Regulator of G-protein Signaling 3 (RGS3) Inhibits Gβ1γ2-induced Inositol Phosphate Production, Mitogen-activated Protein Kinase Activation, and Akt Activation

Shi, Chong Shan; Lee, Sang Bong; Sinnarajah, Srikumar; Dessauer, Carmen W.; Rhee, Sue Goo; Kehrl, John H.

doi:10.1074/jbc.m100089200

Cited by 59 publications

(28 citation statements)

References 41 publications

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“…In fact, its expression level was much lower than that of RGS3, whereas the overall inhibitory effect was almost comparable, consistent with the notion that the C-terminal part of RGS3 contains structural domains important for signal modulation (39,40). Via its C-terminal region RGS3 can directly interact with G␤␥ and inhibit G␤␥-mediated PLC␤ activation (41). This potential interaction is unlikely to play a major role in this study, because PLC␤ activation is mediated predominantly (if not exclusively) by the ␣ subunit of G q in the experimental system used (see above).…”

Section: Implications Of Expression Changes Of Key Components Of the supporting

confidence: 58%

Differential Contribution of GTPase Activation and Effector Antagonism to the Inhibitory Effect of RGS Proteins on Gq-mediated Signaling in Vivo

Anger

Zhang

Mende

2004

Journal of Biological Chemistry

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RGS proteins act as negative regulators of G protein signaling by serving as GTPase-activating proteins (GAP) for ␣ subunits of heterotrimeric G proteins (G␣), thereby accelerating G protein inactivation. RGS proteins can also block G␣-mediated signal production by competing with downstream effectors for G␣ binding. Little is known about the relative contribution of GAP and effector antagonism to the inhibitory effect of RGS proteins on G protein-mediated signaling. By comparing the inhibitory effect of RGS2, RGS3, RGS5, and RGS16 on G␣ q -mediated phospholipase C␤ (PLC␤) activation under conditions where GTPase activation is possible versus nonexistent, we demonstrate that members of the R4 RGS subfamily differ significantly in their dependence on GTPase acceleration. COS-7 cells were transiently transfected with either muscarinic M 3 receptors, which couple to endogenous G q protein and mediate a stimulatory effect of carbachol on PLC␤, or constitutively active G␣ q * , which is inert to GTP hydrolysis and activates PLC␤ independent of receptor activation. In M 3 -expressing cells, all of the RGS proteins significantly blunted the efficacy and potency of carbachol. In contrast, G␣ q * -induced PLC␤ activation was inhibited by RGS2 and RGS3 but not RGS5 and RGS16. The observed differential effects were not due to changes in M 3 , G␣ q / G␣ q * , PLC␤, or RGS expression, as shown by receptor binding assays and Western blots. We conclude that closely related R4 RGS family members differ in their mechanism of action. RGS5 and RGS16 appear to depend on G protein inactivation, whereas GAP-independent mechanisms (such as effector antagonism) are sufficient to mediate the inhibitory effect of RGS2 and RGS3.Many extracellular stimuli elicit intracellular responses by activating seven-transmembrane receptors that are coupled to heterotrimeric G proteins comprising ␣ and ␤␥ subunits (1, 2). The duration of the response of a cell to external signals is largely determined by the activation/inactivation cycle of G proteins. Activated receptors trigger GTP-for-GDP exchange on G␣ subunits, thus dissociating G␣ from G␤ ␥ and subsequent activation of downstream effectors (such as enzymes and ion channels). The duration of G protein activation is limited by GTPase activity intrinsic to G␣ subunits that catalyzes the conversion of active GTP-bound G␣ into inactive GDP-bound G␣, which in turn can reassociate with G␤␥ and receptors.RGS proteins belong to a family of more than 20 proteins with a conserved RGS core domain of ϳ120 amino acids that is necessary and sufficient for binding to G␣ subunits (3). They are divided into several subfamilies based on their structural similarities, gene organization, and function. RGS proteins act as regulators of G protein signaling by limiting the signals generated by G protein-coupled receptors. They markedly increase the rate at which G␣ subunits hydrolyze GTP to GDP, a property that defines them as GTPase-activating proteins (or GAPs) 1 (4). Hastening of G␣ inactivation facilitates the reass...

