Distinct modulation of Kv1.2 channel gating by wild type, but not open form, of syntaxin-1A

Leila Neshatian, Yuk M Leung, Youhou Kang, Xiaodong Gao, Huanli Xie, Robert G Tsushima, Herbert Y Gaisano, Nicholas E Diamant

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

SNARE proteins, syntaxin-1A (Syn-1A) and SNAP-25, inhibit delayed rectifier K(+) channels, K(v)1.1 and K(v)2.1, in secretory cells. We showed previously that the mutant open conformation of Syn-1A (Syn-1A L165A/E166A) inhibits K(v)2.1 channels more optimally than wild-type Syn-1A. In this report we examined whether Syn-1A in its wild-type and open conformations would exhibit similar differential actions on the gating of K(v)1.2, a major delayed rectifier K(+) channel in nonsecretory smooth muscle cells and some neuronal tissues. In coexpression and acute dialysis studies, wild-type Syn-1A inhibited K(v)1.2 current magnitude. Of interest, wild-type Syn-1A caused a right shift in the activation curves of K(v)1.2 without affecting its steady-state availability, an inhibition profile opposite to its effects on K(v)2.1 (steady-state availability reduction without changes in voltage dependence of activation). Also, although both wild-type and open-form Syn-1A bound equally well to K(v)1.2 in an expression system, open-form Syn-1A failed to reduce K(v)1.2 current magnitude or affect its gating. This is in contrast to the reported more potent effect of open-form Syn-1A on K(v)2.1 channels in secretory cells. This finding together with the absence of Munc18 and/or 13-1 in smooth muscles suggested that a change to an open conformation Syn-1A, normally facilitated by Munc18/13-1, is not required in nonsecretory smooth muscle cells. Taken together with previous reports, our results demonstrate the multiplicity of gating inhibition of different K(v) channels by Syn-1A and is compatible with versatility of Syn-1A modulation of repolarization in various secretory and nonsecretory (smooth muscle) cell types.

Original languageEnglish (US)
Pages (from-to)G1233-42
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume292
Issue number5
DOIs
StatePublished - May 2007

Keywords

  • Animals
  • Cats
  • Cells, Cultured
  • Epithelial Cells
  • Female
  • Humans
  • Ion Channel Gating
  • Kv1.2 Potassium Channel
  • Male
  • Munc18 Proteins
  • Muscle, Smooth
  • Nerve Tissue Proteins
  • Protein Conformation
  • Rats
  • Syntaxin 1
  • Journal Article
  • Research Support, Non-U.S. Gov't

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