Key result
Experimental methods confirm KCNQ channels require PIP2 and are suppressed when receptor-activated PLC depletes it.
Why the study?
Many membrane proteins including KCNQ channels require PIP2 to function, but the mechanisms regulating their activity via phosphoinositide manipulation needed clarification.
This methodological review outlines techniques to study the dependence of KCNQ channels and other membrane proteins on PIP2.
May inform future antiarrhythmic strategies via PIP2 signaling; leaves open its role in human cardiac physiology.
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.
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Suh et al. (2007) reported a review. Various methods, including lipid-sensitive protein domain translocation and enzyme engineering, demonstrate that KCNQ channels require PIP2 and are suppressed when receptor-activated PLC depletes PIP2.
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