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Section: Implications Of Expression Changes Of Key Components Of the supporting

confidence: 58%

Differential Contribution of GTPase Activation and Effector Antagonism to the Inhibitory Effect of RGS Proteins on Gq-mediated Signaling in Vivo

Anger

Zhang

Mende

2004

Journal of Biological Chemistry

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“…The weak and short-lived Akt phosphorylation in response to thrombin treatment may rely on a reduced availability of G␤␥ subunits. RGS3 has been demonstrated to limit G␤␥-dependent activation of both Akt and ERK1/2 by virtue of its GAP activity for G␣ i subunits and subsequent reassociation of the GDPbound G␣ i and G␤␥ (27). Alternatively, Akt may be more rapidly dephosphorylated by ceramide-sensitive (28) or other protein phosphatases.…”

Section: Fig 6 Pi 3-kinase Inhibition Augments the Pdgf-induced Latmentioning

confidence: 99%

Regulation of Raf by Akt Controls Growth and Differentiation in Vascular Smooth Muscle Cells

Reusch

Zimmermann²,

Schaefer³

et al. 2001

Journal of Biological Chemistry

144

107

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The stimulation of platelet-derived growth factor (PDGF) receptors shifts vascular smooth muscle (VSM) cells toward a more proliferative phenotype. Thrombin activates the same signaling cascades in VSM cells, namely the Ras/Raf/MEK/ERK and the phosphatidylinositol 3-kinase (PI 3-kinase)/Akt pathways. Nonetheless, thrombin was not mitogenic, but rather increased the expression of the smooth muscle-specific myosin heavy chain (SM-MHC) indicative of an in vitro re-differentiation of VSM cells. A more detailed analysis of the temporal pattern and relative signal intensities revealed marked differences. The strong and biphasic phosphorylation of ERK1/2 in response to thrombin correlated with its ability to increase the activity of the SM-MHC promoter whereas Akt was only partially and transiently phosphorylated. During progression of vascular diseases or vascular injury following balloon dilatation, the release of growth factors such as PDGF, 1 epidermal growth factor, or IGF has been shown to increase the smooth muscle cell proliferation and migration (1-3). This de-differentiation is characterized by a decreased expression of contractile proteins.Following ligand binding, tyrosine kinase receptors undergo dimerization which allows transphosphorylation at multiple tyrosine residues. The intracellular signal transduction involves direct interaction of effector molecules via specific domains, e.g. Src homology 2 domains and phosphotyrosine-binding domains. More than 10 different Src homology 2 domaincontaining molecules have been shown to bind to different autophosphorylation sites in the PDGF receptors, including signal transduction molecules with enzymatic activity like phosphatidylinositol 3-kinases (PI 3-kinases), phospholipases C␥, or Src as well as adaptor molecules such as Grb2 and Shc (4). Binding of Grb2/Sos or Shc in turn activates the small GTP-binding protein Ras which couples to the Raf/MEK/ERK cascade. The cellular response of receptor tyrosine kinase signaling is influenced by the strength and the duration of ERK1/2 phosphorylation. Depending on the cellular context, either proliferation or differentiation may result (5). Other signaling cascades initiated by PDGF receptors and their potential cross-talk is currently under extensive investigation. Phosphorylated tyrosine residues (Tyr 740 and Tyr 751 ) on the PDGF ␤-receptor recruit the PI 3-kinases ␣ and ␤ to the plasma membrane via docking of the common p85 regulatory subunit (6, 7). Upon activation, the lipid kinase activity of PI 3-kinases catalyzes the formation of PI(3,4,5)-P 3 , a well defined plasma membrane anchor for the pleckstrin homology domains of 3-phosphoinositide-dependent kinase I and protein kinase B/Akt (8). The plasma membrane recruitment exposes Akt to subsequent activation by 3-phosphoinositide-dependent kinase I and related kinases that phosphorylate Akt at Thr 308 and Ser 473 (9). Akt is a major participant in growth factor-mediated transcription and promotes cell survival by inhibiting apoptosis. These processes appear to invol...

