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Sample records for channel voltage dependence

  1. Voltage-dependent sodium channels in an invertebrate striated muscle.

    Science.gov (United States)

    Schwartz, L M; Stühmer, W

    1984-08-01

    Striated skeletal muscles from the planktonic arrowworm Sagitta elegans (phylum Chaetognatha) were voltage-clamped. The muscles displayed classical voltage-dependent sodium channels that (i) showed peak transient currents when the membrane was depolarized 90 millivolts from rest, (ii) opened rapidly with peak currents flowing within 0.4 milliseconds at 4 degrees C, (iii) showed voltage-dependent inactivation with 50 percent inactivation at +25 millivolts from rest, and (iv) were blocked by 500 nanomolar tetrodotoxin. PMID:6330898

  2. Conductance hysteresis in the voltage-dependent anion channel.

    Science.gov (United States)

    Rappaport, Shay M; Teijido, Oscar; Hoogerheide, David P; Rostovtseva, Tatiana K; Berezhkovskii, Alexander M; Bezrukov, Sergey M

    2015-09-01

    Hysteresis in the conductance of voltage-sensitive ion channels is observed when the transmembrane voltage is periodically varied with time. Although this phenomenon has been used in studies of gating of the voltage-dependent anion channel, VDAC, from the outer mitochondrial membrane for nearly four decades, full hysteresis curves have never been reported, because the focus was solely on the channel opening branches of the hysteresis loops. We studied the hysteretic response of a multichannel VDAC system to a triangular voltage ramp the frequency of which was varied over three orders of magnitude, from 0.5 mHz to 0.2 Hz. We found that in this wide frequency range the area encircled by the hysteresis curves changes by less than a factor of three, suggesting broad distribution of the characteristic times and strongly non-equilibrium behavior. At the same time, quasi-equilibrium two-state behavior is observed for hysteresis branches corresponding to VDAC opening. This enables calculation of the usual equilibrium gating parameters, gating charge and voltage of equipartitioning, which were found to be almost insensitive to the ramp frequency. To rationalize this peculiarity, we hypothesize that during voltage-induced closure and opening the system explores different regions of the complex free energy landscape, and, in the opening branch, follows quasi-equilibrium paths. PMID:26094068

  3. Localization and pharmacological characterization of voltage dependent calcium channels in cultured neocortical neurons

    DEFF Research Database (Denmark)

    Timmermann, D B; Lund, T M; Belhage, B;

    2001-01-01

    in cytosolic calcium concentration. The results of this investigation demonstrate that pharmacologically distinct types of voltage dependent calcium channels are differentially localized in cell bodies, neurites and nerve terminals of mouse cortical neurons but that the Q-type calcium channel appears......The physiological significance and subcellular distribution of voltage dependent calcium channels was defined using calcium channel blockers to inhibit potassium induced rises in cytosolic calcium concentration in cultured mouse neocortical neurons. The cytosolic calcium concentration was measured...... using the fluorescent calcium chelator fura-2. The types of calcium channels present at the synaptic terminal were determined by the inhibitory action of calcium channel blockers on potassium-induced [3H]GABA release in the same cell preparation. L-, N-, P-, Q- and R-/T-type voltage dependent calcium...

  4. 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...

  5. 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

  6. Localization and pharmacological characterization of voltage dependent calcium channels in cultured neocortical neurons

    DEFF Research Database (Denmark)

    Timmermann, D B; Lund, Trine Meldgaard; Belhage, B;

    2001-01-01

    The physiological significance and subcellular distribution of voltage dependent calcium channels was defined using calcium channel blockers to inhibit potassium induced rises in cytosolic calcium concentration in cultured mouse neocortical neurons. The cytosolic calcium concentration was measured...... using the fluorescent calcium chelator fura-2. The types of calcium channels present at the synaptic terminal were determined by the inhibitory action of calcium channel blockers on potassium-induced [3H]GABA release in the same cell preparation. L-, N-, P-, Q- and R-/T-type voltage dependent calcium...... most important voltage dependent calcium channel in all parts of the neuron. After treatment with thapsigargin the increase in cytosolic calcium was halved, indicating that calcium release from thapsigargin sensitive intracellular calcium stores is an important component of the potassium induced rise...

  7. Fractal analysis of a voltage-dependent potassium channel from cultured mouse hippocampal neurons.

    Science.gov (United States)

    Liebovitch, L S; Sullivan, J M

    1987-12-01

    The kinetics of ion channels have been widely modeled as a Markov process. In these models it is assumed that the channel protein has a small number of discrete conformational states and the kinetic rate constants connecting these states are constant. In the alternative fractal model the spontaneous fluctuations of the channel protein at many different time scales are represented by a kinetic rate constant k = At1-D, where A is the kinetic setpoint and D the fractal dimension. Single-channel currents were recorded at 146 mM external K+ from an inwardly rectifying, 120 pS, K+ selective, voltage-sensitive channel in cultured mouse hippocampal neurons. The kinetics of these channels were found to be statistically self-similar at different time scales as predicted by the fractal model. The fractal dimensions were approximately 2 for the closed times and approximately 1 for the open times and did not depend on voltage. For both the open and closed times the logarithm of the kinetic setpoint was found to be proportional to the applied voltage, which indicates that the gating of this channel involves the net inward movement of approximately one negative charge when this channel opens. Thus, the open and closed times and the voltage dependence of the gating of this channel are well described by the fractal model. PMID:2447974

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

    Directory of Open Access Journals (Sweden)

    Mark Alan Zaydman

    2014-05-01

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

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

    Directory of Open Access Journals (Sweden)

    Xiaohui eSun

    2012-04-01

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

  10. Molecular basis for differential modulation of BK channel voltage-dependent gating by auxiliary γ subunits.

    Science.gov (United States)

    Li, Qin; Fan, Fei; Kwak, Ha Rim; Yan, Jiusheng

    2015-06-01

    Large conductance Ca(2+)- and voltage-activated potassium (BK) channels are comprised of pore-forming α subunits and various regulatory auxiliary subunits. The BK channel auxiliary γ (BKγ) subunits are a newly identified class of proteins containing an extracellular leucine-rich repeat domain (LRRD), a single transmembrane (TM) segment, and a short cytoplasmic C-terminal tail (C-tail). Although each of the four BKγ proteins shifts the voltage dependence of BK channel activation in a hyperpolarizing direction, they show markedly different efficacies, mediating shifts over a range of 15-145 mV. Analyses of chimeric BKγ subunits created by swapping individual structural elements, and of BKγ deletion and substitution mutants, revealed that differential modulation of BK gating by the four BKγ subunits depends on a small region consisting of the TM segment and the adjacent intracellular cluster of positively charged amino acids. The γ1 and γ2 TM segments contributed approximately -100 mV, and the γ1 and γ3 C-tails contributed approximately -40 mV, to shifting the voltage dependence of BK channel activation, whereas the γ3 and γ4 TM segments and the γ2 and γ4 C-tails contributed much less. The large extracellular LRRDs were mainly functionally interchangeable, although the γ1 LRRD was slightly less effective at enhancing (or slightly more effective at attenuating) the shift in BK channel voltage-dependent gating toward hyperpolarizing potentials than those of the other BKγ subunits. Analysis of mutated BKγ subunits revealed that juxta-membrane clusters of positively charged amino acids determine the functions of the γ1 and γ3 C-tails. Therefore, the modulatory functions of BKγ subunits are coarse- and fine-tuned, respectively, through variations in their TM segments and in the adjacent intracellular positively charged regions. Our results suggest that BK channel modulation by auxiliary γ subunits depends on intra- and/or juxta-membrane mechanisms

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Gaudioso, Christelle; Carlier, Edmond; Youssouf, Fahamoe [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France); Clare, Jeffrey J. [Eaton Pharma Consulting, Eaton Socon, Cambridgeshire PE19 8EF (United Kingdom); Debanne, Dominique [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France); Alcaraz, Gisele, E-mail: gisele.alcaraz@univmed.fr [INSERM U641, Institut Jean Roche, Marseille F-13344 (France); Universite de la Mediterranee, Faculte de Medecine Secteur Nord, IFR 11, Marseille F-13344 (France)

    2011-07-29

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

  13. Voltage dependence of rate functions for Na+ channel inactivation within a membrane

    CERN Document Server

    Vaccaro, Samuel R

    2015-01-01

    The inactivation of a Na+ channel occurs when the activation of the charged S4 segment of domain IV, with rate functions $\\alpha_{i}$ and $\\beta_{i}$, is followed by the binding of an intracellular hydrophobic motif which blocks conduction through the ion pore, with rate functions $\\gamma_{i}$ and $\\delta_{i}$. During a voltage clamp of the Na+ channel, the solution of the master equation for inactivation reduces to the relaxation of a rate equation when the binding of the inactivation motif is rate limiting ($\\alpha_{i} \\gg \\gamma_{i}$ and $\\beta_{i} \\gg \\delta_{i}$). The voltage dependence of the derived forward rate function for Na+ channel inactivation has an exponential dependence on the membrane potential for small depolarizations and approaches a constant value for larger depolarizations, whereas the voltage dependence of the backward rate function is exponential, and each rate has a similar form to the Hodgkin-Huxley empirical rate functions for Na+ channel inactivation in the squid axon.

  14. Lavender Oil-Potent Anxiolytic Properties via Modulating Voltage Dependent Calcium Channels

    OpenAIRE

    Schuwald, Anita M.; Nölder, Michael; Wilmes, Thomas; Klugbauer, Norbert; Leuner, Kristina; Müller, Walter E.

    2013-01-01

    Recent clinical data support the clinical use of oral lavender oil in patients suffering from subsyndromal anxiety. We identified the molecular mechanism of action that will alter the perception of lavender oil as a nonspecific ingredient of aromatherapy to a potent anxiolytic inhibiting voltage dependent calcium channels (VOCCs) as highly selective drug target. In contrast to previous publications where exorbitant high concentrations were used, the effects of lavender oil in behavioral, bioc...

  15. Comparison of Single Channel Potassium Current in Biological and Synthetic Systems - Dependence on Voltage

    International Nuclear Information System (INIS)

    The influence of an external field on an ion current pattern in biological and synthetic systems was investigated. The patch clamp recordings of potassium current through a big conductance locust potassium channel (BK-channel) and a track-etched polyethylene terephthalate membrane were examined by the power spectrum, fractal analysis and relative dispersion analysis. A similar dependence of potassium current behaviour on the external voltage in both systems was found. The generalized dimension formalism is redefined to make it applicable to the analysis of time series. (author)

  16. Modulation of the voltage-dependent anion channel of mitochondria by elaidic acid.

    Science.gov (United States)

    Tewari, Debanjan; Bera, Amal Kanti

    2016-08-26

    Dietary trans fatty acids (TFAs) are known to increase the risk of cardiovascular diseases by altering plasma lipid profile and activating various inflammatory signaling pathways. Here we show that elaidic acid (EA), the most abundant TFA in diet, alters the electrophysiological properties of voltage-dependent anion channel (VDAC) of mitochondria. Purified bovine brain VDAC, when incorporated in the planar lipid bilayer (PLB) composed of 1,2-diphytanoyl-sn-glycero-3 phosphatidyl choline (DPhPC) and EA in a 9 to 1 ratio (wt/wt), exhibited complete closing events at different voltages. The closing events were observed at even -10 mV, a voltage at which VDAC usually remains fully open all the time. Additionally, the voltage sensitivity of VDAC was lost in presence of EA; the channel conductance did not decrease with increasing voltages. In identical experimental conditions, membrane containing oleic acid (OA), the cis isomer of EA did not produce any such effect. We propose that EA possibly exerts its adverse effect by modulating VDAC. PMID:27318085

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

    Directory of Open Access Journals (Sweden)

    Ting-Feng Lin

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

  18. Voltage dependence of Hodgkin-Huxley rate functions for a two-stage K channel voltage sensor within a membrane

    CERN Document Server

    Vaccaro, Samuel R

    2014-01-01

    The activation of a K channel sensor in two sequential stages during a voltage clamp may be described as the translocation of a Brownian particle in an energy landscape with two large barriers between states. A solution of the Smoluchowski equation for a square-well approximation to the potential function of the S4 sensor satisfies a master equation, and has two frequencies that may be determined from the forward and backward rate functions. When the higher frequency terms have small amplitude, the solution reduces to the relaxation of a rate equation, where the derived two-state rate functions are dependent on the relative magnitude of the forward rates ($\\alpha$ and $\\gamma$) and the backward rates ($\\beta$ and $\\delta$) for each stage. In particular, the voltage dependence of the Hodgkin-Huxley \\ rate functions for a K channel may be derived by assuming that the rate functions of the first stage are large relative to those of the second stage - $\\alpha \\gg \\gamma $, and $\\beta \\gg \\delta$. For a {\\em Shake...

  19. Do Voltage-Dependent K^+ Channels Require Ca2+? A Critical Test Employing a Heterologous Expression System

    Science.gov (United States)

    Armstrong, Clay M.; Miller, Christopher

    1990-10-01

    Removal of Ca2+ from the solution bathing neurons is known in many cases to alter the gating properties of voltage-dependent K^+ channels and to induce a large, nonselective "leak" conductance. We used a heterologous expression system to test whether the leak conductance observed in neurons is mediated by voltage-dependent K^+ channels in an altered, debased conformation. Voltage-dependent K^+ channels were expressed in an insect cell line infected with a recombinant baculovirus carrying the cDNA for Drosophila Shaker "A-type" K^+ channels. These expressed channels respond to low Ca2+ identically to voltage-dependent K^+ channels in native neuronal membranes; upon removal of external Ca2+, Shaker K^+ currents disappear and are replaced by a steady, nonselective leak conductance. However, control cells devoid of Shaker channels were free of any voltage-dependent conductances and did not generate a leak when external Ca2+ was removed. These results show that Ca2+ is essential for proper function of voltage-dependent K^+ channels and is required to stabilize the native conformations of these membrane proteins.

  20. The effects of S4 segments on the voltage-dependence of inactivation for Cav3.1 calcium channels

    Institute of Scientific and Technical Information of China (English)

    LI JunYing

    2007-01-01

    T-type calcium channels exhibit fast voltage-dependent inactivation,for which the underlying structure-function relationship still remains unclear.To investigate the roles of S4 segments in voltage-dependent inactivation of T-type calcium channels,we created S4 replacement chimeras between Cav3.1 calcium channels(fast voltage-dependent inactivation)and Cav1.2 calcium channels(little oltage-dependent inactivation)by replacing S4s in Cav3.1 with the corresponding regions in Cav1.2.Wild type and chimeric channels were expressed in Xenopus oocytes and channel currents were recorded with two-electrode voltage-clamp.We showed that replacing S4 region in domain I shifted voltage-dependence for inactivation of Cav3.1 to the left,and the V0.5 inact and kinact value were significantly changed.However replacing S4s in domains Ⅱ-Ⅳ had no effects on the voltage-dependent inactivation properties.These results suggest that the roles of S4 segments in domains Ⅰ-Ⅳ are different,and S4 in domain I is likely to be involved in voltage-dependent Inactivation process.Its movement during membrane depolarization may trigger a conformational change in the inactivation gate.

  1. A voltage-dependent chloride channel fine-tunes photosynthesis in plants.

    Science.gov (United States)

    Herdean, Andrei; Teardo, Enrico; Nilsson, Anders K; Pfeil, Bernard E; Johansson, Oskar N; Ünnep, Renáta; Nagy, Gergely; Zsiros, Ottó; Dana, Somnath; Solymosi, Katalin; Garab, Győző; Szabó, Ildikó; Spetea, Cornelia; Lundin, Björn

    2016-01-01

    In natural habitats, plants frequently experience rapid changes in the intensity of sunlight. To cope with these changes and maximize growth, plants adjust photosynthetic light utilization in electron transport and photoprotective mechanisms. This involves a proton motive force (PMF) across the thylakoid membrane, postulated to be affected by unknown anion (Cl(-)) channels. Here we report that a bestrophin-like protein from Arabidopsis thaliana functions as a voltage-dependent Cl(-) channel in electrophysiological experiments. AtVCCN1 localizes to the thylakoid membrane, and fine-tunes PMF by anion influx into the lumen during illumination, adjusting electron transport and the photoprotective mechanisms. The activity of AtVCCN1 accelerates the activation of photoprotective mechanisms on sudden shifts to high light. Our results reveal that AtVCCN1, a member of a conserved anion channel family, acts as an early component in the rapid adjustment of photosynthesis in variable light environments. PMID:27216227

  2. Selective modulation of cellular voltage dependent calcium channels by hyperbaric pressure - a suggested HPNS partial mechanism

    Directory of Open Access Journals (Sweden)

    Ben eAviner

    2014-05-01

    Full Text Available Professional deep sea divers experience motor and cognitive impairment, known as High Pressure Neurological Syndrome (HPNS, when exposed to pressures of 100 msw (1.1MPa and above, considered to be the result of synaptic transmission alteration. Previous studies have indicated modulation of presynaptic Ca2+ currents at high pressure. We directly measured for the first time pressure effects on the currents of voltage dependent Ca2+ channels (VDCCs expressed in Xenopus oocytes. Pressure selectivity augmented the current in CaV1.2 and depressed it in CaV3.2 channels. Pressure application also affected the channels' kinetics, such as ƮRise, ƮDecay. Pressure modulation of VDCCs seems to play an important role in generation of HPNS signs and symptoms.

  3. Functional interaction of endothelial nitric oxide synthase with a voltage-dependent anion channel

    Science.gov (United States)

    Sun, Jianxin; Liao, James K.

    2002-01-01

    Endothelium-derived nitric oxide (NO) is an important regulator of vascular function. NO is produced by endothelial NO synthase (eNOS) whose function is modulated, in part, by specific protein interactions. By coimmunoprecipitation experiments followed by MS analyses, we identified a human voltage-dependent anion/cation channel or porin as a binding partner of eNOS. The interaction between porin and eNOS was demonstrated by coimmunoprecipitation studies in nontransfected human endothelial cells and Cos-7 cells transiently transfected with eNOS and porin cDNAs. In vitro binding studies with glutathione S-transferase–porin indicated that porin binds directly to eNOS and that this interaction augmented eNOS activity. The calcium ionophore, A23187, and bradykinin, which are known to activate eNOS, markedly increased porin–eNOS interaction, suggesting a potential role of intracellular Ca2+ in mediating this interaction. Theses results indicate that the interaction between a voltage-dependent membrane channel and eNOS may be important for regulating eNOS activity. PMID:12228731

  4. Voltage dependent potassium channel remodeling in murine intestinal smooth muscle hypertrophy induced by partial obstruction.

    Directory of Open Access Journals (Sweden)

    Dong-Hai Liu

    Full Text Available Partial obstruction of the small intestine causes obvious hypertrophy of smooth muscle cells and motility disorder in the bowel proximate to the obstruction. To identify electric remodeling of hypertrophic smooth muscles in partially obstructed murine small intestine, the patch-clamp and intracellular microelectrode recording methods were used to identify the possible electric remodeling and Western blot, immunofluorescence and immunoprecipitation were utilized to examine the channel protein expression and phosphorylation level changes in this research. After 14 days of obstruction, partial obstruction caused obvious smooth muscle hypertrophy in the proximally located intestine. The slow waves of intestinal smooth muscles in the dilated region were significantly suppressed, their amplitude and frequency were reduced, whilst the resting membrane potentials were depolarized compared with normal and sham animals. The current density of voltage dependent potassium channel (KV was significantly decreased in the hypertrophic smooth muscle cells and the voltage sensitivity of KV activation was altered. The sensitivity of KV currents (IKV to TEA, a nonselective potassium channel blocker, increased significantly, but the sensitivity of IKv to 4-AP, a KV blocker, stays the same. The protein levels of KV4.3 and KV2.2 were up-regulated in the hypertrophic smooth muscle cell membrane. The serine and threonine phosphorylation levels of KV4.3 and KV2.2 were significantly increased in the hypertrophic smooth muscle cells. Thus this study represents the first identification of KV channel remodeling in murine small intestinal smooth muscle hypertrophy induced by partial obstruction. The enhanced phosphorylations of KV4.3 and KV2.2 may be involved in this process.

  5. Calcineurin Controls Voltage-Dependent-Inactivation (VDI) of the Normal and Timothy Cardiac Channels.

    Science.gov (United States)

    Cohen-Kutner, Moshe; Yahalom, Yfat; Trus, Michael; Atlas, Daphne

    2012-01-01

    Ca(2+)-entry in the heart is tightly controlled by Cav1.2 inactivation, which involves Ca(2+)-dependent inactivation (CDI) and voltage-dependent inactivation (VDI) components. Timothy syndrome, a subtype-form of congenital long-QT syndrome, results from a nearly complete elimination of VDI by the G406R mutation in the α(1)1.2 subunit of Cav1.2. Here, we show that a single (A1929P) or a double mutation (H1926A-H1927A) within the CaN-binding site at the human C-terminal tail of α(1)1.2, accelerate the inactivation rate and enhances VDI of both wt and Timothy channels. These results identify the CaN-binding site as the long-sought VDI-regulatory motif of the cardiac channel. The substantial increase in VDI and the accelerated inactivation caused by the selective inhibitors of CaN, cyclosporine A and FK-506, which act at the same CaN-binding site, further support this conclusion. A reversal of enhanced-sympathetic tone by VDI-enhancing CaN inhibitors could be beneficial for improving Timothy syndrome complications such as long-QT and autism. PMID:22511998

  6. Over Expression of Voltage Dependent Anion Channel 2 (VDAC2 in Muscles of Electrically Stunned Chickens

    Directory of Open Access Journals (Sweden)

    Norshahida Abu Samah, Azura Amid, and Faridah Yusof

    2011-12-01

    Full Text Available Water bath stunning is a common practice in commercial slaughterhouses. Such treatment is economic and in line with animal welfare practice. However, the conditions applied for the stunning process may vary from a slaughterhouse to another slaughterhouse. Such a loose regulation on the stunning procedure has opened up doors for food adulteration such as over dose stunning. In this study, a simple and reliable approach using proteomics have been developed to study the effect of different currents and voltages in stunning on the protein expression of the chickens. Protein profiles of the chickens were constructed in order to detect any differences in protein expression and modifications. The different voltage studied were 10 V, 40 V and 70 V while the values for current studied were 0.25 A, 0.5 A, and 0.75 A. After the proteomics analyses using 2D Platinum ImageMaster 6.0 and Matrix-assisted laser desorption ionization- time of flight (MALDI TOF spectrometry identification, Voltage dependent anion channel 2 (VDAC2 was identified to be over expressed in the muscle sample of over stunned chicken. The over expression of VDAC2 was confirmed at the transcriptional level of RNA expression. Real Time PCR showed that all over stunned samples contained higher mRNA expression level for VDAC2 genes. The mRNA level of VDAC2 was up-regulated by 59.87 fold change when normalized with housekeeping gene. In conclusion, VDAC2 could serve as potential biomarkers for identification of electrically stimulated chickens. The existence of these biomarkers will help to monitor the slaughtering and stunning process in the future. It will revolutionize the food authentication field and give a new breathe to the meat industry.ABSTRAK: Kaedah "waterbath stunning" merupakan amalan biasa di pusat-pusat penyembelihan. Kaedah ini adalah ekonomik dan selari dengan amalan kebajikan haiwan. Walaubagaimanapun, syarat-syarat yang digunakan untuk proses kejutan tersebut mungkin

  7. Molecular endpoints of Ca2+/calmodulin- and voltage-dependent inactivation of Cav1.3 channels

    OpenAIRE

    Tadross, Michael R.; Johny, Manu Ben; Yue, David T.

    2010-01-01

    Ca2+/calmodulin- and voltage-dependent inactivation (CDI and VDI) comprise vital prototypes of Ca2+ channel modulation, rich with biological consequences. Although the events initiating CDI and VDI are known, their downstream mechanisms have eluded consensus. Competing proposals include hinged-lid occlusion of channels, selectivity filter collapse, and allosteric inhibition of the activation gate. Here, novel theory predicts that perturbations of channel activation should alter inactivation i...

  8. 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

  9. Cyclic AMP-dependent phosphorylation of voltage-sensitive sodium channels in primary cultures of rat brain cells

    Energy Technology Data Exchange (ETDEWEB)

    Rossie, S.; Catterall, W.A.

    1986-03-05

    The ..cap alpha.. subunit of the voltage-sensitive Na channel from rat brain is phosphorylated by cAMP-dependent protein kinase in purified preparations and in synaptosomes. The authors have begun to study cAMP-dependent phosphorylation of Na channels in intact cells. Rat brain cells collected at embryonic day 15 and maintained in culture for approximately 21 days were subjected to treatments designed to increase intracellular cAMP. Cells were solubilized and Na channels were isolated by immunoprecipitation, then rephosphorylated with the catalytic subunit of cAMP-dependent protein kinase and /sup 32/P-ATP, to allow incorporation of /sup 32/P into available cAMP-dependent phosphorylation sites of Na channels. The amount of /sup 32/P incorporated into channel is inversely proportional to the extent of endogenous phosphorylation. Treatment of cells with forskolin inhibited rephosphorylation of Na channels, indicating that enhanced endogenous phosphorylation of channels had occurred. The effect of forskolin on cell surface Na channels occurred rapidly, was sustained over 30 min., and was half-maximal at 6..mu..M. 8-Br-cAMP, (EC/sub 50/-5mM) and isobutylmethylxanthine (EC/sub 50/-60..mu..M) also caused inhibition of /sup 32/P incorporation into Na channels. These results indicate that the extent of cAMP-dependent phosphorylation of voltage-sensitive Na channels in intact brain neurons is modified by changes in intracellular levels of cAMP.

  10. Effects of arsenic trioxide on voltage-dependent potassium channels and on cell proliferation of human multiple myeloma cells

    Institute of Scientific and Technical Information of China (English)

    ZHOU Jin; WANG Wei; WEI Qing-fang; FENG Tie-ming; TAN Li-jun; YANG Bao-feng

    2007-01-01

    @@ Arsenic trioxide (ATO) can induce cellular apoptosis and inhibit the activities of multiple myeloma (MM)cells in vitro,1 but how it works is not very clear. Recent studies showed that ATO worked on the voltagedependent potassium channel and L-type calcium channel in myocardial cells,2-5 but the effect of ATO on ion channels of tumor cells was rarely reported. As the potassium channel plays an important role in controlling cell proliferation,6 we studied the effects of ATO on the voltage-dependent potassium current (Ikv) of the voltage-dependent potassium channel in an MM cell line,and probed into the relationship between changes of the Ikv caused by ATO and cell proliferation.

  11. 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. PMID

  12. 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...

  13. Use-dependent block of the voltage-gated Na+ channel by tetrodotoxin and saxitoxin: Effect of pore mutations that change ionic selectivity

    OpenAIRE

    Huang, Chien-Jung; Schild, Laurent; Moczydlowski, Edward G.

    2012-01-01

    Voltage-gated Na+ channels (NaV channels) are specifically blocked by guanidinium toxins such as tetrodotoxin (TTX) and saxitoxin (STX) with nanomolar to micromolar affinity depending on key amino acid substitutions in the outer vestibule of the channel that vary with NaV gene isoforms. All NaV channels that have been studied exhibit a use-dependent enhancement of TTX/STX affinity when the channel is stimulated with brief repetitive voltage depolarizations from a hyperpolarized starting volta...

  14. Dopamine Induces LTP Differentially in Apical and Basal Dendrites through BDNF and Voltage-Dependent Calcium Channels

    Science.gov (United States)

    Navakkode, Sheeja; Sajikumar, Sreedharan; Korte, Martin; Soong, Tuck Wah

    2012-01-01

    The dopaminergic modulation of long-term potentiation (LTP) has been studied well, but the mechanism by which dopamine induces LTP (DA-LTP) in CA1 pyramidal neurons is unknown. Here, we report that DA-LTP in basal dendrites is dependent while in apical dendrites it is independent of activation of L-type voltage-gated calcium channels (VDCC).…

  15. Lavender oil-potent anxiolytic properties via modulating voltage dependent calcium channels.

    Directory of Open Access Journals (Sweden)

    Anita M Schuwald

    Full Text Available Recent clinical data support the clinical use of oral lavender oil in patients suffering from subsyndromal anxiety. We identified the molecular mechanism of action that will alter the perception of lavender oil as a nonspecific ingredient of aromatherapy to a potent anxiolytic inhibiting voltage dependent calcium channels (VOCCs as highly selective drug target. In contrast to previous publications where exorbitant high concentrations were used, the effects of lavender oil in behavioral, biochemical, and electrophysiological experiments were investigated in physiological concentrations in the nanomolar range, which correlate to a single dosage of 80 mg/d in humans that was used in clinical trials. We show for the first time that lavender oil bears some similarities with the established anxiolytic pregabalin. Lavender oil inhibits VOCCs in synaptosomes, primary hippocampal neurons and stably overexpressing cell lines in the same range such as pregabalin. Interestingly, Silexan does not primarily bind to P/Q type calcium channels such as pregabalin and does not interact with the binding site of pregabalin, the α2δ subunit of VOCCs. Lavender oil reduces non-selectively the calcium influx through several different types of VOCCs such as the N-type, P/Q-type and T-type VOCCs. In the hippocampus, one brain region important for anxiety disorders, we show that inhibition by lavender oil is mainly mediated via N-type and P/Q-type VOCCs. Taken together, we provide a pharmacological and molecular rationale for the clinical use of the oral application of lavender oil in patients suffering from anxiety.

  16. Cloning and Expressional Studies of the Voltage-dependent Anion Channel Gene from Brassica rapa L.

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The voltage-dependent anion channel (VDAC) plays an essential role in the permeability of mitochondrial membrane. In the present study, we isolated a novel VDAC gene (brvdac) based on the assembly of expressed sequence tag sequences from Brassica rapa L. and explored its differential expression patterns in growth,tissues, abiotic stress, and stress recovery. Results of a tissue-specific expression study in young seedlings indicated that, of all tissues tested, brvdac expression was the highest in the leaves. Under cold, drought, and salt stresses, brvdac expression showed a transient increase, and then returned to normal levels when the stress was removed. When plants were exposed to heat shock, there was no increase in brvdac expression,whereas during recovery a quick and considerable increase in expression was observed. These observations indicate that dissimilar modulations of brvdac transcription may occur when plant cells encounter heat shock and the other three types of stress. In addition, phylogenetic analysis implied that an earlier duplication of vdac probably occurred before the divergence between monocotyledons and dicotyledons.

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

    International Nuclear Information System (INIS)

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

  18. Down-regulation of voltage-dependent sodium channels initiated by sodium influx in developing neurons

    International Nuclear Information System (INIS)

    To address the issue of whether regulatory feedback exists between the electrical activity of a neuron and ion-channel density, the authors investigated the effect of Na+-channel activators (scorpion α toxin, batrachotoxin, and veratridine) on the density of Na+ channels in fetal rat brain neurons in vitro. A partial but rapid (t1/2, 15 min) disappearance of surface Na+ channels was observed as measured by a decrease in the specific binding of [3H]saxitoxin and 125I-labeled scorpion β toxin and a decrease in specific 22Na+ uptake. Moreover, the increase in the number of Na+ channels that normally occurs during neuronal maturation in vitro was inhibited by chronic channel activator treatment. The induced disappearance of Na+ channels was abolished by tetrodotoxin, was found to be dependent on the external Na+ concentration, and was prevented when either choline (a nonpermeant ion) or Li+ (a permeant ion) was substituted for Na+. Amphotericin B, a Na+ ionophore, and monensin were able to mimick the effect of Na+-channel activators, while a KCl depolarization failed to do this. This feedback regulation seems to be a neuronal property since Na+-channel density in cultured astrocytes was not affected by channel activator treatment or by amphotericin B. The present evidence suggests that an increase in intracellular Na+ concentration, whether elicited by Na+-channel activators or mediated by a Na+ ionophore, can induce a decrease in surface Na+ channels and therefore is involved in down-regulation of Na+-channel density in fetal rat brain neurons in vitro

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

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Liu-Min Fan

    2009-01-01

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

  20. Airway Hydration, Apical K(+) Secretion, and the Large-Conductance, Ca(2+)-activated and Voltage-dependent Potassium (BK) Channel.

    Science.gov (United States)

    Kis, Adrian; Krick, Stefanie; Baumlin, Nathalie; Salathe, Matthias

    2016-04-01

    Large-conductance, calcium-activated, and voltage-gated K(+) (BK) channels are expressed in many tissues of the human body, where they play important roles in signaling not only in excitable but also in nonexcitable cells. Because BK channel properties are rendered in part by their association with four β and four γ subunits, their channel function can differ drastically, depending on in which cellular system they are expressed. Recent studies verify the importance of apically expressed BK channels for airway surface liquid homeostasis and therefore of their significant role in mucociliary clearance. Here, we review evidence that inflammatory cytokines, which contribute to airway diseases, can lead to reduced BK activity via a functional down-regulation of the γ regulatory subunit LRRC26. Therefore, manipulation of LRRC26 and pharmacological opening of BK channels represent two novel concepts of targeting epithelial dysfunction in inflammatory airway diseases. PMID:27115952

  1. Molecular characterization and functional expression of the Apis mellifera voltage-dependent Ca2+ channels.

    Science.gov (United States)

    Cens, Thierry; Rousset, Matthieu; Collet, Claude; Charreton, Mercedes; Garnery, Lionel; Le Conte, Yves; Chahine, Mohamed; Sandoz, Jean-Christophe; Charnet, Pierre

    2015-03-01

    Voltage-gated Ca(2+) channels allow the influx of Ca(2+) ions from the extracellular space upon membrane depolarization and thus serve as a transducer between membrane potential and cellular events initiated by Ca(2+) transients. Most insects are predicted to possess three genes encoding Cavα, the main subunit of Ca(2+) channels, and several genes encoding the two auxiliary subunits, Cavβ and Cavα2δ; however very few of these genes have been cloned so far. Here, we cloned three full-length cDNAs encoding the three Cavα subunits (AmelCav1a, AmelCav2a and AmelCav3a), a cDNA encoding a novel variant of the Cavβ subunit (AmelCavβc), and three full-length cDNAs encoding three Cavα2δ subunits (AmelCavα2δ1 to 3) of the honeybee Apis mellifera. We identified several alternative or mutually exclusive exons in the sequence of the AmelCav2 and AmelCav3 genes. Moreover, we detected a stretch of glutamine residues in the C-terminus of the AmelCav1 subunit that is reminiscent of the motif found in the human Cav2.1 subunit of patients with Spinocerebellar Ataxia type 6. All these subunits contain structural domains that have been identified as functionally important in their mammalian homologues. For the first time, we could express three insect Cavα subunits in Xenopus oocytes and we show that AmelCav1a, 2a and 3a form Ca(2+) channels with distinctive properties. Notably, the co-expression of AmelCav1a or AmelCav2a with AmelCavβc and AmCavα2δ1 produces High Voltage-Activated Ca(2+) channels. On the other hand, expression of AmelCav3a alone leads to Low Voltage-Activated Ca(2+) channels. PMID:25602183

  2. Two Components of Voltage-Dependent Inactivation in Cav1.2 Channels Revealed by Its Gating Currents

    OpenAIRE

    Ferreira, Gonzalo; Ríos, Eduardo; Reyes, Nicolás

    2003-01-01

    Voltage-dependent inactivation (VDI) was studied through its effects on the voltage sensor in Cav1.2 channels expressed in tsA 201 cells. Two kinetically distinct phases of VDI in onset and recovery suggest the presence of dual VDI processes. Upon increasing duration of conditioning depolarizations, the half-distribution potential (V1/2) of intramembranous mobile charge was negatively shifted as a sum of two exponential terms, with time constants 0.5 s and 4 s, and relative amplitudes near 50...

  3. Voltage-gated lipid ion channels

    DEFF Research Database (Denmark)

    Blicher, Andreas; Heimburg, Thomas Rainer

    2013-01-01

    probability as a function of voltage. The voltage-dependence of the lipid pores is found comparable to that of protein channels. Lifetime distributions of open and closed events indicate that the channel open distribution does not follow exponential statistics but rather power law behavior for long open times......Synthetic lipid membranes can display channel-like ion conduction events even in the absence of proteins. We show here that these events are voltage-gated with a quadratic voltage dependence as expected from electrostatic theory of capacitors. To this end, we recorded channel traces and current...

  4. Fast exocytosis mediated by T- and L-type channels in chromaffin cells: distinct voltage-dependence but similar Ca2+ -dependence.

    Science.gov (United States)

    Carabelli, V; Marcantoni, A; Comunanza, V; Carbone, E

    2007-09-01

    Expression, spatial distribution and specific roles of different Ca(2+) channels in stimulus-secretion coupling of chromaffin cells are intriguing issues still open to discussion. Most of the evidence supports a role of high-voltage activated (HVA) Ca(2+) channels (L-, N-, P/Q- and R-types) in the control of exocytosis: some suggesting a preferential coupling of specific Ca(2+) channel subunits with the secretory apparatus, others favoring the idea of a contribution to secretion proportional to the expression density and gating properties of Ca(2+) channels. In this work we review recent findings and bring new evidence in favor of the hypothesis that also the LVA (low-voltage-activated, T-type) Ca(2+) channels effectively control fast exocytosis near resting potential in adrenal chromaffin cells of adult rats. T-type channels recruited after long-term treatments with pCPT-cAMP (or chronic hypoxia) are shown to control exocytosis with the same efficacy of L-type channels, which are the dominant Ca(2+) channel types expressed in rodent chromaffin cells. A rigorous comparison of T- and L-type channel properties shows that, although operating at different potentials and with different voltage-sensitivity, the two channels possess otherwise similar Ca(2+)-dependence of exocytosis, size and kinetics of depletion of the immediately releasable pool and mobilize vesicles of the same quantal size. Thus, T- and L-type channels are coupled with the same Ca(2+)-efficiency to the secretory apparatus and deplete the same number of vesicles ready for release. The major difference of the secretory signals controlled by the two channels appear to be the voltage range of operation, suggesting the idea that stressful conditions (hypoxia and persistent beta-adrenergic stimulation) can lower the threshold of cell excitability by recruiting new Ca(2+) channels and activate an additional source of catecholamine secretion. PMID:17340096

  5. Expression and motor functional roles of voltage-dependent type 7 K(+) channels in the human taenia coli.

    Science.gov (United States)

    Adduci, Alice; Martire, Maria; Taglialatela, Maurizio; Arena, Vincenzo; Rizzo, Gianluca; Coco, Claudio; Currò, Diego

    2013-12-01

    Voltage-dependent type 7 K(+) (KV7 or KCNQ) channels modulate the excitability of neurons and muscle cells. The aims of the present study were to investigate the motor effects of KV7 channel modulators and the expression of KV7 channels in the human taenia coli. The effects of KV7 channel modulators on the muscle tone of human taenia coli strips were investigated under nonadrenergic non-nitrergic conditions by organ bath studies. Gene expression and tissue localisation of channels were studied by real-time PCR and immunohistochemistry, respectively. Under basal conditions, the KV7 channel blocker XE-991 induced concentration-dependent contractions, with mean EC50 and Emax of 18.7 μM and 30.5% respectively of the maximal bethanechol-induced contraction, respectively. The KV7 channel activators retigabine and flupirtine concentration-dependently relaxed the taenia coli, with mean EC50s of 19.2 μM and 29.9 μM, respectively. Retigabine also relaxed bethanechol-precontracted strips, with maximal relaxations of 79.2% of the bethanecol-induced precontraction. The motor effects induced by the KV7 channel modulators were not affected by tetrodotoxin or ω-conotoxin GVIA. XE-991 greatly reduced retigabine- and flupirtine-induced relaxations. Transcripts encoded by all KCNQ genes were detected in the taenia coli, with KCNQ4 showing the highest expression levels. KV7.4 channels were clearly visualised by immunohistochemistry in colonic epithelium, circular muscle layer and taenia coli. KV7 channels appear to contribute to the resting muscle tone of the human taenia coli. In addition, KV7 channel activators significantly relax the taenia coli. Thus, they could be useful therapeutic relaxant agents for colonic motor disorders. PMID:24120659

  6. Calcineurin Controls Voltage-Dependent-Inactivation (VDI) of the Normal and Timothy Cardiac Channels

    OpenAIRE

    Cohen-Kutner, Moshe; Yahalom, Yfat; Trus, Michael; Atlas, Daphne

    2012-01-01

    Ca2+-entry in the heart is tightly controlled by Cav1.2 inactivation, which involves Ca2+-dependent inactivation (CDI) and voltage-dependent inactivation (VDI) components. Timothy syndrome, a subtype-form of congenital long-QT syndrome, results from a nearly complete elimination of VDI by the G406R mutation in the α11.2 subunit of Cav1.2. Here, we show that a single (A1929P) or a double mutation (H1926A-H1927A) within the CaN-binding site at the human C-terminal tail of α11.2, accelerate the ...

  7. Voltage-dependent calcium channels in skeletal muscle transverse tubules. Measurements of calcium efflux in membrane vesicles

    International Nuclear Information System (INIS)

    Transverse tubule membranes isolated from rabbit skeletal muscle consist mainly of sealed vesicles that are oriented primarily inside out. These membranes contain a high density of binding sites for 1,4-dihydropyridine calcium channel antagonists. The presence of functional voltage-dependent calcium channels in these membranes has been demonstrated by their ability to mediate 45Ca2+ efflux in response to changes in membrane potential. Fluorescence changes of the voltage-sensitive dye, 3,3'-dipropyl-2,2'-thiadicarbocyanine, have shown that transverse tubule vesicles may generate and maintain membrane potentials in response to establishing potassium gradients across the membrane in the presence of valinomycin. A two-step procedure has been developed to measure voltage-dependent calcium fluxes. Vesicles loaded with 45Ca2+ are first diluted into a buffer designed to generate a membrane potential mimicking the resting state of the cell and to reduce the extravesicular Ca2+ to sub-micromolar levels. 45Ca2+ efflux is then measured upon subsequent depolarization. Flux responses are modulated with appropriate pharmacological specificity by 1,4-dihydropyridines and are inhibited by other calcium channel antagonists such as lanthanum and verapamil

  8. Multiple calcium channels in synaptosomes: voltage dependence of 1,4-dihydropyridine binding and effects on function

    International Nuclear Information System (INIS)

    The voltage dependence of binding of the calcium channel antagonist, (+)-(3H]PN200-110, to rat brain synaptosomes and the effects of dihydropyridines on 45Ca2+ uptake have been investigated. Under nondepolarizing conditions (+)-(3H)PN200-110 binds to a single class of sites with a K/sub d/ of 0.07 nM and a binding capacity of 182 fmol/mg of protein. When the synaptosomal membrane potential was dissipated either by osmotic lysis of the synaptosomes or by depolarization induced by raising the external K+ concentration, there was a decrease in affinity with no change in the number of sites. The effects of calcium channel ligands on 45Ca2+ uptake by synaptosomes have been measured as a function of external potassium concentration, i.e., membrane potential. Depolarization led to a rapid influx of 45Ca2+ whose magnitude was voltage-dependent. Verapamil almost completely inhibited calcium uptake at all potassium concentrations studies. In contrast, the effects of dihydropyridines (2 μM) appear to be voltage-sensitive. At relatively low levels of depolarization nitrendipine and PN200-110 completely inhibited 45Ca2+ influx, whereas the agonist Bay K8644 slightly potentiated the response. At higher K+ concentrations an additional dihydropyridine-insensitive component of calcium uptake was observed. These results provide evidence for the presence of dihydropyridine-sensitive calcium channels in synaptosomes which may be activated under conditions of partial depolarization

  9. Inhibition of the voltage-dependent chloride channel of Torpedo electric organ by diisopropylfluorophosphate and its reversal by oximes

    International Nuclear Information System (INIS)

    Diisopropylfluorophosphate (DFP), a potent organophosphate inhibitor of cholinesterases, was found to inhibit the specific binding of [35S]t-butylbicyclophosphorothionate (TBPS), specific chloride channels ligand, to the electric organ membranes of Torpedo, with a Ki of 21 +/- 3 μM. The binding sites of [35S]TBPS in the Torpedo membranes were found not to be GABA receptors or nicotinic acetylcholine receptors as previously described. Interestingly, a stimulation of the binding of [35S]TBPS was observed in the presence of atropine and three oximes, monopyridinium oxime 2-PAM, bispyridinium bis-oxime TMB-4 and H-oxime HI-6. The maximal stimulation was 300-500% of control, after which, the stimulation was reversed at higher concentrations. The three oximes protected by more than 95% the inhibition by 1 mM DFP of the binding of [35S]TBPS to the voltage-dependent chloride channel. However, atropine protected only 20% of the inhibited channel. These results, thus, suggest that the protection against the toxic effects of DFP or other anticholinesterase agents by the tested oximes may not be solely a result of the reactivation of cholinesterases but also the protection of the voltage-dependent chloride channel

  10. Voltage-dependent Ca2+ channels, not ryanodine receptors, activate Ca2+-dependent BK potassium channels in human retinal pigment epithelial cells

    OpenAIRE

    Wimmers, Sönke; Halsband, Claire; Seyler, Sebastian; Milenkovic, Vladimir; Strauß, Olaf

    2008-01-01

    Purpose In different tissues the activation of large conductance Ca2+-activated (BK) potassium channels has been shown to be coupled to voltage-gated Ca2+ channels as well as ryanodine receptors. As activation of BK channels leads to hyperpolarization of the cell, these channels provide a negative feedback mechanism for Ca2+-induced functions. Many cellular functions of the retinal pigment epithelium (RPE) are coupled to changes in [Ca2+]i. The aim of this study was to identify which Ca2+-ent...

  11. The Timothy syndrome mutation differentially affects voltage- and calcium-dependent inactivation of CaV1.2 L-type calcium channels

    OpenAIRE

    Barrett, Curtis F.; Tsien, Richard W.

    2008-01-01

    Calcium entry into excitable cells is an important physiological signal, supported by and highly sensitive to the activity of voltage-gated Ca2+ channels. After membrane depolarization, Ca2+ channels first open but then undergo various forms of negative feedback regulation including voltage- and calcium-dependent inactivation (VDI and CDI, respectively). Inactivation of Ca2+ channel activity is perturbed in a rare yet devastating disorder known as Timothy syndrome (TS), whose features include...

  12. Cell swelling activates ATP-dependent voltage-gated chloride channels in M-1 mouse cortical collecting duct cells.

    Science.gov (United States)

    Meyer, K; Korbmacher, C

    1996-09-01

    In the present study we used whole-cell patch clamp recordings to investigate swelling-activated Cl-currents (ICl-swell) in M-1 mouse cortical collecting duct (CCD) cells. Hypotonic cell swelling reversibly increased the whole-cell Cl- conductance by about 30-fold. The I-V relationship was outwardly-rectifying and ICl-swell displayed a characteristic voltage-dependence with relatively fast inactivation upon large depolarizing and slow activation upon hyperpolarizing voltage steps. Reversal potential measurements revealed a selectivity sequence SCN- > I- > Br- > Cl- > > gluconate. ICl-swell was inhibited by tamoxifen, NPPB (5-nitro-2(3-phenylpropylamino)-benzoate), DIDS (4,4'-diisothiocyanostilbene-2,2'-disulphonic acid), flufenamic acid, niflumic acid, and glibenclamide, in descending order of potency. Extracellular cAMP had no significant effect. ICl-swell was Ca2+ independent, but current activation depended on the presence of a high-energy gamma-phosphate group from intracellular ATP or ATP gamma S. Moreover, it depended on the presence of intracellular Mg2+ and was inhibited by staurosporine, which indicates that a phosphorylation step is involved in channel activation. Increasing the cytosolic Ca2+ concentration by using ionomycin stimulated Cl- currents with a voltage dependence different from that of ICl-swell. Analysis of whole-cell current records during early onset of ICl-swell and during final recovery revealed discontinuous step-like changes of the whole-cell current level which were not observed under nonswelling conditions. A single-channel I-V curve constructed using the smallest resolvable current transitions detected at various holding potentials and revealed a slope conductance of 55, 15, and 8 pS at +120, 0, and -120 mV, respectively. The larger current steps observed in these recordings had about 2, 3, or 4 times the size of the putative single-channel current amplitude, suggesting a coordinated gating of several individual channels or channel

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

    International Nuclear Information System (INIS)

    We investigated the effects of the calmodulin inhibitor CGS 9343B on voltage-dependent K+ (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 (IC50) 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−1 s−1 and 2.55 ± 1.50 s−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

  14. Differential expression of T- and L-type voltage-dependent calcium channels in renal resistance vessels

    DEFF Research Database (Denmark)

    Hansen, Pernille B. Lærkegaard; Jensen, Boye L.; Andreasen, D;

    2001-01-01

    The distribution of voltage-dependent calcium channels in kidney pre- and postglomerular resistance vessels was determined at the molecular and functional levels. Reverse transcription-polymerase chain reaction analysis of microdissected rat preglomerular vessels and cultured smooth muscle cells...... showed coexpression of mRNAs for T-type subunits (Ca(V)3.1, Ca(V)3.2) and for an L-type subunit (Ca(V)1.2). The same expression pattern was observed in juxtamedullary efferent arterioles and outer medullary vasa recta. No calcium channel messages were detected in cortical efferent arterioles. Ca(V)1.......2 protein was demonstrated by immunochemical labeling of rat preglomerular vasculature and juxtamedullary efferent arterioles and vasa recta. Cortical efferent arterioles were not immunopositive. Recordings of intracellular calcium concentration with digital fluorescence imaging microscopy showed a...

  15. trans-Caryophyllene, a Natural Sesquiterpene, Causes Tracheal Smooth Muscle Relaxation through Blockade of Voltage-Dependent Ca2+ Channels

    Directory of Open Access Journals (Sweden)

    Jader Santos Cruz

    2012-10-01

    Full Text Available trans-Caryophyllene is a major component in the essential oils of various species of medicinal plants used in popular medicine in Brazil. It belongs to the chemical class of the sesquiterpenes and has been the subject of a number of studies. Here, we evaluated the effects of this compound in airway smooth muscle. The biological activities of trans-caryophyllene were examined in isolated bath organs to investigate the effect in basal tonus. Electromechanical and pharmacomechanical couplings were evaluated through the responses to K+ depolarization and exposure to acetylcholine (ACh, respectively. Isolated cells of rat tracheal smooth muscle were used to investigate trans-caryophyllene effects on voltage-dependent Ca2+ channels by using the whole-cell voltage-clamp configuration of the patch-clamp technique. trans-Caryophyllene showed more efficiency in the blockade of electromechanical excitation-contraction coupling while it has only minor inhibitory effect on pharmacomechanical coupling. Epithelium removal does not modify tracheal smooth muscle response elicited by trans-caryophyllene in the pharmacomechanical coupling. Under Ca2+-free conditions, pre-exposure to trans-caryophyllene did not reduce the contraction induced by ACh in isolated rat tracheal smooth muscle, regardless of the presence of intact epithelium. In the whole-cell configuration, trans-caryophyllene (3 mM, inhibited the inward Ba2+ current (IBa to approximately 50% of control levels. Altogether, our results demonstrate that trans-caryophyllene has anti-spasmodic activity on rat tracheal smooth muscle which could be explained, at least in part, by the voltage-dependent Ca2+ channels blockade.

  16. Multiphasic profiles for voltage-dependent K+ channels: Reanalysis of data of MacKinnon and coworkers

    CERN Document Server

    Nissen, Per

    2016-01-01

    In a study of the role that voltage-dependent K+ channels may have in the mechanosensation of living cells (Schmidt et al. Proc Soc Natl Acad Sci USA 109: 10352-10357. 2012), the data were as conventionally done fitted by a Boltzmann function. However, as also found for other data for ion channels, this interpretation must be rejected in favor of a multiphasic profile, a series of straight lines separated by discontinuous transitions, quite often in the form of noncontiguities (jumps). The data points in the present study are often very unevenly distributed around the curvilinear profiles. Thus, for 43 of the 75 profiles, the probability is less than 5% that the uneven distribution is due to chance, for 26 the probability is less than 1%, and for 12 the probability is less than 0.1%, giving a vanishingly low overall probability for all profiles. Especially at low voltages, the differences between the fits to curvilinear and multiphasic profiles may be huge. In the multiphasic profiles, adjacent lines are quit...

  17. Reduced KCNQ4-encoded voltage-dependent potassium channel activity underlies impaired ß-adrenoceptor-mediated relaxation of renal arteries in hypertension

    DEFF Research Database (Denmark)

    Chadha, Preet S; Zunke, Friederike; Zhu, Hai-Lei;

    2012-01-01

    KCNQ4-encoded voltage-dependent potassium (Kv7.4) channels are important regulators of vascular tone that are severely compromised in models of hypertension. However, there is no information as to the role of these channels in responses to endogenous vasodilators. We used a molecular knockdown st...

  18. THE VOLTAGE DEPENDENCE OF GATING CURRENTS OF THE NEURONAL CAV3.3 CHANNEL IS DETERMINED BY THE GATING BRAKE IN THE I-II LOOP

    Science.gov (United States)

    Karmažínová, Mária; Baumgart, Joel; Perez-Reyes, Edward; Lacinová, L'ubica

    2012-01-01

    Low-voltage activated CaV3 Ca2+ channels have an activation threshold around −60 mV, which is lower than the activation threshold of other voltage-dependent calcium channels (VDCC). The kinetics of their activation at membrane voltages just above the activation threshold is much slower than the activation kinetics of other VDCCs. It was demonstrated recently that the intracellular loop connecting repeats I and II of all three CaV3 channels contains a so-called “gating brake.” Disruption of this brake yields channels that activate at even more hyperpolarized potentials with significantly accelerated kinetics. We have compared gating of a wild type CaV3.3 channel and a mutated ID12 channel, in which the putative gating brake at the proximal part of the I-II loop was removed. Voltage dependence of the gating current activation was shifted by 34.6 mV towards more hyperpolarized potentials in ID12 channel. Kinetics of the on-charge activation was significantly accelerated, while kinetics of the off-charge was not altered. We conclude that the putative gating brake in I-II loop hinders not only the opening of the conducting pore but also the activating movement of voltage sensing S4 segments, stabilizing the channel in its closed state. PMID:21340458

  19. Current-voltage curve of sodium channels and concentration dependence of sodium permeability in frog skin

    DEFF Research Database (Denmark)

    Fuchs, W; Larsen, Erik Hviid; Lindemann, B

    1977-01-01

    1. The inward facing membranes of in vitro frog skin epithelium were depolarized with solutions of high K concentration. The electrical properties of the epithelium are then expected to be governed by the outward facing, Na-selective membrane.2. In this state, the transepithelial voltage (V) was...

  20. Sodium channel from rat brain. Reconstitution of voltage-dependent scorpion toxin binding in vesicles of defined lipid composition

    International Nuclear Information System (INIS)

    Purified sodium channels incorporated into phosphatidylcholine (PC) vesicles mediate neurotoxin-activated 22Na+ influx but do not bind the alpha-scorpion toxin from Leiurus quinquestriatus (LqTx) with high affinity. Addition of phosphatidylethanolamine (PE) or phosphatidylserine to the reconstitution mixture restores high affinity LqTx binding with KD = 1.9 nM for PC/PE vesicles at -90 mV and 36 degrees C in sucrose-substituted medium. Other lipids tested were markedly less effective. The binding of LqTx in vesicles of PC/PE (65:35) is sensitive to both the membrane potential formed by sodium gradients across the reconstituted vesicle membrane and the cation concentration in the extravesicular medium. Binding of LqTx is reduced 3- to 4-fold upon depolarization to 0 mV from -50 to -60 mV in experiments in which [Na+]out/[Na+]in is varied by changing [Na+]in or [Na+]out at constant extravesicular ionic strength. It is concluded that the purified sodium channel contains the receptor site for LqTx in functional form and that restoration of high affinity, voltage-dependent binding of LqTx by the purified sodium channel requires an appropriate ratio of PC to PE and/or phosphatidylserine in the vesicle membrane

  1. Sodium channel gating in clonal pituitary cells. The inactivation step is not voltage dependent

    OpenAIRE

    1989-01-01

    We have determined the time course of Na channel inactivation in clonal pituitary (GH3) cells by comparing records before and after the enzymatic removal of inactivation. The cells were subjected to whole- cell patch clamp, with papain included in the internal medium. Inactivation was slowly removed over the course of 10 min, making it possible to obtain control records before the enzyme acted. Papain caused a large (4-100x) increase in current magnitude for small depolarizations (near -40 mV...

  2. Impaired control of L-type voltage-dependent calcium channels in experimental hypertension

    Czech Academy of Sciences Publication Activity Database

    Pintérová, Mária; Líšková, Silvia; Dobešová, Zdenka; Behuliak, M.; Kuneš, Jaroslav; Zicha, Josef

    2009-01-01

    Roč. 58, Suppl.2 (2009), S43-S54. ISSN 0862-8408 R&D Projects: GA ČR(CZ) GA305/08/0139; GA ČR(CZ) GA305/09/0336; GA AV ČR(CZ) IAA500110902; GA MŠk(CZ) 1M0510 Institutional research plan: CEZ:AV0Z50110509 Keywords : calcium-activated K+ and Cl- channels * vasoactive systems * EDCF Subject RIV: ED - Physiology Impact factor: 1.430, year: 2009

  3. A whole-cell and single-channel study of the voltage-dependent outward potassium current in avian hepatocytes

    OpenAIRE

    1988-01-01

    Voltage-dependent membrane currents were studied in dissociated hepatocytes from chick, using the patch-clamp technique. All cells had voltage-dependent outward K+ currents; in 10% of the cells, a fast, transient, tetrodotoxin-sensitive Na+ current was identified. None of the cells had voltage-dependent inward Ca2+ currents. The K+ current activated at a membrane potential of about -10 mV, had a sigmoidal time course, and did not inactivate in 500 ms. The maximum outward conductance was 6.6 +...

  4. Tubulin tail sequences and post-translational modifications regulate closure of mitochondrial voltage-dependent anion channel (VDAC).

    Science.gov (United States)

    Sheldon, Kely L; Gurnev, Philip A; Bezrukov, Sergey M; Sackett, Dan L

    2015-10-30

    It was previously shown that tubulin dimer interaction with the mitochondrial outer membrane protein voltage-dependent anion channel (VDAC) blocks traffic through the channel and reduces oxidative metabolism and that this requires the unstructured anionic C-terminal tail peptides found on both α- and β-tubulin subunits. It was unclear whether the α- and β-tubulin tails contribute equally to VDAC blockade and what effects might be due to sequence variations in these tail peptides or to tubulin post-translational modifications, which mostly occur on the tails. The nature of the contribution of the tubulin body beyond acting as an anchor for the tails had not been clarified either. Here we present peptide-protein chimeras to address these questions. These constructs allow us to easily combine a tail peptide with different proteins or combine different tail peptides with a particular protein. The results show that a single tail grafted to an inert protein is sufficient to produce channel closure similar to that observed with tubulin. We show that the β-tail is more than an order of magnitude more potent than the α-tail and that the lower α-tail activity is largely due to the presence of a terminal tyrosine. Detyrosination activates the α-tail, and activation is reversed by the removal of the glutamic acid penultimate to the tyrosine. Nitration of tyrosine reverses the tyrosine inhibition of binding and even induces prolonged VDAC closures. Our results demonstrate that small changes in sequence or post-translational modification of the unstructured tails of tubulin result in substantial changes in VDAC closure. PMID:26306046

  5. The mitochondrial voltage-dependent anion channel 1 in tumor cells.

    Science.gov (United States)

    Shoshan-Barmatz, Varda; Ben-Hail, Danya; Admoni, Lee; Krelin, Yakov; Tripathi, Shambhoo Sharan

    2015-10-01

    VDAC as critical for deciphering how this channel can perform such a variety of roles, all of which are important for cell life and death. Finally, this review will also provide insight into VDAC function in Ca2+ homeostasis, protection against oxidative stress, regulation of apoptosis and involvement in several diseases, as well as its role in the action of different drugs. We will discuss the use of VDAC1-based strategies to attack the altered metabolism and apoptosis of cancer cells. These strategies include specific siRNA able to impair energy and metabolic homeostasis, leading to arrested cancer cell growth and tumor development, as well VDAC1-based peptides that interact with anti-apoptotic proteins to induce apoptosis, thereby overcoming the resistance of cancer cell to chemotherapy. Finally, small molecules targeting VDAC1 can induce apoptosis. VDAC1 can thus be considered as standing at the crossroads between mitochondrial metabolite transport and apoptosis and hence represents an emerging cancer drug target. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers. PMID:25448878

  6. Spexin Enhances Bowel Movement through Activating L-type Voltage-dependent Calcium Channel via Galanin Receptor 2 in Mice

    Science.gov (United States)

    Lin, Cheng-yuan; Zhang, Man; Huang, Tao; Yang, Li-ling; Fu, Hai-bo; Zhao, Ling; Zhong, Linda LD; Mu, Huai-xue; Shi, Xiao-ke; Leung, Christina FP; Fan, Bao-min; Jiang, Miao; Lu, Ai-ping; Zhu, Li-xin; Bian, Zhao-xiang

    2015-01-01

    A novel neuropeptide spexin was found to be broadly expressed in various endocrine and nervous tissues while little is known about its functions. This study investigated the role of spexin in bowel movement and the underlying mechanisms. In functional constipation (FC) patients, serum spexin levels were significantly decreased. Consistently, in starved mice, the mRNA of spexin was significantly decreased in intestine and colon. Spexin injection increased the velocity of carbon powder propulsion in small intestine and decreased the glass beads expulsion time in distal colon in mice. Further, spexin dose-dependently stimulated the intestinal/colonic smooth muscle contraction. Galanin receptor 2 (GALR2) antagonist M871, but not Galanin receptor 3 (GALR3) antagonist SNAP37899, effectively suppressed the stimulatory effects of spexin on intestinal/colonic smooth muscle contraction, which could be eliminated by extracellular [Ca2+] removal and L-type voltage-dependentCa2+ channel (VDCC) inhibitor nifedipine. Besides, spexin dramatically increased the [Ca2+]i in isolated colonic smooth muscle cells. These data indicate that spexin can act on GALR2 receptor to regulate bowel motility by activating L-type VDCC. Our findings provide evidence for important physiological roles of spexin in GI functions. Selective action on spexin pathway might have therapeutic effects on GI diseases with motility disorders. PMID:26160593

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

    Indian Academy of Sciences (India)

    Rashmi P Rao; J Prakasa Rao

    2010-12-01

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

  8. State- and Use-Dependent Block of Muscle Nav1.4 and Neuronal Nav1.7 Voltage-Gated Na+ Channel Isoforms by Ranolazine

    OpenAIRE

    Wang, Ging Kuo; Calderon, Joanna; Wang, Sho-Ya

    2007-01-01

    Ranolazine is an antianginal agent that targets a number of ion channels in the heart, including cardiac voltage-gated Na+ channels. However, ranolazine block of muscle and neuronal Na+ channel isoforms has not been examined. We compared the state- and use-dependent ranolazine block of Na+ currents carried by muscle Nav1.4, cardiac Nav1.5, and neuronal Nav1.7 isoforms expressed in human embryonic kidney 293T cells. Resting and inactivated block of Na+ channels by ranolazine were generally wea...

  9. Charged residues distribution modulates selectivity of the open state of human isoforms of the voltage dependent anion-selective channel.

    Science.gov (United States)

    Amodeo, Giuseppe Federico; Scorciapino, Mariano Andrea; Messina, Angela; De Pinto, Vito; Ceccarelli, Matteo

    2014-01-01

    Voltage Dependent Anion-selective Channels (VDACs) are pore-forming proteins located in the outer mitochondrial membrane. They are responsible for the access of ions and energetic metabolites into the inner membrane transport systems. Three VDAC isoforms exist in mammalian, but their specific role is unknown. In this work we have performed extensive (overall ∼5 µs) Molecular Dynamics (MD) simulations of the human VDAC isoforms to detect structural and conformational variations among them, possibly related to specific functional roles of these proteins. Secondary structure analysis of the N-terminal domain shows a high similarity among the three human isoforms of VDAC but with a different plasticity. In particular, the N-terminal domain of the hVDAC1 is characterized by a higher plasticity, with a ∼20% occurrence for the 'unstructured' conformation throughout the folded segment, while hVDAC2, containing a peculiar extension of 11 amino acids at the N-terminal end, presents an additional 310-helical folded portion comprising residues 10' to 3, adhering to the barrel wall. The N-terminal sequences of hVDAC isoforms are predicted to have a low flexibility, with possible consequences in the dynamics of the human VDACs. Clear differences were found between hVDAC1 and hVDAC3 against hVDAC2: a significantly modified dynamics with possible important consequence on the voltage-gating mechanism. Charge distribution inside and at the mouth of the pore is responsible for a different preferential localization of ions with opposite charge and provide a valuable rationale for hVDAC1 and hVDAC3 having a Cl-/K+ selectivity ratio of 1.8, whereas hVDAC2 of 1.4. Our conclusion is that hVDAC isoforms, despite sharing a similar scaffold, have modified working features and a biological work is now requested to give evidence to the described dissimilarities. PMID:25084457

  10. Charged residues distribution modulates selectivity of the open state of human isoforms of the voltage dependent anion-selective channel.

    Directory of Open Access Journals (Sweden)

    Giuseppe Federico Amodeo

    Full Text Available Voltage Dependent Anion-selective Channels (VDACs are pore-forming proteins located in the outer mitochondrial membrane. They are responsible for the access of ions and energetic metabolites into the inner membrane transport systems. Three VDAC isoforms exist in mammalian, but their specific role is unknown. In this work we have performed extensive (overall ∼5 µs Molecular Dynamics (MD simulations of the human VDAC isoforms to detect structural and conformational variations among them, possibly related to specific functional roles of these proteins. Secondary structure analysis of the N-terminal domain shows a high similarity among the three human isoforms of VDAC but with a different plasticity. In particular, the N-terminal domain of the hVDAC1 is characterized by a higher plasticity, with a ∼20% occurrence for the 'unstructured' conformation throughout the folded segment, while hVDAC2, containing a peculiar extension of 11 amino acids at the N-terminal end, presents an additional 310-helical folded portion comprising residues 10' to 3, adhering to the barrel wall. The N-terminal sequences of hVDAC isoforms are predicted to have a low flexibility, with possible consequences in the dynamics of the human VDACs. Clear differences were found between hVDAC1 and hVDAC3 against hVDAC2: a significantly modified dynamics with possible important consequence on the voltage-gating mechanism. Charge distribution inside and at the mouth of the pore is responsible for a different preferential localization of ions with opposite charge and provide a valuable rationale for hVDAC1 and hVDAC3 having a Cl-/K+ selectivity ratio of 1.8, whereas hVDAC2 of 1.4. Our conclusion is that hVDAC isoforms, despite sharing a similar scaffold, have modified working features and a biological work is now requested to give evidence to the described dissimilarities.

  11. Functional Apical Large Conductance, Ca2+-activated, and Voltage-dependent K+ Channels Are Required for Maintenance of Airway Surface Liquid Volume*

    OpenAIRE

    Manzanares, Dahis; Gonzalez, Carlos; Ivonnet, Pedro; Chen, Ren-Shiang; Valencia-Gattas, Monica; Gregory E. Conner; Larsson, H. Peter; Salathe, Matthias

    2011-01-01

    Large conductance, Ca2+-activated, and voltage-dependent K+ (BK) channels control a variety of physiological processes in nervous, muscular, and renal epithelial tissues. In bronchial airway epithelia, extracellular ATP-mediated, apical increases in intracellular Ca2+ are important signals for ion movement through the apical membrane and regulation of water secretion. Although other, mainly basolaterally expressed K+ channels are recognized as modulators of ion transport in airway epithelial ...

  12. The Voltage-dependent Anion Channel 1 Mediates Amyloid β Toxicity and Represents a Potential Target for Alzheimer Disease Therapy.

