Attenuation of G i - and G q -mediated signaling by expression of RGS4 or GAIP in mammalian cells

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Abstract
Protein regulators of G protein signaling (RGS proteins) were discovered as negative regulators of heterotrimeric G protein-mediated signal transduction in yeast and worms. Experiments with purified recombinant proteins in vitro have established that RGS proteins accelerate the GTPase activity of certain G protein α subunits (the reaction responsible for their deactivation); they can also act as effector antagonists. We demonstrate herein that either of two such RGS proteins, RGS4 or GAIP, attenuated signal transduction mediated by endogenous receptors, G proteins, and effectors when stably expressed as tagged proteins in transfected mammalian cells. The pattern of selectivity observed in vivo was similar to that seen in vitro . RGS4 and GAIP both attenuated G i -mediated inhibition of cAMP synthesis. RGS4 was more effective than GAIP in blocking G q -mediated activation of phospholipase Cβ.