1
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Zaytseva AK, Kulichik OE, Kostareva AA, Zhorov BS. Biophysical mechanisms of myocardium sodium channelopathies. Pflugers Arch 2024; 476:735-753. [PMID: 38424322 DOI: 10.1007/s00424-024-02930-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 02/15/2024] [Accepted: 02/16/2024] [Indexed: 03/02/2024]
Abstract
Genetic variants of gene SCN5A encoding the alpha-subunit of cardiac voltage-gated sodium channel Nav1.5 are associated with various diseases, including long QT syndrome (LQT3), Brugada syndrome (BrS1), and progressive cardiac conduction disease (PCCD). In the last decades, the great progress in understanding molecular and biophysical mechanisms of these diseases has been achieved. The LQT3 syndrome is associated with gain-of-function of sodium channels Nav1.5 due to impaired inactivation, enhanced activation, accelerated recovery from inactivation or the late current appearance. In contrast, BrS1 and PCCD are associated with the Nav1.5 loss-of-function, which in electrophysiological experiments can be manifested as reduced current density, enhanced fast or slow inactivation, impaired activation, or decelerated recovery from inactivation. Genetic variants associated with congenital arrhythmias can also disturb interactions of the Nav1.5 channel with different proteins or drugs and cause unexpected reactions to drug administration. Furthermore, mutations can affect post-translational modifications of the channels and their sensitivity to pH and temperature. Here we briefly review the current knowledge on biophysical mechanisms of LQT3, BrS1 and PCCD. We focus on limitations of studies that use heterologous expression systems and induced pluripotent stem cells (iPSC) derived cardiac myocytes and summarize our understanding of genotype-phenotype relations of SCN5A mutations.
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Affiliation(s)
- Anastasia K Zaytseva
- Almazov National Medical Research Centre, St. Petersburg, Russia.
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia.
| | - Olga E Kulichik
- Almazov National Medical Research Centre, St. Petersburg, Russia
| | | | - Boris S Zhorov
- Almazov National Medical Research Centre, St. Petersburg, Russia
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
- McMaster University, Hamilton, Canada
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2
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Goodchild SJ, Ahern CA. Conformational photo-trapping in Na V1.5: Inferring local motions at the "inactivation gate". Biophys J 2024:S0006-3495(24)00279-0. [PMID: 38664963 DOI: 10.1016/j.bpj.2024.04.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 03/22/2024] [Accepted: 04/18/2024] [Indexed: 05/12/2024] Open
Abstract
Rapid and effectual inactivation in voltage-gated sodium channels is required for canonical action-potential firing. This "fast" inactivation arises from swift and reversible protein conformational changes that utilize transmembrane segments and the cytoplasmic linker between channel domains III and IV. Until recently, fast inactivation had been accepted to rely on a "ball-and-chain" mechanism whereby a hydrophobic triplet of DIII-IV amino acids (IFM) impairs conductance by binding to a site in central pore of the channel made available by channel opening. New structures of sodium channels have upended this model. Specifically, cryo-electron microscopic structures of eukaryotic sodium channels depict a peripheral binding site for the IFM motif, outside of the pore, opening the possibility of a yet unidentified allosteric mechanism of fast-inactivation gating. We set out to study fast inactivation by photo-trapping human sodium channels in various functional states under voltage control. This was achieved by genetically encoding the crosslinking unnatural amino acid benzophenone phenylalanine at various sites within the DIII-IV linker in the cardiac sodium channel NaV1.5. These data show dynamic state- and positional-dependent trapping of the transient conformations associated with fast inactivation, each yielding different phenotypes and rates of trapping. These data reveal distinct conformational changes that underlie fast inactivation and point to a dynamic environment around the IFM locus.
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Affiliation(s)
- Samuel J Goodchild
- Department of Anesthesiology, Pharmacology and Therapeutics, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada
| | - Christopher A Ahern
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa.
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3
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Chen JL, Kuo CC. Inhibition of resurgent Na + currents by rufinamide. Neuropharmacology 2024; 247:109835. [PMID: 38228283 DOI: 10.1016/j.neuropharm.2024.109835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 12/29/2023] [Accepted: 12/31/2023] [Indexed: 01/18/2024]
Abstract
Na+ channels are essential for the genesis of action potentials in most neurons. After opening by membrane depolarization, Na+ channels enter a series of inactivated states (e.g. the fast, intermediate, and slow inactivated states; or If, Ii, and Is). The inactivated Na+ channel may recover via the open state upon membrane repolarization, giving rise to "resurgent" Na+ currents which could be critical for densely repetitive or burst discharges. We incubated CHO-K1 cells transfected with human NaV1.7 cDNA and measured resurgent currents with whole-cell patch recordings. We found Ii is the major inactivated state responsible for the genesis of resurgent currents. Rufinamide, in therapeutic concentrations, could selectively bind to Ii to slow the recovery process and dose-dependently inhibit resurgent currents. The other Na+ channel-inhibiting antiseizure medications (ASM), such as phenytoin and lacosamide (selectively binds to If and Is, separately), fail to show a similar inhibitory effect in clinically relevant concentrations. Resurgent currents are decreased with lengthening of the prepulse, presumably because of redistribution of the channel from Ii to If. Rufinamide could accentuate the decrease to mimic a use-dependent inhibitory effect. The molecular action of slowing of recovery from inactivation by binding to Ii also explains the highly correlative inhibitory effect of rufinamide on both transient and resurgent Na+ currents. The modest but correlative inhibition of both currents may make a novel synergistic effect and thus strong-enough suppression of pathological repetitive and especially burst discharges. Rufinamide may thus have a unique spectrum of therapeutic applications for disorders with excessive neural excitabilities.
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Affiliation(s)
- Jian-Lin Chen
- Department of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan.
| | - Chung-Chin Kuo
- Department of Physiology, National Taiwan University College of Medicine, Taipei, Taiwan; Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan.
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4
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Liu Y, Bassetto CAZ, Pinto BI, Bezanilla F. A mechanistic reinterpretation of fast inactivation in voltage-gated Na + channels. Nat Commun 2023; 14:5072. [PMID: 37604801 PMCID: PMC10442390 DOI: 10.1038/s41467-023-40514-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 07/25/2023] [Indexed: 08/23/2023] Open
Abstract
The hinged-lid model was long accepted as the canonical model for fast inactivation in Nav channels. It predicts that the hydrophobic IFM motif acts intracellularly as the gating particle that binds and occludes the pore during fast inactivation. However, the observation in recent high-resolution structures that the bound IFM motif is located far from the pore, contradicts this preconception. Here, we provide a mechanistic reinterpretation of fast inactivation based on structural analysis and ionic/gating current measurements. We demonstrate that in Nav1.4 the final inactivation gate is comprised of two hydrophobic rings at the bottom of S6 helices. These rings function in series and close downstream of IFM binding. Reducing the volume of the sidechain in both rings leads to a partially conductive, leaky inactivated state and decreases the selectivity for Na+ ion. Altogether, we present an alternative molecular framework to describe fast inactivation.
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Affiliation(s)
- Yichen Liu
- Department of Neurobiology, University of Chicago, Chicago, IL, USA
| | - Carlos A Z Bassetto
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Bernardo I Pinto
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Francisco Bezanilla
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA.
- Centro Interdisciplinario de Neurociencias de Valparaíso, Valparaíso, Chile.
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5
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Liu Y, Bassetto CAZ, Pinto BI, Bezanilla F. A Mechanistic Reinterpretation of Fast Inactivation in Voltage-Gated Na + Channels. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.27.538555. [PMID: 37162849 PMCID: PMC10168311 DOI: 10.1101/2023.04.27.538555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Fast Inactivation in voltage-gated Na + channels plays essential roles in numerous physiological functions. The canonical hinged-lid model has long predicted that a hydrophobic motif in the DIII-DIV linker (IFM) acts as the gating particle that occludes the permeation pathway during fast inactivation. However, the fact that the IFM motif is located far from the pore in recent high-resolution structures of Nav + channels contradicts this status quo model. The precise molecular determinants of fast inactivation gate once again, become an open question. Here, we provide a mechanistic reinterpretation of fast inactivation based on ionic and gating current data. In Nav1.4 the actual inactivation gate is comprised of two hydrophobic rings at the bottom of S6. These function in series and closing once the IFM motif binds. Reducing the volume of the sidechain in both rings led to a partially conductive inactivated state. Our experiments also point to a previously overlooked coupling pathway between the bottom of S6 and the selectivity filter.
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Affiliation(s)
- Yichen Liu
- Department of Neurobiology, University of Chicago, Chicago, IL, USA
| | - Carlos A Z Bassetto
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Bernardo I Pinto
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
| | - Francisco Bezanilla
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA
- Centro Interdisciplinario de Neurociencias de Valparaiso, Valparaiso, Chile
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6
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Gamal El-Din TM. When the Gates Swing Open Only: Arrhythmia Mutations That Target the Fast Inactivation Gate of Na v1.5. Cells 2022; 11:cells11233714. [PMID: 36496974 PMCID: PMC9735811 DOI: 10.3390/cells11233714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 11/17/2022] [Accepted: 11/17/2022] [Indexed: 11/23/2022] Open
Abstract
Nav1.5 is the main voltage-gated sodium channel found in cardiac muscle, where it facilitates the fast influx of Na+ ions across the cell membrane, resulting in the fast depolarization phase-phase 0 of the cardiac action potential. As a result, it plays a major role in determining the amplitude and the upstroke velocity of the cardiac impulse. Quantitively, cardiac sodium channel activates in less than a millisecond to trigger the cardiac action potential and inactivates within 2-3 ms to facilitate repolarization and return to the resting state in preparation for firing the next action potential. Missense mutations in the gene that encodes Nav1.5 (SCN5A), change these time constants which leads to a wide spectrum of cardiac diseases ranging from long QT syndrome type 3 (LQT3) to sudden cardiac death. In this mini-review I will focus on the missense mutations in the inactivation gate of Nav1.5 that results in arrhythmia, attempting to correlate the location of the missense mutation to their specific phenotype.
