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Sample records for voltage-gated sodium potassium

  1. Whole-cell recordings of voltage-gated Calcium, Potassium and Sodium currents in acutely isolated hippocampal pyramidal neurons

    Institute of Scientific and Technical Information of China (English)

    Shuyun Huang; Qing Cai; Weitian Liu; Xiaoling Wang; Tao Wang

    2009-01-01

    Objective:To record Calcium, Potassium and Sodium currents in acutely isolated hippocampal pyramidal neurons. Methods:Hip-pocampal CA3 neurons were freshly isolated by 1 mg protease/3 ml SES and mechanical trituration with polished pipettes of progressively smaller tip diameters. Patch clamp technique in whole-cell mode was employed to record voltage-gated channel currents. Results:The procedure dissociated hippocampal neurons, preserving apical dendrites and several basal dendrites, without impairing the electrical characteristics of the neurons. Whole-cell patch clamp configuration was successfully used to record voltage-gated Ca2+ currents, delayed rectifier K+ current and voltage-gated Na+ currents. Conclusion:Protease combined with mechanical trituration may be used for the dissociation of neurons from rat hippocampus. Voltage-gated channels currents could be recorded using a patch clamp technique.

  2. VKCDB: Voltage-gated potassium channel database

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    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.

  3. Neuronal trafficking of voltage-gated potassium channels

    DEFF Research Database (Denmark)

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

    2011-01-01

    The computational ability of CNS neurons depends critically on the specific localization of ion channels in the somatodendritic and axonal membranes. Neuronal dendrites receive synaptic inputs at numerous spines and integrate them in time and space. The integration of synaptic potentials....... The 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...... is regulated by voltage-gated potassium (Kv) channels, such as Kv4.2, which are specifically localized in the dendritic membrane. The synaptic potentials eventually depolarize the membrane of the axon initial segment, thereby activating voltage-gated sodium channels to generate action potentials. Specific Kv...

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

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    Rikard eBlunck

    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

  5. Sleep disturbances in voltage-gated potassium channel antibody syndrome.

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    Barone, Daniel A; Krieger, Ana C

    2016-05-01

    Voltage-gated potassium channels (VGKCs) are a family of membrane proteins responsible for controlling cell membrane potential. The presence of antibodies (Ab) against neuronal VGKC complexes aids in the diagnosis of idiopathic and paraneoplastic autoimmune neurologic disorders. The diagnosis of VGKC Ab-associated encephalopathy (VCKC Ab syndrome) should be suspected in patients with subacute onset of disorientation, confusion, and memory loss in the presence of seizures or a movement disorder. VGKC Ab syndrome may present with sleep-related symptoms, and the purpose of this communication is to alert sleep and neurology clinicians of this still-under-recognized condition. In this case, we are presenting the VGKC Ab syndrome which improved after treatment with solumedrol. The prompt recognition and treatment of this condition may prevent the morbidity associated with cerebral atrophy and the mortality associated with intractable seizures and electrolyte disturbances.

  6. Excitability constraints on voltage-gated sodium channels.

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    Elaine Angelino

    2007-09-01

    Full Text Available We study how functional constraints bound and shape evolution through an analysis of mammalian voltage-gated sodium channels. The primary function of sodium channels is to allow the propagation of action potentials. Since Hodgkin and Huxley, mathematical models have suggested that sodium channel properties need to be tightly constrained for an action potential to propagate. There are nine mammalian genes encoding voltage-gated sodium channels, many of which are more than approximately 90% identical by sequence. This sequence similarity presumably corresponds to similarity of function, consistent with the idea that these properties must be tightly constrained. However, the multiplicity of genes encoding sodium channels raises the question: why are there so many? We demonstrate that the simplest theoretical constraints bounding sodium channel diversity--the requirements of membrane excitability and the uniqueness of the resting potential--act directly on constraining sodium channel properties. We compare the predicted constraints with functional data on mammalian sodium channel properties collected from the literature, including 172 different sets of measurements from 40 publications, wild-type and mutant, under a variety of conditions. The data from all channel types, including mutants, obeys the excitability constraint; on the other hand, channels expressed in muscle tend to obey the constraint of a unique resting potential, while channels expressed in neuronal tissue do not. The excitability properties alone distinguish the nine sodium channels into four different groups that are consistent with phylogenetic analysis. Our calculations suggest interpretations for the functional differences between these groups.

  7. Voltage-gated sodium channels: mutations, channelopathies and targets.

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    Andavan, G S B; Lemmens-Gruber, R

    2011-01-01

    Voltage-gated sodium channels produce fast depolarization, which is responsible for the rising phase of the action potential in neurons, muscles and heart. These channels are very large membrane proteins and are encoded by ten genes in mammals. Sodium channels are a crucial component of excitable tissues; hence, they are a target for various neurotoxins that are produced by plants and animals for defence and protection, such as tetrodotoxin, scorpion toxins and batrachotoxin. Several mutations in various sodium channel subtypes cause multiple inherited diseases known as channelopathies. When these mutated sodium channel subtypes are expressed in various tissues, channelopathies in brain, skeletal muscle and cardiac muscle develop as well as neuropathic pain. In this review, we discuss aspects of voltage-gated sodium channel genes with an emphasis on cardiac muscle sodium channels. In addition, we report novel mutations that underlie a spectrum of diseases, such as Brugada, long QT syndrome and inherited conduction disorders. Furthermore, this review explains commonalities and differences among the channel subtypes, the channelopathies caused by the sodium channel gene mutation and the specificity of toxins and blockers of the channel subtypes.

  8. Voltage-gated sodium channels in taste bud cells

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    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.

  9. Genistein inhibition of OGD-induced brain neuron death correlates with its modulation of apoptosis, voltage-gated potassium and sodium currents and glutamate signal pathway.

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    Ma, Xue-Ling; Zhang, Feng; Wang, Yu-Xiang; He, Cong-Cong; Tian, Kun; Wang, Hong-Gang; An, Di; Heng, Bin; Liu, Yan-Qiang

    2016-07-25

    In the present study, we established an in vitro model of hypoxic-ischemia via exposing primary neurons of newborn rats to oxygen-glucose deprivation (OGD) and observing the effects of genistein, a soybean isoflavone, on hypoxic-ischemic neuron viability, apoptosis, voltage-activated potassium (Kv) and sodium (Nav) currents, and glutamate receptor subunits. The results indicated that OGD exposure reduced the viability and increased the apoptosis of brain neurons. Meanwhile, OGD exposure caused changes in the current-voltage curves and current amplitude values of voltage-activated potassium and sodium currents; OGD exposure also decreased GluR2 expression and increased NR2 expression. However, genistein at least partially reversed the effects caused by OGD. The results suggest that hypoxic-ischemia-caused neuronal apoptosis/death is related to an increase in K(+) efflux, a decrease in Na(+) influx, a down-regulation of GluR2, and an up-regulation of NR2. Genistein may exert some neuroprotective effects via the modulation of Kv and Nav currents and the glutamate signal pathway, mediated by GluR2 and NR2.

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

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    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. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Voltage-gated sodium channels: biophysics, pharmacology, and related channelopathies

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    Eleonora eSavio Galimberti

    2012-07-01

    Full Text Available Voltage-gated sodium channels (VGSC are multi-molecular protein complexes expressed in both excitable and non-excitable cells. They are primarily formed by a pore-forming multi-spanning integral membrane glycoprotein (α-subunit that can be associated with one or more regulatory β-subunits. The latter are single-span integral membrane proteins that modulate the sodium current (INa and can also function as cell-adhesion molecules (CAMs. In-vitro some of the cell-adhesive functions of the β-subunits may play important physiological roles independently of the α-subunits. Other endogenous regulatory proteins named channel partners or channel interacting proteins (ChiPs like caveolin-3 and calmodulin/calmodulin kinase II (CaMKII can also interact and modulate the expression and/or function of VGSC. In addition to their physiological roles in cell excitability and cell adhesion, VGSC are the site of action of toxins (like tetrodotoxin and saxitoxin, and pharmacologic agents (like antiarrhythmic drugs, local anesthetics, antiepileptic drugs, and newly developed analgesics. Mutations in genes that encode α- and/or β-subunits as well as the ChiPs can affect the structure and biophysical properties of VGSC, leading to the development of diseases termed sodium channelopathies. This review will outline the structure, function and biophysical properties of VGSC as well as their pharmacology and associated channelopathies and highlight some of the recent advances in this field

  12. Voltage-Gated Sodium Channels: Biophysics, Pharmacology, and Related Channelopathies

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    Savio-Galimberti, Eleonora; Gollob, Michael H.; Darbar, Dawood

    2012-01-01

    Voltage-gated sodium channels (VGSC) are multi-molecular protein complexes expressed in both excitable and non-excitable cells. They are primarily formed by a pore-forming multi-spanning integral membrane glycoprotein (α-subunit) that can be associated with one or more regulatory β-subunits. The latter are single-span integral membrane proteins that modulate the sodium current (INa) and can also function as cell adhesion molecules. In vitro some of the cell-adhesive functions of the β-subunits may play important physiological roles independently of the α-subunits. Other endogenous regulatory proteins named “channel partners” or “channel interacting proteins” (ChiPs) like caveolin-3 and calmodulin/calmodulin kinase II (CaMKII) can also interact and modulate the expression and/or function of VGSC. In addition to their physiological roles in cell excitability and cell adhesion, VGSC are the site of action of toxins (like tetrodotoxin and saxitoxin), and pharmacologic agents (like antiarrhythmic drugs, local anesthetics, antiepileptic drugs, and newly developed analgesics). Mutations in genes that encode α- and/or β-subunits as well as the ChiPs can affect the structure and biophysical properties of VGSC, leading to the development of diseases termed sodium “channelopathies”.  This review will outline the structure, function, and biophysical properties of VGSC as well as their pharmacology and associated channelopathies and highlight some of the recent advances in this field. PMID:22798951

  13. 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...

  14. Marine Toxins That Target Voltage-gated Sodium Channels

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    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.

  15. [Progress in sodium channelopathies and biological functions of voltage-gated sodium channel blockers].

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    Wang, Hongyan; Gou, Meng; Xiao, Rong; Li, Qingwei

    2014-06-01

    Voltage-gated sodium channels (VGSCs), which are widely distributed in the excitable cells, are the primary mediators of electrical signal amplification and propagation. They play important roles in the excitative conduction of the neurons and cardiac muscle cells. The abnormalities of the structures and functions of VGSCs can change the excitability of the cells, resulting in a variety of diseases such as neuropathic pain, epilepsy and arrhythmia. At present, some voltage-gated sodium channel blockers are used for treating those diseases. In the recent years, several neurotoxins have been purified from the venom of the animals, which could inhibit the current of the voltage-gated sodium channels. Usually, these neurotoxins are compounds or small peptides that have been further designed and modified for targeted drugs of sodium channelopathies in the clinical treatment. In addition, a novel cysteine-rich secretory protein (CRBGP) has been isolated and purified from the buccal gland of the lampreys (Lampetra japonica), and it could inhibit the Na+ current of the hippocampus and dorsal root neurons for the first time. In the present study, the progress of the sodium channelopathies and the biological functions of voltage-gated sodium channel blockers are analyzed and summarized.

  16. The voltage-gated potassium channel subunit, Kv1.3, is expressed in epithelia

    DEFF Research Database (Denmark)

    Grunnet, Morten; Rasmussen, Hanne B; Hay-Schmidt, Anders;

    2003-01-01

    The Shaker-type voltage-gated potassium channel, Kv1.3, is believed to be restricted in distribution to lymphocytes and neurons. In lymphocytes, this channel has gained intense attention since it has been proven that inhibition of Kv1.3 channels compromise T lymphocyte activation. To investigate...

  17. 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

  18. Voltage-gated potassium channelopathy: an expanding spectrum of clinical phenotypes.

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    Shribman, Sam; Patani, Rickie; Deeb, Jacquie; Chaudhuri, Abhijit

    2013-01-10

    Autoimmune voltage-gated potassium channelopathies represent a wide and expanding spectrum of neurological conditions. We present a case demonstrating the phenotypic heterogeneity of antivoltage-gated potassium channels (VGKC)-associated disorders. Such cases may easily be dismissed as functional disorders at first presentation. We propose that there must remain a high index of suspicion for antiVGKC-associated disorders in cases where there are transient neurological disturbances in atypical spatial and temporal distributions.

  19. An update on transcriptional and post-translational regulation of brain voltage-gated sodium channels.

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    Onwuli, Donatus O; Beltran-Alvarez, Pedro

    2016-03-01

    Voltage-gated sodium channels are essential proteins in brain physiology, as they generate the sodium currents that initiate neuronal action potentials. Voltage-gated sodium channels expression, localisation and function are regulated by a range of transcriptional and post-translational mechanisms. Here, we review our understanding of regulation of brain voltage-gated sodium channels, in particular SCN1A (NaV1.1), SCN2A (NaV1.2), SCN3A (NaV1.3) and SCN8A (NaV1.6), by transcription factors, by alternative splicing, and by post-translational modifications. Our focus is strongly centred on recent research lines, and newly generated knowledge.

  20. Encephalitis due to antibodies to voltage gated potassium channel (VGKC with cerebellar involvement in a teenager

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    Megan M Langille

    2015-01-01

    Full Text Available Encephalitis due to antibodies to voltage gated potassium channel (VGKC typically presents with limbic encephalitis and medial temporal lobe involvement on neuroimaging. We describe a case of 13 year girl female with encephalitis due to antibodies to VGKC with signal changes in the cerebellar dentate nuclei bilaterally and clinical features that suggested predominant cerebellar involvement. These have never been reported previously in the literature. Our case expands the phenotypic spectrum of this rare condition.

  1. Encephalitis due to antibodies to voltage gated potassium channel (VGKC) with cerebellar involvement in a teenager.

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    Langille, Megan M; Desai, Jay

    2015-01-01

    Encephalitis due to antibodies to voltage gated potassium channel (VGKC) typically presents with limbic encephalitis and medial temporal lobe involvement on neuroimaging. We describe a case of 13 year girl female with encephalitis due to antibodies to VGKC with signal changes in the cerebellar dentate nuclei bilaterally and clinical features that suggested predominant cerebellar involvement. These have never been reported previously in the literature. Our case expands the phenotypic spectrum of this rare condition.

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

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    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.

  3. Designing a C84 fullerene as a specific voltage-gated sodium channel blocker

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    Hilder, Tamsyn A.; Chung, Shin-Ho

    2013-07-01

    Fullerene derivatives demonstrate considerable potential for numerous biological applications, such as the effective inhibition of HIV protease. Recently, they were identified for their ability to indiscriminately block biological ion channels. A fullerene derivative which specifically blocks a particular ion channel could lead to a new set of drug leads for the treatment of various ion channel-related diseases. Here, we demonstrate their extraordinary potential by designing a fullerene which mimics some of the functions of μ-conotoxin, a peptide derived from cone snail venom which potently binds to the bacterial voltage-gated sodium channel (NavAb). We show, using molecular dynamics simulations, that the C84 fullerene with six lysine derivatives uniformly attached to its surface is selective to NavAb over a voltage-gated potassium channel (Kv1.3). The side chain of one of the lysine residues protrudes into the selectivity filter of the channel, while the methionine residues located just outside of the channel form hydrophobic contacts with the carbon atoms of the fullerene. The modified C84 fullerene strongly binds to the NavAb channel with an affinity of 46 nM but binds weakly to Kv1.3 with an affinity of 3 mM. This potent blocker of NavAb may serve as a structural template from which potent compounds can be designed for the targeting of mammalian Nav channels. There is a genuine need to target mammalian Nav channels as a form of treatment of various diseases which have been linked to their malfunction, such as epilepsy and chronic pain.

  4. Regulation of voltage-gated sodium current by endogenous Src family kinases in cochlear spiral ganglion neurons in culture.

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    Feng, Shuang; Pflueger, Melissa; Lin, Shuang-Xiu; Groveman, Bradley R; Su, Jiping; Yu, Xian-Min

    2012-04-01

    Voltage-gated sodium (Na+) and potassium (K+)channels have been found to be regulated by Src family kinases(SFKs).However, how these channels are regulated by SFKs in cochlear spiral ganglion neurons (SGNs) remains unknown.Here, we report that altering the activity of endogenous SFKs modulated voltage-gated Na+, but not K+, currents recorded in embryonic SGNs in culture. Voltage-gated Na+ current was suppressed by inhibition of endogenous SFKs or just Src and potentiated by the activation of these enzymes. Detailed investigations showed that under basal conditions, SFK inhibitor application did not significantly affect the voltage-dependent activation, but shifted the steady-state inactivation curves of Na+ currents and delayed the recovery of Na+ currents from inactivation. Application of Src specific inhibitor, Src40–58,not only shifted the inactivation curve but also delayed the recovery of Na+ currents and moved the voltage-dependent activation curve towards the left. The pre-inhibition of SFKs occluded all the effects induced by Src40–58 application, except the left shift of the activation curve. The activation of SFKs did not change either steady-state inactivation or recovery of Na+ currents, but caused the left shift of the activation curve.SFK inhibitor application effectively prevented all the effects induced by SFK activation, suggesting that both the voltage-dependent activation and steady-state inactivation of Na+ current are subjects of SFK regulation. The different effects induced by activation versus inhibition of SFKs implied that under basal conditions, endogenously active and inactive SFKs might be differentially involved in the regulation of voltage-gated Na+ channels in SGNs.

  5. Modeling of the Binding of Peptide Blockers to Voltage-Gated Potassium Channels: Approaches and Evidence.

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    Novoseletsky, V N; Volyntseva, A D; Shaitan, K V; Kirpichnikov, M P; Feofanov, A V

    2016-01-01

    Modeling of the structure of voltage-gated potassium (KV) channels bound to peptide blockers aims to identify the key amino acid residues dictating affinity and provide insights into the toxin-channel interface. Computational approaches open up possibilities for in silico rational design of selective blockers, new molecular tools to study the cellular distribution and functional roles of potassium channels. It is anticipated that optimized blockers will advance the development of drugs that reduce over activation of potassium channels and attenuate the associated malfunction. Starting with an overview of the recent advances in computational simulation strategies to predict the bound state orientations of peptide pore blockers relative to KV-channels, we go on to review algorithms for the analysis of intermolecular interactions, and then take a look at the results of their application.

  6. Neuregulin directly decreases voltage-gated sodium current in hippocampal ErbB4-expressing interneurons.

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    Janssen, Megan J; Leiva-Salcedo, Elias; Buonanno, Andres

    2012-10-03

    The Neuregulin 1 (NRG1)/ErbB4 signaling pathway has been genetically and functionally implicated in the etiology underlying schizophrenia, and in the regulation of glutamatergic pyramidal neuron function and plasticity. However, ErbB4 receptors are expressed in subpopulations of GABAergic interneurons, but not in hippocampal or cortical pyramidal neurons, indicating that NRG1 effects on principal neurons are indirect. Consistent with these findings, NRG1 effects on hippocampal long-term potentiation at CA1 pyramidal neuron synapses in slices are mediated indirectly by dopamine. Here we studied whether NRG/ErbB signaling directly regulates interneuron intrinsic excitability by pharmacologically isolating ErbB4-expressing neurons in rat dissociated hippocampal cultures, which lack dopaminergic innervation. We found that NRG1 acutely attenuates ErbB4-expressing interneuron excitability by depolarizing the firing threshold; neurons treated with the pan-ErbB inhibitor PD158780 or negative for ErbB4 were unaffected. These effects of NRG1 are primarily attributable to decreased voltage-gated sodium channel activity, as current density was attenuated by ∼60%. In stark contrast, NRG1 had minor effects on whole-cell potassium currents. Our data reveal the direct actions of NRG1 signaling in ErbB4-expressing interneurons, and offer novel insight into how NRG1/ErbB4 signaling can impact hippocampal activity.

  7. Effect of genistein on voltage-gated potassium channels in guinea pig proximal colon smooth muscle cells

    Institute of Scientific and Technical Information of China (English)

    Shi-Ying Li; Bin-Bin Huang; Shou Ouyang

    2006-01-01

    AIM: To investigate the action of genistein (GST), a broad spectrum tyrosine kinase inhibitor, on voltagegated potassium channels in guinea pig proximal colon smooth muscle cells.METHODS: Smooth muscle cells in guinea pig proximal colon were enzymatically isolated. Nystatin-perforated whole cell patch clamp technique was used to record potassium currents including fast transient outward current (IKto) and delayed rectifier current (IKdr), two of which were isolated pharmacologically with 10 mmol/L tetraethylammonium or 5 mmol/L 4-aminopyridine.Contamination of calcium-dependent potassium currents was minimized with no calcium and 0.2 mmol/L CdCl2 in an external solution.RESULTS: GST (10-100 μmol/L) reversibly and dosedependently reduced the peak amplitude of IKto with an IC50value of 22.0±6.9 μmol/L. To a lesser extent, IKdr was also inhibited in both peak current and sustained current.GST could not totally block the outward potassium current as a fraction of the outWard potassium current,which was insensitive to GST. GST had no effect on the steady-state activation (n = 6) and inactivation kinetics(n =6) of IKto. Sodium orthovanadate (1 mmol/L), a potent inhibitor of tyrosine phosphatase, significantly inhibited GST-induced inhibition (P< 0.05).CONCLUSION: GST can dose-dependently and reversibly block voltage-gated potassium channels in guinea pig proximal colon smooth muscle cells.

  8. Flufenamic acid decreases neuronal excitability through modulation of voltage-gated sodium channel gating.

    Science.gov (United States)

    Yau, Hau-Jie; Baranauskas, Gytis; Martina, Marco

    2010-10-15

    The electrophysiological phenotype of individual neurons critically depends on the biophysical properties of the voltage-gated channels they express. Differences in sodium channel gating are instrumental in determining the different firing phenotypes of pyramidal cells and interneurons; moreover, sodium channel modulation represents an important mechanism of action for many widely used CNS drugs. Flufenamic acid (FFA) is a non-steroidal anti-inflammatory drug that has been long used as a blocker of calcium-dependent cationic conductances. Here we show that FFA inhibits voltage-gated sodium currents in hippocampal pyramidal neurons; this effect is dose-dependent with IC(50) = 189 μm. We used whole-cell and nucleated patch recordings to investigate the mechanisms of FFA modulation of TTX-sensitive voltage-gated sodium current. Our data show that flufenamic acid slows down the inactivation process of the sodium current, while shifting the inactivation curve ~10 mV toward more hyperpolarized potentials. The recovery from inactivation is also affected in a voltage-dependent way, resulting in slower recovery at hyperpolarized potentials. Recordings from acute slices demonstrate that FFA reduces repetitive- and abolishes burst-firing in CA1 pyramidal neurons. A computational model based on our data was employed to better understand the mechanisms of FFA action. Simulation data support the idea that FFA acts via a novel mechanism by reducing the voltage dependence of the sodium channel fast inactivation rates. These effects of FFA suggest that it may be an effective anti-epileptic drug.

  9. Modulation of voltage-gated potassium Kv2.1 via the cytoplasmic C terminal

    Institute of Scientific and Technical Information of China (English)

    Man Jin; Peiyuan Lu

    2011-01-01

    Voltage-gated potassium channels comprise 12 subtypes (Kv1-Kv12). Kv2.1, which is expressed in most mammalian central neurons, provides the majority of delayed-rectifier K current in cortical and hippocampal pyramidal neurons, and plays an especially prominent role in repolarizing membrane potential, as well as in facilitation of exocytosis. Kv2.1-encoded K efflux is essential for neuronal apoptosis programming. The human form of the Kv2.1 potassium channel contains large intracellular regions. The cytoplasmic C-terminal plays a key role in modulating Kv2.1 gating. The present manuscript summarized Kv2.1 structure and modulation in neurons and analyzed the roles of the cytoplasmic C-terminal.

  10. The Structural Basis and Functional Consequences of Interactions Between Tetrodotoxin and Voltage-Gated Sodium Channels

    Directory of Open Access Journals (Sweden)

    C. Ruben

    2006-04-01

    Full Text Available Abstract: Tetrodotoxin (TTX is a highly specific blocker of voltage-gated sodium channels. The dissociation constant of block varies with different channel isoforms. Until recently, channel resistance was thought to be primarily imparted by amino acid substitutions at a single position in domain I. Recent work reveals a novel site for tetrodotoxin resistance in the P-region of domain IV.

  11. Developmental expression of Kv1 voltage-gated potassium channels in the avian hypothalamus.

    Science.gov (United States)

    Doczi, Megan A; Vitzthum, Carl M; Forehand, Cynthia J

    2016-03-11

    Specialized hypothalamic neurons integrate the homeostatic balance between food intake and energy expenditure, processes that may become dysregulated during the development of diabetes, obesity, and other metabolic disorders. Shaker family voltage-gated potassium channels (Kv1) contribute to the maintenance of resting membrane potential, action potential characteristics, and neurotransmitter release in many populations of neurons, although hypothalamic Kv1 channel expression has been largely unexplored. Whole-cell patch clamp recordings from avian hypothalamic brain slices demonstrate a developmental shift in the electrophysiological properties of avian arcuate nucleus neurons, identifying an increase in outward ionic current that corresponds with action potential maturation. Additionally, RT-PCR experiments identified the early expression of Kv1.2, Kv1.3, and Kv1.5 mRNA in the embryonic avian hypothalamus, suggesting that these channels may underlie the electrophysiological changes observed in these neurons. Real-time quantitative PCR analysis on intact microdissections of embryonic hypothalamic tissue revealed a concomitant increase in Kv1.2 and Kv1.5 gene expression at key electrophysiological time points during development. This study is the first to demonstrate hypothalamic mRNA expression of Kv1 channels in developing avian embryos and may suggest a role for voltage-gated ion channel regulation in the physiological patterning of embryonic hypothalamic circuits governing energy homeostasis. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  12. Bidirectional regulation of dendritic voltage-gated potassium channels by the fragile X mental retardation protein.

    Science.gov (United States)

    Lee, Hye Young; Ge, Woo-Ping; Huang, Wendy; He, Ye; Wang, Gordon X; Rowson-Baldwin, Ashley; Smith, Stephen J; Jan, Yuh Nung; Jan, Lily Yeh

    2011-11-17

    How transmitter receptors modulate neuronal signaling by regulating voltage-gated ion channel expression remains an open question. Here we report dendritic localization of mRNA of Kv4.2 voltage-gated potassium channel, which regulates synaptic plasticity, and its local translational regulation by fragile X mental retardation protein (FMRP) linked to fragile X syndrome (FXS), the most common heritable mental retardation. FMRP suppression of Kv4.2 is revealed by elevation of Kv4.2 in neurons from fmr1 knockout (KO) mice and in neurons expressing Kv4.2-3'UTR that binds FMRP. Moreover, treating hippocampal slices from fmr1 KO mice with Kv4 channel blocker restores long-term potentiation induced by moderate stimuli. Surprisingly, recovery of Kv4.2 after N-methyl-D-aspartate receptor (NMDAR)-induced degradation also requires FMRP, likely due to NMDAR-induced FMRP dephosphorylation, which turns off FMRP suppression of Kv4.2. Our study of FMRP regulation of Kv4.2 deepens our knowledge of NMDAR signaling and reveals a FMRP target of potential relevance to FXS.

  13. Thalamic microinfusion of antibody to a voltage-gated potassium channel restores consciousness during anesthesia.

    Science.gov (United States)

    Alkire, Michael T; Asher, Christopher D; Franciscus, Amanda M; Hahn, Emily L

    2009-04-01

    The Drosophila Shaker mutant fruit-fly, with its malfunctioning voltage-gated potassium channel, exhibits anesthetic requirements that are more than twice normal. Shaker mutants with an abnormal Kv1.2 channel also demonstrate significantly reduced sleep. Given the important role the thalamus plays in both sleep and arousal, the authors investigated whether localized central medial thalamic (CMT) microinfusion of an antibody designed to block the pore of the Kv1.2 channel might awaken anesthetized rats. Male Sprague-Dawley rats were implanted with a cannula aimed at the CMT or lateral thalamus. One week later, unconsciousness was induced with either desflurane (3.6 +/- 0.2%; n = 55) or sevoflurane (1.2 +/- 0.1%; n = 51). Arousal effects of a single 0.5-microl infusion of Kv1.2 potassium channel blocking antibody (0.1- 0.2 mg/ml) or a control infusion of Arc-protein antibody (0.2 mg/ml) were then determined. The Kv1.2 antibody, but not the control antibody, temporarily restored consciousness in 17% of all animals and in 75% of those animals where infusions occurred within the CMT (P Consciousness returned on average (+/- SD) 170 +/- 99 s after infusion and lasted a median time of 398 s (interquartile range: 279-510 s). Temporary seizures, without apparent consciousness, predominated in 33% of all animals. These findings support the idea that the CMT plays a role in modulating levels of arousal during anesthesia and further suggest that voltage-gated potassium channels in the CMT may contribute to regulating arousal or may even be relevant targets of anesthetic action.

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

    Science.gov (United States)

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

    2014-06-05

    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 the rare instance when a positive VGKC complex antibody titre occurs in a definite case of prion disease. We present a pathologically and genetically confirmed case of CJD with elevated serum VGKC complex antibody titres. This case highlights the importance of interpreting the result of a positive VGKC complex antibody with caution and in the context of the overall clinical manifestation.

  15. 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.

  16. High grade glioma mimicking voltage gated potassium channel complex associated antibody limbic encephalitis.

    Science.gov (United States)

    Athauda, Dilan; Delamont, R S; Pablo-Fernandez, E De

    2014-01-01

    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.

  17. 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.

  18. 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.

  19. Ionic selectivity and thermal adaptations within the voltage-gated sodium channel family of alkaliphilic Bacillus.

    Science.gov (United States)

    DeCaen, Paul G; Takahashi, Yuka; Krulwich, Terry A; Ito, Masahiro; Clapham, David E

    2014-11-11

    Entry and extrusion of cations are essential processes in living cells. In alkaliphilic prokaryotes, high external pH activates voltage-gated sodium channels (Nav), which allows Na(+) to enter and be used as substrate for cation/proton antiporters responsible for cytoplasmic pH homeostasis. Here, we describe a new member of the prokaryotic voltage-gated Na(+) channel family (NsvBa; Non-selective voltage-gated, Bacillus alcalophilus) that is nonselective among Na(+), Ca(2+) and K(+) ions. Mutations in NsvBa can convert the nonselective filter into one that discriminates for Na(+) or divalent cations. Gain-of-function experiments demonstrate the portability of ion selectivity with filter mutations to other Bacillus Nav channels. Increasing pH and temperature shifts their activation threshold towards their native resting membrane potential. Furthermore, we find drugs that target Bacillus Nav channels also block the growth of the bacteria. This work identifies some of the adaptations to achieve ion discrimination and gating in Bacillus Nav channels.

  20. 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.

  1. Kv3 voltage-gated potassium channels regulate neurotransmitter release from mouse motor nerve terminals.

    Science.gov (United States)

    Brooke, Ruth E; Moores, Thomas S; Morris, Neil P; Parson, Simon H; Deuchars, Jim

    2004-12-01

    Voltage-gated potassium (Kv) channels are critical to regulation of neurotransmitter release throughout the nervous system but the roles and identity of the subtypes involved remain unclear. Here we show that Kv3 channels regulate transmitter release at the mouse neuromuscular junction (NMJ). Light- and electron-microscopic immunohistochemistry revealed Kv3.3 and Kv3.4 subunits within all motor nerve terminals of muscles examined [transversus abdominus, lumbrical and flexor digitorum brevis (FDB)]. To determine the roles of these Kv3 subunits, intracellular recordings were made of end-plate potentials (EPPs) in FDB muscle fibres evoked by electrical stimulation of tibial nerve. Tetraethylammonium (TEA) applied at low concentrations (0.05-0.5 mM), which blocks only a few known potassium channels including Kv3 channels, did not affect muscle fibre resting potential but significantly increased the amplitude of all EPPs tested. Significantly, this effect of TEA was still observed in the presence of the large-conductance calcium-activated potassium channel blockers iberiotoxin (25-150 nM) and Penitrem A (100 nM), suggesting a selective action on Kv3 subunits. Consistent with this, 15-microM 4-aminopyridine, which blocks Kv3 but not large-conductance calcium-activated potassium channels, enhanced evoked EPP amplitude. Unexpectedly, blood-depressing substance-I, a toxin selective for Kv3.4 subunits, had no effect at 0.05-1 microM. The combined presynaptic localization of Kv3 subunits and pharmacological enhancement of EPP amplitude indicate that Kv3 channels regulate neurotransmitter release from presynaptic terminals at the NMJ.

  2. A novel mechanism for fine-tuning open-state stability in a voltage-gated potassium channel

    DEFF Research Database (Denmark)

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

    2013-01-01

    Voltage-gated potassium channels elicit membrane hyperpolarization through voltage-sensor domains that regulate the conductive status of the pore domain. To better understand the inherent basis for the open-closed equilibrium in these channels, we undertook an atomistic scan using synthetic fluor...... that the intrinsic open-state destabilization via aromatic repulsion represents a new mechanism by which ion channels, and likely other proteins, fine-tune conformational equilibria.......Voltage-gated potassium channels elicit membrane hyperpolarization through voltage-sensor domains that regulate the conductive status of the pore domain. To better understand the inherent basis for the open-closed equilibrium in these channels, we undertook an atomistic scan using synthetic...... fluorinated derivatives of aromatic residues previously implicated in the gating of Shaker potassium channels. Here we show that stepwise dispersion of the negative electrostatic surface potential of only one site, Phe481, stabilizes the channel open state. Furthermore, these data suggest that this apparent...

  3. Brivaracetam Differentially Affects Voltage-Gated Sodium Currents Without Impairing Sustained Repetitive Firing in Neurons

    Science.gov (United States)

    Niespodziany, Isabelle; André, Véronique Marie; Leclère, Nathalie; Hanon, Etienne; Ghisdal, Philippe; Wolff, Christian

    2015-01-01

    Aims Brivaracetam (BRV) is an antiepileptic drug in Phase III clinical development. BRV binds to synaptic vesicle 2A (SV2A) protein and is also suggested to inhibit voltage-gated sodium channels (VGSCs). To evaluate whether the effect of BRV on VGSCs represents a relevant mechanism participating in its antiepileptic properties, we explored the pharmacology of BRV on VGSCs in different cell systems and tested its efficacy at reducing the sustained repetitive firing (SRF). Methods Brivaracetam investigations on the voltage-gated sodium current (INa) were performed in N1E-155 neuroblastoma cells, cultured rat cortical neurons, and adult mouse CA1 neurons. SRF was measured in cultured cortical neurons and in CA1 neurons. All BRV (100–300 μM) experiments were performed in comparison with 100 μM carbamazepine (CBZ). Results Brivaracetam and CBZ reduced INa in N1E-115 cells (30% and 40%, respectively) and primary cortical neurons (21% and 47%, respectively) by modulating the fast-inactivated state of VGSCs. BRV, in contrast to CBZ, did not affect INa in CA1 neurons and SRF in cortical and CA1 neurons. CBZ consistently inhibited neuronal SRF by 75–93%. Conclusions The lack of effect of BRV on SRF in neurons suggests that the reported inhibition of BRV on VGSC currents does not contribute to its antiepileptic properties. PMID:25444522

  4. Actions of a hydrogen sulfide donor (NaHS) on transient sodium, persistent sodium, and voltage-gated calcium currents in neurons of the subfornical organ.

    Science.gov (United States)

    Kuksis, Markus; Ferguson, Alastair V

    2015-09-01

    Hydrogen sulfide (H2S) is an endogenously found gasotransmitter that has been implicated in a variety of beneficial physiological functions. This study was performed to investigate the cellular mechanisms underlying actions of H2S previously observed in subfornical organ (SFO), where H2S acts to regulate blood pressure through a depolarization of the membrane and an overall increase in the excitability of SFO neurons. We used whole cell patch-clamp electrophysiology in the voltage-clamp configuration to analyze the effect of 1 mM NaHS, an H2S donor, on voltage-gated potassium, sodium, and calcium currents. We observed no effect of NaHS on potassium currents; however, both voltage-gated sodium currents (persistent and transient) and the N-type calcium current had a depolarized activation curve and an enhanced peak-induced current in response to a series of voltage-step and ramp protocols run in the control and NaHS conditions. These effects were not responsible for the previously observed depolarization of the membrane potential, as depolarizing effects of H2S were still observed following block of these conductances with tetrodotoxin (5 μM) and ω-conotoxin-GVIA (100 nM). Our studies are the first to investigate the effect of H2S on a variety of voltage-gated conductances in a single brain area, and although they do not explain mechanisms underlying the depolarizing actions of H2S on SFO neurons, they provide evidence of potential mechanisms through which this gasotransmitter influences the excitability of neurons in this important brain area as a consequence of the modulation of multiple ion channels.

  5. Voltage-gated potassium currents within the dorsal vagal nucleus: inhibition by BDS toxin.

    Science.gov (United States)

    Dallas, Mark L; Morris, Neil P; Lewis, David I; Deuchars, Susan A; Deuchars, Jim

    2008-01-16

    Voltage-gated potassium (Kv) channels are essential components of neuronal excitability. The Kv3.4 channel protein is widely distributed throughout the central nervous system (CNS), where it can form heteromeric or homomeric Kv3 channels. Electrophysiological studies reported here highlight a functional role for this channel protein within neurons of the dorsal vagal nucleus (DVN). Current clamp experiments revealed that blood depressing substance (BDS) and intracellular dialysis of an anti-Kv3.4 antibody prolonged the action potential duration. In addition, a BDS sensitive, voltage-dependent, slowly inactivating outward current was observed in voltage clamp recordings from DVN neurons. Electrical stimulation of the solitary tract evoked EPSPs and IPSPs in DVN neurons and BDS increased the average amplitude and decreased the paired pulse ratio, consistent with a presynaptic site of action. This presynaptic modulation was action potential dependent as revealed by ongoing synaptic activity. Given the role of the Kv3 proteins in shaping neuronal excitability, these data highlight a role for homomeric Kv3.4 channels in spike timing and neurotransmitter release in low frequency firing neurons of the DVN.

  6. The Molecular Basis of Polyunsaturated Fatty Acid Interactions with the Shaker Voltage-Gated Potassium Channel.

    Directory of Open Access Journals (Sweden)

    Samira Yazdi

    2016-01-01

    Full Text Available Voltage-gated potassium (KV channels are membrane proteins that respond to changes in membrane potential by enabling K+ ion flux across the membrane. Polyunsaturated fatty acids (PUFAs induce channel opening by modulating the voltage-sensitivity, which can provide effective treatment against refractory epilepsy by means of a ketogenic diet. While PUFAs have been reported to influence the gating mechanism by electrostatic interactions to the voltage-sensor domain (VSD, the exact PUFA-protein interactions are still elusive. In this study, we report on the interactions between the Shaker KV channel in open and closed states and a PUFA-enriched lipid bilayer using microsecond molecular dynamics simulations. We determined a putative PUFA binding site in the open state of the channel located at the protein-lipid interface in the vicinity of the extracellular halves of the S3 and S4 helices of the VSD. In particular, the lipophilic PUFA tail covered a wide range of non-specific hydrophobic interactions in the hydrophobic central core of the protein-lipid interface, while the carboxylic head group displayed more specific interactions to polar/charged residues at the extracellular regions of the S3 and S4 helices, encompassing the S3-S4 linker. Moreover, by studying the interactions between saturated fatty acids (SFA and the Shaker KV channel, our study confirmed an increased conformational flexibility in the polyunsaturated carbon tails compared to saturated carbon chains, which may explain the specificity of PUFA action on channel proteins.

  7. 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.)

  8. Voltage-gated potassium channels autoantibodies in a child with rasmussen encephalitis.

    Science.gov (United States)

    Spitz, Marie-Aude; Dubois-Teklali, Fanny; Vercueil, Laurent; Sabourdy, Cécile; Nugues, Frédérique; Vincent, Angela; Oliver, Viviana; Bulteau, Christine

    2014-10-01

    Rasmussen encephalitis (RE) is a severe epileptic and inflammatory encephalopathy of unknown etiology, responsible for focal neurological signs and cognitive decline. The current leading hypothesis suggests a sequence of immune reactions induced by an indeterminate factor. This sequence is thought to be responsible for the production of autoantibody-mediated central nervous system degeneration. However, these autoantibodies are not specific to the disease and not all patients present with them. We report the case of a 4-year-old girl suffering from RE displaying some atypical features such as fast evolution and seizures of left parietal onset refractory to several antiepileptics, intravenous immunoglobulins, and corticosteroids. Serum autoantibodies directed against voltage-gated potassium channels (VGKC) were evidenced at 739 pM, a finding never previously reported in children. This screening was performed because of an increased signal in the temporolimbic areas on brain magnetic resonance imaging, which was similar to what is observed during limbic encephalitis. The patient experienced epilepsia partialis continua with progressive right hemiplegia and aphasia. She underwent left hemispherotomy at the age of 5.5 years after which she became seizure free with great cognitive improvement. First described in adults, VGKC autoantibodies have been recently described in children with various neurological manifestations. The implication of VGKC autoantibodies in RE is a new observation and opens up new physiopathological and therapeutic avenues of investigation.

  9. Voltage-Gated Potassium Channel Antibody Paraneoplastic Limbic Encephalitis Associated with Acute Myeloid Leukemia

    Directory of Open Access Journals (Sweden)

    Marion Alcantara

    2013-05-01

    Full Text Available Among paraneoplastic syndromes (PNS associated with malignant hemopathies, there are few reports of PNS of the central nervous system and most of them are associated with lymphomas. Limbic encephalitis is a rare neurological syndrome classically diagnosed in the context of PNS. We report the case of a 81-year-old man who presented with a relapsed acute myeloid leukemia (AML with minimal maturation. He was admitted for confusion with unfavorable evolution as he presented a rapidly progressive dementia resulting in death. A brain magnetic resonance imaging, performed 2 months after the onset, was considered normal. An electroencephalogram showed non-specific bilateral slow waves. We received the results of the blood screening of neuronal autoantibodies after the patient's death and detected the presence of anti-voltage-gated potassium channel (VGKC antibodies at 102 pmol/l (normal at <30 pmol/l. Other etiologic studies, including the screening for another cause of rapidly progressive dementia, were negative. To our knowledge, this is the first case of anti-VGKC paraneoplastic limbic encephalitis related to AML.

  10. 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.

  11. Voltage-gated potassium channel antibody paraneoplastic limbic encephalitis associated with acute myeloid leukemia.

    Science.gov (United States)

    Alcantara, Marion; Bennani, Omar; Verdure, Pierre; Leprêtre, Stéphane; Tilly, Hervé; Jardin, Fabrice

    2013-05-01

    Among paraneoplastic syndromes (PNS) associated with malignant hemopathies, there are few reports of PNS of the central nervous system and most of them are associated with lymphomas. Limbic encephalitis is a rare neurological syndrome classically diagnosed in the context of PNS. We report the case of a 81-year-old man who presented with a relapsed acute myeloid leukemia (AML) with minimal maturation. He was admitted for confusion with unfavorable evolution as he presented a rapidly progressive dementia resulting in death. A brain magnetic resonance imaging, performed 2 months after the onset, was considered normal. An electroencephalogram showed non-specific bilateral slow waves. We received the results of the blood screening of neuronal autoanti-bodies after the patient's death and detected the presence of anti-voltage-gated potassium channel (VGKC) antibodies at 102 pmol/l (normal at <30 pmol/l). Other etiologic studies, including the screening for another cause of rapidly progressive dementia, were negative. To our knowledge, this is the first case of anti-VGKC paraneoplastic limbic encephalitis related to AML.

  12. SCN9A mutations define primary erythermalgia as a neuropathic disorder of voltage gated sodium channels.

    Science.gov (United States)

    Drenth, Joost P H; te Morsche, Rene H M; Guillet, Gerard; Taieb, Alain; Kirby, R Lee; Jansen, Jan B M J

    2005-06-01

    Primary erythermalgia is a rare disorder characterized by recurrent attacks of red, warm and painful hands, and/or feet. We previously localized the gene for primary erythermalgia to a 7.94 cM region on chromosome 2q. Recently, Yang et al identified two missense mutations of the sodium channel alpha subunit SCN9A in patients with erythermalgia. The presence of voltage-gated sodium channels in sensory neurons is thought to play a crucial role in several chronic painful neuropathies. We examined four different families and two sporadic cases and detected missense sequence variants in SCN9A to be present in primary erythermalgia patients. A total of five of six mutations were located in highly conserved regions. One family with autosomal dominantly inherited erythermalgia was double heterozygous for two separate SCN9A mutations. These data establish primary erythermalgia as a neuropathic disorder and offers hope for treatment of this incapacitating painful disorder.

  13. Analysis of the selectivity filter of the voltage-gated sodium channel NavRh

    Institute of Scientific and Technical Information of China (English)

    Xu Zhang; Mengdie Xia; Yang Li; Huihui Liu; Xin Jiang; Wenlin Ren; Jianping Wu

    2013-01-01

    NaChBac is a bacterial voltage-gated sodium (Nav) channel that shows sequence similarity to voltage-gated calcium channels.To understand the ion-permeation mechanism of Nav channels,we combined molecular dynamics simulation,structural biology and electrophysiological approaches to investigate the recently determined structure of NavRh,a marine bacterial NaChBac ortholog.Two Na+ binding sites are identified in the selectivity filter (SF) in our simulations:The extracellular Na+ ion first approaches site 1 constituted by the side groups of Ser181 and Glu183,and then spontaneously arrives at the energetically more favorable site 2 formed by the carbonyi oxygens of Leu179 and Thr178.In contrast,Ca2+ ions are prone to being trapped by Glu183 at site 1,which then blocks the entrance of both Na+ and Ca2+ to the vestibule of the SF.In addition,Na+ permeates through the selective filter in an asymmetrical manner,a feature that resembles that of the mammalian Nav orthologs.The study reported here provides insights into the mechanism of ion selectivity on Na+ over Ca2+ in mammalian Nav channels.

  14. PROPERTIES OF VOLTAGE-GATED SODIUM CHANNELS IN DEVELOPING AUDITORY NEURONS OF THE MOUSE IN VITRO

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Objective. To investigate the properties of voltage-gated sodium (Na+) channels in developing auditoryneurons during early postnatal stages in the mammalian central nervous system.Methods. Using the whole-cell voltage-clamp technique, we have studied changes in the electrophysi-ological properties of Na+ channels in the principal neurons of the medial nucleus of the trapezoid body (MNTB).Results. We found that MNTB neurons already express functional Na+ channels at postnatal day 1 (P1),and that channel density begins to increase at P5 when the neurons receive synaptic innervation andreach its maximum (~3 fold) at P11 when functional hearing onsets. These changes were paralleled byan age-dependent acceleration in both inactivation and recovery from inactivation. In contrast, there wasvery little alteration in the voltage-dependence of inactivation.Conclusion. These profound changes in the properties of voltage-gated Na+ channels may increase theexcitability of MNTB neurons and enhance their phase-locking fidelity and capacity during high-frequencysynaptic transmission.

  15. 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.

  16. Hlf is a genetic modifier of epilepsy caused by voltage-gated sodium channel mutations.

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    Hawkins, Nicole A; Kearney, Jennifer A

    2016-01-01

    Mutations in voltage-gated sodium channel genes cause several types of human epilepsies. Often, individuals with the same sodium channel mutation exhibit diverse phenotypes. This suggests that factors beyond the primary mutation influence disease severity, including genetic modifiers. Mouse epilepsy models with voltage-gated sodium channel mutations exhibit strain-dependent phenotype variability, supporting a contribution of genetic modifiers in epilepsy. The Scn2a(Q54) (Q54) mouse model has a strain-dependent epilepsy phenotype. Q54 mice on the C57BL/6J (B6) strain exhibit delayed seizure onset and improved survival compared to [B6xSJL/J]F1.Q54 mice. We previously mapped two dominant modifier loci that influence Q54 seizure susceptibility and identified Hlf (hepatic leukemia factor) as a candidate modifier gene at one locus. Hlf and other PAR bZIP transcription factors had previously been associated with spontaneous seizures in mice thought to be caused by down-regulation of the pyridoxine pathway. An Hlf targeted knockout mouse model was used to evaluate the effect of Hlf deletion on Q54 phenotype severity. Hlf(KO/KO);Q54 double mutant mice exhibited elevated frequency and reduced survival compared to Q54 controls. To determine if direct modulation of the pyridoxine pathway could alter the Q54 phenotype, mice were maintained on a pyridoxine-deficient diet for 6 weeks. Dietary pyridoxine deficiency resulted in elevated seizure frequency and decreased survival in Q54 mice compared to control diet. To determine if Hlf could modify other epilepsies, Hlf(KO/+) mice were crossed with the Scn1a(KO/+) Dravet syndrome mouse model to examine the effect on premature lethality. Hlf(KO/+);Scn1a(KO/+) offspring exhibited decreased survival compared to Scn1a(KO/+) controls. Together these results demonstrate that Hlf is a genetic modifier of epilepsy caused by voltage-gated sodium channel mutations and that modulation of the pyridoxine pathway can also influence phenotype

  17. Leucine-rich glioma inactivated-1 and voltage gated potassium channel autoimmune encephalitis associated with ischemic stroke; A Case Report

    Directory of Open Access Journals (Sweden)

    Marisa Patryce McGinley

    2016-05-01

    Full Text Available Autoimmune encephalitis is associated with a wide variety of antibodies and clinical presentations. Voltage gated potassium channel (VGKC antibodies are a cause of autoimmune non-paraneoplastic encephalitis characterized by memory impairment, psychiatric symptoms, and seizures. We present a case of VGKC encephalitis likely preceding an ischemic stroke. Reports of autoimmune encephalitis associated with ischemic stroke are rare. Several hypothesizes linking these two disease processes are proposed.

  18. Comparative study of the gating motif and C-type inactivation in prokaryotic voltage-gated sodium channels.

    Science.gov (United States)

    Irie, Katsumasa; Kitagawa, Kazuya; Nagura, Hitoshi; Imai, Tomoya; Shimomura, Takushi; Fujiyoshi, Yoshinori

    2010-02-05

    Prokaryotic voltage-gated sodium channels (Na(V)s) are homotetramers and are thought to inactivate through a single mechanism, named C-type inactivation. Here we report the voltage dependence and inactivation rate of the NaChBac channel from Bacillus halodurans, the first identified prokaryotic Na(V), as well as of three new homologues cloned from Bacillus licheniformis (Na(V)BacL), Shewanella putrefaciens (Na(V)SheP), and Roseobacter denitrificans (Na(V)RosD). We found that, although activated by a lower membrane potential, Na(V)BacL inactivates as slowly as NaChBac. Na(V)SheP and Na(V)RosD inactivate faster than NaChBac. Mutational analysis of helix S6 showed that residues corresponding to the "glycine hinge" and "PXP motif" in voltage-gated potassium channels are not obligatory for channel gating in these prokaryotic Na(V)s, but mutations in the regions changed the inactivation rates. Mutation of the region corresponding to the glycine hinge in Na(V)BacL (A214G), Na(V)SheP (A216G), and NaChBac (G219A) accelerated inactivation in these channels, whereas mutation of glycine to alanine in the lower part of helix S6 in NaChBac (G229A), Na(V)BacL (G224A), and Na(V)RosD (G217A) reduced the inactivation rate. These results imply that activation gating in prokaryotic Na(V)s does not require gating motifs and that the residues of helix S6 affect C-type inactivation rates in these channels.

  19. Regulation of voltage-gated potassium channels by PI(4,5)P2.

    Science.gov (United States)

    Kruse, Martin; Hammond, Gerald R V; Hille, Bertil

    2012-08-01

    Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) regulates activities of numerous ion channels including inwardly rectifying potassium (K(ir)) channels, KCNQ, TRP, and voltage-gated calcium channels. Several studies suggest that voltage-gated potassium (K(V)) channels might be regulated by PI(4,5)P(2). Wide expression of K(V) channels in different cells suggests that such regulation could have broad physiological consequences. To study regulation of K(V) channels by PI(4,5)P(2), we have coexpressed several of them in tsA-201 cells with a G protein-coupled receptor (M(1)R), a voltage-sensitive lipid 5-phosphatase (Dr-VSP), or an engineered fusion protein carrying both lipid 4-phosphatase and 5-phosphatase activity (pseudojanin). These tools deplete PI(4,5)P(2) with application of muscarinic agonists, depolarization, or rapamycin, respectively. PI(4,5)P(2) at the plasma membrane was monitored by Förster resonance energy transfer (FRET) from PH probes of PLCδ1 simultaneously with whole-cell recordings. Activation of Dr-VSP or recruitment of pseudojanin inhibited K(V)7.1, K(V)7.2/7.3, and K(ir)2.1 channel current by 90-95%. Activation of M(1)R inhibited K(V)7.2/7.3 current similarly. With these tools, we tested for potential PI(4,5)P(2) regulation of activity of K(V)1.1/K(V)β1.1, K(V)1.3, K(V)1.4, and K(V)1.5/K(V)β1.3, K(V)2.1, K(V)3.4, K(V)4.2, K(V)4.3 (with different KChIPs and DPP6-s), and hERG/KCNE2. Interestingly, we found a substantial removal of inactivation for K(V)1.1/K(V)β1.1 and K(V)3.4, resulting in up-regulation of current density upon activation of M(1)R but no changes in activity upon activating only VSP or pseudojanin. The other channels tested except possibly hERG showed no alteration in activity in any of the assays we used. In conclusion, a depletion of PI(4,5)P(2) at the plasma membrane by enzymes does not seem to influence activity of most tested K(V) channels, whereas it does strongly inhibit members of the K(V)7 and K(ir) families.

  20. Scorpion beta-toxins and voltage-gated sodium channels: interactions and effects.

    Science.gov (United States)

    Pedraza Escalona, Martha; Possani, Lourival D

    2013-01-01

    Scorpion beta-toxins (beta-ScTxs) modify the activity of voltage-gated sodium (Nav) channels, thereby producing neurotoxic effects in diverse organisms. For this reason, beta-ScTxs are essential tools not only for discriminating among different channel sub-types but also for studying the mechanisms of channel gating and the structure-function relationship involved in this process. This review considers both the structural and the functional implications of the beta-ScTxs after they bind to their receptor sites, in accord with their classification into a) anti-mammalian beta-ScTxs, b) anti-insect selective excitatory beta-ScTxs, c) anti-insect selective depressant beta-ScTxs and d) beta-ScTxs active on both insect and mammals Nav channels. Additionally, the molecular mechanism of toxin action by the "voltage sensor trapping" model is discussed, and the systemic effects produced by these toxins are reviewed.

  1. Voltage-gated sodium channels: pharmaceutical targets via anticonvulsants to treat epileptic syndromes.

    Science.gov (United States)

    Abdelsayed, Mena; Sokolov, Stanislav

    2013-01-01

    Epilepsy is a brain disorder characterized by seizures and convulsions. The basis of epilepsy is an increase in neuronal excitability that, in some cases, may be caused by functional defects in neuronal voltage gated sodium channels, Nav1.1 and Nav1.2. The effects of antiepileptic drugs (AEDs) as effective therapies for epilepsy have been characterized by extensive research. Most of the classic AEDs targeting Nav share a common mechanism of action by stabilizing the channel's fast-inactivated state. In contrast, novel AEDs, such as lacosamide, stabilize the slow-inactivated state in neuronal Nav1.1 and Nav1.7 isoforms. This paper reviews the different mechanisms by which this stabilization occurs to determine new methods for treatment.

  2. Transient Receptor Potential Vanilloid 4-Induced Modulation of Voltage-Gated Sodium Channels in Hippocampal Neurons.

    Science.gov (United States)

    Hong, Zhiwen; Jie, Pinghui; Tian, Yujing; Chen, Tingting; Chen, Lei; Chen, Ling

    2016-01-01

    Transient receptor potential vanilloid 4 (TRPV4) is reported to control the resting membrane potential and increase excitability in many types of cells. Voltage-gated sodium channels (VGSCs) play an important role in initiating action potentials in neurons. However, whether VGSCs can be modulated by the activation of TRPV4 in hippocampal pyramidal neurons remains unknown. In this study, we tested the effect of TRPV4 agonists (GSK1016790A and 4α-PDD) on voltage-gated sodium current (I Na) in hippocampal CA1 pyramidal neurons and the protein levels of α/β-subunit of VGSCs in the hippocampus of mice subjected to intracerebroventricular (icv.) injection of GSK1016790A (GSK-injected mice). Herein, we report that I Na was inhibited by acute application of GSK1016790A or 4α-PDD. In the presence of TRPV4 agonists, the voltage-dependent inactivation curve shifted to the hyperpolarization, whereas the voltage-dependent activation curve remained unchanged. The TRPV4 agonist-induced inhibition of I Na was blocked by the TRPV4 antagonist or tetrodotoxin. Moreover, blocking protein kinase A (PKA) markedly attenuated the GSK1016790A-induced inhibition of I Na, whereas antagonism of protein kinase C or p38 mitogen-activated protein kinase did not change GSK1016790A action. Finally, the protein levels of Nav1.1, Nav1.2, and Nav1.6 in the hippocampus increased in GSK-injected mice, whereas those of Nav1.3 and Navβ1 remained nearly unchanged. We conclude that I Na is inhibited by the acute activation of TRPV4 through PKA signaling pathway in hippocampal pyramidal neurons, but protein expression of α-subunit of VGSCs is increased by sustained TRPV4 activation, which may compensate for the acute inhibition of I Na and provide a possibility for hyper-excitability upon sustained TRPV4 activation.

  3. The role of voltage-gated potassium channels in the regulation of mouse uterine contractility.

    Science.gov (United States)

    Smith, Ryan C; McClure, Marisa C; Smith, Margaret A; Abel, Peter W; Bradley, Michael E

    2007-11-02

    Uterine smooth muscle cells exhibit ionic currents that appear to be important in the control of uterine contractility, but how these currents might produce the changes in contractile activity seen in pregnant myometrium has not been established. There are conflicting reports concerning the role of voltage-gated potassium (Kv) channels and large-conductance, calcium-activated potassium (BK) channels in the regulation of uterine contractility. In this study we provide molecular and functional evidence for a role for Kv channels in the regulation of spontaneous contractile activity in mouse myometrium, and also demonstrate a change in Kv channel regulation of contractility in pregnant mouse myometrium. Functional assays which evaluated the effects of channel blockers and various contractile agonists were accomplished by quantifying contractility of isolated uterine smooth muscle obtained from nonpregnant mice as well as mice at various stages of pregnancy. Expression of Kv channel proteins in isolated uterine smooth muscle was evaluated by Western blots. The Kv channel blocker 4-aminopyridine (4-AP) caused contractions in nonpregnant mouse myometrium (EC50 = 54 micromolar, maximal effect at 300 micromolar) but this effect disappeared in pregnant mice; similarly, the Kv4.2/Kv4.3 blocker phrixotoxin-2 caused contractions in nonpregnant, but not pregnant, myometrium. Contractile responses to 4-AP were not dependent upon nerves, as neither tetrodotoxin nor storage of tissues at room temperature significantly altered these responses, nor were responses dependent upon the presence of the endometrium. Spontaneous contractions and contractions in response to 4-AP did not appear to be mediated by BK, as the BK channel-selective blockers iberiotoxin, verruculogen, or tetraethylammonium failed to affect either spontaneous contractions or 4-AP-elicited responses. A number of different Kv channel alpha subunit proteins were found in isolated myometrium from both nonpregnant and

  4. The role of voltage-gated potassium channels in the regulation of mouse uterine contractility

    Directory of Open Access Journals (Sweden)

    Abel Peter W

    2007-11-01

    Full Text Available Abstract Background Uterine smooth muscle cells exhibit ionic currents that appear to be important in the control of uterine contractility, but how these currents might produce the changes in contractile activity seen in pregnant myometrium has not been established. There are conflicting reports concerning the role of voltage-gated potassium (Kv channels and large-conductance, calcium-activated potassium (BK channels in the regulation of uterine contractility. In this study we provide molecular and functional evidence for a role for Kv channels in the regulation of spontaneous contractile activity in mouse myometrium, and also demonstrate a change in Kv channel regulation of contractility in pregnant mouse myometrium. Methods Functional assays which evaluated the effects of channel blockers and various contractile agonists were accomplished by quantifying contractility of isolated uterine smooth muscle obtained from nonpregnant mice as well as mice at various stages of pregnancy. Expression of Kv channel proteins in isolated uterine smooth muscle was evaluated by Western blots. Results The Kv channel blocker 4-aminopyridine (4-AP caused contractions in nonpregnant mouse myometrium (EC50 = 54 micromolar, maximal effect at 300 micromolar but this effect disappeared in pregnant mice; similarly, the Kv4.2/Kv4.3 blocker phrixotoxin-2 caused contractions in nonpregnant, but not pregnant, myometrium. Contractile responses to 4-AP were not dependent upon nerves, as neither tetrodotoxin nor storage of tissues at room temperature significantly altered these responses, nor were responses dependent upon the presence of the endometrium. Spontaneous contractions and contractions in response to 4-AP did not appear to be mediated by BK, as the BK channel-selective blockers iberiotoxin, verruculogen, or tetraethylammonium failed to affect either spontaneous contractions or 4-AP-elicited responses. A number of different Kv channel alpha subunit proteins were

  5. A novel anticonvulsant modulates voltage-gated sodium channel inactivation and prevents kindling-induced seizures.

    Science.gov (United States)

    Ashraf, Muhammad N; Gavrilovici, Cezar; Shah, Syed U Ali; Shaheen, Farzana; Choudhary, Muhammad I; Rahman, Atta-ur; Fahnestock, Margaret; Simjee, Shabana U; Poulter, Michael O

    2013-09-01

    Here, we explore the mechanism of action of isoxylitone (ISOX), a molecule discovered in the plant Delphinium denudatum, which has been shown to have anticonvulsant properties. Patch-clamp electrophysiology assayed the activity of ISOX on voltage-gated sodium channels (VGSCs) in both cultured neurons and brain slices isolated from controls and rats with experimental epilepsy(kindling model). Quantitative transcription polymerase chain reaction (qRT-PCR) (QPCR) assessed brain-derived neurotrophic factor (BDNF) mRNA expression in kindled rats, and kindled rats treated with ISOX. ISOX suppressed sodium current (I(Na)) showing an IC50 value of 185 nM in cultured neurons. ISOX significantly slowed the recovery from inactivation (ISOX τ = 18.7 ms; Control τ = 9.4 ms; p kindled cortical neurons, the IC50 for sodium current block was identical to that found in cultured neurons. ISOX prevented kindled stage 5 seizures and decreased the enhanced BDNF mRNA expression that is normally associated with kindling (p kindling is likely a secondary outcome that nevertheless would suppress epileptogenesis. These data show a new class of anti-seizure compound that inhibits sodium channel function and prevents the development of epileptic seizures.

  6. Arrangement and mobility of the voltage sensor domain in prokaryotic voltage-gated sodium channels.

    Science.gov (United States)

    Shimomura, Takushi; Irie, Katsumasa; Nagura, Hitoshi; Imai, Tomoya; Fujiyoshi, Yoshinori

    2011-03-04

    Prokaryotic voltage-gated sodium channels (Na(V)s) form homotetramers with each subunit contributing six transmembrane α-helices (S1-S6). Helices S5 and S6 form the ion-conducting pore, and helices S1-S4 function as the voltage sensor with helix S4 thought to be the essential element for voltage-dependent activation. Although the crystal structures have provided insight into voltage-gated K channels (K(V)s), revealing a characteristic domain arrangement in which the voltage sensor domain of one subunit is close to the pore domain of an adjacent subunit in the tetramer, the structural and functional information on Na(V)s remains limited. Here, we show that the domain arrangement in NaChBac, a firstly cloned prokaryotic Na(V), is similar to that in K(V)s. Cysteine substitutions of three residues in helix S4, Q107C, T110C, and R113C, effectively induced intersubunit disulfide bond formation with a cysteine introduced in helix S5, M164C, of the adjacent subunit. In addition, substituting two acidic residues with lysine, E43K and D60K, shifted the activation of the channel to more positive membrane potentials and consistently shifted the preferentially formed disulfide bond from T110C/M164C to Q107C/M164C. Because Gln-107 is located closer to the extracellular side of helix S4 than Thr-110, this finding suggests that the functional shift in the voltage dependence of activation is related to a restriction of the position of helix S4 in the lipid bilayer. The domain arrangement and vertical mobility of helix S4 in NaChBac indicate that the structure and the mechanism of voltage-dependent activation in prokaryotic Na(V)s are similar to those in canonical K(V)s.

  7. Mapping of scorpion toxin receptor sites at voltage-gated sodium channels.

    Science.gov (United States)

    Gurevitz, Michael

    2012-09-15

    Scorpion alpha and beta toxins interact with voltage-gated sodium channels (Na(v)s) at two pharmacologically distinct sites. Alpha toxins bind at receptor site-3 and inhibit channel inactivation, whereas beta toxins bind at receptor site-4 and shift the voltage-dependent activation toward more hyperpolarizing potentials. The two toxin classes are subdivided to distinct pharmacological groups according to their binding preferences and ability to compete for the receptor sites at Na(v) subtypes. To elucidate the toxin-channel surface of interaction at both receptor sites and clarify the molecular basis of varying toxin preferences, an efficient bacterial system for their expression in recombinant form was established. Mutagenesis accompanied by toxicity, binding and electrophysiological assays, in parallel to determination of the three-dimensional structure using NMR and X-ray crystallography uncovered a bipartite bioactive surface in toxin representatives of all pharmacological groups. Exchange of external loops between the mammalian brain channel rNa(v)1.2a and the insect channel DmNa(v)1 highlighted channel regions involved in the varying sensitivity to assorted toxins. In parallel, thorough mutagenesis of channel external loops illuminated points of putative interaction with the toxins. Amino acid substitutions at external loops S1-S2 and S3-S4 of the voltage sensor module in domain II of rNa(v)1.2a had prominent impact on the activity of the beta-toxin Css4 (from Centruroides suffusus suffusus), and substitutions at external loops S1-S2 and S3-S4 of the voltage sensor module in domain IV affected the activity of the alpha-toxin Lqh2 (from Leiurus quinquestriatus hebraeus). Rosetta modeling of toxin-Na(v) interaction using the voltage sensor module of the potassium channel as template raises commonalities in the way alpha and beta toxins interact with the channel. Css4 interacts with rNa(v)1.2a at a crevice between S1-S2 and S3-S4 transmembrane segments in domain

  8. 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.

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

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    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.

  10. The sorting receptor Rer1 controls Purkinje cell function via voltage gated sodium channels

    Science.gov (United States)

    Valkova, Christina; Liebmann, Lutz; Krämer, Andreas; Hübner, Christian A.; Kaether, Christoph

    2017-01-01

    Rer1 is a sorting receptor in the early secretory pathway that controls the assembly and the cell surface transport of selected multimeric membrane protein complexes. Mice with a Purkinje cell (PC) specific deletion of Rer1 showed normal polarization and differentiation of PCs and normal development of the cerebellum. However, PC-specific loss of Rer1 led to age-dependent motor deficits in beam walk, ladder climbing and gait. Analysis of brain sections revealed a specific degeneration of PCs in the anterior cerebellar lobe in old animals. Electrophysiological recordings demonstrated severe deficits in spontaneous action potential generation. Measurements of resurgent currents indicated decreased surface densities of voltage-gated sodium channels (Nav), but not changes in individual channels. Analysis of mice with a whole brain Rer1-deletion demonstrated a strong down-regulation of Nav1.6 and 1.1 in the absence of Rer1, whereas protein levels of the related Cav2.1 and of Kv3.3 and 7.2 channels were not affected. The data suggest that Rer1 controls the assembly and transport of Nav1.1 and 1.6, the principal sodium channels responsible for recurrent firing, in PCs. PMID:28117367

  11. 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.

  12. 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.

  13. 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.

  14. Targeting voltage-gated sodium channels for treatment for chronic visceral pain

    Institute of Scientific and Technical Information of China (English)

    Fei-Hu Qi; You-Lang Zhou; Guang-Yin Xu

    2011-01-01

    Voltage-gated sodium channels (VGSCs) play a fundamental role in controlling cellular excitability, and their abnormal activity is related to several pathological processes, including cardiac arrhythmias, epilepsy, neurodegenerative diseases, spasticity and chronic pain. In particular, chronic visceral pain, the central symptom of functional gastrointestinal disorders such as irritable bowel syndrome, is a serious clinical problem that affects a high percentage of the world population. In spite of intense research efforts and after the dedicated decade of pain control and research, there are not many options to treat chronic pain conditions. However, there is a wealth of evidence emerging to give hope that a more refined approach may be achievable. By using electronic databases, available data on structural and functional properties of VGSCs in chronic pain, particularly functional gastrointestinal hypersensitivity, were reviewed. We summarize the involvement and molecular bases of action of VGSCs in the pathophysiology of several organic and functional gastrointestinal disorders. We also describe the efficacy of VGSC blockers in the treatment of these neurological diseases, and outline future developments that may extend the therapeutic use of compounds that target VGSCs. Overall, clinical and experimental data indicate that isoform-specific blockers of these channels or targeting of their modulators may provide effective and novel approaches for visceral pain therapy.