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“…Moreover, there is at least one report of a mammalian RGS protein that can directly bind and inhibit an effector enzyme, adenylyl cyclase (108). RGS proteins have also been reported to bind to receptors (8,109), possibly in competition with G␣ (8), as well as to G␤␥, possibly in competition with G␣ or effectors (42,103,119,125). Regardless of mechanism, inhibition of G protein subunit association will indirectly prevent receptor activation, since receptors recog-VOL.…”

mentioning

confidence: 99%

Genome-Scale Analysis Reveals Sst2 as the Principal Regulator of Mating Pheromone Signaling in the Yeast Saccharomyces cerevisiae

Chasse¹,

Flanary²,

Parnell³

et al. 2006

Eukaryot Cell

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A common property of G protein-coupled receptors is that they become less responsive with prolonged stimulation. Regulators of G protein signaling (RGS proteins) are well known to accelerate G protein GTPase activity and do so by stabilizing the transition state conformation of the G protein ␣ subunit. In the yeast Saccharomyces cerevisiae there are four RGS-homologous proteins (Sst2, Rgs2, Rax1, and Mdm1) and two G␣ proteins (Gpa1 and Gpa2). We show that Sst2 is the only RGS protein that binds selectively to the transition state conformation of Gpa1. The other RGS proteins also bind Gpa1 and modulate pheromone signaling, but to a lesser extent and in a manner clearly distinct from Sst2. To identify other candidate pathway regulators, we compared pheromone responses in 4,349 gene deletion mutants representing nearly all nonessential genes in yeast. A number of mutants produced an increase (sst2, bar1, asc1, and ygl024w) or decrease (cla4) in pheromone sensitivity or resulted in pheromone-independent signaling (sst2, pbs2, gas1, and ygl024w). These findings suggest that Sst2 is the principal regulator of Gpa1-mediated signaling in vivo but that other proteins also contribute in distinct ways to pathway regulation.G protein-coupled receptors respond to a vast array of chemical and sensory signals, including hormones, neurotransmitters, odors, and light. Approximately one-third of all drugs act by binding directly to receptors of this class (64). Upon agonist stimulation of the receptor, a cognate G protein ␣ subunit will exchange GDP for GTP and undergo dissociation from the G protein ␤␥ subunit dimer. The dissociated subunits bind to effector enzymes, which in turn activate protein kinases, trigger new gene transcription, and ultimately produce programmed changes in cell homeostasis or differentiation (90). Regulators of G protein signaling (RGS proteins) function as GTPase-accelerating proteins (GAPs) and, in this manner, promote rapid inactivation or desensitization of the signal (89).Whereas mammalian genome analysis has revealed at least 16 G␣-and ϳ40 RGS-encoding genes (89, 106), a similar analysis in the yeast Saccharomyces cerevisiae reveals only two G␣ subunits but at least four RGS protein homologues. Gpa1 mediates cellular responses to mating pheromones. These pheromones, called a-factor and ␣-factor, are produced by haploid a and ␣ cells and bind to G protein-coupled receptors on cells of the opposite mating type. Upon activation of pheromone receptors, Gpa1 binds to GTP and dissociates from the G␤␥ dimer Ste4/Ste18, and the dissociated subunits activate a multitude of downstream effectors leading to cell fusion (mating) to form an a/␣ diploid (36, 50). Prominent among the known effectors are components of a MAP (mitogen-activated protein) kinase cascade comprised of Ste20, Ste11, Ste7, and Fus3. A parallel signaling pathway responds to glucose stimulation, leading to activation of a distinct receptor (Gpr1) (66,73,76,99,124), a distinct G protein ␣ subunit (Gpa2), and an atypical G protein ␤␥ complex ...

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Regulator of G-protein Signaling 3 (RGS3) Inhibits Gβ1γ2-induced Inositol Phosphate Production, Mitogen-activated Protein Kinase Activation, and Akt Activation

Cited by 59 publications

References 41 publications

Differential Contribution of GTPase Activation and Effector Antagonism to the Inhibitory Effect of RGS Proteins on Gq-mediated Signaling in Vivo

Differential Contribution of GTPase Activation and Effector Antagonism to the Inhibitory Effect of RGS Proteins on Gq-mediated Signaling in Vivo

Regulation of Raf by Akt Controls Growth and Differentiation in Vascular Smooth Muscle Cells

Genome-Scale Analysis Reveals Sst2 as the Principal Regulator of Mating Pheromone Signaling in the Yeast Saccharomyces cerevisiae

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