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7
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Jiang D, Zhang J, Xia Z. Structural Advances in Voltage-Gated Sodium Channels. Front Pharmacol 2022; 13:908867. [PMID: 35721169 PMCID: PMC9204039 DOI: 10.3389/fphar.2022.908867] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 05/23/2022] [Indexed: 11/17/2022] Open
Abstract
Voltage-gated sodium (NaV) channels are responsible for the rapid rising-phase of action potentials in excitable cells. Over 1,000 mutations in NaV channels are associated with human diseases including epilepsy, periodic paralysis, arrhythmias and pain disorders. Natural toxins and clinically-used small-molecule drugs bind to NaV channels and modulate their functions. Recent advances from cryo-electron microscopy (cryo-EM) structures of NaV channels reveal invaluable insights into the architecture, activation, fast inactivation, electromechanical coupling, ligand modulation and pharmacology of eukaryotic NaV channels. These structural analyses not only demonstrate molecular mechanisms for NaV channel structure and function, but also provide atomic level templates for rational development of potential subtype-selective therapeutics. In this review, we summarize recent structural advances of eukaryotic NaV channels, highlighting the structural features of eukaryotic NaV channels as well as distinct modulation mechanisms by a wide range of modulators from natural toxins to synthetic small-molecules.
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Affiliation(s)
- Daohua Jiang
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
- *Correspondence: Daohua Jiang,
| | - Jiangtao Zhang
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- Key Laboratory of Molecular Biophysics of MOE, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Zhanyi Xia
- Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
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8
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Körner J, Albani S, Sudha Bhagavath Eswaran V, Roehl AB, Rossetti G, Lampert A. Sodium Channels and Local Anesthetics-Old Friends With New Perspectives. Front Pharmacol 2022; 13:837088. [PMID: 35418860 PMCID: PMC8996304 DOI: 10.3389/fphar.2022.837088] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 02/16/2022] [Indexed: 12/11/2022] Open
Abstract
The long history of local anesthetics (LAs) starts out in the late 19th century when the content of coca plant leaves was discovered to alleviate pain. Soon after, cocaine was established and headed off to an infamous career as a substance causing addiction. Today, LAs and related substances-in modified form-are indispensable in our clinical everyday life for pain relief during and after minor and major surgery, and dental practices. In this review, we elucidate on the interaction of modern LAs with their main target, the voltage-gated sodium channel (Navs), in the light of the recently published channel structures. Knowledge of the 3D interaction sites of the drug with the protein will allow to mechanistically substantiate the comprehensive data available on LA gating modification. In the 1970s it was suggested that LAs can enter the channel pore from the lipid phase, which was quite prospective at that time. Today we know from cryo-electron microscopy structures and mutagenesis experiments, that indeed Navs have side fenestrations facing the membrane, which are likely the entrance for LAs to induce tonic block. In this review, we will focus on the effects of LA binding on fast inactivation and use-dependent inhibition in the light of the proposed new allosteric mechanism of fast inactivation. We will elaborate on subtype and species specificity and provide insights into modelling approaches that will help identify the exact molecular binding orientation, access pathways and pharmacokinetics. With this comprehensive overview, we will provide new perspectives in the use of the drug, both clinically and as a tool for basic ion channel research.
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Affiliation(s)
- Jannis Körner
- Institute of Physiology, Aachen, Germany.,Clinic of Anesthesiology, Medical Faculty, Uniklinik RWTH Aachen, Aachen, Germany
| | - Simone Albani
- Institute for Neuroscience and Medicine (INM-9/IAS-5), Forschungszentrum Jülich, Jülich, Germany.,Faculty of Mathematics, Computer Science and Natural Sciences, RWTH Aachen, Aachen, Germany
| | | | - Anna B Roehl
- Clinic of Anesthesiology, Medical Faculty, Uniklinik RWTH Aachen, Aachen, Germany
| | - Giulia Rossetti
- Institute for Neuroscience and Medicine (INM-9/IAS-5), Forschungszentrum Jülich, Jülich, Germany.,Jülich Supercomputing Center (JSC), Forschungszentrum Jülich, Aachen, Germany.,Department of Neurology, University Hospital Aachen, RWTH Aachen University, Aachen, Germany
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9
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Peng S, Chen M, Xiao Z, Xiao X, Luo S, Liang S, Zhou X, Liu Z. A Novel Spider Toxin Inhibits Fast Inactivation of the Na v1.9 Channel by Binding to Domain III and Domain IV Voltage Sensors. Front Pharmacol 2021; 12:778534. [PMID: 34938190 PMCID: PMC8685421 DOI: 10.3389/fphar.2021.778534] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 11/05/2021] [Indexed: 11/13/2022] Open
Abstract
Venomous animals have evolved to produce peptide toxins that modulate the activity of voltage-gated sodium (Nav) channels. These specific modulators are powerful probes for investigating the structural and functional features of Nav channels. Here, we report the isolation and characterization of δ-theraphotoxin-Gr4b (Gr4b), a novel peptide toxin from the venom of the spider Grammostola rosea. Gr4b contains 37-amino acid residues with six cysteines forming three disulfide bonds. Patch-clamp analysis confirmed that Gr4b markedly slows the fast inactivation of Nav1.9 and inhibits the currents of Nav1.4 and Nav1.7, but does not affect Nav1.8. It was also found that Gr4b significantly shifts the steady-state activation and inactivation curves of Nav1.9 to the depolarization direction and increases the window current, which is consistent with the change in the ramp current. Furthermore, analysis of Nav1.9/Nav1.8 chimeric channels revealed that Gr4b preferentially binds to the voltage-sensor of domain III (DIII VSD) and has additional interactions with the DIV VSD. The site-directed mutagenesis analysis indicated that N1139 and L1143 in DIII S3-S4 linker participate in toxin binding. In sum, this study reports a novel spider peptide toxin that may slow the fast inactivation of Nav1.9 by binding to the new neurotoxin receptor site-DIII VSD. Taken together, these findings provide insight into the functional role of the Nav channel DIII VSD in fast inactivation and activation.
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Affiliation(s)
- Shuijiao Peng
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Minzhi Chen
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Zhen Xiao
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Xin Xiao
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Sen Luo
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Songping Liang
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Xi Zhou
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Zhonghua Liu
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, China
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10
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Jiang D, Banh R, Gamal El-Din TM, Tonggu L, Lenaeus MJ, Pomès R, Zheng N, Catterall WA. Open-state structure and pore gating mechanism of the cardiac sodium channel. Cell 2021; 184:5151-5162.e11. [PMID: 34520724 DOI: 10.1016/j.cell.2021.08.021] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 07/07/2021] [Accepted: 08/16/2021] [Indexed: 11/17/2022]
Abstract
The heartbeat is initiated by voltage-gated sodium channel NaV1.5, which opens rapidly and triggers the cardiac action potential; however, the structural basis for pore opening remains unknown. Here, we blocked fast inactivation with a mutation and captured the elusive open-state structure. The fast inactivation gate moves away from its receptor, allowing asymmetric opening of pore-lining S6 segments, which bend and rotate at their intracellular ends to dilate the activation gate to ∼10 Å diameter. Molecular dynamics analyses predict physiological rates of Na+ conductance. The open-state pore blocker propafenone binds in a high-affinity pose, and drug-access pathways are revealed through the open activation gate and fenestrations. Comparison with mutagenesis results provides a structural map of arrhythmia mutations that target the activation and fast inactivation gates. These results give atomic-level insights into molecular events that underlie generation of the action potential, open-state drug block, and fast inactivation of cardiac sodium channels, which initiate the heartbeat.
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Affiliation(s)
- Daohua Jiang
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA; Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
| | - Richard Banh
- Molecular Medicine, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | | | - Lige Tonggu
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Michael J Lenaeus
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA; Division of General Internal Medicine, Department of Medicine, University of Washington, Seattle, WA 98195, USA
| | - Régis Pomès
- Molecular Medicine, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Ning Zheng
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA.
| | - William A Catterall
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA.
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11
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Nowicka-Bauer K, Szymczak-Cendlak M. Structure and Function of Ion Channels Regulating Sperm Motility-An Overview. Int J Mol Sci 2021; 22:ijms22063259. [PMID: 33806823 PMCID: PMC8004680 DOI: 10.3390/ijms22063259] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 03/18/2021] [Accepted: 03/19/2021] [Indexed: 12/18/2022] Open
Abstract
Sperm motility is linked to the activation of signaling pathways that trigger movement. These pathways are mainly dependent on Ca2+, which acts as a secondary messenger. The maintenance of adequate Ca2+ concentrations is possible thanks to proper concentrations of other ions, such as K+ and Na+, among others, that modulate plasma membrane potential and the intracellular pH. Like in every cell, ion homeostasis in spermatozoa is ensured by a vast spectrum of ion channels supported by the work of ion pumps and transporters. To achieve success in fertilization, sperm ion channels have to be sensitive to various external and internal factors. This sensitivity is provided by specific channel structures. In addition, novel sperm-specific channels or isoforms have been found with compositions that increase the chance of fertilization. Notably, the most significant sperm ion channel is the cation channel of sperm (CatSper), which is a sperm-specific Ca2+ channel required for the hyperactivation of sperm motility. The role of other ion channels in the spermatozoa, such as voltage-gated Ca2+ channels (VGCCs), Ca2+-activated Cl-channels (CaCCs), SLO K+ channels or voltage-gated H+ channels (VGHCs), is to ensure the activation and modulation of CatSper. As the activation of sperm motility differs among metazoa, different ion channels may participate; however, knowledge regarding these channels is still scarce. In the present review, the roles and structures of the most important known ion channels are described in regard to regulation of sperm motility in animals.
