Active Gα_q subunits and M3 acetylcholine receptors promote distinct modes of association of RGS2 with the plasma membrane

Abstract

RGS proteins accelerate the GTPase activity of heterotrimeric G proteins at the plasma membrane. Association of RGS proteins with the plasma membrane can be mediated by interactions with other membrane proteins and by direct interactions with the lipid bilayer. Here we use fluorescence recovery after photobleaching (FRAP) to characterize interactions between RGS2 and M3 acetylcholine receptors (M3Rs), Ga subunits and the lipid bilayer. Active Ga q and M3Rs both recruited RGS2-EGFP to the plasma membrane. RGS2-EGFP remained bound to the plasma membrane between interactions with active Ga q , but rapidly exchanged between membrane-associated and cytosolic pools when recruited by M3Rs.

R4 RGS proteins: Regulation of G-protein signaling and beyond

“…Recent FRET studies of fluorescently-tagged GPCRs and G proteins found no evidence for precoupling in living cells (Hein, et al, 2005). In a separate study, RGS2 did not affect association of fluorescently-tagged GPCRs and G proteins detected by FRET in living cells (Clark, et al, 2007). Thus, it is unclear how RGS scaffolding might affect receptor-G protein and heterotrimer interactions during the GTPase cycle as these results do not support a role for RGS proteins act as physical scaffolds, at least for this particular GPCR-G protein combination.…”

“…Fluorescence resonance energy transfer (FRET) experiments showed that RGS8-YFP protein associated with Gα regardless of the activation state or receptor-ligand interaction. In contrast, a separate set of experiments revealed that membrane association of an RGS protein (RGS2) was stable in the presence of a constitutively active, immobile G protein [Gαq(R183C)] but was only transiently recruited to the membrane by expression of a GPCR (M 3 R) (Clark, et al, 2007). The localization of RGS2 after ligand stimulation of the receptor was not examined in the latter study.…”

RGS16 Inhibits Breast Cancer Cell Growth by Mitigating Phosphatidylinositol 3-Kinase Signaling

“…Most R4 RGS proteins such as RGS13 and RGS16 are localized in the cytoplasm under steadystate conditions but may be recruited to the membrane or other organelles (33)(34)(35). Preliminary evidence suggests that in mast cells, RGS13 is rapidly and transiently localized at the plasma membrane after IgE-antigen stimulation of Fc⑀RI on mast cells.…”

Regulators of G-Protein-Signaling Proteins: Negative Modulators of G-Protein-Coupled Receptor Signaling

“…A proposed reasoning behind this implicates that increased G-protein deactivation by RGS proteins probably improves the efficiency of the GTPase cycle by improving proteineprotein interactions in the GPCR-heterotrimeric G-protein complex (Ross and Wilkie, 2000). FRET studies have shown that an RGS8-YFP fusion protein is able to associate with Ga irregardless of receptoreligand interaction or the activation state of RGS (Clark et al, 2007). This has led to speculation that RGS proteins could act as scaffolding proteins between Gabg and respective receptors but little concrete evidence exists.…”