title: Regulation of Na+channel inactivation by the DIII and DIV voltage-sensing domains.
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 NaVchannel 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 NaVchannel 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.
authors.affiliation: Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Hsu
authors.affiliation: Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130.
authors.forename: Wandi
authors.initials: W
authors.lastname: Zhu
authors.affiliation: Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130.
authors.forename: Angela R
authors.identifier: http://orcid.org/0000-0003-3743-8818
authors.initials: AR
authors.lastname: Schubert
authors.affiliation: Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130.
authors.forename: Taylor
authors.initials: T
authors.lastname: Voelker
authors.affiliation: MTA-DE-NAP B Ion Channel Structure-Function Research Group, Research Center for Molecular Medicine (RCMM), University of Debrecen, Debrecen H-4032, Hungary.
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Varga
authors.affiliation: Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130 jonsilva@wustl.edu.
authors.forename: Jonathan R
authors.identifier: http://orcid.org/0000-0002-3696-3955
authors.initials: JR
authors.lastname: Silva
mesh_terms: D000818:Animals; D004594:Electrophysiology; D015640:Ion Channel Gating / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D009865:Oocytes; D015222:Sodium Channels / Q000378:metabolism*; D014981:Xenopus
chemical_list: D015222:Sodium Channels