title: Recruitment of RGS2 and RGS4 to the plasma membrane by G proteins and receptors reflects functional interactions.
abstract: N-terminally green fluorescent protein (GFP)-tagged regulator of G protein signaling (RGS) 2 and RGS4 fusion proteins expressed in human embryonic kidney 293 cells localized to the nucleus and cytosol, respectively. They were selectively recruited to the plasma membrane by G proteins and correspondingly by receptors that activate those G proteins: GFP-RGS2 when coexpressed with Galphas, beta2-adrenergic receptor, Galphaq, or AT1A angiotensin II receptor, and GFP-RGS4 when coexpressed with Galphai2 or M2 muscarinic receptor. G protein mutants with reduced RGS affinity did not produce this effect, implying that the recruitment involves direct binding to G proteins and is independent of downstream signaling events. Neither agonists nor inverse agonists altered receptor-promoted RGS association with the plasma membrane, and expressing either constitutively activated or poorly activated G protein mutants produced effects similar to those of their wild-type counterparts. Thus, intracellular interactions between these proteins seem to be relatively stable and insensitive to the activation state of the G protein, in contrast to the transient increases in RGS-G protein association known to be caused by G protein activation in solution-based assays. G protein effects on RGS localization were mirrored by RGS effects on G protein function. RGS4 was more potent than RGS2 in promoting steady-state Gi GTPase activity, whereas RGS2 inhibited Gs-dependent increases in intracellular cAMP, suggesting that G protein signaling in cells is regulated by the selective recruitment of RGS proteins to the plasma membrane.
authors.affiliation: Department of Physiology and Pharmacology, Medical Sciences Building, University of Western Ontario, London, Ontario N6A 5C1, Canada.
authors.forename: Anju Anne
authors.initials: AA
authors.lastname: Roy
authors.forename: Kara E
authors.initials: KE
authors.lastname: Lemberg
authors.forename: Peter
authors.initials: P
authors.lastname: Chidiac
mesh_terms: D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D002522:Chlorocebus aethiops; D004305:Dose-Response Relationship, Drug; D019204:GTP-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism / Q000502:physiology; D021381:Protein Transport; D020710:RGS Proteins / Q000378:metabolism* / Q000502:physiology; D011956:Receptors, Cell Surface / Q000819:agonists / Q000378:metabolism* / Q000502:physiology
chemical_list: D020710:RGS Proteins; C087182:RGS2 protein, human; D011956:Receptors, Cell Surface; C098799:RGS4 protein; D019204:GTP-Binding Proteins