title: Proton sensors in the pore domain of the cardiac voltage-gated sodium channel.
abstract: Protons impart isoform-specific modulation of inactivation in neuronal, skeletal muscle, and cardiac voltage-gated sodium (Na(V)) channels. Although the structural basis of proton block in Na(V) channels has been well described, the amino acid residues responsible for the changes in Na(V) kinetics during extracellular acidosis are as yet unknown. We expressed wild-type (WT) and two pore mutant constructs (H880Q and C373F) of the human cardiac Na(V) channel, Na(V)1.5, in Xenopus oocytes. C373F and H880Q both attenuated proton block, abolished proton modulation of use-dependent inactivation, and altered pH modulation of the steady-state and kinetic parameters of slow inactivation. Additionally, C373F significantly reduced the maximum probability of use-dependent inactivation and slow inactivation, relative to WT. H880Q also significantly reduced the maximum probability of slow inactivation and shifted the voltage dependence of activation and fast inactivation to more positive potentials, relative to WT. These data suggest that Cys-373 and His-880 in Na(V)1.5 are proton sensors for use-dependent and slow inactivation and have implications in isoform-specific modulation of Na(V) channels.
authors.affiliation: Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
authors.forename: David K
authors.initials: DK
authors.lastname: Jones
authors.forename: Colin H
authors.initials: CH
authors.lastname: Peters
authors.forename: Charlene R
authors.initials: CR
authors.lastname: Allard
authors.forename: Tom W
authors.initials: TW
authors.lastname: Claydon
authors.forename: Peter C
authors.initials: PC
authors.lastname: Ruben
mesh_terms: D000138:Acidosis / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000378:metabolism; D004594:Electrophysiology / Q000379:methods; D005260:Female; D006801:Humans; D007511:Ischemia; D008969:Molecular Sequence Data; D017202:Myocardial Ischemia / Q000378:metabolism; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000737:chemistry / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011522:Protons; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels; D013997:Time Factors; D061566:Voltage-Gated Sodium Channels / Q000378:metabolism*; D014981:Xenopus
chemical_list: D062554:NAV1.5 Voltage-Gated Sodium Channel; D011522:Protons; C568320:SCN5A protein, human; D015222:Sodium Channels; D061566:Voltage-Gated Sodium Channels