Heterotrimeric G proteins play a pivotal role in GPCR signalling; they link receptors to intracellular\ud effectors and their inactivation by RGS proteins is a key factor in resetting the pathway following\ud stimulation. The precise GPCR:G protein:RGS combination determines the nature and duration of\ud the response. Investigating the activity of particular combinations is difficult in cells which contain\ud multiples of each component. We have therefore utilised a previously characterised yeast system to\ud express mammalian proteins in isolation. Human Gαq and Gα11 spontaneously activated the yeast\ud pheromone-response pathway by a mechanism which required the formation of Gα-GTP. This\ud provided an assay for the specific activity of human RGS proteins. RGS1, RGS2, RGS3 and RGS4\ud inhibited the spontaneous activity of both Gαq and Gα11 but, in contrast, RGS5 and RGS16 were\ud much less effective against Gα11 than Gαq. Interestingly, RGS2 and RGS3 were able to inhibit\ud signalling from the constitutively active Gαq\ud QL/Gα11\ud QL mutants, confirming the GAP-independent\ud activity of these RGS proteins. To determine if the RGS-Gα specificity was maintained under\ud conditions of GPCR stimulation, minor modifications to the C-terminus of Gαq/Gα11 enabled\ud coupling to an endogenous receptor. RGS2 and RGS3 were effective inhibitors of both Gα subunits\ud even at high levels of receptor stimulation, emphasising their GAP-independent activity. At low\ud levels of stimulation RGS5 and RGS16 retained their differential Gα activity, further highlighting\ud that RGS proteins can discriminate between two very closely related Gα subunits
To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.