Referenced in: none

Automatically associated channels: Kir2.1 , Kir2.2 , Kir3.1 , Kir3.2 , Slo1

Title: Signal transduction pathway for the substance P-induced inhibition of rat Kir3 (GIRK) channel.

Authors: Maki Koike-Tani, John M Collins, Takeharu Kawano, Peng Zhao, Qi Zhao, Tohru Kozasa, Shigehiro Nakajima, Yasuko Nakajima

Journal, date & volume: J. Physiol. (Lond.), 2005 Apr 15 , 564, 489-500

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/15731196

Abstract
Certain transmitters inhibit Kir3 (GIRK) channels, resulting in neuronal excitation. We analysed signalling mechanisms for substance P (SP)-induced Kir3 inhibition in relation to the role of phosphatidylinositol 4,5-bisphosphate (PIP(2)). SP rapidly - with a half-time of approximately 10 s with intracellular GTPgammaS and approximately 14 s with intracellular GTP - inhibits a robustly activated Kir3.1/Kir3.2 current. A mutant Kir3 channel, Kir3.1(M223L)/Kir3.2(I234L), which has a stronger binding to PIP(2) than does the wild type Kir3.1/Kir3.2, is inhibited by SP as rapidly as the wild type Kir3.1/Kir3.2. This result contradicts the idea that Kir3 inhibition originates from the depletion of PIP(2). A Kir2.1 (IRK1) mutant, Kir2.1(R218Q), despite having a weaker binding to PIP(2) than wild type Kir3.1/Kir3.2, shows a SP-induced inhibition slower than the wild type Kir3.1/Kir3.2 channel, again conflicting with the PIP(2) theory of channel inhibition. Co-immunoprecipitation reveals that Galpha(q) binds with Kir3.2, but not with Kir2.2 or Kir2.1. These functional results and co-immunoprecipitation data suggest that G(q) activation rapidly inhibits Kir3 (but not Kir2), possibly by direct binding of Galpha(q) to the channel.