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Proc Natl Acad Sci U S A. 1997 Jan 21;94(2):428-32.

RGS4 and GAIP are GTPase-activating proteins for Gq alpha and block activation of phospholipase C beta by gamma-thio-GTP-Gq alpha.

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Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235-9041, USA.


RGS proteins constitute a newly appreciated and large group of negative regulators of G protein signaling. Four members of the RGS family act as GTPase-activating proteins (GAPs) with apparent specificity for members of the Gi alpha subfamily of G protein subunits. We demonstrate here that two RGS proteins, RGS4 and GAIP, also act as GAPs for Gq alpha, the G alpha protein responsible for activation of phospholipase C beta. Furthermore, these RGS proteins block activation of phospholipase C beta by guanosine 5'-(3-O-thio) triphosphate-Gq alpha. GAP activity does not explain this effect, which apparently results from occlusion of the binding site on G alpha for effector. Inhibitory effects of RGS proteins on G protein-mediated signaling pathways can be demonstrated by simple mixture of RGS4 or GAIP with plasma membranes.

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