  15. Conotoxins Targeting Neuronal Voltage-Gated Sodium Channel Subtypes: Potential Analgesics?

    Directory of Open Access Journals (Sweden)

    Jeffrey R. McArthur

    2012-11-01

    Full Text Available Voltage-gated sodium channels (VGSC are the primary mediators of electrical signal amplification and propagation in excitable cells. VGSC subtypes are diverse, with different biophysical and pharmacological properties, and varied tissue distribution. Altered VGSC expression and/or increased VGSC activity in sensory neurons is characteristic of inflammatory and neuropathic pain states. Therefore, VGSC modulators could be used in prospective analgesic compounds. VGSCs have specific binding sites for four conotoxin families: μ-, μO-, δ- and ί-conotoxins. Various studies have identified that the binding site of these peptide toxins is restricted to well-defined areas or domains. To date, only the μ- and μO-family exhibit analgesic properties in animal pain models. This review will focus on conotoxins from the μ- and μO-families that act on neuronal VGSCs. Examples of how these conotoxins target various pharmacologically important neuronal ion channels, as well as potential problems with the development of drugs from conotoxins, will be discussed.

  16. 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.

  17. The voltage-gated sodium channel NaV 1.9 in visceral pain.

    Science.gov (United States)

    Hockley, J R F; Winchester, W J; Bulmer, D C

    2016-03-01

    Visceral pain is a common symptom for patients with gastrointestinal (GI) disease. It is unpleasant, debilitating, and represents a large unmet medical need for effective clinical treatments. Recent studies have identified NaV 1.9 as an important regulator of afferent sensitivity in visceral pain pathways to mechanical and inflammatory stimuli, suggesting that NaV 1.9 could represent an important therapeutic target for the treatment of visceral pain. This potential has been highlighted by the identification of patients who have an insensitivity to pain or painful neuropathies associated with mutations in SCN11A, the gene encoding voltage-gated sodium channel subtype 1.9 (NaV 1.9). Here, we address the role of NaV 1.9 in visceral pain and what known human NaV 1.9 mutants can tell us about NaV 1.9 function in gut physiology and pathophysiology. © 2015 John Wiley & Sons Ltd.

  18. Mutation in the neuronal voltage-gated sodium channel SCN1A in familial hemiplegic migraine.

    Science.gov (United States)

    Dichgans, Martin; Freilinger, Tobias; Eckstein, Gertrud; Babini, Elena; Lorenz-Depiereux, Bettina; Biskup, Saskia; Ferrari, Michel D; Herzog, Jürgen; van den Maagdenberg, Arn M J M; Pusch, Michael; Strom, Tim M

    Familial hemiplegic migraine is an autosomal dominant severe subtype of migraine with aura characterised by some degree of hemiparesis during the attacks. So far, mutations in two genes regulating ion translocation-CACNA1A and ATP1A2-have been identified in pedigrees with this disease. To identify additional genes for familial hemiplegic migraine, we did a genome-wide linkage analysis of two disease pedigrees without mutations in CACNA1A and ATP1A2. Ion channel genes in the candidate interval were analysed for mutations, and the functional consequences of the recorded sequence alteration were determined. We identified a novel locus for familial hemiplegic migraine on chromosome 2q24. Sequencing of candidate genes in this region revealed a heterozygous missense mutation (Gln1489Lys) in the neuronal voltage-gated sodium channel gene SCN1A, mutations of which have been associated with epilepsy. This same mutation was present in three families with familial hemiplegic migraine. It results in a charge-altering aminoacid exchange in the so-called hinged-lid domain of the protein, which is critical for fast inactivation of the channel. Whole-cell recordings in transiently transfected tsA201 cells expressing the highly homologous SCN5A sodium channel showed that the mutation induces a two-fold to four-fold accelerated recovery from fast inactivation without altering any of the other channel parameters investigated. Dysfunction of the neuronal sodium channel SCN1A can cause familial hemiplegic migraine. Our findings have implications for the understanding of migraine aura. Moreover, our study reinforces the molecular links between migraine and epilepsy, two common paroxysmal disorders.

  19. Regulation of membrane excitability: a convergence on voltage-gated sodium conductance.

    Science.gov (United States)

    Lin, Wei-Hsiang; Baines, Richard A

    2015-02-01

    The voltage-gated sodium channel (Nav) plays a key role in regulation of neuronal excitability. Aberrant regulation of Nav expression and/or function can result in an imbalance in neuronal activity which can progress to epilepsy. Regulation of Nav activity is achieved by coordination of a multitude of mechanisms including RNA alternative splicing and translational repression. Understanding of these regulatory mechanisms is complicated by extensive genetic redundancy: the mammalian genome encodes ten Navs. By contrast, the genome of the fruitfly, Drosophila melanogaster, contains just one Nav homologue, encoded by paralytic (DmNa v ). Analysis of splicing in DmNa v shows variants exhibit distinct gating properties including varying magnitudes of persistent sodium current (INaP). Splicing by Pasilla, an identified RNA splicing factor, alters INaP magnitude as part of an activity-dependent mechanism. Enhanced INaP promotes membrane hyperexcitability that is associated with seizure-like behaviour in Drosophila. Nova-2, a mammalian Pasilla homologue, has also been linked to splicing of Navs and, moreover, mouse gene knockouts display seizure-like behaviour.Expression level of Navs is also regulated through a mechanism of translational repression in both flies and mammals. The translational repressor Pumilio (Pum) can bind to Na v transcripts and repress the normal process of translation, thus regulating sodium current (INa) density in neurons. Pum2-deficient mice exhibit spontaneous EEG abnormalities. Taken together, aberrant regulation of Nav function and/or expression is often epileptogenic. As such, a better understanding of regulation of membrane excitability through RNA alternative splicing and translational repression of Navs should provide new leads to treat epilepsy.

  20. 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.

  1. Solution structure and alanine scan of a spider toxin that affects the activation of mammalian voltage-gated sodium channels.

    Science.gov (United States)

    Corzo, Gerardo; Sabo, Jennifer K; Bosmans, Frank; Billen, Bert; Villegas, Elba; Tytgat, Jan; Norton, Raymond S

    2007-02-16

    Magi 5, from the hexathelid spider Macrothele gigas, is a 29-residue polypeptide containing three disulfide bridges. It binds specifically to receptor site 4 on mammalian voltage-gated sodium channels and competes with scorpion beta-toxins, such as Css IV from Centruroides suffusus suffusus. As a consequence, Magi 5 shifts the activation voltage of the mammalian rNav1.2a channel to more hyperpolarized voltages, whereas the insect channel, DmNav1, is not affected. To gain insight into toxin-channel interactions, Magi 5 and 23 analogues were synthesized. The three-dimensional structure of Magi 5 in aqueous solution was determined, and its voltage-gated sodium channel-binding surfaces were mapped onto this structure using data from electrophysiological measurements on a series of Ala-substituted analogues. The structure clearly resembles the inhibitor cystine knot structural motif, although the triple-stranded beta-sheet typically found in that motif is partially distorted in Magi 5. The interactive surface of Magi 5 toward voltage-gated sodium channels resembles in some respects the Janus-faced atracotoxins, with functionally important charged residues on one face of the toxin and hydrophobic residues on the other. Magi 5 also resembles the scorpion beta-toxin Css IV, which has distinct nonpolar and charged surfaces that are critical for channel binding and has a key Glu involved in voltage sensor trapping. These two distinct classes of toxin, with different amino acid sequences and different structures, may utilize similar groups of residues on their surface to achieve the common end of modifying voltage-gated sodium channel function.

  2. Adaptive evolution of voltage-gated sodium channels: the first 800 million years.

    Science.gov (United States)

    Zakon, Harold H

    2012-06-26

    Voltage-gated Na(+)-permeable (Nav) channels form the basis for electrical excitability in animals. Nav channels evolved from Ca(2+) channels and were present in the common ancestor of choanoflagellates and animals, although this channel was likely permeable to both Na(+) and Ca(2+). 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 in early chordates Nav channels evolved a motif that allowed them to cluster at axon initial segments, 50 million years later with the evolution of myelin, Nav channels "capitalized" on this property and clustered at nodes of Ranvier. The enhancement of conduction velocity along with the evolution of jaws likely made early gnathostomes fierce predators and the dominant vertebrates in the ocean. Later in vertebrate evolution, the Nav channel gene family expanded in parallel in tetrapods and teleosts (∼9 to 10 genes in amniotes, 8 in teleosts). This expansion occurred during or after the late Devonian extinction, when teleosts and tetrapods each diversified in their respective habitats, and coincided with an increase in the number of telencephalic nuclei in both groups. The expansion of Nav channels may have allowed for more sophisticated neural computation and tailoring of Nav channel kinetics with potassium channel kinetics to enhance energy savings. Nav channels show adaptive sequence evolution for increasing diversity in communication signals (electric fish), in protection against lethal Nav channel toxins (snakes, newts, pufferfish, insects), and in specialized habitats (naked mole rats).

  3. Molecular Model of Anticonvulsant Drug Binding to the Voltage-Gated Sodium Channel Inner Pore

    Science.gov (United States)

    Lipkind, Gregory M.

    2010-01-01

    The tricyclic anticonvulsant drugs phenytoin, carbamazepine, and lamotrigine block neuronal voltage-gated Na+ channels, and their binding sites to domain IV-S6 in the channel's inner pore overlap with those of local anesthetic drugs. These anticonvulsants are neutral, in contrast to the mostly positively charged local anesthetics, but their open/inactivated-state blocking affinities are similar. Using a model of the open pore of the Na+ channel that we developed by homology with the crystal structures of potassium channels, we have docked these three anticonvulsants with residues identified by mutagenesis as important for their binding energy. The three drugs show a common pharmacophore, including an aromatic ring that has an aromatic-aromatic interaction with Tyr-1771 of NaV1.2 and a polar amide or imide that interacts with the aromatic ring of Phe-1764 by a low-energy amino-aromatic hydrogen bond. The second aromatic ring is nearly at a right angle to the pharmacophore and fills the pore lumen, probably interacting with the other S6 segments and physically occluding the inner pore to block Na+ permeation. Hydrophobic interactions with this second aromatic ring may contribute an important component to binding for anticonvulsants, which compensates energetically for the absence of positive charge in their structures. Voltage dependence of block, their important therapeutic property, results from their interaction with Phe-1764, which connects them to the voltage sensors. Their use dependence is modest and this results from being neutral, with a fast drug off-rate after repolarization, allowing a normal action potential rate in the presence of the drugs. PMID:20643904

  4. Modulation of voltage-gated sodium channels hyperpolarizes the voltage threshold for activation in spinal motoneurones.

    Science.gov (United States)

    Power, Kevin E; Carlin, Kevin P; Fedirchuk, Brent

    2012-03-01

    Previous work has shown that motoneurone excitability is enhanced by a hyperpolarization of the membrane potential at which an action potential is initiated (V(th)) at the onset, and throughout brainstem-evoked fictive locomotion in the adult decerebrate cat and neonatal rat. Modeling work has suggested the modulation of Na(+) conductance as a putative mechanism underlying this state-dependent change in excitability. This study sought to determine whether modulation of voltage-gated sodium channels could induce V(th) hyperpolarization. Whole-cell patch-clamp recordings were made from antidromically identified lumbar spinal motoneurones in an isolated neonatal rat spinal cord preparation. Recordings were made with and without the bath application of veratridine, a plant alkaloid neurotoxin that acts as a sodium channel modulator. As seen in HEK 293 cells expressing Nav1.2 channels, veratridine-modified channels demonstrated a hyperpolarizing shift in their voltage-dependence of activation and a slowing of inactivation that resulted in an enhanced inward current in response to voltage ramp stimulations. In the native rat motoneurones, veratridine-modified sodium channels induced a hyperpolarization of V(th) in all 29 neonatal rat motoneurones examined (mean hyperpolarization: -6.6 ± 4.3 mV). V(th) hyperpolarization was not due to the effects on Ca(2+) and/or K(+) channels as blockade of these currents did not alter V(th). Veratridine also significantly increased the amplitude of persistent inward currents (PICs; mean increase: 72.5 ± 98.5 pA) evoked in response to slow depolarizing current ramps. However, the enhancement of the PIC amplitude had a slower time course than the hyperpolarization of V(th), and the PIC onset voltage could be either depolarized or hyperpolarized, suggesting that PIC facilitation did not mediate the V(th) hyperpolarization. We therefore suggest that central neuronal circuitry in mammals could affect V(th) in a mechanism similar to that of

  5. SKF-96365 strongly inhibits voltage-gated sodium current in rat ventricular myocytes.

    Science.gov (United States)

    Chen, Kui-Hao; Liu, Hui; Yang, Lei; Jin, Man-Wen; Li, Gui-Rong

    2015-06-01

    SKF-96365 (1-(beta-[3-(4-methoxy-phenyl) propoxy]-4-methoxyphenethyl)-1H-imidazole hydrochloride) is a general TRPC channel antagonist commonly used to characterize the potential functions of TRPC channels in cardiovascular system. Recent reports showed that SKF-96365 induced a reduction in cardiac conduction. The present study investigates whether the reduced cardiac conduction caused by SKF-96365 is related to the blockade of voltage-gated sodium current (I Na) in rat ventricular myocytes using the whole-cell patch voltage-clamp technique. It was found that SKF-96365 inhibited I Na in rat ventricular myocytes in a concentration-dependent manner. The compound (1 μM) negatively shifted the potential of I Na availability by 9.5 mV, increased the closed-state inactivation of I Na, and slowed the recovery of I Na from inactivation. The inhibition of cardiac I Na by SKF-96365 was use-dependent and frequency-dependent, and the IC₅₀ was decreased from 1.36 μM at 0.5 Hz to 1.03, 0.81, 0.61, 0.56 μM at 1, 2, 5, 10 Hz, respectively. However, the selective TRPC3 antagonist Pyr3 decreased cardiac I Na by 8.5% at 10 μM with a weak use and frequency dependence. These results demonstrate that the TRPC channel antagonist SKF-96365 strongly blocks cardiac I Na in use-dependent and frequency-dependent manners. Caution should be taken for interpreting the alteration of cardiac electrical activity when SKF-96365 is used in native cells as a TRPC antagonist.

  6. Sinomenine produces peripheral analgesic effects via inhibition of voltage-gated sodium currents.

    Science.gov (United States)

    Lee, Jeong-Yun; Yoon, Seo-Yeon; Won, Jonghwa; Kim, Han-Byul; Kang, Youngnam; Oh, Seog Bae

    2017-09-01

    Sinomenium acutum has been used in traditional medicine to treat a painful disease such as rheumatic arthritis and neuralgia. Sinomenine, which is a main bioactive ingredient in Sinomenium acutum, has been reported to have an analgesic effect in diverse pain animal models. However little is known about the detailed mechanisms underlying peripheral analgesic effect of sinomenine. In the present study, we aimed to elucidate its cellular mechanism by using formalin-induced acute inflammatory pain model in mice. We found that intraperitoneal (i.p.) administration of sinomenine (50mg/kg) suppressed formalin-induced paw licking behavior in both the first and the second phase. Formalin-induced c-Fos protein expression was also suppressed by sinomenine (50mg/kg i.p.) in the superficial dorsal horn of spinal cord. Whole-cell patch-clamp recordings from small-sized dorsal root ganglion (DRG) neurons revealed that sinomenine reversibly increased the spike threshold and the threshold current intensity for evoking a single spike and decreased firing frequency of action potentials evoked in response to a long current pulse. Voltage-gated sodium currents (INa) were also significantly reduced by sinomenine in a dose-dependent manner (IC50=2.3±0.2mM). Finally, we confirmed that intraplantar application of sinomenine suppressed formalin-induced pain behavior only in the first phase, but not the second phase. Taken together, our results suggest that sinomenine has a peripheral analgesic effect by inhibiting INa. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

  7. Crystal structure of a voltage-gated sodium channel in two potentially inactivated states.

    Science.gov (United States)

    Payandeh, Jian; Gamal El-Din, Tamer M; Scheuer, Todd; Zheng, Ning; Catterall, William A

    2012-05-20

    In excitable cells, voltage-gated sodium (Na(V)) channels activate to initiate action potentials and then undergo fast and slow inactivation processes that terminate their ionic conductance. Inactivation is a hallmark of Na(V) channel function and is critical for control of membrane excitability, but the structural basis for this process has remained elusive. Here we report crystallographic snapshots of the wild-type Na(V)Ab channel from Arcobacter butzleri captured in two potentially inactivated states at 3.2 Å resolution. Compared to previous structures of Na(V)Ab channels with cysteine mutations in the pore-lining S6 helices (ref. 4), the S6 helices and the intracellular activation gate have undergone significant rearrangements: one pair of S6 helices has collapsed towards the central pore axis and the other S6 pair has moved outward to produce a striking dimer-of-dimers configuration. An increase in global structural asymmetry is observed throughout our wild-type Na(V)Ab models, reshaping the ion selectivity filter at the extracellular end of the pore, the central cavity and its residues that are analogous to the mammalian drug receptor site, and the lateral pore fenestrations. The voltage-sensing domains have also shifted around the perimeter of the pore module in wild-type Na(V)Ab, compared to the mutant channel, and local structural changes identify a conserved interaction network that connects distant molecular determinants involved in Na(V) channel gating and inactivation. These potential inactivated-state structures provide new insights into Na(V) channel gating and novel avenues to drug development and therapy for a range of debilitating Na(V) channelopathies.

  8. Mutations in voltage-gated potassium channel KCNC3 cause degenerative and developmental central nervous system phenotypes.

    Science.gov (United States)

    Waters, Michael F; Minassian, Natali A; Stevanin, Giovanni; Figueroa, Karla P; Bannister, John P A; Nolte, Dagmar; Mock, Allan F; Evidente, Virgilio Gerald H; Fee, Dominic B; Müller, Ulrich; Dürr, Alexandra; Brice, Alexis; Papazian, Diane M; Pulst, Stefan M

    2006-04-01

    Potassium channel mutations have been described in episodic neurological diseases. We report that K+ channel mutations cause disease phenotypes with neurodevelopmental and neurodegenerative features. In a Filipino adult-onset ataxia pedigree, the causative gene maps to 19q13, overlapping the SCA13 disease locus described in a French pedigree with childhood-onset ataxia and cognitive delay. This region contains KCNC3 (also known as Kv3.3), encoding a voltage-gated Shaw channel with enriched cerebellar expression. Sequencing revealed two missense mutations, both of which alter KCNC3 function in Xenopus laevis expression systems. KCNC3(R420H), located in the voltage-sensing domain, had no channel activity when expressed alone and had a dominant-negative effect when co-expressed with the wild-type channel. KCNC3(F448L) shifted the activation curve in the negative direction and slowed channel closing. Thus, KCNC3(R420H) and KCNC3(F448L) are expected to change the output characteristics of fast-spiking cerebellar neurons, in which KCNC channels confer capacity for high-frequency firing. Our results establish a role for KCNC3 in phenotypes ranging from developmental disorders to adult-onset neurodegeneration and suggest voltage-gated K+ channels as candidates for additional neurodegenerative diseases.

  9. Diverse roles for auxiliary subunits in phosphorylation-dependent regulation of mammalian brain voltage-gated potassium channels.

    Science.gov (United States)

    Vacher, Helene; Trimmer, James S

    2011-11-01

    Voltage-gated ion channels are a diverse family of signaling proteins that mediate rapid electrical signaling events. Among these, voltage-gated potassium or Kv channels are the most diverse partly due to the large number of principal (or α) subunits and auxiliary subunits that can assemble in different combinations to generate Kv channel complexes with distinct structures and functions. The diversity of Kv channels underlies much of the variability in the active properties between different mammalian central neurons and the dynamic changes that lead to experience-dependent plasticity in intrinsic excitability. Recent studies have revealed that Kv channel α subunits and auxiliary subunits are extensively phosphorylated, contributing to additional structural and functional diversity. Here, we highlight recent studies that show that auxiliary subunits exert some of their profound effects on dendritic Kv4 and axonal Kv1 channels through phosphorylation-dependent mechanisms, either due to phosphorylation on the auxiliary subunit itself or by influencing the extent and/or impact of α subunit phosphorylation. The complex effects of auxiliary subunits and phosphorylation provide a potent mechanism to generate additional diversity in the structure and function of Kv4 and Kv1 channels, as well as allowing for dynamic reversible regulation of these important ion channels.

  10. Simulating the Activation of Voltage Sensing Domain for a Voltage-Gated Sodium Channel Using Polarizable Force Field.

    Science.gov (United States)

    Sun, Rui-Ning; Gong, Haipeng

    2017-03-02

    Voltage-gated sodium (NaV) channels play vital roles in the signal transduction of excitable cells. Upon activation of a NaV channel, the change of transmembrane voltage triggers conformational change of the voltage sensing domain, which then elicits opening of the pore domain and thus allows an influx of Na(+) ions. Description of this process with atomistic details is in urgent demand. In this work, we simulated the partial activation process of the voltage sensing domain of a prokaryotic NaV channel using a polarizable force field. We not only observed the conformational change of the voltage sensing domain from resting to preactive state, but also rigorously estimated the free energy profile along the identified reaction pathway. Comparison with the control simulation using an additive force field indicates that voltage-gating thermodynamics of NaV channels may be inaccurately described without considering the electrostatic polarization effect.

  11. Actions of Tefluthrin on Rat Nav1.7 Voltage-Gated Sodium Channels Expressed in Xenopus Oocytes

    OpenAIRE

    Tan, Jianguo; Soderlund, David M.

    2011-01-01

    In rats expression of the Nav1.7 voltage-gated sodium channel isoform is restricted to the peripheral nervous system and is abundant in the sensory neurons of the dorsal root ganglion. We expressed the rat Nav1.7 sodium channel α subunit together with the rat auxiliary β1 and β2 subunits in Xenopus laevis oocytes and assessed the effects of the pyrethroid insecticide tefluthrin on the expressed currents using the two-electrode voltage clamp method. Tefluthrin at 100 µM modified of Nav1.7 chan...

  12. A case study of voltage-gated potassium channel antibody-related limbic encephalitis with PET/MRI findings

    Directory of Open Access Journals (Sweden)

    Brian K. Day

    2015-01-01

    Full Text Available Preclinical and clinical studies have demonstrated the significance of inflammation and autoantibodies in epilepsy, and the use of immunotherapies in certain situations has become an established practice. Temporal lobe epilepsy can follow paraneoplastic or nonparaneoplastic limbic encephalitis associated with antibodies directed against brain antigens. Here, we focus on a patient with worsening confusion and temporal lobe seizures despite treatment with antiepileptic medications. Serial brain MRIs did not conclusively reveal structural abnormalities, so the patient underwent brain PET/MRI to simultaneously evaluate brain structure and function, revealing bitemporal abnormalities. The patient was diagnosed with voltage-gated potassium channel antibody-related limbic encephalitis based on clinical presentation, imaging findings, and antibody testing. Treatment included the addition of a second antiepileptic agent and oral steroids. His seizures and cognitive deficits improved and stabilized.

  13. Post-translational modifications of voltage-gated sodium channels in chronic pain syndromes.

    Directory of Open Access Journals (Sweden)

    Cédric James Laedermann

    2015-11-01

    Full Text Available In the peripheral sensory nervous system the neuronal expression of voltage-gated sodium channels (Navs is a very important for the transmission of nociceptive information since they give rise to the upstroke of the action potential. Navs are composed of 9 different isoforms with distinct biophysical properties. Studying the mutations associated with the increase or absence of pain sensitivity in humans, as well as other expression studies, have highlighted Nav1.7, Nav1.8 and Nav1.9 as being the most important contributors to the control of nociceptive neuronal electrogenesis. Modulating their expression and/or function can impact the shape of the action potential and consequently modify pain transmission, a process that is observed in persistent pain conditions.Post-translational modification (PTM of Navs is a well-known process that modifies their expression and function. In chronic pain syndromes, the release of inflammatory molecules into the direct environment of dorsal root ganglia (DRG sensory neurons leads to an abnormal activation of enzymes that induce Navs PTM. The addition of small molecules, i.e. peptides, phosphoryl groups, ubiquitin moieties and/or carbohydrates, can modify the function of Navs in two different ways: via direct physical interference with the subunit of Nav gating, or via the control of Nav trafficking. Both mechanisms have a profound impact on neuronal excitability. In this review we will discuss the role of Protein Kinase A, B and C, Mitogen Activated Protein Kinases and Ca++/Calmodulin-dependent Kinase II in peripheral chronic pain syndromes. We will also discuss more recent findings that the ubiquitination of Nav1.7 by Nedd4-2 and the effect of methylglyoxal on Nav1.8 are also implicated in the development of experimental neuropathic pain. We will address the potential roles of other PTMs in chronic pain and highlight the need for further investigation of PTMs of Navs in order to develop new pharmacological

  14. The ethylene bis-dithiocarbamate fungicide Mancozeb activates voltage-gated KCNQ2 potassium channel.

    Science.gov (United States)

    Li, Ping; Zhu, Jin; Kong, Qingya; Jiang, Baifeng; Wan, Xia; Yue, Jinfeng; Li, Min; Jiang, Hualiang; Li, Jian; Gao, Zhaobing

    2013-06-07

    Mancozeb (manganese/zinc ethylene bis-dithiocarbamate) is an organometallic fungicide that has been associated with human neurotoxicity and neurodegeneration. In a high-throughput screen for modulators of KCNQ2 channel, a fundamental player modulating neuronal excitability, Mancozeb, was found to significantly potentiate KCNQ2 activity. Mancozeb was validated electrophysiologically as a KCNQ2 activator with an EC50 value of 0.92±0.23μM. Further examination showed that manganese but not zinc ethylene bis-dithiocarbamate is the active component for the positive modulation effects. In addition, the compounds are effective when the metal ions are substituted by iron but lack potentiation activity when the metal ions are substituted by sodium, signifying the importance of the metal ion. However, the iron (Fe(3+)) alone, organic ligands alone or the mixture of iron with the organic ligand did not show any potentiation effect, suggesting as the active ingredient is a specific complex rather than two separate additive or synergistic components. Our study suggests that potentiation on KCNQ2 potassium channels might be the possible mechanism of Mancozeb toxicity in the nervous system.

  15. Voltage-Gated Channels as Causative Agents for Epilepsies

    Directory of Open Access Journals (Sweden)

    Mutasem Abuhamed

    2008-01-01

    Full Text Available Problem statement: Epilepsy is a common neurological disorder that afflicts 1-2% of the general population worldwide. It encompasses a variety of disorders with seizures. Approach: Idiopathic epilepsies were defined as a heterogeneous group of seizure disorders that show no underlying cause .Voltage-gated ion channels defect were recognized etiology of epilepsy in the central nervous system. The aim of this article was to provide an update on voltage-gated channels and their mutation as causative agents for epilepsies. We described the structures of the voltage-gated channels, discuss their current genetic studies, and then review the effects of voltage-gated channels as causative agents for epilepsies. Results: Channels control the flow of ions in and out of the cell causing depolarization and hyper polarization of the cell. Voltage-gated channels were classified into four types: Sodium, potassium calcium ands chloride. Voltage-gated channels were macromolecular protein complexes within the lipid membrane. They were divided into subunits. Each subunit had a specific function and was encoded by more than one gen. Conclusion: Current genetic studies of idiopathic epilepsies show the importance of genetic influence on Voltage-gated channels. Different genes may regulate a function in a channel; the channel defect was directly responsible for neuronal hyper excitability and seizures.

  16. The effect of protein kinase C on voltage-gated potassium channel in pulmonary artery smooth muscle cells from rats exposed to chronic hypoxia

    Institute of Scientific and Technical Information of China (English)

    张永昶; 倪望; 张珍祥; 徐永健

    2004-01-01

    Background Chronic hypoxia can cause pulmonary hypertension and pulmonary heart disease with high mortality.The signal transduction pathway of protein kinase C (PKC) plays an important role in chronic pulmonary hypertension. So it is necessary to investigate the effect of PKC on voltage-gated potassium (K+) channels in pulmonary artery smooth muscle cells of rats exposed to chronic hypoxia.Methods Male Wistar rats were randomly divided into a control group (group A) and a chronic hypoxia group (group B). Group B received hypoxia [oxygen concentration (10±1)%] eight hours per day for four consecutive weeks. Single pulmonary artery smooth muscle cells were obtained using an acute enzyme separation method. Conventional whole cell patch clamp technique was used to record resting membrane potential, membrane capacitance and voltage-gated K+ currents. The changes in voltage-gated K+ currents before and after applying paramethoxyamphetamine (PMA) (500 nmol/L), an agonist of PKC, and PMA plus carbohydrate mixture of glucose, fructose and xylitol (GFX) (30 nmol/L), an inhibitor of PKC, were compared between the two groups. Results The resting membrane potential in group B was significantly lower than that of group A: -(29.0±4.8) mV (n=18) vs -(42.5±4.6) mV (n=35) (P0.05). The voltage-gated K+ currents were significantly inhibited by PMA in group A, and this effect was reversed by GFX. However, the voltage-gated K+ currents in group B were not affected by PMA.Conclusions The resting membrane potential and voltage-gated K+ currents in pulmonary artery smooth muscle cells from rats exposed to chronic hypoxia decreased significantly. It seems that PKC has different effects on the voltage-gated K+ currents of pulmonary artery smooth muscle cells under different conditions.

  17. 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

    2014-07-01

    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.

  18. Locating the route of entry and binding sites of benzocaine and phenytoin in a bacterial voltage gated sodium channel.

    Directory of Open Access Journals (Sweden)

    Lewis J Martin

    2014-07-01

    Full Text Available 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.

  19. Tolperisone-type drugs inhibit spinal reflexes via blockade of voltage-gated sodium and calcium channels.

    Science.gov (United States)

    Kocsis, Pál; Farkas, Sándor; Fodor, László; Bielik, Norbert; Thán, Márta; Kolok, Sándor; Gere, Anikó; Csejtei, Mónika; Tarnawa, István

    2005-12-01

    The spinal reflex depressant mechanism of tolperisone and some of its structural analogs with central muscle relaxant action was investigated. Tolperisone (50-400 microM), eperisone, lanperisone, inaperisone, and silperisone (25-200 microM) dose dependently depressed the ventral root potential of isolated hemisected spinal cord of 6-day-old rats. The local anesthetic lidocaine (100-800 microM) produced qualitatively similar depression of spinal functions in the hemicord preparation, whereas its blocking effect on afferent nerve conduction was clearly stronger. In vivo, tolperisone and silperisone as well as lidocaine (10 mg/kg intravenously) depressed ventral root reflexes and excitability of motoneurons. However, in contrast with lidocaine, the muscle relaxant drugs seemed to have a more pronounced action on the synaptic responses than on the excitability of motoneurons. Whole-cell measurements in dorsal root ganglion cells revealed that tolperisone and silperisone depressed voltage-gated sodium channel conductance at concentrations that inhibited spinal reflexes. Results obtained with tolperisone and its analogs in the [3H]batrachotoxinin A 20-alpha-benzoate binding in cortical neurons and in a fluorimetric membrane potential assay in cerebellar neurons further supported the view that blockade of sodium channels may be a major component of the action of tolperisone-type centrally acting muscle relaxant drugs. Furthermore, tolperisone, eperisone, and especially silperisone had a marked effect on voltage-gated calcium channels, whereas calcium currents were hardly influenced by lidocaine. These data suggest that tolperisone-type muscle relaxants exert their spinal reflex inhibitory action predominantly via a presynaptic inhibition of the transmitter release from the primary afferent endings via a combined action on voltage-gated sodium and calcium channels.

  20. Molecular Surface of JZTX-V (β-Theraphotoxin-Cj2a Interacting with Voltage-Gated Sodium Channel Subtype NaV1.4

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    Ji Luo

    2014-07-01

    Full Text Available Voltage-gated sodium channels (VGSCs; NaV1.1–NaV1.9 have been proven to be critical in controlling the function of excitable cells, and human genetic evidence shows that aberrant function of these channels causes channelopathies, including epilepsy, arrhythmia, paralytic myotonia, and pain. The effects of peptide toxins, especially those isolated from spider venom, have shed light on the structure–function relationship of these channels. However, most of these toxins have not been analyzed in detail. In particular, the bioactive faces of these toxins have not been determined. Jingzhaotoxin (JZTX-V (also known as β-theraphotoxin-Cj2a is a 29-amino acid peptide toxin isolated from the venom of the spider Chilobrachys jingzhao. JZTX-V adopts an inhibitory cysteine knot (ICK motif and has an inhibitory effect on voltage-gated sodium and potassium channels. Previous experiments have shown that JZTX-V has an inhibitory effect on TTX-S and TTX-R sodium currents on rat DRG cells with IC50 values of 27.6 and 30.2 nM, respectively, and is able to shift the activation and inactivation curves to the depolarizing and the hyperpolarizing direction, respectively. Here, we show that JZTX-V has a much stronger inhibitory effect on NaV1.4, the isoform of voltage-gated sodium channels predominantly expressed in skeletal muscle cells, with an IC50 value of 5.12 nM, compared with IC50 values of 61.7–2700 nM for other heterologously expressed NaV1 subtypes. Furthermore, we investigated the bioactive surface of JZTX-V by alanine-scanning the effect of toxin on NaV1.4 and demonstrate that the bioactive face of JZTX-V is composed of three hydrophobic (W5, M6, and W7 and two cationic (R20 and K22 residues. Our results establish that, consistent with previous assumptions, JZTX-V is a Janus-faced toxin which may be a useful tool for the further investigation of the structure and function of sodium channels.

  1. The insecticidal neurotoxin Aps III is an atypical knottin peptide that potently blocks insect voltage-gated sodium channels.

    Science.gov (United States)

    Bende, Niraj S; Kang, Eunji; Herzig, Volker; Bosmans, Frank; Nicholson, Graham M; Mobli, Mehdi; King, Glenn F

    2013-05-15

    One of the most potent insecticidal venom peptides described to date is Aps III from the venom of the trapdoor spider Apomastus schlingeri. Aps III is highly neurotoxic to lepidopteran crop pests, making it a promising candidate for bioinsecticide development. However, its disulfide-connectivity, three-dimensional structure, and mode of action have not been determined. Here we show that recombinant Aps III (rAps III) is an atypical knottin peptide; three of the disulfide bridges form a classical inhibitor cystine knot motif while the fourth disulfide acts as a molecular staple that restricts the flexibility of an unusually large β hairpin loop that often houses the pharmacophore in this class of toxins. We demonstrate that the irreversible paralysis induced in insects by rAps III results from a potent block of insect voltage-gated sodium channels. Channel block by rAps III is voltage-independent insofar as it occurs without significant alteration in the voltage-dependence of channel activation or steady-state inactivation. Thus, rAps III appears to be a pore blocker that plugs the outer vestibule of insect voltage-gated sodium channels. This mechanism of action contrasts strikingly with virtually all other sodium channel modulators isolated from spider venoms that act as gating modifiers by interacting with one or more of the four voltage-sensing domains of the channel. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. IDENTIFIKASI MUTASI NOKTAH PADA” GEN VOLTAGE GATED SODIUM CHANNEL” Aedes aegypti RESISTEN TERHADAP INSEKTISIDA PYRETHROID DI SEMARANG JAWA TENGAH

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    Widiarti Widiarti

    2012-11-01

    Full Text Available Abstract The identification of a point mutation in voltage-gated sodium channel gene was conducted on the major of dengue vector Aedes aegypti from Simongan Village, Semarang Municypality Central Java, which occurred to be resistant toward malathion and cypermethrin base on WHO methodology standard (impregnated paper.  The objectives of this studi was to identify the point mutation on the codon 1014  of voltage gated sodium channel gene of Ae. aegypti mosquitoes which was associated  with the vector resistance of pyrethroid group. The detection of a point mutation of  voltage-gated sodium channel was conducted using DNA extraction and semi nested polymerase chain reaction (PCR amplification of the mosquitoes resistant strain. The susceptibility test (as a screening resistant phenotype showed that few samples of Ae. aegypti from Simongan Village, Semarang Municypality Central Java resistant to malathion 0,8 % ( organophosphate group and cypermethrin 0,25 % (pyrethroid group. The sequencing result showed that there has been a mutation from the leucine (TTA which turned to be phenylalanin (TTT (kdr-w type on the codon 1014 at the voltage gated sodium channel gene of Ae. aegypti mosquitoes from  Simongan Village, Semarang Municypality Central Java, which was associated with the pyrethroid insecticide resistance. There were 78 % mosquitoes which brought  mutation alel kdr-w type on the codon 1014 F. Therefore dengue vector control activities should not use any pyrethroid insecticide group. Key  Words :  Resistance,  Aedes   aegypti,  Voltage   Gated   Sodium  Channel    (VGSC,  Point  Mutation. Abstrak Identifikasi mutasi noktah pada  gen Voltage Gated Sodium Channel (VGSC telah dilakukan pada nyamuk Aedes aegypti dari Kelurahan Simongan Kota Semarang, yang telah resisten terhadap insektisida Malathion dan Cypermethrin pada screening susceptibility test (Standar WHO Impregnated paper. Tujuan penelitian adalah untuk mendeteksi

  3. Steroid hormone regulation of the voltage-gated, calcium-activated potassium channel expression in developing muscular and neural systems.

    Science.gov (United States)

    Garrison, Sheldon L; Witten, Jane L

    2010-11-01

    A precise organization of gene expression is required for developing neural and muscular systems. Steroid hormones can control the expression of genes that are critical for development. In this study we test the hypothesis that the steroid hormone ecdysone regulates gene expression of the voltage-gated calcium-activated potassium ion channel, Slowpoke or KCNMA1. Late in adult development of the tobacco hawkmoth Manduca sexta, slowpoke (msslo) levels increased contributing to the maturation of the dorsal longitudinal flight muscles (DLMs) and CNS. We show that critical components of ecdysteroid gene regulation were present during upreglation of msslo in late adult DLM and CNS development. Ecdysteroid receptor complex heterodimeric partner proteins, the ecdysteroid receptor (EcR) and ultraspiracle (USP), and the ecdysone-induced early gene, msE75B, were expressed at key developmental time points, suggesting that ecdysteroids direct aspects of gene expression in the DLMs during these late developmental stages. We provide evidence that ecdysteroids suppress msslo transcription in the DLMs; when titers decline msslo transcript levels increase. These results are consistent with msslo being a downstream gene in an ecdysteroid-mediated gene cascade during DLM development. We also show that the ecdysteroids regulate msslo transcript levels in the developing CNS. These results will contribute to our understanding of how the spatiotemporal regulation of slowpoke transcription contributes to tailoring cell excitability to the differing physiological and behavioral demands during development.

  4. Voltage-gated potassium channels involved in regulation of physiological function in MrgprA3-specific itch neurons.

    Science.gov (United States)

    Tang, Min; Wu, Guanyi; Wang, Zhongli; Yang, Niuniu; Shi, Hao; He, Qian; Zhu, Chan; Yang, Yan; Yu, Guang; Wang, Changming; Yuan, Xiaolin; Liu, Qin; Guan, Yun; Dong, Xinzhong; Tang, Zongxiang

    2016-04-01

    Itch is described as an unpleasant or irritating skin sensation that elicits the desire or reflex to scratch. MrgprA3, one of members of the Mrgprs family, is specifically expressed in a subpopulation of dorsal root ganglion (DRG) in the peripheral nervous system (PNS). These MrgprA3-expressing DRG neurons have been identified as itch-specific neurons. They can be activated by the compound, chloroquine, which is used as a drug to treat malaria. In the present study, we labeled these itch-specific neurons using the method of molecular genetic markers, and then studied their electrophysiological properties. We also recorded the cutaneous MrgprA3(-) neurons retrogradely labeled by Dil dye (MrgprA3(-)-Dil). We first found that MrgprA3(+) neurons have a lower excitability than MrgprA3(-) neurons (MrgprA3(-)-non-Dil and MrgprA3(-)-Dil). The number of action potential (AP) was reduced more obviously in MrgprA3(+) neurons than that of in MrgprA3(-) neurons. In most cases, MrgprA3(+) neurons only generated single AP; however, in MrgprA3(-) neurons, the same stimulation could induce multiple AP firing due to the greater voltage-gated potassium (Kv) current existence in MrgprA3(+) than in MrgprA3(-) neurons. Thus, Kv current plays an important role in the regulation of excitability in itch-specific neurons.

  5. Modulatory effect of auxiliary β1 subunit on Nav1.3 voltage-gated sodium channel expressed in Xenopus oocyte

    Institute of Scientific and Technical Information of China (English)

    WANG Ying-wei; CHENG Zhi-jun; TAN Hong; XIA Yi-meng; REN Rong-rong; DING Yu-qiang

    2007-01-01

    @@ Voltage-gated sodium channels play an important role in the generation and propagation of action potentials in excitable cells. They are composed of a pore-forming α subunit and auxiliary β subunits. To date,nine subtypes of the α subunit, designated Nav 1.1 to Nav1.9, have been shown to form functional sodium channels.

  6. Towards a Unified Theory of Calmodulin Regulation (Calmodulation) of Voltage-Gated Calcium and Sodium Channels.

    Science.gov (United States)

    Ben-Johny, Manu; Dick, Ivy E; Sang, Lingjie; Limpitikul, Worawan B; Kang, Po Wei; Niu, Jacqueline; Banerjee, Rahul; Yang, Wanjun; Babich, Jennifer S; Issa, John B; Lee, Shin Rong; Namkung, Ho; Li, Jiangyu; Zhang, Manning; Yang, Philemon S; Bazzazi, Hojjat; Adams, Paul J; Joshi-Mukherjee, Rosy; Yue, Daniel N; Yue, David T

    2015-01-01

    Voltage-gated Na and Ca(2+) channels represent two major ion channel families that enable myriad biological functions including the generation of action potentials and the coupling of electrical and chemical signaling in cells. Calmodulin regulation (calmodulation) of these ion channels comprises a vital feedback mechanism with distinct physiological implications. Though long-sought, a shared understanding of the channel families remained elusive for two decades as the functional manifestations and the structural underpinnings of this modulation often appeared to diverge. Here, we review recent advancements in the understanding of calmodulation of Ca(2+) and Na channels that suggest a remarkable similarity in their regulatory scheme. This interrelation between the two channel families now paves the way towards a unified mechanistic framework to understand vital calmodulin-dependent feedback and offers shared principles to approach related channelopathic diseases. An exciting era of synergistic study now looms.

  7. Therapeutic plasma exchange as a steroid-sparing therapy in a patient with limbic encephalitis due to antibodies to voltage-gated potassium channels.

    Science.gov (United States)

    Martin, Isabella W; Martin, Christi-Lynn B; Dunbar, Nancy M; Lee, Stephen L; Szczepiorkowski, Zbigniew M

    2016-02-01

    Autoantibodies to the voltage-gated potassium channel (VGKC) complex cause a spectrum of non-paraneoplastic neurologic syndromes including limbic encephalitis (LE). We report a case of a man with LE who underwent a course of therapeutic plasma exchange (TPE) in addition to other immunomodulatory therapies and experienced sustained clinical resolution of his symptoms. This report adds to the existing literature supporting TPE in cases of LE due to VGKC complex autoantibodies.

  8. Leucine-Rich Glioma Inactivated-1 and Voltage-Gated Potassium Channel Autoimmune Encephalitis Associated with Ischemic Stroke: A Case Report.

    Science.gov (United States)

    McGinley, Marisa; Morales-Vidal, Sarkis; Ruland, Sean

    2016-01-01

    Autoimmune encephalitis is associated with a wide variety of antibodies and clinical presentations. Voltage-gated potassium channel (VGKC) antibodies are a cause of autoimmune non-paraneoplastic encephalitis characterized by memory impairment, psychiatric symptoms, and seizures. We present a case of VGKC encephalitis likely preceding an ischemic stroke. Reports of autoimmune encephalitis associated with ischemic stroke are rare. Several hypotheses linking these two disease processes are proposed.

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

    DEFF Research Database (Denmark)

    Tiran, Zohar; Peretz, Asher; Sines, Tal

    2006-01-01

    Tyrosine phosphatases (PTPs) epsilon and alpha are closely related and share several molecular functions, such as regulation of Src family kinases and voltage-gated potassium (Kv) channels. Functional interrelationships between PTPepsilon and PTPalpha and the mechanisms by which they regulate K...... but are not fully redundant. We conclude that PTPepsilon and PTPalpha differ significantly in their regulation of Kv channels and Src in the system examined and that similarity between PTPs does not necessarily result in full functional redundancy in vivo....

  10. Update on the frequency of Ile1016 mutation in voltage-gated sodium channel gene of Aedes aegypti in Mexico.

    Science.gov (United States)

    Siller, Quetzaly; Ponce, Gustavo; Lozano, Saul; Flores, Adriana E

    2011-12-01

    We analyzed 790 Aedes aegypti from 14 localities of Mexico in 2009 to update information on the frequency of the Ile1016 allele in the voltage-gated sodium channel gene that confers resistance to pyrethroids and DDT. The Ile1016 mutation was present in all 17 collections, and was close to fixation in Acapulco (frequency = 0.97), Iguala (0.93), and San Nicolas (0.90). Genotypes at the 1016 locus were not in Hardy-Weinberg proportions in collections from Panuco, Veracruz, Cosoleacaque, Coatzacoalcos, Tantoyuca, and Monterrey due in every case to an excess of homozygotes. The high frequencies of this mutation in Ae. aegypti are probably due to selection pressure from pyrethroid insecticides, particularly permethrin, which has been used in mosquito control programs for >10 years in Mexico.

  11. Ion conduction and conformational flexibility of a bacterial voltage-gated sodium channel.

    Science.gov (United States)

    Boiteux, Céline; Vorobyov, Igor; Allen, Toby W

    2014-03-04

    Voltage-gated Na(+) channels play an essential role in electrical signaling in the nervous system and are key pharmacological targets for a range of disorders. The recent solution of X-ray structures for the bacterial channel NavAb has provided an opportunity to study functional mechanisms at the atomic level. This channel's selectivity filter exhibits an EEEE ring sequence, characteristic of mammalian Ca(2+), not Na(+), channels. This raises the fundamentally important question: just what makes a Na(+) channel conduct Na(+) ions? Here we explore ion permeation on multimicrosecond timescales using the purpose-built Anton supercomputer. We isolate the likely protonation states of the EEEE ring and observe a striking flexibility of the filter that demonstrates the necessity for extended simulations to study conduction in this channel. We construct free energy maps to reveal complex multi-ion conduction via knock-on and "pass-by" mechanisms, involving concerted ion and glutamate side chain movements. Simulations in mixed ionic solutions reveal relative energetics for Na(+), K(+), and Ca(2+) within the pore that are consistent with the modest selectivity seen experimentally. We have observed conformational changes in the pore domain leading to asymmetrical collapses of the activation gate, similar to proposed inactivated structures of NavAb, with helix bending involving conserved residues that are critical for slow inactivation. These structural changes are shown to regulate access to fenestrations suggested to be pathways for lipophilic drugs and provide deeper insight into the molecular mechanisms connecting drug activity and slow inactivation.

  12. Regulatory role of voltage-gated sodium channel β subunits in sensory neurons

    Directory of Open Access Journals (Sweden)

    Mohamed eChahine

    2011-11-01

    Full Text Available Voltage-gated Na+ channels are transmembrane-bound proteins incorporating aqueous conduction pores that are highly selective for Na+. The opening of these channels results in the rapid influx of Na+ ions that depolarize the cell and drive the rapid upstroke of nerve and muscle action potentials. While the concept of a Na+-selective ion channel had been formulated in the 1940s, it was not until the 1980s that the biochemical properties of the 260-kDa and 36-kDa auxiliary β subunits (β1, β2 were first described. Subsequent cloning and heterologous expression studies revealed that the  subunit forms the core of the channel and is responsible for both voltage-dependent gating and ionic selectivity. To date, ten isoforms of the Na+ channel α subunit have been identified that vary in their primary structures, tissue distribution, biophysical properties, and sensitivity to neurotoxins. Four β subunits (β1-β4 and two splice variants (β1A, β1B have been identified that modulate the subcellular distribution, cell surface expression, and functional properties of the α subunits. The purpose of this review is to provide a broad overview of β subunit expression and function in peripheral sensory neurons and examine their contributions to neuropathic pain.

  13. Nonequilibrium response of a voltage gated sodium ion channel and biophysical characterization of dynamic hysteresis.

    Science.gov (United States)

    Pal, Krishnendu; Das, Biswajit; Gangopadhyay, Gautam

    2017-02-21

    Here we have studied the dynamic as well as the non-equilibrium thermodynamic response properties of voltage-gated Na-ion channel. Using sinusoidally oscillating external voltage protocol we have both kinetically and energetically studied the non-equilibrium steady state properties of dynamic hysteresis in details. We have introduced a method of estimating the work done associated with the dynamic memory due to a cycle of oscillating voltage. We have quantitatively characterised the loop area of ionic current which gives information about the work done to sustain the dynamic memory only for ion conduction, while the loop area of total entropy production rate gives the estimate of work done for overall gating dynamics. The maximum dynamic memory of Na-channel not only depends on the frequency and amplitude but it also depends sensitively on the mean of the oscillating voltage and here we have shown how the system optimize the dynamic memory itself in the biophysical range of field parameters. The relation between the average ionic current with increasing frequency corresponds to the nature of the average dissipative work done at steady state. It is also important to understand that the utilization of the energy from the external field can not be directly obtained only from the measurement of ionic current but also requires nonequilibrium thermodynamic study.

  14. Molecular determinants of prokaryotic voltage-gated sodium channels for recognition of local anesthetics.

    Science.gov (United States)

    Shimomura, Takushi; Irie, Katsumasa; Fujiyoshi, Yoshinori

    2016-08-01

    Local anesthetics (LAs) inhibit mammalian voltage-gated Na(+) channels (Navs) and are thus clinically important. LAs also inhibit prokaryotic Navs (BacNavs), which have a simpler structure than mammalian Navs. To elucidate the detailed mechanisms of LA inhibition to BacNavs, we used NavBh, a BacNav from Bacillus halodurans, to analyze the interactions of several LAs and quaternary ammoniums (QAs). Based on the chemical similarity of QA with the tertiary-alkylamine (TAA) group of LAs, QAs were used to determine the residues required for the recognition of TAA by NavBh. We confirmed that two residues, Thr220 and Phe227, are important for LA binding; a methyl group of Thr220 is important for recognizing both QAs and LAs, whereas Phe227 is involved in holding blockers at the binding site. In addition, we found that NavBh holds blockers in a closed state, consistent with the large inner cavity observed in the crystal structures of BacNavs. These findings reveal the inhibition mechanism of LAs in NavBh, where the methyl group of Thr220 provides the main receptor site for the TAA group and the bulky phenyl group of Phe227 holds the blockers inside the large inner cavity. These two residues correspond to the two LA recognition residues in mammalian Navs, which suggests the relevance of the LA recognition between BacNavs and mammalian Navs. © 2016 Federation of European Biochemical Societies.

  15. Current view on regulation of voltage-gated sodium channels by calcium and auxiliary proteins.

    Science.gov (United States)

    Pitt, Geoffrey S; Lee, Seok-Yong

    2016-09-01

    In cardiac and skeletal myocytes, and in most neurons, the opening of voltage-gated Na(+) channels (NaV channels) triggers action potentials, a process that is regulated via the interactions of the channels' intercellular C-termini with auxiliary proteins and/or Ca(2+) . The molecular and structural details for how Ca(2+) and/or auxiliary proteins modulate NaV channel function, however, have eluded a concise mechanistic explanation and details have been shrouded for the last decade behind controversy about whether Ca(2+) acts directly upon the NaV channel or through interacting proteins, such as the Ca(2+) binding protein calmodulin (CaM). Here, we review recent advances in defining the structure of NaV intracellular C-termini and associated proteins such as CaM or fibroblast growth factor homologous factors (FHFs) to reveal new insights into how Ca(2+) affects NaV function, and how altered Ca(2+) -dependent or FHF-mediated regulation of NaV channels is perturbed in various disease states through mutations that disrupt CaM or FHF interaction.

  16. 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.

  17. The voltage-gated potassium channel subfamily KQT member 4 (KCNQ4) displays parallel evolution in echolocating bats.

    Science.gov (United States)

    Liu, Yang; Han, Naijian; Franchini, Lucía F; Xu, Huihui; Pisciottano, Francisco; Elgoyhen, Ana Belén; Rajan, Koilmani Emmanuvel; Zhang, Shuyi

    2012-05-01

    Bats are the only mammals that use highly developed laryngeal echolocation, a sensory mechanism based on the ability to emit laryngeal sounds and interpret the returning echoes to identify objects. Although this capability allows bats to orientate and hunt in complete darkness, endowing them with great survival advantages, the genetic bases underlying the evolution of bat echolocation are still largely unknown. Echolocation requires high-frequency hearing that in mammals is largely dependent on somatic electromotility of outer hair cells. Then, understanding the molecular evolution of outer hair cell genes might help to unravel the evolutionary history of echolocation. In this work, we analyzed the molecular evolution of two key outer hair cell genes: the voltage-gated potassium channel gene KCNQ4 and CHRNA10, the gene encoding the α10 nicotinic acetylcholine receptor subunit. We reconstructed the phylogeny of bats based on KCNQ4 and CHRNA10 protein and nucleotide sequences. A phylogenetic tree built using KCNQ4 amino acid sequences showed that two paraphyletic clades of laryngeal echolocating bats grouped together, with eight shared substitutions among particular lineages. In addition, our analyses indicated that two of these parallel substitutions, M388I and P406S, were probably fixed under positive selection and could have had a strong functional impact on KCNQ4. Moreover, our results indicated that KCNQ4 evolved under positive selection in the ancestral lineage leading to mammals, suggesting that this gene might have been important for the evolution of mammalian hearing. On the other hand, we found that CHRNA10, a gene that evolved adaptively in the mammalian lineage, was under strong purifying selection in bats. Thus, the CHRNA10 amino acid tree did not show echolocating bat monophyly and reproduced the bat species tree. These results suggest that only a subset of hearing genes could underlie the evolution of echolocation. The present work continues to

  18. Functional and molecular characterization of voltage-gated sodium channels in uteri from nonpregnant rats.

    Science.gov (United States)

    Seda, Marian; Pinto, Francisco M; Wray, Susan; Cintado, Cristina G; Noheda, Pedro; Buschmann, Helmut; Candenas, Luz

    2007-11-01

    We investigated the function and expression of voltage-gated Na(+) channels (VGSC) in the uteri of nonpregnant rats using organ bath techniques, intracellular [Ca(2+)] fluorescence measurements, and RT-PCR. In longitudinally arranged whole-tissue uterine strips, veratridine, a VGSC activator, caused the rapid appearance of phasic contractions of irregular frequency and amplitude. After 50-60 min in the continuous presence of veratridine, rhythmic contractions of very regular frequency and slightly increasing amplitude occurred and were sustained for up to 12 h. Both the early and late components of the contractile response to veratridine were inhibited in a concentration-dependent manner by tetrodotoxin (TTX). In small strips dissected from the uterine longitudinal smooth muscle layer and loaded with Fura-2, veratridine also caused rhythmic contractions, accompanied by transient increases in [Ca(2+)](i), which were abolished by treatment with 0.1 microM TTX. Using end-point and real-time quantitative RT-PCR, we detected the presence of the VGSC alpha subunits Scn2a1, Scn3a, Scn5a, and Scn8a in the cDNA from longitudinal muscle. The mRNAs of the auxiliary beta subunits Scbn1b, Scbn2b, Scbn4b, and traces of Scn3b were also present. These data show for the first time that Scn2a1, Scn3a, Scn5a, and Scn8a, as well as all VGSC beta subunits are expressed in the longitudinal smooth muscle layer of the rat myometrium. In addition, our data show that TTX-sensitive VGSC are able to mediate phasic contractions maintained over long periods of time in the uteri of nonpregnant rats.

  19. Characterization of a novel radiolabeled peptide selective for a subpopulation of voltage-gated potassium channels in mammalian brain.

    Science.gov (United States)

    Racapé, Judith; Lecoq, Alain; Romi-Lebrun, Régine; Liu, Jessica; Kohler, Martin; Garcia, Maria L; Ménez, André; Gasparini, Sylvaine

    2002-02-08

    BgK, a 37-amino acid voltage-gated potassium (Kv) 1 channel blocker isolated from the sea anemone Bunodosoma granulifera, can be modified at certain positions to alter its pharmacological profile (Alessandri-Haber, N., Lecoq, A., Gasparini, S., Grangier-Macmath, G., Jacquet, G., Harvey, A. L., de Medeiros, C., Rowan, E. G., Gola, M., Ménez, A., and Crest, M. (1999) J. Biol. Chem. 274, 35653-35661). In the present study, we report the design of two BgK analogs that have been radiolabeled with (125)INa. Whereas BgK(W5Y/Y26F) and its radiolabeled derivative, (125)I-BgK(W5Y/Y26F), bind to Kv1.1, Kv1.2, and Kv1.6 channels with potencies similar to those for the parent peptide, BgK, BgK(W5Y/F6A/Y26F) and its monoiodo-tyrosine derivative, (125)I-BgK(W5Y/F6A/Y26F), display a distinctive and unique pharmacological profile; they bind with high affinity to homomultimeric Kv1.1 and Kv1.6 channels, but not to Kv1.2 channels. Interaction of BgK(W5Y/F6A/Y26F) with potassium channels depends on the nature of a residue in the mouth of the channel, at a position that determines channel sensitivity to external tetraethylammonium. In native brain tissue, (125)I-BgK(W5Y/F6A/Y26F) binds to a population of Kv1 channels that appear to consist of at least two sensitive (Kv1.1 and/or Kv1.6) subunits, in adjacent position. Given its unique pharmacological properties, (125)I-BgK(W5Y/F6A/Y26F) represents a new tool for studying subpopulations of Kv1 channels in native tissues.

  20. 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

  1. 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 < 0.05) knockdown in gene expression between 30–60%. Expression was also significantly (p < 0.05) reduced in pupae following injection causing 30% and 42% knockdown for early and late pupal stages, respectively. Oral delivery of dsRNA caused dose-dependant mortalities of between 19 and 51.34%; this was accompanied by significant (p < 0.05) knockdown in gene expression following 3 days of continuous feeding. The majority of larvae injected with, or fed, dsRNA died during the final larval stage prior to pupation. This work provides evidence of a viable RNAi-based strategy for insect control. PMID:27411529

  2. The modulatory effect of zinc ions on voltage-gated potassium currents in cultured rat hippocampal neurons is not related to Kv1.3 channels.

    Science.gov (United States)

    Teisseyre, A; Mercik, K; Mozrzymas, J W

    2007-12-01

    We applied the whole-cell patch-clamp technique to study the influence of zinc ions (Zn(2+)) and extracellular protons at acidic pH (pH(o)) on voltage-gated potassium currents in cultured rat hippocampal neurons. The first goal of the study was to estimate whether Kv1.3 currents significantly contributed to voltage-gated potassium currents in examined cells. Then, the influence of both ions on the activity of other voltage-gated potassium currents in the neurons was examined. We examined both the total current and the delayed - rectifier component. Results obtained in both cases were not significantly different from each other. Available data argued against any significant contribution of Kv1.3 currents to the recorded currents. Nevertheless, application of Zn(2+) in the concentration range from 100 microM to 5 mM reversibly modulated the recorded currents. The activation midpoint was shifted by about 40 mV (total current) and 30 mV (delayed-rectifier current) towards positive membrane potentials and the activation kinetics were slowed significantly (2 - 3 fold) upon application of Zn(2+). The inactivation midpoint was also shifted towards positive membrane potentials, but less significantly (about 14 mV). The current amplitudes were reduced in a concentration-dependent manner to about 0.5 of the control value. The effects of Zn(2+) were saturated at the concentration of 1 mM. Raising extracellular proton concentration by lowering the pH(o) from 7.35 to 6.4 did not affect significantly the currents. Possible mechanisms underlying the observed phenomena and their possible physiological significance are discussed.

  3. Seeing the forest through the trees: towards a unified view on physiological calcium regulation of voltage-gated sodium channels.

    Science.gov (United States)

    Van Petegem, Filip; Lobo, Paolo A; Ahern, Christopher A

    2012-12-05

    Voltage-gated sodium channels (Na(V)s) underlie the upstroke of the action potential in the excitable tissues of nerve and muscle. After opening, Na(V)s rapidly undergo inactivation, a crucial process through which sodium conductance is negatively regulated. Disruption of inactivation by inherited mutations is an established cause of lethal cardiac arrhythmia, epilepsy, or painful syndromes. Intracellular calcium ions (Ca(2+)) modulate sodium channel inactivation, and multiple players have been suggested in this process, including the cytoplasmic Na(V) C-terminal region including two EF-hands and an IQ motif, the Na(V) domain III-IV linker, and calmodulin. Calmodulin can bind to the IQ domain in both Ca(2+)-bound and Ca(2+)-free conditions, but only to the DIII-IV linker in a Ca(2+)-loaded state. The mechanism of Ca(2+) regulation, and its composite effect(s) on channel gating, has been shrouded in much controversy owing to numerous apparent experimental inconsistencies. Herein, we attempt to summarize these disparate data and propose a novel, to our knowledge, physiological mechanism whereby calcium ions promote sodium current facilitation due to Ca(2+) memory at high-action-potential frequencies where Ca(2+) levels may accumulate. The available data suggest that this phenomenon may be disrupted in diseases where cytoplasmic calcium ion levels are chronically high and where targeted phosphorylation may decouple the Ca(2+) regulatory machinery. Many Na(V) disease mutations associated with electrical dysfunction are located in the Ca(2+)-sensing machinery and misregulation of Ca(2+)-dependent channel modulation is likely to contribute to disease phenotypes.

  4. Effects of dragon's blood resin and its component loureirin B on tetrodotoxin-sensitive voltage-gated sodium currents in rat dorsal root ganglion neurons

    Institute of Scientific and Technical Information of China (English)

    LIU Xiangming; CHEN Su; YIN Shijin; MEI Zhinan

    2004-01-01

    Using whole-cell patch clamp technique on the membrane of freshly isolated dorsal root ganglion(DRG)neurons,the effects of dragon's blood resin and its important component Ioureirin B on tetrodotoxin-sensitive(TTX-S)voltage-gated sodium currents were observed.The results show that both blood resin and loureirin B could suppress TTX-S voltage-gated sodium currents in a dose-dependent way.The peak current amplitudes and the steady-state activation and inactivation curves are also made to shift by 0.05% blood resin and 0.2 mmol/L loureirin B.These results demonstrate that the effects of blood resin on TTX-S sodium current may contribute to loureirin B in blood resin.Perhaps the analgesic effect of blood resin is caused partly by loureirin B directly interfering with the nociceptive transmission of primary sensory neurons.

  5. Effects of dragon's blood resin and its component loureirin B on tetrodotoxin-sensitive voltage-gated sodium currents in rat dorsal root ganglion neurons.

    Science.gov (United States)

    Xiangming, Liu; Su, Chen; Shijin, Yin; Zhinan, Mei

    2004-08-01

    Using whole-cell patch clamp technique on the membrane of freshly isolated dorsal root ganglion (DRG) neurons, the effects of dragon's blood resin and its important component loureirin B on tetrodotoxin-sensitive (TTX-S) voltage-gated sodium currents were observed. The results show that both blood resin and loureirin B could suppress TTX-S voltage-gated sodium currents in a dose-dependent way. The peak current amplitudes and the steady-state activation and inactivation curves are also made to shift by 0.05% blood resin and 0.2 mmol/L loureirin B. These results demonstrate that the effects of blood resin on TTX-S sodium current may contribute to loureirin B in blood resin. Perhaps the analgesic effect of blood resin is caused partly by loureirin B directly interfering with the nociceptive transmission of primary sensory neurons.

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

    Directory of Open Access Journals (Sweden)

    Fernando Lazcano-Pérez

    2016-05-01

    Full Text Available 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.

  7. Voltage gated potassium channel antibodies positive autoimmune encephalopathy in a child: A case report and literature review of an under-recognized condition

    Directory of Open Access Journals (Sweden)

    Subramanian Ganesan

    2013-01-01

    Full Text Available Autoimmune limbic encephalitis (LE associated with voltage gated potassium channel antibodies (VGKC-Abs in children is more common than previously thought and is not always paraneoplastic. Non-neoplastic, autoimmune LE associated with VGKC-Abs has been described recently. However, only few case reports in children as the disease is predominantly described in the adult population. It is likely that this type of autoimmune encephalitis is currently under-diagnosed and hence, under-treated, especially in children. We present a 13-year-old previously fit and healthy African girl diagnosed with LE and we reviewed the literature for its current management.

  8. [An autopsy case of amyotrophic lateral sclerosis with prominent muscle cramps, fasciculation, and high titer of anti-voltage gated potassium channel (VGKC) complex antibody].

    Science.gov (United States)

    Sato, Aki; Sakai, Naoko; Shinbo, Junsuke; Hashidate, Hideki; Igarashi, Shuichi; Kakita, Akiyoshi; Yamazaki, Motoyoshi

    2014-01-01

    The patient was a 55-year-old male who had prominent fasciculation and muscle cramps. Muscle weakness and atrophy of the trunk, respiratory system, and extremities gradually progressed. On the basis of these features, we diagnosed this patient as having amyotrophic lateral sclerosis (ALS), however, the upper motor neuron signs were not significant. Following the detection of the anti-voltage gated potassium channel (VGKC) complex antibody at 907.5 pM (normal VGKC complex antibody in the development of cramp-fasciculation syndrome has been speculated. In this ALS patient, the antibodies might be associated with pathomechanisms underlying the characteristic symptoms.

  9. Morvan's syndrome with anti contactin associated protein like 2 – voltage gated potassium channel antibody presenting with syndrome of inappropriate antidiuretic hormone secretion

    Directory of Open Access Journals (Sweden)

    Anjani Kumar Sharma

    2016-01-01

    Full Text Available Morvan's syndrome is a rare autoimmune disorder characterized by triad of peripheral nerve hyperexcitability, autonomic dysfunction, and central nervous system symptoms. Antibodies against contactin-associated protein-like 2 (CASPR2, a subtype of voltage-gated potassium channel (VGKC complex, are found in a significant proportion of patients with Morvan's syndrome and are thought to play a key role in peripheral as well as central clinical manifestations. We report a patient of Morvan's syndrome with positive CASPR2–anti-VGKC antibody having syndrome of inappropriate antidiuretic hormone as a cause of persistent hyponatremia.

  10. Morvan's syndrome with anti contactin associated protein like 2 – voltage gated potassium channel antibody presenting with syndrome of inappropriate antidiuretic hormone secretion

    Science.gov (United States)

    Sharma, Anjani Kumar; Kaur, Manminder; Paul, Madhuparna

    2016-01-01

    Morvan's syndrome is a rare autoimmune disorder characterized by triad of peripheral nerve hyperexcitability, autonomic dysfunction, and central nervous system symptoms. Antibodies against contactin-associated protein-like 2 (CASPR2), a subtype of voltage-gated potassium channel (VGKC) complex, are found in a significant proportion of patients with Morvan's syndrome and are thought to play a key role in peripheral as well as central clinical manifestations. We report a patient of Morvan's syndrome with positive CASPR2–anti-VGKC antibody having syndrome of inappropriate antidiuretic hormone as a cause of persistent hyponatremia. PMID:27695240

  11. 电压门控性钾通道与认知功能障碍的研究进展%Voltage-gated potassium channels in cognitive dysfunction

    Institute of Scientific and Technical Information of China (English)

    颜文慧; 王萌(综述); 陈莉娜(审校)

    2015-01-01

    The growing number of cognitive dysfunction patients is bringing heavy mental and financial burdens to the society and families.Voltage-gated potassium channels (Kv), which consist of delayed rectifier potassium channels and transient outward po -tassium channels , are involved in the incidence of cognitive dysfunction .This review summarized the role of Kv channels in cognitive dysfunction and their relationship with N-methyl-D-aspartic acid receptors ( NMDARs) that play an important role in the process of learning and memory .%认知功能障碍患者的增多给社会、家庭带来了沉重的精神和经济负担。电压门控性钾通道( voltage-gated potas-sium channels, Kv)主要分为延迟整流钾通道和瞬时外向钾通道,参与认知功能障碍的发生。文中对Kv通道与认知功能障碍,以及Kv通道与在学习和记忆过程中起重要作用的N-甲基-D-天冬氨酸(N-methyl-D-aspartic acid, NMDA)受体之间的关系作一综述。

  12. Functional Expression of Voltage-Gated Sodium Channels Navl.5 in Human Breast Caner Cell Line MDA-MB-231

    Institute of Scientific and Technical Information of China (English)

    Rui GAO; Jing WANG; Yi SHEN; Ming LEI; Zehua WANG

    2009-01-01

    Voltage-gated sodium channels (VGSCs) are known to be involved in the initiation and progression of many malignancies,and the different subtypes of VGSCs play important roles in the metastasis cascade of many tumors.This study investigated the functional expression of Nav 1.5 and its effect on invasion behavior of human breast cancer cell line MDA-MB-231.The mRNA and pro-tein expression of Navl.5 was detected by real time PCR,Western Blot and immunofluorescence.The effects of Navl.5 on cell proliferation,migration and invasion were respectively assessed by MTT and Transwell.The effects of Nav1.5 on the secretion of matrix metalloproteases (MMPs) by MDA-MB-231 were analyzed by RT-PCR.The over-expressed Navl.5 was present on the membrane of MDA-MB-231 cells.The invasion ability in vitro and the MMP-9 mRNA expression were respec-tively decreased to (47.82±0.53)% and (43.97±0.64)% (P<0.05) respectively in MDA-MB-231 cells treated with VGSCs specific inhibitor tetrodotoxin (TTX) by blocking Navl.5 activity.It was con-eluded that Nav1.5 functional expression potentiated the invasive behavior of human breast cancer cell line MDA-MB-231 by increasing the secretion of MMP-9.

