Regulation of KCNQ channels by manipulation of phosphoinositides.
Activation of phospholipase C (PLC) through G-protein-coupled receptors produces a large number of second messengers and regulates many physiological processes. Many membrane proteins including ion channels require the phosphoinositide phosphatidylinositol 4,5-bisphosphate (PIP(2)) to function. Activation of PLC can shut down their activity if it depletes the PIP(2) pool strongly. Such a mechanism accounts for the muscarinic suppression of current in KCNQ channels. We describe a variety of methods used to show that these channels require PIP(2) and that current in the channels is suppressed when receptor-activated PLC depletes PIP(2). The methods include observing translocation of lipid-sensitive protein domains, overexpression of enzymes of phosphoinositide metabolism, engineering these enzymes to move to the plasma membrane in response to a chemical signal, and direct chemical analysis of phospholipids. These approaches are general and can be used to test for PIP(2) requirements of other membrane proteins.
Suh
Byung-Chang
BC
Department of Physiology and Biophysics University of Washington School of Medicine, Seattle, WA 98195, USA. hille@u.washington.edu
Hille
Bertil
B
D019870:1-Phosphatidylinositol 4-Kinase / Q000378:metabolism; D000818:Animals; D006706:Homeostasis; D006801:Humans; D051656:KCNQ Potassium Channels / Q000502:physiology*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D010716:Phosphatidylinositols / Q000502:physiology*; D015290:Second Messenger Systems / Q000502:physiology; D010738:Type C Phospholipases / Q000378:metabolism
D051656:KCNQ Potassium Channels; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D019870:1-Phosphatidylinositol 4-Kinase; D010738:Type C Phospholipases