Matthew J.; Choi, Won-Gyu

    2016-01-01

    Plants exhibit rapid, systemic signaling systems that allow them to coordinate physiological and developmental responses throughout the plant body, even to highly localized and quickly changing environmental stresses. The propagation of these signals is thought to include processes ranging from electrical and hydraulic networks to waves of reactive oxygen species (ROS) and cytoplasmic Ca2+ traveling throughout the plant. For the Ca2+ wave system, the involvement of the vacuolar ion channel TWO PORE CHANNEL1 (TPC1) has been reported. However, the precise role of this channel and the mechanism of cell-to-cell propagation of the wave have remained largely undefined. Here, we use the fire-diffuse-fire model to analyze the behavior of a Ca2+ wave originating from Ca2+ release involving the TPC1 channel in Arabidopsis (Arabidopsis thaliana). We conclude that a Ca2+ diffusion-dominated calcium-induced calcium-release mechanism is insufficient to explain the observed wave transmission speeds. The addition of a ROS-triggered element, however, is able to quantitatively reproduce the observed transmission characteristics. The treatment of roots with the ROS scavenger ascorbate and the NADPH oxidase inhibitor diphenyliodonium and analysis of Ca2+ wave propagation in the Arabidopsis respiratory burst oxidase homolog D (AtrbohD) knockout background all led to reductions in Ca2+ wave transmission speeds consistent with this model. Furthermore, imaging of extracellular ROS production revealed a systemic spread of ROS release that is dependent on both AtRBOHD and TPC1. These results suggest that, in the root, plant systemic signaling is supported by a ROS-assisted calcium-induced calcium-release mechanism intimately involving ROS production by AtRBOHD and Ca2+ release dependent on the vacuolar channel TPC1. PMID:27261066

  17. Inhibition of Hyperpolarization-Activated Cation Current in Medium-Sized DRG Neurons Contributed to the Antiallodynic Effect of Methylcobalamin in the Rat of a Chronic Compression of the DRG

    Directory of Open Access Journals (Sweden)

    Ming Zhang

    2015-01-01

    Full Text Available Recently several lines of evidence demonstrated that methylcobalamin (MeCbl might have potential analgesic effect in experimental and clinical studies. However, it was reported that MeCbl had no effect on treating lumbar spinal stenosis induced pain. Thus, the effects of short-term and long-term administration of MeCbl were examined in the chronic compression of dorsal root ganglion (CCD model. We found that mechanical allodynia was significantly inhibited by a continuous application of high dose and a single treatment of a super high dose of MeCbl. Little is known about mechanisms underlying the analgesia of MeCbl. We examined the effect of MeCbl on the spontaneous activity (SA, the excitability, and hyperpolarization-activated nonselective cation ion current in compressed medium-sized dorsal root ganglion (DRG neurons using extracellular single fiber recording in vivo and whole-cell patch clamp in vitro. We found that MeCbl significantly inhibited the SA of A-type sensory neurons in a dose-dependent manner and inhibited the excitability of medium-sized DRG neurons. In addition, MeCbl also decreased Ih current density in injured medium-sized DRG neurons. Our results proved that MeCbl might exert an analgesic effect through the inhibition Ih current and then might inhibit the hyperexcitability of primary sensory neurons under neuropathic pain state.

  18. Inhibition of Hyperpolarization-Activated Cation Current in Medium-Sized DRG Neurons Contributed to the Antiallodynic Effect of Methylcobalamin in the Rat of a Chronic Compression of the DRG.

    Science.gov (United States)

    Zhang, Ming; Han, Wenjuan; Zheng, Jianyong; Meng, Fancheng; Jiao, Xiying; Hu, Sanjue; Xu, Hui

    2015-01-01

    Recently several lines of evidence demonstrated that methylcobalamin (MeCbl) might have potential analgesic effect in experimental and clinical studies. However, it was reported that MeCbl had no effect on treating lumbar spinal stenosis induced pain. Thus, the effects of short-term and long-term administration of MeCbl were examined in the chronic compression of dorsal root ganglion (CCD) model. We found that mechanical allodynia was significantly inhibited by a continuous application of high dose and a single treatment of a super high dose of MeCbl. Little is known about mechanisms underlying the analgesia of MeCbl. We examined the effect of MeCbl on the spontaneous activity (SA), the excitability, and hyperpolarization-activated nonselective cation ion current in compressed medium-sized dorsal root ganglion (DRG) neurons using extracellular single fiber recording in vivo and whole-cell patch clamp in vitro. We found that MeCbl significantly inhibited the SA of A-type sensory neurons in a dose-dependent manner and inhibited the excitability of medium-sized DRG neurons. In addition, MeCbl also decreased I h current density in injured medium-sized DRG neurons. Our results proved that MeCbl might exert an analgesic effect through the inhibition I h current and then might inhibit the hyperexcitability of primary sensory neurons under neuropathic pain state.

  19. Extracellular acid block and acid-enhanced inactivation of the Ca2+-activated cation channel TRPM5 involve residues in the S3-S4 and S5-S6 extracellular domains.

    Science.gov (United States)

    Liu, Dan; Zhang, Zheng; Liman, Emily R

    2005-05-27

    TRPM5, a member of the superfamily of transient receptor potential ion channels, is essential for the detection of bitter, sweet, and amino acid tastes. In heterologous cell types it forms a nonselective cation channel that is activated by intracellular Ca(2+). TRPM5 is likely to be part of the taste transduction cascade, and regulators of TRPM5 are likely to affect taste sensation. In this report we show that TRPM5, but not the related channel TRPM4b, is potently blocked by extracellular acidification. External acidification has two effects, a fast reversible block of the current (IC(50) pH = 6.2) and a slower irreversible enhancement of current inactivation. Mutation of a single Glu residue in the S3-S4 linker and a His residue in the pore region each reduced sensitivity of TRPM5 currents to fast acid block (IC(50) pH = 5.8 for both), and the double mutant was nearly insensitive to acidic pH (IC(50) pH = 5.0). Prolonged exposure to acidic pH enhanced inactivation of TRPM5 currents, and mutant channels that were less sensitive to acid block were also less sensitive to acid-enhanced inactivation, suggesting an intimate association between the two processes. These processes are, however, distinct because the pore mutant H896N, which has normal sensitivity to acid block, shows significant recovery from acid-enhanced inactivation. These data show that extracellular acidification acts through specific residues on TRPM5 to block conduction through two distinct but related mechanisms and suggest a possible interaction between extracellular pH and activation and adaptation of bitter, sweet, and amino acid taste transduction.

  20. Using blue whale (Balaenoptera musculus) photographic-identification sightings to assess potential vessel-whale encounters in the Santa Barbara Channel

    OpenAIRE

    Stingle, Kelli Faye

    2012-01-01

    In 2007 six blue whales (Balaenoptera musculus) were found dead in the Southern California Bight with four of the deaths resulting from vessel strikes. To reduce the spatial overlap of vessels and whales, the United States Coast Guard proposed shifting the southern Santa Barbara Channel shipping lane north by one nmi. We used sighting rate predictions from generalized additive models to assess potential vessel-whale encounters in the current and proposed traffic separation schemes. Sightings ...

  1. Calcitriol inhibits Ether-a go-go potassium channel expression and cell proliferation in human breast cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Becerra, Rocio [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Diaz, Lorenza, E-mail: lorenzadiaz@gmail.com [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Camacho, Javier [Department of Pharmacology, Centro de Investigacion y de Estudios Avanzados, Instituto Politecnico Nacional, Av. Instituto Politecnico Nacional 2508, San Pedro Zacatenco 07360, Mexico, D.F. (Mexico); Barrera, David; Ordaz-Rosado, David; Morales, Angelica [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Ortiz, Cindy Sharon [Department of Pathology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Avila, Euclides [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico); Bargallo, Enrique [Department of Breast Tumors, Instituto Nacional de Cancerologia, Av. San Fernando No. 22, Tlalpan 14080, Mexico, D.F. (Mexico); Arrecillas, Myrna [Department of Pathology, Instituto Nacional de Cancerologia, Av. San Fernando No. 22, Tlalpan 14080, Mexico, D.F. (Mexico); Halhali, Ali; Larrea, Fernando [Department of Reproductive Biology, Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran, Vasco de Quiroga No. 15, Tlalpan 14000 Mexico, D.F. (Mexico)

    2010-02-01

    Antiproliferative actions of calcitriol have been shown to occur in many cell types; however, little is known regarding the molecular basis of this process in breast carcinoma. Ether-a-go-go (Eag1) potassium channels promote oncogenesis and are implicated in breast cancer cell proliferation. Since calcitriol displays antineoplastic effects while Eag1 promotes tumorigenesis, and both factors antagonically regulate cell cycle progression, we investigated a possible regulatory effect of calcitriol upon Eag1 as a mean to uncover new molecular events involved in the antiproliferative activity of this hormone in human breast tumor-derived cells. RT real-time PCR and immunocytochemistry showed that calcitriol suppressed Eag1 expression by a vitamin D receptor (VDR)-dependent mechanism. This effect was accompanied by inhibition of cell proliferation, which was potentiated by astemizole, a nonspecific Eag1 inhibitor. Immunohistochemistry and Western blot demonstrated that Eag1 and VDR abundance was higher in invasive-ductal carcinoma than in fibroadenoma, and immunoreactivity of both proteins was located in ductal epithelial cells. Our results provide evidence of a novel mechanism involved in the antiproliferative effects of calcitriol and highlight VDR as a cancer therapeutic target for breast cancer treatment and prevention.

  2. Calcitriol inhibits Ether-a go-go potassium channel expression and cell proliferation in human breast cancer cells

    International Nuclear Information System (INIS)

    Antiproliferative actions of calcitriol have been shown to occur in many cell types; however, little is known regarding the molecular basis of this process in breast carcinoma. Ether-a-go-go (Eag1) potassium channels promote oncogenesis and are implicated in breast cancer cell proliferation. Since calcitriol displays antineoplastic effects while Eag1 promotes tumorigenesis, and both factors antagonically regulate cell cycle progression, we investigated a possible regulatory effect of calcitriol upon Eag1 as a mean to uncover new molecular events involved in the antiproliferative activity of this hormone in human breast tumor-derived cells. RT real-time PCR and immunocytochemistry showed that calcitriol suppressed Eag1 expression by a vitamin D receptor (VDR)-dependent mechanism. This effect was accompanied by inhibition of cell proliferation, which was potentiated by astemizole, a nonspecific Eag1 inhibitor. Immunohistochemistry and Western blot demonstrated that Eag1 and VDR abundance was higher in invasive-ductal carcinoma than in fibroadenoma, and immunoreactivity of both proteins was located in ductal epithelial cells. Our results provide evidence of a novel mechanism involved in the antiproliferative effects of calcitriol and highlight VDR as a cancer therapeutic target for breast cancer treatment and prevention.

  3. Calcitriol inhibits Ether-à go-go potassium channel expression and cell proliferation in human breast cancer cells.

    Science.gov (United States)

    García-Becerra, Rocío; Díaz, Lorenza; Camacho, Javier; Barrera, David; Ordaz-Rosado, David; Morales, Angélica; Ortiz, Cindy Sharon; Avila, Euclides; Bargallo, Enrique; Arrecillas, Myrna; Halhali, Ali; Larrea, Fernando

    2010-02-01

    Antiproliferative actions of calcitriol have been shown to occur in many cell types; however, little is known regarding the molecular basis of this process in breast carcinoma. Ether-à-go-go (Eag1) potassium channels promote oncogenesis and are implicated in breast cancer cell proliferation. Since calcitriol displays antineoplastic effects while Eag1 promotes tumorigenesis, and both factors antagonically regulate cell cycle progression, we investigated a possible regulatory effect of calcitriol upon Eag1 as a mean to uncover new molecular events involved in the antiproliferative activity of this hormone in human breast tumor-derived cells. RT real-time PCR and immunocytochemistry showed that calcitriol suppressed Eag1 expression by a vitamin D receptor (VDR)-dependent mechanism. This effect was accompanied by inhibition of cell proliferation, which was potentiated by astemizole, a nonspecific Eag1 inhibitor. Immunohistochemistry and Western blot demonstrated that Eag1 and VDR abundance was higher in invasive-ductal carcinoma than in fibroadenoma, and immunoreactivity of both proteins was located in ductal epithelial cells. Our results provide evidence of a novel mechanism involved in the antiproliferative effects of calcitriol and highlight VDR as a cancer therapeutic target for breast cancer treatment and prevention. PMID:19932096

  4. Sulfonation of 17{beta}-estradiol and inhibition of sulfotransferase activity by polychlorobiphenylols and celecoxib in channel catfish, Ictalurus punctatus

    Energy Technology Data Exchange (ETDEWEB)

    Wang Liquan [Department of Medicinal Chemistry, College of Pharmacy, University of Florida, Gainesville, FL 32610 (United States); James, Margaret O. [Department of Medicinal Chemistry, College of Pharmacy, University of Florida, Gainesville, FL 32610 (United States)]. E-mail: mojames@ufl.edu

    2007-03-10

    The sulfonation of 17{beta}-estradiol (E2) by human liver and recombinant sulfotransferases is influenced by environmental contaminants such as hydroxylated metabolites of polychlorinated biphenyls (OH-PCBs), which are potent inhibitors, and the therapeutic drug, celecoxib, which affects positional sulfonation of E2. In some locations, the aquatic environment is contaminated by PCBs, OH-PCBs and widely used therapeutic drugs. The objectives of this study were to investigate the sulfonation kinetics of E2 in liver cytosol from channel catfish (Ictalurus punctatus); to examine the effect of OH-PCBs on E2 sulfonation; and to determine if celecoxib altered the position of E2 sulfonation, as it does with human liver cytosol. E2 was converted to both 3- and 17-sulfates by catfish liver cytosol. At E2 concentrations below 1{mu}M, formation of E2-3-sulfate (E2-3-S) predominated, but substrate inhibition was observed at higher concentrations. Rates of E2-3-S formation at different E2 concentrations were fit to a substrate inhibition model, with K{sup '}{sub m} and V{sup '}{sub max} values of 0.40+/-0.10{mu}M and 91.0+/-4.7pmol/min/mg protein, respectively and K{sub i} of 1.08+/-0.09{mu}M. The formation of E2-17-S fit Michaelis-Menten kinetics over the concentration range 25nM to 2.5{mu}M, with K{sub m} and V{sub max} values of 1.07+/-0.23{mu}M and 25.7+/-4.43pmol/min/mg protein, respectively. The efficiency (V{sub max}/K{sub m}) of formation of E2-3-S was 9.8-fold higher than that of E2-17-S. Several OH-PCBs inhibited E2 3-sulfonation, measured at an E2 concentration of 1nM. Of those tested, the most potent inhibitor was 4'-OH-CB79, with two chlorine atoms flanking the OH group (IC{sub 50}: 94nM). The inhibition of estrogen sulfonation by OH-PCBs may disrupt the endocrine system and thus contribute to the known toxic effects of these compounds. Celecoxib did not stimulate E2-17-S formation, as is the case with human liver cytosol, but did inhibit the

  5. Inhibition of in vivo [(3)H]MK-801 binding by NMDA receptor open channel blockers and GluN2B antagonists in rats and mice.

    Science.gov (United States)

    Fernandes, Alda; Wojcik, Trevor; Baireddy, Praveena; Pieschl, Rick; Newton, Amy; Tian, Yuan; Hong, Yang; Bristow, Linda; Li, Yu-Wen

    2015-11-01

    N-methyl-D-aspartate (NMDA) receptor antagonists, including open channel blockers and GluN2B receptor subtype selective antagonists, have been developed for the treatment of depression. The current study investigated effects of systemically administered NMDA channel blockers and GluN2B receptor antagonists on NMDA receptor activity in rodents using in vivo [(3)H]MK-801 binding. The receptor occupancy of GluN2B antagonists was measured using ex vivo [(3)H]Ro 25-6981 binding. Ketamine, a NMDA receptor channel blocker, produced a dose/exposure- and time-dependent inhibition of in vivo [(3)H]MK-801 binding that was maximal at ~100%. The complete inhibition of in vivo [(3)H]MK-801 binding was also observed with NMDA receptor channel blockers, AZD6765 (Lanicemine) and MK-801 (Dizocilpine). CP-101,606 (Traxoprodil), a GluN2B antagonist, produced a dose/exposure- and time-dependent inhibition of in vivo [(3)H]MK-801 binding that was maximal at ~60%. Partial inhibition was also observed with other GluN2B antagonists including MK-0657 (CERC-301), EVT-101, Ro 25-6981 and radiprodil. For all GluN2B antagonists tested, partial [(3)H]MK-801 binding inhibition was achieved at doses saturating GluN2B receptor occupancy. Combined treatment with ketamine (10mg/kg, i.p.) and Ro 25-6981(10mg/kg, i.p.) produced a level of inhibition of in vivo [(3)H]MK-801 binding that was similar to treatment with either agent alone. In conclusion, this in vivo [(3)H]MK-801 binding study shows that NMDA receptor activity in the rodent forebrain can be inhibited completely by channel blockers, but only partially (~60%) by GluN2B receptor antagonists. At doses effective in preclinical models of depression, ketamine may preferentially inhibit the same population of NMDA receptors as Ro 25-6981, namely those containing the GluN2B subunit. PMID:26325093

  6. Anti-addiction drug ibogaine inhibits voltage-gated ionic currents: A study to assess the drug's cardiac ion channel profile

    International Nuclear Information System (INIS)

    The plant alkaloid ibogaine has promising anti-addictive properties. Albeit not licenced as a therapeutic drug, and despite hints that ibogaine may perturb the heart rhythm, this alkaloid is used to treat drug addicts. We have recently reported that ibogaine inhibits human ERG (hERG) potassium channels at concentrations similar to the drugs affinity for several of its known brain targets. Thereby the drug may disturb the heart's electrophysiology. Here, to assess the drug's cardiac ion channel profile in more detail, we studied the effects of ibogaine and its congener 18-Methoxycoronaridine (18-MC) on various cardiac voltage-gated ion channels. We confirmed that heterologously expressed hERG currents are reduced by ibogaine in low micromolar concentrations. Moreover, at higher concentrations, the drug also reduced human Nav1.5 sodium and Cav1.2 calcium currents. Ion currents were as well reduced by 18-MC, yet with diminished potency. Unexpectedly, although blocking hERG channels, ibogaine did not prolong the action potential (AP) in guinea pig cardiomyocytes at low micromolar concentrations. Higher concentrations (≥ 10 μM) even shortened the AP. These findings can be explained by the drug's calcium channel inhibition, which counteracts the AP-prolonging effect generated by hERG blockade. Implementation of ibogaine's inhibitory effects on human ion channels in a computer model of a ventricular cardiomyocyte, on the other hand, suggested that ibogaine does prolong the AP in the human heart. We conclude that therapeutic concentrations of ibogaine have the propensity to prolong the QT interval of the electrocardiogram in humans. In some cases this may lead to cardiac arrhythmias. - Highlights: • We study effects of anti-addiction drug ibogaine on ionic currents in cardiomyocytes. • We assess the cardiac ion channel profile of ibogaine. • Ibogaine inhibits hERG potassium, sodium and calcium channels. • Ibogaine’s effects on ion channels are a potential

  7. Anti-addiction drug ibogaine inhibits voltage-gated ionic currents: A study to assess the drug's cardiac ion channel profile

    Energy Technology Data Exchange (ETDEWEB)

    Koenig, Xaver; Kovar, Michael; Rubi, Lena; Mike, Agnes K.; Lukacs, Peter; Gawali, Vaibhavkumar S.; Todt, Hannes [Center for Physiology and Pharmacology, Department of Neurophysiology and -pharmacology, Medical University of Vienna, 1090 Vienna (Austria); Hilber, Karlheinz, E-mail: karlheinz.hilber@meduniwien.ac.at [Center for Physiology and Pharmacology, Department of Neurophysiology and -pharmacology, Medical University of Vienna, 1090 Vienna (Austria); Sandtner, Walter [Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090 Vienna (Austria)

    2013-12-01

    The plant alkaloid ibogaine has promising anti-addictive properties. Albeit not licenced as a therapeutic drug, and despite hints that ibogaine may perturb the heart rhythm, this alkaloid is used to treat drug addicts. We have recently reported that ibogaine inhibits human ERG (hERG) potassium channels at concentrations similar to the drugs affinity for several of its known brain targets. Thereby the drug may disturb the heart's electrophysiology. Here, to assess the drug's cardiac ion channel profile in more detail, we studied the effects of ibogaine and its congener 18-Methoxycoronaridine (18-MC) on various cardiac voltage-gated ion channels. We confirmed that heterologously expressed hERG currents are reduced by ibogaine in low micromolar concentrations. Moreover, at higher concentrations, the drug also reduced human Na{sub v}1.5 sodium and Ca{sub v}1.2 calcium currents. Ion currents were as well reduced by 18-MC, yet with diminished potency. Unexpectedly, although blocking hERG channels, ibogaine did not prolong the action potential (AP) in guinea pig cardiomyocytes at low micromolar concentrations. Higher concentrations (≥ 10 μM) even shortened the AP. These findings can be explained by the drug's calcium channel inhibition, which counteracts the AP-prolonging effect generated by hERG blockade. Implementation of ibogaine's inhibitory effects on human ion channels in a computer model of a ventricular cardiomyocyte, on the other hand, suggested that ibogaine does prolong the AP in the human heart. We conclude that therapeutic concentrations of ibogaine have the propensity to prolong the QT interval of the electrocardiogram in humans. In some cases this may lead to cardiac arrhythmias. - Highlights: • We study effects of anti-addiction drug ibogaine on ionic currents in cardiomyocytes. • We assess the cardiac ion channel profile of ibogaine. • Ibogaine inhibits hERG potassium, sodium and calcium channels. • Ibogaine’s effects on

  8. GABA/sub B/ receptor activation inhibits Ca/sup 2 +/-activated potassium channels in synaptosomes: involvement of G-proteins

    Energy Technology Data Exchange (ETDEWEB)

    Ticku, M.K.; Delgado, A.

    1989-01-01

    /sup 86/Rb-efflux assay from preloaded synaptosomes of rat cerebral cortex was developed to study the effect of GABA/sub B/ receptor agonist baclofen on Ca/sup 2 +/-activated K/sup +/-channels. Depolarization of /sup 86/Rb-loaded synaptosomes in physiological buffer increased Ca/sup 2 +/-activated /sup 86/Rb-efflux by 400%. The /sup 86/Rb-efflux was blocked by quinine sulfate, tetraethylammonium, and La/sup 3 +/ indicating the involvement of Ca/sup 2 +/-activated K/sup +/-channels. (-)Baclofen inhibited Ca/sup 2 +/-activated /sup 86/Rb-efflux in a stereospecific manner. The inhibitory effect of (-)baclofen was mediated by GABA/sub B/ receptor activation, since it was blocked by GABA/sub B/ antagonist phaclofen, but not by bicuculline. Further, pertussis toxin also blocked the ability of baclofen or depolarizing action to affect Ca/sup 2 +/-activated K/sup +/-channels. These results suggest that baclofen inhibits Ca/sup 2 +/-activated K/sup +/-channels in synaptosomes and these channels are regulated by G-proteins. This assay may provide an ideal in vitro model to study GABA/sub B/ receptor pharmacology.

  9. Transient receptor potential channels in essential hypertension

    DEFF Research Database (Denmark)

    Liu, Daoyan; Scholze, Alexandra; Zhu, Zhiming;

    2006-01-01

    The role of nonselective cation channels of the transient receptor potential channel (TRPC) family in essential hypertension has not yet been investigated.......The role of nonselective cation channels of the transient receptor potential channel (TRPC) family in essential hypertension has not yet been investigated....

  10. Anti-tumor Necrosis Factor Alpha (Infliximab) Attenuates Apoptosis, Oxidative Stress, and Calcium Ion Entry Through Modulation of Cation Channels in Neutrophils of Patients with Ankylosing Spondylitis.

    Science.gov (United States)

    Ugan, Yunus; Nazıroğlu, Mustafa; Şahin, Mehmet; Aykur, Mehmet

    2016-08-01

    Ankylosing Spondylitis (AS) is known to be associated with increased neutrophil activation and oxidative stress, however, the mechanism of neutrophil activation is still unclear. We have hypothesized that the antioxidant and anti-tumor necrosis factor properties of infliximab may affect intracellular Ca(2+) concentration in the neutrophils of AS patients. The objective of this study was to investigate the effects of infliximab on calcium signaling, oxidative stress, and apoptosis in neutrophils of AS patients. Neutrophils collected from ten patients with AS and ten healthy controls were used in the study. In a cell viability test, the ideal non-toxic dose and incubation time of infliximab were found as 100 μM and 1 h, respectively. In some experiments, the neutrophils were incubated with the voltage-gated calcium channel (VGCC) blockers verapamil + diltiazem (V + D) and the TRPM2 channel blocker 2-aminoethyl diphenylborinate (2-APB). Intracellular Ca(2+) concentration, lipid peroxidation, apoptosis, caspase 3, and caspase 9 values were high in neutrophils of AS patients and were reduced with infliximab treatment. Reduced glutathione level and glutathione peroxidase activity were low in the patients and increased with infliximab treatment. The intracellular Ca(2+) concentrations were low in 2-APB and V + D groups. In conclusion, the current study suggests that infliximab is useful against apoptotic cell death and oxidative stress in neutrophils of patients with AS, which seem to be dependent on increased levels of intracellular Ca(2+) through activation of TRPM2 and VGCC. PMID:26956056

  11. Cilnidipine, but not amlodipine, ameliorates osteoporosis in ovariectomized hypertensive rats through inhibition of the N-type calcium channel.

    Science.gov (United States)

    Shimizu, Hideo; Nakagami, Hironori; Yasumasa, Natsuki; Mariana, Osako Kiomy; Kyutoku, Mariko; Koriyama, Hiroshi; Nakagami, Futoshi; Shimamura, Munehisa; Rakugi, Hiromi; Morishita, Ryuichi

    2012-01-01

    Both osteoporosis and high blood pressure are major diseases in aging populations. Recent studies demonstrated that some antihypertensive drugs reduced the risk of bone fracture in elderly patients. Although calcium channel blockers (CCB) are widely used as first-line antihypertensive agents, there is no evidence that they prevent osteoporosis. In this study, we investigated the effects of two types of CCB on bone metabolism: cilnidipine (L-/N-type CCB), which suppresses norepinephrine release from the sympathetic nerve, and amlodipine (L-type CCB). In ovariectomized female spontaneous hypertensive rats, administration of cilnidipine, but not amlodipine, resulted in a significant increase in the ratio of alkaline phosphatase to tartrate-resistant acid phosphatase (TRAP) and a decrease in the number of osteoclasts, as assessed by TRAP staining in the proximal tibia. Bone mineral density, moreover, was significantly higher in the cilnidipine group as compared with the amlodipine group and was associated with a significant decrease in a urinary collagen degradation product (deoxypyridinoline). The degree of prevention of osteoporosis by cilnidipine was similar to that of carvedilol (a β-blocker) because β-blockers reduce fracture risks though the inhibition of osteoclast activation. Interestingly, these effects cannot be attributed to the reduction of blood pressure because all three drugs significantly decreased blood pressure. In contrast, both cilnidipine and carvedilol, but not amlodipine, significantly decreased heart rate, indicating that both cilnidipine and carvedilol suppressed sympathetic nervous activity. Overall, our present data showed that cilnidipine (L-/N-type CCB) ameliorated osteoporosis in ovariectomized hypertensive rats. These pleiotropic effects of antihypertensive drugs such as cilnidipine and carvedilol might provide additional benefits in the treatment of hypertensive postmenopausal women.

  12. Calcium Occupancy of N-terminal Sites within Calmodulin Induces Inhibition of the Ryanodine Receptor Calcium Release Channel

    Energy Technology Data Exchange (ETDEWEB)

    Boschek, Curt B; Jones, Terry E; Squier, Thomas C; Bigelow, Diana J

    2007-08-01

    Calmodulin (CaM) regulates calcium release from intracellular stores in skeletal muscle through its association with the ryanodine receptor (RyR1) calcium release channel, where CaM association enhances channel opening at resting calcium levels and its closing at micromolar calcium levels associated with muscle contraction. A high-affinity CaM-binding sequence (RyRp) has been identified in RyR1, which corresponds to a 30-residue sequence (i.e., K3614 – N3643) located within the central portion of the primary sequence. However, it is currently unclear whether the identified CaM-binding sequence a) senses calcium over the physiological range of calcium-concentrations associated with RyR1 regulation or b) plays a structural role unrelated to the calcium-dependent modulation of RyR1 function. Therefore, we have measured the calcium-dependent activation of the individual domains of CaM in association with RyRp and their relationship to the CaM-dependent regulation of RyR1. These measurements utilize an engineered CaM, permitting the site-specific incorporation of N-(1-pyrene) maleimide at either T34C (PyN-CaM) or T110C (PyC-CaM) in the N- and C-domains, respectively. Consistent with prior measurements, we observe a high-affinity association between both apo- and calcium-activated CaM and RyRp. Upon association with RyRp, fluorescence changes in PyN-CaM or PyC-CaM permit the measurement of the calcium-activation of these individual domains. Fluorescence changes upon calcium-activation of PyC-CaM in association with RyRp are indicative of high-affinity calcium-dependent activation of the C-terminal domain of CaM bound to RyRp at resting calcium levels and the activation of the N-terminal domain at levels of calcium associated cellular activation. In comparison, occupancy of calcium-binding sites in the N-domain of CaM mirrors the calcium-dependence of RyR1 inhibition observed at activating calcium levels, where [Ca]1/2 = 4.3 0.4 μM, suggesting a direct regulation of Ry

  13. Gramicidin Channels: Versatile Tools

    Science.gov (United States)

    Andersen, Olaf S.; Koeppe, Roger E., II; Roux, Benoît

    Gramicidin channels are miniproteins in which two tryptophan-rich subunits associate by means of transbilayer dimerization to form the conducting channels. That is, in contrast to other ion channels, gramicidin channels do not open and close; they appear and disappear. Each subunit in the bilayer-spanning channel is tied to the bilayer/solution interface through hydrogen bonds that involve the indole NH groups as donors andwater or the phospholipid backbone as acceptors. The channel's permeability characteristics are well-defined: gramicidin channels are selective for monovalent cations, with no measurable permeability to anions or polyvalent cations; ions and water move through a pore whose wall is formed by the peptide backbone; and the single-channel conductance and cation selectivity vary when the amino acid sequence is varied, even though the permeating ions make no contact with the amino acid side chains. Given the plethora of available experimental information—for not only the wild-type channels but also for channels formed by amino acid-substituted gramicidin analogues—gramicidin channels continue to provide important insights into the microphysics of ion permeation through bilayer-spanning channels. For similar reasons, gramicidin channels constitute a system of choice for evaluating computational strategies for obtaining mechanistic insights into ion permeation through the more complex channels formed by integral membrane proteins.

  14. Ginsenoside Rb1 selectively inhibits the activity of L-type voltage-gated calcium channels in cultured rat hippocampal neurons

    Institute of Scientific and Technical Information of China (English)

    Zhi-ying LIN; Li-min CHEN; Jing ZHANG; Xiao-dong PAN; Yuan-gui ZHU; Qin-yong YE; Hua-pin HUANG; Xiao-chun CHEN

    2012-01-01

    Aim:To investigate the effect of ginsenoside Rb1 on voltage-gated calcium currents in cultured rat hippocampal neurons and the modulatory mechanism.Methods:Cultured hippocampal neurons were prepared from Sprague Dawley rat embryos.Whole-cell configuration of the patchclamp technique was used to record the voltage-gated calcium currents (VGCCs)from the hippocampal neurons,and the effect of Rb1 was examined.Results:Rb1 (2-100 μmol/L)inhibited VGCCs in a concentration-dependent manner,and the current was mostly recovered upon wash-out.The specific L-type Ca2+ channel inhibitor nifedipine (10 μmol/L)occluded Rb1-induced inhibition on VGCCs.Neither the selective N-type Ca2+ channel blocker ω-conotoxin-GVlA (1 μmoVL),nor the selective P/Q-type Ca2+ channel blocker ωo-agatoxin IVA (30 nmol/L)diminished Rb1-sensitive VGCCs.Rb1 induced a leftward shift of the steady-state inactivation curve of Ica to a negative potential without affecting its activation kinetics or reversal potential in the I-V curve.The inhibitory effect of Rb1 was neither abolished by the adenylyl cyclase activator forskolin (10 μmol/L),nor by the PKA inhibitor H-89 (10 μmol/L).Conclusion:Ginsenoside Rb1 selectively inhibits the activity of L-type voltage-gated calcium channels,without affecting the N-type or P/Q-type Ca2+ channels in hippocampal neurons,cAMP-PKA signaling pathway is not involved in this effect.

  15. The Drosophila TRPP cation channel, PKD2 and Dmel/Ced-12 act in genetically distinct pathways during apoptotic cell clearance.

    Directory of Open Access Journals (Sweden)

    Emeline Van Goethem

    Full Text Available Apoptosis, a genetically programmed cell death, allows for homeostasis and tissue remodelling during development of all multi-cellular organisms. Phagocytes swiftly recognize, engulf and digest apoptotic cells. Yet, to date the molecular mechanisms underlying this phagocytic process are still poorly understood. To delineate the molecular mechanisms of apoptotic cell clearance in Drosophila, we have carried out a deficiency screen and have identified three overlapping phagocytosis-defective mutants, which all delete the fly homologue of the ced-12 gene, known as Dmel\\ced12. As anticipated, we have found that Dmel\\ced-12 is required for apoptotic cell clearance, as for its C. elegans and mammalian homologues, ced-12 and elmo, respectively. However, the loss of Dmel\\ced-12 did not solely account for the phenotypes of all three deficiencies, as zygotic mutations and germ line clones of Dmel\\ced-12 exhibited weaker phenotypes. Using a nearby genetically interacting deficiency, we have found that the polycystic kidney disease 2 gene, pkd2, which encodes a member of the TRPP channel family, is also required for phagocytosis of apoptotic cells, thereby demonstrating a novel role for PKD2 in this process. We have also observed genetic interactions between pkd2, simu, drpr, rya-r44F, and retinophilin (rtp, also known as undertaker (uta, a gene encoding a MORN-repeat containing molecule, which we have recently found to be implicated in calcium homeostasis during phagocytosis. However, we have not found any genetic interaction between Dmel\\ced-12 and simu. Based on these genetic interactions and recent reports demonstrating a role for the mammalian pkd-2 gene product in ER calcium release during store-operated calcium entry, we propose that PKD2 functions in the DRPR/RTP pathway to regulate calcium homeostasis during this process. Similarly to its C. elegans homologue, Dmel\\Ced-12 appears to function in a genetically distinct pathway.

  16. p-Trifluoromethyldiazirinyl-etomidate: a potent photoreactive general anesthetic derivative of etomidate that is selective for ligand-gated cationic ion channels.

    Science.gov (United States)

    Husain, S Shaukat; Stewart, Deirdre; Desai, Rooma; Hamouda, Ayman K; Li, S Guo-Dong; Kelly, Elizabeth; Dostalova, Zuzana; Zhou, Xiaojuan; Cotten, Joseph F; Raines, Douglas E; Olsen, Richard W; Cohen, Jonathan B; Forman, Stuart A; Miller, Keith W

    2010-09-01

    We synthesized the R- and S-enantiomers of ethyl 1-(1-(4-(3-((trifluoromethyl)-3H-diazirin-3-yl)phenyl)ethyl)-1H-imidazole-5-carboxylate (trifluoromethyldiazirinyl-etomidate), or TFD-etomidate, a novel photoactivable derivative of the stereoselective general anesthetic etomidate (R-(2-ethyl 1-(phenylethyl)-1H-imidazole-5-carboxylate)). Anesthetic potency was similar to etomidate's, but stereoselectivity was reversed and attenuated. Relative to etomidate, TFD-etomidate was a more potent inhibitor of the excitatory receptors, nAChR (nicotinic acetylcholine receptor) ((alpha1)(2)beta1delta1gamma1) and 5-HT(3A)R (serotonin type 3A receptor), causing significant inhibition at anesthetic concentrations. S- but not R-TFD-etomidate enhanced currents elicited from inhibitory alpha1beta2gamma2L GABA(A)Rs by low concentrations of GABA, but with a lower efficacy than R-etomidate, and site-directed mutagenesis suggests they act at different sites. [(3)H]TFD-etomidate photolabeled the alpha-subunit of the nAChR in a manner allosterically regulated by agonists and noncompetitive inhibitors. TFD-etomidate's novel pharmacology is unlike that of etomidate derivatives with photoactivable groups in the ester position, which behave like etomidate, suggesting that it will further enhance our understanding of anesthetic mechanisms. PMID:20704351

  17. Inhibition of SK4 Potassium Channels Suppresses Cell Proliferation, Migration and the Epithelial-Mesenchymal Transition in Triple-Negative Breast Cancer Cells.

    Directory of Open Access Journals (Sweden)

    Panshi Zhang

    Full Text Available Treatments for triple-negative breast cancer (TNBC are limited; intermediate-conductance calcium-activated potassium (SK4 channels are closely involved in tumor progression, but little is known about these channels in TNBC. We aimed to investigate whether SK4 channels affect TNBC. First, by immunohistochemistry (IHC and western blotting (WB, increased SK4 protein expression in breast tumor tissues was detected relative to that in non-tumor breast tissues, but there was no apparent expression difference between various subtypes of breast cancer (p>0.05. Next, functional SK4 channels were detected in the TNBC cell line MDA-MB-231 using WB, real-time PCR, immunofluorescence and patch-clamp recording. By employing SK4 specific siRNAs and blockers, including TRAM-34 and clotrimazole, in combination with an MTT assay, a colony-formation assay, flow cytometry and a cell motility assay, we found that the suppression of SK4 channels significantly inhibited cell proliferation and migration and promoted apoptosis in MDA-MB-231 cells (p<0.05. Further investigation revealed that treatment with epidermal growth factor (EGF/basic fibroblast growth factor (bFGF caused MDA-MB-231 cells to undergo the epithelial-mesenchymal transition (EMT and to show increased SK4 mRNA expression. In addition, the down-regulation of SK4 expression inhibited the EMT markers Vimentin and Snail1. Collectively, our findings suggest that SK4 channels are expressed in TNBC and are involved in the proliferation, apoptosis, migration and EMT processes of TNBC cells.

  18. Inhibition of collagen synthesis by select calcium and sodium channel blockers can be mitigated by ascorbic acid and ascorbyl palmitate

    OpenAIRE

    Ivanov, Vadim; Ivanova, Svetlana; KALINOVSKY, TATIANA; NIEDZWIECKI, ALEKSANDRA; RATH, MATTHIAS

    2016-01-01

    Calcium, sodium and potassium channel blockers are widely prescribed medications for a variety of health problems, most frequently for cardiac arrhythmias, hypertension, angina pectoris and other disorders. However, chronic application of channel blockers is associated with numerous side effects, including worsening cardiac pathology. For example, nifedipine, a calcium-channel blocker was found to be associated with increased mortality and increased risk for myocardial infarction. In addition...

  19. Berberine Reduces cAMP-Induced Chloride Secretion in T84 Human Colonic Carcinoma Cells through Inhibition of Basolateral KCNQ1 Channels.

    LENUS (Irish Health Repository)

    Alzamora, Rodrigo

    2012-02-01

    Berberine is a plant alkaloid with multiple pharmacological actions, including antidiarrhoeal activity and has been shown to inhibit Cl(-) secretion in distal colon. The aims of this study were to determine the molecular signaling mechanisms of action of berberine on Cl(-) secretion and the ion transporter targets. Monolayers of T84 human colonic carcinoma cells grown in permeable supports were placed in Ussing chambers and short-circuit current measured in response to secretagogues and berberine. Whole-cell current recordings were performed in T84 cells using the patch-clamp technique. Berberine decreased forskolin-induced short-circuit current in a concentration-dependent manner (IC(50) 80 +\\/- 8 muM). In apically permeabilized monolayers and whole-cell current recordings, berberine inhibited a cAMP-dependent and chromanol 293B-sensitive basolateral membrane K(+) current by 88%, suggesting inhibition of KCNQ1 K(+) channels. Berberine did not affect either apical Cl(-) conductance or basolateral Na(+)-K(+)-ATPase activity. Berberine stimulated p38 MAPK, PKCalpha and PKA, but had no effect on p42\\/p44 MAPK and PKCdelta. However, berberine pre-treatment prevented stimulation of p42\\/p44 MAPK by epidermal growth factor. The inhibitory effect of berberine on Cl(-) secretion was partially blocked by HBDDE ( approximately 65%), an inhibitor of PKCalpha and to a smaller extent by inhibition of p38 MAPK with SB202190 ( approximately 15%). Berberine treatment induced an increase in association between PKCalpha and PKA with KCNQ1 and produced phosphorylation of the channel. We conclude that berberine exerts its inhibitory effect on colonic Cl(-) secretion through inhibition of basolateral KCNQ1 channels responsible for K(+) recycling via a PKCalpha-dependent pathway.