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Affiliation(s)
- Karolina Nowicka-Bauer
- Department of Chemical Physics, Faculty of Chemistry, Adam Mickiewicz University in Poznań, 61-614 Poznan, Poland
- Correspondence:
| | - Monika Szymczak-Cendlak
- Department of Animal Physiology and Development, Faculty of Biology, Adam Mickiewicz University in Poznań, 61-614 Poznan, Poland;
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12
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Kistamás K, Hézső T, Horváth B, Nánási PP. Late sodium current and calcium homeostasis in arrhythmogenesis. Channels (Austin) 2020; 15:1-19. [PMID: 33258400 PMCID: PMC7757849 DOI: 10.1080/19336950.2020.1854986] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The cardiac late sodium current (INa,late) is the small sustained component of the sodium current active during the plateau phase of the action potential. Several studies demonstrated that augmentation of the current can lead to cardiac arrhythmias; therefore, INa,late is considered as a promising antiarrhythmic target. Fundamentally, enlarged INa,late increases Na+ influx into the cell, which, in turn, is converted to elevated intracellular Ca2+ concentration through the Na+/Ca2+ exchanger. The excessive Ca2+ load is known to be proarrhythmic. This review describes the behavior of the voltage-gated Na+ channels generating INa,late in health and disease and aims to discuss the physiology and pathophysiology of Na+ and Ca2+ homeostasis in context with the enhanced INa,late demonstrating also the currently accessible antiarrhythmic choices.
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Affiliation(s)
- Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary
| | - Tamás Hézső
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary
| | - Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary.,Department of Dental Physiology, Faculty of Dentistry, University of Debrecen , Debrecen, Hungary
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13
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Solé L, Tamkun MM. Trafficking mechanisms underlying Na v channel subcellular localization in neurons. Channels (Austin) 2020; 14:1-17. [PMID: 31841065 PMCID: PMC7039628 DOI: 10.1080/19336950.2019.1700082] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 11/13/2019] [Indexed: 01/06/2023] Open
Abstract
Voltage gated sodium channels (Nav) play a crucial role in action potential initiation and propagation. Although the discovery of Nav channels dates back more than 65 years, and great advances in understanding their localization, biophysical properties, and links to disease have been made, there are still many questions to be answered regarding the cellular and molecular mechanisms involved in Nav channel trafficking, localization and regulation. This review summarizes the different trafficking mechanisms underlying the polarized Nav channel localization in neurons, with an emphasis on the axon initial segment (AIS), as well as discussing the latest advances regarding how neurons regulate their excitability by modifying AIS length and location. The importance of Nav channel localization is emphasized by the relationship between mutations, impaired trafficking and disease. While this review focuses on Nav1.6, other Nav isoforms are also discussed.
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Affiliation(s)
- Laura Solé
- Molecular, Cellular and Integrative Neurosciences Graduate Program, Colorado State University, Fort Collins, CO, USA
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Michael M. Tamkun
- Molecular, Cellular and Integrative Neurosciences Graduate Program, Colorado State University, Fort Collins, CO, USA
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, USA
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14
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Jiang D, Shi H, Tonggu L, Gamal El-Din TM, Lenaeus MJ, Zhao Y, Yoshioka C, Zheng N, Catterall WA. Structure of the Cardiac Sodium Channel. Cell 2019; 180:122-134.e10. [PMID: 31866066 DOI: 10.1016/j.cell.2019.11.041] [Citation(s) in RCA: 163] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 11/18/2019] [Accepted: 11/27/2019] [Indexed: 12/19/2022]
Abstract
Voltage-gated sodium channel Nav1.5 generates cardiac action potentials and initiates the heartbeat. Here, we report structures of NaV1.5 at 3.2-3.5 Å resolution. NaV1.5 is distinguished from other sodium channels by a unique glycosyl moiety and loss of disulfide-bonding capability at the NaVβ subunit-interaction sites. The antiarrhythmic drug flecainide specifically targets the central cavity of the pore. The voltage sensors are partially activated, and the fast-inactivation gate is partially closed. Activation of the voltage sensor of Domain III allows binding of the isoleucine-phenylalanine-methionine (IFM) motif to the inactivation-gate receptor. Asp and Ala, in the selectivity motif DEKA, line the walls of the ion-selectivity filter, whereas Glu and Lys are in positions to accept and release Na+ ions via a charge-delocalization network. Arrhythmia mutation sites undergo large translocations during gating, providing a potential mechanism for pathogenic effects. Our results provide detailed insights into Nav1.5 structure, pharmacology, activation, inactivation, ion selectivity, and arrhythmias.
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Affiliation(s)
- Daohua Jiang
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Hui Shi
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA
| | - Lige Tonggu
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | | | - Michael J Lenaeus
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA; Division of General Internal Medicine, Department of Medicine, University of Washington, Seattle, WA 98195, USA
| | - Yan Zhao
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Craig Yoshioka
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Ning Zheng
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA.
| | - William A Catterall
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA.
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15
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Shandell MA, Quejada JR, Yazawa M, Cornish VW, Kass RS. Detection of Na v1.5 Conformational Change in Mammalian Cells Using the Noncanonical Amino Acid ANAP. Biophys J 2019; 117:1352-1363. [PMID: 31521331 PMCID: PMC6818161 DOI: 10.1016/j.bpj.2019.08.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 07/29/2019] [Accepted: 08/19/2019] [Indexed: 12/27/2022] Open
Abstract
Nav1.5 inactivation is necessary for healthy conduction of the cardiac action potential. Genetic mutations of Nav1.5 perturb inactivation and cause potentially fatal arrhythmias associated with long QT syndrome type 3. The exact structural dynamics of the inactivation complex is unknown. To sense inactivation gate conformational change in live mammalian cells, we incorporated the solvatochromic fluorescent noncanonical amino acid 3-((6-acetylnaphthalen-2-yl)amino)-2-aminopropanoic acid (ANAP) into single sites in the Nav1.5 inactivation gate. ANAP was incorporated in full-length and C-terminally truncated Nav1.5 channels using mammalian cell synthetase-tRNA technology. ANAP-incorporated channels were expressed in mammalian cells, and they exhibited pathophysiological function. A spectral imaging potassium depolarization assay was designed to detect ANAP emission shifts associated with Nav1.5 conformational change. Site-specific intracellular ANAP incorporation affords live-cell imaging and detection of Nav1.5 inactivation gate conformational change in mammalian cells.
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Affiliation(s)
- Mia A Shandell
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York.
| | - Jose R Quejada
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York; Department of Rehabilitation and Regenerative Medicine, Columbia Stem Cell Initiative, Columbia University, New York, New York
| | - Masayuki Yazawa
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York; Department of Rehabilitation and Regenerative Medicine, Columbia Stem Cell Initiative, Columbia University, New York, New York
| | - Virginia W Cornish
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York; Department of Chemistry, Columbia University, New York, New York.
| | - Robert S Kass
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York.
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16
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Flood E, Boiteux C, Lev B, Vorobyov I, Allen TW. Atomistic Simulations of Membrane Ion Channel Conduction, Gating, and Modulation. Chem Rev 2019; 119:7737-7832. [DOI: 10.1021/acs.chemrev.8b00630] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Emelie Flood
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Céline Boiteux
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Bogdan Lev
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Igor Vorobyov
- Department of Physiology & Membrane Biology/Department of Pharmacology, University of California, Davis, 95616, United States
| | - Toby W. Allen
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
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17
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Johnson CN. Calcium modulation of cardiac sodium channels. J Physiol 2019; 598:2835-2846. [PMID: 30707447 DOI: 10.1113/jp277553] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Accepted: 01/08/2019] [Indexed: 12/28/2022] Open
Abstract
Modification of voltage-gated Na+ channel (NaV ) function by intracellular Ca2+ has been a topic of much controversy. Early studies relied on measuring NaV function in the absence or presence of intracellular Ca2+ , and generated seemingly disparate results. Subsequent investigations revealed the mechanism(s) of Ca2+ -driven NaV modulation are complex and involve multiple accessory proteins. The Ca2+ -sensing protein calmodulin (CaM) has a central role in tuning NaV function to [Ca2+ ]i , but the mechanism has been obscured by other proteins (such as fibroblast growth factors (FGF) or CaM-dependent kinase II (CaMKII)) that can also modify channel function or exert an influence in a Ca2+ -dependent manner. Significant progress has been made in understanding the architecture of full-length ion channels and the structural and biophysical details of NaV -accessory protein interactions. Interdisciplinary structure-function studies are beginning to resolve the effect each interaction has on NaV gating. Carefully designed structure-guided or strategically selected disease-associated mutations are able to impair NaV -accessory protein interactions without altering other properties of channel function. Recently CaM was found to engage part of NaV 1.5 that is required for channel inactivation with high affinity. Careful impairment of this interaction disrupted NaV 1.5's ability to recover from inactivation. Such results support a paradigm of CaM-facilitated recovery from inactivation (CFRI). How NaV -CaM, CaMKII and FGF/fibroblast growth factor homologous factor interactions affect the timing or function of CFRI in cardiomyocytes remain open questions that are discussed herein. Moreover whether CFRI dysfunction or premature activation underlie certain NaV channelopathies are important questions that will require further investigation.
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Affiliation(s)
- Christopher N Johnson
- The Ohio State Wexner Medical Centre, Dorothy M. Davis Heart & Lung Research Institute, Columbus, OH, USA.,Vanderbilt Centre for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Nashville, TN, USA
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18
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Abstract
A new study reveals that conformational flexibility in the pore of a voltage-gated sodium channel may underlie slow inactivation.