    Science.gov (United States)

    Smilansky, Angela; Dangoor, Liron; Nakdimon, Itay; Ben-Hail, Danya; Mizrachi, Dario; Shoshan-Barmatz, Varda

    2015-12-25

    The voltage-dependent anion channel 1 (VDAC1), found in the mitochondrial outer membrane, forms the main interface between mitochondrial and cellular metabolisms, mediates the passage of a variety of molecules across the mitochondrial outer membrane, and is central to mitochondria-mediated apoptosis. VDAC1 is overexpressed in post-mortem brains of Alzheimer disease (AD) patients. The development and progress of AD are associated with mitochondrial dysfunction resulting from the cytotoxic effects of accumulated amyloid β (Aβ). In this study we demonstrate the involvement of VDAC1 and a VDAC1 N-terminal peptide (VDAC1-N-Ter) in Aβ cell penetration and cell death induction. Aβ directly interacted with VDAC1 and VDAC1-N-Ter, as monitored by VDAC1 channel conductance, surface plasmon resonance, and microscale thermophoresis. Preincubated Aβ interacted with bilayer-reconstituted VDAC1 and increased its conductance ∼ 2-fold. Incubation of cells with Aβ resulted in mitochondria-mediated apoptotic cell death. However, the presence of non-cell-penetrating VDAC1-N-Ter peptide prevented Aβ cellular entry and Aβ-induced mitochondria-mediated apoptosis. Likewise, silencing VDAC1 expression by specific siRNA prevented Aβ entry into the cytosol as well as Aβ-induced toxicity. Finally, the mode of Aβ-mediated action involves detachment of mitochondria-bound hexokinase, induction of VDAC1 oligomerization, and cytochrome c release, a sequence of events leading to apoptosis. As such, we suggest that Aβ-mediated toxicity involves mitochondrial and plasma membrane VDAC1, leading to mitochondrial dysfunction and apoptosis induction. The VDAC1-N-Ter peptide targeting Aβ cytotoxicity is thus a potential new therapeutic strategy for AD treatment. PMID:26542804

  13. Characterization and expression analysis of Paralichthys olivaceus voltage-dependent anion channel (VDAC) gene in response to virus infection.

    Science.gov (United States)

    Lü, Ai-Jun; Dong, Cai-Wen; Du, Chang-Sheng; Zhang, Qi-Ya

    2007-09-01

    Voltage-dependent anion channel (VDAC, also known as mitochondrial porin) is acknowledged to play an important role in stress-induced mammalian apoptosis. In this study, Paralichthys olivaceus VDAC (PoVDAC) gene was identified as a virally induced gene from Scophthalmus Maximus Rhabdovirus (SMRV)-infected flounder embryonic cells (FEC). The full length of PoVDAC cDNA is 1380 bp with an open reading frame of 852 bp encoding a 283 amino acid protein. The deduced PoVDAC contains one alpha-helix, 13 transmembrane beta-strands and one eukaryotic mitochondrial porin signature motif. Constitutive expression of PoVDAC was confirmed in all tested tissues by real-time PCR. Further expression analysis revealed PoVDAC mRNA was upregulated by viral infection. We prepared fish antiserum against recombinant VDAC proteins and detected the PoVDAC in heart lysates from flounder as a 32 kDa band on western blot. Overexpression of PoVDAC in fish cells induced apoptosis. Immunofluoresence localization indicated that the significant distribution changes of PoVDAC have occurred in virus-induced apoptotic cells. This is the first report on the inductive expression of VDAC by viral infection, suggesting that PoVDAC might be mediated flounder antiviral immune response through induction of apoptosis. PMID:17467295

  14. Cell swelling activates ATP-dependent voltage-gated chloride channels in M-1 mouse cortical collecting duct cells

    OpenAIRE

    1996-01-01

    In the present study we used whole-cell patch clamp recordings to investigate swelling-activated Cl-currents (ICl-swell) in M-1 mouse cortical collecting duct (CCD) cells. Hypotonic cell swelling reversibly increased the whole-cell Cl- conductance by about 30-fold. The I-V relationship was outwardly-rectifying and ICl-swell displayed a characteristic voltage-dependence with relatively fast inactivation upon large depolarizing and slow activation upon hyperpolarizing voltage steps. Reversal po...

  15. Altered ischemic cerebral injury in mice lacking αIE subunit of the voltage-dependent Ca2+ channel

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Objective ①To set up a stable and reproducible focal cerebral infarct modelin mice; (②To examine theinvolvement of αIE subunit of voltage-dependent Ca2 + channel in cerebral ischemic injury. Methods Male C57BL/6J Jclmice 8 ~ 12w and F4 ~ F6αIE subunit of Ca2+ channel mutant mice were both used in this study. All animals were allowedto freely access to food and water before and after operation. Animals were anesthetized with pentobarbital sodium 60mg/kg,ip. Rectal temperature was continuously monitored before, during and after operation, and maintained at (36.6 +0.1 )°C by a autoregulating pad. To produce pilot models, the middle cerebral artery (MCA) was occluded either by sur-gical ligation or electrical coagulation and in some models the common carotid artery (CCA) was surgically ligated in tan-dem. In our latter work the MCA was cut off soon after it was ligated or coagulated in order to make sure that the bloodflow was occluded completely. The MCA was coagulated or ligated with a bipolar coagulator or microsurgery suture at thesite just superior to the rhinal fissure. Twenty~four hours after the operation, the mice were anesthetized and decapitated,then their brains were dissected from the skull and put into cold artificial brain spinal fluid as soon as possible. Lmm thickcoronal sections were cut by vibratome and stained with 2% 2,3,5-triphenyltetrazolium chloride (TTC) at 37°C for30min. Every section was photographed positively and the whole infarction volume was calculated by summing up the in-farction volumes of all sections by NIH Image System. Infarction ratio ( % ) was also calculated by the following fommula:(contralateral volume-ipsilateral undamaged volume)/contralateral volume × 100% to eliminate the influence of edema.In brief, the mutant mice were produced with gene targeting technique. F4 ~ F6 mice were used in this experiment. Alloffsprings were genotyped by the polymerase chain reaction (PCR) and the genotypes remained umknown

  16. Voltage-dependent and -independent titration of specific residues accounts for complex gating of a ClC chloride channel by extracellular protons.

    Science.gov (United States)

    Niemeyer, María Isabel; Cid, L Pablo; Yusef, Yamil R; Briones, Rodolfo; Sepúlveda, Francisco V

    2009-04-01

    The ClC transport protein family comprises both Cl(-) ion channel and H(+)/Cl(-) and H(+)/NO(3)(-) exchanger members. Structural studies on a bacterial ClC transporter reveal a pore obstructed at its external opening by a glutamate side-chain which acts as a gate for Cl(-) passage and in addition serves as a staging post for H(+) exchange. This same conserved glutamate acts as a gate to regulate Cl(-) flow in ClC channels. The activity of ClC-2, a genuine Cl(-) channel, has a biphasic response to extracellular pH with activation by moderate acidification followed by abrupt channel closure at pH values lower than approximately 7. We have now investigated the molecular basis of this complex gating behaviour. First, we identify a sensor that couples extracellular acidification to complete closure of the channel. This is extracellularly-facing histidine 532 at the N-terminus of transmembrane helix Q whose neutralisation leads to channel closure in a cooperative manner. We go on to show that acidification-dependent activation of ClC-2 is voltage dependent and probably mediated by protonation of pore gate glutamate 207. Intracellular Cl(-) acts as a voltage-independent modulator, as though regulating the pK(a) of the protonatable residue. Our results suggest that voltage dependence of ClC-2 is given by hyperpolarisation-dependent penetration of protons from the extracellular side to neutralise the glutamate gate deep within the channel, which allows Cl(-) efflux. This is reminiscent of a partial exchanger cycle, suggesting that the ClC-2 channel evolved from its transporter counterparts. PMID:19153159

  17. Mild Alkalization Acutely Triggers the Warburg Effect by Enhancing Hexokinase Activity via Voltage-Dependent Anion Channel Binding

    Science.gov (United States)

    Lee, Jin Hee; Park, Jin Won; Moon, Seung Hwan; Cho, Young Seok; Choe, Yearn Seong; Lee, Kyung-Han

    2016-01-01

    To fully understand the glycolytic behavior of cancer cells, it is important to recognize how it is linked to pH dynamics. Here, we evaluated the acute effects of mild acidification and alkalization on cancer cell glucose uptake and glycolytic flux and investigated the role of hexokinase (HK). Cancer cells exposed to buffers with graded pH were measured for 18F-fluorodeoxyglucose (FDG) uptake, lactate production and HK activity. Subcellular localization of HK protein was assessed by western blots and confocal microscopy. The interior of T47D breast cancer cells was mildly alkalized to pH 7.5 by a buffer pH of 7.8, and this was accompanied by rapid increases of FDG uptake and lactate extrusion. This shift toward glycolytic flux led to the prompt recovery of a reversed pH gradient. In contrast, mild acidification rapidly reduced cellular FDG uptake and lactate production. Mild acidification decreased and mild alkalization increased mitochondrial HK translocation and enzyme activity. Cells transfected with specific siRNA against HK-1, HK-2 and voltage-dependent anion channel (VDAC)1 displayed significant attenuation of pH-induced changes in FDG uptake. Confocal microscopy showed increased co-localization of HK-1 and HK-2 with VDAC1 by alkaline treatment. In isolated mitochondria, acidic pH increased and alkaline pH decreased release of free HK-1 and HK-2 from the mitochondrial pellet into the supernatant. Furthermore, experiments using purified proteins showed that alkaline pH promoted co-immunoprecipitation of HK with VDAC protein. These findings demonstrate that mild alkalization is sufficient to acutely trigger cancer cell glycolytic flux through enhanced activity of HK by promoting its mitochondrial translocation and VDAC binding. This process might serve as a mechanism through which cancer cells trigger the Warburg effect to maintain a dysregulated pH. PMID:27479079

  18. "Slow" Voltage-Dependent Inactivation of CaV2.2 Calcium Channels Is Modulated by the PKC Activator Phorbol 12-Myristate 13-Acetate (PMA.

    Directory of Open Access Journals (Sweden)

    Lei Zhu

    Full Text Available CaV2.2 (N-type voltage-gated calcium channels (Ca2+ channels play key roles in neurons and neuroendocrine cells including the control of cellular excitability, neurotransmitter / hormone secretion, and gene expression. Calcium entry is precisely controlled by channel gating properties including multiple forms of inactivation. "Fast" voltage-dependent inactivation is relatively well-characterized and occurs over the tens-to- hundreds of milliseconds timeframe. Superimposed on this is the molecularly distinct, but poorly understood process of "slow" voltage-dependent inactivation, which develops / recovers over seconds-to-minutes. Protein kinases can modulate "slow" inactivation of sodium channels, but little is known about if/how second messengers control "slow" inactivation of Ca2+ channels. We investigated this using recombinant CaV2.2 channels expressed in HEK293 cells and native CaV2 channels endogenously expressed in adrenal chromaffin cells. The PKC activator phorbol 12-myristate 13-acetate (PMA dramatically prolonged recovery from "slow" inactivation, but an inactive control (4α-PMA had no effect. This effect of PMA was prevented by calphostin C, which targets the C1-domain on PKC, but only partially reduced by inhibitors that target the catalytic domain of PKC. The subtype of the channel β-subunit altered the kinetics of inactivation but not the magnitude of slowing produced by PMA. Intracellular GDP-β-S reduced the effect of PMA suggesting a role for G proteins in modulating "slow" inactivation. We postulate that the kinetics of recovery from "slow" inactivation could provide a molecular memory of recent cellular activity and help control CaV2 channel availability, electrical excitability, and neurotransmission in the seconds-to-minutes timeframe.

  19. Neuroprotective effect of interleukin-6 regulation of voltage-gated Na+ channels of cortical neurons is time- and dose-dependent

    Directory of Open Access Journals (Sweden)

    Wei Xia

    2015-01-01

    Full Text Available Interleukin-6 has been shown to be involved in nerve injury and nerve regeneration, but the effects of long-term administration of high concentrations of interleukin-6 on neurons in the central nervous system is poorly understood. This study investigated the effects of 24 hour exposure of interleukin-6 on cortical neurons at various concentrations (0.1, 1, 5 and 10 ng/mL and the effects of 10 ng/mL interleukin-6 exposure to cortical neurons for various durations (2, 4, 8, 24 and 48 hours by studying voltage-gated Na + channels using a patch-clamp technique. Voltage-clamp recording results demonstrated that interleukin-6 suppressed Na + currents through its receptor in a time- and dose-dependent manner, but did not alter voltage-dependent activation and inactivation. Current-clamp recording results were consistent with voltage-clamp recording results. Interleukin-6 reduced the action potential amplitude of cortical neurons, but did not change the action potential threshold. The regulation of voltage-gated Na + channels in rat cortical neurons by interleukin-6 is time- and dose-dependent.

  20. Graded Ca2+/calmodulin-dependent coupling of voltage-gated CaV1.2 channels

    Science.gov (United States)

    Dixon, Rose E; Moreno, Claudia M; Yuan, Can; Opitz-Araya, Ximena; Binder, Marc D; Navedo, Manuel F; Santana, Luis F

    2015-01-01

    In the heart, reliable activation of Ca2+ release from the sarcoplasmic reticulum during the plateau of the ventricular action potential requires synchronous opening of multiple CaV1.2 channels. Yet the mechanisms that coordinate this simultaneous opening during every heartbeat are unclear. Here, we demonstrate that CaV1.2 channels form clusters that undergo dynamic, reciprocal, allosteric interactions. This ‘functional coupling’ facilitates Ca2+ influx by increasing activation of adjoined channels and occurs through C-terminal-to-C-terminal interactions. These interactions are initiated by binding of incoming Ca2+ to calmodulin (CaM) and proceed through Ca2+/CaM binding to the CaV1.2 pre-IQ domain. Coupling fades as [Ca2+]i decreases, but persists longer than the current that evoked it, providing evidence for ‘molecular memory’. Our findings suggest a model for CaV1.2 channel gating and Ca2+-influx amplification that unifies diverse observations about Ca2+ signaling in the heart, and challenges the long-held view that voltage-gated channels open and close independently. DOI: http://dx.doi.org/10.7554/eLife.05608.001 PMID:25714924

  1. Potent and voltage-dependent block by philanthotoxin-343 of neuronal nicotinic receptor/channels in PC12 cells

    OpenAIRE

    Min LIU; Nakazawa, Ken; Inou, Kazuhide; Ohno, Yasuo

    1997-01-01

    Block by philanthotoxin-343 (PhTX-343), a neurotoxin from wasps, of ionic currents mediated through neuronal nicotinic acetylcholine (ACh) receptor/channels was characterized in rat phaeochromocytoma PC12 cells, by use of whole cell voltage-clamp techniques.In the cells held at −60 mV, PhTX-343 at 0.1 and 1 μM inhibited an inward current activated by 100 μM ACh. The current inhibition was relieved by depolarizing steps, and augmented at negative potentials, suggesting that PhTX-343 blocks the...

  2. An autism-associated mutation in CaV1.3 channels has opposing effects on voltage- and Ca2+-dependent regulation

    Science.gov (United States)

    Limpitikul, Worawan B.; Dick, Ivy E.; Ben-Johny, Manu; Yue, David T.

    2016-01-01

    CaV1.3 channels are a major class of L-type Ca2+ channels which contribute to the rhythmicity of the heart and brain. In the brain, these channels are vital for excitation-transcription coupling, synaptic plasticity, and neuronal firing. Moreover, disruption of CaV1.3 function has been associated with several neurological disorders. Here, we focus on the de novo missense mutation A760G which has been linked to autism spectrum disorder (ASD). To explore the role of this mutation in ASD pathogenesis, we examined the effects of A760G on CaV1.3 channel gating and regulation. Introduction of the mutation severely diminished the Ca2+-dependent inactivation (CDI) of CaV1.3 channels, an important feedback system required for Ca2+ homeostasis. This reduction in CDI was observed in two major channel splice variants, though to different extents. Using an allosteric model of channel gating, we found that the underlying mechanism of CDI reduction is likely due to enhanced channel opening within the Ca2+-inactivated mode. Remarkably, the A760G mutation also caused an opposite increase in voltage-dependent inactivation (VDI), resulting in a multifaceted mechanism underlying ASD. When combined, these regulatory deficits appear to increase the intracellular Ca2+ concentration, thus potentially disrupting neuronal development and synapse formation, ultimately leading to ASD. PMID:27255217

  3. An autism-associated mutation in CaV1.3 channels has opposing effects on voltage- and Ca(2+)-dependent regulation.

    Science.gov (United States)

    Limpitikul, Worawan B; Dick, Ivy E; Ben-Johny, Manu; Yue, David T

    2016-01-01

    CaV1.3 channels are a major class of L-type Ca(2+) channels which contribute to the rhythmicity of the heart and brain. In the brain, these channels are vital for excitation-transcription coupling, synaptic plasticity, and neuronal firing. Moreover, disruption of CaV1.3 function has been associated with several neurological disorders. Here, we focus on the de novo missense mutation A760G which has been linked to autism spectrum disorder (ASD). To explore the role of this mutation in ASD pathogenesis, we examined the effects of A760G on CaV1.3 channel gating and regulation. Introduction of the mutation severely diminished the Ca(2+)-dependent inactivation (CDI) of CaV1.3 channels, an important feedback system required for Ca(2+) homeostasis. This reduction in CDI was observed in two major channel splice variants, though to different extents. Using an allosteric model of channel gating, we found that the underlying mechanism of CDI reduction is likely due to enhanced channel opening within the Ca(2+)-inactivated mode. Remarkably, the A760G mutation also caused an opposite increase in voltage-dependent inactivation (VDI), resulting in a multifaceted mechanism underlying ASD. When combined, these regulatory deficits appear to increase the intracellular Ca(2+) concentration, thus potentially disrupting neuronal development and synapse formation, ultimately leading to ASD. PMID:27255217

  4. Heparin/heparan sulfates bind to and modulate neuronal L-type (Cav1.2) voltage-dependent Ca2+ channels

    DEFF Research Database (Denmark)

    Garau, Gianpiero; Magotti, Paola; Heine, Martin;

    2015-01-01

    Our previous studies revealed that L-type voltage-dependent Ca2+ channels (Cav1.2 L-VDCCs) are modulated by the neural extracellular matrix backbone, polyanionic glycan hyaluronic acid. Here we used isothermal titration calorimetry and screened a set of peptides derived from the extracellular...... domains of Cav1.2α1 to identify putative binding sites between the channel and hyaluronic acid or another class of polyanionic glycans, such as heparin/heparan sulfates. None of the tested peptides showed detectable interaction with hyaluronic acid, but two peptides derived from the first pore...

  5. A quantitative and comparative study of the effects of a synthetic ciguatoxin CTX3C on the kinetic properties of voltage-dependent sodium channels

    OpenAIRE

    Yamaoka, Kaoru; Inoue, Masayuki; Miyahara, Hidemichi; Miyazaki, Keisuke; Hirama, Masahiro

    2004-01-01

    Ciguatoxins (CTXs) are known to bind to receptor site 5 of the voltage-dependent Na channel, but the toxin's physiological effects are poorly understood. In this study, we investigated the effects of a ciguatoxin congener (CTX3C) on three different Na-channel isoforms, rNav1.2, rNav1.4, and rNav1.5, which were transiently expressed in HEK293 cells.The toxin (1.0 μmol l−1) shifted the activation potential (V1/2 of activation curve) in the negative direction by 4–9 mV and increased the slope fa...

  6. A comparative study of the effect of ciguatoxins on voltage-dependent Na+ and K+ channels in cerebellar neurons.

    Science.gov (United States)

    Pérez, Sheila; Vale, Carmen; Alonso, Eva; Alfonso, Carmen; Rodríguez, Paula; Otero, Paz; Alfonso, Amparo; Vale, Paulo; Hirama, Masahiro; Vieytes, Mercedes R; Botana, Luis M

    2011-04-18

    Ciguatera is a global disease caused by the consumption of certain warm-water fish (ciguateric fish) that have accumulated orally effective levels of sodium channel activator toxins (ciguatoxins) through the marine food chain. The effect of ciguatoxin standards and contaminated ciguatoxin samples was evaluated by electrophysiological recordings in cultured cerebellar neurons. The toxins affected both voltage-gated sodium (Nav) and potassium channels (Kv) although with different potencies. CTX 3C was the most active toxin blocking the peak inward sodium currents, followed by P-CTX 1B and 51-OH CTX 3C. In contrast, P-CTX 1B was more effective in blocking potassium currents. The analysis of six different samples of contaminated fish, in which a ciguatoxin analogue of mass 1040.6, not identical with the standard 51-OH CTX 3C, was the most prevalent compound, indicated an additive effect of the different ciguatoxins present in the samples. The results presented here constitute the first comparison of the potencies of three different purified ciguatoxins on sodium and potassium channels in the same neuronal preparation and indicate that electrophysiological recordings from cultured cerebellar neurons may provide a valuable tool to detect and quantify ciguatoxins in the very low nanomolar range. PMID:21351754

  7. Stereoselectivity of butylidenephthalide on non-adrenergic prejunctional voltage-dependent Ca(2+) channels in prostatic portion of rat vas deferens.

    Science.gov (United States)

    Shih, Chung-Hung; Chen, Chi-Ming; Ko, Wun-Chang

    2016-09-01

    The naturally occurring and synthetic butylinenephthalide (Bdph) has two geometric isomers. Z- and E-Bdph were reported to have geometric stereoselectivity for voltage-dependent calcium channels (VDCCs) in guinea-pig ileum. The aim of this study was to investigate whether the binding of Z- and E-Bdph on prejunctional VDCCs of rat vas deferens (RVD) is stereoselective. The twitch responses to electrical field stimulation (EFS, supramaximal voltage, 1 ms, 0.2Hz) were recorded on a polygraph. Z- and E-Bdph concentration-dependently inhibited the twitch responses to EFS in full tissue, prostatic portion and epididymal portion of RVD. The pIC50 value of Z-Bdph was greater than that of E-Bdph in the electrically stimulated prostatic portion of RVD, suggesting that the binding of Bdph on the non-adrenergic prejunctional VDCCs of cell membrane is stereoselective. In the prostatic portion, exogenous Ca(2+) only partially reversed the twitch inhibition by Z-Bdph, but effectively reversed those by Ca(2+) channel blockers, such as verapamil, diltiazem and aspaminol, suggesting that the action mechanisms may be different from those of Ca(2+) channel blockers. K(+) channel blockers, such as tetraethylammonium (TEA) and 4-aminopyridine (4-AP), may prolong duration of action potential to allow greater Ca(2+) entry and induced more release of transmitters. Therefore both blockers via their prejunctional actions reversed the twitch inhibition induced by Z-Bdph in all preparations of RVD by a non-specific antagonism. PMID:27238973

  8. Ropivacaine-Induced Contraction Is Attenuated by Both Endothelial Nitric Oxide and Voltage-Dependent Potassium Channels in Isolated Rat Aortae

    Directory of Open Access Journals (Sweden)

    Seong-Ho Ok

    2013-01-01

    Full Text Available This study investigated endothelium-derived vasodilators and potassium channels involved in the modulation of ropivacaine-induced contraction. In endothelium-intact rat aortae, ropivacaine concentration-response curves were generated in the presence or absence of the following inhibitors: the nonspecific nitric oxide synthase (NOS inhibitor Nω-nitro-L-arginine methyl ester (L-NAME, the neuronal NOS inhibitor Nω-propyl-L-arginine hydrochloride, the inducible NOS inhibitor 1400W dihydrochloride, the nitric oxide-sensitive guanylyl cyclase (GC inhibitor ODQ, the NOS and GC inhibitor methylene blue, the phosphoinositide-3 kinase inhibitor wortmannin, the cytochrome p450 epoxygenase inhibitor fluconazole, the voltage-dependent potassium channel inhibitor 4-aminopyridine (4-AP, the calcium-activated potassium channel inhibitor tetraethylammonium (TEA, the inward-rectifying potassium channel inhibitor barium chloride, and the ATP-sensitive potassium channel inhibitor glibenclamide. The effect of ropivacaine on endothelial nitric oxide synthase (eNOS phosphorylation in human umbilical vein endothelial cells was examined by western blotting. Ropivacaine-induced contraction was weaker in endothelium-intact aortae than in endothelium-denuded aortae. L-NAME, ODQ, and methylene blue enhanced ropivacaine-induced contraction, whereas wortmannin, Nω-propyl-L-arginine hydrochloride, 1400W dihydrochloride, and fluconazole had no effect. 4-AP and TEA enhanced ropivacaine-induced contraction; however, barium chloride and glibenclamide had no effect. eNOS phosphorylation was induced by ropivacaine. These results suggest that ropivacaine-induced contraction is attenuated primarily by both endothelial nitric oxide and voltage-dependent potassium channels.

  9. CaBP1 regulates voltage-dependent inactivation and activation of Ca(V)1.2 (L-type) calcium channels.

    Science.gov (United States)

    Oz, Shimrit; Tsemakhovich, Vladimir; Christel, Carl J; Lee, Amy; Dascal, Nathan

    2011-04-22

    CaBP1 is a Ca(2+)-binding protein that regulates the gating of voltage-gated (Ca(V)) Ca(2+) channels. In the Ca(V)1.2 channel α(1)-subunit (α(1C)), CaBP1 interacts with cytosolic N- and C-terminal domains and blunts Ca(2+)-dependent inactivation. To clarify the role of the α(1C) N-terminal domain in CaBP1 regulation, we compared the effects of CaBP1 on two alternatively spliced variants of α(1C) containing a long or short N-terminal domain. In both isoforms, CaBP1 inhibited Ca(2+)-dependent inactivation but also caused a depolarizing shift in voltage-dependent activation and enhanced voltage-dependent inactivation (VDI). In binding assays, CaBP1 interacted with the distal third of the N-terminal domain in a Ca(2+)-independent manner. This segment is distinct from the previously identified calmodulin-binding site in the N terminus. However, deletion of a segment in the proximal N-terminal domain of both α(1C) isoforms, which spared the CaBP1-binding site, inhibited the effect of CaBP1 on VDI. This result suggests a modular organization of the α(1C) N-terminal domain, with separate determinants for CaBP1 binding and transduction of the effect on VDI. Our findings expand the diversity and mechanisms of Ca(V) channel regulation by CaBP1 and define a novel modulatory function for the initial segment of the N terminus of α(1C). PMID:21383011

  10. Coexpression of voltage-dependent calcium channels Cav1.2, 2.1a, and 2.1b in vascular myocytes

    DEFF Research Database (Denmark)

    Andreasen, Ditte; Friis, Ulla Glenert; Uhrenholt, Torben Rene;

    2006-01-01

    Voltage-dependent Ca2+ channels Cav1.2 (L type) and Cav2.1 (P/Q type) are expressed in vascular smooth muscle cells (VSMCs) and are important for the contraction of renal resistance vessels. In the present study we examined whether native renal VSMCs coexpress L-, P-, and Q-type Ca2+ currents. The...... microscopy revealed expression of both channels in all of the smooth muscle cells. Whole-cell patch clamp on single preglomerular VSMCs from mice showed L-, P-, and Q-type currents. Blockade of the L-type currents by calciseptine (20 nmol/L) inhibited 35.6+/-3.9% of the voltage-dependent Ca2+ current, and...... blocking P-type currents (omega-agatoxin IVA 10 nmol/L) led to 20.2+/-3.0% inhibition, whereas 300 nmol/L of omega agatoxin IVA (blocking P/Q-type) inhibited 45.0+/-7.3%. In rat aortic smooth muscle cells (A7r5), blockade of L-type channels resulted in 28.5+/-6.1% inhibition, simultaneous blockade of L...

  11. Modulation of voltage-dependent Ca channel current by arachidonic acid and other long-chain fatty acids in rabbit intestinal smooth muscle

    OpenAIRE

    1992-01-01

    The effects of arachidonic acid (AA) and other long-chain fatty acids on voltage-dependent Ca channel current (ICa) were investigated, with the whole cell patch clamp method, in longitudinal smooth muscle cells of rabbit ileum. 10-30 microM AA caused a gradual depression of ICa. The inhibitory effect of AA was not prevented by indomethacin (10 microM) (an inhibitor of cyclooxygenase) or nordihydroguaiaretic acid (10 microM) (an inhibitor of lipoxygenase). 1-(5-Isoquinolinesulfonyl)- 2-methylp...

  12. 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.

  13. Voltage Dependence of Supercapacitor Capacitance

    Directory of Open Access Journals (Sweden)

    Szewczyk Arkadiusz

    2016-09-01

    Full Text Available Electronic Double-Layer Capacitors (EDLC, called Supercapacitors (SC, are electronic devices that are capable to store a relatively high amount of energy in a small volume comparing to other types of capacitors. They are composed of an activated carbon layer and electrolyte solution. The charge is stored on electrodes, forming the Helmholtz layer, and in electrolyte. The capacitance of supercapacitor is voltage- dependent. We propose an experimental method, based on monitoring of charging and discharging a supercapacitor, which enables to evaluate the charge in an SC structure as well as the Capacitance-Voltage (C-V dependence. The measurement setup, method and experimental results of charging/discharging commercially available supercapacitors in various voltage and current conditions are presented. The total charge stored in an SC structure is proportional to the square of voltage at SC electrodes while the charge on electrodes increases linearly with the voltage on SC electrodes. The Helmholtz capacitance increases linearly with the voltage bias while a sublinear increase of total capacitance was found. The voltage on SC increases after the discharge of electrodes due to diffusion of charges from the electrolyte to the electrodes. We have found that the recovery voltage value is linearly proportional to the initial bias voltage value.

  14. VKCDB: Voltage-gated potassium channel database

    Directory of Open Access Journals (Sweden)

    Gallin Warren J

    2004-01-01

    Full Text Available Abstract Background The family of voltage-gated potassium channels comprises a functionally diverse group of membrane proteins. They help maintain and regulate the potassium ion-based component of the membrane potential and are thus central to many critical physiological processes. VKCDB (Voltage-gated potassium [K] Channel DataBase is a database of structural and functional data on these channels. It is designed as a resource for research on the molecular basis of voltage-gated potassium channel function. Description Voltage-gated potassium channel sequences were identified by using BLASTP to search GENBANK and SWISSPROT. Annotations for all voltage-gated potassium channels were selectively parsed and integrated into VKCDB. Electrophysiological and pharmacological data for the channels were collected from published journal articles. Transmembrane domain predictions by TMHMM and PHD are included for each VKCDB entry. Multiple sequence alignments of conserved domains of channels of the four Kv families and the KCNQ family are also included. Currently VKCDB contains 346 channel entries. It can be browsed and searched using a set of functionally relevant categories. Protein sequences can also be searched using a local BLAST engine. Conclusions VKCDB is a resource for comparative studies of voltage-gated potassium channels. The methods used to construct VKCDB are general; they can be used to create specialized databases for other protein families. VKCDB is accessible at http://vkcdb.biology.ualberta.ca.

  15. Ca2+ and Na+ permeability of high-threshold Ca2+ channels and their voltage-dependent block by Mg2+ ions in chick sensory neurones.

    Science.gov (United States)

    Carbone, E; Lux, H D; Carabelli, V; Aicardi, G; Zucker, H

    1997-10-01

    1. The Mg2+ block of Na+ and Ca2+ currents through high-voltage activated (HVA; L- and N-type) Ca2+ channels was studied in chick dorsal root ganglion neurones. 2. In low extracellular [Ca2+] ( 1.45 x 10(8) M-1 S-1 when Na+ is the permeating ion and a rate approximately 3 orders of magnitude smaller for Ca2+. 6. Mg2+ unblock of HVA Na+ currents at +100 mV was independent of the size of outward currents, whether Na+, Cs+ or NMG+ were the main internal cations. 7. Consistent with the idea of a high-affinity binding site for Ca2+ inside the channel, micromolar amounts of Ca2+ caused a strong depression of Na+ currents between -40 and 0 mV, which was effectively relieved with more positive as well as with negative potentials (KD = 0.7 microM in 120 mM Na+ at -20 mV). In this case, the kinetics of re-block could be resolved and gave rates of entry and exit for Ca2+ of 1.4 x 10(8) M-1 S-1 and 2.95 x 10(2) s-1, respectively. 8. The strong voltage dependence and weak current dependence of HVA channel block by divalent cations and the markedly different KD values of Na+ and Ca2+ current block by Mg2+ can be well described by a previously proposed model for Ca2+ channel permeation based on interactions between the permeating ion and the negative charges forming the high-affinity binding site for Ca2+ inside the pore (Lux, Carbone & Zucker, 1990). PMID:9350613

  16. The class III anti-arrhythmic agent, amiodarone, inhibits voltage-dependent K(+) channels in rabbit coronary arterial smooth muscle cells.

    Science.gov (United States)

    Li, Hongliang; Kim, Han Sol; Kim, Hye Won; Shin, Sung Eun; Jung, Won-Kyo; Ha, Kwon-Soo; Han, Eun-Taek; Hong, Seok-Ho; Firth, Amy L; Bae, Young Min; Choi, Il-Whan; Park, Won Sun

    2016-07-01

    We examined the inhibitory effect of amiodarone, a class III anti-arrhythmic agent, on voltage-dependent K(+) (Kv) currents in freshly isolated rabbit coronary arterial smooth muscle cells, using a whole-cell patch clamp technique. Amiodarone inhibited Kv currents in a concentration-dependent manner, with a half-maximal inhibitory concentration (IC50) value of 3.9 ± 1.44 μM and a Hill coefficient of 0.45 ± 0.14. Amiodarone did not have a significant effect on the steady-state activation of Kv channels, but shifted the inactivation current toward a more negative potential. Application of consecutive pulses progressively augmented the amiodarone-induced Kv channel inhibition. Another class III anti-arrhythmic agent, dofetilide, did not inhibit the Kv current or change the inhibitory effect of amiodarone on Kv channels. Therefore, these results strongly suggest that amiodarone inhibits Kv currents in a concentration- and state-dependent manner. PMID:27030392

  17. S-acylation dependent post-translational cross-talk regulates large conductance calcium- and voltage- activated potassium (BK channels

    Directory of Open Access Journals (Sweden)

    MichaelJShipston

    2014-08-01

    Full Text Available Mechanisms that control surface expression and/or activity of large conductance calcium-activated potassium (BK channels are important determinants of their (pathophysiological function. Indeed, BK channel dysfunction is associated with major human disorders ranging from epilepsy to hypertension and obesity. S-acylation (S-palmitoylation represents a major reversible, post-translational modification controlling the properties and function of many proteins including ion channels. Recent evidence reveals that both pore-forming and regulatory subunits of BK channels are S-acylated and control channel trafficking and regulation by AGC-family protein kinases. The pore-forming α-subunit is S-acylated at two distinct sites within the N- and C-terminus, each site being regulated by different palmitoyl acyl transferases (zDHHCs and acyl thioesterases. (APTs. S-acylation of the N-terminus controls channel trafficking and surface expression whereas S-acylation of the C-terminal domain determines regulation of channel activity by AGC-family protein kinases. S-acylation of the regulatory β4-subunit controls ER exit and surface expression of BK channels but does not affect ion channel kinetics at the plasma membrane. Furthermore, a significant number of previously identified BK-channel interacting proteins have been shown, or are predicted to be, S-acylated. Thus, the BK channel multi-molecular signalling complex may be dynamically regulated by this fundamental post-translational modification and thus S-acylation likely represents an important determinant of BK channel physiology in health and disease.

  18. Relationship of sperm small heat-shock protein 10 and voltage-dependent anion channel 2 with semen freezability in boars.

    Science.gov (United States)

    Vilagran, Ingrid; Yeste, Marc; Sancho, Sílvia; Casas, Isabel; Rivera del Álamo, Maria M; Bonet, Sergi

    2014-08-01

    Freezability differences between boar ejaculates exist, but there is no useful method to predict the ejaculate freezability before sperm cryopreservation takes place. In this context, the present study sought to determine whether the amounts of small heat-shock protein 10 (also known as outer dense fiber protein 1) (ODF1/HSPB10) and voltage-dependent anion channel 2 (VDAC2) may be used as boar sperm freezability markers. With this aim, 26 boar ejaculates were split into two fractions: one for protein extraction and the other for cryopreservation purposes. Ejaculates were subsequently classified into two groups (good freezability ejaculates [GFE] and poor freezability ejaculates [PFE]) based on viability and sperm motility assessments after 30 and 240 minutes of after thawing. Although the VDAC2 amounts, analyzed through Western blot, were significantly higher (P cryopreservation procedures. PMID:24933094

  19. 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; Bennekou, P.

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

  20. Mefenamic acid as a novel activator of L-type voltage-dependent Ca2+ channels in smooth muscle cells from pig proximal urethra

    OpenAIRE

    Teramoto, Noriyoshi; Tomoda, Toshihisa; Ito, Yushi

    2005-01-01

    The effects of mefenamic acid and Bay K 8644 on voltage-dependent nifedipine-sensitive inward Ba2+ currents in pig urethral myocytes were investigated by use of conventional whole-cell configuration patch clamp.Mefenamic acid increased the peak amplitude of voltage-dependent nifedipine-sensitive inward Ba2+ current without shifting the position of the current–voltage relationship.Mefenamic acid (300 μM) caused little shift in the activation curve although the voltage dependence of the steady-...

  1. Expression of mRNA for voltage-dependent and inward-rectifying K channels in GH3/B6 cells and rat pituitary.

    Science.gov (United States)

    Wulfsen, I; Hauber, H P; Schiemann, D; Bauer, C K; Schwarz, J R

    2000-03-01

    The expression of mRNA for voltage-dependent (Kv) and inward-rectifying K channels (Kir) was studied in clonal rat somato-mammotroph cells (GH3/B6 cells) and rat pituitary using reverse transcription-polymerase chain reaction (RT-PCR). In GH3/B6 cells transcripts for 16 different Kv channel alpha-subunits (seven Shaker-related: Kv1.2, Kv1.4, Kv1.5, Kv2.1, Kv3.2, Kv4.1, Kv5.1; six EAG: eag1, erg1, erg2, elk1-elk3; three KCNQ: KCNQ1-KCNQ3) and for five different Kir channel alpha-subunits (Kir1.1, Kir2.3, Kir3.2, Kir3.3, Kir6.2) were found. In addition, transcripts for a short isoform of Kvbeta2 and transcripts for Kvbeta3 subunits were present. In rat pituitary transcripts for 21 different Kv channel alpha-subunits (11 Shaker-related: Kv1.3, Kv1.4, Kv1.6, Kv2.1, Kv2.2, Kv3.2, Kv3.4, Kv4.1, Kv4.2, Kv4.3, Kv6.1; seven EAG: eag1, erg1-erg3, elk1-elk3; three KCNQ: KCNQ1-KCNQ3) and nine Kir channel alpha-subunits (Kir1.1, Kir2.2, Kir3.1-Kir3.4, Kir4.1, Kir6.1, Kir6. 2) were found. In addition, all tested auxiliary subunits (Kvbeta1-Kvbeta3, minK, SUR1, SUR2) are expressed in the pituitary. The results indicate that the macroscopic K currents in GH3/B6 and pituitary cells are presumably mediated by K channels constructed by a larger number of K channel alpha-subunits and auxiliary beta-subunits than previously distinguished electrophysiologically and pharmacologically. PMID:10718922

  2. Biophysical characterization of the honeybee DSC1 orthologue reveals a novel voltage-dependent Ca2+ channel subfamily: CaV4.

    Science.gov (United States)

    Gosselin-Badaroudine, Pascal; Moreau, Adrien; Simard, Louis; Cens, Thierry; Rousset, Matthieu; Collet, Claude; Charnet, Pierre; Chahine, Mohamed

    2016-08-01

    Bilaterian voltage-gated Na(+) channels (NaV) evolved from voltage-gated Ca(2+) channels (CaV). The Drosophila melanogaster Na(+) channel 1 (DSC1), which features a D-E-E-A selectivity filter sequence that is intermediate between CaV and NaV channels, is evidence of this evolution. Phylogenetic analysis has classified DSC1 as a Ca(2+)-permeable Na(+) channel belonging to the NaV2 family because of its sequence similarity with NaV channels. This is despite insect NaV2 channels (DSC1 and its orthologue in Blatella germanica, BSC1) being more permeable to Ca(2+) than Na(+) In this study, we report the cloning and molecular characterization of the honeybee (Apis mellifera) DSC1 orthologue. We reveal several sequence variations caused by alternative splicing, RNA editing, and genomic variations. Using the Xenopus oocyte heterologous expression system and the two-microelectrode voltage-clamp technique, we find that the channel exhibits slow activation and inactivation kinetics, insensitivity to tetrodotoxin, and block by Cd(2+) and Zn(2+) These characteristics are reminiscent of CaV channels. We also show a strong selectivity for Ca(2+) and Ba(2+) ions, marginal permeability to Li(+), and impermeability to Mg(2+) and Na(+) ions. Based on current ion channel nomenclature, the D-E-E-A selectivity filter, and the properties we have uncovered, we propose that DSC1 homologues should be classified as CaV4 rather than NaV2. Indeed, channels that contain the D-E-E-A selectivity sequence are likely to feature the same properties as the honeybee's channel, namely slow activation and inactivation kinetics and strong selectivity for Ca(2+) ions. PMID:27432995

  3. Autoradiographic localization of voltage-dependent sodium channels on the mouse neuromuscular junction using 125I-alpha scorpion toxin. I. Preferential labeling of glial cells on the presynaptic side

    International Nuclear Information System (INIS)

    Alpha-scorpion toxins bind specifically to the voltage-sensitive sodium channel in excitable membranes, and binding is potential-dependent. The radioiodinated toxin II from the scorpion Androctonus australis Hector (alpha ScTx) was used to localize voltage-sensitive sodium channels on the presynaptic side of mouse neuromuscular junctions (NMJ) by autoradiography using both light and electron microscopy. Silver grain localization was analyzed by the cross-fire method. At the light-microscopic level, grain density over NMJ appeared 6-8x higher than over nonjunctional muscle membrane. The specificity of labeling was verified by competition/displacement with an excess of native alpha ScTx. Labeling was also inhibited by incubation in depolarizing conditions, showing its potential-dependence. At the electron-microscopic level, analysis showed that voltage-sensitive sodium channels labeled with alpha ScTx were almost exclusively localized on membranes, as expected. Due to washout after incubation, appreciable numbers of binding sites were not found on the postsynaptic membranes. However, on the presynaptic side, alpha ScTx-labeled voltage-sensitive sodium channels were localized on the membrane of non-myelin-forming Schwann cells covering NMJ. The axonal presynaptic membrane was not labeled. These results show that voltage-sensitive sodium channels are present on glial cells in vivo, as already demonstrated in vitro. It is proposed that these glial channels could be indirectly involved in the ionic homeostasis of the axonal environment

  4. The selectivity, voltage-dependence and acid sensitivity of the tandem pore potassium channel TASK-1: contributions of the pore domains

    OpenAIRE

    Yuill, KH; Stansfeld, PJ; Ashmole, I; Sutcliffe, MJ; Stanfield, PR

    2007-01-01

    We have investigated the contribution to ionic selectivity of residues in the selectivity filter and pore helices of the P1 and P2 domains in the acid sensitive potassium channel TASK-1. We used site directed mutagenesis and electrophysiological studies, assisted by structural models built through computational methods. We have measured selectivity in channels expressed in Xenopus oocytes, using voltage clamp to measure shifts in reversal potential and current amplitudes when Rb+ or Na+ repla...

  5. Time- and state-dependent effects of methanethiosulfonate ethylammonium (MTSEA) exposure differ between heart and skeletal muscle voltage-gated Na(+) channels.

    Science.gov (United States)

    O'Reilly, John P; Shockett, Penny E

    2012-03-01

    The substituted-cysteine scanning method (SCAM) is used to study conformational changes in proteins. Experiments using SCAM involve site-directed mutagenesis to replace native amino acids with cysteine and subsequent exposure to a methanethiosulfonate (MTS) reagent such as methanethiosulfonate ethylammonium (MTSEA). These reagents react with substituted-cysteines and can provide functional information about relative positions of amino acids within a protein. In the human heart voltage-gated Na(+) channel hNav1.5 there is a native cysteine at position C373 that reacts rapidly with MTS reagents resulting in a large reduction in whole-cell Na(+) current (I(Na)). Therefore, in order to use SCAM in studies in this isoform, this native cysteine is mutated to a non-reactive residue, e.g., tyrosine. This mutant, hNav1.5-C373Y, is resistant to the MTS-mediated decrease in I(Na). Here we show that this resistance is time- and state-dependent. With relatively short exposure times to MTSEA (<4min), there is little effect on I(Na). However, with longer exposures (4-8min), there is a large decrease in I(Na), but this effect is only found when hNav1.5-C373Y is inactivated (fast or slow) - MTSEA has little effect in the closed state. Additionally, this long-term, state-dependent effect is not seen in human skeletal muscle Na(+) channel isoform hNav1.4, which has a native tyrosine at the homologous site C407. We conclude that differences in molecular determinants of inactivation between hNav1.4 and hNav1.5 underlie the difference in response to MTSEA exposure. PMID:22155680

  6. Role of voltage-dependent potassium channels and myo-endothelial gap junctions in 4-aminopyridine-induced inhibition of acetylcholine relaxation in rat carotid artery.

    Science.gov (United States)

    Gupta, Praveen K; Subramani, Jaganathan; Leo, Marie Dennis Marcus; Sikarwar, Anurag S; Parida, Subhashree; Prakash, Vellanki Ravi; Mishra, Santosh K

    2008-09-01

    The present study examined the role of voltage-gated potassium (K(v)) channels and myo-endothelial gap junctions in 4-aminopyridine-induced inhibition of acetylcholine-evoked endothelium-dependent relaxation and NO release in the rat carotid artery. The acetylcholine-induced relaxation was drastically inhibited by 94% and 82%, respectively in the presence of either 100 microM N(G)-nitro-l-arginine methyl ester (L-NAME) or 10 microM 1H-[1,2,4]oxadiazolo[4,3,a]quinoxalin-1-one (ODQ), while it was abolished following endothelium removal. 4-aminopyridine (1 mM), a preferential blocker of the K(v) channels significantly decreased the vasodilator potency, as well as efficacy of acetylcholine (pD(2) 5.7+/-0.09, R(max) 86.1+/-3.5% versus control 6.7+/-0.10 R(max) 106+/-3.5%, n=6), but had no effect on the relaxations elicited by either sodium nitroprusside (SNP) or 8-bromo-cyclic guanosine monophosphate (8-Br-cGMP). 4-AP (1 mM) also inhibited acetylcholine (3 microM)-stimulated nitrite release in the carotid artery segments (99.4+/-4.93 pmol/mg tissue weight wt; n=6 versus control 123.8+/-7.43 pmol/mg tissue weight wt, n=6). 18alpha-glycyrrhetinic acid (18alpha-GA, 5 microM), a gap junction blocker, completely prevented the inhibition of acetylcholine-induced relaxation, as well as nitrite release by 4-AP. In the pulmonary artery, however antagonism of acetylcholine-evoked relaxation by 4-AP was not reversed by 18alpha-GA. These results suggest that 4-AP-induced inhibition of endothelium-dependent relaxation and NO release involves electrical coupling between vascular smooth muscle and endothelial cells via myo-endothelial gap junctions in the rat carotid artery, but not in the pulmonary artery. Further, direct activation of 4-AP-sensitive vascular K(v) channels by endothelium-derived NO is not evident in the carotid blood vessel, while this appears to be an important mechanism of acetylcholine-induced relaxation in the pulmonary artery. PMID:18577383

  7. 线粒体电压依赖性阴离子通道与心血管疾病%Voltage-dependent Anion Channel and Cardiovascular Diseases

    Institute of Scientific and Technical Information of China (English)

    夏晶

    2013-01-01

    电压依赖性阴离子通道(VDAC)是位于线粒体外膜的通道蛋白,是线粒体与细胞质之间转运ATP以及其他代谢产物的主要通道,在线粒体代谢和细胞生长中发挥重要调控作用.近期研究发现,在心肌缺血再灌、糖尿病、心衰、高血压和动脉粥样硬化时,VDAC表达明显增加,引起细胞内钙离子循环紊乱、氧化应激,进而导致细胞凋亡,已成为心血管疾病研究的新热点.本文就VDAC的分子功能,调控及其在心血管疾病中的作用和相关机制进行综述.%The voltage-dependent anion channel (VDAC),a mitochondrial membrane channel protein located in the outer of mitochondrial membrane,is the main pathway between mitochondria and cytoplasm exchanging ADP,ATP,and other metabolites,and plays an important role in mitochondrial metabolism and cell growth.A growing evidence showed that VDAC was increased in cardiovascular diseases including myocardial ischemia and reperfusion,diabetes,heart failure,hypertension and atherosclerosis.The abnormal state of VDAC will result in cell death by inducing calcium cycling dysfunction and oxidative stress.And VDAC has become a hot topic in the field of cardiovascular diseases research.In this article,we will introduce the molecular function and regulation of VDAC and its role in cardiovascular diseases.

  8. The role of glutamate release on voltage-dependent anion channels (VDAC-mediated apoptosis in an eleven vessel occlusion model in rats.

    Directory of Open Access Journals (Sweden)

    Eunkuk Park

    Full Text Available Voltage-dependent anion channel (VDAC is the main protein in mitochondria-mediated apoptosis, and the modulation of VDAC may be induced by the excessive release of extracellular glutamate. This study examined the role of glutamate release on VDAC-mediated apoptosis in an eleven vessel occlusion model in rats. Male Sprague-Dawley rats (250-350 g were used for the 11 vessel occlusion ischemic model, which were induced for a 10-min transient occlusion. During the ischemic and initial reperfusion episode, the real-time monitoring of the extracellular glutamate concentration was measured using an amperometric microdialysis biosensor and the cerebral blood flow (CBF was monitored by laser-Doppler flowmetry. To confirm neuronal apoptosis, the brains were removed 72 h after ischemia to detect the neuron-specific nuclear protein and pro-apoptotic proteins (cleaved caspase-3, VDAC, p53 and BAX. The changes in the mitochondrial morphology were measured by atomic force microscopy. A decrease in the % of CBF was observed, and an increase in glutamate release was detected after the onset of ischemia, which continued to increase during the ischemic period. A significantly higher level of glutamate release was observed in the ischemia group. The increased glutamate levels in the ischemia group resulted in the activation of VDAC and pro-apoptotic proteins in the hippocampus with morphological alterations to the mitochondria. This study suggests that an increase in glutamate release promotes VDAC-mediated apoptosis in an 11 vessel occlusion ischemic model.

  9. Scanning mutagenesis of the I-II loop of the Cav2.2 calcium channel identifies residues Arginine 376 and Valine 416 as molecular determinants of voltage dependent G protein inhibition

    Directory of Open Access Journals (Sweden)

    Tedford Hugo W

    2010-02-01

    Full Text Available Abstract Direct interaction with the β subunit of the heterotrimeric G protein complex causes voltage-dependent inhibition of N-type calcium channels. To further characterize the molecular determinants of this interaction, we performed scanning mutagenesis of residues 372-387 and 410-428 of the N-type channel α1 subunit, in which individual residues were replaced by either alanine or cysteine. We coexpressed wild type Gβ1γ2 subunits with either wild type or point mutant N-type calcium channels, and voltage-dependent, G protein-mediated inhibition of the channels (VDI was assessed using patch clamp recordings. The resulting data indicate that Arg376 and Val416 of the α1 subunit, residues which are surface-exposed in the presence of the calcium channel β subunit, contribute significantly to the functional inhibition by Gβ1. To further characterize the roles of Arg376 and Val416 in this interaction, we performed secondary mutagenesis of these residues, coexpressing the resulting mutants with wild type Gβ1γ2 subunits and with several isoforms of the auxiliary β subunit of the N-type channel, again assessing VDI using patch clamp recordings. The results confirm the importance of Arg376 for G protein-mediated inhibition and show that a single amino acid substitution to phenylalanine drastically alters the abilities of auxiliary calcium channel subunits to regulate G protein inhibition of the channel.

  10. Voltage-Gated Calcium Channels in Nociception

    Science.gov (United States)

    Yasuda, Takahiro; Adams, David J.

    Voltage-gated calcium channels (VGCCs) are a large and functionally diverse group of membrane ion channels ubiquitously expressed throughout the central and peripheral nervous systems. VGCCs contribute to various physiological processes and transduce electrical activity into other cellular functions. This chapter provides an overview of biophysical properties of VGCCs, including regulation by auxiliary subunits, and their physiological role in neuronal functions. Subsequently, then we focus on N-type calcium (Cav2.2) channels, in particular their diversity and specific antagonists. We also discuss the role of N-type calcium channels in nociception and pain transmission through primary sensory dorsal root ganglion neurons (nociceptors). It has been shown that these channels are expressed predominantly in nerve terminals of the nociceptors and that they control neurotransmitter release. To date, important roles of N-type calcium channels in pain sensation have been elucidated genetically and pharmacologically, indicating that specific N-type calcium channel antagonists or modulators are particularly useful as therapeutic drugs targeting chronic and neuropathic pain.

  11. Hypermorphic mutation of the voltage-gated sodium channel encoding gene Scn10a causes a dramatic stimulus-dependent neurobehavioral phenotype

    OpenAIRE

    Blasius, Amanda L.; Dubin, Adrienne E.; Petrus, Matt J.; Lim, Byung-Kwan; Narezkina, Anna; Criado, José R.; Wills, Derek N.; Xia, Yu; Moresco, Eva Marie Y.; Ehlers, Cindy; Knowlton, Kirk U.; Patapoutian, Ardem; Beutler, Bruce

    2011-01-01

    The voltage-gated sodium channel Nav1.8 is known to function in the transmission of pain signals induced by cold, heat, and mechanical stimuli. Sequence variants of human Nav1.8 have been linked to altered cardiac conduction. We identified an allele of Scn10a encoding the α-subunit of Nav1.8 among mice homozygous for N-ethyl-N-nitrosourea-induced mutations. The allele creates a dominant neurobehavioral phenotype termed Possum, characterized by transient whole-body tonic immobility induced by ...

  12. R-phenibut binds to the α2-δ subunit of voltage-dependent calcium channels and exerts gabapentin-like anti-nociceptive effects.

    Science.gov (United States)

    Zvejniece, Liga; Vavers, Edijs; Svalbe, Baiba; Veinberg, Grigory; Rizhanova, Kristina; Liepins, Vilnis; Kalvinsh, Ivars; Dambrova, Maija

    2015-10-01

    Phenibut is clinically used anxiolytic, mood elevator and nootropic drug. R-phenibut is responsible for the pharmacological activity of racemic phenibut, and this activity correlates with its binding affinity for GABAB receptors. In contrast, S-phenibut does not bind to GABAB receptors. In this study, we assessed the binding affinities of R-phenibut, S-phenibut, baclofen and gabapentin (GBP) for the α2-δ subunit of the voltage-dependent calcium channel (VDCC) using a subunit-selective ligand, radiolabelled GBP. Binding experiments using rat brain membrane preparations revealed that the equilibrium dissociation constants (Kis) for R-phenibut, S-phenibut, baclofen and GBP were 23, 39, 156 and 0.05μM, respectively. In the pentylenetetrazole (PTZ)-induced seizure test, we found that at doses up to 100mg/kg, R-phenibut did not affect PTZ-induced seizures. The anti-nociceptive effects of R-phenibut were assessed using the formalin-induced paw-licking test and the chronic constriction injury (CCI) of the sciatic nerve model. Pre-treatment with R-phenibut dose-dependently decreased the nociceptive response during both phases of the test. The anti-nociceptive effects of R-phenibut in the formalin-induced paw-licking test were not blocked by the GABAB receptor-selective antagonist CGP35348. In addition, treatment with R- and S-phenibut alleviated the mechanical and thermal allodynia induced by CCI of the sciatic nerve. Our data suggest that the binding affinity of R-phenibut for the α2-δ subunit of the VDCC is 4 times higher than its affinity for the GABAB receptor. The anti-nociceptive effects of R-phenibut observed in the tests of formalin-induced paw licking and CCI of the sciatic nerve were associated with its effect on the α2-δ subunit of the VDCC rather than with its effects on GABAB receptors. In conclusion, our results provide experimental evidence for GBP-like, anti-nociceptive properties of R-phenibut, which might be used clinically to treat neuropathic pain

  13. Evidence from radiotracer flux and binding studies suggests the methylmercury blocks Ca channels in a voltage-dependent manner and may interact with more than one type of Ca channel

    International Nuclear Information System (INIS)

    The interactions of methylmercury (MeHg) with neuronal Ca channels were characterized by measuring the time course and voltage-dependence of MeHg's block of 45Ca influx into synaptosomes and the ability of MeHg to antagonize the binding of [125I]-ω-conotoxin GVIA (CgTx) to synaptosomes and pheochromocytoma (PC12) cells. In synaptosomes depolarized in 41.2 mM K+ solution, the block of 45Ca uptake by 50 μM MeHg increased with time; reaching a maximum effect of approximately 90% after 10s. In addition, block of 2s of 45Ca uptake by 100 μM MeHg increased from approximately 20% to 50% as [K+] was increased from 5 to 41.2 mM, indicating that MeHg blocks 45Ca uptake in a voltage-dependent manner. CgTx bound to a single high-affinity site in synaptosomes and PC12 cells with KD values of 317±58 and 266±60 pM and Bmax values of 593±89 and 88±19 fmol/mg protein, respectively. In synaptosomes, 100 μM MeHg significantly increased the KD value to 1900 pM. In PC12 cells, however, MeHg did not alter KD, but did decrease Bmax to 30±9 fmol/mg protein. These results suggest that MeHg interacts with the CgTx receptor in synaptosomes and PC12 cells, but that the receptors in these two systems are fundamentally different

  14. Research Progress in Voltage-dependent Anion Channel%电压依赖性阴离子通道的研究进展

    Institute of Scientific and Technical Information of China (English)

    戴琼艳(综述); 段满林(审校)

    2015-01-01

    电压依赖性阴离子通道( VDAC)位于线粒体外膜,形成了线粒体和代谢产物之间的分界,作为“守门员”控制着代谢产物的进出以及线粒体与其他细胞器的对话,同时,VDAC 也是线粒体介导凋亡的关键成员。除了调节线粒体的代谢和产能功能,VDAC 通过与不同配体和蛋白相互作用,作为细胞生存和死亡信号的汇聚点,这些功能可能使VDAC成为合理的新治疗发展的靶点。现就哺乳动物VDAC蛋白(尤其是VDAC1)的结构、功能、与相关蛋白的关系以及 VDAC 参与的疾病作一综述。%Found at the outer mitochondrial membrane , the voltage-dependent anion channel ( VDAC ) forms the main interface between the mitochondria and cellular metabolisms,thus functions as a gatekeeper, controlling cross-talk between mitochondria and the rest of the cell.Meanwhile,VDAC has also been recog-nized as a key protein in mitochondria-mediated apoptosis.In addition to regulating the metabolic and ener-getic functions of mitochondria,VDAC appears to be a convergence point for cell survival and cell death sig-nals via its association with various ligands and proteins ,making it to be a rational target for new therapeu-tics.Here is to make a review of mammalian VDAC ,especially VDAC1,addressing its structure,functions, the relationship between associated proteins and its involvement in several diseases .

  15. 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...

  16. Sine-wave electrical stimulation initiates a voltage-gated potassium channel-dependent soft tissue response characterized by induction of hemocyte recruitment and collagen deposition.

    Science.gov (United States)

    Franklin, Brandon M; Maroudas, Eleni; Osborn, Jeffrey L

    2016-06-01

    Soft tissue repair is a complex process that requires specific communication between multiple cell types to orchestrate effective restoration of physiological functions. Macrophages play a critical role in this wound healing process beginning at the onset of tissue injury. Understanding the signaling mechanisms involved in macrophage recruitment to the wound site is an essential step for developing more effective clinical therapies. Macrophages are known to respond to electrical fields, but the underlying cellular mechanisms mediating this response is unknown. This study demonstrated that low-amplitude sine-wave electrical stimulation (ES) initiates a soft tissue response in the absence of injury in Procambarus clarkii This cellular response was characterized by recruitment of macrophage-like hemocytes to the stimulation site indicated by increased hemocyte density at the site. ES also increased tissue collagen deposition compared to sham treatment (P < 0.05). Voltage-gated potassium (KV) channel inhibition with either 4-aminopyridine or astemizole decreased both hemocyte recruitment and collagen deposition compared to saline infusion (P < 0.05), whereas inhibition of calcium-permeable channels with ruthenium red did not affect either response to ES Thus, macrophage-like hemocytes in P. clarkii elicit a wound-like response to exogenous ES and this is accompanied by collagen deposition. This response is mediated by KV channels but independent of Ca(2+) channels. We propose a significant role for KV channels that extends beyond facilitating Ca(2+) transport via regulation of cellular membrane potentials during ES of soft tissue. PMID:27335435

  17. Chronic electroconvulsive stimulation but not chronic restraint stress modulates mRNA expression of voltage-dependent potassium channels Kv7.2 and Kv11.1 in the rat piriform cortex

    DEFF Research Database (Denmark)

    Hjæresen, Marie-Louise; Hageman, Ida; Plenge, Per;

    2008-01-01

    The mechanisms by which stress and electroconvulsive therapy exert opposite effects on the course of major depression are not known. Potential candidates might include the voltage-dependent potassium channels. Potassium channels play an important role in maintaining the resting membrane potential...... in situ hybridization. Repeated, but not acute, electroconvulsive stimulation increased Kv7.2 and Kv11.1 mRNA levels in the piriform cortex. In contrast, restraint stress had no significant effect on mRNA expression of Kv7.2, Kv11.1, or Kv11.3 in any of the brain regions examined. Thus, it appears...

  18. Fast and slow activation kinetics of voltage-gated sodium channels in molluscan neurons.

    Science.gov (United States)

    Gilly, W F; Gillette, R; McFarlane, M

    1997-05-01

    Whole cell patch-clamp recordings of Na current (I(Na)) were made under identical experimental conditions from isolated neurons from cephalopod (Loligo, Octopus) and gastropod (Aplysia, Pleurobranchaea, Doriopsilla) species to compare properties of activation gating. Voltage dependence of peak Na conductance (gNa) is very similar in all cases, but activation kinetics in the gastropod neurons studied are markedly slower. Kinetic differences are very pronounced only over the voltage range spanned by the gNa-voltage relation. At positive and negative extremes of voltage, activation and deactivation kinetics of I(Na) are practically indistinguishable in all species studied. Voltage-dependent rate constants underlying activation of the slow type of Na channel found in gastropods thus appear to be much more voltage dependent than are the equivalent rates in the universally fast type of channel that predominates in cephalopods. Voltage dependence of inactivation kinetics shows a similar pattern and is representative of activation kinetics for the two types of Na channels. Neurons with fast Na channels can thus make much more rapid adjustments in the number of open Na channels at physiologically relevant voltages than would be possible with only slow Na channels. This capability appears to be an adaptation that is highly evolved in cephalopods, which are well known for their high-speed swimming behaviors. Similarities in slow and fast Na channel subtypes in molluscan and mammalian neurons are discussed. PMID:9163364

  19. Structure and function of the voltage sensor of sodium channels probed by a beta-scorpion toxin. : Voltage Sensor of Sodium Channels Probed by a β-Scorpion Toxin

    OpenAIRE

    Cestèle, Sandrine; Yarov-Yarovoy, Vladimir; Qu, Yusheng; Sampieri, François; Scheuer, Todd; Catterall, William,

    2006-01-01

    Voltage sensing by voltage-gated sodium channels determines the electrical excitability of cells, but the molecular mechanism is unknown. beta-Scorpion toxins bind specifically to neurotoxin receptor site 4 and induce a negative shift in the voltage dependence of activation through a voltage sensor-trapping mechanism. Kinetic analysis showed that beta-scorpion toxin binds to the resting state, and subsequently the bound toxin traps the voltage sensor in the activated state in a voltage-depend...

  20. Removal of gating in voltage-dependent ClC-2 chloride channel by point mutations affecting the pore and C-terminus CBS-2 domain.

    Science.gov (United States)

    Yusef, Yamil R; Zúñiga, Leandro; Catalán, Marcelo; Niemeyer, María Isabel; Cid, L Pablo; Sepúlveda, Francisco V

    2006-04-01

    Functional and structural studies demonstrate that Cl(-) channels of the ClC family have a dimeric double-barrelled structure, with each monomer contributing an identical pore. Studies with ClC-0, the prototype ClC channel, show the presence of independent mechanisms gating the individual pores or both pores simultaneously. A single-point mutation in the CBS-2 domain of ClC-0 has been shown to abolish slow gating. We have taken advantage of the high conservation of CBS domains in ClC channels to test for the presence of a slow gate in ClC-2 by reproducing this mutation (H811A). ClC-2-H811A showed faster opening kinetics and opened at more positive potentials than ClC-2. There was no difference in [Cl(-)](i) dependence. Additional neutralization of a putative pore gate glutamate side chain (E207V) abolished all gating. Resolving slow and fast gating relaxations, however, revealed that the H811A mutation affected both fast and slow gating processes in ClC-2. This suggests that slow and fast gating in ClC-2 are coupled, perhaps with slow gating contributing to the operation of the pore E207 as a protopore gate. PMID:16469788

  1. Gate voltage dependent 1/f noise variance model based on physical noise generation mechanisms in n-channel metal-oxide-semiconductor field-effect transistors

    Science.gov (United States)

    Arai, Yukiko; Aoki, Hitoshi; Abe, Fumitaka; Todoroki, Shunichiro; Khatami, Ramin; Kazumi, Masaki; Totsuka, Takuya; Wang, Taifeng; Kobayashi, Haruo

    2015-04-01

    1/f noise is one of the most important characteristics for designing analog/RF circuits including operational amplifiers and oscillators. We have analyzed and developed a novel 1/f noise model in the strong inversion, saturation, and sub-threshold regions based on SPICE2 type model used in any public metal-oxide-semiconductor field-effect transistor (MOSFET) models developed by the University of California, Berkeley. Our model contains two noise generation mechanisms that are mobility and interface trap number fluctuations. Noise variability dependent on gate voltage is also newly implemented in our model. The proposed model has been implemented in BSIM4 model of a SPICE3 compatible circuit simulator. Parameters of the proposed model are extracted with 1/f noise measurements for simulation verifications. The simulation results show excellent agreements between measurement and simulations.

  2. Pandinus imperator scorpion venom blocks voltage-gated potassium channels in GH3 cells

    OpenAIRE

    Pappone, PA; Lucero, MT

    1988-01-01

    We examined the effects of Pandinus imperator scorpion venom on voltage-gated potassium channels in cultured clonal rat anterior pituitary cells (GH3 cells) using the gigohm-seal voltage-clamp method in the whole-cell configuration. We found that Pandinus venom blocks the voltage-gated potassium channels of GH3 cells in a voltage-dependent and dose-dependent manner. Crude venom in concentrations of 50-500 micrograms/ml produced 50-70% block of potassium currents measured at -20 mV, compared w...

  3. Dual Regulation of Voltage-Sensitive Ion Channels by PIP2

    Directory of Open Access Journals (Sweden)

    AldoARodríguez Menchaca

    2012-09-01

    Full Text Available Over the past 16 years, there has been an impressive number of ion channels shown to be sensitive to the major phosphoinositide in the plasma membrane, phosphatidilinositol 4,5-bisphosphate (PIP2. Among them are voltage-gated channels, which are crucial for both neuronal and cardiac excitability. Voltage-gated calcium (Cav channels were shown to be regulated bidirectionally by PIP2. On one hand, PIP2 stabilized their activity by reducing current rundown but on the other hand it produced a voltage-dependent inhibition by shifting the activation curve to more positive voltages. For voltage-gated potassium (Kv channels PIP2 was first shown to prevent N-type inactivation. Careful examination of the effects of PIP2 on the activation mechanism of Kv1.2 has shown a similar bidirectional regulation as in the Cav channels. The two effects could be distinguished kinetically, in terms of their sensitivities to PIP2 and by distinct molecular determinants. The rightward shift of the Kv1.2 voltage dependence implicated basic residues in the S4-S5 linker and was consistent with stabilization of the inactive state of the voltage sensor. A third type of a voltage-gated ion channel modulated by PIP2 is the hyperpolarization-activated cyclic nucleotide-gated (HCN channel. PIP2 has been shown to enhance the opening of HCN channels by shifting their voltage-dependent activation toward depolarized potentials. The sea urchin HCN channel, SpIH, showed again a PIP2-mediated bidirectional effect but in reverse order than the depolarization-activated Cav and Kv channels: a voltage-dependent potentiation, like the mammalian HCN channels, but also an inhibition of the cGMP-induced current activation. Just like the Kv1.2 channels, distinct molecular determinants underlied the PIP2 dual effects on SpIH channels. The dual regulation of these very different ion channels, all of which are voltage dependent, points to conserved mechanisms of regulation of these channels by PIP2.

  4. 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...

  5. Mechanism of electromechanical coupling in voltage-gated potassium channels

    Directory of Open Access Journals (Sweden)

    RikardBlunck

    2012-09-01

    Full Text Available Voltage-gated ion channels play a central role in the generation of action potentials in the nervous system. They are selective for one type of ion – sodium, calcium or potassium. Voltage-gated ion channels are composed of a central pore that allows ions to pass through the membrane and four peripheral voltage sensing domains that respond to changes in the membrane potential. Upon depolarization, voltage sensors in voltage-gated potassium channels (Kv undergo conformational changes driven by positive charges in the S4 segment and aided by pairwise electrostatic interactions with the surrounding voltage sensor. Structure-function relations of Kv channels have been investigated in detail, and the resulting models on the movement of the voltage sensors now converge to a consensus; the S4 segment undergoes a combined movement of rotation, tilt and vertical displacement in order to bring 3-4 e+ each through the electric field focused in this region. Nevertheless, the mechanism by which the voltage sensor movement leads to pore opening, the electromechanical coupling, is still not fully understood. Thus, recently, electromechanical coupling in different Kv channels has been investigated with a multitude of techniques including electrophysiology, 3D crystal structures, fluorescence spectroscopy and molecular dynamics simulations. Evidently, the S4-S5 linker, the covalent link between the voltage sensor and pore, plays a crucial role. The linker transfers the energy from the voltage sensor movement to the pore domain via an interaction with the S6 C-termini, which are pulled open during gating. In addition, other contact regions have been proposed. This review aims to provide (i an in-depth comparison of the molecular mechanisms of electromechanical coupling in different Kv channels; (ii insight as to how the voltage sensor and pore domain influence one another; and (iii theoretical predictions on the movement of the cytosolic face of the KV channels

  6. Contributions of Counter-Charge in a Potassium Channel Voltage-Sensor Domain

    Science.gov (United States)

    Pless, Stephan A.; Galpin, Jason D.; Niciforovic, Ana P.; Ahern, Christopher A.

    2016-01-01

    Voltage-sensor domains couple membrane potential to conformational changes in voltage-gated ion channels and phosphatases. Highly co-evolved acidic and aromatic side-chains assist the transfer of cationic side-chains across the transmembrane electric field during voltage-sensing. We investigated the functional contribution of negative electrostatic potentials from these residues to channel gating and voltage-sensing with unnatural amino acid mutagenesis, electrophysiology, voltage-clamp fluorometry and ab initio calculations. The data show that neutralization of two conserved acidic side-chains in transmembrane segments S2 and S3, Glu293 and Asp316 in Shaker potassium channels, have little functional effect on conductance-voltage relationships, although Glu293 appears to catalyze S4 movement. Our results suggest that neither Glu293 nor Asp316 engages in electrostatic state-dependent charge-charge interactions with S4, likely because they occupy, and possibly help create, a water-filled vestibule. PMID:21785425

  7. Topographical localization of the C-terminal region of the voltage-dependent sodium channel from Electrophorus electricus using antibodies raised against a synthetic peptide.

    OpenAIRE

    Gordon, R D; Fieles, W E; Schotland, D L; Hogue-Angeletti, R; Barchi, R. L.

    1987-01-01

    A peptide corresponding to amino acid residues 1783-1794 near the C terminus of the electric eel sodium channel primary sequence of the eel (Electrophorus electricus) sodium channel has been synthesized and used to raise an antiserum in rabbits. This antiserum specifically recognized the peptide in a solid-phase radioimmunoassay. Specificity of the antiserum for the native channel protein was shown by its specific binding to a 280-kDa protein in immunoblots of eel electroplax membrane protein...

  8. Endothelin induces two types of contractions of rat uterus: phasic contractions by way of voltage-dependent calcium channels and developing contractions through a second type of calcium channels

    International Nuclear Information System (INIS)

    Effects of endothelin on nonvascular smooth muscle have been examined using rat uterine horns and two modes of endothelin action have been revealed. Endothelin (0.3 nM) caused rhythmic contractions of isolated uterus in the presence of extracellular calcium. The rhythmic contractions were completely inhibited by calcium channel antagonists. These characteristics of endothelin-induced contractions were very similar to those induced by oxytocin. Binding assays using 125I-endothelin showed that endothelin and the calcium channel blockers did not compete for the binding sites. However, endothelin was unique in that it caused, in addition to rhythmic contractions, a slowly developing monophasic contraction that was insensitive to calcium channel blockers. This developing contraction became dominant at higher concentrations of endothelin and was also calcium dependent

  9. Endothelin induces two types of contractions of rat uterus: phasic contractions by way of voltage-dependent calcium channels and developing contractions through a second type of calcium channels

    Energy Technology Data Exchange (ETDEWEB)

    Kozuka, M.; Ito, T.; Hirose, S.; Takahashi, K.; Hagiwara, H.

    1989-02-28

    Effects of endothelin on nonvascular smooth muscle have been examined using rat uterine horns and two modes of endothelin action have been revealed. Endothelin (0.3 nM) caused rhythmic contractions of isolated uterus in the presence of extracellular calcium. The rhythmic contractions were completely inhibited by calcium channel antagonists. These characteristics of endothelin-induced contractions were very similar to those induced by oxytocin. Binding assays using /sup 125/I-endothelin showed that endothelin and the calcium channel blockers did not compete for the binding sites. However, endothelin was unique in that it caused, in addition to rhythmic contractions, a slowly developing monophasic contraction that was insensitive to calcium channel blockers. This developing contraction became dominant at higher concentrations of endothelin and was also calcium dependent.

  10. Voltage-Gated Proton Channels: Molecular Biology, Physiology, and Pathophysiology of the HV Family

    OpenAIRE

    DeCoursey, Thomas E.

    2013-01-01

    Voltage-gated proton channels (HV) are unique, in part because the ion they conduct is unique. HV channels are perfectly selective for protons and have a very small unitary conductance, both arguably manifestations of the extremely low H+ concentration in physiological solutions. They open with membrane depolarization, but their voltage dependence is strongly regulated by the pH gradient across the membrane (ΔpH), with the result that in most species they normally conduct only outward current...

  11. Topographical localization of the C-terminal region of the voltage-dependent sodium channel from Electrophorus electricus using antibodies raised against a synthetic peptide

    Energy Technology Data Exchange (ETDEWEB)

    Gordon, R.D.; Fieles, W.E.; Schotland, D.L.; Hogue-Angeletti, R.; Barchi, R.L.

    1987-01-01

    A peptide corresponding to amino acid residues 1783-1794 near the C terminus of the electric eel sodium channel primary sequence of the eel (Electrophorus electricus) sodium channel has been synthesized and used to raise an antiserum in rabbits. This antiserum specifically recognized the peptide in a solid-phase radioimmunoassay. Specificity of the antiserum for the native channel protein was shown by its specific binding to a 280-kDa protein in immunoblots of eel electroplax membrane proteins. The antiserum also specifically labeled the innervated membrane of the eel electroplax in immunofluorescent studies. The membrane topology of the peptide recognized by this antiserum was proved in binding studies using oriented electroplax membrane vesicles. These vesicles were 98% right-side-out as determined by (/sup 3/H)saxitoxin binding. Binding of the antipeptide antiserum to this fraction was measured before and after permeabilization with 0.01% saponin. Specific binding to intact vesicles was low, but this binding increased 10-fold after permeabilization, implying a cytoplasmic orientation for the peptide. Confirmation for this orientation was then sought by localizing the antibody bound to intact electroplax cells with immunogold electron microscopy. The data imply that the region of the sodium channel primary sequence near the C terminus that is recognized by the anitserum is localized on the cytoplasmic side of the membrane; this localization provides some further constraints on models of sodium channel tertiary structure.

  12. Topographical localization of the C-terminal region of the voltage-dependent sodium channel from Electrophorus electricus using antibodies raised against a synthetic peptide

    International Nuclear Information System (INIS)

    A peptide corresponding to amino acid residues 1783-1794 near the C terminus of the electric eel sodium channel primary sequence of the eel (Electrophorus electricus) sodium channel has been synthesized and used to raise an antiserum in rabbits. This antiserum specifically recognized the peptide in a solid-phase radioimmunoassay. Specificity of the antiserum for the native channel protein was shown by its specific binding to a 280-kDa protein in immunoblots of eel electroplax membrane proteins. The antiserum also specifically labeled the innervated membrane of the eel electroplax in immunofluorescent studies. The membrane topology of the peptide recognized by this antiserum was proved in binding studies using oriented electroplax membrane vesicles. These vesicles were 98% right-side-out as determined by [3H]saxitoxin binding. Binding of the antipeptide antiserum to this fraction was measured before and after permeabilization with 0.01% saponin. Specific binding to intact vesicles was low, but this binding increased 10-fold after permeabilization, implying a cytoplasmic orientation for the peptide. Confirmation for this orientation was then sought by localizing the antibody bound to intact electroplax cells with immunogold electron microscopy. The data imply that the region of the sodium channel primary sequence near the C terminus that is recognized by the anitserum is localized on the cytoplasmic side of the membrane; this localization provides some further constraints on models of sodium channel tertiary structure

  13. Time- and state-dependent effects of methanethiosulfonate ethylammonium (MTSEA) exposure differ between heart and skeletal muscle voltage-gated Na+ channels

    OpenAIRE

    O’Reilly, John P.; Shockett, Penny E.

    2011-01-01

    The substituted-cysteine scanning method (SCAM) is used to study conformational changes in proteins. Experiments using SCAM involve site-directed mutagenesis to replace native amino acids with cysteine and subsequent exposure to a methanethiosulfonate (MTS) reagent such as methanethiosulfonate ethylammonium (MTSEA). These reagents react with substituted-cysteines and can provide functional information about relative positions of amino acids within a protein. In the human heart voltage-gated N...

  14. Vascular smooth muscle cells express the alpha(1A) subunit of a P-/Q-type voltage-dependent Ca(2+)Channel, and It is functionally important in renal afferent arterioles

    DEFF Research Database (Denmark)

    Hansen, Pernille B. Lærkegaard; Jensen, Boye L.; Andreasen, D;

    2000-01-01

    In the present study, we tested whether the alpha(1A) subunit, which encodes a neuronal isoform of voltage-dependent Ca(2+) channels (VDCCs) (P-/Q-type), was present and functional in vascular smooth muscle and renal resistance vessels. By reverse transcription-polymerase chain reaction and...... Southern blotting analysis, mRNA encoding the alpha(1A) subunit was detected in microdissected rat preglomerular vessels and vasa recta, in cultures of rat preglomerular vascular smooth muscle cells (VSMCs), and in cultured rat mesangial cells. With immunoblots, alpha(1A) subunit protein was demonstrated...... in rat aorta, brain, aortic smooth muscle cells (A7r5), VSMCs, and mesangial cells. Immunolabeling with an anti-alpha(1A) antibody was positive in acid-macerated, microdissected preglomerular vessels and in A7r5 cells. Patch-clamp experiments on aortic A7r5 cells showed 22+/-4% (n=6) inhibition of...

  15. Ion Selectivity in Voltage-gated Biological Ion Channels

    OpenAIRE

    Finnerty, J. J.; Peyser, Alexander; Carloni, Paolo

    2014-01-01

    We demonstrate that a combination of calculating the exact electrostatic potential and approximate volume exclusion within the sub-nanometer selectivity filter of a biological ion channel is critical for estimating the selectivity of the ion channel. Biological membranes separate solutions of different ionic composition which can lead to significant transmembrane voltages and chemical potentials. Ion selective biological ion channels are used by nature to manage these potentials. The high cha...

  16. Poly(Ethylene Glycol)-Cholesterol Inhibits L-Type Ca2+ Channel Currents and Augments Voltage-Dependent Inactivation in A7r5 Cells

    OpenAIRE

    Ochi, Rikuo; Chettimada, Sukrutha; Gupte, Sachin A.

    2014-01-01

    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...

  17. Unique Bell-shaped Voltage-dependent Modulation of Na+ Channel Gating by Novel Insect-selective Toxins from the Spider Agelena orientalis*

    OpenAIRE

    Billen, Bert; Vassilevski, Alexander; Nikolsky, Anton; Debaveye, Sarah; Tytgat, Jan; Grishin, Eugene

    2010-01-01

    Spider venoms provide a highly valuable source of peptide toxins that act on a wide diversity of membrane-bound receptors and ion channels. In this work, we report isolation, biochemical analysis, and pharmacological characterization of a novel family of spider peptide toxins, designated β/δ-agatoxins. These toxins consist of 36–38 amino acid residues and originate from the venom of the agelenid funnel-web spider Agelena orientalis. The presented toxins show considerable amino acid sequence s...

  18. Ion channel voltage sensors: structure, function, and pathophysiology.

    Science.gov (United States)

    Catterall, William A

    2010-09-23

    Voltage-gated ion channels generate electrical signals in species from bacteria to man. Their voltage-sensing modules are responsible for initiation of action potentials and graded membrane potential changes in response to synaptic input and other physiological stimuli. Extensive structure-function studies, structure determination, and molecular modeling are now converging on a sliding-helix mechanism for electromechanical coupling in which outward movement of gating charges in the S4 transmembrane segments catalyzed by sequential formation of ion pairs pulls the S4-S5 linker, bends the S6 segment, and opens the pore. Impairment of voltage-sensor function by mutations in Na+ channels contributes to several ion channelopathies, and gating pore current conducted by mutant voltage sensors in Na(V)1.4 channels is the primary pathophysiological mechanism in hypokalemic periodic paralysis. The emerging structural model for voltage sensor function opens the way to development of a new generation of ion-channel drugs that act on voltage sensors rather than blocking the pore. PMID:20869590

  19. Voltage-gated potassium channel KCNV2 (Kv8.2) contributes to epilepsy susceptibility

    OpenAIRE

    Jorge, Benjamin S.; Campbell, Courtney M.; Miller, Alison R.; Rutter, Elizabeth D.; Gurnett, Christina A; Vanoye, Carlos G; George, Alfred L.; Kearney, Jennifer A.

    2011-01-01

    Mutations in voltage-gated ion channels are responsible for several types of epilepsy. Genetic epilepsies often exhibit variable severity in individuals with the same mutation, which may be due to variation in genetic modifiers. The Scn2aQ54 transgenic mouse model has a sodium channel mutation and exhibits epilepsy with strain-dependent severity. We previously mapped modifier loci that influence Scn2aQ54 phenotype severity and identified Kcnv2, encoding the voltage-gated potassium channel sub...

  20. Voltage Clamp Fluorimetry Reveals a Novel Outer Pore Instability in a Mammalian Voltage-gated Potassium Channel

    OpenAIRE

    Vaid, Moninder; Claydon, Thomas W.; Rezazadeh, Saman; Fedida, David

    2008-01-01

    Voltage-gated potassium (Kv) channel gating involves complex structural rearrangements that regulate the ability of channels to conduct K+ ions. Fluorescence-based approaches provide a powerful technique to directly report structural dynamics underlying these gating processes in Shaker Kv channels. Here, we apply voltage clamp fluorimetry, for the first time, to study voltage sensor motions in mammalian Kv1.5 channels. Despite the homology between Kv1.5 and the Shaker channel, attaching TMRM ...

  1. Mechanism of Inactivation in Voltage-Gated Na(+) Channels.

    Science.gov (United States)

    Gawali, V S; Todt, H

    2016-01-01

    Voltage-gated Na(+) channels (VGSCs) initiate action potentials thereby giving rise to rapid transmission of electrical signals along cell membranes and between cells. Depolarization of the cell membrane causes VGSCs to open but also gives rise to a nonconducting state termed inactivation. Inactivation of VGSCs serves a critical physiologic function as it determines the extent of excitability of neurons and of muscle cells. Depending on the time course of development and removal of inactivation both "fast-" and "slow"-inactivated states have been described. Evidence from mutagenesis studies suggests that fast inactivation is produced by a block of the internal vestibule by a tethered inactivation particle that has been mapped to the internal linker between domains III and IV. The motion of this linker may be regulated by parts of the internal C-terminus. The molecular mechanism of slow inactivation is less clear. However, aside from a high number of mutagenesis studies, the recent availability of 3D structures of crystallized prokaryotic VGSCs offers insights into the molecular motions associated with slow inactivation. One possible scenario is that slow movements of the voltage sensors are transmitted to the external vestibule giving rise to a conformational change of this region. This molecular rearrangement is transmitted to the S6 segments giving rise to collapse of the internal vestibule. PMID:27586291

  2. A Non-canonical Voltage-Sensing Mechanism Controls Gating in K2P K(+) Channels.

    Science.gov (United States)

    Schewe, Marcus; Nematian-Ardestani, Ehsan; Sun, Han; Musinszki, Marianne; Cordeiro, Sönke; Bucci, Giovanna; de Groot, Bert L; Tucker, Stephen J; Rapedius, Markus; Baukrowitz, Thomas

    2016-02-25

    Two-pore domain (K2P) K(+) channels are major regulators of excitability that endow cells with an outwardly rectifying background "leak" conductance. In some K2P channels, strong voltage-dependent activation has been observed, but the mechanism remains unresolved because they lack a canonical voltage-sensing domain. Here, we show voltage-dependent gating is common to most K2P channels and that this voltage sensitivity originates from the movement of three to four ions into the high electric field of an inactive selectivity filter. Overall, this ion-flux gating mechanism generates a one-way "check valve" within the filter because outward movement of K(+) induces filter opening, whereas inward movement promotes inactivation. Furthermore, many physiological stimuli switch off this flux gating mode to convert K2P channels into a leak conductance. These findings provide insight into the functional plasticity of a K(+)-selective filter and also refine our understanding of K2P channels and the mechanisms by which ion channels can sense voltage. PMID:26919430

  3. Ion Channel Voltage Sensors: Structure, Function, and Pathophysiology

    OpenAIRE

    Catterall, William A.

    2010-01-01

    Voltage-gated ion channels generate electrical signals in species from bacteria to man. Their voltage-sensing modules are responsible for initiation of action potentials and graded membrane potential changes in response to synaptic input and other physiological stimuli. Extensive structure-function studies, structure determination, and molecular modeling are now converging on a sliding-helix mechanism for electromechanical coupling in which outward movement of gating charges in the S4 transme...

  4. Measurement of voltage dependence of capacitance of planar bilayer lipid membrane with a patch clamp amplifier.

    OpenAIRE

    Toyama, S.; Nakamura, A; Toda, F

    1991-01-01

    The voltage dependence of capacitance was measured by using the setup which was almost the same as that for the study of ion channels. The coefficient which represents the voltage dependence of capacitance itself also changes as a function of the duration of voltage application if hexadecane is contained in bilayer lipid membrane (BLM). The method of Alvarez, O., and R. Latorre (1978. Biophys. J. 21:1-17) was extended to treat BLM with hexadecane.

  5. 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.

  6. VGIchan: Prediction and Classification of Voltage-Gated Ion Channels

    Institute of Scientific and Technical Information of China (English)

    Sudipto Saha; Jyoti Zack; Balvinder Singh; G.P.S. Raghava

    2006-01-01

    This study describes methods for predicting and classifying voltage-gated ion channels. Firstly, a standard support vector machine (SVM) method was developed for predicting ion channels by using amino acid composition and dipeptide composition, with an accuracy of 82.89% and 85.56%, respectively. The accuracy of this SVM method was improved from 85.56% to 89.11% when combined with PSIBLAST similarity search. Then we developed an SVM method for classifying ion channels (potassium, sodium, calcium, and chloride) by using dipeptide composition and achieved an overall accuracy of 96.89%. We further achieved a classification accuracy of 97.78% by using a hybrid method that combines dipeptidebased SVM and hidden Markov model methods. A web server VGIchan has been developed for predicting and classifying voltage-gated ion channels using the above approaches. VGIchan is freely available at www.imtech.res.in/raghava/vgichan/.

  7. Synthetic analogue of voltage-gated channels

    Science.gov (United States)

    Nguyen, Gael Hoang

    Fluids in nanopores with diameters of charges on the nanopore surface and the fluid within the nanopore. The influence of these electrostatic effects is determined from a characteristic screening length for the system known as the Debye length. Typical nanopore systems have diameters on the scale of the Debye length and require the consideration of electrostatic effects which do not need to be considered in micrometer systems. Nanofluidic components may be designed by considering the effect of these surface interactions to control ionic transport and incorporate them in devices.In this study we present single conically shaped polymer nanopores with controlled chemistry of the pore walls and pore opening diameter between 5 nm and 30 nm. Two types of pores were examined. The first group of pores contained a junction between two zones with different surface charges. The first group consists of bipolar diodes, which have a two zones composed of positive and negative surface charges, and unipolar diodes, which have two zones composed of a charged zone and a neutral zone. We find that both bipolar and unipolar diodes show a substantial increase in asymmetrical behavior of current-voltage curves over a conical nanopore with a uniform surface charge. Further is it shown that while both diodes show an increase in current rectification, bipolar diodes in particular have superior rectification abilities. The second group of pores are modified by tethering single-stranded DNA molecules to the pore wall. We find that the DNA occludes the narrow opening of nanopores and that the this occlusion effect decreases with an increase in the concentration of the electrolyte. The results are explained by the persistence length of DNA. At low KCl concentrations (10 mM) the molecules are in an extended configuration, thereby blocking the opening and restricting the flow of ionic current to a greater extent than for high salt concentrations. Attaching DNA creates a system with varying

  8. Ciguatoxins: Cyclic Polyether Modulators of Voltage-gated Iion Channel Function

    Directory of Open Access Journals (Sweden)

    Richard J. Lewis

    2006-04-01

    Full Text Available Ciguatoxins are cyclic polyether toxins, derived from marine dinoflagellates, which are responsible for the symptoms of ciguatera poisoning. Ingestion of tropical and subtropical fin fish contaminated by ciguatoxins results in an illness characterised by neurological, cardiovascular and gastrointestinal disorders. The pharmacology of ciguatoxins is characterised by their ability to cause persistent activation of voltage-gated sodium channels, to increase neuronal excitability and neurotransmitter release, to impair synaptic vesicle recycling, and to cause cell swelling. It is these effects, in combination with an action to block voltage-gated potassium channels at high doses, which are believed to underlie the complex of symptoms associated with ciguatera. This review examines the sources, structures and pharmacology of ciguatoxins. In particular, attention is placed on their cellular modes of actions to modulate voltage-gated ion channels and other Na+-dependent mechanisms in numerous cell types and to current approaches for detection and treatment of ciguatera.

  9. 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

  10. Voltage-Gated Proton Channels: Molecular Biology, Physiology, and Pathophysiology of the HV Family

    Science.gov (United States)

    2013-01-01

    Voltage-gated proton channels (HV) are unique, in part because the ion they conduct is unique. HV channels are perfectly selective for protons and have a very small unitary conductance, both arguably manifestations of the extremely low H+ concentration in physiological solutions. They open with membrane depolarization, but their voltage dependence is strongly regulated by the pH gradient across the membrane (ΔpH), with the result that in most species they normally conduct only outward current. The HV channel protein is strikingly similar to the voltage-sensing domain (VSD, the first four membrane-spanning segments) of voltage-gated K+ and Na+ channels. In higher species, HV channels exist as dimers in which each protomer has its own conduction pathway, yet gating is cooperative. HV channels are phylogenetically diverse, distributed from humans to unicellular marine life, and perhaps even plants. Correspondingly, HV functions vary widely as well, from promoting calcification in coccolithophores and triggering bioluminescent flashes in dinoflagellates to facilitating killing bacteria, airway pH regulation, basophil histamine release, sperm maturation, and B lymphocyte responses in humans. Recent evidence that hHV1 may exacerbate breast cancer metastasis and cerebral damage from ischemic stroke highlights the rapidly expanding recognition of the clinical importance of hHV1. PMID:23589829

  11. Voltage-gated proton channels: molecular biology, physiology, and pathophysiology of the H(V) family.

    Science.gov (United States)

    DeCoursey, Thomas E

    2013-04-01

    Voltage-gated proton channels (H(V)) are unique, in part because the ion they conduct is unique. H(V) channels are perfectly selective for protons and have a very small unitary conductance, both arguably manifestations of the extremely low H(+) concentration in physiological solutions. They open with membrane depolarization, but their voltage dependence is strongly regulated by the pH gradient across the membrane (ΔpH), with the result that in most species they normally conduct only outward current. The H(V) channel protein is strikingly similar to the voltage-sensing domain (VSD, the first four membrane-spanning segments) of voltage-gated K(+) and Na(+) channels. In higher species, H(V) channels exist as dimers in which each protomer has its own conduction pathway, yet gating is cooperative. H(V) channels are phylogenetically diverse, distributed from humans to unicellular marine life, and perhaps even plants. Correspondingly, H(V) functions vary widely as well, from promoting calcification in coccolithophores and triggering bioluminescent flashes in dinoflagellates to facilitating killing bacteria, airway pH regulation, basophil histamine release, sperm maturation, and B lymphocyte responses in humans. Recent evidence that hH(V)1 may exacerbate breast cancer metastasis and cerebral damage from ischemic stroke highlights the rapidly expanding recognition of the clinical importance of hH(V)1. PMID:23589829

  12. Shellfish Toxins Targeting Voltage-Gated Sodium Channels

    OpenAIRE

    Fan Zhang; Xunxun Xu; Tingting Li; Zhonghua Liu

    2013-01-01

    Voltage-gated sodium channels (VGSCs) play a central role in the generation and propagation of action potentials in excitable neurons and other cells and are targeted by commonly used local anesthetics, antiarrhythmics, and anticonvulsants. They are also common targets of neurotoxins including shellfish toxins. Shellfish toxins are a variety of toxic secondary metabolites produced by prokaryotic cyanobacteria and eukaryotic dinoflagellates in both marine and fresh water systems, which can acc...

  13. Cardiac voltage-gated calcium channel macromolecular complexes.

    Science.gov (United States)

    Rougier, Jean-Sébastien; Abriel, Hugues

    2016-07-01

    Over the past 20years, a new field of research, called channelopathies, investigating diseases caused by ion channel dysfunction has emerged. Cardiac ion channels play an essential role in the generation of the cardiac action potential. Investigators have largely determined the physiological roles of different cardiac ion channels, but little is known about the molecular determinants of their regulation. The voltage-gated calcium channel Cav1.2 shapes the plateau phase of the cardiac action potential and allows the influx of calcium leading to cardiomyocyte contraction. Studies suggest that the regulation of Cav1.2 channels is not uniform in working cardiomyocytes. The notion of micro-domains containing Cav1.2 channels and different calcium channel interacting proteins, called macro-molecular complex, has been proposed to explain these observations. The objective of this review is to summarize the currently known information on the Cav1.2 macromolecular complexes in the cardiac cell and discuss their implication in cardiac function and disorder. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel. PMID:26707467

  14. Voltage-Sensitive Ion Channels Biophysics of Molecular Excitability

    CERN Document Server

    Leuchtag, H. Richard

    2008-01-01

    Voltage-sensitive ion channels are macromolecules embedded in the membranes of nerve and muscle fibers of animals. Because of their physiological functions, biochemical structures and electrical switching properties, they are at an intersection of biology, chemistry and physics. Despite decades of intensive research under the traditional approach of gated structural pores, the relation between the structure of these molecules and their function remains enigmatic. This book critically examines physically oriented approaches not covered in other ion-channel books. It looks at optical and thermal as well as electrical data, and at studies in the frequency domain as well as in the time domain. Rather than presenting the reader with only an option of mechanistic models at an inappropriate pseudo-macroscopic scale, it emphasizes concepts established in organic chemistry and condensed state physics. The book’s approach to the understanding of these unique structures breaks with the unproven view of ion channels as...

  15. Voltage-gated sodium channels in taste bud cells

    Directory of Open Access Journals (Sweden)

    Williams Mark E

    2009-03-01

    Full Text Available Abstract Background Taste bud cells transmit information regarding the contents of food from taste receptors embedded in apical microvilli to gustatory nerve fibers innervating basolateral membranes. In particular, taste cells depolarize, activate voltage-gated sodium channels, and fire action potentials in response to tastants. Initial cell depolarization is attributable to sodium influx through TRPM5 in sweet, bitter, and umami cells and an undetermined cation influx through an ion channel in sour cells expressing PKD2L1, a candidate sour taste receptor. The molecular identity of the voltage-gated sodium channels that sense depolarizing signals and subsequently initiate action potentials coding taste information to gustatory nerve fibers is unknown. Results We describe the molecular and histological expression profiles of cation channels involved in electrical signal transmission from apical to basolateral membrane domains. TRPM5 was positioned immediately beneath tight junctions to receive calcium signals originating from sweet, bitter, and umami receptor activation, while PKD2L1 was positioned at the taste pore. Using mouse taste bud and lingual epithelial cells collected by laser capture microdissection, SCN2A, SCN3A, and SCN9A voltage-gated sodium channel transcripts were expressed in taste tissue. SCN2A, SCN3A, and SCN9A were expressed beneath tight junctions in subsets of taste cells. SCN3A and SCN9A were expressed in TRPM5 cells, while SCN2A was expressed in TRPM5 and PKD2L1 cells. HCN4, a gene previously implicated in sour taste, was expressed in PKD2L1 cells and localized to cell processes beneath the taste pore. Conclusion SCN2A, SCN3A and SCN9A voltage-gated sodium channels are positioned to sense initial depolarizing signals stemming from taste receptor activation and initiate taste cell action potentials. SCN2A, SCN3A and SCN9A gene products likely account for the tetrodotoxin-sensitive sodium currents in taste receptor cells.

  16. Chloride dependence of hyperpolarization-activated chloride channel gates.

    Science.gov (United States)

    Pusch, M; Jordt, S E; Stein, V; Jentsch, T J

    1999-03-01

    1. ClC proteins are a class of voltage-dependent Cl- channels with several members mutated in human diseases. The prototype ClC-0 Torpedo channel is a dimeric protein; each subunit forms a pore that can gate independently from the other one. A common slower gating mechanism acts on both pores simultaneously; slow gating activates ClC-0 at hyperpolarized voltages. The ClC-2 Cl- channel is also activated by hyperpolarization, as are some ClC-1 mutants (e.g. D136G) and wild-type (WT) ClC-1 at certain pH values. 2. We studied the dependence on internal Cl- ([Cl-]i) of the hyperpolarization-activated gates of several ClC channels (WT ClC-0, ClC-0 mutant P522G, ClC-1 mutant D136G and an N-terminal deletion mutant of ClC-2), by patch clamping channels expressed in Xenopus oocytes. 3. With all these channels, reducing [Cl-]i shifted activation to more negative voltages and reduced the maximal activation at most negative voltages. 4. We also investigated the external halide dependence of WT ClC-2 using two-electrode voltage-clamp recording. Reducing external Cl- ([Cl-]o) activated ClC-2 currents. Replacing [Cl-]o by the less permeant Br- reduced channel activity and accelerated deactivation. 5. Gating of the ClC-2 mutant K566Q in normal [Cl-]o resembled that of WT ClC-2 in low [Cl-]o, i.e. channels had a considerable open probability (Po) at resting membrane potential. Substituting external Cl- by Br- or I- led to a decrease in Po. 6. The [Cl-]i dependence of the hyperpolarization-activated gates of various ClC channels suggests a similar gating mechanism, and raises the possibility that the gating charge for the hyperpolarization-activated gate is provided by Cl-. 7. The external halide dependence of hyperpolarization-activated gating of ClC-2 suggests that it is mediated or modulated by anions as in other ClC channels. In contrast to the depolarization-activated fast gates of ClC-0 and ClC-1, the absence of Cl- favours channel opening. Lysine 556 may be important for the

  17. Unfolding of a Temperature-Sensitive Domain Controls Voltage-Gated Channel Activation.

    Science.gov (United States)

    Arrigoni, Cristina; Rohaim, Ahmed; Shaya, David; Findeisen, Felix; Stein, Richard A; Nurva, Shailika Reddy; Mishra, Smriti; Mchaourab, Hassane S; Minor, Daniel L

    2016-02-25

    Voltage-gated ion channels (VGICs) are outfitted with diverse cytoplasmic domains that impact function. To examine how such elements may affect VGIC behavior, we addressed how the bacterial voltage-gated sodium channel (BacNa(V)) C-terminal cytoplasmic domain (CTD) affects function. Our studies show that the BacNa(V) CTD exerts a profound influence on gating through a temperature-dependent unfolding transition in a discrete cytoplasmic domain, the neck domain, proximal to the pore. Structural and functional studies establish that the BacNa(V) CTD comprises a bi-partite four-helix bundle that bears an unusual hydrophilic core whose integrity is central to the unfolding mechanism and that couples directly to the channel activation gate. Together, our findings define a general principle for how the widespread four-helix bundle cytoplasmic domain architecture can control VGIC responses, uncover a mechanism underlying the diverse BacNa(V) voltage dependencies, and demonstrate that a discrete domain can encode the temperature-dependent response of a channel. PMID:26919429

  18. Marine Toxins That Target Voltage-gated Sodium Channels

    Directory of Open Access Journals (Sweden)

    Robert J. French

    2006-04-01

    Full Text Available Abstract: Eukaryotic, voltage-gated sodium (NaV channels are large membrane proteins which underlie generation and propagation of rapid electrical signals in nerve, muscle and heart. Nine different NaV receptor sites, for natural ligands and/or drugs, have been identified, based on functional analyses and site-directed mutagenesis. In the marine ecosystem, numerous toxins have evolved to disrupt NaV channel function, either by inhibition of current flow through the channels, or by modifying the activation and inactivation gating processes by which the channels open and close. These toxins function in their native environment as offensive or defensive weapons in prey capture or deterrence of predators. In composition, they range from organic molecules of varying size and complexity to peptides consisting of ~10-70 amino acids. We review the variety of known NaV-targeted marine toxins, outlining, where known, their sites of interaction with the channel protein and their functional effects. In a number of cases, these natural ligands have the potential applications as drugs in clinical settings, or as models for drug development.

  19. Biophysical Adaptations of Prokaryotic Voltage-Gated Sodium Channels.

    Science.gov (United States)

    Vien, T N; DeCaen, P G

    2016-01-01

    This chapter describes the adaptive features found in voltage-gated sodium channels (NaVs) of prokaryotes and eukaryotes. These two families are distinct, having diverged early in evolutionary history but maintain a surprising degree of convergence in function. While prokaryotic NaVs are required for growth and motility, eukaryotic NaVs selectively conduct fast electrical currents for short- and long-range signaling across cell membranes in mammalian organs. Current interest in prokaryotic NaVs is stoked by their resolved high-resolution structures and functional features which are reminiscent of eukaryotic NaVs. In this chapter, comparisons between eukaryotic and prokaryotic NaVs are made to highlight the shared and unique aspects of ion selectivity, voltage sensitivity, and pharmacology. Examples of prokaryotic and eukaryotic NaV convergent evolution will be discussed within the context of their structural features. PMID:27586280

  20. Interfacial gating triad is crucial for electromechanical transduction in voltage-activated potassium channels

    Science.gov (United States)

    Chowdhury, Sandipan; Haehnel, Benjamin M.

    2014-01-01

    Voltage-dependent potassium channels play a crucial role in electrical excitability and cellular signaling by regulating potassium ion flux across membranes. Movement of charged residues in the voltage-sensing domain leads to a series of conformational changes that culminate in channel opening in response to changes in membrane potential. However, the molecular machinery that relays these conformational changes from voltage sensor to the pore is not well understood. Here we use generalized interaction-energy analysis (GIA) to estimate the strength of site-specific interactions between amino acid residues putatively involved in the electromechanical coupling of the voltage sensor and pore in the outwardly rectifying KV channel. We identified candidate interactors at the interface between the S4–S5 linker and the pore domain using a structure-guided graph theoretical approach that revealed clusters of conserved and closely packed residues. One such cluster, located at the intracellular intersubunit interface, comprises three residues (arginine 394, glutamate 395, and tyrosine 485) that interact with each other. The calculated interaction energies were 3–5 kcal, which is especially notable given that the net free-energy change during activation of the Shaker KV channel is ∼14 kcal. We find that this triad is delicately maintained by balance of interactions that are responsible for structural integrity of the intersubunit interface while maintaining sufficient flexibility at a critical gating hinge for optimal transmission of force to the pore gate. PMID:25311635

  1. Voltage-gated Ca2+ channel in mouse myeloma cells.

    OpenAIRE

    Fukushima, Y; Hagiwara, S.

    1983-01-01

    Electrical properties of the cell membrane were studied in the neoplastic lymphocyte, mouse myeloma cell line S194, by using the whole-cell patch clamp technique. Inward Ca2+ currents due to voltage-gated Ca2+ channels were found. The current, which decayed exponentially after reaching a peak, was first activated at about -50 mV and attained its maximum peak amplitude at about -20 mV in a 10 mM Ca2+ solution. Outward current was negligible for the potential range more negative than +30 mV. Th...

  2. 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.

  3. Wiretap Channel with Action-Dependent Channel State Information

    Directory of Open Access Journals (Sweden)

    Bin Dai

    2013-01-01

    Full Text Available In this paper, we investigate the model of wiretap channel with action-dependent channel state information. Given the message to be communicated, the transmitter chooses an action sequence that affects the formation of the channel states, and then generates the channel input sequence based on the state sequence and the message. The main channel and the wiretap channel are two discrete memoryless channels (DMCs, and they are connected with the legitimate receiver and the wiretapper, respectively. Moreover, the transition probability distribution of the main channel depends on the channel state. Measuring wiretapper’s uncertainty about the message by equivocation, inner and outer bounds on the capacity-equivocation region are provided both for the case where the channel inputs are allowed to depend non-causally on the state sequence and the case where they are restricted to causal dependence. Furthermore, the secrecy capacities for both cases are bounded, which provide the best transmission rate with perfect secrecy. The result is further explained via a binary example.

  4. Computational identification of residues that modulate voltage sensitivity of voltage-gated potassium channels

    Directory of Open Access Journals (Sweden)

    Li Bin

    2005-08-01

    Full Text Available Abstract Background Studies of the structure-function relationship in proteins for which no 3D structure is available are often based on inspection of multiple sequence alignments. Many functionally important residues of proteins can be identified because they are conserved during evolution. However, residues that vary can also be critically important if their variation is responsible for diversity of protein function and improved phenotypes. If too few sequences are studied, the support for hypotheses on the role of a given residue will be weak, but analysis of large multiple alignments is too complex for simple inspection. When a large body of sequence and functional data are available for a protein family, mature data mining tools, such as machine learning, can be applied to extract information more easily, sensitively and reliably. We have undertaken such an analysis of voltage-gated potassium channels, a transmembrane protein family whose members play indispensable roles in electrically excitable cells. Results We applied different learning algorithms, combined in various implementations, to obtain a model that predicts the half activation voltage of a voltage-gated potassium channel based on its amino acid sequence. The best result was obtained with a k-nearest neighbor classifier combined with a wrapper algorithm for feature selection, producing a mean absolute error of prediction of 7.0 mV. The predictor was validated by permutation test and evaluation of independent experimental data. Feature selection identified a number of residues that are predicted to be involved in the voltage sensitive conformation changes; these residues are good target candidates for mutagenesis analysis. Conclusion Machine learning analysis can identify new testable hypotheses about the structure/function relationship in the voltage-gated potassium channel family. This approach should be applicable to any protein family if the number of training examples and

  5. Adaptive evolution of voltage-gated sodium channels: The first 800 million years

    OpenAIRE

    Zakon, Harold H.

    2012-01-01

    Voltage-gated Na+-permeable (Nav) channels form the basis for electrical excitability in animals. Nav channels evolved from Ca2+ channels and were present in the common ancestor of choanoflagellates and animals, although this channel was likely permeable to both Na+ and Ca2+. Thus, like many other neuronal channels and receptors, Nav channels predated neurons. Invertebrates possess two Nav channels (Nav1 and Nav2), whereas vertebrate Nav channels are of the Nav1 family. Approximately 500 Mya ...

  6. Photocontrol of Voltage-Gated Ion Channel Activity by Azobenzene Trimethylammonium Bromide in Neonatal Rat Cardiomyocytes.

    Directory of Open Access Journals (Sweden)

    Sheyda R Frolova

    Full Text Available The ability of azobenzene trimethylammonium bromide (azoTAB to sensitize cardiac tissue excitability to light was recently reported. The dark, thermally relaxed trans- isomer of azoTAB suppressed spontaneous activity and excitation propagation speed, whereas the cis- isomer had no detectable effect on the electrical properties of cardiomyocyte monolayers. As the membrane potential of cardiac cells is mainly controlled by activity of voltage-gated ion channels, this study examined whether the sensitization effect of azoTAB was exerted primarily via the modulation of voltage-gated ion channel activity. The effects of trans- and cis- isomers of azoTAB on voltage-dependent sodium (INav, calcium (ICav, and potassium (IKv currents in isolated neonatal rat cardiomyocytes were investigated using the whole-cell patch-clamp technique. The experiments showed that azoTAB modulated ion currents, causing suppression of sodium (Na+ and calcium (Ca2+ currents and potentiation of net potassium (K+ currents. This finding confirms that azoTAB-effect on cardiac tissue excitability do indeed result from modulation of voltage-gated ion channels responsible for action potential.

  7. Dynamic memory of a single voltage-gated potassium ion channel: A stochastic nonequilibrium thermodynamic analysis

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Kinshuk, E-mail: kbpchem@gmail.com [Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Kolkata 700 009 (India)

    2015-05-14

    In this work, we have studied the stochastic response of a single voltage-gated potassium ion channel to a periodic external voltage that keeps the system out-of-equilibrium. The system exhibits memory, resulting from time-dependent driving, that is reflected in terms of dynamic hysteresis in the current-voltage characteristics. The hysteresis loop area has a maximum at some intermediate voltage frequency and disappears in the limits of low and high frequencies. However, the (average) dissipation at long-time limit increases and finally goes to saturation with rising frequency. This raises the question: how diminishing hysteresis can be associated with growing dissipation? To answer this, we have studied the nonequilibrium thermodynamics of the system and analyzed different thermodynamic functions which also exhibit hysteresis. Interestingly, by applying a temporal symmetry analysis in the high-frequency limit, we have analytically shown that hysteresis in some of the periodic responses of the system does not vanish. On the contrary, the rates of free energy and internal energy change of the system as well as the rate of dissipative work done on the system show growing hysteresis with frequency. Hence, although the current-voltage hysteresis disappears in the high-frequency limit, the memory of the ion channel is manifested through its specific nonequilibrium thermodynamic responses.

  8. Dynamic memory of a single voltage-gated potassium ion channel: A stochastic nonequilibrium thermodynamic analysis.

    Science.gov (United States)

    Banerjee, Kinshuk

    2015-05-14

    In this work, we have studied the stochastic response of a single voltage-gated potassium ion channel to a periodic external voltage that keeps the system out-of-equilibrium. The system exhibits memory, resulting from time-dependent driving, that is reflected in terms of dynamic hysteresis in the current-voltage characteristics. The hysteresis loop area has a maximum at some intermediate voltage frequency and disappears in the limits of low and high frequencies. However, the (average) dissipation at long-time limit increases and finally goes to saturation with rising frequency. This raises the question: how diminishing hysteresis can be associated with growing dissipation? To answer this, we have studied the nonequilibrium thermodynamics of the system and analyzed different thermodynamic functions which also exhibit hysteresis. Interestingly, by applying a temporal symmetry analysis in the high-frequency limit, we have analytically shown that hysteresis in some of the periodic responses of the system does not vanish. On the contrary, the rates of free energy and internal energy change of the system as well as the rate of dissipative work done on the system show growing hysteresis with frequency. Hence, although the current-voltage hysteresis disappears in the high-frequency limit, the memory of the ion channel is manifested through its specific nonequilibrium thermodynamic responses. PMID:25978913

  9. Dynamic memory of a single voltage-gated potassium ion channel: A stochastic nonequilibrium thermodynamic analysis

    International Nuclear Information System (INIS)

    In this work, we have studied the stochastic response of a single voltage-gated potassium ion channel to a periodic external voltage that keeps the system out-of-equilibrium. The system exhibits memory, resulting from time-dependent driving, that is reflected in terms of dynamic hysteresis in the current-voltage characteristics. The hysteresis loop area has a maximum at some intermediate voltage frequency and disappears in the limits of low and high frequencies. However, the (average) dissipation at long-time limit increases and finally goes to saturation with rising frequency. This raises the question: how diminishing hysteresis can be associated with growing dissipation? To answer this, we have studied the nonequilibrium thermodynamics of the system and analyzed different thermodynamic functions which also exhibit hysteresis. Interestingly, by applying a temporal symmetry analysis in the high-frequency limit, we have analytically shown that hysteresis in some of the periodic responses of the system does not vanish. On the contrary, the rates of free energy and internal energy change of the system as well as the rate of dissipative work done on the system show growing hysteresis with frequency. Hence, although the current-voltage hysteresis disappears in the high-frequency limit, the memory of the ion channel is manifested through its specific nonequilibrium thermodynamic responses

  10. The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential.

    Science.gov (United States)

    Zamponi, Gerald W; Striessnig, Joerg; Koschak, Alexandra; Dolphin, Annette C

    2015-10-01

    Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type Ca(V)1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (Ca(V)3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (Ca(V)2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., Ca(V)1.2 and Ca(V)1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective Ca(V)1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson's disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep

  11. Shellfish Toxins Targeting Voltage-Gated Sodium Channels

    Directory of Open Access Journals (Sweden)

    Fan Zhang

    2013-11-01

    Full Text Available Voltage-gated sodium channels (VGSCs play a central role in the generation and propagation of action potentials in excitable neurons and other cells and are targeted by commonly used local anesthetics, antiarrhythmics, and anticonvulsants. They are also common targets of neurotoxins including shellfish toxins. Shellfish toxins are a variety of toxic secondary metabolites produced by prokaryotic cyanobacteria and eukaryotic dinoflagellates in both marine and fresh water systems, which can accumulate in marine animals via the food chain. Consumption of shellfish toxin-contaminated seafood may result in potentially fatal human shellfish poisoning. This article provides an overview of the structure, bioactivity, and pharmacology of shellfish toxins that act on VGSCs, along with a brief discussion on their pharmaceutical potential for pain management.

  12. Molecular identity of dendritic voltage-gated sodium channels.

    Science.gov (United States)

    Lorincz, Andrea; Nusser, Zoltan

    2010-05-14

    Active invasion of the dendritic tree by action potentials (APs) generated in the axon is essential for associative synaptic plasticity and neuronal ensemble formation. In cortical pyramidal cells (PCs), this AP back-propagation is supported by dendritic voltage-gated Na+ (Nav) channels, whose molecular identity is unknown. Using a highly sensitive electron microscopic immunogold technique, we revealed the presence of the Nav1.6 subunit in hippocampal CA1 PC proximal and distal dendrites. Here, the subunit density is lower by a factor of 35 to 80 than that found in axon initial segments. A gradual decrease in Nav1.6 density along the proximodistal axis of the dendritic tree was also detected without any labeling in dendritic spines. Our results reveal the characteristic subcellular distribution of the Nav1.6 subunit, identifying this molecule as a key substrate enabling dendritic excitability. PMID:20466935

  13. Modulation of Neuronal Voltage-Activated Calcium and Sodium Channels by Polyamines and pH

    OpenAIRE

    Chen, Wenyan; Harnett, Mark T.; Smith, Stephen M.

    2007-01-01

    The endogenous polyamines spermine, spermidine and putrescine are present at high concentrations inside neurons and can be released into the extracellular space where they have been shown to modulate ion channels. Here, we have examined polyamine modulation of voltage-activated Ca2+ channels (VACCs) and voltage-activated Na+ channels (VANCs) in rat superior cervical ganglion neurons using whole-cell voltage-clamp at physiological divalent concentrations. Polyamines inhibited VACCs in a concen...

  14. A 16 channel high-voltage driver with 14 bit resolution for driving piezoelectric actuators

    OpenAIRE

    Pierco, Ramses; Torfs, Guy; Verbrugghe, Jochen; Bakeroot, Benoit; Bauwelinck, Johan

    2015-01-01

    A high-voltage, 16 channel driver with a maximum voltage of 72 volt and 14 bit resolution in a high-voltage CMOS (HV-CMOS) process is presented. This design incorporates a 14 bit monotonic by design DAC together with a high-voltage complementary class AB output stage for each channel. All 16 channels are used for driving a piezoelectric actuator within the control loop of a micropositioning system. Since the output voltages are static most of the time, a class AB amplifier is used, implementi...

  15. Molecular Interactions between Tarantula Toxins and Low-Voltage-Activated Calcium Channels

    OpenAIRE

    Autoosa Salari; Benjamin S. Vega; Milescu, Lorin S.; Mirela Milescu

    2016-01-01

    Few gating-modifier toxins have been reported to target low-voltage-activated (LVA) calcium channels, and the structural basis of toxin sensitivity remains incompletely understood. Studies of voltage-gated potassium (Kv) channels have identified the S3b–S4 “paddle motif,” which moves at the protein-lipid interface to drive channel opening, as the target for these amphipathic neurotoxins. Voltage-gated calcium (Cav) channels contain four homologous voltage sensor domains, suggesting multiple t...

  16. Voltage-Gated Ion Channels in Cancer Cell Proliferation

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Vidhya R.; Perez-Neut, Mathew [Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago 2160 S. 1st Ave, Maywood, IL 60153 (United States); Kaja, Simon [Department of Ophthalmology and Vision Research Center, School of Medicine, University of Missouri-Kansas City, 2411 Holmes St., Kansas City, MO 64108 (United States); Gentile, Saverio, E-mail: sagentile@luc.edu [Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago 2160 S. 1st Ave, Maywood, IL 60153 (United States)

    2015-05-22

    Changes of the electrical charges across the surface cell membrane are absolutely necessary to maintain cellular homeostasis in physiological as well as in pathological conditions. The opening of ion channels alter the charge distribution across the surface membrane as they allow the diffusion of ions such as K{sup +}, Ca{sup ++}, Cl{sup −}, Na{sup +}. Traditionally, voltage-gated ion channels (VGIC) are known to play fundamental roles in controlling rapid bioelectrical signaling including action potential and/or contraction. However, several investigations have revealed that these classes of proteins can also contribute significantly to cell mitotic biochemical signaling, cell cycle progression, as well as cell volume regulation. All these functions are critically important for cancer cell proliferation. Interestingly, a variety of distinct VGICs are expressed in different cancer cell types, including metastasis but not in the tissues from which these tumors were generated. Given the increasing evidence suggesting that VGIC play a major role in cancer cell biology, in this review we discuss the role of distinct VGIC in cancer cell proliferation and possible therapeutic potential of VIGC pharmacological manipulation.

  17. Voltage Gated Ion Channel Function: Gating, Conduction, and the Role of Water and Protons

    Directory of Open Access Journals (Sweden)

    Alisher M. Kariev

    2012-02-01

    Full Text Available Ion channels, which are found in every biological cell, regulate the concentration of electrolytes, and are responsible for multiple biological functions, including in particular the propagation of nerve impulses. The channels with the latter function are gated (opened by a voltage signal, which allows Na+ into the cell and K+ out. These channels have several positively charged amino acids on a transmembrane domain of their voltage sensor, and it is generally considered, based primarily on two lines of experimental evidence, that these charges move with respect to the membrane to open the channel. At least three forms of motion, with greatly differing extents and mechanisms of motion, have been proposed. There is a “gating current”, a capacitative current preceding the channel opening, that corresponds to several charges (for one class of channel typically 12–13 crossing the membrane field, which may not require protein physically crossing a large fraction of the membrane. The coupling to the opening of the channel would in these models depend on the motion. The conduction itself is usually assumed to require the “gate” of the channel to be pulled apart to allow ions to enter as a section of the protein partially crosses the membrane, and a selectivity filter at the opposite end of the channel determines the ion which is allowed to pass through. We will here primarily consider K+ channels, although Na+ channels are similar. We propose that the mechanism of gating differs from that which is generally accepted, in that the positively charged residues need not move (there may be some motion, but not as gating current. Instead, protons may constitute the gating current, causing the gate to open; opening consists of only increasing the diameter at the gate from approximately 6 Å to approximately 12 Å. We propose in addition that the gate oscillates rather than simply opens, and the ion experiences a barrier to its motion across the

  18. Modulation of metabolic communication through gap junction channels by transjunctional voltage; synergistic and antagonistic effects of gating and ionophoresis

    OpenAIRE

    Palacios-Prado, Nicolás; Bukauskas, Feliksas F.

    2011-01-01

    Gap junction (GJ) channels assembled from connexin (Cx) proteins provide a structural basis for direct electrical and metabolic cell-cell communication. Here, we focus on gating and permeability properties of Cx43/Cx45 heterotypic GJs exhibiting asymmetries of both voltage-gating and transjunctional flux (Jj) of fluorescent dyes depending on transjunctional voltage (Vj). Relatively small differences in the resting potential of communicating cells can substantially reduce or enhance this flux ...

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

    Institute of Scientific and Technical Information of China (English)

    Nasrin NFJATBAKHSH; Zhong-ping FENG

    2011-01-01

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

  20. New Role of P/Q-type Voltage-gated Calcium Channels

    DEFF Research Database (Denmark)

    Hansen, Pernille B L

    2015-01-01

    Voltage-gated calcium channels are important for the depolarization-evoked contraction of vascular smooth muscle cells (SMCs), with L-type channels being the classical channel involved in this mechanism. However, it has been demonstrated that the CaV2.1 subunit, which encodes a neuronal isoform of...... the voltage-gated calcium channels (P/Q-type), is also expressed and contributes functionally to contraction of renal blood vessels in both mice and humans. Furthermore, preglomerular vascular SMCs and aortic SMCs coexpress L-, P-, and Q-type calcium channels within the same cell. Calcium channel...... blockers are widely used as pharmacological treatments. However, calcium channel antagonists vary in their selectivity for the various calcium channel subtypes, and the functional contribution from P/Q-type channels as compared with L-type should be considered. Confirming the presence of P/Q-type voltage...

  1. Hydrogen bonds as molecular timers for slow inactivation in voltage-gated potassium channels

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Galpin, Jason D; Niciforovic, Ana P;

    2013-01-01

    Voltage-gated potassium (Kv) channels enable potassium efflux and membrane repolarization in excitable tissues. Many Kv channels undergo a progressive loss of ion conductance in the presence of a prolonged voltage stimulus, termed slow inactivation, but the atomic determinants that regulate the k...... subunit(s). DOI: http://dx.doi.org/10.7554/eLife.01289.001....

  2. Voltage-Gated Calcium Channel Antagonists and Traumatic Brain Injury

    Directory of Open Access Journals (Sweden)

    Bruce Lyeth

    2013-06-01

    Full Text Available Traumatic brain injury (TBI is a leading cause of death and disability in the United States. Despite more than 30 years of research, no pharmacological agents have been identified that improve neurological function following TBI. However, several lines of research described in this review provide support for further development of voltage gated calcium channel (VGCC antagonists as potential therapeutic agents. Following TBI, neurons and astrocytes experience a rapid and sometimes enduring increase in intracellular calcium ([Ca2+]i. These fluxes in [Ca2+]i drive not only apoptotic and necrotic cell death, but also can lead to long-term cell dysfunction in surviving cells. In a limited number of in vitro experiments, both L-type and N-type VGCC antagonists successfully reduced calcium loads as well as neuronal and astrocytic cell death following mechanical injury. In rodent models of TBI, administration of VGCC antagonists reduced cell death and improved cognitive function. It is clear that there is a critical need to find effective therapeutics and rational drug delivery strategies for the management and treatment of TBI, and we believe that further investigation of VGCC antagonists should be pursued before ruling out the possibility of successful translation to the clinic.

  3. Voltage-gated calcium channel autoimmune cerebellar degeneration

    Science.gov (United States)

    McKasson, Marilyn; Clawson, Susan A.; Hill, Kenneth E.; Wood, Blair; Carlson, Noel; Bromberg, Mark; Greenlee, John E.

    2016-01-01

    Objectives: To describe response to treatment in a patient with autoantibodies against voltage-gated calcium channels (VGCCs) who presented with autoimmune cerebellar degeneration and subsequently developed Lambert-Eaton myasthenic syndrome (LEMS), and to study the effect of the patient's autoantibodies on Purkinje cells in rat cerebellar slice cultures. Methods: Case report and study of rat cerebellar slice cultures incubated with patient VGCC autoantibodies. Results: A 53-year-old man developed progressive incoordination with ataxic speech. Laboratory evaluation revealed VGCC autoantibodies without other antineuronal autoantibodies. Whole-body PET scans 6 and 12 months after presentation detected no malignancy. The patient improved significantly with IV immunoglobulin G (IgG), prednisone, and mycophenolate mofetil, but worsened after IV IgG was halted secondary to aseptic meningitis. He subsequently developed weakness with electrodiagnostic evidence of LEMS. The patient's IgG bound to Purkinje cells in rat cerebellar slice cultures, followed by neuronal death. Reactivity of the patient's autoantibodies with VGCCs was confirmed by blocking studies with defined VGCC antibodies. Conclusions: Autoimmune cerebellar degeneration associated with VGCC autoantibodies may precede onset of LEMS and may improve with immunosuppressive treatment. Binding of anti-VGCC antibodies to Purkinje cells in cerebellar slice cultures may be followed by cell death. Patients with anti-VGCC autoantibodies may be at risk of irreversible neurologic injury over time, and treatment should be initiated early. PMID:27088118

  4. On The Pixel Level Estimation of Pinning Voltage, Pinned Photodiode Capacitance and Transfer Gate Channel Potential

    OpenAIRE

    Goiffon, Vincent; Michelot, Julien; Magnan, Pierre; Estribeau, Magali; Marcelot, Olivier; Cervantes, Paola; Pelamatti, Alice; Martin-Gonthier, Philippe

    2013-01-01

    The pinning voltage extraction method proposed by Tan et al. is analyzed to clarify its benefits and limitations. It is demonstrated that this simple measurement can bring much more useful information than the pinning voltage, such as the pinned photodiode capacitance and the transfer gate channel potential. Objective criteria to compare the pinning voltage on different devices are also discussed.

  5. Contributions of counter-charge in a potassium channel voltage-sensor domain

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Galpin, Jason D; Niciforovic, Ana P;

    2011-01-01

    Voltage-sensor domains couple membrane potential to conformational changes in voltage-gated ion channels and phosphatases. Highly coevolved acidic and aromatic side chains assist the transfer of cationic side chains across the transmembrane electric field during voltage sensing. We investigated the...

  6. Local anesthetic and antiepileptic drug access and binding to a bacterial voltage-gated sodium channel.

    Science.gov (United States)

    Boiteux, Céline; Vorobyov, Igor; French, Robert J; French, Christopher; Yarov-Yarovoy, Vladimir; Allen, Toby W

    2014-09-01

    Voltage-gated sodium (Nav) channels are important targets in the treatment of a range of pathologies. Bacterial channels, for which crystal structures have been solved, exhibit modulation by local anesthetic and anti-epileptic agents, allowing molecular-level investigations into sodium channel-drug interactions. These structures reveal no basis for the "hinged lid"-based fast inactivation, seen in eukaryotic Nav channels. Thus, they enable examination of potential mechanisms of use- or state-dependent drug action based on activation gating, or slower pore-based inactivation processes. Multimicrosecond simulations of NavAb reveal high-affinity binding of benzocaine to F203 that is a surrogate for FS6, conserved in helix S6 of Domain IV of mammalian sodium channels, as well as low-affinity sites suggested to stabilize different states of the channel. Phenytoin exhibits a different binding distribution owing to preferential interactions at the membrane and water-protein interfaces. Two drug-access pathways into the pore are observed: via lateral fenestrations connecting to the membrane lipid phase, as well as via an aqueous pathway through the intracellular activation gate, despite being closed. These observations provide insight into drug modulation that will guide further developments of Nav inhibitors. PMID:25136136

  7. Dependence of corona discharge plasma on voltage pulse characteristics

    International Nuclear Information System (INIS)

    The dynamical behavior of corona discharge plasma at atmospheric pressure has been investigated. The plasma is produced in a coaxial chamber of 1 inch inner diameter, where high voltage pulses of 10 to 30 kV are applied. The properties of the discharge plasma depend strongly on the pulse characteristics, i.e., voltage strength, pulse width, pulse repetition frequency. At a voltage of less than 15 kV, a corona discharge is produced near the center electrode. Subsequently, as the applied voltage is increased, arcing begins. The authors believe it is due to the fact that in the low voltage case, the self energy for instability is not sufficiently high to cause plasma disruption. Though spurious arcing occurs at higher voltages, a glow or sustained plasma dominates as the pulse repetition frequency is increased. The time resolved discharge data shows a monotonically increasing characteristic impedance with nearly constant discharge current. It appears that the plasma at the end of a pulse does not immediately disappear, but remains in the chamber to help ignite plasma at the next pulse as a seed plasma. These observed behaviors will be compared with the numerical results from transport equations. Finally, as an application of this corona discharge plasma for air purification, the effectiveness on the gas destruction rate will be compared between plasmas produced at different voltage characteristics

  8. Investigation on onset voltage and conduction channel temperature in voltage-induced metal-insulator transition of vanadium dioxide

    Science.gov (United States)

    Yoon, Joonseok; Kim, Howon; Mun, Bongjin Simon; Park, Changwoo; Ju, Honglyoul

    2016-03-01

    The characteristics of onset voltages and conduction channel temperatures in the metal-insulator transition (MIT) of vanadium dioxide (VO2) devices are investigated as a function of dimensions and ambient temperature. The MIT onset voltage varies from 18 V to 199 V as the device length increases from 5 to 80 μm at a fixed width of 100 μm. The estimated temperature at local conduction channel increases from 110 to 370 °C, which is higher than the MIT temperature (67 °C) of VO2. A simple Joule-heating model is employed to explain voltage-induced MIT as well as to estimate temperatures of conduction channel appearing after MIT in various-sized devices. Our findings on VO2 can be applied to micro- to nano-size tunable heating devices, e.g., microscale scanning thermal cantilevers and gas sensors.

  9. The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential

    OpenAIRE

    Gerald W Zamponi; Striessnig, Joerg; Koschak, Alexandra; Dolphin, Annette C.

    2015-01-01

    Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type ...

  10. Pharmacological blockade of voltage-gated calcium channels as a potential cardioprotective strategy

    OpenAIRE

    Pushparaj, Charumathi

    2014-01-01

    Voltage-gated Ca2+ channels (VGCCs) are essential for initiating and regulating cardiac function. During the cardiac action potential, Ca2+ influx through L-type channels triggers the sarcoplasmic reticulum Ca2+ release that enables the EC coupling. Ca2+ can also enter cardiac myocytes through low-voltage-activated T-type channels, which are expressed throughout cardiac development until the end of the neonatal period, and can contribute to pacemaker activity as well as EC coupling to some ex...

  11. Gambierol inhibition of voltage-gated potassium channels augments spontaneous Ca2+ oscillations in cerebrocortical neurons.

    Science.gov (United States)

    Cao, Zhengyu; Cui, Yanjun; Busse, Eric; Mehrotra, Suneet; Rainier, Jon D; Murray, Thomas F

    2014-09-01

    Gambierol is a marine polycyclic ether toxin produced by the marine dinoflagellate Gambierdiscus toxicus and is a member of the ciguatoxin toxin family. Gambierol has been demonstrated to be either a low-efficacy partial agonist/antagonist of voltage-gated sodium channels or a potent blocker of voltage-gated potassium channels (Kvs). Here we examined the influence of gambierol on intact cerebrocortical neurons. We found that gambierol produced both a concentration-dependent augmentation of spontaneous Ca(2+) oscillations, and an inhibition of Kv channel function with similar potencies. In addition, an array of selective as well as universal Kv channel inhibitors mimicked gambierol in augmenting spontaneous Ca(2+) oscillations in cerebrocortical neurons. These data are consistent with a gambierol blockade of Kv channels underlying the observed increase in spontaneous Ca(2+) oscillation frequency. We also found that gambierol produced a robust stimulation of phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2). Gambierol-stimulated ERK1/2 activation was dependent on both inotropic [N-methyl-d-aspartate (NMDA)] and type I metabotropic glutamate receptors (mGluRs) inasmuch as MK-801 [NMDA receptor inhibitor; (5S,10R)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate], S-(4)-CGP [S-(4)-carboxyphenylglycine], and MTEP [type I mGluR inhibitors; 3-((2-methyl-4-thiazolyl)ethynyl) pyridine] attenuated the response. In addition, 2-aminoethoxydiphenylborane, an inositol 1,4,5-trisphosphate receptor inhibitor, and U73122 (1-[6-[[(17b)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione), a phospholipase C inhibitor, both suppressed gambierol-induced ERK1/2 activation, further confirming the role of type I mGluR-mediated signaling in the observed ERK1/2 activation. Finally, we found that gambierol produced a concentration-dependent stimulation of neurite outgrowth that was mimicked by 4-aminopyridine, a universal

  12. Neuronal trafficking of voltage-gated potassium channels

    DEFF Research Database (Denmark)

    Jensen, Camilla S; Rasmussen, Hanne Borger; Misonou, Hiroaki

    2011-01-01

    physiological significance of proper Kv channel localization is emphasized by the fact that defects in the trafficking of Kv channels are observed in several neurological disorders including epilepsy. In this review, we will summarize the current understanding of the mechanisms of Kv channel trafficking and...

  13. Cellular hyper-excitability caused by mutations that alter the activation process of voltage-gated sodium channels

    Directory of Open Access Journals (Sweden)

    Mohamed-Yassine eAMAROUCH

    2015-02-01

    Full Text Available Voltage-gated sodium channels (Nav are widely expressed as macro-molecular complexes in both excitable and non-excitable tissues. In excitable tissues, the upstroke of the action potential is the result of the passage of a large and rapid influx of sodium ions through these channels. NaV dysfunction has been associated with an increasingly wide range of neurological, muscular and cardiac disorders. The purpose of this review is to summarize the recently identified sodium channel mutations that are linked to hyper-excitability phenotypes and associated with the alteration of the activation process of voltage gated sodium channels. Indeed, several clinical manifestations that demonstrate an alteration of tissue excitability were recently shown to be strongly associated with the presence of mutations that affect the activation process of the voltage-gated sodium channels. These emerging genotype-phenotype correlations have expanded the clinical spectrum of sodium channelopathies to include disorders which feature a hyper-excitability phenotype that may or may not be associated with a cardiomyopathy. The p.I141V mutation in SCN4A and SCN5A, as well as its homologous p.I136V mutation in SCN9A, are interesting examples of mutations that have been linked to inherited hyperexcitability myotonia, exercise-induced polymorphic ventricular arrhythmias and erythromelalgia, respectively. Regardless of which sodium channel isoform is investigated, the substitution of the isoleucine to valine in the locus 141 induces similar modifications in the biophysical properties of the voltage-gated sodium channels by shifting the voltage-dependence of steady state activation towards more negative potentials.

  14. Voltage-Gated Potassium Channels: A Structural Examination of Selectivity and Gating.

    Science.gov (United States)

    Kim, Dorothy M; Nimigean, Crina M

    2016-01-01

    Voltage-gated potassium channels play a fundamental role in the generation and propagation of the action potential. The discovery of these channels began with predictions made by early pioneers, and has culminated in their extensive functional and structural characterization by electrophysiological, spectroscopic, and crystallographic studies. With the aid of a variety of crystal structures of these channels, a highly detailed picture emerges of how the voltage-sensing domain reports changes in the membrane electric field and couples this to conformational changes in the activation gate. In addition, high-resolution structural and functional studies of K(+) channel pores, such as KcsA and MthK, offer a comprehensive picture on how selectivity is achieved in K(+) channels. Here, we illustrate the remarkable features of voltage-gated potassium channels and explain the mechanisms used by these machines with experimental data. PMID:27141052

  15. Integrated design optimization of voltage channel distribution and control voltages for tracking the dynamic shapes of smart plates

    International Nuclear Information System (INIS)

    This paper investigates a control scheme for tracking the dynamic shapes of structures with limited numbers of voltage channels. Integrated design optimization of voltage channel distribution and control parameters for structural dynamic shape control is formulated as an optimization problem with discrete variables and continuous variables coexisting. A two-level optimization method based on a simulated annealing algorithm is proposed. In the first level, the optimum channel distribution is determined by optimizing the objective function which is the optimal value obtained in the second level. The optimum control parameters are obtained by using a sequential linear least-squares algorithm in the second level. The effectiveness of the present design methodology and optimization scheme is then demonstrated through numerical examples for tracking the dynamic shapes of composite plates

  16. Neurotoxins and Their Binding Areas on Voltage-Gated Sodium Channels

    OpenAIRE

    Stevens, Marijke; Peigneur, Steve; Tytgat, Jan

    2011-01-01

    Voltage-gated sodium channels (VGSCs) are large transmembrane proteins that conduct sodium ions across the membrane and by doing so they generate signals of communication between many kinds of tissues. They are responsible for the generation and propagation of action potentials in excitable cells, in close collaboration with other channels like potassium channels. Therefore, genetic defects in sodium channel genes can cause a wide variety of diseases, generally called “channelopathies.” The f...

  17. Neurotoxins and their binding areas on voltage-gated sodium channels

    OpenAIRE

    Marijke eStevens; Steve ePeigneur; Jan eTytgat

    2011-01-01

    Voltage-gated Sodium Channels (VGSCs) are large transmembrane proteins that conduct sodium ions across the membrane and by doing so they generate signals of communication between many kinds of tissues. They are responsible for the generation and propagation of action potentials in excitable cells, in close collaboration with other channels like potassium channels. Genetic defects in sodium channel genes therefore can cause a wide variety of diseases, generally called ‘channelopathies’.The f...