  20. Berberine Reduces cAMP-Induced Chloride Secretion in T84 Human Colonic Carcinoma Cells through Inhibition of Basolateral KCNQ1 Channels.

    LENUS (Irish Health Repository)

    Alzamora, Rodrigo

    2011-01-01

    Berberine is a plant alkaloid with multiple pharmacological actions, including antidiarrhoeal activity and has been shown to inhibit Cl(-) secretion in distal colon. The aims of this study were to determine the molecular signaling mechanisms of action of berberine on Cl(-) secretion and the ion transporter targets. Monolayers of T84 human colonic carcinoma cells grown in permeable supports were placed in Ussing chambers and short-circuit current measured in response to secretagogues and berberine. Whole-cell current recordings were performed in T84 cells using the patch-clamp technique. Berberine decreased forskolin-induced short-circuit current in a concentration-dependent manner (IC(50) 80 ± 8 μM). In apically permeabilized monolayers and whole-cell current recordings, berberine inhibited a cAMP-dependent and chromanol 293B-sensitive basolateral membrane K(+) current by 88%, suggesting inhibition of KCNQ1 K(+) channels. Berberine did not affect either apical Cl(-) conductance or basolateral Na(+)-K(+)-ATPase activity. Berberine stimulated p38 MAPK, PKCα and PKA, but had no effect on p42\\/p44 MAPK and PKCδ. However, berberine pre-treatment prevented stimulation of p42\\/p44 MAPK by epidermal growth factor. The inhibitory effect of berberine on Cl(-) secretion was partially blocked by HBDDE (∼65%), an inhibitor of PKCα and to a smaller extent by inhibition of p38 MAPK with SB202190 (∼15%). Berberine treatment induced an increase in association between PKCα and PKA with KCNQ1 and produced phosphorylation of the channel. We conclude that berberine exerts its inhibitory effect on colonic Cl(-) secretion through inhibition of basolateral KCNQ1 channels responsible for K(+) recycling via a PKCα-dependent pathway.

  1. Synergistic antiarrhythmic effect of combining inhibition of Ca(2+)-activated K(+) (SK) channels and voltage-gated Na(+) channels in an isolated heart model of atrial fibrillation

    DEFF Research Database (Denmark)

    Kirchhoff, Jeppe Egedal; Goldin Diness, Jonas; Sheykhzade, Majid;

    2015-01-01

    would be subefficacious as monotherapy, may prevent atrial fibrillation (AF) and have reduced proarrhythmic potential in the ventricles. METHODS: Subefficacious concentrations of ranolazine, flecainide, and lidocaine were tested alone or in combination with the SK channel blocker N-(pyridin-2-yl)-4...

  2. Ghrelin inhibits proliferation and increases T-type Ca{sup 2+} channel expression in PC-3 human prostate carcinoma cells

    Energy Technology Data Exchange (ETDEWEB)

    Diaz-Lezama, Nundehui; Hernandez-Elvira, Mariana [Laboratory of Neuroendocrinology, Institute of Physiology, Autonomous University of Puebla (BUAP), Puebla (Mexico); Sandoval, Alejandro [School of Medicine FES Iztacala, National Autonomous University of Mexico (UNAM), Tlalnepantla (Mexico); Monroy, Alma; Felix, Ricardo [Department of Cell Biology, Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav-IPN), Mexico City (Mexico); Monjaraz, Eduardo, E-mail: emguzman@siu.buap.mx [Laboratory of Neuroendocrinology, Institute of Physiology, Autonomous University of Puebla (BUAP), Puebla (Mexico)

    2010-12-03

    Research highlights: {yields} Ghrelin decreases prostate carcinoma PC-3 cells proliferation. {yields} Ghrelin favors apoptosis in PC-3 cells. {yields} Ghrelin increase in intracellular free Ca{sup 2+} levels in PC-3 cells. {yields} Grelin up-regulates expression of T-type Ca{sup 2+} channels in PC-3 cells. {yields} PC-3 cells express T-channels of the Ca{sub V}3.1 and Ca{sub V}3.2 subtype. -- Abstract: Ghrelin is a multifunctional peptide hormone with roles in growth hormone release, food intake and cell proliferation. With ghrelin now recognized as important in neoplastic processes, the aim of this report is to present findings from a series of in vitro studies evaluating the cellular mechanisms involved in ghrelin regulation of proliferation in the PC-3 human prostate carcinoma cells. The results showed that ghrelin significantly decreased proliferation and induced apoptosis. Consistent with a role in apoptosis, an increase in intracellular free Ca{sup 2+} levels was observed in the ghrelin-treated cells, which was accompanied by up-regulated expression of T-type voltage-gated Ca{sup 2+} channels. Interestingly, T-channel antagonists were able to prevent the effects of ghrelin on cell proliferation. These results suggest that ghrelin inhibits proliferation and may promote apoptosis by regulating T-type Ca{sup 2+} channel expression.

  3. Molecular basis of the inhibition of the fast inactivation of voltage-gated sodium channel Nav1.5 by tarantula toxin Jingzhaotoxin-II.

    Science.gov (United States)

    Huang, Ying; Zhou, Xi; Tang, Cheng; Zhang, Yunxiao; Tao, Huai; Chen, Ping; Liu, Zhonghua

    2015-06-01

    Jingzhaotoxin-II (JZTX-II) is a 32-residue peptide from the Chinese tarantula Chilobrachys jingzhao venom, and preferentially inhibits the fast inactivation of the voltage-gated sodium channels (VGSCs) in rat cardiac myocytes. In the present study, we elucidated the action mechanism of JZTX-II inhibiting hNav1.5, a VGSC subtype mainly distributed in human cardiac myocytes. Among the four VGSC subtypes tested, hNav1.5 was the most sensitive to JZTX-II (EC50=125±4nM). Although JZTX-II had little or no effect on steady-state inactivation of the residual currents conducted by hNav1.5, it caused a 10mV hyperpolarized shift of activation. Moreover, JZTX-II increased the recovery rate of hNav1.5 channels, which should lead to a shorter transition from the inactivation to closed state. JZTX-II dissociated from toxin-channel complex via extreme depolarization and subsequently rebound to the channel upon repolarization. Mutagenesis analyses showed that the domain IV (DIV) voltage-sensor domain (VSD) was critical for JZTX-II binding to hNav1.5 and some mutations located in S1-S2 and S3-S4 extracellular loops of hNav1.5 DIV additively reduced the toxin sensitivity of hNav1.5. Our data identified the mechanism underlying JZTX-II inhibiting hNav1.5, similar to scorpion α-toxins, involving binding to neurotoxin receptor site 3. PMID:25817910

  4. A mechanism for the auto-inhibition of hyperpolarization-activated cyclic nucleotide-gated (HCN) channel opening and its relief by cAMP.

    Science.gov (United States)

    Akimoto, Madoka; Zhang, Zaiyong; Boulton, Stephen; Selvaratnam, Rajeevan; VanSchouwen, Bryan; Gloyd, Melanie; Accili, Eric A; Lange, Oliver F; Melacini, Giuseppe

    2014-08-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels control neuronal and cardiac electrical rhythmicity. There are four homologous isoforms (HCN1-4) sharing a common multidomain architecture that includes an N-terminal transmembrane tetrameric ion channel followed by a cytoplasmic "C-linker," which connects a more distal cAMP-binding domain (CBD) to the inner pore. Channel opening is primarily stimulated by transmembrane elements that sense membrane hyperpolarization, although cAMP reduces the voltage required for HCN activation by promoting tetramerization of the intracellular C-linker, which in turn relieves auto-inhibition of the inner pore gate. Although binding of cAMP has been proposed to relieve auto-inhibition by affecting the structure of the C-linker and CBD, the nature and extent of these cAMP-dependent changes remain limitedly explored. Here, we used NMR to probe the changes caused by the binding of cAMP and of cCMP, a partial agonist, to the apo-CBD of HCN4. Our data indicate that the CBD exists in a dynamic two-state equilibrium, whose position as gauged by NMR chemical shifts correlates with the V½ voltage measured through electrophysiology. In the absence of cAMP, the most populated CBD state leads to steric clashes with the activated or "tetrameric" C-linker, which becomes energetically unfavored. The steric clashes of the apo tetramer are eliminated either by cAMP binding, which selects for a CBD state devoid of steric clashes with the tetrameric C-linker and facilitates channel opening, or by a transition of apo-HCN to monomers or dimer of dimers, in which the C-linker becomes less structured, and channel opening is not facilitated.

  5. Inhibitive effect of Ce(III) and La(III) cations for AA2219 aluminium alloy corrosion in sodium chloride medium

    Energy Technology Data Exchange (ETDEWEB)

    Venkatasubramanian, G., E-mail: venkatguru_1966@yahoo.co.in [Department of Chemistry, Sathyabama University, Jeppiaar Nagar, Chennai 600119 (India); Sheik Mideen, A. [Department of Chemistry, Sathyabama University, Jeppiaar Nagar, Chennai 600119 (India); Jha, Abhay K. [Materials Processing Division, Vikram Sarabhai Space Centre, Indian Space Research Organisation, Thiruvananthapuram 695022 (India); Kulandainathan, M. Anbu [Electro Organic Chemistry Division, Central Electrochemical Research Institute, Karaikudi 630006 (India)

    2014-11-14

    In this paper, the rare earth chlorides were used to mitigate the dealloying of Al{sub 2}Cu intermetallic particles in aluminium alloy 2219-T87 plate exposed to 0.6 M NaCl solution. The negative shift of cathodic branches of potentiodynamic polarisation curves revealed the cathodic inhibition towards intermetallic dealloying. The low and high frequency time constants obtained from electrochemical impedance spectra revealed an increase in the corrosion resistance due to precipitation of rare earth oxides/hydroxides on the porous surface of native oxide film of aluminium alloy. Scanning electron microscopy coupled with energy dispersive X-ray analysis and atomic force microscopy revealed that intermetallic inclusions are the sites for the formation of cerium and lanthanum deposits which suppress copper redeposition and minimise galvanic interactions between the matrix and Al{sub 2}Cu particles. - Graphical abstract: Scanning electron microscopy and atomic force microscopy reveal the intermetallic inclusions, the sites for the formation of cerium and lanthanum oxide/hydroxide precipitates which prevent intermetallic de-alloying, suppress copper redeposition and minimise galvanic interactions in aluminium alloy 2219-T87 plate. - Highlights: • Ce{sup 3+} and La{sup 3+} act as cathodic inhibitors for AA2219-T87 aluminium alloy in 0.6 M NaCl. • Al{sub 2}Cu intermetallic particles are the sites for the formation of Ce and La precipitates. • The decrease in surface potential by rare earth chlorides confirms their inhibition.

  6. Inhibitive effect of Ce(III) and La(III) cations for AA2219 aluminium alloy corrosion in sodium chloride medium

    International Nuclear Information System (INIS)

    In this paper, the rare earth chlorides were used to mitigate the dealloying of Al2Cu intermetallic particles in aluminium alloy 2219-T87 plate exposed to 0.6 M NaCl solution. The negative shift of cathodic branches of potentiodynamic polarisation curves revealed the cathodic inhibition towards intermetallic dealloying. The low and high frequency time constants obtained from electrochemical impedance spectra revealed an increase in the corrosion resistance due to precipitation of rare earth oxides/hydroxides on the porous surface of native oxide film of aluminium alloy. Scanning electron microscopy coupled with energy dispersive X-ray analysis and atomic force microscopy revealed that intermetallic inclusions are the sites for the formation of cerium and lanthanum deposits which suppress copper redeposition and minimise galvanic interactions between the matrix and Al2Cu particles. - Graphical abstract: Scanning electron microscopy and atomic force microscopy reveal the intermetallic inclusions, the sites for the formation of cerium and lanthanum oxide/hydroxide precipitates which prevent intermetallic de-alloying, suppress copper redeposition and minimise galvanic interactions in aluminium alloy 2219-T87 plate. - Highlights: • Ce3+ and La3+ act as cathodic inhibitors for AA2219-T87 aluminium alloy in 0.6 M NaCl. • Al2Cu intermetallic particles are the sites for the formation of Ce and La precipitates. • The decrease in surface potential by rare earth chlorides confirms their inhibition

  7. Selective inhibition of the Kir2 family of inward rectifier potassium channels by a small molecule probe: the discovery, SAR and pharmacological characterization of ML133

    Science.gov (United States)

    Wang, Hao-Ran; Wu, Meng; Yu, Haibo; Long, Shunyou; Stevens, Amy; Engers, Darren W.; Sackin, Henry; Daniels, J. Scott; Dawson, Eric S.; Hopkins, Corey R.; Lindsley, Craig W.; Li, Min; McManus, Owen B

    2011-01-01

    The Kir inward rectifying potassium channels have a broad tissue distribution and are implicated in a variety of functional roles. At least seven classes (Kir1 – Kir7) of structurally related inward rectifier potassium channels are known, and there are no selective small molecule tools to study their function. In an effort to develop selective Kir2.1 inhibitors, we performed a high-throughput screen (HTS) of more than 300,000 small molecules within the MLPCN for modulators of Kir2.1 function. Here we report one potent Kir2.1 inhibitor, ML133, which inhibits Kir2.1 with IC50 of 1.8 μM at pH 7.4 and 290 nM at pH 8.5, but exhibits little selectivity against other members of Kir2.x family channels. However, ML133 has no effect on Kir1.1 (IC50 > 300 μM), and displays weak activity for Kir4.1 (76 μM) and Kir7.1 (33 μM), making ML133 the most selective small molecule inhibitor of the Kir family reported to date. Due to the high homology within the Kir family, the channels share a common design of a pore region flanked by two transmembrane domains, identification of site(s) critical for isoform specificity would be an important basis for future development of more specific and potent Kir inhibitors. Using chimeric channels between Kir2.1 and Kir1.1 and site-directed mutagenesis, we have identified D172 and I176 within M2 segment of Kir2.1 as molecular determinants critical for the potency of ML133 mediated inhibition. Double mutation of the corresponding residues of Kir1.1 to those of Kir2.1 (N171D and C175I) transplants ML133 inhibition to Kir1.1. Together, the combination of a potent, Kir2 family selective inhibitor and identification of molecular determinants for the specificity provides both a tool and a model system to enable further mechanistic studies of modulation of Kir2 inward rectifier potassium channels. PMID:21615117

  8. A distinct three-helix centipede toxin SSD609 inhibits I(ks) channels by interacting with the KCNE1 auxiliary subunit.

    Science.gov (United States)

    Sun, Peibei; Wu, Fangming; Wen, Ming; Yang, Xingwang; Wang, Chenyang; Li, Yiming; He, Shufang; Zhang, Longhua; Zhang, Yun; Tian, Changlin

    2015-01-01

    KCNE1 is a single-span transmembrane auxiliary protein that modulates the voltage-gated potassium channel KCNQ1. The KCNQ1/KCNE1 complex in cardiomyocytes exhibited slow activated potassium (I(ks)) currents. Recently, a novel 47-residue polypeptide toxin SSD609 was purified from Scolopendra subspinipes dehaani venom and showed I(ks) current inhibition. Here, chemically synthesized SSD609 was shown to exert I(ks) inhibition in extracted guinea pig cardiomyocytes and KCNQ1/KCNE1 current attenuation in CHO cells. The K(+) current attenuation of SSD609 showed decent selectivity among different auxiliary subunits. Solution nuclear magnetic resonance analysis of SSD609 revealed a distinctive three-helix conformation that was stabilized by a new disulfide bonding pattern as well as segregated surface charge distribution. Structure-activity studies demonstrated that negatively charged Glu19 in the amphipathic extracellular helix of KCNE1 was the key residue that interacted with SSD609. The distinctive three-helix centipede toxin SSD609 is known to be the first polypeptide toxin acting on channel auxiliary subunit KCNE1, which suggests a new type of pharmacological regulation for ion channels in cardiomyocytes. PMID:26307551

  9. Lutein inhibits the function of the transient receptor potential A1 ion channel in different in vitro and in vivo models.

    Science.gov (United States)

    Horváth, Györgyi; Szoke, Éva; Kemény, Ágnes; Bagoly, Teréz; Deli, József; Szente, Lajos; Pál, Szilárd; Sándor, Katalin; Szolcsányi, János; Helyes, Zsuzsanna

    2012-01-01

    Transient receptor potential (TRP) ion channels, such as TRP vanilloid 1 and ankyrin repeat domain 1 (TRPV1 and TRPA1), are expressed on primary sensory neurons. Lutein, a natural tetraterpene carotenoid, can be incorporated into membranes and might modulate TRP channels. Therefore, the effects of the water-soluble randomly methylated-β-cyclodextrin (RAMEB) complex of lutein were investigated on TRPV1 and TRPA1 activation. RAMEB-lutein (100 μM) significantly diminished Ca(2+) influx to cultured rat trigeminal neurons induced by TRPA1 activation with mustard oil, but not by TRPV1 stimulation with capsaicin, as determined with microfluorimetry. Calcitonin gene-related peptide release from afferents of isolated tracheae evoked by mustard oil, but not by capsaicin, was inhibited by RAMEB-lutein. Mustard oil-induced neurogenic mouse ear swelling was also significantly decreased by 100 μg/ml s.c. RAMEB-lutein pretreatment, while capsaicin-evoked edema was not altered. Myeloperoxidase activity indicating non-neurogenic granulocyte accumulation in the ear was not influenced by RAMEB-lutein in either case. It is concluded that lutein inhibits TRPA1, but not TRPV1 stimulation-induced responses on cell bodies and peripheral terminals of sensory neurons in vitro and in vivo. Based on these distinct actions and the carotenoid structure, the ability of lutein to modulate lipid rafts in the membrane around TRP channels can be suggested.

  10. 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

  11. The transient receptor potential vanilloid 2 cation channel is abundant in macrophages accumulating at the peri-infarct zone and may enhance their migration capacity towards injured cardiomyocytes following myocardial infarction.

    Directory of Open Access Journals (Sweden)

    Michal Entin-Meer

    Full Text Available PURPOSE: A novel family of transient receptor potential (TRP channels, that may hold a role in calcium homeostasis, has recently been described. By employing a GeneChip array analysis we have demonstrated a clear and specific upregulation of the TRP vanilloid 2 (TRPV2 mRNA in the left ventricles (LV 3-5 days post-acute myocardial infarction (MI compared to sham-operated controls, both in rats and in mice. We sought to characterize the cardiac cellular subpopulations in which TRPV2 is overexpressed upon acute MI. METHODS: Lewis rats underwent an acute MI by ligation of the left anterior descending artery or chest opening only (sham. The animals were terminated at various time points and an immunohistochemical (IHC and immunofluorescent (IFC staining of the LV sections as well as a flow cytometry analysis of LV-derived cells were carried out, using anti-TRPV2 and anti-monocyte/macrophage antibodies. Rat alveolar macrophage cells, NR8383, transiently transfected with TRPV2 siRNA were allowed to migrate towards hypoxic conditioned media of the rat cardiac myoblast line H9C2 using a trans-well migration assay. The macrophage cells migrating to the bottom side of the inserts were counted. RESULTS: The IHC and IFC staining as well as the flow cytometry data demonstrated a substantial expression of TRPV2 in infiltrating macrophages in the peri-infarct region 3-5 days post-acute MI. The in vitro migration assay data demonstrated that following inhibition of the TRPV2 channel, the number of migrating macrophages towards conditioned medium of hypoxic cardiomyocytes was significantly reduced. CONCLUSIONS: TRPV2 is highly expressed on the peri-infarct infiltrating macrophages and may play an important role in post-MI phagocytosis. Better characterization of this channel may pave the way for identifying a new target for modulating the dramatic post-MI immune reactions.

  12. Cloned delta-opioid receptors in GH(3) cells inhibit spontaneous Ca(2+) oscillations and prolactin release through K(IR) channel activation.

    Science.gov (United States)

    Piros, E T; Charles, R C; Song, L; Evans, C J; Hales, T G

    2000-05-01

    Opioid receptors can couple to K(+) and Ca(2+) channels, adenylyl cyclase, and phosphatidyl inositol turnover. Any of these actions may be important in the regulation of neurotransmitter and hormone release from excitable cells. GH(3) cells exhibit spontaneous oscillations of intracellular Ca(2+) concentration ([Ca(2+)](i)) and prolactin release. Activation of cloned delta-opioid receptors stably expressed in GH(3) cells inhibits both spontaneous Ca(2+) signaling and basal prolactin release. The objective of this study was to examine a possible role for K(+) channels in these processes using the patch-clamp technique, fluorescence imaging, and a sensitive ELISA for prolactin. The selective delta receptor agonist [D-Pen(2), D-Pen(2)]enkephalin (DPDPE) inhibited [Ca(2+)](i) oscillations in GH(3) cells expressing both mu and delta receptors (GH(3)MORDOR cells) but had no effect on control GH(3) cells or cells expressing mu receptors alone (GH(3)MOR cells). The inhibition of [Ca(2+)](i) oscillations by DPDPE was unaffected by thapsigargin pretreatment, suggesting that this effect is independent of inositol 1,4,5-triphosphate-sensitive Ca(2+) stores. DPDPE caused a concentration-dependent inhibition of prolactin release from GH(3)MORDOR cells with an IC(50) of 4 nM. DPDPE increased inward K(+) current recorded from GH(3)MORDOR cells but had no significant effect on K(+) currents recorded from control GH(3) cells or GH(3)MOR cells. The mu receptor agonist morphine also had no effect on currents recorded from control cells but activated inward K(+) currents recorded from GH(3)MOR and GH(3)MORDOR cells. Somatostatin activated inward currents recorded from all three cell lines. The DPDPE-sensitive K(+) current was inwardly rectifying and was inhibited by Ba(2+) but not TEA. DPDPE had no effect on delayed rectifier-, Ca(2+)-, and voltage-activated or A-type K(+) currents, recorded from GH(3)MORDOR cells. Ba(2+) attenuated the inhibition of [Ca(2+)](i) and prolactin release

  13. Inhibition of Voltage-Gated Calcium Channels After Subchronic and Repeated Exposure of PC12 Cells to Different Classes of Insecticides.

    Science.gov (United States)

    Meijer, Marieke; Brandsema, Joske A R; Nieuwenhuis, Desirée; Wijnolts, Fiona M J; Dingemans, Milou M L; Westerink, Remco H S

    2015-10-01

    We previously demonstrated that acute inhibition of voltage-gated calcium channels (VGCCs) is a common mode of action for (sub)micromolar concentrations of chemicals, including insecticides. However, because human exposure to chemicals is usually chronic and repeated, we investigated if selected insecticides from different chemical classes (organochlorines, organophosphates, pyrethroids, carbamates, and neonicotinoids) also disturb calcium homeostasis after subchronic (24 h) exposure and after a subsequent (repeated) acute exposure. Effects on calcium homeostasis were investigated with single-cell fluorescence (Fura-2) imaging of PC12 cells. Cells were depolarized with high-K(+) saline to study effects of subchronic or repeated exposure on VGCC-mediated Ca(2+) influx. The results demonstrate that except for carbaryl and imidacloprid, all selected insecticides inhibited depolarization (K(+))-evoked Ca(2+) influx after subchronic exposure (IC50's: approximately 1-10 µM) in PC12 cells. These inhibitory effects were not or only slowly reversible. Moreover, repeated exposure augmented the inhibition of the K(+)-evoked increase in intracellular calcium concentration induced by subchronic exposure to cypermethrin, chlorpyrifos, chlorpyrifos-oxon, and endosulfan (IC50's: approximately 0.1-4 µM). In rat primary cortical cultures, acute and repeated chlorpyrifos exposure also augmented inhibition of VGCCs compared with subchronic exposure. In conclusion, compared with subchronic exposure, repeated exposure increases the potency of insecticides to inhibit VGCCs. However, the potency of insecticides to inhibit VGCCs upon repeated exposure was comparable with the inhibition previously observed following acute exposure, with the exception of chlorpyrifos. The data suggest that an acute exposure paradigm is sufficient for screening chemicals for effects on VGCCs and that PC12 cells are a sensitive model for detection of effects on VGCCs.

  14. Inhibition of Schistosoma mansoni ether-a-go-go related gene-encoded potassium channels leads to hypermotility and impaired egg production.

    Science.gov (United States)

    Parker-Manuel, S J; Hahnel, S; Grevelding, C G

    2015-11-01

    The purpose of this work was to investigate the effect of ether-a-go-go related gene (ERG) potassium channel inhibition on Schistosoma mansoni. Use of dofetilide to block the schistosome ERGs resulted in a striking 'corkscrew' effect. The worms were unable to control their motility; they were hypermotile. The treated worms produced abnormal eggs, some of which consisted of little more than a spine. One of the S. mansoni ERGs (SmERGs), Smp_161140, was chosen for further study by RNAi. The transcript was knocked down to 50% compared to the controls. These RNAi-treated worms demonstrated seizure-like movements. In S. mansoni, as in other organisms, ERG channels seem to play a role in regulating muscle excitability. This work shows that egg production can be greatly reduced by effectively targeting muscle coordination in these important parasites. PMID:26188142

  15. Combined hERG channel inhibition and disruption of trafficking in drug-induced long QT syndrome by fluoxetine: a case-study in cardiac safety pharmacology

    OpenAIRE

    Hancox, J. C.; Mitcheson, J S

    2006-01-01

    Drug-induced prolongation of the rate-corrected QT interval (QTCI) on the electrocardiogram occurs as an unwanted effect of diverse clinical and investigational drugs and carries a risk of potentially fatal cardiac arrhythmias. hERG (human ether-à-go-go-related gene) is the gene encoding the α-subunit of channels mediating the rapid delayed rectifier K+ current, which plays a vital role in repolarising the ventricles of the heart. Most QTCI prolonging drugs can inhibit the function of recombi...

  16. Apelin-13 inhibits large-conductance Ca2+-activated K+ channels in cerebral artery smooth muscle cells via a PI3-kinase dependent mechanism.

    Directory of Open Access Journals (Sweden)

    Amit Modgil

    Full Text Available Apelin-13 causes vasoconstriction by acting directly on APJ receptors in vascular smooth muscle (VSM cells; however, the ionic mechanisms underlying this action at the cellular level remain unclear. Large-conductance Ca(2+-activated K(+ (BKCa channels in VSM cells are critical regulators of membrane potential and vascular tone. In the present study, we examined the effect of apelin-13 on BK(Ca channel activity in VSM cells, freshly isolated from rat middle cerebral arteries. In whole-cell patch clamp mode, apelin-13 (0.001-1 μM caused concentration-dependent inhibition of BK(Ca in VSM cells. Apelin-13 (0.1 µM significantly decreased BK(Ca current density from 71.25 ± 8.14 pA/pF to 44.52 ± 7.10 pA/pF (n=14 cells, P<0.05. This inhibitory effect of apelin-13 was confirmed by single channel recording in cell-attached patches, in which extracellular application of apelin-13 (0.1 µM decreased the open-state probability (NPo of BK(Ca channels in freshly isolated VSM cells. However, in inside-out patches, extracellular application of apelin-13 (0.1 µM did not alter the NPo of BK(Ca channels, suggesting that the inhibitory effect of apelin-13 on BKCa is not mediated by a direct action on BK(Ca. In whole cell patches, pretreatment of VSM cells with LY-294002, a PI3-kinase inhibitor, markedly attenuated the apelin-13-induced decrease in BK(Ca current density. In addition, treatment of arteries with apelin-13 (0.1 µM significantly increased the ratio of phosphorylated-Akt/total Akt, indicating that apelin-13 significantly increases PI3-kinase activity. Taken together, the data suggest that apelin-13 inhibits BK(Ca channel via a PI3-kinase-dependent signaling pathway in cerebral artery VSM cells, which may contribute to its regulatory action in the control of vascular tone.

  17. CACNA1H(M1549V) Mutant Calcium Channel Causes Autonomous Aldosterone Production in HAC15 Cells and Is Inhibited by Mibefradil.

    Science.gov (United States)

    Reimer, Esther N; Walenda, Gudrun; Seidel, Eric; Scholl, Ute I

    2016-08-01

    We recently demonstrated that a recurrent gain-of-function mutation in a T-type calcium channel, CACNA1H(M1549V), causes a novel Mendelian disorder featuring early-onset primary aldosteronism and hypertension. This variant was found independently in five families. CACNA1H(M1549V) leads to impaired channel inactivation and activation at more hyperpolarized potentials, inferred to cause increased calcium entry. We here aimed to study the effect of this variant on aldosterone production. We heterologously expressed empty vector, CACNA1H(WT) and CACNA1H(M1549V) in the aldosterone-producing adrenocortical cancer cell line H295R and its subclone HAC15. Transfection rates, expression levels, and subcellular distribution of the channel were similar between CACNA1H(WT) and CACNA1H(M1549V). We measured aldosterone production by an ELISA and CYP11B2 (aldosterone synthase) expression by real-time PCR. In unstimulated cells, transfection of CACNA1H(WT) led to a 2-fold increase in aldosterone levels compared with vector-transfected cells. Expression of CACNA1H(M1549V) caused a 7-fold increase in aldosterone levels. Treatment with angiotensin II or increased extracellular potassium levels further stimulated aldosterone production in both CACNA1H(WT)- and CACNA1H(M1549V)-transfected cells. Similar results were obtained for CYP11B2 expression. Inhibition of CACNA1H channels with the T-type calcium channel blocker Mibefradil completely abrogated the effects of CACNA1H(WT) and CACNA1H(M1549V) on CYP11B2 expression. These results directly link CACNA1H(M1549V) to increased aldosterone production. They suggest that calcium channel blockers may be beneficial in the treatment of a subset of patients with primary aldosteronism. Such blockers could target CACNA1H or both CACNA1H and the L-type calcium channel CACNA1D that is also expressed in the adrenal gland and mutated in patients with primary aldosteronism. PMID:27258646

  18. Inhibition of Nav1.7 channels by methyl eugenol as a mechanism underlying its antinociceptive and anesthetic actions

    OpenAIRE

    Wang, Ze-Jun; Tabakoff, Boris; Levinson, Simon R.; Heinbockel, Thomas

    2015-01-01

    Aim: Methyl eugenol is a major active component extracted from the Chinese herb Asari Radix et Rhizoma, which has been used to treat toothache and other pain. Previous in vivo studies have shown that methyl eugenol has anesthetic and antinociceptive effects. The aim of this study was to determine the possible mechanism underlying its effect on nervous system disorders. Methods: The direct interaction of methyl eugenol with Na+ channels was explored and characterized using electrophysiological...

  19. Bile Acids Acutely Stimulate Insulin Secretion of Mouse β-Cells via Farnesoid X Receptor Activation and KATP Channel Inhibition

    OpenAIRE

    Düfer, Martina; Hörth, Katrin; Wagner, Rebecca; Schittenhelm, Björn; Prowald, Susanne; Wagner, Thomas F. J.; Oberwinkler, Johannes; Lukowski, Robert; Gonzalez, Frank J.; Krippeit-Drews, Peter; Drews, Gisela

    2012-01-01

    Type 2 diabetes mellitus is associated with alterations in bile acid (BA) signaling. The aim of our study was to test whether pancreatic β-cells contribute to BA-dependent regulation of glucose homeostasis. Experiments were performed with islets from wild-type, farnesoid X receptor (FXR) knockout (KO), and β-cell ATP-dependent K+ (KATP) channel gene SUR1 (ABCC8) KO mice, respectively. Sodium taurochenodeoxycholate (TCDC) increased glucose-induced insulin secretion. This effect was mimicked by...

  20. Inhibition of the K+ channel K(Ca3.1 reduces TGF-β1-induced premature senescence, myofibroblast phenotype transition and proliferation of mesangial cells.

    Directory of Open Access Journals (Sweden)

    Rong-Guo Fu

    Full Text Available OBJECTIVE: K(Ca3.1 channel participates in many important cellular functions. This study planned to investigate the potential involvement of K(Ca3.1 channel in premature senescence, myofibroblast phenotype transition and proliferation of mesangial cells. METHODS & MATERIALS: Rat mesangial cells were cultured together with TGF-β1 (2 ng/ml and TGF-β1 (2 ng/ml + TRAM-34 (16 nM separately for specified times from 0 min to 60 min. The cells without treatment served as controls. The location of K(Ca3.1 channels in mesangial cells was determined with Confocal laser microscope, the cell cycle of mesangial cells was assessed with flow cytometry, the protein and mRNA expression of K(Ca3.1, α-smooth muscle actin (α-SMA and fibroblast-specific protein-1 (FSP-1 were detected with Western blot and RT-PCR. One-way analysis of variance (ANOVA and Student-Newman-Keuls-q test (SNK-q were used to do statistical analysis. Statistical significance was considered at P<0.05. RESULTS: Kca3.1 channels were located in the cell membranes and/or in the cytoplasm of mesangial cells. The percentage of cells in G0-G1 phase and the expression of K(ca3.1, α-SMA and FSP-1 were elevated under the induction of TGF-β1 when compared to the control and decreased under the induction of TGF-β1+TRAM-34 when compared to the TGF-β1 induced (P<0.05 or P<0.01. CONCLUSION: Targeted disruption of K(Ca3.1 inhibits TGF-β1-induced premature aging, myofibroblast-like phenotype transdifferentiation and proliferation of mesangial cells.

  1. Two new octahedral/pyramidal frameworks containing both cation channels and lone-pair channels: syntheses and structures of Ba2MnIIMn2III(SeO3)6 and PbFe2(SeO3)4

    International Nuclear Information System (INIS)

    The hydrothermal syntheses, single crystal structures, and some properties of Ba2MnIIMn2III(SeO3)6 and PbFe2(SeO3)4 are reported. These related phases contain three-dimensional frameworks of vertex (FeO6) and vertex/edge linked (MnO6) octahedra and SeO3 pyramids. In each case, the MO6/SeO3 framework encloses two types of 8 ring channels, one of which encapsulates the extra-framework cations and one of which provides space for the SeIV lone pairs. Crystal data: Ba2Mn3(SeO3)6, Mr=1201.22, monoclinic, P21/c (No. 14), a=5.4717 (3)A, b=9.0636 (4)A, c=17.6586 (9)A, β=94.519 (1)o, V=873.03 (8)A3, Z=2, R(F)=0.031, wR(F2)=0.070; PbFe2(SeO3)4, Mr=826.73, triclinic, P1-bar (No. 2), a=5.2318 (5)A, b=6.7925 (6)A, c=7.6445 (7)A, α=94.300 (2)o, β=90.613 (2)o, γ=95.224 (2)o, V=269.73 (4)A3, Z=1, R(F)=0.051, wR(F2)=0.131

  2. Silencing of Kv4.1 potassium channels inhibits cell proliferation of tumorigenic human mammary epithelial cells

    International Nuclear Information System (INIS)

    Potassium channel activity has been shown to facilitate cell proliferation in cancer cells. In the present study, the role of Kv4.1 channels in immortal and tumorigenic human mammary epithelial cells was investigated. Kv4.1 protein expression was positively correlated with tumorigenicity. Moreover, transfection with siRNAs targeting Kv4.1 mRNA suppressed proliferation of tumorigenic mammary epithelial cells. Experiments using mRNA isolated from human breast cancer tissues revealed that the level of Kv4.1 mRNA expression varied depending on the stage of the tumor. Kv4.1 protein expression increased during stages T2 and T3 compared to normal tissue. These results demonstrated that Kv4.1 plays a role in proliferation of tumorigenic human mammary epithelial cells. In addition, elevated Kv4.1 expression may be useful as a diagnostic marker for staging mammary tumors and selective blockers of Kv4.1 may serve to suppress tumor cell proliferation.

  3. IgG anti-GalNAc-GD1a antibody inhibits the voltage-dependent calcium channel currents in PC12 pheochromocytoma cells.

    Science.gov (United States)

    Nakatani, Yoshihiko; Nagaoka, Takumi; Hotta, Sayako; Utsunomiya, Iku; Yoshino, Hiide; Miyatake, Tadashi; Hoshi, Keiko; Taguchi, Kyoji

    2007-03-01

    We investigated the effects of IgG anti-GalNAc-GD1a antibodies, produced by immunizing rabbits with GalNAc-GD1a, on the voltage-dependent calcium channel (VDCCs) currents in nerve growth factor (NGF)-differentiated PC12 pheochromocytoma cells. VDCCs currents in NGF-differentiated PC12 cells were recorded using the whole-cell patch-clamp technique. Immunized rabbit serum that had a high titer of anti-GalNAc-GD1a antibodies inhibited the VDCCs currents in the NGF-differentiated PC12 cells (36.0+/-9.6% reduction). The inhibitory effect of this serum was reversed to some degree within 3-4 min by washing with bath solution. Similarly, application of purified IgG from rabbit serum immunized with GalNAc-GD1a significantly inhibited the VDCCs currents in PC12 cells (30.6+/-2.5% reduction), and this inhibition was recovered by washing with bath solution. Furthermore, the inhibitory effect was also observed in the GalNAc-GD1a affinity column binding fraction (reduction of 31.1+/-9.85%), while the GalNAc-GD1a affinity column pass-through fraction attenuated the inhibitory effect on VDCCs currents. Normal rabbit serum and normal rabbit IgG did not affect the VDCCs currents in the PC12 cells. In an immunocytochemical study using fluorescence staining, the PC12 cells were stained using GalNAc-GD1a binding fraction. These results indicate that anti-GalNAc-GD1a antibodies inhibit the VDCCs currents in NGF-differentiated PC12 cells.

  4. Activation of delta-opioid receptors inhibits neuronal-like calcium channels and distal steps of Ca(2+)-dependent secretion in human small-cell lung carcinoma cells.

    Science.gov (United States)

    Sher, E; Cesare, P; Codignola, A; Clementi, F; Tarroni, P; Pollo, A; Magnelli, V; Carbone, E

    1996-06-01

    Human small-cell lung carcinoma (SCLC) cells express neuronal-like voltage-operated calcium channels (VOCCs) and release mitogenic hormones such as serotonin (5-HT). Opioid peptides, on the other hand, have been shown to reduce SCLC cell proliferation by an effective autocrine pathway. Here we show that in GLC8 SCLC cells, only delta-opioid receptor subtype mRNA is expressed. Consistently, the selective delta-opioid agonist [D-Pen2-Pen5]-enkephalin (DPDPE), but not mu and kappa agonists, potently and dose-dependently inhibits high-threshold (HVA) VOCCs in these cells. As in peripheral neurons, this modulation is largely voltage-dependent, mediated by pertussis toxin (PTX)-sensitive G-proteins, cAMP-independent, and mainly affecting N-type VOCCs. With the same potency and selectivity, DPDPE also antagonizes the Ca(2+)-dependent release of [3H]serotonin ([3H]5-HT) from GLC8 cells. However, DPDPE inhibits not only the depolarization-induced release, but also the Ca(2+)-dependent secretion induced by thapsigargin or ionomycin. This suggests that besides inhibiting HVA VOCCs, opioids also exert a direct depressive action on the secretory apparatus in GLC8 cells. This latter effect also is mediated by a PTX-sensitive G-protein but, contrary to VOCC inhibition, it can be reversed by elevations of cAMP levels. These results show for the first time that opioids effectively depress both Ca2+ influx and Ca(2+)-dependent hormone release in SCLC cells by using multiple modulatory pathways. It can be speculated that the two mechanisms may contribute to the opioid antimitogenic action on lung neuroendocrine carcinoma cells. PMID:8642411

  5. Poly(ethylene glycol-cholesterol inhibits L-type Ca2+ channel currents and augments voltage-dependent inactivation in A7r5 cells.

