title: Spontaneous receptor-independent heterotrimeric G-protein signalling in an RGS mutant.
abstract: Tripartite G-protein-coupled receptors (GPCRs) represent one of the largest groups of signal transducers, transmitting signals from hormones, neuropeptides, odorants, food and light. Ligand-bound receptors catalyse GDP/GTP exchange on the G-protein alpha-subunit (Galpha), leading to alpha-GTP separation from the betagamma subunits and pathway activation. Activating mutations in the receptors or G proteins underlie many human diseases, including some cancers, dwarfism and premature puberty. Regulators of G-protein signalling (RGS proteins) are known to modulate the level and duration of ligand-induced signalling by accelerating the intrinsic GTPase activity of the Galpha subunit, and thus reformation of the inactive GDP-bound Galpha. Here we find that even in the absence of receptor, mutation of the RGS family member Sst2 (refs 6-9) permits spontaneous activation of the G-protein-coupled mating pathway in Saccharomyces cerevisiae at levels normally seen only in the presence of ligand. Our work demonstrates the occurrence of spontaneous tripartite G-protein signalling in vivo and identifies a requirement for RGS proteins in preventing such receptor-independent activation.
authors.affiliation: Department of Molecular and Cell Biology, University of California Berkeley, 401 Barker Hall, Berkeley, CA 94720-3202, USA.
authors.forename: Daria E
authors.initials: DE
authors.lastname: Siekhaus
authors.forename: David G
authors.initials: DG
authors.lastname: Drubin
mesh_terms: D002469:Cell Separation; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D020710:RGS Proteins; D011956:Receptors, Cell Surface; D020962:Heterotrimeric GTP-Binding Proteins