  18. Kinetic changes and modulation by carbamazepine on voltage-gated sodium channels in rat CA1 neurons after epilepsy

    Institute of Scientific and Technical Information of China (English)

    Guang-chun SUN; Taco WERKMAN; Wytse J WADMAN

    2006-01-01

    Aim: To study whether the functional properties of sodium channels, and subsequently the channel modulation by carbamazepine (CBZ) in hippocampal CA1 neurons can be changed after epileptic seizures. Methods: We used the acutely dissociated hippocampal CA1 pyramidal cells from epilepsy model rats 3 weeks and 3 months respectively after kainate injection, and whole-cell voltage-clamp techniques. Results: After long-term epileptic seizures, both sodium channel voltage-dependence of activation and steady-state inactivation shifted to more hyperpolarizing potentials, which resulted in the enlarged window current; the membrane density of sodium current decreased and the time constant of recovery from inactivation increased. CBZ displayed unchanged efficacy on sodium channels, with a similar binding rate to them, except that at higher concentrations, the voltage shift of inactivation was reduced. For the short-term kainate model rats, no differences were detected between the control and epilepsy groups. Conclusion: These results indicate that the properties of sodium channels in acutely dissociated hippocampal neurons could be changed following long-term epilepsy, but the alternation might not be enough to induce the channel resistance to CBZ.

  19. Intrinsic oscillatory activity arising within the electrically coupled AII amacrine-ON cone bipolar cell network is driven by voltage-gated Na + channels

    OpenAIRE

    Trenholm, S; Borowska, J; Zhang, J; Hoggarth, A; Johnson, K.; Barnes, S.; Lewis, TJ; Awatramani, GB

    2012-01-01

    In the rd1 mouse model for retinal degeneration, the loss of photoreceptors results in oscillatory activity (∼10-20 Hz) within the remnant electrically coupled network of retinal ON cone bipolar and AII amacrine cells. We tested the role of hyperpolarization-activated currents (I h), voltage-gated Na + channels and gap junctions in mediating such oscillatory activity. Blocking I h (1 mm Cs +) hyperpolarized the network and augmented activity, while antagonizing voltage-dependent Na + channels...

  20. Atomic-level simulation of current–voltage relationships in single-file ion channels

    OpenAIRE

    Jensen, Morten Ø.; Jogini, Vishwanath; Eastwood, Michael P.; Shaw, David E.

    2013-01-01

    The difficulty in characterizing ion conduction through membrane channels at the level of individual permeation events has made it challenging to elucidate the mechanistic principles underpinning this fundamental physiological process. Using long, all-atom simulations enabled by special-purpose hardware, we studied K+ permeation across the KV1.2/2.1 voltage-gated potassium channel. At experimentally accessible voltages, which include the physiological range, the simulated permeation rate was ...

  1. Electrophysiology properties of voltage-gated potassium channels in rat peritoneal macrophages

    OpenAIRE

    Wu, Bao-ming; Wang, Xiao-Hua; Zhao, Bin; Bian, Er-Bao; Yan, Huang; Cheng, Huang; Lv, Xiong-Wen; Xiong, Zhi-Gang; Li, Jun

    2013-01-01

    Ion channels are important for the functions of excitable and non-excitable cells. Using the whole-cell patch clamp technique, we analyzed the electrophysiological and pharmacological properties of voltage-gated potassium channels in primary rat peritoneal macrophages. With intracellular solution contained K+ as the main charge carrier, all cells showed outward currents in response to membrane depolarization. The currents can be inhibited by TEA (10 mM), a non-selective blocker for voltage-ga...

  2. Manipulating the voltage dependence of tunneling spin torques

    KAUST Repository

    Manchon, Aurelien

    2012-10-01

    Voltage-driven spin transfer torques in magnetic tunnel junctions provide an outstanding tool to design advanced spin-based devices for memory and reprogrammable logic applications. The non-linear voltage dependence of the torque has a direct impact on current-driven magnetization dynamics and on devices performances. After a brief overview of the progress made to date in the theoretical description of the spin torque in tunnel junctions, I present different ways to alter and control the bias dependence of both components of the spin torque. Engineering the junction (barrier and electrodes) structural asymmetries or controlling the spin accumulation profile in the free layer offer promising tools to design effcient spin devices.

  3. Voltage dependence of Na-Ca exchanger conformational currents.

    OpenAIRE

    Niggli, E; P. Lipp

    1994-01-01

    Properties of a transient current (Icont) believed to reflect a conformational change of the Na-Ca exchanger molecules after Ca2+ binding were investigated. Intracellular Ca2+ concentration jumps in isolated cardiac myocytes were generated with flash photolysis of caged Ca2+ dimethoxynitrophenamine, and membrane currents were simultaneously measured using the whole-cell variant of the patch-clamp technique. A previously unresolved shallow voltage dependence of Icont was revealed after develop...

  4. Molecular Interactions between Tarantula Toxins and Low-Voltage-Activated Calcium Channels.

    Science.gov (United States)

    Salari, Autoosa; Vega, Benjamin S; Milescu, Lorin S; Milescu, Mirela

    2016-01-01

    Few gating-modifier toxins have been reported to target low-voltage-activated (LVA) calcium channels, and the structural basis of toxin sensitivity remains incompletely understood. Studies of voltage-gated potassium (Kv) channels have identified the S3b-S4 "paddle motif," which moves at the protein-lipid interface to drive channel opening, as the target for these amphipathic neurotoxins. Voltage-gated calcium (Cav) channels contain four homologous voltage sensor domains, suggesting multiple toxin binding sites. We show here that the S3-S4 segments within Cav3.1 can be transplanted into Kv2.1 to examine their individual contributions to voltage sensing and pharmacology. With these results, we now have a more complete picture of the conserved nature of the paddle motif in all three major voltage-gated ion channel types (Kv, Nav, and Cav). When screened with tarantula toxins, the four paddle sequences display distinct toxin binding properties, demonstrating that gating-modifier toxins can bind to Cav channels in a domain specific fashion. Domain III was the most commonly and strongly targeted, and mutagenesis revealed an acidic residue that is important for toxin binding. We also measured the lipid partitioning strength of all toxins tested and observed a positive correlation with their inhibition of Cav3.1, suggesting a key role for membrane partitioning. PMID:27045173

  5. Voltage fluctuations in mesoscopic conductors with single-channel leads: Electronic speckle patterns

    Energy Technology Data Exchange (ETDEWEB)

    Feng, S.; Spivak, B.Z. (Department of Physics, University of California, Los Angeles, California (USA) II. Physikalisches Institut, Universitaet zu Koeln, 77 Zuepicher Strasse, 5000 Koeln 41 (Federal Republic of Germany))

    1991-08-15

    We study theoretically the voltage fluctuations of a mesoscopic disordered conductor that is connected to single-channel current leads in the four-probe configuration. We find dramatically enhanced voltage fluctuations, which are interpreted as the electronic equivalent of laser speckle patterns. We also compute the correlation functions of the electrochemical potential and the current density inside the sample, which provide a general description for transport with single-channel leads (for either the current leads or the voltage leads, or for both).

  6. Voltage fluctuations in mesoscopic conductors with single-channel leads: Electronic speckle patterns

    International Nuclear Information System (INIS)

    We study theoretically the voltage fluctuations of a mesoscopic disordered conductor that is connected to single-channel current leads in the four-probe configuration. We find dramatically enhanced voltage fluctuations, which are interpreted as the electronic equivalent of laser speckle patterns. We also compute the correlation functions of the electrochemical potential and the current density inside the sample, which provide a general description for transport with single-channel leads (for either the current leads or the voltage leads, or for both)

  7. The hitchhiker's guide to the voltage-gated sodium channel galaxy.

    Science.gov (United States)

    Ahern, Christopher A; Payandeh, Jian; Bosmans, Frank; Chanda, Baron

    2016-01-01

    Eukaryotic voltage-gated sodium (Nav) channels contribute to the rising phase of action potentials and served as an early muse for biophysicists laying the foundation for our current understanding of electrical signaling. Given their central role in electrical excitability, it is not surprising that (a) inherited mutations in genes encoding for Nav channels and their accessory subunits have been linked to excitability disorders in brain, muscle, and heart; and (b) Nav channels are targeted by various drugs and naturally occurring toxins. Although the overall architecture and behavior of these channels are likely to be similar to the more well-studied voltage-gated potassium channels, eukaryotic Nav channels lack structural and functional symmetry, a notable difference that has implications for gating and selectivity. Activation of voltage-sensing modules of the first three domains in Nav channels is sufficient to open the channel pore, whereas movement of the domain IV voltage sensor is correlated with inactivation. Also, structure-function studies of eukaryotic Nav channels show that a set of amino acids in the selectivity filter, referred to as DEKA locus, is essential for Na(+) selectivity. Structures of prokaryotic Nav channels have also shed new light on mechanisms of drug block. These structures exhibit lateral fenestrations that are large enough to allow drugs or lipophilic molecules to gain access into the inner vestibule, suggesting that this might be the passage for drug entry into a closed channel. In this Review, we will synthesize our current understanding of Nav channel gating mechanisms, ion selectivity and permeation, and modulation by therapeutics and toxins in light of the new structures of the prokaryotic Nav channels that, for the time being, serve as structural models of their eukaryotic counterparts. PMID:26712848

  8. Gating motions in voltage-gated potassium channels revealed by coarse-grained molecular dynamics simulations

    NARCIS (Netherlands)

    Treptow, W.; Marrink, S.J.; Tarek, M.

    2008-01-01

    Voltage-gated potassium (Kv) channels are ubiquitous transmembrane proteins involved in electric signaling of excitable tissues. A fundamental property of these channels is the ability to open or close in response to changes in the membrane potential. To date, their structure-based activation mechan

  9. Chemoselective tarantula toxins report voltage activation of wild-type ion channels in live cells.

    Science.gov (United States)

    Tilley, Drew C; Eum, Kenneth S; Fletcher-Taylor, Sebastian; Austin, Daniel C; Dupré, Christophe; Patrón, Lilian A; Garcia, Rita L; Lam, Kit; Yarov-Yarovoy, Vladimir; Cohen, Bruce E; Sack, Jon T

    2014-11-01

    Electrically excitable cells, such as neurons, exhibit tremendous diversity in their firing patterns, a consequence of the complex collection of ion channels present in any specific cell. Although numerous methods are capable of measuring cellular electrical signals, understanding which types of ion channels give rise to these signals remains a significant challenge. Here, we describe exogenous probes which use a novel mechanism to report activity of voltage-gated channels. We have synthesized chemoselective derivatives of the tarantula toxin guangxitoxin-1E (GxTX), an inhibitory cystine knot peptide that binds selectively to Kv2-type voltage gated potassium channels. We find that voltage activation of Kv2.1 channels triggers GxTX dissociation, and thus GxTX binding dynamically marks Kv2 activation. We identify GxTX residues that can be replaced by thiol- or alkyne-bearing amino acids, without disrupting toxin folding or activity, and chemoselectively ligate fluorophores or affinity probes to these sites. We find that GxTX-fluorophore conjugates colocalize with Kv2.1 clusters in live cells and are released from channels activated by voltage stimuli. Kv2.1 activation can be detected with concentrations of probe that have a trivial impact on cellular currents. Chemoselective GxTX mutants conjugated to dendrimeric beads likewise bind live cells expressing Kv2.1, and the beads are released by channel activation. These optical sensors of conformational change are prototype probes that can indicate when ion channels contribute to electrical signaling. PMID:25331865

  10. Congruent pattern of accessibility identifies minimal pore gate in a non-symmetric voltage-gated sodium channel.

    Science.gov (United States)

    Oelstrom, Kevin; Chanda, Baron

    2016-01-01

    Opening and closing of the central ion-conducting pore in voltage-dependent ion channels is gated by changes in membrane potential. Although a gate residue in the eukaryotic voltage-gated sodium channel has been identified, the minimal molecular determinants of this gate region remain unknown. Here, by measuring the closed- and open-state reactivity of MTSET to substituted cysteines in all the pore-lining helices, we show that the state-dependent accessibility is delineated by four hydrophobic residues at homologous positions in each domain. Introduced cysteines above these sites do not react with intracellular MTSET while the channels are closed and yet are rapidly modified while the channels are open. These findings, in conjunction with state-dependent metal cross-bridging, support the notion that the gate residues in each of the four S6 segments of the eukaryotic sodium channel form an occlusion for ions in the closed state and are splayed open on activation. PMID:27186888

  11. A tester for multi-channel high voltage power supply with load

    International Nuclear Information System (INIS)

    The authors will introduce a test system used for multi-channel high voltage power supply, and also briefly introduce circuit construction and circuit design, operation principle and specification. This instrument is mainly used to test single channel or multi-channel high voltage power supply in laboratory or in open field. Especially, it is very useful for the testing of detector's biases. The maximum high voltage value can be tested by this instrument is 6 kV. The range of output current of high voltage power supply under-test is from 100 μA to 10 mA. This instrument is portable, and with simple construction, high integration, small dimension. It can be operated with AC/DC power supply

  12. Computer controlled multiple channel high voltage power supply [Paper No.: L8

    International Nuclear Information System (INIS)

    This paper describes the design of a computer controlled high voltage multiple channel power supply for use in Gamma Ray Astrophysics Experiment (GRAPE). Each channel is rated for 2.5 kV, 1mA with over current protection and output voltage read back facility. A single HV supply on a single width NIM module has been tried successfully. At present 8 channels on a module is being tried to make a very compact HV system. (author). 2 refs., 2 figs

  13. The role of voltage-gated calcium channels in neurotransmitter phenotype specification: Coexpression and functional analysis in Xenopus laevis

    OpenAIRE

    Lewis, Brittany B.; Miller, Lauren E.; Herbst, Wendy A; Saha, Margaret S.

    2014-01-01

    Calcium activity has been implicated in many neurodevelopmental events, including the specification of neurotransmitter phenotypes. Higher levels of calcium activity lead to an increased number of inhibitory neural phenotypes, whereas lower levels of calcium activity lead to excitatory neural phenotypes. Voltage-gated calcium channels (VGCCs) allow for rapid calcium entry and are expressed during early neural stages, making them likely regulators of activity-dependent neurotransmitter phenoty...

  14. Study of Selectivity and Permeation In Voltage-Gated Ion Channels

    OpenAIRE

    Giri, Janhavi

    2012-01-01

    Ion channels are membrane proteins responsible for an enormous range of biological functions. Ion selectivity and permeation are based on simple laws of physics and chemistry. Ion channels are therefore ideal candidates for physical investigation. A reduced model generates the selectivity of voltage-gated L-type calcium channel under a wide range of ionic conditions using only two parameters with unchanging values. The reasons behind the success of this reduced model are investigated. Monte C...

  15. Chemoselective tarantula toxins report voltage activation of wild-type ion channels in live cells

    OpenAIRE

    Tilleya, DC; Euma, KS; Fletcher-Taylor, S; Austina, DC; Dupré, C; Patrón, LA; Garcia, RL; Lam, K; Yarov-Yarovoy, V; Cohenc, BE; Sack, JT

    2014-01-01

    Electrically excitable cells, such as neurons, exhibit tremendous diversity in their firing patterns, a consequence of the complex collection of ion channels present in any specific cell. Although numerous methods are capable of measuring cellular electrical signals, understanding which types of ion channels give rise to these signals remains a significant challenge. Here, we describe exogenous probes which use a novel mechanism to report activity of voltage-gated channels. We have synthesize...

  16. Asymmetric functional contributions of acidic and aromatic side chains in sodium channel voltage-sensor domains

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Elstone, Fisal D; Niciforovic, Ana P; Galpin, Jason D; Yang, Runying; Kurata, Harley T; Ahern, Christopher A

    2014-01-01

    largely enigmatic. To this end, natural and unnatural side chain substitutions were made in the S2 hydrophobic core (HC), the extracellular negative charge cluster (ENC), and the intracellular negative charge cluster (INC) of the four VSDs of the skeletal muscle sodium channel isoform (NaV1.4). The......Voltage-gated sodium (NaV) channels mediate electrical excitability in animals. Despite strong sequence conservation among the voltage-sensor domains (VSDs) of closely related voltage-gated potassium (KV) and NaV channels, the functional contributions of individual side chains in Nav VSDs remain...... functional phenotypes that are different from those observed previously in Kv VSDs. In contrast, and similar to results obtained with Kv channels, individually neutralizing acidic side chains with synthetic derivatives and with natural amino acid substitutions in the INC had little or no effect on the...

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

    DEFF Research Database (Denmark)

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

    2011-01-01

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

  18. Investigation of capacitance voltage characteristics of strained Si/SiGe n-channel MODFET varactor

    Science.gov (United States)

    Elogail, Y.; Kasper, E.; Gunzer, F.; Shaker, A.; Schulze, J.

    2016-06-01

    This work is concerned with the investigation of Capacitance-Voltage (CV) behavior of n-channel Si/SiGe MODFET varactors. This investigation provides a valuable insight into the high frequency response of the device under test and its dependence on design parameters; especially regarding the modulation layer doping concentration. The heterostructure under consideration is much more complicated than conventional MOS varactor with respect to non-uniform doping, energy band offsets and the pn-junction in series. Subsequently, CV characterization has never been applied to such MODFET varactor structure. Experimental CV measurements have shown a non-monotonic behavior with a transition point minimum and higher saturation levels on both sides, in contradiction to the conventional high frequency MOS characteristics. This behavior was confirmed qualitatively using simulations. Moreover, we explain some fundamental capacitance properties of the structure, which provide already very interesting perceptions of the MODFET varactor operation, modeling and possible applications using the obtained stimulating results.

  19. Progress in the structural understanding of voltage-gated calcium channel (CaV) function and modulation.

    Science.gov (United States)

    Minor, Daniel L; Findeisen, Felix

    2010-01-01

    Voltage-gated calcium channels (CaVs) are large, transmembrane multiprotein complexes that couple membrane depolarization to cellular calcium entry. These channels are central to cardiac action potential propagation, neurotransmitter and hormone release, muscle contraction, and calcium-dependent gene transcription. Over the past six years, the advent of high-resolution structural studies of CaV components from different isoforms and CaV modulators has begun to reveal the architecture that underlies the exceptionally rich feedback modulation that controls CaV action. These descriptions of CaV molecular anatomy have provided new, structure-based insights into the mechanisms by which particular channel elements affect voltage-dependent inactivation (VDI), calcium‑dependent inactivation (CDI), and calcium‑dependent facilitation (CDF). The initial successes have been achieved through structural studies of soluble channel domains and modulator proteins and have proven most powerful when paired with biochemical and functional studies that validate ideas inspired by the structures. Here, we review the progress in this growing area and highlight some key open challenges for future efforts. PMID:21139419

  20. Uplink Channel Dependent Scheduling for Future Cellular Systems

    OpenAIRE

    Jersenius, Kristina

    2007-01-01

    One goal in the development of future cellular systems is to increase performance. Channel dependent scheduling can possibly contribute to a performance enhancement. It requires channel qualityinformation and uplink channel knowledge is often incomplete. This master thesis work compares channel dependent scheduling and channel independent scheduling for a Single Carrier Frequency Division Multiple Access-based uplink in time domain and time and frequencydomain assuming continuous channel qual...

  1. Voltage-gated calcium channel and antisense oligonucleotides thereto

    Science.gov (United States)

    Hruska, Keith A. (Inventor); Friedman, Peter A. (Inventor); Barry, Elizabeth L. R. (Inventor); Duncan, Randall L. (Inventor)

    1998-01-01

    An antisense oligonucleotide of 10 to 35 nucleotides in length that can hybridize with a region of the .alpha..sub.1 subunit of the SA-Cat channel gene DNA or mRNA is provided, together with pharmaceutical compositions containing and methods utilizing such antisense oligonucleotide.

  2. Strategies for Investigating G-Protein Modulation of Voltage-Gated Ca2+ Channels.

    Science.gov (United States)

    Lu, Van B; Ikeda, Stephen R

    2016-01-01

    G-protein-coupled receptor modulation of voltage-gated ion channels is a common means of fine-tuning the response of channels to changes in membrane potential. Such modulation impacts physiological processes such as synaptic transmission, and hence therapeutic strategies often directly or indirectly target these pathways. As an exemplar of channel modulation, we examine strategies for investigating G-protein modulation of CaV2.2 or N-type voltage-gated Ca(2+) channels. We focus on biochemical and genetic tools for defining the molecular mechanisms underlying the various forms of CaV2.2 channel modulation initiated following ligand binding to G-protein-coupled receptors. PMID:27140924

  3. 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

  4. Vincamine and vincanol are potent blockers of voltage-gated Na+ channels.

    Science.gov (United States)

    Erdo, S A; Molnár, P; Lakics, V; Bence, J Z; Tömösközi, Z

    1996-10-24

    The effects of three vinca derivatives on [3H]batrachotoxin binding in rat cortical synaptosomes, on the inhibition of whole-cell Na+ currents evoked in voltage-clamped cortical neurones of the rat, on the protection against veratridine-induced cell death in cortical cultures and on the maximal electroshock-induced seizures in mice were compared. Vinpocetine, vincamine and vincanol reduced [3H]batrachotoxin binding with IC50 values of 0.34, 1.9 and 10.7 microM, blocked Na+ currents with IC50 values of 44.72 and 40 microM, and protected cortical against veratridine-induced cell death with IC50 values of 0.49, 26 and 33 microM, respectively. Upon i.p. administration, vinpocetine, vincamine and vincanol attenuated maximal electric shock-induced convulsions in a dose-dependent manner with ED50 values of 27, 15.4 and 14.6 mg/kg, respectively. The present findings indicate that the three vinca derivatives are potent blockers of voltage-gated Na+ channels, a mechanism that may contribute at least in part to the pharmacological/therapeutic benefit of these drugs. PMID:8957220

  5. Combinatorial augmentation of voltage-gated KCNQ potassium channels by chemical openers

    Science.gov (United States)

    Xiong, Qiaojie; Sun, Haiyan; Zhang, Yangming; Nan, Fajun; Li, Min

    2008-01-01

    Noninactivating potassium current formed by KCNQ2 (Kv7.2) and KCNQ3 (Kv7.3) subunits resembles neuronal M-currents which are activated by voltage and play a critical role in controlling membrane excitability. Activation of voltage-gated potassium channels by a chemical opener is uncommon. Therefore, the mechanisms of action are worthy further investigation. Retigabine and zinc pyrithione are two activators for KCNQ channels but their molecular interactions with KCNQ channel remain largely elusive. Here we report that retigabine and zinc pyrithione recognize two different sites of KCNQ2 channels. Their agonistic actions are noncompetitive and allow for simultaneous binding of two different activators on the same channel complex, hence giving rise to combinatorial potentiation with characteristic properties of both openers. Examining their effects on mutant channels, we showed zinc pyrithione is capable of opening nonconductive channels and coapplication of zinc pyrithione and retigabine could restore a disease mutant channel similar to wild type. Our results indicate two independent activator binding sites present in KCNQ channels. The resultant combinatorial potentiation by multiple synthetic chemical openers indicates that KCNQ channels are accessible to various types and combinations of pharmacological regulation. PMID:18272489

  6. Interplay of Voltage and Ca-dependent inactivation of L-type Ca current

    OpenAIRE

    Grandi, Eleonora; Morotti, Stefano; Ginsburg, Kenneth S.; Severi, Stefano; Bers, Donald M.

    2010-01-01

    Inactivation of L-type Ca channels (LTCC) is regulated by both Ca and voltage-dependent processes (CDI and VDI). To differentiate VDI and CDI, several experimental and theoretical studies have considered the inactivation of Ba current through LTCC (IBa) as a measure of VDI. However, there is evidence that Ba can weakly mimic Ca, such that IBa inactivation is still a mixture of CDI and VDI. To avoid this complication, some have used the monovalent cation current through LTCC (INS), which can b...

  7. Cellular defibrillation: interaction of micro-scale electric fields with voltage-gated ion channels.

    Science.gov (United States)

    Kargol, Armin; Malkinski, Leszek; Eskandari, Rahmatollah; Carter, Maya; Livingston, Daniel

    2015-09-01

    We study the effect of micro-scale electric fields on voltage-gated ion channels in mammalian cell membranes. Such micro- and nano-scale electric fields mimic the effects of multiferroic nanoparticles that were recently proposed [1] as a novel way of controlling the function of voltage-sensing biomolecules such as ion channels. This article describes experimental procedures and initial results that reveal the effect of the electric field, in close proximity of cells, on the ion transport through voltage-gated ion channels. We present two configurations of the whole-cell patch-clamping apparatus that were used to detect the effect of external stimulation on ionic currents and discuss preliminary results that indicate modulation of the ionic currents consistent with the applied stimulus. PMID:26067055

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

    Science.gov (United States)

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

    2016-09-01

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

  9. Cloning and molecular characterization of a putative voltage-gated sodium channel gene in the crayfish.

    Science.gov (United States)

    Coskun, Cagil; Purali, Nuhan

    2016-06-01

    Voltage-gated sodium channel genes and associated proteins have been cloned and studied in many mammalian and invertebrate species. However, there is no data available about the sodium channel gene(s) in the crayfish, although the animal has frequently been used as a model to investigate various aspects of neural cellular and circuit function. In the present work, by using RNA extracts from crayfish abdominal ganglia samples, the complete open reading frame of a putative sodium channel gene has firstly been cloned and molecular properties of the associated peptide have been analyzed. The open reading frame of the gene has a length of 5793 bp that encodes for the synthesis of a peptide, with 1930 amino acids, that is 82% similar to the α-peptide of a sodium channel in a neighboring species, Cancer borealis. The transmembrane topology analysis of the crayfish peptide indicated a pattern of four folding domains with several transmembrane segments, as observed in other known voltage-gated sodium channels. Upon analysis of the obtained sequence, functional regions of the putative sodium channel responsible for the selectivity filter, inactivation gate, voltage sensor, and phosphorylation have been predicted. The expression level of the putative sodium channel gene, as defined by a qPCR method, was measured and found to be the highest in nervous tissue. PMID:27032955

  10. Effects of Voltage-Gated K+ Channel on Cell Proliferation in Multiple Myeloma

    OpenAIRE

    Wei Wang,; Yuying Fan; Shuye Wang; Lianjie Wang; Wanting He; Qiu Zhang; Xiaoxia Li

    2014-01-01

    Objective. To study the effects and underlying mechanisms of voltage-gated K+ channels on the proliferation of multiple myeloma cells. Methods. RPMI-8226 MM cell line was used for the experiments. Voltage-gated K+ currents and the resting potential were recorded by whole-cell patch-clamp technique. RT-PCR detected Kv channel mRNA expression. Cell viability was analyzed with MTT assay. Cell counting system was employed to monitor cell proliferation. DNA contents and cell volume were analyzed b...

  11. Molecular basis for the toxin insensitivity of scorpion voltage-gated potassium channel MmKv1.

    Science.gov (United States)

    Zhang, Chuangeng; Xie, Zili; Li, Xinxin; Chen, Jing; Feng, Jing; Lang, Yange; Yang, Weishan; Li, Wenxin; Chen, Zongyun; Yao, Jing; Cao, Zhijian; Wu, Yingliang

    2016-05-01

    Scorpions are insensitive to their own venoms, which contain various neurotoxins specific for mammalian or insect ion channels, whose molecular mechanism remains unsolved. Using MmKv1, a potassium channel identified from the genome of the scorpion Mesobuthus martensii, channel kinetic experiments showed that MmKv1 was a classical voltage-gated potassium channel with a voltage-dependent fast activation and slow inactivation. Compared with the human Kv1.3 channel (hKv1.3), the MmKv1 channel exhibited a remarkable insensitivity to both scorpion venom and toxin. The chimaeric channels of MmKv1 and hKv1.3 revealed that both turret and filter regions of the MmKv1 channel were critical for the toxin insensitivity of MmKv1. Furthermore, mutagenesis of the chimaeric channel indicated that two basic residues (Arg(399) and Lys(403)) in the MmKv1 turret region and Arg(425) in the MmKv1 filter region significantly affected its toxin insensitivity. Moreover, when these three basic residues of MmKv1 were simultaneously substituted with the corresponding residues from hKv1.3, the MmKv1-R399T/K403S/R425H mutant channels exhibited similar sensitivity to both scorpion venom and toxin to hKv1.3, which revealed the determining role of these three basic residues in the toxin insensitivity of the MmKv1 channel. More strikingly, a similar triad sequence structure is present in all Shaker-like channels from venomous invertebrates, which suggested a possible convergent functional evolution of these channels to enable them to resist their own venoms. Together, these findings first illustrate the mechanism by which scorpions are insensitive to their own venoms at the ion channel receptor level and enrich our knowledge of the insensitivity of scorpions and other venomous animals to their own venoms. PMID:26951716

  12. Temperature and voltage dependent current-voltage behavior of single-walled carbon nanotube transparent conducting films

    Science.gov (United States)

    Zhang, Ze-Chen; Geng, Hong-Zhang; Wang, Yan; Yang, Hai-Jie; Da, Shi-Xun; Ding, Er-Xiong; Liu, Juncheng; Yu, Ping; Fu, Yun-Qiao; Li, Xu; Pan, Hui

    2015-11-01

    High purified single-walled carbon nanotubes (SWCNTs) were dispersed in water and transparent conducting films (TCFs) were fabricated by a spray coating. The produced uniform SWCNT-TCFs treated by nitric acid have a relatively low sheet resistance and high transmittance. The current-voltage (I-V) behaviors of the TCFs were measured at room to higher temperature during the heating or cooling process. It was found that the I-V behavior of TCFs strongly dependent on the temperature and applied voltage. The sheet resistance showed semiconductor behavior at low temperature and low voltage, while it showed metallic behavior at high temperature and high voltage.

  13. Reprint of : Correlated voltage probe model of relaxation in two Coulomb-coupled edge channels

    Science.gov (United States)

    Nigg, Simon E.

    2016-08-01

    A phenomenological correlated voltage probe model is introduced to mimic the effects of inelastic scattering between particles in different conduction channels of a phase coherent conductor. As an illustration, the non-equilibrium distribution functions of two noisy co-propagating chiral edge channels of the integer quantum Hall effect are calculated and compared with recent experiments. The method is further applied to calculate the linear response current noise through an interacting Mach-Zehnder interferometer.

  14. Correlated voltage probe model of relaxation in two Coulomb-coupled edge channels

    Science.gov (United States)

    Nigg, Simon E.

    2016-01-01

    A phenomenological correlated voltage probe model is introduced to mimic the effects of inelastic scattering between particles in different conduction channels of a phase coherent conductor. As an illustration, the non-equilibrium distribution functions of two noisy co-propagating chiral edge channels of the integer quantum Hall effect are calculated and compared with recent experiments. The method is further applied to calculate the linear response current noise through an interacting Mach-Zehnder interferometer.

  15. Size-dependent forced PEG partitioning into channels: VDAC, OmpC, and α-hemolysin

    Science.gov (United States)

    Aksoyoglu, M. Alphan; Podgornik, Rudolf; Bezrukov, Sergey M.; Gurnev, Philip A.; Muthukumar, Murugappan; Parsegian, V. Adrian

    2016-01-01

    Nonideal polymer mixtures of PEGs of different molecular weights partition differently into nanosize protein channels. Here, we assess the validity of the recently proposed theoretical approach of forced partitioning for three structurally different β-barrel channels: voltage-dependent anion channel from outer mitochondrial membrane VDAC, bacterial porin OmpC (outer membrane protein C), and bacterial channel-forming toxin α-hemolysin. Our interpretation is based on the idea that relatively less-penetrating polymers push the more easily penetrating ones into nanosize channels in excess of their bath concentration. Comparison of the theory with experiments is excellent for VDAC. Polymer partitioning data for the other two channels are consistent with theory if additional assumptions regarding the energy penalty of pore penetration are included. The obtained results demonstrate that the general concept of “polymers pushing polymers” is helpful in understanding and quantification of concrete examples of size-dependent forced partitioning of polymers into protein nanopores. PMID:27466408

  16. Block of voltage-gated potassium channels by Pacific ciguatoxin-1 contributes to increased neuronal excitability in rat sensory neurons

    International Nuclear Information System (INIS)

    The present study investigated the actions of the polyether marine toxin Pacific ciguatoxin-1 (P-CTX-1) on neuronal excitability in rat dorsal root ganglion (DRG) neurons using patch-clamp recording techniques. Under current-clamp conditions, bath application of 2-20 nM P-CTX-1 caused a rapid, concentration-dependent depolarization of the resting membrane potential in neurons expressing tetrodotoxin (TTX)-sensitive voltage-gated sodium (Nav) channels. This action was completely suppressed by the addition of 200 nM TTX to the external solution, indicating that this effect was mediated through TTX-sensitive Nav channels. In addition, P-CTX-1 also prolonged action potential and afterhyperpolarization (AHP) duration. In a subpopulation of neurons, P-CTX-1 also produced tonic action potential firing, an effect that was not accompanied by significant oscillation of the resting membrane potential. Conversely, in neurons expressing TTX-resistant Nav currents, P-CTX-1 failed to alter any parameter of neuronal excitability examined in this study. Under voltage-clamp conditions in rat DRG neurons, P-CTX-1 inhibited both delayed-rectifier and 'A-type' potassium currents in a dose-dependent manner, actions that occurred in the absence of alterations to the voltage dependence of activation. These actions appear to underlie the prolongation of the action potential and AHP, and contribute to repetitive firing. These data indicate that a block of potassium channels contributes to the increase in neuronal excitability, associated with a modulation of Nav channel gating, observed clinically in response to ciguatera poisoning

  17. 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.

  18. Activity of Palythoa caribaeorum Venom on Voltage-Gated Ion Channels in Mammalian Superior Cervical Ganglion Neurons

    Science.gov (United States)

    Lazcano-Pérez, Fernando; Castro, Héctor; Arenas, Isabel; García, David E.; González-Muñoz, Ricardo; Arreguín-Espinosa, Roberto

    2016-01-01

    The Zoanthids are an order of cnidarians whose venoms and toxins have been poorly studied. Palythoa caribaeorum is a zoanthid commonly found around the Mexican coastline. In this study, we tested the activity of P. caribaeorum venom on voltage-gated sodium channel (NaV1.7), voltage-gated calcium channel (CaV2.2), the A-type transient outward (IA) and delayed rectifier (IDR) currents of KV channels of the superior cervical ganglion (SCG) neurons of the rat. These results showed that the venom reversibly delays the inactivation process of voltage-gated sodium channels and inhibits voltage-gated calcium and potassium channels in this mammalian model. The compounds responsible for these effects seem to be low molecular weight peptides. Together, these results provide evidence for the potential use of zoanthids as a novel source of cnidarian toxins active on voltage-gated ion channels. PMID:27164140

  19. Activity of Palythoa caribaeorum Venom on Voltage-Gated Ion Channels in Mammalian Superior Cervical Ganglion Neurons.

    Science.gov (United States)

    Lazcano-Pérez, Fernando; Castro, Héctor; Arenas, Isabel; García, David E; González-Muñoz, Ricardo; Arreguín-Espinosa, Roberto

    2016-01-01

    The Zoanthids are an order of cnidarians whose venoms and toxins have been poorly studied. Palythoa caribaeorum is a zoanthid commonly found around the Mexican coastline. In this study, we tested the activity of P. caribaeorum venom on voltage-gated sodium channel (NaV1.7), voltage-gated calcium channel (CaV2.2), the A-type transient outward (IA) and delayed rectifier (IDR) currents of KV channels of the superior cervical ganglion (SCG) neurons of the rat. These results showed that the venom reversibly delays the inactivation process of voltage-gated sodium channels and inhibits voltage-gated calcium and potassium channels in this mammalian model. The compounds responsible for these effects seem to be low molecular weight peptides. Together, these results provide evidence for the potential use of zoanthids as a novel source of cnidarian toxins active on voltage-gated ion channels. PMID:27164140

  20. Chronic ciguatoxin treatment induces synaptic scaling through voltage gated sodium channels in cortical neurons.

    Science.gov (United States)

    Martín, Víctor; Vale, Carmen; Rubiolo, Juan A; Roel, Maria; Hirama, Masahiro; Yamashita, Shuji; Vieytes, Mercedes R; Botana, Luís M

    2015-06-15

    Ciguatoxins are sodium channels activators that cause ciguatera, one of the most widespread nonbacterial forms of food poisoning, which presents with long-term neurological alterations. In central neurons, chronic perturbations in activity induce homeostatic synaptic mechanisms that adjust the strength of excitatory synapses and modulate glutamate receptor expression in order to stabilize the overall activity. Immediate early genes, such as Arc and Egr1, are induced in response to activity changes and underlie the trafficking of glutamate receptors during neuronal homeostasis. To better understand the long lasting neurological consequences of ciguatera, it is important to establish the role that chronic changes in activity produced by ciguatoxins represent to central neurons. Here, the effect of a 30 min exposure of 10-13 days in vitro (DIV) cortical neurons to the synthetic ciguatoxin CTX 3C on Arc and Egr1 expression was evaluated using real-time polymerase chain reaction approaches. Since the toxin increased the mRNA levels of both Arc and Egr1, the effect of CTX 3C in NaV channels, membrane potential, firing activity, miniature excitatory postsynaptic currents (mEPSCs), and glutamate receptors expression in cortical neurons after a 24 h exposure was evaluated using electrophysiological and western blot approaches. The data presented here show that CTX 3C induced an upregulation of Arc and Egr1 that was prevented by previous coincubation of the neurons with the NaV channel blocker tetrodotoxin. In addition, chronic CTX 3C caused a concentration-dependent shift in the activation voltage of NaV channels to more negative potentials and produced membrane potential depolarization. Moreover, 24 h treatment of cortical neurons with 5 nM CTX 3C decreased neuronal firing and induced synaptic scaling mechanisms, as evidenced by a decrease in the amplitude of mEPSCs and downregulation in the protein level of glutamate receptors that was also prevented by tetrodotoxin

  1. EXAMINATION OF THE ANTICONVULSANT PROPERTIES OF VOLTAGE-SENSITIVE CALCIUM CHANNEL INHIBITORS IN AMYGDALA KINDLED SEIZURES

    Science.gov (United States)

    Representatives from three different classes of voltage-sensitive calcium (VSC) channel inhibitors were assessed for their protection against amygdala kindled seizures. dult male long Evans rats (n=12) were implanted with electrodes in the amygdala and were stimulated once daily ...

  2. L-type Voltage-Gated Calcium Channels in Conditioned Fear: A Genetic and Pharmacological Analysis

    Science.gov (United States)

    McKinney, Brandon C.; Sze, Wilson; White, Jessica A.; Murphy, Geoffrey G.

    2008-01-01

    Using pharmacological approaches, others have suggested that L-type voltage-gated calcium channels (L-VGCCs) mediate both consolidation and extinction of conditioned fear. In the absence of L-VGCC isoform-specific antagonists, we have begun to investigate the subtype-specific role of LVGCCs in consolidation and extinction of conditioned fear…

  3. Ciguatoxins: Cyclic Polyether Modulators of Voltage-gated Iion Channel Function

    OpenAIRE

    Lewis, Richard J; Nicholson, Graham M.

    2006-01-01

    Ciguatoxins are cyclic polyether toxins, derived from marine dinoflagellates, which are responsible for the symptoms of ciguatera poisoning. Ingestion of tropical and subtropical fin fish contaminated by ciguatoxins results in an illness characterised by neurological, cardiovascular and gastrointestinal disorders. The pharmacology of ciguatoxins is characterised by their ability to cause persistent activation of voltage-gated sodium channels, to increase neuronal excitability and neurotransmi...

  4. Molecular insights into the local anesthetic receptor within voltage-gated sodium channels using hydroxylated analogues of mexiletine

    Directory of Open Access Journals (Sweden)

    Jean-François eDesaphy

    2012-02-01

    Full Text Available We previously showed that the β-adrenoceptor modulators, clenbuterol and propranolol, directly blocked voltage-gated sodium channels, whereas salbutamol and nadolol did not (Desaphy et al., 2003, suggesting the presence of two hydroxyl groups on the aromatic moiety of the drugs as a molecular requisite for impeding sodium channel block. To verify such an hypothesis, we synthesized five new mexiletine analogues by adding one or two hydroxyl groups to the aryl moiety of the sodium channel blocker and tested these compounds on hNav1.4 channels expressed in HEK293 cells. Concentration-response relationships were constructed using an holding potential of -120 mV at 0.1 Hz (tonic block and 10 Hz (use-dependent block stimulation frequencies. The half-maximum inhibitory concentrations (IC50 were linearly correlated to drug lipophilicity: the less lipophilic the drug, minor was the block. The same compounds were also tested on F1586C and Y1593C hNav1.4 channel mutants, to gain further information on the molecular interactions of mexiletine with its receptor within the sodium channel pore. Alteration of tonic block suggests that the aryl moiety of mexiletine may interact either directly or indirectly with Phe1586 in the closed sodium channel to produce low-affinity binding block, and that this interaction depends on the electrostatic potential of the drug aromatic tail. Alteration of use-dependent block suggests that addition of hydroxyl groups to the aryl moiety may modify high-affinity binding of the drug ammine terminal to Phe1586 through cooperativity between the two pharmacophores, this effect being mainly related to drug lipophilicity. Mutation of Tyr1593 further impaired such cooperativity. In conclusion, these results confirm our former hypothesis showing that the presence of hydroxyl groups to the aryl moiety of mexiletine greatly reduced sodium channel block, and provide molecular insights into the intimate interaction of local anesthetics with

  5. Two-pore channels provide insight into the evolution of voltage-gated Ca2+ and Na+ channels

    OpenAIRE

    Rahman, Taufiq; Cai, Xinjiang; Brailoiu, G. Cristina; Abood, Mary E; Brailoiu, Eugen; Patel, Sandip

    2014-01-01

    Four-domain voltage-gated Ca2+ and Na+ channels (CaV, NaV) underpin nervous system function and likely emerged upon intragenic duplication of a primordial two-domain precursor. To investigate if two-pore channels (TPCs) may represent an intermediate in this evolutionary transition, we performed molecular docking simulations with a homology model of TPC1, which suggested that the pore region could bind antagonists of CaV or NaV. CaV or NaV antagonists blocked NAADP-evoked Ca2+ signals in sea u...

  6. Neurotoxins and their binding areas on voltage-gated sodium channels.

    Science.gov (United States)

    Stevens, Marijke; Peigneur, Steve; Tytgat, Jan

    2011-01-01

    Voltage-gated sodium channels (VGSCs) are large transmembrane proteins that conduct sodium ions across the membrane and by doing so they generate signals of communication between many kinds of tissues. They are responsible for the generation and propagation of action potentials in excitable cells, in close collaboration with other channels like potassium channels. Therefore, genetic defects in sodium channel genes can cause a wide variety of diseases, generally called "channelopathies." The first insights into the mechanism of action potentials and the involvement of sodium channels originated from Hodgkin and Huxley for which they were awarded the Nobel Prize in 1963. These concepts still form the basis for understanding the function of VGSCs. When VGSCs sense a sufficient change in membrane potential, they are activated and consequently generate a massive influx of sodium ions. Immediately after, channels will start to inactivate and currents decrease. In the inactivated state, channels stay refractory for new stimuli and they must return to the closed state before being susceptible to a new depolarization. On the other hand, studies with neurotoxins like tetrodotoxin (TTX) and saxitoxin (STX) also contributed largely to our today's understanding of the structure and function of ion channels and of VGSCs specifically. Moreover, neurotoxins acting on ion channels turned out to be valuable lead compounds in the development of new drugs for the enormous range of diseases in which ion channels are involved. A recent example of a synthetic neurotoxin that made it to the market is ziconotide (Prialt(®), Elan). The original peptide, ω-MVIIA, is derived from the cone snail Conus magus and now FDA/EMA-approved for the management of severe chronic pain by blocking the N-type voltage-gated calcium channels in pain fibers. This review focuses on the current status of research on neurotoxins acting on VGSC, their contribution to further unravel the structure and function of

  7. Neurotoxins and their binding areas on voltage-gated sodium channels

    Directory of Open Access Journals (Sweden)

    Marijke eStevens

    2011-11-01

    Full Text Available Voltage-gated Sodium Channels (VGSCs are large transmembrane proteins that conduct sodium ions across the membrane and by doing so they generate signals of communication between many kinds of tissues. They are responsible for the generation and propagation of action potentials in excitable cells, in close collaboration with other channels like potassium channels. Genetic defects in sodium channel genes therefore can cause a wide variety of diseases, generally called ‘channelopathies’.The first insights into the mechanism of action potentials and the involvement of sodium channels originated from Hodgkin and Huxley for which they were awarded the Nobel Prize in 1963. Until now, these concepts still form the basis for understanding the functioning of VGSCs. When VGSCs sense a sufficient change in membrane potential, they are activated and will generate a massive influx of sodium ions. Immediately after, channels will start inactivating and currents decrease. In the inactivated state channels stay refractory for any new stimulus and they must return to the closed state before being susceptible to any new depolarization. On the other hand, studies with neurotoxins like tetrodotoxin (TTX and saxitoxin (STX also contributed largely to our today’s understanding of the structure and function of ion channels and specifically of VGSCs. Moreover, neurotoxins acting on ion channels turned out to be valuable tools in the development of new drugs for the enormous range of diseases in which ion channels are involved. A recent example of a synthetic neurotoxin that made it to the market is ziconotide (Prialt®, Elan. The original peptide, -MVIIA, is derived from the cone snail Conus magus and now FDA/EMEA-approved for the management of severe chronic pain by blocking the N-type voltage-gated calcium channels in neurons.This review focuses on the current status of research on neurotoxins acting on VGSC, their contribution to further unravel the

  8. Computational Structural Pharmacology and Toxicology of Voltage-Gated Sodium Channels.

    Science.gov (United States)

    Zhorov, B S; Tikhonov, D B

    2016-01-01

    Voltage-gated sodium channels are targets for many toxins and medically important drugs. Despite decades of intensive studies in industry and academia, atomic mechanisms of action are still not completely understood. The major cause is a lack of high-resolution structures of eukaryotic channels and their complexes with ligands. In these circumstances a useful approach is homology modeling that employs as templates X-ray structures of potassium channels and prokaryotic sodium channels. On one hand, due to inherent limitations of this approach, results should be treated with caution. In particular, models should be tested against relevant experimental data. On the other hand, docking of drugs and toxins in homology models provides a unique possibility to integrate diverse experimental data provided by mutational analysis, electrophysiology, and studies of structure-activity relations. Here we describe how homology modeling advanced our understanding of mechanisms of several classes of ligands. These include tetrodotoxins and mu-conotoxins that block the outer pore, local anesthetics that block of the inner pore, batrachotoxin that binds in the inner pore but, paradoxically, activates the channel, pyrethroid insecticides that activate the channel by binding at lipid-exposed repeat interfaces, and scorpion alpha and beta-toxins, which bind between the pore and voltage-sensing domains and modify the channel gating. We emphasize importance of experimental data for elaborating the models. PMID:27586283

  9. Endothelium modulates anion channel-dependent aortic contractions to iodide.

    Science.gov (United States)

    Lamb, F S; Barna, T J

    2000-05-01

    Anion currents contribute to vascular smooth muscle (VSM) membrane potential. The substitution of extracellular chloride (Cl) with iodide (I) or bromide (Br) initially inhibited and then potentiated isometric contractile responses of rat aortic rings to norepinephrine. Anion substitution alone produced a small relaxation, which occurred despite a lack of active tone and minimal subsequent contraction of endothelium-intact rings (4.2 +/- 1.2% of the response to 90 mM KCl). Endothelium-denuded rings underwent a similar initial relaxation but then contracted vigorously (I > Br). Responses to 130 mM I (93.7 +/- 1.9% of 90 mM KCl) were inhibited by nifedipine (10(-6) M), niflumic acid (10(-5) M), tamoxifen (10(-5) M), DIDS (10(-4) M), and HCO(-)(3)-free buffer (HEPES 10 mM) but not by bumetanide (10(-5) M). Intact rings treated with N(omega)-nitro-L-arginine (10(-4) M) responded weakly to I (15.5 +/- 2.1% of 90 mM KCl), whereas hemoglobin (10(-5) M), indomethacin (10(-6) M), 17-octadecynoic acid (10(-5) M), and 1H-[1,2, 4]oxadiazole[4,3-a]quinoxalin-1-one (10(-6) M) all failed to augment the response of intact rings to I. We hypothesize that VSM takes up I primarily via an anion exchanger. Subsequent I efflux through anion channels having a selectivity of I > Br > Cl produces depolarization. In endothelium-denuded or agonist-stimulated vessels, this current is sufficient to activate voltage-dependent calcium channels and cause contraction. Neither nitric oxide nor prostaglandins are the primary endothelial modulator of these anion channels. If they are regulated by an endothelium-dependent hyperpolarizing factor it is not a cytochrome P-450 metabolite. PMID:10775130

  10. Structure of the inactivating gate from the Shaker voltage gated K+ channel analyzed by NMR spectroscopy

    International Nuclear Information System (INIS)

    Rapid inactivation of voltage-gated K+ (KV) channels is mediated by an N-terminal domain (inactivating ball domain) which blocks the open channel from the cytoplasmic side. Inactivating ball domains of various KV channels are also biologically active when synthesized separately and added as a peptide to the solution. Synthetic inactivating ball domains from different KV channels with hardly any sequence homology mediate quite similar effects even on unrelated KV channel subtypes whose inactivation domain has been deleted. The solution structure of the inactivating ball peptide from Shaker (Sh-P22) was analyzed with NMR spectroscopy. The NMR data indicate a non-random structure in an aqueous environment. However, while other inactivating ball peptides showed well-defined three-dimensional structures under these conditions, Sh-P22 does not have a unique, compactly folded structure in solution. (orig.)

  11. 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 ...

  12. Molecular cloning and analysis of zebrafish voltage-gated sodium channel beta subunit genes: implications for the evolution of electrical signaling in vertebrates

    OpenAIRE

    Zhong Tao P; Watanabe Hiroshi; Chopra Sameer S; Roden Dan M

    2007-01-01

    Abstract Background Action potential generation in excitable cells such as myocytes and neurons critically depends on voltage-gated sodium channels. In mammals, sodium channels exist as macromolecular complexes that include a pore-forming alpha subunit and 1 or more modulatory beta subunits. Although alpha subunit genes have been cloned from diverse metazoans including flies, jellyfish, and humans, beta subunits have not previously been identified in any non-mammalian species. To gain further...

  13. Local Sequence Information-based Support Vector Machine to Classify Voltage-gated Potassium Channels

    Institute of Scientific and Technical Information of China (English)

    Li-Xia LIU; Meng-Long LI; Fu-Yuan TAN; Min-Chun LU; Ke-Long WANG; Yan-Zhi GUO; Zhi-Ning WEN; Lin JIANG

    2006-01-01

    In our previous work, we developed a computational tool, PreK-ClassK-ClassKv, to predict and classify potassium (K+) channels. For K+ channel prediction (PreK) and classification at family level (ClassK), this method performs well. However, it does not perform so well in classifying voltage-gated potassium (Kv) channels (ClassKv). In this paper, a new method based on the local sequence information of Kv channels is introduced to classify Kv channels. Six transmembrane domains of a Kv channel protein are used to define a protein, and the dipeptide composition technique is used to transform an amino acid sequence to a numerical sequence. A Kv channel protein is represented by a vector with 2000 elements, and a support vector machine algorithm is applied to classify Kv channels. This method shows good performance with averages of total accuracy (Acc), sensitivity (SE), specificity (SP); reliability (R) and Matthews correlation coefficient (MCC) of 98.0%, 89.9%, 100%, 0.95 and 0.94 respectively. The results indicate that the local sequence information-based method is better than the global sequence information-based method to classify Kv channels.

  14. 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.…

  15. The L-Type Voltage-Gated Calcium Channel Ca[subscript v]1.3 Mediates Consolidation, but Not Extinction, of Contextually Conditioned Fear in Mice

    Science.gov (United States)

    McKinney, Brandon C.; Murphy, Geoffrey G.

    2006-01-01

    Using pharmacological techniques, it has been demonstrated that both consolidation and extinction of Pavlovian fear conditioning are dependent to some extent upon L-type voltage-gated calcium channels (LVGCCs). Although these studies have successfully implicated LVGCCs in Pavlovian fear conditioning, they do not provide information about the…

  16. Effect of inhibition of tyrosine phosphatases on voltage-operated calcium channel currents in rabbit isolated ear artery cells

    OpenAIRE

    Wijetunge, S; Lymn, J S; Hughes, A.D.

    1998-01-01

    The effect of increasing cellular tyrosine phosphorylation by inhibiting endogenous tyrosine phosphatases was examined on voltage-operated calcium channel currents in vascular smooth muscle cells.In single ear artery smooth muscle cells of the rabbit, studied by the whole cell voltage clamp technique, intracellular application of the tyrosine phosphatase inhibitors, sodium orthovanadate (100 μM) and peroxyvanadate (100 μM orthovanadate+1 mM H2O2) increased voltage-operated calcium channel cur...

  17. MOLECULAR PATHOPHYSIOLOGY AND PHARMACOLOGY OF THE VOLTAGE-SENSING DOMAIN OF NEURONAL ION CHANNELS

    Directory of Open Access Journals (Sweden)

    Maurizio Taglialatela

    2015-07-01

    Full Text Available Voltage-gated ion channels (VGIC are membrane proteins that switch from a closed to open state in response to changes in membrane potential, thus enabling ion fluxes across the cell membranes. The mechanism that regulate the structural rearrangements occurring in VGIC in response to changes in membrane potential still remains one of the most challenging topic of modern biophysics. Na+, Ca2+ and K+ voltage-gated channels are structurally formed by the assembly of four similar domains, each comprising six transmembrane segments. Each domain can be divided in two main regions: the Pore Module (PM and the Voltage-Sensing Module (VSM. The PM (helices S5 and S6 and intervening linker is responsible for gate opening and ion selectivity; by contrast, the VSM, comprising the first four transmembrane helices (S1-S4, undergoes the first conformational changes in response to membrane voltage. In particular, the S4 segment of each domain, which contains several positively charged residues interspersed with hydrophobic amino acids, is located within the membrane electric field and plays an essential role in voltage sensing. In neurons, specific gating properties of each channel subtype underlie a variety of biological events, ranging from the generation and propagation of electrical impulses, to the secretion of neurotransmitters, to the regulation of gene expression. Given the important functional role played by the VSM in neuronal VGICs, it is not surprising that various VSM mutations affecting the gating process of these channels are responsible for human diseases, and that compounds acting on the VSM have emerged as important investigational tools with great therapeutic potential. In the present review we will briefly describe the most recent discoveries concerning how the VSM exerts its function, how genetically inherited diseases caused by mutations occurring in the VSM affects gating in VGICs, and how several classes of drugs and toxins selectively

  18. Where is the spike generator of the cochlear nerve? Voltage-gated sodium channels in the mouse cochlea.

    OpenAIRE

    Hossain, Waheeda A.; Antic, Srdjan D.; Yang, Yang; Rasband, Matthew N; Morest, D. Kent

    2005-01-01

    The origin of the action potential in the cochlea has been a long-standing puzzle. Since voltage-dependent Na+ (Nav) channels are essential for action potential generation, we investigated the detailed distribution of Nav1.6 and Nav1.2 in the cochlear ganglion, cochlear nerve, and organ of Corti, including the Type I and Type II ganglion cells. In most Type I ganglion cells, Nav1.6 was present at the first nodes flanking the myelinated bipolar cell body and at subsequent nodes of Ranvier. In ...

  19. Functional role of voltage gated Ca2+ channels in heart automaticity

    Directory of Open Access Journals (Sweden)

    Pietro eMesirca

    2015-02-01

    Full Text Available Pacemaker activity of automatic cardiac myocytes controls the heartbeat in everyday life. Cardiac automaticity is under the control of several neurotransmitters and hormones and is constantly regulated by the autonomic nervous system to match the physiological needs of the organism. Several classes of ion channels and proteins involved in intracellular Ca2+ dynamics contribute to pacemaker activity. The functional role of voltage-gated calcium channels (VGCCs in heart automaticity and impulse conduction has been matter of debate for 30 years. However, growing evidence shows that VGCCs are important regulators of the pacemaker mechanisms and play also a major role in atrio-ventricular impulse conduction. Incidentally, studies performed in genetically modified mice lacking L-type Cav1.3 (Cav1.3-/- or T-type Cav3.1 (Cav3.1-/- channels show that genetic inactivation of these channels strongly impacts pacemaking. In cardiac pacemaker cells, VGCCs activate at negative voltages at the beginning of the diastolic depolarization and importantly contribute to this phase by supplying inward current. Loss-of-function of these channels also impairs atrio-ventricular conduction. Furthermore, inactivation of Cav1.3 channels promotes also atrial fibrillation and flutter in knockout mice suggesting that these channels can play a role in stabilizing atrial rhythm. Genomic analysis demonstrated that Cav1.3 and Cav3.1 channels are widely expressed in pacemaker tissue of mice, rabbits and humans. Importantly, human diseases of pacemaker activity such as congenital bradycardia and heart block have been attributed to loss-of-function of Cav1.3 and Cav3.1 channels. In this article, we will review the current knowledge on the role of VGCCs in the generation and regulation of heart rate and rhythm. We will discuss also how loss of Ca2+ entry through VGCCs could influence intracellular Ca2+ handling and promote atrial arrhythmias.

  20. A Theoretical Model for Calculating Voltage Sensitivity of Ion Channels and the Application on Kv1.2 Potassium Channel

    Science.gov (United States)

    Yang, Huaiyu; Gao, Zhaobing; Li, Ping; Yu, Kunqian; Yu, Ye; Xu, Tian-Le; Li, Min; Jiang, Hualiang

    2012-01-01

    Voltage sensing confers conversion of a change in membrane potential to signaling activities underlying the physiological processes. For an ion channel, voltage sensitivity is usually experimentally measured by fitting electrophysiological data to Boltzmann distributions. In our study, a two-state model of the ion channel and equilibrium statistical mechanics principle were used to test the hypothesis of empirically calculating the overall voltage sensitivity of an ion channel on the basis of its closed and open conformations, and determine the contribution of individual residues to the voltage sensing. We examined the theoretical paradigm by performing experimental measurements with Kv1.2 channel and a series of mutants. The correlation between the calculated values and the experimental values is at respective level, R2 = 0.73. Our report therefore provides in silico prediction of key conformations and has identified additional residues critical for voltage sensing. PMID:22768937

  1. Voltage-gated sodium channel expression and action potential generation in differentiated NG108-15 cells

    OpenAIRE

    Liu Jinxu; Tu Huiyin; Zhang Dongze; Zheng Hong; Li Yu-Long

    2012-01-01

    Abstract Background The generation of action potential is required for stimulus-evoked neurotransmitter release in most neurons. Although various voltage-gated ion channels are involved in action potential production, the initiation of the action potential is mainly mediated by voltage-gated Na+ channels. In the present study, differentiation-induced changes of mRNA and protein expression of Na+ channels, Na+ currents, and cell membrane excitability were investigated in NG108-15 cells. Result...

  2. A Molecular Switch between the Outer and the Inner Vestibules of the Voltage-gated Na+ Channel*

    OpenAIRE

    Zarrabi, Touran; Cervenka, Rene; Sandtner, Walter; Lukacs, Peter; Koenig, Xaver; Hilber, Karlheinz; Mille, Markus; Lipkind, Gregory M; Fozzard, Harry A.; Todt, Hannes

    2010-01-01

    Voltage-gated ion channels are transmembrane proteins that undergo complex conformational changes during their gating transitions. Both functional and structural data from K+ channels suggest that extracellular and intracellular parts of the pore communicate with each other via a trajectory of interacting amino acids. No crystal structures are available for voltage-gated Na+ channels, but functional data suggest a similar intramolecular communication involving the inner and outer vestibules. ...

  3. Voltage-Gated Sodium Channels: Mechanistic Insights From Atomistic Molecular Dynamics Simulations.

    Science.gov (United States)

    Oakes, V; Furini, S; Domene, C

    2016-01-01

    The permeation of ions and other molecules across biological membranes is an inherent requirement of all cellular organisms. Ion channels, in particular, are responsible for the conduction of charged species, hence modulating the propagation of electrical signals. Despite the universal physiological implications of this property, the molecular functioning of ion channels remains ambiguous. The combination of atomistic structural data with computational methodologies, such as molecular dynamics (MD) simulations, is now considered routine to investigate structure-function relationships in biological systems. A fuller understanding of conduction, selectivity, and gating, therefore, is steadily emerging due to the applicability of these techniques to ion channels. However, because their structure is known at atomic resolution, studies have consistently been biased toward K(+) channels, thus the molecular determinants of ionic selectivity, activation, and drug blockage in Na(+) channels are often overlooked. The recent increase of available crystallographic data has eminently encouraged the investigation of voltage-gated sodium (NaV) channels via computational methods. Here, we present an overview of simulation studies that have contributed to our understanding of key principles that underlie ionic conduction and selectivity in Na(+) channels, in comparison to the K(+) channel analogs. PMID:27586285

  4. The voltage-gated sodium channel nav1.8 is expressed in human sperm.

    Directory of Open Access Journals (Sweden)

    Antonio Cejudo-Roman

    Full Text Available The role of Na(+ fluxes through voltage-gated sodium channels in the regulation of sperm cell function remains poorly understood. Previously, we reported that several genes encoding voltage-gated Na(+ channels were expressed in human testis and mature spermatozoa. In this study, we analyzed the presence and function of the TTX-resistant VGSC α subunit Nav1.8 in human capacitated sperm cells. Using an RT-PCR assay, we found that the mRNA of the gene SCN10A, that encode Na v1.8, was abundantly and specifically expressed in human testis and ejaculated spermatozoa. The Na v1.8 protein was detected in capacitated sperm cells using three different specific antibodies against this channel. Positive immunoreactivity was mainly located in the neck and the principal piece of the flagellum. The presence of Na v1.8 in sperm cells was confirmed by Western blot. Functional studies demonstrated that the increases in progressive motility produced by veratridine, a voltage-gated sodium channel activator, were reduced in sperm cells preincubated with TTX (10 μM, the Na v1.8 antagonist A-803467, or a specific Na v1.8 antibody. Veratridine elicited similar percentage increases in progressive motility in sperm cells maintained in Ca(2+-containing or Ca(2+-free solution and did not induce hyperactivation or the acrosome reaction. Veratridine caused a rise in sperm intracellular Na(+, [Na(+]i, and the sustained phase of the response was inhibited in the presence of A-803467. These results verify that the Na(+ channel Na v1.8 is present in human sperm cells and demonstrate that this channel participates in the regulation of sperm function.

  5. Proton Dependent Inhibition of the Cardiac Sodium Channel Nav1.5 by Ranolazine

    Directory of Open Access Journals (Sweden)

    PeterCRuben

    2013-06-01

    Full Text Available Ranolazine is clinically approved for treatment of angina pectoris and is a potential candidate for antiarrhythmic, antiepileptic and analgesic applications. These therapeutic effects of ranolazine hinge on its ability to inhibit persistent or late Na+ currents in a variety of voltage-gated sodium channels. Extracellular acidosis, typical of ischemic events, may alter the efficiency of drug/channel interactions. In this study, we examined pH modulation of ranolazine’s interaction with the cardiac sodium channel, Nav1.5. We performed whole-cell path clamp experiments at extracellular pH 7.4 and 6.0 on Nav1.5 transiently expressed in HEK293 cell line. Consistent with previous studies, we found that ranolazine induced a stable conformational state in the cardiac sodium channel with onset/recovery kinetics and voltage-dependence resembling intrinsic slow inactivation. This interaction diminished the availability of the channels in a voltage- and use-dependent manner. Low extracellular pH impaired inactivation states leading to an increase in late Na+ currents. Ranolazine interaction with the channel was also slowed 4-5 fold. However, ranolazine restored the voltage-dependent steady-state availability profile, thereby reducing window/persistent currents at pH 6.0 in a manner comparable to pH 7.4. These results suggest that ranolazine is effective at therapeutically relevant concentrations (10µM, in acidic extracellular pH, where it compensates for impaired native slow inactivation.

  6. History-dependent dynamics in a generic model of ion channels - an analytic study

    Directory of Open Access Journals (Sweden)

    Daniel Soudry

    2010-04-01

    Full Text Available Recent experiments have demonstrated that the timescale of adaptation of single neurons and ion channel populations to stimuli slows down as the length of stimulation increases; in fact, no upper bound on temporal time-scales seems to exist in such systems. Furthermore, patch clamp experiments on single ion channels have hinted at the existence of large, mostly unobservable, inactivation state spaces within a single ion channel. This raises the question of the relation between this multitude of inactivation states and the observed behavior. In this work we propose a minimal model for ion channel dynamics which does not assume any specific structure of the inactivation state space. The model is simple enough to render an analytical study possible. This leads to a clear and concise explanation of the experimentally observed exponential history-dependent relaxation in sodium channels in a voltage clamp setting, and shows that their recovery rate from slow inactivation must be voltage dependent. Furthermore, we predict that history-dependent relaxation cannot be created by overly sparse spiking activity. While the model was created with ion channel populations in mind, its simplicity and genericalness render it a good starting point for modeling similar effects in other systems, and for scaling up to higher levels such as single neurons which are also known to exhibit multiple time scales.

  7. 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...

  8. How do taste cells lacking synapses mediate neurotransmission? CALHM1, a voltage-gated ATP channel

    OpenAIRE

    Taruno, Akiyuki; Matsumoto, Ichiro; Ma, Zhongming; Marambaud, Philippe; Foskett, J. Kevin

    2013-01-01

    CALHM1 was recently demonstrated to be a voltage-gated ATP-permeable ion channel and to serve as a bona fide conduit for ATP release from sweet-, umami-, and bitter-sensing type II taste cells. Calhm1 is expressed in taste buds exclusively in type II cells and its product has structural and functional similarities with connexins and pannexins, two families of channel protein candidates for ATP release by type II cells. Calhm1 knockout in mice leads to loss of perception of sweet, umami, and b...

  9. On the multiple roles of the voltage gated sodium channel β1 subunit in genetic diseases

    Directory of Open Access Journals (Sweden)

    Debora eBaroni

    2015-05-01

    Full Text Available Voltage-gated sodium channels are intrinsic plasma membrane proteins that initiate the action potential in electrically excitable cells. They are composed of a pore-forming α-subunit and associated β-subunits. The β1-subunit was the first accessory subunit to be cloned. It can be important for controlling cell excitability and modulating multiple aspects of sodium channel physiology. Mutations of β1 are implicated in a wide variety of inherited pathologies, including epilepsy and cardiac conduction diseases. This review summarizes β1-subunit related channelopathies pointing out the current knowledge concerning their genetic background and their underlying molecular mechanisms.

  10. Identification of both GABAA receptors and voltage-activated Na+ channels as molecular targets of anticonvulsant α-asarone

    Directory of Open Access Journals (Sweden)

    Ze-JunWang

    2014-03-01

    Full Text Available Alpha (α-asarone, a major effective component isolated from the Chinese medicinal herb Acorus tatarinowii, is clinically used as medication for treating epilepsy, cough, bronchitis, and asthma. In the present study, we demonstrated that α-asarone targets central nervous system GABAA receptor as well as voltage-gated Na+ channels. Using whole-cell patch-clamp recording, -asarone inhibited spontaneous firing of output neurons, mitral cells (MCs, in mouse olfactory bulb brain slice preparations and hyperpolarized the membrane potential of MCs. The inhibitory effect of α-asarone persisted in the presence of ionotropic glutamate receptor blockers but was eliminated after adding a GABAA receptor blocker, suggesting that GABAA receptors mediated the inhibition of MCs by α-asarone. This hypothesis was supported by the finding that α-asarone evoked an outward current, but did not influence inhibitory postsynaptic currents (IPSCs. In addition to inhibiting spontaneous firing, α-asarone also inhibited the Nav1.2 channel, a dominant rat brain Na+ channel subtype. The effects of α-asarone on a defined Nav1.2 were characterized using transfected cells that stably expressed the Nav1.2 channel isoform. α-Asarone displayed strong tonic inhibition of Nav1.2 currents in a concentration- and membrane potential-dependent fashion. α-Asarone reduced channel availability in steady-state inactivation protocols by enhancing or stabilizing Na+ channel inactivation. Both Na+ channel blockade and activation of GABAA receptors provide a possible mechanism for the known anti-epileptic effects of α-asarone. It also suggests that α-asarone could benefit patients with cough possibly through inhibiting a Na+ channel subtype to inhibit peripheral and/or central sensitization of cough reflexes.