    Directory of Open Access Journals (Sweden)

    Rikuo Ochi

    Full Text Available Cholesterol distributes at a high density in the membrane lipid raft and modulates ion channel currents. Poly(ethylene glycol cholesteryl ether (PEG-cholesterol is a nonionic amphipathic lipid consisting of lipophilic cholesterol and covalently bound hydrophilic PEG. PEG-cholesterol is used to formulate lipoplexes to transfect cultured cells, and liposomes for encapsulated drug delivery. PEG-cholesterol is dissolved in the external leaflet of the lipid bilayer, and expands it to flatten the caveolae and widen the gap between the two leaflets. We studied the effect of PEG-cholesterol on whole cell L-type Ca(2+ channel currents (I(Ca,L recorded from cultured A7r5 arterial smooth muscle cells. The pretreatment of cells with PEG-cholesterol decreased the density of ICa,L and augmented the voltage-dependent inactivation with acceleration of time course of inactivation and negative shift of steady-state inactivation curve. Methyl-β-cyclodextrin (MβCD is a cholesterol-binding oligosaccharide. The enrichment of cholesterol by the MβCD:cholesterol complex (cholesterol (MβCD caused inhibition of I(Ca,L but did not augment voltage-dependent inactivation. Incubation with MβCD increased I(Ca,L, slowed the time course of inactivation and shifted the inactivation curve to a positive direction. Additional pretreatment by a high concentration of MβCD of the cells initially pretreated with PEG-cholesterol, increased I(Ca,L to a greater level than the control, and removed the augmented voltage-dependent inactivation. Due to the enhancement of the voltage-dependent inactivation, PEG-cholesterol inhibited window I(Ca,L more strongly as compared with cholesterol (MβCD. Poly(ethylene glycol conferred to cholesterol the efficacy to induce sustained augmentation of voltage-dependent inactivation of I(Ca,L.

  6. Inhibition of TRPA1 channel activity in sensory neurons by the glial cell line-derived neurotrophic factor family member, artemin

    Directory of Open Access Journals (Sweden)

    Wang Shenglan

    2011-05-01

    Full Text Available Abstract Background The transient receptor potential (TRP channel subtype A1 (TRPA1 is known to be expressed on sensory neurons and respond to changes in temperature, pH and local application of certain noxious chemicals such as allyl isothiocyanate (AITC. Artemin is a neuronal survival and differentiation factor and belongs to the glial cell line-derived neurotrophic factor (GDNF family. Both TRPA1 and artemin have been reported to be involved in pathological pain initiation and maintenance. In the present study, using whole-cell patch clamp recording technique, in situ hybridization and behavioral analyses, we examined the functional interaction between TRPA1 and artemin. Results We found that 85.8 ± 1.9% of TRPA1-expressing neurons also expressed GDNF family receptor alpha 3 (GFR α3, and 87.5 ± 4.1% of GFRα3-expressing neurons were TRPA1-positive. In whole-cell patch clamp analysis, a short-term treatment of 100 ng/ml artemin significantly suppressed the AITC-induced TRPA1 currents. A concentration-response curve of AITC resulting from the effect of artemin showed that this inhibition did not change EC50 but did lower the AITC-induced maximum response. In addition, pre-treatment of artemin significantly suppressed the number of paw lifts induced by intraplantar injection of AITC, as well as the formalin-induced pain behaviors. Conclusions These findings that a short-term application of artemin inhibits the TRPA1 channel's activity and the sequential pain behaviors suggest a role of artemin in regulation of sensory neurons.

  7. Vitamin K3 inhibits mouse uterine contraction in vitro via interference with the calcium transfer and the potassium channels.

    Science.gov (United States)

    Zhang, Xian-Xia; Lu, Li-Min; Wang, Li

    2016-08-01

    Previous studies have demonstrated vitamin K3 had a great relief to smooth muscle spastic disorders, but no researches have yet pinpointed its possible anti-contractile activity in the uterus. Here, we evaluated the effect of vitamin K3 on myometrial contractility and explored the possible mechanisms of vitamin K3 action. Myograph apparatus were used to record the changes in contractility of isolated mouse uterine strips in a tissue bath. Uterine strips were exposed to vitamin K3 or vehicle. Vitamin K3 suppressed spontaneous contractions in a concentration dependent manner. It significantly decreased the contractile frequency induced by PGF2ɑ but not their amplitude (expect 58.0 μM). Prior incubation with vitamin K3 reduced the effectiveness of PGF2ɑ-induced contraction. The antispasmodic effect of vitamin K3 was also sensitive to potassium channel blockers, such as tetraethylammonium, 4-aminopyridine, iberiotoxin) but not to the nitric oxide related pathway blockers. High concentrations (29.0, 58.0 μM) of vitamin K3 weakened the Ca(2+) dose response and inhibited phase 1 contraction (intracellular stored calcium release). These dates suggest that vitamin K3 specifically suppresses myometrial contractility by affecting calcium and potassium channels; thus, this approach has potential therapy for uterine contractile activity related disorders. PMID:27237971

  8. NEUROSCIENCE. Natural light-gated anion channels: A family of microbial rhodopsins for advanced optogenetics.

    Science.gov (United States)

    Govorunova, Elena G; Sineshchekov, Oleg A; Janz, Roger; Liu, Xiaoqin; Spudich, John L

    2015-08-01

    Light-gated rhodopsin cation channels from chlorophyte algae have transformed neuroscience research through their use as membrane-depolarizing optogenetic tools for targeted photoactivation of neuron firing. Photosuppression of neuronal action potentials has been limited by the lack of equally efficient tools for membrane hyperpolarization. We describe anion channel rhodopsins (ACRs), a family of light-gated anion channels from cryptophyte algae that provide highly sensitive and efficient membrane hyperpolarization and neuronal silencing through light-gated chloride conduction. ACRs strictly conducted anions, completely excluding protons and larger cations, and hyperpolarized the membrane of cultured animal cells with much faster kinetics at less than one-thousandth of the light intensity required by the most efficient currently available optogenetic proteins. Natural ACRs provide optogenetic inhibition tools with unprecedented light sensitivity and temporal precision.

  9. Hyaluronan Export through Plasma Membranes Depends on Concurrent K+ Efflux by Kir Channels

    OpenAIRE

    Daniel Hagenfeld; Beatrice Borkenhagen; Tobias Schulz; Hermann Schillers; Udo Schumacher; Peter Prehm

    2012-01-01

    Hyaluronan is synthesized within the cytoplasm and exported into the extracellular matrix through the cell membrane of fibroblasts by the MRP5 transporter. In order to meet the law of electroneutrality, a cation is required to neutralize the emerging negative hyaluronan charges. As we previously observed an inhibiting of hyaluronan export by inhibitors of K(+) channels, hyaluronan export was now analysed by simultaneously measuring membrane potential in the presence of drugs. This was done by...

  10. Inhibition of cell proliferation by a selective inhibitor of the Ca{sup 2+}-activated Cl{sup -} channel, Ano1

    Energy Technology Data Exchange (ETDEWEB)

    Mazzone, Amelia; Eisenman, Seth T.; Strege, Peter R. [Enteric NeuroScience Program, Mayo Clinic, Rochester, MN (United States); Yao, Zhen [Laboratory of Molecular Genetics, UCSF, San Francisco, CA (United States); Ordog, Tamas; Gibbons, Simon J. [Enteric NeuroScience Program, Mayo Clinic, Rochester, MN (United States); Farrugia, Gianrico, E-mail: farrugia.gianrico@mayo.edu [Enteric NeuroScience Program, Mayo Clinic, Rochester, MN (United States)

    2012-10-19

    Highlights: Black-Right-Pointing-Pointer T16A{sub inh}-A01 blocked Ano1 currents in HEK cells expressing Ano1. Black-Right-Pointing-Pointer T16A{sub inh}-A01 reduced proliferation in ICC primary cultures and CFPAC-1 cell line. Black-Right-Pointing-Pointer T16A{sub inh}-A01 reduced proliferation of ICC in intact smooth muscle strips. -- Abstract: Background: Ion channels play important roles in regulation of cellular proliferation. Ano1 (TMEM16A) is a Ca{sup 2+}-activated Cl{sup -} channel expressed in several tumors and cell types. In the muscle layers of the gastrointestinal tract Ano1 is selectively expressed in interstitial cells of Cajal (ICC) and appears to be required for normal gastrointestinal slow wave electrical activity. However, Ano1 is expressed in all classes of ICC, including those that do not generate slow waves suggesting that Ano1 may have other functions. Indeed, a role for Ano1 in regulating proliferation of tumors and ICC has been recently suggested. Recently, a high-throughput screen identified a small molecule, T16A{sub inh}-A01 as a specific inhibitor of Ano1. Aim: To investigate the effect of the T16A{sub inh}-A01 inhibitor on proliferation in ICC and in the Ano1-expressing human pancreatic cancer cell line CFPAC-1. Methods: Inhibition of Ano1 was demonstrated by whole cell voltage clamp recordings of currents in cells transfected with full-length human Ano1. The effect of T16A{sub inh}-A01 on ICC proliferation was examined in situ in organotypic cultures of intact mouse small intestinal smooth muscle strips and in primary cell cultures prepared from these tissues. ICC were identified by Kit immunoreactivity. Proliferating ICC and CFPAC-1 cells were identified by immunoreactivity for the nuclear antigen Ki67 or EdU incorporation, respectively. Results: T16A{sub inh}-A01 inhibited Ca{sup 2+}-activated Cl{sup -} currents by 60% at 10 {mu}M in a voltage-independent fashion. Proliferation of ICC was significantly reduced in primary cultures

  11. Negative impact of AQP-4 channel inhibition on survival of retinal ganglion cells and glutamate metabolism after crushing optic nerve.

    Science.gov (United States)

    Nishikawa, Yuko; Oku, Hidehiro; Morishita, Seita; Horie, Taeko; Kida, Teruyo; Mimura, Masashi; Fukumoto, Masanori; Kojima, Shota; Ikeda, Tsunehiko

    2016-05-01

    The purpose of this study was to determine whether inhibition of aquaporin 4 (AQP4) is neuroprotective or neurodestructive after crushing the optic nerve of rats. The left optic nerves of rats were crushed, and TGN-020 (5.0 mg/kg, crush TGN-020) or its vehicle (DMSO, crush placebo) was injected intraperitoneally just after the crushing. As controls, the left optic nerves were exposed but not touched in other rats (sham controls). The retinal damages were determined by the density of retinal ganglion cells (RGCs) and the ratio of BAX/Bcl-2 on day 7. The glutamate level in the optic nerve on day 1 after the crushing was determined. The expressions of glutamine synthetase, glutamate-aspartate transporter (GLAST), and AQP4 were determined on day 3 by immunoblotting. The effects of AQP4 inhibition on the glutamate-induced changes of AQP4 expression and on the glutamate uptake were determined for optic nerve astrocytes in culture. The results showed that the density of RGCs was 2040 ± 91.3 cells/mm(2) (n = 6) in the sham control, and it was significantly decreased to 1072 ± 134.3 cells/mm(2) after crushing the optic nerve (P crush placebo, n = 7; Fisher). An intraperitoneal injection of TGN-020 led to a further significant (P = 0.02, Fisher) decrease of the density of RGCs to 743 ± 371 cells/mm(2) (crush TGN-020, n = 7). The mRNA level of BAX/Bcl-2 ratio was 0.37 ± 0.05 in the sham control (n = 6) which was significantly increased to 0.88 ± 0.10 after crushing the optic nerve (placebo crush, n = 7; P = 0.0001, Scheffe). TGN-020 also significantly increased the BAX/Bcl-2 ratio to 1.29 ± 0.4 (n = 6) from the crush placebo group (P = 0.04, Scheffe). Immunoblotting showed similar changes in the protein levels. The glutamate level in the optic nerve was significantly increased to 53.7 ± 6.0 μM/mg/protein on day 1 (n = 4) from the sham control level of 45.9 ± 3.1 μM/mg/protein (n = 4; P = 0.04, t test). TGN-020

  12. Interpreting Thermodynamic Profiles of Aminoadamantane Compounds Inhibiting the M2 Proton Channel of Influenza A by Free Energy Calculations.

    Science.gov (United States)

    Homeyer, Nadine; Ioannidis, Harris; Kolarov, Felix; Gauglitz, Günter; Zikos, Christos; Kolocouris, Antonios; Gohlke, Holger

    2016-01-25

    The development of novel anti-influenza drugs is of great importance because of the capability of influenza viruses to occasionally cross interspecies barriers and to rapidly mutate. One class of anti-influenza agents, aminoadamantanes, including the drugs amantadine and rimantadine now widely abandoned due to virus resistance, bind to and block the pore of the transmembrane domain of the M2 proton channel (M2TM) of influenza A. Here, we present one of the still rare studies that interprets thermodynamic profiles from isothermal titration calorimetry (ITC) experiments in terms of individual energy contributions to binding, calculated by the computationally inexpensive implicit solvent/implicit membrane molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) approach, for aminoadamantane compounds binding to M2TM of the avian "Weybridge" strain. For all eight pairs of aminoadamantane compounds considered, the trend of the predicted relative binding free energies and their individual components, effective binding energies and changes in the configurational entropy, agrees with experimental measures (ΔΔG, ΔΔH, TΔΔS) in 88, 88, and 50% of the cases. In addition, information yielded by the MM-PBSA approach about determinants of binding goes beyond that available in component quantities (ΔH, ΔS) from ITC measurements. We demonstrate how one can make use of such information to link thermodynamic profiles from ITC with structural causes on the ligand side and, ultimately, to guide decision making in lead optimization in a prospective manner, which results in an aminoadamantane derivative with improved binding affinity against M2TM(Weybridge). PMID:26690735

  13. 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

  14. Transverse relaxation dispersion of the p7 membrane channel from hepatitis C virus reveals conformational breathing

    Energy Technology Data Exchange (ETDEWEB)

    Dev, Jyoti; Brüschweiler, Sven [Harvard Medical School, Department of Biological Chemistry and Molecular Pharmacology (United States); Ouyang, Bo [Chinese Academy of Sciences, State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology (China); Chou, James J., E-mail: james-chou@hms.harvard.edu [Harvard Medical School, Department of Biological Chemistry and Molecular Pharmacology (United States)

    2015-04-15

    The p7 membrane protein encoded by hepatitis C virus (HCV) assembles into a homo-hexamer that selectively conducts cations. An earlier solution NMR structure of the hexameric complex revealed a funnel-like architecture and suggests that a ring of conserved asparagines near the narrow end of the funnel are important for cation interaction. NMR based drug-binding experiments also suggest that rimantadine can allosterically inhibit ion conduction via a molecular wedge mechanism. These results suggest the presence of dilation and contraction of the funnel tip that are important for channel activity and that the action of the drug is attenuating this motion. Here, we determined the conformational dynamics and solvent accessibility of the p7 channel. The proton exchange measurements show that the cavity-lining residues are largely water accessible, consistent with the overall funnel shape of the channel. Our relaxation dispersion data show that residues Val7 and Leu8 near the asparagine ring are subject to large chemical exchange, suggesting significant intrinsic channel breathing at the tip of the funnel. Moreover, the hinge regions connecting the narrow and wide regions of the funnel show strong relaxation dispersion and these regions are the binding sites for rimantadine. Presence of rimantadine decreases the conformational dynamics near the asparagine ring and the hinge area. Our data provide direct observation of μs–ms dynamics of the p7 channel and support the molecular wedge mechanism of rimantadine inhibition of the HCV p7 channel.

  15. Computational modeling of voltage-gated Ca channels inhibition: identification of different effects on uterine and cardiac action potentials

    Directory of Open Access Journals (Sweden)

    Wing Chiu eTong

    2014-10-01

    Full Text Available The uterus and heart share the important physiological feature whereby contractile activation of the muscle tissue is regulated by the generation of periodic, spontaneous electrical action potentials (APs. Preterm birth arising from premature uterine contractions is a major complication of pregnancy and there remains a need to pursue avenues of research that facilitate the use of drugs, tocolytics, to limit these inappropriate contractions without deleterious actions on cardiac electrical excitation. A novel approach is to make use of mathematical models of uterine and cardiac APs, which incorporate many ionic currents contributing to the AP forms, and test the cell-specific responses to interventions. We have used three such models – of uterine smooth muscle cells (USMC, cardiac sinoatrial node cells (SAN and ventricular cells – to investigate the relative effects of reducing two important voltage-gated Ca currents – the L-type (ICaL and T-type (ICaT Ca currents. Reduction of ICaL (10% alone, or ICaT (40% alone, blunted USMC APs with little effect on ventricular APs and only mild effects on SAN activity. Larger reductions in either current further attenuated the USMC APs but with also greater effects on SAN APs. Encouragingly, a combination of ICaL and ICaT reduction did blunt USMC APs as intended with little detriment to APs of either cardiac cell type. Subsequent overlapping maps of ICaL and ICaT inhibition profiles from each model revealed a range of combined reductions of ICaL and ICaT over which an appreciable diminution of USMC APs could be achieved with no deleterious action on cardiac SAN or ventricular APs. This novel approach illustrates the potential for computational biology to inform us of possible uterine and cardiac cell-specific mechanisms. Incorporating such computational approaches in future studies directed at designing new, or repurposing existing, tocolytics will be beneficial for establishing a desired uterine

  16. Identification of TRPM7 channels in human intestinal interstitial cells of Cajal

    Institute of Scientific and Technical Information of China (English)

    Byung Joo Kim; Kyu Joo Park; Hyung Woo Kim; Seok Choi; Jae Yeoul Jun; In Youb Chang; Ju-Hong Jeon; Insuk So; Seon Jeong Kim

    2009-01-01

    AIM: To investigate the characteristics of slow electrical waves and the presence of transient receptor potential melastatin-type 7 (TRPM7) in the human gastrointestinal (GI) tract. METHODS: Conventional microelectrode techniques were used to record intracellular electrical responses from human GI smooth muscle tissue. Immunohistochemistry was used to identify TRPM7 channels in interstitial cells of Cajal (ICCs). RESULTS: The human GI tract generated slow electrical waves and had ICCs which functioned as pacemaker cells. Flufenamic acid, a nonselective cation channel blocker, and 2-APB (2-aminoethoxydiphenyl borate) and La3~+, TRPM7 channel blockers, inhibited the slow waves. Also, TRPM7 channels were expressed in ICCs in human tissue. CONCLUSION: These results suggest that the human GI tract generates slow waves and that TRPM7 channels expressed in the ICCs may be involved in the generation of the slow waves.

  17. Structurally Distinct Cation Channelrhodopsins from Cryptophyte Algae.

    Science.gov (United States)

    Govorunova, Elena G; Sineshchekov, Oleg A; Spudich, John L

    2016-06-01

    Microbial rhodopsins are remarkable for the diversity of their functional mechanisms based on the same protein scaffold. A class of rhodopsins from cryptophyte algae show close sequence homology with haloarchaeal rhodopsin proton pumps rather than with previously known channelrhodopsins from chlorophyte (green) algae. In particular, both aspartate residues that occupy the positions of the chromophore Schiff base proton acceptor and donor, a hallmark of rhodopsin proton pumps, are conserved in these cryptophyte proteins. We expressed the corresponding polynucleotides in human embryonic kidney (HEK293) cells and studied electrogenic properties of the encoded proteins with whole-cell patch-clamp recording. Despite their lack of residues characteristic of the chlorophyte cation channels, these proteins are cation-conducting channelrhodopsins that carry out light-gated passive transport of Na(+) and H(+). These findings show that channel function in rhodopsins has evolved via multiple routes. PMID:27233115

  18. Inhibition of T-Type Voltage Sensitive Calcium Channel Reduces Load-Induced OA in Mice and Suppresses the Catabolic Effect of Bone Mechanical Stress on Chondrocytes.

    Directory of Open Access Journals (Sweden)

    Padma P Srinivasan

    Full Text Available Voltage-sensitive calcium channels (VSCC regulate cellular calcium influx, one of the earliest responses to mechanical stimulation in osteoblasts. Here, we postulate that T-type VSCCs play an essential role in bone mechanical response to load and participate in events leading to the pathology of load-induced OA. Repetitive mechanical insult was used to induce OA in Cav3.2 T-VSCC null and wild-type control mouse knees. Osteoblasts (MC3T3-E1 and chondrocytes were treated with a selective T-VSCC inhibitor and subjected to fluid shear stress to determine how blocking of T-VSCCs alters the expression profile of each cell type upon mechanical stimulation. Conditioned-media (CM obtained from static and sheared MC3T3-E1 was used to assess the effect of osteoblast-derived factors on the chondrocyte phenotype. T-VSCC null knees exhibited significantly lower focal articular cartilage damage than age-matched controls. In vitro inhibition of T-VSCC significantly reduced the expression of both early and late mechanoresponsive genes in osteoblasts but had no effect on gene expression in chondrocytes. Furthermore, treatment of chondrocytes with CM obtained from sheared osteoblasts induced expression of markers of hypertrophy in chondrocytes and this was nearly abolished when osteoblasts were pre-treated with the T-VSCC-specific inhibitor. These results indicate that T-VSCC plays a role in signaling events associated with induction of OA and is essential to the release of osteoblast-derived factors that promote an early OA phenotype in chondrocytes. Further, these findings suggest that local inhibition of T-VSCC may serve as a therapy for blocking load-induced bone formation that results in cartilage degeneration.

  19. Current status of hyperpolarization-activated cyclic nucleotide-gated cation channel%超极化激活环核苷酸门控阳离子通道的研究现状

    Institute of Scientific and Technical Information of China (English)

    严慧; 黄裕新; 王景杰

    2009-01-01

    @@ 0 引言 超极化激活环核苷酸门控的超极化阳离子通道(hyperpolarization-activated cyclic nucleotide-gated cation chan-nel,HCN)的研究起源于Ih的发现,Noma和Irisawa已经在研究窦房结起搏活动时发现这一离子流并命名为Ih(hyperpolar-ization-activated current),20世纪80年代初Di Francesco和Irisawa等

  20. Evidence for a common pharmacological interaction site on K(Ca)2 channels providing both selective activation and selective inhibition of the human K(Ca)2.1 subtype

    DEFF Research Database (Denmark)

    Hougaard, Charlotte; Hammami, Sofia; Eriksen, Birgitte L;

    2012-01-01

    ]pyrimidines, act either as activators or as inhibitors of the human K(Ca)2.1 channel. Whereas (-)-CM-TPMF activates K(Ca)2.1 with an EC(50) value of 24 nM, (-)-B-TPMF inhibits the channel with an IC(50) value of 31 nM. In contrast, their (+)-enantiomers are 40 to 100 times less active. Both (-)-CM-TPMF and (-)-B......-TPMF are subtype-selective, with 10- to 20-fold discrimination toward other K(Ca)2 channels and the K(Ca)3 channel. Coapplication experiments reveal competitive-like functional interactions between the effects of (-)-CM-TPMF and (-)-B-TPMF. Despite belonging to a different chemical class than GW542573X, the K(Ca)2......-TPMF is 10 times more potent on K(Ca)2.1 than NS309 (6,7-dichloro-1H-indole-2,3-dione 3-oxime), an unselective but hitherto the most potent K(Ca)3/K(Ca)2 channel activator. (-)-B-TPMF is the first small-molecule inhibitor with significant selectivity among the K(Ca)2 channel subtypes. In contrast to peptide...

  1. TRPM7-like channels are functionally expressed in oocytes and modulate post-fertilization embryo development in mouse

    Science.gov (United States)

    Carvacho, Ingrid; Ardestani, Goli; Lee, Hoi Chang; McGarvey, Kaitlyn; Fissore, Rafael A.; Lykke-Hartmann, Karin

    2016-01-01

    The Transient Receptor Potential (TRP) channels are a family of cationic ion channels widely distributed in mammalian tissues. In general, the global genetic disruption of individual TRP channels result in phenotypes associated with impairment of a particular tissue and/or organ function. An exception is the genetic ablation of the TRP channel TRPM7, which results in early embryonic lethality. Nevertheless, the function of TRPM7 in oocytes, eggs and pre-implantation embryos remains unknown. Here, we described an outward rectifying non-selective current mediated by a TRP ion channel in immature oocytes (germinal vesicle stage), matured oocytes (metaphase II eggs) and 2-cell stage embryos. The current is activated by specific agonists and inhibited by distinct blockers consistent with the functional expression of TRPM7 channels. We demonstrated that the TRPM7-like channels are homo-tetramers and their activation mediates calcium influx in oocytes and eggs, which is fundamental to support fertilization and egg activation. Lastly, we showed that pharmacological inhibition of the channel function delays pre-implantation embryo development and reduces progression to the blastocyst stage. Our data demonstrate functional expression of TRPM7-like channels in mouse oocytes, eggs and embryos that may play an essential role in the initiation of embryo development. PMID:27681336

  2. Role of extracellular cations in cell motility, polarity, and chemotaxis

    Directory of Open Access Journals (Sweden)

    Soll D

    2011-04-01

    Full Text Available David R Soll1, Deborah Wessels1, Daniel F Lusche1, Spencer Kuhl1, Amanda Scherer1, Shawna Grimm1,21Monoclonal Antibody Research Institute, Developmental Studies, Hybridoma Bank, Department of Biology, University of Iowa, Iowa City; 2Mercy Medical Center, Surgical Residency Program, Des Moines, Iowa, USAAbstract: The concentration of cations in the aqueous environment of free living organisms and cells within the human body influence motility, shape, and chemotaxis. The role of extracellular cations is usually perceived to be the source for intracellular cations in the process of homeostasis. The role of surface molecules that interact with extracellular cations is believed to be that of channels, transporters, and exchangers. However, the role of Ca2+ as a signal and chemoattractant and the discovery of the Ca2+ receptor have demonstrated that extracellular cations can function as signals at the cell surface, and the plasma membrane molecules they interact with can function as bona fide receptors that activate coupled signal transduction pathways, associated molecules in the plasma membrane, or the cytoskeleton. With this perspective in mind, we have reviewed the cationic composition of aqueous environments of free living cells and cells that move in multicellular organisms, most notably humans, the range of molecules interacting with cations at the cell surface, the concept of a cell surface cation receptor, and the roles extracellular cations and plasma membrane proteins that interact with them play in the regulation of motility, shape, and chemotaxis. Hopefully, the perspective of this review will increase awareness of the roles extracellular cations play and the possibility that many of the plasma membrane proteins that interact with them could also play roles as receptors.Keywords: extracellular cations, chemotaxis, transporters, calcium, receptors

  3. Channel allo cation game algorithm based on lifetime mo del in wireless sensor network%基于生命期模型的无线传感器网络信道分配博弈算法∗

    Institute of Scientific and Technical Information of China (English)

    郝晓辰; 姚宁; 汝小月; 刘伟静; 辛敏洁

    2015-01-01

    针对无线传感器网络中节点因干扰过大导致重传能耗增加,进而节点过早失效、网络生命期缩短的问题,根据网络拓扑信息和路由信息设计节点的负载模型,从而构建了节点的生命期模型。然后利用博弈论将路径增益、交叉干扰和节点生命期等性能参数融入到效益函数中,构建信道分配博弈模型。理论分析证明该博弈模型存在纳什均衡。进而运用最佳回应策略,在所构建的信道分配博弈模型的基础上,设计了一种优化网络生命期的抗干扰信道分配算法。该算法使节点在选择信道时避免与网络中交叉干扰较大的节点和生命期较小的节点使用相同信道,实现干扰小、能耗低且均衡的信道选择。理论分析与仿真结果证明该算法最终能够快速地收敛到纳什均衡,且具有较小的信息复杂度,从而减小算法本身的通信能耗。同时,该算法具有良好的抗干扰性和信道均衡性,能够有效地延长网络生命期。%In wireless sensor network, the lager interference makes the data transmission failed, thus leading to data retrans-mission of nodes. This situation exacerbates the energy consumption of retransmission. As a result, some nodes will prematurely fail to work, thus reducing the network lifetime. In order to deal with the above issue, this paper takes full advantage of the topology and route information to design a novel load model of nodes. Then, a lifetime model of each node is constructed based on the load model. Subsequently, the path gain, intersecting interference and node lifetime are integrated into a utility function to construct a channel allocation game model called channel allocation based-game (CABG) by taking advantage of the game theory. The theoretical analysis proves the existence of the Nash Equilibrium of CABG. And then, using the best response dynamics, a channel allocation game algorithm for anti

  4. Corticolimbic expression of TRPC4 and TRPC5 channels in the rodent brain.

    Directory of Open Access Journals (Sweden)

    Melissa A Fowler

    Full Text Available The canonical transient receptor potential (TRPC channels are a family of non-selective cation channels that are activated by increases in intracellular Ca(2+ and G(q/phospholipase C-coupled receptors. We used quantitative real-time PCR, in situ hybridization, immunoblots and patch-clamp recording from several brain regions to examine the expression of the predominant TRPC channels in the rodent brain. Quantitative real-time PCR of the seven TRPC channels in the rodent brain revealed that TRPC4 and TRPC5 channels were the predominant TRPC subtypes in the adult rat brain. In situ hybridization histochemistry and immunoblotting further resolved a dense corticolimbic expression of the TRPC4 and TRPC5 channels. Total protein expression of HIP TRPC4 and 5 proteins increased throughout development and peaked late in adulthood (6-9 weeks. In adults, TRPC4 expression was high throughout the frontal cortex, lateral septum (LS, pyramidal cell layer of the hippocampus (HIP, dentate gyrus (DG, and ventral subiculum (vSUB. TRPC5 was highly expressed in the frontal cortex, pyramidal cell layer of the HIP, DG, and hypothalamus. Detailed examination of frontal cortical layer mRNA expression indicated TRPC4 mRNA is distributed throughout layers 2-6 of the prefrontal cortex (PFC, motor cortex (MCx, and somatosensory cortex (SCx. TRPC5 mRNA expression was concentrated specifically in the deep layers 5/6 and superficial layers 2/3 of the PFC and anterior cingulate. Patch-clamp recording indicated a strong metabotropic glutamate-activated cation current-mediated depolarization that was dependent on intracellular Ca(2+and inhibited by protein kinase C in brain regions associated with dense TRPC4 or 5 expression and absent in regions lacking TRPC4 and 5 expression. Overall, the dense corticolimbic expression pattern suggests that these Gq/PLC coupled nonselective cation channels may be involved in learning, memory, and goal-directed behaviors.

  5. Interaction of Tarantula Venom Peptide ProTx-II with Lipid Membranes Is a Prerequisite for Its Inhibition of Human Voltage-gated Sodium Channel NaV1.7.

    Science.gov (United States)

    Henriques, Sónia Troeira; Deplazes, Evelyne; Lawrence, Nicole; Cheneval, Olivier; Chaousis, Stephanie; Inserra, Marco; Thongyoo, Panumart; King, Glenn F; Mark, Alan E; Vetter, Irina; Craik, David J; Schroeder, Christina I

    2016-08-12

    ProTx-II is a disulfide-rich peptide toxin from tarantula venom able to inhibit the human voltage-gated sodium channel 1.7 (hNaV1.7), a channel reported to be involved in nociception, and thus it might have potential as a pain therapeutic. ProTx-II acts by binding to the membrane-embedded voltage sensor domain of hNaV1.7, but the precise peptide channel-binding site and the importance of membrane binding on the inhibitory activity of ProTx-II remain unknown. In this study, we examined the structure and membrane-binding properties of ProTx-II and several analogues using NMR spectroscopy, surface plasmon resonance, fluorescence spectroscopy, and molecular dynamics simulations. Our results show a direct correlation between ProTx-II membrane binding affinity and its potency as an hNaV1.7 channel inhibitor. The data support a model whereby a hydrophobic patch on the ProTx-II surface anchors the molecule at the cell surface in a position that optimizes interaction of the peptide with the binding site on the voltage sensor domain. This is the first study to demonstrate that binding of ProTx-II to the lipid membrane is directly linked to its potency as an hNaV1.7 channel inhibitor. PMID:27311819

  6. 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

  7. Stimulation of large-conductance calcium-activated potassium channels inhibits neurogenic contraction of human bladder from patients with urinary symptoms and reverses acetic acid-induced bladder hyperactivity in rats.

    Science.gov (United States)

    La Fuente, José M; Fernández, Argentina; Cuevas, Pedro; González-Corrochano, Rocío; Chen, Mao Xiang; Angulo, Javier

    2014-07-15

    We have analysed the effects of large-conductance calcium-activated potassium channel (BK) stimulation on neurogenic and myogenic contraction of human bladder from healthy subjects and patients with urinary symptoms and evaluated the efficacy of activating BK to relief bladder hyperactivity in rats. Bladder specimens were obtained from organ donors and from men with benign prostatic hyperplasia (BPH). Contractions elicited by electrical field stimulation (EFS) and carbachol (CCh) were evaluated in isolated bladder strips. in vivo cystometric recordings were obtained in anesthetized rats under control and acetic acid-induced hyperactive conditions. Neurogenic contractions of human bladder were potentiated by blockade of BK and small-conductance calcium-activated potassium channels (SK) but were unaffected by the blockade of intermediate calcium-activated potassium channels (IK). EFS-induced contractions were inhibited by BK stimulation with NS-8 or NS1619 or by SK/IK stimulation with NS309 (3µM). CCh-induced contractions were not modified by blockade or stimulation of BK, IK or SK. The anti-cholinergic agent, oxybutynin (0.3µM) inhibited either neurogenic or CCh-induced contractions. Neurogenic contractions of bladders from BPH patients were less sensitive to BK inhibition and more sensitive to BK activation than healthy bladders. The BK activator, NS-8 (5mg/kg; i.v.), reversed bladder hyperactivity induced by acetic acid in rats, while oxybutynin was ineffective. NS-8 did not significantly impact blood pressure or heart rate. BK stimulation specifically inhibits neurogenic contractions in patients with urinary symptoms and relieves bladder hyperactivity in vivo without compromising bladder contractile capacity or cardiovascular safety, supporting its potential therapeutic use for relieving bladder overactivity. PMID:24747752

  8. Pharmacologic inhibition of small-conductance calcium-activated potassium (SK) channels by NS8593 reveals atrial antiarrhythmic potential in horses

    DEFF Research Database (Denmark)

    Haugaard, Maria Mathilde; Hesselkilde, Eva Zander; Pehrson, Steen Michael;

    2015-01-01

    . METHODS: Cardiac biopsies were analyzed to investigate the expression level of the most prominent cardiac ion channels, with special focus on SK channels, in the equine heart. Subcellular distribution of SK isoform 2 (SK2) was assessed by immunohistochemistry and confocal microscopy......, and ventricular depolarization and repolarization times. RESULTS: Analysis revealed equivalent mRNA transcript levels of the 3 SK channel isoforms in atria compared to ventricles. Immunohistochemistry and confocal microscopy displayed a widespread distribution of SK2 in both atrial and ventricular cardiomyocytes...

  9. Zinc-induced neurotoxicity mediated by transient receptor potential melastatin 7 channels.

    Science.gov (United States)

    Inoue, Koichi; Branigan, Deborah; Xiong, Zhi-Gang

    2010-03-01

    Transient receptor potential melastatin 7 (TRPM7) channels are novel Ca(2+)-permeable non-selective cation channels ubiquitously expressed. Activation of TRPM7 channels has been shown to be involved in cellular Mg(2+) homeostasis, diseases caused by abnormal magnesium absorption, and in Ca(2+)-mediated neuronal injury under ischemic conditions. Here we show strong evidence suggesting that TRPM7 channels also play an important role in cellular Zn(2+) homeostasis and in Zn(2+)-mediated neuronal injury. Using a combination of fluorescent Zn(2+) imaging, small interfering RNA, pharmacological analysis, and cell injury assays, we show that activation of TRPM7 channels augmented Zn(2+)-induced injury of cultured mouse cortical neurons. The Zn(2+)-mediated neurotoxicity was inhibited by nonspecific TRPM7 blockers Gd(3+) or 2-aminoethoxydiphenyl borate, and by knockdown of TRPM7 channels with small interfering RNA. In addition, Zn(2+)-mediated neuronal injury under oxygen-glucose deprivation conditions was also diminished by silencing TRPM7. Furthermore, we show that overexpression of TRPM7 channels in HEK293 cells increased intracellular Zn(2+) accumulation and Zn(2+)-induced cell injury, while silencing TRPM7 by small interfering RNA attenuated the Zn(2+)-mediated cell toxicity. Thus, TRPM7 channels may represent a novel target for neurological disorders where Zn(2+) toxicity plays an important role. PMID:20048154

  10. Characterization of the slow calcium channel binding sites for [3H]SR 33557 in rat heart sarcolemmal membranes

    International Nuclear Information System (INIS)

    SR 33557 represents a new class of compounds (indolizine sulfone) that inhibit L-type Ca2+ channels. [3H]SR 33557 has been shown to bind with high affinity (Kd congruent to 0.36 nM, calculated from saturation isotherms and association/dissociation kinetics) to a single class of sites in a purified preparation of rat cardiac sarcolemmal membranes. The binding was found to be saturable and reversible. The maximal binding capacity was in approximately 1:1 stoichiometry with that of other Ca2+ channel antagonists. Various divalent cations (Mg2+, Mn2+, Ca2+, Ba2+, and Cd2+) were shown to inhibit specific [3H]SR 33557 binding, with Cd2+ being the most potent. Among several receptor or channel ligands (including omega-conotoxin and Na+ and K+ channel modulators), only the L-type Ca2+ channel antagonists were found to displace [3H]SR 33557. However, dihydropyridines, phenylalkylamines, benzothiazepines, and diphenylbutylpiperidines were found to inhibit [3H]SR 33557 in a noncompetitive manner as demonstrated by displacement and saturation experiments in addition to dissociation kinetics. From these results, we suggest that SR 33557 binds with high affinity to a unique site on the L-type Ca2+ channel found in rat cardiac sarcolemmal membranes

  11. Competitive Effects of 2+ and 3+ Cations on DNA Compaction

    CERN Document Server

    Tongu, C; Yoshikawa, Y; Zinchenko, A A; Chen, N; Yoshikawa, K

    2016-01-01

    By using single-DNA observation with fluorescence microscopy, we observed the effects of divalent and trivalent cations on the higher-order structure of giant DNA (T4 DNA with 166 kbp). It was found that divalent cations, such as Mg(2+) and Ca(2+), inhibit DNA compaction induced by a trivalent cation, spermidine (SPD(3+)). On the other hand, in the absence of SPD(3+), divalent cations cause the shrinkage of DNA. These experimental observations are inconsistent with the well-established Debye-Huckel scheme regarding the shielding effect of counter ions, which is given as the additivity of contributions of cations with different valences. We interpreted the competition between 2+ and 3+ cations in terms of the change in the translational entropy of the counter ions before and after the folding transition of DNA. For the compaction with SPD(3+), we considered the increase in translational entropy due to the ion-exchange of the intrinsic monovalent cations condensing on a highly-charged polyelectrolyte, double-st...

  12. Effect of heavy metal cations on the activity of cathepsin D (in vitro study) Effect of heavy metal cations on the activity of cathepsin D (in vitro study)

    OpenAIRE

    Alicja Karwowska; Radosław Łapiński; Marek Gacko; Ewa Grzegorczyk; Joanna Żurawska; Jan K. Karczewski

    2012-01-01

    We studied the effect of heavy metal cations: Fe 2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+ on the activity of
    cathepsin D in human aorta homogenate and blood serum. The concentration of cations was 1 mmol/l. Hemoglobin
    was the cathepsin D substrate. The activity of cathepsin D was determined at pH 3.5. Only Hg2+ cations
    inhibit the activity of cathepsin D. Cations Hg2+ damage lysosomes and release cathepsin D from these organelles.We studied the effect of heavy metal c...

  13. 20-Hydroxyeicosatetraenoic acid contributes to the inhibition of K+ channel activity and vasoconstrictor response to angiotensin II in rat renal microvessels.