  13. A surface plasmon resonance approach to monitor toxin interactions with an isolated voltage-gated sodium channel paddle motif.

    Science.gov (United States)

    Martin-Eauclaire, Marie-France; Ferracci, Géraldine; Bosmans, Frank; Bougis, Pierre E

    2015-02-01

    Animal toxins that inhibit voltage-gated sodium (Na(v)) channel fast inactivation can do so through an interaction with the S3b-S4 helix-turn-helix region, or paddle motif, located in the domain IV voltage sensor. Here, we used surface plasmon resonance (SPR), an optical approach that uses polarized light to measure the refractive index near a sensor surface to which a molecule of interest is attached, to analyze interactions between the isolated domain IV paddle and Na(v) channel-selective α-scorpion toxins. Our SPR analyses showed that the domain IV paddle can be removed from the Na(v) channel and immobilized on sensor chips, and suggest that the isolated motif remains susceptible to animal toxins that target the domain IV voltage sensor. As such, our results uncover the inherent pharmacological sensitivities of the isolated domain IV paddle motif, which may be exploited to develop a label-free SPR approach for discovering ligands that target this region.

  14. Frequency-dependent reduction of voltage-gated sodium current modulates retinal ganglion cell response rate to electrical stimulation

    Science.gov (United States)

    Tsai, David; Morley, John W.; Suaning, Gregg J.; Lovell, Nigel H.

    2011-10-01

    The ability to elicit visual percepts through electrical stimulation of the retina has prompted numerous investigations examining the feasibility of restoring sight to the blind with retinal implants. The therapeutic efficacy of these devices will be strongly influenced by their ability to elicit neural responses that approximate those of normal vision. Retinal ganglion cells (RGCs) can fire spikes at frequencies greater than 200 Hz when driven by light. However, several studies using isolated retinas have found a decline in RGC spiking response rate when these cells were stimulated at greater than 50 Hz. It is possible that the mechanism responsible for this decline also contributes to the frequency-dependent 'fading' of electrically evoked percepts recently reported in human patients. Using whole-cell patch clamp recordings of rabbit RGCs, we investigated the causes for the spiking response depression during direct subretinal stimulation of these cells at 50-200 Hz. The response depression was not caused by inhibition arising from the retinal network but, instead, by a stimulus-frequency-dependent decline of RGC voltage-gated sodium current. Under identical experimental conditions, however, RGCs were able to spike at high frequency when driven by light stimuli and intracellular depolarization. Based on these observations, we demonstrated a technique to prevent the spiking response depression.

  15. Spider-venom peptides that target voltage-gated sodium channels: pharmacological tools and potential therapeutic leads.

    Science.gov (United States)

    Klint, Julie K; Senff, Sebastian; Rupasinghe, Darshani B; Er, Sing Yan; Herzig, Volker; Nicholson, Graham M; King, Glenn F

    2012-09-15

    Voltage-gated sodium (Na(V)) channels play a central role in the propagation of action potentials in excitable cells in both humans and insects. Many venomous animals have therefore evolved toxins that modulate the activity of Na(V) channels in order to subdue their prey and deter predators. Spider venoms in particular are rich in Na(V) channel modulators, with one-third of all known ion channel toxins from spider venoms acting on Na(V) channels. Here we review the landscape of spider-venom peptides that have so far been described to target vertebrate or invertebrate Na(V) channels. These peptides fall into 12 distinct families based on their primary structure and cysteine scaffold. Some of these peptides have become useful pharmacological tools, while others have potential as therapeutic leads because they target specific Na(V) channel subtypes that are considered to be important analgesic targets. Spider venoms are conservatively predicted to contain more than 10 million bioactive peptides and so far only 0.01% of this diversity been characterised. Thus, it is likely that future research will reveal additional structural classes of spider-venom peptides that target Na(V) channels.

  16. Phenolic acids isolated from the fungus Schizophyllum commune exert analgesic activity by inhibiting voltage-gated sodium channels.

    Science.gov (United States)

    Yao, Hui-Min; Wang, Gan; Liu, Ya-Ping; Rong, Ming-Qiang; Shen, Chuan-Bin; Yan, Xiu-Wen; Luo, Xiao-Dong; Lai, Ren

    2016-09-01

    The present study was designed to search for compounds with analgesic activity from the Schizophyllum commune (SC), which is widely consumed as edible and medicinal mushroom world. Thin layer chromatography (TLC), tosilica gel column chromatography, sephadex LH 20, and reverse-phase high performance liquid chromatography (RP-HPLC) were used to isolate and purify compounds from SC. Structural analysis of the isolated compounds was based on nuclear magnetic resonance (NMR). The effects of these compounds on voltage-gated sodium (NaV) channels were evaluated using patch clamp. The analgesic activity of these compounds was tested in two types of mouse pain models induced by noxious chemicals. Five phenolic acids identified from SC extracts in the present study included vanillic acid, m-hydroxybenzoic acid, o-hydroxybenzeneacetic acid, 3-hydroxy-5-methybenzoic acid, and p-hydroxybenzoic acid. They inhibited the activity of both tetrodotoxin-resistant (TTX-r) and tetrodotoxin-sensitive (TTX-s) NaV channels. All the compounds showed low selectivity on NaV channel subtypes. After intraperitoneal injection, three compounds of these compounds exerted analgesic activity in mice. In conclusion, phenolic acids identified in SC demonstrated analgesic activity, facilitating the mechanistic studies of SC in the treatment of neurasthenia.

  17. Peptide-rich venom from the spider Heteropoda venatoria potently inhibits insect voltage-gated sodium channels.

    Science.gov (United States)

    Huang, Yazhou; Wu, Xinzhou; Zhang, Peng; Duan, Zhigui; Zhou, Xi; Chen, Minzhi; Farooq, Athar; Liang, Songping; Liu, Zhonghua

    2017-01-01

    Heteropoda venatoria is a venomous spider species distributed worldwide and has a characteristic habit of feeding on insects. Reverse-phase high-performance liquid chromatography and matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry analyses revealed that H. venatoria venom contains hundreds of peptides with a predominant molecular weights of 3000-5000 Da. Intra-abdominal injection of the venom had severe toxic effects on cockroaches and caused death at higher concentrations. The LD50 was 28.18 μg/g of body weight in the cockroach. It was found that the venom had potent inhibitory effect on voltage-gated sodium channels (VGSCs) in Periplaneta americana cockroach dorsal unpaired median (DUM) neurons with an IC50 values of 6.25 ± 0.02 μg/mL. However, 100 μg/mL venom only partially blocked VGSC currents in rat dorsal root ganglion cells, a much lower inhibitory effect than that on DUM VGSCs. Our results indicate that the venom of H. venatoria contains diverse neurotoxins that might become new leads for bioinsecticides. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Structure and function of splice variants of the cardiac voltage-gated sodium channel Na(v)1.5.

    Science.gov (United States)

    Schroeter, Annett; Walzik, Stefan; Blechschmidt, Steve; Haufe, Volker; Benndorf, Klaus; Zimmer, Thomas

    2010-07-01

    Voltage-gated sodium channels mediate the rapid upstroke of the action potential in excitable tissues. The tetrodotoxin (TTX) resistant isoform Na(v)1.5, encoded by the SCN5A gene, is the predominant isoform in the heart. This channel plays a key role for excitability of atrial and ventricular cardiomyocytes and for rapid impulse propagation through the specific conduction system. During recent years, strong evidence has been accumulated in support of the expression of several Na(v)1.5 splice variants in the heart, and in various other tissues and cell lines including brain, dorsal root ganglia, breast cancer cells and neuronal stem cell lines. This review summarizes our knowledge on the structure and putative function of nine Na(v)1.5 splice variants detected so far. Attention will be paid to the distinct biophysical properties of the four functional splice variants, to the pronounced tissue- and species-specific expression, and to the developmental regulation of Na(v)1.5 splicing. The implications of alternative splicing for SCN5A channelopathies, and for a better understanding of genotype-phenotype correlations, are discussed.

  19. Frequency-dependent reliability of spike propagation is function of axonal voltage-gated sodium channels in cerebellar Purkinje cells.

    Science.gov (United States)

    Yang, Zhilai; Wang, Jin-Hui

    2013-12-01

    The spike propagation on nerve axons, like synaptic transmission, is essential to ensure neuronal communication. The secure propagation of sequential spikes toward axonal terminals has been challenged in the neurons with a high firing rate, such as cerebellar Purkinje cells. The shortfall of spike propagation makes some digital spikes disappearing at axonal terminals, such that the elucidation of the mechanisms underlying spike propagation reliability is crucial to find the strategy of preventing loss of neuronal codes. As the spike propagation failure is influenced by the membrane potentials, this process is likely caused by altering the functional status of voltage-gated sodium channels (VGSC). We examined this hypothesis in Purkinje cells by using pair-recordings at their somata and axonal blebs in cerebellar slices. The reliability of spike propagation was deteriorated by elevating spike frequency. The frequency-dependent reliability of spike propagation was attenuated by inactivating VGSCs and improved by removing their inactivation. Thus, the functional status of axonal VGSCs influences the reliability of spike propagation.

  20. 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

  1. 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.

  2. Functional interaction between S1 and S4 segments in voltage-gated sodium channels revealed by human channelopathies.

    Science.gov (United States)

    Amarouch, Mohamed-Yassine; Kasimova, Marina A; Tarek, Mounir; Abriel, Hugues

    2014-01-01

    The p.I141V mutation of the voltage-gated sodium channel is associated with several clinical hyper-excitability phenotypes. To understand the structural bases of the p.I141V biophysical alterations, molecular dynamics simulations were performed. These simulations predicted that the p.I141V substitution induces the formation of a hydrogen bond between the Y168 residue of the S2 segment and the R225 residue of the S4 segment. We generated a p.I141V-Y168F double mutant for both the Nav1.4 and Nav1.5 channels. The double mutants demonstrated the abolition of the functional effects of the p.I141V mutation, consistent with the formation of a specific interaction between Y168-S2 and R225-S4. The single p.Y168F mutation, however, positively shifted the activation curve, suggesting a compensatory role of these residues on the stability of the voltage-sensing domain.

  3. SCN9A mutations define primary erythermalgia as a neuropathic disorder of voltage gated sodium channels.

    NARCIS (Netherlands)

    Drenth, J.P.H.; Morsche, R.H.M. te; Guillet, G.; Taieb, A.; Kirby, R.L.; Jansen, J.B.M.J.

    2005-01-01

    Primary erythermalgia is a rare disorder characterized by recurrent attacks of red, warm and painful hands, and/or feet. We previously localized the gene for primary erythermalgia to a 7.94 cM region on chromosome 2q. Recently, Yang et al identified two missense mutations of the sodium channel alpha

  4. Pyrethroids differentially alter voltage-gated sodium channels from the honeybee central olfactory neurons.

    Directory of Open Access Journals (Sweden)

    Aklesso Kadala

    Full Text Available The sensitivity of neurons from the honey bee olfactory system to pyrethroid insecticides was studied using the patch-clamp technique on central 'antennal lobe neurons' (ALNs in cell culture. In these neurons, the voltage-dependent sodium currents are characterized by negative potential for activation, fast kinetics of activation and inactivation, and the presence of cumulative inactivation during train of depolarizations. Perfusion of pyrethroids on these ALN neurons submitted to repetitive stimulations induced (1 an acceleration of cumulative inactivation, and (2 a marked slowing of the tail current recorded upon repolarization. Cypermethrin and permethrin accelerated cumulative inactivation of the sodium current peak in a similar manner and tetramethrin was even more effective. The slow-down of channel deactivation was markedly dependent on the type of pyrethroid. With cypermethrin, a progressive increase of the tail current amplitude along with successive stimulations reveals a traditionally described use-dependent recruitment of modified sodium channels. However, an unexpected decrease in this tail current was revealed with tetramethrin. If one considers the calculated percentage of modified channels as an index of pyrethroids effects, ALNs are significantly more susceptible to tetramethrin than to permethrin or cypermethrin for a single depolarization, but this difference attenuates with repetitive activity. Further comparison with peripheral neurons from antennae suggest that these modifications are neuron type specific. Modeling the sodium channel as a multi-state channel with fast and slow inactivation allows to underline the effects of pyrethroids on a set of rate constants connecting open and inactivated conformations, and give some insights to their specificity. Altogether, our results revealed a differential sensitivity of central olfactory neurons to pyrethroids that emphasize the ability for these compounds to impair detection and

  5. Dopaminergic modulation of the voltage-gated sodium current in the cochlear afferent neurons of the rat.

    Directory of Open Access Journals (Sweden)

    Catalina Valdés-Baizabal

    Full Text Available The cochlear inner hair cells synapse onto type I afferent terminal dendrites, constituting the main afferent pathway for auditory information flow. This pathway receives central control input from the lateral olivocochlear efferent neurons that release various neurotransmitters, among which dopamine (DA plays a salient role. DA receptors activation exert a protective role in the over activation of the afferent glutamatergic synapses, which occurs when an animal is exposed to intense sound stimuli or during hypoxic events. However, the mechanism of action of DA at the cellular level is still not completely understood. In this work, we studied the actions of DA and its receptor agonists and antagonists on the voltage-gated sodium current (INa in isolated cochlear afferent neurons of the rat to define the mechanisms of dopaminergic control of the afferent input in the cochlear pathway. Experiments were performed using the voltage and current clamp techniques in the whole-cell configuration in primary cultures of cochlear spiral ganglion neurons (SGNs. Recordings of the INa showed that DA receptor activation induced a significant inhibition of the peak current amplitude, leading to a significant decrease in cell excitability. Inhibition of the INa was produced by a phosphorylation of the sodium channels as shown by the use of phosphatase inhibitor that produced an inhibition analogous to that caused by DA receptor activation. Use of specific agonists and antagonists showed that inhibitory action of DA was mediated both by activation of D1- and D2-like DA receptors. The action of the D1- and D2-like receptors was shown to be mediated by a Gαs/AC/cAMP/PKA and Gαq/PLC/PKC pathways respectively. These results showed that DA receptor activation constitutes a significant modulatory input to SGNs, effectively modulating their excitability and information flow in the auditory pathway.

  6. Dopaminergic modulation of the voltage-gated sodium current in the cochlear afferent neurons of the rat.

    Science.gov (United States)

    Valdés-Baizabal, Catalina; Soto, Enrique; Vega, Rosario

    2015-01-01

    The cochlear inner hair cells synapse onto type I afferent terminal dendrites, constituting the main afferent pathway for auditory information flow. This pathway receives central control input from the lateral olivocochlear efferent neurons that release various neurotransmitters, among which dopamine (DA) plays a salient role. DA receptors activation exert a protective role in the over activation of the afferent glutamatergic synapses, which occurs when an animal is exposed to intense sound stimuli or during hypoxic events. However, the mechanism of action of DA at the cellular level is still not completely understood. In this work, we studied the actions of DA and its receptor agonists and antagonists on the voltage-gated sodium current (INa) in isolated cochlear afferent neurons of the rat to define the mechanisms of dopaminergic control of the afferent input in the cochlear pathway. Experiments were performed using the voltage and current clamp techniques in the whole-cell configuration in primary cultures of cochlear spiral ganglion neurons (SGNs). Recordings of the INa showed that DA receptor activation induced a significant inhibition of the peak current amplitude, leading to a significant decrease in cell excitability. Inhibition of the INa was produced by a phosphorylation of the sodium channels as shown by the use of phosphatase inhibitor that produced an inhibition analogous to that caused by DA receptor activation. Use of specific agonists and antagonists showed that inhibitory action of DA was mediated both by activation of D1- and D2-like DA receptors. The action of the D1- and D2-like receptors was shown to be mediated by a Gαs/AC/cAMP/PKA and Gαq/PLC/PKC pathways respectively. These results showed that DA receptor activation constitutes a significant modulatory input to SGNs, effectively modulating their excitability and information flow in the auditory pathway.

  7. Secondary neurotransmitter deficiencies in epilepsy caused by voltage-gated sodium channelopathies: A potential treatment target?

    Science.gov (United States)

    Horvath, Gabriella A; Demos, Michelle; Shyr, Casper; Matthews, Allison; Zhang, Linhua; Race, Simone; Stockler-Ipsiroglu, Sylvia; Van Allen, Margot I; Mancarci, Ogan; Toker, Lilah; Pavlidis, Paul; Ross, Colin J; Wasserman, Wyeth W; Trump, Natalie; Heales, Simon; Pope, Simon; Cross, J Helen; van Karnebeek, Clara D M

    2016-01-01

    We describe neurotransmitter abnormalities in two patients with drug-resistant epilepsy resulting from deleterious de novo mutations in sodium channel genes. Whole exome sequencing identified a de novo SCN2A splice-site mutation (c.2379+1G>A, p.Glu717Gly.fs*30) resulting in deletion of exon 14, in a 10-year old male with early onset global developmental delay, intermittent ataxia, autism, hypotonia, epileptic encephalopathy and cerebral/cerebellar atrophy. In the cerebrospinal fluid both homovanillic acid and 5-hydroxyindoleacetic acid were significantly decreased; extensive biochemical and genetic investigations ruled out primary neurotransmitter deficiencies and other known inborn errors of metabolism. In an 8-year old female with an early onset intractable epileptic encephalopathy, developmental regression, and progressive cerebellar atrophy, a previously unreported de novo missense mutation was identified in SCN8A (c.5615G>A; p.Arg1872Gln), affecting a highly conserved residue located in the C-terminal of the Nav1.6 protein. Aside from decreased homovanillic acid and 5-hydroxyindoleacetic acid, 5-methyltetrahydrofolate was also found to be low. We hypothesize that these channelopathies cause abnormal synaptic mono-amine metabolite secretion/uptake via impaired vesicular release and imbalance in electrochemical ion gradients, which in turn aggravate the seizures. Treatment with oral 5-hydroxytryptophan, l-Dopa/Carbidopa, and a dopa agonist resulted in mild improvement of seizure control in the male case, most likely via dopamine and serotonin receptor activated signal transduction and modulation of glutamatergic, GABA-ergic and glycinergic neurotransmission. Neurotransmitter analysis in other sodium channelopathy patients will help validate our findings, potentially yielding novel treatment opportunities. Copyright © 2015 Elsevier Inc. All rights reserved.

  8. 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

  9. The up-regulation of voltage-gated sodium channels subtypes coincides with an increased sodium current in hippocampal neuronal culture model.

    Science.gov (United States)

    Guo, Feng; Xu, Xiaoxue; Cai, Jiqun; Hu, Huiyuan; Sun, Wei; He, Guilin; Shao, Dongxue; Wang, Lei; Chen, Tianbao; Shaw, Chris; Zhu, Tong; Hao, Liying

    2013-02-01

    Voltage-gated sodium channels (VGSC) have been linked to inherited forms of epilepsy. The expression and biophysical properties of VGSC in the hippocampal neuronal culture model have not been clarified. In order to evaluate mechanisms of epileptogenesis that are related to VGSC, we examined the expression and function of VGSC in the hippocampal neuronal culture model in vitro and spontaneously epileptic rats (SER) in vivo. Our data showed that the peak amplitude of transient, rapidly-inactivating Na(+) current (I(Na,T)) in model neurons was significantly increased compared with control neurons, and the activation curve was shifted to the negative potentials in model neurons in whole cell recording by patch-clamp. In addition, channel activity of persistent, non-inactivating Na(+) current (I(Na,P)) was obviously increased in the hippocampal neuronal culture model as judged by single-channel patch-clamp recording. Furthermore, VGSC subtypes Na(V)1.1, Na(V)1.2 and Na(V)1.3 were up-regulated at the protein expression level in model neurons and SER as assessed by Western blotting. Four subtypes of VGSC proteins in SER were clearly present throughout the hippocampus, including CA1, CA3 and dentate gyrus regions, and neurons expressing VGSC immunoreactivity were also detected in hippocampal neuronal culture model by immunofluorescence. These findings suggested that the up-regulation of voltage-gated sodium channels subtypes in neurons coincided with an increased sodium current in the hippocampal neuronal culture model, providing a possible explanation for the observed seizure discharge and enhanced excitability in epilepsy.

  10. Rufinamide attenuates mechanical allodynia in a model of neuropathic pain in the mouse and stabilizes voltage-gated sodium channel inactivated state.

    Science.gov (United States)

    Suter, Marc R; Kirschmann, Guylène; Laedermann, Cedric J; Abriel, Hugues; Decosterd, Isabelle

    2013-01-01

    Voltage-gated sodium channels dysregulation is important for hyperexcitability leading to pain persistence. Sodium channel blockers currently used to treat neuropathic pain are poorly tolerated. Getting new molecules to clinical use is laborious. We here propose a drug already marketed as anticonvulsant, rufinamide. We compared the behavioral effect of rufinamide to amitriptyline using the Spared Nerve Injury neuropathic pain model in mice. We compared the effect of rufinamide on sodium currents using in vitro patch clamp in cells expressing the voltage-gated sodium channel Nav1.7 isoform and on dissociated dorsal root ganglion neurons to amitriptyline and mexiletine. In naive mice, amitriptyline (20 mg/kg) increased withdrawal threshold to mechanical stimulation from 1.3 (0.6-1.9) (median [95% CI]) to 2.3 g (2.2-2.5) and latency of withdrawal to heat stimulation from 13.1 (10.4-15.5) to 30.0 s (21.8-31.9), whereas rufinamide had no effect. Rufinamide and amitriptyline alleviated injury-induced mechanical allodynia for 4 h (maximal effect: 0.10 ± 0.03 g (mean ± SD) to 1.99 ± 0.26 g for rufinamide and 0.25 ± 0.22 g to 1.92 ± 0.85 g for amitriptyline). All drugs reduced peak current and stabilized the inactivated state of voltage-gated sodium channel Nav1.7, with similar effects in dorsal root ganglion neurons. At doses alleviating neuropathic pain, amitriptyline showed alteration of behavioral response possibly related to either alteration of basal pain sensitivity or sedative effect or both. Side-effects and drug tolerance/compliance are major problems with drugs such as amitriptyline. Rufinamide seems to have a better tolerability profile and could be a new alternative to explore for the treatment of neuropathic pain.

  11. A clinico-radiological phenotype of voltage-gated potassium channel complex antibody-mediated disorder presenting with seizures and basal ganglia changes.

    Science.gov (United States)

    Hacohen, Yael; Wright, Sukhvir; Siddiqui, Ata; Pandya, Nikki; Lin, Jean-Pierre; Vincent, Angela; Lim, Ming

    2012-12-01

    In childhood, central nervous system (CNS) presentations associated with antibodies to voltage-gated potassium channel (VGKC) complex include limbic encephalitis, status epilepticus, epileptic encephalopathy, and autistic regression. We report the cases of two individuals (a 6-year-old male and an 11-year-old female) who presented with an acute-onset explosive seizure disorder with positive VGKC complex antibodies and bilateral basal ganglia changes on magnetic resonance imaging (MRI). Both patients made a complete clinical recovery, without immunotherapy, with resolution of the MRI changes and normalization of the antibody levels. Extended antibody testing, including testing for leucine-rich glioma-inactivated 1 (LGI1), contactin-associated protein 2, and contactin-2 was negative. This could suggest that the clinico-radiological phenotype in our patients may in fact be associated with a novel autoreactive target(s) within the VGKC complex, as may be the case in other children with VGKC complex-mediated CNS disorders.

  12. Miniaturization of Scorpion β-Toxins Uncovers a Putative Ancestral Surface of Interaction with Voltage-gated Sodium Channels*♦

    OpenAIRE

    2008-01-01

    The bioactive surface of scorpion β-toxins that interact with receptor site-4 at voltage-gated sodium channels is constituted of residues of the conserved βαββ core and the C-tail. In an attempt to evaluate the extent by which residues of the toxin core contribute to bioactivity, the anti-insect and anti-mammalian β-toxins Bj-xtrIT and Css4 were truncated at their N and C termini, resulting in miniature peptides composed essentially of the core secondary structure motives. The truncated β-tox...

  13. Blockage of the Upregulation of Voltage-Gated Sodium Channel Nav1.3 Improves Outcomes after Experimental Traumatic Brain Injury

    OpenAIRE

    HUANG, XIAN-JIAN; Li, Wei-Ping; Lin, Yong; Feng, Jun-Feng; Jia,Feng; Mao, Qing; Jiang, Ji-yao

    2014-01-01

    Excessive active voltage-gated sodium channels are responsible for the cellular abnormalities associated with secondary brain injury following traumatic brain injury (TBI). We previously presented evidence that significant upregulation of Nav1.3 expression occurs in the rat cortex at 2 h and 12 h post-TBI and is correlated with TBI severity. In our current study, we tested the hypothesis that blocking upregulation of Nav1.3 expression in vivo in the acute stage post-TBI attenuates the seconda...

  14. Expression of Voltage-Gated Sodium Channel Nav1.3 Is Associated with Severity of Traumatic Brain Injury in Adult Rats

    OpenAIRE

    Huang, Xian-jian; Mao, Qing; Lin, Yong; Feng, Jun-Feng; Jiang, Ji-Yao

    2013-01-01

    During the secondary injury period after traumatic brain injury (TBI), depolarization of neurons mediated by voltage-gated sodium channels (VGSCs) leads to cellular abnormalities and neurological dysfunction. Alterations in expression of different α subunits of VGSCs can affect early brain pathology following TBI. This study detected the expression of Nav1.3 mRNA and protein in the rat cortex post-TBI. Adult male Sprague–Dawley rats were randomly assigned to sham-TBI, mild-TBI (mTBI), or seve...

  15. 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/.

  16. Voltage-gated sodium channel gene repertoire of lampreys: gene duplications, tissue-specific expression and discovery of a long-lost gene.

    Science.gov (United States)

    Zakon, Harold H; Li, Weiming; Pillai, Nisha E; Tohari, Sumanty; Shingate, Prashant; Ren, Jianfeng; Venkatesh, Byrappa

    2017-09-27

    Studies of the voltage-gated sodium (Nav) channels of extant gnathostomes have made it possible to deduce that ancestral gnathostomes possessed four voltage-gated sodium channel genes derived from a single ancestral chordate gene following two rounds of genome duplication early in vertebrates. We investigated the Nav gene family in two species of lampreys (the Japanese lamprey Lethenteron japonicum and sea lamprey Petromyzon marinus) (jawless vertebrates-agnatha) and compared them with those of basal vertebrates to better understand the origin of Nav genes in vertebrates. We noted six Nav genes in both lamprey species, but orthology with gnathostome (jawed vertebrate) channels was inconclusive. Surprisingly, the Nav2 gene, ubiquitously found in invertebrates and believed to have been lost in vertebrates, is present in lampreys, elephant shark (Callorhinchus milii) and coelacanth (Latimeria chalumnae). Despite repeated duplication of the Nav1 family in vertebrates, Nav2 is only in single copy in those vertebrates in which it is retained, and was independently lost in ray-finned fishes and tetrapods. Of the other five Nav channel genes, most were expressed in brain, one in brain and heart, and one exclusively in skeletal muscle. Invertebrates do not express Nav channel genes in muscle. Thus, early in the vertebrate lineage Nav channels began to diversify and different genes began to express in heart and muscle. © 2017 The Author(s).

  17. Immunohistochemical investigation of voltage-gated potassium channel-interacting protein 1 in normal rat brain and Pentylenettrazole-induced seizures

    Institute of Scientific and Technical Information of China (English)

    Tao SU; Ai-Hua LUO; Wen-Dong CONG; Wei-Wen SUN; Wei-Yi DENG; Qi-Hua ZHAO; Zhuo-Hua ZHANG; Wei-Ping LIAO

    2006-01-01

    Objective To explore the possible role of voltage-gated potassium channel-interacting protein 1 (KChIP1) in the pathogenesis of epilepsy. Methods Sprague Dawley female adult rats were treated with pentylenettrazole (PTZ) to develop acute and chronic epilepsy models. The approximate coronal sections of normal and epilepsy rat brain were processed for immunohistochemistry. Double-labeling confocal microscopy was used to determine the coexistence of KChIP1 and gamma-aminobutyric acid (GABA). Results KChIP1 was expressed abundantly throughout adult rat brain.KChIP1 is highly co-localize with GABA transmitter in hippocampus and cerebral cortex. In the acute PTZ-induced convulsive rats, the number of KChIP1-postive cells was significantly increased especially in the regions of CA 1 and CA3 (P < 0.05); whereas the chronic PTZ-induced convulsive rats were found no changes. The number of GABA-labeled and co-labeled neurons in the hippocampus appeared to have no significant alteration responding to the epilepsy-genesis treatments. Conclusion KChIP1 might be involved in the PTZ-induced epileptogenesis process as a regulator to neuronal excitability through influencing the properties of potassium channels. KChIP1 is preferentially expressed in GABAergic neurons, but its changes did not couple with GABA in the epileptic models.

  18. p.D1690N sodium voltage-gated channel α subunit 5 mutation reduced sodium current density and is associated with Brugada syndrome.

    Science.gov (United States)

    Zeng, Zhipeng; Xie, Qiang; Huang, Yuan; Zhao, Yuanyuan; Li, Weihua; Huang, Zhengrong

    2016-06-01

    Brugada syndrome (BrS) is an inherited primary arrhythmia disorder, leading to sudden cardiac death due to ventricular tachyarrhythmia, but does not exhibit clinical cardiac abnormalities. The sodium voltage-gated channel α subunit 5 (SCN5A) gene, which encodes the α subunit of the cardiac sodium channel, Nav1.5, is the most common pathogenic gene, although ≥22 BrS‑susceptibility genes have previously been identified. In the present study, a novel genetic variant (p.D1690N) localized in the S5‑S6 linker of domain IV of the Nav1.5 channels was identified in a Chinese Han family. Wild‑type (WT) and p.D1690N Nav1.5 channels were transiently over‑expressed in HEK293 cells and analyzed via the whole-cell patch clamp technique. The p.D1690N mutation significantly reduced the peak sodium current density to 23% of WT (at ‑20 mV; P<0.01), shifted steady‑state activation by 7 mV to increasingly positive potentials (P<0.01). Furthermore, prolonging of the recovery from inactivation was observed in the p.D1690N mutant. No significant change was identified in steady‑state inactivation. Thus, the mutant‑induced changes contributed to the loss of function of Nav1.5 channels, which indicates that the p.D1690N variant may have a pathogenic role in BrS.

  19. [Effects of beta-cypermethrin on voltage-gated potassium channels in rat hippocampal CA3 neurons].

    Science.gov (United States)

    Fu, Zhi-Yan; DU, Chun-Yun; Yao, Yang; Liu, Chao-Wei; Tian, Yu-Tao; He, Bing-Jun; Zhang, Tao; Yang, Zhuo

    2007-02-25

    The effects of beta-cypermethrin (consisting of alpha-cypermethrin and theta-cypermethrin) on the transient outward potassium current (I(A)) and delayed rectifier potassium current (I(K)) in freshly dissociated hippocampal CA3 neurons of rats were studied using whole-cell patch-clamp technique. The results indicated that alpha-cypermethrin increased the value of I(A) and theta-cypermethrin decreased the value of I(A), though both of them shifted steady activation curve of I(A) towards negative potential. theta-cypermethrin contributed to the inactivation of I(A). The results also showed that alpha-cypermethrin and theta-cypermethrin decreased the value of I(K), and shifted the steady state activation curve of I(K) towards negative potential. Both alpha-cypermethrin and theta-cypermethrin had no obvious effects on the inactivation of I(K). theta-cypermethrin prolonged recovery process of I(K). These results imply that both transient outward potassium channels and delayed rectified potassium channels are the targets of beta-cypermethrin, which may explain the mechanism of toxical effects of beta-cypermethrin on mammalian neurons.

  20. Voltage-gated sodium channel expressed in cultured human smooth muscle cells: involvement of SCN9A.

    Science.gov (United States)

    Jo, Taisuke; Nagata, Taiji; Iida, Haruko; Imuta, Hiroyuki; Iwasawa, Kuniaki; Ma, Ji; Hara, Kei; Omata, Masao; Nagai, Ryozo; Takizawa, Hajime; Nagase, Takahide; Nakajima, Toshiaki

    2004-06-04

    Voltage-gated Na(+) channel (I(Na)) is expressed under culture conditions in human smooth muscle cells (hSMCs) such as coronary myocytes. The aim of this study is to clarify the physiological, pharmacological and molecular characteristics of I(Na) expressed in cultured hSMCs obtained from bronchus, main pulmonary and coronary artery. I(Na), was recorded in these hSMCs and inhibited by tetrodotoxin (TTX) with an IC(50) value of approximately 10 nM. Reverse transcriptase/polymerase chain reaction (RT-PCR) analysis of mRNA showed the prominent expression of transcripts for SCN9A, which was consistent with the results of real-time quantitative RT-PCR. These results provide novel evidence that TTX-sensitive Na(+) channel expressed in cultured hSMCs is mainly composed of Na(v)1.7.

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

    DEFF Research Database (Denmark)

    Rougier, Jean-Sébastien; van Bemmelen, Miguel X; Bruce, M Christine

    2004-01-01

    -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......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...... 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....

  2. Antagonist action of progesterone at σ-receptors in the modulation of voltage-gated sodium channels.

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    Johannessen, Molly; Fontanilla, Dominique; Mavlyutov, Timur; Ruoho, Arnold E; Jackson, Meyer B

    2011-02-01

    σ-Receptors are integral membrane proteins that have been implicated in a number of biological functions, many of which involve the modulation of ion channels. A wide range of synthetic ligands activate σ-receptors, but endogenous σ-receptor ligands have proven elusive. One endogenous ligand, dimethyltryptamine (DMT), has been shown to act as a σ-receptor agonist. Progesterone and other steroids bind σ-receptors, but the functional consequences of these interactions are unclear. Here we investigated progesterone binding to σ(1)- and σ(2)-receptors and evaluated its effect on σ-receptor-mediated modulation of voltage-gated Na(+) channels. Progesterone binds both σ-receptor subtypes in liver membranes with comparable affinities and blocks photolabeling of both subtypes in human embryonic kidney 293 cells that stably express the human cardiac Na(+) channel Na(v)1.5. Patch-clamp recording in this cell line tested Na(+) current modulation by the σ-receptor ligands ditolylguanidine, PB28, (+)SKF10047, and DMT. Progesterone inhibited the action of these ligands to varying degrees, and some of these actions were reduced by σ(1)-receptor knockdown with small interfering RNA. Progesterone inhibition of channel modulation by drugs was consistent with stronger antagonism of σ(2)-receptors. By contrast, progesterone inhibition of channel modulation by DMT was consistent with stronger antagonism of σ(1)-receptors. Progesterone binding to σ-receptors blocks σ-receptor-mediated modulation of a voltage-gated ion channel, and this novel membrane action of progesterone may be relevant to changes in brain and cardiovascular function during endocrine transitions.

  3. Mutation in the kv3.3 voltage-gated potassium channel causing spinocerebellar ataxia 13 disrupts sound-localization mechanisms.

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    Middlebrooks, John C; Nick, Harry S; Subramony, S H; Advincula, Joel; Rosales, Raymond L; Lee, Lillian V; Ashizawa, Tetsuo; Waters, Michael F

    2013-01-01

    Normal sound localization requires precise comparisons of sound timing and pressure levels between the two ears. The primary localization cues are interaural time differences, ITD, and interaural level differences, ILD. Voltage-gated potassium channels, including Kv3.3, are highly expressed in the auditory brainstem and are thought to underlie the exquisite temporal precision and rapid spike rates that characterize brainstem binaural pathways. An autosomal dominant mutation in the gene encoding Kv3.3 has been demonstrated in a large Filipino kindred manifesting as spinocerebellar ataxia type 13 (SCA13). This kindred provides a rare opportunity to test in vivo the importance of a specific channel subunit for human hearing. Here, we demonstrate psychophysically that individuals with the mutant allele exhibit profound deficits in both ITD and ILD sensitivity, despite showing no obvious impairment in pure-tone sensitivity with either ear. Surprisingly, several individuals exhibited the auditory deficits even though they were pre-symptomatic for SCA13. We would expect that impairments of binaural processing as great as those observed in this family would result in prominent deficits in localization of sound sources and in loss of the "spatial release from masking" that aids in understanding speech in the presence of competing sounds.

  4. Control of voltage-gated potassium channel Kv2.2 expression by pyruvate-isocitrate cycling regulates glucose-stimulated insulin secretion.

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    Jensen, Mette V; Haldeman, Jonathan M; Zhang, Hengtao; Lu, Danhong; Huising, Mark O; Vale, Wylie W; Hohmeier, Hans E; Rosenberg, Paul; Newgard, Christopher B

    2013-08-09

    Recent studies have shown that the pyruvate-isocitrate cycling pathway, involving the mitochondrial citrate/isocitrate carrier and the cytosolic NADP-dependent isocitrate dehydrogenase (ICDc), is involved in control of glucose-stimulated insulin secretion (GSIS). Here we demonstrate that pyruvate-isocitrate cycling regulates expression of the voltage-gated potassium channel family member Kv2.2 in islet β-cells. siRNA-mediated suppression of ICDc, citrate/isocitrate carrier, or Kv2.2 expression impaired GSIS, and the effect of ICDc knockdown was rescued by re-expression of Kv2.2. Moreover, chronic exposure of β-cells to elevated fatty acids, which impairs GSIS, resulted in decreased expression of Kv2.2. Surprisingly, knockdown of ICDc or Kv2.2 increased rather than decreased outward K(+) current in the 832/13 β-cell line. Immunoprecipitation studies demonstrated interaction of Kv2.1 and Kv2.2, and co-overexpression of the two channels reduced outward K(+) current compared with overexpression of Kv2.1 alone. Also, siRNA-mediated knockdown of ICDc enhanced the suppressive effect of the Kv2.1-selective inhibitor stromatoxin1 on K(+) currents. Our data support a model in which a key function of the pyruvate-isocitrate cycle is to maintain levels of Kv2.2 expression sufficient to allow it to serve as a negative regulator of Kv channel activity.

  5. IgG and complement deposition and neuronal loss in cats and humans with epilepsy and voltage-gated potassium channel complex antibodies.

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    Klang, Andrea; Schmidt, Peter; Kneissl, Sibylle; Bagó, Zoltán; Vincent, Angela; Lang, Bethan; Moloney, Teresa; Bien, Christian G; Halász, Péter; Bauer, Jan; Pákozdy, Akos

    2014-05-01

    Voltage-gated potassium channel complex (VGKC-complex) antibody (Ab) encephalitis is a well-recognized form of limbic encephalitis in humans, usually occurring in the absence of an underlying tumor. The patients have a subacute onset of seizures, magnetic resonance imaging findings suggestive of hippocampal inflammation, and high serum titers of Abs against proteins of the VGKC-complex, particularly leucine-rich, glioma-inactivated 1 (LGI1). Most patients are diagnosed promptly and recover substantially with immunotherapies; consequently, neuropathological data are limited. We have recently shown that feline complex partial cluster seizures with orofacial involvement (FEPSO) in cats can also be associated with Abs against VGKC-complexes/LGI1. Here we examined the brains of cats with FEPSO and compared the neuropathological findings with those in a human with VGKC-complex-Ab limbic encephalitis. Similar to humans, cats with VGKC-complex-Ab and FEPSO have hippocampal lesions with only moderate T-cell infiltrates but with marked IgG infiltration and complement C9neo deposition on hippocampal neurons, associated with neuronal loss. These findings provide further evidence that FEPSO is a feline form of VGKC-complex-Ab limbic encephalitis and provide a model for increasing understanding of the human disease.

  6. Limbic encephalitis associated with anti-voltage-gated potassium channel complex antibodies as a cause of adult-onset mesial temporal lobe epilepsy.

    Science.gov (United States)

    Toyota, Tomoko; Akamatsu, Naoki; Tsuji, Sadatoshi; Nishizawa, Shigeru

    2014-06-01

    Recently, some reports have indicated that limbic encephalitis associated with anti-voltage-gated potassium channel complex antibodies (VGKC-Ab) is a cause of adult-onset mesial temporal lobe epilepsy (MTLE). We report a 53-year-old woman who had her first epileptic seizure at the age of 50 years old. Examination by 3-Tesla brain MRI revealed left hippocampal high signal intensity and swelling on fluid-attenuated inversion recovery (FLAIR) and T2-weighted imaging at 2 months after her first seizure. The patient received intravenous methylprednisolone and carbamazepine 300 mg/day. One month later, MRI revealed improvement of her left hippocampal abnormalities. Thereafter, she had no seizures, however, three years after her first seizure, EEG revealed a seizure pattern in the left temporal region. Brain MRI revealed left hippocampal high signal intensity and brain fluorodeoxyglucose positron emission tomography revealed hypermetabolism. Her serum VGKC-Ab levels were 118 pM(normal VGKC-Ab levels decreased to 4.4 pM. Remission of the epileptic seizures was also observed. This MTLE in the middle age was considered as limbic encephalitis associated with anti- VGKC-Ab. In cases of unexplained adult-onset MTLE, limbic encephalitis associated with anti-VGKC-Ab, which responds well to immunotherapy, should be considered in the differential diagnosis.

  7. Mutation in the kv3.3 voltage-gated potassium channel causing spinocerebellar ataxia 13 disrupts sound-localization mechanisms.

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    John C Middlebrooks

    Full Text Available Normal sound localization requires precise comparisons of sound timing and pressure levels between the two ears. The primary localization cues are interaural time differences, ITD, and interaural level differences, ILD. Voltage-gated potassium channels, including Kv3.3, are highly expressed in the auditory brainstem and are thought to underlie the exquisite temporal precision and rapid spike rates that characterize brainstem binaural pathways. An autosomal dominant mutation in the gene encoding Kv3.3 has been demonstrated in a large Filipino kindred manifesting as spinocerebellar ataxia type 13 (SCA13. This kindred provides a rare opportunity to test in vivo the importance of a specific channel subunit for human hearing. Here, we demonstrate psychophysically that individuals with the mutant allele exhibit profound deficits in both ITD and ILD sensitivity, despite showing no obvious impairment in pure-tone sensitivity with either ear. Surprisingly, several individuals exhibited the auditory deficits even though they were pre-symptomatic for SCA13. We would expect that impairments of binaural processing as great as those observed in this family would result in prominent deficits in localization of sound sources and in loss of the "spatial release from masking" that aids in understanding speech in the presence of competing sounds.

  8. Serum Starvation-Induced Voltage-Gated Potassium Channel Kv7.5 Expression and Its Regulation by Sp1 in Canine Osteosarcoma Cells

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    Bo Hyung Lee

    2014-01-01

    Full Text Available The KCNQ gene family, whose members encode Kv7 channels, belongs to the voltage-gated potassium (Kv channel group. The roles of this gene family have been widely investigated in nerve and muscle cells. In the present study, we investigated several characteristics of Kv7.5, which is strongly expressed in the canine osteosarcoma cell line, CCL-183. Serum starvation upregulated Kv7.5 expression, and the Kv7 channel opener, flupirtine, attenuated cell proliferation by arresting cells in the G0/G1 phase. We also showed that Kv7.5 knockdown helps CCL-183 cells to proliferate. In an effort to find an endogenous regulator of Kv7.5, we used mithramycin A to reduce the level of the transcription factor Sp1, and it strongly inhibited the induction of Kv7.5 in CCL-183 cells. These results suggest that the activation of Kv7.5 by flupirtine may exert an anti-proliferative effect in canine osteosarcoma. Therefore, Kv7.5 is a possible molecular target for canine osteosarcoma therapy.

  9. Multi-country Survey Revealed Prevalent and Novel F1534S Mutation in Voltage-Gated Sodium Channel (VGSC Gene in Aedes albopictus.

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    Jiabao Xu

    2016-05-01

    Full Text Available Aedes albopictus is an important dengue vector because of its aggressive biting behavior and rapid spread out of its native home range in Southeast Asia. Pyrethroids are widely used for adult mosquito control, and resistance to pyrethroids should be carefully monitored because vector control is the only effective method currently available to prevent dengue transmission. The voltage-gated sodium channel gene is the target site of pyrethroids, and mutations in this gene cause knockdown resistance (kdr. Previous studies reported various mutations in the voltage-gated sodium channel (VGSC gene, but the spatial distribution of kdr mutations in Ae. albopictus has not been systematically examined, and the association between kdr mutation and phenotypic resistance has not been established.A total of 597 Ae. albopictus individuals from 12 populations across Asia, Africa, America and Europe were examined for mutations in the voltage-gated sodium channel gene. Three domains for a total of 1,107 bp were sequenced for every individual. Two populations from southern China were examined for pyrethroid resistance using the World Health Organization standard tube bioassay, and the association between kdr mutations and phenotypic resistance was tested.A total of 29 synonymous mutations were found across domain II, III and IV of the VGSC gene. Non-synonymous mutations in two codons of the VGSC gene were detected in 5 populations from 4 countries. A novel mutation at 1532 codon (I1532T was found in Rome, Italy with a frequency of 19.7%. The second novel mutation at codon 1534 (F1534S was detected in southern China and Florida, USA with a frequency ranging from 9.5-22.6%. The WHO insecticide susceptibility bioassay found 90.1% and 96.1% mortality in the two populations from southern China, suggesting resistance and probable resistance. Positive association between kdr mutations with deltamethrin resistance was established in these two populations.Two novel kdr

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

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    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

  11. The receptor-like pseudokinase MRH1 interacts with the voltage-gated potassium channel AKT2

    Science.gov (United States)

    Sklodowski, Kamil; Riedelsberger, Janin; Raddatz, Natalia; Riadi, Gonzalo; Caballero, Julio; Chérel, Isabelle; Schulze, Waltraud; Graf, Alexander; Dreyer, Ingo

    2017-03-01

    The potassium channel AKT2 plays important roles in phloem loading and unloading. It can operate as inward-rectifying channel that allows H+-ATPase-energized K+ uptake. Moreover, through reversible post-translational modifications it can also function as an open, K+-selective channel, which taps a ‘potassium battery’, providing additional energy for transmembrane transport processes. Knowledge about proteins involved in the regulation of the operational mode of AKT2 is very limited. Here, we employed a large-scale yeast two-hybrid screen in combination with fluorescence tagging and null-allele mutant phenotype analysis and identified the plasma membrane localized receptor-like kinase MRH1/MDIS2 (AT4G18640) as interaction partner of AKT2. The phenotype of the mrh1-1 knockout plant mirrors that of akt2 knockout plants in energy limiting conditions. Electrophysiological analyses showed that MRH1/MDIS2 failed to exert any functional regulation on AKT2. Using structural protein modeling approaches, we instead gathered evidence that the putative kinase domain of MRH1/MDIS2 lacks essential sites that are indispensable for a functional kinase suggesting that MRH1/MDIS2 is a pseudokinase. We propose that MRH1/MDIS2 and AKT2 are likely parts of a bigger protein complex. MRH1 might help to recruit other, so far unknown partners, which post-translationally regulate AKT2. Additionally, MRH1 might be involved in the recognition of chemical signals.

  12. Voltage-gated potassium currents are targets of diurnal changes in estradiol feedback regulation and kisspeptin action on gonadotropin-releasing hormone neurons in mice.

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    Pielecka-Fortuna, Justyna; DeFazio, R Anthony; Moenter, Suzanne M

    2011-11-01

    Estradiol has both negative and positive feedback actions upon gonadotropin-releasing hormone (GnRH) release; the latter actions trigger the preovulatory GnRH surge. Although neurobiological mechanisms of the transitions between feedback modes are becoming better understood, the roles of voltage-gated potassium currents, major contributors to neuronal excitability, are unknown. Estradiol alters two components of potassium currents in these cells: a transient current, I(A), and a sustained current, I(K). Kisspeptin is a potential mediator between estradiol and GnRH neurons and can act directly on GnRH neurons. We examined how estradiol, time of day, and kisspeptin interact to regulate these conductances in a mouse model exhibiting daily switches between estradiol negative (morning) and positive feedback (evening). Whole-cell voltage clamp recordings were made from GnRH neurons in brain slices from ovariectomized (OVX) mice and from OVX mice treated with estradiol (OVX+E). There were no diurnal changes in either I(A) or I(K) in GnRH neurons from OVX mice. In contrast, in GnRH neurons from OVX+E mice, I(A) and I(K) were greater during the morning when GnRH neuron activity is low and smaller in the evening when GnRH neuron activity is high. Estradiol increased I(A) in the morning and decreased it in the evening, relative to that in cells from OVX mice. Exogenously applied kisspeptin reduced I(A) regardless of time of day or estradiol status. Estradiol, interacting with time of day, and kisspeptin both depolarized I(A) activation. These findings extend our understanding of both the neurobiological mechanisms of estradiol negative vs. positive regulation of GnRH neurons and of kisspeptin action on these cells.

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

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    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.

  14. Autosomal dominant erythermalgia associated with a novel mutation in the voltage-gated sodium channel alpha subunit Nav1.7.

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    Michiels, Jan J; te Morsche, Rene H M; Jansen, Jan B M J; Drenth, Joost P H

    2005-10-01

    Autosomal dominant primary erythermalgia is a rare disorder characterized by recurrent attacks of red, warm, and painful hands and/or feet. To describe the phenotypes and molecular data of a 10-member family with 5 symptomatic living patients with erythermalgia. The clinical phenotype of this family was featured by episodic or continuous symmetrical red swelling, irritating warmth, and burning pain of feet and lower legs provoked or aggravated by warmth and exercise, and relief was always obtained by application of cold, such as putting feet in (ice-) cold water. The symptoms in this family were only partially controlled by analgesics and sedatives. All affected family members were heterozygous for a novel mutation (S241T) of the voltage-gated sodium channel alpha subunit Nav1.7. Primary erythermalgia may be a neuropathic disorder of the small peripheral sensory and sympathetic neurons, and may be caused by hyperexcitability of Nav1.7.

  15. Therapeutic value of voltage-gated sodium channel inhibitors in breast, colorectal and prostate cancer: a systematic review

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    Fabiola eMartin

    2015-11-01

    Full Text Available Although survival rates of breast, colon and prostate cancers are improving, deaths from these tumors frequently occur due to metastasis. Voltage-gated Na+ channels (VGSCs are membrane proteins, which regulate membrane current and cellular migration during nervous system organogenesis. VGSCs are also expressed in fibroblasts, immune cells, glia and metastatic cancer cells. VGSCs regulate migration and invasion of breast, bowel and prostate cancer cells, suggesting that they may be novel anti-metastatic targets. We conducted a systematic review of clinical and preclinical studies testing the effects of VGSC-inhibiting drugs in cancer. 204 publications were identified, of which two human, two mouse and 20 in vitro publications were included. In the clinical studies, the effect of these drugs on survival and metastatic relapse is not clear. The 22 preclinical studies collectively suggest that several VGSC-inhibiting drugs inhibit cancer proliferation, migration and invasion. None of the human and only six of the preclinical studies directly investigated the effect of the drugs on VGSC activity. Studies were difficult to compare due to lack of standardized methodology and outcome measures. We conclude that the benefits of VGSC inhibitors require further investigation. Standardization of future studies and outcome measures should enable meaningful study comparisons.

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

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    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.

  17. S3-S4 linker length modulates the relaxed state of a voltage-gated potassium channel.

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    Priest, Michael F; Lacroix, Jérôme J; Villalba-Galea, Carlos A; Bezanilla, Francisco

    2013-11-19

    Voltage-sensing domains (VSDs) are membrane protein modules found in ion channels and enzymes that are responsible for a large number of fundamental biological tasks, such as neuronal electrical activity. The VSDs switch from a resting to an active conformation upon membrane depolarization, altering the activity of the protein in response to voltage changes. Interestingly, numerous studies describe the existence of a third distinct state, called the relaxed state, also populated at positive potentials. Although some physiological roles for the relaxed state have been suggested, little is known about the molecular determinants responsible for the development and modulation of VSD relaxation. Several lines of evidence have suggested that the linker (S3-S4 linker) between the third (S3) and fourth (S4) transmembrane segments of the VSD alters the equilibrium between resting and active conformations. By measuring gating currents from the Shaker potassium channel, we demonstrate here that shortening the S3-S4 linker stabilizes the relaxed state, whereas lengthening the linker or splitting it and coinjecting two fragments of the channel have little effect. We propose that natural variations of the length of the S3-S4 linker in various VSD-containing proteins may produce differential VSD relaxation in vivo.

  18. Statistical epistasis and functional brain imaging support a role of voltage-gated potassium channels in human memory.

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    Angela Heck

    Full Text Available Despite the current progress in high-throughput, dense genome scans, a major portion of complex traits' heritability still remains unexplained, a phenomenon commonly termed "missing heritability." The negligence of analytical approaches accounting for gene-gene interaction effects, such as statistical epistasis, is probably central to this phenomenon. Here we performed a comprehensive two-way SNP interaction analysis of human episodic memory, which is a heritable complex trait, and focused on 120 genes known to show differential, memory-related expression patterns in rat hippocampus. Functional magnetic resonance imaging was also used to capture genotype-dependent differences in memory-related brain activity. A significant, episodic memory-related interaction between two markers located in potassium channel genes (KCNB2 and KCNH5 was observed (P(nominal combined=0.000001. The epistatic interaction was robust, as it was significant in a screening (P(nominal=0.0000012 and in a replication sample (P(nominal=0.01. Finally, we found genotype-dependent activity differences in the parahippocampal gyrus (P(nominal=0.001 supporting the behavioral genetics finding. Our results demonstrate the importance of analytical approaches that go beyond single marker statistics of complex traits.

  19. Alternative splicing modulates inactivation of type 1 voltage-gated sodium channels by toggling an amino acid in the first S3-S4 linker.

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    Fletcher, Emily V; Kullmann, Dimitri M; Schorge, Stephanie

    2011-10-21

    Voltage-gated sodium channels underlie the upstroke of action potentials and are fundamental to neuronal excitability. Small changes in the behavior of these channels are sufficient to change neuronal firing and trigger seizures. These channels are subject to highly conserved alternative splicing, affecting the short linker between the third transmembrane segment (S3) and the voltage sensor (S4) in their first domain. The biophysical consequences of this alternative splicing are incompletely understood. Here we focus on type 1 sodium channels (Nav1.1) that are implicated in human epilepsy. We show that the functional consequences of alternative splicing are highly sensitive to recording conditions, including the identity of the major intracellular anion and the recording temperature. In particular, the inactivation kinetics of channels containing the alternate exon 5N are more sensitive to intracellular fluoride ions and to changing temperature than channels containing exon 5A. Moreover, Nav1.1 channels containing exon 5N recover from inactivation more rapidly at physiological temperatures. Three amino acids differ between exons 5A and 5N. However, the changes in sensitivity and stability of inactivation were reproduced by a single conserved change from aspartate to asparagine in channels containing exon 5A, which was sufficient to make them behave like channels containing the complete exon 5N sequence. These data suggest that splicing at this site can modify the inactivation of sodium channels and reveal a possible interaction between splicing and anti-epileptic drugs that stabilize sodium channel inactivation.

  20. Voltage-gated sodium (NaV) channel blockade by plant cannabinoids does not confer anticonvulsant effects per se.

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    Hill, Andrew J; Jones, Nicholas A; Smith, Imogen; Hill, Charlotte L; Williams, Claire M; Stephens, Gary J; Whalley, Benjamin J

    2014-04-30

    Cannabidiol (CBD) is a non-psychoactive, well-tolerated, anticonvulsant plant cannabinoid, although its mechanism(s) of seizure suppression remains unknown. Here, we investigate the effect of CBD and the structurally similar cannabinoid, cannabigerol (CBG), on voltage-gated Na(+) (NaV) channels, a common anti-epileptic drug target. CBG's anticonvulsant potential was also assessed in vivo. CBD effects on NaV channels were investigated using patch-clamp recordings from rat CA1 hippocampal neurons in brain slices, human SH-SY5Y (neuroblastoma) cells and mouse cortical neurons in culture. CBG effects were also assessed in SH-SY5Y cells and mouse cortical neurons. CBD and CBG effects on veratridine-stimulated human recombinant NaV1.1, 1.2 or 1.5 channels were assessed using a membrane potential-sensitive fluorescent dye high-throughput assay. The effect of CBG on pentyleneterazole-induced (PTZ) seizures was assessed in rat. CBD (10μM) blocked NaV currents in SH-SY5Y cells, mouse cortical neurons and recombinant cell lines, and affected spike parameters in rat CA1 neurons; CBD also significantly decreased membrane resistance. CBG blocked NaV to a similar degree to CBD in both SH-SY5Y and mouse recordings, but had no effect (50-200mg/kg) on PTZ-induced seizures in rat. CBD and CBG are NaV channel blockers at micromolar concentrations in human and murine neurons and recombinant cells. In contrast to previous reports investigating CBD, CBG had no effect upon PTZ-induced seizures in rat, indicating that NaV blockade per se does not correlate with anticonvulsant effects. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  1. Four and a half LIM protein 1C (FHL1C: a binding partner for voltage-gated potassium channel K(v1.5.

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    Ivana Poparic

    Full Text Available Four-and-a-half LIM domain protein 1 isoform A (FHL1A is predominantly expressed in skeletal and cardiac muscle. Mutations in the FHL1 gene are causative for several types of hereditary myopathies including X-linked myopathy with postural muscle atrophy (XMPMA. We here studied myoblasts from XMPMA patients. We found that functional FHL1A protein is completely absent in patient myoblasts. In parallel, expression of FHL1C is either unaffected or increased. Furthermore, a decreased proliferation rate of XMPMA myoblasts compared to controls was observed but an increased number of XMPMA myoblasts was found in the G(0/G(1 phase. Furthermore, low expression of K(v1.5, a voltage-gated potassium channel known to alter myoblast proliferation during the G(1 phase and to control repolarization of action potential, was detected. In order to substantiate a possible relation between K(v1.5 and FHL1C, a pull-down assay was performed. A physical and direct interaction of both proteins was observed in vitro. In addition, confocal microscopy revealed substantial colocalization of FHL1C and K(v1.5 within atrial cells, supporting a possible interaction between both proteins in vivo. Two-electrode voltage clamp experiments demonstrated that coexpression of K(v1.5 with FHL1C in Xenopus laevis oocytes markedly reduced K(+ currents when compared to oocytes expressing K(v1.5 only. We here present the first evidence on a biological relevance of FHL1C.

  2. Molecular Characterization of Voltage-Gated Sodium Channels and Their Relations with Paralytic Shellfish Toxin Bioaccumulation in the Pacific Oyster Crassostrea gigas

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    Floriane Boullot

    2017-01-01

    Full Text Available Paralytic shellfish toxins (PST bind to voltage-gated sodium channels (Nav and block conduction of action potential in excitable cells. This study aimed to (i characterize Nav sequences in Crassostrea gigas and (ii investigate a putative relation between Nav and PST-bioaccumulation in oysters. The phylogenetic analysis highlighted two types of Nav in C. gigas: a Nav1 (CgNav1 and a Nav2 (CgNav2 with sequence properties of sodium-selective and sodium/calcium-selective channels, respectively. Three alternative splice transcripts of CgNav1 named A, B and C, were characterized. The expression of CgNav1, analyzed by in situ hybridization, is specific to nervous cells and to structures corresponding to neuromuscular junctions. Real-time PCR analyses showed a strong expression of CgNav1A in the striated muscle while CgNav1B is mainly expressed in visceral ganglia. CgNav1C expression is ubiquitous. The PST binding site (domain II of CgNav1 variants possess an amino acid Q that could potentially confer a partial saxitoxin (STX-resistance to the channel. The CgNav1 genotype or alternative splicing would not be the key point determining PST bioaccumulation level in oysters.

  3. Crystal Structure of a Fibroblast Growth Factor Homologous Factor (FHF) Defines a Conserved Surface on FHFs for Binding and Modulation of Voltage-gated Sodium Channels

    Energy Technology Data Exchange (ETDEWEB)

    Goetz, R.; Dover, K; Laezza, F; Shtraizent, N; Huang, X; Tchetchik, D; Eliseenkova, A; Goldfarb, M; Mohammadi, M; et. al.

    2009-01-01

    Voltage-gated sodium channels (Nav) produce sodium currents that underlie the initiation and propagation of action potentials in nerve and muscle cells. Fibroblast growth factor homologous factors (FHFs) bind to the intracellular C-terminal region of the Nav alpha subunit to modulate fast inactivation of the channel. In this study we solved the crystal structure of a 149-residue-long fragment of human FHF2A which unveils the structural features of the homology core domain of all 10 human FHF isoforms. Through analysis of crystal packing contacts and site-directed mutagenesis experiments we identified a conserved surface on the FHF core domain that mediates channel binding in vitro and in vivo. Mutations at this channel binding surface impaired the ability of FHFs to co-localize with Navs at the axon initial segment of hippocampal neurons. The mutations also disabled FHF modulation of voltage-dependent fast inactivation of sodium channels in neuronal cells. Based on our data, we propose that FHFs constitute auxiliary subunits for Navs.

  4. Molecular Characterization of Voltage-Gated Sodium Channels and Their Relations with Paralytic Shellfish Toxin Bioaccumulation in the Pacific Oyster Crassostrea gigas

    Science.gov (United States)

    Boullot, Floriane; Castrec, Justine; Bidault, Adeline; Dantas, Natanael; Payton, Laura; Perrigault, Mickael; Tran, Damien; Amzil, Zouher; Boudry, Pierre; Soudant, Philippe; Hégaret, Hélène; Fabioux, Caroline

    2017-01-01

    Paralytic shellfish toxins (PST) bind to voltage-gated sodium channels (Nav) and block conduction of action potential in excitable cells. This study aimed to (i) characterize Nav sequences in Crassostrea gigas and (ii) investigate a putative relation between Nav and PST-bioaccumulation in oysters. The phylogenetic analysis highlighted two types of Nav in C. gigas: a Nav1 (CgNav1) and a Nav2 (CgNav2) with sequence properties of sodium-selective and sodium/calcium-selective channels, respectively. Three alternative splice transcripts of CgNav1 named A, B and C, were characterized. The expression of CgNav1, analyzed by in situ hybridization, is specific to nervous cells and to structures corresponding to neuromuscular junctions. Real-time PCR analyses showed a strong expression of CgNav1A in the striated muscle while CgNav1B is mainly expressed in visceral ganglia. CgNav1C expression is ubiquitous. The PST binding site (domain II) of CgNav1 variants possess an amino acid Q that could potentially confer a partial saxitoxin (STX)-resistance to the channel. The CgNav1 genotype or alternative splicing would not be the key point determining PST bioaccumulation level in oysters. PMID:28106838

  5. Expression of mRNA coding voltage - gated sodium channel α-subunit in spontaneously epileptic rat

    Institute of Scientific and Technical Information of China (English)

    DUWa; CAIJi-Qun

    2004-01-01

    OBJECTIVE Subtypes Ⅰ,Ⅱ and Ⅲ of sodium channel α- subunit mRNA were analyzed in adult rat brain of spontaneously epileptic rats, and investigated the relationship between sodium channel expression and epilepsy. METHODS Tissue samples were microdissected from occipital neocortex, CA1 and CA3 hippocampus areas and dentate gyms, observe

  6. TNF-α enhances the currents of voltage gated sodium channels in uninjured dorsal root ganglion neurons following motor nerve injury.

    Science.gov (United States)

    Chen, Xi; Pang, Rui-Ping; Shen, Kai-Feng; Zimmermann, Manfred; Xin, Wen-Jun; Li, Yong-Yong; Liu, Xian-Guo

    2011-02-01

    The ectopic discharges observed in uninjured dorsal root ganglion (DRG) neurons following various lesions of spinal nerves have been attributed to functional alterations of voltage-gated sodium channels (VGSCs). Such mechanisms may be important for the development of neuropathic pain. However, the pathophysiology underlying the functional modulation of VGSCs following nerve injury is largely unknown. Here, we studied this issue with use of a selective lumbar 5 ventral root transection (L5-VRT) model, in which dorsal root ganglion (DRG) neurons remain intact. We found that the L5-VRT increased the current densities of TTX-sensitive Na channels as well as currents in Nav1.8, but not Nav1.9 channels in uninjured DRG neurons. The thresholds of action potentials decreased and firing rates increased in DRG neurons following L5-VRT. As we found that levels of tumor necrosis factor-alpha (TNF-α) increased in cerebrospinal fluid (CSF) and in DRG tissue after L5-VRT, we tested whether the increased TNF-α might result in the changes in sodium channels. Indeed, recombinant rat TNF (rrTNF) enhanced the current densities of TTX-S and Nav1.8 in cultured DRG neurons dose-dependently. Furthermore, genetic deletion of TNF receptor 1 (TNFR-1) in mice attenuated the mechanical allodynia and prevented the increase in sodium currents in DRG neurons induced by L5-VRT. These data suggest that the increase in sodium currents in uninjured DRG neurons following nerve injury might be mediated by over-production of TNF-α.

  7. 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.

  8. Benchmarking the stability of human detergent-solubilised voltage-gated sodium channels for structural studies using eel as a reference

    Science.gov (United States)

    Slowik, Daria; Henderson, Richard

    2015-01-01

    With the ultimate goal of detailed structural analysis of mammalian and particularly human voltage-gated sodium channels (VGSCs), we have investigated the relative stability of human and rat VGSCs and compared them with electric eel VGSC. We found that NaV1.3 from rat was the most stable after detergent solubilisation. The order of stability was rNaV1.3 > hNaV1.2 > hNaV1.1 > hNaV1.6 > hNaV1.3 > hNaV1.4. However, a comparison with the VGSC from Electrophorus electricus, which is most similar to NaV1.4, shows that the eel VGSC is considerably more stable in detergent than the human VGSCs examined. We conclude that current methods of structural analysis, such as single particle electron cryomicroscopy (cryoEM), may be most usefully targeted to eel VGSC or rNaV1.3, but that structural analysis on the full spectrum of VGSCs, by methods that require greater stability such as crystallisation and X-ray crystallography, will require further stabilisation of the channel. PMID:25838126

  9. A recombinant fusion protein containing a spider toxin specific for the insect voltage-gated sodium ion channel shows oral toxicity towards insects of different orders.

    Science.gov (United States)

    Yang, Sheng; Pyati, Prashant; Fitches, Elaine; Gatehouse, John A

    2014-04-01

    Recombinant fusion protein technology allows specific insecticidal protein and peptide toxins to display activity in orally-delivered biopesticides. The spider venom peptide δ-amaurobitoxin-PI1a, which targets insect voltage-gated sodium channels, was fused to the "carrier" snowdrop lectin (GNA) to confer oral toxicity. The toxin itself (PI1a) and an amaurobitoxin/GNA fusion protein (PI1a/GNA) were produced using the yeast Pichia pastoris as expression host. Although both proteins caused mortality when injected into cabbage moth (Mamestra brassicae) larvae, the PI1a/GNA fusion was approximately 6 times as effective as recombinant PI1a on a molar basis. PI1a alone was not orally active against cabbage moth larvae, but a single 30 μg dose of the PI1a/GNA fusion protein caused 100% larval mortality within 6 days when fed to 3rd instar larvae, and caused significant reductions in survival, growth and feeding in 4th - 6th instar larvae. Transport of fusion protein from gut contents to the haemolymph of cabbage moth larvae, and binding to the nerve chord, was shown by Western blotting. The PI1a/GNA fusion protein also caused mortality when delivered orally to dipteran (Musca domestica; housefly) and hemipteran (Acyrthosiphon pisum; pea aphid) insects, making it a promising candidate for development as a biopesticide.

  10. Benchmarking the stability of human detergent-solubilised voltage-gated sodium channels for structural studies using eel as a reference.

    Science.gov (United States)

    Slowik, Daria; Henderson, Richard

    2015-07-01

    With the ultimate goal of detailed structural analysis of mammalian and particularly human voltage-gated sodium channels (VGSCs), we have investigated the relative stability of human and rat VGSCs and compared them with electric eel VGSC. We found that NaV1.3 from rat was the most stable after detergent solubilisation. The order of stability was rNaV1.3>hNaV1.2>hNaV1.1>hNaV1.6>hNaV1.3>hNaV1.4. However, a comparison with the VGSC from Electrophorus electricus, which is most similar to NaV1.4, shows that the eel VGSC is considerably more stable in detergent than the human VGSCs examined. We conclude that current methods of structural analysis, such as single particle electron cryomicroscopy (cryoEM), may be most usefully targeted to eel VGSC or rNaV1.3, but that structural analysis on the full spectrum of VGSCs, by methods that require greater stability such as crystallisation and X-ray crystallography, will require further stabilisation of the channel.