  11. CK2 activity is required for the interaction of FGF14 with voltage-gated sodium channels and neuronal excitability.

    Science.gov (United States)

    Hsu, Wei-Chun J; Scala, Federico; Nenov, Miroslav N; Wildburger, Norelle C; Elferink, Hannah; Singh, Aditya K; Chesson, Charles B; Buzhdygan, Tetyana; Sohail, Maveen; Shavkunov, Alexander S; Panova, Neli I; Nilsson, Carol L; Rudra, Jai S; Lichti, Cheryl F; Laezza, Fernanda

    2016-06-01

    Recent data shows that fibroblast growth factor 14 (FGF14) binds to and controls the function of the voltage-gated sodium (Nav) channel with phenotypic outcomes on neuronal excitability. Mutations in the FGF14 gene in humans have been associated with brain disorders that are partially recapitulated in Fgf14(-/-) mice. Thus, signaling pathways that modulate the FGF14:Nav channel interaction may be important therapeutic targets. Bioluminescence-based screening of small molecule modulators of the FGF14:Nav1.6 complex identified 4,5,6,7 -: tetrabromobenzotriazole (TBB), a potent casein kinase 2 (CK2) inhibitor, as a strong suppressor of FGF14:Nav1.6 interaction. Inhibition of CK2 through TBB reduces the interaction of FGF14 with Nav1.6 and Nav1.2 channels. Mass spectrometry confirmed direct phosphorylation of FGF14 by CK2 at S228 and S230, and mutation to alanine at these sites modified FGF14 modulation of Nav1.6-mediated currents. In 1 d in vitro hippocampal neurons, TBB induced a reduction in FGF14 expression, a decrease in transient Na(+) current amplitude, and a hyperpolarizing shift in the voltage dependence of Nav channel steady-state inactivation. In mature neurons, TBB reduces the axodendritic polarity of FGF14. In cornu ammonis area 1 hippocampal slices from wild-type mice, TBB impairs neuronal excitability by increasing action potential threshold and lowering firing frequency. Importantly, these changes in excitability are recapitulated in Fgf14(-/-) mice, and deletion of Fgf14 occludes TBB-dependent phenotypes observed in wild-type mice. These results suggest that a CK2-FGF14 axis may regulate Nav channels and neuronal excitability.-Hsu, W.-C. J., Scala, F., Nenov, M. N., Wildburger, N. C., Elferink, H., Singh, A. K., Chesson, C. B., Buzhdygan, T., Sohail, M., Shavkunov, A. S., Panova, N. I., Nilsson, C. L., Rudra, J. S., Lichti, C. F., Laezza, F. CK2 activity is required for the interaction of FGF14 with voltage-gated sodium channels and neuronal

  12. Modulation of voltage-gated channel currents by harmaline and harmane

    OpenAIRE

    Splettstoesser, Frank; Bonnet, Udo; Wiemann, Martin; Bingmann, Dieter; Büsselberg, Dietrich

    2004-01-01

    Harmala alkaloids are endogenous substances, which are involved in neurodegenerative disorders such as M. Parkinson, but some of them also have neuroprotective effects in the nervous system.While several sites of action at the cellular level (e.g. benzodiazepine receptors, 5-HT and GABAA receptors) have been identified, there is no report on how harmala alkaloids interact with voltage-gated membrane channels.The aim of this study was to investigate the effects of harmaline and harmane on volt...

  13. Presence of voltage-gated potassium channel complex antibody in a case of genetic prion disease

    OpenAIRE

    Jammoul, Adham; Lederman, Richard J; Tavee, Jinny; Li, Yuebing

    2014-01-01

    Voltage-gated potassium channel (VGKC) complex antibody-mediated encephalitis is a recently recognised entity which has been reported to mimic the clinical presentation of Creutzfeldt-Jakob disease (CJD). Testing for the presence of this neuronal surface autoantibody in patients presenting with subacute encephalopathy is therefore crucial as it may both revoke the bleak diagnosis of prion disease and allow institution of potentially life-saving immunotherapy. Tempering this optimistic view is...

  14. 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.

  15. Reciprocal voltage sensor-to-pore coupling leads to potassium channel C-type inactivation

    Science.gov (United States)

    Conti, Luca; Renhorn, Jakob; Gabrielsson, Anders; Turesson, Fredrik; Liin, Sara I.; Lindahl, Erik; Elinder, Fredrik

    2016-06-01

    Voltage-gated potassium channels open at depolarized membrane voltages. A prolonged depolarization causes a rearrangement of the selectivity filter which terminates the conduction of ions – a process called slow or C-type inactivation. How structural rearrangements in the voltage-sensor domain (VSD) cause alteration in the selectivity filter, and vice versa, are not fully understood. We show that pulling the pore domain of the Shaker potassium channel towards the VSD by a Cd2+ bridge accelerates C-type inactivation. Molecular dynamics simulations show that such pulling widens the selectivity filter and disrupts the K+ coordination, a hallmark for C-type inactivation. An engineered Cd2+ bridge within the VSD also affect C-type inactivation. Conversely, a pore domain mutation affects VSD gating-charge movement. Finally, C-type inactivation is caused by the concerted action of distant amino acid residues in the pore domain. All together, these data suggest a reciprocal communication between the pore domain and the VSD in the extracellular portion of the channel.

  16. Reciprocal voltage sensor-to-pore coupling leads to potassium channel C-type inactivation

    Science.gov (United States)

    Conti, Luca; Renhorn, Jakob; Gabrielsson, Anders; Turesson, Fredrik; Liin, Sara I; Lindahl, Erik; Elinder, Fredrik

    2016-01-01

    Voltage-gated potassium channels open at depolarized membrane voltages. A prolonged depolarization causes a rearrangement of the selectivity filter which terminates the conduction of ions – a process called slow or C-type inactivation. How structural rearrangements in the voltage-sensor domain (VSD) cause alteration in the selectivity filter, and vice versa, are not fully understood. We show that pulling the pore domain of the Shaker potassium channel towards the VSD by a Cd2+ bridge accelerates C-type inactivation. Molecular dynamics simulations show that such pulling widens the selectivity filter and disrupts the K+ coordination, a hallmark for C-type inactivation. An engineered Cd2+ bridge within the VSD also affect C-type inactivation. Conversely, a pore domain mutation affects VSD gating-charge movement. Finally, C-type inactivation is caused by the concerted action of distant amino acid residues in the pore domain. All together, these data suggest a reciprocal communication between the pore domain and the VSD in the extracellular portion of the channel. PMID:27278891

  17. IonWorks Barracuda Assay for Assessment of State-Dependent Sodium Channel Modulators.

    Science.gov (United States)

    Cerne, Rok; Wakulchik, Mark; Krambis, Michael J; Burris, Kevin D; Priest, Birgit T

    2016-03-01

    Voltage-gated sodium channels represent important drug targets. The implementation of higher throughput electrophysiology assays is necessary to characterize the interaction of test compounds with several conformational states of the channel, but has presented significant challenges. We describe a novel high throughput approach to assess the effects of test agents on voltage-gated sodium currents. The multiple protocol mode of the automated electrophysiology instrument IonWorks Barracuda was used to control the level of inactivation and monitor current stability. Good temporal stability of currents and spatial uniformity of inactivation were obtained by optimizing the experimental conditions. The resulting assay allowed for robust assessment of state-dependent effects of test agents and enabled direct comparison of compound potency across several sodium channel subtypes at equivalent levels of inactivation. PMID:26844665

  18. Urinary Bladder-Relaxant Effect of Kurarinone Depending on Potentiation of Large-Conductance Ca2+-Activated K+ Channels.

    Science.gov (United States)

    Lee, Sojung; Chae, Mee Ree; Lee, Byoung-Cheol; Kim, Yong-Chul; Choi, Jae Sue; Lee, Sung Won; Cheong, Jae Hoon; Park, Chul-Seung

    2016-08-01

    The large-conductance calcium-activated potassium channel (BKCa channel) plays critical roles in smooth muscle relaxation. In urinary bladder smooth muscle, BKCa channel activity underlies the maintenance of the resting membrane potential and repolarization of the spontaneous action potential triggering the phasic contraction. To identify novel BKCa channel activators, we screened a library of natural compounds using a cell-based fluorescence assay and a hyperactive mutant BKCa channel (Lee et al., 2013). From 794 natural compounds, kurarinone, a flavanone from Sophora flavescens, strongly potentiated BKCa channels. When treated from the extracellular side, this compound progressively shifted the conductance-voltage relationship of BKCa channels to more negative voltages and increased the maximum conductance in a dose-dependent manner. Whereas kurarinone strongly potentiated the homomeric BKCa channel composed of only the α subunit, its effects were much smaller on heteromeric channels coassembled with auxiliary β subunits. Although the activation kinetics was not altered significantly, the deactivation of BKCa channels was dramatically slowed by kurarinone treatment. At the single-channel level, kurarinone increased the open probability of the BKCa channel without affecting its single-channel conductance. Kurarinone potently relaxed acetylcholine-induced contraction of rat bladder smooth muscle and thus decreased the micturition frequency of rats with overactive bladder symptoms. These results indicate that kurarinone can directly potentiate BKCa channels and demonstrate the therapeutic potentials of kurarinone and its derivatives for developing antioveractive bladder medications and supplements. PMID:27251362

  19. Simulation of spontaneous Ca2+ oscillations in astrocytes mediated by voltage-gated calcium channels.

    Science.gov (United States)

    Zeng, Shuai; Li, Bing; Zeng, Shaoqun; Chen, Shangbin

    2009-11-01

    The purpose of this computational study was to investigate the possible role of voltage-gated Ca(2+) channels in spontaneous Ca(2+) oscillations of astrocytes. By incorporating different types of voltage-gated Ca(2+) channels and a previous model, this study reproduced typical Ca(2+) oscillations in silico. Our model could mimic the oscillatory phenomenon under a wide range of experimental conditions, including resting membrane potential (-75 to -60 mV), extracellular Ca(2+) concentration (0.1 to 1500 muM), temperature (20 to 37 degrees C), and blocking specific Ca(2+) channels. By varying the experimental conditions, the amplitude and duration of Ca(2+) oscillations changed slightly (both astrocytes might be an all-or-none process, which might be frequency-encoded in signaling. Moreover, the properties of Ca(2+) oscillations were found to be related to the dynamics of Ca(2+) influx, and not only to a constant influx. Therefore, calcium channels dynamics should be used in studying Ca(2+) oscillations. This work provides a platform to explore the still unclear mechanism of spontaneous Ca(2+) oscillations in astrocytes. PMID:19883585

  20. A homology model of the pore domain of a voltage-gated calcium channel is consistent with available SCAM data.

    Science.gov (United States)

    Bruhova, Iva; Zhorov, Boris S

    2010-03-01

    In the absence of x-ray structures of calcium channels, their homology models are used to rationalize experimental data and design new experiments. The modeling relies on sequence alignments between calcium and potassium channels. Zhen et al. (2005. J. Gen. Physiol. doi:10.1085/jgp.200509292) used the substituted cysteine accessibility method (SCAM) to identify pore-lining residues in the Ca(v)2.1 channel and concluded that their data are inconsistent with the symmetric architecture of the pore domain and published sequence alignments between calcium and potassium channels. Here, we have built K(v)1.2-based models of the Ca(v)2.1 channel with 2-(trimethylammonium)ethyl methanethiosulfonate (MTSET)-modified engineered cysteines and used Monte Carlo energy minimizations to predict their energetically optimal orientations. We found that depending on the position of an engineered cysteine in S6 and S5 helices, the ammonium group in the long flexible MTSET-modified side chain can orient into the inner pore, an interface between domains (repeats), or an interface between S5 and S6 helices. Different local environments of equivalent positions in the four repeats can lead to different SCAM results. The reported current inhibition by MTSET generally decreases with the predicted distances between the ammonium nitrogen and the pore axis. A possible explanation for outliers of this correlation is suggested. Our calculations rationalize the SCAM data, validate one of several published sequence alignments between calcium and potassium channels, and suggest similar spatial dispositions of S5 and S6 helices in voltage-gated potassium and calcium channels. PMID:20176854

  1. Temperature and Bias Voltage Dependence of the MPPC Detectors

    OpenAIRE

    Dinu, N.; Bazin, C; Chaumat, C.; Cheikali, C.; Para, A.; Puill, V.; Sylvia, C.; Vagnucci, J.-F.

    2010-01-01

    This work reports on the characterization of the Multi-Pixel Photon Counter (MPPC) detectors as a function of the temperature and bias voltage. Devices of 1x1 mm2 and 3x3 mm2 total area and 50x50 µm2 µcell size produced by Hamamatsu Photonics have been studied. The temperature has been varied from -110°C to -50°C using a cryostat cooled by liquid nitrogen and from 0 to 38°C using a climatic chamber. Important electrical parameters of the MPPC detectors as gain, breakdown voltage, quenching re...

  2. Venom Peptides From Cone Snails: Pharmacological Probes for Voltage-Gated Sodium Channels.

    Science.gov (United States)

    Green, B R; Olivera, B M

    2016-01-01

    The venoms of cone snails provide a rich source of neuroactive peptides (conotoxins). Several venom peptide families have been identified that are either agonists (ι- and δ-conotoxins) or antagonists (μ- and μO-conotoxins) of voltage-gated sodium channels (VGSCs). Members of these conotoxin classes have been integral in identifying and characterizing specific neurotoxin binding sites on the channel. Furthermore, given the specificity of some of these peptides for one sodium channel subtype over another, conotoxins have also proven useful in exploring differences between VGSC subtypes. This chapter summarizes the current knowledge of the structure and function based on the results of conotoxin interactions with VGSCs and correlates the peptides with the phylogeny of the Conus species from which they were derived. PMID:27586281

  3. In vivo potency of different ligands on voltage-gated sodium channels.

    Science.gov (United States)

    Safrany-Fark, Arpad; Petrovszki, Zita; Kekesi, Gabriella; Liszli, Peter; Benedek, Gyorgy; Keresztes, Csilla; Horvath, Gyongyi

    2015-09-01

    The Ranvier nodes of thick myelinated nerve fibers contain almost exclusively voltage-gated sodium channels (Navs), while the unmyelinated fibers have several receptors (e.g., cannabinoid, transient receptor potential vanilloid receptor 1), too. Therefore, a nerve which contains only motor fibers can be an appropriate in vivo model for selective influence of Navs. The goals were to evaluate the potency of local anesthetic drugs on such a nerve in vivo; furthermore, to investigate the effects of ligands with different structures (arachidonic acid, anandamide, capsaicin and nisoxetine) that were proved to inhibit Navs in vitro with antinociceptive properties. The marginal mandibular branch of the facial nerve was explored in anesthetized Wistar rats; after its stimulation, the electrical activity of the vibrissae muscles was registered following the perineural injection of different drugs. Lidocaine, bupivacaine and ropivacaine evoked dose-dependent decrease in electromyographic activity, i.e., lidocaine had lower potency than bupivacaine or ropivacaine. QX-314 did not cause any effect by itself, but its co-application with lidocaine produced a prolonged inhibition. Nisoxetine had a very low potency. While anandamide and capsaicin in high doses caused about 50% decrease in the amplitude of action potential, arachidonic acid did not influence the responses. We proved that the classical local anesthetics have high potency on motor nerves, suggesting that this method might be a reliable model for selective targeting of Navs in vivo circumstances. It is proposed that the effects of these endogenous lipids and capsaicin on sensory fibers are not primarily mediated by Navs. PMID:26033207

  4. Voltage-gated Na+ Channel Activity Increases Colon Cancer Transcriptional Activity and Invasion Via Persistent MAPK Signaling

    Science.gov (United States)

    House, Carrie D.; Wang, Bi-Dar; Ceniccola, Kristin; Williams, Russell; Simaan, May; Olender, Jacqueline; Patel, Vyomesh; Baptista-Hon, Daniel T.; Annunziata, Christina M.; Silvio Gutkind, J.; Hales, Tim G.; Lee, Norman H.

    2015-06-01

    Functional expression of voltage-gated Na+ channels (VGSCs) has been demonstrated in multiple cancer cell types where channel activity induces invasive activity. The signaling mechanisms by which VGSCs promote oncogenesis remain poorly understood. We explored the signal transduction process critical to VGSC-mediated invasion on the basis of reports linking channel activity to gene expression changes in excitable cells. Coincidentally, many genes transcriptionally regulated by the SCN5A isoform in colon cancer have an over-representation of cis-acting sites for transcription factors phosphorylated by ERK1/2 MAPK. We hypothesized that VGSC activity promotes MAPK activation to induce transcriptional changes in invasion-related genes. Using pharmacological inhibitors/activators and siRNA-mediated gene knockdowns, we correlated channel activity with Rap1-dependent persistent MAPK activation in the SW620 human colon cancer cell line. We further demonstrated that VGSC activity induces downstream changes in invasion-related gene expression via a PKA/ERK/c-JUN/ELK-1/ETS-1 transcriptional pathway. This is the first study illustrating a molecular mechanism linking functional activity of VGSCs to transcriptional activation of invasion-related genes.

  5. Functional chromaffin cell plasticity in response to stress: focus on nicotinic, gap junction, and voltage-gated Ca2+ channels.

    Science.gov (United States)

    Guérineau, Nathalie C; Desarménien, Michel G; Carabelli, Valentina; Carbone, Emilio

    2012-10-01

    An increase in circulating catecholamines constitutes one of the mechanisms whereby human body responds to stress. In response to chronic stressful situations, the adrenal medullary tissue exhibits crucial morphological and functional changes that are consistent with an improvement of chromaffin cell stimulus-secretion coupling efficiency. Stimulus-secretion coupling encompasses multiple intracellular (chromaffin cell excitability, Ca(2+) signaling, exocytosis, endocytosis) and intercellular pathways (splanchnic nerve-mediated synaptic transmission, paracrine and endocrine communication, gap junctional coupling), each of them being potentially subjected to functional remodeling upon stress. This review focuses on three chromaffin cell incontrovertible actors, the cholinergic nicotinic receptors and the voltage-dependent T-type Ca(2+) channels that are directly involved in Ca(2+)-dependent events controlling catecholamine secretion and electrical activity, and the gap junctional communication involved in the modulation of catecholamine secretion. We show here that these three actors react differently to various stressors, sometimes independently, sometimes in concert or in opposition. PMID:22252244

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

    Science.gov (United States)

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

    2014-03-19

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

  7. Bupivacaine inhibits large conductance, voltage- and Ca2+- activated K+ channels in human umbilical artery smooth muscle cells

    OpenAIRE

    Martín, Pedro; Enrique, Nicolás; Palomo, Ana R. Roldán; Rebolledo, Alejandro; Milesi, Veronica

    2012-01-01

    Bupivacaine is a local anesthetic compound belonging to the amino amide group. Its anesthetic effect is commonly related to its inhibitory effect on voltage-gated sodium channels. However, several studies have shown that this drug can also inhibit voltage-operated K+ channels by a different blocking mechanism. This could explain the observed contractile effects of bupivacaine on blood vessels. Up to now, there were no previous reports in the literature about bupivacaine effects on large condu...

  8. Identification and cellular localisation of voltage-operated calcium channels in immature rat testis.

    Science.gov (United States)

    Fragale, A; Aguanno, S; Kemp, M; Reeves, M; Price, K; Beattie, R; Craig, P; Volsen, S; Sher, E; D'Agostino, A

    2000-04-25

    Sertoli cells regulate the spermatogenic process mainly through the secretion of a complex fluid into the lumen of the seminiferous tubules behind the blood-testis barrier, containing many of the essential proteins necessary for maintenance and maturation of male germ cells. Thus, the study of Sertoli cell secretory processes is strictly correlated with the understanding of the regulatory mechanisms of spermatogenesis. In this work the authors have explored the voltage-sensitive calcium channel variety in the immature rat testis, their localisation and distribution within the seminiferous epithelium and peritubular and interstitial tissues as well as the possible role in the control of Sertoli cell secretion. The results reported in this paper, obtained by in situ hybridisation, immunohistology of rat testicular sections and Western blot analysis of Sertoli cell plasma membranes, show that mammalian Sertoli cells express mRNA encoding for several voltage-operated calcium channel subunits and express such proteins on their surface. Experiments performed on Sertoli cell monolayers cultured in the presence of specific toxins indicate that both N and P/Q-type Ca(2+) channels are involved in the regulation of protein secretion. PMID:10854695

  9. New Conotoxin SO-3 Targeting N-type Voltage-Sensitive Calcium Channels

    Directory of Open Access Journals (Sweden)

    Lei Wen

    2006-04-01

    Full Text Available Selective blockers of the N-type voltage-sensitive calcium (CaV channels are useful in the management of severe chronic pain. Here, the structure and function characteristics of a novel N-type CaV channel blocker, SO-3, are reviewed. SO-3 is a 25-amino acid conopeptide originally derived from the venom of Conus striatus, and contains the same 4-loop, 6-cysteine framework (C-C-CC-C-C as O-superfamily conotoxins. The synthetic SO-3 has high analgesic activity similar to ω-conotoxin MVIIA (MVIIA, a selective N-type CaV channel blocker approved in the USA and Europe for the alleviation of persistent pain states. In electrophysiological studies, SO-3 shows more selectivity towards the N-type CaV channels than MVIIA. The dissimilarity between SO-3 and MVIIA in the primary and tertiary structures is further discussed in an attempt to illustrate the difference in selectivity of SO-3 and MVIIA towards N-type CaV channels.

  10. Modeling of high composition AlGaN channel high electron mobility transistors with large threshold voltage

    International Nuclear Information System (INIS)

    We report on the potential of high electron mobility transistors (HEMTs) consisting of high composition AlGaN channel and barrier layers for power switching applications. Detailed two-dimensional (2D) simulations show that threshold voltages in excess of 3 V can be achieved through the use of AlGaN channel layers. We also calculate the 2D electron gas mobility in AlGaN channel HEMTs and evaluate their power figures of merit as a function of device operating temperature and Al mole fraction in the channel. Our models show that power switching transistors with AlGaN channels would have comparable on-resistance to GaN-channel based transistors for the same operation voltage. The modeling in this paper shows the potential of high composition AlGaN as a channel material for future high threshold enhancement mode transistors

  11. Spin and edge channel dependent transport through quantum dots

    International Nuclear Information System (INIS)

    We investigate the influence of spin polarized currents and non-equilibrated edge channels on the transport properties of a single quantum dot. Polarized currents are realized by the manual depletion of edge channels in high magnetic fields via a metallic top gate covering the source contact in the system. We observe a suppression and enhancement in the conductance of the quantum dot dependent on the edge channel configuration in the leads.

  12. Spin and edge channel dependent transport through quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Ridder, T; Rogge, M C; Haug, R J [Institut fuer Festkoerperphysik, Gottfried Wilhelm Leibniz Universitaet Hannover, Appelstrasse 2, D-30167 Hannover (Germany)], E-mail: ridder@nano.uni-hannover.de

    2008-11-12

    We investigate the influence of spin polarized currents and non-equilibrated edge channels on the transport properties of a single quantum dot. Polarized currents are realized by the manual depletion of edge channels in high magnetic fields via a metallic top gate covering the source contact in the system. We observe a suppression and enhancement in the conductance of the quantum dot dependent on the edge channel configuration in the leads.

  13. Studies of the voltage-sensitive calcium channels in smooth muscle, neuronal, and cardiac tissues using 1,4-dihydropyridine calcium channel antagonists and activators

    International Nuclear Information System (INIS)

    This study describes the investigation of the voltage-sensitive Ca+ channels in vascular and intestinal smooth muscle, chick neural retina cells and neonatal rat cardiac myocytes using 1,4-dihydropyridine Ca2+ channel antagonists and activators. In rat aorta, the tumor promoting phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA) produced Ca2+-dependent contractile responses. The responses to TPA were blocked by the Ca2+ channel antagonists. The effects of the enantiomers of Bay K 8644 and 202-791 were characterized in both rat tail artery and guinea pig ileal longitudinal smooth muscle preparations using pharmacologic and radioligand binding assays. The (S)-enantiomers induced contraction and potentiated the responses to K+ depolarization. The (R)-enantiomers inhibited the tension responses to K+. All the enantiomers inhibited specific [3H]nitrendipine binding. The pharmacologic activities of both activator and antagonist ligands correlated on a 1:1 basis with the binding affinities. In chick neural retina cells the (S)-enantiomers of Bay K 8644 and 202-791 enhanced Ca2+ influx. In contrast, the (R)-enantiomers inhibited Ca2+ influx. The enantiomers of Bay K 8644 and 202-791 inhibited specific [3H]PN 200-110 binding competitively. Binding of 1,4-dihydropyridines was characterized in neonatal rat heart cells

  14. Membrane tension influences the spike propagation between voltage-gated ion channel clusters of excitable membranes

    International Nuclear Information System (INIS)

    Ion channels of excitable membranes are known to be sensitive to various kinds of stimuli, but the case of simultaneous occurrence of different stimuli is poorly understood. Here, we theoretically analyze the influence of membrane tension on the dynamics of voltage-gated ion channels of excitable membranes. To do so, we develop a modification of the well–known Hodgkin–Huxley model to study numerically the spike generation and propagation in a single and two coupled excitable cells. We find that these cells can use membrane tension to trigger sub-threshold spike propagation, to suppress spike propagation and to alter the intensity of the signal transmission. These effects indicate that cells could use membrane tension to regulate cell-to-cell communication. (paper)

  15. Vector spin modeling for magnetic tunnel junctions with voltage dependent effects

    Science.gov (United States)

    Manipatruni, Sasikanth; Nikonov, Dmitri E.; Young, Ian A.

    2014-05-01

    Integration and co-design of CMOS and spin transfer devices requires accurate vector spin conduction modeling of magnetic tunnel junction (MTJ) devices. A physically realistic model of the MTJ should comprehend the spin torque dynamics of nanomagnet interacting with an injected vector spin current and the voltage dependent spin torque. Vector spin modeling allows for calculation of 3 component spin currents and potentials along with the charge currents/potentials in non-collinear magnetic systems. Here, we show 4-component vector spin conduction modeling of magnetic tunnel junction devices coupled with spin transfer torque in the nanomagnet. Nanomagnet dynamics, voltage dependent spin transport, and thermal noise are comprehended in a self-consistent fashion. We show comparison of the model with experimental magnetoresistance (MR) of MTJs and voltage degradation of MR with voltage. Proposed model enables MTJ circuit design that comprehends voltage dependent spin torque effects, switching error rates, spin degradation, and back hopping effects.

  16. Vector spin modeling for magnetic tunnel junctions with voltage dependent effects

    Energy Technology Data Exchange (ETDEWEB)

    Manipatruni, Sasikanth, E-mail: sasikanth.manipatruni@intel.com; Nikonov, Dmitri E.; Young, Ian A. [Exploratory Integrated Circuits, Components Research, Intel Corp., Hillsboro, Oregon 97124 (United States)

    2014-05-07

    Integration and co-design of CMOS and spin transfer devices requires accurate vector spin conduction modeling of magnetic tunnel junction (MTJ) devices. A physically realistic model of the MTJ should comprehend the spin torque dynamics of nanomagnet interacting with an injected vector spin current and the voltage dependent spin torque. Vector spin modeling allows for calculation of 3 component spin currents and potentials along with the charge currents/potentials in non-collinear magnetic systems. Here, we show 4-component vector spin conduction modeling of magnetic tunnel junction devices coupled with spin transfer torque in the nanomagnet. Nanomagnet dynamics, voltage dependent spin transport, and thermal noise are comprehended in a self-consistent fashion. We show comparison of the model with experimental magnetoresistance (MR) of MTJs and voltage degradation of MR with voltage. Proposed model enables MTJ circuit design that comprehends voltage dependent spin torque effects, switching error rates, spin degradation, and back hopping effects.

  17. Vector spin modeling for magnetic tunnel junctions with voltage dependent effects

    International Nuclear Information System (INIS)

    Integration and co-design of CMOS and spin transfer devices requires accurate vector spin conduction modeling of magnetic tunnel junction (MTJ) devices. A physically realistic model of the MTJ should comprehend the spin torque dynamics of nanomagnet interacting with an injected vector spin current and the voltage dependent spin torque. Vector spin modeling allows for calculation of 3 component spin currents and potentials along with the charge currents/potentials in non-collinear magnetic systems. Here, we show 4-component vector spin conduction modeling of magnetic tunnel junction devices coupled with spin transfer torque in the nanomagnet. Nanomagnet dynamics, voltage dependent spin transport, and thermal noise are comprehended in a self-consistent fashion. We show comparison of the model with experimental magnetoresistance (MR) of MTJs and voltage degradation of MR with voltage. Proposed model enables MTJ circuit design that comprehends voltage dependent spin torque effects, switching error rates, spin degradation, and back hopping effects

  18. Mechanism of Ion Permeation in Mammalian Voltage-Gated Sodium Channels.

    Directory of Open Access Journals (Sweden)

    Somayeh Mahdavi

    Full Text Available Recent determination of the crystal structures of bacterial voltage-gated sodium (NaV channels have raised hopes that modeling of the mammalian counterparts could soon be achieved. However, there are substantial differences between the pore domains of the bacterial and mammalian NaV channels, which necessitates careful validation of mammalian homology models constructed from the bacterial NaV structures. Such a validated homology model for the NaV1.4 channel was constructed recently using the extensive mutagenesis data available for binding of μ-conotoxins. Here we use this NaV1.4 model to study the ion permeation mechanism in mammalian NaV channels. Linking of the DEKA residues in the selectivity filter with residues in the neighboring domains is found to be important for keeping the permeation pathway open. Molecular dynamics simulations and potential of mean force calculations reveal that there is a binding site for a Na+ ion just inside the DEKA locus, and 1-2 Na+ ions can occupy the vestibule near the EEDD ring. These sites are separated by a low free energy barrier, suggesting that inward conduction occurs when a Na+ ion in the vestibule goes over the free energy barrier and pushes the Na+ ion in the filter to the intracellular cavity, consistent with the classical knock-on mechanism. The NaV1.4 model also provides a good description of the observed Na+/K+ selectivity.

  19. The signature sequence of voltage-gated potassium channels projects into the external vestibule.

    Science.gov (United States)

    Aiyar, J; Rizzi, J P; Gutman, G A; Chandy, K G

    1996-12-01

    A highly conserved motif, GYGD, contributes to the formation of the ion selectivity filter in voltage-gated K+ channels and is thought to interact with the scorpion toxin residue, Lys27. By probing the pore of the Kv1.3 channel with synthetic kaliotoxin-Lys27 mutants, each containing a non-natural lysine analog of a different length, and using mutant cycle analysis, we determined the spatial locations of Tyr400 and Asp402 in the GYGD motif, relative to His404 located at the base of the outer vestibule. Our data indicate that the terminal amines of the shorter Lys27 analogs lie close to His404 and to Asp402, while Lys27 itself interacts with Tyr400. Based on these data, we developed a molecular model of this region of the channel. The junction between the outer vestibule and the pore is defined by a ring ( approximately 8-9-A diameter) formed from alternating Asp402 and His404 residues. Tyr400 lies 4-6 A deeper into the pore, and its interaction with kaliotoxin-Lys27 is in competition with K+ ions. Studies with dimeric Kv1.3 constructs suggest that two Tyr400 residues in the tetramer are sufficient to bind K+ ions. Thus, at least part of the K+ channel signature sequence extends into a shallow trough at the center of a wide external vestibule. PMID:8940091

  20. Lysine and the Na+/K+ Selectivity in Mammalian Voltage-Gated Sodium Channels.

    Science.gov (United States)

    Li, Yang; Liu, Huihui; Xia, Mengdie; Gong, Haipeng

    2016-01-01

    Voltage-gated sodium (Nav) channels are critical in the generation and transmission of neuronal signals in mammals. The crystal structures of several prokaryotic Nav channels determined in recent years inspire the mechanistic studies on their selection upon the permeable cations (especially between Na+ and K+ ions), a property that is proposed to be mainly determined by residues in the selectivity filter. However, the mechanism of cation selection in mammalian Nav channels lacks direct explanation at atomic level due to the difference in amino acid sequences between mammalian and prokaryotic Nav homologues, especially at the constriction site where the DEKA motif has been identified to determine the Na+/K+ selectivity in mammalian Nav channels but is completely absent in the prokaryotic counterparts. Among the DEKA residues, Lys is of the most importance since its mutation to Arg abolishes the Na+/K+ selectivity. In this work, we modeled the pore domain of mammalian Nav channels by mutating the four residues at the constriction site of a prokaryotic Nav channel (NavRh) to DEKA, and then mechanistically investigated the contribution of Lys in cation selection using molecular dynamics simulations. The DERA mutant was generated as a comparison to understand the loss of ion selectivity caused by the K-to-R mutation. Simulations and free energy calculations on the mutants indicate that Lys facilitates Na+/K+ selection by electrostatically repelling the cation to a highly Na+-selective location sandwiched by the carboxylate groups of Asp and Glu at the constriction site. In contrast, the electrostatic repulsion is substantially weakened when Lys is mutated to Arg, because of two intrinsic properties of the Arg side chain: the planar geometric design and the sparse charge distribution of the guanidine group. PMID:27584582

  1. Voltage-gated potassium channel Kvl.3 in rabbit ciliary epithelium regulates the membrane potential via coupling intracellular calcium

    Institute of Scientific and Technical Information of China (English)

    LI Yan-feng; ZHUO Ye-hong; BI Wei-na; BAI Yu-jing; LI Yan-na; WANG Zhi-jian

    2008-01-01

    Background The cell layer of the ciliary epithelium is responsible for aqueous humor secretion and maintenance.Ion channels play an important role in these processes.The main aim of this study was to determine whether the well-characterized members of the Kvl family (Kv1.3) contribute to the Kv currents in ciliary epithelium.Methods New Zealand White rabbits were maintained in a 12 hours light/dark cycle.Ciliary epithelium samples were isolated from the rabbits.We used Western blotting and immunocytochemistry to identify the expression and location of a voltage-gated potassium channel Kvl.3 in ciliary body epithelium.Membrane potential change after adding of Kv1.3 inhibitor margatoxin (MgTX) was observed with a fluorescence method.Results Western blotting and immunocytochemical studies showed that the Kv1.3 protein expressed in pigment ciliary epithelium and nonpigment ciliary epithelium,however it seemed to express more in the apical membrane of the nonpigmented epithelial cells.One nmol/L margatoxin,a specific inhibitor of Kv1.3 channels caused depolarization of the cultured nonpigmented epithelium (NPE) membrane potential.The cytosotic calcium increased after NPE cell depolarization,this increase of cytosolic calcium was partially blocked by 12.5 μmol/L dantrolene and 10 μmol/L nifedipine.These observations suggest that Kv1.3 channels modulate ciliary epithelium potential and effect calcium dependent mechanisms.Conclusion Kv1.3 channels contribute to K+ efflux at the membrane of rabbit ciliary epithelium.

  2. ¬cAMP promotes the differentiation of neural progenitor cells in vitro via modulation of voltage-gated calcium channels

    Directory of Open Access Journals (Sweden)

    Guilherme Lepski

    2013-09-01

    Full Text Available The molecular mechanisms underlying the differentiation of neural progenitor cells (NPCs remain poorly understood. In this study we investigated the role of Ca2+ and cAMP (cyclic adenosine monophosphate in the differentiation of NPCs extracted from the subventricular zone of E14.5 rat embryos. Patch clamp recordings revealed that increasing cAMP-signaling with Forskolin or IBMX (3-isobutyl-1-methylxantine significantly facilitated neuronal functional maturation. A continuous application of IBMX to the differentiation medium substantially increased the functional expression of voltage-gated Na+ and K+ channels, as well as neuronal firing frequency. Furthermore, we observed an increase in the frequency of spontaneous synaptic currents and in the amplitude of evoked glutamatergic and GABAergic synaptic currents. The most prominent acute effect of applying IBMX was an increase in L-type Ca2+currents. Conversely, blocking L-type channels strongly inhibited dendritic outgrowth and synapse formation even in the presence of IBMX, indicating that voltage-gated Ca2+ influx plays a major role in neuronal differentiation. Finally, we found that nifedipine completely blocks IBMX-induced CREB phosphorylation (cAMP-response-element-binding protein, indicating that the activity of this important transcription factor equally depends on both enhanced cAMP and voltage-gated Ca2+-signaling. Taken together, these data indicate that the up-regulation of voltage-gated L-type Ca2+-channels and early electrical excitability are critical steps in the cAMP-dependent differentiation of SVZ-derived NPCs into functional neurons. To our knowledge, this is the first demonstration of the acute effects of cAMP on voltage-gated Ca+2channels in NPC-derived developing neurons.

  3. On the structural basis for ionic selectivity among Na+, K+, and Ca2+ in the voltage-gated sodium channel.

    OpenAIRE

    Favre, I; Moczydlowski, E; Schild, L

    1996-01-01

    Voltage-sensitive sodium channels and calcium channels are homologous proteins with distinctly different selectivity for permeation of inorganic cations. This difference in function is specified by amino acid residues located within P-region segments that link presumed transmembrane elements S5 and S6 in each of four repetitive Domains I, II, III, and IV. By analyzing the selective permeability of Na+, K+, and Ca2+ in various mutants of the mu 1 rat muscle sodium channel, the results in this ...

  4. Primary structure of peptides and ion channels. Role of amino acid side chains in voltage gating of melittin channels.

    OpenAIRE

    Tosteson, M T; Alvarez, O; Hubbell, W; Bieganski, R M; Attenbach, C; Caporales, L H; Levy, J J; Nutt, R F; Rosenblatt, M.; Tosteson, D. C.

    1990-01-01

    Melittin produces a voltage-dependent increase in the conductance of planar lipid bilayers. The conductance increases when the side of the membrane to which melittin has been added (cis-side) is made positive. This paper reports observations on the effect of modifying two positively charged amino acid residues within the NH2-terminal region of the molecule: lysine at position 7 (K7), and the NH2-terminal glycine (G1). We have synthesized melittin analogues in which K7 is replaced by asparagin...

  5. Entrance-channel dependence of fission transients

    OpenAIRE

    Charity, R. J.

    2004-01-01

    Fission transients describe the fission rate as it evolves towards the quasistationary value given by Kramers' formula. The nature of fission transients is dependent on the assumed initial distribution of the compound nuclei along the fission coordinate. Although the standard initial assumption of a near-spherical object leads to a transient suppression of the fission rate (fission delay), a moderate initial fissionlike deformation can reduce the magnitude of this suppression. For still large...

  6. CNS Voltage-gated Calcium Channel Gene Variation And Prolonged Recovery Following Sport-related Concussion

    Science.gov (United States)

    McDevitt, Jane

    2016-01-01

    Objectives: To examine the association between concussion duration and two calcium channel, voltage-dependent, R type, alpha 1E subunit (CACNA1E) single nucleotide polymorphisms (i.e., rs35737760 and rs704326). A secondary purpose was to examine the association between CACNA1E single nucleotide polymorphisms (SNPs) and three acute concussion severity scores (i.e., vestibule-ocular reflex test, balance error scoring scale, and Immediate Post-Concussion Assessment and Cognitive Testing). Methods: Forty athletes with a diagnosed concussion from a hospital concussion program completed a standardized initial evaluation. Concussion injury characteristics, acute signs and symptoms followed by an objective screening (i.e., vestibular ocular assessments, balance error scoring system test, and Immediate Post-Concussion Assessment and Cognitive Testing exam) were assessed. Enrolled participants provided salivary samples for isolation of DNA. Two exon SNPs rs35737760 and rs704326 within CACNA1E were genotyped. Results: There was a significant difference found between acute balance deficits and prolonged recovery group (X2 = 5.66, p = 0.017). There was an association found between the dominant model GG genotype (X2 = 5.41, p = 0.027) within the rs704326 SNP and prolonged recovery group. Significant differences were identified for the rs704326 SNP within the dominant model GG genotype (p = 0.030) for VOR scores by recovery. A significant difference was found between the rs704326 SNP codominant model AA (p = 0.042) and visual memory. There was an association between acute balance deficits and prolonged recovery (X2 = 5.66, p = 0.017) for the rs35737760 SNP. No significant associations between concussion severity and genotype for rs35737760 SNP. Conclusion: Athletes carrying the CACNA1E rs704326 homozygous genotype GG are at a greater risk of a prolonged recovery. Athletes that reported balance deficits at the time of injury were more likely to have prolonged recovery. These

  7. Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25

    Directory of Open Access Journals (Sweden)

    Medler Kathryn F

    2006-03-01

    Full Text Available Abstract Background Taste receptor cells are responsible for transducing chemical stimuli from the environment and relaying information to the nervous system. Bitter, sweet and umami stimuli utilize G-protein coupled receptors which activate the phospholipase C (PLC signaling pathway in Type II taste cells. However, it is not known how these cells communicate with the nervous system. Previous studies have shown that the subset of taste cells that expresses the T2R bitter receptors lack voltage-gated Ca2+ channels, which are normally required for synaptic transmission at conventional synapses. Here we use two lines of transgenic mice expressing green fluorescent protein (GFP from two taste-specific promoters to examine Ca2+ signaling in subsets of Type II cells: T1R3-GFP mice were used to identify sweet- and umami-sensitive taste cells, while TRPM5-GFP mice were used to identify all cells that utilize the PLC signaling pathway for transduction. Voltage-gated Ca2+ currents were assessed with Ca2+ imaging and whole cell recording, while immunocytochemistry was used to detect expression of SNAP-25, a presynaptic SNARE protein that is associated with conventional synapses in taste cells. Results Depolarization with high K+ resulted in an increase in intracellular Ca2+ in a small subset of non-GFP labeled cells of both transgenic mouse lines. In contrast, no depolarization-evoked Ca2+ responses were observed in GFP-expressing taste cells of either genotype, but GFP-labeled cells responded to the PLC activator m-3M3FBS, suggesting that these cells were viable. Whole cell recording indicated that the GFP-labeled cells of both genotypes had small voltage-dependent Na+ and K+ currents, but no evidence of Ca2+ currents. A subset of non-GFP labeled taste cells exhibited large voltage-dependent Na+ and K+ currents and a high threshold voltage-gated Ca2+ current. Immunocytochemistry indicated that SNAP-25 was expressed in a separate population of taste cells

  8. Complex N-Glycans Influence the Spatial Arrangement of Voltage Gated Potassium Channels in Membranes of Neuronal-Derived Cells.

    Directory of Open Access Journals (Sweden)

    M Kristen Hall

    Full Text Available The intrinsic electrical properties of a neuron depend on expression of voltage gated potassium (Kv channel isoforms, as well as their distribution and density in the plasma membrane. Recently, we showed that N-glycosylation site occupancy of Kv3.1b modulated its placement in the cell body and neurites of a neuronal-derived cell line, B35 neuroblastoma cells. To extrapolate this mechanism to other N-glycosylated Kv channels, we evaluated the impact of N-glycosylation occupancy of Kv3.1a and Kv1.1 channels. Western blots revealed that wild type Kv3.1a and Kv1.1 α-subunits had complex and oligomannose N-glycans, respectively, and that abolishment of the N-glycosylation site(s generated Kv proteins without N-glycans. Total internal reflection fluorescence microscopy images revealed that N-glycans of Kv3.1a contributed to its placement in the cell membrane while N-glycans had no effect on the distribution of Kv1.1. Based on particle analysis of EGFP-Kv proteins in the adhered membrane, glycosylated forms of Kv3.1a, Kv1.1, and Kv3.1b had differences in the number, size or density of Kv protein clusters in the cell membrane of neurites and cell body of B35 cells. Differences were also observed between the unglycosylated forms of the Kv proteins. Cell dissociation assays revealed that cell-cell adhesion was increased by the presence of complex N-glycans of Kv3.1a, like Kv3.1b, whereas cell adhesion was similar in the oligomannose and unglycosylated Kv1.1 subunit containing B35 cells. Our findings provide direct evidence that N-glycans of Kv3.1 splice variants contribute to the placement of these glycoproteins in the plasma membrane of neuronal-derived cells while those of Kv1.1 were absent. Further when the cell membrane distribution of the Kv channel was modified by N-glycans then the cell-cell adhesion properties were altered. Our study demonstrates that N-glycosylation of Kv3.1a, like Kv3.1b, provides a mechanism for the distribution of these

  9. 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

  10. Reprint of : Time dependent electronic transport in chiral edge channels

    Science.gov (United States)

    Fève, G.; Berroir, J.-M.; Plaçais, B.

    2016-08-01

    We study time dependent electronic transport along the chiral edge channels of the quantum Hall regime, focusing on the role of Coulomb interaction. In the low frequency regime, the a.c. conductance can be derived from a lumped element description of the circuit. At higher frequencies, the propagation equations of the Coulomb coupled edge channels need to be solved. As a consequence of the interchannel coupling, a charge pulse emitted in a given channel fractionalized in several pulses. In particular, Coulomb interaction between channels leads to the fractionalization of a charge pulse emitted in a given channel in several pulses. We finally study how the Coulomb interaction, and in particular the fractionalization process, affects the propagation of a single electron in the circuit. All the above-mentioned topics are illustrated by experimental realizations.

  11. Barbiturates inhibit ATP-K+ channels and voltage-activated currents in CRI-G1 insulin-secreting cells.

    OpenAIRE

    Kozlowski, R. Z.; Ashford, M. L.

    1991-01-01

    1. Patch-clamp recording techniques were used to examine the effects of barbiturates upon the ATP-K+ channel, and voltage-activated channels present in the plasma membrane of CRI-G1 insulin-secreting cells. 2. Thiopentone inhibited ATP-K+ channel activity when applied to cell-attached patches or the intracellular or extracellular surface of cell-free patches. Secobarbitone and pentobarbitone were also effective inhibitors of ATP-K+ channels in cell-free patches, whereas phenobarbitone was ine...

  12. High Grade Glioma Mimicking Voltage Gated Potassium Channel Complex Associated Antibody Limbic Encephalitis

    Directory of Open Access Journals (Sweden)

    Dilan Athauda

    2014-01-01

    Full Text Available Though raised titres of voltage gated potassium channel (VGKC complex antibodies have been occasionally associated with extracranial tumours, mainly presenting as Morvan's Syndrome or neuromyotonia, they have not yet been reported to be associated with an intracranial malignancy. This is especially important as misdiagnosis of these conditions and delay of the appropriate treatment can have important prognostic implications. We describe a patient with a high grade glioma presenting with clinical, radiological, and serological features consistent with the diagnosis of VGKC antibody associated limbic encephalitis (LE. This is the first association between a primary brain tumour and high titre of VGKC complex antibodies. Clinicoradiological progression despite effective immunosuppressive treatment should prompt clinicians to look for alternative diagnoses. Further studies to elucidate a possible association between VGKC complex and other surface antigen antibodies with primary brain tumours should be carried out.

  13. Characterization of voltage calcium channels in a clonal pituitary cell line

    International Nuclear Information System (INIS)

    The authors have pharmacologically characterized voltage sensitive calcium channels (VSCCs) in GH3 cells, an anterior pituitary clonal cell line known to secrete prolactin and growth hormone. Raising the medium K+ concentration from 5 to 50 mM caused an immediate increase in net 45Ca2+ uptake which remained apparent over a 15 minute time course. 45Ca2+ uptake was maximally stimulated nearly 10-fold over basal levels. This K+-induced stimulation of Ca2+ uptake was not prevented by 10-5M tetrodotoxin or by replacing sodium with choline in the assay medium. Ca2+ uptake was, however, inhibited by several VSCC antagonists: nitrendipine, D-600, diltiazem and Ca2+. Further, the novel dihydropyridine VSCC agonists, BAY K8644 and CGP 28392, enhanced 50-mM K+-stimulated 45Ca2+ uptake and these effects were blocked by nitrendipine. 40 references, 3 figures

  14. A guanine nucleotide-binding protein mediates the inhibition of voltage-dependent calcium current by somatostatin in a pituitary cell line.

    OpenAIRE

    Lewis, D L; Weight, F F; Luini, A

    1986-01-01

    Somatostatin reduces voltage-dependent Ca2+ current (ICa) and intracellular free Ca2+ concentration in the AtT-20/D16-16 pituitary cell line. We tested whether guanine nucleotide-binding proteins (G or N proteins) are involved in the signal transduction mechanism between the somatostatin receptor and voltage-dependent Ca2+ channels. Treatment of the cells with pertussis toxin, which selectively ADP ribosylates the GTP binding proteins Gi and Go and suppresses the ability of Gi to couple inhib...

  15. Lack of direct evidence for a functional role of voltage-operated calcium channels in juxtaglomerular cells

    OpenAIRE

    Kurtz, Armin; Skott, O.; Chegini, S; Penner, R

    1990-01-01

    In this study we have examined the role of voltage-gated calcium channels in the regulation of calcium in juxtaglomerular cells. Using a combination of patch-clamp and single-cell calcium measurement we obtained evidence neither for voltage-operated calcium currents nor for changes of the intracellular calcium concentration upon acute depolarizations of the cell membrane. Increases of the extracellular concentration of potassium to 80 mmol/l depolarized the juxtaglomerular cells close to the ...

  16. Voltage-dependent parameter extraction for graphene nanoribbon interconnect model through ab initio approach

    International Nuclear Information System (INIS)

    This paper presents electrical parameter extraction for metallic graphene nanoribbon (GNR) interconnects utilizing ab initio approach. Unlike the studies taking the kinetic inductance, quantum capacitance and Fermi velocity as constant values, voltage-dependencies of these parameters are obtained for GNR transmission line model. The variations of the kinetic energy and the current by the applied voltage are taken as bases for voltage-dependent kinetic inductance calculation. Quantum capacitance and the Fermi velocity are also computed from the kinetic inductance variation. It is concluded that voltage-dependencies of the kinetic inductance and the quantum capacitance have to be taken into account for accurate GNR modelling in nanoelectronic design. - Highlights: • Metallic graphene nanoribbon interconnects are studied using ab initio approach. • Variations of the kinetic inductance (LK) and the current are obtained. • Voltage-dependency of the kinetic inductance is extracted. • The variations of quantum capacitance (CQ) and Fermi velocity are calculated. • LK and CQ change by 34% in the voltage range of 0–1 V

  17. Voltage-dependent parameter extraction for graphene nanoribbon interconnect model through ab initio approach

    Energy Technology Data Exchange (ETDEWEB)

    Yamacli, Serhan, E-mail: syamacli@nny.edu.tr

    2014-07-01

    This paper presents electrical parameter extraction for metallic graphene nanoribbon (GNR) interconnects utilizing ab initio approach. Unlike the studies taking the kinetic inductance, quantum capacitance and Fermi velocity as constant values, voltage-dependencies of these parameters are obtained for GNR transmission line model. The variations of the kinetic energy and the current by the applied voltage are taken as bases for voltage-dependent kinetic inductance calculation. Quantum capacitance and the Fermi velocity are also computed from the kinetic inductance variation. It is concluded that voltage-dependencies of the kinetic inductance and the quantum capacitance have to be taken into account for accurate GNR modelling in nanoelectronic design. - Highlights: • Metallic graphene nanoribbon interconnects are studied using ab initio approach. • Variations of the kinetic inductance (L{sub K}) and the current are obtained. • Voltage-dependency of the kinetic inductance is extracted. • The variations of quantum capacitance (C{sub Q}) and Fermi velocity are calculated. • L{sub K} and C{sub Q} change by 34% in the voltage range of 0–1 V.

  18. Low operating voltage n-channel organic field effect transistor using epoxy based photoresist gate dielectric

    International Nuclear Information System (INIS)

    We report a systematic study on the dielectric properties of epoxy based positive tone photoresist and its use as a gate dielectric for n-channel organic field effect transistors (OFETs) made with N,N’-Dioctyl-3,4,9,10-perylenedicarboximinde (PTCDI-C8) as the active semiconducting layer. We find that the photoresist has high dielectric constant (k = 12 at 10 kHz) and thus can be used in fabricating low operating voltage OFET devices. Highly smooth gate dielectric surface was obtained using the photoresist with the highest root mean square (rms) roughness of 0.239 nm for the films annealed at 200 °C. Consequently, the semiconducting layer (on photoresist dielectric annealed at 100 °C) also exhibited highly uniform surface with rms roughness of 0.382 nm. The turn-on voltage (VT), inverse subthreshold slope (S) and saturation mobility of electrons (μsat) of the transistor device were estimated to be 4.3 V, 13 V decade−1 and 6 × 10−5 cm2 Vs−1, respectively, when the device was operated in ambient, which is better than some of the earlier reported works under similar experimental conditions. (paper)

  19. Current-voltage characteristics of quantum-point contacts in the closed-channel regime: Transforming the bias voltage into an energy scale

    DEFF Research Database (Denmark)

    Gloos, K.; Utko, P.; Aagesen, M.;

    2006-01-01

    .2 mu m) contacts are typically found to consist of very short (similar to 0.2 mu m) barriers. We have mapped the height of the barrier as a function of the gate voltage, and found that its behavior differs strongly from that extrapolated using conventional bias spectroscopy in the open-channel regime......We investigate the I(V) characteristics (current versus bias voltage) of side-gated quantum-point contacts, defined in GaAs/AlxGa1-xAs heterostructures. These point contacts are operated in the closed-channel regime, that is, at fixed gate voltages below zero-bias pinch-off for conductance. Our...... we are using the channel length remains the only adjustable parameter since the barrier height can be experimentally determined. For short (similar to 0.06 mu m) contacts, the I(V)-derived lengths agree rather well with those estimated from the geometrical layout, whereas nominally long (similar to 1...

  20. Dependence of Signal-to-Noise Ratio on Operating Voltage in Photomultipliers.

    Science.gov (United States)

    Jonas, M; Alon, Y

    1971-11-01

    The dependence of SNR on operating voltage at low light intensities was investigated in PM's of box-and-grid and venetian-blind structure, utilizing both the photon-counting and the dc methods of detection. SNR was found to be reasonably constant at both tube types in the tested range of operating voltages with the dc method of detection. In the photon-counting mode at a constant discriminating bias, SNR improved with rising operating voltage in the box-and-grid structure tube, but changed little in the venetian-blind structure tube. PMID:20111351

  1. Expression patterns, mutation detection and RNA interference of Rhopalosiphum padi voltage-gated sodium channel genes

    Science.gov (United States)

    Zuo, Yayun; Peng, Xiong; Wang, Kang; Lin, Fangfei; Li, Yuting; Chen, Maohua

    2016-07-01

    The voltage-gated sodium channel (VGSC) is the target of sodium-channel-blocking insecticides. Traditionally, animals were thought to have only one VGSC gene comprising a α-subunit with four homologous domains (DI–DIV). The present study showed that Rhopalosiphum padi, an economically important crop pest, owned a unique heterodimeric VGSC (H1 and H2 subunits) encoded by two genes (Rpvgsc1 and Rpvgsc2), which is unusual in insects and other animals. The open reading frame (ORF) of Rpvgsc1 consisted 1150 amino acids, and the ORF of Rpvgsc2 had 957 amino acids. Rpvgsc1 showed 64.1% amino acid identity to DI–DII of Drosophila melanogaster VGSC and Rpvgsc2 showed 64.0% amino acid identity to DIII–DIV of D. melanogaster VGSC. A M918L mutation previously reported in pyrethroids-resistant strains of other insects was found in the IIS4-S6 region of R. padi field sample. The two R. padi VGSC genes were expressed at all developmental stages and showed similar expression patterns after treatment with beta-cypermethrin. Knockdown of Rpvgsc1 or Rpvgsc2 caused significant reduction in mortality rate of R. padi after exposure to beta-cypermethrin. These findings suggest that the two R. padi VGSC genes are both functional genes.

  2. On the Natural and Unnatural History of the Voltage-Gated Na(+) Channel.

    Science.gov (United States)

    Moczydlowski, E G

    2016-01-01

    This review glances at the voltage-gated sodium (Na(+)) channel (NaV) from the skewed perspective of natural history and the history of ideas. Beginning with the earliest natural philosophers, the objective of biological science and physiology was to understand the basis of life and discover its intimate secrets. The idea that the living state of matter differs from inanimate matter by an incorporeal spirit or mystical force was central to vitalism, a doctrine based on ancient beliefs that persisted until the last century. Experimental electrophysiology played a major role in the abandonment of vitalism by elucidating physiochemical mechanisms that explained the electrical excitability of muscle and nerve. Indeed, as a principal biomolecule underlying membrane excitability, the NaV channel may be considered as the physical analog or surrogate for the vital spirit once presumed to animate higher forms of life. NaV also epitomizes the "other secret of life" and functions as a quantal transistor element of biological intelligence. Subplots of this incredible but true story run the gamut from electric fish to electromagnetism, invention of the battery, venomous animals, neurotoxins, channelopathies, arrhythmia, anesthesia, astrobiology, etc. PMID:27586279

  3. Mechanism underlying blockade of voltage-gated calcium channels by agmatine in cultured rat hippocampal neurons

    Institute of Scientific and Technical Information of China (English)

    Jian-quan ZHENG; Xie-chuan WENG; Xiao-dan GAI; Jin LI; Wen-bin XIAO

    2004-01-01

    AIM: To investigate whether agmatine could selectively block a given type of the voltage-gated calcium channels (VGCC) and whether related receptors are involved in the blocking effect of agmatine on VGCC. METHODS: The whole-cell patch recording technique was performed to record VGCC currents in the cultured neonatal rat hippocampal neurons. RESULTS: Verapamil (100 μmol/L), a selective blocker of L-type calcium channel, significantly inhibited VGCC current by 80 %± 7 %. Agmatine (100 μmol/L) could further depress the remained currents by 25 %±6 %. The α2-adrenoceptor antagonist yohimbine (10 μmol/L) and the I2 imidazoline receptor antagonist idazoxon (10 and 40 μmol/L) had no significant effect on VGCC currents when used respectively. When the mixture of yohimbine and agmatine was applied, VGCC currents were still depressed remarkably. However, the blocking effect of agmatine was decreased by 29 %± 8 % in the presence of idazoxon (10 μmol/L). The effect of idazoxon did not increase at a higher concentration (40 μmol/L). CONCLUSION: Agmatine could block the L- and other types of VGCC currents in the cultured rat hippocampal neurons. Blocking effect of agmatine on VGCC was partially related to I2 imidazoline receptor and had no relationship with α2-adrenoceptors.

  4. Voltage-Gated Ion Channels in the PNS: Novel Therapies for Neuropathic Pain?

    Science.gov (United States)

    Tibbs, Gareth R; Posson, David J; Goldstein, Peter A

    2016-07-01

    Neuropathic pain arises from injury to the nervous system. Conditions associated with neuropathic pain are diverse, and lesions and/or pathological changes in the central nervous system (CNS) or peripheral nervous system (PNS) can frequently, but not always, be identified. It is difficult to treat, with patients often on multiple, different classes of medications, all with appreciable adverse side effect profiles. Consequently, there is a pressing need for the development of new medications. The development of such therapeutics is predicated on a clear understanding of the relevant molecular and cellular processes that contribute to the development, and maintenance, of the neuropathic pain state. One proposed mechanism thought to contribute to the ontogeny of neuropathic pain is altered expression, trafficking, and functioning of ion channels expressed by primary sensory neurons. Here, we will focus on three voltage-gated ion channel families, CaV, HCN, and NaV, first reviewing the preclinical data and then the human data where it exists. PMID:27233519

  5. Influence of Permeant Ions on Voltage Sensor Function in the Kv2.1 Potassium Channel

    OpenAIRE

    Consiglio, Joseph F.; Korn, Stephen J.

    2004-01-01

    We previously demonstrated that the outer vestibule of activated Kv2.1 potassium channels can be in one of two conformations, and that K+ occupancy of a specific selectivity filter site determines which conformation the outer vestibule is in. These different outer vestibule conformations result in different sensitivities to internal and external TEA, different inactivation rates, and different macroscopic conductances. The [K+]-dependent switch in outer vestibule conformation is also associat...

  6. Identification of BACE1 cleavage sites in human voltage-gated sodium channel beta 2 subunit

    Directory of Open Access Journals (Sweden)

    Kovacs Dora M

    2010-12-01

    Full Text Available Abstract Background The voltage-gated sodium channel β2 subunit (Navβ2 is a physiological substrate of BACE1 (β-site APP cleaving enzyme and γ-secretase, two proteolytic enzymes central to Alzheimer's disease pathogenesis. Previously, we have found that the processing of Navβ2 by BACE1 and γ-secretase regulates sodium channel metabolism in neuronal cells. In the current study we identified the BACE1 cleavage sites in human Navβ2. Results We found a major (147-148 L↓M, where ↓ indicates the cleavage site and a minor (144145 L↓Q BACE1 cleavage site in the extracellular domain of human Navβ2 using a cell-free BACE1 cleavage assay followed by mass spectrometry. Next, we introduced two different double mutations into the identified major BACE1 cleavage site in human Navβ2: 147LM/VI and 147LM/AA. Both mutations dramatically decreased the cleavage of human Navβ2 by endogenous BACE1 in cell-free BACE1 cleavage assays. Neither of the two mutations affected subcellular localization of Navβ2 as confirmed by confocal fluorescence microscopy and subcellular fractionation of cholesterol-rich domains. Finally, wildtype and mutated Navβ2 were expressed along BACE1 in B104 rat neuroblastoma cells. In spite of α-secretase still actively cleaving the mutant proteins, Navβ2 cleavage products decreased by ~50% in cells expressing Navβ2 (147LM/VI and ~75% in cells expressing Navβ2 (147LM/AA as compared to cells expressing wildtype Navβ2. Conclusion We identified a major (147-148 L↓M and a minor (144-145 L↓Q BACE1 cleavage site in human Navβ2. Our in vitro and cell-based results clearly show that the 147-148 L↓M is the major BACE1 cleavage site in human Navβ2. These findings expand our understanding of the role of BACE1 in voltage-gated sodium channel metabolism.

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

    OpenAIRE

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

    2014-01-01

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

  8. Atom-by-atom engineering of voltage-gated ion channels: Magnified insights into function and pharmacology

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Kim, Robin Y; Ahern, Christopher A;

    2015-01-01

    Unnatural amino acid incorporation into ion channels has proven to be a valuable approach to interrogate detailed hypotheses arising from atomic resolution structures. In this short review, we provide a brief overview of some of the basic principles and methods for incorporation of unnatural amino...... acids into proteins. We also review insights into the function and pharmacology of voltage-gated ion channels that have emerged from unnatural amino acid mutagenesis approaches....

  9. GM counter deadtime dependence on applied voltage, operating temperature and fatigue

    International Nuclear Information System (INIS)

    This paper utilized standard two-source method and the simple non-paralyzing model assumption to examine a GM counter's deadtime dependence on applied voltage, operating temperature, and fatigue. Both 60Co and 137Cs sources were used for deadtime measurements. The results gathered suggest the presence of three distinct regions of deadtime behavior. At low voltages, the deadtime decreases as the voltage increases (Region I) followed by a region of stable deadtime plateau (Region II) and finally a region of increasing deadtime with increasing voltage. Region II is the best region for operating with a minimum deadtime which is not sensitive to the applied voltage. Typical deadtime values for GM counters were between 100 and 300 μs; the deadtime values in Region II were within this range. The results examined in this study also indicate a strong temperature dependence of deadtime, with a correlation coefficient of 0.93. The GM counter deadtime for various fatigues (aging) were investigated for three fatigue levels with a correlation coefficient of 0.48. The experimental results confirm that deadtime increases as both temperature and fatigue increase. The fundamental nature of deadtime seems to be different for voltages lower than the stable deadtime plateau (Region II) and for voltages higher than the plateau. - Highlights: • GM counter deadtime dependence on applied voltage, operating temperature and fatigue. • Standard two-source method and simple non-paralyzing model assumption. • Three distinct regions of the deadtime behavior with low deadtime plateau in the middle. • Exponential increase in deadtime with increasing temperature. • Increase in deadtime with fatigue

  10. Molecular determinants of voltage-gated sodium channel regulation by the Nedd4/Nedd4-like proteins.

    Science.gov (United States)

    Rougier, Jean-Sébastien; van Bemmelen, Miguel X; Bruce, M Christine; Jespersen, Thomas; Gavillet, Bruno; Apothéloz, Florine; Cordonier, Sophie; Staub, Olivier; Rotin, Daniela; Abriel, Hugues

    2005-03-01

    The voltage-gated Na(+) channels (Na(v)) form a family composed of 10 genes. The COOH termini of Na(v) contain a cluster of amino acids that are nearly identical among 7 of the 10 members. This COOH-terminal sequence, PPSYDSV, is a PY motif known to bind to WW domains of E3 protein-ubiquitin ligases of the Nedd4 family. We recently reported that cardiac Na(v)1.5 is regulated by Nedd4-2. In this study, we further investigated the molecular determinants of regulation of Na(v) proteins. When expressed in HEK-293 cells and studied using whole cell voltage clamping, the neuronal Na(v)1.2 and Na(v)1.3 were also downregulated by Nedd4-2. Pull-down experiments using fusion proteins bearing the PY motif of Na(v)1.2, Na(v)1.3, and Na(v)1.5 indicated that mouse brain Nedd4-2 binds to the Na(v) PY motif. Using intrinsic tryptophan fluorescence imaging of WW domains, we found that Na(v)1.5 PY motif binds preferentially to the fourth WW domain of Nedd4-2 with a K(d) of approximately 55 muM. We tested the binding properties and the ability to ubiquitinate and downregulate Na(v)1.5 of three Nedd4-like E3s: Nedd4-1, Nedd4-2, and WWP2. Despite the fact that along with Nedd4-2, Nedd4-1 and WWP2 bind to Na(v)1.5 PY motif, only Nedd4-2 robustly ubiquitinated and downregulated Na(v)1.5. Interestingly, coexpression of WWP2 competed with the effect of Nedd4-2. Finally, using brefeldin A, we found that Nedd4-2 accelerated internalization of Na(v)1.5 stably expressed in HEK-293 cells. This study shows that Nedd4-dependent ubiquitination of Na(v) channels may represent a general mechanism regulating the excitability of neurons and myocytes via modulation of channel density at the plasma membrane. PMID:15548568

  11. Ranolazine inhibits voltage-gated mechanosensitive sodium channels in human colon circular smooth muscle cells.

    Science.gov (United States)

    Neshatian, Leila; Strege, Peter R; Rhee, Poong-Lyul; Kraichely, Robert E; Mazzone, Amelia; Bernard, Cheryl E; Cima, Robert R; Larson, David W; Dozois, Eric J; Kline, Crystal F; Mohler, Peter J; Beyder, Arthur; Farrugia, Gianrico

    2015-09-15

    Human jejunum smooth muscle cells (SMCs) and interstitial cells of Cajal (ICCs) express the SCN5A-encoded voltage-gated, mechanosensitive sodium channel NaV1.5. NaV1.5 contributes to small bowel excitability, and NaV1.5 inhibitor ranolazine produces constipation by an unknown mechanism. We aimed to determine the presence and molecular identity of Na(+) current in the human colon smooth muscle and to examine the effects of ranolazine on Na(+) current, mechanosensitivity, and smooth muscle contractility. Inward currents were recorded by whole cell voltage clamp from freshly dissociated human colon SMCs at rest and with shear stress. SCN5A mRNA and NaV1.5 protein were examined by RT-PCR and Western blots, respectively. Ascending human colon strip contractility was examined in a muscle bath preparation. SCN5A mRNA and NaV1.5 protein were identified in human colon circular muscle. Freshly dissociated human colon SMCs had Na(+) currents (-1.36 ± 0.36 pA/pF), shear stress increased Na(+) peaks by 17.8 ± 1.8% and accelerated the time to peak activation by 0.7 ± 0.3 ms. Ranolazine (50 μM) blocked peak Na(+) current by 43.2 ± 9.3% and inhibited shear sensitivity by 25.2 ± 3.2%. In human ascending colon strips, ranolazine decreased resting tension (31%), reduced the frequency of spontaneous events (68%), and decreased the response to smooth muscle electrical field stimulation (61%). In conclusion, SCN5A-encoded NaV1.5 is found in human colonic circular smooth muscle. Ranolazine blocks both peak amplitude and mechanosensitivity of Na(+) current in human colon SMCs and decreases contractility of human colon muscle strips. Our data provide a likely mechanistic explanation for constipation induced by ranolazine. PMID:26185330

  12. Differential state-dependent modification of rat Nav1.6 sodium channels expressed in human embryonic kidney (HEK293) cells by the pyrethroid insecticides tefluthrin and deltamethrin

    International Nuclear Information System (INIS)

    We expressed rat Nav1.6 sodium channels in combination with the rat β1 and β2 auxiliary subunits in human embryonic kidney (HEK293) cells and evaluated the effects of the pyrethroid insecticides tefluthrin and deltamethrin on expressed sodium currents using the whole-cell patch clamp technique. Both pyrethroids produced concentration-dependent, resting modification of Nav1.6 channels, prolonging the kinetics of channel inactivation and deactivation to produce persistent “late” currents during depolarization and tail currents following repolarization. Both pyrethroids also produced concentration dependent hyperpolarizing shifts in the voltage dependence of channel activation and steady-state inactivation. Maximal shifts in activation, determined from the voltage dependence of the pyrethroid-induced late and tail currents, were ∼ 25 mV for tefluthrin and ∼ 20 mV for deltamethrin. The highest attainable concentrations of these compounds also caused shifts of ∼ 5–10 mV in the voltage dependence of steady-state inactivation. In addition to their effects on the voltage dependence of inactivation, both compounds caused concentration-dependent increases in the fraction of sodium current that was resistant to inactivation following strong depolarizing prepulses. We assessed the use-dependent effects of tefluthrin and deltamethrin on Nav1.6 channels by determining the effect of trains of 1 to 100 5-ms depolarizing prepulses at frequencies of 20 or 66.7 Hz on the extent of channel modification. Repetitive depolarization at either frequency increased modification by deltamethrin by ∼ 2.3-fold but had no effect on modification by tefluthrin. Tefluthrin and deltamethrin were equally potent as modifiers of Nav1.6 channels in HEK293 cells using the conditions producing maximal modification as the basis for comparison. These findings show that the actions of tefluthrin and deltamethrin of Nav1.6 channels in HEK293 cells differ from the effects of these compounds on

  13. 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.