    Directory of Open Access Journals (Sweden)

    Fan Fan

    Full Text Available The present study examined whether 20-hydroxyeicosatetraenoic acid (HETE contributes to the vasoconstrictor effect of angiotensin II (ANG II in renal microvessels by preventing activation of the large conductance Ca(2+-activated K(+ channel (KCa in vascular smooth muscle (VSM cells. ANG II increased the production of 20-HETE in rat renal microvessels. This response was attenuated by the 20-HETE synthesis inhibitors, 17-ODYA and HET0016, a phospholipase A2 inhibitor AACOF3, and the AT1 receptor blocker, Losartan, but not by the AT2 receptor blocker, PD123319. ANG II (10(-11 to 10(-6 M dose-dependently decreased the diameter of renal microvessels by 41 ± 5%. This effect was blocked by 17-ODYA. ANG II (10(-7 M did not alter KCa channel activity recorded from cell-attached patches on renal VSM cells under control conditions. However, it did reduce the NPo of the KCa channel by 93.4 ± 3.1% after the channels were activated by increasing intracellular calcium levels with ionomycin. The inhibitory effect of ANG II on KCa channel activity in the presence of ionomycin was attenuated by 17-ODYA, AACOF3, and the phospholipase C (PLC inhibitor U-73122. ANG II induced a peak followed by a steady-state increase in intracellular calcium concentration in renal VSM cells. 17-ODYA (10(-5 M had no effect on the peak response, but it blocked the steady-state increase. These results indicate that ANG II stimulates the formation of 20-HETE in rat renal microvessels via the AT1 receptor activation and that 20-HETE contributes to the vasoconstrictor response to ANG II by blocking activation of KCa channel and facilitating calcium entry.

  14. Nonselective block by La3+ of Arabidopsis ion channels involved in signal transduction

    Science.gov (United States)

    Lewis, B. D.; Spalding, E. P.; Evans, M. L. (Principal Investigator)

    1998-01-01

    Lanthanide ions such as La3+ are frequently used as blockers to test the involvement of calcium channels in plant and animal signal transduction pathways. For example, the large rise in cytoplasmic Ca2+ concentration triggered by cold shock in Arabidopsis seedlings is effectively blocked by 10 mM La3+ and we show here that the simultaneous large membrane depolarization is similarly blocked. However, a pharmacological tool is only as useful as it is selective and the specificity of La3+ for calcium channels was brought into question by our finding that it also blocked a blue light (BL)-induced depolarization that results from anion channel activation and believed not to involve calcium channels. This unexpected inhibitory effect of La3+ on the BL-induced depolarization is explained by our finding that 10 mM La3+ directly and completely blocked the BL-activated anion channel when applied to excised patches. We have investigated the ability of La3+ to block noncalcium channels in Arabidopsis. In addition to the BL-activated anion channel, 10 mM La3+ blocked a cation channel and a stretch-activated channel in patches of plasma membrane excised from hypocotyl cells. In root cells, 10 mM La3+ inhibited the activity of an outward-rectifying potassium channel at the whole cell and single-channel level by 47% and 58%, respectively. We conclude that La3+ is a nonspecific blocker of multiple ionic conductances in Arabidopsis and may disrupt signal transduction processes independently of any effect on Ca2+ channels.

  15. Expression of tetraspan protein CD63 activates protein-tyrosine kinase (PTK) and enhances the PTK-induced inhibition of ROMK channels.

    NARCIS (Netherlands)

    Lin, D.; Kamsteeg, E.J.; Zhang, Y.; Jin, Y.; Sterling, H.; Yue, P.; Roos, M.; Duffield, A.; Spencer, J.; Caplan, M.; Wang, W.H.

    2008-01-01

    In the present study, we tested the role of CD63 in regulating ROMK1 channels by protein-tyrosine kinase (PTK). Immunocytochemical staining shows that CD63 and receptor-linked tyrosine phosphatase alpha (RPTPalpha) are expressed in the cortical collecting duct and outer medulla collecting duct. Immu

  16. Chemo-nociceptive signalling from the colon is enhanced by mild colitis and blocked by inhibition of transient receptor potential ankyrin 1 channels

    DEFF Research Database (Denmark)

    Mitrovic, Martina; Shahbazian, Anaid; Bock, Elisabeth;

    2010-01-01

    Transient receptor potential ankyrin 1 (TRPA1) channels are expressed by primary afferent neurones and activated by irritant chemicals including allyl isothiocyanate (AITC). Here we investigated whether intracolonic AITC causes afferent input to the spinal cord and whether this response is modifi...

  17. Cryohydrocytosis: increased activity of cation carriers in red cells from a patient with a band 3 mutation

    DEFF Research Database (Denmark)

    Bogdanova, Anna; Goede, Jeroen S; Weiss, Erwin;

    2009-01-01

    blockers of anion and cation channels was assessed. RESULTS: In the cold, the cryohydrocytosis patient's erythrocytes swelled in KCl-containing, but not in NaCl-containing or KNO(3)-containing media indicating that volume changes were mediated by an anion-coupled cation transporter. In NaCl......-selective cation channel. The present study was performed to characterize so far unexplored ion transport pathways that may render erythrocytes of a single cryohydrocytosis patient cation-leaky. DESIGN AND METHODS: Cold-induced changes in cell volume were monitored using ektacytometry and density gradient...

  18. Ion exchange behaviour of polymeric zirconium cations

    International Nuclear Information System (INIS)

    Polymeric zirconium cations formed in weakly acid solutions (pH2) are taken up strongly into macroporous cation exchange resins, while uptake into normal cation exchange resins (pore diameter about 1 nm) is low. Macroporous cation exchange resins loaded with polymeric Zr cations are shown to function as ligand exchange sorbents. (Authors)

  19. Effect of activation on adhesion of flowing neutrophils to cultured endothelium: time course and inhibition by a calcium channel blocker (nitrendipine).

    OpenAIRE

    PERRY, I; Buttrum, S. M.; Nash, G. B.

    1993-01-01

    1. Adhesion of neutrophils to vascular endothelium plays an important role in inflammation and thrombosis. Modulation of adhesion may be therapeutic in these conditions. 2. A flow model was used to quantify adhesion of neutrophils to human cultured umbilical vein endothelial cells. The time course of the neutrophil response to activation by N-formyl-methionyl-leucylphenylalanine (fMLP, 10(-7) M) was studied and the inhibitory effects of the calcium-channel blockers, nitrendipine and nifedipin...

  20. Influence of epithelium on the inhibition of melittin-induced contraction of guinea-pig isolated trachea by the potassium channel opener NIP-121.

    OpenAIRE

    Shikada, K.; Tanaka, S

    1993-01-01

    1. We have investigated the effect of the potassium channel opener, NIP-121, on contraction elicited by melittin (a phospholipase A2 activator) in epithelium-intact and epithelium-denuded trachea isolated from guinea-pigs. The effects of NIP-121 were compared with those of isoprenaline, aminophylline and hydrocortisone. 2. In the presence of the cyclo-oxygenase inhibitor, indomethacin (5 microM), melittin (3 micrograms ml-1) caused time-dependent contraction. The melittin-induced contractile ...

  1. Tarantula Huwentoxin-IV Inhibits Neuronal Sodium Channels by Binding to Receptor Site 4 and Trapping the Domain II Voltage Sensor in the Closed Configuration*S⃞

    OpenAIRE

    Xiao, Yucheng; Bingham, Jon-Paul; Zhu, Weiguo; Moczydlowski, Edward; Liang, Songping; Cummins, Theodore R.

    2008-01-01

    Peptide toxins with high affinity, divergent pharmacological functions, and isoform-specific selectivity are powerful tools for investigating the structure-function relationships of voltage-gated sodium channels (VGSCs). Although a number of interesting inhibitors have been reported from tarantula venoms, little is known about the mechanism for their interaction with VGSCs. We show that huwentoxin-IV (HWTX-IV), a 35-residue peptide from tarantula Ornithoctonus huwena v...

  2. σ-1 Receptor Inhibition of ASIC1a Channels is Dependent on a Pertussis Toxin-Sensitive G-Protein and an AKAP150/Calcineurin Complex.

    Science.gov (United States)

    Mari, Yelenis; Katnik, Christopher; Cuevas, Javier

    2015-10-01

    ASIC1a channels play a major role in various pathophysiological conditions including depression, anxiety, epilepsy, and neurodegeneration following ischemic stroke. Sigma-1 (σ-1) receptor stimulation depresses the activity of ASIC1a channels in cortical neurons, but the mechanism(s) by which σ-1 receptors exert their influence on ASIC1a remains unknown. Experiments were undertaken to elucidate the signaling cascade linking σ-1 receptors to ASIC1a channels. Immunohistochemical studies showed that σ-1 receptors, ASIC1a and A-kinase anchoring peptide 150 colocalize in the plasma membrane of the cell body and processes of cortical neurons. Fluorometric Ca(2+) imaging experiments showed that disruption of the macromolecular complexes containing AKAP150 diminished the effects of the σ-1 on ASIC1a, as did application of the calcineurin inhibitors, cyclosporin A and FK-506. Moreover, whole-cell patch clamp experiments showed that σ-1 receptors were less effective at decreasing ASIC1a-mediated currents in the presence of the VIVIT peptide, which binds to calcineurin and prevents cellular effects dependent on AKAP150/calcineurin interaction. The coupling of σ-1 to ASIC1a was also disrupted by preincubation of the neurons in the G-protein inhibitor, pertussis toxin (PTX). Taken together, our data reveal that σ-1 receptor block of ASIC1a function is dependent on activation of a PTX-sensitive G-protein and stimulation of AKAP150 bound calcineurin. PMID:24925261

  3. Characterization of functional TRPV1 channels in the sarcoplasmic reticulum of mouse skeletal muscle.

    Directory of Open Access Journals (Sweden)

    Sabine Lotteau

    Full Text Available TRPV1 represents a non-selective cation channel activated by capsaicin, acidosis and high temperature. In the central nervous system where TRPV1 is highly expressed, its physiological role in nociception is clearly identified. In skeletal muscle, TRPV1 appears implicated in energy metabolism and exercise endurance. However, how as a Ca(2+ channel, it contributes to intracellular calcium concentration ([Ca(2+]i maintenance and muscle contraction remains unknown. Here, as in rats, we report that TRPV1 is functionally expressed in mouse skeletal muscle. In contrast to earlier reports, our analysis show TRPV1 presence only at the sarcoplasmic reticulum (SR membrane (preferably at the longitudinal part in the proximity of SERCA1 pumps. Using intracellular Ca(2+ imaging, we directly accessed to the channel functionality in intact FDB mouse fibers. Capsaicin and resiniferatoxin, both agonists as well as high temperature (45°C elicited an increase in [Ca(2+]i. TRPV1-inhibition by capsazepine resulted in a strong inhibition of TRPV1-mediated functional responses and abolished channel activation. Blocking the SR release (with ryanodine or dantrolene led to a reduced capsaicin-induced Ca(2+ elevation suggesting that TRPV1 may participate to a secondary SR Ca(2+ liberation of greater amplitude. In conclusion, our experiments point out that TRPV1 is a functional SR Ca(2+ leak channel and may crosstalk with RyR1 in adult mouse muscle fibers.

  4. Role of Tryptophan Residues in Gramicidin Channel Organization and Function

    OpenAIRE

    Chattopadhyay, Amitabha; RAWAT, SATINDER S.; Greathouse, Denise V.; Kelkar, Devaki A.; Koeppe, Roger E.

    2008-01-01

    The linear peptide gramicidin forms prototypical ion channels specific for monovalent cations and has been used extensively to study the organization, dynamics, and function of membrane-spanning channels. The tryptophan residues in gramicidin channels are crucial for maintaining the structure and function of the channel. We explored the structural basis for the reduction in channel conductance in the case of single-tryptophan analogs of gramicidin with three Trp → hydrophobic substitutions us...

  5. Identification of ML204, a Novel Potent Antagonist That Selectively Modulates Native TRPC4/C5 Ion Channels*

    Science.gov (United States)

    Miller, Melissa; Shi, Jie; Zhu, Yingmin; Kustov, Maksym; Tian, Jin-bin; Stevens, Amy; Wu, Meng; Xu, Jia; Long, Shunyou; Yang, Pu; Zholos, Alexander V.; Salovich, James M.; Weaver, C. David; Hopkins, Corey R.; Lindsley, Craig W.; McManus, Owen; Li, Min; Zhu, Michael X.

    2011-01-01

    Transient receptor potential canonical (TRPC) channels are Ca2+-permeable nonselective cation channels implicated in diverse physiological functions, including smooth muscle contractility and synaptic transmission. However, lack of potent selective pharmacological inhibitors for TRPC channels has limited delineation of the roles of these channels in physiological systems. Here we report the identification and characterization of ML204 as a novel, potent, and selective TRPC4 channel inhibitor. A high throughput fluorescent screen of 305,000 compounds of the Molecular Libraries Small Molecule Repository was performed for inhibitors that blocked intracellular Ca2+ rise in response to stimulation of mouse TRPC4β by μ-opioid receptors. ML204 inhibited TRPC4β-mediated intracellular Ca2+ rise with an IC50 value of 0.96 μm and exhibited 19-fold selectivity against muscarinic receptor-coupled TRPC6 channel activation. In whole-cell patch clamp recordings, ML204 blocked TRPC4β currents activated through either μ-opioid receptor stimulation or intracellular dialysis of guanosine 5′-3-O-(thio)triphosphate (GTPγS), suggesting a direct interaction of ML204 with TRPC4 channels rather than any interference with the signal transduction pathways. Selectivity studies showed no appreciable block by 10–20 μm ML204 of TRPV1, TRPV3, TRPA1, and TRPM8, as well as KCNQ2 and native voltage-gated sodium, potassium, and calcium channels in mouse dorsal root ganglion neurons. In isolated guinea pig ileal myocytes, ML204 blocked muscarinic cation currents activated by bath application of carbachol or intracellular infusion of GTPγS, demonstrating its effectiveness on native TRPC4 currents. Therefore, ML204 represents an excellent novel tool for investigation of TRPC4 channel function and may facilitate the development of therapeutics targeted to TRPC4. PMID:21795696

  6. Effect of heavy metal cations on the activity of cathepsin D (in vitro study).

    Science.gov (United States)

    Karwowska, Alicja; Łapiński, Radosław; Gacko, Marek; Grzegorczyk, Ewa; Żurawska, Joanna; Karczewski, Jan K

    2012-01-01

    We studied the effect of heavy metal cations: Fe²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺ on the activity of cathepsin D in human aorta homogenate and blood serum. The concentration of cations was 1 mmol/l. Hemoglobin was the cathepsin D substrate. The activity of cathepsin D was determined at pH 3.5. Only Hg²⁺ cations inhibit the activity of cathepsin D. Cations Hg²⁺ damage lysosomes and release cathepsin D from these organelles. PMID:23042275

  7. Menthol inhibits detrusor contractility independently of TRPM8 activation.

    Directory of Open Access Journals (Sweden)

    Antonio Celso Saragossa Ramos-Filho

    Full Text Available Agonists such as icilin and menthol can activate the cool temperature-sensitive ion channel TRPM8. However, biological responses to menthol may occur independently of TRPM8 activation. In the rodent urinary bladder, menthol facilitates the micturition reflex but inhibits muscarinic contractions of the detrusor smooth muscle. The site(s of TRPM8 expression in the bladder are controversial. In this study we investigated the regulation of bladder contractility in vitro by menthol. Bladder strips from wild type and TRPM8 knockout male mice (25-30 g were dissected free and mounted in organ baths. Isometric contractions to carbachol (1 nM-30 µM, CaCl2 (1 µM to 100 mM and electrical field stimulation (EFS; 8, 16, 32 Hz were measured. Strips from both groups contracted similarly in response to both carbachol and EFS. Menthol (300 µM or nifedipine (1 µM inhibited carbachol and EFS-induced contractions in both wild type and TRPM8 knockout bladder strips. Incubation with the sodium channel blocker tetrodotoxin (1 µM, replacement of extracellular sodium with the impermeant cation N-Methyl-D-Glucamine, incubation with a cocktail of potassium channel inhibitors (100 nM charybdotoxin, 1 µM apamin, 10 µM glibenclamide and 1 µM tetraethylammonium or removal of the urothelium did not affect the inhibitory actions of menthol. Contraction to CaCl2 was markedly inhibited by either menthol or nifedipine. In cultured bladder smooth muscle cells, menthol or nifedipine abrogated the carbachol or KCl-induced increases in [Ca2+]i. Intravesical administration of menthol increased voiding frequency while decreasing peak voiding pressure. We conclude that menthol inhibits muscarinic bladder contractions through blockade of L-type calcium channels, independently of TRPM8 activation.

  8. Effect of heavy metal cations on the activity of cathepsin D (in vitro study Effect of heavy metal cations on the activity of cathepsin D (in vitro study

    Directory of Open Access Journals (Sweden)

    Alicja Karwowska

    2012-10-01

    Full Text Available We studied the effect of heavy metal cations: Fe 2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+ on the activity of
    cathepsin D in human aorta homogenate and blood serum. The concentration of cations was 1 mmol/l. Hemoglobin
    was the cathepsin D substrate. The activity of cathepsin D was determined at pH 3.5. Only Hg2+ cations
    inhibit the activity of cathepsin D. Cations Hg2+ damage lysosomes and release cathepsin D from these organelles.We studied the effect of heavy metal cations: Fe 2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+ on the activity of
    cathepsin D in human aorta homogenate and blood serum. The concentration of cations was 1 mmol/l. Hemoglobin
    was the cathepsin D substrate. The activity of cathepsin D was determined at pH 3.5. Only Hg2+ cations
    inhibit the activity of cathepsin D. Cations Hg2+ damage lysosomes and release cathepsin D from these organelles.

  9. Inhibition of T-Type Voltage Sensitive Calcium Channel Reduces Load-Induced OA in Mice and Suppresses the Catabolic Effect of Bone Mechanical Stress on Chondrocytes

    OpenAIRE

    Srinivasan, Padma P.; Parajuli, Ashutosh; Price, Christopher; Wang, Liyun; Duncan, Randall L.; Kirn-Safran, Catherine B.

    2015-01-01

    Voltage-sensitive calcium channels (VSCC) regulate cellular calcium influx, one of the earliest responses to mechanical stimulation in osteoblasts. Here, we postulate that T-type VSCCs play an essential role in bone mechanical response to load and participate in events leading to the pathology of load-induced OA. Repetitive mechanical insult was used to induce OA in Cav3.2 T-VSCC null and wild-type control mouse knees. Osteoblasts (MC3T3-E1) and chondrocytes were treated with a selective T-VS...

  10. Berberine reduces cAMP-induced chloride secretion in T84 human colonic carcinoma cells through inhibition of basolateral KCNQ1 channels

    OpenAIRE

    Alzamora, Rodrigo; O’Mahony, Fiona; Ko, Wing-Hung; Yip, Tiffany Wai-Nga; Carter, Derek; Irnaten, Mustapha; Harvey, Brian Joseph

    2011-01-01

    Berberine is a plant alkaloid with multiple pharmacological actions, including antidiarrhoeal activity and has been shown to inhibit Cl- secretion in distal colon. The aims of this study were to determine the molecular signalling mechanisms of action of berberine on Cl- secretion and the ion transporter targets. Monolayers of T84 human colonic carcinoma cells grown in permeable supports were placed in Ussing chambers and short-circuit current measured in response to secretagogues and berberin...

  11. On the membrane translocation of diphtheria toxin: at low pH the toxin induces ion channels on cells.

    Science.gov (United States)

    Papini, E; Sandoná, D; Rappuoli, R; Montecucco, C

    1988-01-01

    Diphtheria toxin (DT) in acidic media forms ion-conducting channels across the plasma membrane and inhibits protein synthesis of both highly and poorly DT-sensitive cell lines. This results in loss of cell potassium and in entry of both sodium and protons with a concomitant rapid lowering of membrane potential. The pH dependency of the permeability changes is similar to that of the inhibition of cell protein synthesis. DT-induced ion channels close when the pH of the external medium is returned to neutrality and cells recover their normal monovalent cation content. Similar permeability changes were induced by two DT mutants defective either in enzymatic activity or in cell binding, but not with a mutant defective in membrane translocation. The implication of these findings for the mechanism of DT membrane translocation is discussed. PMID:2463157

  12. Fusion Pore Diameter Regulation by Cations Modulating Local Membrane Anisotropy

    Directory of Open Access Journals (Sweden)

    Doron Kabaso

    2012-01-01

    Full Text Available The fusion pore is an aqueous channel that is formed upon the fusion of the vesicle membrane with the plasma membrane. Once the pore is open, it may close again (transient fusion or widen completely (full fusion to permit vesicle cargo discharge. While repetitive transient fusion pore openings of the vesicle with the plasma membrane have been observed in the absence of stimulation, their frequency can be further increased using a cAMP-increasing agent that drives the opening of nonspecific cation channels. Our model hypothesis is that the openings and closings of the fusion pore are driven by changes in the local concentration of cations in the connected vesicle. The proposed mechanism of fusion pore dynamics is considered as follows: when the fusion pore is closed or is extremely narrow, the accumulation of cations in the vesicle (increased cation concentration likely leads to lipid demixing at the fusion pore. This process may affect local membrane anisotropy, which reduces the spontaneous curvature and thus leads to the opening of the fusion pore. Based on the theory of membrane elasticity, we used a continuum model to explain the rhythmic opening and closing of the fusion pore.

  13. 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.

  14. Tris(triazole) tripodal receptors as selective probes for citrate anion recognition and multichannel transition and heavy metal cation sensing.

    Science.gov (United States)

    González, María del Carmen; Otón, Francisco; Espinosa, Arturo; Tárraga, Alberto; Molina, Pedro

    2015-02-01

    The three-armed pyrenyl-triazole receptor 1 behaves as a highly selective fluorescent molecular sensor for citrate anions over similar carboxylates such as malate or tartrate. In addition, this receptor senses Cu(2+) cations through absorption and emission channels even in the presence of Hg(2+) metal cations. The related three-armed ferrocenyl-triazole receptor 2 behaves as a highly selective dual (redox and chromogenic) chemosensor molecule for Pb(2+) metal cations.

  15. Highly Selective Artificial K(+) Channels: An Example of Selectivity-Induced Transmembrane Potential.

    Science.gov (United States)

    Gilles, Arnaud; Barboiu, Mihail

    2016-01-13

    Natural KcsA K(+) channels conduct at high rates with an extraordinary selectivity for K(+) cations, excluding the Na(+) or other cations. Biomimetic artificial channels have been designed in order to mimick the ionic activity of KcSA channels, but simple artificial systems presenting high K(+)/Na(+) selectivity are rare. Here we report an artificial ion channel of H-bonded hexyl-benzoureido-15-crown-5-ether, where K(+) cations are highly preferred to Na(+) cations. The K(+)-channel conductance is interpreted as arising in the formation of oligomeric highly cooperative channels, resulting in the cation-induced membrane polarization and enhanced transport rates without or under pH-active gradient. These channels are selectively responsive to the presence of K(+) cations, even in the presence of a large excess of Na(+). From the conceptual point of view, these channels express a synergistic adaptive behavior: the addition of the K(+) cation drives the selection and the construction of constitutional polarized ion channels toward the selective conduction of the K(+) cation that promotes their generation in the first place.

  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. Characterization of ryanodine receptor type 1 single channel activity using "on-nucleus" patch clamp.

    Science.gov (United States)

    Wagner, Larry E; Groom, Linda A; Dirksen, Robert T; Yule, David I

    2014-08-01

    In this study, we provide the first description of the biophysical and pharmacological properties of ryanodine receptor type 1 (RyR1) expressed in a native membrane using the on-nucleus configuration of the patch clamp technique. A stable cell line expressing rabbit RyR1 was established (HEK-RyR1) using the FLP-in 293 cell system. In contrast to untransfected cells, RyR1 expression was readily demonstrated by immunoblotting and immunocytochemistry in HEK-RyR1 cells. In addition, the RyR1 agonists 4-CMC and caffeine activated Ca(2+) release that was inhibited by high concentrations of ryanodine. On nucleus patch clamp was performed in nuclei prepared from HEK-RyR1 cells. Raising the [Ca(2+)] in the patch pipette resulted in the appearance of a large conductance cation channel with well resolved kinetics and the absence of prominent subconductance states. Current versus voltage relationships were ohmic and revealed a chord conductance of ∼750pS or 450pS in symmetrical 250mM KCl or CsCl, respectively. The channel activity was markedly enhanced by caffeine and exposure to ryanodine resulted in the appearance of a subconductance state with a conductance ∼40% of the full channel opening with a Po near unity. In total, these properties are entirely consistent with RyR1 channel activity. Exposure of RyR1 channels to cyclic ADP ribose (cADPr), nicotinic acid adenine dinucleotide phosphate (NAADP) or dantrolene did not alter the single channel activity stimulated by Ca(2+), and thus, it is unlikely these molecules directly modulate RyR1 channel activity. In summary, we describe an experimental platform to monitor the single channel properties of RyR channels. We envision that this system will be influential in characterizing disease-associated RyR mutations and the molecular determinants of RyR channel modulation.

  18. Inhibition of Inactive States of Tetrodotoxin-Sensitive Sodium Channels Reduces Spontaneous Firing of C-Fiber Nociceptors and Produces Analgesia in Formalin and Complete Freund's Adjuvant Models of Pain.

    Directory of Open Access Journals (Sweden)

    David J Matson

    Full Text Available While genetic evidence shows that the Nav1.7 voltage-gated sodium ion channel is a key regulator of pain, it is unclear exactly how Nav1.7 governs neuronal firing and what biophysical, physiological, and distribution properties of a pharmacological Nav1.7 inhibitor are required to produce analgesia. Here we characterize a series of aminotriazine inhibitors of Nav1.7 in vitro and in rodent models of pain and test the effects of the previously reported "compound 52" aminotriazine inhibitor on the spiking properties of nociceptors in vivo. Multiple aminotriazines, including some with low terminal brain to plasma concentration ratios, showed analgesic efficacy in the formalin model of pain. Effective concentrations were consistent with the in vitro potency as measured on partially-inactivated Nav1.7 but were far below concentrations required to inhibit non-inactivated Nav1.7. Compound 52 also reversed thermal hyperalgesia in the complete Freund's adjuvant (CFA model of pain. To study neuronal mechanisms, electrophysiological recordings were made in vivo from single nociceptive fibers from the rat tibial nerve one day after CFA injection. Compound 52 reduced the spontaneous firing of C-fiber nociceptors from approximately 0.7 Hz to 0.2 Hz and decreased the number of action potentials evoked by suprathreshold tactile and heat stimuli. It did not, however, appreciably alter the C-fiber thresholds for response to tactile or thermal stimuli. Surprisingly, compound 52 did not affect spontaneous activity or evoked responses of Aδ-fiber nociceptors. Results suggest that inhibition of inactivated states of TTX-S channels, mostly likely Nav1.7, in the peripheral nervous system produces analgesia by regulating the spontaneous discharge of C-fiber nociceptors.

  19. Berberine induces pacemaker potential inhibition via cGMP-dependent ATP-sensitive K+ channels by stimulating mu/delta opioid receptors in cultured interstitial cells of Cajal from mouse small intestine.

    Science.gov (United States)

    Kim, Hyun Jung; Kim, Hyungwoo; Jung, Myeong Ho; Kwon, Young Kyu; Kim, Byung Joo

    2016-10-01

    Berberine is traditionally used to treat gastrointestinal (GI) motility disorders. The interstitial cells of Cajal (ICCs) are the pacemaker cells of the gastrointestinal tract, which are responsible for the production of gut movements. The present study aimed to investigate the effects of berberine on pacemaker potentials (PPs) in cultured ICC clusters from the mouse small intestine, and sought to identify the receptors involved and the underlying mechanisms of action. All experiments were performed on cultured ICCs, and a whole‑cell patch‑clamp configuration was used to record PPs from ICC clusters (current clamp mode). Under current clamp mode, berberine was shown to decrease the amplitude and frequency of PPs. However, these effects were suppressed by treatment with glibenclamide, a specific ATP‑sensitive K+ channel blocker. Nor‑binaltorphimine dihydrochloride (a kappa opioid receptor antagonist) did not suppress berberine‑induced PP inhibition, whereas ICI 174,864 (a delta opioid receptor antagonist) and CTOP (a mu opioid receptor antagonist) did suppress the inhibitory effects of berberine. Pretreatment with SQ‑22536 (an adenylate cyclase inhibitor) or with KT‑5720 (a protein kinase A inhibitor) did not suppress the effects of berberine; however, pretreatment with 1H‑[1,2,4] oxadiazolo [4,3‑a] quinoxalin‑1‑one (a guanylate cyclase inhibitor) or KT‑5823 [a protein kinase G (PKG) inhibitor] did. In addition, berberine stimulated cyclic guanosine monophosphate (cGMP) production in ICCs. These observations indicate that berberine may inhibit the pacemaker activity of ICC clusters via ATP‑sensitive K+ channels and the cGMP‑PKG‑dependent pathway by stimulating mu and delta opioid receptors. Therefore, berberine may provide a basis for the development of novel agents for the treatment of GI motility dysfunction. PMID:27601272

  20. Acute and Chronic Toxicity, Cytochrome P450 Enzyme Inhibition, and hERG Channel Blockade Studies with a Polyherbal, Ayurvedic Formulation for Inflammation

    Directory of Open Access Journals (Sweden)

    Debendranath Dey

    2015-01-01

    Full Text Available Ayurvedic plants are known for thousands of years to have anti-inflammatory and antiarthritic effect. We have recently shown that BV-9238, a proprietary formulation of Withania somnifera, Boswellia serrata, Zingiber officinale, and Curcuma longa, inhibits LPS-induced TNF-alpha and nitric oxide production from mouse macrophage and reduces inflammation in different animal models. To evaluate the safety parameters of BV-9238, we conducted a cytotoxicity study in RAW 264.7 cells (0.005–1 mg/mL by MTT/formazan method, an acute single dose (2–10 g/kg bodyweight toxicity study and a 180-day chronic study with 1 g and 2 g/kg bodyweight in Sprague Dawley rats. Some sedation, ptosis, and ataxia were observed for first 15–20 min in very high acute doses and hence not used for further chronic studies. At the end of 180 days, gross and histopathology, blood cell counts, liver and renal functions were all at normal levels. Further, a modest attempt was made to assess the effects of BV-9238 (0.5 µg/mL on six major human cytochrome P450 enzymes and 3H radioligand binding assay with human hERG receptors. BV-9238 did not show any significant inhibition of these enzymes at the tested dose. All these suggest that BV-9238 has potential as a safe and well tolerated anti-inflammatory formulation for future use.

  1. Liquid-solid extraction of cationic metals by cationic amphiphiles

    International Nuclear Information System (INIS)

    In the field of selective separation for recycling of spent nuclear fuel, liquid-liquid extraction processes are widely used (PUREX, DIAMEX..) in industrial scale. In order to guarantee a sustainable nuclear energy for the forthcoming generations, alternative reprocessing techniques are under development. One of them bases on the studies from Heckmann et al in the 80's and consists in selectively precipitating actinides from aqueous waste solutions by cationic surfactants (liquid-solid extraction). This technique has some interesting advantages over liquid-liquid extraction techniques, because several steps are omitted like stripping or solvent washing. Moreover, the amount of waste is decreased considerably, since no contaminated organic solvent is produced. In this thesis, we have carried out a physico-chemical study to understand the specific interactions between the metallic cations with the cationic surfactant. First, we have analysed the specific effect of the different counter-ions (Cl-, NO3-, C2O42-) and then the effect of alkaline cations on the structural properties of the surfactant aggregation in varying thermodynamical conditions. Finally, different multivalent cations (Cu2+, Zn2+, UO22+, Fe3+, Nd3+, Eu3+, Th4+) were considered; we have concluded that depending on the anionic complex of these metals formed in acidic media, we can observe either an adsorption at the micellar interface or not. This adsorption has a large influence of the surfactant aggregation properties and determines the limits of the application in term of ionic strength, temperature and surfactant concentration. (author)

  2. Novel role for the transient potential receptor melastatin 4 channel in guinea pig detrusor smooth muscle physiology.

    Science.gov (United States)

    Smith, Amy C; Hristov, Kiril L; Cheng, Qiuping; Xin, Wenkuan; Parajuli, Shankar P; Earley, Scott; Malysz, John; Petkov, Georgi V

    2013-03-01

    Members of the transient receptor potential (TRP) channel superfamily, including the Ca(2+)-activated monovalent cation-selective TRP melastatin 4 (TRPM4) channel, have been recently identified in the urinary bladder. However, their expression and function at the level of detrusor smooth muscle (DSM) remain largely unexplored. In this study, for the first time we investigated the role of TRPM4 channels in guinea pig DSM excitation-contraction coupling using a multidisciplinary approach encompassing protein detection, electrophysiology, live-cell Ca(2+) imaging, DSM contractility, and 9-phenanthrol, a recently characterized selective inhibitor of the TRPM4 channel. Western blot and immunocytochemistry experiments demonstrated the expression of the TRPM4 channel in whole DSM tissue and freshly isolated DSM cells with specific localization on the plasma membrane. Perforated whole cell patch-clamp recordings and real-time Ca(2+) imaging experiments with fura 2-AM, both using freshly isolated DSM cells, revealed that 9-phenanthrol (30 μM) significantly reduced the cation current and decreased intracellular Ca(2+) levels. 9-Phenanthrol (0.1-30 μM) significantly inhibited spontaneous, 0.1 μM carbachol-induced, 20 mM KCl-induced, and nerve-evoked contractions in guinea pig DSM-isolated strips with IC50 values of 1-7 μM and 70-80% maximum inhibition. 9-Phenanthrol also reduced nerve-evoked contraction amplitude induced by continuous repetitive electrical field stimulation of 10-Hz frequency and shifted the frequency-response curve (0.5-50 Hz) relative to the control. Collectively, our data demonstrate the novel finding that TRPM4 channels are expressed in guinea pig DSM and reveal their critical role in the regulation of guinea pig DSM excitation-contraction coupling.

  3. The role of transient receptor potential channels in metabolic syndrome

    DEFF Research Database (Denmark)

    Liu, Daoyan; Zhu, Zhiming; Tepel, Martin

    2008-01-01

    Metabolic syndrome is correlated with increased cardiovascular risk and characterized by several factors, including visceral obesity, hypertension, insulin resistance, and dyslipidemia. Several members of a large family of nonselective cation entry channels, e.g., transient receptor potential (TRP...

  4. 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.

  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.

    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

  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 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

  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

    2016-01-05

    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.

  8. Sustained inhibition of the NaV1.7 sodium channel by engineered dimers of the domain II binding peptide GpTx-1.

    Science.gov (United States)

    Murray, Justin K; Biswas, Kaustav; Holder, J Ryan; Zou, Anruo; Ligutti, Joseph; Liu, Dong; Poppe, Leszek; Andrews, Kristin L; Lin, Fen-Fen; Meng, Shi-Yuan; Moyer, Bryan D; McDonough, Stefan I; Miranda, Les P

    2015-11-01

    Many efforts are underway to develop selective inhibitors of the voltage-gated sodium channel NaV1.7 as new analgesics. Thus far, however, in vitro selectivity has proved difficult for small molecules, and peptides generally lack appropriate pharmacokinetic properties. We previously identified the NaV1.7 inhibitory peptide GpTx-1 from tarantula venom and optimized its potency and selectivity via structure-guided analoging. To further understand GpTx-1 binding to NaV1.7, we have mapped the binding site to transmembrane segments 1-4 of the second pseudosubunit internal repeat (commonly referred to as Site 4) using NaV1.5/NaV1.7 chimeric protein constructs. We also report that select GpTx-1 amino acid residues apparently not contacting NaV1.7 can be derivatized with a hydrophilic polymer without adversely affecting peptide potency. Homodimerization of GpTx-1 with a bifunctional polyethylene glycol (PEG) linker resulted in a compound with increased potency and a significantly reduced off-rate, demonstrating the ability to modulate the function and properties of GpTx-1 by linking to additional molecules. PMID:26112439

  9. Membrane lipid modulations remove divalent open channel block from TRP-like and NMDA channels.

    Science.gov (United States)

    Parnas, Moshe; Katz, Ben; Lev, Shaya; Tzarfaty, Vered; Dadon, Daniela; Gordon-Shaag, Ariela; Metzner, Henry; Yaka, Rami; Minke, Baruch

    2009-02-25

    Open channel block is a process in which ions bound to the inside of a channel pore block the flow of ions through that channel. Repulsion of the blocking ions by depolarization is a known mechanism of open channel block removal. For the NMDA channel, this mechanism is necessary for channel activation and is involved in neuronal plasticity. Several types of transient receptor potential (TRP) channels, including the Drosophila TRP and TRP-like (TRPL) channels, also exhibit open channel block. Therefore, removal of open channel block is necessary for the production of the physiological response to light. Because there is no membrane depolarization before the light response develops, it is not clear how the open channel block is removed, an essential step for the production of a robust light response under physiological conditions. Here we present a novel mechanism to alleviate open channel block in the absence of depolarization by membrane lipid modulations. The results of this study show open channel block removal by membrane lipid modulations in both TRPL and NMDA channels of the photoreceptor cells and CA1 hippocampal neurons, respectively. Removal of open channel block is characterized by an increase in the passage-rate of the blocking cations through the channel pore. We propose that the profound effect of membrane lipid modulations on open channel block alleviation, allows the productions of a robust current in response to light in the absence of depolarization.

  10. Binding of alkaline cations to the double-helical form of gramicidin.

    OpenAIRE

    Chen, Y; Wallace, B.A.

    1996-01-01

    Gramicidin is a polypeptide antibiotic that forms monovalent cation-specific channels in membrane environments. In organic solvents and in lipids containing unsaturated fatty acid chains, it forms a double-helical "pore" structure, in which two monomers are intertwined. This form of gramicidin can bind two cations inside its lumen, and the crystal structures of both an ion complex and an ion-free form have been determined. In this study, we have used circular dichroism (CD) spectroscopy to ex...

  11. Cationic speciation in nonaqueous media

    International Nuclear Information System (INIS)

    Electronic spectra of solutions of d transition elements in the superacids HF, H2SO4, HSO3F, and CF3SO3H and in chloroaluminate melts indicate that in acidic monaqueous media the elements are present as solvated cations, whereas in basic media the speciation is anionic, the same situation as in aqueous solutions. Further, in very highly acidic media, cations in very low oxidation states are stable (e.g., Ti2+), but these disproportionate on addition of base to the system. In this paper spectra, where available, of U, Np, and Pu in oxidation states III and IV in aqueous media, in protonic superacids, and in chloroaluminates are presented to postulate cationic speciation of these early actinides in highly acidic media

  12. Tumor Necrosis Factor Alpha Inhibits L-Type Ca2+ Channels in Sensitized Guinea Pig Airway Smooth Muscle through ERK 1/2 Pathway

    Science.gov (United States)

    Reyes-García, Jorge; Flores-Soto, Edgar; Solís-Chagoyán, Héctor; Sommer, Bettina; Díaz-Hernández, Verónica; García-Hernández, Luz María

    2016-01-01

    Tumor necrosis factor alpha (TNF-α) is a potent proinflammatory cytokine that plays a significant role in the pathogenesis of asthma by inducing hyperresponsiveness and airway remodeling. TNF-α diminishes the L-type voltage dependent Ca2+ channel (L-VDCC) current in cardiac myocytes, an observation that seems paradoxical. In guinea pig sensitized tracheas KCl responses were lower than in control tissues. Serum from sensitized animals (Ser-S) induced the same phenomenon. In tracheal myocytes from nonsensitized (NS) and sensitized (S) guinea pigs, an L-VDCC current (ICa) was observed and diminished by Ser-S. The same decrease was detected in NS myocytes incubated with TNF-α, pointing out that this cytokine might be present in Ser-S. We observed that a small-molecule inhibitor of TNF-α (SMI-TNF) and a TNF-α receptor 1 (TNFR1) antagonist (WP9QY) reversed ICa decrease induced by Ser-S in NS myocytes, confirming the former hypothesis. U0126 (a blocker of ERK 1/2 kinase) also reverted the decrease in ICa. Neither cycloheximide (a protein synthesis inhibitor) nor actinomycin D (a transcription inhibitor) showed any effect on the TNF-α-induced ICa reduction. We found that CaV1.2 and CaV1.3 mRNA and proteins were expressed in tracheal myocytes and that sensitization did not modify them. In cardiac myocytes, ERK 1/2 phosphorylates two sites of the L-VDCC, augmenting or decreasing ICa; we postulate that, in guinea pig tracheal smooth muscle, TNF-α diminishes ICa probably by phosphorylating the L-VDCC site that reduces its activity through the ERK1/2 MAP kinase pathway. PMID:27445440

  13. Tumor Necrosis Factor Alpha Inhibits L-Type Ca(2+) Channels in Sensitized Guinea Pig Airway Smooth Muscle through ERK 1/2 Pathway.