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19
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Boiteux C, Flood E, Allen TW. Comparison of permeation mechanisms in sodium-selective ion channels. Neurosci Lett 2018; 700:3-8. [PMID: 29807068 DOI: 10.1016/j.neulet.2018.05.036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 05/24/2018] [Accepted: 05/25/2018] [Indexed: 12/27/2022]
Abstract
Voltage-gated sodium channels are the molecular components of electrical signaling in the body, yet the molecular origins of Na+-selective transport remain obscured by diverse protein chemistries within this family of ion channels. In particular, bacterial and mammalian sodium channels are known to exhibit similar relative ion permeabilities for Na+ over K+ ions, despite their distinct signature EEEE and DEKA sequences. Atomic-level molecular dynamics simulations using high-resolution bacterial channel structures and mammalian channel models have begun to describe how these sequences lead to analogous high field strength ion binding sites that drive Na+ conduction. Similar complexes have also been identified in unrelated acid sensing ion channels involving glutamate and aspartate side chains that control their selectivity. These studies suggest the possibility of a common origin for Na+ selective binding and transport.
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Affiliation(s)
- Céline Boiteux
- School of Science, RMIT University, Melbourne, Australia
| | - Emelie Flood
- School of Science, RMIT University, Melbourne, Australia
| | - Toby W Allen
- School of Science, RMIT University, Melbourne, Australia.
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20
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Johnson CN, Potet F, Thompson MK, Kroncke BM, Glazer AM, Voehler MW, Knollmann BC, George AL, Chazin WJ. A Mechanism of Calmodulin Modulation of the Human Cardiac Sodium Channel. Structure 2018; 26:683-694.e3. [PMID: 29606593 DOI: 10.1016/j.str.2018.03.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 01/26/2018] [Accepted: 03/08/2018] [Indexed: 12/26/2022]
Abstract
The function of the human cardiac sodium channel (NaV1.5) is modulated by the Ca2+ sensor calmodulin (CaM), but the underlying mechanism(s) are controversial and poorly defined. CaM has been reported to bind in a Ca2+-dependent manner to two sites in the intracellular loop that is critical for inactivation of NaV1.5 (inactivation gate [IG]). The affinity of CaM for the complete IG was significantly stronger than that of fragments that lacked both complete binding sites. Structural analysis by nuclear magnetic resonance, crystallographic, and scattering approaches revealed that CaM simultaneously engages both IG sites using an extended configuration. Patch-clamp recordings for wild-type and mutant channels with an impaired CaM-IG interaction revealed CaM binding to the IG promotes recovery from inactivation while impeding the kinetics of inactivation. Models of full-length NaV1.5 suggest that CaM binding to the IG directly modulates channel function by destabilizing the inactivated state, which would promote resetting of the IG after channels close.
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Affiliation(s)
- Christopher N Johnson
- Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN 37240, USA; Department of Biochemistry, Vanderbilt University, Nashville, TN 37205, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA; Center for Arrhythmia Research and Therapeutics, Vanderbilt University, Nashville, TN 37240, USA.
| | - Franck Potet
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago IL 60611, USA
| | - Matthew K Thompson
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37205, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Brett M Kroncke
- Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN 37240, USA; Center for Arrhythmia Research and Therapeutics, Vanderbilt University, Nashville, TN 37240, USA
| | - Andrew M Glazer
- Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN 37240, USA; Center for Arrhythmia Research and Therapeutics, Vanderbilt University, Nashville, TN 37240, USA
| | - Markus W Voehler
- Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Bjorn C Knollmann
- Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN 37240, USA; Center for Arrhythmia Research and Therapeutics, Vanderbilt University, Nashville, TN 37240, USA
| | - Alfred L George
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago IL 60611, USA
| | - Walter J Chazin
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37205, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA; Center for Structural Biology, Vanderbilt University, Nashville, TN 37232, USA.
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21
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Thompson A, Infield DT, Smith AR, Smith GT, Ahern CA, Zakon HH. Rapid evolution of a voltage-gated sodium channel gene in a lineage of electric fish leads to a persistent sodium current. PLoS Biol 2018; 16:e2004892. [PMID: 29584718 PMCID: PMC5870949 DOI: 10.1371/journal.pbio.2004892] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 02/21/2018] [Indexed: 11/26/2022] Open
Abstract
Most weakly electric fish navigate and communicate by sensing electric signals generated by their muscle-derived electric organs. Adults of one lineage (Apteronotidae), which discharge their electric organs in excess of 1 kHz, instead have an electric organ derived from the axons of specialized spinal neurons (electromotorneurons [EMNs]). EMNs fire spontaneously and are the fastest-firing neurons known. This biophysically extreme phenotype depends upon a persistent sodium current, the molecular underpinnings of which remain unknown. We show that a skeletal muscle–specific sodium channel gene duplicated in this lineage and, within approximately 2 million years, began expressing in the spinal cord, a novel site of expression for this isoform. Concurrently, amino acid replacements that cause a persistent sodium current accumulated in the regions of the channel underlying inactivation. Therefore, a novel adaptation allowing extreme neuronal firing arose from the duplication, change in expression, and rapid sequence evolution of a muscle-expressing sodium channel gene. The electrical properties of excitable cells, such as those in muscle and nervous tissue, were enabled in large part by the evolution of voltage-gated ion channel genes. The regulated conduction of ions through these channels results in the propagation of electrical signals, facilitating communication between cells. Here, we investigated how voltage-gated sodium (Nav) channels contributed to the evolution of a novel electric organ system in the Apteronotids—a lineage of weakly electric fish. This organ is developmentally derived from motor neurons and used for communication between individual fish, as well as for probing their nocturnal environment. We used transcriptomic data to show that the gene encoding a broadly conserved muscle-specific sodium channel was duplicated in an ancestral fish. One duplicated gene copy subsequently gained expression in the spinal cord, where the electric organ is located. Through evolutionary analysis and biophysical experiments, we demonstrate that sequence changes in this new sodium channel transformed its function to cause novel electrical properties that can facilitate spontaneous high-frequency action potentials. This study shows that duplicate genes can gain highly novel expression patterns and quickly adapt to contribute to the phenotypic evolution of novel organ systems.
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Affiliation(s)
- Ammon Thompson
- Department of Integrative Biology, The University of Texas, Austin, Texas, United States of America
- Department of Neuroscience, The University of Texas, Austin, Texas, United States of America
- * E-mail:
| | - Daniel T. Infield
- Department of Molecular Physiology and Biophysics, Iowa Neuroscience Institute, The University of Iowa, Iowa City, Iowa, United States of America
| | - Adam R. Smith
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, Indiana, United States of America
| | - G. Troy Smith
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, Indiana, United States of America
| | - Christopher A. Ahern
- Department of Molecular Physiology and Biophysics, Iowa Neuroscience Institute, The University of Iowa, Iowa City, Iowa, United States of America
| | - Harold H. Zakon
- Department of Integrative Biology, The University of Texas, Austin, Texas, United States of America
- Department of Neuroscience, The University of Texas, Austin, Texas, United States of America
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22
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Distinct modulation of inactivation by a residue in the pore domain of voltage-gated Na + channels: mechanistic insights from recent crystal structures. Sci Rep 2018; 8:631. [PMID: 29330525 PMCID: PMC5766632 DOI: 10.1038/s41598-017-18919-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 12/18/2017] [Indexed: 12/19/2022] Open
Abstract
Inactivation of voltage-gated Na+ channels (VGSC) is essential for the regulation of cellular excitability. The molecular rearrangement underlying inactivation is thought to involve the intracellular linker between domains III and IV serving as inactivation lid, the receptor for the lid (domain III S4-S5 linker) and the pore-lining S6 segements. To better understand the role of the domain IV S6 segment in inactivation we performed a cysteine scanning mutagenesis of this region in rNav 1.4 channels and screened the constructs for perturbations in the voltage-dependence of steady state inactivation. This screen was performed in the background of wild-type channels and in channels carrying the mutation K1237E, which profoundly alters both permeation and gating-properties. Of all tested constructs the mutation I1581C was unique in that the mutation-induced gating changes were strongly influenced by the mutational background. This suggests that I1581 is involved in specific short-range interactions during inactivation. In recently published crystal structures VGSCs the respective amino acids homologous to I1581 appear to control a bend of the S6 segment which is critical to the gating process. Furthermore, I1581 may be involved in the transmission of the movement of the DIII voltage-sensor to the domain IV S6 segment.
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23
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Abstract
Voltage-gated sodium (Na+) channels are expressed in virtually all electrically excitable tissues and are essential for muscle contraction and the conduction of impulses within the peripheral and central nervous systems. Genetic disorders that disrupt the function of these channels produce an array of Na+ channelopathies resulting in neuronal impairment, chronic pain, neuromuscular pathologies, and cardiac arrhythmias. Because of their importance to the conduction of electrical signals, Na+ channels are the target of a wide variety of local anesthetic, antiarrhythmic, anticonvulsant, and antidepressant drugs. The voltage-gated family of Na+ channels is composed of α-subunits that encode for the voltage sensor domains and the Na+-selective permeation pore. In vivo, Na+ channel α-subunits are associated with one or more accessory β-subunits (β1-β4) that regulate gating properties, trafficking, and cell-surface expression of the channels. The permeation pore of Na+ channels is divided in two parts: the outer mouth of the pore is the site of the ion selectivity filter, while the inner cytoplasmic pore serves as the channel activation gate. The cytoplasmic lining of the permeation pore is formed by the S6 segments that include highly conserved aromatic amino acids important for drug binding. These residues are believed to undergo voltage-dependent conformational changes that alter drug binding as the channels cycle through the closed, open, and inactivated states. The purpose of this chapter is to broadly review the mechanisms of Na+ channel gating and the models used to describe drug binding and Na+ channel inhibition.
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Affiliation(s)
- M E O'Leary
- Cooper Medical School of Rowan University, Camden, NJ, USA
| | - M Chahine
- CERVO Brain Research Center, Institut universitaire en santé mentale de Québec, Quebec City, QC, Canada.
- Department of Medicine, Université Laval, Quebec City, QC, Canada.