  11. Frequency of V1016I and F1534C mutations in the voltage-gated sodium channel gene in Aedes aegypti in Venezuela.

    Science.gov (United States)

    Alvarez, Leslie C; Ponce, Gustavo; Saavedra-Rodriguez, Karla; Lopez, Beatriz; Flores, Adriana E

    2015-06-01

    The V1016I and F1534C mutations in the voltage-gated sodium channel gene have been associated with resistance to pyrethroids and DDT in Aedes aegypti mosquitoes. A study was carried out to determine the frequency of I1016 and C1534 by real-time PCR in five natural populations of Ae. aegypti in Venezuela during 2008, 2010 and 2012, as well as in a strain selected with 0.14 µg of deltamethrin for 15 generations. In natural populations, frequencies of I1016 varied between 0.01 and 0.37, and frequencies of C1534 between 0.35 and 1.0. In the Pampanito strain, the frequency of I1016 increased from 0.02 in F1 up to 0.5 in F15 and from 0.35 up to fixation for C1534 after selection with deltamethrin. The results showed that C1534 frequencies are higher than I1016 frequencies in natural populations of Ae. aegypti in Venezuela, and that deltamethrin selected the C1534 more rapidly than I1016. © 2014 Society of Chemical Industry.

  12. A thermosensitive mutation alters the effects of lacosamide on slow inactivation in neuronal voltage-gated sodium channels, NaV1.2

    Science.gov (United States)

    Abdelsayed, Mena; Sokolov, Stanislav; Ruben, Peter C.

    2013-01-01

    Epilepsy is a disorder characterized by seizures and convulsions. The basis of epilepsy is an increase in neuronal excitability that, in some cases, may be caused by functional defects in neuronal voltage gated sodium channels (NaVs). The C121W mutation of the β1 subunit, in particular, gives rise to the thermosensitive generalized epilepsy with febrile seizures plus (GEFS+) phenotype. Lacosamide is used to treat epileptic seizures and is distinct from other anti-seizure drugs by targeting NaV slow-inactivation. We studied the effects of a physiologically relevant concentration of lacosamide on the biophysical properties of NaV1.2 channels associated with either WT-β1 or the mutant C121W-β1 subunit. Biophysical parameters were measured at both normal (22°C) and elevated (34°C) temperatures to elicit the differential temperature-sensitivity of C121W. Lacosamide was more effective in NaV1.2 associated with the WT-β1 than with C121W-β1 at either temperature. There is also a more potent effect by lacosamide on slow inactivation at elevated temperatures. Our data suggest a modulatory role is imparted by the β1 subunit in the interaction between the drug and the channel. PMID:24065921

  13. Docking Simulation of the Binding Interactions of Saxitoxin Analogs Produced by the Marine Dinoflagellate Gymnodinium catenatum to the Voltage-Gated Sodium Channel Nav1.4

    Directory of Open Access Journals (Sweden)

    Lorena M. Durán-Riveroll

    2016-05-01

    Full Text Available Saxitoxin (STX and its analogs are paralytic alkaloid neurotoxins that block the voltage-gated sodium channel pore (Nav, impeding passage of Na+ ions into the intracellular space, and thereby preventing the action potential in the peripheral nervous system and skeletal muscle. The marine dinoflagellate Gymnodinium catenatum produces an array of such toxins, including the recently discovered benzoyl analogs, for which the mammalian toxicities are essentially unknown. We subjected STX and its analogs to a theoretical docking simulation based upon two alternative tri-dimensional models of the Nav1.4 to find a relationship between the binding properties and the known mammalian toxicity of selected STX analogs. We inferred hypothetical toxicities for the benzoyl analogs from the modeled values. We demonstrate that these toxins exhibit different binding modes with similar free binding energies and that these alternative binding modes are equally probable. We propose that the principal binding that governs ligand recognition is mediated by electrostatic interactions. Our simulation constitutes the first in silico modeling study on benzoyl-type paralytic toxins and provides an approach towards a better understanding of the mode of action of STX and its analogs.

  14. Effects of (−-Gallocatechin-3-Gallate on Tetrodotoxin-Resistant Voltage-Gated Sodium Channels in Rat Dorsal Root Ganglion Neurons

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    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.

  15. QSAR analyses of DDT analogues and their in silico validation using molecular docking study against voltage-gated sodium channel of Anopheles funestus.

    Science.gov (United States)

    Saini, V; Kumar, A

    2014-01-01

    DDT has enjoyed the reputation of a successful pesticide in disease control programme and agricultural practices along with the serious opposition and ban later on due to its biomagnification and toxic action against non-target organisms. The present work was carried out to develop QSAR models for analysing DDT analogues for their pesticidal activity and in silico validation of these models. A 2D-QSAR model was generated using stepwise with multiple regression, and the model with a value of r(2) = 0.7324; q(2) = 0.6215; pred r(2) = 0.7038, containing five descriptors, was selected for further study. The 3D QSAR with CoMFA analysis showed that steric contribution of 21% and electrostatic contribution of about 79% were required for larvicidal activity of DDT analogues. A set of 3430 molecules was generated using the basic DDT skeleton as template, and these were evaluated for their mosquito larvicidal activity using the generated QSAR models and DDT as standard. Eleven molecules were selected for in silico validation of these models. For this, a docking study of the selected molecules against the homology-modelled voltage-gated sodium channel of Anopheles funestus was conducted. The study showed that the activities of these analogues as predicted by 2D-QSAR, 3D-QSAR with CoMFA and dock score were observed to be well correlated.

  16. Epidermal growth factor potentiates in vitro metastatic behaviour of human prostate cancer PC-3M cells: involvement of voltage-gated sodium channel

    Directory of Open Access Journals (Sweden)

    Uysal-Onganer Pinar

    2007-11-01

    Full Text Available Abstract Background Although a high level of functional voltage-gated sodium channel (VGSC expression has been found in strongly metastatic human and rat prostate cancer (PCa cells, the mechanism(s responsible for the upregulation is unknown. The concentration of epidermal growth factor (EGF, a modulator of ion channels, in the body is highest in prostatic fluid. Thus, EGF could be involved in the VGSC upregulation in PCa. The effects of EGF on VGSC expression in the highly metastatic human PCa PC-3M cell line, which was shown previously to express both functional VGSCs and EGF receptors, were investigated. A quantitative approach, from gene level to cell behaviour, was used. mRNA levels were determined by real-time PCR. Protein expression was studied by Western blots and immunocytochemistry and digital image analysis. Functional assays involved measurements of transverse migration, endocytic membrane activity and Matrigel invasion. Results Exogenous EGF enhanced the cells' in vitro metastatic behaviours (migration, endocytosis and invasion. Endogenous EGF had a similar involvement. EGF increased VGSC Nav1.7 (predominant isoform in PCa mRNA and protein expressions. Co-application of the highly specific VGSC blocker tetrodotoxin (TTX suppressed the effect of EGF on all three metastatic cell behaviours studied. Conclusion 1 EGF has a major involvement in the upregulation of functional VGSC expression in human PCa PC-3M cells. (2 VGSC activity has a significant intermediary role in potentiating effect of EGF in human PCa.

  17. Thermal melt circular dichroism spectroscopic studies for identifying stabilising amphipathic molecules for the voltage-gated sodium channel NavMs.

    Science.gov (United States)

    Ireland, Sam M; Sula, Altin; Wallace, B A

    2017-09-19

    Purified integral membrane proteins require amphipathic molecules to maintain their solubility in aqueous solutions. These complexes, in turn, are used in studies to characterise the protein structures by a variety of biophysical and structural techniques, including spectroscopy, crystallography, and cryo-electron microscopy. Typically the amphilphiles used have been detergent molecules, but more recently they have included amphipols, which are polymers of different sizes and compositions designed to create smaller, more well-defined solubilised forms of the membrane proteins. In this study we used circular dichroism spectroscopy to compare the secondary structures and thermal stabilities of the NavMs voltage-gated sodium channel in different amphipols and detergents as a means of identifying amphipathic environments that maximally maintain the protein structure whilst providing a stabilising environment. These types of characterisations also have potential as means of screening for sample types that may be more suitable for crystallisation and/or cryo-electron microscopy structure determinations. © 2017 The Authors Biopolymers Published by Wiley Periodicals, Inc.

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

    NARCIS (Netherlands)

    G. Sun; T.R. Werkman; W.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 w

  19. Lacosamide Inhibition of Nav1.7 Voltage-Gated Sodium Channels: Slow Binding to Fast-Inactivated States.

    Science.gov (United States)

    Jo, Sooyeon; Bean, Bruce P

    2017-04-01

    Lacosamide is an antiseizure agent that targets voltage-dependent sodium channels. Previous experiments have suggested that lacosamide is unusual in binding selectively to the slow-inactivated state of sodium channels, in contrast to drugs like carbamazepine and phenytoin, which bind tightly to fast-inactivated states. Using heterologously expressed human Nav1.7 sodium channels, we examined the state-dependent effects of lacosamide. Lacosamide induced a reversible shift in the voltage dependence of fast inactivation studied with 100-millisecond prepulses, suggesting binding to fast-inactivated states. Using steady holding potentials, lacosamide block was very weak at -120 mV (3% inhibition by 100 µM lacosamide) but greatly enhanced at -80 mV (43% inhibition by 100 µM lacosamide), where there is partial fast inactivation but little or no slow inactivation. During long depolarizations, lacosamide slowly (over seconds) put channels into states that recovered availability slowly (hundreds of milliseconds) at -120 mV. This resembles enhancement of slow inactivation, but the effect was much more pronounced at -40 mV, where fast inactivation is complete, but slow inactivation is not, than at 0 mV, where slow inactivation is maximal, more consistent with slow binding to fast-inactivated states than selective binding to slow-inactivated states. Furthermore, inhibition by lacosamide was greatly reduced by pretreatment with 300 µM lidocaine or 300 µM carbamazepine, suggesting that lacosamide, lidocaine, and carbamazepine all bind to the same site. The results suggest that lacosamide binds to fast-inactivated states in a manner similar to other antiseizure agents but with slower kinetics of binding and unbinding.

  20. A comparison of 15 Hz sine on-line and off-line magnetic stimulation affecting the voltage-gated sodium channel currents of prefrontal cortex pyramidal neurons

    Science.gov (United States)

    Zheng, Yu; Dong, Lei; Gao, Yang; Dou, Jun-Rong; Li, Ze-yan

    2016-10-01

    Combined with the use of patch-clamp techniques, repetitive transcranial magnetic stimulation (rTMS) has proven to be a noninvasive neuromodulation tool that can inhibit or facilitate excitability of neurons after extensive research. The studies generally focused on the method: the neurons are first stimulated in an external standard magnetic exposure device, and then moved to the patch-clamp to record electrophysiological characteristics (off-line magnetic exposure). Despite its universality, real-time observation of the effects of magnetic stimulation on the neurons is more effective (on-line magnetic stimulation). In this study, we selected a standard exposure device for magnetic fields acting on mouse prefrontal cortex pyramidal neurons, and described a new method that a patch-clamp setup was modified to allow on-line magnetic stimulation. By comparing the off-line exposure and on-line stimulation of the same magnetic field intensity and frequency affecting the voltage-gated sodium channel currents, we succeeded in proving the feasibility of the new on-line stimulation device. We also demonstrated that the sodium channel currents of prefrontal cortex pyramidal neurons increased significantly under the 15 Hz sine 1 mT, and 2 mT off-line magnetic field exposure and under the 1 mT and 2 mT on-line magnetic stimulation, and the rate of acceleration was most significant on 2 mT on-line magnetic stimulation. This study described the development of a new on-line magnetic stimulator and successfully demonstrated its practicability for scientific stimulation of neurons.

  1. Probing kinetic drug binding mechanism in voltage-gated sodium ion channel: open state versus inactive state blockers.

    Science.gov (United States)

    Pal, Krishnendu; Gangopadhyay, Gautam

    2015-01-01

    The kinetics and nonequilibrium thermodynamics of open state and inactive state drug binding mechanisms have been studied here using different voltage protocols in sodium ion channel. We have found that for constant voltage protocol, open state block is more efficient in blocking ionic current than inactive state block. Kinetic effect comes through peak current for mexiletine as an open state blocker and in the tail part for lidocaine as an inactive state blocker. Although the inactivation of sodium channel is a free energy driven process, however, the two different kinds of drug affect the inactivation process in a different way as seen from thermodynamic analysis. In presence of open state drug block, the process initially for a long time remains entropy driven and then becomes free energy driven. However in presence of inactive state block, the process remains entirely entropy driven until the equilibrium is attained. For oscillating voltage protocol, the inactive state blocking is more efficient in damping the oscillation of ionic current. From the pulse train analysis it is found that inactive state blocking is less effective in restoring normal repolarisation and blocks peak ionic current. Pulse train protocol also shows that all the inactive states behave differently as one inactive state responds instantly to the test pulse in an opposite manner from the other two states.

  2. Discovery of Point Mutations in the Voltage-Gated Sodium Channel from African Aedes aegypti Populations: Potential Phylogenetic Reasons for Gene Introgression

    Science.gov (United States)

    Muranami, Yuto; Kawashima, Emiko; Osei, Joseph H. N.; Sakyi, Kojo Yirenkyi; Dadzie, Samuel; de Souza, Dziedzom K.; Appawu, Maxwell; Ohta, Nobuo; Minakawa, Noboru

    2016-01-01

    Background Yellow fever is endemic in some countries in Africa, and Aedes aegpyti is one of the most important vectors implicated in the outbreak. The mapping of the nation-wide distribution and the detection of insecticide resistance of vector mosquitoes will provide the beneficial information for forecasting of dengue and yellow fever outbreaks and effective control measures. Methodology/Principal Findings High resistance to DDT was observed in all mosquito colonies collected in Ghana. The resistance and the possible existence of resistance or tolerance to permethrin were suspected in some colonies. High frequencies of point mutations at the voltage-gated sodium channel (F1534C) and one heterozygote of the other mutation (V1016I) were detected, and this is the first detection on the African continent. The frequency of F1534C allele and the ratio of F1534C homozygotes in Ae. aegypti aegypti (Aaa) were significantly higher than those in Ae. aegypti formosus (Aaf). We could detect the two types of introns between exon 20 and 21, and the F1534C mutations were strongly linked with one type of intron, which was commonly found in South East Asian and South and Central American countries, suggesting the possibility that this mutation was introduced from other continents or convergently selected after the introgression of Aaa genes from the above area. Conclusions/Significance The worldwide eradication programs in 1940s and 1950s might have caused high selection pressure on the mosquito populations and expanded the distribution of insecticide-resistant Ae. aegypti populations. Selection of the F1534C point mutation could be hypothesized to have taken place during this period. The selection of the resistant population of Ae. aegypti with the point mutation of F1534C, and the worldwide transportation of vector mosquitoes in accordance with human activity such as trading of used tires, might result in the widespread distribution of F1534C point mutation in tropical countries

  3. Discovery of Point Mutations in the Voltage-Gated Sodium Channel from African Aedes aegypti Populations: Potential Phylogenetic Reasons for Gene Introgression.

    Directory of Open Access Journals (Sweden)

    Hitoshi Kawada

    2016-06-01

    Full Text Available Yellow fever is endemic in some countries in Africa, and Aedes aegpyti is one of the most important vectors implicated in the outbreak. The mapping of the nation-wide distribution and the detection of insecticide resistance of vector mosquitoes will provide the beneficial information for forecasting of dengue and yellow fever outbreaks and effective control measures.High resistance to DDT was observed in all mosquito colonies collected in Ghana. The resistance and the possible existence of resistance or tolerance to permethrin were suspected in some colonies. High frequencies of point mutations at the voltage-gated sodium channel (F1534C and one heterozygote of the other mutation (V1016I were detected, and this is the first detection on the African continent. The frequency of F1534C allele and the ratio of F1534C homozygotes in Ae. aegypti aegypti (Aaa were significantly higher than those in Ae. aegypti formosus (Aaf. We could detect the two types of introns between exon 20 and 21, and the F1534C mutations were strongly linked with one type of intron, which was commonly found in South East Asian and South and Central American countries, suggesting the possibility that this mutation was introduced from other continents or convergently selected after the introgression of Aaa genes from the above area.The worldwide eradication programs in 1940s and 1950s might have caused high selection pressure on the mosquito populations and expanded the distribution of insecticide-resistant Ae. aegypti populations. Selection of the F1534C point mutation could be hypothesized to have taken place during this period. The selection of the resistant population of Ae. aegypti with the point mutation of F1534C, and the worldwide transportation of vector mosquitoes in accordance with human activity such as trading of used tires, might result in the widespread distribution of F1534C point mutation in tropical countries.

  4. Voltage-sensor movements describe slow inactivation of voltage-gated sodium channels II: a periodic paralysis mutation in Na(V)1.4 (L689I).

    Science.gov (United States)

    Silva, Jonathan R; Goldstein, Steve A N

    2013-03-01

    In skeletal muscle, slow inactivation (SI) of Na(V)1.4 voltage-gated sodium channels prevents spontaneous depolarization and fatigue. Inherited mutations in Na(V)1.4 that impair SI disrupt activity-induced regulation of channel availability and predispose patients to hyperkalemic periodic paralysis. In our companion paper in this issue (Silva and Goldstein. 2013. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.201210909), the four voltage sensors in Na(V)1.4 responsible for activation of channels over microseconds are shown to slowly immobilize over 1-160 s as SI develops and to regain mobility on recovery from SI. Individual sensor movements assessed via attached fluorescent probes are nonidentical in their voltage dependence, time course, and magnitude: DI and DII track SI onset, and DIII appears to reflect SI recovery. A causal link was inferred by tetrodotoxin (TTX) suppression of both SI onset and immobilization of DI and DII sensors. Here, the association of slow sensor immobilization and SI is verified by study of Na(V)1.4 channels with a hyperkalemic periodic paralysis mutation; L689I produces complex changes in SI, and these are found to manifest directly in altered sensor movements. L689I removes a component of SI with an intermediate time constant (~10 s); the mutation also impedes immobilization of the DI and DII sensors over the same time domain in support of direct mechanistic linkage. A model that recapitulates SI attributes responsibility for intermediate SI to DI and DII (10 s) and a slow component to DIII (100 s), which accounts for residual SI, not impeded by L689I or TTX.

  5. Voltage-sensor movements describe slow inactivation of voltage-gated sodium channels II: A periodic paralysis mutation in NaV1.4 (L689I)

    Science.gov (United States)

    Silva, Jonathan R.

    2013-01-01

    In skeletal muscle, slow inactivation (SI) of NaV1.4 voltage-gated sodium channels prevents spontaneous depolarization and fatigue. Inherited mutations in NaV1.4 that impair SI disrupt activity-induced regulation of channel availability and predispose patients to hyperkalemic periodic paralysis. In our companion paper in this issue (Silva and Goldstein. 2013. J. Gen. Physiol. http://dx.doi.org/10.1085/jgp.201210909), the four voltage sensors in NaV1.4 responsible for activation of channels over microseconds are shown to slowly immobilize over 1–160 s as SI develops and to regain mobility on recovery from SI. Individual sensor movements assessed via attached fluorescent probes are nonidentical in their voltage dependence, time course, and magnitude: DI and DII track SI onset, and DIII appears to reflect SI recovery. A causal link was inferred by tetrodotoxin (TTX) suppression of both SI onset and immobilization of DI and DII sensors. Here, the association of slow sensor immobilization and SI is verified by study of NaV1.4 channels with a hyperkalemic periodic paralysis mutation; L689I produces complex changes in SI, and these are found to manifest directly in altered sensor movements. L689I removes a component of SI with an intermediate time constant (∼10 s); the mutation also impedes immobilization of the DI and DII sensors over the same time domain in support of direct mechanistic linkage. A model that recapitulates SI attributes responsibility for intermediate SI to DI and DII (10 s) and a slow component to DIII (100 s), which accounts for residual SI, not impeded by L689I or TTX. PMID:23401572

  6. Co-occurrence of point mutations in the voltage-gated sodium channel of pyrethroid-resistant Aedes aegypti populations in Myanmar.

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    Hitoshi Kawada

    Full Text Available BACKGROUND: Single amino acid substitutions in the voltage-gated sodium channel associated with pyrethroid resistance constitute one of the main causative factors of knockdown resistance in insects. The kdr gene has been observed in several mosquito species; however, point mutations in the para gene of Aedes aegypti populations in Myanmar have not been fully characterized. The aim of the present study was to determine the types and frequencies of mutations in the para gene of Aedes aegypti collected from used tires in Yangon City, Myanmar. METHODOLOGY/PRINCIPAL FINDINGS: We determined high pyrethroid resistance in Aedes aegypti larvae at all collection sites in Yangon City, by using a simplified knockdown bioassay. We showed that V1016G and S989P mutations were widely distributed, with high frequencies (84.4% and 78.8%, respectively. By contrast, we were unable to detect I1011M (or I1011V or L1014F mutations. F1534C mutations were also widely distributed, but with a lower frequency than the V1016G mutation (21.2%. High percentage of co-occurrence of the homozygous V1016G/S989P mutations was detected (65.7%. Additionally, co-occurrence of homozygous V1016G/F1534C mutations (2.9% and homozygous V1016G/F1534C/S989P mutations (0.98% were detected in the present study. CONCLUSIONS/SIGNIFICANCE: Pyrethroid insecticides were first used for malaria control in 1992, and have since been constantly used in Myanmar. This intensive use may explain the strong selection pressure toward Aedes aegypti, because this mosquito is generally a domestic and endophagic species with a preference for indoor breeding. Extensive use of DDT for malaria control before the use of this chemical was banned may also explain the development of pyrethroid resistance in Aedes aegypti.

  7. Three Peptide Modulators of the Human Voltage-Gated Sodium Channel 1.7, an Important Analgesic Target, from the Venom of an Australian Tarantula

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    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.

  8. Co-occurrence of point mutations in the voltage-gated sodium channel of pyrethroid-resistant Aedes aegypti populations in Myanmar.

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    Kawada, Hitoshi; Oo, Sai Zaw Min; Thaung, Sein; Kawashima, Emiko; Maung, Yan Naung Maung; Thu, Hlaing Myat; Thant, Kyaw Zin; Minakawa, Noboru

    2014-01-01

    Single amino acid substitutions in the voltage-gated sodium channel associated with pyrethroid resistance constitute one of the main causative factors of knockdown resistance in insects. The kdr gene has been observed in several mosquito species; however, point mutations in the para gene of Aedes aegypti populations in Myanmar have not been fully characterized. The aim of the present study was to determine the types and frequencies of mutations in the para gene of Aedes aegypti collected from used tires in Yangon City, Myanmar. We determined high pyrethroid resistance in Aedes aegypti larvae at all collection sites in Yangon City, by using a simplified knockdown bioassay. We showed that V1016G and S989P mutations were widely distributed, with high frequencies (84.4% and 78.8%, respectively). By contrast, we were unable to detect I1011M (or I1011V) or L1014F mutations. F1534C mutations were also widely distributed, but with a lower frequency than the V1016G mutation (21.2%). High percentage of co-occurrence of the homozygous V1016G/S989P mutations was detected (65.7%). Additionally, co-occurrence of homozygous V1016G/F1534C mutations (2.9%) and homozygous V1016G/F1534C/S989P mutations (0.98%) were detected in the present study. Pyrethroid insecticides were first used for malaria control in 1992, and have since been constantly used in Myanmar. This intensive use may explain the strong selection pressure toward Aedes aegypti, because this mosquito is generally a domestic and endophagic species with a preference for indoor breeding. Extensive use of DDT for malaria control before the use of this chemical was banned may also explain the development of pyrethroid resistance in Aedes aegypti.

  9. Sodium Channel Voltage-Gated Beta 2 Plays a Vital Role in Brain Aging Associated with Synaptic Plasticity and Expression of COX5A and FGF-2.

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    XiYang, Yan-Bin; Wang, You-Cui; Zhao, Ya; Ru, Jin; Lu, Bing-Tuan; Zhang, Yue-Ning; Wang, Nai-Chao; Hu, Wei-Yan; Liu, Jia; Yang, Jin-Wei; Wang, Zhao-Jun; Hao, Chun-Guang; Feng, Zhong-Tang; Xiao, Zhi-Cheng; Dong, Wei; Quan, Xiong-Zhi; Zhang, Lian-Feng; Wang, Ting-Hua

    2016-03-01

    The role of sodium channel voltage-gated beta 2 (SCN2B) in brain aging is largely unknown. The present study was therefore designed to determine the role of SCN2B in brain aging by using the senescence-accelerated mice prone 8 (SAMP8), a brain senescence-accelerated animal model, together with the SCN2B transgenic mice. The results showed that SAMP8 exhibited impaired learning and memory functions, assessed by the Morris water maze test, as early as 8 months of age. The messenger RNA (mRNA) and protein expressions of SCN2B were also upregulated in the prefrontal cortex at this age. Treatment with traditional Chinese anti-aging medicine Xueshuangtong (Panax notoginseng saponins, PNS) significantly reversed the SCN2B expressions in the prefrontal cortex, resulting in improved learning and memory. Moreover, SCN2B knockdown transgenic mice were generated and bred to determine the roles of SCN2B in brain senescence. A reduction in the SCN2B level by 60.68% resulted in improvement in the hippocampus-dependent spatial recognition memory and long-term potential (LTP) slope of field excitatory postsynaptic potential (fEPSP), followed by an upregulation of COX5A mRNA levels and downregulation of fibroblast growth factor-2 (FGF-2) mRNA expression. Together, the present findings indicated that SCN2B could play an important role in the aging-related cognitive deterioration, which is associated with the regulations of COX5A and FGF-2. These findings could provide the potential strategy of candidate target to develop antisenescence drugs for the treatment of brain aging.

  10. Comparative study of the distribution of the alpha-subunits of voltage-gated sodium channels in normal and axotomized rat dorsal root ganglion neurons.

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    Fukuoka, Tetsuo; Kobayashi, Kimiko; Yamanaka, Hiroki; Obata, Koichi; Dai, Yi; Noguchi, Koichi

    2008-09-10

    We compared the distribution of the alpha-subunit mRNAs of voltage-gated sodium channels Nav1.1-1.3 and Nav1.6-1.9 and a related channel, Nax, in histochemically identified neuronal subpopulations of the rat dorsal root ganglia (DRG). In the naïve DRG, the expression of Nav1.1 and Nav1.6 was restricted to A-fiber neurons, and they were preferentially expressed by TrkC neurons, suggesting that proprioceptive neurons possess these channels. Nav1.7, -1.8, and -1.9 mRNAs were more abundant in C-fiber neurons compared with A-fiber ones. Nax was evenly expressed in both populations. Although Nav1.8 and -1.9 were preferentially expressed by TrkA neurons, other alpha-subunits were expressed independently of TrkA expression. Actually, all IB4(+) neurons expressed both Nav1.8 and -1.9, and relatively limited subpopulations of IB4(+) neurons (3% and 12%, respectively) expressed Nav1.1 and/or Nav1.6. These findings provide useful information in interpreting the electrophysiological characteristics of some neuronal subpopulations of naïve DRG. After L5 spinal nerve ligation, Nav1.3 mRNA was up-regulated mainly in A-fiber neurons in the ipsilateral L5 DRG. Although previous studies demonstrated that nerve growth factor (NGF) and glial cell-derived neurotrophic factor (GDNF) reversed this up-regulation, the Nav1.3 induction was independent of either TrkA or GFRalpha1 expression, suggesting that the induction of Nav1.3 may be one of the common responses of axotomized DRG neurons without a direct relationship to NGF/GDNF supply. (c) 2008 Wiley-Liss, Inc.

  11. β1- and β3- voltage-gated sodium channel subunits modulate cell surface expression and glycosylation of Nav1.7 in HEK293 cells

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    Cedric James Laedermann

    2013-08-01

    Full Text Available Voltage-gated sodium channels (Navs are glycoproteins composed of a pore-forming α-subunit and associated β-subunits that regulate Nav α-subunit plasma membrane density and biophysical properties. Glycosylation of the Nav α-subunit also directly affects Navs gating. β-subunits and glycosylation thus comodulate Nav α-subunit gating. We hypothesized that β-subunits could directly influence α-subunit glycosylation. Whole-cell patch clamp of HEK293 cells revealed that both β1- and β3-subunits coexpression shifted V1/2 of steady-state activation and inactivation and increased Nav1.7-mediated INa density. Biotinylation of cell surface proteins, combined with the use of deglycosydases, confirmed that Nav1.7 α-subunits exist in multiple glycosylated states. The α-subunit intracellular fraction was found in a core-glycosylated state, migrating at approximately 250 kDa. At the plasma membrane, in addition to the core-glycosylated form, a fully glycosylated form of Nav1.7 (~280 kDa was observed. This higher band shifted to an intermediate band (~260 kDa when β1-subunits were coexpressed, suggesting that the β1-subunit promotes an alternative glycosylated form of Nav1.7. Furthermore, the β1-subunit increased the expression of this alternative glycosylated form and the β3-subunit increased the expression of the core-glycosylated form of Nav1.7. This study describes a novel role for β1- and β3-subunits in the modulation of Nav1.7 α-subunit glycosylation and cell surface expression.

  12. Sodium and Potassium Currents Influence Wallerian Degeneration of Injured Drosophila Axons

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    Mishra, Bibhudatta; Carson, Ross; Hume, Richard I.

    2013-01-01

    Axons degenerate after injury and in neuropathies and disease via a self-destruction program whose mechanism is poorly understood. Axons that have lost connection to their cell bodies have altered electrical and synaptic activities, but whether such changes play a role in the axonal degeneration process is not clear. We have used a Drosophila model to study the Wallerian degeneration of motoneuron axons and their neuromuscular junction synapses. We found that degeneration of the distal nerve stump after a nerve crush is greatly delayed when there is increased potassium channel activity (by overexpression of two different potassium channels, Kir2.1 and dORKΔ-C) or decreased voltage-gated sodium channel activity (using mutations in the para sodium channel). Conversely, degeneration is accelerated when potassium channel activity is decreased (by expressing a dominant-negative mutation of Shaker). Despite the effect of altering voltage-gated sodium and potassium channel activity, recordings made after nerve crush demonstrated that the distal stump does not fire action potentials. Rather, a variety of lines of evidence suggest that the sodium and potassium channels manifest their effects upon degeneration through changes in the resting membrane potential, which in turn regulates the level of intracellular free calcium within the isolated distal axon. PMID:24285879

  13. Coordinated role of voltage-gated sodium channels and the Na{sup +}/H{sup +} exchanger in sustaining microglial activation during inflammation

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    Hossain, Muhammad M. [Department of Environmental and Occupational Medicine and Environmental and Occupational Health Sciences Institute, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ (United States); Sonsalla, Patricia K. [Department of Neurology, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ (United States); Richardson, Jason R., E-mail: jricha3@eohsi.rutgers.edu [Department of Environmental and Occupational Medicine and Environmental and Occupational Health Sciences Institute, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ (United States)

    2013-12-01

    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{sup +}/H{sup +} 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{sup +}){sub i}] in BV-2 cells. Pre-treatment of cells with the VGSC antagonist tetrodotoxin (TTX, 1 μM) abolished short-term Na{sup +} influx, but was unable to prevent the accumulation of (Na{sup +}){sub i} observed at 6 and 24 h after LPS exposure. The NHE inhibitor cariporide (1 μM) significantly reduced accumulation of (Na{sup +}){sub 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 H{sub 2}O{sub 2} and expression of gp91{sup phox}, 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 gp91{sup phox}. • Inhibition of VGSC and NHE-1 reduces NADPH oxidase-mediated Tnf-α, ROS, and H{sub 2}O{sub 2} production. • NHE-1 and Na{sub v}1.6 may be viable targets for therapeutic interventions to reduce neuroinflammation in neurodegenerative disease.

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

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    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.

  15. Loss-of-function of the voltage-gated sodium channel NaV1.5 (channelopathies) in patients with irritable bowel syndrome.

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    Beyder, Arthur; Mazzone, Amelia; Strege, Peter R; Tester, David J; Saito, Yuri A; Bernard, Cheryl E; Enders, Felicity T; Ek, Weronica E; Schmidt, Peter T; Dlugosz, Aldona; Lindberg, Greger; Karling, Pontus; Ohlsson, Bodil; Gazouli, Maria; Nardone, Gerardo; Cuomo, Rosario; Usai-Satta, Paolo; Galeazzi, Francesca; Neri, Matteo; Portincasa, Piero; Bellini, Massimo; Barbara, Giovanni; Camilleri, Michael; Locke, G Richard; Talley, Nicholas J; D'Amato, Mauro; Ackerman, Michael J; Farrugia, Gianrico

    2014-06-01

    SCN5A encodes the α-subunit of the voltage-gated sodium channel NaV1.5. Many patients with cardiac arrhythmias caused by mutations in SCN5A also have symptoms of irritable bowel syndrome (IBS). We investigated whether patients with IBS have SCN5A variants that affect the function of NaV1.5. We performed genotype analysis of SCN5A in 584 persons with IBS and 1380 without IBS (controls). Mutant forms of SCN5A were expressed in human embryonic kidney-293 cells, and functions were assessed by voltage clamp analysis. A genome-wide association study was analyzed for an association signal for the SCN5A gene, and replicated in 1745 patients in 4 independent cohorts of IBS patients and controls. Missense mutations were found in SCN5A in 13 of 584 patients (2.2%, probands). Diarrhea-predominant IBS was the most prevalent form of IBS in the overall study population (25%). However, a greater percentage of individuals with SCN5A mutations had constipation-predominant IBS (31%) than diarrhea-predominant IBS (10%; P < .05). Electrophysiologic analysis showed that 10 of 13 detected mutations disrupted NaV1.5 function (9 loss-of-function and 1 gain-of-function function). The p. A997T-NaV1.5 had the greatest effect in reducing NaV1.5 function. Incubation of cells that expressed this variant with mexiletine restored their sodium current and administration of mexiletine to 1 carrier of this mutation (who had constipation-predominant IBS) normalized their bowel habits. In the genome-wide association study and 4 replicated studies, the SCN5A locus was strongly associated with IBS. About 2% of patients with IBS carry mutations in SCN5A. Most of these are loss-of-function mutations that disrupt NaV1.5 channel function. These findings provide a new pathogenic mechanism for IBS and possible treatment options. Copyright © 2014 AGA Institute. Published by Elsevier Inc. All rights reserved.

  16. MiR-30b Attenuates Neuropathic Pain by Regulating Voltage-Gated Sodium Channel Nav1.3 in Rats

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    Songxue Su

    2017-05-01

    Full Text Available Nav1.3 is a tetrodotoxin-sensitive isoform among voltage-gated sodium channels that are closely associated with neuropathic pain. It can be up-regulated following nerve injury, but its biological function remains uncertain. MicroRNAs (miRNAs are endogenous non-coding RNAs that can regulate post-transcriptional gene expression by binding with their target mRNAs. Using Target Scan software, we discovered that SCN3A is the major target of miR-30b, and we then determined whether miR-30b regulated the expression of Nav1.3 by transfecting miR-30b agomir through the stimulation of TNF-α or by transfecting miR-30b antagomir in primary dorsal root ganglion (DRG neurons. The spinal nerve ligation (SNL model was used to determine the contribution of miR-30b to neuropathic pain, to evaluate changes in Nav1.3 mRNA and protein expression, and to understand the sensitivity of rats to mechanical and thermal stimuli. Our results showed that miR-30b agomir transfection down-regulated Nav1.3 mRNA stimulated with TNF-α in primary DRG neurons. Moreover, miR-30b overexpression significantly attenuated neuropathic pain induced by SNL, with decreases in the expression of Nav1.3 mRNA and protein both in DRG neurons and spinal cord. Activation of Nav1.3 caused by miR-30b antagomir was identified. These data suggest that miR-30b is involved in the development of neuropathic pain, probably by regulating the expression of Nav1.3, and might be a novel therapeutic target for neuropathic pain.Perspective: This study is the first to explore the important role of miR-30b and Nav1.3 in spinal nerve ligation-induced neuropathic pain, and our evidence may provide new insight for improving therapeutic approaches to pain.

  17. Intron retention in mRNA encoding ancillary subunit of insect voltage-gated sodium channel modulates channel expression, gating regulation and drug sensitivity.

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    Bourdin, Céline M; Moignot, Bénédicte; Wang, Lingxin; Murillo, Laurence; Juchaux, Marjorie; Quinchard, Sophie; Lapied, Bruno; Guérineau, Nathalie C; Dong, Ke; Legros, Christian

    2013-01-01

    Insect voltage-gated sodium (Nav) channels are formed by a well-known pore-forming α-subunit encoded by para-like gene and ancillary subunits related to TipE from the mutation "temperature-induced-paralysis locus E." The role of these ancillary subunits in the modulation of biophysical and pharmacological properties of Na(+) currents are not enough documented. The unique neuronal ancillary subunit TipE-homologous protein 1 of Drosophila melanogaster (DmTEH1) strongly enhances the expression of insect Nav channels when heterologously expressed in Xenopus oocytes. Here we report the cloning and functional expression of two neuronal DmTEH1-homologs of the cockroach, Periplaneta americana, PaTEH1A and PaTEH1B, encoded by a single bicistronic gene. In PaTEH1B, the second exon encoding the last 11-amino-acid residues of PaTEH1A is shifted to 3'UTR by the retention of a 96-bp intron-containing coding-message, thus generating a new C-terminal end. We investigated the gating and pharmacological properties of the Drosophila Nav channel variant (DmNav1-1) co-expressed with DmTEH1, PaTEH1A, PaTEH1B or a truncated mutant PaTEH1Δ(270-280) in Xenopus oocytes. PaTEH1B caused a 2.2-fold current density decrease, concomitant with an equivalent α-subunit incorporation decrease in the plasma membrane, compared to PaTEH1A and PaTEH1Δ(270-280). PaTEH1B positively shifted the voltage-dependences of activation and slow inactivation of DmNav1-1 channels to more positive potentials compared to PaTEH1A, suggesting that the C-terminal end of both proteins may influence the function of the voltage-sensor and the pore of Nav channel. Interestingly, our findings showed that the sensitivity of DmNav1-1 channels to lidocaine and to the pyrazoline-type insecticide metabolite DCJW depends on associated TEH1-like subunits. In conclusion, our work demonstrates for the first time that density, gating and pharmacological properties of Nav channels expressed in Xenopus oocytes can be modulated by an

  18. Characterization of voltage-gated ionic currents in a peripheral sensory neuron in larval Drosophila

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    Bate Michael

    2010-06-01

    Full Text Available Abstract Background The development, morphology and genetics of sensory neurons have been extensively studied in Drosophila. Sensory neurons in the body wall of larval Drosophila in particular have been the subject of numerous anatomical studies, however, little is known about the intrinsic electrical properties of larval sensory cells. Findings We performed whole cell patch recordings from an identified peripheral sensory cell, the dorsal bipolar sensory neuron (dbd and measured voltage-gated ionic currents in 1st instar larvae. Voltage clamp analysis revealed that dbds have a TEA sensitive, non-inactivating IK type potassium current as well as a 4-AP sensitive, inactivating IA type potassium current. dbds also show a voltage-gated calcium current (ICa and a voltage-gated sodium current (INa. Conclusions This work provides a first characterization of voltage-activated ionic currents in an identified body-wall sensory neuron in larval Drosophila. Overall, we establish baseline physiology data for future studies aimed at understanding the ionic and genetic basis of sensory neuron function in fruit flies and other model organisms.

  19. Structural model of the voltage-gated potassium channel Kv1.1 and molecular docking of Tc1 toxin from Tityus cambridgei to KcsA and Kv1.1

    Science.gov (United States)

    Liu, Hsuan-Liang; Lin, Jin-Chung

    2003-11-01

    In this study, structural model of the pore loop region of the voltage-gated potassium channel Kv1.1 was constructed based on the crystallographic structure of KcsA. Subsequently, molecular docking experiments of Tc1 towards KcsA as well as Kv1.1 were performed. Tc1 forms the most stable complexes with these two channels when the side chain of K14 occupies the first K + binding site. Tc1 binds preferentially towards Kv1.1 than KcsA due to the stronger electrostatic and hydrophobic interactions. Furthermore, surface complementarity of the outer vestibules of the channel to the Tc1 spatial conformations also plays an important role in stabilizing these Tc1/channel complexes.

  20. Treatment with carbamazepine and gabapentin of a patient with primary erythermalgia (erythromelalgia) identified to have a mutation in the SCN9A gene, encoding a voltage-gated sodium channel.

    Science.gov (United States)

    Natkunarajah, J; Atherton, D; Elmslie, F; Mansour, S; Mortimer, P

    2009-12-01

    Primary erythermalgia (erythromelalgia) is a rare autosomal dominant condition characterized by intermittent attacks of erythema, increased skin temperature and severe burning pain in the extremities, in a bilateral symmetrical distribution. Mutations in the SCN9A gene, which encodes a voltage-gated sodium channel have been shown to cause this disease. We report a family identified to have a mutation in the SCN9A gene, in which one severely affected family member has responded to the therapeutic combination of gabapentin and carbamazepine treatment.

  1. Roles of Voltage-Gated Tetrodotoxin-Sensitive Sodium Channels NaV1.3 and NaV1.7 in Diabetes and Painful Diabetic Neuropathy

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    Linlin Yang

    2016-09-01

    Full Text Available Diabetes mellitus (DM is a common chronic medical problem worldwide; one of its complications is painful peripheral neuropathy, which can substantially erode quality of life and increase the cost of management. Despite its clinical importance, the pathogenesis of painful diabetic neuropathy (PDN is complex and incompletely understood. Voltage-gated sodium channels (VGSCs link many physiological processes to electrical activity by controlling action potentials in all types of excitable cells. Two isoforms of VGSCs, NaV1.3 and NaV1.7, which are encoded by the sodium voltage-gated channel alpha subunit 3 and 9 (Scn3A and Scn9A genes, respectively, have been identified in both peripheral nociceptive neurons of dorsal root ganglion (DRG and pancreatic islet cells. Recent advances in our understanding of tetrodotoxin-sensitive (TTX-S sodium channels NaV1.3 and NaV1.7 lead to the rational doubt about the cause–effect relation between diabetes and painful neuropathy. In this review, we summarize the roles of NaV1.3 and NaV1.7 in islet cells and DRG neurons, discuss the link between DM and painful neuropathy, and present a model, which may provide a starting point for further studies aimed at identifying the mechanisms underlying diabetes and painful neuropathy.

  2. Roles of Voltage-Gated Tetrodotoxin-Sensitive Sodium Channels NaV1.3 and NaV1.7 in Diabetes and Painful Diabetic Neuropathy

    Science.gov (United States)

    Yang, Linlin; Li, Quanmin; Liu, Xinming; Liu, Shiguang

    2016-01-01

    Diabetes mellitus (DM) is a common chronic medical problem worldwide; one of its complications is painful peripheral neuropathy, which can substantially erode quality of life and increase the cost of management. Despite its clinical importance, the pathogenesis of painful diabetic neuropathy (PDN) is complex and incompletely understood. Voltage-gated sodium channels (VGSCs) link many physiological processes to electrical activity by controlling action potentials in all types of excitable cells. Two isoforms of VGSCs, NaV1.3 and NaV1.7, which are encoded by the sodium voltage-gated channel alpha subunit 3 and 9 (Scn3A and Scn9A) genes, respectively, have been identified in both peripheral nociceptive neurons of dorsal root ganglion (DRG) and pancreatic islet cells. Recent advances in our understanding of tetrodotoxin-sensitive (TTX-S) sodium channels NaV1.3 and NaV1.7 lead to the rational doubt about the cause–effect relation between diabetes and painful neuropathy. In this review, we summarize the roles of NaV1.3 and NaV1.7 in islet cells and DRG neurons, discuss the link between DM and painful neuropathy, and present a model, which may provide a starting point for further studies aimed at identifying the mechanisms underlying diabetes and painful neuropathy. PMID:27608006

  3. Expresión de canales de potasio voltaje dependientes en ovocitos de Xenopus laevis (Amphibia Voltage gated potassium channels expressed in Xenopus laevis(AMPHIBIA oocytes

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    Clavijo Carlos

    2003-06-01

    Full Text Available La expresión en sistemas heterólogos ha sido una herramienta ampliamente utilizada enlos últimos años para el estudio funcional y estructural de proteínas. Para la carac-terización de las propiedades biofísicas de canales, bombas y transportadores engeneral su expresión en ovocitos de Xenopus laevis, ha sido fundamental. Este estudioreporta la expresión de dos canales de potasio voltaje dependientes, Kv1.1y Shakerenovocitos de X. laevisusando un protocolo ajustado a las condiciones de latitud y altitudde Bogotá para la extracción, aislamiento, cultivo y microinyección de éstas células.Heterologous expression has been an important tool for structural and functionalcharacterization of proteins. The study of biophysical properties of ion channels,pumps and transporters has been possible thanks to their expression in Xenopuslaevisoocytes. Here we report the expression of two voltage gated channels, Kv1.1and Shaker, in X. laevisoocytes using a method for oocyte extraction, isolation, cul-ture, and microinjection adapted to the latitude and altitude conditions of Bogotá,Colombia.

  4. Coevolution of the Ile1,016 and Cys1,534 Mutations in the Voltage Gated Sodium Channel Gene of Aedes aegypti in Mexico.

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    Farah Z Vera-Maloof

    2015-12-01

    Full Text Available Worldwide the mosquito Aedes aegypti (L. is the principal urban vector of dengue viruses. Currently 2.5 billion people are at risk for infection and reduction of Ae. aegypti populations is the most effective means to reduce the risk of transmission. Pyrethroids are used extensively for adult mosquito control, especially during dengue outbreaks. Pyrethroids promote activation and prolong the activation of the voltage gated sodium channel protein (VGSC by interacting with two distinct pyrethroid receptor sites [1], formed by the interfaces of the transmembrane helix subunit 6 (S6 of domains II and III. Mutations of S6 in domains II and III synergize so that double mutants have higher pyrethroid resistance than mutants in either domain alone. Computer models predict an allosteric interaction between mutations in the two domains. In Ae. aegypti, a Ile1,016 mutation in the S6 of domain II was discovered in 2006 and found to be associated with pyrethroid resistance in field populations in Mexico. In 2010 a second mutation, Cys1,534 in the S6 of domain III was discovered and also found to be associated with pyrethroid resistance and correlated with the frequency of Ile1,016.A linkage disequilibrium analysis was performed on Ile1,016 and Cys1,534 in Ae. aegypti collected in Mexico from 2000-2012 to test for statistical associations between S6 in domains II and III in natural populations. We estimated the frequency of the four dilocus haplotypes in 1,016 and 1,534: Val1,016/Phe1,534 (susceptible, Val1,016/Cys1,534, Ile1,016/Phe1,534, and Ile1,016/Cys1,534 (resistant. The susceptible Val1,016/Phe1,534 haplotype went from near fixation to extinction and the resistant Ile1,016/Cys1,534 haplotype increased in all collections from a frequency close to zero to frequencies ranging from 0.5-0.9. The Val1,016/Cys1,534 haplotype increased in all collections until 2008 after which it began to decline as Ile1,016/Cys1,534 increased. However, the Ile1,016/Phe1

  5. Tetrodotoxin-sensitive α-subunits of voltage-gated sodium channels are relevant for inhibition of cardiac sodium currents by local anesthetics.

    Science.gov (United States)

    Stoetzer, C; Doll, T; Stueber, T; Herzog, C; Echtermeyer, F; Greulich, F; Rudat, C; Kispert, A; Wegner, F; Leffler, A

    2016-06-01

    The sodium channel α-subunit (Nav) Nav1.5 is regarded as the most prevalent cardiac sodium channel required for generation of action potentials in cardiomyocytes. Accordingly, Nav1.5 seems to be the main target molecule for local anesthetic (LA)-induced cardiotoxicity. However, recent reports demonstrated functional expression of several "neuronal" Nav's in cardiomyocytes being involved in cardiac contractility and rhythmogenesis. In this study, we examined the relevance of neuronal tetrodotoxin (TTX)-sensitive Nav's for inhibition of cardiac sodium channels by the cardiotoxic LAs ropivacaine and bupivacaine. Effects of LAs on recombinant Nav1.2, 1.3, 1.4, and 1.5 expressed in human embryonic kidney cell line 293 (HEK-293) cells, and on sodium currents in murine, cardiomyocytes were investigated by whole-cell patch clamp recordings. Expression analyses were performed by reverse transcription PCR (RT-PCR). Cultured cardiomyocytes from neonatal mice express messenger RNA (mRNA) for Nav1.2, 1.3, 1.5, 1.8, and 1.9 and generate TTX-sensitive sodium currents. Tonic and use-dependent block of sodium currents in cardiomyocytes by ropivacaine and bupivacaine were enhanced by 200 nM TTX. Inhibition of recombinant Nav1.5 channels was similar to that of TTX-resistant currents in cardiomyocytes but stronger as compared to inhibition of total sodium current in cardiomyocytes. Recombinant Nav1.2, 1.3, 1.4, and 1.5 channels displayed significant differences in regard to use-dependent block by ropivacaine. Finally, bupivacaine blocked sodium currents in cardiomyocytes as well as recombinant Nav1.5 currents significantly stronger in comparison to ropivacaine. Our data demonstrate for the first time that cardiac TTX-sensitive sodium channels are relevant for inhibition of cardiac sodium currents by LAs.

  6. Chronic deficit in the expression of voltage-gated potassium channel Kv3.4 subunit in the hippocampus of pilocarpine-treated epileptic rats.

    Science.gov (United States)

    Pacheco Otalora, Luis F; Skinner, Frank; Oliveira, Mauro S; Farrell, Bianca; Arshadmansab, Massoud F; Pandari, Tarun; Garcia, Ileana; Robles, Leslie; Rosas, Gerardo; Mello, Carlos F; Ermolinsky, Boris S; Garrido-Sanabria, Emilio R

    2011-01-12

    Voltage gated K(+) channels (Kv) are a highly diverse group of channels critical in determining neuronal excitability. Deficits of Kv channel subunit expression and function have been implicated in the pathogenesis of epilepsy. In this study, we investigate whether the expression of the specific subunit Kv3.4 is affected during epileptogenesis following pilocarpine-induced status epilepticus. For this purpose, we used immunohistochemistry, Western blotting assays and comparative analysis of gene expression using TaqMan-based probes and delta-delta cycle threshold (ΔΔCT) method of quantitative real-time polymerase chain reaction (qPCR) technique in samples obtained from age-matched control and epileptic rats. A marked down-regulation of Kv3.4 immunoreactivity was detected in the stratum lucidum and hilus of dentate gyrus in areas corresponding to the mossy fiber system of chronically epileptic rats. Correspondingly, a 20% reduction of Kv3.4 protein levels was detected in the hippocampus of chronic epileptic rats. Real-time quantitative PCR analysis of gene expression revealed that a significant 33% reduction of transcripts for Kv3.4 (gene Kcnc4) occurred after 1 month of pilocarpine-induced status epilepticus and persisted during the chronic phase of the model. These data indicate a reduced expression of Kv3.4 channels at protein and transcript levels in the epileptic hippocampus. Down-regulation of Kv3.4 in mossy fibers may contribute to enhanced presynaptic excitability leading to recurrent seizures in the pilocarpine model of temporal lobe epilepsy.

  7. Allele-dependent changes of olivocerebellar circuit properties in the absence of the voltage-gated potassium channels Kv3.1 and Kv3.3.

    Science.gov (United States)

    McMahon, Anne; Fowler, Stephen C; Perney, Teresa M; Akemann, Walther; Knöpfel, Thomas; Joho, Rolf H

    2004-06-01

    Double-mutant mice (DKO) lacking the two voltage-gated K(+) channels Kv3.1 and Kv3.3 display a series of phenotypic alterations that include ataxia, myoclonus, tremor and alcohol hypersensitivity. The prominent cerebellar expression of mRNAs encoding Kv3.1 and Kv3.3 subunits raised the question as to whether altered electrical activity resulting from the lack of these K(+) channels might be related to the dramatic motor changes. We used the tremorogenic agent harmaline to probe mutant mice lacking different K(+) channel alleles for altered olivocerebellar circuit properties. Harmaline induced the characteristic 13-Hz tremor in wildtype mice (WT); however, no tremor was observed in DKO suggesting that the ensemble properties of the olivocerebellar circuitry are altered in the absence of Kv3.1 and Kv3.3 subunits. Harmaline induced tremor in Kv3.1-single mutants, but it was of smaller amplitude and at a lower frequency indicating the participation of Kv3.1 subunits in normal olivocerebellar system function. In contrast, harmaline tremor was virtually absent in Kv3.3-single mutants indicating an essential role for Kv3.3 subunits in tremor induction by harmaline. Immunohistochemical staining for Kv3.3 showed clear expression in the somata and proximal dendrites of Purkinje cells and in their axonal projections to the deep cerebellar nuclei (DCN). In DCN, both Kv3.1 and Kv3.3 subunits are expressed. Action potential duration is increased by approximately 100% in Purkinje cells from Kv3.3-single mutants compared to WT or Kv3.1-single mutants. We conclude that Kv3.3 channel subunits are essential for the olivocerebellar system to generate and sustain normal harmaline tremor whereas Kv3.1 subunits influence tremor amplitude and frequency.

  8. Multimeric nature of voltage-gated proton channels

    OpenAIRE

    Koch, Hans P.; Kurokawa, Tatsuki; Okochi, Yoshifumi; Sasaki, Mari; Okamura, Yasushi; Larsson, H. Peter

    2008-01-01

    Voltage-gated potassium channels are comprised of four subunits, and each subunit has a pore domain and a voltage-sensing domain (VSD). The four pore domains assemble to form one single central pore, and the four individual VSDs control the gate of the pore. Recently, a family of voltage-gated proton channels, such as HV or voltage sensor only protein (VSOP), was discovered that contain a single VSD but no pore domain. It has been assumed that VSOP channels are monomeric and contain a single ...

  9. Immunohistochemical localisation of the voltage gated potassium ion channel subunit Kv3.3 in the rat medulla oblongata and thoracic spinal cord.

    Science.gov (United States)

    Brooke, Ruth E; Atkinson, Lucy; Edwards, Ian; Parson, Simon H; Deuchars, Jim

    2006-01-27

    Voltage gated K+ channels (Kv) are a diverse group of channels important in determining neuronal excitability. The Kv superfamily is divided into 12 subfamilies (Kv1-12) and members of the Kv3 subfamily are highly abundant in the CNS, with each Kv3 gene (Kv3.1-Kv3.4) exhibiting a unique expression pattern. Since the localisation of Kv subunits is important in defining the roles they play in neuronal function, we have used immunohistochemistry to determine the distribution of the Kv3.3 subunit in the medulla oblongata and spinal cord of rats. Kv3.3 subunit immunoreactivity (Kv3.3-IR) was widespread but present only in specific cell populations where it could be detected in somata, dendrites and synaptic terminals. Labelled neurones were observed in the spinal cord in laminae IV and V, in the region of the central canal and in the ventral horn. In the medulla oblongata, labelled cell bodies were numerous in the spinal trigeminal, cuneate and gracilis nuclei whilst rarer in the lateral reticular nucleus, hypoglossal nucleus and raphe nucleus. Regions containing autonomic efferent neurones were predominantly devoid of labelling with only occasional labelled neurones being observed. Dual immunohistochemistry revealed that some Kv3.3-IR neurones in the ventral medullary reticular nucleus, spinal trigeminal nucleus, dorsal horn, ventral horn and central canal region were also immunoreactive for the Kv3.1b subunit. The presence of Kv3.3 subunits in terminals was confirmed by co-localisation of Kv3.3-IR with the synaptic vesicle protein SV2, the vesicular glutamate transporter VGluT2 and the glycine transporter GlyT2. Co-localisation of Kv3.3-IR was not observed with VGluT1, tyrosine hydroxylase, serotonin or choline acetyl transferase. Electron microscopy confirmed the presence of Kv3.3-IR in terminals and somatic membranes in ventral horn neurones, but not motoneurones. This study provides evidence supporting a role for Kv3.3 subunits in regulating neuronal excitability

  10. 电压门控性钠离子通道Nav1.7与疼痛的研究进展%Progress in the study of voltage-gated sodium channel Nav1.7 in pain

    Institute of Scientific and Technical Information of China (English)

    刘慧丽; 李萍; 李民

    2012-01-01

    Voltage-gated sodium channels(VGSC) are key molecules in pain processing and development. Mutations in the SCN9A gene encoding for Navl. 7 have been identified as important cellular substrates for different heritable pain syndromes, which suggest new Navl. 7 channel blockers could be useful analgesics in the future.%电压门控性钠通道在疼痛的产生和发展中具有关键性作用.而编码Nav1.7的基因突变可能导致一系列遗传性疼痛相关疾病,提示其在疼痛产生机制中的独特作用,可能成为疼痛治疗新的药物靶点.

  11. 电压门控钠离子通道在肿瘤中的研究进展%The research progression of the voltage-gated sodium channels in tumor

    Institute of Scientific and Technical Information of China (English)

    夏健龄

    2016-01-01

    Voltage-gated sodium channels are highly expressed in exciting cells,and play an important role in the depolarization of the membrane potential and the secretion and release of neurotransmitters.The recent research showed that the voltage gated sodium channels are highly expressed in colon cancer,breast cancer,prostate cancer and non-small cell lung cancer,and are closely associated with tumor proliferation,invasion,metastasis and other malignant biological behaviors.However,the mechanisms by which the ion channels regulate the biological behaviors and how the ion channels are mediated are still not clear.%电压门控钠离子通道兴奋性细胞中高表达,并且在总电位的去极化及神经递质的分泌和释放过程中发挥着重要的作用。最新研究表明,电压门控钠离子通道在结肠癌、乳腺癌、前列腺癌及非小细胞肺癌等多种肿瘤中高表达,并且与肿瘤增殖、侵袭、转移等恶性生物学行为密切相关。然而电压门控钠离子通道调控肿瘤恶性生物学行为的机制及其如何受到调控目前仍未清楚。现对电压门控钠离子通道在肿瘤中调控机制做一个综述。

  12. Function and role of voltage-gated sodium channel NaV1.7 expressed in aortic smooth muscle cells.

    Science.gov (United States)

    Meguro, Kentaro; Iida, Haruko; Takano, Haruhito; Morita, Toshihiro; Sata, Masataka; Nagai, Ryozo; Nakajima, Toshiaki

    2009-01-01

    Voltage-gated Na(+) channel currents (I(Na)) are expressed in several types of smooth muscle cells. The purpose of this study was to evaluate the expression of I(Na), its functional role, pathophysiology in cultured human (hASMCs) and rabbit aortic smooth muscle cells (rASMCs), and its association with vascular intimal hyperplasia. In whole cell voltage clamp, I(Na) was observed at potential positive to -40 mV, was blocked by tetrodotoxin (TTX), and replacing extracellular Na(+) with N-methyl-d-glucamine in cultured hASMCs. In contrast to native aorta, cultured hASMCs strongly expressed SCN9A encoding Na(V)1.7, as determined by quantitative RT-PCR. I(Na) was abolished by the treatment with SCN9A small-interfering (si)RNA (P SCN9A siRNA significantly inhibited cell migration (P SCN9A in cultured rASMCs and aorta 48 h after balloon injury but not in native aorta. In conclusion, these studies show that I(Na) is expressed in cultured and diseased conditions but not in normal aorta. The Na(V)1.7 plays an important role in cell migration, endocytosis, and secretion. Na(V)1.7 is also expressed in aorta after balloon injury, suggesting a potential role for Na(V)1.7 in the progression of intimal hyperplasia.

  13. Precise localization of the voltage-gated potassium channel subunits Kv3.1b and Kv3.3 revealed in the molecular layer of the rat cerebellar cortex by a pre-embedding immunogold method.

    Science.gov (United States)

    Puente, Nagore; Mendizabal-Zubiaga, Juan; Elezgarai, Izaskun; Reguero, Leire; Buceta, Ianire; Grandes, Pedro

    2010-10-01

    A proper motor activity relies on a correct cerebellar function. The Kv3.1 and Kv3.3 voltage-gated potassium channels are key proteins involved in cerebellar function and dysfunction, as the lack of these causes severe motor deficits. Both channel subunits are coexpressed in granule cells and are rapidly activated at relatively positive potentials to support the generation of fast action potentials. However, the contribution of each subunit to the molecular architecture of the parallel fibers, the granule cell axons, is so far unknown. The goal of this study was to elucidate the relative distribution of Kv3.1b and Kv3.3 in specific compartments of the rat parallel fibers by using a pre-embedding immunocytochemical method for electron microscopy. Numerous Kv3.1b and Kv3.3 silver-intensified gold particles were associated with membranes of parallel fiber synaptic terminals and their intervaricose segments. Kv3.1b was found in about 85% of parallel fiber synaptic terminals and in about 47% of their intervaricose portions. However, only 28% of intervaricosities and 23% of parallel fiber presynaptic boutons were Kv3.3 immunopositive. The analysis also revealed that 54% of Purkinje cell dendritic spines localized Kv3.3. Although both potassium channel subunits share localization in the same presynaptic parallel fiber compartments, the present results with the method used indicate that there are a higher percentage of parallel fibers labeled for Kv3.1b than for Kv3.3, and that the labeling intensity for each subunit is higher in specific subcompartments analyzed than in others.

  14. 电压依赖性钾离子通道在肺动脉高压发病过程中的作用%Role of voltage-gated potassium channels in the pathogenesis of pulmonary artery hypertension

    Institute of Scientific and Technical Information of China (English)

    李晶; 王军

    2011-01-01

    Pulmonary artery hypertension (PAH) is a syndrome induced by restricted flow of pulmonary artery, which leads to sustainable increases in pulmonary vascular resistance and pulmonary artery pressure and even right heart failure. The predominant pathogenic mechanisms of PAH are pulmonary vasoconstriction, vascular remodeling and in situ thrombus formation. Researches show that down-regulation of potassium channels especially voltage-gated potassium channels (Ky) is associated with the imbalance between proliferation and apoptosis in pulmonary artery smooth muscle cells, which in turn to pulmonary vascular remodeling. This review concentrates on the effect of Kv channels in leading to pulmonary artery remodeling in human PAH and its possible mechanism.%肺动脉高压是一种肺血流受限引起肺血管阻力和压力持续性增高,最终导致右心衰竭甚至死亡的综合征.病理生理学改变主要为肺血管收缩、重塑及原位血栓形成.研究表明,钾离子通道尤其电压依赖性钾离子通道功能与表达水平的降低是引起肺血管平滑肌细胞增殖和凋亡异常、肺血管重塑的关键因素.本文着重论述近年来有关电压依赖性钾离子通道与肺动脉高压肺血管重塑发生相关机制的研究进展.

  15. Evolutionary analyses of KCNQ1 and HERG voltage-gated potassium channel sequences reveal location-specific susceptibility and augmented chemical severities of arrhythmogenic mutations

    Directory of Open Access Journals (Sweden)

    Accili Eric A

    2008-06-01

    Full Text Available Abstract Background Mutations in HERG and KCNQ1 potassium channels have been associated with Long QT syndrome and atrial fibrillation, and more recently with sudden infant death syndrome and sudden unexplained death. In other proteins, disease-associated amino acid mutations have been analyzed according to the chemical severity of the changes and the locations of the altered amino acids according to their conservation over metazoan evolution. Here, we present the first such analysis of arrhythmia-associated mutations (AAMs in the HERG and KCNQ1 potassium channels. Results Using evolutionary analyses, AAMs in HERG and KCNQ1 were preferentially found at evolutionarily conserved sites and unevenly distributed among functionally conserved domains. Non-synonymous single nucleotide polymorphisms (nsSNPs are under-represented at evolutionarily conserved sites in HERG, but distribute randomly in KCNQ1. AAMs are chemically more severe, according to Grantham's Scale, than changes observed in evolution and their severity correlates with the expected chemical severity of the involved codon. Expected chemical severity of a given amino acid also correlates with its relative contribution to arrhythmias. At evolutionarily variable sites, the chemical severity of the changes is also correlated with the expected chemical severity of the involved codon. Conclusion Unlike nsSNPs, AAMs preferentially locate to evolutionarily conserved, and functionally important, sites and regions within HERG and KCNQ1, and are chemically more severe than changes which occur in evolution. Expected chemical severity may contribute to the overrepresentation of certain residues in AAMs, as well as to evolutionary change.

  16. Chimeric agents derived from the functionalized amino acid, lacosamide, and the α-aminoamide, safinamide: evaluation of their inhibitory actions on voltage-gated sodium channels, and antiseizure and antinociception activities and comparison with lacosamide and safinamide.

    Science.gov (United States)

    Park, Ki Duk; Yang, Xiao-Fang; Dustrude, Erik T; Wang, Yuying; Ripsch, Matthew S; White, Fletcher A; Khanna, Rajesh; Kohn, Harold

    2015-02-18

    The functionalized amino acid, lacosamide ((R)-2), and the α-aminoamide, safinamide ((S)-3), are neurological agents that have been extensively investigated and have displayed potent anticonvulsant activities in seizure models. Both compounds have been reported to modulate voltage-gated sodium channel activity. We have prepared a series of chimeric compounds, (R)-7-(R)-10, by merging key structural units in these two clinical agents, and then compared their activities with (R)-2 and (S)-3. Compounds were assessed for their ability to alter sodium channel kinetics for inactivation, frequency (use)-dependence, and steady-state activation and fast inactivation. We report that chimeric compounds (R)-7-(R)-10 in catecholamine A-differentiated (CAD) cells and embryonic rat cortical neurons robustly enhanced sodium channel inactivation at concentrations far lower than those required for (R)-2 and (S)-3, and that (R)-9 and (R)-10, unlike (R)-2 and (S)-3, produce sodium channel frequency (use)-dependence at low micromolar concentrations. We further show that (R)-7-(R)-10 displayed excellent anticonvulsant activities and pain-attenuating properties in the animal formalin model. Of these compounds, only (R)-7 reversed mechanical hypersensitivity in the tibial-nerve injury model for neuropathic pain in rats.

  17. Dopamine midbrain neurons in health and Parkinson's disease: emerging roles of voltage-gated calcium channels and ATP-sensitive potassium channels.

    Science.gov (United States)

    Dragicevic, E; Schiemann, J; Liss, B

    2015-01-22

    Dopamine (DA) releasing midbrain neurons are essential for multiple brain functions, such as voluntary movement, working memory, emotion and cognition. DA midbrain neurons within the substantia nigra (SN) and the ventral tegmental area (VTA) exhibit a variety of distinct axonal projections and cellular properties, and are differentially affected in diseases like schizophrenia, attention deficit hyperactivity disorder, and Parkinson's disease (PD). Apart from having diverse functions in health and disease states, DA midbrain neurons display distinct electrical activity patterns, crucial for DA release. These activity patterns are generated and modulated by specific sets of ion channels. Recently, two ion channels have been identified, not only contributing to these activity patterns and to functional properties of DA midbrain neurons, but also seem to render SN DA neurons particularly vulnerable to degeneration in PD and its animal models: L-type calcium channels (LTCCs) and ATP-sensitive potassium channels (K-ATPs). In this review, we focus on the emerging physiological and pathophysiological roles of these two ion channels (and their complex interplay with other ion channels), particularly in highly vulnerable SN DA neurons, as selective degeneration of these neurons causes the major motor symptoms of PD.

  18. Sequence-specific 1H-NMR assignment and secondary structure of black mamba dendrotoxin I, a highly selective blocker of voltage-gated potassium channels.

    Science.gov (United States)

    Foray, M F; Lancelin, J M; Hollecker, M; Marion, D

    1993-02-01

    The secondary structure of dendrotoxin I, an important constituent of the venom of the African black mamba snake Dendroaspis polylepis polylepis, was determined in aqueous solution by two-dimensional methods. Complete sequence-specific 1H-NMR assignment was obtained with the exception of the backbone amide proton of Gly39 and Cys40. Dendrotoxin I is based on a central antiparallel beta-sheet and two small helices located at the N- and the C-terminal extremities. These secondary-structural units occur at exactly the same places in the amino acid sequence as those of bovine pancreatic trypsin inhibitor (BPTI), with which dendrotoxin I shares 33% sequence similarity. According to the disulfide-bridge positions and the long-range NOE observed these secondary-structural elements fold in a similar manner to BPTI. This similarity allows an hypothesis according to which dendrotoxin I could derive from an ancestral Künitz-type proteinase inhibitor. This ancestor would have been heavily mutated at amino acid positions not critical for gross structure. The spatial locations of the solvent-exposed amino acids concerned could therefore serve as a guideline for interpretation of the structure/activity relationship of dendrotoxin I for the blockage of voltage-sensitive potassium channels of which dendrotoxin I is a strong inhibitor. The possible connections with other polypeptide toxins that block related ion currents is discussed.

  19. Actions and Mechanisms of Polyunsaturated Fatty Acids on Voltage-Gated Ion Channels.

    Science.gov (United States)

    Elinder, Fredrik; Liin, Sara I

    2017-01-01

    Polyunsaturated fatty acids (PUFAs) act on most ion channels, thereby having significant physiological and pharmacological effects. In this review we summarize data from numerous PUFAs on voltage-gated ion channels containing one or several voltage-sensor domains, such as voltage-gated sodium (NaV), potassium (KV), calcium (CaV), and proton (HV) channels, as well as calcium-activated potassium (KCa), and transient receptor potential (TRP) channels. Some effects of fatty acids appear to be channel specific, whereas others seem to be more general. Common features for the fatty acids to act on the ion channels are at least two double bonds in cis geometry and a charged carboxyl group. In total we identify and label five different sites for the PUFAs. PUFA site 1: The intracellular cavity. Binding of PUFA reduces the current, sometimes as a time-dependent block, inducing an apparent inactivation. PUFA site 2: The extracellular entrance to the pore. Binding leads to a block of the channel. PUFA site 3: The intracellular gate. Binding to this site can bend the gate open and increase the current. PUFA site 4: The interface between the extracellular leaflet of the lipid bilayer and the voltage-sensor domain. Binding to this site leads to an opening of the channel via an electrostatic attraction between the negatively charged PUFA and the positively charged voltage sensor. PUFA site 5: The interface between the extracellular leaflet of the lipid bilayer and the pore domain. Binding to this site affects slow inactivation. This mapping of functional PUFA sites can form the basis for physiological and pharmacological modifications of voltage-gated ion channels.