    Science.gov (United States)

    Reyes-García, Jorge; Flores-Soto, Edgar; Solís-Chagoyán, Héctor; Sommer, Bettina; Díaz-Hernández, Verónica; García-Hernández, Luz María; Montaño, Luis M

    2016-01-01

    Tumor necrosis factor alpha (TNF-α) is a potent proinflammatory cytokine that plays a significant role in the pathogenesis of asthma by inducing hyperresponsiveness and airway remodeling. TNF-α diminishes the L-type voltage dependent Ca(2+) channel (L-VDCC) current in cardiac myocytes, an observation that seems paradoxical. In guinea pig sensitized tracheas KCl responses were lower than in control tissues. Serum from sensitized animals (Ser-S) induced the same phenomenon. In tracheal myocytes from nonsensitized (NS) and sensitized (S) guinea pigs, an L-VDCC current (ICa) was observed and diminished by Ser-S. The same decrease was detected in NS myocytes incubated with TNF-α, pointing out that this cytokine might be present in Ser-S. We observed that a small-molecule inhibitor of TNF-α (SMI-TNF) and a TNF-α receptor 1 (TNFR1) antagonist (WP9QY) reversed ICa decrease induced by Ser-S in NS myocytes, confirming the former hypothesis. U0126 (a blocker of ERK 1/2 kinase) also reverted the decrease in ICa. Neither cycloheximide (a protein synthesis inhibitor) nor actinomycin D (a transcription inhibitor) showed any effect on the TNF-α-induced ICa reduction. We found that CaV1.2 and CaV1.3 mRNA and proteins were expressed in tracheal myocytes and that sensitization did not modify them. In cardiac myocytes, ERK 1/2 phosphorylates two sites of the L-VDCC, augmenting or decreasing ICa; we postulate that, in guinea pig tracheal smooth muscle, TNF-α diminishes ICa probably by phosphorylating the L-VDCC site that reduces its activity through the ERK1/2 MAP kinase pathway.

  14. 公丁香提取物抑制CFTR氯离子通道的发现与研究%The extract of clove inhibits CFTR chloride channel

    Institute of Scientific and Technical Information of China (English)

    栾剑; 张耀方; 杨红

    2015-01-01

    Cystic fibrosis transmembrane conductance regulator (CFTR) is an epithelial chloride chan‐nel .In recent years ,the blockers of CFTR become the new hot spot in the treatment of secretory di‐arrhea .The aim of this research is using high‐throughput screening techniques screened blockers of CFTR chloride channel from traditional Chinese medicine .In this study ,after 40000 fractions of Chi‐nese herbal medicine have been screened ,clove extract was found .In cell‐based fluorescence assays and voltage clamp experiments ,the best active fraction‐E06 significantly blocks CFTR chloride chan‐nel .Therefore ,clove extract screened from traditional Chinese medicine blocks CFTR chloride chan‐nel and provides a theoretical basis for the in‐depth study of anti‐diarrheal drugs .%囊性纤维化跨膜电导调节因子(CFTR)是一种上皮细胞顶膜中表达的氯离子通道,是近年来治疗分泌型腹泻的新热点。利用高通量筛选技术,自中国传统中药中筛选能够抑制CFTR氯离子通道的中药组分。结果显示,自500种中草药的40000种中药组分中筛选到公丁香。经细胞荧光实验和电压膜片钳实验验证公丁香最佳活性孔———E06对CFTR具有明显的抑制作用,IC50=103 mg/L 。本研究结果为深入探讨公丁香的抗泻药物研发提供理论依据。

  15. Psychiatric Disorders and TRP Channels: Focus on Psychotropic Drugs

    OpenAIRE

    Nazıroğlu, Mustafa; Demirdaş, Arif

    2015-01-01

    Psychiatric and neurological disorders are mostly associated with the changes in neural calcium ion signaling pathways required for activity-triggered cellular events. One calcium channel family is the TRP cation channel family, which contains seven subfamilies. Results of recent papers have discovered that calcium ion influx through TRP channels is important. We discuss the latest advances in calcium ion influx through TRP channels in the etiology of psychiatric disorders. Activation of TRPC...

  16. Lack of negatively charged residues at the external mouth of Kir2.2 channels enable the voltage-dependent block by external Mg2+.

    Directory of Open Access Journals (Sweden)

    Junwei Li

    Full Text Available Kir channels display voltage-dependent block by cytosolic cations such as Mg2+ and polyamines that causes inward rectification. In fact, cations can regulate K channel activity from both the extracellular and intracellular sides. Previous studies have provided insight into the up-regulation of Kir channel activity by extracellular K+ concentration. In contrast, extracellular Mg2+ has been found to reduce the amplitude of the single-channel current at milimolar concentrations. However, little is known about the molecular mechanism of Kir channel blockade by external Mg2+ and the relationship between the Mg2+ blockade and activity potentiation by permeant K+ ions. In this study, we applied an interactive approach between theory and experiment. Electrophysiological recordings on Kir2.2 and its mutants were performed by heterologous expression in Xenopus laevis oocytes. Our results confirmed that extracellular Mg2+ could reduce heterologously expressed WT Kir2.2 currents in a voltage dependent manner. The kinetics of inhibition and recovery of Mg2+ exhibit a 3∼4s time constant. Molecular dynamics simulation results revealed a Mg2+ binding site located at the extracellular mouth of Kir2.2 that showed voltage-dependent Mg2+ binding. The mutants, G119D, Q126E and H128D, increased the number of permeant K+ ions and reduced the voltage-dependent blockade of Kir2.2 by extracellular Mg2+.

  17. Post-Translational Modifications of TRP Channels

    Directory of Open Access Journals (Sweden)

    Olaf Voolstra

    2014-04-01

    Full Text Available Transient receptor potential (TRP channels constitute an ancient family of cation channels that have been found in many eukaryotic organisms from yeast to human. TRP channels exert a multitude of physiological functions ranging from Ca2+ homeostasis in the kidney to pain reception and vision. These channels are activated by a wide range of stimuli and undergo covalent post-translational modifications that affect and modulate their subcellular targeting, their biophysical properties, or channel gating. These modifications include N-linked glycosylation, protein phosphorylation, and covalent attachment of chemicals that reversibly bind to specific cysteine residues. The latter modification represents an unusual activation mechanism of ligand-gated ion channels that is in contrast to the lock-and-key paradigm of receptor activation by its agonists. In this review, we summarize the post-translational modifications identified on TRP channels and, when available, explain their physiological role.

  18. The chloride channel inhibitor NS3736 [corrected] prevents bone resorption in ovariectomized rats without changing bone formation

    DEFF Research Database (Denmark)

    Schaller, Sophie; Henriksen, Kim; Sveigaard, Christina;

    2004-01-01

    Chloride channel activity is essential for osteoclast function. Consequently, inhibition of the osteoclastic chloride channel should prevent bone resorption. Accordingly, we tested a chloride channel inhibitor on bone turnover and found that it inhibits bone resorption without affecting bone form...

  19. Research progress in cation-π interactions

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Cation-π interaction is a potent intermolecular interaction between a cation and an aromatic system,which has been viewed as a new kind of binding force,as being compared with the classical interactions(e.g. hydrogen bonding,electrostatic and hydrophobic interactions). Cation-π interactions have been observed in a wide range of biological contexts. In this paper,we present an overview of the typical cation-π interactions in biological systems,the experimental and theoretical investigations on cation-π interactions,as well as the research results on cation-π interactions in our group.

  20. Research progress in cation-π interactions

    Institute of Scientific and Technical Information of China (English)

    CHENG JiaGao; LUO XiaoMin; YAN XiuHua; LI Zhong; TANG Yun; JIANG HuaLiang; ZHU WeiLiang

    2008-01-01

    Cation-π interaction is a potent intermolecular interaction between a cation and an aromatic system, which has been viewed as a new kind of binding force, as being compared with the classical interac-tions (e.g. hydrogen bonding, electrostatic and hydrophobic interactions). Cation-π interactions have been observed in a wide range of biological contexts. In this paper, we present an overview of the typi-cal cation-π interactions in biological systems, the experimental and theoretical investigations on cation-π interactions, as well as the research results on cation-π interactions in our group.

  1. Inhibition of a store-operated Ca2+ entry pathway in human endothelial cells by the isoquinoline derivative LOE 908.

    OpenAIRE

    Encabo, A.; Romanin, C; Birke, F. W.; Kukovetz, W. R.; Groschner, K

    1996-01-01

    1. The novel cation channel blocker, LOE 908, was tested for its effects on Ca2+ entry and membrane currents activated by depletion of intracellular Ca2+ stores in human endothelial cells. 2. LOE 908 inhibited store-operated Ca2+ entry induced by direct depletion of Ca2+ stores with 100 nM thapsigargin or 100 nM ionomycin with an EC50 of 2 microM and 4 microM, respectively. 3. LOE 908 did not affect thapsigargin- or ionomycin-induced Ca2+ release from intracellular stores up to concentrations...

  2. Marine Toxins Targeting Ion Channels

    Directory of Open Access Journals (Sweden)

    Hugo R. Arias

    2006-04-01

    Full Text Available Abstract: This introductory minireview points out the importance of ion channels for cell communication. The basic concepts on the structure and function of ion channels triggered by membrane voltage changes, the so-called voltage-gated ion channels (VGICs, as well as those activated by neurotransmitters, the so-called ligand-gated ion channel (LGICs, are introduced. Among the most important VGIC superfamiles, we can name the voltage-gated Na+ (NaV, Ca2+ (CaV, and K+ (KV channels. Among the most important LGIC super families, we can include the Cys-loop or nicotinicoid, the glutamate-activated (GluR, and the ATP-activated (P2XnR receptor superfamilies. Ion channels are transmembrane proteins that allow the passage of different ions in a specific or unspecific manner. For instance, the activation of NaV, CaV, or KV channels opens a pore that is specific for Na+, Ca2+, or K+, respectively. On the other hand, the activation of certain LGICs such as nicotinic acetylcholine receptors, GluRs, and P2XnRs allows the passage of cations (e.g., Na+, K+, and/or Ca2+, whereas the activation of other LGICs such as type A γ-butyric acid and glycine receptors allows the passage of anions (e.g., Cl− and/or HCO3−. In this regard, the activation of NaV and CaV as well as ligand-gated cation channels produce membrane depolarization, which finally leads to stimulatory effects in the cell, whereas the activation of KV as well as ligand-gated anion channels induce membrane hyperpolarization that finally leads to inhibitory effects in the cell. The importance of these ion channel superfamilies is emphasized by considering their physiological functions throughout the body as well as their pathophysiological implicance in several neuronal diseases. In this regard, natural molecules, and especially marine toxins, can be potentially used as modulators (e.g., inhibitors or prolongers of ion channel functions to treat or to alleviate a specific

  3. Relevance of lysine snorkeling in the outer transmembrane domain of small viral potassium ion channels.

    Science.gov (United States)

    Gebhardt, Manuela; Henkes, Leonhard M; Tayefeh, Sascha; Hertel, Brigitte; Greiner, Timo; Van Etten, James L; Baumeister, Dirk; Cosentino, Cristian; Moroni, Anna; Kast, Stefan M; Thiel, Gerhard

    2012-07-17

    Transmembrane domains (TMDs) are often flanked by Lys or Arg because they keep their aliphatic parts in the bilayer and their charged groups in the polar interface. Here we examine the relevance of this so-called "snorkeling" of a cationic amino acid, which is conserved in the outer TMD of small viral K(+) channels. Experimentally, snorkeling activity is not mandatory for Kcv(PBCV-1) because K29 can be replaced by most of the natural amino acids without any corruption of function. Two similar channels, Kcv(ATCV-1) and Kcv(MT325), lack a cytosolic N-terminus, and neutralization of their equivalent cationic amino acids inhibits their function. To understand the variable importance of the cationic amino acids, we reanalyzed molecular dynamics simulations of Kcv(PBCV-1) and N-terminally truncated mutants; the truncated mutants mimic Kcv(ATCV-1) and Kcv(MT325). Structures were analyzed with respect to membrane positioning in relation to the orientation of K29. The results indicate that the architecture of the protein (including the selectivity filter) is only weakly dependent on TMD length and protonation of K29. The penetration depth of Lys in a given protonation state is independent of the TMD architecture, which leads to a distortion of shorter proteins. The data imply that snorkeling can be important for K(+) channels; however, its significance depends on the architecture of the entire TMD. The observation that the most severe N-terminal truncation causes the outer TMD to move toward the cytosolic side suggests that snorkeling becomes more relevant if TMDs are not stabilized in the membrane by other domains.

  4. The effect of the alkali metal cation on the electrocatalytic oxidation of formate on platinum

    OpenAIRE

    Previdello, B.; E. Machado; Varela, H.

    2014-01-01

    Non-covalent interactions between hydrated alkali metal cations and adsorbed oxygenated species on platinum might considerably inhibit some electrocatalytic reactions. We report in this communication the effect exerted by electrolyte alkali metal cations on the electro-oxidation of formate ions on platinum. The system was investigated by means of cyclic voltammetry and chronoamperometry in the presence of an electrolyte containing Li+, Na+, or K+. As already observed for other systems, the ge...

  5. Influence of alkylammonium cation on multisweep cyclic voltammetry of Cu(II) on carbon paste electrode modified with montmorillonite

    OpenAIRE

    Navrátilová, Zuzana; Hranická, Zuzana

    2010-01-01

    Cyclic voltammetry of Cu2+ on the carbon paste electrode modified either with montmorillonite SAz-1 or with montmorillonite SAz-1 pretreated with hexadecyltrimethylammonium cation was performed to find the hexadecyltrimethylammonium cation influence on the Cu2+ sorption. In addition, the hexadecyltrimethylammonium presence in the sorption solution was studied, too. In this case, a significant inhibition on the Cu2+ sorption was found. The inhibition is supposed to be a conse...

  6. Tripodal Receptors for Cation and Anion Sensors

    NARCIS (Netherlands)

    Kuswandi, Bambang; Nuriman,; Verboom, Willem; Reinhoudt, David N.

    2006-01-01

    This review discusses different types of artificial tripodal receptors for the selectiverecognition and sensing of cations and anions. Examples on the relationship between structure andselectivity towards cations and anions are described. Furthermore, their applications as potentiometricion sensing

  7. Features definition exchange cations in sedimentary rocks.

    OpenAIRE

    Bilec'ka V.A.

    2008-01-01

    The research method of determination of exchange cations in calcareous sedimentary rocks of different extractants, the influence of the ratio between the solid and liquid phases on extrusion exchange cations.

  8. Features definition exchange cations in sedimentary rocks.

    Directory of Open Access Journals (Sweden)

    Bilec'ka V.A.

    2008-05-01

    Full Text Available The research method of determination of exchange cations in calcareous sedimentary rocks of different extractants, the influence of the ratio between the solid and liquid phases on extrusion exchange cations.

  9. Cyclic ADP-ribose and hydrogen peroxide synergize with ADP-ribose in the activation of TRPM2 channels.

    Science.gov (United States)

    Kolisek, Martin; Beck, Andreas; Fleig, Andrea; Penner, Reinhold

    2005-04-01

    The melastatin-related transient receptor potential channel TRPM2 is a plasma membrane Ca2+-permeable cation channel that is activated by intracellular adenosine diphosphoribose (ADPR) binding to the channel's enzymatic Nudix domain. Channel activity is also seen with nicotinamide dinucleotide (NAD+) and hydrogen peroxide (H2O2), but their mechanisms of action remain unknown. Here, we identify cyclic adenosine diphosphoribose (cADPR) as an agonist of TRPM2 with dual activity: at concentrations above 100 microM, cADPR can gate the channel by itself, whereas lower concentrations of 10 microM have a potentiating effect that enables ADPR to gate the channel at nanomolar concentrations. ADPR's breakdown product adenosine monophosphate (AMP) specifically inhibits ADPR, but not cADPR-mediated gating of TRPM2, whereas the cADPR antagonist 8-Br-cADPR exhibits the reverse block specificity. Our results establish TRPM2 as a coincidence detector for ADPR and cADPR signaling and provide a functional context for cADPR as a second messenger for Ca2+ influx.

  10. Antiviral effect of cationic compounds on bacteriophages

    Directory of Open Access Journals (Sweden)

    Mai Huong eChatain-Ly

    2013-03-01

    Full Text Available The antiviral activity of several cationic compounds - cetytrimethylammonium (CTAB, chitosan, nisin and lysozyme - was investigated on the bacteriophage c2 (DNA head and non-contractile tail infecting Lactococcus strains and the bacteriophage MS2 (F-specific RNA infecting E.coli. Firstly, these activities were evaluated in a phosphate buffer pH 7- 10 mM. The CTAB had a virucidal effect on the Lactococcus bacteriophages, but not on the MS2. After 1 min of contact with 0.125 mM CTAB, the c2 population was reduced from 6 log(pfu/mL to 1,5 log(pfu/mL and completely deactivated at 1 mM. On the contrary, chitosan inhibited the MS2 more than it did the bacteriophages c2. No antiviral effect was observed for the nisin or the lysozyme on bacteriophages after 1 min of treatment. A 1 and 2.5 log reduction was respectively observed for nisin and lysozyme when the treatment time increased (5 or 10 min. These results showed that the antiviral effect depended both on the virus and structure of the antimicrobial compounds. The antiviral activity of these compounds was also evaluated in different physico-chemical conditions and in complex matrices. The antiviral activity of CTAB was impaired in acid pH and with an increase of the ionic strength. These results might be explained by the electrostatic interactions between cationic compounds and negatively charged particles such as bacteriophages or other compounds in a matrix. Milk proved to be protective suggesting the components of food could interfere with antimicrobial compounds.

  11. Cationic electrodepositable coating composition comprising lignin

    Science.gov (United States)

    Fenn, David; Bowman, Mark P; Zawacky, Steven R; Van Buskirk, Ellor J; Kamarchik, Peter

    2013-07-30

    A cationic electrodepositable coating composition is disclosed. The present invention in directed to a cationic electrodepositable coating composition comprising a lignin-containing cationic salt resin, that comprises (A) the reaction product of: lignin, an amine, and a carbonyl compound; (B) the reaction product of lignin, epichlorohydrin, and an amine; or (C) combinations thereof.

  12. Biosorption of radiocesium by deinococcus radiodurans influenced by cations

    International Nuclear Information System (INIS)

    Deinococcus radiodurans has a strong ability to withstand high doses of radiation, which makes it as an ideal candidate for bioremediation of sites contaminated with radionuclides and toxic chemicals. However, no data is available on whether D. radiodurans has a specific sorption capacity to radiocesium for bioremediation purpose. The radiocesium biosorption capacity of live cells of D. radiodurans in the presence of other interfering cations was investigated. The maximum biosorption capacity of radiocesium by D. radiodurans in equilibrium state was about 2,100 kBq/kg (fresh weight basis). Among the tested monovalent cations, NH4+ had the strongest antagonism on 134Cs biosorption for D. radiodurans. However, this antagonism could only be observed at a concentration as high as 100 mmol/L. Divalent cations, such as Ca2+ and Pb2+ could reduced the biosorption of radiocesium by D. radiodurans. Al3+ and Cr3+ were cytotoxic to D. radiodurans cells, the growth of D. radiodurans cells was inhibited when the concentrations of these cations were greater than 1 mmol/L. (authors)

  13. Fibrin solubilizing properties of certain anionic and cationic detergents.

    Science.gov (United States)

    Chakrabarty, S

    1989-08-15

    The fibrinolytic (fibrin dissolving) properties of several anionic, cationic, nonionic and zwitterionic detergents were assessed in an in vitro fibrin agarose assay. Of the 4 anionic detergents tested, only sodium dodecyl sulfate (SDS) was found to be fibrinolytic. SDS was fibrinolytic either in the absence or presence of factor XIII. Four other cationic detergents were found to possess similar fibrinolytic properties. These cationic detergents were cetyltrimethylammonium bromide (CTAB), mix alkyltrimethyl ammonium bromide (MTAB), hexadecyltrimethylammonium bromide (HTAB) and cetylpyridium chloride (CPC). The nonionic (digitonin, triton X-100/tween 20) and zeitterionic (CHAPS, zeittergent 3-08) detergents were not fibrinolytic. Detergents mediated fibrinolysis, unlike that of tissue type plasminogen activator and urokinase, was independent of the presence of plasminogen. Non-detergents such as polyethylene glycol and highly charged compounds such as poly-1-lysine and poly-1-glutamic acid were not fibrinolytic. Fibrinolytic activity was observed for SDS and the cationic detergents at concentrations ranging from 0.1-10 percent. The effects of these fibrinolytic detergents (SDS, CTAB, MTAB, HTAB and CPC) on clot formation and on pre-formed clots were then assessed, using freshly drawn human venous blood. Incorporation of these detergents into blood inhibited the formation of clots in a concentration dependent manner. The detergents were also able to dissolve pre-formed clots in a similar fashion. SDS was found to be most potent in these properties. PMID:2510356

  14. M channel enhancers and physiological M channel block.

    Science.gov (United States)

    Linley, John E; Pettinger, Louisa; Huang, Dongyang; Gamper, Nikita

    2012-02-15

    M-type (Kv7, KCNQ) K(+) channels control the resting membrane potential of many neurons, including peripheral nociceptive sensory neurons. Several M channel enhancers were suggested as prospective analgesics, and targeting M channels specifically in peripheral nociceptors is a plausible strategy for peripheral analgesia. However, receptor-induced inhibition of M channels in nociceptors is often observed in inflammation and may contribute to inflammatory pain. Such inhibition is predominantly mediated by phospholipase C. We investigated four M channel enhancers (retigabine, flupirtine, zinc pyrithione and H(2)O(2)) for their ability to overcome M channel inhibition via two phospholipase C-mediated mechanisms, namely depletion of membrane phosphatidylinositol 4,5-bisphosphate (PIP(2)) and a rise in intracellular Ca(2+) (an action mediated by calmodulin). Data from overexpressed Kv7.2/Kv7.3 heteromers and native M currents in dorsal root ganglion neurons suggest the following conclusions. (i) All enhancers had a dual effect on M channel activity, a negative shift in voltage dependence and an increase of the maximal current at saturating voltages. The enhancers differed in their efficacy to produce these effects. (ii) Both PIP(2) depletion and Ca(2+)/calmodulin strongly reduced the M current amplitude; however, at voltages near the threshold for M channel activation (-60 mV) all enhancers were able to restore M channel activity to a control level or above, while at saturating voltages the effects were more variable. (iii) Receptor-mediated inhibition of M current in nociceptive dorsal root ganglion neurons did not reduce the efficacy of retigabine or flupirtine to hyperpolarize the resting membrane potential. In conclusion, we show that all four M channel enhancers tested could overcome both PIP(2) and Ca(2+)-calmodulin-induced inhibition of Kv7.2/7.3 at voltages close to the threshold for action potential firing (-60 mV) but generally had reduced efficacy at a

  15. Organometallic cation-exchanged phyllosilicates

    OpenAIRE

    Fleming, Shay

    1991-01-01

    Organotin (IV) complexes formed between 0 01 M dimethyltin dichloride solutions prepared at pH 2 6 and 4 0, and trimethyltin chloride prepared at pH 3 4, with Na- 119 montmori 1lonite clay have been characterised using Sn Mflssbauer spectroscopy, X-ray diffraction, thermogravimetric analysis and water sorption isotherms Following cation exchange, Mttssbauer spectroscopy identified two tin species in the dimethyltin (IV)-exchanged clay prepared at pH 2 6 A cis specie...

  16. The role of transient receptor potential channels in kidney disease.

    NARCIS (Netherlands)

    Woudenberg-Vrenken, T.E.; Bindels, R.J.M.; Hoenderop, J.G.J.

    2009-01-01

    The transient receptor potential (TRP) superfamily consists, in mammals, of six protein subfamilies, TRPC, TRPM, TRPV, TRPA, TRPML and TRPP. TRPs are cation channels involved in many physiological processes and in the pathogenesis of various disorders. In the kidney, TRP channels are expressed along

  17. Movements of native C505 during channel gating in CNGA1 channels.

    NARCIS (Netherlands)

    Nair, A.V.; Anselmi, C.; Mazzolini, M.

    2009-01-01

    We investigated conformational changes occurring in the C-linker and cyclic nucleotide-binding (CNB) domain of CNGA1 channels by analyzing the inhibition induced by thiol-specific reagents in mutant channels Q409C and A414C in the open and closed state. Cd(2+) (200 microM) inhibited irreversibly mut

  18. SNF8, a member of the ESCRT-II complex, interacts with TRPC6 and enhances its channel activity

    Directory of Open Access Journals (Sweden)

    Carrasquillo Robert

    2012-11-01

    Full Text Available Abstract Background Transient receptor potential canonical (TRPC channels are non-selective cation channels involved in receptor-mediated calcium signaling in diverse cells and tissues. The canonical transient receptor potential 6 (TRPC6 has been implicated in several pathological processes, including focal segmental glomerulosclerosis (FSGS, cardiac hypertrophy, and pulmonary hypertension. The two large cytoplasmic segments of the cation channel play a critical role in the proper regulation of channel activity, and are involved in several protein-protein interactions. Results Here we report that SNF8, a component of the endosomal sorting complex for transport-II (ESCRT-II complex, interacts with TRPC6. The interaction was initially observed in a yeast two-hybrid screen using the amino-terminal cytoplasmic domain of TRPC6 as bait, and confirmed by co-immunoprecipitation from eukaryotic cell extracts. The amino-terminal 107 amino acids are necessary and sufficient for the interaction. Overexpression of SNF8 enhances both wild-type and gain-of-function mutant TRPC6-mediated whole-cell currents in HEK293T cells. Furthermore, activation of NFAT-mediated transcription by gain-of-function mutants is enhanced by overexpression of SNF8, and partially inhibited by RNAi mediated knockdown of SNF8. Although the ESCRT-II complex functions in the endocytosis and lysosomal degradation of transmembrane proteins, SNF8 overexpression does not alter the amount of TRPC6 present on the cell surface. Conclusion SNF8 is novel binding partner of TRPC6, binding to the amino-terminal cytoplasmic domain of the channel. Modulating SNF8 expression levels alters the TRPC6 channel current and can modulate activation of NFAT-mediated transcription downstream of gain-of-function mutant TRPC6. Taken together, these results identify SNF8 as a novel regulator of TRPC6.

  19. Differential Effects of TRPA and TRPV Channels on Behaviors of Caenorhabditis elegans

    Science.gov (United States)

    Thies, Jennifer; Neutzler, Vanessa; O’Leary, Fidelma; Liu, He

    2016-01-01

    TRPA and TRPV ion channels are members of the transient receptor potential (TRP) cation channel superfamily, which mediates various sensory transductions. In Caenorhabditis elegans, the TRPV channels are known to affect chemosensation, while the TRPA-1 channel is associated with thermosensation and mechanosensation. We examined thermosensation, chemosensation, and osmosensation in strains lacking TRPA-1 or TRPV channels. We found that TRPV channel knockout worms exhibited similar behavioral deficits associated with thermotaxis as the TRPA-1 channel knockout, suggesting a dual role for TRPV channels. In contrast, chemosensation responses, assessed by both avoidance reversal behavior and NaCl osmosensation, were dependent on TRPV channels but seemed independent of TRPA-1 channel. Our findings suggest that, in addition to TRPA-1 channel, TRPV channels are necessary for thermotaxis and may activate, or modulate, the function of TRPA-1 channels. In contrast, TRPA-1 channels do not have a dual responsibility, as they have no functional role in odorant avoidance or osmosensation. PMID:27168724

  20. Differential Effects of TRPA and TRPV Channels on Behaviors of Caenorhabditis elegans.

    Science.gov (United States)

    Thies, Jennifer; Neutzler, Vanessa; O'Leary, Fidelma; Liu, He

    2016-01-01

    TRPA and TRPV ion channels are members of the transient receptor potential (TRP) cation channel superfamily, which mediates various sensory transductions. In Caenorhabditis elegans, the TRPV channels are known to affect chemosensation, while the TRPA-1 channel is associated with thermosensation and mechanosensation. We examined thermosensation, chemosensation, and osmosensation in strains lacking TRPA-1 or TRPV channels. We found that TRPV channel knockout worms exhibited similar behavioral deficits associated with thermotaxis as the TRPA-1 channel knockout, suggesting a dual role for TRPV channels. In contrast, chemosensation responses, assessed by both avoidance reversal behavior and NaCl osmosensation, were dependent on TRPV channels but seemed independent of TRPA-1 channel. Our findings suggest that, in addition to TRPA-1 channel, TRPV channels are necessary for thermotaxis and may activate, or modulate, the function of TRPA-1 channels. In contrast, TRPA-1 channels do not have a dual responsibility, as they have no functional role in odorant avoidance or osmosensation. PMID:27168724

  1. TRIP Database 2.0: A Manually Curated Information Hub for Accessing TRP Channel Interaction Network

    OpenAIRE

    Young-Cheul Shin; Soo-Yong Shin; Jung Nyeo Chun; Hyeon Sung Cho; Jin Muk Lim; Hong-Gee Kim; Insuk So; Dongseop Kwon; Ju-Hong Jeon

    2012-01-01

    Transient receptor potential (TRP) channels are a family of Ca(2+)-permeable cation channels that play a crucial role in biological and disease processes. To advance TRP channel research, we previously created the TRIP (TRansient receptor potential channel-Interacting Protein) Database, a manually curated database that compiles scattered information on TRP channel protein-protein interactions (PPIs). However, the database needs to be improved for information accessibility and data utilization...

  2. Gramicidin tryptophans mediate formamidinium-induced channel stabilization.

    OpenAIRE

    Seoh, S A; Busath, D

    1995-01-01

    Compared with alkali metal cations, formamidinium ions stabilize the gramicidin A channel molecule in monoolein bilayers (Seoh and Busath, 1993a). A similar effect is observed with N-acetyl gramicidin channel molecules in spite of the modified forces at the dimeric junction (Seoh and Busath, 1993b). Here we use electrophysiological measurements with tryptophan-to-phenylalanine-substituted gramicidin analogs to show that the formamidinium-induced channel molecule stabilization is eliminated wh...

  3. Use of laser induced photoacoustic spectroscopy (LIPAS) to determine equilibrium constants of cation-cation complexes

    International Nuclear Information System (INIS)

    Laser Induced PhotoAcoustic Spectroscopy (LIPAS) is a relatively new, photothermal technique to examine solutions. Studies in the past have shown it to be more sensitive than conventional absorption spectroscopy, while, yielding the same information thus allowing lower concentrations to be used. This study is using LIPAS to examine solutions to determine the equilibrium constants of cation-cation complexes. It has been found that actinyl(V) cations form cation-cation complexes with a variety of cations, including actinyl(VI) cations. The radioactive nature of the actinide elements requires special handling techniques and also require limits be placed on the amount of material that can be used. The sensitivity of some oxidation states of the actinides to oxygen also presents a problem. Preliminary results will be presented for actinyl(V)-actinyl(VI) cation-cation complexes that were studied using a remote LIPAS system incorporating fiber optics for transmission of laser signals

  4. The Free Tricoordinated Silyl Cation Problem

    Directory of Open Access Journals (Sweden)

    Čičak, H.

    2010-03-01

    Full Text Available As the importance and abundance of silicon in our environment is large, it has been thought that silicon might take the place of carbon in forming a host of similar compounds and silicon-based life. However, until today there is no experimental evidence for such a hypothesis and carbon is still unique among the elements in the vast number and variety of compounds it can form. Also, the corresponding derivatives of the two elements show considerable differences in their chemical properties.The essential debate concerning organosilicon chemistry relates to the existence of the free planar tricoordinated silyl cations in condensed phase (R3Si+, in analogy to carbocations (R3C+ which have been known and characterized as free species. Although silyl cations are thermodynamically more stable than their carbon analogs, they are very reactive due to their high inherent electrophilicity and the ability of hypervalent coordination. On the other hand, stabilization by inductive and hyperconjugative effects and larger steric effects of carbocations make them less sensitive to solvation or other environmental effects than silyl cations. Hence, observation of free silyl cations in the condensed phase proved extremely difficult and the actual problem is the question of the degree of the (remaining silyl cation character.The first free silyl cation, trimesitylsilyl cation, and in analogy with it tridurylsilyl cation, were synthesized by Lambert et al. Free silyl cations based on analogy to aromatic ions (homocyclopropenylium and tropylium have also been prepared. However, in these silyl cations the cationic character is reduced by internal π -conjugation. Čičak et al. prepared some silyl-cationic intermediates (Me3Si--CH≡CR+in solid state. With the help of quantum-mechanical calculations it was concluded that these adducts have much more silyl cation than carbocation character.

  5. Structural basis of slow activation gating in the cardiac IKs channel complex

    DEFF Research Database (Denmark)

    Strutz-Seebohm, Nathalie; Pusch, Michael; Wolf, Steffen;

    2011-01-01

    Accessory ß-subunits of the KCNE gene family modulate the function of various cation channel a-subunits by the formation of heteromultimers. Among the most dramatic changes of biophysical properties of a voltage-gated channel by KCNEs are the effects of KCNE1 on KCNQ1 channels. KCNQ1 and KCNE1 ar...

  6. Dependence of NMDA/GSK-3β Mediated Metaplasticity on TRPM2 Channels at Hippocampal CA3-CA1 Synapses

    Directory of Open Access Journals (Sweden)

    Xie Yu-Feng

    2011-12-01

    Full Text Available Abstract Transient receptor potential melastatin 2 (TRPM2 is a calcium permeable non-selective cation channel that functions as a sensor of cellular redox status. Highly expressed within the CNS, we have previously demonstrated the functional expression of these channels in CA1 pyramidal neurons of the hippocampus. Although implicated in oxidative stress-induced neuronal cell death, and potentially in neurodegenerative disease, the physiological role of TRPM2 in the central nervous system is unknown. Interestingly, we have shown that the activation of these channels may be sensitized by co-incident NMDA receptor activation, suggesting a potential contribution of TRPM2 to synaptic transmission. Using hippocampal cultures and slices from TRPM2 null mice we demonstrate that the loss of these channels selectively impairs NMDAR-dependent long-term depression (LTD while sparing long-term potentiation. Impaired LTD resulted from an inhibition of GSK-3β, through increased phosphorylation, and a reduction in the expression of PSD95 and AMPARs. Notably, LTD could be rescued in TRPM2 null mice by recruitment of GSK-3β signaling following dopamine D2 receptor stimulation. We propose that TRPM2 channels play a key role in hippocampal synaptic plasticity.

  7. ASIC3 channels in multimodal sensory perception.

    Science.gov (United States)

    Li, Wei-Guang; Xu, Tian-Le

    2011-01-19

    Acid-sensing ion channels (ASICs), which are members of the sodium-selective cation channels belonging to the epithelial sodium channel/degenerin (ENaC/DEG) family, act as membrane-bound receptors for extracellular protons as well as nonproton ligands. At least five ASIC subunits have been identified in mammalian neurons, which form both homotrimeric and heterotrimeric channels. The highly proton sensitive ASIC3 channels are predominantly distributed in peripheral sensory neurons, correlating with their roles in multimodal sensory perception, including nociception, mechanosensation, and chemosensation. Different from other ASIC subunit composing ion channels, ASIC3 channels can mediate a sustained window current in response to mild extracellular acidosis (pH 7.3-6.7), which often occurs accompanied by many sensory stimuli. Furthermore, recent evidence indicates that the sustained component of ASIC3 currents can be enhanced by nonproton ligands including the endogenous metabolite agmatine. In this review, we first summarize the growing body of evidence for the involvement of ASIC3 channels in multimodal sensory perception and then discuss the potential mechanisms underlying ASIC3 activation and mediation of sensory perception, with a special emphasis on its role in nociception. We conclude that ASIC3 activation and modulation by diverse sensory stimuli represent a new avenue for understanding the role of ASIC3 channels in sensory perception. Furthermore, the emerging implications of ASIC3 channels in multiple sensory dysfunctions including nociception allow the development of new pharmacotherapy. PMID:22778854

  8. Antifungal activity of a synthetic cationic peptide against the plant pathogens Colletotrichum graminicola and three Fusarium species

    Science.gov (United States)

    A small cationic peptide (JH8944) was tested for activity against a number of pathogens of agricultural crops. JH8944 inhibited conidium growth in most of the tested plant pathogens with a dose of 50 µg ml 1, although one isolate of Fusarium oxysporum was inhibited at 5 µg ml 1. Most conidia of Fusa...

  9. Calcium-sensing receptor activation contributed to apoptosis stimulates TRPC6 channel in rat neonatal ventricular myocytes

    International Nuclear Information System (INIS)

    Capacitative calcium entry (CCE) refers to the influx of calcium through plasma membrane channels activated on depletion of endoplasmic sarcoplasmic/reticulum (ER/SR) Ca2+ stores, which is performed mainly by the transient receptor potential (TRP) channels. TRP channels are expressed in cardiomyocytes. Calcium-sensing receptor (CaR) is also expressed in rat cardiac tissue and plays an important role in mediating cardiomyocyte apoptosis. However, there are no data regarding the link between CaR and TRP channels in rat heart. In this study, in rat neonatal myocytes, by Ca2+ imaging, we found that the depletion of ER/SR Ca2+ stores by thapsigargin (TG) elicited a transient rise in cytoplasmic Ca2+ ([Ca2+]i), followed by sustained increase depending on extracellular Ca2+. But, TRP channels inhibitor (SKF96365), not L-type channels or the Na+/Ca2+ exchanger inhibitors, inhibited [Ca2+]i relatively high. Then, we found that the stimulation of CaR with its activator gadolinium chloride (GdCl3) or by an increased extracellular Ca2+([Ca2+]o) increased the concentration of intracelluar Ca2+, whereas, the sustained elevation of [Ca2+]i was reduced in the presence of SKF96365. Similarly, the duration of [Ca2+]i increase was also shortened in the absence of extracellular Ca2+. Western blot analysis showed that GdCl3 increased the expression of TRPC6, which was reversed by SKF96365. Additionally, SKF96365 reduced cardiomyocyte apoptosis induced by GdCl3. Our results suggested that CCE exhibited in rat neonatal myocytes and CaR activation induced Ca2+-permeable cationic channels TRPCs to gate the CCE, for which TRPC6 was one of the most likely candidates. TRPC6 channel was functionally coupled with CaR to enhance the cardiomyocyte apoptosis.

  10. Modulation of ERG channels by XE991

    DEFF Research Database (Denmark)

    Elmedyb, Pernille; Calloe, Kirstine; Schmitt, Nicole;

    2007-01-01

    In neuronal tissue, KCNQ2-5 channels conduct the physiologically important M-current. In some neurones, the M-current may in addition be conducted partly by ERG potassium channels, which have widely overlapping expression with the KCNQ channel subunits. XE991 and linopiridine are known to be...... standard KCNQ potassium channel blockers. These compounds have been used in many different tissues as specific pharmacological tools to discern native currents conducted by KCNQ channels from other potassium currents. In this article, we demonstrate that ERG1-2 channels are also reversibly inhibited by XE......991 in the micromolar range (EC(50) 107 microM for ERG1). The effect has been characterized in Xenopus laevis oocytes expressing ERG1-2 and in the mammalian HEK293 cell line stably expressing ERG1 channels. The IC(50) values for block of KCNQ channels by XE991 range 1-65 microM. In conclusion, great...