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24
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Mangold KE, Brumback BD, Angsutararux P, Voelker TL, Zhu W, Kang PW, Moreno JD, Silva JR. Mechanisms and models of cardiac sodium channel inactivation. Channels (Austin) 2017; 11:517-533. [PMID: 28837385 PMCID: PMC5786193 DOI: 10.1080/19336950.2017.1369637] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 08/14/2017] [Accepted: 08/15/2017] [Indexed: 12/19/2022] Open
Abstract
Shortly after cardiac Na+ channels activate and initiate the action potential, inactivation ensues within milliseconds, attenuating the peak Na+ current, INa, and allowing the cell membrane to repolarize. A very limited number of Na+ channels that do not inactivate carry a persistent INa, or late INa. While late INa is only a small fraction of peak magnitude, it significantly prolongs ventricular action potential duration, which predisposes patients to arrhythmia. Here, we review our current understanding of inactivation mechanisms, their regulation, and how they have been modeled computationally. Based on this body of work, we conclude that inactivation and its connection to late INa would be best modeled with a "feet-on-the-door" approach where multiple channel components participate in determining inactivation and late INa. This model reflects experimental findings showing that perturbation of many channel locations can destabilize inactivation and cause pathological late INa.
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Affiliation(s)
- Kathryn E. Mangold
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Brittany D. Brumback
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Paweorn Angsutararux
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Taylor L. Voelker
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Wandi Zhu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Po Wei Kang
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Jonathan D. Moreno
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Jonathan R. Silva
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA
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25
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Tse G, Liu T, Li KHC, Laxton V, Wong AOT, Chan YWF, Keung W, Chan CW, Li RA. Tachycardia-bradycardia syndrome: Electrophysiological mechanisms and future therapeutic approaches (Review). Int J Mol Med 2017; 39:519-526. [PMID: 28204831 PMCID: PMC5360359 DOI: 10.3892/ijmm.2017.2877] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 01/09/2017] [Indexed: 02/07/2023] Open
Abstract
Sick sinus syndrome (SSS) encompasses a group of disorders whereby the heart is unable to perform its pacemaker function, due to genetic and acquired causes. Tachycardia‑bradycardia syndrome (TBS) is a complication of SSS characterized by alternating tachycardia and bradycardia. Techniques such as genetic screening and molecular diagnostics together with the use of pre-clinical models have elucidated the electrophysiological mechanisms of this condition. Dysfunction of ion channels responsible for initiation or conduction of cardiac action potentials may underlie both bradycardia and tachycardia; bradycardia can also increase the risk of tachycardia, and vice versa. The mainstay treatment option for SSS is pacemaker implantation, an effective approach, but has disadvantages such as infection, limited battery life, dislodgement of leads and catheters to be permanently implanted in situ. Alternatives to electronic pacemakers are gene‑based bio‑artificial sinoatrial node and cell‑based bio‑artificial pacemakers, which are promising techniques whose long-term safety and efficacy need to be established. The aim of this article is to review the different ion channels involved in TBS, examine the three‑way relationship between ion channel dysfunction, tachycardia and bradycardia in TBS and to consider its current and future therapies.
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Affiliation(s)
- Gary Tse
- Department of Medicine and Therapeutics, Chinese University of Hong Kong
- Li Ka Shing Institute of Health Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, SAR
| | - Tong Liu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular Disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin 300211, P.R. China
| | | | - Victoria Laxton
- Intensive Care Department, Royal Brompton and Harefield NHS Foundation Trust, London SW3 6NP, UK
| | - Andy On-Tik Wong
- Stem Cell and Regenerative Medicine Consortium, Li Ka Shing Faculty of Medicine, The University of Hong Kong
- Li Dak-Sum Research Centre-HKU-Karolinska Institutet Collaboration on Regenerative Medicine, University of Hong Kong, Hong Kong, SAR, P.R. China
| | - Yin Wah Fiona Chan
- School of Biological Sciences, University of Cambridge, Cambridge CB2 1AG, UK
| | - Wendy Keung
- Stem Cell and Regenerative Medicine Consortium, Li Ka Shing Faculty of Medicine, The University of Hong Kong
- Li Dak-Sum Research Centre-HKU-Karolinska Institutet Collaboration on Regenerative Medicine, University of Hong Kong, Hong Kong, SAR, P.R. China
| | - Camie W.Y. Chan
- Stem Cell and Regenerative Medicine Consortium, Li Ka Shing Faculty of Medicine, The University of Hong Kong
| | - Ronald A. Li
- Li Dak-Sum Research Centre-HKU-Karolinska Institutet Collaboration on Regenerative Medicine, University of Hong Kong, Hong Kong, SAR, P.R. China
- Ming Wai Lau Centre for Reparative Medicine, Karolinska Institutet, Hong Kong, SAR, P.R. China
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26
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Prešern J, Škorjanc A, Rodič T, Benda J. A single mechanism driving both inactivation and adaptation in rapidly adapting currents of DRG neurons? BIOLOGICAL CYBERNETICS 2016; 110:393-401. [PMID: 27495790 DOI: 10.1007/s00422-016-0693-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 07/22/2016] [Indexed: 06/06/2023]
Abstract
Rapidly adapting (RA) currents expressed in dorsal root ganglia somatosensory neurons reduce their amplitude in response to prolonged and/or repeated mechanical stimulation. Both inactivation of mechanotransducer channels and adaptation of the force acting on the channels have been suggested to independently decrease RA currents. However, these two mechanisms have similar kinetics and dependence on calcium and voltage. These experimental findings suggest that a single mechanism might underlie both. We constructed a simple Hodgkin-Huxley-type model with a single gating variable driving both inactivation and adaptation to test this hypothesis. Predictions of the model successfully describe key features of mechanical activation as well as inactivation, adaptation, and recovery. The model thus supports the possibility of a single mechanism driving inactivation and adaptation in RA currents. On its own, the model can be integrated into higher-order models of touch receptors because of its accurate simulation of RA currents.
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Affiliation(s)
- Janez Prešern
- Department of Apiculture, Agricultural Institute of Slovenia, Hacquetova ul. 17, 1000, Ljubljana, Slovenia
| | - Aleš Škorjanc
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000, Ljubljana, Slovenia
| | - Tomaž Rodič
- Faculty of Natural sciences and Engineering, University of Ljubljana, Aškerčeva cesta 12, 1000, Ljubljana, Slovenia
| | - Jan Benda
- Institute for Neurobiology, University of Tübingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany.
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27
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Ahern CA, Payandeh J, Bosmans F, Chanda B. The hitchhiker's guide to the voltage-gated sodium channel galaxy. ACTA ACUST UNITED AC 2016; 147:1-24. [PMID: 26712848 PMCID: PMC4692491 DOI: 10.1085/jgp.201511492] [Citation(s) in RCA: 217] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
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.
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Affiliation(s)
- Christopher A Ahern
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242
| | - Jian Payandeh
- Department of Structural Biology, Genentech, Inc., South San Francisco, CA 94080
| | - Frank Bosmans
- Department of Physiology and Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD 21205 Department of Physiology and Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, MD 21205
| | - Baron Chanda
- Department of Neuroscience and Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705 Department of Neuroscience and Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI 53705
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Boiteux C, Allen TW. Understanding Sodium Channel Function and Modulation Using Atomistic Simulations of Bacterial Channel Structures. CURRENT TOPICS IN MEMBRANES 2016; 78:145-82. [PMID: 27586284 DOI: 10.1016/bs.ctm.2016.07.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Sodium channels are chief proteins involved in electrical signaling in the nervous system, enabling critical functions like heartbeat and brain activity. New high-resolution X-ray structures for bacterial sodium channels have created an opportunity to see how these proteins operate at the molecular level. An important challenge to overcome is establishing relationships between the structures and functions of mammalian and bacterial channels. Bacterial sodium channels are known to exhibit the main structural features of their mammalian counterparts, as well as several key functional characteristics, including selective ion conduction, voltage-dependent gating, pore-based inactivation and modulation by local anesthetic, antiarrhythmic and antiepileptic drugs. Simulations have begun to shed light on each of these features in the past few years. Despite deviations in selectivity signatures for bacterial and mammalian channels, simulations have uncovered the nature of the multiion conduction mechanism associated with Na(+) binding to a high-field strength site established by charged glutamate side chains. Simulations demonstrated a surprising level of flexibility of the protein, showing that these side chains are active participants in the permeation process. They have also uncovered changes in protein structure, leading to asymmetrical collapses of the activation gate that have been proposed to correspond to inactivated structures. These observations offer the potential to examine the mechanisms of state-dependent drug activity, focusing on pore-blocking and pore-based slow inactivation in bacterial channels, without the complexities of inactivation on multiple timescales seen in eukaryotic channels. Simulations have provided molecular views of the interactions of drugs, consistent with sites predicted in mammalian channels, as well as a wealth of other sites as potential new drug targets. In this chapter, we survey the new insights into sodium channel function that have emerged from studies of simpler bacterial channels, which provide an excellent learning platform, and promising avenues for mechanistic discovery and pharmacological development.
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Affiliation(s)
- C Boiteux
- RMIT University, Melbourne, VIC, Australia
| | - T W Allen
- RMIT University, Melbourne, VIC, Australia; University of California Davis, Davis, CA, United States
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Gawali V, Todt H. Mechanism of Inactivation in Voltage-Gated Na+ Channels. CURRENT TOPICS IN MEMBRANES 2016; 78:409-50. [DOI: 10.1016/bs.ctm.2016.07.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Tse G, Yeo JM. Conduction abnormalities and ventricular arrhythmogenesis: The roles of sodium channels and gap junctions. IJC HEART & VASCULATURE 2015; 9:75-82. [PMID: 26839915 PMCID: PMC4695916 DOI: 10.1016/j.ijcha.2015.10.003] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 10/19/2015] [Indexed: 01/12/2023]
Abstract
Ventricular arrhythmias arise from disruptions in the normal orderly sequence of electrical activation and recovery of the heart. They can be categorized into disorders affecting predominantly cellular depolarization or repolarization, or those involving action potential (AP) conduction. This article briefly discusses the factors causing conduction abnormalities in the form of unidirectional conduction block and reduced conduction velocity (CV). It then examines the roles that sodium channels and gap junctions play in AP conduction. Finally, it synthesizes experimental results to illustrate molecular mechanisms of how abnormalities in these proteins contribute to such conduction abnormalities and hence ventricular arrhythmogenesis, in acquired pathologies such as acute ischaemia and heart failure, as well as inherited arrhythmic syndromes.
