Ion permeation through a voltage- sensitive gating pore in brain sodium channels having voltage sensor mutations.
Voltage-gated sodium channels activate in response to depolarization, but it is unknown whether the voltage-sensing arginines in their S4 segments pivot across the lipid bilayer as voltage sensor paddles or move through the protein in a gating pore. Here we report that mutation of pairs of arginine gating charges to glutamine induces cation permeation through a gating pore in domain II of the Na(V)1.2a channel. Mutation of R850 and R853 induces a K(+)-selective inward cationic current in the resting state that is blocked by activation. Remarkably, mutation of R853 and R856 causes an outward cationic current with the opposite gating polarity. These results support a model in which the IIS4 gating charges move through a narrow constriction in a gating pore in the sodium channel protein during gating. Paired substitutions of glutamine allow cation movement through the constriction when appropriately positioned by the gating movements of the S4 segment.
Sokolov
Stanislav
S
Department of Pharmacology, University of Washington, Seattle, WA 98195, USA.
Scheuer
Todd
T
Catterall
William A
WA
D019943:Amino Acid Substitution; D000818:Animals; D001120:Arginine / Q000235:genetics; D004558:Electric Stimulation / Q000379:methods; D018846:Excitatory Amino Acids / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D016297:Mutagenesis, Site-Directed / Q000502:physiology; D009154:Mutation; D016202:N-Methylaspartate / Q000494:pharmacology; D062551:NAV1.2 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009431:Neural Conduction / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D009865:Oocytes; D018408:Patch-Clamp Techniques / Q000379:methods; D026902:Potassium Channel Blockers / Q000494:pharmacology; D026941:Sodium Channel Blockers / Q000494:pharmacology; D015222:Sodium Channels / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014162:Transfection / Q000379:methods; D014981:Xenopus
D018846:Excitatory Amino Acids; D007473:Ion Channels; D062551:NAV1.2 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins; D026902:Potassium Channel Blockers; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013779:Tetrodotoxin; D016202:N-Methylaspartate; D019789:Tetraethylammonium; D001120:Arginine