  11. Afrikaans Syllabification Patterns

    Directory of Open Access Journals (Sweden)

    Tilla Fick

    2010-01-01

    Full Text Available In contrast to English, automatic hyphenation by computer of Afrikaans words is a problem that still needs to be addressed, since errors are still often encountered in printed text. An initial step in this task is the ability to automatically syllabify words. Since new words are created continuously by joining words, it is necessary to develop an “intelligent” technique for syllabification. As a first phase of the research, we consider only the orthographic information of words, and disregard both syntactic and morphological information. This approach allows us to use machine-learning techniques such as artificial neural networks and decision trees that are known for their pattern recognition abilities. Both these techniques are trained with isolated patterns consisting of input patterns and corresponding outputs (or targets that indicate whether the input pattern should be split at a certain position, or not. In the process of compiling a list of syllabified words from which to generate training data for the  syllabification problem, irregular patterns were identified. The same letter patterns are split differently in different words and complete words that are spelled identically are split differently due to meaning. We also identified irregularities in and between  the different dictionaries that we used. We examined the influence range of letters that are involved in irregularities. For example, for their in agter-ente and vaste-rente we have to consider three letters to the left of r to be certain where the hyphen should be inserted. The influence range of the k in verstek-waarde and kleinste-kwadrate is four to the left and three to the right. In an analysis of letter patterns in Afrikaans words we found that the letter e has the highest frequency overall (16,2% of all letters in the word list. The frequency of words starting with s is the highest, while the frequency of words ending with e is the highest. It is important to

  12. 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.

  13. 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.

  14. Ion Permeation and Mechanotransduction Mechanisms of Mechanosensitive Piezo Channels.

    Science.gov (United States)

    Zhao, Qiancheng; Wu, Kun; Geng, Jie; Chi, Shaopeng; Wang, Yanfeng; Zhi, Peng; Zhang, Mingmin; Xiao, Bailong

    2016-03-16

    Piezo proteins have been proposed as the long-sought-after mechanosensitive cation channels in mammals that play critical roles in various mechanotransduction processes. However, the molecular bases that underlie their ion permeation and mechanotransduction have remained functionally undefined. Here we report our finding of the miniature pore-forming module of Piezo1 that resembles the pore architecture of other trimeric channels and encodes the essential pore properties. We further identified specific residues within the pore module that determine unitary conductance, pore blockage and ion selectivity for divalent and monovalent cations and anions. The non-pore-containing region of Piezo1 confers mechanosensitivity to mechano-insensitive trimeric acid-sensing ion channels, demonstrating that Piezo1 channels possess intrinsic mechanotransduction modules separate from their pore modules. In conclusion, this is the first report on the bona fide pore module and mechanotransduction components of Piezo channels, which define their ion-conducting properties and gating by mechanical stimuli, respectively.

  15. A Bioluminescence Assay System for Imaging Metal Cationic Activities in Urban Aerosols.

    Science.gov (United States)

    Kim, Sung-Bae; Naganawa, Ryuichi; Murata, Shingo; Nakayama, Takayoshi; Miller, Simon; Senda, Toshiya

    2016-01-01

    A bioluminescence-based assay system was fabricated for an efficient determination of the activities of air pollutants. The following four components were integrated into this assay system: (1) an 8-channel assay platform uniquely designed for simultaneously sensing multiple optical samples, (2) single-chain probes illuminating toxic chemicals or heavy metal cations from air pollutants, (3) a microfluidic system for circulating medium mimicking the human body, and (4) the software manimulating the above system. In the protocol, we briefly introduce how to integrate the components into the system and the application to the illumination of the metal cationic activities in air pollutants. PMID:27424913

  16. A Bioluminescence Assay System for Imaging Metal Cationic Activities in Urban Aerosols.

    Science.gov (United States)

    Kim, Sung-Bae; Naganawa, Ryuichi; Murata, Shingo; Nakayama, Takayoshi; Miller, Simon; Senda, Toshiya

    2016-01-01

    A bioluminescence-based assay system was fabricated for an efficient determination of the activities of air pollutants. The following four components were integrated into this assay system: (1) an 8-channel assay platform uniquely designed for simultaneously sensing multiple optical samples, (2) single-chain probes illuminating toxic chemicals or heavy metal cations from air pollutants, (3) a microfluidic system for circulating medium mimicking the human body, and (4) the software manimulating the above system. In the protocol, we briefly introduce how to integrate the components into the system and the application to the illumination of the metal cationic activities in air pollutants.

  17. Neutron irradiation effect on site distribution of cations in non-stoichiometric magnesium aluminate spinel

    International Nuclear Information System (INIS)

    Neutron irradiation effects on cation distribution in non-stoichiometric Mg-Al spinel were examined by ALCHEMI (Atom Location by Channeling Enhanced Microanalysis) method. Parameter n, or non-stoichiometry of MgO . nAl2O3 of the specimens, were n = 1.00, 1.01, 1.10, 1.48. These specimens were neutron-irradiated up to a fluence of 2.3 x 1024 n/m2 (E > 0.1 MeV) at 500-530 deg. C in JMTR. Some specimens contracted by the irradiation and the arrangement of cations became more disorder. The other specimens showed very small swelling by the irradiation and the cation distribution became slightly ordered. The cation distribution of the contracted specimen returned stepwise to the pre-irradiated condition after the annealing at 700 deg. C. The cation distribution of the slightly swollen specimens did not change after the annealing up to 700 deg. C. Cation distribution in the T-site was more sensitively influenced by the irradiation

  18. Localization versus delocalization in diamine radical cations

    DEFF Research Database (Denmark)

    Brouwer, A.M.; Wiering, P.G.; Zwier, J.M.;

    1997-01-01

    The optical absorption spectrum of the radical cation of 1,4-diphenylpiperazine 2a shows a strong transition in the near-IR, and only a weak band at 445 nm, in the region where aniline radical cations normally absorb strongly. This indicates that the charge and spin are delocalized over the two...

  19. Tripodal Receptors for Cation and Anion Sensors

    Directory of Open Access Journals (Sweden)

    David N. Reinhoudt

    2006-08-01

    Full Text Available This review discusses different types of artificial tripodal receptors for the selectiverecognition and sensing of cations and anions. Examples on the relationship between structure andselectivity towards cations and anions are described. Furthermore, their applications as potentiometricion sensing are emphasised, along with their potential applications in optical sensors or optodes.

  20. 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.

  1. TMEM16F is a component of a Ca2+-activated Cl- channel but not a volume-sensitive outwardly rectifying Cl- channel.

    Science.gov (United States)

    Shimizu, Takahiro; Iehara, Takahiro; Sato, Kaori; Fujii, Takuto; Sakai, Hideki; Okada, Yasunobu

    2013-04-15

    TMEM16 (transmembrane protein 16) proteins, which possess eight putative transmembrane domains with intracellular NH2- and COOH-terminal tails, are thought to comprise a Cl(-) channel family. The function of TMEM16F, a member of the TMEM16 family, has been greatly controversial. In the present study, we performed whole cell patch-clamp recordings to investigate the function of human TMEM16F. In TMEM16F-transfected HEK293T cells but not TMEM16K- and mock-transfected cells, activation of membrane currents with strong outward rectification was found to be induced by application of a Ca(2+) ionophore, ionomycin, or by an increase in the intracellular free Ca(2+) concentration. The free Ca(2+) concentration for half-maximal activation of TMEM16F currents was 9.6 μM, which is distinctly higher than that for TMEM16A/B currents. The outwardly rectifying current-voltage relationship for TMEM16F currents was not changed by an increase in the intracellular Ca(2+) level, in contrast to TMEM16A/B currents. The Ca(2+)-activated TMEM16F currents were anion selective, because replacing Cl(-) with aspartate(-) in the bathing solution without changing cation concentrations caused a positive shift of the reversal potential. The anion selectivity sequence of the TMEM16F channel was I(-) > Br(-) > Cl(-) > F(-) > aspartate(-). Niflumic acid, a Ca(2+)-activated Cl(-) channel blocker, inhibited the TMEM16F-dependent Cl(-) currents. Neither overexpression nor knockdown of TMEM16F affected volume-sensitive outwardly rectifying Cl(-) channel (VSOR) currents activated by osmotic swelling or apoptotic stimulation. These results demonstrate that human TMEM16F is an essential component of a Ca(2+)-activated Cl(-) channel with a Ca(2+) sensitivity that is distinct from that of TMEM16A/B and that it is not related to VSOR activity. PMID:23426967

  2. Functional Expression of an Arachnid Sodium Channel Reveals Residues Responsible for Tetrodotoxin Resistance in Invertebrate Sodium Channels*

    OpenAIRE

    Du, Yuzhe; Nomura, Yoshiko; Liu, Zhiqi; Huang, Zachary Y.; Dong, Ke

    2009-01-01

    Tetrodotoxin (TTX) is a potent blocker of voltage-gated sodium channels, but not all sodium channels are equally sensitive to inhibition by TTX. The molecular basis of differential TTX sensitivity of mammalian sodium channels has been largely elucidated. In contrast, our knowledge about the sensitivity of invertebrate sodium channels to TTX remains poor, in part because of limited success in functional expression of these channels. In this study, we report the functional characterization in X...

  3. Calcium homeostasis modulator (CALHM) ion channels.

    Science.gov (United States)

    Ma, Zhongming; Tanis, Jessica E; Taruno, Akiyuki; Foskett, J Kevin

    2016-03-01

    Calcium homeostasis modulator 1 (CALHM1), formerly known as FAM26C, was recently identified as a physiologically important plasma membrane ion channel. CALHM1 and its Caenorhabditis elegans homolog, CLHM-1, are regulated by membrane voltage and extracellular Ca(2+) concentration ([Ca(2+)]o). In the presence of physiological [Ca(2+)]o (∼1.5 mM), CALHM1 and CLHM-1 are closed at resting membrane potentials but can be opened by strong depolarizations. Reducing [Ca(2+)]o increases channel open probability, enabling channel activation at negative membrane potentials. Together, voltage and Ca(2+) o allosterically regulate CALHM channel gating. Through convergent evolution, CALHM has structural features that are reminiscent of connexins and pannexins/innexins/LRRC8 (volume-regulated anion channel (VRAC)) gene families, including four transmembrane helices with cytoplasmic amino and carboxyl termini. A CALHM1 channel is a hexamer of CALHM1 monomers with a functional pore diameter of ∼14 Å. CALHM channels discriminate poorly among cations and anions, with signaling molecules including Ca(2+) and ATP able to permeate through its pore. CALHM1 is expressed in the brain where it plays an important role in cortical neuron excitability induced by low [Ca(2+)]o and in type II taste bud cells in the tongue that sense sweet, bitter, and umami tastes where it functions as an essential ATP release channel to mediate nonsynaptic neurotransmitter release. CLHM-1 is expressed in C. elegans sensory neurons and body wall muscles, and its genetic deletion causes locomotion defects. Thus, CALHM is a voltage- and Ca(2+) o-gated ion channel, permeable to large cations and anions, that plays important roles in physiology. PMID:26603282

  4. Interactions between alpha-latrotoxin and trivalent cations in rat striatal synaptosomal preparations

    Energy Technology Data Exchange (ETDEWEB)

    Scheer, H.W.

    1989-05-01

    The interactions between alpha-latrotoxin (alpha-LTx), a neurosecretagogue purified from the venom of the black widow spider, and the trivalent cations Al3+, Y3+, La3+, Gd3+, and Yb3+ were investigated in rat striatal synaptosomal preparations. All trivalent cations tested were inhibitors of alpha-LTx-induced (/sup 3/H)dopamine ((/sup 3/H)DA) release (order of potency: Yb3+ greater than Gd3+ approximately Y3+ greater than La3+ greater than Al3+). Only with Al3+ could inhibition of (/sup 3/H)DA release be attributed to a block of /sup 125/I-alpha-LTx specific binding to synaptosomal preparations. The inhibitory effect of trivalent ions was reversible provided synaptosomes were washed with buffer containing EDTA. Trivalent ions also inhibited alpha-LTx-induced (/sup 3/H)DA release at times when alpha-LTx-stimulated release was already evident. alpha-LTx-induced synaptosomal membrane depolarization was blocked by La3+, but not affected by Gd3+, Y3+, and Yb3+. alpha-LTx-stimulated uptake of /sup 45/Ca/sup 2 +/ was inhibited by all trivalent cations tested. These results demonstrate that there exist at least three means by which trivalent cations can inhibit alpha-LTx action in rat striatal synaptosomal preparations: (1) inhibition of alpha-LTx binding (Al3+); (2) inhibition of alpha-LTx-induced depolarization (La3+); and (3) inhibition of alpha-LTx-induced /sup 45/Ca/sup 2 +/ uptake (Gd3+, Y3+, Yb3+, La3+).

  5. Functional role of anion channels in cardiac diseases

    Institute of Scientific and Technical Information of China (English)

    Da-yue DUAN; Luis LH LIU; Nathan BOZEAT; Z Maggie HUANG; Sunny Y XIANG; Guan-lei WANG; Linda YE; Joseph R HUME

    2005-01-01

    In comparison to cation (K+, Na+, and Ca2+) channels, much less is currently known about the functional role of anion (Cl-) channels in cardiovascular physiology and pathophysiology. Over the past 15 years, various types of Cl- currents have been recorded in cardiac cells from different species including humans. All cardiac Cl- channels described to date may be encoded by five different Cl- channel genes: the PKA- and PKC-activated cystic fibrosis tansmembrane conductance regulator (CFTR), the volume-regulated ClC-2 and ClC-3, and the Ca2+-activated CLCA or Bestrophin. Recent studies using multiple approaches to examine the functional role of Cl- channels in the context of health and disease have demonstrated that Cl- channels might contribute to: 1) arrhythmogenesis in myocardial injury; 2) cardiac ischemic preconditioning; and 3) the adaptive remodeling of the heart during myocardial hypertrophy and heart failure. Therefore,anion channels represent very attractive novel targets for therapeutic approaches to the treatment of heart diseases. Recent evidence suggests that Cl- channels,like cation channels, might function as a multiprotein complex or functional module.In the post-genome era, the emergence of functional proteomics has necessitated a new paradigm shift to the structural and functional assessment of integrated Cl- channel multiprotein complexes in the heart, which could provide new insight into our understanding of the underlying mechanisms responsible for heart disease and protection.

  6. 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

  7. Cationic Bolaamphiphiles for Gene Delivery

    Science.gov (United States)

    Tan, Amelia Li Min; Lim, Alisa Xue Ling; Zhu, Yiting; Yang, Yi Yan; Khan, Majad

    2014-05-01

    Advances in medical research have shed light on the genetic cause of many human diseases. Gene therapy is a promising approach which can be used to deliver therapeutic genes to treat genetic diseases at its most fundamental level. In general, nonviral vectors are preferred due to reduced risk of immune response, but they are also commonly associated with low transfection efficiency and high cytotoxicity. In contrast to viral vectors, nonviral vectors do not have a natural mechanism to overcome extra- and intracellular barriers when delivering the therapeutic gene into cell. Hence, its design has been increasingly complex to meet challenges faced in targeting of, penetration of and expression in a specific host cell in achieving more satisfactory transfection efficiency. Flexibility in design of the vector is desirable, to enable a careful and controlled manipulation of its properties and functions. This can be met by the use of bolaamphiphile, a special class of lipid. Unlike conventional lipids, bolaamphiphiles can form asymmetric complexes with the therapeutic gene. The advantage of having an asymmetric complex lies in the different purposes served by the interior and exterior of the complex. More effective gene encapsulation within the interior of the complex can be achieved without triggering greater aggregation of serum proteins with the exterior, potentially overcoming one of the great hurdles faced by conventional single-head cationic lipids. In this review, we will look into the physiochemical considerations as well as the biological aspects of a bolaamphiphile-based gene delivery system.

  8. 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.

  9. 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...

  10. Valence selectivity of the gramicidin channel: a molecular dynamics free energy perturbation study.

    OpenAIRE

    Roux, B

    1996-01-01

    The valence selectivity of the gramicidin channel is examined using computer simulations based on atomic models. The channel interior is modeled using a gramicidin-like periodic poly (L,D)-alanine beta-helix. Free energy perturbation calculations are performed to obtain the relative affinity of K+ and Cl- for the channel. It is observed that the interior of the gramicidin channel provides an energetically favorable interaction site for a cation but not for an anion. Relative to solvation in b...

  11. Cationic ruthenium alkylidene catalysts bearing phosphine ligands

    OpenAIRE

    Endo, Koji; Grubbs, Robert H.

    2016-01-01

    The discovery of highly active catalysts and the success of ionic liquid immobilized systems have accelerated attention to a new class of cationic metathesis catalysts. We herein report the facile syntheses of cationic ruthenium catalysts bear-ing bulky phosphine ligands. Simple ligand exchange using silver(I) salts of non-coordinating or weakly coordinating anions pro-vided either PPh3 or chelating Ph2P(CH2)nPPh2 (n = 2 or 3) ligated cationic catalysts. The structures of these newly reported...

  12. The mechanism of kaolin clay flocculation by a cation-independent bioflocculant produced by Chryseobacterium daeguense W6

    Directory of Open Access Journals (Sweden)

    Weijie Liu

    2015-03-01

    Full Text Available In recent years, several novel cation-independent bioflocculants have been reported, which can avoid the secondary contamination caused by addition of cations. However, compared with cation-dependent bioflocculants, the flocculating mechanism of cation-independent bioflocculants is largely unknown. In this study, a cation-independent bioflocculant MBF-W6 produced by Chryseobacterium daeguense W6 was used as a model to investigate the flocculating mechanism. The results showed that the major flocculating component of MBF-W6 is a complex of proteins and polysaccharides. The zeta potential results indicated that kaolin clay particles were not precipitated due to charge neutralization and the bridging mediated by cations did not play a major role in the flocculating process. These results are consistent with the fact that MBF-W6 is a cation-independent bioflocculant. Further scanning electron microscopic observation showed that MBF-W6 induced flocs formed tight packed structure, suggesting that the kaolin clay particles maybe directly attached and bridged by bioflocculant MBF-W6. In addition, we also found out that Fe3+ ions inhibit the flocculating activity of MBF-W6 by affecting –COO− and –NH groups. Therefore this study can improve our understanding on flocculating mechanism of cation-independent bioflocculants.

  13. Opening the Shaker K+ channel with hanatoxin

    OpenAIRE

    Milescu, Mirela; Lee, Hwa C.; Bae, Chan Hyung; Kim, Jae Il; Swartz, Kenton J.

    2013-01-01

    Voltage-activated ion channels open and close in response to changes in membrane voltage, a property that is fundamental to the roles of these channels in electrical signaling. Protein toxins from venomous organisms commonly target the S1–S4 voltage-sensing domains in these channels and modify their gating properties. Studies on the interaction of hanatoxin with the Kv2.1 channel show that this tarantula toxin interacts with the S1–S4 domain and inhibits opening by stabilizing a closed state....

  14. Involvement of peripheral TRPV1 channels in the analgesic effects of thalidomide.

    Science.gov (United States)

    Song, Tieying; Wang, Liwen; Gu, Kunfeng; Yang, Yunliang; Yang, Lijun; Ma, Pengyu; Ma, Xiaojing; Zhao, Jianhui; Yan, Ruyv; Guan, Jiao; Wang, Chunping; Qi, Yan; Ya, Jian

    2015-01-01

    Thalidomide was introduced to the market in 1957 as a sedative and antiemetic agent, and returned to the market for the treatment of myelodysplastic syndrome and multiple myeloma. There are reports and studies of thalidomide as an analgesic or analgesic adjuvant in clinic. However, the underlying mechanism is quite elusive. Many studies suggest that the analgesic effect of thalidomide may be due to its immunomodulatory and anti-inflammatory properties as it suppresses the production of tumor necrosis factor α (TNF-α) selectively. However, it is not clear whether any other mechanisms are implicated in the pain relief. In this study, we demonstrated that the peripheral vanilloid receptor 1 (TRPV1) channel was also involved in the analgesic effect of thalidomide in different cell and animal models. During the activation by its agonist capsaicin, the cation inward influx through TRPV1 channels and the whole-cell current significantly decreased after TRPV1-overexpressed HEK293 cells or dorsal root ganglion (DRG) neurons were pre-treated with thalidomide for 20 minutes. And such attenuation in the TRPV1 activity was in a dose-dependent manner of thalidomide. In an acetic acid writhing test, pre-treatment of thalidomide decreased the writhing number in the wild type mice, while it did not happen in TRPV1 knockout mice, suggesting that the TRPV1 channel was involved in the pain relief by thalidomide. Taken together, the study showed that TRPV1 channels were involved in the analgesic effects of thalidomide. Such alteration in the action of TRPV1 channels by thalidomide may help understand how thalidomide takes analgesic effect in the body in addition to its selective inhibition of TNF-α production. PMID:25929448

  15. Involvement of peripheral TRPV1 channels in the analgesic effects of thalidomide.

    Science.gov (United States)

    Song, Tieying; Wang, Liwen; Gu, Kunfeng; Yang, Yunliang; Yang, Lijun; Ma, Pengyu; Ma, Xiaojing; Zhao, Jianhui; Yan, Ruyv; Guan, Jiao; Wang, Chunping; Qi, Yan; Ya, Jian

    2015-01-01

    Thalidomide was introduced to the market in 1957 as a sedative and antiemetic agent, and returned to the market for the treatment of myelodysplastic syndrome and multiple myeloma. There are reports and studies of thalidomide as an analgesic or analgesic adjuvant in clinic. However, the underlying mechanism is quite elusive. Many studies suggest that the analgesic effect of thalidomide may be due to its immunomodulatory and anti-inflammatory properties as it suppresses the production of tumor necrosis factor α (TNF-α) selectively. However, it is not clear whether any other mechanisms are implicated in the pain relief. In this study, we demonstrated that the peripheral vanilloid receptor 1 (TRPV1) channel was also involved in the analgesic effect of thalidomide in different cell and animal models. During the activation by its agonist capsaicin, the cation inward influx through TRPV1 channels and the whole-cell current significantly decreased after TRPV1-overexpressed HEK293 cells or dorsal root ganglion (DRG) neurons were pre-treated with thalidomide for 20 minutes. And such attenuation in the TRPV1 activity was in a dose-dependent manner of thalidomide. In an acetic acid writhing test, pre-treatment of thalidomide decreased the writhing number in the wild type mice, while it did not happen in TRPV1 knockout mice, suggesting that the TRPV1 channel was involved in the pain relief by thalidomide. Taken together, the study showed that TRPV1 channels were involved in the analgesic effects of thalidomide. Such alteration in the action of TRPV1 channels by thalidomide may help understand how thalidomide takes analgesic effect in the body in addition to its selective inhibition of TNF-α production.

  16. 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.

  17. Cation locations and dislocations in zeolites

    Science.gov (United States)

    Smith, Luis James

    The focus of this dissertation is the extra-framework cation sites in a particular structural family of zeolites, chabazite. Cation sites play a particularly important role in the application of these sieves for ion exchange, gas separation, catalysis, and, when the cation is a proton, acid catalysis. Structural characterization is commonly performed through the use of powder diffraction and Rietveld analysis of powder diffraction data. Use of high-resolution nuclear magnetic resonance, in the study of the local order of the various constituent nuclei of zeolites, complements well the long-range order information produced by diffraction. Recent developments in solid state NMR techniques allow for increased study of disorder in zeolites particularly when such phenomena test the detection limits of diffraction. These two powerful characterization techniques, powder diffraction and NMR, offer many insights into the complex interaction of cations with the zeolite framework. The acids site locations in SSZ-13, a high silica chabazite, and SAPO-34, a silicoaluminophosphate with the chabazite structure, were determined. The structure of SAPO-34 upon selective hydration was also determined. The insensitivity of X-rays to hydrogen was avoided through deuteration of the acid zeolites and neutron powder diffraction methods. Protons at inequivalent positions were found to have different acid strengths in both SSZ-13 and SAPO-34. Other light elements are incorporated into zeolites in the form of extra-framework cations, among these are lithium, sodium, and calcium. Not amenable by X-ray powder diffraction methods, the positions of such light cations in fully ion-exchanged versions of synthetic chabazite were determined through neutron powder diffraction methods. The study of more complex binary cation systems were conducted. Powder diffraction and solid state NMR methods (MAS, MQMAS) were used to examine cation site preferences and dislocations in these mixed-akali chabazites

  18. Cycloaliphatic epoxide resins for cationic UV - cure

    International Nuclear Information System (INIS)

    This paper introduces the cyclo - aliphatic epoxide resins used for the various applications of radiation curing and their comparison with acrylate chemistry. Radiation curable coatings and inks are pre - dominantly based on acrylate chemistry but over the last few years, cationic chemistry has emerged successfully with the unique properties inherent with cyclo - aliphatic epoxide ring structures. Wide variety of cationic resins and diluents, the formulation techniques to achieve the desired properties greatly contributes to the advancement of UV - curing technology

  19. Cations and activated sludge floc structure

    OpenAIRE

    Park, Chul

    2002-01-01

    This research was designed to investigate the effect of cations on activated sludge characteristics and also to determine their influence on digestion performance. For this purpose, cations in solution and in floc were evaluated along with various activated sludge characteristics and the collected waste activated sludge underwent both anaerobic and aerobic digestion. It was found that large amounts of biopolymer (protein + polysaccharide) remained in the effluent of WWTP that received high in...

  20. Test procedure for cation exchange chromatography

    International Nuclear Information System (INIS)

    The purpose of this test plan is to demonstrate the synthesis of inorganic antimonate ion exchangers and compare their performance against the standard organic cation exchangers. Of particular interest is the degradation rate of both inorganic and organic cation exchangers. This degradation rate will be tracked by determining the ion exchange capacity and thermal stability as a function of time, radiation dose, and chemical reaction

  1. Silica-based cationic bilayers as immunoadjuvants

    OpenAIRE

    Carmona-Ribeiro Ana M; da Costa Maria; Faquim-Mauro Eliana; Santana Mariana RA; Lincopan Nilton

    2009-01-01

    Abstract Background Silica particles cationized by dioctadecyldimethylammonium bromide (DODAB) bilayer were previously described. This work shows the efficiency of these particulates for antigen adsorption and presentation to the immune system and proves the concept that silica-based cationic bilayers exhibit better performance than alum regarding colloid stability and cellular immune responses for vaccine design. Results Firstly, the silica/DODAB assembly was characterized at 1 mM NaCl, pH 6...

  2. Constant helical pitch of the gramicidin channel in phospholipid bilayers.

    OpenAIRE

    Katsaras, J.; Prosser, R S; Stinson, R H; Davis, J H

    1992-01-01

    X-ray diffraction has been applied in measuring the helical pitch of the gramicidin channel in oriented bilayers of dilauroylphosphatidylcholine (DLPC) and dimyristoylphosphatidylcholine (DMPC) at a polypeptide concentration of 9.1 mol %. The diffraction data show the helical pitch of gramicidin to be 4.7 +/- 0.2 A in both gel and liquid-crystalline phase bilayers, with and without monovalent cations. In addition, the width of the reflection due to the pitch of the helical gramicidin channel ...

  3. Graphene Oxide Nanofiltration Membranes Stabilized by Cationic Porphyrin for High Salt Rejection.

    Science.gov (United States)

    Xu, Xiao-Ling; Lin, Fu-Wen; Du, Yong; Zhang, Xi; Wu, Jian; Xu, Zhi-Kang

    2016-05-25

    Swelling has great influences on the structure stability and separation performance of graphene oxide laminate membranes (GOLMs) for water desalination and purification. Herein, we report cross-linked GOLMs from GO assembled with cationic tetrakis(1-methyl-pyridinium-4-yl)porphyrin (TMPyP) by a vacuum-assisted strategy. The concave nonoxide regions (G regions) of GO are used as cross-linking sites for the first time to precisely control the channel size for water permeation and salt ion retention. Channels around 1 nm are constructed by modulating the assembly ratio of TMPyP/GO, and these cross-linked GOLMs show high salt rejection. PMID:27158976

  4. Calcium sensitive non-selective cation current promotes seizure-like discharges and spreading depression in a model neuron

    NARCIS (Netherlands)

    G.G. Somjen; H. Kager; W.J. Wadman

    2009-01-01

    As described by others, an extracellular calcium-sensitive non-selective cation channel ([Ca(2+)](o)-sensitive NSCC) of central neurons opens when extracellular calcium level decreases. An other non-selective current is activated by rising intracellular calcium ([Ca(2+)]( i )). The [Ca(2+)](o)-sensi

  5. A novel µ-conopeptide, CnIIIC, exerts potent and preferential inhibition of NaV1.2/1.4 channels and blocks neuronal nicotinic acetylcholine receptors

    NARCIS (Netherlands)

    Favreau, P.; Benoit, E.; Hocking, H.G.; Carlier, L.P.A.; D’ hoedt, D.; Leipold, E.; Markgraf, R.; Boelens, R.; Molgo, J.

    2012-01-01

    BACKGROUND AND PURPOSE The µ-conopeptide family is defined by its ability to block voltage-gated sodium channels (VGSCs), a property that can be used for the development of myorelaxants and analgesics. We characterized the pharmacology of a new µ-conopeptide (µ-CnIIIC) on a range of preparations and

  6. Characterization of dihydropyridine-sensitive calcium channels

    International Nuclear Information System (INIS)

    The structural and regulatory properties of the dihydropyridine-sensitive calcium channel were studied by isolating protein components of the channel complex from both cardiac and skeletal muscle. Hydrodynamic characterization of the (+)-(3H)PN200-110-labeled cardiac calcium channel revealed that the protein components of the complex had a total molecular mass of 370,000 daltons, a Stokes radius of 86 angstrom, and a frictional ratio of 1.3. A technique is described for the rapid incorporation of the CHAPS solubilized skeletal muscle calcium channel complex into phospholipid vesicles. 45Ca2+ uptake into phospholipid vesicles containing calcium channels was inhibited by phenylalkalamine calcium antagonists. Wheat germ lectin followed by DEAE chromatography of the CHAPS solubilized complex resulted in the dissociation of regulatory components of the complex from channel components. The DEAE preparation gave rise to 45Ca2+ uptake that was not inhibited by verapamil but was inhibited by GTPgS activated G0. The inhibition of 45Ca2+ uptake by verapamil was restored by co-reconstitution of wash fractions from wheat germ lectin chromatography. Phosphorylation of polypeptides in this fraction by polypeptide-dependent protein kinase prevented the restoration of verapamil sensitivity. The partial purification of an endogenous skeletal muscle ADP-ribosyltransferase is also described. ADP-ribosylation of the α2 subunit of the calcium channel complex is enhanced by polylysine and inhibited by GTPγS, suggesting that regulation of this enzyme is under the control of GTP binding proteins. These results suggest a complex model, involving a number of different protein components, for calcium channel regulation in skeletal muscle

  7. Joint Single-Channel Speech Separation and Speaker Identification

    DEFF Research Database (Denmark)

    Mowlaee, Pejman; Saeidi, Rahim; Tan, Zheng-Hua;

    2010-01-01

    In this paper, we propose a closed loop system to improve the performance of single-channel speech separation in a speaker independent scenario. The system is composed of two interconnected blocks: a separation block and a speaker identiſcation block. The improvement is accomplished by incorporat...

  8. 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)

  9. Structural Insights into Mitochondrial Calcium Uniporter Regulation by Divalent Cations.

    Science.gov (United States)

    Lee, Samuel K; Shanmughapriya, Santhanam; Mok, Mac C Y; Dong, Zhiwei; Tomar, Dhanendra; Carvalho, Edmund; Rajan, Sudarsan; Junop, Murray S; Madesh, Muniswamy; Stathopulos, Peter B

    2016-09-22

    Calcium (Ca(2+)) flux into the matrix is tightly controlled by the mitochondrial Ca(2+) uniporter (MCU) due to vital roles in cell death and bioenergetics. However, the precise atomic mechanisms of MCU regulation remain unclear. Here, we solved the crystal structure of the N-terminal matrix domain of human MCU, revealing a β-grasp-like fold with a cluster of negatively charged residues that interacts with divalent cations. Binding of Ca(2+) or Mg(2+) destabilizes and shifts the self-association equilibrium of the domain toward monomer. Mutational disruption of the acidic face weakens oligomerization of the isolated matrix domain and full-length human protein similar to cation binding and markedly decreases MCU activity. Moreover, mitochondrial Mg(2+) loading or blockade of mitochondrial Ca(2+) extrusion suppresses MCU Ca(2+)-uptake rates. Collectively, our data reveal that the β-grasp-like matrix region harbors an MCU-regulating acidic patch that inhibits human MCU activity in response to Mg(2+) and Ca(2+) binding.

  10. Mechanotransduction in mouse inner ear hair cells requires transmembrane channel-like genes

    NARCIS (Netherlands)

    Kawashima, Yoshiyuki; Geleoc, Gwenaelle S. G.; Kurima, Kiyoto; Labay, Valentina; Lelli, Andrea; Asai, Yukako; Makishima, Tomoko; Wu, Doris K.; Della Santina, Charles C.; Holt, Jeffrey R.; Griffith, Andrew J.

    2011-01-01

    Inner ear hair cells convert the mechanical stimuli of sound, gravity, and head movement into electrical signals. This mechanotransduction process is initiated by opening of cation channels near the tips of hair cell stereocilia. Since the identity of these ion channels is unknown, and mutations in

  11. Binding of ArgTX-636 in the NMDA receptor ion channel

    DEFF Research Database (Denmark)

    Poulsen, Mette H; Andersen, Jacob; Christensen, Rune;

    2015-01-01

    The N-methyl-d-aspartate receptors (NMDARs) constitute an important class of ligand-gated cation channels that are involved in the majority of excitatory neurotransmission in the human brain. Compounds that bind in the NMDAR ion channel and act as blockers are use- and voltage-dependent inhibitor...

  12. Innate cation sensitivity in a semiconducting polymer.

    Science.gov (United States)

    Althagafi, Talal M; Algarni, Saud A; Grell, Martin

    2016-09-01

    Water-gated organic thin film transistors (OTFTs) using the hole transporting semiconducting polymer, poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT), show an innate response of their threshold voltage to the addition of divalent metal cations to the gating water, without deliberately introducing an ion-sensitive component. A similar threshold response is shown for several divalent cations, but is absent for monovalent cations. Response is absent for transistors using the inorganic semiconductor ZnO, or the similar organic semiconductor poly(3-hexylthiophene) (rrP3HT), instead of PBTTT. We assign innate cation sensitivity to residues of the organometallic Pd(0) complex used as catalyst in PBTTT synthesis which bears strong resemblance to typical metal chelating agents. Organometallic Pd(0) residues are absent from ZnO, and also from rrP3HT which is polymerised with a different type of catalyst. However, when Pd(0) complex is deliberately added to rrP3HT casting solutions, resulting OTFTs also display threshold response to a divalent cation. PMID:27343580

  13. Desorption behavior of cesium from cesium bearing smectite by major cations

    International Nuclear Information System (INIS)

    The desorption behaviors of Cs from Cs bearing smectite by major cations (Na+, K+, Mg2+, Ca2+ and NH4+) were systematically examined. The suspension of the Cs bearing smectite was prepared by reaction of 1 g/L smectite with 75 nM Cs+ solution in 0.02 M NaCl solutions. The desorption behaviors of Cs were examined by adding the major cations of which concentrations ranged from 10-3 to 10-1 N to the smectite suspensions. All cations except for K+ lead to the desorption of Cs from smectite when the concentrations of the added cations increased. On the other hand, K+ plays a role for inhibition of Cs desorption from smectite. The order of the ability for the desorption of Cs from smectite by the major cations was summarized as follow: Ca2+ nearly equals Mg2+ > NH4+ > Na+ > K+. The selectivity coefficients based on Gaines-Thomas convention were estimated from the observed desorption behaviors. (author)

  14. A highly calcium-selective cation current activated by intracellular calcium release in MDCK cells.

    Science.gov (United States)

    Delles, C; Haller, T; Dietl, P

    1995-08-01

    1. The whole-cell patch clamp technique and fluorescence microscopy with the Ca2+ indicators fura-2 and fluo-3 were used to measure the whole-cell current and the free intracellular Ca2+ concentration ([Ca2+]i) in Madin-Darby canine kidney (MDCK) cells. 2. In a Ca(2+)-free bath solution, thapsigargin (TG) caused a transient increase of [Ca2+]i. Subsequent addition of Ca2+ caused a long lasting elevation of [Ca2+]i. 3. In a Ca(2+)-free bath solution, extracellular application of TG, ATP or ionomycin, or intracellular application of inositol 1,4,5-trisphosphate (IP3), caused a small but significant inward current (Iin) and a transient outward Ca(2+)-dependent K+ current (IK(Ca)), consistent with intracellular Ca2+ release. Subsequent addition of Ca2+ induced a prominent Iin with a current density of -4.2 +/- 0.7 pA pF-1. This Iin was unaffected by inositol 1,3,4,5-tetrakisphosphate (IP4). 4. Na+ replacement by mannitol, N-methyl-D-glucamine+ (NMG+), aminomethylidin-trimethanol+ (Tris+) or choline+ reduced Iin by 54, 65, 52 and 56%, respectively. This indicates an apparent Ca2+ selectivity over Na+ of 26:1. Iin was, however, unaffected by replacing Cl- with gluconate- or by the K+ channel blocker charybdotoxin (CTX). 5. Iin was completely blocked by La3+ (IC50 = 0.77 microM). Consistently, La3+ completely reversed the TG-induced elevation of [Ca2+]i. SK&F 96365 (1-[3-(4-methoxyphenyl)-propoxyl]-1-(4-methoxy-phenyl)-ethyl-1H-im idazole) HCl did not inhibit the TG-induced Iin. It did, however, exhibit a biphasic effect on [Ca2+]i, consisting of an initial Ca2+ decay and a subsequent Ca2+ elevation. La3+ completely reversed the SK&F 96365-induced elevation of [Ca2+]i. 6. In the absence of Na+, Iin was dependent on the bath Ca2+ concentration (EC50 = 1.02 mM). Ca2+ replacement by Ba2+ or Mn2+ resulted in a reduction of Iin by 95 and 94%, respectively. 7. From these experiments we conclude that Ca2+ release from intracellular Ca2+ stores, induced by different independent

  15. Forging Colloidal Nanostructures via Cation Exchange Reactions

    Science.gov (United States)

    2016-01-01

    Among the various postsynthesis treatments of colloidal nanocrystals that have been developed to date, transformations by cation exchange have recently emerged as an extremely versatile tool that has given access to a wide variety of materials and nanostructures. One notable example in this direction is represented by partial cation exchange, by which preformed nanocrystals can be either transformed to alloy nanocrystals or to various types of nanoheterostructures possessing core/shell, segmented, or striped architectures. In this review, we provide an up to date overview of the complex colloidal nanostructures that could be prepared so far by cation exchange. At the same time, the review gives an account of the fundamental thermodynamic and kinetic parameters governing these types of reactions, as they are currently understood, and outlines the main open issues and possible future developments in the field. PMID:26891471

  16. Loss of glutathione homeostasis associated with neuronal senescence facilitates TRPM2 channel activation in cultured hippocampal pyramidal neurons

    Directory of Open Access Journals (Sweden)

    Belrose Jillian C

    2012-04-01

    Full Text Available Abstract Background Glutathione (GSH plays an important role in neuronal oxidant defence. Depletion of cellular GSH is observed in neurodegenerative diseases and thereby contributes to the associated oxidative stress and Ca2+ dysregulation. Whether depletion of cellular GSH, associated with neuronal senescence, directly influences Ca2+ permeation pathways is not known. Transient receptor potential melastatin type 2 (TRPM2 is a Ca2+ permeable non-selective cation channel expressed in several cell types including hippocampal pyramidal neurons. Moreover, activation of TRPM2 during oxidative stress has been linked to cell death. Importantly, GSH has been reported to inhibit TRPM2 channels, suggesting they may directly contribute to Ca2+ dysregulation associated with neuronal senescence. Herein, we explore the relation between cellular GSH and TRPM2 channel activity in long-term cultures of hippocampal neurons. Results In whole-cell voltage-clamp recordings, we observe that TRPM2 current density increases in cultured pyramidal neurons over time in vitro. The observed increase in current density was prevented by treatment with NAC, a precursor to GSH synthesis. Conversely, treatment of cultures maintained for 2 weeks in vitro with L-BSO, which depletes GSH by inhibiting its synthesis, augments TRPM2 currents. Additionally, we demonstrate that GSH inhibits TRPM2 currents through a thiol-independent mechanism, and produces a 3.5-fold shift in the dose-response curve generated by ADPR, the intracellular agonist for TRPM2. Conclusion These results indicate that GSH plays a physiologically relevant role in the regulation of TRPM2 currents in hippocampal pyramidal neurons. This interaction may play an important role in aging and neurological diseases associated with depletion of GSH.