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Affiliation(s)
- Gary Tse
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Jie Ming Yeo
- School of Medicine, Imperial College London, SW7 2AZ, UK
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31
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Affiliation(s)
- William A Catterall
- Department of Pharmacology, University of Washington, Seattle, Washington 98195-7280.
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32
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Veerman CC, Wilde AAM, Lodder EM. The cardiac sodium channel gene SCN5A and its gene product NaV1.5: Role in physiology and pathophysiology. Gene 2015; 573:177-87. [PMID: 26361848 DOI: 10.1016/j.gene.2015.08.062] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Revised: 07/31/2015] [Accepted: 08/27/2015] [Indexed: 12/18/2022]
Abstract
The gene SCN5A encodes the main cardiac sodium channel NaV1.5. This channel predominates the cardiac sodium current, INa, which underlies the fast upstroke of the cardiac action potential. As such, it plays a crucial role in cardiac electrophysiology. Over the last 60years a tremendous amount of knowledge regarding its function at the electrophysiological and molecular level has been acquired. Furthermore, genetic studies have shown that mutations in SCN5A are associated with multiple cardiac diseases (e.g. Brugada syndrome, Long QT syndrome, conduction disease and cardiomyopathy), while genetic variation in the general population has been associated with differences in cardiac conduction and risk of arrhythmia through genome wide association studies. In this review we aim to give an overview of the current knowledge (and the gaps therein) on SCN5A and NaV1.5.
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Affiliation(s)
- Christiaan C Veerman
- Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands
| | - Arthur A M Wilde
- Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands.
| | - Elisabeth M Lodder
- Department of Clinical and Experimental Cardiology, Academic Medical Center, Amsterdam, The Netherlands.
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33
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O'Leary ME, Chahine M. MTSET modification of D4S6 cysteines stabilize the fast inactivated state of Nav1.5 sodium channels. Front Pharmacol 2015; 6:118. [PMID: 26150789 PMCID: PMC4472985 DOI: 10.3389/fphar.2015.00118] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 05/20/2015] [Indexed: 11/30/2022] Open
Abstract
The transmembrane S6 segments of Na+ sodium channels form the cytoplasmic entrance of the channel and line the internal aspects of the aqueous pore. This region of the channel has been implicated in Na+ channel permeation, gating, and pharmacology. In this study we utilized cysteine substitutions and methanethiosulfonate reagent (MTSET) to investigate the role of the S6 segment of homologous domain 4 (D4S6) in the gating of the cardiac (Nav1.5) channel. D4S6 cysteine mutants were heterologously expressed in tsA201 cells and currents recorded using whole-cell patch clamp. Internal MTSET reduced the peak Na+ currents, induced hyperpolarizing shifts in steady-state inactivation and slowed the recovery of mutant channels with cysteines inserted near the middle (F1760C, V1763C) and C-terminus (Y1767C) of the D4S6. These findings suggested a link between the MTSET inhibition and fast inactivation. This was confirmed by expressing the V1763C and Y1767C mutations in non-inactivating Nav1.5 channels. Removing inactivation abolished the MTSET inhibition of the V1763C and Y1767C mutants. The data indicate that the MTSET-induced reduction in current primarily results from slower recovery from inactivation that produces hyperpolarizing shifts in fast inactivation and decreases the steady-state availability of the channels. This contrasted with a cysteine inserted near the C-terminus of the D4S6 (I1770C) where MTSET increased the persistent Na+ current at depolarized voltages consistent with impaired fast inactivation. Covalent modification of D4S6 cysteines with MTSET adduct appears to reduce the mobility of the D4S6 segment and stabilize the channels in the fast inactivated state. These findings indicate that residues located near the middle and C-terminus of the D4S6 play an important role in fast inactivation.
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Affiliation(s)
- Michael E O'Leary
- Department of Biomedical Sciences, Cooper Medical School of Rowan University, Camden, NJ USA
| | - Mohamed Chahine
- Department of Medicine, Research Centre, Institute Universitaire en Santé Mentale de Québec, Laval University Québec, QC, Canada
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Abstract
Voltage-gated sodium channels initiate action potentials in nerve, muscle and other excitable cells. Early physiological studies described sodium selectivity, voltage-dependent activation and fast inactivation, and developed conceptual models for sodium channel function. This review article follows the topics of my 2013 Sharpey-Schafer Prize Lecture and gives an overview of research using a combination of biochemical, molecular biological, physiological and structural biological approaches that have elucidated the structure and function of sodium channels at the atomic level. Structural models for voltage-dependent activation, sodium selectivity and conductance, drug block and both fast and slow inactivation are discussed. A perspective for the future envisions new advances in understanding the structural basis for sodium channel function and the opportunity for structure-based discovery of novel therapeutics.
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Affiliation(s)
- William A Catterall
- W. A. Catterall: Department of Pharmacology, Box 357280, University of Washington, Seattle, WA 98195-7280, USA.
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Multiple pore conformations driven by asynchronous movements of voltage sensors in a eukaryotic sodium channel. Nat Commun 2013; 4:1350. [PMID: 23322038 PMCID: PMC3562458 DOI: 10.1038/ncomms2356] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Accepted: 12/04/2012] [Indexed: 11/08/2022] Open
Abstract
Voltage-dependent Na(+) channels are crucial for electrical signalling in excitable cells. Membrane depolarization initiates asynchronous movements in four non-identical voltage-sensing domains of the Na(+) channel. It remains unclear to what extent this structural asymmetry influences pore gating as compared with outwardly rectifying K(+) channels, where channel opening results from a final concerted transition of symmetric pore gates. Here we combine single channel recordings, cysteine accessibility and voltage clamp fluorimetry to probe the relationships between voltage sensors and pore conformations in an inactivation deficient Nav1.4 channel. We observe three distinct conductance levels such that DI-III voltage sensor activation is kinetically correlated with formation of a fully open pore, whereas DIV voltage sensor movement underlies formation of a distinct subconducting pore conformation preceding inactivation in wild-type channels. Our experiments reveal that pore gating in sodium channels involves multiple transitions driven by asynchronous movements of voltage sensors. These findings shed new light on the mechanism of coupling between activation and fast inactivation in voltage-gated sodium channels.
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Catterall WA. Voltage-gated sodium channels at 60: structure, function and pathophysiology. J Physiol 2012; 590:2577-89. [PMID: 22473783 DOI: 10.1113/jphysiol.2011.224204] [Citation(s) in RCA: 472] [Impact Index Per Article: 39.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Voltage-gated sodium channels initiate action potentials in nerve, muscle and other excitable cells. The sodium current that initiates the nerve action potential was discovered by Hodgkin and Huxley using the voltage clamp technique in their landmark series of papers in The Journal of Physiology in 1952. They described sodium selectivity, voltage-dependent activation and fast inactivation, and they developed a quantitative model for action potential generation that has endured for many decades. This article gives an overview of the legacy that has evolved from their work, including development of conceptual models of sodium channel function, discovery of the sodium channel protein, analysis of its structure and function, determination of its structure at high resolution, definition of the mechanism and structural basis for drug block, and exploration of the role of the sodium channel as a target for disease mutations. Structural models for sodium selectivity and conductance, voltage-dependent activation, fast inactivation and drug block are discussed. A perspective for the future envisions new advances in understanding the structural basis for sodium channel function, the role of sodium channels in disease and the opportunity for discovery of novel therapeutics.
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Affiliation(s)
- William A Catterall
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7280, USA.
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Bargeton B, Kellenberger S. The contact region between three domains of the extracellular loop of ASIC1a is critical for channel function. J Biol Chem 2010; 285:13816-26. [PMID: 20215117 DOI: 10.1074/jbc.m109.086843] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Acid-sensing ion channels are members of the epithelial Na(+) channel/degenerin family. They are neuronal nonvoltage-gated Na(+) channels that are activated by extracellular acidification. In this study, we investigated the role of a highly conserved region of the extracellular part of ASIC1a that forms the contact between the finger domain, the adjacent beta-ball, and the upper palm domain in ASIC1a. The finger domain contributes to the pH-dependent gating and is linked via this contact zone to the rest of the protein. We found that mutation to Cys of residues in this region led to decreased channel expression and current amplitudes. Exposure of the engineered Cys residues to Cd(2+) or to charged methane thiosulfonate sulfhydryl reagents further reduced current amplitudes. This current inhibition was not due to changes in acid-sensing ion channel pH dependence or unitary conductance and was likely due to a decrease of the probability of channel opening. For some mutants, the effect of sulfhydryl reagents depended on the pH of exposure in the range 7.4 to 6.8, suggesting that this zone undergoes conformational changes during inactivation. Our study identifies a region in ASIC1a whose integrity is required for normal channel function.
