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Hsu EJ, Zhu W, Schubert AR, Voelker T, Varga Z, Silva JR. Regulation of Na + channel inactivation by the DIII and DIV voltage-sensing domains. J Gen Physiol 2017; 149:389-403. [PMID: 28232510 PMCID: PMC5339511 DOI: 10.1085/jgp.201611678] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 12/02/2016] [Accepted: 01/20/2017] [Indexed: 12/19/2022] Open
Abstract
Functional eukaryotic voltage-gated Na+ (NaV) channels comprise four domains (DI-DIV), each containing six membrane-spanning segments (S1-S6). Voltage sensing is accomplished by the first four membrane-spanning segments (S1-S4), which together form a voltage-sensing domain (VSD). A critical NaV channel gating process, inactivation, has previously been linked to activation of the VSDs in DIII and DIV. Here, we probe this interaction by using voltage-clamp fluorometry to observe VSD kinetics in the presence of mutations at locations that have been shown to impair NaV channel inactivation. These locations include the DIII-DIV linker, the DIII S4-S5 linker, and the DIV S4-S5 linker. Our results show that, within the 10-ms timeframe of fast inactivation, the DIV-VSD is the primary regulator of inactivation. However, after longer 100-ms pulses, the DIII-DIV linker slows DIII-VSD deactivation, and the rate of DIII deactivation correlates strongly with the rate of recovery from inactivation. Our results imply that, over the course of an action potential, DIV-VSDs regulate the onset of fast inactivation while DIII-VSDs determine its recovery.
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Affiliation(s)
- Eric J Hsu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130
| | - Wandi Zhu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130
| | - Angela R Schubert
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130
| | - Taylor Voelker
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130
| | - Zoltan Varga
- MTA-DE-NAP B Ion Channel Structure-Function Research Group, Research Center for Molecular Medicine (RCMM), University of Debrecen, Debrecen H-4032, Hungary
| | - Jonathan R Silva
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130
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Varga Z, Zhu W, Schubert AR, Pardieck JL, Krumholz A, Hsu EJ, Zaydman MA, Cui J, Silva JR. Direct Measurement of Cardiac Na+ Channel Conformations Reveals Molecular Pathologies of Inherited Mutations. Circ Arrhythm Electrophysiol 2015; 8:1228-39. [PMID: 26283144 DOI: 10.1161/circep.115.003155] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 07/26/2015] [Indexed: 01/11/2023]
Abstract
BACKGROUND Dysregulation of voltage-gated cardiac Na(+) channels (NaV1.5) by inherited mutations, disease-linked remodeling, and drugs causes arrhythmias. The molecular mechanisms whereby the NaV1.5 voltage-sensing domains (VSDs) are perturbed to pathologically or therapeutically modulate Na(+) current (INa) have not been specified. Our aim was to correlate INa kinetics with conformational changes within the 4 (DI-DIV) VSDs to define molecular mechanisms of NaV1.5 modulation. METHOD AND RESULTS Four NaV1.5 constructs were created to track the voltage-dependent kinetics of conformational changes within each VSD, using voltage-clamp fluorometry. Each VSD displayed unique kinetics, consistent with distinct roles in determining INa. In particular, DIII-VSD deactivation kinetics were modulated by depolarizing pulses with durations in the intermediate time domain that modulates late INa. We then used the DII-VSD construct to probe the molecular pathology of 2 Brugada syndrome mutations (A735V and G752R). A735V shifted DII-VSD voltage dependence to depolarized potentials, whereas G752R significantly slowed DII-VSD kinetics. Both mutations slowed INa activation, although DII-VSD activation occurred at higher potentials (A735V) or at later times (G752R) than ionic current activation, indicating that the DII-VSD allosterically regulates the rate of INa activation and myocyte excitability. CONCLUSIONS Our results reveal novel mechanisms whereby the NaV1.5 VSDs regulate channel activation and inactivation. The ability to distinguish distinct molecular mechanisms of proximal Brugada syndrome mutations demonstrates the potential of these methods to reveal how inherited mutations, post-translational modifications, and antiarrhythmic drugs alter NaV1.5 at the molecular level.
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Affiliation(s)
- Zoltan Varga
- From the Department of Biomedical Engineering, Washington University in St. Louis, MO (Z.V., W.Z., A.R.S., J.L.P., A.K., E.J.H., M.A.Z., J.C., J.R.S.); and MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, Hungary (Z.V.)
| | - Wandi Zhu
- From the Department of Biomedical Engineering, Washington University in St. Louis, MO (Z.V., W.Z., A.R.S., J.L.P., A.K., E.J.H., M.A.Z., J.C., J.R.S.); and MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, Hungary (Z.V.)
| | - Angela R Schubert
- From the Department of Biomedical Engineering, Washington University in St. Louis, MO (Z.V., W.Z., A.R.S., J.L.P., A.K., E.J.H., M.A.Z., J.C., J.R.S.); and MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, Hungary (Z.V.)
| | - Jennifer L Pardieck
- From the Department of Biomedical Engineering, Washington University in St. Louis, MO (Z.V., W.Z., A.R.S., J.L.P., A.K., E.J.H., M.A.Z., J.C., J.R.S.); and MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, Hungary (Z.V.)
| | - Arie Krumholz
- From the Department of Biomedical Engineering, Washington University in St. Louis, MO (Z.V., W.Z., A.R.S., J.L.P., A.K., E.J.H., M.A.Z., J.C., J.R.S.); and MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, Hungary (Z.V.)
| | - Eric J Hsu
- From the Department of Biomedical Engineering, Washington University in St. Louis, MO (Z.V., W.Z., A.R.S., J.L.P., A.K., E.J.H., M.A.Z., J.C., J.R.S.); and MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, Hungary (Z.V.)
| | - Mark A Zaydman
- From the Department of Biomedical Engineering, Washington University in St. Louis, MO (Z.V., W.Z., A.R.S., J.L.P., A.K., E.J.H., M.A.Z., J.C., J.R.S.); and MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, Hungary (Z.V.)
| | - Jianmin Cui
- From the Department of Biomedical Engineering, Washington University in St. Louis, MO (Z.V., W.Z., A.R.S., J.L.P., A.K., E.J.H., M.A.Z., J.C., J.R.S.); and MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, Hungary (Z.V.)
| | - Jonathan R Silva
- From the Department of Biomedical Engineering, Washington University in St. Louis, MO (Z.V., W.Z., A.R.S., J.L.P., A.K., E.J.H., M.A.Z., J.C., J.R.S.); and MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, Department of Biophysics and Cell Biology, University of Debrecen, Debrecen, Hungary (Z.V.).
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