  17. Channel properties of Nax expressed in neurons.

    Directory of Open Access Journals (Sweden)

    Masahito Matsumoto

    Full Text Available Nax is a sodium-concentration ([Na+]-sensitive Na channel with a gating threshold of ~150 mM for extracellular [Na+] ([Na+]o in vitro. We previously reported that Nax was preferentially expressed in the glial cells of sensory circumventricular organs including the subfornical organ, and was involved in [Na+] sensing for the control of salt-intake behavior. Although Nax was also suggested to be expressed in the neurons of some brain regions including the amygdala and cerebral cortex, the channel properties of Nax have not yet been adequately characterized in neurons. We herein verified that Nax was expressed in neurons in the lateral amygdala of mice using an antibody that was newly generated against mouse Nax. To investigate the channel properties of Nax expressed in neurons, we established an inducible cell line of Nax using the mouse neuroblastoma cell line, Neuro-2a, which is endogenously devoid of the expression of Nax. Functional analyses of this cell line revealed that the [Na+]-sensitivity of Nax in neuronal cells was similar to that expressed in glial cells. The cation selectivity sequence of the Nax channel in cations was revealed to be Na+ ≈ Li+ > Rb+ > Cs+ for the first time. Furthermore, we demonstrated that Nax bound to postsynaptic density protein 95 (PSD95 through its PSD95/Disc-large/ZO-1 (PDZ-binding motif at the C-terminus in neurons. The interaction between Nax and PSD95 may be involved in promoting the surface expression of Nax channels because the depletion of endogenous PSD95 resulted in a decrease in Nax at the plasma membrane. These results indicated, for the first time, that Nax functions as a [Na+]-sensitive Na channel in neurons as well as in glial cells.

  18. Cationically polymerizable monomers derived from renewable sources

    Energy Technology Data Exchange (ETDEWEB)

    Crivello, J.V.

    1992-10-01

    The objectives of this project are to design and synthesize novel monomers which orginate from renewable biological sources and to carry out their rapid, efficient, pollution-free and energy efficient cationic polymerization to useful products under the influence of ultraviolet light or heat. A summary of the results of the past year's research on cationically polymerizable monomers derived from renewable sources is presented. Three major areas of investigation corresponding to the different classes of naturally occurring starting materials were investigated; epoxidized terpenes and natural rubber and vinyl ethers from alcohols and carbohydrates.

  19. Mixed cation effect in sodium aluminosilicate glasses

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Smedskjær, Morten Mattrup; Mauro, John C.;

    , network structure, and the resistances associated with the deformation processes in mixed cation glasses by partially substituting magnesium for calcium and calcium for lithium in sodium aluminosilicate glasses. We use Raman and 27Al NMR spectroscopies to obtain insights into the structural...... and topological features of these glasses and we use AFM to quantify the resistances associated with each deformation process under Vickers indentation. We demonstrate that the mixed cation effect manifests itself as a maximum in the amount of bonded tetrahedral units and as a minimum in liquid fragility index...

  20. Cation Effect on Copper Chemical Mechanical Polishing

    Institute of Scientific and Technical Information of China (English)

    WANG Liang-Yong; LIU Bo; SONG Zhi-Tang; FENG Song-Lin

    2009-01-01

    We examine the effect of cations in solutions containing benzotriazole (BTA) and H2O2 on copper chemical mechanical polishing (CMP). On the base of atomic force microscopy (AFM) and material removal rate (MRR) results, it is found that ammonia shows the highest MRR as well as good surface after CMP, while KOH demon-strates the worst performance. These results reveal a mechanism that sma//molecules with lone-pairs rather than molecules with steric effect and common inorganic cations are better for copper CMP process, which is indirectly confirmed by open circuit potential (OCP).

  1. A novel potassium channel in photosynthetic cyanobacteria.

    Directory of Open Access Journals (Sweden)

    Manuela Zanetti

    Full Text Available Elucidation of the structure-function relationship of a small number of prokaryotic ion channels characterized so far greatly contributed to our knowledge on basic mechanisms of ion conduction. We identified a new potassium channel (SynK in the genome of the cyanobacterium Synechocystis sp. PCC6803, a photosynthetic model organism. SynK, when expressed in a K(+-uptake-system deficient E. coli strain, was able to recover growth of these organisms. The protein functions as a potassium selective ion channel when expressed in Chinese hamster ovary cells. The location of SynK in cyanobacteria in both thylakoid and plasmamembranes was revealed by immunogold electron microscopy and Western blotting of isolated membrane fractions. SynK seems to be conserved during evolution, giving rise to a TPK (two-pore K(+ channel family member which is shown here to be located in the thylakoid membrane of Arabidopsis. Our work characterizes a novel cyanobacterial potassium channel and indicates the molecular nature of the first higher plant thylakoid cation channel, opening the way to functional studies.

  2. TPC1 - SV Channels Gain Shape

    Institute of Scientific and Technical Information of China (English)

    Rainer Hedrich; Irene Marten

    2011-01-01

    T The most prominent ion channel localized in plant vacuoles is the slow activating SV type. Slow vacuolar (SV)channels were discovered by patch clamp studies as early as 1986. In the following two decades, numerous studies revealed that these calcium- and voltage-activated, nonselective cation channels are expressed in the vacuoles of all plants and every plant tissue. The voltage-dependent properties of the SV channel are susceptible to modulation by calcium, pH, redox state, as well as regulatory proteins. In Arabidopsis, the SV channel is encoded by the AtTPC1 gene, and even though its gene product represents the by far largest conductance of the vacuolar membrane, tpc1-loss-of-function mutants appeared not to be impaired in major physiological functions such as growth, development, and reproduction. In contrast, the fou2 gain-of-function point mutation D454N within TPC1 leads to a pronounced growth phenotype and increased synthesis of the stress hormone jasmonate. Since the TPC1 gene is present in all land plants, it likely encodes a very general function. In this review, we will discuss major SV channel properties and their impact on plant cell physiology.

  3. Temperature dependence of gramicidin channel conductance

    Science.gov (United States)

    Song, Hyundeok; Beck, Thomas

    2010-03-01

    The gramicidin channel is the smallest known biological ion channel, and it exhibits cation selectivity. Recently, Dr. John Cuppoletti's group at the University of Cincinnati has shown that the gramicidin channel can function at high temperatures with significant currents. This finding may have implications for fuel cell technologies. In order to explore the effect of temperature on channel conductance, we examined the gramicidin system at 300K, 330K, and 360K by computer simulation. Two forms of gramicidin, the head-to-head helical dimer and the intertwined double helix, were examined. Both the decrease of the free energy barrier and the increase of the diffusion of potassium ions inside the gramicidin channel at high temperatures imply an increase of current. We found that higher temperatures also affect the lifetime of hydrogen bonds, the distribution of the bending angle, the distribution of the distance between dimers, and the size of the pore radius for the helical dimer structure. These finding may be related to the gating of the gramicidin channel.

  4. Simulation and calculation of the contribution of hyperpolarization-activated cyclic nucleotide-gated channels to action potentials

    OpenAIRE

    Liao Liping; Lin Xianguang; Hu Jielin; Wu Xin; Yang Xiaofei; Wang Wei; Li Chenhong

    2016-01-01

    The hyperpolarization-activated cyclic nucleotide-gated (HCN) channel, which mediates the influx of cations, has an important role in action potential generation. In this article, we describe the contribution of the HCN channel to action potential generation. We simulated several common ion channels in neuron membranes based on data from rat dorsal root ganglion cells and modeled the action potential. The ion channel models employed in this paper were based...

  5. Interaction of lanthanide cations and uranyl ion with the calcium/proton antiport system in Mycobacterium phlei.

    Science.gov (United States)

    Agarwal, N; Kalra, V K

    1983-01-19

    Uranyl ions (UO2+(2)) and lanthanide cations (La3+, Nd3+, Sm3+, Eu3+, Tb3+ and Dy3+) at 100-200 microM concentration inhibited active transport of Ca2+, mediated by respiratory linked substrates as well as by ATP hydrolysis, without affecting respiration and membrane-bound ATPase activity, in inside-out membrane vesicles of Mycobacterium phlei. The extent of inhibition in the uptake of Ca2+, mediated by ATP hydrolysis, increased with increase in ionic radii of these cations. Lanthanide cations did not dissipate the formation of a proton gradient, as measured by determining the effect either on the uptake of [14C]methylamine or energy-linked quenching of the fluorescence of 9-aminoacridine. However, uranyl ion (UO2+(2+)) caused reversal of the energy-linked quenching of 9-aminoacridine. UO2+(2)) concentration yielding 50% of Vmax (S0.5) was approx. 15 microM. Kinetic studies revealed that inhibition in the uptake of Ca2+ was competitive with UO2+(2) while non-competitive with rare-earth metals. It is proposed that inhibition in the uptake of Ca2+ by uranyl ion occurs as a result of UO2+(2) transport into the interior of vesicles in exchange for protons, while lanthanide cations are not being transported but affect the binding of Ca2+ to the membrane, presumably to the Ca2+/H+ antiporter. PMID:6838872

  6. Probing S4 and S5 segment proximity in mammalian hyperpolarization-activated HCN channels by disulfide bridging and Cd2+ coordination.

    Science.gov (United States)

    Bell, Damian C; Turbendian, Harma K; Valley, Matthew T; Zhou, Lei; Riley, John H; Siegelbaum, Steven A; Tibbs, Gareth R

    2009-06-01

    We explored the structural basis of voltage sensing in the HCN1 hyperpolarization-activated cyclic nucleotide-gated cation channel by examining the relative orientation of the voltage sensor and pore domains. The opening of channels engineered to contain single cysteine residues at the extracellular ends of the voltage-sensing S4 (V246C) and pore-forming S5 (C303) domains is inhibited by formation of disulfide or cysteine:Cd(2+) bonds. As Cd(2+) coordination is promoted by depolarization, the S4-S5 interaction occurs preferentially in the closed state. The failure of oxidation to catalyze dimer formation, as assayed by Western blotting, indicates the V246C:C303 interaction occurs within a subunit. Intriguingly, a similar interaction has been observed in depolarization-activated Shaker voltage-dependent potassium (Kv) channels at depolarized potentials but such an intrasubunit interaction is inconsistent with the X-ray crystal structure of Kv1.2, wherein S4 approaches S5 of an adjacent subunit. These findings suggest channels of opposite voltage-sensing polarity adopt a conserved S4-S5 orientation in the depolarized state that is distinct from that trapped upon crystallization.

  7. TRP Channels in Respiratory Pathophysiology: The Role of Oxidative, Chemical Irritant and Temperature Stimuli

    OpenAIRE

    Zholos, Alexander V.

    2015-01-01

    There is rapidly growing evidence indicating multiple and important roles of Ca2+-permeable cation TRP channels in the airways, both under normal and disease conditions. The aim of this review was to summarize the current knowledge of TRP channels in sensing oxidative, chemical irritant and temperature stimuli by discussing expression and function of several TRP channels in relevant cell types within the respiratory tract, ranging from sensory neurons to airway smooth muscle and epithelial ce...

  8. 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...

  9. A unifying mechanism for cancer cell death through ion channel activation by HAMLET.

    Science.gov (United States)

    Storm, Petter; Klausen, Thomas Kjaer; Trulsson, Maria; Ho C S, James; Dosnon, Marion; Westergren, Tomas; Chao, Yinxia; Rydström, Anna; Yang, Henry; Pedersen, Stine Falsig; Svanborg, Catharina

    2013-01-01

    Ion channels and ion fluxes control many aspects of tissue homeostasis. During oncogenic transformation, critical ion channel functions may be perturbed but conserved tumor specific ion fluxes remain to be defined. Here we used the tumoricidal protein-lipid complex HAMLET as a probe to identify ion fluxes involved in tumor cell death. We show that HAMLET activates a non-selective cation current, which reached a magnitude of 2.74±0.88 nA within 1.43±0.13 min from HAMLET application. Rapid ion fluxes were essential for HAMLET-induced carcinoma cell death as inhibitors (amiloride, BaCl2), preventing the changes in free cellular Na(+) and K(+) concentrations also prevented essential steps accompanying carcinoma cell death, including changes in morphology, uptake, global transcription, and MAP kinase activation. Through global transcriptional analysis and phosphorylation arrays, a strong ion flux dependent p38 MAPK response was detected and inhibition of p38 signaling delayed HAMLET-induced death. Healthy, differentiated cells were resistant to HAMLET challenge, which was accompanied by innate immunity rather than p38-activation. The results suggest, for the first time, a unifying mechanism for the initiation of HAMLET's broad and rapid lethal effect on tumor cells. These findings are particularly significant in view of HAMLET's documented therapeutic efficacy in human studies and animal models. The results also suggest that HAMLET offers a two-tiered therapeutic approach, killing cancer cells while stimulating an innate immune response in surrounding healthy tissues.

  10. Gating modifier toxins reveal a conserved structural motif in voltage-gated Ca2+ and K+ channels

    OpenAIRE

    Li-Smerin, Yingying; Swartz, Kenton J.

    1998-01-01

    Protein toxins from venomous animals exhibit remarkably specific and selective interactions with a wide variety of ion channels. Hanatoxin and grammotoxin are two related protein toxins found in the venom of the Chilean Rose Tarantula, Phrixotrichus spatulata. Hanatoxin inhibits voltage-gated K+ channels and grammotoxin inhibits voltage-gated Ca2+ channels. Both toxins inhibit their respective channels by interfering with normal operation of the voltage-dependent gating mechanism. The sequenc...

  11. 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...

  12. Water adsorption on free cobalt cluster cations

    NARCIS (Netherlands)

    D.M. Kiawi; J.M. Bakker; J. Oomens; W.J. Buma; Z. Jamshidi; L. Visscher; L.B.F.M. Waters

    2015-01-01

    Cationic cobalt clusters complexed with water Con+-​H2O (n = 6-​20) are produced through laser ablation and investigated via IR multiple photon dissocn. (IR-​MPD) spectroscopy in the 200-​1700 cm-​1 spectral range. All spectra exhibit a resonance close to the 1595 cm-​1 frequency of the free water b

  13. Simultaneous anion and cation mobility in polypyrrole

    DEFF Research Database (Denmark)

    Skaarup, Steen; Bay, Lasse; Vidanapathirana, K.;

    2003-01-01

    Polypyrrole (PPy) polymer films permanently doped with large, immobile anion dodecyl benzene sulfonate (DBS) have been characterized by cyclic voltammetry in order to clarify the roles of cations and anions in the aqueous electrolyte as mobile ions in the film. Aqueous solutions of 0.05-0.1 M alk...

  14. Resonance raman studies of phenylcyclopropane radical cations

    NARCIS (Netherlands)

    Godbout, J.T.; Zuilhof, H.; Heim, G.; Gould, I.R.; Goodman, J.L.; Dinnocenzo, J.P.; Myers Kelley, A.

    2000-01-01

    Resonance Raman spectra of the radical cations of phenylcyclopropane and trans-1-phenyl-2-methylcyclopropane are reported. A near-UV pump pulse excites a photosensitizer which oxidizes the species of interest, and a visible probe pulse delayed by 35 ns obtains the spectrum of the radical ion. The tr

  15. Anionic/cationic complexes in hair care.

    Science.gov (United States)

    O'Lenick, Tony

    2011-01-01

    The formulation of cosmetic products is always more complicated than studying the individual components in aqueous solution. This is because there are numerous interactions between the components, which make the formulation truly more than the sum of the parts. This article will look at interactions between anionic and cationic surfactants and offer insights into how to use these interactions advantageously in making formulations.

  16. Cationic lipids and cationic ligands induce DNA helix denaturation: detection of single stranded regions by KMnO4 probing.

    Science.gov (United States)

    Prasad, T K; Gopal, Vijaya; Rao, N Madhusudhana

    2003-09-25

    Cationic lipids and cationic polymers are widely used in gene delivery. Using 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) as a cationic lipid, we have investigated the stability of the DNA in DOTAP:DNA complexes by probing with potassium permanganate (KMnO4). Interestingly, thymidines followed by a purine showed higher susceptibility to cationic ligand-mediated melting. Similar studies performed with other water-soluble cationic ligands such as polylysine, protamine sulfate and polyethyleneimine also demonstrated melting of the DNA but with variations. Small cations such as spermine and spermidine and a cationic detergent, cetyl trimethylammonium bromide, also rendered the DNA susceptible to modification by KMnO4. The data presented here provide direct proof for melting of DNA upon interaction with cationic lipids. Structural changes subsequent to binding of cationic lipids/ligands to DNA may lead to instability and formation of DNA bubbles in double-stranded DNA.

  17. Cloning and expression of a FMRFamide-gated Na+ channel from Helisoma trivolvis and comparison with the native neuronal channel

    Science.gov (United States)

    Jeziorski, Michael C; Green, Kevin A; Sommerville, John; Cottrell, Glen A

    2000-01-01

    We have cloned a cDNA encoding a Phe-Met-Arg-Phe-NH2 (FMRFamide)-gated Na+ channel from nervous tissue of the pond snail Helisoma trivolvis (HtFaNaC) and expressed the channel in Xenopus oocytes. The deduced amino acid sequence of the protein expressed by HtFaNaC is 65 % identical to that of the FMRFamide-gated channel cloned from Helix aspersa (HaFaNaC). HtFaNaC expressed in oocytes was less sensitive to FMRFamide (EC50 = 70 μM) than HaFaNaC (EC50 = 2 μM). The two had a similar selectivity for Na+. The amplitude of the FMRFamide response of HtFaNaC was increased by reducing the extracellular concentration of divalent cations. The conductance of the two channels was similar, but the mean open time of unitary events was shorter for expressed HtFaNaC compared to expressed HaFaNaC. Each channel was susceptible to peptide block by high agonist concentrations. In marked contrast to HaFaNaC and other amiloride-sensitive Na+ channels, amiloride, and the related drugs benzamil and 5-(N-ethyl-N-isopropyl)-amiloride (EIPA), enhanced the FMRFamide response in oocytes expressing HtFaNaC cRNA. The potentiating effects of EIPA and benzamil were greater than those of amiloride. Unitary current analysis showed that with such drugs, there was channel blockade as well as an increased probability of channel opening. The similar permeability of the oocyte-expressed HtFaNaC and the Helisoma neuronal channel, and the susceptibility of both to agonist blockade and blockade by divalent cations, suggest that the channels are the same. However, neuronal channels were less susceptible to enhancement by amiloride analogues and in some patches were more sensitive to FMRFamide than expressed HtFaNaC. PMID:10878095

  18. Cation disordering in magnesium aluminate spinel crystals induced by electron or ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Soeda, Takeshi E-mail: soeda@regroup5.nucl.kyushu-u.ac.jp; Matsumura, Syo; Kinoshita, Chiken; Zaluzec, Nestor J

    2000-12-01

    Structural changes in magnesium aluminate spinel (MgO {center_dot} nAl{sub 2}O{sub 3}) single crystals, which were irradiated with 900 keV electrons or 1 MeV Ne{sup +} ions at 873 K, were examined by electron channeling enhanced X-ray microanalysis. Unirradiated MgO {center_dot} Al{sub 2}O{sub 3} has a tendency to form the normal spinel configuration, where Mg{sup 2+} ions and Al{sup 3+} ions occupy mainly the tetrahedral and the octahedral sites, respectively. Electron irradiation induces simple cation disordering between the tetrahedral sites and the octahedral sites in MgO {center_dot} Al{sub 2}O{sub 3}. In addition to cation disordering, slight evacuation of cations from the tetrahedral sites to the octahedral sites occurs in a peak-damaged area in MgO {center_dot} Al{sub 2}O{sub 3} irradiated with Ne{sup +} ions. In contrast, cation disordering is suppressed in MgO {center_dot} 2.4Al{sub 2}O{sub 3} irradiated with electrons. The structural vacancies, present in the non-stoichiometric compound, appear to be effective in promoting irradiation damage recovery through interstitial-vacancy recombination.

  19. The sting. Melittin forms channels in lipid bilayers.

    OpenAIRE

    Tosteson, M T; Tosteson, D. C.

    1981-01-01

    Melittin, a toxin of bee venom, is a cationic polypeptide composed of 26 amino acids. The six residues of the C-terminal end are polar and 19 of the 20 residues of the N-terminal end are hydrophobic. Exposure of the lecithin bilayer to melittin results in the formation of channels that are more permeable to anions that to cations. Unilateral addition of melittin produces a voltage-dependent increase in membrane conductance when the side where the polypeptide is present in made positive but no...

  20. Cation-cation interactions, magnetic communication and reactivity of the pentavalent uraniumion [U(NR)2]+

    Energy Technology Data Exchange (ETDEWEB)

    Spencer, Liam P [Los Alamos National Laboratory; Schelter, Eric J [Los Alamos National Laboratory; Boncella, James M [Los Alamos National Laboratory; Yang, Ping [Los Alamos National Laboratory; Gsula, Robyn L [NON LANL; Scott, Brian L [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory; Kiplinger, Jacqueline L [Los Alamos National Laboratory; Batista, Enrique R [Los Alamos National Laboratory

    2009-01-01

    The dimeric bis(imido) uranium complex [{l_brace}U(NtBu)2(I)(tBu2bpy){r_brace}2] (see picture; U green, N blue, I red) has cation-cation interactions between [U(NR)2]+ ions. This f1-f1 system also displays f orbital communication between uranium(V) centers at low temperatures, and can be oxidized to generate uranium(VI) bis(imido) complexes.

  1. New insights into TRP channels: Interaction with pattern recognition receptors.

    Science.gov (United States)

    Han, Huirong; Yi, Fan

    2014-01-01

    An increasing number of studies have implicated that the activation of innate immune system and inflammatory mechanisms are of importance in the pathogenesis of numerous diseases. The innate immune system is present in almost all multicellular organisms in response to pathogens or tissue injury, which is performed via germ-line encoded pattern-recognition receptors (PRRs) to recognize pathogen-associated molecular patterns (PAMPs) or dangers-associated molecular patterns (DAMPs). Intracellular pathways linking immune and inflammatory response to ion channel expression and function have been recently identified. Among ion channels, transient receptor potential (TRP) channels are a major family of non-selective cation-permeable channels that function as polymodal cellular sensors involved in many physiological and pathological processes. In this review, we summarize current knowledge about classifications, functions, and interactions of TRP channels and PRRs, which may provide new insights into their roles in the pathogenesis of inflammatory diseases.

  2. Effects of multivalent cations on cell wall-associated acid phosphatase activity

    Energy Technology Data Exchange (ETDEWEB)

    Tu, S.I.; Brouillette, J.N.; Nagahashi, G.; Kumosinski, T.F.

    1988-09-01

    Primary cell walls, free from cytoplasmic contamination were prepared from corn (Zea mays L.) roots and potato (Solanum tuberosum) tubers. After EDTA treatment, the bound acid phosphatase activities were measured in the presence of various multivalent cations. Under the conditions of minimized Donnan effect and at pH 4.2, the bound enzyme activity of potato tuber cell walls (PCW) was stimulated by Cu/sup 2 +/, Mg/sup 2 +/, Za/sup 2 +/, and Mn/sup 2 +/; unaffected by Ba/sup 2 +/, Cd/sup 2 +/, and Pb/sup 2 +/; and inhibited by Al/sup 3 +/. The bound acid phosphatase of PCW was stimulated by a low concentration but inhibited by a higher concentration of Hg/sup 2 +/. On the other hand, in the case of corn root cells walls (CCW), only inhibition of the bound acid phosphatase by Al/sup 3 +/ and Hg/sup 2 +/ was observed. Kinetic analyses revealed that PCW acid phosphatase exhibited a negative cooperativity under all employed experimental conditions except in the presence of Mg/sup 2 +/. In contrast, CCW acid phosphatase showed no cooperative behavior. The presence of Ca/sup 2 +/ significantly reduced the effects of Hg/sup 2 +/ or Al/sup 3 +/, but not Mg/sup 2 +/, to the bound cell wall acid phosphatases. The salt solubilized (free) acid phosphatases from both PCW and CCW were not affected by the presence of tested cations except for Hg/sup 2 +/ or Al/sup 3 +/ which caused a Ca/sup 2 +/-insensitive inhibition of the enzymes. The induced stimulation or inhibition of bound acid phosphatases was quantitatively related to cation binding in the cell wall structure.

  3. Ligustrazine inhibits high voltage-gated Ca2+ and TTX-resistant Na+ channels of primary sensory neuron and thermal nociception in the rat:a study on peripheral mechanism

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Objective Ligustrazine, also named as tetramethylpyrazine, is a compound purified from Ligusticum chuanxiong hort and has ever been testified to be a calcium antagonist. The present investigation was to determine the antinociceptive effect of ligustrazine and, if any, the peripheral ionic mechanism involved. Methods Paw withdrawal Latency(PWL) to noxious heating was measured in vivo and whole-cell patch recording was performed on small dorsal root ganglion (DRG) neurons. Results Intraplantar injection of ligustrazine (0.5 mg in 25 μl) significantly prolonged the withdrawal latency of ipsilateral hindpaw to noxious heating in the rat. Ligustrazine not only reversibly inhibited high-voltage gated calcium current of dorsal root ganglion (DRG) neuron in dose-dependent manner with IC50 of 1.89 mmol/L, but also decreased tetrodotoxin (TTX) -resistant sodium current in relatively selective and dose-dependent manner with IC50 of2.49 mmol/L. Conclusion The results suggested that ligustrazine could elevate the threshold of thermal nociception through inhibiting the high-voltage gated calcium current and TTX-resistant sodium current of DRG neuron .in the rat.

  4. Emerging roles of alkali cation/proton exchangers in organellar homeostasis

    Science.gov (United States)

    Orlowski, John; Grinstein, Sergio

    2016-01-01

    The regulated movement of monovalent cations such as H+, Li+, Na+ and K+ across biological membranes influences a myriad of cellular processes and is fundamental to all living organisms. This is accomplished by a multiplicity of ion channels, pumps and transporters. Our insight into their molecular, cellular and physiological diversity has increased greatly in the past few years with the advent of genome sequencing, genetic manipulation and sophisticated imaging techniques. One of the revelations from these studies is the emergence of novel alkali cation/protons exchangers that are present in endomembranes, where they function to regulate not only intraorganellar pH but also vesicular biogenesis, trafficking and other aspects of cellular homeostasis. PMID:17646094

  5. 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

  6. Ionic Selectivity and Permeation Properties of Human PIEZO1 Channels.

    Directory of Open Access Journals (Sweden)

    Radhakrishnan Gnanasambandam

    Full Text Available Members of the eukaryotic PIEZO family (the human orthologs are noted hPIEZO1 and hPIEZO2 form cation-selective mechanically-gated channels. We characterized the selectivity of human PIEZO1 (hPIEZO1 for alkali ions: K+, Na+, Cs+ and Li+; organic cations: TMA and TEA, and divalents: Ba2+, Ca2+, Mg2+ and Mn2+. All monovalent ions permeated the channel. At a membrane potential of -100 mV, Cs+, Na+ and K+ had chord conductances in the range of 35-55 pS with the exception of Li+, which had a significantly lower conductance of ~ 23 pS. The divalents decreased the single-channel permeability of K+, presumably because the divalents permeated slowly and occupied the open channel for a significant fraction of the time. In cell-attached mode, 90 mM extracellular divalents had a conductance for inward currents carried by the divalents of: 25 pS for Ba2+ and 15 pS for Ca2+ at -80 mV and 10 pS for Mg2+ at -50 mV. The organic cations, TMA and TEA, permeated slowly and attenuated K+ currents much like the divalents. As expected, the channel K+ conductance increased with K+ concentration saturating at ~ 45 pS and the KD of K+ for the channel was 32 mM. Pure divalent ion currents were of lower amplitude than those with alkali ions and the channel opening rate was lower in the presence of divalents than in the presence of monovalents. Exposing cells to the actin disrupting reagent cytochalasin D increased the frequency of openings in cell-attached patches probably by reducing mechanoprotection.

  7. Radiation chemistry of aromatic dimer radical cations

    International Nuclear Information System (INIS)

    π-π Interactions of aromatic molecules are paid attention much in many fields, especially biology, chemistry, and applied physics, represented as protein, DNA, electron donor-accepter complexes, charge transfers, and self assembly molecules. Aromatic molecules including benzene rings are the simplest case to study the π-π interactions. To interpret the charge resonance (CR) structure in the dimer radical cations, spectroscopic and ESR methods have been carried out. The spectroscopic study on the dimer radical ion of molecules with two chromophores would be profitable to identify the electronic and configurational properties. In this article, dynamics of the dimer radical cation of benzenes, polystyrenes, and resist polymers is described on the basis of direct observation of CR band by the nanosecond pulse radiolysis and low temperature γ-radiolysis methods. (author)

  8. Channel nut tool

    Energy Technology Data Exchange (ETDEWEB)

    Olson, Marvin

    2016-01-12

    A method, system, and apparatus for installing channel nuts includes a shank, a handle formed on a first end of a shank, and an end piece with a threaded shaft configured to receive a channel nut formed on the second end of the shaft. The tool can be used to insert or remove a channel nut in a channel framing system and then removed from the channel nut.

  9. Alkaline earth cation extraction from acid solution

    Science.gov (United States)

    Dietz, Mark; Horwitz, E. Philip

    2003-01-01

    An extractant medium for extracting alkaline earth cations from an aqueous acidic sample solution is described as are a method and apparatus for using the same. The separation medium is free of diluent, free-flowing and particulate, and comprises a Crown ether that is a 4,4'(5')[C.sub.4 -C.sub.8 -alkylcyclohexano]18-Crown-6 dispersed on an inert substrate material.

  10. Cation Permeability in Soybean Aleurone Layer

    OpenAIRE

    Noda, Hiroko; Fukuda, Mitsuru

    1998-01-01

    The permeation of water and ions into bean seeds is essential for processing and cooking of beans. The permeability of cations, K, Na, Ca, and Mg ions, into soybean seed tissue, especially aleurone layer, during water uptake was investigated to characterize the ion permeation into soybeans. Aleurone layers and seed coats contained relatively high concentration of endogenous K and Ca ions, and endogenous Ca ion, respectively. The amounts of Ca ion entered seed coats and aleurone layers were gr...

  11. Calmodulin and calcium interplay in the modulation of TRPC5 channel activity. Identification of a novel C-terminal domain for calcium/calmodulin-mediated facilitation.

    Science.gov (United States)

    Ordaz, Benito; Tang, Jisen; Xiao, Rui; Salgado, Alfonso; Sampieri, Alicia; Zhu, Michael X; Vaca, Luis

    2005-09-01

    TRPC5 forms Ca2+-permeable nonselective cation channels important for neurite outgrowth and growth cone morphology of hippocampal neurons. Here we studied the activation of mouse TRPC5 expressed in Chinese hamster ovary and human embryonic kidney 293 cells by agonist stimulation of several receptors that couple to the phosphoinositide signaling cascade and the role of calmodulin (CaM) on the activation. We showed that exogenous application of 10 microM CaM through patch pipette accelerated the agonist-induced channel activation by 2.8-fold, with the time constant for half-activation reduced from 4.25 +/- 0.4 to 1.56 +/- 0.85 min. We identified a novel CaM-binding site located at the C terminus of TRPC5, 95 amino acids downstream from the previously determined common CaM/IP3R-binding (CIRB) domain for all TRPC proteins. Deletion of the novel CaM-binding site attenuated the acceleration in channel activation induced by CaM. However, disruption of the CIRB domain from TRPC5 rendered the channel irresponsive to agonist stimulation without affecting the cell surface expression of the channel protein. Furthermore, we showed that high (>5 microM) intracellular free Ca2+ inhibited the current density without affecting the time course of TRPC5 activation by receptor agonists. These results demonstrated that intracellular Ca2+ has dual and opposite effects on the activation of TRPC5. The novel CaM-binding site is important for the Ca2+/CaM-mediated facilitation, whereas the CIRB domain is critical for the overall response of receptor-induced TRPC5 channel activation.

  12. Dental enamel cells express functional SOCE channels.

    Science.gov (United States)

    Nurbaeva, Meerim K; Eckstein, Miriam; Concepcion, Axel R; Smith, Charles E; Srikanth, Sonal; Paine, Michael L; Gwack, Yousang; Hubbard, Michael J; Feske, Stefan; Lacruz, Rodrigo S

    2015-10-30

    Dental enamel formation requires large quantities of Ca(2+) yet the mechanisms mediating Ca(2+) dynamics in enamel cells are unclear. Store-operated Ca(2+) entry (SOCE) channels are important Ca(2+) influx mechanisms in many cells. SOCE involves release of Ca(2+) from intracellular pools followed by Ca(2+) entry. The best-characterized SOCE channels are the Ca(2+) release-activated Ca(2+) (CRAC) channels. As patients with mutations in the CRAC channel genes STIM1 and ORAI1 show abnormal enamel mineralization, we hypothesized that CRAC channels might be an important Ca(2+) uptake mechanism in enamel cells. Investigating primary murine enamel cells, we found that key components of CRAC channels (ORAI1, ORAI2, ORAI3, STIM1, STIM2) were expressed and most abundant during the maturation stage of enamel development. Furthermore, inositol 1,4,5-trisphosphate receptor (IP3R) but not ryanodine receptor (RyR) expression was high in enamel cells suggesting that IP3Rs are the main ER Ca(2+) release mechanism. Passive depletion of ER Ca(2+) stores with thapsigargin resulted in a significant raise in [Ca(2+)]i consistent with SOCE. In cells pre-treated with the CRAC channel blocker Synta-66 Ca(2+) entry was significantly inhibited. These data demonstrate that enamel cells have SOCE mediated by CRAC channels and implicate them as a mechanism for Ca(2+) uptake in enamel formation.

  13. Low cation coordination in oxide melts

    Energy Technology Data Exchange (ETDEWEB)

    Skinner, Lawrie [State University of New York, Stony Brook; Benmore, Chris J [Argonne National Laboratory (ANL); Du, Jincheng [University of North Texas; Weber, Richard [Argonne National Laboratory (ANL); Neuefeind, Joerg C [ORNL; Tumber, Sonia [Materials Development, Inc., Evanston, IL; Parise, John B [Stony Brook University (SUNY)

    2014-01-01

    The complete set of Faber-Ziman partial pair distribution functions for a rare earth oxide liquid were measured for the first time by combining aerodynamic levitation, neutron diffraction, high energy x-ray diffraction and isomorphic substitution using Y2 O3 and Ho2 O3 melts. The average Y- O coordination is measured to be 5.5(2), which is significantly less than the octahedral coordination of crystalline Y2 O3 (or Ho2 O3 ). Investigation of high temperature La2 O3 , ZrO2 , SiO2 , and Al2 O3 melts by x-ray diffraction and molecular dynamics simulations also show lower-than-crystal cation- oxygen coordination. These measurements suggest a general trend towards lower M-O coordination compared to their crystalline counterparts. It is found that this coordination number drop is larger for lower field strength, larger radius cations and is negligible for high field strength (network forming) cations. These findings have broad implications for predicting the local structure and related physical properties of metal-oxide melts and oxide glasses.

  14. Low Cation Coordination in Oxide Melts

    Science.gov (United States)

    Skinner, L. B.; Benmore, C. J.; Weber, J. K. R.; Du, J.; Neuefeind, J.; Tumber, S. K.; Parise, J. B.

    2014-04-01

    The complete set of partial pair distribution functions for a rare earth oxide liquid are measured by combining aerodynamic levitation, neutron and x-ray diffraction on Y2O3, and Ho2O3 melts at 2870 K. The average Y-O (or Ho-O) coordination of these isomorphic melts is measured to be 5.5(2), which is significantly less than the octahedral coordination of crystalline Y2O3 (or Ho2O3). Investigation of La2O3, ZrO2, and Al2O3 melts by x-ray diffraction and molecular dynamics simulations also show lower-than-crystal cation-oxygen coordination. These measurements suggest a general trend towards lower coordination compared to their crystalline counterparts. It is found that the coordination drop is larger for lower field strength, larger radius cations and is negligible for high field strength (network forming) cations, such as SiO2. These findings have broad implications for predicting the local structure and related physical properties of metal-oxide melts and oxide glasses.

  15. Limited data speaker identification

    Indian Academy of Sciences (India)

    H S Jayanna; S R Mahadeva Prasanna

    2010-10-01

    In this paper, the task of identifying the speaker using limited training and testing data is addressed. Speaker identification system is viewed as four stages namely, analysis, feature extraction, modelling and testing. The speaker identification performance depends on the techniques employed in these stages. As demonstrated by different experiments, in case of limited training and testing data condition, owing to less data, existing techniques in each stage will not provide good performance. This work demonstrates the following: multiple frame size and rate (MFSR) analysis provides improvement in the analysis stage, combination of mel frequency cepstral coefficients (MFCC), its temporal derivatives $(\\Delta,\\Delta \\Delta)$, linear prediction residual (LPR) and linear prediction residual phase (LPRP) features provides improvement in the feature extraction stage and combination of learning vector quantization (LVQ) and gaussian mixture model – universal background model (GMM–UBM) provides improvement in the modelling stage. The performance is further improved by integrating the proposed techniques at the respective stages and combining the evidences from them at the testing stage. To achieve this, we propose strength voting (SV), weighted borda count (WBC) and supporting systems (SS) as combining methods at the abstract, rank and measurement levels, respectively. Finally, the proposed hierarchical combination (HC) method integrating these three methods provides significant improvement in the performance. Based on these explorations, this work proposes a scheme for speaker identification under limited training and testing data.

  16. An ATP-activated channel is involved in mitogenic stimulation of human T lymphocytes.

    Science.gov (United States)

    Baricordi, O R; Ferrari, D; Melchiorri, L; Chiozzi, P; Hanau, S; Chiari, E; Rubini, M; Di Virgilio, F

    1996-01-15

    We investigated the effect of pharmacologic modulation of the ATP receptor on intracellular ion changes and proliferative response of human peripheral blood lymphocytes (PBLs) and purified T lymphocytes. Extracellular ATP (ATPe) triggered in these cells an increase in the cytoplasmic Ca2+ concentration ([Ca2+]i) and plasma membrane depolarization. Whereas both Ca2+ release from intracellular stores and influx across the plasma membrane were detected in the whole PBL population, only Ca2+ influx was observed in T cells. In the presence of near physiologic extracellular Na+ concentrations (125 mmol/L), Ca2+ permeability through the ATPe-gated channel was very low, suggesting a higher selectivity for monovalent over divalent cations. The selective P2Z agonist benzoylbenzoic ATP (BzATP) increased [Ca2+]i in the presence but not the absence of extracellular Ca2+ and also caused plasma membrane depolarization. The covalent blocker oxidized ATP (oATP), an inhibitor of P2X and P2Z receptors, prevented Ca2+ influx and plasma membrane depolarization, but had no effect on Ca2+ release from stores. Stimulation with ATPe alone had no significant effects on PBL 3H-thymidine incorporation. On the contrary, ATPe or BzATP had a synergistic effect on DNA synthesis stimulated by selective T-cell mitogens such as phytohemagglutinin, anti-CD3 monoclonal antibody, or allogenic PBLs (mixed lymphocyte cultures). Treatment with oATP inhibited mitogenic stimulation by these receptor-directed agents but not by the combined application of the Ca2+ ionophore ionomycin and phorbol myristate acetate. Interleukin-2 partially relieved inhibition by oATP. These results suggest that human T lymphocytes express a plasma membrane channel gated by ATPe that is involved in mitogenic stimulation. PMID:8555491

  17. Mechanism for modulation of gating of connexin26-containing channels by taurine

    OpenAIRE

    Locke, Darren; Kieken, Fabien; Tao, Liang; Sorgen, Paul L.; Harris, Andrew L.