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Affiliation(s)
- Benoîte Bargeton
- Department of Pharmacology and Toxicology, University of Lausanne, CH-1005 Lausanne, Switzerland
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38
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Dib-Hajj SD, Estacion M, Jarecki BW, Tyrrell L, Fischer TZ, Lawden M, Cummins TR, Waxman SG. Paroxysmal extreme pain disorder M1627K mutation in human Nav1.7 renders DRG neurons hyperexcitable. Mol Pain 2008; 4:37. [PMID: 18803825 PMCID: PMC2556659 DOI: 10.1186/1744-8069-4-37] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Accepted: 09/19/2008] [Indexed: 01/20/2023] Open
Abstract
Background Paroxysmal extreme pain disorder (PEPD) is an autosomal dominant painful neuropathy with many, but not all, cases linked to gain-of-function mutations in SCN9A which encodes voltage-gated sodium channel Nav1.7. Severe pain episodes and skin flushing start in infancy and are induced by perianal probing or bowl movement, and pain progresses to ocular and mandibular areas with age. Carbamazepine has been effective in relieving symptoms, while other drugs including other anti-epileptics are less effective. Results Sequencing of SCN9A coding exons from an English patient, diagnosed with PEPD, has identified a methionine 1627 to lysine (M1627K) substitution in the linker joining segments S4 and S5 in domain IV. We confirm that M1627K depolarizes the voltage-dependence of fast-inactivation without substantially altering activation or slow-inactivation, and inactivates from the open state with slower kinetics. We show here that M1627K does not alter development of closed-state inactivation, and that M1627K channels recover from fast-inactivation faster than wild type channels, and produce larger currents in response to a slow ramp stimulus. Using current-clamp recordings, we also show that the M1627K mutant channel reduces the threshold for single action potentials in DRG neurons and increases the number of action potentials in response to graded stimuli. Conclusion M1627K mutation was previously identified in a sporadic case of PEPD from France, and we now report it in an English family. We confirm the initial characterization of mutant M1627K effect on fast-inactivation of Nav1.7 and extend the analysis to other gating properties of the channel. We also show that M1627K mutant channels render DRG neurons hyperexcitable. Our new data provide a link between altered channel biophysics and pain in PEPD patients.
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Affiliation(s)
- Sulayman D Dib-Hajj
- Deptartment of Neurology, Yale University School of Medicine, New Haven, CT 06510, USA.
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An ion-responsive motif in the second transmembrane segment of rhodopsin-like receptors. Amino Acids 2008; 35:1-15. [PMID: 18266053 DOI: 10.1007/s00726-008-0637-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Accepted: 11/06/2007] [Indexed: 12/13/2022]
Abstract
A L(M)xxxD(N, E) motif (x=a non-ionic amino acid residue, most frequently A, S, L or F; small capitals indicating a minor representation) is found in the second transmembrane (tm2) segment of most G-protein coupling metazoan receptors of the rhodopsin family (Rh-GPCRs). Changes in signal transduction, agonist binding and receptor cycling are known for numerous receptors bearing evolved or experimentally introduced mutations in this tm2 motif, especially of its aspartate residue. The [Na(+)] sensitivity of the receptor-agonist interaction relates to this aspartate in a number of Rh-GPCRs. Native non-conservative mutations in the tm2 motif only rarely coincide with significant changes in two other ubiquitous features of the rhodopsin family, the seventh transmembrane N(D)PxxY(F) motif and the D(E)RY(W,F) or analogous sequence at the border of the third transmembrane helix and the second intracellular loop. Native tm2 mutations with Rh-GPCRs frequently result in constitutive signaling, and with visual opsins also in shifts to short-wavelength sensitivity. Substitution of a strongly basic residue for the tm2 aspartate in Taste-2 receptors could be connected to a lack of sodium sensing by these receptors. These properties could be consistent with ionic interactions, and even of ion transfer, that involve the tm2 motif. A decrease in cation sensing by this motif is usually connected to an enhanced constitutive interaction of the mutated receptors with cognate G- proteins, and also relates to both the constitutive and the overall activity of the short-wavelength opsins.
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Sites and molecular mechanisms of modulation of Na(v)1.2 channels by Fyn tyrosine kinase. J Neurosci 2007; 27:11543-51. [PMID: 17959797 DOI: 10.1523/jneurosci.1743-07.2007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Voltage-gated sodium channels are important targets for modulation of electrical excitability by neurotransmitters and neurotrophins acting through protein phosphorylation. Fast inactivation of Na(V)1.2 channels is regulated via tyrosine phosphorylation by Fyn kinase and dephosphorylation by receptor phosphoprotein tyrosine phosphatase-beta, which are associated in a signaling complex. Here we have identified the amino acid residues on Na(V)1.2 channels that coordinate binding of Fyn kinase and mediate inhibition of sodium currents by enhancing fast inactivation. Fyn kinase binds to a Src homology 3 (SH3)-binding motif in the second half of the intracellular loop connecting domains I and II (L(I-II)) of Na(V)1.2, and mutation of that SH3-binding motif prevents Fyn binding and Fyn enhancement of fast inactivation of sodium currents. Analysis of tyrosine phosphorylation sites by mutagenesis and functional expression revealed a multisite regulatory mechanism. Y66 and Y1893, which are in consensus sequences appropriate for binding to the Fyn SH2 domain after phosphorylation, are both required for optimal binding and regulation by Fyn. Y730, which is located near the SH3-binding motif in L(I-II), and Y1497 and Y1498 in the inactivation gate in L(III-IV), are also required for optimal regulation. Phosphorylation of these sites likely promotes fast inactivation. Fast inactivation of the closely related Na(V)1.1 channels is not modulated by Fyn, and these channels do not contain an SH3-binding motif in L(I-II). Subtype-selective modulation by tyrosine phosphorylation/dephosphorylation provides a mechanism for differential regulation of sodium channels by neurotrophins and tyrosine phosphorylation in unmyelinated axons and dendrites, where Na(V)1.2 channels are expressed in brain neurons.
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Szendroedi J, Sandtner W, Zarrabi T, Zebedin E, Hilber K, Dudley SC, Fozzard HA, Todt H. Speeding the recovery from ultraslow inactivation of voltage-gated Na+ channels by metal ion binding to the selectivity filter: a foot-on-the-door? Biophys J 2007; 93:4209-24. [PMID: 17720727 PMCID: PMC2098733 DOI: 10.1529/biophysj.107.104794] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Slow inactivated states in voltage-gated ion channels can be modulated by binding molecules both to the outside and to the inside of the pore. Thus, external K(+) inhibits C-type inactivation in Shaker K(+) channels by a "foot-in-the-door" mechanism. Here, we explore the modulation of a very long-lived inactivated state, ultraslow inactivation (I(US)), by ligand binding to the outer vestibule in voltage-gated Na(+) channels. Blocking the outer vestibule by a mutant mu-conotoxin GIIIA substantially accelerated recovery from I(US). A similar effect was observed if Cd(2+) was bound to a cysteine engineered to the selectivity filter (K1237C). In K1237C channels, exposed to 30 microM Cd(2+), the time constant of recovery from I(US) was decreased from 145.0 +/- 10.2 s to 32.5 +/- 3.3 s (P < 0.001). Recovery from I(US) was only accelerated if Cd(2+) was added to the bath solution during recovery (V = -120 mV) from I(US), but not when the channels were selectively exposed to Cd(2+) during the development of I(US) (-20 mV). These data could be explained by a kinetic model in which Cd(2+) binds with high affinity to a slow inactivated state (I(S)), which is transiently occupied during recovery from I(US). A total of 50 microM Cd(2+) produced an approximately 8 mV hyperpolarizing shift of the steady-state inactivation curve of I(S), supporting this kinetic model. Binding of lidocaine to the internal vestibule significantly reduced the number of channels entering I(US), suggesting that I(US) is associated with a conformational change of the internal vestibule of the channel. We propose a molecular model in which slow inactivation (I(S)) occurs by a closure of the outer vestibule, whereas I(US) arises from a constriction of the internal vestibule produced by a widening of the selectivity filter region. Binding of Cd(2+) to C1237 promotes the closure of the selectivity filter region, thereby hastening recovery from I(US). Thus, Cd(2+) ions may act like a foot-on-the-door, kicking the I(S) gate to close.
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Affiliation(s)
- Julia Szendroedi
- Center for Biomolecular Medicine and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
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Abstract
Electrical activity in the heart depends critically on the interactions of multiple ion channels to coordinate the timing of excitation and contraction of the ventricles. Voltage-gated sodium channels underlie the rapid spread of impulses through the atria and ventricles, but the importance of sodium (Na(+)) channels to the control of the ventricular action potential has only most recently become apparent through the investigation of the relationship between mutation-induced clinical phenotypes and the altered function of mutant Na(+) channels linked to inherited arrhythmias. Investigation into the structural basis of disease-associated mutations of the cardiac Na(+) channel has led to the discovery of novel role of the Na(+) channel carboxy-terminal (CT) domain in controlling channel inactivation. Intramolecular interactions between the carboxy-terminal domain and an intracellular peptide loop that forms the inactivation gate are required to minimize channel reopening during prolonged depolarization. Disruption of this interaction leads to persistent sodium channel current, action potential prolongation, and elevated risk of cardiac arrhythmia.
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Affiliation(s)
- Robert S Kass
- Department of Pharmacology, Columbia University, New York, New York 10032, USA.
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Abstract
The congenital long QT syndrome is a rare disease in which inherited mutations of genes coding for ion channel subunits, or channel interacting proteins, delay repolarization of the human ventricle and predispose mutation carriers to the risk of serious or fatal arrhythmias. Though a rare disorder, the long QT syndrome has provided invaluable insight from studies that have bridged clinical and pre-clinical (basic science) medicine. In this brief review, we summarize some of the key clinical and genetic characteristics of this disease and highlight novel findings about ion channel structure, function, and the causal relationship between channel dysfunction and human disease, that have come from investigations of this disorder.
