Inhibition of somatostatin receptor 5-signaling by mammalian regulators of G-protein signaling (RGS) in yeast.
Regulators of G-protein signaling (RGSs) are negative regulators of G-protein coupled receptor (GPCR)-mediated signaling that function to limit the lifetime of receptor-activated G(alpha)-proteins. Here we show that four mammalian RGSs differentially inhibit the activation of a FUS1--LacZ reporter gene by the STE2 encoded GPCR in yeast. In order to examine the role of the GPCR in modulating RGS function, we functionally expressed the human somatostatin receptor 5 (SST(5)) in yeast. In the absence of RGSs, FUS1--LacZ activation in response to somatostatin increased in a dose-dependent manner in cells expressing SST(5). In contrast to the results obtained with Ste2p, all RGSs completely inhibited SST(5)-mediated signaling even at concentrations of agonist as high as 10(minus sign5) M. The ability of RGSs to inhibit SST(5) signaling was further assessed in cells expressing modified Gpa1 proteins. Even though SST(5)-mediated FUS1--LacZ activation was 5-fold more efficient with a Gpa1p/G(i3alpha) chimera, response to somatostatin was completely abolished by all four RGSs. Furthermore, we demonstrate that RGS1, RGS2 and RGS5 have reduced ability to inhibit SST(5)-mediated activation of the RGS-resistant Gpa1p(Gly302Ser) mutant suggesting that the ability to interact with the G(alpha)-protein is required for the inhibition of signaling. Taken together, our results indicate that RGSs serve as better GAPs for Gpa1p when activated by SST(5) than when this G-protein is activated by Ste2p.
Kong
Janice L
JL
Division of Cardiology, Department of Medicine, McGill University Hospital Center, Montreal, QC, Canada.
Panetta
Rosemarie
R
Song
Wei
W
Somerville
Wendy
W
Greenwood
Michael T
MT
D005656:Fungal Proteins / Q000235:genetics; D044385:GTP-Binding Protein alpha Subunits; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020690:GTPase-Activating Proteins; D017930:Genes, Reporter; D020962:Heterotrimeric GTP-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D009154:Mutation; D010957:Plasmids; D020710:RGS Proteins / Q000378:metabolism* / Q000494:pharmacology; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide / Q000096:biosynthesis / Q000235:genetics; D017481:Receptors, Somatostatin / Q000037:antagonists & inhibitors*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction / Q000187:drug effects; D013004:Somatostatin / Q000494:pharmacology; D014157:Transcription Factors
D005656:Fungal Proteins; D044385:GTP-Binding Protein alpha Subunits; D020690:GTPase-Activating Proteins; D020710:RGS Proteins; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide; D017481:Receptors, Somatostatin; C094301:SST2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C098799:RGS4 protein; D013004:Somatostatin; C094573:somatostatin receptor 5; C084293:GPA1 protein, S cerevisiae; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins