Referenced in: none

Automatically associated channels: Kv1.2

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

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

Journal, date & volume: Am. J. Physiol. Gastrointest. Liver Physiol., 2007 May , 292, G1233-42

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/17234891

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.