  20. Actions and Mechanisms of Polyunsaturated Fatty Acids on Voltage-Gated Ion Channels

    Science.gov (United States)

    Elinder, Fredrik; Liin, Sara I.

    2017-01-01

    Polyunsaturated fatty acids (PUFAs) act on most ion channels, thereby having significant physiological and pharmacological effects. In this review we summarize data from numerous PUFAs on voltage-gated ion channels containing one or several voltage-sensor domains, such as voltage-gated sodium (NaV), potassium (KV), calcium (CaV), and proton (HV) channels, as well as calcium-activated potassium (KCa), and transient receptor potential (TRP) channels. Some effects of fatty acids appear to be channel specific, whereas others seem to be more general. Common features for the fatty acids to act on the ion channels are at least two double bonds in cis geometry and a charged carboxyl group. In total we identify and label five different sites for the PUFAs. PUFA site 1: The intracellular cavity. Binding of PUFA reduces the current, sometimes as a time-dependent block, inducing an apparent inactivation. PUFA site 2: The extracellular entrance to the pore. Binding leads to a block of the channel. PUFA site 3: The intracellular gate. Binding to this site can bend the gate open and increase the current. PUFA site 4: The interface between the extracellular leaflet of the lipid bilayer and the voltage-sensor domain. Binding to this site leads to an opening of the channel via an electrostatic attraction between the negatively charged PUFA and the positively charged voltage sensor. PUFA site 5: The interface between the extracellular leaflet of the lipid bilayer and the pore domain. Binding to this site affects slow inactivation. This mapping of functional PUFA sites can form the basis for physiological and pharmacological modifications of voltage-gated ion channels. PMID:28220076

  1. Voltage-gated Proton Channels

    Science.gov (United States)

    DeCoursey, Thomas E.

    2014-01-01

    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 ~103 smaller than most ion channels, voltage-dependent gating that is strongly modulated by the pH gradient, ΔpH, and potent inhibition by Zn2+ (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:23798303

  2. 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.

  3. Effect of Turkish propolis extracts on expression of voltage-gated ...

    African Journals Online (AJOL)

    Keywords: Propolis, Voltage-gated sodium channel (VGSC), PC-3 Human prostate cancer cells. Tropical Journal ... a number of dietary and lifestyle factors have been implicated ... Propolis samples, produced by honey-bee (Apis mellifera L.) ...

  4. Imidazol-1-ylethylindazole Voltage-Gated Sodium Channel Ligands Are Neuroprotective during Optic Neuritis in a Mouse Model of Multiple Sclerosis

    Science.gov (United States)

    2014-01-01

    A series of imidazol-1-ylethylindazole sodium channel ligands were developed and optimized for sodium channel inhibition and in vitro neuroprotective activity. The molecules exhibited displacement of a radiolabeled sodium channel ligand and selectivity for blockade of the inactivated state of cloned neuronal Nav channels. Metabolically stable analogue 6 was able to protect retinal ganglion cells during optic neuritis in a mouse model of multiple sclerosis. PMID:24601592

  5. Voltage-gated sodium channel Nav1.7 maintains the membrane potential and regulates the activation and chemokine-induced migration of a monocyte-derived dendritic cell subset.

    Science.gov (United States)

    Kis-Toth, Katalin; Hajdu, Peter; Bacskai, Ildiko; Szilagyi, Orsolya; Papp, Ferenc; Szanto, Attila; Posta, Edit; Gogolak, Peter; Panyi, Gyorgy; Rajnavolgyi, Eva

    2011-08-01

    Expression of CD1a protein defines a human dendritic cell (DC) subset with unique functional activities. We aimed to study the expression of the Nav1.7 sodium channel and the functional consequences of its activity in CD1a(-) and CD1a(+) DC. Single-cell electrophysiology (patch-clamp) and quantitative PCR experiments performed on sorted CD1a(-) and CD1a(+) immature DC (IDC) showed that the frequency of cells expressing Na(+) current, current density, and the relative expression of the SCN9A gene encoding Nav1.7 were significantly higher in CD1a(+) cells than in their CD1a(-) counterparts. The activity of Nav1.7 results in a depolarized resting membrane potential (-8.7 ± 1.5 mV) in CD1a(+) IDC as compared with CD1a(-) cells lacking Nav1.7 (-47 ± 6.2 mV). Stimulation of DC by inflammatory signals or by increased intracellular Ca(2+) levels resulted in reduced Nav1.7 expression. Silencing of the SCN9A gene shifted the membrane potential to a hyperpolarizing direction in CD1a(+) IDC, resulting in decreased cell migration, whereas pharmacological inhibition of Nav1.7 by tetrodotoxin sensitized the cells for activation signals. Fine-tuning of IDC functions by a voltage-gated sodium channel emerges as a new regulatory mechanism modulating the migration and cytokine responses of these DC subsets.

  6. NMR analysis of interaction of LqhalphaIT scorpion toxin with a peptide corresponding to the D4/S3-S4 loop of insect para voltage-gated sodium channel.

    Science.gov (United States)

    Schnur, Einat; Turkov, Michael; Kahn, Roy; Gordon, Dalia; Gurevitz, Michael; Anglister, Jacob

    2008-01-22

    Voltage-gated sodium channels (Navs) are large transmembrane proteins that initiate action potential in electrically excitable cells. This central role in the nervous system has made them a primary target for a large number of neurotoxins. Scorpion alpha-neurotoxins bind to Navs with high affinity and slow their inactivation, causing a prolonged action potential. Despite the similarity in their mode of action and three-dimensional structure, alpha-toxins exhibit great variations in selectivity toward insect and mammalian Navs, suggesting differences in the binding surfaces of the toxins and the channels. The scorpion alpha-toxin binding site, termed neurotoxin receptor site 3, has been shown to involve the extracellular S3-S4 loop in domain 4 of the alpha-subunit of voltage-gated sodium channels (D4/S3-S4). In this study, the binding site for peptides corresponding to the D4/S3-S4 loop of the para insect Nav was mapped on the highly insecticidal alpha-neurotoxin, LqhalphaIT, from the scorpion Leiurus quinquestriatus hebraeus, by following changes in the toxin amide 1H and 15N chemical shifts upon binding. This analysis suggests that the five-residue turn (residues LqK8-LqC12) of LqhalphaIT and those residues in its vicinity interact with the D4/S3-S4 loop of Nav. Residues LqR18, LqW38, and LqA39 could also form a patch contributing to the interaction with D4/S3-S4. Moreover, a new bioactive residue, LqV13, was identified as being important for Nav binding and specifically for the interaction with the D4/S3-S4 loop. The contribution of LqV13 to NaV binding was further verified by mutagenesis. Future studies involving other extracellular regions of Navs are required for further characterization of the structure of the LqhalphaIT-Navs binding site.

  7. Identification and Characterization of ProTx-III [μ-TRTX-Tp1a], a New Voltage-Gated Sodium Channel Inhibitor from Venom of the Tarantula Thrixopelma pruriens.

    Science.gov (United States)

    Cardoso, Fernanda C; Dekan, Zoltan; Rosengren, K Johan; Erickson, Andelain; Vetter, Irina; Deuis, Jennifer R; Herzig, Volker; Alewood, Paul F; King, Glenn F; Lewis, Richard J

    2015-08-01

    Spider venoms are a rich source of ion channel modulators with therapeutic potential. Given the analgesic potential of subtype-selective inhibitors of voltage-gated sodium (NaV) channels, we screened spider venoms for inhibitors of human NaV1.7 (hNaV1.7) using a high-throughput fluorescent assay. Here, we describe the discovery of a novel NaV1.7 inhibitor, μ-TRTX-Tp1a (Tp1a), isolated from the venom of the Peruvian green-velvet tarantula Thrixopelma pruriens. Recombinant and synthetic forms of this 33-residue peptide preferentially inhibited hNaV1.7 > hNaV1.6 > hNaV1.2 > hNaV1.1 > hNaV1.3 channels in fluorescent assays. NaV1.7 inhibition was diminished (IC50 11.5 nM) and the association rate decreased for the C-terminal acid form of Tp1a compared with the native amidated form (IC50 2.1 nM), suggesting that the peptide C terminus contributes to its interaction with hNaV1.7. Tp1a had no effect on human voltage-gated calcium channels or nicotinic acetylcholine receptors at 5 μM. Unlike most spider toxins that modulate NaV channels, Tp1a inhibited hNaV1.7 without significantly altering the voltage dependence of activation or inactivation. Tp1a proved to be analgesic by reversing spontaneous pain induced in mice by intraplantar injection in OD1, a scorpion toxin that potentiates hNaV1.7. The structure of Tp1a as determined using NMR spectroscopy revealed a classic inhibitor cystine knot (ICK) motif. The molecular surface of Tp1a presents a hydrophobic patch surrounded by positively charged residues, with subtle differences from other ICK spider toxins that might contribute to its different pharmacological profile. Tp1a may help guide the development of more selective and potent hNaV1.7 inhibitors for treatment of chronic pain.

  8. TPEN, a Specific Zn(2+) Chelator, Inhibits Sodium Dithionite and Glucose Deprivation (SDGD)-Induced Neuronal Death by Modulating Apoptosis, Glutamate Signaling, and Voltage-Gated K(+) and Na(+) Channels.

    Science.gov (United States)

    Zhang, Feng; Ma, Xue-Ling; Wang, Yu-Xiang; He, Cong-Cong; Tian, Kun; Wang, Hong-Gang; An, Di; Heng, Bin; Xie, Lai-Hua; Liu, Yan-Qiang

    2017-03-01

    Hypoxia-ischemia-induced neuronal death is an important pathophysiological process that accompanies ischemic stroke and represents a major challenge in preventing ischemic stroke. To elucidate factors related to and a potential preventative mechanism of hypoxia-ischemia-induced neuronal death, primary neurons were exposed to sodium dithionite and glucose deprivation (SDGD) to mimic hypoxic-ischemic conditions. The effects of N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN), a specific Zn(2+)-chelating agent, on SDGD-induced neuronal death, glutamate signaling (including the free glutamate concentration and expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor (GluR2) and N-methyl-D-aspartate (NMDA) receptor subunits (NR2B), and voltage-dependent K(+) and Na(+) channel currents were also investigated. Our results demonstrated that TPEN significantly suppressed increases in cell death, apoptosis, neuronal glutamate release into the culture medium, NR2B protein expression, and I K as well as decreased GluR2 protein expression and Na(+) channel activity in primary cultured neurons exposed to SDGD. These results suggest that TPEN could inhibit SDGD-induced neuronal death by modulating apoptosis, glutamate signaling (via ligand-gated channels such as AMPA and NMDA receptors), and voltage-gated K(+) and Na(+) channels in neurons. Hence, Zn(2+) chelation might be a promising approach for counteracting the neuronal loss caused by transient global ischemia. Moreover, TPEN could represent a potential cell-targeted therapy.

  9. The role of TNF-alpha/NF-kappa B pathway on the up-regulation of voltage-gated sodium channel Nav1.7 in DRG neurons of rats with diabetic neuropathy.

    Science.gov (United States)

    Huang, Yangliang; Zang, Ying; Zhou, Lijun; Gui, Wenshan; Liu, Xianguo; Zhong, Yi

    2014-09-01

    Diabetic neuropathy (DN) is a common form of peripheral neuropathy, yet the mechanisms responsible for chronic pain in this disease are poorly understood. The up-regulation of the expression and function of voltage-gated sodium channel Nav1.7 has been implicated in DN, however, the exact mechanism is unclear. In the present study, we found that a proportion of streptozotocin (STZ)-treated rats suffered from mechanical allodynia and thermal hyperalgesia for a long-lasting time. Nav1.7 was up-regulated in spinal dorsal root ganglia (DRG) of rats with DN, double immunofluorescence staining showed that the increased Nav1.7 was co-localized with large and small sized neurons but not satellite glial cells. Inhibiting the synthesis of tumor necrosis factor-α (TNF-α) by thalidomide prevented DN, accompanied by strongly blocking the up-regulation of Nav1.7, TNF-α and p-nucleus factor-kappa B (p-NF-κB) in DRG. Intrathecal injection of NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC) significantly attenuated the pain behaviors and over-expression of Nav1.7 in DRG neurons. These data suggest that increased TNF-α may be responsible for up-regulation of Nav1.7 in DRG neurons of rats with DN, and NF-κB signal pathway is involved in this process. The findings might provide potential target for preventing diabetic neuropathy.

  10. Voltage-gated proton (H(v)1) channels, a singular voltage sensing domain.

    Science.gov (United States)

    Castillo, Karen; Pupo, Amaury; Baez-Nieto, David; Contreras, Gustavo F; Morera, Francisco J; Neely, Alan; Latorre, Ramon; Gonzalez, Carlos

    2015-11-14

    The main role of voltage-gated proton channels (Hv1) is to extrude protons from the intracellular milieu when, mediated by different cellular processes, the H(+) concentration increases. Hv1 are exquisitely selective for protons and their structure is homologous to the voltage sensing domain (VSD) of other voltage-gated ion channels like sodium, potassium, and calcium channels. In clear contrast to the classical voltage-dependent channels, Hv1 lacks a pore domain and thus permeation necessarily occurs through the voltage sensing domain. Hv1 channels are activated by depolarizing voltages, and increases in internal proton concentration. It has been proposed that local conformational changes of the transmembrane segment S4, driven by depolarization, trigger the molecular rearrangements that open Hv1. However, it is still unclear how the electromechanical coupling is achieved between the VSD and the potential pore, allowing the proton flux from the intracellular to the extracellular side. Here we provide a revised view of voltage activation in Hv1 channels, offering a comparative scenario with other voltage sensing channels domains.

  11. Elevated neuronal excitability due to modulation of the voltage-gated sodium channel Nav1.6 by Aβ1-42

    Directory of Open Access Journals (Sweden)

    Xi eWang

    2016-03-01

    Full Text Available Aberrant increases in neuronal network excitability may contribute to the cognitive deficits in Alzheimer’s disease (AD. However, the mechanisms underlying hyperexcitability are not fully understood. Such overexcitation of neuronal networks has been detected in the brains of APP/PS1 mice. In the present study, using current-clamp recording techniques, we observed that 12 days in vitro (DIV primary cultured pyramidal neurons from P0 APP/PS1 mice exhibited a more prominent action potential burst and a lower threshold than WT littermates. Moreover, after treatment with Aβ1-42 peptide, 12 DIV primary cultured neurons showed similar changes, to a greater degree than in controls. Voltage-clamp recordings revealed that the voltage-dependent sodium current density of neurons incubated with Aβ1-42 was significantly increased, without change in the voltage-dependent sodium channel kinetic characteristics. Immunohistochemistry and western blot results showed that, after treatment with Aβ1-42, expressions of Nav and Nav1.6 subtype increased in cultured neurons or APP/PS1 brains compared to control groups. The intrinsic neuronal hyperexcitability of APP/PS1 mice might thus be due to an increased expression of voltage-dependent sodium channels induced by Aβ1-42. These results may illuminate the mechanism of aberrant neuronal networks in AD.

  12. Hysteresis in voltage-gated channels.

    Science.gov (United States)

    Villalba-Galea, Carlos A

    2016-09-30

    Ion channels constitute a superfamily of membrane proteins found in all living creatures. Their activity allows fast translocation of ions across the plasma membrane down the ion's transmembrane electrochemical gradient, resulting in a difference in electrical potential across the plasma membrane, known as the membrane potential. A group within this superfamily, namely voltage-gated channels, displays activity that is sensitive to the membrane potential. The activity of voltage-gated channels is controlled by the membrane potential, while the membrane potential is changed by these channels' activity. This interplay produces variations in the membrane potential that have evolved into electrical signals in many organisms. These signals are essential for numerous biological processes, including neuronal activity, insulin release, muscle contraction, fertilization and many others. In recent years, the activity of the voltage-gated channels has been observed not to follow a simple relationship with the membrane potential. Instead, it has been shown that the activity of voltage-gated channel displays hysteresis. In fact, a growing number of evidence have demonstrated that the voltage dependence of channel activity is dynamically modulated by activity itself. In spite of the great impact that this property can have on electrical signaling, hysteresis in voltage-gated channels is often overlooked. Addressing this issue, this review provides examples of voltage-gated ion channels displaying hysteretic behavior. Further, this review will discuss how Dynamic Voltage Dependence in voltage-gated channels can have a physiological role in electrical signaling. Furthermore, this review will elaborate on the current thoughts on the mechanism underlying hysteresis in voltage-gated channels.

  13. 21 CFR 181.34 - Sodium nitrite and potassium nitrite.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrite and potassium nitrite. 181.34...-Sanctioned Food Ingredients § 181.34 Sodium nitrite and potassium nitrite. Sodium nitrite and potassium... fixatives and preservative agents, with or without sodium or potassium nitrate, in the curing of red...

  14. mRNAs coding for neurotransmitter receptors and voltage-gated sodium channels in the adult rabbit visual cortex after monocular deafferentiation

    Science.gov (United States)

    Nguyen, Quoc-Thang; Matute, Carlos; Miledi, Ricardo

    1998-01-01

    It has been postulated that, in the adult visual cortex, visual inputs modulate levels of mRNAs coding for neurotransmitter receptors in an activity-dependent manner. To investigate this possibility, we performed a monocular enucleation in adult rabbits and, 15 days later, collected their left and right visual cortices. Levels of mRNAs coding for voltage-activated sodium channels, and for receptors for kainate/α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N-methyl-d-aspartate (NMDA), γ-aminobutyric acid (GABA), and glycine were semiquantitatively estimated in the visual cortices ipsilateral and contralateral to the lesion by the Xenopus oocyte/voltage-clamp expression system. This technique also allowed us to study some of the pharmacological and physiological properties of the channels and receptors expressed in the oocytes. In cells injected with mRNA from left or right cortices of monocularly enucleated and control animals, the amplitudes of currents elicited by kainate or AMPA, which reflect the abundance of mRNAs coding for kainate and AMPA receptors, were similar. There was no difference in the sensitivity to kainate and in the voltage dependence of the kainate response. Responses mediated by NMDA, GABA, and glycine were unaffected by monocular enucleation. Sodium channel peak currents, activation, steady-state inactivation, and sensitivity to tetrodotoxin also remained unchanged after the enucleation. Our data show that mRNAs for major neurotransmitter receptors and ion channels in the adult rabbit visual cortex are not obviously modified by monocular deafferentiation. Thus, our results do not support the idea of a widespread dynamic modulation of mRNAs coding for receptors and ion channels by visual activity in the rabbit visual system. PMID:9501250

  15. Identification and characterization of the promoter region of the Nav1.7 voltage-gated sodium channel gene (SCN9A).

    Science.gov (United States)

    Diss, James K J; Calissano, Mattia; Gascoyne, Duncan; Djamgoz, Mustafa B A; Latchman, David S

    2008-03-01

    The Nav1.7 sodium channel plays an important role in pain and is also upregulated in prostate cancer. To investigate the mechanisms regulating physiological and pathophysiological Nav1.7 expression we identified the core promoter of this gene (SCN9A) in the human genome. In silico genomic analysis revealed a putative SCN9A 5' non-coding exon approximately 64,000 nucleotides from the translation start site, expression of which commenced at three very closely-positioned transcription initiation sites (TISs), as determined by 5' RACE experiments. The genomic region around these TISs possesses numerous core elements of a TATA-less promoter within a well-defined CpG island. Importantly, it acted as a promoter when inserted upstream of luciferase in a fusion construct. Moreover, the activity of the promoter-luciferase construct ostensibly paralleled endogenous Nav1.7 mRNA levels in vitro, with both increased in a quantitatively and qualitatively similar manner by numerous factors (including NGF, phorbol esters, retinoic acid, and Brn-3a transcription factor over-expression).

  16. Predicting a double mutant in the twilight zone of low homology modeling for the skeletal muscle voltage-gated sodium channel subunit beta-1 (Nav1.4 β1

    Directory of Open Access Journals (Sweden)

    Thomas Scior

    2015-01-01

    Full Text Available The molecular structure modeling of the β1 subunit of the skeletal muscle voltage-gated sodium channel (Nav1.4 was carried out in the twilight zone of very low homology. Structural significance can per se be confounded with random sequence similarities. Hence, we combined (i not automated computational modeling of weakly homologous 3D templates, some with interfaces to analogous structures to the pore-bearing Nav1.4 α subunit with (ii site-directed mutagenesis (SDM, as well as (iii electrophysiological experiments to study the structure and function of the β1 subunit. Despite the distant phylogenic relationships, we found a 3D-template to identify two adjacent amino acids leading to the long-awaited loss of function (inactivation of Nav1.4 channels. This mutant type (T109A, N110A, herein called TANA was expressed and tested on cells of hamster ovary (CHO. The present electrophysiological results showed that the double alanine substitution TANA disrupted channel inactivation as if the β1 subunit would not be in complex with the α subunit. Exhaustive and unbiased sampling of “all β proteins” (Ig-like, Ig resulted in a plethora of 3D templates which were compared to the target secondary structure prediction. The location of TANA was made possible thanks to another “all β protein” structure in complex with an irreversible bound protein as well as a reversible protein–protein interface (our “Rosetta Stone” effect. This finding coincides with our electrophysiological data (disrupted β1-like voltage dependence and it is safe to utter that the Nav1.4 α/β1 interface is likely to be of reversible nature.

  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. Voltage-gated lipid ion channels

    DEFF Research Database (Denmark)

    Blicher, Andreas; Heimburg, Thomas Rainer

    2013-01-01

    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...

  19. DETEKSI MUTASI V1016G PADA GEN VOLTAGE-GATED SODIUM CHANNEL PADA POPULASI Aedes aegypti (DIPTERA: CULICIDAE DI KABUPATEN KLATEN, JAWA TENGAH DENGAN METODE ALLELE-SPECIFIC PCR

    Directory of Open Access Journals (Sweden)

    Dyah Widiastuti

    2015-10-01

    Full Text Available AbstrakMeluasnya kejadian resistensi pada vektor virus Dengue di Jawa Tengah memerlukan strategi pengelolaan resistensi insektisida secara efektif. Oleh karena itu, informasi mengenai mutasi gen pada posisi 1016 di domain II segmen ke­6 gen VGSC pada nyamuk Aedes aegypti yang menyebabkan perubahan asam amino valin (V menjadi glisin (G akan dapat memperkuat penelitian operasional mengenai strategi pemilihan insektisida dalam program­pengendalian­vektor­Dengue.­Penelitian­ini­menggunakan­uji­Allele-Specific­Polymerase­Chain­Reaction(AS­PCR yang dapat mendeteksi mutasi V1016G. Sampel penelitian ini adalah 22 ekor nyamuk Aedes aegypti dari Kabupaten Klaten yang berumur 2­5 hari. Hasil penelitian menunjukkan bahwa 22,7% nyamuk belum mengalami mutasi (V/V, 59,1% nyamuk mengalami mutasi heterozigot (V/G dan 18,2% nyamuk mengalami mutasi homozigot (G/G. Hal ini menunjukkan indikasi terjadinya resistensi populasi nyamuk Ae.aegypti terhadap insektisida sintetik piretroid yang disebabkan oleh mekanisme knockdown resistance.Kata Kunci:­Aedes­aegypti,­mutasi­V1016G,­Allele-Specific­PCR,­VGSCAbstractInsecticides resistance has spread rapidly among dengue vectors from Central Java, and require an effective insecticide resistance management strategies.one of the resistance mechanism in Aedes aegypti may arise through knockdown resistance or kdr which consists of single point mutation within the genes that are targeted by insecticide compounds. Mutation at position 1016 in domain II, segment 6 of the Voltage Gated Sodium Channel gene in Ae. aegypti leads to a valine to glycine substitution (V1016G is associated with resistance to the type II pyrethroid. The result of this study will help us to strengthen basic and operational research on the­development­of­strategies­for­Dengue­vector­control­in­Indonesia.­This­study­utilized­an­allele-specificPolymerase Chain Reaction (AS­PCR assay that could be used to detect the V1016G

  20. 21 CFR 181.33 - Sodium nitrate and potassium nitrate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate and potassium nitrate. 181.33...-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions issued by the U.S. Department of Agriculture for use as sources...

  1. Time to Consider Use of the Sodium-to-Potassium Ratio for Practical Sodium Reduction and Potassium Increase.

    Science.gov (United States)

    Iwahori, Toshiyuki; Miura, Katsuyuki; Ueshima, Hirotsugu

    2017-07-05

    Pathogenetic studies have demonstrated that the interdependency of sodium and potassium affects blood pressure. Emerging evidences on the sodium-to-potassium ratio show benefits for a reduction in sodium and an increase in potassium compared to sodium and potassium separately. As presently there is no known review, this article examined the practical use of the sodium-to-potassium ratio in daily practice. Epidemiological studies suggest that the urinary sodium-to-potassium ratio may be a superior metric as compared to separate sodium and potassium values for determining the relation to blood pressure and cardiovascular disease risks. Higher correlations and better agreements are seen for the casual urine sodium-to-potassium ratio than for casual urine sodium or potassium alone when compared with the 24-h urine values. Repeated measurements of the casual urine provide reliable estimates of the 7-day 24-h urine value with less bias for the sodium-to-potassium ratio as compared to the common formulas used for estimating the single 24-h urine from the casual urine for sodium and potassium separately. Self-monitoring devices for the urinary sodium-to-potassium ratio measurement makes it possible to provide prompt onsite feedback. Although these devices have been evaluated with a view to support an individual approach for sodium reduction and potassium increase, there has yet to be an accepted recommended guideline for the sodium-to-potassium ratio. This review concludes with a look at the practical use of the sodium-to-potassium ratio for assistance in practical sodium reduction and potassium increase.

  2. Multimeric nature of voltage-gated proton channels.

    Science.gov (United States)

    Koch, Hans P; Kurokawa, Tatsuki; Okochi, Yoshifumi; Sasaki, Mari; Okamura, Yasushi; Larsson, H Peter

    2008-07-01

    Voltage-gated potassium channels are comprised of four subunits, and each subunit has a pore domain and a voltage-sensing domain (VSD). The four pore domains assemble to form one single central pore, and the four individual VSDs control the gate of the pore. Recently, a family of voltage-gated proton channels, such as H(V) or voltage sensor only protein (VSOP), was discovered that contain a single VSD but no pore domain. It has been assumed that VSOP channels are monomeric and contain a single VSD that functions as both the VSD and the pore domain. It remains unclear, however, how a protein that contains only a VSD and no pore domain can conduct ions. Using fluorescence measurements and immunoprecipitation techniques, we show here that VSOP channels are expressed as multimeric channels. Further, FRET experiments on constructs with covalently linked subunits show that VSOP channels are dimers. Truncation of the cytoplasmic regions of VSOP reduced the dimerization, suggesting that the dimerization is caused mainly by cytoplasmic protein-protein interactions. However, these N terminus- and C terminus-deleted channels displayed large proton currents. Therefore, we conclude that even though VSOP channels are expressed mainly as dimers in the cell membrane, single VSOP subunits could function independently as proton channels.

  3. Anestésicos locais: interação com membranas biológicas e com o canal de sódio voltagem-dependente Local anesthetics: interaction with biological membranes and with the voltage-gated sodium channel

    Directory of Open Access Journals (Sweden)

    Daniele Ribeiro de Araujo

    2008-01-01

    Full Text Available Many theories about the mechanism of action of local anesthetics (LA are described in the literature. Two types of theories can be distinguished: those that focus on the direct effects of LA on their target protein in the axon membranes, i.e. the voltage-gated sodium channel and the ones that take into account the interaction of anesthetic molecules with the lipid membrane phase for the reversible nerve blockage. Since there is a direct correlation between LA hydrophobicity and potency, it is crucial to take this physico-chemical property into account to understand the mechanism of action of LA, be it on the sodium channel protein, lipid(s, or on the whole membrane phase.

  4. Dravet综合征的临床特点分析及SCN1A基因新突变%Clinical Analysis of Dravet Syndrome and Novel Gene Mutation of Voltage-Gated Sodium Channel α1-Su-bunit

    Institute of Scientific and Technical Information of China (English)

    王新华; 周水珍

    2011-01-01

    Objective To study the clinical characteristics of Dravet syndrome and to screen the voltage -gated sodium channel αl -subunit( SCNI A ) of a newly diagnosed child, hoping to find the gene mutation. Methods The clinical information of 3 Dravet syndrome children were collected,the blood sample of a new diagnostic child was provided. DNA was extracted from peripheral blood leukocytes using relax gene blood DNA system. The total 26 exons of SCN1A were amplified by polymerase chain reaction( PCR), and the PCR products were screened by Denaturing high performance liquid chromatography, then the abnormal fragments were sequenced by Sanger method in order to find the mutations of SCN 1A gene. Results 1. The common manifestations of 3 Dravet syndrome cases: onset during the first year of life; in all children, the seizures were associated with febrile seizures and they changed to afebrile seizures after 1 year; the forms of seizures included clonus,myoclonus and atypical absence;the seizures were difficult to control with anti -epileptic drugs; all children presented some degree of psychomotor development delay; there were sharp - slow waves, spike - slow waves and multi spike - slow waves in EEG of diapause. 2. A missense mutation of SCNI A gene (c. 2867T > G, M956R) was found in the Dravet syndrome child, which had not been reported up to Nov.2010. Conclusions Dravet syndrome is an epileptic encephalopathy with a bad prognosis,and it needs to be differentiate it frome febrile seizures. The missense mutation of SCNIA gene supports the relationship of SCNIA mutation and Dravet syndrom.%目的 分析Dravet综合征的临床特点,并对新诊断患儿进行SCN1A基因筛查,寻找基因突变.方法收集3例Dravet综合征患儿临床资料,留取例1患儿血样标本,提取外周血白细胞基因组DNA,对SCN1A全部外显子进行PCR扩增,通过变性高效液相色谱法对PCR产物进行突变片段筛查,对于变性高效液相色谱法筛查有异常的片段

  5. Sodium retention by insulin may depend on decreased plasma potassium.

    Science.gov (United States)

    Friedberg, C E; Koomans, H A; Bijlsma, J A; Rabelink, T J; Dorhout Mees, E J

    1991-02-01

    Evidence is accumulating that insulin is a hypertensive factor in humans. The involved mechanism may be its sodium-retaining effect. We examined whether insulin causes sodium retention through a direct action on the kidney, as is generally assumed, or indirectly through hypokalemia. Insulin was infused (euglycemic clamp technique) with and without potassium infusion to prevent hypokalemia in six healthy subjects. Without potassium infusion, insulin caused a marked decrease in plasma potassium (-0.75 mmol/L), and decreased urinary sodium and potassium excretions by, approximately 38% and 65%, respectively. Simultaneous potassium infusion largely prevented the decrease in plasma potassium, as well as the decrease in urinary sodium and potassium excretions. These data suggest that the acute antinatriuretic effect of insulin may be largely mediated in an indirect way, ie, through hypokalemia.

  6. 电压门控钠离子通道与口面部疼痛的研究进展%The Progress of Research of Voltage-gated Sodium Channels and Orofacial Pain

    Institute of Scientific and Technical Information of China (English)

    朱凌

    2012-01-01

    The volt age-gated sodium channel is essential in the generation and conduction of action potentials. The biophysical properties of this ion channel can determine the response oi nociceptoi to noxious stimuli as well as the final level of pain. Sodium channels may affect the activation and inactivation of othej ion channels( such as the activation of potassium channels, calcium channels )to change the response of neurons to the stimuli,thus the sodium ion channels are potential targets for the treatment of neuropathic pain. Understanding the ion channel expression is of great importance to the control of neuional excitability as we! as the treatment of pain.%电压门控钠离子通道,在动作电位的产生和传导中至关重要,这种离子通道的生物物理性质决定伤害感受器对有害刺激的应答和最终经历的疼痛水平.钠离子通道可能会影响其他离子通道(如钾离子通道、钙离子通道)的激活和失活,改变神经元对刺激的应答,因而钠离子通道是用于治疗神经性疼痛的潜在目标.了解离子通道的表达对控制神经兴奋性、治疗疼痛具有重要意义.

  7. Study Progress of Nervous Diseases Caused by Genetic Mutation of Voltage-gated Sodium Channel%电压门控钠离子通道相关基因突变致神经系统病变的研究进展

    Institute of Scientific and Technical Information of China (English)

    张鲲

    2012-01-01

    电压门控钠通道是神经元启动和传播动作电位的根源,通过其快速的开放和关闭改变膜电位.当编码离子通道亚单位的基因发生突变或者表达异常,或体内出现针对通道的病理性内源物质时,通道的功能出现不同程度的削减或增强,从而导致机体整体生理功能的紊乱,导致某些先天性和后天获得性疾病.电压门控钠离子通道是离子通道的一种,其相关基因的出现异常导致的神经系统疾病主要见于癫痫、家族性偏头痛、周期性麻痹、原发性红斑肢痛症.%The voltage-gated sodium channel,changing potential through its rapid opening and closing,is the origin of generating and spreading action potential from neurons. When the mutation, abnormal expression or pathological endogeneous substances occurred in subunits of sodium channel, psychological dysfunction comes along with dysfunction in channels,which lead to some congenital or acquired disorders. The voltage-gated sodium channel is a type of ion channel, the nevous system disorders caused by the related gene abnormality include epilepsy, familial migraine, periodic paralysis and primary erythermalgia.

  8. Voltage-gated lipid ion channels

    DEFF Research Database (Denmark)

    Blicher, Andreas; Heimburg, Thomas Rainer

    2013-01-01

    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...... histograms in patch-experiments on lipid membranes. We derived a theoretical current-voltage relationship for pores in lipid membranes that describes the experimental data very well when assuming an asymmetric membrane. We determined the equilibrium constant between closed and open state and the open...... 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...

  9. Inward-rectifying potassium channelopathies: new insights into disorders of sodium and potassium homeostasis.

    Science.gov (United States)

    Cheng, Chih-Jen; Sung, Chih-Chien; Huang, Chou-Long; Lin, Shih-Hua

    2015-03-01

    Inward-rectifying potassium (Kir) channels allow more inward than outward potassium flux when channels are open in mammalian cells. At physiological resting membrane potentials, however, they predominantly mediate outward potassium flux and play important roles in regulating the resting membrane potential in diverse cell types and potassium secretion in the kidneys. Mutations of Kir channels cause human hereditary diseases collectively called Kir channelopathies, many of which are characterized by disorders of sodium and potassium homeostasis. Studies on these genetic Kir channelopathies have shed light on novel pathophysiological mechanisms, including renal sodium and potassium handling, potassium shifting in skeletal muscles, and aldosterone production in the adrenal glands. Here, we review several recent advances in Kir channels and their clinical implications in sodium and potassium homeostasis.

  10. Crystal structure of the sodium-potassium pump

    DEFF Research Database (Denmark)

    Morth, J Preben; Pedersen, Bjørn Panyella; Toustrup-Jensen, Mads S;

    2007-01-01

    The Na+,K+-ATPase generates electrochemical gradients for sodium and potassium that are vital to animal cells, exchanging three sodium ions for two potassium ions across the plasma membrane during each cycle of ATP hydrolysis. Here we present the X-ray crystal structure at 3.5 A resolution of the...

  11. 电压门控性钠通道Nav1.7及其特异性阻断剂在神经病理性痛中的研究进展%Progress of Voltage Gated Sodium Channel Nav1.7 and Its Specifi c Blockers in Neuropathic Pain

    Institute of Scientific and Technical Information of China (English)

    王川; 单彬; 王琼; 张海林

    2015-01-01

    电压门控性钠通道(voltage gated sodium channel,Nav)在痛觉的产生和传导中具有重要作用。在痛觉传导通路中,Nav1.7选择性表达于小直径外周感觉神经元和交感神经节神经元,可通过强化阈下刺激并设定Nav1.8和Nav1.9激活开放的阈值,从而影响神经元兴奋性。该综述将重点阐述由Nav1.7通道基因突变所致的神经病理性痛的研究进展。Nav1.7可作为治疗疼痛的有效靶点,高选择性的Nav1.7阻断剂将对治疗疼痛具有重要的临床应用价值。%Voltage gated sodium channels(Nav) play important roles in generation and conduction of pain. In pain conduction pathway,Nav1.7 is selectively expressed in small-diameter peripheral somatic sensory neurons and sympathetic ganglion neurons. Nav1.7 modulates neuronal excitability through amplifing subthreshold of depolarizations and setting up the thresholds of Nav1.8 and Nav1.9. This review will focus on the progress of neuropathic pain caused by mutations in Nav1.7. Nav1.7 can be used as an effective target for the treatment of pain. Highly selective Nav1.7 blockers will be of great clinical value in the treatment of pain.

  12. Urinary Sodium and Potassium Excretion and Dietary Sources of Sodium in Maputo, Mozambique.

    Science.gov (United States)

    Queiroz, Ana; Damasceno, Albertino; Jessen, Neusa; Novela, Célia; Moreira, Pedro; Lunet, Nuno; Padrão, Patrícia

    2017-08-03

    This study aimed to evaluate the urinary excretion of sodium and potassium, and to estimate the main food sources of sodium in Maputo dwellers. A cross-sectional evaluation of a sample of 100 hospital workers was conducted between October 2012 and May 2013. Sodium and potassium urinary excretion was assessed in a 24-h urine sample; creatinine excretion was used to exclude unlikely urine values. Food intake in the same period of urine collection was assessed using a 24-h dietary recall. The Food Processor Plus(®) was used to estimate sodium intake corresponding to naturally occurring sodium and sodium added to processed foods (non-discretionary sodium). Salt added during culinary preparations (discretionary sodium) was computed as the difference between urinary sodium excretion and non-discretionary sodium. The mean (standard deviation) urinary sodium excretion was 4220 (1830) mg/day, and 92% of the participants were above the World Health Organization (WHO) recommendations. Discretionary sodium contributed 60.1% of total dietary sodium intake, followed by sodium from processed foods (29.0%) and naturally occurring sodium (10.9%). The mean (standard deviation) urinary potassium excretion was 1909 (778) mg/day, and 96% of the participants were below the WHO potassium intake recommendation. The mean (standard deviation) sodium to potassium molar ratio was 4.2 (2.4). Interventions to decrease sodium and increase potassium intake are needed in Mozambique.

  13. Urinary Sodium and Potassium Excretion and Dietary Sources of Sodium in Maputo, Mozambique

    Directory of Open Access Journals (Sweden)

    Ana Queiroz

    2017-08-01

    Full Text Available This study aimed to evaluate the urinary excretion of sodium and potassium, and to estimate the main food sources of sodium in Maputo dwellers. A cross-sectional evaluation of a sample of 100 hospital workers was conducted between October 2012 and May 2013. Sodium and potassium urinary excretion was assessed in a 24-h urine sample; creatinine excretion was used to exclude unlikely urine values. Food intake in the same period of urine collection was assessed using a 24-h dietary recall. The Food Processor Plus® was used to estimate sodium intake corresponding to naturally occurring sodium and sodium added to processed foods (non-discretionary sodium. Salt added during culinary preparations (discretionary sodium was computed as the difference between urinary sodium excretion and non-discretionary sodium. The mean (standard deviation urinary sodium excretion was 4220 (1830 mg/day, and 92% of the participants were above the World Health Organization (WHO recommendations. Discretionary sodium contributed 60.1% of total dietary sodium intake, followed by sodium from processed foods (29.0% and naturally occurring sodium (10.9%. The mean (standard deviation urinary potassium excretion was 1909 (778 mg/day, and 96% of the participants were below the WHO potassium intake recommendation. The mean (standard deviation sodium to potassium molar ratio was 4.2 (2.4. Interventions to decrease sodium and increase potassium intake are needed in Mozambique.

  14. 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.

  15. Subcellular localization of the voltage-gated potassium channels Kv3.1b and Kv3.3 in the cerebellar dentate nucleus of glutamic acid decarboxylase 67-green fluorescent protein transgenic mice.

    Science.gov (United States)

    Alonso-Espinaco, V; Elezgarai, I; Díez-García, J; Puente, N; Knöpfel, T; Grandes, P

    2008-09-09

    Deep cerebellar dentate nuclei are in a key position to control motor planning as a result of an integration of cerebropontine inputs and hemispheric Purkinje neurons signals, and their influence through synaptic outputs onto extracerebellar hubs. GABAergic dentate neurons exhibit broader action potentials and slower afterhyperpolarization than non-GABAergic (presumably glutamatergic) neurons. Specific potassium channels may be involved in these distinct firing profiles, particularly, Kv3.1 and Kv3.3 subunits which rapidly activate at relatively positive potentials to support the generation of fast action potentials. To investigate the subcellular localization of Kv3.1b and Kv3.3 in GAD- and GAD+ dentate neurons of glutamic acid decarboxylase 67-green fluorescent protein (GAD67-GFP) knock-in mice a preembedding immunocytochemical method for electron microscopy was used. Kv3.1b and Kv3.3 were in membranes of cell somata, dendrites, axons and synaptic terminals of both GAD- and GAD+ dentate neurons. The vast majority of GAD- somatodendritic membrane segments domains labeled for Kv3.1b and Kv3.3 (96.1% and 84.7%, respectively) whereas 56.2% and 69.8% of GAD- axonal membrane segments were immunopositive for these subunits. Furthermore, density of Kv3.1b immunoparticles was much higher in GAD- somatodendritic than axonal domains. As to GAD+ neurons, only 70.6% and 50% of somatodendritic membrane segments, and 53.3% and 59.5% of axonal membranes exhibited Kv3.1b and Kv3.3 labeling, respectively. In contrast to GAD- cells, GAD+ cells exhibited a higher density labeling for both Kv3 subunits at their axonal than at their somatodendritic membranes. Taken together, Kv3.1b and Kv3.3 potassium subunits are expressed in both GAD- and GAD+ cells, albeit at different densities and distribution. They likely contribute to the distinct biophysical properties of both GAD- and GAD+ neurons in the dentate nucleus.

  16. Adsorption of Potassium and Sodium Ions by Variable Charge Soils

    Institute of Scientific and Technical Information of China (English)

    LIHONG-YAN; JIGUO-LIANG

    1992-01-01

    Adsorption of potassium and sodium ions by four typical variable charge soils of South China was studied.The results indicated that the variable charge soils saturated with H and Al showed a much higher preference for potassium ions relative to sodium ions,and this tendence could not be changed by such factors as the pH,the concentration of the cations,the dielectric constant of solvent,the accompanying anions and the iron oxide content etc.,suggesting that this difference in affinity is caused by the difference in the nature of the two cations.It was observed that a negative adsorption of sodium ions by latosol and lateritic red soil in a mixed system containing equal amount of potassium and sodium ions at low pH,which is caused by a competitive adsorption of potassium and sodium ions and repulsion of positive charge on the surfaces of soil particles for cations.The adsorption of potassium and sodium ions increased with the decreases in the dielectric constant of solvent and the iron oxide content.Sulfate affected the adsorption of potassium and sodium ions through changing the surface properties of the soils.

  17. Voltage-gated Calcium Channels and Autism Spectrum Disorders.

    Science.gov (United States)

    Breitenkamp, Alexandra F; Matthes, Jan; Herzig, Stefan

    2015-01-01

    Autism spectrum disorder is a complex-genetic disease and its etiology is unknown for the majority of cases. So far, more than one hundred different susceptibility genes were detected. Voltage-gated calcium channels are among the candidates linked to autism spectrum disorder by results of genetic studies. Mutations of nearly all pore-forming and some auxiliary subunits of voltage gated calcium channels have been revealed from investigations of autism spectrum disorder patients and populations. Though there are only few electrophysiological characterizations of voltage-gated calcium channel mutations found in autistic patients these studies suggest their functional relevance. In summary, both genetic and functional data suggest a potential role of voltage-gated calcium channels in autism spectrum disorder. Future studies require refinement of the clinical and systems biological concepts of autism spectrum disorder and an appropriate holistic approach at the molecular level, e.g. regarding all facets of calcium channel functions.

  18. Voltage-Gated Channels as Causative Agents for Epilepsies

    OpenAIRE

    2008-01-01

    Problem statement: Epilepsy is a common neurological disorder that afflicts 1-2% of the general population worldwide. It encompasses a variety of disorders with seizures. Approach: Idiopathic epilepsies were defined as a heterogeneous group of seizure disorders that show no underlying cause .Voltage-gated ion channels defect were recognized etiology of epilepsy in the central nervous system. The aim of this article was to provide an update on voltage-gated ...

  19. Cnidarian Toxins Acting on Voltage-Gated Ion Channels

    Directory of Open Access Journals (Sweden)

    Robert M. Greenberg

    2006-04-01

    Full Text Available Abstract: Voltage-gated ion channels generate electrical activity in excitable cells. As such, they are essential components of neuromuscular and neuronal systems, and are targeted by toxins from a wide variety of phyla, including the cnidarians. Here, we review cnidarian toxins known to target voltage-gated ion channels, the specific channel types targeted, and, where known, the sites of action of cnidarian toxins on different channels.

  20. Urinary Sodium and Potassium Excretion and CKD Progression.

    Science.gov (United States)

    He, Jiang; Mills, Katherine T; Appel, Lawrence J; Yang, Wei; Chen, Jing; Lee, Belinda T; Rosas, Sylvia E; Porter, Anna; Makos, Gail; Weir, Matthew R; Hamm, L Lee; Kusek, John W

    2016-04-01

    CKD is a major risk factor for ESRD, cardiovascular disease, and premature death. Whether dietary sodium and potassium intake affect CKD progression remains unclear. We prospectively studied the association of urinary sodium and potassium excretion with CKD progression and all-cause mortality among 3939 patients with CKD in the Chronic Renal Insufficiency Cohort Study. Urinary sodium and potassium excretion were measured using three 24-hour urine specimens, and CKD progression was defined as incident ESRD or halving of eGFR. During follow-up, 939 CKD progression events and 540 deaths occurred. Compared with the lowest quartile of urinary sodium excretion (CKD progression, 1.45 (1.08 to 1.95) for all-cause mortality, and 1.43 (1.18 to 1.73) for the composite outcome of CKD progression and all-cause mortality after adjusting for multiple covariates, including baseline eGFR. Additionally, compared with the lowest quartile of urinary potassium excretion (CKD progression, 0.98 (0.71 to 1.35) for all-cause mortality, and 1.42 (1.15 to 1.74) for the composite outcome. These data indicate that high urinary sodium and potassium excretion are associated with increased risk of CKD progression. Clinical trials are warranted to test the effect of sodium and potassium reduction on CKD progression.

  1. Outward Rectification of Voltage-Gated K+ Channels Evolved at Least Twice in Life History.

    Science.gov (United States)

    Riedelsberger, Janin; Dreyer, Ingo; Gonzalez, Wendy

    2015-01-01

    Voltage-gated potassium (K+) channels are present in all living systems. Despite high structural similarities in the transmembrane domains (TMD), this K+ channel type segregates into at least two main functional categories-hyperpolarization-activated, inward-rectifying (Kin) and depolarization-activated, outward-rectifying (Kout) channels. Voltage-gated K+ channels sense the membrane voltage via a voltage-sensing domain that is connected to the conduction pathway of the channel. It has been shown that the voltage-sensing mechanism is the same in Kin and Kout channels, but its performance results in opposite pore conformations. It is not known how the different coupling of voltage-sensor and pore is implemented. Here, we studied sequence and structural data of voltage-gated K+ channels from animals and plants with emphasis on the property of opposite rectification. We identified structural hotspots that alone allow already the distinction between Kin and Kout channels. Among them is a loop between TMD S5 and the pore that is very short in animal Kout, longer in plant and animal Kin and the longest in plant Kout channels. In combination with further structural and phylogenetic analyses this finding suggests that outward-rectification evolved twice and independently in the animal and plant kingdom.

  2. Effects of toxin huwentoxin-Ⅲ from the venom of the Chinese bird spider, Ornithoctonus huwena (Araneae: Theraphosidae) on neuronal voltage-gated ion channels in cockroach Periplaneta americana%虎纹捕鸟蛛毒素虎纹毒素-Ⅲ对美洲蜚蠊神经细胞电压门控离子通道的影响

    Institute of Scientific and Technical Information of China (English)

    王瑞兰; 梁宋平

    2009-01-01

    Huwentoxin-Ⅲ purified from the venom of the Chinese bird spider, Ornithoctonus huwena (Wang et al.), is an insect neurotoxic peptide. The effects of huwentoxin-Ⅲ on neuronal voltage-gated ion channels were studied by using whole-cell patch clamp technique. Huwentoxin-Ⅲ specifically inhibited voltage-gated sodium channels in dorsal unpaired median neurons of adult cockroach Periplaneta americana (IC50≈1.106 μmol/L) while having no evident effect on voltage-gated potassium channels. HWTX-Ⅲ inhibited insect voltage-gated sodium channels through a novel mechanism distinctive from other spider toxins, did not affect the activation and inactivation kinetics, and not evidently shift the steady-state inactivation curve. Thus, its specificity and novel mechanism on insect neuronal voltage-gated sodium channels make it an interesting tool for investigating the multiple molecular forms of voltage-gated sodium channels and exploiting new and safe insecticides.%HWTX-Ⅲ是从中国虎纹捕鸟蛛Ornithoctonus huwena粗毒中分离纯化到的一种昆虫神经多肽.通过应用全细胞膜片钳技术研究了HWTX-Ⅲ对美洲蜚蠊Periplaneta americana神经细胞电压门控离子通道的影响.发现HWTX-Ⅲ特异性地抑制美洲蜚蠊背侧不成对中间(dorsal unpaired median,DUM)神经细胞的电压门控钠通道(IC50≈1.106μmol/L),而对电压门控钾通道没有明显的影响.HWTX-Ⅲ通过一种新型的不同于其他蜘蛛毒素的机制抑制昆虫电压门控钠通道,它不影响通道的激活与失活动力学,也不明显地漂移稳态失活曲线.HWTX-Ⅲ对昆虫神经细胞电压门控钠通道的特异性与新型作用机制为研究电压门控钠通道分子结构的多样性以及开发新的安全的杀虫剂提供有用的工具.

  3. Studies of alpha-helicity and intersegmental interactions in voltage-gated Na+ channels: S2D4.

    Directory of Open Access Journals (Sweden)

    Zhongming Ma

    Full Text Available Much data, including crystallographic, support structural models of sodium and potassium channels consisting of S1-S4 transmembrane segments (the "voltage-sensing domain" clustered around a central pore-forming region (S5-S6 segments and the intervening loop. Voltage gated sodium channels have four non-identical domains which differentiates them from the homotetrameric potassium channels that form the basis for current structural models. Since potassium and sodium channels also exhibit many different functional characteristics and the fourth domain (D4 of sodium channels differs in function from other domains (D1-D3, we have explored its structure in order to determine whether segments in D4 of sodium channels differ significantly from that determined for potassium channels. We have probed the secondary and tertiary structure and the role of the individual amino acid residues of the S2D4 of Na(v1.4 by employing cysteine-scanning mutagenesis (with tryptophan and glutamine substituted for native cysteine. A Fourier transform power spectrum of perturbations in free energy of steady-state inactivation gating (using midpoint potentials and slopes of Boltzmann equation fits of channel availability, h(infinity-V plots indicates a substantial amount of alpha-helical structure in S2D4 (peak at 106 degrees, alpha-Periodicity Index (alpha-PI of 3.10, This conclusion is supported by alpha-PI values of 3.28 and 2.84 for the perturbations in rate constants of entry into (beta and exit from (alpha fast inactivation at 0 mV for mutant channels relative to WT channels assuming a simple two-state model for transition from the open to inactivated state. The results of cysteine substitution at the two most sensitive sites of the S2D4 alpha-helix (N1382 and E1392C support the existence of electrostatic network interactions between S2 and other transmembrane segments within Na(v1.4D4 similar to but not identical to those proposed for K+ channels.

  4. Voltage-gated proton channel is expressed on phagosomes.

    Science.gov (United States)

    Okochi, Yoshifumi; Sasaki, Mari; Iwasaki, Hirohide; Okamura, Yasushi

    2009-05-01

    Voltage-gated proton channel has been suggested to help NADPH oxidase activity during respiratory burst of phagocytes through its activities of compensating charge imbalance and regulation of pH. In phagocytes, robust production of reactive oxygen species occurs in closed membrane compartments, which are called phagosomes. However, direct evidence for the presence of voltage-gated proton channels in phagosome has been lacking. In this study, the expression of voltage-gated proton channels was studied by Western blot with the antibody specific to the voltage-sensor domain protein, VSOP/Hv1, that has recently been identified as the molecular correlate for the voltage-gated proton channel. Phagosomal membranes of neutrophils contain VSOP/Hv1 in accordance with subunits of NADPH oxidases, gp91, p22, p47 and p67. Superoxide anion production upon PMA activation was significantly reduced in neutrophils from VSOP/Hv1 knockout mice. These are consistent with the idea that voltage-gated proton channels help NADPH oxidase in phagocytes to produce reactive oxygen species.

  5. A thermosensitive mutation alters the effects of lacosamide on slow inactivation in neuronal voltage-gated sodium channels, NaV 1.2.Mena Abdelsayed1, Stanislav Sokolov1, Peter C. Ruben*1 - These authors contributed equally to this work* - Corresponding author

    Directory of Open Access Journals (Sweden)

    Mena eAbdelsayed

    2013-09-01

    Full Text Available Epilepsy is a disorder characterized by seizures and convulsions. The basis of epilepsy is an increase in neuronal excitability that, in some cases, may be caused by functional defects in neuronal voltage gated sodium channels (NaVs. The C121W mutation of the β1 subunit, in particular, gives rise to the thermosensitive generalized epilepsy with febrile seizures plus (GEFS+ phenotype. Lacosamide is used to treat epileptic seizures and is distinct from other anti-seizure drugs by targeting NaV slow-inactivation. We studied the effects of 100 µM lacosamide on the biophysical properties of NaV1.2 channels associated with either WT-β1 or the mutant C121W-β1 subunit. Biophysical parameters were measured at both normal (22 °C and elevated (34 °C temperatures to elicit the differential temperature-sensitivity of C121W. Lacosamide was less effective in NaV1.2 associated with the C121W-β1 at either temperature than in NaV1.2 + WT-β1. There is also a more potent effect by lacosamide on slow inactivation at elevated temperatures. Our data suggest a modulatory role is imparted by the β1 subunit in the interaction between the drug and the channel.

  6. Molecular basis of the interaction between gating modifier spider toxins and the voltage sensor of voltage-gated ion channels

    Science.gov (United States)

    Lau, Carus H. Y.; King, Glenn F.; Mobli, Mehdi

    2016-01-01

    Voltage-sensor domains (VSDs) are modular transmembrane domains of voltage-gated ion channels that respond to changes in membrane potential by undergoing conformational changes that are coupled to gating of the ion-conducting pore. Most spider-venom peptides function as gating modifiers by binding to the VSDs of voltage-gated channels and trapping them in a closed or open state. To understand the molecular basis underlying this mode of action, we used nuclear magnetic resonance to delineate the atomic details of the interaction between the VSD of the voltage-gated potassium channel KvAP and the spider-venom peptide VSTx1. Our data reveal that the toxin interacts with residues in an aqueous cleft formed between the extracellular S1-S2 and S3-S4 loops of the VSD whilst maintaining lipid interactions in the gaps formed between the S1-S4 and S2-S3 helices. The resulting network of interactions increases the energetic barrier to the conformational changes required for channel gating, and we propose that this is the mechanism by which gating modifier toxins inhibit voltage-gated ion channels. PMID:27677715

  7. Molecular basis of the interaction between gating modifier spider toxins and the voltage sensor of voltage-gated ion channels

    Science.gov (United States)

    Lau, Carus H. Y.; King, Glenn F.; Mobli, Mehdi

    2016-09-01

    Voltage-sensor domains (VSDs) are modular transmembrane domains of voltage-gated ion channels that respond to changes in membrane potential by undergoing conformational changes that are coupled to gating of the ion-conducting pore. Most spider-venom peptides function as gating modifiers by binding to the VSDs of voltage-gated channels and trapping them in a closed or open state. To understand the molecular basis underlying this mode of action, we used nuclear magnetic resonance to delineate the atomic details of the interaction between the VSD of the voltage-gated potassium channel KvAP and the spider-venom peptide VSTx1. Our data reveal that the toxin interacts with residues in an aqueous cleft formed between the extracellular S1-S2 and S3-S4 loops of the VSD whilst maintaining lipid interactions in the gaps formed between the S1-S4 and S2-S3 helices. The resulting network of interactions increases the energetic barrier to the conformational changes required for channel gating, and we propose that this is the mechanism by which gating modifier toxins inhibit voltage-gated ion channels.

  8. Linkage study of voltage-gated potassium channels in familial mesial temporal lobe epilepsy Análise de ligação dos canais de potássio voltagem-dependente na epilepsia de lobo temporal mesial familiar

    Directory of Open Access Journals (Sweden)

    Cláudia Vianna Maurer-Morelli

    2007-03-01

    Full Text Available Voltage-gated potassium channels (VGKCs play a critical role in the regulation of neuronal excitability and have been implicated in some types of epilepsies. Recently, autoimmune limbic encephalitis (LE was associated with antibodies against VGKC. In addition, patients with LE showed partial epilepsy and increased T2 signal abnormalities in limbic structures. We have reported familial mesial temporal lobe epilepsy (FMTLE associated with hippocampal atrophy (HA and other signs of mesial temporal sclerosis detected by magnetic resonance imaging (MRI. In order to investigate whether VGKC may be associated to HA present in FMTLE, we perform linkage study in these candidate genes. Seventy-three microsatellites markers were genotyped in different human autosomal chromosome. Two-point LOD scores did not show evidence for linkage with any of the microsatellite markers genotyped (Zmax ranging from 0.11to-9.53 at theta=0.00. In the present study, linkage data showed no evidence that VGKC are involved in the determination of HA in FMTLE.Canais de potássio voltagem-dependentes (CPVD desempenham importante papel na excitabilidade neuronal e estão associados a determinados tipos de epilepsia. Recentemente, um tipo de encefalite límbica autoimune (EL foi associado com anticorpos contra CPVD. Além disso, há relatos de pacientes com EL e epilepsia parcial, além de hipersinal em regiões límbicas detectadas em imagens de ressonância magnética (IRM. Nós temos descrito a epilepsia de lobo temporal mesial familial (ELTMF associada à atrofia hipocampal (AH e outros sinais de esclerose mesial temporal observadas em IRM. Para investigar se os CPVD podem estar associados com a AH identificada na ELTMF, empregamos o estudo de ligação genética nesses genes candidatos. Setenta e três marcadores microssatélites foram genotipados e o LOD score de dois pontos mostrou Zmax variando de 0.11 a -9.53 para teta=0.00. No presente estudo, os dados obtidos com a an

  9. 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.

  10. Closely packed sodium and potassium nanowires in ultrathin carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jeong Won; Hwang, Ho Jung [Chung-Ang University, Seoul (Korea, Republic of); Lee, Jun Ha; Lee, Hoong Ju [Sangmyung University, Chonan (Korea, Republic of)

    2004-07-15

    We have investigated the structural phases of sodium and potassium encapsulated in ultrathin carbon nanotubes by using a structural optimization process applied to an atomistic simulation method. As the radius of the carbon nanotubes is increased, structures are found in various phases from an atomic strand to multi-shell packs composed of coaxial cylindrical shells and in both helical and layered structures. The numbers of helical atom rows composed of coaxial tubes and the orthogonal vectors of a circular rolling of a triangular network can explain multi-shell phases of sodium and potassium in carbon nanotubes.

  11. 海南捕鸟蛛毒素-Ⅵ,一种新型的抑制昆虫电压门控钠通道失活的狼蛛神经毒素%Hainantoxin-Ⅵ, A Novel Tarantula Neurotoxin Inhibiting Insect Voltage-gated Sodium Channel Inactivation

    Institute of Scientific and Technical Information of China (English)

    王瑞兰; 潘建议; 肖玉成; 王美迟; 梁宋平

    2008-01-01

    The neurotoxin peptide, hainantoxin-Ⅵ (HNTX- Ⅵ), has been isolated from the venom of Chinese tarantula Ornithoconus hainana by a combination of ion exchange chromatography and reverse phase HPLC. The toxin was found to contain 34 amino acid residues with 6 conserved cysteine residues. The effects of HNTX-VI on voltage-gated sodium channels were studied via whole-cell patch clamp techniques. Although several inhibitors of mammalian neuronal sodium channel activation (hainantoxin Ⅰ-Ⅴ) had been characterized from the same venom, the present study indicated that HNTX-Ⅵ had the ability to slow the inactivation kinetics of the sodium channels in Cockroach Periplaneta Americana dorsal unpaired median (DUM) neurons in a similar manner to δ-atractoxins. After HNTX-Ⅵ treatment, steady-state sodium channel inactivation became incomplete, leading to a non-inactivating component at potentials more positive than - 55 mV. The novel function of the tarantula toxin HNTX-Ⅵ not only supplies a useful tool for exploring the gating mechanisms of sodium channels but also provides theoretical foundations for exploiting novel and safe insecticides.%通过阳离子交换和反相HPLC柱层析从海南捕鸟蛛(Ornithoconus hainana)粗毒中分离到一种新型的神经毒素,海南捕鸟蛛毒素-Ⅵ(HNTX-Ⅵ),由34个氨基酸残基组成,含有6个保守的半胱氨酸残基.运用全细胞膜片钳技术,研究了HNTX-Ⅵ对电压门控钠通道的影响.先前从海南捕鸟蛛粗毒中分离到的几种毒素,具有抑制哺乳动物钠通道激活的特性.本文研究结果表明,HNTX-Ⅵ能以类似于δ-atractoxins作用方式延缓蜚蠊背侧不成对中间(dorsal unpaired median,DUM)神经细胞的钠通道的失活,且导致钠通道稳态失活变得不完全,在预钳制电压大于-55 mV时形成不完全失活结构.HNTX-Ⅵ的这种新的功能不仅为探索钠通道的门控机制提供了有用的工具,也为开发新的安全的杀虫剂提供理论基础.

  12. Evaluation of random urine sodium and potassium compensated by creatinine as possible alternative markers for 24 hours urinary sodium and potassium excretion.

    Science.gov (United States)

    Koo, Hyunmin; Lee, Sang-Guk; Kim, Jeong-Ho

    2015-03-01

    Sodium and potassium intake was assessed on the basis of its respective excretion levels in 24 hr urine samples. However, owing to the inconvenience of collection, we evaluated random spot urine for alternative sodium and potassium excretion markers. We included 250 patients who submitted 24 hr- and spot urine for clinical tests. However, 22 patients who showed 24 hr urine creatinine excretion levels creatinine (r=0.34, Pcreatinine (r=0.47, Pcreatinine and potassium/creatinine ratios showed a significant correlation with 24 hr urine sodium and potassium excretion, respectively, further studies are required to develop a spot urine test for individualized monitoring of sodium and potassium excretion.

  13. The thermal decomposition of potassium and sodium-pyrosulfate

    NARCIS (Netherlands)

    Vries, de K.J.; Gellings, P.J.

    1969-01-01

    Proceeding from KHSO4, K2S2O8, NaHSO4 and Na2S2O8, potassium- and sodium-pyrosulfates were prepared and their thermal decomposition was investigated by a T.G.A. method. This was done in order to clarify contradictory values found in the literature. The presence of an intermediate with composition K2

  14. Testing two methods to detect voltage-gated sodium channels gene mutations in Tetranychusurticae%两种方法在二斑叶螨电压门控钠离子通道基因突变检测中的应用

    Institute of Scientific and Technical Information of China (English)

    杨顺义; 岳秀利; 王进军; 沈慧敏; 郭金梅; 沈一凡; 周兴隆

    2014-01-01

    Target mutation produces high levels of resistance to pyrethroid insecticides in the spider mite Tet-ranychusurticae.However,as there are many techniques for detecting target mutations it would be advanta-geous to identify methods that are both economical and effective.Three mutations (L1022V,A1215D and F1538I)have been identified in the voltage-gated sodium channels (VGSCs)of T.urticae.We have tested the ability of two different methods,PCR product direct sequencing and polymerase chain reaction-restriction frag-ment length polymorphism (PCR-RFLP),to detect these VGSC gene mutations in two field strains (WW-R and LZ-R)of T.urticae.The results of PCR product direct sequencing showed that the A1215D and F1538I mutations existed in the VGSC genes of both the WW-R and LZ-R strains,but that the F1022V mutation was not detected.The A1215D mutation was located between domains IIS6 and IIIS1 of the VGSCs,while the F1538I mutation was identified in domain IIIS6.The PCR-RFLP method,however,proved able to identify only the A1215D mutation.Our testing of these two methods shows that detecting VGSC mutations in field strains of T.urticaehas the potential to develop molecular-based monitoring that can be used to manage the species’resistance to pyrethroid insecticides.%靶标突变是二斑叶螨对拟除虫菊酯类药剂产生高抗性的重要原因,而用于靶标突变检测的方法较多,有必要寻找一种经济、灵敏且有效的方法进行突变检测。本研究根据二斑叶螨电压门控钠离子通道(voltage-gated sodi-um channels,VGSCs)基因上已报道的3个点突变(L1022V、A1215D和F1538I),采用PCR产物直接测序和限制性片段长度多态性聚合酶链反应(polymerase chain reaction-restriction fragment length polymorphism,PCR-RFLP)两种不同的方法对二斑叶螨田间种群(WW-R和LZ-R)进行靶标VGSCs 基因突变检测。PCR产物直接测序结果显示,与SS种群相比,WW-R和LZ-R种群VGSCs基

  15. Blood pressure response to changes in sodium and potassium intake: a metaregression analysis of randomised trials

    NARCIS (Netherlands)

    Geleijnse, J.M.; Kok, F.J.; Grobbee, D.E.

    2003-01-01

    The objective of the study was to assess the blood pressure response to changes in sodium and potassium intake and examine effect modification by age, gender, blood pressure, body weight and habitual sodium and potassium intake. Randomised trials of sodium reduction or potassium supplementation and

  16. Modulation of voltage-gated Na+ and K+ channels by pumiliotoxin 251D: a "joint venture" alkaloid from arthropods and amphibians.

    Science.gov (United States)

    Vandendriessche, Thomas; Abdel-Mottaleb, Yousra; Maertens, Chantal; Cuypers, Eva; Sudau, Alexander; Nubbemeyer, Udo; Mebs, Dietrich; Tytgat, Jan

    2008-03-01

    Certain amphibians provide themselves with a chemical defense by accumulating lipophilic alkaloids into skin glands from dietary arthropods. Examples of such alkaloids are pumiliotoxins (PTXs). In general, PTXs are known as positive modulators of voltage-gated sodium channels (VGSCs). Unlike other PTXs, PTX 251D does not share this characteristic. However, mice and insect studies showed that PTX 251D is highly toxic and to date the basis of its toxicity remains unknown. In this work, we searched for the possible target of PTX 251D. The toxin was therefore made synthetically and tested on four VGSCs (mammalian rNa(v)1.2/beta(1), rNa(v)1.4/beta(1), hNa(v)1.5/beta(1) and insect Para/tipE) and five voltage-gated potassium channels (VGPCs) (mammalian rK(v)1.1-1.2, hK(v)1.3, hK(v)11.1 (hERG) and insect Shaker IR) expressed heterologously in Xenopus laevis oocytes, using the two-electrode voltage clamp technique. PTX 251D not only inhibited the Na(+) influx through the mammalian VGSCs but also affected the steady-state activation and inactivation. Interestingly, in the insect ortholog, the inactivation process was dramatically affected. Additionally, PTX 251D inhibited the K(+) efflux through all five tested VGPCs and slowed down the deactivation kinetics of the mammalian VGPCs. hK(v)1.3 was the most sensitive channel, with an IC(50) value 10.8+/-0.5 microM. To the best of our knowledge this is the first report of a PTX affecting VGPCs.

  17. Final report on the safety assessment of sodium sulfite, potassium sulfite, ammonium sulfite, sodium bisulfite, ammonium bisulfite, sodium metabisulfite and potassium metabisulfite.

