title: Dual positive and negative regulation of GPCR signaling by GTP hydrolysis.
abstract: G protein-coupled receptors (GPCRs) regulate a variety of intracellular pathways through their ability to promote the binding of GTP to heterotrimeric G proteins. Regulator of G protein signaling (RGS) proteins increases the intrinsic GTPase activity of Galpha-subunits and are widely regarded as negative regulators of G protein signaling. Using yeast we demonstrate that GTP hydrolysis is not only required for desensitization, but is essential for achieving a high maximal (saturated level) response. Thus RGS-mediated GTP hydrolysis acts as both a negative (low stimulation) and positive (high stimulation) regulator of signaling. To account for this we generated a new kinetic model of the G protein cycle where Galpha(GTP) enters an inactive GTP-bound state following effector activation. Furthermore, in vivo and in silico experimentation demonstrates that maximum signaling output first increases and then decreases with RGS concentration. This unimodal, non-monotone dependence on RGS concentration is novel. Analysis of the kinetic model has revealed a dynamic network motif that shows precisely how inclusion of the inactive GTP-bound state for the Galpha produces this unimodal relationship.
authors.affiliation: Molecular Organization and Assembly of Cells Centre, University of Warwick, Coventry, UK.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Smith
authors.forename: Claire
authors.initials: C
authors.lastname: Hill
authors.forename: Emma L
authors.initials: EL
authors.lastname: Godfrey
authors.forename: David
authors.initials: D
authors.lastname: Rand
authors.forename: Hugo
authors.initials: H
authors.lastname: van den Berg
authors.forename: Steven
authors.initials: S
authors.lastname: Thornton
authors.forename: Matthew
authors.initials: M
authors.lastname: Hodgkin
authors.forename: John
authors.initials: J
authors.lastname: Davey
authors.forename: Graham
authors.initials: G
authors.lastname: Ladds
mesh_terms: D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D017353:Gene Deletion; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006868:Hydrolysis; D008954:Models, Biological; D010675:Pheromones / Q000378:metabolism; D020710:RGS Proteins / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D044385:GTP-Binding Protein alpha Subunits; D010675:Pheromones; D020710:RGS Proteins; D043562:Receptors, G-Protein-Coupled; C489854:Rgs1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D006160:Guanosine Triphosphate