title: RGS6, RGS7, RGS9, and RGS11 stimulate GTPase activity of Gi family G-proteins with differential selectivity and maximal activity.
abstract: Regulator of G-protein signaling (RGS) proteins are GTPase activating proteins (GAPs) of heterotrimeric G-proteins that alter the amplitude and kinetics of receptor-promoted signaling. In this study we defined the G-protein alpha-subunit selectivity of purified Sf9 cell-derived R7 proteins, a subfamily of RGS proteins (RGS6, -7, -9, and -11) containing a Ggamma-like (GGL) domain that mediates dimeric interaction with Gbeta(5). Gbeta(5)/R7 dimers stimulated steady state GTPase activity of Galpha-subunits of the G(i) family, but not of Galpha(q) or Galpha(11), when added to proteoliposomes containing M2 or M1 muscarinic receptor-coupled G-protein heterotrimers. Concentration effect curves of the Gbeta(5)/R7 proteins revealed differences in potencies and efficacies toward Galpha-subunits of the G(i) family. Although all four Gbeta(5)/R7 proteins exhibited similar potencies toward Galpha(o), Gbeta(5)/RGS9 and Gbeta(5)/RGS11 were more potent GAPs of Galpha(i1), Galpha(i2), and Galpha(i3) than were Gbeta(5)/RGS6 and Gbeta(5)/RGS7. The maximal GAP activity exhibited by Gbeta(5)/RGS11 was 2- to 4-fold higher than that of Gbeta(5)/RGS7 and Gbeta(5)/RGS9, with Gbeta(5)/RGS6 exhibiting an intermediate maximal GAP activity. Moreover, the less efficacious Gbeta(5)/RGS7 and Gbeta(5)/RGS9 inhibited Gbeta(5)/RGS11-stimulated GTPase activity of Galpha(o). Therefore, R7 family RGS proteins are G(i) family-selective GAPs with potentially important differences in activities.
authors.affiliation: Department of Pharmacology, University of North Carolina, Chapel Hill 27599, USA. shelleyb@med.unc.edu
authors.forename: Shelley B
authors.initials: SB
authors.lastname: Hooks
authors.forename: Gary L
authors.initials: GL
authors.lastname: Waldo
authors.forename: James
authors.initials: J
authors.lastname: Corbitt
authors.forename: Erik T
authors.initials: ET
authors.lastname: Bodor
authors.forename: Andrejs M
authors.initials: AM
authors.lastname: Krumins
authors.forename: T Kendall
authors.initials: TK
authors.lastname: Harden
mesh_terms: D000818:Animals; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000502:physiology*; D020690:GTPase-Activating Proteins / Q000502:physiology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D020962:Heterotrimeric GTP-Binding Proteins / Q000737:chemistry / Q000502:physiology; D006868:Hydrolysis; D020710:RGS Proteins / Q000502:physiology*; D018411:Spodoptera
chemical_list: D020690:GTPase-Activating Proteins; D020710:RGS Proteins; C400195:RGS11 protein, human; C400194:RGS6 protein, human; C492039:RGS7 protein, human; C485691:Rgs6 protein, rat; C116925:regulator of g-protein signaling 9; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020962:Heterotrimeric GTP-Binding Proteins