    Science.gov (United States)

    Nair, Bindu; Elmore, Amy R

    2003-01-01

    Sodium Sulfite, Ammonium Sulfite, Sodium Bisulfite, Potassium Bisulfite, Ammonium Bisulfite, Sodium Metabisulfite, and Potassium Metabisulfite are inorganic salts that function as reducing agents in cosmetic formulations. All except Sodium Metabisulfite also function as hair-waving/straightening agents. In addition, Sodium Sulfite, Potassium Sulfite, Sodium Bisulfite, and Sodium Metabisulfite function as antioxidants. Although Ammonium Sulfite is not in current use, the others are widely used in hair care products. Sulfites that enter mammals via ingestion, inhalation, or injection are metabolized by sulfite oxidase to sulfate. In oral-dose animal toxicity studies, hyperplastic changes in the gastric mucosa were the most common findings at high doses. Ammonium Sulfite aerosol had an acute LC(50) of >400 mg/m(3) in guinea pigs. A single exposure to low concentrations of a Sodium Sulfite fine aerosol produced dose-related changes in the lung capacity parameters of guinea pigs. A 3-day exposure of rats to a Sodium Sulfite fine aerosol produced mild pulmonary edema and irritation of the tracheal epithelium. Severe epithelial changes were observed in dogs exposed for 290 days to 1 mg/m(3) of a Sodium Metabisulfite fine aerosol. These fine aerosols contained fine respirable particle sizes that are not found in cosmetic aerosols or pump sprays. None of the cosmetic product types, however, in which these ingredients are used are aerosolized. Sodium Bisulfite (tested at 38%) and Sodium Metabisulfite (undiluted) were not irritants to rabbits following occlusive exposures. Sodium Metabisulfite (tested at 50%) was irritating to guinea pigs following repeated exposure. In rats, Sodium Sulfite heptahydrate at large doses (up to 3.3 g/kg) produced fetal toxicity but not teratogenicity. Sodium Bisulfite, Sodium Metabisulfite, and Potassium Metabisulfite were not teratogenic for mice, rats, hamsters, or rabbits at doses up to 160 mg/kg. Generally, Sodium Sulfite, Sodium

  18. Sodium and potassium conductance changes during a membrane action potential.

    Science.gov (United States)

    Bezanilla, F; Rojas, E; Taylor, R E

    1970-12-01

    1. A method for turning a membrane potential control system on and off in less than 10 musec is described. This method was used to record membrane currents in perfused giant axons from Dosidicus gigas and Loligo forbesi after turning on the voltage clamp system at various times during the course of a membrane action potential.2. The membrane current measured just after the capacity charging transient was found to have an almost linear relation to the controlled membrane potential.3. The total membrane conductance taken from these current-voltage curves was found to have a time course during the action potential similar to that found by Cole & Curtis (1939).4. The instantaneous current voltage curves were linear enough to make it possible to obtain a good estimate of the individual sodium and potassium channel conductances, either algebraically or by clamping to the sodium, or potassium, reversal potentials. Good general agreement was obtained with the predictions of the Hodgkin-Huxley equations.5. We consider these results to constitute the first direct experimental demonstration of the conductance changes to sodium and potassium during the course of an action potential.

  19. Intraerythrocytic sodium and potassium concentrations during acute and chronic digitalization.

    Science.gov (United States)

    Pedersen, K E; Koldkjaer, O; Berndtz, N H; Hvidt, S; Kjaer, K; Midtskov, C; Sanchez, G

    1982-01-01

    To assess the cellular effects of digoxin, intraerythrocytic sodium and potassium concentrations were measured in 17 patients during the early phase of digitalization, in 45 patients on long-term therapy and in 64 non-digitalized control patients. Acute digitalization raised intraerythrocytic sodium from 11.6 +/- 0.4 to 16.7 +/- 1.0 mmol/l (mean +/- SEM) (p less than 0.01) and reduced intraerythrocytic potassium from 100.1 +/- 1.3 to 95.9 +/- 1.8 mmol/l (p less than 0.01). These changes were strongly correlated with the steady-state plasma digoxin concentration. During a few weeks of digoxin therapy, the intraerythrocytic cation composition normalized gradually. In patients on chronic treatment, neither intraerythrocytic sodium (11.3 +/- 0.3 mmol/l) nor potassium concentrations (100.0 +/- 0.6 mmol/l) differed significantly from the values of the control group (11.4 +/- 0.2 and 99.9 +/- 0.5 mmol/l, respectively). The changes in intraerythrocytic cation concentrations, induced by acute digitalization, seem to disappear during chronic administration of the drug.

  20. Interaction between Single Nucleotide Polymorphism and Urinary Sodium, Potassium, and Sodium-Potassium Ratio on the Risk of Hypertension in Korean Adults

    Science.gov (United States)

    Park, Yeong Mi; Kwock, Chang Keun; Kim, Kyunga; Kim, Jihye; Yang, Yoon Jung

    2017-01-01

    Hypertension is a complex disease explained with diverse factors including environmental factors and genetic factors. The objectives of this study were to determine the interaction effects between gene variants and 24 h estimated urinary sodium and potassium excretion and sodium-potassium excretion ratios on the risk of hypertension. A total of 8839 participants were included in the genome-wide association study (GWAS) to find genetic factors associated with hypertension. Tanaka and Kawasaki formulas were applied to estimate 24 h urinary sodium and potassium excretion. A total of 4414 participants were included in interaction analyses to identify the interaction effects of gene variants according to 24 h estimated urinary factors on the risk of hypertension. CSK rs1378942 and CSK-MIR4513 rs3784789 were significantly modified by urinary sodium-potassium excretion ratio. In addition, MKLN rs1643270 with urinary potassium excretion, LOC101929750 rs7554672 with urinary sodium and potassium excretion, and TENM4 rs10466739 with urinary sodium-potassium excretion ratio showed significant interaction effects. The present study results indicated that the mutant alleles of CSK rs1378942 and CSK-MIR4513 rs3784789 had the strongest protective effects against hypertension in the middle group of 24 h estimated urinary sodium-potassium excretion ratio. Further studies are needed to replicate these analyses in other populations. PMID:28273873

  1. Interaction between Single Nucleotide Polymorphism and Urinary Sodium, Potassium, and Sodium-Potassium Ratio on the Risk of Hypertension in Korean Adults

    Directory of Open Access Journals (Sweden)

    Yeong Mi Park

    2017-03-01

    Full Text Available Hypertension is a complex disease explained with diverse factors including environmental factors and genetic factors. The objectives of this study were to determine the interaction effects between gene variants and 24 h estimated urinary sodium and potassium excretion and sodium-potassium excretion ratios on the risk of hypertension. A total of 8839 participants were included in the genome-wide association study (GWAS to find genetic factors associated with hypertension. Tanaka and Kawasaki formulas were applied to estimate 24 h urinary sodium and potassium excretion. A total of 4414 participants were included in interaction analyses to identify the interaction effects of gene variants according to 24 h estimated urinary factors on the risk of hypertension. CSK rs1378942 and CSK-MIR4513 rs3784789 were significantly modified by urinary sodium-potassium excretion ratio. In addition, MKLN rs1643270 with urinary potassium excretion, LOC101929750 rs7554672 with urinary sodium and potassium excretion, and TENM4 rs10466739 with urinary sodium-potassium excretion ratio showed significant interaction effects. The present study results indicated that the mutant alleles of CSK rs1378942 and CSK-MIR4513 rs3784789 had the strongest protective effects against hypertension in the middle group of 24 h estimated urinary sodium-potassium excretion ratio. Further studies are needed to replicate these analyses in other populations.

  2. Voltage-gated ion channel dysfunction precedes cardiomyopathy development in the dystrophic heart.

    Directory of Open Access Journals (Sweden)

    Xaver Koenig

    Full Text Available Duchenne muscular dystrophy (DMD, caused by mutations in the dystrophin gene, is associated with severe cardiac complications including cardiomyopathy and cardiac arrhythmias. Recent research suggests that impaired voltage-gated ion channels in dystrophic cardiomyocytes accompany cardiac pathology. It is, however, unknown if the ion channel defects are primary effects of dystrophic gene mutations, or secondary effects of the developing cardiac pathology.To address this question, we first investigated sodium channel impairments in cardiomyocytes derived from dystrophic neonatal mice prior to cardiomyopahty development, by using the whole cell patch clamp technique. Besides the most common model for DMD, the dystrophin-deficient mdx mouse, we also used mice additionally carrying an utrophin mutation. In neonatal cardiomyocytes, dystrophin-deficiency generated a 25% reduction in sodium current density. In addition, extra utrophin-deficiency significantly altered sodium channel gating parameters. Moreover, also calcium channel inactivation was considerably reduced in dystrophic neonatal cardiomyocytes, suggesting that ion channel abnormalities are universal primary effects of dystrophic gene mutations. To assess developmental changes, we also studied sodium channel impairments in cardiomyocytes derived from dystrophic adult mice, and compared them with the respective abnormalities in dystrophic neonatal cells. Here, we found a much stronger sodium current reduction in adult cardiomyocytes. The described sodium channel impairments slowed the upstroke of the action potential in adult cardiomyocytes, and only in dystrophic adult mice, the QRS interval of the electrocardiogram was prolonged.Ion channel impairments precede pathology development in the dystrophic heart, and may thus be considered potential cardiomyopathy triggers.

  3. A Novel Method to Prepare Potassium Sodium Titanate Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Xiao Dong WANG; Zhen Sheng JIN; Xian Ru PEI; Jian Jun YANG; Zhi Jun ZHANG

    2006-01-01

    A novel method, i.e. molten salt method, was adopted to prepare potassium sodium titanate nanotubes. EDX results indicated that the ion-exchange reaction reached an equilibrium state at around 9 h. The 24 h ion-exchanged product maintained nano-tubular and its crystalline structure was consistent with that of Na2Ti2O4(OH)2 nanotubes. The nanotubes have a high specific surface area, possibly making this material a good candidate as controlled release materials,catalyst, electrode materials, etc..

  4. Regulation of cough and action potentials by voltage-gated Na channels.

    Science.gov (United States)

    Carr, Michael J

    2013-10-01

    The classical role ascribed to voltage-gated Na channels is the conduction of action potentials. Some excitable tissues such as cardiac muscle and skeletal muscle predominantly express a single voltage-gated Na channels isoform. Of the nine voltage-gated Na channels, seven are expressed in neurons, of these Nav 1.7, 1.8 and 1.9 are expressed in sensory neurons including vagal sensory neurons that innervate the airways and initiate cough. Nav 1.7 and Nav 1.9 are of particular interest as they represent two extremes in the functional diversity of voltage-gated Na channels. Voltage-gated Na channel isoforms expressed in airway sensory neurons produce multiple distinct Na currents that underlie distinct aspects of sensory neuron function. The interaction between voltage-gated Na currents underlies the characteristic ability of airway sensory nerves to encode encounters with irritant stimuli into action potential discharge and evoke the cough reflex.

  5. Deciphering voltage-gated Na(+) and Ca(2+) channels by studying prokaryotic ancestors.

    Science.gov (United States)

    Catterall, William A; Zheng, Ning

    2015-09-01

    Voltage-gated sodium channels (NaVs) and calcium channels (CaVs) are involved in electrical signaling, contraction, secretion, synaptic transmission, and other physiological processes activated in response to depolarization. Despite their physiological importance, the structures of these closely related proteins have remained elusive because of their size and complexity. Bacterial NaVs have structures analogous to a single domain of eukaryotic NaVs and CaVs and are their likely evolutionary ancestor. Here we review recent work that has led to new understanding of NaVs and CaVs through high-resolution structural studies of their prokaryotic ancestors. New insights into their voltage-dependent activation and inactivation, ion conductance, and ion selectivity provide realistic structural models for the function of these complex membrane proteins at the atomic level. Published by Elsevier Ltd.

  6. 桔小实蝇电压门控钠离子通道基因cDNA克隆及其生物信息学分析%Cloning and Bioinformatics Analysis of Voltage-Gated Sodium Channel Gene cDNA in Bactrocera dorsalis (Hendel)

    Institute of Scientific and Technical Information of China (English)

    蒋玄赵; 魏丹丹; 申光茂; 豆威; 王进军

    2012-01-01

    [目的]克隆获得桔小实蝇(Bactrocera dorsalis)电压门控钠离子通道基因cDNA序列,明确其典型特征,为研究桔小实蝇抗性分子机理奠定基础.[方法]采用RT-PCR和PCR技术,克隆桔小实蝇钠离子通道基因cDNA序列,利用相关软件对其序列进行生物信息学分析.[结果]克隆得到1条长为6 446 bp的cDNA序列,包含1个6 405 bp的完整开放阅读框,共编码2 134个氨基酸.同源比对发现,桔小实蝇与果蝇(Drosophila melanogaster,NP_001188635)和家蝇(Musca domestica,AAB47604)钠离子通道基因相似度分别高达91.7%和86.9%,而与人的钠离子通道Nav1.2基因(Homo sapiens,NP_066287)相似度为42.3%.所克隆序列包含昆虫钠离子通道所有典型特征.[结论]成功地从桔小实蝇中克隆得到钠离子通道基因完整开放阅读框.该钠离子通道基因存在丰富的选择性剪接,发现了3个可能与抗性相关的碱基取代.钠离子通道基因有可能发展成为一种昆虫系统发育研究的分子标记.%[Objective] The objective of this study is to clone voltage-gated sodium channel gene (VGSC) from Bactrocera dorsalis (Hendel), and to identify its typical hallmarks. It will provide basic molecular information for clarifying insecticide resistance mechanism of B. dorsalis. [Method] The cDNA sequence was isolated using RT-PCR and PCR methods. Based on the sequencing results, the bioinformatics analysis of nucleic acid and putative amino acid was conducted. [Result] An almost full-length cDNA sequence (6 446 bp) of VGSC was obtained, including a complete open reading frame (ORF) of 6 405 bp, which encoded 2 134 amino acids and included all the typical hallmarks of VGSC. The amino acid shared 91.7%, 86.9% and 42.3% identity with sodium channel genes of Drosophila melanogaster (NP_001188635), Musca domestica (AAB47604), and Homo sapiens Navl.2 (NP066287), respectively. [Conclusion] A complete ORF of VGSC was sequenced with clone strategy from oriental

  7. Mechanism of voltage-gated channel formation in lipid membranes.

    Science.gov (United States)

    Guidelli, Rolando; Becucci, Lucia

    2016-04-01

    Although several molecular models for voltage-gated ion channels in lipid membranes have been proposed, a detailed mechanism accounting for the salient features of experimental data is lacking. A general treatment accounting for peptide dipole orientation in the electric field and their nucleation and growth kinetics with ion channel formation is provided. This is the first treatment that explains all the main features of the experimental current-voltage curves of peptides forming voltage-gated channels available in the literature. It predicts a regime of weakly voltage-dependent conductance, followed by one of strong voltage-dependent conductance at higher voltages. It also predicts values of the parameters expressing the exponential dependence of conductance upon voltage and peptide bulk concentration for both regimes, in good agreement with those reported in the literature. Most importantly, the only two adjustable parameters involved in the kinetics of nucleation and growth of ion channels can be varied over broad ranges without affecting the above predictions to a significant extent. Thus, the fitting of experimental current-voltage curves stems naturally from the treatment and depends only slightly upon the choice of the kinetic parameters.

  8. Estimating 24-h urinary sodium/potassium ratio from casual ('spot') urinary sodium/potassium ratio: the INTERSALT Study.

    Science.gov (United States)

    Iwahori, Toshiyuki; Miura, Katsuyuki; Ueshima, Hirotsugu; Chan, Queenie; Dyer, Alan R; Elliott, Paul; Stamler, Jeremiah

    2016-12-30

    Association between casual and 24-h urinary sodium-to-potassium (Na/K) ratio is well recognized, although it has not been validated in diverse demographic groups. Our aim was to assess utility across and within populations of casual urine to estimate 24-h urinary Na/K ratio using data from the INTERSALT Study. The INTERSALT Study collected cross-sectional standardized data on casual urinary sodium and potassium and also on timed 24-h urinary sodium and potassium for 10 065 individuals from 52 population samples in 32 countries (1985-87). Pearson correlation coefficients and agreement were computed for Na/K ratio of casual urine against 24-h urinary Na/K ratio both at population and individual levels. Pearson correlation coefficients relating means of 24-h urine and casual urine Na/K ratio were r = 0.96 and r = 0.69 in analyses across populations and individuals, respectively. Correlations of casual urine Na/creatinine and K/creatinine ratios with 24-h urinary Na and K excretion, respectively, were lower than correlation of casual and 24-h urinary Na/K ratio in analyses across populations and individuals. The bias estimate with the Bland-Altman method, defined as the difference between Na/K ratio of 24-h urine and casual urine, was approximately 0.4 across both populations and individuals. Spread around, the mean bias was higher for individuals than populations. With appropriate bias correction, casual urine Na/K ratio may be a useful, low-burden alternative method to 24-h urine for estimation of population urinary Na/K ratio. It may also be applicable for assessment of the urinary Na/K ratio of individuals, with use of repeated measurements to reduce measurement error and increase precision. © The Author 2016. Published by Oxford University Press on behalf of the International Epidemiological Association.

  9. A purified Palythoa venom fraction delays sodium current inactivation in sympathetic neurons.

    Science.gov (United States)

    Lazcano-Pérez, Fernando; Vivas, Oscar; Román-González, Sergio A; Rodríguez-Bustamante, Eduardo; Castro, Héctor; Arenas, Isabel; García, David E; Sánchez-Puig, Nuria; Arreguín-Espinosa, Roberto

    2014-05-01

    Palythoa caribaeorum is a zoanthid (Phylum Cnidaria, class Anthozoa) commonly found in shallow waters of coral reefs along the Mexican Atlantic coast. Little is known on the pharmacological and biochemical properties of the venom components of this animal group. Toxin peptides from other cnidarian venoms, like sea anemones, target sodium and potassium voltage-gated channels. In this study, we tested the activity of a low molecular weight fraction from the venom of P. caribaeorum on voltage-gated sodium channels of the superior cervical ganglion (SCG) neurons of the rat. Our results showed that this fraction delays tetrodotoxin (TTX)-sensitive sodium channel inactivation indicated by a reversible 2-fold increase of the current at the decay. A peptide responsible for this activity was isolated and characterized. Its sequence showed that it does not resemble any previously reported toxin. Together, these results evidence the presence of neurotoxins in P. caribaeorum that act on sodium channels.

  10. Expression of voltage-gated potassium channel Kv3.4 in oral squamous cell carcinoma%口腔鳞状细胞癌及癌前病变组织中钾离子通道Kv3.4表达的研究

    Institute of Scientific and Technical Information of China (English)

    王润; 蔡伯惠; 向娟; 祝心威; 蒋勇

    2016-01-01

    Objective To evaluate the expression of voltage-gated potassium channel Kv3.4 and to determine its significance in oral squamous cell carcinoma(OSCC) and precancerous lesions.Methods Immunohistochemical SP methods were performed to detect the expression of Kv3.4 at tissue level on 57 paraffin-embedded samples collected from Pathology Department of Anhui Province Stomatological Hospital during January 2013 to June 2014.The relationships between the expression of Kv3.4 and precancerous lesion and clinical pathologic factors of oral squamous cell carcinoma,such as pathologic classification,clinical stage and lymph node metastasis,were also analyzed.Totally 6 samples of normal oral mucosa tissue,23 samples of OSCC and 13 samples of precancerous lesions were collected from the Department of Oral and Maxillofacial Surgery of The First Affiliated Hospital of Anhui Medical University during May 2014 to March 2015.Real-time quantitative PCR and Western blotting were used to detect the expression of Kv3.4 in these 42 samples at molecular and protein levels.Results Real-time quantitative PCR showed the relative expression quantity of Kv3.4 in normal oral mucosa,precancerous lesions,and OSCC tissues were 0.85±0.48,3.50±2.51 and 18.48±7.70,respectively.The relative expression quantity of Kv3.4 in OSCC and precancerous lesions were higher than that in normal group,the differences were both statistically significant(P=0.002,P=0.029).The relative expression quantities of Kv3.4 protein in precancerous and OSCC tissues were 0.87±0.14 and 0.35±0.03 respectively by Western blotting,and both were higher than that in normal tissues(0.18±0.10).The differences were statistically significant(P=0.002).In 57 paraffin-embedded samples,the positive expression rates of Kv3.4 in normal,precancerous and OSCC tissues were 2/6,13/18 and 95%(37/39),respectively.The differences were statistically significant(P<0.05).However,the expression of Kv3.4 did not show obvious correlation with

  11. TAURINE REGULATION OF VOLTAGE-GATED CHANNELS IN RETINAL NEURONS

    Science.gov (United States)

    Rowan, Matthew JM; Bulley, Simon; Purpura, Lauren; Ripps, Harris; Shen, Wen

    2017-01-01

    Taurine activates not only Cl−-permeable ionotropic receptors, but also receptors that mediate metabotropic responses. The metabotropic property of taurine was revealed in electrophysiological recordings obtained after fully blocking Cl−-permeable receptors with an inhibitory “cocktail” consisting of picrotoxin, SR95531, and strychnine. We found that taurine’s metabotropic effects regulate voltage-gated channels in retinal neurons. After applying the inhibitory cocktail, taurine enhanced delayed outward rectifier K+ channels preferentially in Off-bipolar cells, and the effect was completely blocked by the specific PKC inhibitor, GF109203X. Additionally, taurine also acted through a metabotropic pathway to suppress both L- and N-type Ca2+ channels in retinal neurons, which were insensitive to the potent GABAB receptor inhibitor, CGP55845. This study reinforces our previous finding that taurine in physiological concentrations produces a multiplicity of metabotropic effects that precisely govern the integration of signals being transmitted from the retina to the brain. PMID:23392926

  12. 21 CFR 73.1125 - Potassium sodium copper chloropyhllin (chlorophyllin-copper complex).

    Science.gov (United States)

    2010-04-01

    ... (chlorophyllin-copper complex). 73.1125 Section 73.1125 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT....1125 Potassium sodium copper chloropyhllin (chlorophyllin-copper complex). (a) Identity. (1) The color additive potassium sodium copper chlorophyllin is a green to black powder obtained from chlorophyll...

  13. 21 CFR 73.2125 - Potassium sodium copper chlorophyllin (chlorophyllin-copper complex).

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Potassium sodium copper chlorophyllin (chlorophyllin-copper complex). 73.2125 Section 73.2125 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT... § 73.2125 Potassium sodium copper chlorophyllin (chlorophyllin-copper complex). (a) Identity...

  14. Transport, signaling, and homeostasis of potassium and sodium in plants

    Institute of Scientific and Technical Information of China (English)

    Eri Adams; Ryoung Shin

    2014-01-01

    Potassium (Kþ) is an essential macronutrient in plants and a lack of Kþ significantly reduces the potential for plant growth and development. By contrast, sodium (Naþ), while beneficial to some extent, at high concentrations it disturbs and inhibits various physiological processes and plant growth. Due to their chemical similarities, some functions of Kþ can be undertaken by Naþ but Kþ homeostasis is severely affected by salt stress, on the other hand. Recent advances have highlighted the fascinating regulatory mechanisms of Kþ and Naþ transport and signaling in plants. This review summarizes three major topics:(i) the transport mechanisms of Kþ and Naþ from the soil to the shoot and to the cellular compartments; (i ) the mechanisms through which plants sense and respond to Kþ and Naþ availability; and (i i) the components involved in maintenance of Kþ/Naþ homeostasis in plants under salt stress.

  15. Opposite Effects of the S4-S5 Linker and PIP(2) on Voltage-Gated Channel Function: KCNQ1/KCNE1 and Other Channels.

    Science.gov (United States)

    Choveau, Frank S; Abderemane-Ali, Fayal; Coyan, Fabien C; Es-Salah-Lamoureux, Zeineb; Baró, Isabelle; Loussouarn, Gildas

    2012-01-01

    Voltage-gated potassium (Kv) channels are tetramers, each subunit presenting six transmembrane segments (S1-S6), with each S1-S4 segments forming a voltage-sensing domain (VSD) and the four S5-S6 forming both the conduction pathway and its gate. S4 segments control the opening of the intracellular activation gate in response to changes in membrane potential. Crystal structures of several voltage-gated ion channels in combination with biophysical and mutagenesis studies highlighted the critical role of the S4-S5 linker (S4S5(L)) and of the S6 C-terminal part (S6(T)) in the coupling between the VSD and the activation gate. Several mechanisms have been proposed to describe the coupling at a molecular scale. This review summarizes the mechanisms suggested for various voltage-gated ion channels, including a mechanism that we described for KCNQ1, in which S4S5(L) is acting like a ligand binding to S6(T) to stabilize the channel in a closed state. As discussed in this review, this mechanism may explain the reverse response to depolarization in HCN-like channels. As opposed to S4S5(L), the phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PIP(2)), stabilizes KCNQ1 channel in an open state. Many other ion channels (not only voltage-gated) require PIP(2) to function properly, confirming its crucial importance as an ion channel cofactor. This is highlighted in cases in which an altered regulation of ion channels by PIP(2) leads to channelopathies, as observed for KCNQ1. This review summarizes the state of the art on the two regulatory mechanisms that are critical for KCNQ1 and other voltage-gated channels function (PIP(2) and S4S5(L)), and assesses their potential physiological and pathophysiological roles.

  16. Opposite effects of the S4-S5 linker and PIP2 on voltage-gated channel function: KCNQ1/KCNE1 and other channels

    Directory of Open Access Journals (Sweden)

    Frank S Choveau

    2012-07-01

    Full Text Available Voltage-gated potassium (Kv channels are tetramers, each subunit presenting six transmembrane segments (S1-S6, with each S1-S4 segments forming a voltage-sensing domain (VSD and the four S5-S6 forming both the conduction pathway and its gate. S4 segments control the opening of the intracellular activation gate in response to changes in membrane potential. Crystal structures of several voltage-gated ion channels in combination with biophysical and mutagenesis studies highlighted the critical role of the S4-S5 linker (S4S5L and of the S6 C-terminal part (S6T in the coupling between the VSD and the activation gate. Several mechanisms have been proposed to describe the coupling at a molecular scale. This review summarizes the mechanisms suggested for various voltage-gated ion channels, including a mechanism that we described for KCNQ1, in which S4S5L is acting like a ligand binding to S6T to stabilize the channel in a closed state. As discussed in this review, this mechanism may explain the reverse response to depolarization in HCN-like channels. As opposed to S4S5L, the phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PIP2, stabilizes KCNQ1 channel in an open state. Many other ion channels (not only voltage-gated require PIP2 to function properly, confirming its crucial importance as an ion channel co-factor. This is highlighted in cases in which an altered regulation of ion channels by PIP2 leads to channelopathies, as observed for KCNQ1. This review summarizes the state of the art on the two regulatory mechanisms that are critical for KCNQ1 and other voltage-gated channels function (PIP2 and S4-S5L, and assesses their potential physiological and pathophysiological roles.

  17. Dietary Impact of Adding Potassium Chloride to Foods as a Sodium Reduction Technique

    Directory of Open Access Journals (Sweden)

    Leo van Buren

    2016-04-01

    Full Text Available Potassium chloride is a leading reformulation technology for reducing sodium in food products. As, globally, sodium intake exceeds guidelines, this technology is beneficial; however, its potential impact on potassium intake is unknown. Therefore, a modeling study was conducted using Dutch National Food Survey data to examine the dietary impact of reformulation (n = 2106. Product-specific sodium criteria, to enable a maximum daily sodium chloride intake of 5 grams/day, were applied to all foods consumed in the survey. The impact of replacing 20%, 50% and 100% of sodium chloride from each product with potassium chloride was modeled. At baseline median, potassium intake was 3334 mg/day. An increase in the median intake of potassium of 453 mg/day was seen when a 20% replacement was applied, 674 mg/day with a 50% replacement scenario and 733 mg/day with a 100% replacement scenario. Reformulation had the largest impact on: bread, processed fruit and vegetables, snacks and processed meat. Replacement of sodium chloride by potassium chloride, particularly in key contributing product groups, would result in better compliance to potassium intake guidelines (3510 mg/day. Moreover, it could be considered safe for the general adult population, as intake remains compliant with EFSA guidelines. Based on current modeling potassium chloride presents as a valuable, safe replacer for sodium chloride in food products.

  18. Balancing Sodium and Potassium: Estimates of Intake in a New Zealand Adult Population Sample

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    Rachael McLean

    2015-10-01

    Full Text Available Dietary intakes of sodium and potassium are important determinants of blood pressure. We assessed sodium and potassium intake in a cross-sectional survey which included a random sample of New Zealand Adults aged 18 to 64 years from two New Zealand cities: Dunedin and Wellington. Participants completed a short questionnaire, had height, weight and blood pressure measured, and collected a 24 h urine sample. Mean 24 h sodium excretion was 3386 mg/day (95% CI 3221, 3551: 3865 mg/day for men and for 2934 mg/day women. Mean 24 h potassium excretion was 2738 mg/day (95% CI 2623, 2855: 3031 mg/day for men and 2436 mg/day for women. Mean sodium:potassium ratio was 1.32 (95% CI 1.26, 1.39; 1.39 for men and 1.26 for women. Sodium intake was higher among younger people, men, those with a higher BMI and higher potassium excretion. Potassium excretion was higher among older people, men and those with a higher sodium excretion. New Zealand adults have high sodium intakes and low potassium intakes compared to recommended levels. This is likely to adversely affect population blood pressure levels as well as incidence of cardiovascular disease. A comprehensive public health programme to reduce dietary sodium intake and increase intake of fruit and vegetables is warranted.

  19. Estimating sodium and potassium intakes and their ratio in the American diet: Data from the 2011-2012 NHANES

    Science.gov (United States)

    Few adults meet the recommendations for sodium or potassium intake, and recent research suggests that the dietary ratio of sodium to potassium (Na:K) is more strongly associated with health outcomes than either nutrient alone. Mean Na:K and food choices contributing to sodium and potassium were ana...

  20. Voltage-gated K+ channels contain multiple intersubunit association sites.

    Science.gov (United States)

    Tu, L; Santarelli, V; Sheng, Z; Skach, W; Pain, D; Deutsch, C

    1996-08-02

    A domain in the cytoplasmic NH2 terminus of voltage-gated K+ channels supervises the proper assembly of specific tetrameric channels (Li, M., Jan, J. M., and Jan, L. Y.(1992) Science 257, 1225-1230; Shen, N. V., Chen X., Boyer, M. M., and Pfaffinger, P. (1993) Neuron 11, 67-76). It is referred to as a first tetramerization domain, or T1 (Shen, N. V., Chen X., Boyer, M. M., and Pfaffinger, P.(1993) Neuron 11, 67-76). However, a deletion mutant of Kv1.3 that lacks the first 141 amino acids, Kv1.3 (T1(-)) forms functional channels, suggesting that additional association sites in the central core of Kv1.3 mediate oligomerization. To characterize these sites, we have tested the abilities of cRNA Kv1.3 (T1(-)) fragments co-injected with Kv1.3 (T1(-)) to suppress current in Xenopus oocytes. The fragments include portions of the six putative transmembrane segments, S1 through S6, specifically: S1, S1-S2, S1-S2-S3, S2-S3, S2-S3-S4, S3-S4, S3-S4-S5, S2 through COOH, S3 through COOH, S4 through COOH, and S5-S6-COOH. Electrophysiologic experiments show that the fragments S1-S2-S3, S3-S4-S5, S2 through COOH, and S3 through COOH strongly suppress Kv1.3 (T1(-)) current, while others do not. Suppression of expressed current is due to specific effects of the translated peptide Kv1.3 fragments, as validated by in vivo immunoprecipitation studies of a strong suppressor and a nonsuppressor. Pulse-chase experiments indicate that translation of truncated peptide fragments neither prevents translation of Kv1.3 (T1(-)) nor increases its rate of degradation. Co-immunoprecipitation experiments suggest that suppression involves direct association of a peptide fragment with Kv1.3 (T1(-)). Fragments that strongly suppress Kv1.3 (T1(-)) also suppress an analogous NH2-terminal deletion mutant of Kv2.1 (Kv2.1 (DeltaN139)), an isoform belonging to a different subfamily. Our results indicate that sites in the central core of Kv1.3 facilitate intersubunit association and that there are suppression

  1. To Bind or to Let Loose: Effectiveness of Sodium Polystyrene Sulfonate in Decreasing Serum Potassium

    Science.gov (United States)

    Sandal, Shaifali; Karachiwala, Hatim; Noviasky, John; Wang, Dongliang; Elliott, William C.; Lehmann, David F.

    2012-01-01

    Background. The use of sodium polystyrene sulfonate in decreasing serum potassium has recently been questioned due to the lack of documented effectiveness. Methods. A retrospective cohort analysis of all hospitalized patients who received sodium polystyrene sulfonate over four months was performed. The change in serum potassium was noted over a period of 24 hours. Patients who received any other form of potassium-altering drug or treatment were excluded. Results. The administration of sodium polystyrene sulfonate reduced serum potassium by 16.7% (P < 0.001) as compared to the baseline serum potassium over a period of 24 hours. During this same time, no change in serum creatinine was identified (P = 0.73). In addition, there was no correlation between potassium and creatinine change (r2 = 0.0004 and P = 0.99). Patients with higher initial serum potassium (≥5.6 mEq/L) reduced their potassium concentration 4% more than those with initial serum potassium of <5.6 mEq/L; however, this reduction did not reach statistical significance (P = 0.32). There was no significant difference in the effectiveness of 15 gm and 30 gm resin preparation (P = 0.54). Thirteen deaths were noted in our cohort, of which one death was due to ischemic colitis. Conclusion. We conclude that sodium polystyrene sulfonate is effective in lowering serum potassium. PMID:23476770

  2. To Bind or to Let Loose: Effectiveness of Sodium Polystyrene Sulfonate in Decreasing Serum Potassium

    Directory of Open Access Journals (Sweden)

    Shaifali Sandal

    2012-01-01

    Full Text Available Background. The use of sodium polystyrene sulfonate in decreasing serum potassium has recently been questioned due to the lack of documented effectiveness. Methods. A retrospective cohort analysis of all hospitalized patients who received sodium polystyrene sulfonate over four months was performed. The change in serum potassium was noted over a period of 24 hours. Patients who received any other form of potassium-altering drug or treatment were excluded. Results. The administration of sodium polystyrene sulfonate reduced serum potassium by 16.7% (P<0.001 as compared to the baseline serum potassium over a period of 24 hours. During this same time, no change in serum creatinine was identified (P=0.73. In addition, there was no correlation between potassium and creatinine change (r2 = 0.0004 and P=0.99. Patients with higher initial serum potassium (≥5.6 mEq/L reduced their potassium concentration 4% more than those with initial serum potassium of <5.6 mEq/L; however, this reduction did not reach statistical significance (P=0.32. There was no significant difference in the effectiveness of 15 gm and 30 gm resin preparation (P=0.54. Thirteen deaths were noted in our cohort, of which one death was due to ischemic colitis. Conclusion. We conclude that sodium polystyrene sulfonate is effective in lowering serum potassium.

  3. The relation of potassium and sodium intakes to diet cost among U.S. adults.

    Science.gov (United States)

    Drewnowski, A; Rehm, C D; Maillot, M; Monsivais, P

    2015-01-01

    The 2010 Dietary Guidelines recommended that Americans increase potassium and decrease sodium intakes to reduce the burden of hypertension. One reason why so few Americans meet the recommended potassium or sodium goals may be perceived or actual food costs. This study explored the monetary costs associated with potassium and sodium intakes using national food prices and a representative sample of US adults. Dietary intake data from the 2001-2002 National Health and Nutrition Examination Survey were merged with a national food prices database. In a population of 4744 adults, the association between the energy-adjusted sodium and potassium intakes, and the sodium-to-potassium ratio (Na:K) and energy-adjusted diet cost was evaluated. Diets that were more potassium-rich or had lower Na:K ratios were associated with higher diet costs, while sodium intakes were not related to cost. The difference in diet cost between extreme quintiles of potassium intakes was $1.49 (95% confidence interval: 1.29, 1.69). A food-level analysis showed that beans, potatoes, coffee, milk, bananas, citrus juices and carrots are frequently consumed and low-cost sources of potassium. Based on existing dietary data and current American eating habits, a potassium-dense diet was associated with higher diet costs, while sodium was not. Price interventions may be an effective approach to improve potassium intakes and reduce the Na:K ratio of the diet. The present methods helped identify some alternative low-cost foods that were effective in increasing potassium intakes. The identification and promotion of lower-cost foods to help individuals meet targeted dietary recommendations could accompany future dietary guidelines.

  4. Forms of potassium and sodium in some species of grasses and herbage

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    Grzegorz Nowak

    2013-12-01

    Full Text Available The forms of occurence of potassium and sodium were studied in the grasses Dactylis glomerata L., Poa annua L., Festuca rubra L. and dendelion (Taraxacum officinale Web. treated with increasing mineral fertilizer doses, magnesium and microelements, under conditions of pot culture. The plants took up potassium in amounts greatly exceeding their requirement, and sodium in very small amounts. Mineral NPK doses increased in the tested plants both the content of potassium and sodium forms soluble in trichloroacetic and acetic acids and water. Magnesium and microelements had no major influence on the content of these potassium forms, but they increased the concentration of analogous forms of sodium in Taraxacum officinale and did not influence their accumulation in the grasses. Potassium and sodium compounds were completely extracted from the plants with trichloroacetic, whereas acetic acid extracted 88-95 percent of potassium and 66-74 percent of sodium. Distilled water extracted 70-77 and 28-33 percent of potassium and sodium, respectively.

  5. How far can sodium substitute for potassium in red beet?

    Science.gov (United States)

    Subbarao, G. V.; Wheeler, R. M.; Stutte, G. W.; Levine, L. H.; Sager, J. C. (Principal Investigator)

    1999-01-01

    Sodium (Na) movement between plants and humans is one of the more critical aspects of bioregenerative systems of life support, which NASA is studying for the establishment of long-term bases on the Lunar or Martian surface. This study was conducted to determine the extent to which Na can replace potassium (K) in red beet (Beta vulgaris L. ssp vulgaris) without adversely affecting metabolic functions such as water relations, photosynthetic rates, and thus growth. Two cultivars, Ruby Queen and Klein Bol, were grown for 42 days at 1200 micromoles mol-1 CO2 in a growth chamber using a re-circulating nutrient film technique with 0%, 75%, 95%, and 98% Na substitution for K in a modified half-strength Hoagland solution. Total biomass of Ruby Queen was greatest at 95% Na substitution and equal at 0% and 98% Na substitution. For Klein Bol, there was a 75% reduction in total biomass at 98% Na substitution. Nearly 95% of the total plant K was replaced with Na at 98% Na substitution in both cultivars. Potassium concentrations in leaves decreased from 120 g kg-1 dwt in 0% Na substitution to 3.5 g kg-1 dwt at 98% Na substitution. Leaf chlorophyll concentration, photosynthetic rate, and osmotic potential were not affected in either cultivar by Na substitution for K. Leaf glycinebetaine levels were doubled at 75% Na substitution in Klein Bol, but decreased at higher levels of Na substitution. For Ruby Queen, glycinebetaine levels in leaf increased with the first increase of Na levels and were maintained at the higher Na levels. These results indicate that in some cultivars of red beet, 95% of the normal tissue K can be replaced by Na without a reduction in growth.

  6. 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.

  7. 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.

  8. Transcriptional regulation of voltage-gated Ca(2+) channels.

    Science.gov (United States)

    González-Ramírez, Ricardo; Felix, Ricardo

    2017-03-31

    The transcriptional regulation of voltage-gated Ca(2+) (CaV ) channels is an emerging research area that promises to improve our understanding of how many relevant physiological events are shaped in the central nervous system, the skeletal muscle, and other tissues. Interestingly, a picture of how transcription of CaV channel subunit genes is controlled is evolving with the identification of the promoter regions required for tissue-specific expression, and the identification of transcription factors that control their expression. These promoters share several characteristics that include multiple transcriptional start sites, lack of a TATA box, and the presence of elements conferring tissue-selective expression. Likewise, changes in CaV channel expression occur throughout development, following ischemia, seizures, or chronic drug administration. This review focuses on insights achieved regarding the control of CaV channel gene expression. To further understand the complexities of expression and to increase the possibilities of detecting CaV channel alterations causing human disease, a deeper knowledge on the structure of the 5' upstream regions of the genes encoding these remarkable proteins will be necessary. This article is protected by copyright. All rights reserved.

  9. Disorders of body fluids, sodium and potassium in chronic renal failure.

    Science.gov (United States)

    Mitch, W E; Wilcox, C S

    1982-03-01

    A stable volume and composition of extracellular fluid are essential for normal functioning of the body. Since the kidney is primarily responsible for regulating extracellular fluid, loss of kidney function should have catastrophic consequences. Fortunately, even with loss of more than 90 percent of renal function, a remarkable capacity to regulate body fluid volumes and sodium and potassium persists. Nevertheless, this capacity is limited to chronic renal disease and this has important consequences for clinical management of these patients. How can sodium and potassium homeostasis be assessed? Methods for evaluating the steady-state regulation of sodium include measurement of body fluids and their distribution in different compartments and measurement of exchangeable and intracellular sodium. Short-term regulation of body sodium can be assessed from measurement of sodium balance during changes in dietary salt. Potassium is predominantly contained within cells and thus the assessment of its regulation requires special emphasis on measurement of steady-state body stores and potassium distribution across cell membranes. However, the methods used to make all of these measurements require assumptions that may not hold in the altered state of uremia. This raises problems in interpretation requiring critical analysis before conclusions can be made regarding sodium and potassium homeostasis in patients with chronic renal failure. This review focuses on abnormalities of body fluids, sodium and potassium in patients with creatinine clearances of less than 20 ml/min due to chronic renal failure and the impact of conservative therapy, dialysis and renal transplantation on these patients.

  10. Differential expression of voltage-gated K+ and Ca2+ currents in bipolar cells in the zebrafish retinal slice.

    Science.gov (United States)

    Connaughton, V P; Maguire, G

    1998-04-01

    Whole-cell voltage-gated currents were recorded from bipolar cells in the zebrafish retinal slice. Two physiological populations of bipolar cells were identified. In the first, depolarizing voltage steps elicited a rapidly activating A-current that reached peak amplitude or = 10 ms after step onset and did not inactivate. IK was antagonized by internal caesium and external tetraethylammonium. Bipolar cells expressing IK also expressed a time-dependent h-current at membrane potentials calcium-dependent potassium current (IK(Ca)) were identified. Depolarizing voltage steps > -50 mV activated ICa, which reached peak amplitude between -20 and -10 mV. ICa was eliminated in Ca+2-free Ringer and blocked by cadmium and cobalt, but not tetrodotoxin. In most cells, Ica was transient, activating rapidly at -50 mV. This current was antagonized by nickel. The remaining bipolar cells expressed a nifedipine-sensitive sustained current that activated between -40 and -30 mV, with both slower kinetics and smaller amplitude than transient ICa. IK(Ca) was elicited by membrane depolarizations > -20 mV. Bipolar cells in the zebrafish retinal slice preparation express an array of voltage-gated currents which contribute to non-linear I-V characteristics. The zebrafish retinal slice preparation is well-suited to patch clamp analyses of membrane mechanisms and provides a suitable model for studying genetic defects in visual system development.

  11. Characterization of voltage-gated K+ currents contributing to subthreshold membrane potential oscillations in hippocampal CA1 interneurons.

    Science.gov (United States)

    Morin, France; Haufler, Darrell; Skinner, Frances K; Lacaille, Jean-Claude

    2010-06-01

    CA1 inhibitory interneurons at the stratum lacunosum-moleculare and radiatum junction (LM/RAD-INs) display subthreshold membrane potential oscillations (MPOs) involving voltage-dependent Na(+) and A-type K(+) currents. LM/RAD-INs also express other voltage-gated K(+) currents, although their properties and role in MPOs remain unclear. Here, we characterized these voltage-gated K(+) currents and investigated their role in MPOs. Using outside-out patch recordings from LM/RAD-IN somata, we distinguished four voltage-gated K(+) currents based on their pharmacology and activation/inactivation properties: a fast delayed rectifier current (I(Kfast)), a slow delayed rectifier current (I(Kslow)), a rapidly inactivating A-type current (I(A)), and a slowly inactivating current (I(D)). Their relative contribution to the total K(+) current was I(A) > I(Kfast) > I(Kslow) = I(D). The presence of I(D) and the relative contributions of K(+) currents in LM/RAD-INs are different from those of other CA1 interneurons, suggesting the presence of differential complement of K(+) currents in subgroups of interneurons. We next determined whether these K(+) currents were sufficient for MPO generation using a single-compartment model of LM/RAD-INs. The model captured the subthreshold voltage dependence of MPOs. Moreover, all K(+) currents were active at subthreshold potentials but I(D), I(A), and the persistent sodium current (I(NaP)) were most active near threshold. Using impedance analysis, we found that I(A) and I(NaP) contribute to MPO generation by modulating peak spectral frequency during MPOs and governing the voltage range over which MPOs occur. Our findings uncover a differential expression of a complement of K(+) channels that underlies intrinsic rhythmic activity in inhibitory interneurons.

  12. 西地那非抑制高肺血流肺动脉高压大鼠肺血管重构和上调肺血管Kv1.5mRNA表达%Sildenafil inhibits pulmonary vascular remodeling and up-regulates voltage-gated potassium channel Kv1.5 mRNA expression in secondary pulmonary hypertension due to left-to-right shunt in rats

    Institute of Scientific and Technical Information of China (English)

    胡蕾; 谈林华; 林隆; 何小军; 范佳杰

    2010-01-01

    Objective To investigate the effects of sildenafil on pulmonary vascular remodeling and voltage-gated potassium channeI Kv1.5 mRNA expression of pulmonary vasculature in secondary pulmonary hypertension due to left-to-right shunt in rats.Methods Male twenty-seven SD rats were randomly divided into sham group(n=9),shunt group(n=9)and shunt+sildenafil group(n=9).A left-to-right shunt was established on shunt group and shunt+sildenafil group rats by making fistula between abdominal aorta and inferior vena cava.Rats of the shunt+sildenafil group were administered sildenafil by gastric gavage at a dose of 10 mg·kg-1·d-1;whereas the rats of the sham group and the shunt group were fed with the same amount of saline. Eleven weeks later,mean pulmonary artery pressure(mPAP)and systolic pulmonary artery pressure(sPAP)were measured.The ratio of right ventricular mass to left ventricular plus septal mass[Rv/(LV+S)]was alao calculated and taken as a marker of the severity of right ventricular hypertrophy.The pathological changes of pulmonary vasculature were evaluated by calculating the relative medial thickness(RMT) of middle and small pulmonary muscularized arteries.The voltage-gated potassium channel Kv1.5 mRNA expression of pulmonary vasculature was qnantifieel using real-time PCIL Results Compared with the rats of sham grouD.the rats of shunt group had higher mPAP,sPAP,RV/(LV+S)ratio,and RMT of middie and small pulmonary muscularized(P0.05).Conclusions Sidenafil inhibits pulmonary vascular remodeling and up-regulates Kv1.5 mRNA expression in rats with secondary pulmonary hypertension due to left-to-right shunt.%目的 观察高肺血流肺动脉高压大鼠肺血管结构重建和肺血管电压依从钾通道Kv1.5mRNA表达变化,探讨口服西地那非对高肺血流肺动脉高压大鼠肺血管重构及肺血管电压依从钾通道Kv1.5mRNA表达的影响.方法 将27只雄性SD大鼠随机分为对照组(n=9)、分流组(n=9)、分流+西地那非组(n=9).后两

  13. The voltage-gated proton channel Hv1/VSOP inhibits neutrophil granule release.

    Science.gov (United States)

    Okochi, Yoshifumi; Aratani, Yasuaki; Adissu, Hibret A; Miyawaki, Nana; Sasaki, Mari; Suzuki, Kazuo; Okamura, Yasushi

    2016-01-01

    Neutrophil granule exocytosis is crucial for host defense and inflammation. Neutrophils contain 4 types of granules, the exocytotic release of which is differentially regulated. This exocytosis is known to be driven by diverse mediators, including calcium and nucleotides, but the precise molecular mechanism remains largely unknown. We show in the present study that voltage-gated proton (Hv) channels are necessary for the proper release of azurophilic granules in neutrophils. On activation of NADPH oxidase by PMA and IgG, neutrophils derived from Hvcn1 gene knockout mouse exhibited greater secretion of MPO and elastase than WT cells. In contrast, release of LTF enriched in specific granules was not enhanced in these cells. The excess release of azurophilic granules in Hv1/VSOP-deficient neutrophils was suppressed by inhibiting NADPH oxidase activity and, in part, by valinomycin, a potassium ionophore. In addition, Hv1/VSOP-deficient mice exhibited more severe lung inflammation after intranasal Candida albicans infection than WT mice. These findings suggest that the Hv channel acts to specifically dampen the release of azurophilic granules through, in part, the suppression of increased positive charges at the plasma membrane accompanied by the activation of NADPH oxidase in neutrophils. © Society for Leukocyte Biology.

  14. KCNE1 and KCNE3: The yin and yang of voltage-gated K(+) channel regulation.

    Science.gov (United States)

    Abbott, Geoffrey W

    2016-01-15

    The human KCNE gene family comprises five genes encoding single transmembrane-spanning ion channel regulatory subunits. The primary function of KCNE subunits appears to be regulation of voltage-gated potassium (Kv) channels, and the best-understood KCNE complexes are with the KCNQ1 Kv α subunit. Here, we review the often opposite effects of KCNE1 and KCNE3 on Kv channel biology, with an emphasis on regulation of KCNQ1. Slow-activating IKs channel complexes formed by KCNQ1 and KCNE1 are essential for human ventricular myocyte repolarization, while constitutively active KCNQ1-KCNE3 channels are important in the intestine. Inherited sequence variants in human KCNE1 and KCNE3 cause cardiac arrhythmias but by different mechanisms, and each is important for hearing in unique ways. Because of their contrasting effects on KCNQ1 function, KCNE1 and KCNE3 have proved invaluable tools in the mechanistic understanding of how channel gating can be manipulated, and each may also provide a window into novel insights and new therapeutic opportunities in K(+) channel pharmacology. Finally, findings from studies of Kcne1(-/-) and Kcne3(-/-) mouse lines serve to illustrate the complexity of KCNE biology and KCNE-linked disease states.

  15. Voltage-gated K+ currents in mouse articular chondrocytes regulate membrane potential.

    Science.gov (United States)

    Clark, Robert B; Hatano, Noriyuki; Kondo, Colleen; Belke, Darrell D; Brown, Barry S; Kumar, Sanjay; Votta, Bartholomew J; Giles, Wayne R

    2010-01-01

    Membrane currents and resting potential of isolated primary mouse articular chondrocytes maintained in monolayer cell culture for 1-9 days were recorded using patch clamp methods. Quantitative RT-PCR showed that the most abundantly expressed transcript of voltage-gated K(+) channels was for K(V)1.6, and immunological methods confirmed the expression of K(V)1.6 α-subunit proteins. These chondrocytes expressed a large time- and potential-dependent, Ca(2+)-independent 'delayed rectifier' K(+) current. Steady-state activation was well-fit by a Boltzmann function with a threshold near -50 mV, and a half-activation potential of -34.5 mV. The current was 50% blocked by 1.48 mM tetraethylammonium, 0.66 mM 4-aminopyridine and 20.6 nM α-dendrotoxin. The current inactivated very slowly at membrane potentials in the range of the resting potential of the chondrocytes. Resting membrane potential of the chondrocytes at room temperature (19-21°C) and in 5 mM external K(+) was -46.4 ± 1.3 mV (mean ± s.e.m; n = 23), near the 'foot' of the activation curve of this K(+) current. Resting potential was depolarized by an average of 4.2 ± 0.8 mV by 25 mM TEA, which blocked about 95% of the K(+) current. At a membrane potential of -50 mV, the apparent time constant of inactivation (tau(in)) was 37.9 s, and the 'steady-state' current level was 19% of that at a holding potential of -90 mV; at -40 mV, tau(in) was 20.3 s, and 'steady-state' current was 5% of that at -90 mV. These results demonstrate that in these primary cultured, mouse articular chondrocytes steady-state activation of a voltage-gated K(+) current contributes to resting membrane potential. However, this current is also likely to have a significant physiological role in repolarizing the chondrocyte following depolarizing stimuli that might occur in conditions of membrane stretch. For example, activation of TRP('transient receptor potential') non-specific cation channels in these cells during cyclic loading and unloading

  16. Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

    Directory of Open Access Journals (Sweden)

    Barbara Malič

    2015-12-01

    Full Text Available The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions and different atmospheres (i.e., defect chemistry on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT.

  17. Sodium and potassium changes in blood bank stored human erythrocytes.

    Science.gov (United States)

    Wallas, C H

    1979-01-01

    Storage of red cells for three weeks at 4 C under blood bank conditions resulted in a rise in intracellular Na+ and a fall in intracellular K+ with concomitant opposite changes in Na+ and K+ levels in the suspending plasma. A decline in red blood cell ATP during the storage period did not appear to be contributing to the changes. Increasing red blood cell ATP to levels 2 to 3 times normal did not prevent the cation changes from occurring. When assayed at 37 C in the presence of added Mg++, ouabain-sensitive membrane ATPase activity and kinetics of activation by Na+ were unaffected by the three week period of cold storage. However, when assayed at 4 C without added Mg++, simulating the conditions of storage, ATPase activity was negligible. Sodium and potassium did not change when red blood cells with normal ATP content were stored at 20 to 24 C even in the absence of added Mg++. Thus, a major cause for the development of cation changes in the red blood cell during blood bank storage in the temperature which inhibits membrane ATPase, allowing cations to leak unopposed into and out of the red blood cells.

  18. Dietary potassium: a key mediator of the cardiovascular response to dietary sodium chloride.

    Science.gov (United States)

    Kanbay, Mehmet; Bayram, Yeter; Solak, Yalcin; Sanders, Paul W

    2013-01-01

    Potassium and sodium share a yin/yang relationship in the regulation of blood pressure (BP). BP is directly associated with the total body sodium and negatively correlated with the total body potassium. Epidemiologic, experimental, and clinical studies have shown that potassium is a significant regulator of BP and further improves cardiovascular outcomes. Hypertensive cardiovascular damage, stroke, and stroke-related death are accelerated by salt intake but might be curbed by increasing dietary potassium intake. The antihypertensive effect of potassium supplementation appears to occur through several mechanisms that include regulation of vascular sensitivity to catecholamines, promotion of natriuresis, limiting plasma renin activity, and improving endothelial function. In the absence of chronic kidney disease, the combined evidence suggests that a diet rich in potassium content serves a vasculoprotective function, particularly in the setting of salt-sensitive hypertension and prehypertension.

  19. Potassium homeostasis during exercise in domestic species: the role of the sodium-potassium pump in skeletal muscle

    NARCIS (Netherlands)

    Everts, Maria E.

    2001-01-01

    In 1997, Jens Christian Skou was awarded the Nobel prize in Chemistry for his discovery and elegant description, some 40 years earlier, of the sodium-potassium (Na+,K+) pump in crab nerve fibres [37]. It is now widely accepted that this cation transport system is essential for cell function, and tha

  20. 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

    2014-01-01

    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......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...... 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...

  1. 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.

  2. Molecular cloning and expression of a Kv1.1-like potassium channel from the electric organ of Electrophorus electricus.

    Science.gov (United States)

    Thornhill, W B; Watanabe, I; Sutachan, J J; Wu, M B; Wu, X; Zhu, J; Recio-Pinto, E

    2003-11-01

    Electrocytes from the electric organ of Electrophorus electricus exhibited sodium action potentials that have been proposed to be repolarized by leak currents and not by outward voltage-gated potassium currents. However, patch-clamp recordings have suggested that electrocytes may contain a very low density of voltage-gated K(+) channels. We report here the cloning of a K(+) channel from an eel electric organ cDNA library, which, when expressed in mammalian tissue culture cells, displayed delayed-rectifier K(+) channel characteristics. The amino-acid sequence of the eel K(+) channel had the highest identity to Kv1.1 potassium channels. However, different important functional regions of eel Kv1.1 had higher amino-acid identity to other Kv1 members, for example, the eel Kv1.1 S4-S5 region was identical to Kv1.5 and Kv1.6. Northern blot analysis indicated that eel Kv1.1 mRNA was expressed at appreciable levels in the electric organ but it was not detected in eel brain, muscle, or cardiac tissue. Because electrocytes do not express robust outward voltage-gated potassium currents we speculate that eel Kv1.1 channels are chronically inhibited in the electric organ and may be functionally recruited by an unknown mechanism.

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

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2014-01-01

    Full Text Available 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 by flow cytometry. Results. Currents recorded in RPMI-8226 cells were confirmed to be voltage-gated K+ channels. A high level of Kv1.3 mRNA was detected but no Kv3.1 mRNA was detected in RPMI-8226 cells. Voltage-gated K+ channel blocker 4-aminopyridine (4-AP (2 mM depolarized the resting potential from −42 ± 1.7 mV to −31.8 ± 2.8 mV (P0.05. Conclusions. In RPMI-8226, voltage-gated K+ channels are involved in proliferation and cell cycle progression its influence on the resting potential and cell volume may be responsible for this process; the inhibitory effect of the voltage-gated K+ channel blocker on RPMI-8226 cell proliferation is a phase-specific event.

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

    Science.gov (United States)

    Koenig, Xaver; Kovar, Michael; Rubi, Lena; Mike, Agnes K.; Lukacs, Peter; Gawali, Vaibhavkumar S.; Todt, Hannes; Hilber, Karlheinz; Sandtner, Walter

    2013-01-01

    The plant alkaloid ibogaine has promising anti-addictive properties. Albeit not licenced as a therapeutic drug, and despite hints that ibogaine may perturb the heart rhythm, this alkaloid is used to treat drug addicts. We have recently reported that ibogaine inhibits human ERG (hERG) potassium channels at concentrations similar to the drugs affinity for several of its known brain targets. Thereby the drug may disturb the heart's electrophysiology. Here, to assess the drug's cardiac ion channel profile in more detail, we studied the effects of ibogaine and its congener 18-Methoxycoronaridine (18-MC) on various cardiac voltage-gated ion channels. We confirmed that heterologously expressed hERG currents are reduced by ibogaine in low micromolar concentrations. Moreover, at higher concentrations, the drug also reduced human Nav1.5 sodium and Cav1.2 calcium currents. Ion currents were as well reduced by 18-MC, yet with diminished potency. Unexpectedly, although blocking hERG channels, ibogaine did not prolong the action potential (AP) in guinea pig cardiomyocytes at low micromolar concentrations. Higher concentrations (≥ 10 μM) even shortened the AP. These findings can be explained by the drug's calcium channel inhibition, which counteracts the AP-prolonging effect generated by hERG blockade. Implementation of ibogaine's inhibitory effects on human ion channels in a computer model of a ventricular cardiomyocyte, on the other hand, suggested that ibogaine does prolong the AP in the human heart. We conclude that therapeutic concentrations of ibogaine have the propensity to prolong the QT interval of the electrocardiogram in humans. In some cases this may lead to cardiac arrhythmias. PMID:23707769

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

    Science.gov (United States)

    Koenig, Xaver; Kovar, Michael; Rubi, Lena; Mike, Agnes K; Lukacs, Peter; Gawali, Vaibhavkumar S; Todt, Hannes; Hilber, Karlheinz; Sandtner, Walter

    2013-12-01

    The plant alkaloid ibogaine has promising anti-addictive properties. Albeit not licensed as a therapeutic drug, and despite hints that ibogaine may perturb the heart rhythm, this alkaloid is used to treat drug addicts. We have recently reported that ibogaine inhibits human ERG (hERG) potassium channels at concentrations similar to the drugs affinity for several of its known brain targets. Thereby the drug may disturb the heart's electrophysiology. Here, to assess the drug's cardiac ion channel profile in more detail, we studied the effects of ibogaine and its congener 18-Methoxycoronaridine (18-MC) on various cardiac voltage-gated ion channels. We confirmed that heterologously expressed hERG currents are reduced by ibogaine in low micromolar concentrations. Moreover, at higher concentrations, the drug also reduced human Nav1.5 sodium and Cav1.2 calcium currents. Ion currents were as well reduced by 18-MC, yet with diminished potency. Unexpectedly, although blocking hERG channels, ibogaine did not prolong the action potential (AP) in guinea pig cardiomyocytes at low micromolar concentrations. Higher concentrations (≥ 10 μM) even shortened the AP. These findings can be explained by the drug's calcium channel inhibition, which counteracts the AP-prolonging effect generated by hERG blockade. Implementation of ibogaine's inhibitory effects on human ion channels in a computer model of a ventricular cardiomyocyte, on the other hand, suggested that ibogaine does prolong the AP in the human heart. We conclude that therapeutic concentrations of ibogaine have the propensity to prolong the QT interval of the electrocardiogram in humans. In some cases this may lead to cardiac arrhythmias. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-12-01

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

  7. Serum Sodium and Potassium Levels in Cerebro-vascular Accident Patients.

    Science.gov (United States)

    Farahmand, Farahmand; Choobi Anzali, Babak; Heshmat, Ramin; Ghafouri, Hamed-Basir; Hamedanchi, Sepehr

    2013-05-01

    We aim to assess serum sodium and potassium levels in patients with different types of cerebro-vascular accidents (CVA) in comparison to control group. A comparative cross-sectional study conducted on patients admitted to the emergency department from January to August 2012. Control group consisted of patients admitted to emergency department due to common cold, urinary tract infection, low back pain, cluster, and tension headache or migraine. Serum sodium and potassium levels were measured via standard laboratory methods. There were 77 patients in control group and 78 in CVA group. Forty nine patients from the CVA group had ischemic CVA, 11 had hemorrhagic CVA and 18 suffered a transient ischemic attack (TIA). Serum sodium level in control group was significantly lower than in patients with TIA, ischemic CVA, and hemorrhagic CVA (P < 0.001). Serum potassium level in control group was higher than patients with TIA, ischemic CVA, and hemorrhagic CVA (P < 0.001). Patients with hemorrhagic CVA showed significantly lower serum potassium level than patients with TIA and ischemic CVA (P < 0.001). Correspondingly, it was observed that serum sodium to potassium ratio was higher in patients with TIA, ischemic CVA, and hemorrhagic CVA (P < 0.001). In patients with hemorrhagic CVA serum sodium to potassium ratio was higher when compared to patients with TIA and ischemic CVA (P < 0.001). This study shows that higher serum sodium and lower serum potassium level may be associated with higher incidence of CVA. Further studies are paramount to elucidate the role of serum electrolyte levels in vascular events.

  8. Effects of aldosterone on intralymphocytic sodium and potassium in patients with primary aldosteronism.

    Science.gov (United States)

    Wehling, M; Kuhls, S; Witzgall, H; Kuhnle, U; Armanini, D; Theisen, K

    1987-12-01

    In vitro effects of aldosterone have been described with regard to the intracellular sodium and potassium concentrations of human mononuclear leukocytes. In the present paper the in vitro effect of aldosterone on the intracellular sodium and potassium of human mononuclear leukocytes in 6 patients with primary aldosteronism was investigated. Except for one patient with elevated intracellular electrolytes, sodium and potassium in mononuclear leukocytes of patients with aldosteronism without incubation were within the range for normals. In the patients, no significant change of intracellular sodium or potassium was observed during incubation with or without aldosterone (1.4 nmol/l), whereas in normals, the loss of sodium and potassium during incubation without aldosterone was prevented by 1.4 nmol/l aldosterone. This insensitivity to aldosterone indicates that intracellular electrolytes in mononuclear leukocytes of patients with primary aldosteronism are kept in normal ranges by mechanism which are independent of mineralocorticoids and may represent the cellular correlate to the renal 'escape' phenomenon in aldosteronism.

  9. Comparison of potassium and sodium binding in vivo and in agarose samples using TQTPPI pulse sequence

    Science.gov (United States)

    Schepkin, Victor D.; Neubauer, Andreas; Nagel, Armin M.; Budinger, Thomas F.

    2017-04-01

    Potassium and sodium specific binding in vivo were explored at 21.1 T by triple quantum (TQ) magnetic resonance (MR) signals without filtration to achieve high sensitivities and precise quantifications. The pulse sequence used time proportional phase increments (TPPI). During simultaneous phase-time increments, it provided total single quantum (SQ) and TQ MR signals in the second dimension at single and triple quantum frequencies, respectively. The detection of both TQ and SQ signals was performed at identical experimental conditions and the resulting TQ signal equals 60 ± 3% of the SQ signal when all ions experience sufficient time for binding. In a rat head in vivo the TQ percentage relative to SQ for potassium is 41.5 ± 3% and for sodium is 16.1 ± 1%. These percentages were compared to the matching values in an agarose tissue model with MR relaxation times similar to those of mammalian brain tissue. The sodium TQ signal in agarose samples decreased in the presence of potassium, suggesting a competitive binding of potassium relative to sodium ions for the same binding sites. The TQTPPI signals correspond to almost two times more effective binding of potassium than sodium. In vivo, up to ∼69% of total potassium and ∼27% of total sodium can be regarded as bound or experiencing an association time in the range of several milliseconds. Experimental data analyses show that more than half of the in vivo total sodium TQ signal could be from extracellular space, which is an important factor for quantification of intracellular MR signals.

  10. STUDY OF SODIUM, POTASSIUM, AND CALCIUM SALTS INFLUENCE ON PROTEIN STABILITY BY DIFFERENTIAL SCANNING CALORIMETRY

    Directory of Open Access Journals (Sweden)

    E. K. Tunieva

    2016-01-01

    Full Text Available Abstract Study of protein stability depending on the various technological factors allows to directionally adjust the physicochemical properties of raw meat and the quality of finished meat products. The paper investigates the possibility of using the DSC to study the influence of monovalent and divalent salts on protein thermal stability. In order to determine the effect of sodium chloride and its substitutes, potassium and calcium salts, on the thermal stability of proteins, the studies were carried out with grinded pork longissimus muscle samples salted with sodium chloride at level of 2.0% and with salt compositions containing reduced by 50% level of sodium chloride (a mixture of sodium and potassium chlorides; a mixture of sodium, potassium, and calcium chlorides using the differential scanning calorimeter DSC Q 2000 in the temperature range of 5 °C to 100 °C and the temperature change rate of 1 K/min. It was found that the addition of potassium chloride instead of 50% of sodium chloride had no significant effect on actin and myosin resistance to thermal denaturation. Meat salting using the mixture of sodium, potassium, and calcium chlorides resulted in decrease of myofibrillar proteins stability indicating the destabilizing effect of calcium on actin and myosin. A negative correlation between the magnitude of the ionic strength and the temperature of myosin and actin denaturation has been found. The correlation coefficients were minus 0.99 and minus 0.95 for myosin and actin respectively. Reduction of denaturation temperature for myofibrillar proteins in the presence of calcium chloride opens perspectives to study the possibility of heat treatment at lower temperatures for meat products with reduced sodium content.

  11. Axonal voltage-gated ion channels as pharmacological targets for pain

    DEFF Research Database (Denmark)

    Moldovan, Mihai; Alvarez, Susana; Romer Rosberg, Mette;

    2013-01-01

    Upon peripheral nerve injury (caused by trauma or disease process) axons of the dorsal root ganglion (DRG) somatosensory neurons have the ability to sprout and regrow/remyelinate to reinnervate distant target tissue or form a tangled scar mass called a neuroma. This regenerative response can become...... maladaptive leading to a persistent and debilitating pain state referred to as chronic pain corresponding to the clinical description of neuropathic/chronic inflammatory pain. There is little agreement to what causes peripheral chronic pain other than hyperactivity of the nociceptive DRG neurons which...... ultimately depends on the function of voltage-gated ion channels. This review focuses on the pharmacological modulators of voltage-gated ion channels known to be present on axonal membrane which represents by far the largest surface of DRG neurons. Blockers of voltage-gated Na(+) channels, openers of voltage...

  12. Direct determination of calcium, sodium and potassium in fermented milk products

    Directory of Open Access Journals (Sweden)

    Kravić Snežana Ž.

    2012-01-01

    Full Text Available The aim of this study was the investigation of the possibilities of direct determination of calcium, sodium and potassium in the commercial and kombucha-based fermented milk products by flame photometry. Two procedures were used for sample preparation: simple dilution with water (direct method and extraction with mineral acid. Calcium, sodium and potassium levels determined after mentioned sample preparation methods were compared. The results showed that the differences between the values obtained for the different sample treatment were within the experimental error at the 95% confidence level. Compared to the method based on extraction with mineral acid, the direct method is efficient, faster, simpler, cheaper, and operates according to the principles of Green Chemistry. Consequently, the proposed method for the direct determination of calcium, sodium and potassium could be applied for the rapid routine analysis of the mineral content in the fermented dairy products. [Projekat Ministarstva nauke Republike Srbije, br. III 46009

  13. Comparison of bioavailability and pharmacokinetics of diclofenac sodium and diclofenac potassium in normal and dehydrated rabbits

    Institute of Scientific and Technical Information of China (English)

    Mahmood AHMAD; Muhammad IQBAL; Ghulam MURTAZA

    2009-01-01

    Two different salts of diclofenac, diclofenac sodium and dielofenae potassium, in tablet dosage form were tested for their bioavailability and disposition kinetics in a group of eighteen rabbits in normal and experimentally induced dehydrated conditions with a wash out period of 7 days between both stages of study. Biochemical and physiological parameters were also measured in both normal and dehydrated states. Diclofenac levels in plasma were determined using a validated reversed phase HPLC method. Primary kinetic parameters i.e. AUC0-∞, Cmax, Tmax and other disposition kinetics were obtained with non-compartmental procedure. Biochemical parameters i.e. packed cell volume, plasma glucose and total lipid concentration in dehydrated rabbits increased significantly. Plasma concentration of diclofenac sodium and diclofenac potassium decreased significantly in water deprived rabbits. In comparison, diclofenac potassium in normal and dehydrated state of the same group of rabbits showed a significantly increased plasma concentration when compared with diclofenac sodium.

