Referenced in: none

Automatically associated channels: Kir2.1 , Kir2.4 , Kir3.4

Title: Activation of inwardly rectifying K+ channels by distinct PtdIns(4,5)P2 interactions.

Authors: H Zhang, C He, X Yan, T Mirshahi, D E Logothetis

Journal, date & volume: Nat. Cell Biol., 1999 Jul , 1, 183-8

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/10559906

Abstract
Direct interactions of phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) with inwardly rectifying potassium channels are stronger with channels rendered constitutively active by binding to PtdIns(4,5)P2, such as IRK1, than with G-protein-gated channels (GIRKs). As a result, PtdIns(4,5)P2 alone can activate IRK1 but not GIRKs, which require extra gating molecules such as the beta gamma subunits of G proteins or sodium ions. Here we identify two conserved residues near the inner-membrane interface of these channels that are critical in interactions with PtdIns(4,5)P2. Between these two arginines, a conservative change of isoleucine residue 229 in GIRK4 to the corresponding leucine found in IRK1 strengthens GIRK4-PtdIns(4,5)P2 interactions, eliminating the need for extra gating molecules. A negatively charged GIRK4 residue, two positions away from the most strongly interacting arginine, mediates stimulation of channel activity by sodium by strengthening channel-PtdIns(4,5)P2 interactions. Our results provide a mechanistic framework for understanding how distinct gating mechanisms of inwardly rectifying potassium channels allow these channels to subserve their physiological roles.