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 G␣s, ␤ 2 -adrenergic receptor, G␣q, or AT 1A angiotensin II receptor, and GFP-RGS4 when coexpressed with G␣i2 or M 2 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 Gsdependent increases in intracellular cAMP, suggesting that G protein signaling in cells is regulated by the selective recruitment of RGS proteins to the plasma membrane.

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

“…This has been reported for different RGS proteins in regulating Gq proteins activated by distinct receptors (Xu et al, 1999); RGS3 and muscarinic m3 receptor; RGS5 and angiotensin AT1a receptor (Wang et al, 2002); RGS8 towards muscarinic m1 and substance P receptors (Saitoh et al, 2002); RGS-R4 subfamily and subtypes of muscarinic acetylcholine receptors (Roy et al, 2003;Bernstein et al, 2004). In the present study, we show that both RGSZ1 and RGSZ2 co-precipitate with m-opioid receptors, and that the association between RGSZ and Ga subunits is altered by a morphine challenge.…”

Stops and starts in mammalian oocytes: recent advances in understanding the regulation of meiotic arrest and oocyte maturation

“…These proteins accelerate the exchange of GTP for GDP on the G-protein a subunit, thereby turning off the G-protein. Although nothing is known about RGS proteins in oocytes, it is interesting to note that RGS2 can inhibit G s -mediated cAMP production (Sinnarajah et al 2001, Kehrl & Sinnarajah 2002, Roy et al 2003. Thus, an RGS protein could potentially inhibit cAMP production in the oocyte following LH stimulation.…”

Chronic olanzapine activates the Stat3 signal transduction pathway and alters expression of components of the 5-HT2A receptor signaling system in rat frontal cortex

“…The mechanism whereby chronic olanzapine causes a redistribution of RGS4 protein is not clear but could be due to the increased expression of G αq /11 protein and 5-HT 2A receptor protein. A previous study demonstrated that localization of RGS protein to the membrane increases with increased expression of G α protein (Roy et al, 2003). However, in the cell culture system used in that study, G αi protein but not G αq protein expression increased association of RGS4 with the cell membrane.…”