  14. Effects of impregnation of coal with potassium and sodium salts

    Energy Technology Data Exchange (ETDEWEB)

    Marsh, H.; Walker, P. L.

    1978-01-01

    Much interest has developed over the addition of potassium salts to potentially caking coals prior to their gasification. It is found that such addition markedly reduces the caking tendency of the coals, enabling them to be more easily handled in reactors. An extra bonus is found in that potassium is a good catalyst for both gasification of carbon in the presence of steam and the production of hydrogen via the water-gas shift reaction. In this report, mechanisms of how potassium salts may affect the fluidity of coal upon heating are considered. But first, what is known about the phenomenon of coking in the absence of potassium is reviewed at some length. The addition of potassium salts to caking coals is thought to reduce their fluidity primarily by increasing the number of cross-links which normally exist between the aromatic and hydroaromatic building blocks in the coal. Such an increase results, in turn, in an increase in molecular weight of the coal, decrease in its fluidity upon heat treatment, and the consequent decrease in mobility of planar regimes preventing their alignment to form anisotropic coke substance. It is suggested that the presence of potassium results in a higher oxygen content being present in the coal upon heating, either by reducing the rate of oxygen evolution from the coal as CO, CO/sub 2/, and/or water or by acting as an intermediate to extract additional oxygen from the steam added as a reactant to the system (that is, steam gasification). Thus, an increased oxygen content results in more crosslinking in the structure probably via ether linkages between aromatic and/or hydroaromatic regimes.

  15. Axonal voltage-gated ion channels as pharmacological targets for pain.

    Science.gov (United States)

    Moldovan, Mihai; Alvarez, Susana; Romer Rosberg, Mette; Krarup, Christian

    2013-05-15

    Upon peripheral nerve injury (caused by trauma or disease process) axons of the dorsal root ganglion (DRG) somatosensory neurons have the ability to sprout and regrow/remyelinate to reinnervate distant target tissue or form a tangled scar mass called a neuroma. This regenerative response can become maladaptive leading to a persistent and debilitating pain state referred to as chronic pain corresponding to the clinical description of neuropathic/chronic inflammatory pain. There is little agreement to what causes peripheral chronic pain other than hyperactivity of the nociceptive DRG neurons which ultimately depends on the function of voltage-gated ion channels. This review focuses on the pharmacological modulators of voltage-gated ion channels known to be present on axonal membrane which represents by far the largest surface of DRG neurons. Blockers of voltage-gated Na(+) channels, openers of voltage-gated K(+) channels and blockers of hyperpolarization-activated cyclic nucleotide-gated channels that were found to reduce neuronal activity were also found to be effective in neuropathic and inflammatory pain states. The isoforms of these channels present on nociceptive axons have limited specificity. The rationale for considering axonal voltage-gated ion channels as targets for pain treatment comes from the accumulating evidence that chronic pain states are associated with a dysregulation of these channels that could alter their specificity and make them more susceptible to pharmacological modulation. This drives the need for further development of subtype-specific voltage-gated ion channels modulators, as well as clinically available neurophysiological techniques for monitoring axonal ion channel function in peripheral nerves.

  16. Patterns of sodium and potassium excretion and blood pressure in the African Diaspora.

    Science.gov (United States)

    Tayo, B O; Luke, A; McKenzie, C A; Kramer, H; Cao, G; Durazo-Arvizu, R; Forrester, T; Adeyemo, A A; Cooper, R S

    2012-05-01

    Habitual levels of dietary sodium and potassium are correlated with age-related increases in blood pressure (BP) and likely have a role in this phenomenon. Although extensive published evidence exists from randomized trials, relatively few large-scale community surveys with multiple 24-h urine collections have been reported. We obtained three 24-h samples from 2704 individuals from Nigeria, Jamaica and the United States to evaluate patterns of intake and within-person relationships with BP. The average (±s.d.) age and weight of the participants across all the three sites were 39.9±8.6 years and 76.1±21.2 kg, respectively, and 55% of the total participants were females. Sodium excretion increased across the East-West gradient (for example, 123.9±54.6, 134.1±48.8, 176.6±71.0 (±s.d.) mmol, Nigeria, Jamaica and US, respectively), whereas potassium was essentially unchanged (for example, 46.3±22.9, 40.7±16.1, 44.7±16.4 (±s.d.) mmol, respectively). In multivariate analyses both sodium (positively) and potassium (negatively) were strongly correlated with BP (P<0.001); quantitatively the association was stronger, and more consistent in each site individually, for potassium. The within-population day-to-day variation was also greater for sodium than for potassium. Among each population group, a significant correlation was observed between sodium and urine volume, supporting the prior finding of sodium as a determinant of fluid intake in free-living individuals. These data confirm the consistency with the possible role of dietary electrolytes as hypertension risk factors, reinforcing the relevance of potassium in these populations.

  17. Effect of heparin and low-molecular weight heparin on serum potassium and sodium levels

    Directory of Open Access Journals (Sweden)

    Girish M Bengalorkar

    2011-01-01

    Full Text Available Introduction: To study the effects of heparin and low-molecular weight heparin (LMWH on potassium and sodium levels in patients with cardiovascular diseases (CVDs and stroke. Materials and Methods : Sixty patients were recruited with 30 patients each receiving heparin and enoxaparin. Patients with CVD and stroke receiving heparin and LMWH were compared for their demographic profile and laboratory data, and this was analyzed by descriptive statistics. Risk factors associated with the development of hyperkalemia were analyzed using multiple logistic regression model. Results : There was an increase in potassium levels and decrease in sodium levels compared with baseline in both the groups. The difference between the groups with respect to sodium and potassium levels was not statistically significant. On analysis, the risk factors for development of hyperkalemia were baseline potassium levels, serum creatinine, and creatinine clearance. The change in sodium and potassium levels on the fifth day of therapy was increased with LMWH compared with heparin, although not statistically significant. Conclusions : The clinician should anticipate hyperkalemia especially in patients with renal impairment receiving these drugs.

  18. Regulation of voltage gated calcium channels by GPCRs and post-translational modification.

    Science.gov (United States)

    Huang, Junting; Zamponi, Gerald W

    2016-10-18

    Calcium entry via voltage gated calcium channels mediates a wide range of physiological functions, whereas calcium channel dysregulation has been associated with numerous pathophysiological conditions. There are myriad cell signaling pathways that act on voltage gated calcium channels to fine tune their activities and to regulate their cell surface expression. These regulatory mechanisms include the activation of G protein-coupled receptors and downstream phosphorylation events, and their control over calcium channel trafficking through direct physical interactions. Calcium channels also undergo post-translational modifications that alter both function and density of the channels in the plasma membrane. Here we focus on select aspects of these regulatory mechanisms and highlight recent developments.

  19. Sodium, potassium and chloride status in Australian foods and diets using neutron activation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Fardy, J.J.; McOrist, G.D.; Farrar, Y.J.; Bowles, C.J. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia)

    1993-12-31

    A study of the status of essential, toxic and trace elements in the foods and diets of Australian has been in progress for six years. Results for sodium, potassium and chloride levels are reported here. The average daily dietary intake of sodium and chloride exceeded the range of values recommended by the National Health and Medical Research Council for most population groups with grain and dairy products the main contributor to these high intakes. In contrast, the average daily intakes of potassium fell well within the recommended values for all age groups with intakes for adult females close to the recommended minimum figure. 9 refs., 1 tab., 2 figs.

  20. AB Initio calculations of thermodynamic parameters of lithium, sodium and potassium peroxides

    Science.gov (United States)

    Zhuravlev, Yu. N.; Aleinikova, M. V.; Korabelnikov, D. V.

    2012-11-01

    Using a linear combination of atomic orbitals within the CRYSTAL09 software code, the oscillation frequencies of the atoms of lithium, sodium, and potassium peroxides are calculated. In a quasiharmonic approximation of the Debye model, the thermodynamic potentials, entropy, thermal capacity, and the coefficient of thermal expansion are calculated, and their dependence on pressure and temperature is investigated. Using sodium peroxide as an example, the critical point for the sublimation process is found.

  1. Enhanced inhibition of Listeria monocytogenes in Frankfurter sausage by the addition of potassium lactate and sodium diacetate mixtures

    NARCIS (Netherlands)

    Stekelenburg, F.K.

    2003-01-01

    Frankfurter-type sausages were prepared with potassium lactate, sodium diacetate and various levels of a mixture of potassium lactate and sodium diacetate. The development of Lactobacillus sake and Listeria monocytogenes and the sensory quality were compared with a reference product without any of t

  2. Enhanced inhibition of Listeria monocytogenes in Frankfurter sausage by the addition of potassium lactate and sodium diacetate mixtures

    NARCIS (Netherlands)

    Stekelenburg, F.K.

    2003-01-01

    Frankfurter-type sausages were prepared with potassium lactate, sodium diacetate and various levels of a mixture of potassium lactate and sodium diacetate. The development of Lactobacillus sake and Listeria monocytogenes and the sensory quality were compared with a reference product without any of

  3. Sodium and potassium intake among U.S. adults, National Health and Nutrition Examination Survey, 2003-2008

    Science.gov (United States)

    The 2010 Dietary Guidelines recommend Americans reduce sodium intake and choose foods that contain potassium to decrease the risk of hypertension and subsequent heart disease and stroke. We estimated the distributions of usual daily sodium and potassium intakes by sociodemographic and health charact...

  4. Comparative Study of Sodium and Potassium in Different Types of Gallstones and in Serum of Subjects with Gallstones and Controls

    Directory of Open Access Journals (Sweden)

    Ali Mohammad Soomro

    2008-06-01

    Full Text Available The study comprises evaluation of sodium and potassium in the pathogenesis of human gallstones as well as measurement of the concentration of these elements in gallstones and in sera of 109 gallstone subjects and 100 controls (age and sex matched with no personal or family history of gallstone disease. It was observed that serum concentrations for both sodium and potassium were comparable (p>0.05 between gallstone subjects and control subjects. In gallstones the concentration of sodium was significantly higher as compared to potassium (p<0.05. Normal sodium to potassium ratio was seen in serum of gallstone subjects, whereas, low sodium to potassium ratio was seen in gallstone carriers. Amongst the different types of gallstones, significantly high (p<0.05 concentrations of sodium and potassium were seen in calcium bilirubinate gallstones. The levels for these mineral elements were also raised in serum of pure calcium carbonate gallstone subjects.The results demonstrate that the higher concentration of sodium and potassium in gallstones may involve in both calcium bilirubinate gallstones and in serum of calcium carbonate gallstone subjects, which indicate their association with calcium in the precipitation of calcium bilirubinate and calcium carbonate in bile. Furthermore, low sodium to potassium ratio in gallstones indicates low ratio in bile of gallstone subjects.

  5. Developmental Expression of Kv Potassium Channels at the Axon Initial Segment of Cultured Hippocampal Neurons

    Science.gov (United States)

    Sánchez-Ponce, Diana; DeFelipe, Javier; Garrido, Juan José; Muñoz, Alberto

    2012-01-01

    Axonal outgrowth and the formation of the axon initial segment (AIS) are early events in the acquisition of neuronal polarity. The AIS is characterized by a high concentration of voltage-dependent sodium and potassium channels. However, the specific ion channel subunits present and their precise localization in this axonal subdomain vary both during development and among the types of neurons, probably determining their firing characteristics in response to stimulation. Here, we characterize the developmental expression of different subfamilies of voltage-gated potassium channels in the AISs of cultured mouse hippocampal neurons, including subunits Kv1.2, Kv2.2 and Kv7.2. In contrast to the early appearance of voltage-gated sodium channels and the Kv7.2 subunit at the AIS, Kv1.2 and Kv2.2 subunits were tethered at the AIS only after 10 days in vitro. Interestingly, we observed different patterns of Kv1.2 and Kv2.2 subunit expression, with each confined to distinct neuronal populations. The accumulation of Kv1.2 and Kv2.2 subunits at the AIS was dependent on ankyrin G tethering, it was not affected by disruption of the actin cytoskeleton and it was resistant to detergent extraction, as described previously for other AIS proteins. This distribution of potassium channels in the AIS further emphasizes the heterogeneity of this structure in different neuronal populations, as proposed previously, and suggests corresponding differences in action potential regulation. PMID:23119056

  6. Energetic role of the paddle motif in voltage gating of Shaker K(+) channels.

    Science.gov (United States)

    Xu, Yanping; Ramu, Yajamana; Shin, Hyeon-Gyu; Yamakaze, Jayden; Lu, Zhe

    2013-05-01

    Voltage-gated ion channels underlie rapid electric signaling in excitable cells. Electrophysiological studies have established that the N-terminal half of the fourth transmembrane segment ((NT)S4) of these channels is the primary voltage sensor, whereas crystallographic studies have shown that (NT)S4 is not located within a proteinaceous pore. Rather, (NT)S4 and the C-terminal half of S3 ((CT)S3 or S3b) form a helix-turn-helix motif, termed the voltage-sensor paddle. This unexpected structural finding raises two fundamental questions: does the paddle motif also exist in voltage-gated channels in a biological membrane, and, if so, what is its function in voltage gating? Here, we provide evidence that the paddle motif exists in the open state of Drosophila Shaker voltage-gated K(+) channels expressed in Xenopus oocytes and that (CT)S3 acts as an extracellular hydrophobic 'stabilizer' for (NT)S4, thus biasing the gating chemical equilibrium toward the open state.

  7. Characterization of voltage-gated Ca(2+ conductances in layer 5 neocortical pyramidal neurons from rats.

    Directory of Open Access Journals (Sweden)

    Mara Almog

    Full Text Available Neuronal voltage-gated Ca(2+ channels are involved in electrical signalling and in converting these signals into cytoplasmic calcium changes. One important function of voltage-gated Ca(2+ channels is generating regenerative dendritic Ca(2+ spikes. However, the Ca(2+ dependent mechanisms used to create these spikes are only partially understood. To start investigating this mechanism, we set out to kinetically and pharmacologically identify the sub-types of somatic voltage-gated Ca(2+ channels in pyramidal neurons from layer 5 of rat somatosensory cortex, using the nucleated configuration of the patch-clamp technique. The activation kinetics of the total Ba(2+ current revealed conductance activation only at medium and high voltages suggesting that T-type calcium channels were not present in the patches. Steady-state inactivation protocols in combination with pharmacology revealed the expression of R-type channels. Furthermore, pharmacological experiments identified 5 voltage-gated Ca(2+ channel sub-types - L-, N-, R- and P/Q-type. Finally, the activation of the Ca(2+ conductances was examined using physiologically derived voltage-clamp protocols including a calcium spike protocol and a mock back-propagating action potential (mBPAP protocol. These experiments enable us to suggest the possible contribution of the five Ca(2+ channel sub-types to Ca(2+ current flow during activation under physiological conditions.

  8. 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…

  9. Effectiveness of the aldosterone-sodium and -potassium feedback control system.

    Science.gov (United States)

    Young, D B; McCaa, R E; Pan, U J; Guyton, A C

    1976-09-01

    This study was conducted to determine the quantitative importance of the aldosterone feedback mechanism in controlling each one of three major factors that have often been associated with aldosterone, namely, extracellular fluid sodium concentration, extracellular fluid potassium concentration, and extracellular fluid volume. To do this, the ability of the body to control these three factors in the face of marked changes in daily sodium or potassium intake was studied under two conditions: 1) in the normal dog, and 2) in the dog in which the aldosterone feedback mechanism was prevented from functioning by removing the adrenal glands and then providing a continuous fixed level of supportive aldosterone and glucocorticoids during the low and high electrolyte intake periods. Under these conditions, removal of feedback control of aldosterone secretion decreased the effectiveness of plasma potassium control by nearly fivefold (39% vs. 8% change in plasma potassium concentration), fluid volume by sixfold (12% vs. 2% change in sodium space) and had no effect on control of plasma sodium concentration (2% change with and without feedback control of aldosterone secretion.)

  10. Magnesium, Calcium, Potassium, and Sodium Intakes and Risk of Stroke in Male Smokers

    NARCIS (Netherlands)

    Larsson, S.C.; Virtanen, M.J.; Mars, M.; Mannisto, S.; Pietinen, P.; Albanes, D.; Virtamo, J.

    2008-01-01

    Background A high intake of magnesium, calcium, and potassium and a low intake of sodium have been hypothesized to reduce the risk of stroke. However, prospective data relating intake of these minerals to risk of stroke are inconsistent. Methods We examined the relationship of dietary magnesium, cal

  11. The Sodium-Activated Potassium Channel Slack Is Required for Optimal Cognitive Flexibility in Mice

    Science.gov (United States)

    Bausch, Anne E.; Dieter, Rebekka; Nann, Yvette; Hausmann, Mario; Meyerdierks, Nora; Kaczmarek, Leonard K.; Ruth, Peter; Lukowski, Robert

    2015-01-01

    "Kcnt1" encoded sodium-activated potassium channels (Slack channels) are highly expressed throughout the brain where they modulate the firing patterns and general excitability of many types of neurons. Increasing evidence suggests that Slack channels may be important for higher brain functions such as cognition and normal intellectual…

  12. SGK3 Sensitivity of Voltage Gated K+ Channel Kv1.5 (KCNA5

    Directory of Open Access Journals (Sweden)

    Musaab Ahmed

    2016-01-01

    Full Text Available Background: The serum & glucocorticoid inducible kinase isoform SGK3 is a powerful regulator of several transporters, ion channels and the Na+/K+ ATPase. Targets of SGK3 include the ubiquitin ligase Nedd4-2, which is in turn a known regulator of the voltage gated K+ channel Kv1.5 (KCNA5. The present study thus explored whether SGK3 modifies the activity of the voltage gated K+ channel KCNA5, which participates in the regulation of diverse functions including atrial cardiac action potential, activity of vascular smooth muscle cells, insulin release and tumour cell proliferation. Methods: cRNA encoding KCNA5 was injected into Xenopus oocytes with and without additional injection of cRNA encoding wild-type SGK3, constitutively active S419DSGK3, inactive K191NSGK3 and/or wild type Nedd4-2. Voltage gated K+ channel activity was quantified utilizing dual electrode voltage clamp. Results: Voltage gated current in KCNA5 expressing Xenopus oocytes was significantly enhanced by wild-type SGK3 and S419DSGK3, but not by K191NSGK3. SGK3 was effective in the presence of ouabain (1 mM and thus did not require Na+/K+ ATPase activity. Coexpression of Nedd4-2 decreased the voltage gated current in KCNA5 expressing Xenopus oocytes, an effect largely reversed by additional coexpression of SGK3. Conclusion: SGK3 is a positive regulator of KCNA5, which is at least partially effective by abrogating the effect of Nedd4-2.

  13. Crystallization field and rate study for the formation of single phase sodium-potassium and potassium clinoptilolite

    Energy Technology Data Exchange (ETDEWEB)

    Guevenir, Oe.; Kalipcilar, H.; Culfaz, A. [Middle East Technical University, Department of Chemical Engineering, 06531 Ankara (Turkey)

    2011-04-15

    Reproducible synthesis of clinoptilolite as the single crystalline phase was achieved in the narrow crystallization field at or around the nominal batch composition of 2.1(Na{sub 2}O+K{sub 2}O):Al{sub 2}O{sub 3}:10SiO{sub 2}:110H{sub 2}O at 140 C. Clinoptilolites of high purity were crystallized in the pure sodium or mixed sodium-potassium cation systems. Partial replacement of hydroxyl anions with the salts of carbonates or chlorides also yielded clinoptilolite as the single crystalline phase although at lower crystallization rates. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Exploring the structure of the voltage-gated Na+ channel by an engineered drug access pathway to the receptor site for local anesthetics.

    Science.gov (United States)

    Lukacs, Peter; Gawali, Vaibhavkumar S; Cervenka, Rene; Ke, Song; Koenig, Xaver; Rubi, Lena; Zarrabi, Touran; Hilber, Karlheinz; Stary-Weinzinger, Anna; Todt, Hannes

    2014-08-01

    Despite the availability of several crystal structures of bacterial voltage-gated Na(+) channels, the structure of eukaryotic Na(+) channels is still undefined. We used predictions from available homology models and crystal structures to modulate an external access pathway for the membrane-impermeant local anesthetic derivative QX-222 into the internal vestibule of the mammalian rNaV1.4 channel. Potassium channel-based homology models predict amino acid Ile-1575 in domain IV segment 6 to be in close proximity to Lys-1237 of the domain III pore-loop selectivity filter. The mutation K1237E has been shown previously to increase the diameter of the selectivity filter. We found that an access pathway for external QX-222 created by mutations of Ile-1575 was abolished by the additional mutation K1237E, supporting the notion of a close spatial relationship between sites 1237 and 1575. Crystal structures of bacterial voltage-gated Na(+) channels predict that the side chain of rNaV1.4 Trp-1531 of the domain IV pore-loop projects into the space between domain IV segment 6 and domain III pore-loop and, therefore, should obstruct the putative external access pathway. Indeed, mutations W1531A and W1531G allowed for exceptionally rapid access of QX-222. In addition, W1531G created a second non-selective ion-conducting pore, bypassing the outer vestibule but probably merging into the internal vestibule, allowing for control by the activation gate. These data suggest a strong structural similarity between bacterial and eukaryotic voltage-gated Na(+) channels. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  15. Exploring the Structure of the Voltage-gated Na+ Channel by an Engineered Drug Access Pathway to the Receptor Site for Local Anesthetics*

    Science.gov (United States)

    Lukacs, Peter; Gawali, Vaibhavkumar S.; Cervenka, Rene; Ke, Song; Koenig, Xaver; Rubi, Lena; Zarrabi, Touran; Hilber, Karlheinz; Stary-Weinzinger, Anna; Todt, Hannes

    2014-01-01

    Despite the availability of several crystal structures of bacterial voltage-gated Na+ channels, the structure of eukaryotic Na+ channels is still undefined. We used predictions from available homology models and crystal structures to modulate an external access pathway for the membrane-impermeant local anesthetic derivative QX-222 into the internal vestibule of the mammalian rNaV1.4 channel. Potassium channel-based homology models predict amino acid Ile-1575 in domain IV segment 6 to be in close proximity to Lys-1237 of the domain III pore-loop selectivity filter. The mutation K1237E has been shown previously to increase the diameter of the selectivity filter. We found that an access pathway for external QX-222 created by mutations of Ile-1575 was abolished by the additional mutation K1237E, supporting the notion of a close spatial relationship between sites 1237 and 1575. Crystal structures of bacterial voltage-gated Na+ channels predict that the side chain of rNaV1.4 Trp-1531 of the domain IV pore-loop projects into the space between domain IV segment 6 and domain III pore-loop and, therefore, should obstruct the putative external access pathway. Indeed, mutations W1531A and W1531G allowed for exceptionally rapid access of QX-222. In addition, W1531G created a second non-selective ion-conducting pore, bypassing the outer vestibule but probably merging into the internal vestibule, allowing for control by the activation gate. These data suggest a strong structural similarity between bacterial and eukaryotic voltage-gated Na+ channels. PMID:24947510

  16. Glucocorticoid Regulation of Rat Renal Sodium Potassium Adenosine Triphosphatase

    Science.gov (United States)

    1990-03-29

    response is not mediated by de novo protein synthesis but is secondary to enhanced sodium influx. The osmotic diuresis seen in uncontrolled...mediated increase in renal NaK-ATPase activity. The administration of anti-insulin serum caused a brisk natriuresis in control rat kidneys while having...hydrocortisone on water diuresis and renal function in man. J. Clin. Invest. 36: 767-779, 1957. Rane, S. and A. Aperia. Ontogeny of Na-K-ATPase

  17. Collisional transfer of population and orientation in sodium potassium

    Science.gov (United States)

    Wolfe, Christopher Matthew

    Collisional spectral satellite lines have been identified in recent optical-optical double resonance (OODR) excitation spectra of the NaK molecule. These satellite lines represent both a transfer of population, and a partial preservation of angular momentum orientation, to a rotational level adjacent to the one directly excited by the pump laser beam. A rate equation model was used to study the intensities of these satellite lines as a function of argon pressure and heat pipe oven temperature, in order to separate the collisional effects of argon and potassium atoms (being the most populous species in the vapor by an order of magnitude over the third most populous). Using a fit of this rate equation model to the data, it was found that collisions between NaK and potassium are more likely to transfer population and destroy orientation than argon collisions, and also more likely to transfer population to rotational levels higher in energy than the one being pumped (i.e. a propensity for positive Delta J collisions). Also, collisions between NaK and argon atoms show a propensity toward even-numbered changes in J. In addition to the above study, an analysis of collisional line broadening and velocity-changes in J-changing collisions was performed, showing potassium has a higher line broadening rate coefficient, as well as a smaller velocity change in J-changing collisions, than argon. A program was also written in Fortran 90/95 which solves the density matrix equations of motion in steady state for a coupled system of 3 (or 4) energy levels with their constituent degenerate magnetic sublevels. The solution to these equations yields the populations of each sublevel in steady state, as well as the laser-induced coherences between each sublevel (which are needed to model the polarization spectroscopy lineshape precisely). Development of an appropriate theoretical model for collisional transfer will yield a more rigorous study of the problem than the empirical rate

  18. Sodium Benzoate and Potassium Sorbate in Processed Meat Products Collected in Ho Chi Minh City, Vietnam

    Directory of Open Access Journals (Sweden)

    Yen T.H. Hoang

    2016-01-01

    Full Text Available Sodium benzoate and potassium sorbates are the two typical preservatives widely used in Vietnam and other countries. The maximum level (ML of sodium benzoate and potassium sorbate in processed meat products imposed by Ministry of Public Health is 1000 ppm. Although there are warnings about overusing of these preservatives that related to human health, many manufacturers do not follow the regulations. The aim of this study was to survey and consider the amounts and presence of these preservatives in processed meat products by using High-performance liquid chromatography (HPLC method. 90 samples of brands and no brands including Vietnamese pork rolls, pâtés, hams, sausages, and fermented pork rolls that available at markets in Ho Chi Minh City were analysed for these two preservatives. There was a preference for using sodium benzoate in all samples. Moreover, Vietnamese pork roll samples had the highest percentage of samples with preservatives concentrations exceeding the ML. Among 90 samples, sodium benzoate was detected in 52.2% of samples and 17.8% of them exceeded the ML, while potassium sorbate was found in 24.4% of samples and only 2.2% of them exceeded the regulated amount. 46.4% of Vietnamese pork rolls, 12.5% of pâtés, and 9.1% of fermented pork rolls had sodium benzoate exceeded the ML, whilst ham and sausage samples contained the concentrations inside the safety limits. Furthermore, only one sample of Vietnamese pork rolls and one sample of sausages had potassium sorbate concentrations surpassing the ML with the level of 1,717.57 mg/kg and 1,814.00 mg/kg, respectively. Furthermore, branded samples showed a significantly different result in compared with no branded samples. Of branded samples, exceeding sodium benzoate level ML was detected in 10% of samples and none of the samples found surpassing potassium sorbate limit amount. Nevertheless, 27.5% and 5% of unbranded samples had sodium benzoate and potassium sorbate higher than

  19. Why and how to implement sodium, potassium, calcium, and magnesium changes in food items and diets?

    Science.gov (United States)

    Karppanen, H; Karppanen, P; Mervaala, E

    2005-12-01

    The present average sodium intakes, approximately 3000-4500 mg/day in various industrialised populations, are very high, that is, 2-3-fold in comparison with the current Dietary Reference Intake (DRI) of 1500 mg. The sodium intakes markedly exceed even the level of 2500 mg, which has been recently given as the maximum level of daily intake that is likely to pose no risk of adverse effects on blood pressure or otherwise. By contrast, the present average potassium, calcium, and magnesium intakes are remarkably lower than the recommended intake levels (DRI). In USA, for example, the average intake of these mineral nutrients is only 35-50% of the recommended intakes. There is convincing evidence, which indicates that this imbalance, that is, the high intake of sodium on one hand and the low intakes of potassium, calcium, and magnesium on the other hand, produce and maintain elevated blood pressure in a big proportion of the population. Decreased intakes of sodium alone, and increased intakes of potassium, calcium, and magnesium each alone decrease elevated blood pressure. A combination of all these factors, that is, decrease of sodium, and increase of potassium, calcium, and magnesium intakes, which are characteristic of the so-called Dietary Approaches to Stop Hypertension diets, has an excellent blood pressure lowering effect. For the prevention and basic treatment of elevated blood pressure, various methods to decrease the intake of sodium and to increase the intakes of potassium, calcium, and magnesium should be comprehensively applied in the communities. The so-called 'functional food/nutraceutical/food-ceutical' approach, which corrects the mineral nutrient composition of extensively used processed foods, is likely to be particularly effective in producing immediate beneficial effects. The European Union and various governments should promote the availability and use of such healthier food compositions by tax reductions and other policies, which make the

  20. Modification of sodium and potassium channel gating kinetics by ether and halothane

    Energy Technology Data Exchange (ETDEWEB)

    Bean, B.P.; Shrager, P.; Goldstein, D.A.

    1981-03-01

    The effects of ether and halothane on the kinetics of sodium and potassium currents were investigated in the crayfish giant axon. Both general anesthetics produced a reversible, dose-dependent speeding up of sodium current inactivation at all membrane potentials, with no change in the rising phase of the currents. Double-pulse inactivation experiments with ether also showed faster inactivation, but the rate of recovery from inactivation at negative potentials was not affected. Ether shifted the midpoint of the steady-state fast inactivation curve in the hyperpolarizing direction and made the curve steeper. The activation of potassium currents was faster with ether present, with no change in the voltage dependence of steady-state potassium currents. Ether and halothane are known to perturb the structure of lipid bilayer membranes; the alterations in sodium and potassium channel gating kinetics are consistent with the hypothesis that the rats of the gating processes of the channels can be affected by the state of the lipids surrounding the channels, but a direct effect of ether and halothane on the protein part of the channels cannot be ruled out.

  1. Short communication: Use of a mixture of sodium nitrite, sodium benzoate, and potassium sorbate in aerobically challenged silages.

    Science.gov (United States)

    Knicky, Martin; Spörndly, Rolf

    2015-08-01

    Aerobic instability is still a common problem with many types of silages, particularly well-fermented silages. This study evaluated the effect of adding an additive mixture based on sodium nitrite, sodium benzoate, and potassium sorbate to a variety of crop materials on fermentation quality and aerobic stability of silages. Ensiling conditions were challenged by using a low packing density (104±4.3kg of dry matter/m(3)) of forage and allowing air ingression into silos (at 14 and 7 d before the end of the storage, for 8 h per event). Additive-treated silages were found to have significantly lower pH and reduced formation of ammonia-N, 2.3-butanediol, and ethanol compared with untreated control silages. Yeast growth was significantly reduced by additive treatment in comparison with untreated control silage. Consequently, additive-treated silages were considerably more aerobically stable (6.7 d) than untreated control silages (0.5 d). Overall, adding 5mL/kg of fresh crop of the additive based on sodium nitrite, sodium benzoate, and potassium sorbate reduced undesirable microorganisms in silages and thereby provided suitable ensiling conditions and prolonged aerobic stability, even under air-challenged laboratory ensiling conditions.

  2. Sodium, potassium and glucose management in organ transplantation.

    Science.gov (United States)

    Keegan, Mark T; Wright, David R

    2010-06-01

    To present current knowledge about the metabolic management of patients undergoing solid organ transplantation, and potential organ donors. Appropriate management of electrolytes and glucose improves outcome after transplantation, although conflicting evidence exists. Patients with cirrhosis-induced hyponatremia can be successfully transplanted but are at increased risk of postoperative complications. A new class of drugs, the vaptans, that antagonizes arginine vasopressin may be an effective treatment for hyponatremia in transplant candidates. Recent literature has documented the implications, predictors and potential therapies for perioperative hyperkalemia in the transplant population. The debate over appropriate targets for serum glucose in perioperative and critically ill patients has been lively. The documented risk of hypoglycemia associated with 'intensive insulin therapy' has led to the adoption of more conservative glycemic targets. Studies of glycemic control in transplant recipients are limited. In patients undergoing solid organ transplants, sodium management should aim to minimize an acute change in sodium concentration. Vaptans may be of future use in optimizing patients with cirrhosis prior to transplantation. Pending further studies, a perioperative 'middle ground' target glucose of between 140 and 180 mg/dl seems reasonable at this time.

  3. Sodium metabisulfite modulation of potassium channels in pain-sensing dorsal root ganglion neurons.

    Science.gov (United States)

    Nie, Aifang; Wei, Cailing; Meng, Ziqiang

    2009-12-01

    The effects of sodium metabisulfite (SMB), a general food preservative, on potassium currents in rat dorsal root ganglion (DRG) neurons were investigated using the whole-cell patch-clamp technique. SMB increased the amplitudes of both transient outward potassium currents and delayed rectifier potassium current in concentration- and voltage-dependent manner. The transient outward potassium currents (TOCs) include a fast inactivating (A-current or IA) current and a slow inactivating (D-current or ID) current. SMB majorly increased IA, and ID was little affected. SMB did not affect the activation process of transient outward currents (TOCs), but the inactivation curve of TOCs was shifted to more positive potentials. The inactivation time constants of TOCs were also increased by SMB. For delayed rectifier potassium current (IK), SMB shifted the activation curve to hyperpolarizing direction. SMB differently affected TOCs and IK, its effects major on A-type K+ channels, which play a role in adjusting pain sensitivity in response to peripheral redox conditions. SMB did not increase TOCs and IK when adding DTT in pipette solution. These results suggested that SMB might oxidize potassium channels, which relate to adjusting pain sensitivity in pain-sensing DRG neurons.

  4. Uncoupling charge movement from channel opening in voltage-gated potassium channels by ruthenium complexes.

    Science.gov (United States)

    Jara-Oseguera, Andrés; Ishida, Itzel G; Rangel-Yescas, Gisela E; Espinosa-Jalapa, Noel; Pérez-Guzmán, José A; Elías-Viñas, David; Le Lagadec, Ronan; Rosenbaum, Tamara; Islas, León D

    2011-05-06

    The Kv2.1 channel generates a delayed-rectifier current in neurons and is responsible for modulation of neuronal spike frequency and membrane repolarization in pancreatic β-cells and cardiomyocytes. As with other tetrameric voltage-activated K(+)-channels, it has been proposed that each of the four Kv2.1 voltage-sensing domains activates independently upon depolarization, leading to a final concerted transition that causes channel opening. The mechanism by which voltage-sensor activation is coupled to the gating of the pore is still not understood. Here we show that the carbon-monoxide releasing molecule 2 (CORM-2) is an allosteric inhibitor of the Kv2.1 channel and that its inhibitory properties derive from the CORM-2 ability to largely reduce the voltage dependence of the opening transition, uncoupling voltage-sensor activation from the concerted opening transition. We additionally demonstrate that CORM-2 modulates Shaker K(+)-channels in a similar manner. Our data suggest that the mechanism of inhibition by CORM-2 may be common to voltage-activated channels and that this compound should be a useful tool for understanding the mechanisms of electromechanical coupling.

  5. Antibodies to voltage-gated potassium and calcium channels in epilepsy.

    NARCIS (Netherlands)

    Majoie, H.J.; Baets, M.H.V. de; Renier, W.O.; Lang, B.; Vincent, A.

    2006-01-01

    OBJECTIVE: To determine the prevalence of antibodies to ion channels in patients with long standing epilepsy. BACKGROUND: Although the CNS is thought to be protected from circulating antibodies by the blood brain barrier, glutamate receptor antibodies have been reported in Rasmussen's encephalitis,

  6. 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.

  7. 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 i...... releases CGRP, and the release is regulated by Ca2+ ions and voltage-gated calcium channels.......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...

  8. 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...

  9. Voltage-gated calcium channels and their auxiliary subunits: physiology and pathophysiology and pharmacology.

    Science.gov (United States)

    Dolphin, Annette C

    2016-10-01

    Voltage-gated calcium channels are essential players in many physiological processes in excitable cells. There are three main subdivisions of calcium channel, defined by the pore-forming α1 subunit, the CaV 1, CaV 2 and CaV 3 channels. For all the subtypes of voltage-gated calcium channel, their gating properties are key for the precise control of neurotransmitter release, muscle contraction and cell excitability, among many other processes. For the CaV 1 and CaV 2 channels, their ability to reach their required destinations in the cell membrane, their activation and the fine tuning of their biophysical properties are all dramatically influenced by the auxiliary subunits that associate with them. Furthermore, there are many diseases, both genetic and acquired, involving voltage-gated calcium channels. This review will provide a general introduction and then concentrate particularly on the role of auxiliary α2 δ subunits in both physiological and pathological processes involving calcium channels, and as a therapeutic target.

  10. Non-silent story on synonymous sites in voltage-gated ion channel genes.

    Science.gov (United States)

    Zhou, Tong; Ko, Eun A; Gu, Wanjun; Lim, Inja; Bang, Hyoweon; Ko, Jae-Hong

    2012-01-01

    Synonymous mutations are usually referred to as "silent", but increasing evidence shows that they are not neutral in a wide range of organisms. We looked into the relationship between synonymous codon usage bias and residue importance of voltage-gated ion channel proteins in mice, rats, and humans. We tested whether translationally optimal codons are associated with transmembrane or channel-forming regions, i.e., the sites that are particularly likely to be involved in the closing and opening of an ion channel. Our hypothesis is that translationally optimal codons are preferred at the sites within transmembrane domains or channel-forming regions in voltage-gated ion channel genes to avoid mistranslation-induced protein misfolding or loss-of-function. Using the Mantel-Haenszel procedure, which applies to categorical data, we found that translationally optimal codons are more likely to be used at transmembrane residues and the residues involved in channel-forming. We also found that the conservation level at synonymous sites in the transmembrane region is significantly higher than that in the non-transmembrane region. This study provides evidence that synonymous sites in voltage-gated ion channel genes are not neutral. Silent mutations at channel-related sites may lead to dysfunction of the ion channel.

  11. Non-silent story on synonymous sites in voltage-gated ion channel genes.

    Directory of Open Access Journals (Sweden)

    Tong Zhou

    Full Text Available Synonymous mutations are usually referred to as "silent", but increasing evidence shows that they are not neutral in a wide range of organisms. We looked into the relationship between synonymous codon usage bias and residue importance of voltage-gated ion channel proteins in mice, rats, and humans. We tested whether translationally optimal codons are associated with transmembrane or channel-forming regions, i.e., the sites that are particularly likely to be involved in the closing and opening of an ion channel. Our hypothesis is that translationally optimal codons are preferred at the sites within transmembrane domains or channel-forming regions in voltage-gated ion channel genes to avoid mistranslation-induced protein misfolding or loss-of-function. Using the Mantel-Haenszel procedure, which applies to categorical data, we found that translationally optimal codons are more likely to be used at transmembrane residues and the residues involved in channel-forming. We also found that the conservation level at synonymous sites in the transmembrane region is significantly higher than that in the non-transmembrane region. This study provides evidence that synonymous sites in voltage-gated ion channel genes are not neutral. Silent mutations at channel-related sites may lead to dysfunction of the ion channel.

  12. Ab Initio Study of Thermodynamic Properties of Lithium, Sodium, and Potassium Sulfates

    Science.gov (United States)

    Zhuravlev, Yu. N.; Bugaeva, I. A.; Zhuravleva, L. V.

    2013-11-01

    The thermodynamic parameters of lithium, sodium, and potassium single and double sulfate crystals are determined by the method of ab initio calculation of a linear combination of atomic orbitals in the gradient approximation of density functional theory using the software package CRYSTAL09 within the framework of the quasi-harmonic approximation of the Debye theory. It is demonstrated that the standard entropies and heat capacities as well as the temperature dependences are in satisfactory agreement with the available experimental data. The average frequency, Debye temperature, and thermal conductivity coefficient increase with external pressure, whereas the Gruneisen parameter decreases. The dependences of the potentials of free and internal energies on the temperature and volume are expressed through the Birch-Murnaghan equation of state and a square-law dependence on these parameters of their vibrational components. The thermodynamic parameters of lithium-potassium sulfate appear closer to potassium sulfate, whereas for sodium-potassium, they lie between the corresponding parameters for single compounds.

  13. 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. Copyright © 2015 the American Physiological Society.

  14. Reduction in Dental Hypersensitivity with Nano-Hydroxyapatite, Potassium Nitrate, Sodium Monoflurophosphate and Antioxidants#

    Science.gov (United States)

    B. Low, Samuel; Allen, Edward P.; Kontogiorgos, Elias D.

    2015-01-01

    Objective: This clinical study aimed to evaluate effectiveness of a commercially available toothpaste containing potassium nitrate, sodium monoflurophosphate, and nano-hydroxyapatite as well as antioxidants phloretin, ferulic acid and silymarin in reducing dental hypersensitivity in adults. Methods: The clinical trial enrolled patients with a history of dentin hypersensitivity. A test toothpaste was introduced into the daily routine, which included initial instruction on usage. Patients completed a five-question visual analog scale (VAS) at the inception/baseline, after two days and after two weeks of using the toothpaste to determine their level of tooth sensitivity at baseline with the use of the toothpaste over time. Results: Patients that had significant sensitivity at baseline had a range of 52% to 76 % improvement after 48 hours and a range of 70% to 84% improvement after two weeks. Conclusion: A toothpaste containing potassium nitrate, sodium monoflurophosphate, and nano-hydroxyapatite plus antioxidants phloretin, ferulic acid and silymarin applied daily significantly decreased tooth pain of dentin hypersensitivity within a two-day and two-week time period. Clinical Significance: Based on the clinical study results, a daily application of a toothpaste containing potassium nitrate, sodium monofluorophosphate, and nano-hydroxyapatite plus antioxidants phloretin, ferulic acid and silymarin can significantly and quickly reduce tooth pain of dentin hypersensitivity. PMID:25834655

  15. Mechanism of functional interaction between potassium channel Kv1.3 and sodium channel NavBeta1 subunit

    Science.gov (United States)

    Kubota, Tomoya; Correa, Ana M.; Bezanilla, Francisco

    2017-01-01

    The voltage-gated potassium channel subfamily A member 3 (Kv1.3) dominantly expresses on T cells and neurons. Recently, the interaction between Kv1.3 and NavBeta1 subunits has been explored through ionic current measurements, but the molecular mechanism has not been elucidated yet. We explored the functional interaction between Kv1.3 and NavBeta1 through gating current measurements using the Cut-open Oocyte Voltage Clamp (COVC) technique. We showed that the N-terminal 1–52 sequence of hKv1.3 disrupts the channel expression on the Xenopus oocyte membrane, suggesting a potential role as regulator of hKv1.3 expression in neurons and lymphocytes. Our gating currents measurements showed that NavBeta1 interacts with the voltage sensing domain (VSD) of Kv1.3 through W172 in the transmembrane segment and modifies the gating operation. The comparison between G-V and Q-V with/without NavBeta1 indicates that NavBeta1 may strengthen the coupling between hKv1.3-VSD movement and pore opening, inducing the modification of kinetics in ionic activation and deactivation. PMID:28349975

  16. Assessment of Sodium and Potassium Intake by 24 h Urinary Excretion in a Healthy Mexican Cohort.

    Science.gov (United States)

    Vallejo, Maite; Colín-Ramírez, Eloisa; Rivera Mancía, Susana; Cartas Rosado, Raúl; Madero, Magdalena; Infante Vázquez, Oscar; Vargas-Barrón, Jesús

    2017-02-01

    A high dietary sodium intake and a low potassium intake are associated with adverse cardiovascular health. Data on these nutrients consumption in Mexico is limited. The aim of this study was to assess sodium and potassium intake by 24 h urinary excretion in a clinically healthy Mexican population. We additionally explored their association with blood pressure. 711 clinically healthy participants aged 20-50 years old recruited in the Tlalpan 2020 cohort from September 2014-December 2015, were included in this cross-sectional analysis. All participants provided a 24 h urine sample and underwent anthropometric, biochemical, and blood pressure evaluations. Univariate and multivariate linear regression analyses were used to assess the association of urinary sodium, potassium, and Na/K ratio with blood pressure. Mean (95% confidence interval [CI]) urinary sodium and potassium in the overall population was 3150.1 (3054.2-3246.0) mg/d and 1909.5 (1859.3-1959.6) mg/d, respectively. Overall, only 121 (17%) met the WHO recommendation for sodium intake (<2000 mg/d) and 16 (2.3%) met the goal for potassium intake (≥3510 mg/d). Urinary sodium (β coefficient 1.3, 95% CI: 0.7, 1.8, p <0.001) and potassium (β coefficient 2.1, 95% CI: 1.0, 3.2, p <0.001) were found to be associated with systolic blood pressure in the univariate analysis but not in the multivariate analysis. Sodium intake was higher and potassium intake was lower than the WHO recommendations in this healthy Mexican population. Sodium and potassium intakes were not associated with blood pressure at the mean levels of intake observed in this population, after adjusting for key variables. Copyright © 2017 IMSS. Published by Elsevier Inc. All rights reserved.

  17. β-Adrenergic receptor agonist increases voltage-gated Na(+) currents in medial prefrontal cortex pyramidal neurons.

    Science.gov (United States)

    Szulczyk, Bartlomiej

    2015-05-19

    The prefrontal cortex does not function properly in neuropsychiatric diseases and during chronic stress. The aim of this study was to test the effects of isoproterenol, a β-adrenergic receptor agonist, on the voltage-dependent fast-inactivating Na(+) currents in medial prefrontal cortex (mPFC) pyramidal neurons obtained from young rats. The recordings were performed in the cell-attached configuration. Isoproterenol (2μM) did not change the peak Na(+) current amplitude but shifted the IV curve of the Na(+) currents toward hyperpolarization. Pretreatment of the cells with the β-adrenergic antagonists propranolol and metoprolol abolished the effect of isoproterenol on the Na(+) currents, suggesting the involvement of β1-adrenergic receptors. The effect of β-adrenergic receptor stimulation on the sodium currents was dependent on kinase A and kinase C; the effect was diminished in the presence of the kinase A antagonist H-89 and the kinase C antagonist chelerythrine and abolished when the antagonists were coapplied. Moreover, isoproterenol depolarized the membrane potential recorded using the perforated-patch method, and this depolarization was abolished by cesium ions. Thus, in mPFC pyramidal neurons, stimulation of β-adrenergic receptors up-regulates the fast-inactivating voltage-gated Na(+) currents evoked by suprathreshold depolarizations.

  18. Preferential targeting of Nav1.6 voltage-gated Na+ Channels to the axon initial segment during development.

    Directory of Open Access Journals (Sweden)

    Elizabeth J Akin

    Full Text Available During axonal maturation, voltage-gated sodium (Nav channels accumulate at the axon initial segment (AIS at high concentrations. This localization is necessary for the efficient initiation of action potentials. The mechanisms underlying channel trafficking to the AIS during axonal development have remained elusive due to a lack of Nav reagents suitable for high resolution imaging of channels located specifically on the cell surface. Using an optical pulse-chase approach in combination with a novel Nav1.6 construct containing an extracellular biotinylation domain we demonstrate that Nav1.6 channels are preferentially inserted into the AIS membrane during neuronal development via direct vesicular trafficking. Single-molecule tracking illustrates that axonal channels are immediately immobilized following delivery, while channels delivered to the soma are often mobile. Neither a Nav1.6 channel lacking the ankyrin-binding motif nor a chimeric Kv2.1 channel containing the Nav ankyrinG-binding domain show preferential AIS insertion. Together these data support a model where ankyrinG-binding is required for preferential Nav1.6 insertion into the AIS plasma membrane. In contrast, ankyrinG-binding alone does not confer the preferential delivery of proteins to the AIS.

  19. KV7 potassium channels

    DEFF Research Database (Denmark)

    Stott, Jennifer B; Jepps, Thomas Andrew; Greenwood, Iain A

    2014-01-01

    identified as being crucial mediators of this process in a variety of smooth muscle. Recently, KV7 channels have been shown to be involved in the pathogenesis of hypertension, as well as being implicated in other smooth muscle disorders, providing a new and inviting target for smooth muscle disorders.......Potassium channels are key regulators of smooth muscle tone, with increases in activity resulting in hyperpolarisation of the cell membrane, which acts to oppose vasoconstriction. Several potassium channels exist within smooth muscle, but the KV7 family of voltage-gated potassium channels have been...

  20. 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.

  1. Use of potassium chloride and flavor enhancers in low sodium Cheddar cheese.

    Science.gov (United States)

    Grummer, J; Bobowski, N; Karalus, M; Vickers, Z; Schoenfuss, T

    2013-03-01

    We investigated use of potassium chloride (KCl) to maintain both the salty flavor and to replace the preservative effects of salt when reducing the sodium content in natural cheese. Because salt replacers can affect flavor because of inherent off-flavors, such as bitter and metallic, we examined the use of flavor enhancers for their ability to modulate some of these undesirable sensory effects. Stirred-curd Cheddar-style cheese was manufactured using 2 cheese-making procedures (different curd knife sizes and target salting titratable acidities), in duplicate. Curd was salted with sodium chloride (NaCl) or 60% reduced sodium blends of NaCl and KCl (2 different sources). Curd was also salted at a 60% reduced sodium rate with NaCl and KCl with added flavor enhancers. A hydrolyzed vegetable protein/yeast extract blend, a natural "potassium-blocking type" flavor, disodium inosinate, or disodium guanylate were each blended with the reduced sodium salt blend and added to curd at the salting step. The resulting blocks of cheese were aged for 5 mo and evaluated monthly for chemical, microbial, and sensory differences. At 5 mo of aging, we measured liking for the cheeses using a consumer panel. Overall, cheeses were well liked by the consumer panel, and the scores of reduced sodium cheese with 2 different KCl sources were not different from those of the full-sodium control. The addition of flavor enhancers to Cheddar curd had mixed results, with one improving the consumer flavor liking only slightly over KCl, and one (disodium inosinate) significantly reducing consumer flavor liking scores, presumably due to the amount of umami flavor it contributed. Potassium chloride replacement salts sourced from different manufacturers affected the chemical and flavor properties of cheese, and changes to pH and temperature targets may be necessary to yield cheese with the moisture and pH targets desired. The cheese-making procedure used also influenced flavors observed, which resulted in

  2. Effect of a sodium-poor diet on lithium clearance at different dietary potassium contents in rats.

    Science.gov (United States)

    Thomsen, K; Leyssac, P P

    1987-10-01

    In rats on a diet with a sodium content of 300 mmol/kg, lithium is reabsorbed exclusively in the proximal tubules, and lithium clearance (CLi) equals the proximal tubular fluid output (Vprox). In rats on a sodium-poor diet (5 mmol/kg), lithium is also reabsorbed in the distal nephron and CLi is therefore lower than Vprox. The present paper examines the reduction of CLi in response to a low sodium diet in Brattleboro rats with hereditary diabetes insipidus maintained on different dietary potassium contents. CLi was reduced by about 60 microliter/min./100 g body weight in response to a low sodium diet. The absolute reduction in CLi caused by low sodium diet was unaffected by an increase of CLi provoked by administration of potassium with the diet, and it was unaffected by variations of CLi which occurred spontaneously within each group. CLi was accordingly reduced by a constant absolute value rather than by a constant percentage. The reduction of CLi (60 microliter/min./100 g body weight) was equal to CLi in the group given a potassium-poor diet with a normal sodium content. In the low-sodium and low-potassium group CLi was reduced to almost zero. Using CLi as a measure of Vprox in the rats on a 300 mmol/kg sodium diet it is concluded that the absolute reduction of CLi in response to a sodium-poor diet is 1) unaffected by increase of Vprox produced by administration of potassium with the food,2) unaffected by spontaneous variations of Vprox, and 3) equal to Vprox in rats given a potassium-poor diet.

  3. Potassium

    Science.gov (United States)

    ... blackberries Root vegetables, such as carrots and potatoes Citrus fruits, such as oranges and grapefruit Your kidneys help to keep the right amount of potassium in your body. If you have chronic kidney disease, your kidneys may not remove extra potassium from ...

  4. Development of voltage-dependent calcium, sodium, and potassium currents in Xenopus spinal neurons.

    Science.gov (United States)

    O'Dowd, D K; Ribera, A B; Spitzer, N C

    1988-03-01

    Action potentials of embryonic nerve and muscle cells often have a different ionic dependence and longer duration than those of mature cells. The action potential of spinal cord neurons from Xenopus laevis exhibits a prominent calcium component at early stages of development that diminishes with age as the impulse becomes principally sodium dependent. Whole-cell voltage-clamp analysis has been undertaken to characterize the changes in membrane currents during development of these neurons in culture. Four voltage-dependent currents of cells were identified and examined during the first day in vitro, when most of the change in the action potential occurs. There are no changes in the peak density of the calcium current (ICa), its voltage dependence, or time to half-maximal activation; a small increase in inactivation is apparent. The major change in sodium current (INa) is a 2-fold increase in its density. In addition, more subtle changes in the kinetics of the macroscopic sodium current were noted. The peak density of voltage-dependent potassium current (IKv) increases 3-fold, and this current becomes activated almost twice as fast. No changes were noted in the extent of its inactivation. The calcium-dependent potassium current (IKc) consists of an inactivating and a sustained component. The former increases 2-fold in peak current density, and the latter increases similarly at less depolarized voltages. The changes in these currents contribute to the decrease in duration and the change in ionic dependence of the impulse.

  5. A voltage-gated H+ channel underlying pH homeostasis in calcifying coccolithophores.

    Directory of Open Access Journals (Sweden)

    Alison R Taylor

    2011-06-01

    Full Text Available Marine coccolithophorid phytoplankton are major producers of biogenic calcite, playing a significant role in the global carbon cycle. Predicting the impacts of ocean acidification on coccolithophore calcification has received much recent attention and requires improved knowledge of cellular calcification mechanisms. Uniquely amongst calcifying organisms, coccolithophores produce calcified scales (coccoliths in an intracellular compartment and secrete them to the cell surface, requiring large transcellular ionic fluxes to support calcification. In particular, intracellular calcite precipitation using HCO₃⁻ as the substrate generates equimolar quantities of H+ that must be rapidly removed to prevent cytoplasmic acidification. We have used electrophysiological approaches to identify a plasma membrane voltage-gated H+ conductance in Coccolithus pelagicus ssp braarudii with remarkably similar biophysical and functional properties to those found in metazoans. We show that both C. pelagicus and Emiliania huxleyi possess homologues of metazoan H(v1 H+ channels, which function as voltage-gated H+ channels when expressed in heterologous systems. Homologues of the coccolithophore H+ channels were also identified in a diversity of eukaryotes, suggesting a wide range of cellular roles for the H(v1 class of proteins. Using single cell imaging, we demonstrate that the coccolithophore H+ conductance mediates rapid H+ efflux and plays an important role in pH homeostasis in calcifying cells. The results demonstrate a novel cellular role for voltage gated H+ channels and provide mechanistic insight into biomineralisation by establishing a direct link between pH homeostasis and calcification. As the coccolithophore H+ conductance is dependent on the trans-membrane H+ electrochemical gradient, this mechanism will be directly impacted by, and may underlie adaptation to, ocean acidification. The presence of this H+ efflux pathway suggests that there is no obligate

  6. [Analysis of preservatives used in cosmetic products: salicylic acid, sodium benzoate, sodium dehydroacetate, potassium sorbate, phenoxyethanol, and parabens].

    Science.gov (United States)

    Ikarashi, Yoshiaki; Uchino, Tadashi; Nishimura, Tetsuji

    2010-01-01

    Preservatives are used to inhibit the growth of microorganisms in cosmetic products. The Japanese standards for cosmetics set restrictions on the maximum amount of each preservative added to cosmetics as per the purpose of use of cosmetics. For the investigation into the actual conditions of commonly used preservatives in commercial cosmetics, we analyzed parabens, phenoxyethanol, sodium benzoate, sodium dehydroacetate, salicylic acid, and potassium sorbate by high-performance liquid chromatography (HPLC). Twenty-one samples were obtained from cosmetic product manufacturers located in 14 prefectures in Japan. Among different acid- and salt-based preservatives, sodium benzoate was observed to have been used in many products. These acid- and salt-based preservatives were used with parabens in personal washing products, such as shampoo and soap. The labels of two of the cosmetic product samples displayed inaccurate ingredient information, that is, a preservative other than the one used in the corresponding product was listed on them. The amount of preservatives used did not exceed regulatory limits in any of the analyzed samples.

  7. Dynamical characterization of inactivation path in voltage-gated Na(+) ion channel by non-equilibrium response spectroscopy.

    Science.gov (United States)

    Pal, Krishnendu; Gangopadhyay, Gautam

    2016-11-01

    Inactivation path of voltage gated sodium channel has been studied here under various voltage protocols as it is the main governing factor for the periodic occurrence and shape of the action potential. These voltage protocols actually serve as non-equilibrium response spectroscopic tools to study the ion channel in non-equilibrium environment. In contrast to a lot of effort in finding the crystal structure based molecular mechanism of closed-state(CSI) and open-state inactivation(OSI); here our approach is to understand the dynamical characterization of inactivation. The kinetic flux as well as energetic contribution of the closed and open- state inactivation path is compared here for voltage protocols, namely constant, pulsed and oscillating. The non-equilibrium thermodynamic quantities used in response to these voltage protocols serve as improved characterization tools for theoretical understanding which not only agrees with the previously known kinetic measurements but also predict the energetically optimum processes to sustain the auto-regulatory mechanism of action potential and the consequent inactivation steps needed. The time dependent voltage pattern governs the population of the conformational states which when couple with characteristic rate parameters, the CSI and OSI selectivity arise dynamically to control the inactivation path. Using constant, pulsed and continuous oscillating voltage protocols we have shown that during depolarization the OSI path is more favored path of inactivation however, in the hyper-polarized situation the CSI is favored. It is also shown that the re-factorisation of inactivated sodium channel to resting state occurs via CSI path. Here we have shown how the subtle energetic and entropic cost due to the change in the depolarization magnitude determines the optimum path of inactivation. It is shown that an efficient CSI and OSI dynamical profile in principle can characterize the open-state drug blocking phenomena.

  8. The position of the fast-inactivation gate during lidocaine block of voltage-gated Na+ channels.

    Science.gov (United States)

    Vedantham, V; Cannon, S C

    1999-01-01

    Lidocaine produces voltage- and use-dependent inhibition of voltage-gated Na+ channels through preferential binding to channel conformations that are normally populated at depolarized potentials and by slowing the rate of Na+ channel repriming after depolarizations. It has been proposed that the fast-inactivation mechanism plays a crucial role in these processes. However, the precise role of fast inactivation in lidocaine action has been difficult to probe because gating of drug-bound channels does not involve changes in ionic current. For that reason, we employed a conformational marker for the fast-inactivation gate, the reactivity of a cysteine substituted at phenylalanine 1304 in the rat adult skeletal muscle sodium channel alpha subunit (rSkM1) with [2-(trimethylammonium)ethyl]methanethiosulfonate (MTS-ET), to determine the position of the fast-inactivation gate during lidocaine block. We found that lidocaine does not compete with fast-inactivation. Rather, it favors closure of the fast-inactivation gate in a voltage-dependent manner, causing a hyperpolarizing shift in the voltage dependence of site 1304 accessibility that parallels a shift in the steady state availability curve measured for ionic currents. More significantly, we found that the lidocaine-induced slowing of sodium channel repriming does not result from a slowing of recovery of the fast-inactivation gate, and thus that use-dependent block does not involve an accumulation of fast-inactivated channels. Based on these data, we propose a model in which transitions along the activation pathway, rather than transitions to inactivated states, play a crucial role in the mechanism of lidocaine action.

  9. Meteoritic influence on sodium and potassium abundance in the lunar exosphere measured by LADEE

    Science.gov (United States)

    Szalay, Jamey R.; Horányi, Mihály; Colaprete, Anthony; Sarantos, Menelaos

    2016-06-01

    The Lunar Atmosphere and Dust Environment Explorer (LADEE) orbited the Moon for approximately 6 months, taking data with the Lunar Dust Experiment (LDEX), Ultraviolet-Visible Spectrometer (UVS), and Neutral Mass Spectrometer (NMS). Here we compare coincident LDEX measurements of meteoritic influx to exospheric column densities of Na and K derived by UVS. We report a strong correlation of exospheric potassium and meteoroid ejecta during the Geminids meteoroid shower, exhibiting a much stronger response than sodium. With the exception of the Geminids, we find a weak correlation between the sporadic meteoroid influx as measured by LDEX and exospheric density as measured by UVS.

  10. SODIUM-POTASSIUM-CHLORIDE COTRANSPORT IN THE REGULATION OF VASCULAR MYOGENIC TONE

    Directory of Open Access Journals (Sweden)

    S. N. Orlov

    2014-01-01

    Full Text Available The article discusses the data on the functioning of Na+,K+,2Cl– cotransport – the carrier providing electroneutral symport of sodium, potassium and chloride, as well as molecular mechanisms of the regulation and physiological significance of this carrier. We analyzed the novel data on involvement of ubiquitous isoform of Na+,K+,2Cl–cotransporter (NKCC1 in regulation of vascular smooth muscle contraction, and role of this carrier in the regulation of cell volume and intracellular chloride concentration.

  11. [The relationship between PMI and concentration of potassium ion and sodium ion in swine aqueous humor after death].

    Science.gov (United States)

    Han, Ju; Yu, Guang-biao; Dong, Ye-qiang; Fang, Chao; Jing, Hua-lan; Luo, Si-min

    2010-04-01

    To explored the relationship between the concentration of potassium ion as well as sodium ion in the aqueous humor and post-mortem interval (PMI). The concentrations of potassium ion and sodium ion in the aqueous humor of swine within 48 h after death at 4 degrees C and 28 degrees C were detected using Z-500 atomic absorption spectrophotometer. The concentrations of potassium ion and sodium ion in aqueous humor of isolated swine eyeballs within 48 h after death when the environmental temperature was 4 degrees C were significantly related to PMI. The relationship between PMI and the concentration of potassium ion was PMI = -0.178[K+]2 + 49.978 (R2 = 0.995). The relationship between PMI and the rate of sodium ion and potassium ion was PMI = 120.987/[Na+/K+]-28.834 (R2 = 0.905). The concentration of potassium in aqueous humor of isolated swine eyeballs may be one of the reference indicators to estimate PMI of the corpses at lower temperatures.

  12. The feasibility of meeting the WHO guidelines for sodium and potassium: a cross-national comparison study.

    Science.gov (United States)

    Drewnowski, Adam; Rehm, Colin D; Maillot, Matthieu; Mendoza, Alfonso; Monsivais, Pablo

    2015-03-20

    To determine joint compliance with the WHO sodium-potassium goals in four different countries, using data from nationally representative dietary surveys. Compared to national and international recommendations and guidelines, the world's population consumes too much sodium and inadequate amounts of potassium. The WHO recommends consuming less than 2000 mg sodium (86 mmol) and at least 3510 mg potassium (90 mmol) per person per day. Dietary surveillance data were obtained from the National Health and Nutrition Examination Survey (NHANES 2007-2010) for the USA; the Encuesta Nacional de Salud y Nutrición 2012 for Mexico; the Individual and National Study on Food Consumption (INCA2) for France; and the National Diet and Nutrition Survey (NDNS) for the UK. We estimated the proportion of adults meeting the joint WHO sodium-potassium goals in the USA, the UK, France and Mexico. The upper bounds of joint compliance with the WHO sodium-potassium goals were estimated at 0.3% in the USA, 0.15% in Mexico, 0.5% in France and 0.1% in the UK. Given prevailing food consumption patterns and the current food supply, implementing WHO guidelines will be an enormous challenge for global public health. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  13. Potassium

    Science.gov (United States)

    ... high in potassium include bananas, cantaloupe, grapefruit, oranges, tomato or prune juice, honeydew melons, prunes, molasses and ... of a Heart Attack 10 Angina (Chest Pain) *Red Dress ™ DHHS, Go Red ™ AHA ; National Wear Red ...

  14. Epidermal growth factor upregulates motility of Mat-LyLu rat prostate cancer cells partially via voltage-gated Na+ channel activity

    Science.gov (United States)

    Ding, Yanning; Brackenbury, William J.; Onganer, Pinar U.; Montano, Ximena; Porter, Louise M.; Bates, Lucy F.; Djamgoz, Mustafa B. A.

    2014-01-01

    The main aim of this investigation was to determine whether a functional relationship existed between epidermal growth factor (EGF) and voltage-gated sodium channel (VGSC) upregulation, both associated with strongly metastatic prostate cancer cells. Incubation with EGF for 24 h more than doubled VGSC current density. Similar treatment with EGF significantly and dose-dependently enhanced the cells’ migration through Transwell filters. Both the patch clamp recordings and the migration assay suggested that endogenous EGF played a similar role. Importantly, co-application of EGF and tetrodotoxin, a highly selective VGSC blocker, abolished 65% of the potentiating effect of EGF. It is suggested that a significant portion of the EGF-induced enhancement of migration occurred via VGSC activity. PMID:17960590

  15. 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

  16. Aging-associated changes in motor axon voltage-gated Na(+) channel function in mice.

    Science.gov (United States)

    Moldovan, Mihai; Rosberg, Mette Romer; Alvarez, Susana; Klein, Dennis; Martini, Rudolf; Krarup, Christian

    2016-03-01

    Accumulating myelin abnormalities and conduction slowing occur in peripheral nerves during aging. In mice deficient of myelin protein P0, severe peripheral nervous system myelin damage is associated with ectopic expression of Nav1.8 voltage-gated Na(+) channels on motor axons aggravating the functional impairment. The aim of the present study was to investigate the effect of regular aging on motor axon function with particular emphasis on Nav1.8. We compared tibial nerve conduction and excitability measures by threshold tracking in 12 months (mature) and 20 months (aged) wild-type (WT) mice. With aging, deviations during threshold electrotonus were attenuated and the resting current-threshold slope and early refractoriness were increased. Modeling indicated that, in addition to changes in passive membrane properties, motor fibers in aged WT mice were depolarized. An increased Nav1.8 isoform expression was found by immunohistochemistry. The depolarizing excitability features were absent in Nav1.8 null mice, and they were counteracted in WT mice by a Nav1.8 blocker. Our data suggest that alteration in voltage-gated Na(+) channel isoform expression contributes to changes in motor axon function during aging.

  17. Functionality of the voltage-gated proton channel truncated in S4.

    Science.gov (United States)

    Sakata, Souhei; Kurokawa, Tatsuki; Nørholm, Morten H H; Takagi, Masahiro; Okochi, Yoshifumi; von Heijne, Gunnar; Okamura, Yasushi

    2010-02-02

    The voltage sensor domain (VSD) is the key module for voltage sensing in voltage-gated ion channels and voltage-sensing phosphatases. Structurally, both the VSD and the recently discovered voltage-gated proton channels (Hv channels) voltage sensor only protein (VSOP) and Hv1 contain four transmembrane segments. The fourth transmembrane segment (S4) of Hv channels contains three periodically aligned arginines (R1, R2, R3). It remains unknown where protons permeate or how voltage sensing is coupled to ion permeation in Hv channels. Here we report that Hv channels truncated just downstream of R2 in the S4 segment retain most channel properties. Two assays, site-directed cysteine-scanning using accessibility of maleimide-reagent as detected by Western blotting and insertion into dog pancreas microsomes, both showed that S4 inserts into the membrane, even if it is truncated between the R2 and R3 positions. These findings provide important clues to the molecular mechanism underlying voltage sensing and proton permeation in Hv channels.

  18. Emerging roles of L-type voltage gated and other calcium channels in T lymphocytes.

    Directory of Open Access Journals (Sweden)

    Abdallah eBadou

    2013-08-01

    Full Text Available In T lymphocytes, calcium ion controls a variety of biological processes including development, survival, proliferation, and effector functions. These distinct and specific roles are regulated by different calcium signals, which are generated by various plasma membrane calcium channels. The repertoire of calcium-conducting proteins in T lymphocytes includes store-operated CRAC channels, transient receptor potential (TRP channels, P2X channels, and L-type voltage-gated calcium (Cav1 channels. In this paper, we will focus mainly on the role of the Cav1 channels found expressed by T lymphocytes, where these channels appear to operate in a TCR stimulation-dependent and voltage-sensor independent manner. We will review their expression profile at various differentiation stages of CD4 and CD8 T lymphocytes. Then, we will present crucial genetic evidence in favor of a role of these Cav1 channels and related regulatory proteins in both CD4 and CD8 T cell functions such as proliferation, survival, cytokine production and cytolysis. Finally, we will provide evidence and speculate on how these voltage-gated channels might function in the T lymphocyte, a non-excitable cell.

  19. Ephaptic coupling rescues conduction failure in weakly coupled cardiac tissue with voltage-gated gap junctions

    Science.gov (United States)

    Weinberg, S. H.

    2017-09-01

    Electrical conduction in cardiac tissue is usually considered to be primarily facilitated by gap junctions, providing a pathway between the intracellular spaces of neighboring cells. However, recent studies have highlighted the role of coupling via extracellular electric fields, also known as ephaptic coupling, particularly in the setting of reduced gap junction expression. Further, in the setting of reduced gap junctional coupling, voltage-dependent gating of gap junctions, an oft-neglected biophysical property in computational studies, produces a positive feedback that promotes conduction failure. We hypothesized that ephaptic coupling can break the positive feedback loop and rescue conduction failure in weakly coupled cardiac tissue. In a computational tissue model incorporating voltage-gated gap junctions and ephaptic coupling, we demonstrate that ephaptic coupling can rescue conduction failure in weakly coupled tissue. Further, ephaptic coupling increased conduction velocity in weakly coupled tissue, and importantly, reduced the minimum gap junctional coupling necessary for conduction, most prominently at fast pacing rates. Finally, we find that, although neglecting gap junction voltage-gating results in negligible differences in well coupled tissue, more significant differences occur in weakly coupled tissue, greatly underestimating the minimal gap junctional coupling that can maintain conduction. Our study suggests that ephaptic coupling plays a conduction-preserving role, particularly at rapid heart rates.