  14. Ozone synthesis improves by increasing number density of plasma channels and lower voltage in a nonthermal plasma

    Science.gov (United States)

    Arif Malik, Muhammad; Hughes, David

    2016-04-01

    Improvements in ozone synthesis from air and oxygen by increasing the number density of plasma channels and lower voltage for the same specific input energy (SIE) were explored in a nonthermal plasma based on a sliding discharge. The number of plasma channels and energy per pulse increased in direct proportion to the increase in the effective length of the anode (the high voltage electrode). Decreasing the discharge gap increased the energy per pulse for the same length and allowed the installation of more electrode pairs in the same space. It allowed the increase of the number of plasma channels in the same space to achieve the same SIE at a lower peak voltage with less energy per plasma channel. The ozone concentration gradually increased to ~1500 ppmv (140 to 50 g kWh-1) from air and to ~6000 ppmv (400 to 200 g kWh-1) from oxygen with a gradual increase in the SIE to ~200 J L-1, irrespective of the variations in electrode geometry, applied voltage or flow rate of the feed gas. A gradual increase in SIE beyond 200 J L-1 gradually increased the ozone concentration to a certain maximum value followed by a decline, but the rate of increase and the maximum value was higher for the greater number of plasma channels and lower peak voltage combination. The maximum ozone concentration was ~5000 ppmv (~30 g kWh-1) from air and ~22 000 ppmv (~80 g kWh-1) from oxygen. The results are explained on the basis of characteristics of the plasma and ozone synthesis mechanism.

  15. L-type voltage-operated calcium channels contribute to astrocyte activation In vitro.

    Science.gov (United States)

    Cheli, Veronica T; Santiago González, Diara A; Smith, Jessica; Spreuer, Vilma; Murphy, Geoffrey G; Paez, Pablo M

    2016-08-01

    We have found a significant upregulation of L-type voltage-operated Ca(++) channels (VOCCs) in reactive astrocytes. To test if VOCCs are centrally involved in triggering astrocyte reactivity, we used in vitro models of astrocyte activation in combination with pharmacological inhibitors, siRNAs and the Cre/lox system to reduce the activity of L-type VOCCs in primary cortical astrocytes. The endotoxin lipopolysaccharide (LPS) as well as high extracellular K(+) , glutamate, and ATP promote astrogliosis in vitro. L-type VOCC inhibitors drastically reduce the number of reactive cells, astrocyte hypertrophy, and cell proliferation after these treatments. Astrocytes transfected with siRNAs for the Cav1.2 subunit that conducts L-type Ca(++) currents as well as Cav1.2 knockout astrocytes showed reduce Ca(++) influx by ∼80% after plasma membrane depolarization. Importantly, Cav1.2 knock-down/out prevents astrocyte activation and proliferation induced by LPS. Similar results were found using the scratch wound assay. After injuring the astrocyte monolayer, cells extend processes toward the cell-free scratch region and subsequently migrate and populate the scratch. We found a significant increase in the activity of L-type VOCCs in reactive astrocytes located in the growing line in comparison to quiescent astrocytes situated away from the scratch. Moreover, the migration of astrocytes from the scratching line as well as the number of proliferating astrocytes was reduced in Cav1.2 knock-down/out cultures. In summary, our results suggest that Cav1.2 L-type VOCCs play a fundamental role in the induction and/or proliferation of reactive astrocytes, and indicate that the inhibition of these Ca(++) channels may be an effective way to prevent astrocyte activation. GLIA 2016. GLIA 2016;64:1396-1415. PMID:27247164

  16. Voltage-gated potassium channel-complex autoimmunity and associated clinical syndromes.

    Science.gov (United States)

    Irani, Sarosh R; Vincent, Angela

    2016-01-01

    Voltage-gated potassium channel (VGKC)-complex antibodies are defined by the radioimmunoprecipitation of Kv1 potassium channel subunits from brain tissue extracts and were initially discovered in patients with peripheral nerve hyperexcitability (PNH). Subsequently, they were found in patients with PNH plus psychosis, insomnia, and dysautonomia, collectively termed Morvan's syndrome (MoS), and in a limbic encephalopathy (LE) with prominent amnesia and frequent seizures. Most recently, they have been described in patients with pure epilepsies, especially in patients with the novel and distinctive semiology termed faciobrachial dystonic seizures (FBDS). In each of these conditions, there is a close correlation between clinical measures and antibody levels. The VGKC-complex is a group of proteins that are strongly associated in situ and after extraction in mild detergent. Two major targets of the autoantibodies are leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein 2 (CASPR2). The patients with PNH or MoS are most likely to have CASPR2 antibodies, whereas LGI1 antibodies are found characteristically in patients with FBDS and LE. Crucially, each of these conditions has a good response to immunotherapies, often corticosteroids and plasma exchange, although optimal regimes require further study. VGKC-complex antibodies have also been described in neuropathic pain syndromes, chronic epilepsies, a polyradiculopathy in porcine abattoir workers, and some children with status epilepticus. Increasingly, however, the antigenic targets in these patients are not defined and in some cases the antibodies may be secondary rather than the primary cause. Future serologic studies should define all the antigenic components of the VGKC-complex, and further inform mechanisms of antibody pathogenicity and related inflammation. PMID:27112678

  17. Functional Importance of L- and P/Q-Type Voltage-Gated Calcium Channels in Human Renal Vasculature

    DEFF Research Database (Denmark)

    Hansen, Pernille B; Poulsen, Christian B; Walter, Steen;

    2011-01-01

    revealed signals for Ca(v) 2.1 and Ca(v) 3.1 associated with smooth muscle cells of preglomerular and postglomerular vessels. In human intrarenal arteries, depolarization with potassium induced a contraction inhibited by the L-type antagonist nifedipine, EC(50) 1.2×10(-8) mol/L. The T-type antagonist...... L- and P/Q-type channels are of functional importance for the depolarization-induced vasoconstriction. The contribution of P/Q-type channels to contraction in the human vasculature is a novel mechanism for the regulation of renal blood flow and suggests that clinical treatment with calcium blockers......Calcium channel blockers are widely used for treatment of hypertension, because they decrease peripheral vascular resistance through inhibition of voltage-gated calcium channels. Animal studies of renal vasculature have shown expression of several types of calcium channels that are involved in...

  18. RF voltage modulation at discrete frequencies with applications to crystal channeling extraction

    International Nuclear Information System (INIS)

    RF voltage modulation at a finite number of discrete frequencies is described in a Hamiltonian resonance framework. The theory is applied to the problem of parasitic extraction of a fixed target beam from a high energy proton collider, using a bent crystal as a thin ''septum'' within an effective width of about one micron. Three modes of employment of discrete resonances are proposed.First, a single relatively strong static ''drive'' resonance may be used to excite a test proton so that it will penetrate deeply into the channeling crystal. Second, a moderately strong ''feed'' resonance with a ramped modulation tune may be used to adiabatically trap protons near the edge of the beam core, and transport them to the drive resonance. Third, several weak resonances may be overlapped to create a chaotic amplitude band, either to transport protons to the drive resonance, or to provide a ''pulse stretching'' buffer between a feed resonance and the drive resonance. Extraction efficiency is semi- quantitatively described in terms of characteristic ''penetration,'' ''depletion,'' and ''repetition'' times. simulations are used to quantitatively confirm the fundamental results of the theory, and to show that a prototypical extraction scheme using all three modes promises good extraction performance

  19. Supratentorial white matter blurring associated with voltage-gated potassium channel-complex limbic encephalitis

    Energy Technology Data Exchange (ETDEWEB)

    Urbach, H.; Mader, I. [University Medical Center Freiburg, Department of Neuroradiology, Freiburg (Germany); Rauer, S.; Baumgartner, A. [University Medical Center Freiburg, Department of Neurology, Freiburg (Germany); Paus, S. [University Medical Center, Department of Neurology, Bonn (Germany); Wagner, J. [University Medical Center, Department of Epileptology, Bonn (Germany); Malter, M.P. [University of Cologne, Department of Neurology, Cologne (Germany); Pruess, H. [Charite - Universitaetsmedizin Berlin, Department of Neurology, Berlin (Germany); Lewerenz, J.; Kassubek, J. [Ulm University, Department of Neurology, Ulm (Germany); Hegen, H.; Auer, M.; Deisenhammer, F. [University Innsbruck, Department of Neurology, Innsbruck (Austria); Ufer, F. [University Medical Center, Department of Neurology, Hamburg (Germany); Bien, C.G. [Epilepsy Centre Bethel, Bielefeld-Bethel (Germany)

    2015-12-15

    Limbic encephalitis (LE) associated with voltage-gated potassium channel-complex antibodies (VGKC-LE) is frequently non-paraneoplastic and associated with marked improvement following corticosteroid therapy. Mesial temporal lobe abnormalities are present in around 80 % of patients. If associated or preceded by faciobrachial dystonic seizures, basal ganglia signal changes may occur. In some patients, blurring of the supratentorial white matter on T2-weighted images (SWMB) may be seen. The purpose of this study was to evaluate the incidence of SWMB and whether it is specific for VGKC-LE. Two experienced neuroradiologists independently evaluated signal abnormalities on FLAIR MRI in 79 patients with LE while unaware on the antibody type. SWMB was independently assessed as present in 10 of 36 (28 %) compared to 2 (5 %) of 43 non-VGKC patients (p = 0.009). It was not related to the presence of LGI1 or CASPR2 proteins of VGKC antibodies. MRI showed increased temporomesial FLAIR signal in 22 (61 %) VGKC compared to 14 (33 %) non-VGKC patients (p = 0.013), and extratemporomesial structures were affected in one VGKC (3 %) compared to 11 (26 %) non-VGKC patients (p = 0.005). SWMB is a newly described MRI sign rather specific for VGKC-LE. (orig.)

  20. Supratentorial white matter blurring associated with voltage-gated potassium channel-complex limbic encephalitis

    International Nuclear Information System (INIS)

    Limbic encephalitis (LE) associated with voltage-gated potassium channel-complex antibodies (VGKC-LE) is frequently non-paraneoplastic and associated with marked improvement following corticosteroid therapy. Mesial temporal lobe abnormalities are present in around 80 % of patients. If associated or preceded by faciobrachial dystonic seizures, basal ganglia signal changes may occur. In some patients, blurring of the supratentorial white matter on T2-weighted images (SWMB) may be seen. The purpose of this study was to evaluate the incidence of SWMB and whether it is specific for VGKC-LE. Two experienced neuroradiologists independently evaluated signal abnormalities on FLAIR MRI in 79 patients with LE while unaware on the antibody type. SWMB was independently assessed as present in 10 of 36 (28 %) compared to 2 (5 %) of 43 non-VGKC patients (p = 0.009). It was not related to the presence of LGI1 or CASPR2 proteins of VGKC antibodies. MRI showed increased temporomesial FLAIR signal in 22 (61 %) VGKC compared to 14 (33 %) non-VGKC patients (p = 0.013), and extratemporomesial structures were affected in one VGKC (3 %) compared to 11 (26 %) non-VGKC patients (p = 0.005). SWMB is a newly described MRI sign rather specific for VGKC-LE. (orig.)

  1. The investigation of an electric arc in the long cylindrical channel of the powerful high-voltage AC plasma torch

    International Nuclear Information System (INIS)

    The comparison of conductivity obtained in experiments with calculated values is made in this paper. Powerful stationary plasma torches with prolonged period of continuous work are popular for modern plasmachemical applications. The maximum electrode lifetime with the minimum erosion can be reached while working on rather low currents. Meanwhile it is required to provide voltage arc drop for the high power achievement. Electric field strength in the arc column of the high-voltage plasma torch, using air as a plasma-forming gas, does not exceed 15 V/cm. It is possible to obtain the high voltage drop in the long arc stabilized in the channel by the intensive gas flow under given conditions. Models of high voltage plasma torches with rod electrodes with power up to 50 kW have been developed and investigated. The plasma torch arcs are burning in cylindrical channels. Present investigations are directed at studying the possibility of developing long arc plasma torches with higher power. The advantage of AC power supplies usage is the possibility of the loss minimization due to the reactive power compensation. The theoretical maximum of voltage arc drop for power supplies with inductive current limitations is about 50 % of the no-load voltage for a single-phase circuit and about 30 % for the three-phase circuit. Burning of intensively blown arcs in the long cylindrical channel using the AC power supply with 10 kV no-load voltage is experimentally investigated in the work. Voltage drops close to the maximum possible had been reached in the examined arcs in single-phase and three-phase modes. Operating parameters for single-phase mode were: current −30 A, voltage drop −5 kV, air flow rate 35 g/s; for three-phase mode: current (40–85) A, voltage drop (2.5–3.2) kV, air flow rate (60–100) g/s. Arc length in the installations exceeded 2 m.

  2. Proadrenomedullin NH2-terminal 20 peptide inhibits the voltage-gated Ca2+ channel current through a pertussis toxin-sensitive G protein in rat pheochromocytoma-derived PC 12 cells.

    OpenAIRE

    Takano, K; Yamashita, N; Fujita, T.

    1996-01-01

    The effect of proadrenomedullin NH2-terminal 20 peptide (PAMP) on the voltage-gated Ca2+ channel current was investigated using the perforated whole-cell clamp technique on NGF-treated PC12 cells. PAMP inhibited the Ba2+ current through N-type Ca2+ channels in a concentration dependent manner. Injection of GDPbetaS into the cell abolished the inhibition while injection of GTPgammaS into the cell made the inhibition irreversible, indicating that the PAMP-induced inhibition of the voltage-gated...

  3. Cardiac voltage-gated sodium channel Nav1.5 is regulated by Nedd4-2 mediated ubiquitination.

    Science.gov (United States)

    van Bemmelen, Miguel X; Rougier, Jean-Sébastien; Gavillet, Bruno; Apothéloz, Florine; Daidié, Dorothée; Tateyama, Michihiro; Rivolta, Ilaria; Thomas, Marc A; Kass, Robert S; Staub, Olivier; Abriel, Hugues

    2004-08-01

    Na(v)1.5, the cardiac isoform of the voltage-gated Na+ channel, is critical to heart excitability and conduction. However, the mechanisms regulating its expression at the cell membrane are poorly understood. The Na(v)1.5 C-terminus contains a PY-motif (xPPxY) that is known to act as binding site for Nedd4/Nedd4-like ubiquitin-protein ligases. Because Nedd4-2 is well expressed in the heart, we investigated its role in the ubiquitination and regulation of Na(v)1.5. Yeast two-hybrid and GST-pulldown experiments revealed an interaction between Na(v)1.5 C-terminus and Nedd4-2, which was abrogated by mutating the essential tyrosine of the PY-motif. Ubiquitination of Na(v)1.5 was detected in both transfected HEK cells and heart extracts. Furthermore, Nedd4-2-dependent ubiquitination of Na(v)1.5 was observed. To test for a functional role of Nedd4-2, patch-clamp experiments were performed on HEK cells expressing wild-type and mutant forms of both Na(v)1.5 and Nedd4-2. Na(v)1.5 current density was decreased by 65% upon Nedd4-2 cotransfection, whereas the PY-motif mutant channels were not affected. In contrast, a catalytically inactive Nedd4-2 had no effect, indicating that ubiquitination mediates this downregulation. However, Nedd4-2 did not alter the whole-cell or the single channel biophysical properties of Na(v)1.5. Consistent with the functional findings, localization at the cell periphery of Na(v)1.5-YFP fusion proteins was reduced upon Nedd4-2 coexpression. The Nedd4-1 isoform did not regulate Na(v)1.5, suggesting that Nedd4-2 is a specific regulator of Na(v)1.5. These results demonstrate that Na(v)1.5 can be ubiquitinated in heart tissues and that the ubiquitin-protein ligase Nedd4-2 acts on Na(v)1.5 by decreasing the channel density at the cell surface. PMID:15217910

  4. G-protein- and cAMP-dependent L-channel gating modulation: a manyfold system to control calcium entry in neurosecretory cells.

    Science.gov (United States)

    Carbone, E; Carabelli, V; Cesetti, T; Baldelli, P; Hernández-Guijo, J M; Giusta, L

    2001-09-01

    Voltage-gated Ca2+ channels are crucial to the control of Ca2+ entry in neurosecretory cells. In the chromaffin cells of adrenal medulla, paracrinally or autocrinally released neurotransmitters induce profound changes in Ca2+ channel gating and Ca2+-dependent events controlling catecholamine secretion and cell activity. The generally held view of these processes is that neurotransmitter-induced modulation of the most widely expressed Ca2+ channels in these cells (N-, P/Q- and L-type) follows two distinct pathways: a direct membrane-delimited Gi/o-protein-induced inhibition of N- and P/Q-type and a remote cAMP-mediated facilitation of L-channels. Both actions depend on voltage, although with remarkably different molecular and kinetic aspects. Recent findings, however, challenge this simple scheme and suggest that L-channels do not require strong pre-pulses to be recruited or facilitated. They are available during normal depolarizations and may be tonically inhibited by Gi/o proteins activated by the released neurotransmitters. Like the N- and P/Q-channels, this autocrine modulation is localized to membrane microareas. Unlike N- and P/Q-channels, however, the inhibition of L-channels is largely independent of voltage and develops in parallel with cAMP-mediated potentiation of channel gating. As L-channels play a crucial role in the control of catecholamine release in chromaffin cells, the two opposite modulations mediated by Gi/o proteins and cAMP may represent an effective way to broaden the dynamic range of Ca2+ signals controlling exocytosis. Here, we review the basic features of this novel L-type channel inhibition comparing it to the well-established forms of L-channel potentiation and voltage-dependent facilitation. PMID:11680611

  5. Locating the Route of Entry and Binding Sites of Benzocaine and Phenytoin in a Bacterial Voltage Gated Sodium Channel

    Science.gov (United States)

    Martin, Lewis J.; Corry, Ben

    2014-01-01

    Sodium channel blockers are used to control electrical excitability in cells as a treatment for epileptic seizures and cardiac arrhythmia, and to provide short term control of pain. Development of the next generation of drugs that can selectively target one of the nine types of voltage-gated sodium channel expressed in the body requires a much better understanding of how current channel blockers work. Here we make use of the recently determined crystal structure of the bacterial voltage gated sodium channel NavAb in molecular dynamics simulations to elucidate the position at which the sodium channel blocking drugs benzocaine and phenytoin bind to the protein as well as to understand how these drugs find their way into resting channels. We show that both drugs have two likely binding sites in the pore characterised by nonspecific, hydrophobic interactions: one just above the activation gate, and one at the entrance to the the lateral lipid filled fenestrations. Three independent methods find the same sites and all suggest that binding to the activation gate is slightly more favourable than at the fenestration. Both drugs are found to be able to pass through the fenestrations into the lipid with only small energy barriers, suggesting that this can represent the long posited hydrophobic entrance route for neutral drugs. Our simulations highlight the importance of a number of residues in directing drugs into and through the fenestration, and in forming the drug binding sites. PMID:24992293

  6. Inhibition of voltage-gated potassium channels mediates uncarboxylated osteocalcin-regulated insulin secretion in rat pancreatic β cells.

    Science.gov (United States)

    Gao, Jingying; Zhong, Xiangqin; Ding, Yaqin; Bai, Tao; Wang, Hui; Wu, Hongbin; Liu, Yunfeng; Yang, Jing; Zhang, Yi

    2016-04-15

    Insulin secretion from pancreatic β cells is important to maintain glucose homeostasis and is regulated by electrical activities. Uncarboxylated osteocalcin, a bone-derived protein, has been reported to regulate glucose metabolism by increasing insulin secretion, stimulating β cell proliferation and improving insulin sensitivity. But the underlying mechanisms of uncarboxylated osteocalcin-modulated insulin secretion remain unclear. In the present study, we investigated the relationship of uncarboxylated osteocalcin-regulated insulin secretion and voltage-gated potassium (KV) channels, voltage-gated calcium channels in rat β cells. Insulin secretion was measured by radioimmunoassay. Channel currents and membrane action potentials were recorded using the conventional whole-cell patch-clamp technique. Calcium imaging system was used to analyze intracellular Ca(2+) concentration ([Ca(2+)]i). The data show that under 16.7mmol/l glucose conditions uncarboxylated osteocalcin alone increased insulin secretion and [Ca(2+)]i, but with no such effects on insulin secretion and [Ca(2+)]i in the presence of a KV channel blocker, tetraethylammonium chloride. In the patch-clamp experiments, uncarboxylated osteocalcin lengthened action potential duration and significantly inhibited KV currents, but had no influence on the characteristics of voltage-gated calcium channels. These results indicate that KV channels are involved in uncarboxylated osteocalcin-regulated insulin secretion in rat pancreatic β cells. By inhibiting KV channels, uncarboxylated osteocalcin prolongs action potential duration, increases intracellular Ca(2+) concentration and finally promotes insulin secretion. This finding provides new insight into the mechanisms of osteocalcin-modulated insulin secretion. PMID:26927753

  7. Computational Tools for Interpreting Ion Channel pH-Dependence.

    Directory of Open Access Journals (Sweden)

    Ivan Sazanavets

    Full Text Available Activity in many biological systems is mediated by pH, involving proton titratable groups with pKas in the relevant pH range. Experimental analysis of pH-dependence in proteins focusses on particular sidechains, often with mutagenesis of histidine, due to its pKa near to neutral pH. The key question for algorithms that predict pKas is whether they are sufficiently accurate to effectively narrow the search for molecular determinants of pH-dependence. Through analysis of inwardly rectifying potassium (Kir channels and acid-sensing ion channels (ASICs, mutational effects on pH-dependence are probed, distinguishing between groups described as pH-coupled or pH-sensor. Whereas mutation can lead to a shift in transition pH between open and closed forms for either type of group, only for pH-sensor groups does mutation modulate the amplitude of the transition. It is shown that a hybrid Finite Difference Poisson-Boltzmann (FDPB - Debye-Hückel continuum electrostatic model can filter mutation candidates, providing enrichment for key pH-coupled and pH-sensor residues in both ASICs and Kir channels, in comparison with application of FDPB alone.

  8. Voltage gating by molecular subunits of Na+ and K+ ion channels: higher-dimensional cubic kinetics, rate constants, and temperature.

    Science.gov (United States)

    Fohlmeister, Jürgen F

    2015-06-01

    The structural similarity between the primary molecules of voltage-gated Na and K channels (alpha subunits) and activation gating in the Hodgkin-Huxley model is brought into full agreement by increasing the model's sodium kinetics to fourth order (m(3) → m(4)). Both structures then virtually imply activation gating by four independent subprocesses acting in parallel. The kinetics coalesce in four-dimensional (4D) cubic diagrams (16 states, 32 reversible transitions) that show the structure to be highly failure resistant against significant partial loss of gating function. Rate constants, as fitted in phase plot data of retinal ganglion cell excitation, reflect the molecular nature of the gating transitions. Additional dimensions (6D cubic diagrams) accommodate kinetically coupled sodium inactivation and gating processes associated with beta subunits. The gating transitions of coupled sodium inactivation appear to be thermodynamically irreversible; response to dielectric surface charges (capacitive displacement) provides a potential energy source for those transitions and yields highly energy-efficient excitation. A comparison of temperature responses of the squid giant axon (apparently Arrhenius) and mammalian channel gating yields kinetic Q10 = 2.2 for alpha unit gating, whose transitions are rate-limiting at mammalian temperatures; beta unit kinetic Q10 = 14 reproduces the observed non-Arrhenius deviation of mammalian gating at low temperatures; the Q10 of sodium inactivation gating matches the rate-limiting component of activation gating at all temperatures. The model kinetics reproduce the physiologically large frequency range for repetitive firing in ganglion cells and the physiologically observed strong temperature dependence of recovery from inactivation. PMID:25867741

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

    Science.gov (United States)

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

    1990-01-01

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

  10. A distinct sodium channel voltage-sensor locus determines insect selectivity of the spider toxin Dc1a

    Science.gov (United States)

    Bende, Niraj S.; Dziemborowicz, Sławomir; Mobli, Mehdi; Herzig, Volker; Gilchrist, John; Wagner, Jordan; Nicholson, Graham M.; King, Glenn F.; Bosmans, Frank

    2014-07-01

    β-Diguetoxin-Dc1a (Dc1a) is a toxin from the desert bush spider Diguetia canities that incapacitates insects at concentrations that are non-toxic to mammals. Dc1a promotes opening of German cockroach voltage-gated sodium (Nav) channels (BgNav1), whereas human Nav channels are insensitive. Here, by transplanting commonly targeted S3b-S4 paddle motifs within BgNav1 voltage sensors into Kv2.1, we find that Dc1a interacts with the domain II voltage sensor. In contrast, Dc1a has little effect on sodium currents mediated by PaNav1 channels from the American cockroach even though their domain II paddle motifs are identical. When exploring regions responsible for PaNav1 resistance to Dc1a, we identified two residues within the BgNav1 domain II S1-S2 loop that when mutated to their PaNav1 counterparts drastically reduce toxin susceptibility. Overall, our results reveal a distinct region within insect Nav channels that helps determine Dc1a sensitivity, a concept that will be valuable for the design of insect-selective insecticides.

  11. Evidence for functional diversity between the voltage-gated proton channel Hv1 and its closest related protein HVRP1.

    Directory of Open Access Journals (Sweden)

    Iris H Kim

    Full Text Available The Hv1 channel and voltage-sensitive phosphatases share with voltage-gated sodium, potassium, and calcium channels the ability to detect changes in membrane potential through voltage-sensing domains (VSDs. However, they lack the pore domain typical of these other channels. NaV, KV, and CaV proteins can be found in neurons and muscles, where they play important roles in electrical excitability. In contrast, VSD-containing proteins lacking a pore domain are found in non-excitable cells and are not involved in neuronal signaling. Here, we report the identification of HVRP1, a protein related to the Hv1 channel (from which the name Hv1 Related Protein 1 is derived, which we find to be expressed primarily in the central nervous system, and particularly in the cerebellum. Within the cerebellar tissue, HVRP1 is specifically expressed in granule neurons, as determined by in situ hybridization and immunohistochemistry. Analysis of subcellular distribution via electron microscopy and immunogold labeling reveals that the protein localizes on the post-synaptic side of contacts between glutamatergic mossy fibers and the granule cells. We also find that, despite the similarities in amino acid sequence and structural organization between Hv1 and HVRP1, the two proteins have distinct functional properties. The high conservation of HVRP1 in vertebrates and its cellular and subcellular localizations suggest an important function in the nervous system.

  12. Light and voltage dependence of the junction transport properties of CdTe/CdS photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Linam, D.L.; McClure, J.C.; Lush, G.B. [Electrical and Computer Engineering Department, University of Texas El Paso-UTEP, 79968-0520 El Paso, TX (United States); Singh, V.P. [Electrical Engineering Department, University of Kentucky, 40506 Lexington, KY (United States); Mathew, X.; Sebastian, P.J. [Centro de Investigacion en Energia, UNAM, Temixco, Morelos (Mexico)

    2001-12-31

    The J-V curve of CdTe/CdS photovoltaics does not consist of a simple superposition of a loss current and a light generated current with a considerable loss in conversion efficiency. This paper uses capacitance/voltage measurements and J-V measurements at a variety of temperatures and light levels to develop a model for this non-superposition. It was found that a light dependent tunneling mechanism dominates at low voltages. Moreover, the tunneling takes place from a trap level within the CdTe.

  13. Coordinated role of voltage-gated sodium channels and the Na+/H+ exchanger in sustaining microglial activation during inflammation

    International Nuclear Information System (INIS)

    Persistent neuroinflammation and microglial activation play an integral role in the pathogenesis of many neurological disorders. We investigated the role of voltage-gated sodium channels (VGSC) and Na+/H+ exchangers (NHE) in the activation of immortalized microglial cells (BV-2) after lipopolysaccharide (LPS) exposure. LPS (10 and 100 ng/ml) caused a dose- and time-dependent accumulation of intracellular sodium [(Na+)i] in BV-2 cells. Pre-treatment of cells with the VGSC antagonist tetrodotoxin (TTX, 1 μM) abolished short-term Na+ influx, but was unable to prevent the accumulation of (Na+)i observed at 6 and 24 h after LPS exposure. The NHE inhibitor cariporide (1 μM) significantly reduced accumulation of (Na+)i 6 and 24 h after LPS exposure. Furthermore, LPS increased the mRNA expression and protein level of NHE-1 in a dose- and time-dependent manner, which was significantly reduced after co-treatment with TTX and/or cariporide. LPS increased production of TNF-α, ROS, and H2O2 and expression of gp91phox, an active subunit of NADPH oxidase, in a dose- and time-dependent manner, which was significantly reduced by TTX or TTX + cariporide. Collectively, these data demonstrate a closely-linked temporal relationship between VGSC and NHE-1 in regulating function in activated microglia, which may provide avenues for therapeutic interventions aimed at reducing neuroinflammation. - Highlights: • LPS causes immediate increase in sodium through VGSC and subsequently through the NHE-1. • Inhibition of VGSC reduces increases in NHE-1 and gp91phox. • Inhibition of VGSC and NHE-1 reduces NADPH oxidase-mediated Tnf-α, ROS, and H2O2 production. • NHE-1 and Nav1.6 may be viable targets for therapeutic interventions to reduce neuroinflammation in neurodegenerative disease

  14. Calcium currents in the A7r5 smooth muscle-derived cell line. Increase in current and selective removal of voltage-dependent inactivation by intracellular trypsin

    OpenAIRE

    1991-01-01

    We studied the effects of trypsin on L-type calcium current in the A7r5 smooth muscle cell line. Intracellular dialysis with trypsin increased the whole-cell current up to fivefold. The effect was concentration dependent, and was prevented by soybean trypsin inhibitor. Ensemble analysis indicated an increase in the number of functional channels, and possibly a smaller increase in the open probability, with no change in the single channel current. The shape of the current-voltage curve was una...

  15. Voltage-Dependent Electronic Transport Properties of Reduced Graphene Oxide with Various Coverage Ratios

    Institute of Scientific and Technical Information of China (English)

    Serhan Yamacli

    2015-01-01

    Graphene is mainly implemented by these methods: exfoliating, unzipping of carbon nanotubes, chemical vapour deposition, epitaxial growth and the reduction of graphene oxide. The latter option has the advantage of low cost and precision. However, reduced graphene oxide (rGO) contains hydrogen and/or oxygen atoms hence the structure and properties of the rGO and intrinsic graphene are different. Considering the advantages of the implementation and utili-zation of rGO, voltage-dependent electronic transport properties of several rGO samples with various coverage ratios are investigated in this work. Ab initio simulations based on density functional theory combined with non-equilibrium Green’s function formalism are used to obtain the current–voltage characteristics and the voltage-dependent transmission spectra of rGO samples. It is shown that the transport properties of rGO are strongly dependent on the coverage ratio. Obtained results indicate that some of the rGO samples have negative differential resistance characteristics while normally insulating rGO can behave as conducting beyond a certain threshold voltage. The reasons of the peculiar electronic transport behaviour of rGO samples are further investigated, taking the transmission eigenstates and their localization degree into consideration. The findings of this study are expected to be helpful for engineering the characteristics of rGO structures.

  16. Surface Potential and Threshold Voltage Model of Fully Depleted Narrow Channel SOI MOSFET Using Analytical Solution of 3D Poisson’s Equation

    Directory of Open Access Journals (Sweden)

    Prashant Mani

    2015-06-01

    Full Text Available The present paper is about the modeling of surface potential and threshold voltage of Fully Depleted Silicon on Insulator MOSFET. The surface potential is calculated by solving the 3D Poisson’s equation analytically. The appropriate boundary conditions are used in calculations. The effect of narrow channel width and short channel length for suppression of SCE is analyzed. The narrow channel width effect in the threshold voltage is analyzed for thin film Fully Depleted SOI MOSFET.

  17. Time scales of bias voltage effects in FE/MgO-based magnetic tunnel junctions with voltage-dependent perpendicular anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Lytvynenko, Ia.M. [Sumy State University, 2, Rimskogo-Korsakova Str., 40007 Sumy (Ukraine); Hauet, T., E-mail: thomas.hauet@univ-lorraine.fr [Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, 54506 Vandoeuvre les Nancy (France); Montaigne, F. [Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, 54506 Vandoeuvre les Nancy (France); Bibyk, V.V. [Sumy State University, 2, Rimskogo-Korsakova Str., 40007 Sumy (Ukraine); Andrieu, S. [Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, 54506 Vandoeuvre les Nancy (France)

    2015-12-15

    Interplay between voltage-induced magnetic anisotropy transition and voltage-induced atomic diffusion is studied in epitaxial V/Fe (0.7 nm)/ MgO/ Fe(5 nm)/Co/Au magnetic tunnel junction where thin Fe soft electrode has in-plane or out-of-plane anisotropy depending on the sign of the bias voltage. We investigate the origin of the slow resistance variation occurring when switching bias voltage in opposite polarity. We demonstrate that the time to reach resistance stability after voltage switching is reduced when increasing the voltage amplitude or the temperature. A single energy barrier of about 0.2 eV height is deduced from temperature dependence. Finally, we demonstrate that the resistance change is not correlated to a change in soft electrode anisotropy. This conclusion contrasts with observations recently reported on analogous systems. - Highlights: • Voltage-induced time dependence of resistance is studied in epitaxial Fe/MgO/Fe. • Resistance change is not related to the bottom Fe/MgO interface. • The effect is thermally activated with an energy barrier of the order of 0.2 eV height.

  18. Time scales of bias voltage effects in FE/MgO-based magnetic tunnel junctions with voltage-dependent perpendicular anisotropy

    International Nuclear Information System (INIS)

    Interplay between voltage-induced magnetic anisotropy transition and voltage-induced atomic diffusion is studied in epitaxial V/Fe (0.7 nm)/ MgO/ Fe(5 nm)/Co/Au magnetic tunnel junction where thin Fe soft electrode has in-plane or out-of-plane anisotropy depending on the sign of the bias voltage. We investigate the origin of the slow resistance variation occurring when switching bias voltage in opposite polarity. We demonstrate that the time to reach resistance stability after voltage switching is reduced when increasing the voltage amplitude or the temperature. A single energy barrier of about 0.2 eV height is deduced from temperature dependence. Finally, we demonstrate that the resistance change is not correlated to a change in soft electrode anisotropy. This conclusion contrasts with observations recently reported on analogous systems. - Highlights: • Voltage-induced time dependence of resistance is studied in epitaxial Fe/MgO/Fe. • Resistance change is not related to the bottom Fe/MgO interface. • The effect is thermally activated with an energy barrier of the order of 0.2 eV height

  19. First direct electron microscopic visualization of a tight spatial coupling between GABAA-receptors and voltage-sensitive calcium channels

    DEFF Research Database (Denmark)

    Hansen, Gert Helge; Belhage, B; Schousboe, A

    1992-01-01

    Using cerebellar granule neurons in culture it was demonstrated that exposure of the cells to the GABAA receptor agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) leads to an increase in the number of voltage-gated calcium channels as revealed by quantitative preembedding indirect...... immunogold labelling using a monoclonal antibody specific for phenylalkylamine and dihydropyridine sensitive Ca2+ channels. Using the same technique and a monoclonal antibody (bd-17) to the beta 2/beta 3-subunit of the GABAA-receptor, double labelling of Ca2+ channels and GABAA-receptors with gold particles...... of different and well defined sizes were performed. This showed that in THIP-treated cultures 20% of GABAA-receptors in cell processes were located in close proximity (i.e. within 40 nm) of Ca2+ channels in the plasma membrane. This was not observed in non-treated cultures nor was it observed in cell...

  20. Time and material dependence of the voltage noise generated by cathodic vacuum arcs

    International Nuclear Information System (INIS)

    The high frequency fluctuations of the burning voltage of cathodic vacuum arcs have been investigated in order to extract information on cathode processes, especially concerning evolution in time after arc ignition. Eight cathode materials (W, Ta, Hf, Ti, Ni, Au, Sn, Bi) were selected covering a wide range of cohesive energy. The voltage noise was recorded using both a broad-band voltage divider and an attenuator connected to a fast oscilloscope (limits 1 GHz analog and 5 GS s-1 digital). Fast Fourier transform revealed a power spectrum that is linear in log-log presentation, with a slope of 1/f 2, where f is the frequency (brown noise). The amplitude of the spectral power of the voltage noise was found to scale with the cohesive energy, in agreement with earlier measurements at lower resolution. These basic results do not depend on the time after arc initiation. However, lower arc current in the beginning of the pulse shows greater voltage noise, suggesting an inverse relation between the noise amplitude and number of emission sites (cathode spot fragments)

  1. Role for voltage gated calcium channels in calcitonin gene-related peptide release in the rat trigeminovascular system

    DEFF Research Database (Denmark)

    Amrutkar, D V; Ploug, K B; Olesen, J;

    2011-01-01

    Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons and are...... potassium releases CGRP, and the release is regulated by Ca2+ ions and voltage-gated calcium channels....... potassium induced CGRP release. In the absence of calcium ions (Ca2+) and in the presence of a cocktail of blockers, the stimulated CGRP release from dura mater was reduced almost to the same level as basal CGRP release. In the TG ω-conotoxin GVIA inhibited the potassium induced CGRP release significantly...

  2. Role for voltage gated calcium channels in calcitonin gene-related peptide release in the rat trigeminovascular system

    DEFF Research Database (Denmark)

    Amrutkar, D V; Ploug, K B; Olesen, J;

    2011-01-01

    Clinical and genetic studies have suggested a role for voltage gated calcium channels (VGCCs) in the pathogenesis of migraine. Release of calcitonin gene-related peptide (CGRP) from trigeminal neurons has also been implicated in migraine. The VGCCs are located presynaptically on neurons and are...... potassium releases CGRP, and the release is regulated by Ca2+ ions and voltage-gated calcium channels....... potassium induced CGRP release. In the absence of calcium ions (Ca2+) and in the presence of a cocktail of blockers, the stimulated CGRP release from dura mater was reduced almost to the same level as basal CGRP release. In the TG ¿-conotoxin GVIA inhibited the potassium induced CGRP release significantly...

  3. Targeting voltage-gated calcium channels: developments in peptide and small-molecule inhibitors for the treatment of neuropathic pain

    OpenAIRE

    Vink, S.; Alewood, PF

    2012-01-01

    Chronic pain affects approximately 20% of people worldwide and places a large economic and social burden on society. Despite the availability of a range of analgesics, this condition is inadequately treated, with complete alleviation of symptoms rarely occurring. In the past 30 years, the voltage-gated calcium channels (VGCCs) have been recognized as potential targets for analgesic development. Although the majority of the research has been focused on Cav2.2 in particular, other VGCC subtypes...

  4. Colonic Hypersensitivity and Sensitization of Voltage-gated Sodium Channels in Primary Sensory Neurons in Rats with Diabetes

    OpenAIRE

    Hu, Ji; Song, Zhen-Yuan; Zhang, Hong-Hong; Qin, Xin; Hu, Shufen; Jiang, Xinghong; Xu, Guang-Yin

    2016-01-01

    Background/Aims Patients with long-standing diabetes often demonstrate intestinal dysfunction and abdominal pain. However, the pathophysiology of abdominal pain in diabetic patients remains elusive. The purpose of study was to determine roles of voltage-gated sodium channels in dorsal root ganglion (DRG) in colonic hypersensitivity of rats with diabetes. Methods Diabetic models were induced by a single intraperitoneal injection of streptozotocin (STZ; 65 mg/kg) in adult female rats, while the...

  5. Analytical Model for Voltage-Dependent Photo and Dark Currents in Bulk Heterojunction Organic Solar Cells

    Directory of Open Access Journals (Sweden)

    Mesbahus Saleheen

    2016-05-01

    Full Text Available A physics-based explicit mathematical model for the external voltage-dependent forward dark current in bulk heterojunction (BHJ organic solar cells is developed by considering Shockley-Read-Hall (SRH recombination and solving the continuity equations for both electrons and holes. An analytical model for the external voltage-dependent photocurrent in BHJ organic solar cells is also proposed by incorporating exponential photon absorption, dissociation efficiency of bound electron-hole pairs (EHPs, carrier trapping, and carrier drift and diffusion in the photon absorption layer. Modified Braun’s model is used to compute the electric field-dependent dissociation efficiency of the bound EHPs. The overall net current is calculated considering the actual solar spectrum. The mathematical models are verified by comparing the model calculations with various published experimental results. We analyze the effects of the contact properties, blend compositions, charge carrier transport properties (carrier mobility and lifetime, and cell design on the current-voltage characteristics. The power conversion efficiency of BHJ organic solar cells mostly depends on electron transport properties of the acceptor layer. The results of this paper indicate that improvement of charge carrier transport (both mobility and lifetime and dissociation of bound EHPs in organic blend are critically important to increase the power conversion efficiency of the BHJ solar cells.

  6. Low operating voltage n-channel organic field effect transistors using lithium fluoride/PMMA bilayer gate dielectric

    International Nuclear Information System (INIS)

    Highlights: • Alternative to chemically crosslinking of PMMA to achieve low leakage in provided. • Effect of LiF in reducing gate leakage through the OFET device is studied. • Effect of gate leakage on transistor performance has been investigated. • Low voltage operable and low temperature processed n-channel OFETs were fabricated. - Abstract: We report low temperature processed, low voltage operable n-channel organic field effect transistors (OFETs) using N,N′-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) organic semiconductor and poly(methylmethacrylate) (PMMA)/lithium fluoride (LiF) bilayer gate dielectric. We have studied the role of LiF buffer dielectric in effectively reducing the gate leakage through the device and thus obtaining superior performance in contrast to the single layer PMMA dielectric devices. The bilayer OFET devices had a low threshold voltage (Vt) of the order of 5.3 V. The typical values of saturation electron mobility (μs), on/off ratio and inverse sub-threshold slope (S) for the range of devices made were estimated to be 2.8 × 10−3 cm2/V s, 385, and 3.8 V/decade respectively. Our work thus provides a potential substitution for much complicated process of chemically crosslinking PMMA to achieve low leakage, high capacitance, and thus low operating voltage OFETs

  7. Low operating voltage n-channel organic field effect transistors using lithium fluoride/PMMA bilayer gate dielectric

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, S.; Dhar, A., E-mail: adhar@phy.iitkgp.ernet.in

    2015-10-15

    Highlights: • Alternative to chemically crosslinking of PMMA to achieve low leakage in provided. • Effect of LiF in reducing gate leakage through the OFET device is studied. • Effect of gate leakage on transistor performance has been investigated. • Low voltage operable and low temperature processed n-channel OFETs were fabricated. - Abstract: We report low temperature processed, low voltage operable n-channel organic field effect transistors (OFETs) using N,N′-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C{sub 8}) organic semiconductor and poly(methylmethacrylate) (PMMA)/lithium fluoride (LiF) bilayer gate dielectric. We have studied the role of LiF buffer dielectric in effectively reducing the gate leakage through the device and thus obtaining superior performance in contrast to the single layer PMMA dielectric devices. The bilayer OFET devices had a low threshold voltage (V{sub t}) of the order of 5.3 V. The typical values of saturation electron mobility (μ{sub s}), on/off ratio and inverse sub-threshold slope (S) for the range of devices made were estimated to be 2.8 × 10{sup −3} cm{sup 2}/V s, 385, and 3.8 V/decade respectively. Our work thus provides a potential substitution for much complicated process of chemically crosslinking PMMA to achieve low leakage, high capacitance, and thus low operating voltage OFETs.

  8. Molecular cloning and analysis of zebrafish voltage-gated sodium channel beta subunit genes: implications for the evolution of electrical signaling in vertebrates

    Directory of Open Access Journals (Sweden)

    Zhong Tao P

    2007-07-01

    Full Text Available Abstract Background Action potential generation in excitable cells such as myocytes and neurons critically depends on voltage-gated sodium channels. In mammals, sodium channels exist as macromolecular complexes that include a pore-forming alpha subunit and 1 or more modulatory beta subunits. Although alpha subunit genes have been cloned from diverse metazoans including flies, jellyfish, and humans, beta subunits have not previously been identified in any non-mammalian species. To gain further insight into the evolution of electrical signaling in vertebrates, we investigated beta subunit genes in the teleost Danio rerio (zebrafish. Results We identified and cloned single zebrafish gene homologs for beta1-beta3 (zbeta1-zbeta3 and duplicate genes for beta4 (zbeta4.1, zbeta4.2. Sodium channel beta subunit loci are similarly organized in fish and mammalian genomes. Unlike their mammalian counterparts, zbeta1 and zbeta2 subunit genes display extensive alternative splicing. Zebrafish beta subunit genes and their splice variants are differentially-expressed in excitable tissues, indicating tissue-specific regulation of zbeta1-4 expression and splicing. Co-expression of the genes encoding zbeta1 and the zebrafish sodium channel alpha subunit Nav1.5 in Chinese Hamster Ovary cells increased sodium current and altered channel gating, demonstrating functional interactions between zebrafish alpha and beta subunits. Analysis of the synteny and phylogeny of mammalian, teleost, amphibian, and avian beta subunit and related genes indicated that all extant vertebrate beta subunits are orthologous, that beta2/beta4 and beta1/beta3 share common ancestry, and that beta subunits are closely related to other proteins sharing the V-type immunoglobulin domain structure. Vertebrate sodium channel beta subunit genes were not identified in the genomes of invertebrate chordates and are unrelated to known subunits of the para sodium channel in Drosophila. Conclusion The

  9. Size and voltage dependence of effective anisotropy in sub-100-nm perpendicular magnetic tunnel junctions

    Science.gov (United States)

    Piotrowski, Stephan K.; Bapna, Mukund; Oberdick, Samuel D.; Majetich, Sara A.; Li, Mingen; Chien, C. L.; Ahmed, Rizvi; Victora, R. H.

    2016-07-01

    Magnetic tunnel junctions with perpendicular magnetic anisotropy are investigated using a conductive atomic force microscope. The 1.23 -nm Co40Fe40B20 recording layer coercivity exhibits a size dependence which suggests single-domain behavior for diameters ≤100 nm. Focusing on devices with diameters smaller than 100 nm, we determine the effect of voltage and size on the effective device anisotropy Keff using two different techniques. Keff is extracted both from distributions of the switching fields of the recording and reference layers and from measurement of thermal fluctuations of the recording layer magnetization when a field close to the switching field is applied. The results from both sets of measurements reveal that Keff increases monotonically with decreasing junction diameter, consistent with the size dependence of the demagnetization energy density. We demonstrate that Keff can be controlled with a voltage down to the smallest size measured, 64 nm.

  10. Effect of intracellular diffusion on current-voltage curves in potassium channels

    OpenAIRE

    Andreucci, D.; Bellaveglia, D.; Cirillo, E. N. M.; S. Marconi

    2012-01-01

    We study the effect of intracellular ion diffusion on ionic currents permeating through the cell membrane. Ion flux across the cell membrane is mediated by special proteins forming specific channels. The structure of potassium channels have been widely studied in recent years with remarkable results: very precise measurements of the true current across a single channel are now available. Nevertheless, a complete understanding of the behavior of the channel is still lacking, though molecular d...

  11. Voltage-dependent excitation of motoneurones from spinal locomotor centres in the cat.

    Science.gov (United States)

    Brownstone, R M; Gossard, J P; Hultborn, H

    1994-01-01

    Lumbar motoneurones were recorded intracellularly during fictive locomotion induced by stimulation of the mesencephalic locomotor region in decerebrate cats. After blocking the action potentials using intracellular QX-314, and by using a discontinuous current clamp, it is shown that the excitatory component of the locomotor drive potentials behaves in a voltage-dependent manner, such that its amplitude increases with depolarisation. As the input to motoneurones during locomotion is comprised of alternating excitation and inhibition, it was desirable to examine the excitatory input in relative isolation. This was accomplished in spinalised decerebrate cats treated with nialamide and L-dihydroxy-phenylalanine (L-DOPA) by studying the excitatory post-synaptic potentials (EPSPs) evoked from the "flexor reflex afferents" (FRA) and extensor Ib afferents, both of which are likely to be mediated via the locomotor network. As expected, these EPSPs also demonstrate a voltage-dependent increase in amplitude. In addition, the input to motoneurones from the network for scratching, which is thought to share interneurones with the locomotor network, also results in voltage-dependent excitation. The possible underlying mechanisms of NMDA-mediated excitation and plateau potentials are discussed: both may contribute to the observed effect. It is suggested that this nonlinear increase in excitation contributes to the mechanisms involved in the production of the high rates of repetitive firing of motoneurones typically seen during locomotion, thus ensuring appropriate muscle contraction. PMID:7895797

  12. Lack of variation in voltage-gated sodium channels of common bottlenose dolphins (Tursiops truncatus) exposed to neurotoxic algal blooms.

    Science.gov (United States)

    Cammen, Kristina M; Rosel, Patricia E; Wells, Randall S; Read, Andrew J

    2014-12-01

    In coastal marine ecosystems, neurotoxins produced by harmful algal blooms (HABs) often result in large-scale mortality events of many marine species. Historical and frequent exposure to HABs therefore may provide a strong selective pressure for adaptations that result in toxin resistance. Neurotoxin resistance has independently evolved in a variety of terrestrial and marine species via mutations in genes encoding the toxin binding sites within the voltage-gated sodium channel gene complex. Accordingly, we tested the hypothesis that genetic variation in the putative binding site of brevetoxins in common bottlenose dolphins (Tursiops truncatus) explains differences among individuals or populations in resistance to harmful Karenia brevis blooms in the Gulf of Mexico. We found very little variation in the sodium channel exons encoding the putative brevetoxin binding site among bottlenose dolphins from central-west Florida and the Florida Panhandle. Our study included samples from several bottlenose dolphin mortality events associated with HABs, but we found no association between genetic variation and survival. We observed a significant effect of geographic region on genetic variation for some sodium channel isoforms, but this can be primarily explained by rare private alleles and is more likely a reflection of regional genetic differentiation than the cause of different levels of HAB resistance between regions. In contrast to many other previously studied neurotoxin-resistant species, we conclude that bottlenose dolphins have not evolved resistance to HABs via mutations in genes encoding the brevetoxin binding site on the voltage-gated sodium channels. PMID:25456229

  13. The tarantula toxin jingzhaotoxin-XI (κ-theraphotoxin-Cj1a) regulates the activation and inactivation of the voltage-gated sodium channel Nav1.5.

    Science.gov (United States)

    Tang, Cheng; Zhou, Xi; Huang, Yin; Zhang, Yunxiao; Hu, Zhaotun; Wang, Meichi; Chen, Ping; Liu, Zhonghua; Liang, Songping

    2014-12-15

    Specific peptide toxins interact with voltage-gated sodium channels by regulating the activation or inactivation of targeted channels. However, few toxins possessing dual effects have been identified. In the present study, we showed that jingzhaotoxin-XI/κ-theraphotoxin-Cj1a (JZTX-XI), a 34-residue peptide from the venom of the Chinese spider Chilobrachys jingzhao, inhibits the sodium conductance (IC50 = 124 ± 26 nM) and slows the fast inactivation (EC50 = 1.18 ± 0.2 μM) of Nav1.5 expressed in Chinese hamster ovary (CHO-K1) cells. JZTX-XI significantly shifted the activation to more depolarized voltages and decreased the deactivation of Nav1.5 currents upon extreme depolarization, but only slightly affected voltage-dependence of steady-state inactivation. In addition, JZTX-XI caused an approximately five-fold decrease in the rate of recovery from inactivation and an approximately 1.9-fold reduction in the closed-state inactivation rate. Our data suggest that JZTX-XI integrates the functions of site 3 toxins (α-scorpion toxins) with site 4 toxins (β-scorpion and spider toxins) by targeting multiple sites on Nav1.5. The unique properties displayed by JZTX-XI in its inhibitory activity on Nav1.5 suggest that its mechanism of action is distinct from those of site 3 and site 4 toxins, making JZTX-XI a useful probe for investigating the gating mechanism of Nav1.5 and toxin-channel interactions. PMID:25240294

  14. Temperature-dependent ballistic transport in a channel with length below the scattering-limited mean free path

    Science.gov (United States)

    Arora, Vijay K.; Zainal Abidin, Mastura Shafinaz; Tan, Michael L. P.; Riyadi, Munawar A.

    2012-03-01

    The temperature-dependent ballistic transport, using nonequilibrium Arora distribution function (NEADF), is shown to result in mobility degradation with reduction in channel length, in direct contrast to expectation of a collision-free transport. The ballistic mean free path (mfp) is much higher than the scattering-limited long-channel mfp, yet the mobility is amazingly lower. High-field effects, converting stochastic velocity vectors to streamlined ones, are found to be negligible when the applied voltage is less than the critical voltage appropriate for a ballistic mfp, especially at cryogenic temperatures. Excellent agreement with the experimental data on a metal-oxide-semiconductor field-effect transistor is obtained. The applications of NEADF are shown to cover a wide spectrum, covering regimes from the scattering-limited to ballistic, from nondegenerate to degenerate, from nanowire to bulk, from low- to high-temperature, and from a low electric field to an extremely high electric field.

  15. RNAi-mediated knockdown of the voltage gated sodium ion channel TcNav causes mortality in Tribolium castaneum

    Science.gov (United States)

    Abd El Halim, Hesham M.; Alshukri, Baida M. H.; Ahmad, Munawar S.; Nakasu, Erich Y. T.; Awwad, Mohammed H.; Salama, Elham M.; Gatehouse, Angharad M. R.; Edwards, Martin G.

    2016-01-01

    The voltage-gated sodium ion channel (VGSC) belongs to the largest superfamily of ion channels. Since VGSCs play key roles in physiological processes they are major targets for effective insecticides. RNA interference (RNAi) is widely used to analyse gene function, but recently, it has shown potential to contribute to novel strategies for selectively controlling agricultural insect pests. The current study evaluates the delivery of dsRNA targeted to the sodium ion channel paralytic A (TcNav) gene in Tribolium castaneum as a viable means of controlling this insect pest. Delivery of TcNav dsRNA caused severe developmental arrest with larval mortalities up to 73% post injection of dsRNA. Injected larvae showed significant (p insect control. PMID:27411529

  16. Hair cell-type dependent expression of basolateral ion channels shapes response dynamics in the frog utricle

    Directory of Open Access Journals (Sweden)

    Alessandro eVenturino

    2015-09-01

    Full Text Available The dynamics of vestibular afferent responses are thought to be strongly influenced by presynaptic properties. In this paper, by performing whole-cell perforated-patch experiments in the frog utricle, we characterized voltage-dependent currents and voltage responses to current steps and 0.3-100 Hz sinusoids. Current expression and voltage responses are strongly related to hair cell type. In particular, voltage responses of extrastriolar type eB (low pass, -3 dB corner at 52.512.8 Hz and striolar type F cells (resonant, tuned at 6046 Hz agree with the dynamics (tonic and phasic, respectively of the afferent fibers they contact. On the other hand, hair cell release (measured with single-sine membrane Cm measurements was linearly related to Ca in both cell types, and therefore did not appear to contribute to dynamics differences. As a tool for quantifying the relative contribution of basolateral currents and other presynaptic factors to afferent dynamics, the recorded current, voltage and release data were used to build a NEURON model of the average extrastriolar type eB and striolar type F hair cell. The model contained all recorded conductances, a basic mechanosensitive hair bundle and a ribbon synapse sustained by stochastic voltage-dependent Ca channels, and could reproduce the recorded hair cell voltage responses. Simulated release obtained from eB-type and F-type models display significant differences in dynamics, supporting the idea that basolateral currents are able to contribute to afferent dynamics; however, release in type eB and F cell models does not reproduce tonic and phasic dynamics, mainly because of an excessive phase lag present in both cell types. This suggests the presence in vestibular hair cells of an additional, phase-advancing mechanism, in cascade with voltage modulation.

  17. Identification of Amino Acid Residues in Fibroblast Growth Factor 14 (FGF14) Required for Structure-Function Interactions with Voltage-gated Sodium Channel Nav1.6.

    Science.gov (United States)

    Ali, Syed R; Singh, Aditya K; Laezza, Fernanda

    2016-05-20

    The voltage-gated Na(+) (Nav) channel provides the basis for electrical excitability in the brain. This channel is regulated by a number of accessory proteins including fibroblast growth factor 14 (FGF14), a member of the intracellular FGF family. In addition to forming homodimers, FGF14 binds directly to the Nav1.6 channel C-tail, regulating channel gating and expression, properties that are required for intrinsic excitability in neurons. Seeking amino acid residues with unique roles at the protein-protein interaction interface (PPI) of FGF14·Nav1.6, we engineered model-guided mutations of FGF14 and validated their impact on the FGF14·Nav1.6 complex and the FGF14:FGF14 dimer formation using a luciferase assay. Divergence was found in the β-9 sheet of FGF14 where an alanine (Ala) mutation of Val-160 impaired binding to Nav1.6 but had no effect on FGF14:FGF14 dimer formation. Additional analysis revealed also a key role of residues Lys-74/Ile-76 at the N-terminal of FGF14 in the FGF14·Nav1.6 complex and FGF14:FGF14 dimer formation. Using whole-cell patch clamp electrophysiology, we demonstrated that either the FGF14(V160A) or the FGF14(K74A/I76A) mutation was sufficient to abolish the FGF14-dependent regulation of peak transient Na(+) currents and the voltage-dependent activation and steady-state inactivation of Nav1.6; but only V160A with a concomitant alanine mutation at Tyr-158 could impede FGF14-dependent modulation of the channel fast inactivation. Intrinsic fluorescence spectroscopy of purified proteins confirmed a stronger binding reduction of FGF14(V160A) to the Nav1.6 C-tail compared with FGF14(K74A/I76A) Altogether these studies indicate that the β-9 sheet and the N terminus of FGF14 are well positioned targets for drug development of PPI-based allosteric modulators of Nav channels. PMID:26994141

  18. Importance of the Voltage Dependence of Cardiac Na/K ATPase Isozymes.

    Science.gov (United States)

    Stanley, Christopher M; Gagnon, Dominique G; Bernal, Adam; Meyer, Dylan J; Rosenthal, Joshua J; Artigas, Pablo

    2015-11-01

    Cardiac cells express more than one isoform of the Na, K-ATPase (NKA), the heteromeric enzyme that creates the Na(+) and K(+) gradients across the plasmalemma. Cardiac isozymes contain one catalytic α-subunit isoform (α1, α2, or α3) associated with an auxiliary β-subunit isoform (β1 or β2). Past studies using biochemical approaches have revealed minor kinetic differences between isozymes formed by different α-β isoform combinations; these results make it difficult to understand the physiological requirement for multiple isoforms. In intact cells, however, NKA enzymes operate in a more complex environment, which includes a substantial transmembrane potential. We evaluated the voltage dependence of human cardiac NKA isozymes expressed in Xenopus oocytes, and of native NKA isozymes in rat ventricular myocytes, using normal mammalian physiological concentrations of Na(+)o and K(+)o. We demonstrate that although α1 and α3 pumps are functional at all physiologically relevant voltages, α2β1 pumps and α2β2 pumps are inhibited by ∼75% and ∼95%, respectively, at resting membrane potentials, and only activate appreciably upon depolarization. Furthermore, phospholemman (FXYD1) inhibits pump function without significantly altering the pump's voltage dependence. Our observations provide a simple explanation for the physiological relevance of the α2 subunit (∼20% of total α subunits in rat ventricle): they act as a reserve and are recruited into action for extra pumping during the long-lasting cardiac action potential, where most of the Na(+) entry occurs. This strong voltage dependence of α2 pumps also helps explain how cardiotonic steroids, which block NKA pumps, can be a beneficial treatment for heart failure: by only inhibiting the α2 pumps, they selectively reduce NKA activity during the cardiac action potential, leading to an increase in systolic Ca(2+), due to reduced extrusion through the Na/Ca exchanger, without affecting resting Na(+) and Ca(2

  19. Ca2+- and voltage-gated potassium (BK) channel activators in the 5β-cholanic acid-3α-ol analogue series with modifications in lateral chain

    OpenAIRE

    Bukiya, Anna N.; Patil, Shivaputra; Li, Wei; Miller, Duane; Dopico, Alex M.

    2012-01-01

    Large conductance, calcium- and voltage-gated potassium (BK) channels regulate various physiological processes and represent an attractive target for drug discovery. Numerous BK channel activators are available. However, these agents usually interact with the ubiquitously distributed channel-forming subunit and thus cannot selectively target a particular tissue. Here, we performed structure-activity relationship study of lithocholic acid (LCA), a cholane that activates BK channels via the acc...

  20. The role of voltage-gated calcium channels in neurotransmitter phenotype specification: Coexpression and functional analysis in Xenopus laevis.

    Science.gov (United States)

    Lewis, Brittany B; Miller, Lauren E; Herbst, Wendy A; Saha, Margaret S

    2014-08-01

    Calcium activity has been implicated in many neurodevelopmental events, including the specification of neurotransmitter phenotypes. Higher levels of calcium activity lead to an increased number of inhibitory neural phenotypes, whereas lower levels of calcium activity lead to excitatory neural phenotypes. Voltage-gated calcium channels (VGCCs) allow for rapid calcium entry and are expressed during early neural stages, making them likely regulators of activity-dependent neurotransmitter phenotype specification. To test this hypothesis, multiplex fluorescent in situ hybridization was used to characterize the coexpression of eight VGCC α1 subunits with the excitatory and inhibitory neural markers xVGlut1 and xVIAAT in Xenopus laevis embryos. VGCC coexpression was higher with xVGlut1 than xVIAAT, especially in the hindbrain, spinal cord, and cranial nerves. Calcium activity was also analyzed on a single-cell level, and spike frequency was correlated with the expression of VGCC α1 subunits in cell culture. Cells expressing Cav 2.1 and Cav 2.2 displayed increased calcium spiking compared with cells not expressing this marker. The VGCC antagonist diltiazem and agonist (-)BayK 8644 were used to manipulate calcium activity. Diltiazem exposure increased the number of glutamatergic cells and decreased the number of γ-aminobutyric acid (GABA)ergic cells, whereas (-)BayK 8644 exposure decreased the number of glutamatergic cells without having an effect on the number of GABAergic cells. Given that the expression and functional manipulation of VGCCs are correlated with neurotransmitter phenotype in some, but not all, experiments, VGCCs likely act in combination with a variety of other signaling factors to determine neuronal phenotype specification. PMID:24477801

  1. Activation of Ca-dependent K channels by carbamoylcholine in rat lacrimal glands.

    OpenAIRE

    Trautmann, A; Marty, A.

    1984-01-01

    Electrical properties of the membranes of lacrimal gland cells were investigated using patch-clamp techniques [Hamill, O.P., Marty A., Neher, E., Sakmann, B. & Sigworth, F.J. (1981) Pflügers Arch. 391, 85-100]. The membranes were found to contain a specific kind of voltage- and Ca2+ -activated K+ channel ("BK channels"). These channels account for the strong rectification of the cell current-voltage curve as obtained in tight-seal whole-cell recordings. Application of low concentrations of ca...

  2. Frequency-dependence of the switching voltage in electronic switching of Pt-dispersed SiO2 thin films

    Science.gov (United States)

    Choi, Byung Joon; Chen, I.-Wei

    2016-06-01

    The switching time-voltage dependence of electronic resistive switching was studied for understanding the switching dynamics in Pt-dispersed SiO2 thin film devices. Trapezoidal voltage pulses with opposite polarities were consecutively introduced and thereby transient on-switching and offswitching were examined. A prior on-switching voltage determines the off-switching voltage regardless of the sweeping rate of the pulse for the prior on-switching. However, the off-switching voltage was sensitive to the sweeping rate of the subsequent pulses for off-switching. The frequencydependent impedance of both the device and the surrounding circuit element are thought to result in the variation of the off-switching voltage; otherwise, the switching voltage is independent of time.

  3. Modulation of Voltage-Gated Sodium Channels by Activation of Tumor Necrosis Factor Receptor-1 and Receptor-2 in Small DRG Neurons of Rats

    Directory of Open Access Journals (Sweden)

    M. Leo

    2015-01-01

    Full Text Available Tumor necrosis factor- (TNF- α is a proinflammatory cytokine involved in the development and maintenance of inflammatory and neuropathic pain. Its effects are mediated by two receptors, TNF receptor-1 (TNFR-1 and TNF receptor-2 (TNFR-2. These receptors play a crucial role in the sensitization of voltage-gated sodium channels (VGSCs, a key mechanism in the pathogenesis of chronic pain. Using the whole-cell patch-clamp technique, we examined the influence of TNFR-1 and TNFR-2 on VGSCs and TTX-resistant NaV1.8 channels in isolated rat dorsal root ganglion neurons by using selective TNFR agonists. The TNFR-1 agonist R32W (10 pg/mL caused an increase in the VGSC current (INa(V by 27.2 ± 5.1%, while the TNFR-2 agonist D145 (10 pg/mL increased the current by 44.9 ± 2.6%. This effect was dose dependent. Treating isolated NaV1.8 with R32W (100 pg/mL resulted in an increase in INaV(1.8 by 18.9 ± 1.6%, while treatment with D145 (100 pg/mL increased the current by 14.5 ± 3.7%. Based on the current-voltage relationship, 10 pg of R32W or D145 led to an increase in INa(V in a bell-shaped, voltage-dependent manner with a maximum effect at −30 mV. The effects of TNFR activation on VGSCs promote excitation in primary afferent neurons and this might explain the sensitization mechanisms associated with neuropathic and inflammatory pain.

  4. Dependence of Structure and Haemocompatibility of Amorphous Carbon Films on Substrate Bias Voltage

    Institute of Scientific and Technical Information of China (English)

    GUO Yang-Ming; MO Dang; LI Zhe-Yi; LIU Yi; HE Zhen-Hui; CHEN Di-Hu

    2004-01-01

    @@ Tetrahedral amorphous hydrogenated carbon (ta-C:H) films on Si(100) substrates were prepared by using a magnetic-field-filter plasma stream deposition system. Samples with different ratios of spa-bond to sp2-bond were obtained by changing the bias voltage applied to the substrates. The ellipsometric spectra of various carbon films in the photon energy range of 1.9-5.4eV were measured. The refractive index n and the relative sp3 C ratio of these films were obtained by simulating their ellipsometric spectra using the Forouhi-Bloomer model and by using the Bruggeman effective medium approximation, respectively. The haemocompatibility of these ta-C:H films was analysed by observation of platelet adhesion and measurement of kinetic clotting time. The results show that the sp3 C fraction is dependent on the substrate bias voltage, and the haemocompatibility is dependent on the ratio of sp3-bond to sp2-bond. A good haemocompatibility material of ta-C:H films with a suitable sp3 C fraction can be prepared by changing the substrate bias voltage.

