p-RGS9-1 Background Information
Heterotrimeric G proteins function to relay information from cell surface receptors to various intracellular effectors. G proteins comprise a, b and g subunits, and following activation the a subunit binds GTP and dissociates from the bg complex (1). A large group of proteins have been identified as GTPase-activating proteins (GAPs), including the RGS (regulator of G protein signaling) family, which serve to deactivate specific Ga isoforms by increasing the rate at which they convert GTP to GDP (2,3). A subfamily of RGS proteins expressed in the central nervous system contain, in addition to the highly conserved RGS domain, a characteristic GGL domain, or G protein g subunit-like domain, which mediates binding to Gb 5 subunits (4,5). This subfamily, which includes RGS6, RGS7, RGS9 and RGS11, associates with Gb 5 to form active GAP complexes that are predominantly localized to the cytosol (6). RGS/b5 complexes preferentially target Gao subunit for hydrolysis and inhibit Gb1g2-mediated activation of phospholipase C (7).