  20. Down-regulation of endogenous KLHL1 decreases voltage-gated calcium current density.

    Science.gov (United States)

    Perissinotti, Paula P; Ethington, Elizabeth G; Cribbs, Leanne; Koob, Michael D; Martin, Jody; Piedras-Rentería, Erika S

    2014-05-01

    The actin-binding protein Kelch-like 1 (KLHL1) can modulate voltage-gated calcium channels in vitro. KLHL1 interacts with actin and with the pore-forming subunits of Cav2.1 and CaV3.2 calcium channels, resulting in up-regulation of P/Q and T-type current density. Here we tested whether endogenous KLHL1 modulates voltage gated calcium currents in cultured hippocampal neurons by down-regulating the expression of KLHL1 via adenoviral delivery of shRNA targeted against KLHL1 (shKLHL1). Control adenoviruses did not affect any of the neuronal properties measured, yet down-regulation of KLHL1 resulted in HVA current densities ~68% smaller and LVA current densities 44% smaller than uninfected controls, with a concomitant reduction in α(1A) and α(1H) protein levels. Biophysical analysis and western blot experiments suggest Ca(V)3.1 and 3.3 currents are also present in shKLHL1-infected neurons. Synapsin I levels, miniature postsynaptic current frequency, and excitatory and inhibitory synapse number were reduced in KLHL1 knockdown. This study corroborates the physiological role of KLHL1 as a calcium channel modulator and demonstrates a novel, presynaptic role.

  1. Voltage-gated sodium channels in cerebellar Purkinje cells of mormyrid fish

    NARCIS (Netherlands)

    M.M. de Ruiter (Martijn); C.I. de Zeeuw (Chris); C.R.W. Hansel (Christian)

    2006-01-01

    textabstractCerebellar Purkinje cells of mormyrid fish differ in some morphological as well as physiological parameters from their counterparts in mammals. Morphologically, Purkinje cells of mormyrids have larger dendrites that are characterized by a lower degree of branching in the molecular layer.

  2. Neuregulin Directly Decreases Voltage-Gated Sodium Current in Hippocampal ErbB4-Expressing Interneurons

    OpenAIRE

    Janssen, Megan J.; Leiva-Salcedo, Elias; Buonanno, Andres

    2012-01-01

    The Neuregulin 1 (NRG1)/ErbB4 signaling pathway has been genetically and functionally implicated in the etiology underlying schizophrenia, and in the regulation of glutamatergic pyramidal neuron function and plasticity. However, ErbB4 receptors are expressed in subpopulations of GABAergic interneurons, but not in hippocampal or cortical pyramidal neurons, indicating that NRG1 effects on principal neurons are indirect. Consistent with these findings, NRG1 effects on hippocampal long-term poten...

  3. Serum and Glucocorticoid Regulated Kinase 1 in Sodium Homeostasis

    Directory of Open Access Journals (Sweden)

    Yiyun Lou

    2016-08-01

    Full Text Available The ubiquitously expressed serum and glucocorticoid regulated kinase 1 (SGK1 is tightly regulated by osmotic and hormonal signals, including glucocorticoids and mineralocorticoids. Recently, SGK1 has been implicated as a signal hub for the regulation of sodium transport. SGK1 modulates the activities of multiple ion channels and carriers, such as epithelial sodium channel (ENaC, voltage-gated sodium channel (Nav1.5, sodium hydrogen exchangers 1 and 3 (NHE1 and NHE3, sodium-chloride symporter (NCC, and sodium-potassium-chloride cotransporter 2 (NKCC2; as well as the sodium-potassium adenosine triphosphatase (Na+/K+-ATPase and type A natriuretic peptide receptor (NPR-A. Accordingly, SGK1 is implicated in the physiology and pathophysiology of Na+ homeostasis. Here, we focus particularly on recent findings of SGK1’s involvement in Na+ transport in renal sodium reabsorption, hormone-stimulated salt appetite and fluid balance and discuss the abnormal SGK1-mediated Na+ reabsorption in hypertension, heart disease, edema with diabetes, and embryo implantation failure.

  4. Salt microspheres and potassium chloride usage for sodium reduction: Case study with sushi.

    Science.gov (United States)

    Đorđević, Đani; Buchtová, Hana; Macharáčková, Blanka

    2017-01-01

    The aim of the study was to estimate possibilities of salt substitutes usage in the preparation of two sushi types (nigiri and maki) prepared with different seafood (salmon: Salmo salar, tuna: Thunnus albacares, and shrimp: Pleoticus muelleri). Potassium chloride (Mary samples), Soda-Lo (hollowed microsphere of regular salt crystals), and regular salt (sodium chloride) were used in the experiment. Sushi samples (n = 1960) were evaluated by 40 trained panelists who noticed that maki shrimp samples prepared with Mary salt had higher bitterness (21.48 ± 28.01) in comparison with 2% sodium chloride (7.91 ± 8.80). The saltiness was lower in nigiri tuna prepared with Mary (49.59 ± 17.47) than 2% sodium chloride (61.11 ± 15.75). The study clearly showed the possibility of lowering sodium content in sushi meal with the usage of salt substitutes, with emphasis that Soda-Lo should be considered as a better option due to the retention of sensory properties in sushi samples prepared with this salt substitute.

  5. Impact of intensive horticulture practices on groundwater content of nitrates, sodium, potassium, and pesticides.

    Science.gov (United States)

    Melo, Armindo; Pinto, Edgar; Aguiar, Ana; Mansilha, Catarina; Pinho, Olívia; Ferreira, Isabel M P L V O

    2012-07-01

    A monitoring program of nitrate, nitrite, potassium, sodium, and pesticides was carried out in water samples from an intensive horticulture area in a vulnerable zone from north of Portugal. Eight collecting points were selected and water-analyzed in five sampling campaigns, during 1 year. Chemometric techniques, such as cluster analysis, principal component analysis (PCA), and discriminant analysis, were used in order to understand the impact of intensive horticulture practices on dug and drilled wells groundwater and to study variations in the hydrochemistry of groundwater. PCA performed on pesticide data matrix yielded seven significant PCs explaining 77.67% of the data variance. Although PCA rendered considerable data reduction, it could not clearly group and distinguish the sample types. However, a visible differentiation between the water samples was obtained. Cluster and discriminant analysis grouped the eight collecting points into three clusters of similar characteristics pertaining to water contamination, indicating that it is necessary to improve the use of water, fertilizers, and pesticides. Inorganic fertilizers such as potassium nitrate were suspected to be the most important factors for nitrate contamination since highly significant Pearson correlation (r = 0.691, P < 0.01) was obtained between groundwater nitrate and potassium contents. Water from dug wells is especially prone to contamination from the grower and their closer neighbor's practices. Water from drilled wells is also contaminated from distant practices.

  6. Biowaiver monographs for immediate release solid oral dosage forms: diclofenac sodium and diclofenac potassium.

    Science.gov (United States)

    Chuasuwan, B; Binjesoh, V; Polli, J E; Zhang, H; Amidon, G L; Junginger, H E; Midha, K K; Shah, V P; Stavchansky, S; Dressman, J B; Barends, D M

    2009-04-01

    Literature data are reviewed regarding the scientific advisability of allowing a waiver of in vivo bioequivalence (BE) testing for the approval of immediate release (IR) solid oral dosage forms containing either diclofenac potassium and diclofenac sodium. Within the biopharmaceutics classification system (BCS), diclofenac potassium and diclofenac sodium are each BCS class II active pharmaceutical ingredients (APIs). However, a biowaiver can be recommended for IR drug products of each salt form, due to their therapeutic use, therapeutic index, pharmacokinetic properties, potential for excipient interactions, and performance in reported BE/bioavailability (BA) studies, provided: (a) test and comparator contain the same diclofenac salt; (b) the dosage form of the test and comparator is identical; (c) the test product contains only excipients present in diclofenac drug products approved in ICH or associated countries in the same dosage form, for instance as presented in this paper; (d) test drug product and comparator dissolve 85% in 30 min or less in 900 mL buffer pH 6.8, using the paddle apparatus at 75 rpm or the basket apparatus at 100 rpm; and (e) test product and comparator show dissolution profile similarity in pH 1.2, 4.5, and 6.8.

  7. Antagonism of the Sodium-Potassium ATPase Impairs Chikungunya Virus Infection

    Directory of Open Access Journals (Sweden)

    Alison W. Ashbrook

    2016-05-01

    Full Text Available Chikungunya virus (CHIKV is a reemerging alphavirus that has caused epidemics of fever, arthralgia, and rash worldwide. There are currently no licensed vaccines or antiviral therapies available for the prevention or treatment of CHIKV disease. We conducted a high-throughput, chemical compound screen that identified digoxin, a cardiac glycoside that blocks the sodium-potassium ATPase, as a potent inhibitor of CHIKV infection. Treatment of human cells with digoxin or a related cardiac glycoside, ouabain, resulted in a dose-dependent decrease in infection by CHIKV. Inhibition by digoxin was cell type-specific, as digoxin treatment of either murine or mosquito cells did not diminish CHIKV infection. Digoxin displayed antiviral activity against other alphaviruses, including Ross River virus and Sindbis virus, as well as mammalian reovirus and vesicular stomatitis virus. The digoxin-mediated block to CHIKV and reovirus infection occurred at one or more postentry steps, as digoxin inhibition was not bypassed by fusion of CHIKV at the plasma membrane or infection with cell surface-penetrating reovirus entry intermediates. Selection of digoxin-resistant CHIKV variants identified multiple mutations in the nonstructural proteins required for replication complex formation and synthesis of viral RNA. These data suggest a role for the sodium-potassium ATPase in promoting postentry steps of CHIKV replication and provide rationale for modulation of this pathway as a broad-spectrum antiviral strategy.

  8. Synthesis of potassium sodium niobate powders using an EDTA/citrate complexing sol-gel method

    Institute of Scientific and Technical Information of China (English)

    Yang Cao; Kongjun Zhu; Hongjuan Zheng; Jinhao Qiu; Honghui Gu

    2012-01-01

    Potassium sodium niobate (KNN) powders were synthesized by a modified sol-gel method,using as starting chemicals potassium carbonate,sodium carbonate,and niobium hydroxide,and,as esterification and chelating agents,respectively,ethylene glycol (EG) and ethylene diamine tetraacetic acid (EDTA)/citrate.The effects of citric acid (CA),EG,and EDTA on the stability of the precursor sol were systemically investigated.The powders and gels were characterized by X-ray diffraction,scanning electron microscopy,Fourier transform infrared spectroscopy,and thermogravimetric analysis-differential scanning calorimetry (TGA-DSC).The results indicated that a stable precursor sol was formed when n(CA)∶n(Mn+)=3∶1,n(EDTA)∶n(NH4OH) =1∶3.5,and n(CA)∶n(EG) =1∶2.The xerogel was calcined at 500-950 ℃ to prepare the KNN powder.Pure KNN perovskite phase with a cube-like structure was synthesized at 850 ℃ from the precursor sol for a K/Na molar ratio of 1.2.The formation mechanism of the KNN perovskite phase was also discussed.

  9. Sodium-potassium balance in the regulation of high blood pressure

    Directory of Open Access Journals (Sweden)

    Luis Hernán Zárate Méndez

    2012-02-01

    Full Text Available The World Health Organization considers essential hypertension as a primary cause of death. Twenty-five percent of the population over 15 has high blood pressure (HBP, equivalent to a billion people. It has been predicted that this group will increase by 60%, lineal with age increase in the overall population. Unfortunately, detection, treatment and effective control of HBP, are deficient both in Chile and in the rest of the world, making it an unresolved health problem demanding urgent attention. The recently conducted Chilean National Health Survey (2009-2010 revealed a 26.9% prevalence of this condition in the population, sixty-five percent of individuals are aware of their condition, 37.6% are in treatment and only 16,49% are effectively controlled. Furthermore, the survey reveals unhealthy life-style markers, which explains the epidemic that besets the country as there are multiple risk factors at stake. This review focuses mainly on the importance of the sodium-potassium relationship in the regulation of high blood pressure. It must be pointed out that all of the studies underscore the importance of sodium in the genesis of hypertension because of its effects of blood pressure, especially in sensitive individuals, while little attention has been given to the manifold beneficial actions of potassium in the regulation of blood pressure.

  10. The Effect of Sodium and Potassium in the Low Sodium Salt%低钠盐暨钠、钾的作用

    Institute of Scientific and Technical Information of China (English)

    石昌来; 魏峰

    2014-01-01

    Sodium and potassium play important physiological roles in the human body, and it is harmful to humans when they are in excessive intake or deficiency. This paper introduces the role of the sodium and potassium in detail and meanwhile, it also focus on introducing the significance of taking low sodium salt and the scientific taking methods and the suitable crowd for the pubcility and promotion of the low sodium salt.%钠、钾在人体中具有重要的生理功能,在过量和缺乏时都会对人体产生危害。本文详述了钠、钾的作用,同时还重点介绍了使用低钠盐的意义、科学的使用方法及适宜人群,以便于低钠盐的宣传和推广。

  11. Urinary and dietary sodium and potassium associated with blood pressure control in treated hypertensive kidney transplant recipients: an observational study

    Directory of Open Access Journals (Sweden)

    Saint-Remy Annie

    2012-09-01

    Full Text Available Abstract Background In kidney transplant (Kt recipients , hypertension is a major risk for cardiovascular complications but also for graft failure. Blood pressure (BP control is therefore mandatory. Office BP (OBP remains frequently used for clinical decisions, however home BP (HBP have brought a significant improvement in the BP control. Sodium is a modifiable risk factor, many studies accounted for a decrease of BP with a sodium restricted diet. Increased potassium intake has been also recommended in hypertension management. Using an agreement between office and home BP, the present study investigated the relations between the BP control in Kt recipients and their urinary excretion and dietary consumption of sodium and potassium. Methods The BP control defined by OBP 30. Results Using an agreement between OBP and HBP, we identified controlled (21% and uncontrolled recipients (49%. Major confounding effects susceptible to interfere with the BP regulation did not differ between groups, the amounts of sodium excretion were similar (154 ± 93 vs 162 ± 88 mmol/24 h but uncontrolled patients excreted less potassium (68 ± 14 vs 54 ± 20 mmol/24 h; P = 0.029 and had significantly lower potassium intakes (3279 ± 753 vs 2208 ± 720 mg/24 h; P = 0.009, associated with a higher urinary Na+/K + ratio. Systolic HBP was inversely and significantly correlated to urinary potassium (r = −0.48; P = 0.002, a positive but non significant relation was observed with urinary sodium (r = 0,30;P = 0.074. Conclusions Half of the treated hypertensive Kt recipients remained uncontrolled in office and at home. Restoring a well-balanced sodium/potassium ratio intakes could be a non pharmacological opportunity to improve blood pressure control.

  12. High-Spectral Resolution, Ground-Based Observations of the Lunar Sodium and Potassium Exosphere During the LADEE Mission.

    Science.gov (United States)

    Kuruppuaratchi, D. C. P.; Oliversen, R. J.; Mierkiewicz, E. J.; Derr, N. J.; Freer, C. W.; Gallant, M. A.; Gardner, D. D.; Lupie, O. L.; Spalsbury, L. C.; Wilson, M. L.

    2014-12-01

    We apply high resolution spectroscopy to investigate the lunar exosphere by measuring sodium and potassium spectral line profiles to determine the variations in exospheric effective temperatures and velocities. Observations were made at the National Solar Observatory McMath-Pierce Telescope concurrent with the Lunar Atmosphere and Dust Environment Explorer (LADEE) science phase. We used a dual-etalon Fabry-Perot spectrometer with a resolving power of 200,000 to measure the line widths and radial velocity Doppler shifts of the sodium D2 (5889.951 Å) and potassium D1 (7698.965 Å) emission lines. Data were taken during the full moon periods from November 2013 through May 2014 with the exception of March 2014. The instrument's Field of View (FOV) of 3 arcmin (~360 km) was positioned at several locations, centered at 1.5 arcmin, off the East and West limbs. The deconvolved line widths indicate sodium temperatures pre- and post- magnetotail passage are on the order of 1600 K while temperatures during passage through the magnetotail are on the order of a several thousand Kelvin. Unlike sodium, the potassium deconvolved line widths indicate pre-magnetotail passage several hundred degrees hotter than the post-magnetotail passage temperatures. Additionally, both sodium and potassium intensities were brighter after magnetotail passage than before. This work was partially supported by the NASA Planetary Astronomy programs, NNX11AE38G and NNX13AL30G.

  13. Effect of changes in dietary sodium and potassium on blood pressure and cellular electrolyte handling in young normotensive subjects.

    Science.gov (United States)

    Weissberg, P L; West, M J; Kendall, M J; Ingram, M; Woods, K L

    1985-10-01

    In a study on 22 normotensive male subjects, a change in dietary sodium intake from 29.6 +/- 6.0 to 332.5 +/- 13.9 mmol/day (mean +/- s.e.m.), over 7 days, was associated with a significant rise in supine and standing systolic blood pressure and a fall in sodium pump activity. Intracellular sodium remained constant, while intracellular potassium fell. These changes appeared to be reversed by the addition of potassium (96 mmol/day) to the high sodium diet. The 12 subjects with a family history of essential hypertension, as determined by measurement of parental blood pressure, did not differ in their response from those whose parents were normotensive.

  14. Syntheses and structures of dimeric sodium and potassium complexes of 2,6-diisopropyl-anilidophosphine borane ligand

    Indian Academy of Sciences (India)

    Kishor Naktode; Jayeeta Bhattacharjee; Anirban Chakrabarti; Tarun K Panda

    2015-02-01

    We report here the syntheses and structural studies of dimeric sodium and potassium complexes of composition [Na(THF)2{Ph2P(BH3)N(2,6-iPr2C6H6)}]2 (2) and [K(THF)2{Ph2P(BH3)N(2,6-iPr2C6H6)}]2(3). The sodium complex 2 was readily prepared by the reaction of sodium bis(trimethylsilyl)amide with 2,6-diisopropylanilidophosphine-borane ligand [2,6-iPr2C6H3NHP(BH3)Ph2] (1-H) at ambient temperature. The potassium complex 3 was prepared by two synthetic routes: in the first method, the ligand 1-H was made to react with potassium hydride at room temperature to afford the corresponding potassium complex. The potassium bis(trimethylsilyl)amides were made to react with protic ligand 1-H in the second method to eliminate the volatile bis(trimethyl)silyl amine. Solid-state structures of both the new complexes were established by single crystal X-ray diffraction analysis. In the molecular structures of complexes 2, the sodium metal is coordinated by the anilido nitrogen (1) and borane group (1) attached to the phosphorus atom of ligand 1. In contrast, for compound 2, ligand 1 displays 6-arene interaction from 2,6-diisopopylphenyl ring with potassium atom along with 3 interaction of BH3 group due to larger ionic radius of potassium ion.

  15. Aging-associated changes in motor axon voltage-gated Na(+) channel function in mice

    DEFF Research Database (Denmark)

    Moldovan, Mihai; Rosberg, Mette Romer; Alvarez, Susana

    2016-01-01

    Accumulating myelin abnormalities and conduction slowing occur in peripheral nerves during aging. In mice deficient of myelin protein P0, severe peripheral nervous system myelin damage is associated with ectopic expression of Nav1.8 voltage-gated Na(+) channels on motor axons aggravating...... the functional impairment. The aim of the present study was to investigate the effect of regular aging on motor axon function with particular emphasis on Nav1.8. We compared tibial nerve conduction and excitability measures by threshold tracking in 12 months (mature) and 20 months (aged) wild-type (WT) mice....... With aging, deviations during threshold electrotonus were attenuated and the resting current-threshold slope and early refractoriness were increased. Modeling indicated that, in addition to changes in passive membrane properties, motor fibers in aged WT mice were depolarized. An increased Nav1.8 isoform...

  16. Two-pore channels (TPCs): Novel voltage-gated ion channels with pleiotropic functions.

    Science.gov (United States)

    Feijóo-Bandín, Sandra; García-Vence, María; García-Rúa, Vanessa; Roselló-Lletí, Esther; Portolés, Manuel; Rivera, Miguel; González-Juanatey, José Ramón; Lago, Francisca

    2017-01-02

    Two-pore channels (TPC1-3) comprise a subfamily of the eukaryotic voltage-gated ion channels (VGICs) superfamily that are mainly expressed in acidic stores in plants and animals. TPCS are widespread across the animal kingdom, with primates, mice and rats lacking TPC3, and mainly act as Ca(+) and Na(+) channels, although it was also suggested that they could be permeable to other ions. Nowadays, TPCs have been related to the development of different diseases, including Parkinson´s disease, obesity or myocardial ischemia. Due to this, their study has raised the interest of the scientific community to try to understand their mechanism of action in order to be able to develop an efficient drug that could regulate TPCs activity. In this review, we will provide an updated view regarding TPCs structure, function and activation, as well as their role in different pathophysiological processes.

  17. Voltage-gated calcium channel subunits from platyhelminths: Potential role in praziquantel action✩

    Science.gov (United States)

    Jeziorski, Michael C.; Greenberg, Robert M.

    2013-01-01

    Voltage-gated calcium (Ca2+) channels provide the pathway for Ca2+ influxes that underlie Ca2+-dependent responses in muscles, nerves and other excitable cells. They are also targets of a wide variety of drugs and toxins. Ca2+ channels are multisubunit protein complexes consisting of a pore-forming α1 subunit and other modulatory subunits, including the β subunit. Here, we review the structure and function of schistosome Ca2+ channel subunits, with particular emphasis on variant Ca2+ channel β subunits (Cavβvar) found in these parasites. In particular, we examine the role these β subunits may play in the action of praziquantel, the current drug of choice against schistosomiasis. We also present evidence that Cavβvar homologs are found in other praziquantel-sensitive platyhelminths such as the pork tapeworm, Taenia solium, and that these variant β subunits may thus represent a platyhelminth-specific gene family. PMID:16545816

  18. Regulation of KCNQ/Kv7 family voltage-gated K(+) channels by lipids.

    Science.gov (United States)

    Taylor, Keenan C; Sanders, Charles R

    2017-04-01

    Many years of studies have established that lipids can impact membrane protein structure and function through bulk membrane effects, by direct but transient annular interactions with the bilayer-exposed surface of protein transmembrane domains, and by specific binding to protein sites. Here, we focus on how phosphatidylinositol 4,5-bisphosphate (PIP2) and polyunsaturated fatty acids (PUFAs) impact ion channel function and how the structural details of the interactions of these lipids with ion channels are beginning to emerge. We focus on the Kv7 (KCNQ) subfamily of voltage-gated K(+) channels, which are regulated by both PIP2 and PUFAs and play a variety of important roles in human health and disease. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider.

  19. Hydrophobic plug functions as a gate in voltage-gated proton channels.

    Science.gov (United States)

    Chamberlin, Adam; Qiu, Feng; Rebolledo, Santiago; Wang, Yibo; Noskov, Sergei Y; Larsson, H Peter

    2014-01-14

    Voltage-gated proton (Hv1) channels play important roles in the respiratory burst, in pH regulation, in spermatozoa, in apoptosis, and in cancer metastasis. Unlike other voltage-gated cation channels, the Hv1 channel lacks a centrally located pore formed by the assembly of subunits. Instead, the proton permeation pathway in the Hv1 channel is within the voltage-sensing domain of each subunit. The gating mechanism of this pathway is still unclear. Mutagenic and fluorescence studies suggest that the fourth transmembrane (TM) segment (S4) functions as a voltage sensor and that there is an outward movement of S4 during channel activation. Using thermodynamic mutant cycle analysis, we find that the conserved positively charged residues in S4 are stabilized by countercharges in the other TM segments both in the closed and open states. We constructed models of both the closed and open states of Hv1 channels that are consistent with the mutant cycle analysis. These structural models suggest that electrostatic interactions between TM segments in the closed state pull hydrophobic residues together to form a hydrophobic plug in the center of the voltage-sensing domain. Outward S4 movement during channel activation induces conformational changes that remove this hydrophobic plug and instead insert protonatable residues in the center of the channel that, together with water molecules, can form a hydrogen bond chain across the channel for proton permeation. This suggests that salt bridge networks and the hydrophobic plug function as the gate in Hv1 channels and that outward movement of S4 leads to the opening of this gate.

  20. Molecular and functional characterization of the voltage-gated proton channel in zebrafish neutrophils.

    Science.gov (United States)

    Ratanayotha, Adisorn; Kawai, Takafumi; Higashijima, Shin-Ichi; Okamura, Yasushi

    2017-08-01

    Voltage-gated proton channels (Hv1/VSOP) are expressed in various cells types, including phagocytes, and are involved in diverse physiological processes. Although hvcn1, the gene encoding Hv1, has been identified across a wide range of species, most of the knowledge about its physiological function and expression profile is limited to mammals. In this study, we investigated the basic properties of DrHv1, the Hv1 ortholog in zebrafish (Danio rerio) which is an excellent animal model owing to the transparency, as well as its functional expression in native cells. Electrophysiological analysis using a heterologous expression system confirmed the properties of a voltage-gated proton channel are conserved in DrHv1 with differences in threshold and activation kinetics as compared to mouse (Mus musculus) Hv1 (mHv1). RT-PCR analysis revealed that hvcn1 is expressed in zebrafish neutrophils, as is the case in mammals. Subsequent electrophysiological analysis confirmed the functional expression of DrHv1 in zebrafish neutrophils, which suggests Hv1 function in phagocytes is conserved among vertebrates. We also found that DrHv1 is comparatively resistant to extracellular Zn(2+), which is a potent inhibitor of mammalian Hv1, and this phenomenon appears to reflect variation in the Zn(2+)-coordinating residue (histidine) within the extracellular linker region in mammalian Hv1. Notably, the serum Zn(2+) concentration is much higher in zebrafish than in mouse, raising the possibility that Zn(2+) sensitivity was acquired in accordance with a change in the serum Zn(2+) concentration. This study highlights the biological variation and importance of Hv1 in different animal species. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

  1. Difference of Sodium Currents between Pediatric and Adult Human Atrial Myocytes: Evidence for Developmental Changes of Sodium Channels

    Directory of Open Access Journals (Sweden)

    Benzhi Cai, Xiaoqin Mu, Dongmei Gong, Shulin Jiang, Jianping Li, Qingxin Meng, Yunlong Bai, Yanju Liu, Xinyue Wang, Xueying Tan, Baofeng Yang, Yanjie Lu

    2011-01-01

    Full Text Available Voltage-gated calcium currents and potassium currents were shown to undergo developmental changes in postnatal human and animal cardiomocytes. However, so far, there is no evidence whether sodium currents also presented the developmental changes in postnatal human atrial cells. The aim of this study was to observe age-related changes of sodium currents between pediatric and adult atrial myocytes. Human atrial myocytes were acutely isolated and the whole-cell patch clamp technique was used to record sodium currents isolated from pediatric and adult atrial cardiomocytes. The peak amplitude of sodium currents recorded in adult atrial cells was significantly larger than that in pediatric atrial myocytes. However, there was no significant difference of the activation voltage for peak sodium currents between two kinds of atrial myocytes. The time constants for the activation and inactivation of sodium currents were smaller in adult atria than pediatric atria. The further study revealed that the voltage-dependent inactivation of sodium currents were more slow in adult atrial cardiomyocytes than pediatric atrial cells. A significant difference was also observed in the recovery process of sodium channel from inactivation. In summary, a few significant differences were demonstrated in sodium currents characteristics between pediatric and adult atrial myocytes, which indicates that sodium currents in human atria also undergo developmental changes.

  2. Analgesic effect of intrathecal bumetanide is accompanied by changes in spinal sodium-potassium-chloride co-transporter 1 and potassium-chloride co-transporter 2 expression in a rat model of incisional pain

    Institute of Scientific and Technical Information of China (English)

    Yanbing He; Shiyuan Xu; Junjie Huang; Qingjuan Gong

    2014-01-01

    Accumulating evidence has demonstrated that the sodium-potassium-chloride co-transporter 1 and potassium-chloride co-transporter 2 have a role in the modulation of pain transmission at the spinal level through chloride regulation in the pain pathway and by effecting neuronal excitability and pain sensitization. The present study aimed to investigate the analgesic effect of the speciifc sodium-potassium-chloride co-transporter 1 inhibitor bumetanide, and the change in spinal sodium-potassium-chloride co-transporter 1 and potassium-chloride co-transporter 2 expression in a rat model of incisional pain. Results showed that intrathecal bumetanide could decrease cumulative pain scores, and could increase thermal and mechanical pain thresholds in a rat model of incisional pain. Sodium-potassium-chloride co-transporter 1 expression in-creased in neurons from dorsal root ganglion and the deep laminae of the ipsilateral dorsal horn following incision. By contrast, potassium-chloride co-transporter 2 expression decreased in neurons of the deep laminae from the ipsilateral dorsal horn. These ifndings suggest that spinal sodium-potassium-chloride co-transporter 1 expression was up-regulated and spinal potassi-um-chloride co-transporter 2 expression was down-regulated following incision. Intrathecal bumetanide has analgesic effects on incisional pain through inhibition of sodium-potassi-um-chloride co-transporter 1.

  3. FACTORS WHICH MODIFY THE EFFECT OF SODIUM AND POTASSIUM ON BACTERIAL CELL MEMBRANES.

    Science.gov (United States)

    HENNEMAN, D H; UMBREIT, W W

    1964-06-01

    Henneman, Dorothy H. (Rutgers, The State University, New Brunswick, N.J.), and W. W. Umbreit. Factors which modify the effect of sodium and potassium on bacterial cell membranes. J. Bacteriol. 87:1266-1273. 1964.-Suspensions of Escherichia coli B, when placed in 0.2 to 0.5 m solutions of NaCl, KCl, or LiCl, show an increased turbidity. With NaCl, this increased turbidity is stable with time; with KCl and LiCl, it is gradually lost. The stability to NaCl with time is due to substances removable from the cell by incubation in phosphate buffer; these materials exist in water washings from such phosphate-incubated cells.

  4. Diffusion of sodium, potassium, calcium, manganese, and radon in tuff and clinoptilolite under leaching

    Science.gov (United States)

    Dikii, N. P.; Dovbnya, A. N.; Lyashko, Yu. V.; Medvedev, D. V.; Medvedeva, E. P.; Uvarov, V. L.; Achkasov, K. V.

    2011-07-01

    Nuclear physics methods are used to determine the diffusion coefficients of Na, Ca, Mn, K, and 222Rn in clinoptilolite (Sokirnitsa occurrence, Ukraine) and in natural tuff (Yucca Mountain, Nevada, United States) and in tuff irradiated by γ-quanta ( E max = 23 MeV) to a dose of 107 Gy at a leaching temperature of 37°C. The diffusion coefficients of sodium and potassium in clinoptilolite are found to differ considerably: 4 × 10-17 and 2 × 10-20 m2/s, respectively. This indicates the influence of aquacomplexes on the cation transfer. The diffusion coefficient of radon in these materials is determined: in clinoptilolite it equals 2.5 × 10-12 m2/s.

  5. Surface charge induced enhanced crystallization on the piezoelectric sodium potassium niobate substrate

    Science.gov (United States)

    Dubey, Ashutosh Kumar; Yamada, Hiroaki; Kakimoto, Ken-ichi

    2013-11-01

    The present work demonstrates the influence of negatively charged surface on piezoelectric Li-modified sodium potassium niobate substrate in inducing the crystallization of KCl, NaCl and Na2SO4 ionic crystals from their respective aqueous solutions. The crystallization ability and morphology of the grown crystal were examined on unpoled, poled and poled as well heat-treated substrate surfaces. It has been observed that the crystallization process can be controlled by varying the surface charge density through the heat treatment of polarized substrate at different temperatures. Thermally stimulated depolarization current (TSDC) measurement suggested that the charge affecting the crystal growth and morphology is likely to be generated in the space charge region.

  6. Ab initio calculations of the thermodynamic parameters of lithium, sodium, and potassium oxides under pressure

    Science.gov (United States)

    Zhuravlev, Yu. N.; Korabel'nikov, D. V.; Aleinikova, M. V.

    2012-07-01

    The parameters of the equation of state and Grüneisen parameters for lithium, sodium, and potassium oxides have been calculated in the generalized gradient approximation of the density functional theory using a linear combination of atomic orbitals with the CRYSTAL09 software package. The frequencies of long-wavelength normal mode vibrations have also been calculated and the dependence of these frequencies on the pressure has been established. The Debye temperature has been determined from the elastic characteristics of the compounds. The dependences of the Debye temperature, compressibility, thermodynamic potential, entropy, specific heat, thermal expansion coefficient, and thermal conductivity coefficient on the pressure in the range from -3 to -15 GPa and on the temperature have been calculated in the quasi-harmonic Debye model. The results obtained are in satisfactory agreement with the available reference and experimental data.

  7. Theoretical study of the thermodynamic properties of lithium, sodium, and potassium nitrates

    Science.gov (United States)

    Korabel'nikov, D. V.; Zhuravlev, Yu. N.

    2013-08-01

    The thermal properties of lithium, sodium, and potassium nitrates have been studied in a gradient approximation of the density functional theory using the method of linear combination of atomic orbitals of the CRYSTAL09 program package. The long-wave frequencies and corresponding mode Grüneisen parameters are calculated. The quasi-harmonic Debye-Einstein model is used to calculate the parameters of the equation of states and also the dependences of the thermodynamic potentials, the entropy, the heat capacity, the thermal expansion coefficient, and the Grüneisen parameter on pressure and temperature. The role of external and intramolecular vibrations in the interpretation of thermodynamic properties is determined. The obtained results agree well with the available experimental data.

  8. Assembly and Thermal Hydraulic Test of a Stainless Steel Sodium-Potassium Circuit

    Science.gov (United States)

    Garber, A.; Godfroy, T.; Webster, K.

    2007-01-01

    Early Flight Fission Test Facilities (EFF-TF) team has been tasked by the NASA Marshall Space Flight Center Nuclear Systems Office to design, fabricate, and test an actively pumped alkali metal flow circuit. The system was originally built for use with lithium, but due to a shift in focus, it was redesigned for use with a eutectic mixture of sodium potassium (NaK). Basic circuit components include: reactor segment, NaK to gas heat exchanger, electromagnetic (EM) liquid metal pump, load/drain reservoir, expansion reservoir, instrumentation, and a spill reservoir. A 37-pin partial-array core (pin and flow path dimensions are the same as those in a full design) was selected for fabrication and test. This paper summarizes the first fill and checkout testing of the Stainless Steel NaK-Cooled Circuit (SNaKC).

  9. Doubts about the sodium-potassium pump are not permissible in modern bioscience.

    Science.gov (United States)

    Edelmann, L

    2005-12-16

    The sodium-potassium pump--the central molecular model of the generally accepted membrane pump theory (MPT)--is a misconception, according to the alternative association-induction hypothesis (AIH) of Gilbert Ling. With a discreet fraud coupled with the practice of appraising scientific publications and grant proposals by the peer-review system, the academic establishment--inadvertently or not--hinders a general discussion and acceptance of decisive arguments of the AIH. As a result, important discoveries over many decades, as well as new ways of basic research promising success remain largely unknown. The habit of funding safe research on ideas that have a false premise persists, and the wrong theory gets ever deeper entrenched. Science suffers.

  10. The distribution of potassium and sodium concentrations in the erythrocytes of some breeds of cattle.

    Science.gov (United States)

    Arranz, J J; Bayón, Y; Primitivo, F

    1994-01-12

    The distribution of erythrocyte potassium and sodium concentrations was studied in Sayaguesa (n = 150), Brown Swiss (n = 163) and two populations of Avileña-Negra Ibérica cattle (n = 141 and 141 respectively). No polymorphism was detected for red-cell cation content in any of the breeds investigated. Mean values of potassium concentrations varied between 21.42 and 24.92 mmol/l red cells, those of sodium contents ranging from 77.50-93.44 mmol/1. The cattle studied can thus be considered as belonging to the 'low potassium' (LK) type. Significant differences were found both in potassium and sodium concentrations between one of the populations of Avileña-Negra Ibérica and the other groups examined. Mean values of sodium levels in Brown Swiss were also significantly different from the other groups. ZUSAMMENFASSUNG: Verteilung von Kalium- und Natriumblutspiegelwerten in Erythrozyten einiger Rinderrassen Die Verteilung von Kalium- und Natriumkonzentrationen in Erythrozyten wurde in vier Gruppen untersucht: Sayaguesa (n = 150), Braunvieh (n = 163) und zwei Gruppen von Avileña-Negra Ibérica Rindern (n = 141). In keiner der untersuchten Gruppen wurde Polymorphismus für den Cationenspiegel gefunden. Mittelwerte für Kaliumkonzentration schwankten zwischen 21,4 und 24,9 mmol/l roter Zellen, die für Natriumgehalt zwischen 77,5 und 93,4 mmol/1. Die Rinder könnten daher als 'niedrigere Kalium' Type bezeichnet werden. Signifikante Unterschiede wurden sowohl für den Kalium-als auch für der Natriumspiegel zwischen den beiden Avileña-Negra Ibérica Gruppen gefunden. Die Mittelwerte für Natriumspiegel in Braunvieh waren ebenfalls significant unterscniedlich im Vergleich zu den anderen. RESUMEN: Distributión del potasio y sodio eritrocitarios en algunas razas de ganado vacuno Se estudió la distribución de las concentraciones de potasio y sodio eritrocitarios en cuatro grupos de ganado vacuno: Sayaguesa (n = 150), Pardo Alpina (n = 163) y dos poblaciones de Avile

  11. [Concentrations of calcium, magnesium, sodium and potassium in human milk and infant formulas].

    Science.gov (United States)

    Rodríguez Rodríguez, E M; Sanz Alaejos, M; Díaz Romero, C

    2002-12-01

    Concentrations of calcium, magnesium, sodium and potassium were determined in 55 samples of mature human milk from Canary women and 5 samples of powdered infant formula. According to the literature our data fell within the normal intervals described for each kind of milk. The mean concentration of Ca, Mg, Na y K of powdered infant formula was higher than those concentrations found in the human milks. Significant differences among the concentrations of Ca, Mg and Na for the milks of the considered mothers were observed. Only the Ca intakes for infants fed with human milk were lower than those requirements recommended by the Food and Nutrition Board (1989). However, the infants fed with powdered infant formula had an adequate intake of all the studied metals. A progressive decrease of the Na, K and Ca concentrations with the lactation stage was observed. Maternal age, parity and sex of the newborns did not affect the metal concentrations significantly.

  12. Raman Spectroscopy of Conformational Changes in Membrane-Bound Sodium Potassium ATPase

    DEFF Research Database (Denmark)

    Helix Nielsen, Claus; Abdali, Salim; Lundbæk, Jens August

    2007-01-01

    In this investigation we assess the potential of Raman spectroscopy as a tool for probing conformational changes in membrane-spanning proteins — in this case, the sodium potassium adenosine triphosphatase (Na+,K+-ATPase). Spectral analysis of protein-lipid complexes is complicated by the presence....... This illustrates the stabilizing role of the N-terminal domain under physiological conditions. More generally, it shows that Raman spectroscopy might be a useful tool in understanding the relationship between functional states and structural changes in membrane-bound proteins.......+,K+-ATPase stabilized by N-terminal truncation differs from that induced by Na+ binding, and that the N-terminal truncation leads to changes in protein structure that affect the average hydrophobic environment of protein Tyr, possibly reflecting changes in the hydrophobic coupling between protein and membrane...

  13. Toxicity detection of sodium nitrite, borax and aluminum potassium sulfate using electrochemical method

    Institute of Scientific and Technical Information of China (English)

    Dengbin Yu; Daming Yong; Shaojun Dong

    2013-01-01

    Based on the inhibition effect on the respiratory chain activity of microorganisms by toxicants,an electrochemical method has been developed to measure the current variation of a mediator in the presence of microorganisms contacted with a toxicant.Microelectrode arrays were adopted in this study,which can accelerate the mass transfer rate of an analyte to the electrode and also increase the total current signal,resulting in an improvement in detection sensitivity.We selected Escherichia coli as the testee and the standard glucoseglutamic acid as an exogenous material.Under oxygen restriction,the experiments in the presence of toxicant were performed at optimum conditions (solution pH 7.0,37℃ and reaction for 3 hr).The resulting solution was then separated from the suspended microorganisms and was measured by an electrochemical method,using ferricyanide as a mediator.The current signal obtained represents the re oxidation of ferrocyanide,which was transformed to inhibiting efficiency,IC50,as a quantitative measure of toxicity.The IC50 values measured were 410,570 and 830 mg/L for sodium nitrite,borax and aluminum potassium sulfate,respectively.The results show that the toxicity sequence for these three food additives is consistent with the value reported by other methods.Furthermore,the order of damage degree to the microorganism was also observed to be:sodium nitrite > borax > aluminum potassium sulfate >blank,according to the atomic force microscopy images of E.coli after being incubated for 3 hr with the toxic compound in buffer solutions.The electrochemical method is expected to be a sensitive and simple alternative to toxicity screening for chemical food additives.

  14. Dietary sodium, potassium, and alcohol: key players in the pathophysiology, prevention, and treatment of human hypertension.

    Science.gov (United States)

    Koliaki, Chrysi; Katsilambros, Nicholas

    2013-06-01

    Western industrialized societies are currently experiencing an epidemic expansion of hypertension (HTN), which extends alarmingly even to children and adolescents. HTN constitutes an independent risk factor for cardiorenal disease and represents an extremely common comorbidity of diabetes and obesity. Numerous randomized clinical trials and meta-analyses have provided robust scientific evidence that reduced dietary salt intake, increased dietary potassium intake, moderation of alcohol consumption, optimal weight maintenance, and the adoption of "heart-friendly" dietary patterns such as the Dietary Approaches to Stop Hypertension or the Mediterranean diet can effectively lower blood pressure. Interestingly, the susceptibility of blood pressure to nutritional interventions is greatly variable among individuals, depending on age, race, genetic background, and comorbidities. The purpose of this review is to provide a comprehensive overview of currently available scientific evidence in the constantly evolving field of diet and HTN, placing particular emphasis on the key role of dietary sodium, dietary potassium, and alcohol intake in the pathophysiology, prevention, and treatment of human hypertension. © 2013 International Life Sciences Institute.

  15. Synthesis, Spectroscopic Properties and Structural Characterization of Sodium Potassium Citrato Oxotungstate(VI) Dimer

    Institute of Scientific and Technical Information of China (English)

    王耿; 周朝晖; 章慧; 叶剑良; 万惠霖

    2000-01-01

    The sodium-potassium citrato oxotungstate(VI) dimer, Na4K2[W2O5-(VI) and excess potassium citrate monobasic (KH3cit) in neutral solution. The crystal data for the title compound.: monoclinic, C12H30K2Na4W2O30, Mr= 1192. 21, space groupP21/n, a=17.427(4), b=10.022(2), c=18.637(3) A, β=92.62(1)°, V=3252 (2) A3, Z=4, Dc=2. 435 g/cm3, μ(MoKa)=76.38 cm-1, F(000)=2288.The structure was refined to R= 0. 0434 for 6327 independent observed reflections with I > 3σ (I). The complex anion contains a quasi-centrosymmetric (O2W)Ob (WO2) core with a bent bridging oxo group [W-Ob-W 175.0(4)°]. Each citrate as tridentate ligand coordinates to a tungsten atom through the alkoxy, α-carboxyl, and oneβ-carboxyl group, while the other β-carboxyl group remains uncoordinated. Principal dimensions are: W-Ob 1. 883(6) A, (W=O,)av 1.715(6) A, W-O (alkoxy) 1. 959(6) A , W-O (α-carboxy) 2. 176(6) A and W-O (β-carboxy) 2.231(6) A. The tungsten atom is located in a distorted-octahedron environment.

  16. Effects of sodium and potassium supplementation on blood pressure and arterial stiffness : a fully controlled dietary intervention study

    NARCIS (Netherlands)

    Gijsbers, L.; Dower, J. I.; Mensink, M.; Siebelink, E.; Bakker, S. J. L.; Geleijnse, J. M.

    2015-01-01

    We performed a randomised, placebo-controlled, crossover study to examine the effects of sodium and potassium supplementation on blood pressure (BP) and arterial stiffness in untreated (pre) hypertensive individuals. During the study, subjects were on a fully controlled diet that was relatively low

  17. Sodium and potassium intake and risk of cardiovascular events and all-cause mortality: the Rotterdam Study

    NARCIS (Netherlands)

    Geleijnse, J.M.; Witteman, J.C.M.; Stijnen, T.; Kloos, M.W.; Hofman, A.; Grobbee, D.E.

    2007-01-01

    Background Dietary electrolytes influence blood pressure, but their effect on clinical outcomes remains to be established. We examined sodium and potassium intake in relation to cardiovascular disease (CVD) and mortality in an unselected older population. Methods A case¿cohort analysis was performed

  18. Sodium and potassium intake and risk of cardiovascular events and all-cause mortality: the Rotterdam Study

    NARCIS (Netherlands)

    Geleijnse, J.M.; Witteman, J.C.M.; Stijnen, T.; Kloos, M.W.; Hofman, A.; Grobbee, D.E.

    2007-01-01

    Background Dietary electrolytes influence blood pressure, but their effect on clinical outcomes remains to be established. We examined sodium and potassium intake in relation to cardiovascular disease (CVD) and mortality in an unselected older population. Methods A case¿cohort analysis was performed

  19. Pooled results from five validation studies of dietary self-report instruments using recovery biomarkers for potassium and sodium intake

    Science.gov (United States)

    We have pooled data from five large validation studies of dietary self-report instruments that used recovery biomarkers as referents to assess food frequency questionnaires (FFQs) and 24-hour recalls. We reported on total potassium and sodium intakes, their densities, and their ratio. Results were...

  20. 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 i...

  1. CONTROL AND CANCEROUS TISSUES OF HUMAN STOMACH, SMALL INTESTINE AND LARGE INTESTINE - THE AVERAGE CONTENT OF SODIUM AND POTASSIUM

    Directory of Open Access Journals (Sweden)

    Marta Głogowska

    2015-02-01

    Full Text Available Sodium and potassium regulate the total amount of water in the body and the transmission of sodium into and out of individual cells also plays a role in critical body functions. The movement of sodium is critical in generation of these electrical signals. Research was conducted on samples taken from women and men aged 20-90 years, derived from the stomach, small intestine and large intestine. Samples were dried at 80ºC for 24 hours, and then increased temperature to 105ºC and dried for seven days until dry mass was obtained. All dry material of each sample was weighted and placed in a separate mineralization tubes and mixed with 1 cm3 of 65% HNO3 and heated at 105°C for 120 minutes in a thermostat-controlled digestion block, VELP Scientifica DK 20. Metals such as sodium and potassium were detected using FAAS method. The average content of sodium in patients diagnosed with stomach cancer is lower, than in healthy person. Indicate higher mean content of sodium in the control tissues of stomach (2151,730 μg•g-1d.m., compared to a sodium content in tissues adjacent to the tumor (1813,958 μg•g-1d.m. and tumor tissues (2029,442 μg•g-1d.m.. In the case of colon, control tissues have lower average content of sodium (2160,886 μg•g-1d.m., than the tissues surrounding the tumor (3325,963 μg•g-1d.m. and tumor tissues (3037,121 μg•g-1d.m.. The potassium level is higher in the control tissues of stomach (1428,993 μg•g-1d.m., than in the tissues adjacent to the tumor (1091,544 μg•g-1d.m. and tumor tissues (1220,471 μg•g-1d.m.. In the large intestine higher average content of potassium is characterized by tumor tissues (2307,234 μg•g-1d.m. and tissues adjacent to the tumor (1712,779 μg•g-1d.m., than control tissue (1389,703 μg•g-1d.m.. Comparing this relationship with data on potassium channels, it can be assumed that in the some case of malignant transformation in the colon, potassium channels also play a big role.

  2. Relationship of nutrition knowledge and self-reported dietary behaviors with urinary excretion of sodium and potassium: comparison between dietitians and nondietitians.

    Science.gov (United States)

    Sugimoto, Minami; Asakura, Keiko; Masayasu, Shizuko; Sasaki, Satoshi

    2016-05-01

    The effectiveness of better nutrition knowledge and dietary behavior on healthier dietary intake is still controversial. We hypothesized that nutritional knowledge and dietary behavior are associated with sodium and potassium intake in adult women. A cross-sectional study was conducted at welfare facilities located in 20 areas of Japan. Ninety-nine female dietitians and 117 nondietitians aged 20 to 69 years participated. Sodium and potassium intake were assessed with two 24-hour urine collections and 4-day semiweighed diet records. Nutritional knowledge and dietary behavior were accessed with 3 questionnaires. Analysis of covariance was performed to compare sodium and potassium excretion and selected nutrition and food intake between dietitians and nondietitians. After adjustment for age and smoking habit, sodium and potassium excretion did not significantly differ between the 2 groups (3857 vs 3959 mg/d, P = .57, and 2016 vs 1886 mg/d, P = .10, respectively). Sodium/potassium ratio was significantly lower in the dietitians (P = .044). The dietitians used food labels for sodium contents more often than the nondietitians and consumed more fruits and vegetables (P = .048 and P sodium or potassium excretion but were moderately associated with sodium/potassium ratio.

  3. Pretreatment of formula with sodium polystyrene sulfonate to reduce dietary potassium intake.

    Science.gov (United States)

    Bunchman, T E; Wood, E G; Schenck, M H; Weaver, K A; Klein, B L; Lynch, R E

    1991-01-01

    Sodium polystyrene sulfonate (SPSS) is commonly administered for the acute and chronic treatment of hyperkalemia. Its oral intake is complicated by poor compliance due to multifaceted reasons. We therefore analyzed a method of reducing potassium (K) in formula by pretreatment with SPSS. If effective, this would bypass complications of enterally administered SPSS and provide low-K formula. Thirteen formulas and nutritional supplements were pretreated with SPSS to determine if one could bind K and provide formulas with decreased K contents. Using an SPSS concentration of 1 g/l mEq K in the formula, 62 +/- 2.6% (P less than 0.01, mean +/- SEM) of the K was removed in 30 min, while the sodium (Na) concentration was increased by 234 +/- 37% (P less than 0.01). Analysis suggests that the disproportionate increase in Na is due to exchange for calcium (Ca) and magnesium (Mg), interaction with proteins, and Na suspended with SPSS in the formula. Thus, SPSS pretreatment of formula is an effective method of making low-K formula, but the increase in Na exceeds the K reduction. Attention to possible complications of increased Na intake as well as decreased Ca and Mg intake is warranted.

  4. Beyond Sodium, Phosphate and Potassium: Potential Dietary Interventions in Kidney Disease.

    Science.gov (United States)

    Kelly, Jaimon T; Rossi, Megan; Johnson, David W; Campbell, Katrina L

    2017-05-01

    People with kidney disease are advised to restrict individual nutrients, such as sodium, potassium, and phosphate, in line with current best practice guidelines. However, there is limited evidence to support the efficacy of single nutrient strategies, and compliance remains a challenge for clinicians to overcome. Many factors contribute to poor compliance with dietary prescriptions, including conflicting priorities for single nutrient restriction, the arduous self-monitoring required, and the health-related knock-on effects resulting from targeting these nutrients in isolation. This paper reviews the evidence base for the overall pattern of eating as a potential tool to deliver a diet intervention in which all the nutrients and foods work cumulatively and synergistically to improve clinical outcomes. These interventions may assist in kidney disease management and overcome these innate challenges that single nutrient interventions possess. Healthy dietary patterns are typically plant-based and lower in sodium and animal proteins. These patterns may have numerous mechanistic benefits for cardiovascular health in kidney disease, most notably through the increase in fruit, vegetables, and plant-based protein, as well as improved gut health through the increase in dietary fiber. The evidence to date on optimal dietary patterns points toward use of a predominantly plant-based diet, and suggests its adoption may improve clinical outcomes in dialysis patients. However, clinical trials are needed to determine whether these diet interventions are feasible, safe, and effective in this patient population. © 2017 Wiley Periodicals, Inc.

  5. Chemiluminescence behavior of sodium hydrogen carbonate in the potassium permanganate-hydrogen peroxide reaction

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Chemiluminescence (CL) phenomenon of hydrogen peroxide with potassium permanganate in the presence of sodium hydrogen carbonate was reported.Effects of the surfactant on the CL system were investigated.Nonionic surfactants could effectively increase the CL signal.Radical scavengers and organic reagents such as nitro blue tetrazolium chloride (NBT),cytochrome c,sodium azide,ascorbic acid,thiourea,tert-butanol and dimethyl sulphoxide were used to study the emitting species.CL emission spectrum was recorded and the results showed that the maximal emission wavelengths of NaHCO3-H2O2-KMnO4 system were 440 and 634 nm.The mechanism was discussed based on electron spin resonance (ESR) spectra,fluorescence spectra and UV-vis absorption spectra.The addition of rhodamine B or uranine into this CL system enhanced the CL signal.It was due to part of the energy transfer from singlet oxygen and excited triplet dimers of two CO2 molecules to rhodamine B or uranine.The CL could be induced by excited rhodamine B or uranine.

  6. Effect of Salinity Stress on Chloride, Sodium, Potassium, Chlorophyll and Soluble Sugars Content in Citrus Genotypes

    Directory of Open Access Journals (Sweden)

    B. Golein

    2013-06-01

    Full Text Available To determine salinity-tolerant genotypes among the citrus germplasm present in Kotra collection, a greenhouse experiment was carried out as factorial, completely randomized design with three replications, at four levels of NaCl (0, 2, 4 and 6 dS/m and 10 unknown genotypes, for 16 weeks. Cleopatra mandarin and Swingle Citromelo, as tolerant (control and sensitive cultivars, respectively, were used. After 6 months of seedlings growth in pots containing equal amounts of perlite, sand and garden soil, the irrigation water, containing different concentrations of sodium chloride was applied every 5 days (considering climatic conditions and plant requirements. At the end of the experiment, concentration of chloride and sodium in leaf and root, chlorophyll a and b and total chlorophyll content and concentration of soluble sugars in leaves were measured. Results showed that salinity increased chloride and sodium concentration in root and leaf. The lowest level of accumulation of chloride in leaf was related to genotype g9 and Cleopatra mandarin. Potassium concentration and chlorophyll a and b content decreased with salinity, while the interaction of genotype and salinity did not show significant difference in these characteristics. Genotypes were different in content of soluble sugars, in response to salinity. Based on the results, genotype g9, because of the lowest increase in leaf chloride content and also the lower decrease in total chlorophyll content, in comparison with most of the studied genotypes, can be considered as a tolerant genotype to salinity stress, and could be utilized in breeding programs of rootstocks.

  7. Whole-cell recordings of calcium and potassium currents in acutely isolated smooth muscle cells

    Institute of Scientific and Technical Information of China (English)

    Qing Cai; Zhong-Liang Zhu; Xiao-Li Fan

    2006-01-01

    AIM: To record calcium and potassium currents in acutely isolated smooth muscle cells of mesenteric arterial branches in rats.METHODS: Smooth muscle cells were freshly isolated by collagenase digest and mechanical trituration with polished pipettes. Patch clamp technique in whole-cell mode was employed to record calcium and potassium currents.RESULTS: The procedure dissociated smooth muscle cells without impairing the electrophysiological characteristics of the cells. The voltage-gated Ca2+ and potassium currents were successfully recorded using whole-cell patch clamp configuration.CONCLUSION: The method dissociates smooth muscle cells from rat mesenteric arterial branches. Voltage-gated channel currents can be recorded in this preparation.

  8. The feasibility of meeting the WHO guidelines for sodium and potassium: a cross-national comparison study

    Science.gov (United States)

    Drewnowski, Adam; Maillot, Matthieu; Mendoza, Alfonso; Monsivais, Pablo

    2015-01-01

    Objective To determine joint compliance with the WHO sodium–potassium goals in four different countries, using data from nationally representative dietary surveys. Setting Compared to national and international recommendations and guidelines, the world's population consumes too much sodium and inadequate amounts of potassium. The WHO recommends consuming less than 2000 mg sodium (86 mmol) and at least 3510 mg potassium (90 mmol) per person per day. Participants Dietary surveillance data were obtained from the National Health and Nutrition Examination Survey (NHANES 2007–2010) for the USA; the Encuesta Nacional de Salud y Nutrición 2012 for Mexico; the Individual and National Study on Food Consumption (INCA2) for France; and the National Diet and Nutrition Survey (NDNS) for the UK. Primary outcome measures We estimated the proportion of adults meeting the joint WHO sodium–potassium goals in the USA, the UK, France and Mexico. Results The upper bounds of joint compliance with the WHO sodium–potassium goals were estimated at 0.3% in the USA, 0.15% in Mexico, 0.5% in France and 0.1% in the UK. Conclusions Given prevailing food consumption patterns and the current food supply, implementing WHO guidelines will be an enormous challenge for global public health. PMID:25795689

  9. Early infantile epileptic encephalopathy associated with a high voltage gated calcium channelopathy.

    Science.gov (United States)

    Edvardson, Simon; Oz, Shimrit; Abulhijaa, Fida Aziz; Taher, Flora Barghouthi; Shaag, Avraham; Zenvirt, Shamir; Dascal, Nathan; Elpeleg, Orly

    2013-02-01

    Early infantile epileptic encephalopathies usually manifest as severely impaired cognitive and motor development and often result in a devastating permanent global developmental delay and intellectual disability. A large set of genes has been implicated in the aetiology of this heterogeneous group of disorders. Among these, the ion channelopathies play a prominent role. In this study, we investigated the genetic cause of infantile epilepsy in three affected siblings. Homozygosity mapping in DNA samples followed by exome analysis in one of the patients resulted in the identification of a homozygous mutation, p.L1040P, in the CACNA2D2 gene. This gene encodes the auxiliary α(2)δ2 subunit of high voltage gated calcium channels. The expression of the α(2)δ2-L1040P mutant instead of α(2)δ2 wild-type (WT) in Xenopus laevis oocytes was associated with a notable reduction of current density of both N (Ca(V)2.2) and L (Ca(V)1.2) type calcium channels. Western blot and confocal imaging analyses showed that the α(2)δ2-L1040P mutant was synthesised normally in oocyte but only the α(2)δ2-WT, and not the α(2)δ2-L1040P mutant, increased the expression of α(1B), the pore forming subunit of Ca(V)2.2, at the plasma membrane. The expression of α(2)δ2-WT with Ca(V)2.2 increased the surface expression of α(1B) 2.5-3 fold and accelerated current inactivation, whereas α(2)δ2-L1040P did not produce any of these effects. L1040P mutation in the CACNA2D2 gene is associated with dysfunction of α(2)δ2, resulting in reduced current density and slow inactivation in neuronal calcium channels. The prolonged calcium entry during depolarisation and changes in surface density of calcium channels caused by deficient α(2)δ2 could underlie the epileptic phenotype. This is the first report of an encephalopathy caused by mutation in the auxiliary α(2)δ subunit of high voltage gated calcium channels in humans, illustrating the importance of this subunit in normal physiology of the

  10. Effects of high dietary sodium chloride content on performance and sodium and potassium balance in growing pigs.

    Science.gov (United States)

    Chittavong, Malavanh; Jansson, Anna; Lindberg, Jan Erik

    2013-10-01

    Thirty castrated male Moo Lath pigs (6-8 weeks of age) were used in a 15-week growth trial to study the effect of high dietary sodium chloride (NaCl) content on feed and water intake, performance, sodium (Na) and potassium (K) balance, and plasma aldosterone concentration. The pigs were randomly allocated (ten per treatment) to diets containing 0.24 % Na (Na0.24), 0.28 % Na (Na0.28), and 0.32 % Na (Na0.32) per kg diet. Feed and water was provided ad libitum, and water consumption, feed offered, and feed residues were recorded daily. Every third week, the pigs were weighed, blood samples were collected, and a 3-day total collection of urine and feces was performed. Water intake was higher (P = 0.001) in pigs fed with diets Na0.28 (3.7 L/day) and Na0.32 (3.9 L/day) than in pigs fed with diet Na0.24 (3.4 L/day), and dry matter (DM) intake was higher on diet Na0.32 (P = 0.041) than on the other diets. The average daily body weight (BW) gain was higher on diet Na0.32 than on the other diets (P = 0.031). The feed conversion ratio (in kilogram feed DM to kilogram BW gain) was 4.6, 4.6, and 4.1 on treatments Na0.24, Na0.28, and Na0.32, respectively (P = 0.14). The highest Na balance was observed on diet Na0.32 followed by diets Na0.28 and Na0.24 (P < 0.001), while there was no treatment-related pattern for the K balance. The Na/K ratio in feces and urine increased (P < 0.001), and the K/Na ratio in feces (P < 0.001) decreased with increasing Na content in the diet. Plasma aldosterone concentration decreased (P < 0.001) with increasing dietary content of Na. These results indicate that high NaCl intake and free access to water will increase Na balance but do not negatively influence feed intake and performance of growing local pigs.

  11. Modification of sodium and potassium channel kinetics by diethyl ether and studies on sodium channel inactivation in the crayfish giant axon membrane

    Energy Technology Data Exchange (ETDEWEB)

    Bean, Bruce Palmer

    1979-01-01

    The effects of ether and halothane on membrane currents in the voltage clamped crayfish giant axon membrane were investigated. Concentrations of ether up to 300 mM and of halothane up to 32 mM had no effect on resting potential or leakage conductance. Ether and halothane reduced the size of sodium currents without changing the voltage dependence of the peak currents or their reversal potential. Ether and halothane also produced a reversible, dose-dependent speeding of sodium current decay at all membrane potentials. Ether reduced the time constants for inactivation, and also shifted the midpoint of the steady-state inactivation curve in the hyperpolarizing direction. Potassium currents were smaller with ether present, with no change in the voltage dependence of steady-state currents. The activation of potassium channels was faster with ether present. There was no apparent change in the capacitance of the crayfish giant axon membrane with ether concentrations of up to 100 mM. Experiments on sodium channel inactivation kinetics were performed using 4-aminopyridine to block potassium currents. Sodium currents decayed with a time course generally fit well by a single exponential. The time constant of decay was a steep function of voltage, especially in the negative resistance region of the peak current vs voltage relation.The time course of inactivation was very similar to that of the decay of the current at the same potential. The measurement of steady-state inactivation curves with different test pulses showed no shifts along the voltage asix. The voltage-dependence of the integral of sodium conductance was measured to test models of sodium channel inactivation in which channels must open before inactivating; the results appear inconsistent with some of the simplest cases of such models.

  12. Alkali activated fly ash binders. A comparative study between sodium and potassium activators

    Directory of Open Access Journals (Sweden)

    Criado, M.

    2006-03-01

    Full Text Available This paper shows the effect of the nature of some alkaline activators in the microstructural development of thermal-alkali activated f/y ash systems. The alkaline compounds employed in this investigation were: NaOH, KOH, Na2C03, K2C03, sodium silicate and potassium silicate. Results confirm that the main reaction product of the activation process (throughout the studied systems is the amorphous alkaline aluminosilicate gel with a three-dimensional structure already observed in earlier research. It has been proved that the type of anion and cation involved in the activation reaction of the ashes not only affects the microstructural development of the systems but the Si/Al ratio of that prezeolitic gel too. For example, in the presence of soluble silicate ions the content of Si in the final structure is notably increased (Si/Al =2.7-3.0, however carbonate ions play a different role since the formation of Sodium or Potassium carbonate/bicarbonate acidifies the system and consequently the reaction rate is considerably slowed. Finally it is evident that; when all experimental conditions are equal, sodium has a greater capacity than potassium to accelerate the setting and hardening reactions of fly ash and also to stimulate the growth of certain zeolitic crystals (reaction by-products. In general it can be affirmed that OH- ion acts as a reaction catalyst; and the alkaline metal (M+ acts as a structure-forming element.Este trabajo muestra el efecto de la naturaleza del activador alcalino en el desarrollo microestructural de sistemas de ceniza volante, activados térmica y alcalinamente. Los componentes alcalinos empleados en esta investigación fueron: NaOH, KOH, Na2C03, K2C03, silicato sódico y silicato potásico. Los resultados obtenidos confirman que el principal producto de reacción del proceso de activación (a través de los sistemas estudiados es un gel de aluminosilicato alcalino amorfo con estructura tridimensional ya observada en trabajos

  13. Ligustrazine inhibits high voltage-gated Ca2+ and TTX-resistant Na+ channels of primary sensory neuron and thermal nociception in the rat:a study on peripheral mechanism

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Objective Ligustrazine, also named as tetramethylpyrazine, is a compound purified from Ligusticum chuanxiong hort and has ever been testified to be a calcium antagonist. The present investigation was to determine the antinociceptive effect of ligustrazine and, if any, the peripheral ionic mechanism involved. Methods Paw withdrawal Latency(PWL) to noxious heating was measured in vivo and whole-cell patch recording was performed on small dorsal root ganglion (DRG) neurons. Results Intraplantar injection of ligustrazine (0.5 mg in 25 μl) significantly prolonged the withdrawal latency of ipsilateral hindpaw to noxious heating in the rat. Ligustrazine not only reversibly inhibited high-voltage gated calcium current of dorsal root ganglion (DRG) neuron in dose-dependent manner with IC50 of 1.89 mmol/L, but also decreased tetrodotoxin (TTX) -resistant sodium current in relatively selective and dose-dependent manner with IC50 of2.49 mmol/L. Conclusion The results suggested that ligustrazine could elevate the threshold of thermal nociception through inhibiting the high-voltage gated calcium current and TTX-resistant sodium current of DRG neuron .in the rat.

  14. An exploratory study of sodium, potassium, and fluid nutrition status of tube-fed nonambulatory children with severe cerebral palsy.

    Science.gov (United States)

    McGowan, Joan Elizabeth; Fenton, Tanis R; Wade, Andrew William; Branton, Jodi Lynn; Robertson, Marli

    2012-08-01

    Children with severe cerebral palsy (CP) often have lower mineral intakes than healthy children. It is unknown if their lower nutrient intakes are adequate to meet their needs. The objective of this study was to examine the sodium, potassium, phosphate, and fluid status of primarily tube-fed nonambulatory children with severe CP. The design consisted of a cross-sectional exploratory study and a clinical trial of sodium supplementation. Nutritional status was determined among primarily tube-fed children (aged 2 to 17 years) with CP based on blood and urine samples, anthropometry, and 3-day food records. Mineral and fluid status was evaluated by a nephrologist blind to nutrient intakes. Twenty children supplied food records, blood samples, and anthropometric measurements, and 16 supplied urine samples. Six (37.5%) of those who provided urine samples were considered possibly dehydrated, as urine osmolality was >600 mmol·kg(-1). Six (60%) of the 10 children with satisfactory fluid status (low urine osmolality) were considered to have a possible dietary sodium deficiency based on a very low urine sodium concentration (<20 mmol·L(-1)). Those considered to have a possible dietary sodium deficiency had a significantly lower sodium intake (48% ± 15% Adequate Intake (AI)) compared with those considered sodium sufficient (73% ± 20% AI) (p = 0.031). One child was considered possibly phosphorus deficient, but none was assessed as likely potassium deficient. The conclusion was that sodium deficiencies were likely prevalent among the children. The findings from this small observational study suggest that sodium intakes for tube-fed children with CP should be maintained near the AI for their age. Hydration status of children receiving hypercaloric formulas should be monitored.

  15. Sodium and Potassium Intake in Healthy Adults in Thessaloniki Greater Metropolitan Area-The Salt Intake in Northern Greece (SING) Study.

    Science.gov (United States)

    Vasara, Eleni; Marakis, Georgios; Breda, Joao; Skepastianos, Petros; Hassapidou, Maria; Kafatos, Anthony; Rodopaios, Nikolaos; Koulouri, Alexandra A; Cappuccio, Francesco P

    2017-04-22

    A reduction in population sodium (as salt) consumption is a global health priority, as well as one of the most cost-effective strategies to reduce the burden of cardiovascular disease. High potassium intake is also recommended to reduce cardiovascular disease. To establish effective policies for setting targets and monitoring effectiveness within each country, the current level of consumption should be known. Greece lacks data on actual sodium and potassium intake. The aim of the present study was therefore to assess dietary salt (using sodium as biomarker) and potassium intakes in a sample of healthy adults in northern Greece, and to determine whether adherence to a Mediterranean diet is related to different sodium intakes or sodium-to-potassium ratio. A cross-sectional survey was carried out in the Thessaloniki greater metropolitan area (northern Greece) (n = 252, aged 18-75 years, 45.2% males). Participants' dietary sodium and potassium intakes were determined by 24-hour urinary sodium and potassium excretions. In addition, we estimated their adherence to Mediterranean diet by the use of an 11-item MedDietScore (range 0-55). The mean sodium excretion was 175 (SD 72) mmol/day, equivalent to 4220 (1745) mg of sodium or 10.7 (4.4) g of salt per day, and the potassium excretion was 65 (25) mmol/day, equivalent to 330