RGS2-mediated regulation of Gqalpha.

Regulators of G-protein signaling (RGS) proteins are GTPase-activating proteins (GAPs) that attenuate signaling by heterotrimeric G proteins. In RGS2, three unique residues within the G-protein-binding (RGS) domain have been shown to direct its selective inhibition of Gqalpha function. The function of RGS2 as a regulator of Gq is also dependent on regulatory sequences in its amino-terminal domain that direct its localization to the plasma membrane. This work details various approaches that have been used to characterize the relative contribution of the RGS and regulatory domains in RGS2 to its function as a regulator of Gq signaling. Specifically, assays describing (i) the identification of alpha subunit binding partners for RGS2 (ii) the characterization of RGS2-mediated inhibition of Gq-dependent phosphatidylinositol signaling in tissue culture models, and (iii) the measurement of Gq-dependent calcium responses in vascular smooth muscle cells from RGS2-deficient mice are presented. Results from these studies have been used to demonstrate the high relative potency of RGS2 for the regulation of Gq signaling at the biochemical, cellular, and physiologic level.