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Affiliation(s)
- R S Kass
- Department of Pharmacology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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The YK, Fernandes J, Popa MO, Alekov AK, Timmer J, Lerche H. Modeling of single noninactivating Na+ channels: evidence for two open and several fast inactivated states. Biophys J 2006; 90:3511-22. [PMID: 16513781 PMCID: PMC1440733 DOI: 10.1529/biophysj.105.073072] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated Na(+) channels play a fundamental role in the excitability of nerve and muscle cells. Defects in fast Na(+) channel inactivation can cause hereditary muscle diseases with hyper- or hypoexcitability of the sarcolemma. To explore the kinetics and gating mechanisms of noninactivating muscle Na(+) channels on a molecular level, we analyzed single channel currents from wild-type and five mutant Na(+) channels. The mutations were localized in different protein regions which have been previously shown to be important for fast inactivation (D3-D4-linker, D3/S4-S5, D4/S4-S5, D4/S6) and exhibited distinct grades of defective fast inactivation with varying levels of persistent Na(+) currents caused by late channel reopenings. Different gating schemes were fitted to the data using hidden Markov models with a correction for time interval omission and compared statistically. For all investigated channels including the wild-type, two open states were necessary to describe our data. Whereas one inactivated state was sufficient to fit the single channel behavior of wild-type channels, modeling the mutants with impaired fast inactivation revealed evidence for several inactivated states. We propose a single gating scheme with two open and three inactivated states to describe the behavior of all five examined mutants. This scheme provides a biological interpretation of the collected data, based on previous investigations in voltage-gated Na(+) and K(+) channels.
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Affiliation(s)
- Yu-Kai The
- Institut für Physik, Freiburger Zentrum für Datenanalyse und Modellbildung, Universität Freiburg, Freiburg, Germany
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Zhu Y, Kyle JW, Lee PJ. Flecainide sensitivity of a Na channel long QT mutation shows an open-channel blocking mechanism for use-dependent block. Am J Physiol Heart Circ Physiol 2006; 291:H29-37. [PMID: 16501012 DOI: 10.1152/ajpheart.01317.2005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A long QT mutation in the cardiac sodium channel, D1790G (DG), shows enhanced flecainide use-dependent block (UDB). The relative importance of open and inactivated states of the channel in flecainide UDB has been controversial. We used a modifiable, inactivation-deficient mutant channel that contains the F1486C mutation in the IFM motif to investigate the UDB difference between the wild-type (WT-ICM) and DG (DG-ICM) channels. UDB at 5 Hz was greater in DG-ICM than WT-ICM, and IC50 values for steady-state UDB were 7.19 and 18.06 microM, respectively. When [2-(trimethyammonium) ethyl]methanethiosulfonate bromide (MTSET) was included in the pipette and fast inactivation was disabled, IC50 was 5.04 microM for DG-ICM and 12.63 microM for WT-ICM. We measured open-channel block by flecainide directly in MTSET-treated, noninactivating ICM channels. Steady-state block was higher for DG-ICM than WT-ICM (IC50 was 2.34 microM for DG-ICM and 5.87 microM for WT-ICM), suggesting that open-channel block is an important determinant of flecainide UDB. We obtained association (kon) and dissociation (koff) rates for open-channel block by the Langmuir-isotherm model. They were koff = 31.37 s(-1), kon = 5.83 s(-1).microM(-1), and calculated Kd = 5.38 microM for WT-ICM (where Kd = koff/kon); and koff = 24.88 s(-1), kon = 9.54 s(-1).microM(-1), and calculated Kd = 2.61 microM for DG-ICM. These Kd values were similar to IC50 measured from steady-state open-channel block. Furthermore, we modeled UDB mathematically by using these kinetic rates and found that the model predicted experimental UDB accurately. The recovery from UDB had a minor contribution to UDB. Flecainide UDB is predominantly determined by an open-channel blocking mechanism, and DG-ICM channels appeared to have an altered open-channel state with higher flecainide affinity than WT-ICM.
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Affiliation(s)
- Yujie Zhu
- Department of Medicine and Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, IL 60612, USA
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Abstract
Voltage-gated sodium channels open (activate) when the membrane is depolarized and close on repolarization (deactivate) but also on continuing depolarization by a process termed inactivation, which leaves the channel refractory, i.e., unable to open again for a period of time. In the “classical” fast inactivation, this time is of the millisecond range, but it can last much longer (up to seconds) in a different slow type of inactivation. These two types of inactivation have different mechanisms located in different parts of the channel molecule: the fast inactivation at the cytoplasmic pore opening which can be closed by a hinged lid, the slow inactivation in other parts involving conformational changes of the pore. Fast inactivation is highly vulnerable and affected by many chemical agents, toxins, and proteolytic enzymes but also by the presence of β-subunits of the channel molecule. Systematic studies of these modulating factors and of the effects of point mutations (experimental and in hereditary diseases) in the channel molecule have yielded a fairly consistent picture of the molecular background of fast inactivation, which for the slow inactivation is still lacking.
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Affiliation(s)
- Werner Ulbricht
- Psychologisches Institut, University of Kiel, Hermann-Rodewald-Strasse 5, D-24118 Kiel, Germany.
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47
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Affiliation(s)
- Robert S Kass
- Department of Pharmacology, Columbia University, New York, NY 10027, USA
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48
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Sheets MF, Hanck DA. Charge immobilization of the voltage sensor in domain IV is independent of sodium current inactivation. J Physiol 2004; 563:83-93. [PMID: 15576449 PMCID: PMC1665564 DOI: 10.1113/jphysiol.2004.077644] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Recovery from fast inactivation in voltage-dependent Na+ channels is associated with a slow component in the time course of gating charge during repolarization (i.e. charge immobilization), which results from the slow movement of the S4 segments in domains III and IV (S4-DIII and S4-DIV). Previous studies have shown that the non-specific removal of fast inactivation by the proteolytic enzyme pronase eliminated charge immobilization, while the specific removal of fast inactivation (by intracellular MTSET modification of a cysteine substituted for the phenylalanine in the IFM motif, ICMMTSET, in the inactivation particle formed by the linker between domains III and IV) only reduced the amount of charge immobilization by nearly one-half. To investigate the molecular origin of the remaining slow component of charge immobilization we studied the human cardiac Na+ channel (hH1a) in which the outermost arginine in the S4-DIV, which contributes approximately 20% to total gating charge (Qmax), was mutated to a cysteine (R1C-DIV). Gating charge could be fully restored in R1C-DIV by exposure to extracellular MTSEA, a positively charged methanethiosulphonate reagent. The RIC-DIV mutation was combined with ICMMTSET to remove fast inactivation, and the gating currents of R1C-DIV-ICM(MTSET) were recorded before and after modification with MTSEAo. Prior to MTSEAo, the time course of the gating charge during repolarization (off-charge) was best described by a single fast time constant. After MTSEA, the off-charge had both fast and slow components, with the slow component accounting for nearly 35% of Qmax. These results demonstrate that the slow movement of the S4-DIV during repolarization is not dependent upon the normal binding of the inactivation particle.
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Affiliation(s)
- Michael F Sheets
- The Nora Eccles Harrison Cardiovascular Research & Training Institute and Department of Internal Medicine, University of Utah, Salt Lake City, UT 84112, USA.
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49
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Abstract
Mibefradil is a T-type Ca2+ channel antagonist with reported cross-reactivity with other classes of ion channels, including K+, Cl-, and Na+ channels. Using whole-cell voltage clamp, we examined mibefradil block of four Na+ channel isoforms expressed in human embryonic kidney cells: Nav1.5 (cardiac), Nav1.4 (skeletal muscle), Nav1.2 (brain), and Nav1.7 (peripheral nerve). Mibefradil blocked Nav1.5 in a use/frequency-dependent manner, indicating preferential binding to states visited during depolarization. Mibefradil blocked currents of all Na+ channel isoforms with similar affinity and a dependence on holding potential, and drug off-rate was slowed at depolarized potentials (k(off) was 0.024/s at -130 mV and 0.007/s at -100 mV for Nav1.5). We further probed the interaction of mibefradil with inactivated Nav1.5 channels. Neither the degree nor the time course of block was dependent on the stimulus duration, which dramatically changed the residency time of channels in the fast-inactivated state. In addition, inhibiting the binding of the fast inactivation lid (Nav1.5 ICM + MTSET) did not alter mibefradil block, confirming that the drug does not preferentially interact with the fast-inactivated state. We also tested whether mibefradil interacted with slow-inactivated state(s). When selectively applied to channels after inducing slow inactivation with a 60-s pulse to -10 mV, mibefradil (1 microM) produced 45% fractional block in Nav1.5 and greater block (88%) in an isoform (Nav1.4) that slow-inactivates more completely. Our results suggest that mibefradil blocks Na+ channels in a state-dependent manner that does not depend on fast inactivation but probably involves interaction with one or more slow-inactivated state(s).
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Affiliation(s)
- Megan M McNulty
- Department of Neurobiology, University of Chicago, Illinois, USA
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50
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Motoike HK, Liu H, Glaaser IW, Yang AS, Tateyama M, Kass RS. The Na+ channel inactivation gate is a molecular complex: a novel role of the COOH-terminal domain. ACTA ACUST UNITED AC 2004; 123:155-65. [PMID: 14744988 PMCID: PMC2217430 DOI: 10.1085/jgp.200308929] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Electrical activity in nerve, skeletal muscle, and heart requires finely tuned activity of voltage-gated Na+ channels that open and then enter a nonconducting inactivated state upon depolarization. Inactivation occurs when the gate, the cytoplasmic loop linking domains III and IV of the alpha subunit, occludes the open pore. Subtle destabilization of inactivation by mutation is causally associated with diverse human disease. Here we show for the first time that the inactivation gate is a molecular complex consisting of the III-IV loop and the COOH terminus (C-T), which is necessary to stabilize the closed gate and minimize channel reopening. When this interaction is disrupted by mutation, inactivation is destabilized allowing a small, but important, fraction of channels to reopen, conduct inward current, and delay cellular repolarization. Thus, our results demonstrate for the first time that physiologically crucial stabilization of inactivation of the Na+ channel requires complex interactions of intracellular structures and indicate a novel structural role of the C-T domain in this process.
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Affiliation(s)
- Howard K Motoike
- Department of Pharmacology, College of Physicians & Surgeons of Columbia University, New York, NY 10032, USA
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