  5. Solution structure of the N-terminal A domain of the human voltage-gated Ca2+channel beta4a subunit.

    Science.gov (United States)

    Vendel, Andrew C; Rithner, Christopher D; Lyons, Barbara A; Horne, William A

    2006-02-01

    Ca2+ channel beta subunits regulate trafficking and gating (opening and closing) of voltage-dependent Ca2+ channel alpha1 subunits. Based on primary sequence comparisons, they are thought to be modular structures composed of five domains (A-E) that are related to the large family of membrane associated guanylate-kinase (MAGUK) proteins. The crystal structures of the beta subunit core, B-D, domains have recently been reported; however, very little is known about the structures of the A and E domains. The N-terminal A domain is a hypervariable region that differs among the four subtypes of Ca2+ channel beta subunits (beta1-beta4). Furthermore, this domain undergoes alternative splicing to create multiple N-terminal structures within a given gene class that have distinct effects on gating. We have solved the solution structure of the A domain of the human beta4a subunit, a splice variant that we have shown previously to have alpha1 subunit subtype-specific effects on Ca2+ channel trafficking and gating. PMID:16385006

  6. A molecular switch between the outer and the inner vestibule of the voltage-gated Na+ channel

    International Nuclear Information System (INIS)

    Na+ channels permit rapid transmission of depolarizing impulses throughout cells and cell networks, and are essential to the proper function of skeletal muscle, the heart and the nervous system. The selectivity filter of the channel is considered to be formed by the amino acids D400, E755, K1237, and A1529 ('DEKA' motif) which are located at the innermost turn of the P-loops connecting S5 and S6 segments of each domain. The inner vestibule is believed to be lined by four S6 helices, one from each domain. Comparison of crystal structures of K+ channels in open and closed states as well as electron paramagnetic resonance spectroscopic studies suggest that the activation gate of voltage-gated ion channels is located at the inner part of the S6 segments. This may also hold true for voltage-gated Na+ channels because mutations in S6 segments alter activation gating. The gate for fast inactivation of the channel has been mapped to the intracellular linker between domains III and IV. This intracellular loop is currently considered to produce channel inactivation by transiently occluding the intracellular vestibule of the channel. The time constants of entry into and recovery from fast inactivation are on the order of milliseconds. Apart from 'fast inactivation' a number of slower inactivated states have been described. During very long depolarizations, on the order of several minutes, rNaV1.4 channels enter a very stable inactivated state which we refer to as 'ultra-slow' inactivation (IUS). In these channels the likelihood of entry into IUS is substantially increased by a mutation in the selectivity filter, K1237E. IUS can be modulated by molecules binding to the outer vestibule, suggesting that a conformational change of the outer vestibule gives rise to this kinetic state. On the other hand, the local anesthetic drug lidocaine, which binds to the internal part of the channel pore, inhibits entry into IUS by a 'foot-in-the-door' mechanism indicating that a

  7. Linearisation of λDNA molecules by instantaneous variation of the trapping electrode voltage inside a micro-channel

    International Nuclear Information System (INIS)

    Because long DNA molecules usually exist in random coil states due to the entropic effect, linearisation is required for devices equipped with nanopores where electrical sequencing is necessary during single-file translocation. We present a novel technique for linearising DNA molecules in a micro-channel. In our device, electrodes are embedded in the bottom surface of the channel. The application of a voltage induces the trapping of λDNA molecules on the positive electrode. An instantaneous voltage drop is used to put the λDNA molecules in a partly released state and the hydrodynamic force of the solution induces linearisation. Phenomena were directly observed using an optical microscopy system equipped with a high-speed camera and the linearisation principle was explored in detail. Furthermore, we estimate the tensile characteristics produced by the flow of the solution through a numerical model of a tethered polymer subject to a Poiseuille flow. The mean tensile force is in the range of 0.1–1 pN. This is sufficiently smaller than the structural transition point of λDNA but counterbalances the entropic elasticity that causes the random coil shape of λDNA molecules in solution. We show the important role of thermal fluctuation in the manipulation of molecules in solution and clarify the tensile conditions required for DNA linearisation using a combination of solution flow and voltage variation in a microchannel. (paper)

  8. Voltage dependence of the differential capacitance of a p+-n junction

    International Nuclear Information System (INIS)

    The dependences of the differential capacitance and current of a p+-n junction with a uniformly doped n region on the voltage in the junction region are calculated. The p+-n junction capacitance controls the charge change in the junction region taking into account a change in the electric field of the quasi-neutral n region and a change in its bipolar drift mobility with increasing excess charge-carrier concentration. It is shown that the change in the sign of the p+-n junction capacitance with increasing injection level is caused by a decrease in the bipolar drift mobility as the electron-hole pair concentration in the n region increases. It is shown that the p+-n junction capacitance decreases with increasing reverse voltage and tends to a constant positive value.

  9. Beyond ion-conduction: Channel-dependent and -independent roles of TRP channels during development and tissue homeostasis.

    Science.gov (United States)

    Vrenken, Kirsten S; Jalink, Kees; van Leeuwen, Frank N; Middelbeek, Jeroen

    2016-06-01

    Transient receptor potential (TRP) channels comprise a family of cation channels implicated in a variety of cellular processes, including proliferation, cell migration and cell survival. As a consequence, members of this ion family play prominent roles during embryonic development, tissue maintenance and cancer progression. Although most TRP channels are non-selective, many cellular responses, mediated by TRP channels, appear to be calcium-dependent. In addition, there is mounting evidence for channel-independent roles for TRP channels. In this review, we will discuss how both these channel-dependent and -independent mechanisms affect cellular programs essential during embryonic development, and how perturbations in these pathways contribute to a variety of pathologies. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen. PMID:26585368

  10. Forced-exercise delays neuropathic pain in experimental diabetes: effects on voltage-activated calcium channels.

    Science.gov (United States)

    Shankarappa, Sahadev A; Piedras-Rentería, Erika S; Stubbs, Evan B

    2011-07-01

    Physical exercise produces a variety of psychophysical effects, including altered pain perception. Elevated levels of centrally produced endorphins or endocannabinoids are implicated as mediators of exercise-induced analgesia. The effect of exercise on the development and persistence of disease-associated acute/chronic pain remains unclear. In this study, we quantified the physiological consequence of forced-exercise on the development of diabetes-associated neuropathic pain. Euglycemic control or streptozotocin (STZ)-induced diabetic adult male rats were subdivided into sedentary or forced-exercised (2-10 weeks, treadmill) subgroups and assessed for changes in tactile responsiveness. Two weeks following STZ-treatment, sedentary rats developed a marked and sustained hypersensitivity to von Frey tactile stimulation. By comparison, STZ-treated diabetic rats undergoing forced-exercise exhibited a 4-week delay in the onset of tactile hypersensitivity that was independent of glucose control. Exercise-facilitated analgesia in diabetic rats was reversed, in a dose-dependent manner, by naloxone. Small-diameter (exercise attenuated diabetes-associated changes in HVA Ca(2+) current density while preventing the depolarizing shift in steady-state inactivation of LVA Ca(2+) currents. Forced-exercise markedly delays the onset of diabetes-associated neuropathic pain, in part, by attenuating associated changes in HVA and LVA Ca(2+) channel function within small-diameter DRG neurons possibly by altering opioidergic tone. PMID:21554321

  11. Effect of ionizing radiation on voltage-sensitive sodium channels in the brain

    International Nuclear Information System (INIS)

    It has generally been assumed that the mature central nervous system is not sensitive to ionizing radiation because cell division of neurons no longer occurs. In general, rather large doses have been required in order to observe changes in morphological, physiological, biochemical, and behavioral endpoints. In order to focus on one of the most fundamental mechanisms in the generation and propagation of action potentials, experiments were undertaken to determine whether ionizing radiation could alter the ability of the neurotoxins, veratridine and batrachotoxin, to stimulate /sup 22/Na uptake into synaptosomes. Synaptosomal preparations were irradiated with varying doses of high-energy electrons or gamma photons. Both qualities of radiation reduced /sup 22/Na uptake stimulated by either toxin after doses as low as 100 rad in a concentration-dependent manner. When concentration-response curves for the neurotoxins were derived at increasing doses of radiation, the maximum effectiveness of the toxins was progressively diminished. The data suggest that the central nervous system may be more sensitive to the effects of ionizing radiation than previously believed and that the effects observed may reflect a loss of viable sodium channels. Such effects may have biological significance

  12. The mechanism of KV4.3 voltage-gated potassium channel in arrhythmia induced by sleep deprivation in rat

    Directory of Open Access Journals (Sweden)

    Ya-jing ZHANG

    2011-03-01

    Full Text Available Objective To investigate the effect of sleep deprivation(SD on the changes in electrocardiogram and mRNA and protein expression of KV4.3 voltage-gated potassium channel in rats,and explore the related mechanisms of arrhythmia induced by SD.Methods A total of 48 adult male SD rats were randomly divided into 6 groups(8 each: normal control(CC group,tank control(TC group,1-,3-,5-and 7-day SD group.Animal model of SD was established by modified multiple platform method,and electrocardiogram was recorded on 1st,3rd,5th,and 7th of experiment.Protein and mRNA expressions of KV4.3 voltage-gated potassium channel were measured by real-time PCR and Western blotting analysis.Results The main changes on electrocardiogram following SD were arrhythmia.Compared with the CC group,rats in TC group showed sinus tachycardia in electrocardiogram: frequent atrial premature beats were observed one day after SD;ventricular arrhythmias,such as frequent polymorphic ventricular premature beats and paroxysmal ventricular tachycardia were observed three days after SD;incomplete right bundle branch block wave occurred five days after SD;the electrocardiogram showed third-degree atrioventricular(AV block wave seven days after SD,which indicated atrial arrhythmia and ventricular arrhythmia respectively.Ventricular escape beat,sinus arrest as well as the fusion of obviously elevated ST segment and T-wave were also observed.The expression levels of KV4.3 voltage-gated potassium channel decreased with prolongation of SD time.The expression of mRNA and protein of KV4.3 potassium channel in 7-day SD rats were only the one ninth and one fourth of levels in CC group.Conclusion Sleep deprivation can cause arrhythmia,and decreased expression of KV4.3 voltage-gated potassium channel may possibly be one of the reasons of arrhythmia induced by SD.

  13. Voltage-Activated Calcium Channels as Functional Markers of Mature Neurons in Human Olfactory Neuroepithelial Cells: Implications for the Study of Neurodevelopment in Neuropsychiatric Disorders

    Science.gov (United States)

    Solís-Chagoyán, Héctor; Flores-Soto, Edgar; Reyes-García, Jorge; Valdés-Tovar, Marcela; Calixto, Eduardo; Montaño, Luis M.; Benítez-King, Gloria

    2016-01-01

    In adulthood, differentiation of precursor cells into neurons continues in several brain structures as well as in the olfactory neuroepithelium. Isolated precursors allow the study of the neurodevelopmental process in vitro. The aim of this work was to determine whether the expression of functional Voltage-Activated Ca2+ Channels (VACC) is dependent on the neurodevelopmental stage in neuronal cells obtained from the human olfactory epithelium of a single healthy donor. The presence of channel-forming proteins in Olfactory Sensory Neurons (OSN) was demonstrated by immunofluorescent labeling, and VACC functioning was assessed by microfluorometry and the patch-clamp technique. VACC were immunodetected only in OSN. Mature neurons responded to forskolin with a five-fold increase in Ca2+. By contrast, in precursor cells, a subtle response was observed. The involvement of VACC in the precursors’ response was discarded for the absence of transmembrane inward Ca2+ movement evoked by step depolarizations. Data suggest differential expression of VACC in neuronal cells depending on their developmental stage and also that the expression of these channels is acquired by OSN during maturation, to enable specialized functions such as ion movement triggered by membrane depolarization. The results support that VACC in OSN could be considered as a functional marker to study neurodevelopment. PMID:27314332

  14. Voltage-Activated Calcium Channels as Functional Markers of Mature Neurons in Human Olfactory Neuroepithelial Cells: Implications for the Study of Neurodevelopment in Neuropsychiatric Disorders

    Directory of Open Access Journals (Sweden)

    Héctor Solís-Chagoyán

    2016-06-01

    Full Text Available In adulthood, differentiation of precursor cells into neurons continues in several brain structures as well as in the olfactory neuroepithelium. Isolated precursors allow the study of the neurodevelopmental process in vitro. The aim of this work was to determine whether the expression of functional Voltage-Activated Ca2+ Channels (VACC is dependent on the neurodevelopmental stage in neuronal cells obtained from the human olfactory epithelium of a single healthy donor. The presence of channel-forming proteins in Olfactory Sensory Neurons (OSN was demonstrated by immunofluorescent labeling, and VACC functioning was assessed by microfluorometry and the patch-clamp technique. VACC were immunodetected only in OSN. Mature neurons responded to forskolin with a five-fold increase in Ca2+. By contrast, in precursor cells, a subtle response was observed. The involvement of VACC in the precursors’ response was discarded for the absence of transmembrane inward Ca2+ movement evoked by step depolarizations. Data suggest differential expression of VACC in neuronal cells depending on their developmental stage and also that the expression of these channels is acquired by OSN during maturation, to enable specialized functions such as ion movement triggered by membrane depolarization. The results support that VACC in OSN could be considered as a functional marker to study neurodevelopment.

  15. Energy dependences and product channels of ion-molecule-reactions

    International Nuclear Information System (INIS)

    For the investigation of ion-molecule-reactions a drift technique has been developed, making use of selected ion injection into a slow flow drift tube through an aspirator system similar to the one of Adams and Smith but operating under buffer flow rates as small as a few STP cm3 sec-1. Three groups of results have been obtained so far with this apparatus: 1) Proton and Deuteron transfer from Ar H+ and ArD+. The proton and deuteron transfer from ArH+ and ArD+ to H2 and D2 respectively proceeds fast, with rate coefficients close to the theoretical limits. No isotopic exchange is observed in these reactions. Besides these investigations performed in a helium buffer, equilibrium measurements in an argon buffer allows to obtain the equilibrium constant K for the reactions ArH+ + H2 H3+ + Ar in the range from O 2+(4πsub(u)) in the charge transfer of Ar+ with 02. At elevated kinetic energies KEsub(cm) >- 1 eV a considerable fraction of the charge transfer from Ar+ to 02 proceeds via the slightly endoergic channel into 02+(4πsub(u)). This was proved indirectly by reacting the so produced 02+ further with Ar to which 02+(4πsub(u)) does charge transfer with a fast rate2 while 02+(X) cannot. 3) The charge transfer from Ne+ to various neutrals and the respective branching ratios have been investigated from near thermal to a few eV, KEsub(cm). Especially the slow reactions (at room temperatures), such as Ne+ with CH4, CO2 and CO show strong dependences and also their product channels change dramatically with energy, indicating the opening of endoergic channels at higher KEsub(cm). (Author)

  16. Engineering of a genetically encodable fluorescent voltage sensor exploiting fast Ci-VSP voltage-sensing movements

    DEFF Research Database (Denmark)

    Lundby, Alicia; Mutoh, Hiroki; Dimitrov, Dimitar; Akemann, Walther; Knöpfel, Thomas

    2008-01-01

    Ci-VSP contains a voltage-sensing domain (VSD) homologous to that of voltage-gated potassium channels. Using charge displacement ('gating' current) measurements we show that voltage-sensing movements of this VSD can occur within 1 ms in mammalian membranes. Our analysis lead to development of a g...... genetically encodable fluorescent protein voltage sensor (VSFP) in which the fast, voltage-dependent conformational changes of the Ci-VSP voltage sensor are transduced to similarly fast fluorescence read-outs....

  17. Analysis of recoverable and permanent components of threshold voltage shift in NBT stressed p-channel power VDMOSFET

    Science.gov (United States)

    Danijel, Danković; Ninoslav, Stojadinović; Zoran, Prijić; Ivica, Manić; Vojkan, Davidović; Aneta, Prijić; Snežana, Djorić-Veljković; Snežana, Golubović

    2015-10-01

    In this study we investigate the dynamic recovery effects in IRF9520 commercial p-channel power vertical double diffused metal-oxide semiconductor field-effect transistors (VDMOSFETs) subjected to negative bias temperature (NBT) stressing under the particular pulsed bias. Particular values of the pulsed stress voltage frequency and duty cycle are chosen in order to analyze the recoverable and permanent components of stress-induced threshold voltage shift in detail. The results are discussed in terms of the mechanisms responsible for buildup of oxide charge and interface traps. The partial recovery during the low level of pulsed gate voltage is ascribed to the removal of recoverable component of degradation, i.e., to passivation/neutralization of shallow oxide traps that are not transformed into the deeper traps (permanent component). Considering the value of characteristic time constant associated with complete removal of the recoverable component of degradation, it is shown that by selecting an appropriate combination of the frequency and duty cycle, the threshold voltage shifts induced under the pulsed negative bias temperature stress conditions can be significantly reduced, which may be utilized for improving the device lifetime in real application circuits. Project supported by the Fund from the Ministry of Education, Science and Technological Development of the Republic of Serbia (Grant Nos. OI-171026 and TR-32026) and the Ei PCB Factory, Niš.

  18. Analysis of recoverable and permanent components of threshold voltage shift in NBT stressed p-channel power VDMOSFET

    Institute of Scientific and Technical Information of China (English)

    Danijel Dankovi´c; Ninoslav Stojadinovi´c; Zoran Priji´c; Ivica Mani´c; Vojkan Davidovi´c; Aneta Priji´c; Sneˇzana Djori´c-Veljkovi´c; Sneˇzana Golubovi´c

    2015-01-01

    In this study we investigate the dynamic recovery effects in IRF9520 commercial p-channel power vertical double diffused metal–oxide semiconductor field-effect transistors (VDMOSFETs) subjected to negative bias temperature (NBT) stressing under the particular pulsed bias. Particular values of the pulsed stress voltage frequency and duty cycle are chosen in order to analyze the recoverable and permanent components of stress-induced threshold voltage shift in detail. The results are discussed in terms of the mechanisms responsible for buildup of oxide charge and interface traps. The partial recovery during the low level of pulsed gate voltage is ascribed to the removal of recoverable component of degradation, i.e., to passivation/neutralization of shallow oxide traps that are not transformed into the deeper traps (permanent component). Considering the value of characteristic time constant associated with complete removal of the recoverable component of degradation, it is shown that by selecting an appropriate combination of the frequency and duty cycle, the threshold voltage shifts induced under the pulsed negative bias temperature stress conditions can be significantly reduced, which may be utilized for improving the device lifetime in real application circuits.

  19. Effects of (−-Gallocatechin-3-Gallate on Tetrodotoxin-Resistant Voltage-Gated Sodium Channels in Rat Dorsal Root Ganglion Neurons

    Directory of Open Access Journals (Sweden)

    Jian-Min Jiang

    2013-05-01

    Full Text Available The (−-gallocatechin-3-gallate (GCG concentration in some tea beverages can account for as much as 50% of the total catechins. It has been shown that catechins have analgesic properties. Voltage-gated sodium channels (Nav mediate neuronal action potentials. Tetrodotoxin inhibits all Nav isoforms, but Nav1.8 and Nav1.9 are relatively tetrodotoxin-resistant compared to other isoforms and functionally linked to nociception. In this study, the effects of GCG on tetrodotoxin-resistant Na+ currents were investigated in rat primary cultures of dorsal root ganglion neurons via the whole-cell patch-clamp technique. We found that 1 μM GCG reduced the amplitudes of peak current density of tetrodotoxin-resistant Na+ currents significantly. Furthermore, the inhibition was accompanied by a depolarizing shift of the activation voltage and a hyperpolarizing shift of steady-state inactivation voltage. The percentage block of GCG (1 μM on tetrodotoxin-resistant Na+ current was 45.1% ± 1.1% in 10 min. In addition, GCG did not produce frequency-dependent block of tetrodotoxin-resistant Na+ currents at stimulation frequencies of 1 Hz, 2 Hz and 5 Hz. On the basis of these findings, we propose that GCG may be a potential analgesic agent.

  20. Lung adenocarcinoma with Lambert–Eaton myasthenic syndrome indicated by voltage-gated calcium channel: a case report

    Directory of Open Access Journals (Sweden)

    Arai Hiromasa

    2012-09-01

    Full Text Available Abstract Introduction Lambert–Eaton myasthenic syndrome is a rare disorder and it is known as a paraneoplastic neurological syndrome. Small cell lung cancer often accompanies this syndrome. Lambert–Eaton myasthenic syndrome associated with lung adenocarcinoma is extremely rare; there are only a few reported cases worldwide. Case presentation A 75-year-old Japanese man with a past history of chronic rheumatoid arthritis and Sjögren syndrome was diagnosed with Lambert–Eaton myasthenic syndrome by electromyography and serum anti-P/Q-type voltage-gated calcium channel antibody level preceding the diagnosis of lung cancer. A chest computed tomography to screen for malignant lesions revealed an abnormal shadow in the lung. Although a histopathological examination by bronchoscopic study could not reveal the malignancy, lung cancer was mostly suspected after the results of a chest computed tomography and [18F]-fluorodeoxyglucose positron emission tomography. An intraoperative diagnosis based on the frozen section obtained by tumor biopsy was adenocarcinoma so the patient underwent a lobectomy of the right lower lobe and lymph node dissection with video-assisted thoracoscopic surgery. The permanent pathological examination was the same as the frozen diagnosis (pT2aN1M0: Stage IIa: TNM staging 7th edition. Immunohistochemistry revealed that most of the cancer cells were positive for P/Q-type voltage-gated calcium channel. Conclusions Our case is a rare combination of Lambert–Eaton myasthenic syndrome associated with lung adenocarcinoma, rheumatoid arthritis and Sjögren syndrome, and to the best of our knowledge it is the first report that indicates the presence of voltage-gated calcium channel in lung adenocarcinoma by immunostaining.

  1. Modulation of major voltage- and ligand-gated ion channels in cultured neurons of the rat inferior colliculus by lidocaine

    Institute of Scientific and Technical Information of China (English)

    Mu YU; Lin CHEN

    2008-01-01

    Aim: The purpose of the present study was to explore how lidocaine as a thera-peutic drug for tinnitus targets voltage- and ligand-gated ion channels and changes the excitability of central auditory neurons. Methods: Membrane cur-rents mediated by major voltage- and ligand-gated channels were recorded from primary cultured neurons of the inferior colliculus (IC) in rats with whole-cell patch-clamp techniques in the presence and absence of lidocaine. The effects of lidocaine on the current-evoked firing of action potentials were also exam-ined. Results: Lidocaine at 100 μmol/L significantly suppressed voltage-gated sodium currents, transient outward potassium currents, and the glycine-induced chloride currents to 87.66%±2.12%, 96.33%±0.35%, and 91.46%±2.69% of that of the control level, respectively. At 1 mmol/L, lidocaine further suppressed the 3 currents to 70.26%±4.69%, 62.80% ±2.61%, and 89.11%±3.17% of that of the control level, respectively, However, lidocaine at concentrations lower than 1 mmol/L did not significantly affect GABA- or aspartate-induced currents. At a higher concentration (3 retool/L), lidocaine slightly depressed the GABA-in-duced current to 87.70%±1.87% of that of the control level. Finally, lidocaine at 100 μmol/L was shown to significantly suppress the current-evoked firing of IC neurons to 58.62%±11.22% of that of the control level, indicating that lidocaine decreases neuronal excitability. Conclusion: Although the action of lidocaine on the ion channels and receptors is complex and non-specific, it has an overall inhibitory effect on IC neurons at a clinically-relevant concentration, suggesting a central mechanism for lidocaine to suppress tinnitus.

  2. Thickness dependence of voltage-driven magnetization switching in FeCo/PI/piezoelectric actuator heterostructures

    International Nuclear Information System (INIS)

    Strain mediated magnetization switching of ferromagnetic/substrate/piezoelectric actuator heterostructures has become a hot issue due to the advantage of low-power consumption. In this work, Fe65Co35 thin films were deposited on a flexible polyamides (PI) substrate, which has quite low Young’s module (∼4 GPa for PI as compared to ∼180 GPa for Si) and benefits from complete transfer of the strain from the piezoelectric actuator to magnetic thin films. A complete 90° transition of the magnetic easy axis was realized in 50 nm thick FeCo films under the voltage of 70 V, while a less than 90° rotation angle of the magnetic easy axis direction was observed in other samples, which was ascribed to the distribution of the anisotropy field and/or the orthogonal misalignment between stress induced anisotropy and original uniaxial anisotropy. A model considering two uniaxial anisotropies with orthogonal arrangement was used to quantitatively understand the observed results and the linear-like voltage dependent anisotropy field, especially for 10 nm FeCo films, in which the switching mechanism along the easy axis direction can be explained by the domain wall depinning model. It indicates that the magnetic domain-wall movement velocity may be controlled by strain through tuning the energy barrier of the pinning in heterostructures. Moreover, voltage-driven 90° magnetization switching with low-power consumption was achieved in this work. (paper)

  3. Thickness dependence of voltage-driven magnetization switching in FeCo/PI/piezoelectric actuator heterostructures

    Science.gov (United States)

    Cui, B. S.; Guo, X. B.; Wu, K.; Li, D.; Zuo, Y. L.; Xi, L.

    2016-03-01

    Strain mediated magnetization switching of ferromagnetic/substrate/piezoelectric actuator heterostructures has become a hot issue due to the advantage of low-power consumption. In this work, Fe65Co35 thin films were deposited on a flexible polyamides (PI) substrate, which has quite low Young’s module (~4 GPa for PI as compared to ~180 GPa for Si) and benefits from complete transfer of the strain from the piezoelectric actuator to magnetic thin films. A complete 90° transition of the magnetic easy axis was realized in 50 nm thick FeCo films under the voltage of 70 V, while a less than 90° rotation angle of the magnetic easy axis direction was observed in other samples, which was ascribed to the distribution of the anisotropy field and/or the orthogonal misalignment between stress induced anisotropy and original uniaxial anisotropy. A model considering two uniaxial anisotropies with orthogonal arrangement was used to quantitatively understand the observed results and the linear-like voltage dependent anisotropy field, especially for 10 nm FeCo films, in which the switching mechanism along the easy axis direction can be explained by the domain wall depinning model. It indicates that the magnetic domain-wall movement velocity may be controlled by strain through tuning the energy barrier of the pinning in heterostructures. Moreover, voltage-driven 90° magnetization switching with low-power consumption was achieved in this work.

  4. Stress-Dependent Voltage Offsets From Polymer Insulators Used in Rock Mechanics and Material Testing

    Science.gov (United States)

    Carlson, G. G.; Dahlgren, Robert; Gray, Amber; Vanderbilt, V. C.; Freund, F.; Johnston, M. J.; Dunson, C.

    2013-01-01

    Dielectric insulators are used in a variety of laboratory settings when performing experiments in rock mechanics, petrology, and electromagnetic studies of rocks in the fields of geophysics,material science, and civil engineering. These components may be used to electrically isolate geological samples from the experimental equipment, to perform a mechanical compliance function between brittle samples and the loading equipment, to match ultrasonic transducers, or perform other functions. In manyexperimental configurations the insulators bear the full brunt of force applied to the sample but do not need to withstand high voltages, therefore the insulators are often thin sheets of mechanically tough polymers. From an instrument perspective, transduction from various types of mechanical perturbation has beenqualitatively compared for a number of polymers [1, 2] and these error sources are readily apparent duringhigh-impedance measurements if not mitigated. However even when following best practices, a force dependent voltage signal still remains and its behavior is explored in this presentation. In this experimenttwo thin sheets (0.25 mm) of high-density polyethylene (HDPE) were set up in a stack, held alternatelybetween three aluminum bars; this stack was placed on the platen of a 60T capacity hydraulic testingmachine. The surface area, A, over which the force is applied to the PE sheets in this sandwich is roughly 40 square cm, each sheet forming a parallel-plate capacitor having roughly 320 pF [3], assuming therelative dielectric permittivity of PE is approximately 2.3. The outer two aluminum bars were connected to the LO input ofthe electrometer and the central aluminum bar was connected to the HI input of a Keithley model 617 electrometer. Once the stack is mechanically well-seated with no air gaps, the voltage offset is observed tobe a linear function of the baseline voltage for a given change in applied force. For a periodically appliedforce of 66.7 kN the

  5. Reversible dementia: two nursing home patients with voltage-gated potassium channel antibody-associated limbic encephalitis.

    Science.gov (United States)

    Reintjes, Wesley; Romijn, Marloes D M; Hollander, Daan; Ter Bruggen, Jan P; van Marum, Rob J

    2015-09-01

    Voltage-gated potassium channel antibody-associated limbic encephalitis (VGKC-LE) is a rare disease that is a diagnostic and therapeutic challenge for medical practitioners. Two patients with VGKC-LE, both developing dementia are presented. Following treatment, both patients showed remarkable cognitive and functional improvement enabling them to leave the psychogeriatric nursing homes they both were admitted to. Patients with VGKC-LE can have a major cognitive and functional improvement even after a diagnostic delay of more than 1 year. Medical practitioners who treat patients with unexplained cognitive decline, epileptic seizures, or psychiatric symptoms should be aware of LE as an underlying rare cause. PMID:26170033

  6. Design and implementation of channel estimation for low-voltage power line communication systems based on OFDM

    Institute of Scientific and Technical Information of China (English)

    Zhao Huidong; Hei Yong; Qiao Shushan; Ye Tianchun

    2012-01-01

    An optimized channel estimation algorithm based on a time-spread structure in OFDM low-voltage power line communication (PLC) systems is proposed to achieve a lower bit error rate (BER).This paper optimizes the best maximum multi-path delay of the linear minimum mean square error (LMMSE) algorithm in time-domain spread OFDM systems.Simulation results indicate that the BER of the improved method is lower than that of conventional LMMSE algorithm,especially when the signal-to-noise ratio (SNR) is lower than 0 dB.Both the LMMSE algorithm and the proposed algorithm are implemented and fabricated in CSMC 0.18 μm technology.This paper analyzes and compares the hardware complexity and performance of the two algorithms.Measurements indicate that the proposed channel estimator has better performance than the conventional estimator.

  7. Blockade by sigma site ligands of high voltage-activated Ca2+ channels in rat and mouse cultured hippocampal pyramidal neurones.

    OpenAIRE

    Church, J; Fletcher, E. J.

    1995-01-01

    1. The effects of a series of structurally-dissimilar sigma site ligands were examined on high voltage-activated Ca2+ channel activity in two preparations of cultured hippocampal pyramidal neurones. 2. In mouse hippocampal neurones under whole-cell voltage-clamp, voltage-activated Ca2+ channel currents carried by barium ions (IBa) were reduced with the rank order (IC50 values in microM): 1S,2R-(-)-cis-N-methyl-N-[2-(3,4-dichlorophenyl)ethyl]- 2-(1-pyrrolidinyl)cyclohexylamine (7.8) > rimcazol...

  8. Inhibitory effect of resveratrol on the proliferation of GH3 pituitary-adenoma cells and voltage-dependent potassium current

    Institute of Scientific and Technical Information of China (English)

    Ming Chu; Lanlan Wei; Chao Wang; Yu Cheng; Kongbin Yang; Baofeng Yang

    2006-01-01

    BACKGROUND:Recent researches indicate that activation of potassium channel is likely to cause many kinds of cells to proliferate and differentiate;using chemical to block the potassium channel can restrain the proliferation of small lung-cancer cells.breast cancer.prostate cancer and human lymphocyte,etc.Previous researches proved that resveratrol(RE),a selective estrogen receptor modulator(SERM).could inhibit growth of GH3 calls,induce apoptosis,and resist tumor through interfering K+ channel.OBJECTIVE:To investigate the effects of RE on Voltage-dependent K+ current [Ik(v)] and cell proliferation in GH3 pituitary-tumor cells.DESIGN:Observational contrast study.SETTING:Department of Neurosurgery.the First Clinical Hospital of Harbin Medical University;Department of Microbiology,Harbin Medical University;Department of Pharmacology,Harbin Medical University.MATERIALS: GH3 pituitary-tumor cell line of rats was purchased from the American Type Culture Collection (ATCC).RE and[3-(4,5-dimethylthiazo1-2-y1)-2.5-diphenyl-tetrazolium bromide](MTT)were obtained from Sigma Chemical CO,St Louis,USA;Ham's F-10 medium from Gibco BRL;Equine serum and fetal bovine serum from Hyclone Laboratories,Logan,UT;FACSCalibur flow cytometer from BD Company,USA.RE was dissolved in ethanol and stored at-20 ℃.It was diluted to different concentrations (10.50,100 μmol/L)with medium and extra cellular solution when needed.rhe final concentration of ethanol was Jess than 0.01%.METHODS:The experiment was carried out in the Department of Microbiology and Pharmacology of Harbin Medical University from March 2005 to January 2006.①Cell preparation:Proliferating indexes affected by 10.50 and 100 μmol/L RE were measured with MTT,respectively.0.0001 volume fraction of ethan ol was added into control group.Inhibitory rate of cellular growth was calculated as the following formula:Inhibitory rate (%)=(1-A value in experimental group/A value in control group)x100%.The experiments mentioned above were

  9. Regionally specific expression of high-voltage-activated calcium channels in thalamic nuclei of epileptic and non-epileptic rats.

    Science.gov (United States)

    Kanyshkova, Tatyana; Ehling, Petra; Cerina, Manuela; Meuth, Patrick; Zobeiri, Mehrnoush; Meuth, Sven G; Pape, Hans-Christian; Budde, Thomas

    2014-07-01

    The polygenic origin of generalized absence epilepsy results in dysfunction of ion channels that allows the switch from physiological asynchronous to pathophysiological highly synchronous network activity. Evidence from rat and mouse models of absence epilepsy indicates that altered Ca(2+) channel activity contributes to cellular and network alterations that lead to seizure activity. Under physiological circumstances, high voltage-activated (HVA) Ca(2+) channels are important in determining the thalamic firing profile. Here, we investigated a possible contribution of HVA channels to the epileptic phenotype using a rodent genetic model of absence epilepsy. In this study, HVA Ca(2+) currents were recorded from neurons of three different thalamic nuclei that are involved in both sensory signal transmission and rhythmic-synchronized activity during epileptic spike-and-wave discharges (SWD), namely the dorsal part of the lateral geniculate nucleus (dLGN), the ventrobasal thalamic complex (VB) and the reticular thalamic nucleus (NRT) of epileptic Wistar Albino Glaxo rats from Rijswijk (WAG/Rij) and non-epileptic August Copenhagen Irish (ACI) rats. HVA Ca(2+) current densities in dLGN neurons were significantly increased in epileptic rats compared with non-epileptic controls while other thalamic regions revealed no differences between the strains. Application of specific channel blockers revealed that the increased current was carried by L-type Ca(2+) channels. Electrophysiological evidence of increased L-type current correlated with up-regulated mRNA and protein expression of a particular L-type channel, namely Cav1.3, in dLGN of epileptic rats. No significant changes were found for other HVA Ca(2+) channels. Moreover, pharmacological inactivation of L-type Ca(2+) channels results in altered firing profiles of thalamocortical relay (TC) neurons from non-epileptic rather than from epileptic rats. While HVA Ca(2+) channels influence tonic and burst firing in ACI and WAG

  10. Molecular determinant for the tarantula toxin Jingzhaotoxin-I slowing the fast inactivation of voltage-gated sodium channels.

    Science.gov (United States)

    Tao, Huai; Chen, Xia; Lu, Min; Wu, Yuanyuan; Deng, Meichun; Zeng, Xiongzhi; Liu, Zhonghua; Liang, Songping

    2016-03-01

    Peptide toxins often have divergent pharmacological functions and are powerful tools for a deep review on the current understanding of the structure-function relationships of voltage-gated sodium channels (VGSCs). However, knowing about the interaction of site 3 toxins from tarantula venoms with VGSCs is not sufficient. In the present study, using whole-cell patch clamp technique, we determined the effects of Jingzhaotoxin-I (JZTX-I) on five VGSC subtypes expressed in HEK293 cells. The results showed that JZTX-I could inhibit the inactivation of rNav1.2, rNav1.3, rNav1.4, hNav1.5 and hNav1.7 channels with the IC50 of 870 ± 8 nM, 845 ± 4 nM, 339 ± 5 nM, 335 ± 9 nM, and 348 ± 6 nM, respectively. The affinity of the toxin interaction with subtypes (rNav1.4, hNav1.5, and hNav1.7) was only 2-fold higher than that for subtypes (rNav1.2 and rNav1.3). The toxin delayed the inactivation of VGSCs without affecting the activation and steady-state inactivation kinetics in the physiological range of voltages. Site-directed mutagenesis indicated that the toxin interacted with site 3 located at the extracellular S3-S4 linker of domain IV, and the acidic residue Asp at the position1609 in hNav1.5 was crucial for JZTX-I activity. Our results provide new insights in single key residue that allows toxins to recognize distinct ion channels with similar potency and enhance our understanding of the structure-function relationships of toxin-channel interactions. PMID:26721415

  11. GABA(A) Increases Calcium in Subventricular Zone Astrocyte-Like Cells Through L- and T-Type Voltage-Gated Calcium Channels

    DEFF Research Database (Denmark)

    Young, Stephanie Z; Platel, Jean-Claude; Nielsen, Jakob V;

    2010-01-01

    induced Ca(2+) increases in 40-50% of SVZ astrocytes. GABA(A)-induced Ca(2+) increases were prevented with nifedipine and mibefradil, blockers of L- and T-type voltage-gated calcium channels (VGCC). The L-type Ca(2+) channel activator BayK 8644 increased the percentage of GABA(A)-responding astrocyte...

  12. Sodium Channels: Ionic Model of Slow Inactivation and State-Dependent Drug Binding

    OpenAIRE

    Tikhonov, Denis B.; Zhorov, Boris S.

    2007-01-01

    Inactivation is a fundamental property of voltage-gated ion channels. Fast inactivation of Na+ channels involves channel block by the III–IV cytoplasmic interdomain linker. The mechanisms of nonfast types of inactivation (intermediate, slow, and ultraslow) are unclear, although the ionic environment and P-loops rearrangement appear to be involved. In this study, we employed a TTX-based P-loop domain model of a sodium channel and the MCM method to investigate a possible role of P-loop rearrang...

  13. Activation of CRH receptor type 1 expressed on glutamatergic neurons increases excitability of CA1 pyramidal neurons by the modulation of voltage-gated ion channels

    Directory of Open Access Journals (Sweden)

    Stephan eKratzer

    2013-07-01

    Full Text Available Corticotropin-releasing hormone (CRH plays an important role in a substantial number of patients with stress-related mental disorders, such as anxiety disorders and depression. CRH has been shown to increase neuronal excitability in the hippocampus, but the underlying mechanisms are poorly understood. The effects of CRH on neuronal excitability were investigated in acute hippocampal brain slices. Population spikes (PS and field excitatory postsynaptic potentials (fEPSP were evoked by stimulating Schaffer-collaterals and recorded simultaneously from the somatic and dendritic region of CA1 pyramidal neurons. CRH was found to increase PS amplitudes (mean  Standard error of the mean; 231.8  31.2% of control; n=10 while neither affecting fEPSPs (104.3 ± 4.2%; n=10 nor long-term potentiation (LTP. However, when Schaffer-collaterals were excited via action potentials (APs generated by stimulation of CA3 pyramidal neurons, CRH increased fEPSP amplitudes (119.8 ± 3.6%; n=8 and the magnitude of LTP in the CA1 region. Experiments in slices from transgenic mice revealed that the effect on PS amplitude is mediated exclusively by CRH receptor 1 (CRHR1 expressed on glutamatergic neurons. The effects of CRH on PS were dependent on phosphatase-2B, L- and T-type calcium channels and voltage-gated potassium channels but independent on intracellular Ca2+-elevation. In patch-clamp experiments, CRH increased the frequency and decay times of APs and decreased currents through A-type and delayed-rectifier potassium channels. These results suggest that CRH does not affect synaptic transmission per se, but modulates voltage-gated ion currents important for the generation of APs and hence elevates by this route overall neuronal activity.

  14. Voltage dependence of Landau-Lifshitz-Gilbert damping of a spin in a current driven tunnel junction

    OpenAIRE

    Katsura, Hosho; Balatsky, Alexander V.; Nussinov, Zohar; Nagaosa, Naoto

    2006-01-01

    We present a theory of Landau-Lifshitz-Gilbert damping $\\alpha$ for a localized spin ${\\vec S}$ in the junction coupled to the conduction electrons in both leads under an applied volatege $V$. We find the voltage dependence of the damping term reflecting the energy dependence of the density of states. We find the effect is linear in the voltage and cotrolled by particle-hole asymmetry of the leads.

  15. Apo-states of calmodulin and CaBP1 control CaV1 voltage-gated calcium channel function through direct competition for the IQ domain

    Science.gov (United States)

    Findeisen, Felix; Rumpf, Christine; Minor, Daniel L.

    2013-01-01

    In neurons, binding of calmodulin (CaM) or calcium-binding protein 1 (CaBP1) to the CaV1 (L-type) voltage-gated calcium channel IQ domain endows the channel with diametrically opposed properties. CaM causes calcium-dependent inactivation (CDI) and limits calcium entry, whereas CaBP1 blocks CDI and allows sustained calcium influx. Here, we combine isothermal titration calorimetry (ITC) with cell-based functional measurements and mathematical modeling to show that these calcium sensors behave in a competitive manner that is explained quantitatively by their apo-state binding affinities for the IQ domain. This competition can be completely blocked by covalent tethering of CaM to the channel. Further, we show that Ca2+/CaM has a sub-picomolar affinity for the IQ domain that is achieved without drastic alteration of calcium binding properties. The observation that the apo-forms of CaM and CaBP1 compete with each other demonstrates a simple mechanism for direct modulation of CaV1 function and suggests a means by which excitable cells may dynamically tune CaV activity. PMID:23811053

  16. Regulation of Voltage-Gated Ca2+ Currents by Ca2+/Calmodulin-dependent Protein Kinase II in Resting Sensory Neurons

    OpenAIRE

    Kostic, Sandra; Pan, Bin; Guo, Yuan; Yu, Hongwei; Sapunar, Damir; Kwok, Wai-Meng; Hudmon, Andy; Wu, Hsiang-en; Hogan, Quinn H

    2014-01-01

    Calcium/calmodulin-dependent protein kinase II (CaMKII) is recognized as a key element in encoding depolarization activity of excitable cells into facilitated voltage-gated Ca2+ channel (VGCC) function. Less is known about the participation of CaMKII in regulating VGCCs in resting cells. We examined constitutive CaMKII control of Ca2+ currents in peripheral sensory neurons acutely isolated from dorsal root ganglia (DRGs) of adult rats. The small molecule CaMKII inhibitor KN-93 (1.0μM) reduced...

  17. Excessive blinking and ataxia in a child with occult neuroblastoma and voltage-gated potassium channel antibodies.

    LENUS (Irish Health Repository)

    Allen, Nicholas M

    2012-05-01

    A previously healthy 9-year-old girl presented with a 10-day history of slowly progressive unsteadiness, slurred speech, and behavior change. On examination there was cerebellar ataxia and dysarthria, excessive blinking, subtle perioral myoclonus, and labile mood. The finding of oligoclonal bands in the cerebrospinal fluid prompted paraneoplastic serological evaluation and search for an occult neural crest tumor. Antineuronal nuclear autoantibody type 1 (anti-Hu) and voltage-gated potassium channel complex antibodies were detected in serum. Metaiodobenzylguanidine scan and computed tomography scan of the abdomen showed a localized abdominal mass in the region of the porta hepatis. A diagnosis of occult neuroblastoma was made. Resection of the stage 1 neuroblastoma and treatment with pulsed corticosteroids resulted in resolution of all symptoms and signs. Excessive blinking has rarely been described with neuroblastoma, and, when it is not an isolated finding, it may be a useful clue to this paraneoplastic syndrome. Although voltage-gated potassium channel complex autoimmunity has not been described previously in the setting of neuroblastoma, it is associated with a spectrum of paraneoplastic neurologic manifestations in adults, including peripheral nerve hyperexcitability disorders.

  18. Development of three channel linear bipolar high voltage amplifier (±2 KV) for electrostatic steerer

    International Nuclear Information System (INIS)

    Electrostatic steerers and scanners are planned for low energy ion beam facilities at IUAC to steer and scan the ion beam on target. The power supplies for electrostatic steerers are high voltage bipolar DC amplifiers and for scanners are bipolar AC amplifiers. To fulfil the requirements a common unit has been designed and assembled for AC and DC applications. It can be used with electrostatic devices in scanning, steering and sweeping of low energy ion beams at high frequencies to attain uniform implantation. The unit consist of three independent limited bandwidth high voltage, linear bipolar amplifiers (for X-axis, Y-axis and Y1-dog leg plates). The unit has been provided with both local and remote control. (author)

  19. Hyperactivation of L-type voltage-gated Ca2+ channels in Caenorhabditis elegans striated muscle can result from point mutations in the IS6 or the IIIS4 segment of the α1 subunit.

    Science.gov (United States)

    Lainé, Viviane; Ségor, Jean Rony; Zhan, Hong; Bessereau, Jean-Louis; Jospin, Maelle

    2014-11-01

    Several human diseases, including hypokalemic periodic paralysis and Timothy syndrome, are caused by mutations in voltage-gated calcium channels. The effects of these mutations are not always well understood, partially because of difficulties in expressing these channels in heterologous systems. The use of Caenorhabditis elegans could be an alternative approach to determine the effects of mutations on voltage-gated calcium channel function because all the main types of voltage-gated calcium channels are found in C. elegans, a large panel of mutations already exists and efficient genetic tools are available to engineer customized mutations in any gene. In this study, we characterize the effects of two gain-of-function mutations in egl-19, which encodes the L-type calcium channel α1 subunit. One of these mutations, ad695, leads to the replacement of a hydrophobic residue in the IIIS4 segment. The other mutation, n2368, changes a conserved glycine of IS6 segment; this mutation has been identified in patients with Timothy syndrome. We show that both egl-19 (gain-of-function) mutants have defects in locomotion and morphology that are linked to higher muscle tone. Using in situ electrophysiological approaches in striated muscle cells, we provide evidence that this high muscle tone is due to a shift of the voltage dependency towards negative potentials, associated with a decrease of the inactivation rate of the L-type Ca(2+) current. Moreover, we show that the maximal conductance of the Ca(2+) current is decreased in the strongest mutant egl-19(n2368), and that this decrease is correlated with a mislocalization of the channel. PMID:25214488

  20. The Kunitz-Type Protein ShPI-1 Inhibits Serine Proteases and Voltage-Gated Potassium Channels.

    Science.gov (United States)

    García-Fernández, Rossana; Peigneur, Steve; Pons, Tirso; Alvarez, Carlos; González, Lidice; Chávez, María A; Tytgat, Jan

    2016-01-01

    The bovine pancreatic trypsin inhibitor (BPTI)-Kunitz-type protein ShPI-1 (UniProt: P31713) is the major protease inhibitor from the sea anemone Stichodactyla helianthus. This molecule is used in biotechnology and has biomedical potential related to its anti-parasitic effect. A pseudo wild-type variant, rShPI-1A, with additional residues at the N- and C-terminal, has a similar three-dimensional structure and comparable trypsin inhibition strength. Further insights into the structure-function relationship of rShPI-1A are required in order to obtain a better understanding of the mechanism of action of this sea anemone peptide. Using enzyme kinetics, we now investigated its activity against other serine proteases. Considering previous reports of bifunctional Kunitz-type proteins from anemones, we also studied the effect of rShPI-1A on voltage-gated potassium (Kv) channels. rShPI-1A binds Kv1.1, Kv1.2, and Kv1.6 channels with IC50 values in the nM range. Hence, ShPI-1 is the first member of the sea anemone type 2 potassium channel toxins family with tight-binding potency against several proteases and different Kv1 channels. In depth sequence analysis and structural comparison of ShPI-1 with similar protease inhibitors and Kv channel toxins showed apparent non-sequence conservation for known key residues. However, we detected two subtle patterns of coordinated amino acid substitutions flanking the conserved cysteine residues at the N- and C-terminal ends. PMID:27089366

  1. Matrix Metalloproteinase (MMP) Proteolysis of the Extracellular Loop of Voltage-gated Sodium Channels and Potential Alterations in Pain Signaling.

    Science.gov (United States)

    Remacle, Albert G; Kumar, Sonu; Motamedchaboki, Khatereh; Cieplak, Piotr; Hullugundi, Swathi; Dolkas, Jennifer; Shubayev, Veronica I; Strongin, Alex Y

    2015-09-18

    Congenital insensitivity to pain (CIP) or congenital analgesia is a rare monogenic hereditary condition. This disorder is characterized by the inability to perceive any form of pain. Nonsense mutations in Nav.1.7, the main pain signaling voltage-gated sodium channel, lead to its truncations and, consequently, to the inactivation of the channel functionality. However, a non-truncating homozygously inherited missense mutation in a Bedouin family with CIP (Nav1.7-R907Q) has also been reported. Based on our currently acquired in-depth knowledge of matrix metalloproteinase (MMP) cleavage preferences, we developed the specialized software that predicts the presence of the MMP cleavage sites in the peptide sequences. According to our in silico predictions, the peptide sequence of the exposed extracellular unstructured region linking the S5-S6 transmembrane segments in the DII domain of the human Nav1.7 sodium channel is highly sensitive to MMP-9 proteolysis. Intriguingly, the CIP R907Q mutation overlaps with the predicted MMP-9 cleavage site sequence. Using MMP-9 proteolysis of the wild-type, CIP, and control peptides followed by mass spectrometry of the digests, we demonstrated that the mutant sequence is severalfold more sensitive to MMP-9 proteolysis relative to the wild type. Because of the substantial level of sequence homology among sodium channels, our data also implicate MMP proteolysis in regulating the cell surface levels of the Nav1.7, Nav1.6, and Nav1.8 channels, but not Nav1.9. It is likely that the aberrantly accelerated MMP-9 proteolysis during neurogenesis is a biochemical rational for the functional inactivation in Nav1.7 and that the enhanced cleavage of the Nav1.7-R907Q mutant is a cause of CIP in the Bedouin family. PMID:26283785

  2. The Kunitz-Type Protein ShPI-1 Inhibits Serine Proteases and Voltage-Gated Potassium Channels

    Science.gov (United States)

    García-Fernández, Rossana; Peigneur, Steve; Pons, Tirso; Alvarez, Carlos; González, Lidice; Chávez, María A.; Tytgat, Jan

    2016-01-01

    The bovine pancreatic trypsin inhibitor (BPTI)-Kunitz-type protein ShPI-1 (UniProt: P31713) is the major protease inhibitor from the sea anemone Stichodactyla helianthus. This molecule is used in biotechnology and has biomedical potential related to its anti-parasitic effect. A pseudo wild-type variant, rShPI-1A, with additional residues at the N- and C-terminal, has a similar three-dimensional structure and comparable trypsin inhibition strength. Further insights into the structure-function relationship of rShPI-1A are required in order to obtain a better understanding of the mechanism of action of this sea anemone peptide. Using enzyme kinetics, we now investigated its activity against other serine proteases. Considering previous reports of bifunctional Kunitz-type proteins from anemones, we also studied the effect of rShPI-1A on voltage-gated potassium (Kv) channels. rShPI-1A binds Kv1.1, Kv1.2, and Kv1.6 channels with IC50 values in the nM range. Hence, ShPI-1 is the first member of the sea anemone type 2 potassium channel toxins family with tight-binding potency against several proteases and different Kv1 channels. In depth sequence analysis and structural comparison of ShPI-1 with similar protease inhibitors and Kv channel toxins showed apparent non-sequence conservation for known key residues. However, we detected two subtle patterns of coordinated amino acid substitutions flanking the conserved cysteine residues at the N- and C-terminal ends. PMID:27089366

  3. Proton Dependent Inhibition of the Cardiac Sodium Channel Nav1.5 by Ranolazine

    OpenAIRE

    PeterCRuben; SridharanRajamani

    2013-01-01

    Ranolazine is clinically approved for treatment of angina pectoris and is a potential candidate for antiarrhythmic, antiepileptic and analgesic applications. These therapeutic effects of ranolazine hinge on its ability to inhibit persistent or late Na+ currents in a variety of voltage-gated sodium channels. Extracellular acidosis, typical of ischemic events, may alter the efficiency of drug/channel interactions. In this study, we examined pH modulation of ranolazine’s interaction with the ca...

  4. Proton-dependent inhibition of the cardiac sodium channel Nav1.5 by ranolazine

    OpenAIRE

    Sokolov, S.; Peters, C. H.; Rajamani, S; Ruben, P C

    2013-01-01

    Ranolazine is clinically approved for treatment of angina pectoris and is a potential candidate for antiarrhythmic, antiepileptic, and analgesic applications. These therapeutic effects of ranolazine hinge on its ability to inhibit persistent or late Na+ currents in a variety of voltage-gated sodium channels. Extracellular acidosis, typical of ischemic events, may alter the efficiency of drug/channel interactions. In this study, we examined pH modulation of ranolazine's interaction with the ca...

  5. Biophysical Methods to Analyze Direct G-Protein Regulation of Neuronal Voltage-Gated Calcium Channels

    Czech Academy of Sciences Publication Activity Database

    Weiss, Norbert; De Waard, M.

    New York: Humana Press, 2016 - (Luján, R.; Ciruela, F.), s. 357-368. (Neuromethods. 110). ISBN 978-1-4939-3063-0 Institutional support: RVO:61388963 Keywords : calciumchannel * Ca(v)2 channel * G-protein-coupled receptor * G-proteins * G beta gamma-dimer Subject RIV: CE - Biochemistry

  6. Differential expression of genes encoding subthreshold-operating voltage-gated K+ channels in brain.

    Science.gov (United States)

    Saganich, M J; Machado, E; Rudy, B

    2001-07-01

    The members of the three subfamilies (eag, erg, and elk) of the ether-a-go-go (EAG) family of potassium channel pore-forming subunits express currents that, like the M-current (I(M)), could have considerable influence on the subthreshold properties of neuronal membranes, and hence the control of excitability. A nonradioactive in situ hybridization (NR-ISH) study of the distribution of the transcripts encoding the eight known EAG family subunits in rat brain was performed to identify neuronal populations in which the physiological roles of EAG channels could be studied. These distributions were compared with those of the mRNAs encoding the components of the classical M-current (Kcnq2 and Kcnq3). NR-ISH was combined with immunohistochemistry to specific neuronal markers to help identify expressing neurons. The results show that each EAG subunit has a specific pattern of expression in rat brain. EAG and Kcnq transcripts are prominent in several types of excitatory neurons in the cortex and hippocampus; however, only one of these channel components (erg1) was consistently expressed in inhibitory interneurons in these areas. Some neuronal populations express more than one product of the same subfamily, suggesting that the subunits may form heteromeric channels in these neurons. Many neurons expressed multiple EAG family and Kcnq transcripts, such as CA1 pyramidal neurons, which contained Kcnq2, Kcnq3, eag1, erg1, erg3, elk2, and elk3. This indicates that the subthreshold current in many neurons may be complex, containing different components mediated by a number of channels with distinct properties and neuromodulatory responses. PMID:11425889

  7. Mechanisms of temperature dependence of threshold voltage in high-k/metal gate transistors with different TiN thicknesses

    Science.gov (United States)

    Nishida, Yukio; Yokoyama, Shin

    2016-04-01

    The change in temperature coefficient of the threshold voltage (=dVth/dT) for poly-Si/TiN/high-k gate insulator metal-oxide-semiconductor field-effect transistors (MOSFETs) was systematically investigated with respect to various TiN thicknesses for both n- and p-channel MOSFETs. With increasing TiN thickness, dVth/dT shifts towards negative values for both n- and p-MOSFETs. A mechanism that changes dVth/dT, depending on TiN thickness is proposed. The main origins are the work function of TiN (ΦTiN) and its temperature coefficient (dΦTiN/dT). These are revealed to change when decreasing the thickness of the TiN layer, because the crystallinity of the TiN layer is degraded for thinner films, which was confirmed by ultraviolet photoelectron spectroscopy (UPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD).

  8. Resonance effect in the voltage state of intrinsic Josephson junction stacks with multiple tunneling channels

    Science.gov (United States)

    Koyama, Tomio; Ota, Yukihiro; Machida, Masahiko

    2011-06-01

    We investigate the resonance effect caused by the Josephson-Leggett (JL) mode in intrinsic Josephson junction stacks (IJJs) formed by a stack of multigap superconducting layers. Such an IJJ system is expected to be realized in a single crystal of highly anisotropic iron-based superconductors with thick blocking layers. It is shown that the JL mode is resonantly excited by the Josephson oscillations in the voltage state with inhomogeneous electric-field distribution along the c axis. The resonance creates a steplike structure with a negative resistance region in the I-V characteristics.

  9. Activation of voltage-gated KCNQ/Kv7 channels by anticonvulsant retigabine attenuates mechanical allodynia of inflammatory temporomandibular joint in rats

    Directory of Open Access Journals (Sweden)

    Xu Wen

    2010-08-01

    Full Text Available Abstract Background Temporomandibular disorders (TMDs are characterized by persistent orofacial pain and have diverse etiologic factors that are not well understood. It is thought that central sensitization leads to neuronal hyperexcitability and contributes to hyperalgesia and spontaneous pain. Nonsteroidal anti-inflammatory drugs (NSAIDs are currently the first choice of drug to relieve TMD pain. NSAIDS were shown to exhibit anticonvulsant properties and suppress cortical neuron activities by enhancing neuronal voltage-gated potassium KCNQ/Kv7 channels (M-current, suggesting that specific activation of M-current might be beneficial for TMD pain. Results In this study, we selected a new anticonvulsant drug retigabine that specifically activates M-current, and investigated the effect of retigabine on inflammation of the temporomandibular joint (TMJ induced by complete Freund's adjuvant (CFA in rats. The results show that the head withdrawal threshold for escape from mechanical stimulation applied to facial skin over the TMJ in inflamed rats was significantly lower than that in control rats. Administration of centrally acting M-channel opener retigabine (2.5 and 7.5 mg/kg can dose-dependently raise the head withdrawal threshold of mechanical allodynia, and this analgesic effect can be reversed by the specific KCNQ channel blocker XE991 (3 mg/kg. Food intake is known to be negatively associated with TMJ inflammation. Food intake was increased significantly by the administration of retigabine (2.5 and 7.5 mg/kg, and this effect was reversed by XE991 (3 mg/kg. Furthermore, intracerebralventricular injection of retigabine further confirmed the analgesic effect of central retigabine on inflammatory TMJ. Conclusions Our findings indicate that central sensitization is involved in inflammatory TMJ pain and pharmacological intervention for controlling central hyperexcitability by activation of neuronal KCNQ/M-channels may have therapeutic potential for

  10. Small-polaron hopping via defect centres: anomalous temperature and voltage dependence of current through fatty-acid monolayers

    International Nuclear Information System (INIS)

    We study electron hopping in thin metal-insulator-metal structures which involves two defect centres with a strong electron-phonon coupling. We calculate the dependences of the current, J, on voltage, V, and temperature, T, and show that they are consistent with those observed in molecular monolayers of fatty acids. We analyse in detail an unusual, near-exponential temperature dependence of the current: J(T) ∝ exp (T/T0) T ≥ 50 K in eicosanoic acid (C20) organic monolayers sandwiched between Pt electrodes, where the parameter T0 increases with the bias voltage. We show that at relatively high voltages the two-defect small-polaron hopping results in N-shape current-voltage characteristics which were observed in some organic molecular monolayers

  11. A method for the extraction of the voltage-dependent quantum capacitance of carbon nanotubes using ab initio simulations

    International Nuclear Information System (INIS)

    In this paper, a method to obtain the quantum capacitance of carbon nanotubes (CNTs) using ab initio simulations is presented. As an example of the usage of the proposed method, the quantum capacitance of a metallic (6,6) CNT section is calculated. The quantum capacitance is extracted for various bias voltages applied to metallic CNT interconnects in the range 0-2.5 V, which is the operating voltage range of VLSI circuits. The obtained quantum capacitance values are found to be in good agreement with the experimental values. The average Fermi velocity of electrons dependent on the bias voltage is also obtained and plotted.

  12. Voltage-independent autocrine modulation of L-type channels mediated by ATP, opioids and catecholamines in rat chromaffin cells.

    Science.gov (United States)

    Hernández-Guijo, J M; Carabelli, V; Gandía, L; García, A G; Carbone, E

    1999-10-01

    The inhibition of L-type channels induced by either bath application of ATP, opioids and catecholamines or by endogenously released neurotransmitters was investigated in rat chromaffin cells with whole-cell recordings (5 mM Ba2+). In both cases, the L-type current, isolated pharmacologically using omega-toxin peptides and potentiated by Bay K 8644, was inhibited by approximately 50% with nearly no changes to the activation-inactivation kinetics. Inhibition was voltage independent at a wide range of potentials (-20 to +50 mV) and insensitive to depolarizing prepulses (+100 mV, 50 ms). Onset and offset of the inhibition were fast (time constants: tau(on) approximately 0.9 s, tau(off) approximately 3.6 s), indicating a rapid mechanism of channel modulation. Whether induced exogenously or from the released granules content in conditions of stopped cell superfusion, the neurotransmitter action was reversible and largely prevented by either intracellular GDP-beta-S, cell treatment with pertussis toxin or simultaneous application of P2y,2x delta/mu-opioidergic and alpha/beta-adrenergic antagonists. This suggests the existence of converging modulatory pathways by which autoreceptors-activated G-proteins reduce the activity of L-type channels through fast interactions. The autocrine inhibition of L-type currents, which was absent in superfused isolated cells, was effective on cell clusters, suggesting that L-type channels may be potently inhibited by cell exocytosis under physiological conditions resembling the intact adrenal glands. PMID:10564365

  13. 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

  14. Three Peptide Modulators of the Human Voltage-Gated Sodium Channel 1.7, an Important Analgesic Target, from the Venom of an Australian Tarantula.

    Science.gov (United States)

    Chow, Chun Yuen; Cristofori-Armstrong, Ben; Undheim, Eivind A B; King, Glenn F; Rash, Lachlan D

    2015-07-01

    Voltage-gated sodium (NaV) channels are responsible for propagating action potentials in excitable cells. NaV1.7 plays a crucial role in the human pain signalling pathway and it is an important therapeutic target for treatment of chronic pain. Numerous spider venom peptides have been shown to modulate the activity of NaV channels and these peptides represent a rich source of research tools and therapeutic lead molecules. The aim of this study was to determine the diversity of NaV1.7-active peptides in the venom of an Australian Phlogius sp. tarantula and to characterise their potency and subtype selectivity. We isolated three novel peptides, μ-TRTX-Phlo1a, -Phlo1b and -Phlo2a, that inhibit human NaV1.7 (hNaV1.7). Phlo1a and Phlo1b are 35-residue peptides that differ by one amino acid and belong in NaSpTx family 2. The partial sequence of Phlo2a revealed extensive similarity with ProTx-II from NaSpTx family 3. Phlo1a and Phlo1b inhibit hNaV1.7 with IC50 values of 459 and 360 nM, respectively, with only minor inhibitory activity on rat NaV1.2 and hNaV1.5. Although similarly potent at hNaV1.7 (IC50 333 nM), Phlo2a was less selective, as it also potently inhibited rNaV1.2 and hNaV1.5. All three peptides cause a depolarising shift in the voltage-dependence of hNaV1.7 activation. PMID:26134258

  15. Three Peptide Modulators of the Human Voltage-Gated Sodium Channel 1.7, an Important Analgesic Target, from the Venom of an Australian Tarantula

    Directory of Open Access Journals (Sweden)

    Chun Yuen Chow

    2015-06-01

    Full Text Available Voltage-gated sodium (NaV channels are responsible for propagating action potentials in excitable cells. NaV1.7 plays a crucial role in the human pain signalling pathway and it is an important therapeutic target for treatment of chronic pain. Numerous spider venom peptides have been shown to modulate the activity of NaV channels and these peptides represent a rich source of research tools and therapeutic lead molecules. The aim of this study was to determine the diversity of NaV1.7-active peptides in the venom of an Australian Phlogius sp. tarantula and to characterise their potency and subtype selectivity. We isolated three novel peptides, μ-TRTX-Phlo1a, -Phlo1b and -Phlo2a, that inhibit human NaV1.7 (hNaV1.7. Phlo1a and Phlo1b are 35-residue peptides that differ by one amino acid and belong in NaSpTx family 2. The partial sequence of Phlo2a revealed extensive similarity with ProTx-II from NaSpTx family 3. Phlo1a and Phlo1b inhibit hNaV1.7 with IC50 values of 459 and 360 nM, respectively, with only minor inhibitory activity on rat NaV1.2 and hNaV1.5. Although similarly potent at hNaV1.7 (IC50 333 nM, Phlo2a was less selective, as it also potently inhibited rNaV1.2 and hNaV1.5. All three peptides cause a depolarising shift in the voltage-dependence of hNaV1.7 activation.

  16. Analysis of the dependence of the microwave generation power of a low-voltage vircator on controlling parameters

    Science.gov (United States)

    Egorov, E. N.; Kalinin, Yu. A.; Koronovskiĭ, A. A.; Hramov, A. E.

    2007-10-01

    The results of experimental and theoretical analysis of the dependence of the generation power of a low-voltage vircator, viz., a nonrelativistic electrovacuum device based on a high-intensity electron beam with a virtual cathode, on the values of controlling parameters are considered. The dependences of the generation power on the decelerating potential and on the beam current are analyzed.

  17. Asymmetric synthesis of crambescin A-C carboxylic acids and their inhibitory activity on voltage-gated sodium channels.

    Science.gov (United States)

    Nakazaki, Atsuo; Nakane, Yoshiki; Ishikawa, Yuki; Yotsu-Yamashita, Mari; Nishikawa, Toshio

    2016-06-21

    Synthesis of both enantiomers of crambescin B carboxylic acid is described. A cis-enyne starting material was epoxidized under the conditions of Katsuki asymmetric epoxidation to give 95% ee of the epoxide, which was transformed to crambescin B carboxylic acid via bromocation-triggered cascade cyclization as the key step. Enantiomerically pure crambescin A and C carboxylic acids were also synthesized from the product of the cascade reaction. Structure-activity relationship (SAR) studies against voltage-gated sodium channel (VGSC) inhibition using those synthetic compounds revealed that the natural enantiomer of crambescin B carboxylic acid was most active and comparable to tetrodotoxin, and the unalkylated cyclic guanidinium structure is indispensible, while the carboxylate moiety is not important. The absolute stereochemistry of crambescin A was determined by a comparison of the methyl ester derived from natural crambescin A with that derived from the stereochemically defined crambescin A carboxylic acid synthesized in this study. PMID:27215973

  18. Auditory hallucinations as ictal phenomena in a patient with voltage-gated potassium channel antibody-associated limbic encephalitis.

    Science.gov (United States)

    Boyd, Michael; Attarian, Hrayr; Raizer, Jeffrey; Kumthekar, Priya; Macken, Micheal P; Schuele, Stephan U; Gerard, Elizabeth

    2013-12-01

    Limbic encephalitis involving anti-voltage-gated potassium channel antibodies (VGKC-LE) has become increasingly recognised, with seizures and psychotic features, such as hallucinations being typical clinical manifestations. Though the literature supports auditory hallucinations as ictal phenomena, there are no reported cases of these hallucinations correlating with electrographic seizure for this disease entity. Early recognition of auditory hallucinations as seizures could alter treatment and subsequently affect short-term outcomes in these patients. We report the case of a patient with auditory hallucinations and progressive cognitive decline, as well as serological evidence of VGKC antibodies, in whom ictal hallucinations were identified by continuous video-EEG monitoring. This case highlights the subtlety of this entity, in both clinical and electrographic detection. [Published with video sequences]. PMID:24571022

  19. Application of Stochastic Automata Networks for Creation of Continuous Time Markov Chain Models of Voltage Gating of Gap Junction Channels

    Directory of Open Access Journals (Sweden)

    Mindaugas Snipas

    2015-01-01

    Full Text Available The primary goal of this work was to study advantages of numerical methods used for the creation of continuous time Markov chain models (CTMC of voltage gating of gap junction (GJ channels composed of connexin protein. This task was accomplished by describing gating of GJs using the formalism of the stochastic automata networks (SANs, which allowed for very efficient building and storing of infinitesimal generator of the CTMC that allowed to produce matrices of the models containing a distinct block structure. All of that allowed us to develop efficient numerical methods for a steady-state solution of CTMC models. This allowed us to accelerate CPU time, which is necessary to solve CTMC models, ∼20 times.

  20. Two heterozygous Cav3.2 channel mutations in a pediatric chronic pain patient: recording condition-dependent biophysical effects.

