Molecular determinants of β1 subunit-induced gating modulation in voltage-dependent Na+ channels

Naomasa Makita, Paul B. Bennett, Alfred L. George*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

102 Scopus citations

Abstract

Recombinant brain, skeletal muscle, and heart voltage-gated Na+ channel α subunits differ in their functional responses to an accessory β1 subunit when coexpressed in Xenopus oocytes. We exploited the distinct β1 subunit responses observed for the human heart (hH1) and human skeletal muscle (hSkM1) isoforms to identify determinants of this response. Chimeric α subunits were constructed by exchanging the S5-S6 interhelical loops of each domain between hilt and hSkM1 and then examined for effects on inactivation induced by coexpressed β1 subunit in oocytes. Substitution of single S5-S6 loops in either domain 1 (D1/S5-S6) or domain 4 (D4/S5-S6) of hSkM1 by the corresponding segments of hill produced channels that exhibited an attenuated response to coexpressed β1 subunit. Substitutions of both D1/S5-S6 and D4/S5-S6 in hSkM1 by the corresponding loops from hilt completely abolished the effects of the β1 subunit on inactivation. The reciprocal chimera in which both D1/S5-S6 and D4/S5-S6 from hSkM1 were transplanted into hill exhibited significant β1 responsiveness (accelerated inactivation). The region within D4/S5-S6 that conferred β1 responsiveness was determined to reside primarily within an extracellular loop between the putative pore- forming segment SS2 and D4/S6. Gating modulation was also demonstrated using a chimeric β subunit consisting of the extracellular domains of β1 and the transmembrane and C-terminal domains of the rat brain β2 subunit. These results suggest that the D1/S5-S6 and D4/S5-S6 loops in the α subunit and the extracellular domain of the β1 subunit are important determinants of the β1 subunit-induced gating modulation in Na+ channels.

Original languageEnglish (US)
Pages (from-to)7117-7127
Number of pages11
JournalJournal of Neuroscience
Volume16
Issue number22
DOIs
StatePublished - Nov 15 1996

Keywords

  • Na channel
  • SCN4A
  • SCNSA
  • electrophysiology
  • hH1
  • hSkM1
  • heart
  • human ion channels
  • ion channel gating
  • skeletal muscle
  • subunit interaction

ASJC Scopus subject areas

  • Neuroscience(all)

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