Selective Regulation of Gαq/11 by an RGS Domain in the G Protein-coupled Receptor Kinase, GRK2

Abstract

؊ . This revealed the specific ability of bovine brain G␣ q/11 to bind to both GRK2 and GRK3 in an AlF 4 ؊ -dependent manner. In contrast, G␣ s , G␣ i , and G␣ 12/13 did not bind to GRK2 or GRK3 despite their presence in the extract. Additional studies revealed that bovine brain G␣ q/11 could also bind to an N-terminal construct of GRK2, while no binding of G␣ q/11 , G␣ s , G␣ i , or G␣ 12/13 to comparable constructs of GRK5 or GRK6 was observed. Experiments using purified G␣ q revealed significant binding of both G␣ q GDP/AlF 4 ؊ and G␣ q (GTP␥S), but not G␣ q (GDP), to GRK2. Activation-dependent binding was also observed in both COS-1 and HEK293 cells as GRK2 significantly co-immunoprecipitated constitutively active G␣ q (R183C) but not wild type G␣ q . In vitro analysis revealed that GRK2 possesses weak GAP activity toward G␣ q that is dependent on the presence of a G proteincoupled receptor. However, GRK2 effectively inhibited G␣ q -mediated activation of phospholipase C-␤ both in vitro and in cells, possibly through sequestration of activated G␣ q . These data suggest that a subfamily of the GRKs may be bifunctional regulators of G protein-coupled receptor signaling operating directly on both receptors and G proteins.

The RGSZ2 Protein Exists in a Complex with μ-Opioid Receptors and Regulates the Desensitizing Capacity of Gz Proteins

“…In situations in which RGS proteins bind to GaGTP subunits but display little or no GAP activity on them, effector antagonism will occur. Sequestering of activated Gaq subunits has been observed for the RGS domain of the kinase of GPCRs type 2 (GRK2), thereby interfering in the regulation of phospholipase Cb (Carman et al, 1999). Similarly, sequestering of Ga subunits by RGS-R7 proteins reduces the effects mediated by m receptors in the CNS Sánchez-Blázquez et al, 2003, while that of Gaq by RGS-Rz proteins reduces calcium mobilization (Mao et al, 2004).…”

Non-visual GRKs: are we seeing the whole picture?

“…All non-visual GRKs have a regulator of G-protein signalling (RGS) domain within the N-terminus region (Figure 1), which provides a potential mechanism by which GRKs might regulate GPCR signalling via phosphorylation-independent mechanisms. Indeed, growing evidence suggests that this could be the case for GRK2 and GRK3 [22][23][24] (Box 1). GRK4 -6 possess a highly conserved binding site (amino acids 22 -29 for GRK5) for phosphatidylinositol (4,5)-bisphosphate [PtdIns(4,5)P 2 ], which is thought to enhance catalytic activity [10].…”

“…In a key study, Carman et al [22] revealed that although the N-terminal regulator of G-protein signalling (RGS)-like domains of GRK2 and GRK3 (see Figures 1 and 2 in the main text) possess only modest GTPaseactivating protein (GAP) activity, they bind avidly to activated Ga q/11 to inhibit inositol (1,4,5)-trisphosphate [Ins(1,4,5)P 3 ] generation. Crucially, the expression of this RGS-like domain alone can inhibit the ability of several GPCRs to stimulate PLC activity, while exerting no effect on cAMP production [23].…”

“…The structure of non-visual G-protein-coupled receptor kinases (GRKs). All GRKs possess a conserved N-terminal regulator of G-protein signalling (RGS)-like domain [22], the relevance of which is discussed in Box 1. In addition, all GRKs have a highly conserved central serine/threonine kinase catalytic domain.…”

A Regulator of G Protein Signaling-containing Kinase Is Important for Chemotaxis and Multicellular Development inDictyostelium

“…Seven G protein receptor kinase (GRK) family members contain an N-terminal atypical RGS domain (Siderovski et al, 1996;Penn et al, 2000). Although very little is known about the function of the RGS domain in most of these proteins, it has been shown that the RGS domain of GRK2 binds to G␣ q/11 and inhibits G␣ q -mediated activation of phospholipase C-␤ (Carman et al, 1999).…”