    Science.gov (United States)

    Souza, Ivana A; Gandini, Maria A; Wan, Miranda M; Zamponi, Gerald W

    2016-04-01

    We report expression system-dependent effects of heterozygous mutations (P769L and A1059S) in the Cav3.2 CACNA1H gene identified in a pediatric patient with chronic pain and absence seizures. The mutations were introduced individually into recombinant channels and then analyzed by means of electrophysiology. When both mutants were co-expressed in tsA-201 cells, we observed a loss of channel function, with significantly smaller current densities across a wide range of voltages (-40 to +20 mV). In addition, when both mutant channels were co-expressed, the channels opened at a more depolarizing potential with a ~5-mV right shift in the half-activation potential, with no changes in half-inactivation potential and the rate of recovery from inactivation. Interestingly, when both mutants were co-expressed in the neuronal-derived CAD cells in a different extracellular milieu, the effect was remarkably different. Although not statistically significant (p replacement of extracellular sodium and potassium with tetraethylammonium chloride. Our results show that experimental conditions can be a confounding factor in the biophysical effects of T-type calcium channel mutations found in certain neurological disorders. PMID:26706850

  1. AHR-16303B, a novel antagonist of 5-HT2 receptors and voltage-sensitive calcium channels

    International Nuclear Information System (INIS)

    In vivo and in vitro methods were used to characterize AHR-16303B, a novel compound with antagonistic action at 5-HT2 receptors and voltage-sensitive calcium channels. The 5-HT2 receptor-antagonistic properties of AHR-16303B were demonstrated by inhibition of (a) [3H]ketanserin binding to rat cerebral cortical membranes (IC50 = 165 nM); (b) 5-hydroxytryptamine (5-HT)-induced foot edema in rats (minimum effective dose, (MED) = 0.32 mg/kg orally, p.o.); (c) 5-HT-induced vasopressor responses in spontaneously hypertensive rats (SHR) (ID50 = 0.18 mg/kg intravenously (i.v.), 1.8 mg/kg p.o.), (d) 5-HT-induced antidiuresis in rats (MED = 1 mg/kg p.o.), and (e) platelet aggregation induced by 5-HT + ADP (IC50 = 1.5 mM). The calcium antagonist properties of AHR-16303B were demonstrated by inhibition of (a) [3H]nimodipine binding to voltage-sensitive calcium channels on rabbit skeletal muscle membranes (IC50 = 15 nM), (b) KCl-stimulated calcium flux into cultured PC12 cells (IC50 = 81 nM), and (c) CaCl2-induced contractions of rabbit thoracic aortic strips (pA2 = 8.84). AHR-16303B had little or no effect on binding of radioligands to dopamine2 (DA2) alpha 1, alpha 2, H1, 5-HT1 alpha, beta 2, muscarinic M1, or sigma opioid receptors; had no effect on 5-HT3 receptor-mediated vagal bradycardia; and had only minor negative inotropic, chronotropic, and dromotropic effects on isolated guinea pig atria. In conscious SHR, 30 mg/kg p.o. AHR-16303B completely prevented the vasopressor responses to i.v. 5-HT, and decreased blood pressure (BP) by 24% 3 h after dosing

  2. Channel layer thickness dependence of In-Ti-Zn-O thin-film transistors fabricated using pulsed laser deposition

    Science.gov (United States)

    Zhang, Q.; Shan, F. K.; Liu, G. X.; Liu, A.; Lee, W. J.; Shin, B. C.

    2014-05-01

    Amorphous indium-titanium-zinc-oxide (ITZO) thin-film transistors (TFTs) with various channel thicknesses were fabricated at room temperature by using pulsed laser deposition. The channel layer thickness (CLT) dependence of the TFTs was investigated. All the ITZO thin films were amorphous, and the surface roughnesses decreased slightly first and then increased with increasing CLT. With increasing CLT from 35 to 140 nm, the on/off current ratio and the field-effect mobility increased, and the subthreshold swing decreased. The TFT with a CLT of 210 nm exhibited the worst performance, while the ITZO TFT with a CLT of 140 nm exhibited the best performance with a subthreshold voltage of 2.86 V, a mobility of 53.9 cm2V-1s-1, a subthreshold swing of 0.29 V/decade and an on/off current ratio of 109.

  3. Channel layer thickness dependence of In-Ti-Zn-O thin-film transistors fabricated using pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Q.; Shan, F. K.; Liu, G. X.; Liu, A. [Qingdao University, Qingdao (China); DongEui University, Busan (Korea, Republic of); Lee, W. J.; Shin, B. C. [DongEui University, Busan (Korea, Republic of)

    2014-05-15

    Amorphous indium-titanium-zinc-oxide (ITZO) thin-film transistors (TFTs) with various channel thicknesses were fabricated at room temperature by using pulsed laser deposition. The channel layer thickness (CLT) dependence of the TFTs was investigated. All the ITZO thin films were amorphous, and the surface roughnesses decreased slightly first and then increased with increasing CLT. With increasing CLT from 35 to 140 nm, the on/off current ratio and the field-effect mobility increased, and the subthreshold swing decreased. The TFT with a CLT of 210 nm exhibited the worst performance, while the ITZO TFT with a CLT of 140 nm exhibited the best performance with a subthreshold voltage of 2.86 V, a mobility of 53.9 cm{sup 2}V{sup -1}s{sup -1}, a subthreshold swing of 0.29 V/decade and an on/off current ratio of 10{sup 9}.

  4. Channel layer thickness dependence of In-Ti-Zn-O thin-film transistors fabricated using pulsed laser deposition

    International Nuclear Information System (INIS)

    Amorphous indium-titanium-zinc-oxide (ITZO) thin-film transistors (TFTs) with various channel thicknesses were fabricated at room temperature by using pulsed laser deposition. The channel layer thickness (CLT) dependence of the TFTs was investigated. All the ITZO thin films were amorphous, and the surface roughnesses decreased slightly first and then increased with increasing CLT. With increasing CLT from 35 to 140 nm, the on/off current ratio and the field-effect mobility increased, and the subthreshold swing decreased. The TFT with a CLT of 210 nm exhibited the worst performance, while the ITZO TFT with a CLT of 140 nm exhibited the best performance with a subthreshold voltage of 2.86 V, a mobility of 53.9 cm2V-1s-1, a subthreshold swing of 0.29 V/decade and an on/off current ratio of 109.

  5. Structure-function of proteins interacting with the alpha1 pore-forming subunit of high voltage-activated calcium channel

    Directory of Open Access Journals (Sweden)

    Alan eNeely

    2014-06-01

    Full Text Available Openings of high-voltage-activated calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, high-voltage-activated calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1 associated with four additional polypeptide chains β, α2, δ and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of high-voltage-activated calcium channels.

  6. Arginine side chain interactions and the role of arginine as a gating charge carrier in voltage sensitive ion channels

    Science.gov (United States)

    Armstrong, Craig T.; Mason, Philip E.; Anderson, J. L. Ross; Dempsey, Christopher E.

    2016-02-01

    Gating charges in voltage-sensing domains (VSD) of voltage-sensitive ion channels and enzymes are carried on arginine side chains rather than lysine. This arginine preference may result from the unique hydration properties of the side chain guanidinium group which facilitates its movement through a hydrophobic plug that seals the center of the VSD, as suggested by molecular dynamics simulations. To test for side chain interactions implicit in this model we inspected interactions of the side chains of arginine and lysine with each of the 19 non-glycine amino acids in proteins in the protein data bank. The arginine guanidinium interacts with non-polar aromatic and aliphatic side chains above and below the guanidinium plane while hydrogen bonding with polar side chains is restricted to in-plane positions. In contrast, non-polar side chains interact largely with the aliphatic part of the lysine side chain. The hydration properties of arginine and lysine are strongly reflected in their respective interactions with non-polar and polar side chains as observed in protein structures and in molecular dynamics simulations, and likely underlie the preference for arginine as a mobile charge carrier in VSD.

  7. Action of aluminum on high voltage-dependent calcium current and its modulation by ginkgolide B

    Institute of Scientific and Technical Information of China (English)

    Lei CHEN; Chang-jin LIU; Ming TANG; Ai LI; Xin-wu HU; Yi-mei DU; Jing-jing SHEN; Yong-li LU; Jurgen HESCHLER

    2005-01-01

    Aim: To investigate the effect of aluminum (Al) on high voltage-dependent calcium current (IHVA) and its modulation by ginkgolide B (Gin B). Methods: The whole-cell, patch-clamp technique was used to record IHVA from acutely isolated hippocampal CA1 pyramydal neurons in rats. Results: Al 0.1 mmol/L (low concentration) reduced IHVA; Al 0.75 and 1.0 mmol/L (high concentrations) increased IHVA, and Al decreased and increased IHVA at intermediate concentrations of 0.25 and 0.5 mmol/L. The increase of IHVA by Al 1.0 mmol/L was enhanced by the adenylyl cyclase (AC) agonist forskolin and was partly abolished by the cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) antagonist H-89, whereas the decrease observed with Al0.1 mmol/L was neither reversed by forskolin nor affected by H-89. Gin B had no effect on IHVA in normal neurons,but canceled the increase in IHVA by 1.0 mmol/L Al. Conclusion: The results indicate that the mechanism of Al affecting IHVA differs at different concentrations,and this may be attributed to its complex actions. Gin B could prevent neurons from injury by inhibiting calcium influx.

  8. Frequency dependent rectifier memristor bridge used as a programmable synaptic membrane voltage generator

    Directory of Open Access Journals (Sweden)

    Oliver Pabst

    2013-03-01

    Full Text Available Reasoned by its dynamical behavior, the memristor enables a lot of new applications in analog circuit design. Since some realizations have been shown (e.g. 2007 by Hewlett Packard, the development of applications with memristors becomes more and more interesting. Besides applications in neural networks and storage devices, analog memristive circuits also promise further applications. Therefore, this article proposes a frequency dependent rectifier memristor bridge for different purposes, for example, using as a programmable synaptic membrane voltage generator for Spike-Time-Dependent-Plasticity and describes the circuit theory. In this context it is shown that the Picard Iteration is one possibility to analytically solve the system of nonlinear state equations of memristor circuits. An intuitive picture of how a memristor works in a network in general is given as well and in this context some research on the dynamical behavior of a HP memristor should be done. After all it is suggested to use the memristor bridge as a neuron.

  9. Calcium channel-dependent molecular maturation of photoreceptor synapses.

    Directory of Open Access Journals (Sweden)

    Nawal Zabouri

    Full Text Available Several studies have shown the importance of calcium channels in the development and/or maturation of synapses. The Ca(V1.4(α(1F knockout mouse is a unique model to study the role of calcium channels in photoreceptor synapse formation. It features abnormal ribbon synapses and aberrant cone morphology. We investigated the expression and targeting of several key elements of ribbon synapses and analyzed the cone morphology in the Ca(V1.4(α(1F knockout retina. Our data demonstrate that most abnormalities occur after eye opening. Indeed, scaffolding proteins such as Bassoon and RIM2 are properly targeted at first, but their expression and localization are not maintained in adulthood. This indicates that either calcium or the Ca(V1.4 channel, or both are necessary for the maintenance of their normal expression and distribution in photoreceptors. Other proteins, such as Veli3 and PSD-95, also display abnormal expression in rods prior to eye opening. Conversely, vesicle related proteins appear normal. Our data demonstrate that the Ca(V1.4 channel is important for maintaining scaffolding proteins in the ribbon synapse but less vital for proteins related to vesicular release. This study also confirms that in adult retinae, cones show developmental features such as sprouting and synaptogenesis. Overall we present evidence that in the absence of the Ca(V1.4 channel, photoreceptor synapses remain immature and are unable to stabilize.

  10. Modelling of Remote Area Broadband Technology Over Low Voltage Power Line Channel

    Directory of Open Access Journals (Sweden)

    Abdallah Mahmoud Mousa Altrad

    2012-10-01

    Full Text Available Several broadband development initiatives have been proposed in Malaysia in order to Bridging DigitalDivide (BDD through the provisions of the Information and Communication Technology (ICT servicesto facilitate wide access to the internet through corporates government and private sector for high levelof scio-economy. Nevertheless, there is delay in provide broadband services due to the high cost ofdeployment in the remote area. Therefore, this paper investigates on Broadband over Power Lines (BPLtechnology and Malaysia’s broadband initiatives. BPL transmission technology model of using electricalpower lines for data, video and voice transmission is proposed. Furthermore, indoor part of theproposed model is carried out on Matlab/Simulink to explore the validity of power line channel transferfunction.

  11. Mechanism of action of two insect toxins huwentoxin-III and hainantoxin-VI on voltage-gated sodium channels.

    Science.gov (United States)

    Wang, Rui-lan; Yi, Su; Liang, Song-ping

    2010-06-01

    Selenocosmia huwena and Selenocosmia hainana are two tarantula species found in southern China. Their venoms contain abundant peptide toxins. Two new neurotoxic peptides, huwentoxin-III (HWTX-III) and hainantoxin-VI (HNTX-VI), were obtained from the venom using ion-exchange chromatography and reverse-phase high performance liquid chromatography (RP-HPLC). The mechanism of action of HWTX-III and HNTX-VI on insect neuronal voltage-gated sodium channels (VGSCs) was studied via whole-cell patch clamp techniques. In a fashion similar to delta-atracotoxins, HNTX-VI can induce a slowdown of current inactivation of the VGSC and reduction in the peak of Na+ current in cockroach dorsal unpaired median (DUM) neurons. Meanwhile, 10 micromol/L HNTX-IV caused a positive shift of steady-state inactivation of sodium channel. HWTX-III inhibited VGSCs on DUM neurons (concentration of toxin at half-maximal inhibition (IC(50)) approximately 1.106 micromol/L) in a way much similar to tetrodotoxin (TTX). HWTX-III had no effect on the kinetics of activation and inactivation. The shift in the steady-state inactivation curve was distinct from other depressant spider toxins. The diverse effect and the mechanism of action of the two insect toxins illustrate the diverse biological activities of spider toxins and provide a fresh theoretical foundation to design and develop novel insecticides. PMID:20506577

  12. Microsecond molecular dynamics simulations of the open state structure of a bacterial voltage-gated sodium channel reveal mechanisms of ion selectivity and conduction

    OpenAIRE

    Ulmschneider, Martin B.; Bagneris, Claire; McCusker, Emily C.; Ulmschneider, J.P.; Wallace, Bonnie A.

    2013-01-01

    Microsecond atomic detail equilibrium molecular dynamics simulations based on the open-state crystal structure (McCusker et al, 2012, Nature Comm) of a bacterial voltage-gated sodium channel (NavMs) have been employed to characterize the mechanisms underlying ion selectivity and conductance of the channel embedded in a lipid bilayer membrane. This approach captured the full plethora of conduction events, revealing a complex mixture of single and multi-ion phenomena, with decoupled rapid bi-di...

  13. Structure-function of proteins interacting with the α1 pore-forming subunit of high-voltage-activated calcium channels

    OpenAIRE

    AlanNeely

    2014-01-01

    Openings of high-voltage-activated calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of...

  14. Glutamate and N-methyl-D-aspartate affect release from crayfish axon terminals in a voltage-dependent manner.

    OpenAIRE

    Parnas, H; Parnas, I.; Ravin, R; Yudelevitch, B

    1994-01-01

    In the crayfish neuromuscular junction, the excitatory transmitter is glutamate. The present study shows that at concentrations as low as 5 x 10(-7) M, glutamate affects the depolarization-evoked release of neurotransmitter. Furthermore, the effect of glutamate on release is voltage-dependent and depends on the level of the depolarizing pulse. Nerve terminals were exposed to 5 x 10(-7) M tetrodotoxin and then depolarized to different levels by a macropatch electrode. Depending on the amplitud...

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

    DEFF Research Database (Denmark)

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

    2006-01-01

    + channels and Src were analyzed in vivo in mice lacking either or both PTPs. Lack of either PTP increases Kv channel activity and phosphorylation in Schwann cells, indicating these PTPs inhibit Kv current amplitude in vivo. Open probability and unitary conductance of Kv channels are unchanged, suggesting an......Tyrosine phosphatases (PTPs) epsilon and alpha are closely related and share several molecular functions, such as regulation of Src family kinases and voltage-gated potassium (Kv) channels. Functional interrelationships between PTPepsilon and PTPalpha and the mechanisms by which they regulate K...... effect on channel number or organization. PTPalpha inhibits Kv channels more strongly than PTPepsilon; this correlates with constitutive association of PTPalpha with Kv2.1, driven by membranal localization of PTPalpha. PTPalpha, but not PTPepsilon, activates Src in sciatic nerve extracts, suggesting Src...

  16. Types of voltage—dependent calcium channels involved in high potassium depolarization—induced amylase secretion in the exocrine pancreatic tumour cell line AR4—2J

    Institute of Scientific and Technical Information of China (English)

    CUIZONGJIE

    1998-01-01

    In the perifused fura-2 loaded exocrine pancreatic acinar cell line AR4-2J pulses of high potassium induced repetitive increases in intracellular calcium,Attached cells when stimulated with high potassium secreted large amount of amylase.High potassium-induced secretion was dependent both on the concentration of potassium and duration of stimulation.High potassium induced increases in intracellular calcium were inhibited by voltage-dependent calcium channel anatagonists with an order of potency as follows:nifedipine>ω-agatoxin IVA>ω-conotoxin GVIA.In contrast,the L-type calcium channel anatagonist nifedipine almost completely inhibited potassium-induced amylase secretion,whereas the N-type channel antagonist ω-conotoxin GVIA was without effect.The P-type channel antagonist ω-agatoxin IVA had a small inhibitory effect,but this inhibition was not significant at the level of amylase secretion.In conclusion,the AR4-2J cell line posesses different voltage-dependent calcium channels(L,P,N)with the L-type predominantly involved in depolarization induced amylase secretion.

  17. N- and L-Type Voltage-Gated Calcium Channels Mediate Fast Calcium Transients in Axonal Shafts of Mouse Peripheral Nerve

    Science.gov (United States)

    Barzan, Ruxandra; Pfeiffer, Friederike; Kukley, Maria

    2016-01-01

    In the peripheral nervous system (PNS) a vast number of axons are accommodated within fiber bundles that constitute peripheral nerves. A major function of peripheral axons is to propagate action potentials along their length, and hence they are equipped with Na+ and K+ channels, which ensure successful generation, conduction and termination of each action potential. However little is known about Ca2+ ion channels expressed along peripheral axons and their possible functional significance. The goal of the present study was to test whether voltage-gated Ca2+ channels (VGCCs) are present along peripheral nerve axons in situ and mediate rapid activity-dependent Ca2+ elevations under physiological circumstances. To address this question we used mouse sciatic nerve slices, Ca2+ indicator Oregon Green BAPTA-1, and 2-photon Ca2+ imaging in fast line scan mode (500 Hz). We report that transient increases in intra-axonal Ca2+ concentration take place along peripheral nerve axons in situ when axons are stimulated electrically with single pulses. Furthermore, we show for the first time that Ca2+ transients in peripheral nerves are fast, i.e., occur in a millisecond time-domain. Combining Ca2+ imaging and pharmacology with specific blockers of different VGCCs subtypes we demonstrate that Ca2+ transients in peripheral nerves are mediated mainly by N-type and L-type VGCCs. Discovery of fast Ca2+ entry into the axonal shafts through VGCCs in peripheral nerves suggests that Ca2+ may be involved in regulation of action potential propagation and/or properties in this system, or mediate neurotransmitter release along peripheral axons as it occurs in the optic nerve and white matter of the central nervous system (CNS). PMID:27313508

  18. Temperature-Dependent Current-Voltage (I-V) and Capacitance-Voltage (C-V) Characteristics of Ni/Cu/n-InP Schottky Barrier Diodes

    Science.gov (United States)

    Munikrishana Reddy, Y.; Nagaraj, M. K.; Siva Pratap Reddy, M.; Lee, Jung-Hee; Rajagopal Reddy, V.

    2013-04-01

    The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Ni/Cu/n-InP Schottky barrier diodes are studied over a wide temperature range, from 210 K to 420 K. The I-V characteristics display anomalous thermal behavior. The apparent barrier height decays, and the ideality factor grows at low temperatures, and the series resistances resulting from Cheung's and Norde's procedures are markedly temperature dependent. The nonlinearity of the Richardson plot and the strong temperature dependence of the Schottky-barrier parameters indicate that the interface is spatially inhomogeneous. Plots of the zero-bias barrier height as a function of 1/(2kT) points to a Gaussian distribution of barrier heights with 0.90 eV mean height and 0.014 eV standard deviation. When this distribution is accounted for, a Richardson of 6.5 A/(cm K)2 results, relatively close to the 9.4/(cm K)2 predicted by theory. We conclude that, combined with a Gaussian distribution of barrier heights, the thermionic-emission mechanism explains the temperature-dependent I-V and C-V characteristics of the studied Schottky-barrier diodes.

  19. Alternative splicing at C terminus of Ca(V)1.4 calcium channel modulates calcium-dependent inactivation, activation potential, and current density.

    Science.gov (United States)

    Tan, Gregory Ming Yeong; Yu, Dejie; Wang, Juejin; Soong, Tuck Wah

    2012-01-01

    The Ca(V)1.4 voltage-gated calcium channel is predominantly expressed in the retina, and mutations to this channel have been associated with human congenital stationary night blindness type-2. The L-type Ca(V)1.4 channel displays distinct properties such as absence of calcium-dependent inactivation (CDI) and slow voltage-dependent inactivation (VDI) due to the presence of an autoinhibitory domain (inhibitor of CDI) in the distal C terminus. We hypothesized that native Ca(V)1.4 is subjected to extensive alternative splicing, much like the other voltage-gated calcium channels, and employed the transcript scanning method to identify alternatively spliced exons within the Ca(V)1.4 transcripts isolated from the human retina. In total, we identified 19 alternative splice variations, of which 16 variations have not been previously reported. Characterization of the C terminus alternatively spliced exons using whole-cell patch clamp electrophysiology revealed a splice variant that exhibits robust CDI. This splice variant arose from the splicing of a novel alternate exon (43*) that can be found in 13.6% of the full-length transcripts screened. Inclusion of exon 43* inserts a stop codon that truncates half the C terminus. The Ca(V)1.4 43* channel exhibited robust CDI, a larger current density, a hyperpolarized shift in activation potential by ∼10 mV, and a slower VDI. Through deletional experiments, we showed that the inhibitor of CDI was responsible for modulating channel activation and VDI, in addition to CDI. Calcium currents in the photoreceptors were observed to exhibit CDI and are more negatively activated as compared with currents elicited from heterologously expressed full-length Ca(V)1.4. Naturally occurring alternative splice variants may in part contribute to the properties of the native Ca(V)1.4 channels. PMID:22069316

  20. Expression, purification, crystallization and preliminary crystallographic study of the carboxyl-terminal domain of the human voltage-gated proton channel Hv1

    International Nuclear Information System (INIS)

    Here, the C-terminal domain of the human voltage-gated proton channel Hv1 (C-Hv1) was overexpressed in Escherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. The voltage-gated proton channel Hv1 is essential to proton permeation and contains a voltage-sensor domain without a pore domain. It contains three predicted domains: an N-terminal acid and proline-rich domain, a transmembrane voltage-sensor domain and a C-terminal domain that is responsible for the dimeric architecture of Hv1. Here, the C-terminal domain of the human voltage-gated proton channel Hv1 (C-Hv1) was overexpressed in Escherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. The crystals have a tetragonal form and diffraction data were collected to 2.5 Å resolution in-house. The crystal belongs to space group P41212, with unit-cell parameters a = b = 37.76, c = 137.52 Å. Structural determination of C-Hv1 is in progress

  1. EFFECTS OF PYRETHROIDS ON VOLTAGE-SENSITIVE CALCIUM CHANNELS: A CRITICAL EVALUATION OF STRENGTHS, WEAKNESSES, DATA NEEDS, AND RELATIONSHIP TO ASSESSMENT OF CUMULATIVE NEUROTOXICITY.

    Science.gov (United States)

    A recently published review (Soderlund et al., 2002, Toxicology 171, 3-59.) of the mechanisms of acute neurotoxicity of pyrethroid compounds postulated that voltage-sensitive calcium channels (VSCC) may be a target of some pyrethroid compounds and that effects on VSCC may contrib...

  2. Inventory management for dual sales channels with inventory-level-dependent demand

    OpenAIRE

    Tingting Li; Xiaobo Zhao; Jinxing Xie

    2015-01-01

    This paper studies the inventory management problem of dual channels operated by one vendor. Demands of dual channels are inventory-level-dependent. We propose a multi-period stochastic dynamic programming model which shows that under mild conditions, the myopic inventory policy is optimal for the infinite horizon problem. To investigate the importance of capturing demand dependency on inventory levels, we consider a heuristic where the vendor ignores demand dependency on inventory levels, an...

  3. History dependent vortex flow dynamics in mesoscopic channels

    International Nuclear Information System (INIS)

    Intriguing and novel physical aspects related to the vortex flow dynamics have been recently observed in mesoscopic channel devices of a-NbGe with NbN channel edges. In this work we have studied the flow properties of such confined vortices as a function of the magnetic field history, using dc-transport and mode-locking (ML) measurements. As opposed to the field down situation, in field up case a kink anomaly in the dc I-V curves is detected. The mode-locking measurements unveil the dynamic change in the flow configurations around this anomaly: n moving rows of vortex array at low velocity changes suddenly to n + 2 rows at high velocity around the anomaly

  4. Serum Starvation-Induced Voltage-Gated Potassium Channel Kv7.5 Expression and Its Regulation by Sp1 in Canine Osteosarcoma Cells

    OpenAIRE

    Bo Hyung Lee; Pan Dong Ryu; So Yeong Lee

    2014-01-01

    The KCNQ gene family, whose members encode Kv7 channels, belongs to the voltage-gated potassium (Kv) channel group. The roles of this gene family have been widely investigated in nerve and muscle cells. In the present study, we investigated several characteristics of Kv7.5, which is strongly expressed in the canine osteosarcoma cell line, CCL-183. Serum starvation upregulated Kv7.5 expression, and the Kv7 channel opener, flupirtine, attenuated cell proliferation by arresting cells in the G0/G...

  5. Electrical characterization of Cu(In,Ga)Se2-solar cells by voltage dependent time-resolved photoluminescence

    International Nuclear Information System (INIS)

    Time-resolved photoluminescence (TRPL) is a promising method for the investigation of charge carrier dynamics and recombination kinetics in semiconductor devices. To characterize Cu(In,Ga)Se2 (CIGSe) solar cells, we measured TRPL for different applied external forward voltages. We show that the TRPL decay time increases with increasing voltage in case of a high excitation intensity. This result is valid for a wide range of excitation frequencies of the laser. By simulation of the measured transients we determined semiconductor parameters which allow fitting the experimental photoluminescence transients for different voltages. The deduced quantities are the lifetime for deep defect assisted Schockley-Read-Hall recombination, doping density and charge carrier mobilities of the solar cell's absorber layer with values of 10 ns, 2 × 1015 cm−3 and 1 cm2 V−1 s−1, respectively, for a standard CIGSe solar cell. We further studied the appearance of a photovoltage in TRPL experiments with single-photon-counting methods. By experimental results we show a dependence of the open circuit voltage on the laser repetition rate, which influences the TRPL decay. - Highlights: • Time-resolved photoluminescence on Cu(In,Ga)Se2-solar for different bias voltages • Build up of a photovoltage that varies luminescence decay for open circuit conditions • Inhibition of luminescence decay for increasing bias forward voltages • Determination of charge carrier mobilities and minority carrier lifetime by simulations

  6. Channel length dependence of negative-bias-illumination-stress in amorphous-indium-gallium-zinc-oxide thin-film transistors

    International Nuclear Information System (INIS)

    We have investigated the dependence of Negative-Bias-illumination-Stress (NBIS) upon channel length, in amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). The negative shift of the transfer characteristic associated with NBIS decreases for increasing channel length and is practically suppressed in devices with L = 100-μm. The effect is consistent with creation of donor defects, mainly in the channel regions adjacent to source and drain contacts. Excellent agreement with experiment has been obtained by an analytical treatment, approximating the distribution of donors in the active layer by a double exponential with characteristic length LD ∼ Ln ∼ 10-μm, the latter being the electron diffusion length. The model also shows that a device with a non-uniform doping distribution along the active layer is in all equivalent, at low drain voltages, to a device with the same doping averaged over the active layer length. These results highlight a new aspect of the NBIS mechanism, that is, the dependence of the effect upon the relative magnitude of photogenerated holes and electrons, which is controlled by the device potential/band profile. They may also provide the basis for device design solutions to minimize NBIS

  7. Channel length dependence of negative-bias-illumination-stress in amorphous-indium-gallium-zinc-oxide thin-film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Um, Jae Gwang; Mativenga, Mallory; Jang, Jin, E-mail: jjang@khu.ac.kr [Advanced Display Research Center, Department of Information Display, Kyung Hee University, Dongdaemun-gu, Seoul 130-701 (Korea, Republic of); Migliorato, Piero [Advanced Display Research Center, Department of Information Display, Kyung Hee University, Dongdaemun-gu, Seoul 130-701 (Korea, Republic of); Electrical Engineering Division, Department of Engineering, Cambridge University, Cambridge CB3 0FA (United Kingdom)

    2015-06-21

    We have investigated the dependence of Negative-Bias-illumination-Stress (NBIS) upon channel length, in amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). The negative shift of the transfer characteristic associated with NBIS decreases for increasing channel length and is practically suppressed in devices with L = 100-μm. The effect is consistent with creation of donor defects, mainly in the channel regions adjacent to source and drain contacts. Excellent agreement with experiment has been obtained by an analytical treatment, approximating the distribution of donors in the active layer by a double exponential with characteristic length L{sub D} ∼ L{sub n} ∼ 10-μm, the latter being the electron diffusion length. The model also shows that a device with a non-uniform doping distribution along the active layer is in all equivalent, at low drain voltages, to a device with the same doping averaged over the active layer length. These results highlight a new aspect of the NBIS mechanism, that is, the dependence of the effect upon the relative magnitude of photogenerated holes and electrons, which is controlled by the device potential/band profile. They may also provide the basis for device design solutions to minimize NBIS.

  8. Leukotriene B4 release by human lung macrophages via receptor- not voltage-operated Ca2+ channels.

    Science.gov (United States)

    Finney-Hayward, T K; Bahra, P; Li, S; Poll, C T; Nicholson, A G; Russell, R E K; Ford, P A; Westwick, J; Fenwick, P S; Barnes, P J; Donnelly, L E

    2009-05-01

    Increased numbers of macrophages and neutrophils in the lung is a key feature of chronic obstructive pulmonary disease (COPD). The major neutrophil chemotactic agent in the airways of COPD patients is leukotriene (LT)B(4) and is released by macrophages. The present study examines the role and mechanism of Ca(2+) in platelet-activating factor (PAF)-stimulated LTB(4) release from human lung macrophages. Macrophages were isolated from lung tissue of subjects undergoing lung resection surgery and monocyte-derived macrophages (MDM) were obtained from nonsmokers, smokers without obstruction and COPD patients. Cells were stimulated with PAF and LTB(4) release and [Ca(2+)](i) was measured. Lung macrophages and MDM released LTB(4) following stimulation with PAF (mean effective concentration: 0.08+/-0.06 microM (n = 5) versus 0.17+/-0.12 microM (n = 17), respectively). Compared with MDM, lung macrophages released approximately eight-fold more LTB(4). Neither smoking nor COPD altered MDM responses. PAF-stimulated LTB(4) release was abrogated by ethylene glycol tetraacetic acid suggesting a role for extracellular Ca(2+). This was substantiated by using store-operated channel blockers econazole, SK&F96365 and Gd(3+). However, econazole and SK&F96365 were more effective in MDM than lung macrophages. Neither LOE908 nor nifedipine could attenuate this response. These data suggest that platelet-activating factor-stimulated leukotriene B(4) release from human lung macrophages is mediated, in part, by Ca(2+) influx through receptor- but not voltage-operated Ca(2+) channels. PMID:19164358

  9. The effects of flavoxate hydrochloride on voltage-dependent L-type Ca2+ currents in human urinary bladder

    OpenAIRE

    Tomoda, Toshihisa; Aishima, Manami; Takano, Naruaki; Nakano, Toshiaki; Seki, Narihito; Yonemitsu, Yoshikazu; Sueishi, Katsuo; Naito, Seiji; Ito, Yushi; Teramoto, Noriyoshi

    2005-01-01

    The effects of flavoxate hydrochloride (Bladderon®, piperidinoethyl-3-methylflavone-8-carboxylate; hereafter referred as flavoxate) on voltage-dependent nifedipine-sensitive inward Ba2+ currents in human detrusor myocytes were investigated using a conventional whole-cell patch-clamp. Tension measurement was also performed to study the effects of flavoxate on K+-induced contraction in human urinary bladder.Flavoxate caused a concentration-dependent reduction of the K+-induced contraction of hu...

  10. Voltage and cosubstrate dependence of the Na-HCO3 cotransporter kinetics in renal proximal tubule cells.

    OpenAIRE

    Gross, E.; Hopfer, U

    1998-01-01

    The voltage dependence of the kinetics of the sodium bicarbonate cotransporter was studied in proximal tubule cells. This electrogenic cotransporter transports one Na+, three HCO3-, and two negative charges. Cells were grown to confluence on a permeable support, mounted on a Ussing-type chamber, and permeabilized apically to small monovalent ions with amphotericin B. The steady-state, di-nitro-stilbene-di-sulfonate-sensitive current was shown to be sodium and bicarbonate dependent and therefo...

  11. Effective description of tunneling in a time-dependent potential with applications to voltage switching in Josephson junctions

    DEFF Research Database (Denmark)

    Andersen, Christian Kraglund; Mølmer, Klaus

    2013-01-01

    variable: the phase change across a Josephson junction. The Josephson junction phase variable behaves as the position coordinate of a particle moving in a tilted washboard potential, and our general solution to the motion in such a potential with a time-dependent tilt reproduces a number of features...... associated with voltage switching in Josephson junctions. Apart from applications as artificial atoms in quantum information studies, the Josephson junction may serve as an electric field sensitive detector, and our studies provide a detailed understanding of how the voltage switching dynamics couples to the...

  12. Targeting voltage-gated calcium channels: developments in peptide and small-molecule inhibitors for the treatment of neuropathic pain.

    Science.gov (United States)

    Vink, S; Alewood, P F

    2012-11-01

    Chronic pain affects approximately 20% of people worldwide and places a large economic and social burden on society. Despite the availability of a range of analgesics, this condition is inadequately treated, with complete alleviation of symptoms rarely occurring. In the past 30 years, the voltage-gated calcium channels (VGCCs) have been recognized as potential targets for analgesic development. Although the majority of the research has been focused on Ca(v) 2.2 in particular, other VGCC subtypes such as Ca(v) 3.2 have recently come to the forefront of analgesic research. Venom peptides from marine cone snails have been proven to be a valuable tool in neuroscience, playing a major role in the identification and characterization of VGCC subtypes and producing the first conotoxin-based drug on the market, the ω-conotoxin, ziconotide. This peptide potently and selectively inhibits Ca(v) 2.2, resulting in analgesia in chronic pain states. However, this drug is only available via intrathecal administration, and adverse effects and a narrow therapeutic window have limited its use in the clinic. Other Ca(v) 2.2 inhibitors are currently in development and offer the promise of an improved route of administration and safety profile. This review assesses the potential of targeting VGCCs for analgesic development, with a main focus on conotoxins that block Ca(v) 2.2 and the developments made to transform them into therapeutics. PMID:22725651

  13. Human voltage-gated proton channel hv1: a new potential biomarker for diagnosis and prognosis of colorectal cancer.

    Directory of Open Access Journals (Sweden)

    Yifan Wang

    Full Text Available Solid tumors exist in a hypoxic microenvironment, and possess high-glycolytic metabolites. To avoid the acidosis, tumor cells must exhibit a dynamic cytosolic pH regulation mechanism(s. The voltage-gated proton channel Hv1 mediates NADPH oxidase function by compensating cellular loss of electrons with protons. Here, we showed for the first time, that Hv1 expression is increased in colorectal tumor tissues and cell lines, associated with poor prognosis. Immunohistochemistry showed that Hv1 is strongly expressed in adenocarcinomas but not or lowly expressed in normal colorectal or hyperplastic polyps. Hv1 expression in colorectal cancer is significantly associated with the tumor size, tumor classification, lymph node status, clinical stage and p53 status. High Hv1 expression is associated significantly with shorter overall and recurrence-free survival. Furthermore, real-time RT-PCR and immunocytochemistry showed that Hv1 is highly expressed in colorectal cancer cell lines, SW620, HT29, LS174T and Colo205, but not in SW480. Inhibitions of Hv1 expression and activity in the highly metastatic SW620 cells by small interfering RNA (siRNA and Zn(2+ respectively, markedly decrease the cell invasion and migration, restraint proton extrusion and the intracellular pH recovery. Our results suggest that Hv1 may be used as a potential biomarker for diagnosis and prognosis of colorectal carcinoma, and a potential target for anticancer drugs in colorectal cancer therapy.

  14. Three dimensional neuronal cell cultures more accurately model voltage gated calcium channel functionality in freshly dissected nerve tissue.

    Directory of Open Access Journals (Sweden)

    Yinzhi Lai

    Full Text Available It has been demonstrated that neuronal cells cultured on traditional flat surfaces may exhibit exaggerated voltage gated calcium channel (VGCC functionality. To gain a better understanding of this phenomenon, primary neuronal cells harvested from mice superior cervical ganglion (SCG were cultured on two dimensional (2D flat surfaces and in three dimensional (3D synthetic poly-L-lactic acid (PLLA and polystyrene (PS polymer scaffolds. These 2D- and 3D-cultured cells were compared to cells in freshly dissected SCG tissues, with respect to intracellular calcium increase in response to high K(+ depolarization. The calcium increases were identical for 3D-cultured and freshly dissected, but significantly higher for 2D-cultured cells. This finding established the physiological relevance of 3D-cultured cells. To shed light on the mechanism behind the exaggerated 2D-cultured cells' functionality, transcriptase expression and related membrane protein distributions (caveolin-1 were obtained. Our results support the view that exaggerated VGCC functionality from 2D cultured SCG cells is possibly due to differences in membrane architecture, characterized by uniquely organized caveolar lipid rafts. The practical implication of use of 3D-cultured cells in preclinical drug discovery studies is that such platforms would be more effective in eliminating false positive hits and as such improve the overall yield from screening campaigns.

  15. Reciprocal regulation of reactive oxygen species and phospho-CREB regulates voltage gated calcium channel expression during Mycobacterium tuberculosis infection.

    Directory of Open Access Journals (Sweden)

    Arti Selvakumar

    Full Text Available Our previous work has demonstrated the roles played by L-type Voltage Gated Calcium Channels (VGCC in regulating Mycobacterium tuberculosis (M. tb survival and pathogenesis. Here we decipher mechanisms and pathways engaged by the pathogen to regulate VGCC expression in macrophages. We show that M. tb and its antigen Rv3416 use phospho-CREB (pCREB, Reactive Oxygen Species (ROS, Protein Kinase C (PKC and Mitogen Activated Protein Kinase (MAPK to modulate VGCC expression in macrophages. siRNA mediated knockdown of MyD88, IRAK1, IRAK2 or TRAF6 significantly inhibited antigen mediated VGCC expression. Inhibiting Protein Kinase C (PKC or MEK-ERK1/2 further increased VGCC expression. Interestingly, inhibiting intracellular calcium release upregulated antigen mediated VGCC expression, while inhibiting extracellular calcium influx had no significant effect. siRNA mediated knockdown of transcription factors c-Jun, SOX5 and CREB significantly inhibited Rv3416 mediated VGCC expression. A dynamic reciprocal cross-regulation between ROS and pCREB was observed that in turn governed VGCC expression with ROS playing a limiting role in the process. Further dissection of the mechanisms such as the interplay between ROS and pCREB would improve our understanding of the regulation of VGCC expression during M. tb infection.

  16. Novel Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Varroa destructor Populations from the Southeastern USA.

    Science.gov (United States)

    González-Cabrera, Joel; Rodríguez-Vargas, Sonia; Davies, T G Emyr; Field, Linda M; Schmehl, Daniel; Ellis, James D; Krieger, Klemens; Williamson, Martin S

    2016-01-01

    The parasitic mite Varroa destructor has a significant worldwide impact on bee colony health. In the absence of control measures, parasitized colonies invariably collapse within 3 years. The synthetic pyrethroids tau-fluvalinate and flumethrin have proven very effective at managing this mite within apiaries, but intensive control programs based mainly on one active ingredient have led to many reports of pyrethroid resistance. In Europe, a modification of leucine to valine at position 925 (L925V) of the V. destructor voltage-gated sodium channel was correlated with resistance, the mutation being found at high frequency exclusively in hives with a recent history of pyrethroid treatment. Here, we identify two novel mutations, L925M and L925I, in tau-fluvalinate resistant V. destructor collected at seven sites across Florida and Georgia in the Southeastern region of the USA. Using a multiplexed TaqMan® allelic discrimination assay, these mutations were found to be present in 98% of the mites surviving tau-fluvalinate treatment. The mutations were also found in 45% of the non-treated mites, suggesting a high potential for resistance evolution if selection pressure is applied. The results from a more extensive monitoring programme, using the Taqman® assay described here, would clearly help beekeepers with their decision making as to when to include or exclude pyrethroid control products and thereby facilitate more effective mite management programmes. PMID:27191597

  17. Novel Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Varroa destructor Populations from the Southeastern USA.

    Directory of Open Access Journals (Sweden)

    Joel González-Cabrera

    Full Text Available The parasitic mite Varroa destructor has a significant worldwide impact on bee colony health. In the absence of control measures, parasitized colonies invariably collapse within 3 years. The synthetic pyrethroids tau-fluvalinate and flumethrin have proven very effective at managing this mite within apiaries, but intensive control programs based mainly on one active ingredient have led to many reports of pyrethroid resistance. In Europe, a modification of leucine to valine at position 925 (L925V of the V. destructor voltage-gated sodium channel was correlated with resistance, the mutation being found at high frequency exclusively in hives with a recent history of pyrethroid treatment. Here, we identify two novel mutations, L925M and L925I, in tau-fluvalinate resistant V. destructor collected at seven sites across Florida and Georgia in the Southeastern region of the USA. Using a multiplexed TaqMan® allelic discrimination assay, these mutations were found to be present in 98% of the mites surviving tau-fluvalinate treatment. The mutations were also found in 45% of the non-treated mites, suggesting a high potential for resistance evolution if selection pressure is applied. The results from a more extensive monitoring programme, using the Taqman® assay described here, would clearly help beekeepers with their decision making as to when to include or exclude pyrethroid control products and thereby facilitate more effective mite management programmes.

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

    OpenAIRE

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

    2014-01-01

    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 constrict...

  19. Voltage-gated calcium channels are abnormal in cultured spinal motoneurons in the G93A-SOD1 transgenic mouse model of ALS.

    Science.gov (United States)

    Chang, Qing; Martin, Lee J

    2016-09-01

    Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive loss of motoneurons. Hyperexcitability and excitotoxicity have been implicated in the early pathogenesis of ALS. Studies addressing excitotoxic motoneuron death and intracellular Ca(2+) overload have mostly focused on Ca(2+) influx through AMPA glutamate receptors. However, intrinsic excitability of motoneurons through voltage-gated ion channels may also have a role in the neurodegeneration. In this study we examined the function and localization of voltage-gated Ca(2+) channels in cultured spinal cord motoneurons from mice expressing a mutant form of human superoxide dismutase-1 with a Gly93→Ala substitution (G93A-SOD1). Using whole-cell patch-clamp recordings, we showed that high voltage activated (HVA) Ca(2+) currents are increased in G93A-SOD1 motoneurons, but low voltage activated Ca(2+) currents are not affected. G93A-SOD1 motoneurons also have altered persistent Ca(2+) current mediated by L-type Ca(2+) channels. Quantitative single-cell RT-PCR revealed higher levels of Ca1a, Ca1b, Ca1c, and Ca1e subunit mRNA expression in G93A-SOD1 motoneurons, indicating that the increase of HVA Ca(2+) currents may result from upregulation of Ca(2+) channel mRNA expression in motoneurons. The localizations of the Ca1B N-type and Ca1D L-type Ca(2+) channels in motoneurons were examined by immunocytochemistry and confocal microscopy. G93A-SOD1 motoneurons had increased Ca1B channels on the plasma membrane of soma and dendrites. Ca1D channels are similar on the plasma membrane of soma and lower on the plasma membrane of dendrites of G93A-SOD1 motoneurons. Our study demonstrates that voltage-gated Ca(2+) channels have aberrant functions and localizations in ALS mouse motoneurons. The increased HVA Ca(2+) currents and PCCa current could contribute to early pathogenesis of ALS. PMID:27151771

  20. Boosting of synaptic potentials and spine Ca transients by the peptide toxin SNX-482 requires alpha-1E-encoded voltage-gated Ca channels.

    Directory of Open Access Journals (Sweden)

    Andrew J Giessel

    Full Text Available The majority of glutamatergic synapses formed onto principal neurons of the mammalian central nervous system are associated with dendritic spines. Spines are tiny protuberances that house the proteins that mediate the response of the postsynaptic cell to the presynaptic release of glutamate. Postsynaptic signals are regulated by an ion channel signaling cascade that is active in individual dendritic spines and involves voltage-gated calcium (Ca channels, small conductance (SK-type Ca-activated potassium channels, and NMDA-type glutamate receptors. Pharmacological studies using the toxin SNX-482 indicated that the voltage-gated Ca channels that signal within spines to open SK channels belong to the class Ca(V2.3, which is encoded by the Alpha-1E pore-forming subunit. In order to specifically test this conclusion, we examined the effects of SNX-482 on synaptic signals in acute hippocampal slices from knock-out mice lacking the Alpha-1E gene. We find that in these mice, application of SNX-482 has no effect on glutamate-uncaging evoked synaptic potentials and Ca influx, indicating that that SNX-482 indeed acts via the Alpha-1E-encoded Ca(V2.3 channel.

  1. Voltage-probe-position dependence and magnetic-flux contribution to the measured voltage in ac transport measurements: which measuring circuit determines the real losses?

    International Nuclear Information System (INIS)

    The voltage Vab measured between two voltage taps a and b during magnetic flux transport in a type-II superconductor carrying current I is the sum of two contributions, the line integral from a to b of the electric field along an arbitrary path Cs through the superconductor and a term proportional to the time rate of change of magnetic flux through the area bounded by the path Cs and the measuring circuit leads. When the current I(t) is oscillating with time t, the apparent ac loss (the time average of the product IVab) depends upon the measuring circuit used. Only when the measuring-circuit leads are brought out far from the surface does the apparent power dissipation approach the real (or true) ac loss associated with the length of sample probed. Calculations showing comparisons between the apparent and real ac losses in a flat strip of rectangular cross section will be presented, showing the behavior as a function of the measuring-circuit dimensions. Corresponding calculations also are presented for a sample of elliptical cross section

  2. Voltage-probe-position dependence and magnetic-flux contribution to the measured voltage in AC transport measurements: which measuring circuit determines the real losses?

    International Nuclear Information System (INIS)

    The voltage Vab measured between two voltage taps a and b during magnetic flux transport in a type-II superconductor carrying current I is the sum of two contributions, the line integral from a to b of the electric field along an arbitrary path Cs through the superconductor and a term proportional to the time rate of change of magnetic flux through the area bounded by the path Cs and the measuring circuit leads. When the current I(t) is oscillating with time t, the apparent AC loss (the time average of the product IVab) depends upon the measuring circuit used. Only when the measuring-circuit leads are brought out far from the surface does the apparent power dissipation approach the real (or true) AC loss associated with the length of sample probed. Calculations showing comparisons between the apparent and real AC losses in a flat strip of rectangular cross section will be presented, showing the behavior as a function of the measuring-circuit, dimensions. Corresponding calculations also are presented for a sample of elliptical cross section. (orig.)

  3. Ablation of Ca(V2.1 voltage-gated Ca²⁺ channels in mouse forebrain generates multiple cognitive impairments.

    Directory of Open Access Journals (Sweden)

    Robert Theodor Mallmann

    Full Text Available Voltage-gated Ca(V2.1 (P/Q-type Ca²⁺ channels located at the presynaptic membrane are known to control a multitude of Ca²⁺-dependent cellular processes such as neurotransmitter release and synaptic plasticity. Our knowledge about their contributions to complex cognitive functions, however, is restricted by the limited adequacy of existing transgenic Ca(V2.1 mouse models. Global Ca(V2.1 knock-out mice lacking the α1 subunit Cacna1a gene product exhibit early postnatal lethality which makes them unsuitable to analyse the relevance of Ca(V2.1 Ca²⁺ channels for complex behaviour in adult mice. Consequently we established a forebrain specific Ca(V2.1 knock-out model by crossing mice with a floxed Cacna1a gene with mice expressing Cre-recombinase under the control of the NEX promoter. This novel mouse model enabled us to investigate the contribution of Ca(V2.1 to complex cognitive functions, particularly learning and memory. Electrophysiological analysis allowed us to test the specificity of our conditional knock-out model and revealed an impaired synaptic transmission at hippocampal glutamatergic synapses. At the behavioural level, the forebrain-specific Ca(V2.1 knock-out resulted in deficits in spatial learning and reference memory, reduced recognition memory, increased exploratory behaviour and a strong attenuation of circadian rhythmicity. In summary, we present a novel conditional Ca(V2.1 knock-out model that is most suitable for analysing the in vivo functions of Ca(V2.1 in the adult murine forebrain.

  4. Regulation of store-operated and voltage-operated Ca2+ channels in the proliferation and death of oligodendrocyte precursor cells by golli proteins

    Directory of Open Access Journals (Sweden)

    Pablo M Paez

    2009-04-01

    Full Text Available OPCs (oligodendrocyte precursor cells) express golli proteins which, through regulation of Ca2+ influx, appear to be important in OPC process extension/retraction and migration. The aim of the present study was to examine further the role of golli in regulating OPC development. The effects of golli ablation and overexpression were examined in primary cultures of OPCs prepared from golli-KO (knockout) and JOE (golli J37-overexpressing) mice. In OPCs lacking golli, or overexpressing golli, differentiation induced by growth factor withdrawal was impaired. Proliferation analysis in the presence of PDGF (platelet-derived growth factor), revealed that golli enhanced the mitogen-stimulated proliferation of OPCs through activation of SOCCs (store-operated Ca2+ channels). PDGF treatment induced a biphasic increase in OPC intracellular Ca2+, and golli specifically increased Ca2+ influx during the second SOCC-dependent phase that followed the initial release of Ca2+ from intracellular stores. This store-operated Ca2+ uptake appeared to be essential for cell division, since specific SOCC antagonists completely blocked the effects of PDGF and golli on OPC proliferation. Additionally, in OPCs overexpressing golli, increased cell death was observed after mitogen withdrawal. This phenomenon could be prevented by exposure to VOCC (voltage-operated Ca2+ channel) blockers, indicating that the effect of golli on cell death involved increased Ca2+ influx through VOCCs. The results showed a clear effect of golli on OPC development and support a role for golli in modulating multiple Ca2+-regulatory events through VOCCs and SOCCs. Our results also suggest that PDGF engagement of its receptor resulting in OPC proliferation proceeds through activation of SOCCs.

  5. On the Capacity of Compound State-Dependent Channels with States Known at the Transmitter

    CERN Document Server

    Piantanida, Pablo

    2010-01-01

    This paper investigates the capacity of compound state-dependent channels with non-causal state information available at only the transmitter. A new lower bound on the capacity of this class of channels is derived. This bound is shown to be tight for the special case of compound channels with stochastic degraded components, yielding the full characterization of the capacity. Specific results are derived for the compound Gaussian Dirty-Paper (GDP) channel. This model consists of an additive white Gaussian noise (AWGN) channel corrupted by an additive Gaussian interfering signal, known at the transmitter only, where the input and the state signals are affected by fading coefficients whose realizations are unknown at the transmitter. Our bounds are shown to be tight for specific cases. Applications of these results arise in a variety of wireless scenarios as multicast channels, cognitive radio and problems with interference cancellation.

  6. A narrow bandgap SiGe channel superlattice bandgap engineered 1T DRAM cell for low voltage operation and extended hole retention time

    International Nuclear Information System (INIS)

    We propose a SiGe channel superlattice bandgap engineered (SiGe SBE) 1-transistor dynamic random access memory (1T DRAM) cell structure for improved generation and extended retention of hot holes adopting a narrow bandgap Si0.8Ge0.2 channel even with an extremely short gate length of 30 nm. The proposed SiGe channel SBE 1T DRAM shows longer retention time than the Si channel SBE 1T DRAM. It also provides improved design flexibility by optimizing the structural and process parameters, so the retention characteristics get better. Especially, it should be noted that the retention time can be further improved if the doping concentration of the Si buffer layer decreases. The narrow bandgap SiGe channel SBE structure also allows the 1T DRAM cell to generate more electron–hole pairs during the write '1' operation through the impact ionization in the channel under a high electric field. In addition to the long retention time with the SBE structure, the narrow bandgap SiGe channel SBE 1T DRAM cell enables the 1T DRAM cell to have a fast write speed and to operate at lower voltage, thanks to the narrow bandgap Si0.8Ge0.2 channel

  7. Effect of mitochondrial KATP channel on voltage-gated K+ channel in 24 hour-hypoxic human pulmonary artery smooth muscle cells

    Institute of Scientific and Technical Information of China (English)

    WANG Tao; ZHANG Zhen-xiang; XU Yong-jian

    2005-01-01

    Background Hypoxic pulmonary hypertension (HPH) is initiated by inhibition of O2-sensitive, voltage-gated (Kv) channels in pulmonary arterial smooth muscle cells (PASMCs). The mechanism of hypoxic pulmonary hypertension has not yet been fully elucidated. The mitochondrial ATP-sensitive K+ channel (MitoKATP) is extremely sensitive to hypoxia, and is a decisive factor in the control of mitochondrial membrane potential (ΔΨm). This study investigated the changes of cell membrane potential and Kv channel in cultured human pulmonary artery smooth muscle cell (hPASMC) exposed to 24 hour-hypoxia, and explored the role of MitoKATP and ΔΨm in this condition.Results After exposure to diazoxide for 24 hours, the intensity of R-123 fluorescence in normoxic hPASMCs was significantly increased compared with control group (P<0.05), but there were no significant changes in these tests after the hPASMCs had been exposed to 5-HD for 24 hours. Twenty-four hour-hypoxia or 24 hour-hypoxia + diazoxide could markedly increase the intensity of R-123 fluorescence in hPASMC and the changes were more significant in 24 hour-hypoxia +diazoxide group than in 24 hour-hypoxia group (P<0.05) although 5-HD could partly weaken the effect of 24 hour-hypoxia on the intensity of R-123 fluorescence. After exposure to diazoxide for 24 hours, the cell membrane K+ currents and the expression of cell membrane Kv1.5 mRNA and protein in normoxic hPASMCs were significantly decreased compared with control group (P<0.05), but there were no significant changes in these tests after the hPASMCs had been exposed to 5-HD for 24 hours. Also, 24 hour-hypoxia or 24 hour-hypoxia + diazoxide decreased the cell membrane K+ currents and the expression of Kv1.5 mRNA and protein (P<0.05) but the changes were more significant in 24 hour-hypoxia + diazoxide group than in 24 hour-hypoxia group (P<0.05). Again, 5-HD could partly weaken the inhibitory effect of 24 hour-hypoxia on the cell membrane K+ currents and the expression

  8. Effect of combined platinum and electron on the temperature dependence of forward voltage in fast recovery diode

    Science.gov (United States)

    Jia, Yun-Peng; Zhao, Bao; Yang, Fei; Wu, Yu; Zhou, Xuan; Li, Zhe; Tan, Jian

    2015-12-01

    The temperature dependences of forward voltage drop (VF) of the fast recovery diodes (FRDs) are remarkably influenced by different lifetime controlled treatments. In this paper the results of an experimental study are presented, which are the lifetime controls of platinum treatment, electron irradiation treatment, and the combined treatment of the above ones. Based on deep level transient spectroscopy (DLTS) measurements, a new level E6 (EC-0.376 eV) is found in the combined lifetime treated (CLT) sample, which is different from the levels of the individual platinum and electron irradiation ones. Comparing the tested VF results of CLT samples with the others, the level E6 is responsible for the degradation of temperature dependence of the forward voltage drop in the FRD. Project supported by the Doctoral Fund of Ministry of Education of China (Grant No. 20111103120016) and the State Grid Corporation of China Program of Science and Technology, China (Grant No. 5455DW140003).

  9. Comprehensive behavioral analysis of voltage-gated calcium channel beta-anchoring and -regulatory protein knockout mice

    Directory of Open Access Journals (Sweden)

    Takafumi Miki

    2015-06-01

    Full Text Available Calcium (Ca2+ influx through voltage-gated Ca2+ channels (VGCCs induces numerous intracellular events such as neuronal excitability, neurotransmitter release, synaptic plasticity, and gene regulation. It has been shown that genes related to Ca2+ signaling, such as the CACNA1C, CACNB2, and CACNA1I genes that encode VGCC subunits, are associated with schizophrenia and other psychiatric disorders. Recently, VGCC beta-anchoring and -regulatory protein (BARP was identified as a novel regulator of VGCC activity via the interaction of VGCC β subunits. To examine the role of the BARP in higher brain functions, we generated BARP knockout (KO mice and conducted a comprehensive battery of behavioral tests. BARP KO mice exhibited greatly reduced locomotor activity, as evidenced by decreased vertical activity, stereotypic counts in the open field test, and activity level in the home cage, and longer latency to complete a session in spontaneous T-maze alteration test, which reached “study-wide significance”. Acoustic startle response was also reduced in the mutants. Interestingly, they showed multiple behavioral phenotypes that are seemingly opposite to those seen in the mouse models of schizophrenia and its related disorders, including increased working memory, flexibility, prepulse inhibition, and social interaction, and decreased locomotor activity, though many of these phenotypes are statistically weak and require further replications. These results demonstrate that BARP is involved in the regulation of locomotor activity and, possibly, emotionality. The possibility was also suggested that BARP KO mice may serve as a unique tool for investigating the pathogenesis/pathophysiology of schizophrenia and related disorders. Further evaluation of the molecular and physiological phenotypes of the mutant mice would provide new insights into the role of BARP in higher brain functions.

  10. Dependence of effective linear attenuation coefficient on X-ray tube voltage ripple

    International Nuclear Information System (INIS)

    The physical importance of the effective linear coefficient of attenuation μ-bar is described and the basic mathematical relations derived. A calculation program was written for calculating μ-bar. Tabulated are analytical waveforms of voltage U(t) and current i(t) for the tube of the given types of generator. (E.S.). 1 tab., 1 ref

  11. Three Peptide Modulators of the Human Voltage-Gated Sodium Channel 1.7, an Important Analgesic Target, from the Venom of an Australian Tarantula

    OpenAIRE

    Chun Yuen Chow; Ben Cristofori-Armstrong; Undheim, Eivind A.B.; Glenn F. King; Rash, Lachlan D

    2015-01-01

    Voltage-gated sodium (NaV) channels are responsible for propagating action potentials in excitable cells. NaV1.7 plays a crucial role in the human pain signalling pathway and it is an important therapeutic target for treatment of chronic pain. Numerous spider venom peptides have been shown to modulate the activity of NaV channels and these peptides represent a rich source of research tools and therapeutic lead molecules. The aim of this study was to determine the diversity of NaV1.7-active pe...

  12. Properties of BK-type Ca++-dependent K+ channel currents in medial prefrontal cortex (PFC pyramidal neurons in rats of different ages

    Directory of Open Access Journals (Sweden)

    Bartłomiej Paweł Szulczyk

    2013-10-01

    Full Text Available The medial prefrontal cortex (PFC is involved in cognitive functions, which undergo profound changes during adolescence. This alteration of the PFC function derives from neuron activity, which, in turn, may depend on age-dependent properties and the expression of neuronal ion channels. BK-type channels are involved in controlling both the Ca++ ion concentration in the cell interior and cell excitability. The purpose of this study was to test the properties of BK currents in the medial PFC pyramidal neurons of young (18–22-day-old, adolescent (38–42-day-old and adult (58–62-day-old rats. Whole-cell currents evoked by depolarizing voltage steps were recorded from dispersed medial PFC pyramidal neurons. A selective BK channel blocker – paxilline (10 µM – irreversibly decreased the non-inactivating K+ current in neurons that were isolated from the young and adult rats. This current was not significantly affected by paxilline in the neurons obtained from adolescent rats. The properties of single-channel K+ currents were recorded from the soma of dispersed medial PFC pyramidal neurons in the cell-attached configuration. Of the K+ channel currents that were recorded, ~90% were BK and leak channel currents. The BK-type channel currents were dependent on the Ca++ concentration and the voltage and were inhibited by paxilline. The biophysical properties of the BK channel currents did not differ among the pyramidal neurons isolated from young, adolescent and adult rats. Among all of the recorded K+ channel currents, 38.9%, 12.7% and 21.1% were BK-type channel currents in the neurons isolated from the young, adolescent and adult rats, respectively. Furthermore, application of paxilline effectively prolonged the half-width of the action potential in pyramidal neurons in slices isolated from young and adult rats but not in neurons isolated from adolescent rats. We conclude that the availability of BK channel currents decreases in medial PFC

  13. GABAB receptors inhibit low-voltage activated and high-voltage activated Ca(2+) channels in sensory neurons via distinct mechanisms.

    Science.gov (United States)

    Huang, Dongyang; Huang, Sha; Peers, Chris; Du, Xiaona; Zhang, Hailin; Gamper, Nikita

    2015-09-18

    Growing evidence suggests that mammalian peripheral somatosensory neurons express functional receptors for gamma-aminobutyric acid, GABAA and GABAB. Moreover, local release of GABA by pain-sensing (nociceptive) nerve fibres has also been suggested. Yet, the functional significance of GABA receptor triggering in nociceptive neurons is not fully understood. Here we used patch-clamp recordings from small-diameter cultured DRG neurons to investigate effects of GABAB receptor agonist baclofen on voltage-gated Ca(2+) currents. We found that baclofen inhibited both low-voltage activated (LVA, T-type) and high-voltage activated (HVA) Ca(2+) currents in a proportion of DRG neurons by 22% and 32% respectively; both effects were sensitive to Gi/o inhibitor pertussis toxin. Inhibitory effect of baclofen on both current types was about twice less efficacious as compared to that of the μ-opioid receptor agonist DAMGO. Surprisingly, only HVA but not LVA current modulation by baclofen was partially prevented by G protein inhibitor GDP-β-S. In contrast, only LVA but not HVA current modulation was reversed by the application of a reducing agent dithiothreitol (DTT). Inhibition of T-type Ca(2+) current by baclofen and the recovery of such inhibition by DTT were successfully reconstituted in the expression system. Our data suggest that inhibition of LVA current in DRG neurons by baclofen is partially mediated by an unconventional signaling pathway that involves a redox mechanism. These findings reinforce the idea of targeting peripheral GABA receptors for pain relief. PMID:26239659

  14. Influence of Gold Coating and Interplate Voltage on the Performance of Chevron Micro-Channel Plates for the Time and Space Resolved Single Particle Detection

    CERN Document Server

    Hoendervanger, Lynn; Aspect, Alain; Westbrook, Christoph I; Dowek, Danielle; PICARD, Yan; Boiron, Denis

    2012-01-01

    We present a study of two sets of Micro-Channel Plates used for time and space resolved single particle detection. We investigate the effects of the gold layer and that of introducing an interplate voltage between the two chevron plates for the detection of single particles. We find that the gold layer increases the count rate of the detector and the pulse amplitude as previously reported for non-spatially resolved setups. The interplate voltage also increases count rates. In addition, we find that the interplate voltage leads to better spatial accuracy in determining the arrival position of incoming single particles (by 20%) while the gold layer has a negative effect (by 30%).

  15. A structural view of ligand-dependent activation in thermoTRP channels

    Directory of Open Access Journals (Sweden)

    SebastianBrauchi

    2014-05-01

    Full Text Available Transient Receptor Potential (TRP proteins are a large family of ion channels, grouped intoseven sub-families. Although great advances have been made regarding the activation andmodulation of TRP channel activity, detailed molecular mechanisms governing TRPchannel gating are still needed. Sensitive to electric, chemical, mechanical, and thermalcues, TRP channels are tightly associated with the detection and integration of sensoryinput, emerging as a model to study the polymodal activation of ion channel proteins.Among TRP channels, the temperature-activated kind constitute a subgroup by itself,formed by Vanilloid receptors 1-4, Melastatin receptors 2, 4, 5 and 8, TRPC5, and TRPA1.Some of the so-called “thermoTRP” channels participate in the detection of noxious stimulimaking them an interesting pharmacological target for the treatment of pain. However, thepoor specificity of the compounds available in the market represents an important obstacleto overcome. Understanding the molecular mechanics underlying ligand-dependentmodulation of TRP channels may help with the rational design of novel syntheticanalgesics. The present review focuses on the structural basis of ligand-dependentactivation of TRPV1 and TRPM8 channels. Special attention is drawn to the dissection ofligand-binding sites within TRPV1, PIP 2 -dependent modulation of TRP channels, and thestructure of natural and synthetic ligands.

  16. Effect of Gender on the Pharmacokinetics of Eslicarbazepine Acetate (BIA 2-093), a New Voltage-gated Sodium Channel Blocker

    OpenAIRE

    Falcão, Amílcar; Maia, Joana; Almeida, Luís; Mazur, Dago; Gellert, Manfred; Soares-da-Silva, Patrício

    2007-01-01

    Purpose. To determine the effect of gender on the pharmacokinetics of eslicarbazepine acetate, a novel voltage-gated sodium channel blocker in the development for the treatment of epilepsy and bipolar disorder. Methods. Single-centre, open-label, parallel-group study in 12 female and 12 male healthy subjects. The study consisted of a single-dose (600 mg) period and a multiple-dose (600 mg, oncedaily, for 8 days) period, separated by 4 days. Results. Eslicarbazepine acetate w...

  17. 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...

  18. Polymorphism of intron-1 in the voltage-gated sodium channel gene of Anopheles gambiae s.s. populations from Cameroon with emphasis on insecticide knockdown resistance mutations

    OpenAIRE

    Etang, J; Vicente, J. L.; Nwane, P.; Chouaibou, M.; Morlais, Isabelle; Do Rosario, V. E.; Simard, Frédéric; Awono Ambéné, P.; Toto, J. C.; Pinto, J

    2009-01-01

    Sequence variation at the intron-1 of the voltage-gated sodium channel gene in Anopheles gambiae M- and S-forms from Cameroon was assessed to explore the number of mutational events originating knockdown resistance (kdr) alleles. Mosquitoes were sampled between December 2005 and June 2006 from three geographical areas: (i) Magba in the western region; (ii) Loum, Tiko, Douala, Kribi, and Campo along the Atlantic coast; and (iii) Bertoua, in the eastern continental plateau. Both 1014S and 1014F...

  19. Carbon monoxide stimulates Ca2+ -dependent big-conductance K channels in the cortical collecting duct.

    Science.gov (United States)

    Wang, Zhijian; Yue, Peng; Lin, Dao-Hong; Wang, Wen-Hui

    2013-03-01

    We used the patch-clamp technique to examine the role of carbon monoxide (CO) in regulating Ca(2+)-activated big-conductance K (BK) channels in the principal cell of the cortical collecting duct (CCD). Application of CORM3 or CORM2, a CO donor, activated BK channels in the CCD, whereas adding inactivated CORM2/3 had no effect. Superfusion of the CCD with CO-bubbled bath solution also activated the BK channels in the cell-attached patches. The effect of CO on BK channels was not dependent on nitric oxide synthase (NOS) because the effect of CORM3 was also observed in the CCD treated with l-NAME, an agent that inhibits the NOS. Adding a membrane-permeable cGMP analog, 8-bromo-cGMP, significantly increased the BK channel in the CCD. However, inhibition of soluble guanylate cyclase failed to abolish the stimulatory effect of CORM3 on BK channels. Moreover, inhibition of cGMP-dependent protein kinase G did not block the stimulatory effect of CORM3 on the BK channels, suggesting that the stimulatory effect of CO on the BK channels was, at least partially, induced by a cGMP-independent mechanism. Western blot demonstrated that heme oxygenase type 1 (HO-1) and HO-2 were expressed in the kidney. Moreover, a high-K (HK) intake increased the expression of HO-1 but not HO-2 in the kidney. A HK intake also increased renal HO activity defined by NADPH-dependent CO generation following addition of heme in the cell lysate from renal cortex and outer medulla. The role of HO in regulating BK channel activity in the CCD was also suggested by experiments in which application of hemin increased the BK channels. The stimulatory effect of hemin on the BK channels was blocked by SnMP, a HO inhibitor. But, adding CORM3 was still able to activate the BK channels in the presence of SnMP. We conclude that CO activates the BK channels, at least partially, through a NO-cGMP-independent pathway and that HO plays a role in mediating the effect of HK intake on the BK channels in the CCD. PMID

  20. Nonlinear voltage dependence of the shot noise in mesoscopic degenerate conductors with strong electron-electron scattering

    OpenAIRE

    Mishchenko, E. G.

    2000-01-01

    It is shown that measurements of zero-frequency shot-noise can provide information on electron-electron interaction, because the strong interaction results in the nonlinear voltage dependence of the shot noise in metallic wires. This is due to the fact that the Wiedemann-Franz law is no longer valid in the case of considerable electron-electron interaction. The deviations from this law increase the noise power and make it dependent strongly on the ratio of electron-electron and electron-impur...