    2011-01-01

    The mechanisms of action of endogenous modulatory ligands of connexin channels are largely unknown. Previous work showed that protonated aminosulfonates (AS), notably taurine, directly and reversibly inhibit homomeric and heteromeric channels that contain Cx26, a widely distributed connexin, but not homomeric Cx32 channels. The present study investigated the molecular mechanisms of connexin channel modulation by taurine, using hemichannels and junctional channels composed of Cx26 (homomeric) ...

  18. Nifedipine, a calcium channel blocker, inhibits advanced glycation end product (AGE)-elicited mesangial cell damage by suppressing AGE receptor (RAGE) expression via peroxisome proliferator-activated receptor-gamma activation

    International Nuclear Information System (INIS)

    The interaction between advanced glycation end products (AGE) and their receptor RAGE mediates the progressive alteration in renal architecture and loss of renal function in diabetic nephropathy. Oxidative stress generation and inflammation also play a central role in diabetic nephropathy. This study investigated whether and how nifedipine, a calcium channel blocker (CCB), blocked the AGE-elicited mesangial cell damage in vitro. Nifedipine, but not amlodipine, a control CCB, down-regulated RAGE mRNA levels and subsequently reduced reactive oxygen species (ROS) generation in AGE-exposed mesangial cells. AGE increased mRNA levels of vascular cell adhesion molecule-1 (VCAM-1) and induced monocyte chemoattractant protein-1 (MCP-1) production in mesangial cells, both of which were prevented by the treatment with nifedipine, but not amlodipine. The beneficial effects of nifedipine on AGE-exposed mesangial cells were blocked by the simultaneous treatment of GW9662, an inhibitor of peroxisome proliferator-activated receptor-γ (PPAR-γ). Although nifedipine did not affect expression levels of PPAR-γ, it increased the PPAR-γ transcriptional activity in mesangial cells. Our present study provides a unique beneficial aspect of nifedipine on diabetic nephropathy; it could work as an anti-inflammatory agent against AGE by suppressing RAGE expression in cultured mesangial cells via PPAR-γ activation.

  19. Functional effects of KCNQ K+ channels in airway smooth muscle

    OpenAIRE

    AlexeyIEvseev; IuriiSemenov; JorgeMedina

    2013-01-01

    KCNQ (Kv7) channels underlie a voltage-gated K+ current best known for control of neuronal excitability, and its inhibition by Gq/11-coupled, muscarinic signaling. Studies have indicated expression of KCNQ channels in airway smooth muscle (ASM), a tissue that is predominantly regulated by muscarinic receptor signaling. Therefore we investigated the function of KCNQ channels in rodent ASM and their interplay with Gq/11-coupled M3 muscarinic receptors. Perforated-patch clamp of dissociated ASM...

  20. Functional effects of KCNQ K+ channels in airway smooth muscle

    OpenAIRE

    Evseev, Alexey I.; Semenov, Iurii; Archer, Crystal R.; Medina, Jorge L.; Dube, Peter H.; Shapiro, Mark S.; Brenner, Robert

    2013-01-01

    KCNQ (Kv7) channels underlie a voltage-gated K+ current best known for control of neuronal excitability, and its inhibition by Gq/11-coupled, muscarinic signaling. Studies have indicated expression of KCNQ channels in airway smooth muscle (ASM), a tissue that is predominantly regulated by muscarinic receptor signaling. Therefore, we investigated the function of KCNQ channels in rodent ASM and their interplay with Gq/11-coupled M3 muscarinic receptors. Perforated-patch clamp of dissociated ASM...

  1. Tarantula toxins interacting with voltage sensors in potassium channels

    OpenAIRE

    Swartz, Kenton J.

    2006-01-01

    Voltage-activated ion channels open and close in response to changes in membrane voltage, a process that is crucial for electrical signaling in the nervous system. The venom from many poisonous creatures contains a diverse array of small protein toxins that bind to voltage-activated channels and modify the gating mechanism. Hanatoxin and a growing number of related tarantula toxins have been shown to inhibit activation of voltage-activated potassium (Kv) channels by interacting with their vol...

  2. Alkali cation specific adsorption onto fcc(111) transition metal electrodes.

    Science.gov (United States)

    Mills, J N; McCrum, I T; Janik, M J

    2014-07-21

    The presence of alkali cations in electrolyte solutions is known to impact the rate of electrocatalytic reactions, though the mechanism of such impact is not conclusively determined. We use density functional theory (DFT) to examine the specific adsorption of alkali cations to fcc(111) electrode surfaces, as specific adsorption may block catalyst sites or otherwise impact surface catalytic chemistry. Solvation of the cation-metal surface structure was investigated using explicit water models. Computed equilibrium potentials for alkali cation adsorption suggest that alkali and alkaline earth cations will specifically adsorb onto Pt(111) and Pd(111) surfaces in the potential range of hydrogen oxidation and hydrogen evolution catalysis in alkaline solutions.

  3. 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.

  4. Regulation of TRP-like muscarinic cation current in gastrointestinal smooth muscle with special reference to PLC/InsP3/Ca2+ system

    Institute of Scientific and Technical Information of China (English)

    Alexander V ZHOLOS

    2006-01-01

    Acetylcholine,the main enteric excitatory neuromuscular transmitter,evokes membrane depolarization and contraction of gastrointestinal smooth muscle cells by activating G protein-coupled muscarinic receptors.Although the cholinergic excitation is generally underlined by the multiplicity of ion channel effects,the primary event appears to be the opening of cation-selective channels;among them the 60 pS channel has been recently identified as the main target for the acetylcholine action in gastrointestinal myocytes.The evoked cation current,termed mICAT,causes either an oscillatory or a more sustained membrane depolarization response,which in turn leads to increases of the open probability of voltage-gated Ca2+ channels.thus providing Ca2+ entry in parallel with Ca2+ release for intracellular Ca2+ concentration rise and contraction.In recent years there have been several significant developments in our understanding of the signaling processes underlying mIcAT generation.They have revealed important synergistic interactions between M2 and M3 receptor subtypes,single channel mechanisms,and the involvement of TRPC-encoded proteins as essential components of native muscarinic cation channels.This review summarizes these recent findings and in particular discusses the roles of the phospholipase C/InsP3/intracellular Ca2+ release system in the mICAT physiological regulation.

  5. Elevated extracellular calcium increases expression of bone morphogenetic protein-2 gene via a calcium channel and ERK pathway in human dental pulp cells

    International Nuclear Information System (INIS)

    Dental pulp cells, which have been shown to share phenotypical features with osteoblasts, are capable of differentiating into odontoblast-like cells and generating a dentin-like mineral structure. Elevated extracellular Ca2+Cao2+ has been implicated in osteogenesis by stimulating the proliferation and differentiation of osteoblasts; however, the role of Cao2+ signaling in odontogenesis remains unclear. We found that elevated Cao2+ increases bone morphogenetic protein (BMP)-2 gene expression in human dental pulp cells. The increase was modulated not only at a transcriptional level but also at a post-transcriptional level, because treatment with Ca2+ increased the stability of BMP-2 mRNA in the presence of actinomycin D, an inhibitor of transcription. A similar increase in BMP-2 mRNA level was observed in other human mesenchymal cells from oral tissue; periodontal ligament cells and gingival fibroblasts. However, the latter cells exhibited considerably lower expression of BMP-2 mRNA compared with dental pulp cells and periodontal ligament cells. The BMP-2 increase was markedly inhibited by pretreatment with an extracellular signal-regulated kinase (ERK) inhibitor, PD98059, and partially inhibited by the L-type Ca2+ channels inhibitor, nifedipine. However, pretreatment with nifedipine had no effect on ERK1/2 phosphorylation triggered by Ca2+, suggesting that the Ca2+ influx from Ca2+ channels may operate independently of ERK signaling. Dental pulp cells do not express the transcript of Ca2+-sensing receptors (CaSR) and only respond slightly to other cations such as Sr2+ and spermine, suggesting that dental pulp cells respond to Cao2+ to increase BMP-2 mRNA expression in a manner different from CaSR and rather specific for Cao2+ among cations.

  6. Multi-Channel Retailing

    Directory of Open Access Journals (Sweden)

    Dirk Morschett, Dr.,

    2005-01-01

    Full Text Available Multi-channel retailing entails the parallel use by retailing enterprises of several sales channels. The results of an online buyer survey which has been conducted to investigate the impact of multi-channel retailing (i.e. the use of several retail channels by one retail company on consumer behaviour show that the frequently expressed concern that the application of multi-channel systems in retailing would be associated with cannibalization effects, has proven unfounded. Indeed, the appropriate degree of similarity, consistency, integration and agreement achieves the exact opposite. Different channels create different advantages for consumers. Therefore the total benefit an enterprise which has a multi-channel system can offer to its consumers is larger, the greater the number of available channels. The use of multi-channel systems is associated with additional purchases in the different channels. Such systems are thus superior to those offering only one sales channel to their customers. Furthermore, multi-channel systems with integrated channels are superior to those in which the channels are essentially autonomous and independent of one another. In integrated systems, consumers can achieve synergy effects in the use of sales-channel systems. Accordingly, when appropriately formulated, multi-channel systems in retailing impact positively on consumers. They use the channels more frequently, buy more from them and there is a positive customer-loyalty impact. Multi-channel systems are strategic options for achieving customer loyalty, exploiting customer potential and for winning new customers. They are thus well suited for approaching differing and varied target groups.

  7. Choline but not its derivative betaine blocks slow vacuolar channels in the halophyte Chenopodium quinoa: implications for salinity stress responses.

    Science.gov (United States)

    Pottosin, Igor; Bonales-Alatorre, Edgar; Shabala, Sergey

    2014-11-01

    Activity of tonoplast slow vacuolar (SV, or TPC1) channels has to be under a tight control, to avoid undesirable leak of cations stored in the vacuole. This is particularly important for salt-grown plants, to ensure efficient vacuolar Na(+) sequestration. In this study we show that choline, a cationic precursor of glycine betaine, efficiently blocks SV channels in leaf and root vacuoles of the two chenopods, Chenopodium quinoa (halophyte) and Beta vulgaris (glycophyte). At the same time, betaine and proline, two major cytosolic organic osmolytes, have no significant effect on SV channel activity. Physiological implications of these findings are discussed. PMID:25240200

  8. Calcium channel blockers ameliorate iron overload-associated hepatic fibrosis by altering iron transport and stellate cell apoptosis.

    Science.gov (United States)

    Zhang, Ying; Zhao, Xin; Chang, Yanzhong; Zhang, Yuanyuan; Chu, Xi; Zhang, Xuan; Liu, Zhenyi; Guo, Hui; Wang, Na; Gao, Yonggang; Zhang, Jianping; Chu, Li

    2016-06-15

    Liver fibrosis is the principal cause of morbidity and mortality in patients with iron overload. Calcium channel blockers (CCBs) can antagonize divalent cation entry into renal and myocardial cells and inhibit fibrogenic gene expression. We investigated the potential of CCBs to resolve iron overload-associated hepatic fibrosis. Kunming mice were assigned to nine groups (n=8 per group): control, iron overload, deferoxamine, high and low dose verapamil, high and low dose nimodipine, and high and low dose diltiazem. Iron deposition and hepatic fibrosis were measured in mouse livers. Expression levels of molecules associated with transmembrane iron transport were determined by molecular biology approaches. In vitro HSC-T6 cells were randomized into nine groups (the same groups as the mice). Changes in proliferation, apoptosis, and metalloproteinase expression in cells were detected to assess the anti-fibrotic effects of CCBs during iron overload conditions. We found that CCBs reduced hepatic iron content, intracellular iron deposition, the number of hepatic fibrotic areas, collagen expression levels, and hydroxyproline content. CCBs rescued abnormal expression of α1C protein in L-type voltage-dependent calcium channel (LVDCC) and down-regulated divalent metal transporter-1 (DMT-1) expression in mouse livers. In iron-overloaded HSC-T6 cells, CCBs reduced iron deposition, inhibited proliferation, induced apoptosis, and elevated expression of matrix metalloproteinase-13 (MMP-13) and tissue inhibitor of metalloproteinase-1 (TIMP-1). CCBs are potential therapeutic agents that can be used to address hepatic fibrosis during iron overload. They resolve hepatic fibrosis probably correlated with regulating transmembrane iron transport and inhibiting HSC growth. PMID:27095094

  9. Differential effect of HOE642 on two separate monovalent cation transporters in the human red cell membrane

    DEFF Research Database (Denmark)

    Bernhardt, Ingolf; Weiss, Erwin; Robinson, Hannah C;

    2007-01-01

    Residual K(+) fluxes in red blood cells can be stimulated in conditions of low ionic strength. Previous studies have identified both the non-selective, voltage-dependent cation (NSVDC) channel and the K(+)(Na(+))/H(+) exchanger as candidate pathways mediating this effect, although it is possible...... showed that HOE642 exerted differential effects on the NSVDC channel and the K(+)(Na(+))/H(+) exchanger, confirming that the salt loss observed in low ionic strength solutions represents contributions from at least two independent ion transport pathways. The findings are discussed in the context of red...... blood cell apoptosis (eryptosis) and disease....

  10. Metal cation sensing material based on the assembly of meso-terakis(4-N,N,N-trimethylamiophenyl) porphyrin and mesoporous molecular sieve MCM-41

    Institute of Scientific and Technical Information of China (English)

    ZHANG Huidong; SUN Yinghui; ZHANG Ping; YE Kaiqi; ZHANG Jingying; WANG Yue

    2005-01-01

    The metal cation sensing material was prepared by entrapment of a water-soluble porphyrin compound, mesoterakis(4-N,N,N-trimethylamiophenyl) porphyrin (TTMAPP), in mesoporous molecular sieve MCM-41. The powder X-ray diffraction (XRD) spectra results demonstrated that after the introduction of TTMAPP, the ordered channel arrangement of MCM-41 remained. The assembly material, TTMAPP/MCM-41, exhibited a typical absorption feature of porphyrin compound. Emission spectrum study revealed that the introduction of zinc (II) cation resulted in the formation of a new emission peak at 600 nm for TTMAPP/MCM-41, while the presence of copper (II) cation at low concentration led to that the luminescent intensity of TTMAPP/MCM-41 was obviously reduced by 68.42%. The experiment results demonstrated that TTMAPP/MCM-41 is a cation sensing materials with good performance.

  11. Evaluation of cationic micropeptides derived from the innate immune system as inhibitors of marine biofouling.

    Science.gov (United States)

    Trepos, Rozenn; Cervin, Gunnar; Pile, Claire; Pavia, Henrik; Hellio, Claire; Svenson, Johan

    2015-01-01

    A series of 13 short synthetic amphiphilic cationic micropeptides, derived from the antimicrobial iron-binding innate defence protein lactoferrin, have been evaluated for their capacity to inhibit the marine fouling process. The whole biofouling process was studied and microfouling organisms such as marine bacteria and microalgae were included as well as the macrofouling barnacle Balanus improvisus. In total 19 different marine fouling organisms (18 microfoulers and one macrofouler) were included and both the adhesion and growth of the microfoulers were investigated. It was shown that the majority of the peptides inhibited barnacle cyprid settlement via a reversible nontoxic mechanism, with IC50 values as low as 0.5 μg ml(-1). Six peptides inhibited adhesion and growth of microorganisms. Two of these were particularly active against the microfoulers with MIC-values ranging between 0.01 and 1 μg ml(-1), which is comparable with the commercial reference antifoulant SeaNine.

  12. Aza Cope Rearrangement of Propargyl Enammonium Cations Catalyzed By a Self-Assembled `Nanozyme

    Energy Technology Data Exchange (ETDEWEB)

    Hastings, Courntey J.; Fiedler, Dorothea; Bergman, Robert G.; Raymond, Kenneth N.

    2008-02-27

    The tetrahedral [Ga{sub 4}L{sub 6}]{sup 12-} assembly (L = N,N-bis(2,3-dihydroxybenzoyl)-1,5-diaminonaphthalene) encapsulates a variety of cations, including propargyl enammonium cations capable of undergoing the aza Cope rearrangement. For propargyl enammonium substrates that are encapsulated in the [Ga{sub 4}L{sub 6}]{sup 12-} assembly, rate accelerations of up to 184 are observed when compared to the background reaction. After rearrangement, the product iminium ion is released into solution and hydrolyzed allowing for catalytic turnover. The activation parameters for the catalyzed and uncatalyzed reaction were determined, revealing that a lowered entropy of activation is responsible for the observed rate enhancements. The catalyzed reaction exhibits saturation kinetics; the rate data obey the Michaelis-Menten model of enzyme kinetics, and competitive inhibition using a non-reactive guest has been demonstrated.

  13. The effect of cation-πinteractions in electrolyte/organic nanofiltration systems

    Institute of Scientific and Technical Information of China (English)

    Gang Yang; Yu Ma; Weihong Xing

    2016-01-01

    The rejection properties of a nanofiltration organic membrane were investigated using KCl solutions, NaCl solutions, NaCl/benzyl alcohol hybrid solutions and KCl/benzyl alcohol hybrid solutions. The presence of benzyl alcohol (3.7 mol · m−3) caused a decrease in electrolyte rejection within the range of 0 to 6%. The mechanism of the decrease was discussed. The cation–πbond was assumed to form in the hybrid solution and to further induce the partial dehydration of the cation. The steric and charge density inhibition of the salt activity was strength-ened, and the salt rejection was thus decreased. A simulation was performed to evaluate the radius of the cation. © 2015 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.

  14. Inhibition of a store-operated Ca2+ entry pathway in human endothelial cells by the isoquinoline derivative LOE 908.

    Science.gov (United States)

    Encabo, A; Romanin, C; Birke, F W; Kukovetz, W R; Groschner, K

    1996-10-01

    1. The novel cation channel blocker, LOE 908, was tested for its effects on Ca2+ entry and membrane currents activated by depletion of intracellular Ca2+ stores in human endothelial cells. 2. LOE 908 inhibited store-operated Ca2+ entry induced by direct depletion of Ca2+ stores with 100 nM thapsigargin or 100 nM ionomycin with an EC50 of 2 microM and 4 microM, respectively. 3. LOE 908 did not affect thapsigargin- or ionomycin-induced Ca2+ release from intracellular stores up to concentrations of 3 microM. 4. LOE 908 reversibly suppressed thapsigargin- as well as ionomycin-induced whole-cell membrane currents. 5. The LOE 908-sensitive membrane conductance corresponded to a cation permeability of 5.5 and 6.9 fold selectivity for Ca2+ over K+ in the presence of thapsigargin and ionomycin, respectively. 6. Our results suggest that the isoquinoline, LOE 908 is a novel, potent inhibitor of the store-operated (capacitive) Ca2+ entry pathway in endothelial cells. PMID:8904644

  15. Effect of synthetic cationic protein on mechanoexcitability of vagal afferent nerve subtypes in guinea pig esophagus.

    Science.gov (United States)

    Yu, Shaoyong; Ouyang, Ann

    2011-12-01

    Eosinophilic esophagitis is characterized by increased infiltration and degranulation of eosinophils in the esophagus. Whether eosinophil-derived cationic proteins regulate esophageal sensory nerve function is still unknown. Using synthetic cationic protein to investigate such effect, we performed extracellular recordings from vagal nodose or jugular neurons in ex vivo esophageal-vagal preparations with intact nerve endings in the esophagus. Nerve excitabilities were determined by comparing action potentials evoked by esophageal distensions before and after perfusion of synthetic cationic protein poly-L-lysine (PLL) with or without pretreatment with poly-L-glutamic acid (PLGA), which neutralized cationic charges of PLL. Perfusion with PLL did not evoke action potentials in esophageal nodose C fibers but increased their responses to esophageal distension. This potentiation effect lasted for 30 min after washing out of PLL. Pretreatment with PLGA significantly inhibited PLL-induced mechanohyperexcitability of esophageal nodose C fibers. In esophageal nodose Aδ fibers, perfusion with PLL did not evoke action potentials. In contrast to nodose C fibers, both the spontaneous discharges and the responses to esophageal distension in nodose Aδ fibers were decreased by perfusion with PLL, which can be restored after washing out PLL for 30-60 min. Pretreatment with PLGA attenuated PLL-induced decrease in spontaneous discharge and mechanoexcitability of esophageal nodose Aδ fibers. In esophageal jugular C fibers, PLL neither evoked action potentials nor changed their responses to esophageal distension. Collectively, these data demonstrated that synthetic cationic protein did not evoke action potential discharges of esophageal vagal afferents but had distinctive sensitization effects on their responses to esophageal distension.

  16. Calcium channel blocker overdose

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002580.htm Calcium channel blocker overdose To use the sharing features on this page, please enable JavaScript. Calcium channel blockers are a type of medicine used ...

  17. Complex Macromolecular Architectures by Living Cationic Polymerization

    KAUST Repository

    Alghamdi, Reem D.

    2015-05-01

    Poly (vinyl ether)-based graft polymers have been synthesized by the combination of living cationic polymerization of vinyl ethers with other living or controlled/ living polymerization techniques (anionic and ATRP). The process involves the synthesis of well-defined homopolymers (PnBVE) and co/terpolymers [PnBVE-b-PCEVE-b-PSiDEGVE (ABC type) and PSiDEGVE-b-PnBVE-b-PSiDEGVE (CAC type)] by sequential living cationic polymerization of n-butyl vinyl ether (nBVE), 2-chloroethyl vinyl ether (CEVE) and tert-butyldimethylsilyl ethylene glycol vinyl ether (SiDEGVE), using mono-functional {[n-butoxyethyl acetate (nBEA)], [1-(2-chloroethoxy) ethyl acetate (CEEA)], [1-(2-(2-(t-butyldimethylsilyloxy)ethoxy) ethoxy) ethyl acetate (SiDEGEA)]} or di-functional [1,4-cyclohexanedimethanol di(1-ethyl acetate) (cHMDEA), (VEMOA)] initiators. The living cationic polymerizations of those monomers were conducted in hexane at -20 0C using Et3Al2Cl3 (catalyst) in the presence of 1 M AcOEt base.[1] The PCEVE segments of the synthesized block terpolymers were then used to react with living macroanions (PS-DPE-Li; poly styrene diphenyl ethylene lithium) to afford graft polymers. The quantitative desilylation of PSiDEGVE segments by n-Bu4N+F- in THF at 0 °C led to graft co- and terpolymers in which the polyalcohol is the outer block. These co-/terpolymers were subsequently subjected to “grafting-from” reactions by atom transfer radical polymerization (ATRP) of styrene to afford more complex macromolecular architectures. The base assisted living cationic polymerization of vinyl ethers were also used to synthesize well-defined α-hydroxyl polyvinylether (PnBVE-OH). The resulting polymers were then modified into an ATRP macro-initiator for the synthesis of well-defined block copolymers (PnBVE-b-PS). Bifunctional PnBVE with terminal malonate groups was also synthesized and used as a precursor for more complex architectures such as H-shaped block copolymer by “grafting-from” or

  18. Aggregate Formed by a Cationic Fluorescence Probe

    Institute of Scientific and Technical Information of China (English)

    TIAN, Juan; SANG, Da-Yong; JI, Guo-Zhen

    2007-01-01

    The aggregation behavior of a cationic fluorescence probe 10-(4,7,10,13,16-pentaoxa-1-azacyclooctadecyl-methyl)anthracen-9-ylmethyl dodecanoate (1) was observed and studied by a fluorescence methodology in acidic and neutral conditions. By using the Py scale, differences between simple aggregates and micelles have been discussed. The stability of simple aggregates was discussed in terms of hydrophobic interaction and electrostatic repulsion. The absence of excimer emission of the anthrancene moiety of probe 1 in neutral condition was attributed to the photoinduced electron transfer mechanism instead of photodimerization.

  19. Purification and Characterization of Two Voltage-Dependent Anion Channel Isoforms from Plant Seeds1

    Science.gov (United States)

    Abrecht, Helge; Wattiez, Ruddy; Ruysschaert, Jean-Marie; Homblé, Fabrice

    2000-01-01

    Mitochondria were isolated from imbibed seeds of lentil (Lens culinaris) and Phaseolus vulgaris. We copurified two voltage-dependent anion channel from detergent solubilized mitochondria in a single purification step using hydroxyapatite. The two isoforms from P. vulgaris were separated by chromatofocusing chromatography in 4 m urea without any loss of channel activity. Channel activity of each isoform was characterized upon reconstitution into diphytanoyl phosphatidylcholine planar lipid bilayers. Both isoforms form large conductance channels that are slightly anion selective and display cation selective substates. PMID:11080295

  20. Purification and characterization of two voltage-dependent anion channel isoforms from plant seeds.

    Science.gov (United States)

    Abrecht, H; Wattiez, R; Ruysschaert, J M; Homblé, F

    2000-11-01

    Mitochondria were isolated from imbibed seeds of lentil (Lens culinaris) and Phaseolus vulgaris. We copurified two voltage-dependent anion channel from detergent solubilized mitochondria in a single purification step using hydroxyapatite. The two isoforms from P. vulgaris were separated by chromatofocusing chromatography in 4 M urea without any loss of channel activity. Channel activity of each isoform was characterized upon reconstitution into diphytanoyl phosphatidylcholine planar lipid bilayers. Both isoforms form large conductance channels that are slightly anion selective and display cation selective substates.

  1. Channel-resolved above-threshold double ionization of acetylene.

    Science.gov (United States)

    Gong, Xiaochun; Song, Qiying; Ji, Qinying; Lin, Kang; Pan, Haifeng; Ding, Jingxin; Zeng, Heping; Wu, Jian

    2015-04-24

    We experimentally investigate the channel-resolved above-threshold double ionization (ATDI) of acetylene in the multiphoton regime using an ultraviolet femtosecond laser pulse centered at 395 nm by measuring all the ejected electrons and ions in coincidence. As compared to the sequential process, diagonal lines in the electron-electron joint energy spectrum are observed for the nonsequential ATDI owing to the correlative sharing of the absorbed multiphoton energies. We demonstrate that the distinct channel-resolved sequential and nonsequential ATDI spectra can clearly reveal the photon-induced acetylene-vinylidene isomerization via proton migration on the cation or dication states. PMID:25955049

  2. Dynamic channel allocation

    OpenAIRE

    Kaminsky, Andrew D.

    2003-01-01

    Approved for public release; distribution in unlimited. Dynamic Channel Allocation (DCA) offers the possibility of capturing unused channel capacity by allocating unused resources between competing network nodes. This can reduce or possibly eliminate channels sitting idle while information awaits transmission. This holds potential for increasing throughput on bandwidth constrained networks. The purpose of this thesis is to examine the techniques used to allocate channels on demand and acc...

  3. 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.

  4. Desynched channels on IRCnet

    CERN Document Server

    Hansen, Michael

    2008-01-01

    In this paper we describe what a desynchronised channel on IRC is. We give procedures on how to create such a channel and how to remove desynchronisation. We explain which types of desynchronisation there are, what properties desynchronised channels have, and which properties can be exploited.

  5. 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.

  6. Quantum Multiple Access Channel

    Institute of Scientific and Technical Information of China (English)

    侯广; 黄民信; 张永德

    2002-01-01

    We consider the transmission of classical information over a quantum channel by many senders, which is a generalization of the two-sender case. The channel capacity region is shown to be a convex hull bound by the yon Neumann entropy and the conditional yon Neumann entropies. The result allows a reasonable distribution of channel capacity over the senders.

  7. Cardiac potassium channel subtypes

    DEFF Research Database (Denmark)

    Schmitt, Nicole; Grunnet, Morten; Olesen, Søren-Peter

    2014-01-01

    About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K(+) channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K(+) channels...

  8. 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...

  9. A calcium-permeable cGMP-activated cation conductance in hippocampal neurons

    Science.gov (United States)

    Leinders-Zufall, T.; Rosenboom, H.; Barnstable, C. J.; Shepherd, G. M.; Zufall, F.

    1995-01-01

    Whole-cell patch clamp recordings detected a previously unidentified cGMP-activated membrane conductance in cultured rat hippocampal neurons. This conductance is nonselectively permeable for cations and is completely but reversibly blocked by external Cd2+. The Ca2+ permeability of the hippocampal cGMP-activated conductance was examined in detail, indicating that the underlying ion channels display a high relative permeability for Ca2+. The results indicate that hippocampal neurons contain a cGMP-activated membrane conductance that has some properties similar to the cyclic nucleotide-gated channels previously shown in sensory receptor cells and retinal neurons. In hippocampal neurons this conductance similarly could mediate membrane depolarization and Ca2+ fluxes in response to intracellular cGMP elevation.

  10. Functional expression of an arachnid sodium channel reveals residues responsible for tetrodotoxin resistance in invertebrate sodium channels.

    Science.gov (United States)

    Du, Yuzhe; Nomura, Yoshiko; Liu, Zhiqi; Huang, Zachary Y; Dong, Ke

    2009-12-01

    Tetrodotoxin (TTX) is a potent blocker of voltage-gated sodium channels, but not all sodium channels are equally sensitive to inhibition by TTX. The molecular basis of differential TTX sensitivity of mammalian sodium channels has been largely elucidated. In contrast, our knowledge about the sensitivity of invertebrate sodium channels to TTX remains poor, in part because of limited success in functional expression of these channels. In this study, we report the functional characterization in Xenopus oocytes of the first non-insect, invertebrate voltage-gated sodium channel from the varroa mite (Varroa destructor), an ecto-parasite of the honeybee. This arachnid sodium channel activates and inactivates rapidly with half-maximal activation at -18 mV and half-maximal fast inactivation at -29 mV. Interestingly, this arachnid channel showed surprising TTX resistance. TTX blocked this channel with an IC(50) of 1 microM. Subsequent site-directed mutagenesis revealed two residues, Thr-1674 and Ser-1967, in the pore-forming region of domains III and IV, respectively, which were responsible for the observed resistance to inhibition by TTX. Furthermore, sequence comparison and additional amino acid substitutions suggested that sequence polymorphisms at these two positions could be a widespread mechanism for modulating TTX sensitivity of sodium channels in diverse invertebrates. PMID:19828457

  11. Cationic Antimicrobial Polymers and Their Assemblies

    Directory of Open Access Journals (Sweden)

    Ana Maria Carmona-Ribeiro

    2013-05-01

    Full Text Available Cationic compounds are promising candidates for development of antimicrobial agents. Positive charges attached to surfaces, particles, polymers, peptides or bilayers have been used as antimicrobial agents by themselves or in sophisticated formulations. The main positively charged moieties in these natural or synthetic structures are quaternary ammonium groups, resulting in quaternary ammonium compounds (QACs. The advantage of amphiphilic cationic polymers when compared to small amphiphilic molecules is their enhanced microbicidal activity. Besides, many of these polymeric structures also show low toxicity to human cells; a major requirement for biomedical applications. Determination of the specific elements in polymers, which affect their antimicrobial activity, has been previously difficult due to broad molecular weight distributions and random sequences characteristic of radical polymerization. With the advances in polymerization control, selection of well defined polymers and structures are allowing greater insight into their structure-antimicrobial activity relationship. On the other hand, antimicrobial polymers grafted or self-assembled to inert or non inert vehicles can yield hybrid antimicrobial nanostructures or films, which can act as antimicrobials by themselves or deliver bioactive molecules for a variety of applications, such as wound dressing, photodynamic antimicrobial therapy, food packing and preservation and antifouling applications.

  12. Cobalt 60 cation exchange with mexican clays

    International Nuclear Information System (INIS)

    Mexican clays can be used to remove radioactive elements from contaminated aqueous solutions. Cation exchange experiments were performed with 60 Co radioactive solution. In the present work the effect of contact time on the sorption of Co 2+ was studied. The contact time in hydrated montmorillonite was from 5 to 120 minutes and in dehydrated montmorillonite 5 to 1400 minutes. The Co 2+ uptake value was, in hydrated montmorillonite, between 0.3 to 0.85 m eq/g and in dehydrated montmorillonite, between 0.6 to 1.40 m eq/g. The experiments were done in a pH 5.1 to 5.7 and normal conditions. XRD patterns were used to characterize the samples. The crystallinity was determined by X-ray Diffraction and it was maintained before and after the cation exchange. DTA thermo grams showed the temperatures of the lost humidity and crystallization water. Finally, was observed that dehydrated montmorillonite adsorb more cobalt than hydrated montmorillonite. (Author)

  13. Photodissociation of Cerium Oxide Nanocluster Cations.

    Science.gov (United States)

    Akin, S T; Ard, S G; Dye, B E; Schaefer, H F; Duncan, M A

    2016-04-21

    Cerium oxide cluster cations, CexOy(+), are produced via laser vaporization in a pulsed nozzle source and detected with time-of-flight mass spectrometry. The mass spectrum displays a strongly preferred oxide stoichiometry for each cluster with a specific number of metal atoms x, with x ≤ y. Specifically, the most prominent clusters correspond to the formula CeO(CeO2)n(+). The cluster cations are mass selected and photodissociated with a Nd:YAG laser at either 532 or 355 nm. The prominent clusters dissociate to produce smaller species also having a similar CeO(CeO2)n(+) formula, always with apparent leaving groups of (CeO2). The production of CeO(CeO2)n(+) from the dissociation of many cluster sizes establishes the relative stability of these clusters. Furthermore, the consistent loss of neutral CeO2 shows that the smallest neutral clusters adopt the same oxidation state (IV) as the most common form of bulk cerium oxide. Clusters with higher oxygen content than the CeO(CeO2)n(+) masses are present with much lower abundance. These species dissociate by the loss of O2, leaving surviving clusters with the CeO(CeO2)n(+) formula. Density functional theory calculations on these clusters suggest structures composed of stable CeO(CeO2)n(+) cores with excess oxygen bound to the surface as a superoxide unit (O2(-)). PMID:27035210

  14. Critical assessment of OmpF channel selectivity: merging information from different experimental protocols

    International Nuclear Information System (INIS)

    The ion selectivity of a channel can be quantified in several ways by using different experimental protocols. A wide, mesoscopic channel, the OmpF porin of the outer membrane of E. coli, serves as a case study for comparing and analysing several measures of the channel cation-anion permeability in chlorides of alkali metals (LiCl, NaCl, KCl, CsCl). We show how different insights can be gained and integrated to rationalize the global image of channel selectivity. To this end, reversal potential, channel conductance and bi-ionic potential (two different salts with a common anion on each side of the channel but with the same concentration) experiments are discussed in light of an electrodiffusion model based on the Poisson-Nernst-Planck formalism. Measurements and calculations based on the atomic crystal structure of the channel show that each protocol displays a particular balance between the different sources of selectivity.

  15. Cation-selective transporters are critical to the AMPK-mediated antiproliferative effects of metformin in human breast cancer cells.

    Science.gov (United States)

    Cai, Hao; Zhang, Yunhui; Han, Tianxiang Kevin; Everett, Ruth S; Thakker, Dhiren R

    2016-05-01

    The antidiabetic drug metformin exerts antineoplastic effects against breast cancer and other cancers. One mechanism by which metformin is believed to exert its anticancer effect involves activation of its intracellular target, adenosine monophosphate-activated protein kinase (AMPK), which is also implicated in the antidiabetic effect of metformin. It is proposed that in cancer cells, AMPK activation leads to inhibition of the mammalian target of rapamycin (mTOR) and the downstream pS6K that regulates cell proliferation. Due to its hydrophilic and cationic nature, metformin requires cation-selective transporters to enter cells and activate AMPK. This study demonstrates that expression levels of cation-selective transporters correlate with the antiproliferative and antitumor efficacy of metformin in breast cancer. Metformin uptake and antiproliferative activity were compared between a cation-selective transporter-deficient human breast cancer cell line, BT-20, and a BT-20 cell line that was engineered to overexpress organic cation transporter 3 (OCT3), a representative of cation-selective transporters and a predominant transporter in human breast tumors. Metformin uptake was minimal in BT-20 cells, but increased by >13-fold in OCT3-BT20 cells, and its antiproliferative potency was >4-fold in OCT3-BT20 versus BT-20 cells. This increase in antiproliferative activity was associated with greater AMPK phosphorylation and decreased pS6K phosphorylation in OCT3-BT20 cells. In vitro data were corroborated by in vivo observations of significantly greater antitumor efficacy of metformin in xenograft mice bearing OCT3-overexpressing tumors versus low transporter-expressing wildtype tumors. Collectively, these findings establish a clear relationship between cation-selective transporter expression, the AMPK-mTOR-pS6K signaling cascade, and the antiproliferative activity of metformin in breast cancer. PMID:26669511

  16. Cation-selective transporters are critical to the AMPK-mediated antiproliferative effects of metformin in human breast cancer cells.

    Science.gov (United States)

    Cai, Hao; Zhang, Yunhui; Han, Tianxiang Kevin; Everett, Ruth S; Thakker, Dhiren R

    2016-05-01

    The antidiabetic drug metformin exerts antineoplastic effects against breast cancer and other cancers. One mechanism by which metformin is believed to exert its anticancer effect involves activation of its intracellular target, adenosine monophosphate-activated protein kinase (AMPK), which is also implicated in the antidiabetic effect of metformin. It is proposed that in cancer cells, AMPK activation leads to inhibition of the mammalian target of rapamycin (mTOR) and the downstream pS6K that regulates cell proliferation. Due to its hydrophilic and cationic nature, metformin requires cation-selective transporters to enter cells and activate AMPK. This study demonstrates that expression levels of cation-selective transporters correlate with the antiproliferative and antitumor efficacy of metformin in breast cancer. Metformin uptake and antiproliferative activity were compared between a cation-selective transporter-deficient human breast cancer cell line, BT-20, and a BT-20 cell line that was engineered to overexpress organic cation transporter 3 (OCT3), a representative of cation-selective transporters and a predominant transporter in human breast tumors. Metformin uptake was minimal in BT-20 cells, but increased by >13-fold in OCT3-BT20 cells, and its antiproliferative potency was >4-fold in OCT3-BT20 versus BT-20 cells. This increase in antiproliferative activity was associated with greater AMPK phosphorylation and decreased pS6K phosphorylation in OCT3-BT20 cells. In vitro data were corroborated by in vivo observations of significantly greater antitumor efficacy of metformin in xenograft mice bearing OCT3-overexpressing tumors versus low transporter-expressing wildtype tumors. Collectively, these findings establish a clear relationship between cation-selective transporter expression, the AMPK-mTOR-pS6K signaling cascade, and the antiproliferative activity of metformin in breast cancer.

  17. On 1-qubit channels

    OpenAIRE

    Uhlmann, Armin

    2000-01-01

    The entropy H_T(rho) of a state rho with respect to a channel T and the Holevo capacity of the channel require the solution of difficult variational problems. For a class of 1-qubit channels, which contains all the extremal ones, the problem can be significantly simplified by associating an Hermitian antilinear operator theta to every channel of the considered class. The concurrence of the channel can be expressed by theta and turns out to be a flat roof. This allows to write down an explicit...

  18. On 1-qubit channels

    CERN Document Server

    Uhlmann, A

    2001-01-01

    The entropy H_T(rho) of a state rho with respect to a channel T and the Holevo capacity of the channel require the solution of difficult variational problems. For a class of 1-qubit channels, which contains all the extremal ones, the problem can be significantly simplified by associating an Hermitian antilinear operator theta to every channel of the considered class. The concurrence of the channel can be expressed by theta and turns out to be a flat roof. This allows to write down an explicit expression for H_T. Its maximum would give the Holevo (1-shot) capacity.

  19. The voltage-gated potassium channel subunit, Kv1.3, is expressed in epithelia

    DEFF Research Database (Denmark)

    Grunnet, Morten; Rasmussen, Hanne B; Hay-Schmidt, Anders;

    2003-01-01

    The Shaker-type voltage-gated potassium channel, Kv1.3, is believed to be restricted in distribution to lymphocytes and neurons. In lymphocytes, this channel has gained intense attention since it has been proven that inhibition of Kv1.3 channels compromise T lymphocyte activation. To investigate...

  20. Source and Channel Coding for Correlated Sources Over Multiuser Channels

    OpenAIRE

    Gunduz, Deniz; Erkip, Elza; Goldsmith, Andrea; Poor, H. Vincent

    2008-01-01

    Source and channel coding over multiuser channels in which receivers have access to correlated source side information is considered. For several multiuser channel models necessary and sufficient conditions for optimal separation of the source and channel codes are obtained. In particular, the multiple access channel, the compound multiple access channel, the interference channel and the two-way channel with correlated sources and correlated receiver side information are considered, and the o...