RGS-Insensitive G-Protein Mutations to Study the Role of Endogenous RGS Proteins

The extent and temporal characteristics of G protein–coupled receptor (GPCR) signaling are shaped by the regulator of G protein signaling (RGS) proteins, which promote G protein deactivation. With hundreds of GPCRs and dozens of RGS proteins, compartmentalization plays a key role in establishing signaling specificity. However, the molecular details and mechanisms of this process are poorly understood. In this paper, we report that the R7 group of RGS regulators is controlled by interaction with two previously uncharacterized orphan GPCRs: GPR158 and GPR179. We show that GPR158/179 recruited RGS complexes to the plasma membrane and augmented their ability to regulate GPCR signaling. The loss of GPR179 in a mouse model of night blindness prevented targeting of RGS to the postsynaptic compartment of bipolar neurons in the retina, illuminating the role of GPR179 in night vision. We propose that the interaction of RGS proteins with orphan GPCRs promotes signaling selectivity in G protein pathways.

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The Role Of P115 Rhogef In The Rho Mediated Effects Of Lpa On The Actin Cytoskeleton.

Microscopy and Microanalysis ◽

10.1017/s1431927600019954 ◽

1999 ◽

Vol 5 (S2) ◽

pp. 1326-1327

Author(s):

C.L. Schwartz ◽

C. Wells ◽

X. Jiang ◽

H.J. Arnott ◽

P.C. Sternweis ◽

...

Keyword(s):

G Protein ◽

Fibroblast Cell ◽

Stress Fiber ◽

Fiber Formation ◽

Rgs Proteins ◽

Nucleotide Exchange ◽

Lpa Receptor ◽

Stress Fiber Formation ◽

P115 Rhogef

In the fibroblast cell line, 3T3, lysophosphatidic acid (LPA) induces stress fiber formation. Stress fibers participate in physiological functions such as cell motility. LPA acts through a receptor coupled to a PTX-insensitive G-protein, G13. It was shown that a constitutively activated mutant of α13 (Q226L) induces stress fiber formation in Swiss3T3 cells through a second messenger cascade that involves a monomeric G-protein, Rho. The recently discovered guanine nucleotide exchange factor, p115 RhoGEF (p115) forms a link between a n and Rho A. In the presence of α13, p115 activates Rho. The N-terminus of p115 contains a regulator of G-protein signaling (RGS) box. RGS proteins act as negative regulators of G-protein dependent signaling by increasing GTPase activity and “locking” the G-protein in an inactive state. We have tested a role of p115 in the pathway coupling the LPA receptor to stress fiber formation by Rho in NTH-3T3 cells.

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Up-regulation of Endogenous RGS2 Mediates Cross-desensitization between Gs and Gq Signaling in Osteoblasts

Journal of Biological Chemistry ◽

10.1074/jbc.m604416200 ◽

2006 ◽

Vol 281 (43) ◽

pp. 32684-32693 ◽

Cited By ~ 46

Author(s):

Anju Anne Roy ◽

Caroline Nunn ◽

Hong Ming ◽

Min-Xu Zou ◽

Josef Penninger ◽

...

Keyword(s):

G Protein ◽

Calcium Release ◽

Inositol Phosphates ◽

Primary Cultures ◽

G Protein Signaling ◽

Rgs Proteins ◽

Camp Accumulation ◽

Protein Signaling ◽

Wild Type

Regulator of G protein signaling (RGS) proteins limit G protein signals. In this study, we investigated the role of RGS2 in the control of G protein signaling cascades in osteoblasts, the cells responsible for bone formation. Expression of RGS2 was up-regulated in primary cultures of mouse calvarial osteoblasts by parathyroid hormone-related peptide (PTHrP)-(1-34), which stimulates Gs signaling. RGS2 was also up-regulated by extracellular ATP, which selectively activates Gq, as well as by forskolin and phorbol myristate acetate, which activate targets downstream of Gs and Gq, respectively. To assess the role of endogenous RGS2, we characterized Gs and Gq signaling in osteoblasts derived from wild type and rgs2-/- mice. Under control conditions, nucleotide-stimulated calcium release, endothelin-stimulated accumulation of inositol phosphates, and PTHrP-stimulated cAMP accumulation were equivalent in osteoblasts isolated from wild type and rgs2-/- mice. Thus, basal levels of endogenous RGS2 do not appear to regulate Gs or Gq signaling in osteoblasts. Interestingly, forskolin treatment of wild type but not rgs2-/- osteoblasts suppressed both endothelin-stimulated accumulation of inositol phosphates and nucleotide-stimulated calcium release, indicating that up-regulation of RGS2 by Gs signaling desensitizes Gq signals. Furthermore, pretreatment with ATP suppressed PTHrP-dependent cAMP accumulation in wild type but not rgs2-/- osteoblasts, implying that up-regulation of RGS2 by Gq signaling desensitizes Gs signals. Our findings demonstrate that endogenously expressed RGS2 can limit Gs signaling. Moreover, up-regulation of RGS2 contributes to cross-desensitization of Gs- and Gq-coupled signals.

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A newly identified complex of spinophilin and the tyrosine phosphatase, SHP-1, modulates platelet activation by regulating G protein–dependent signaling

Blood ◽

10.1182/blood-2011-10-387910 ◽

2012 ◽

Vol 119 (8) ◽

pp. 1935-1945 ◽

Cited By ~ 42

Author(s):

Peisong Ma ◽

Aleksandra Cierniewska ◽

Rachel Signarvic ◽

Marcin Cieslak ◽

Hong Kong ◽

...

Keyword(s):

G Protein ◽

Platelet Activation ◽

Tyrosine Phosphatase ◽

G Protein Signaling ◽

Rgs Proteins ◽

Protein Signaling ◽

Normal Hemostasis ◽

The Impact ◽

Constitutive Phosphorylation

Abstract Platelets are essential for normal hemostasis, but close regulation is required to avoid the destructive effects of either inappropriate platelet activation or excessive responses to injury. Here, we describe a novel complex comprising the scaffold protein, spinophilin (SPL), and the tyrosine phosphatase, SHP-1, and show that it can modulate platelet activation by sequestering RGS10 and RGS18, 2 members of the regulator of G protein signaling family. We also show that SPL/RGS/SHP1 complexes are present in resting platelets where constitutive phosphorylation of SPL(Y398) creates an atypical binding site for SHP-1. Activation of the SHP-1 occurs on agonist-induced phosphorylation of SHP-1(Y536), triggering dephosphorylation and decay of the SPL/RGS/SHP1 complex. Preventing SHP-1 activation blocks decay of the complex and produces a gain of function. Conversely, deleting spinophilin in mice inhibits platelet activation. It also attenuates the rise in platelet cAMP normally caused by endothelial prostacyclin (PGI2). Thus, we propose that the role of the SPL/RGS/SHP1 complex in platelets is time and context dependent. Before injury, the complex helps maintain the quiescence of circulating platelets by maximizing the impact of PGI2. After injury, the complex gradually releases RGS proteins, limiting platelet activation and providing a mechanism for temporal coordination of pro thrombotic and antithrombotic inputs.

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