Taxonomic distribution of proteins containing RGS domains

The RGS domain within your query sequence starts at position 67 and ends at position 184, and its E-value is 3.42e-44.

Regulators of G protein signaling: a bestiary of modular protein binding domains.

Burchett SA
J Neurochem. 2000; 75: 1335-51

Members of the newly discovered regulator of G protein signaling (RGS) families of proteins have a common RGS domain. This RGS domain is necessary for conferring upon RGS proteins the capacity to regulate negatively a variety of Galpha protein subunits. However, RGS proteins are more than simply negative regulators of signaling. RGS proteins can function as effector antagonists, and recent evidence suggests that RGS proteins can have positive effects on signaling as well. Many RGS proteins possess additional C- and N-terminal modular protein-binding domains and motifs. The presence of these additional modules within the RGS proteins provides for multiple novel regulatory interactions performed by these molecules. These regions are involved in conferring regulatory selectivity to specific Galpha-coupled signaling pathways, enhancing the efficacy of the RGS domain, and the translocation or targeting of RGS proteins to intracellular membranes. In other instances, these domains are involved in cross-talk between different Galpha-coupled signaling pathways and, in some cases, likely serve to integrate small GTPases with these G protein signaling pathways. This review discusses these C- and N-terminal domains and their roles in the biology of the brain-enriched RGS proteins. Methods that can be used to investigate the function of these domains are also discussed.

GTPase-activating proteins for heterotrimeric G proteins: regulators of G protein signaling (RGS) and RGS-like proteins.

Ross EM, Wilkie TM
Annu Rev Biochem. 2000; 69: 795-827

GTPase-activating proteins (GAPs) regulate heterotrimeric G proteins by increasing the rates at which their subunits hydrolyze bound GTP and thus return to the inactive state. G protein GAPs act allosterically on G subunits, in contrast to GAPs for the Ras-like monomeric GTP-binding proteins. Although they do not contribute directly to the chemistry of GTP hydrolysis, G protein GAPs can accelerate hydrolysis >2000-fold. G protein GAPs include both effector proteins (phospholipase C-?, p115RhoGEF) and a growing family of regulators of G protein signaling (RGS proteins) that are found throughout the animal and fungal kingdoms. GAP activity can sharpen the termination of a signal upon removal of stimulus, attenuate a signal either as a feedback inhibitor or in response to a second input, promote regulatory association of other proteins, or redirect signaling within a G protein signaling network. GAPs are regulated by various controls of their cellular concentrations, by complex interactions with G? or with G?5 through an endogenous G-like domain, and by interaction with multiple other proteins.

A regulator of G protein signaling interaction surface linked to effector specificity.

Sowa ME, He W, Wensel TG, Lichtarge O
Proc Natl Acad Sci U S A. 2000; 97: 1483-8

Proteins of the regulator of G protein signaling (RGS) family accelerate GTP hydrolysis by the alpha subunits (G(alpha)) of G proteins, leading to rapid recovery of signaling cascades. Many different RGS proteins can accelerate GTP hydrolysis by an individual G(alpha), and GTP hydrolysis rates of different G(alpha)s can be enhanced by the same RGS protein. Consequently, the mechanisms for specificity in RGS regulation and the residues involved remain unclear. Using the evolutionary trace (ET) method, we have identified a cluster of residues in the RGS domain that includes the RGS-G(alpha) binding interface and extends to include additional functionally important residues on the surface. One of these is within helix alpha3, two are in alpha5, and three are in the loop connecting alpha5 and alpha6. A cluster of surface residues on G(alpha) previously identified by ET, and composed predominantly of residues from the switch III region and helix alpha3, is spatially contiguous with the ET-identified residues in the RGS domain. This cluster includes residues proposed to interact with the gamma subunit of G(talpha)'s effector, cGMP phosphodiesterase (PDEgamma). The proximity of these clusters suggests that they form part of an interface between the effector and the RGS-G(alpha) complex. Sequence variations in these residues correlate with PDEgamma effects on GTPase acceleration. Because ET identifies residues important for all members of a protein family, these residues likely form a general site for regulation of G protein-coupled signaling cascades, possibly by means of effector interactions.

Raf-like Ras/Rap-binding domains in RGS12- and still-life-like signalling proteins.

Ponting CP
J Mol Med. 1999; 77: 695-8

Ras proteins play critical roles in regulating cell growth and differentiation, and mutated Ras genes are expressed in a variety of human cancers. Consequently, much interest has centered on the binding partners of Ras, including the Ras-binding domain (RBD) of Raf kinase. Here evidence is presented that domains homologous to the Raf RBD are present in tandem in RGS12, RGS14 and LOCO, and singly in molecules similar to mouse Tiam-1. In addition, RGS12, RGS14 and LOCO are shown to contain single "LGN motifs" that are guanine nucleotide exchange factors specific for the alpha-subunit of G proteins. These findings indicate "cross-talk" interactions between signalling pathways involving Ras and Rap and pathways involving Rho, Rac and G alpha GTPases.

Structural and biochemical analysis of Ras-effector signaling via RalGDS.

Vetter IR, Linnemann T, Wohlgemuth S, Geyer M, Kalbitzer HR, Herrmann C, Wittinghofer A
FEBS Lett. 1999; 451: 175-80

The structure of the complex of Ras with the Ras-binding domain of its effector RalGDS (RGS-RBD), the first genuine Ras-effector complex, has been solved by X-ray crystallography. As with the Rap-RafRBD complex (Nasser et al., 1995), the interaction is via an inter-protein beta-sheet between the switch I region of Ras and the second strand of the RGS-RBD sheet, but the details of the interactions in the interface are remarkably different. Mutational studies were performed to investigate the contribution of selected interface residues to the binding affinity. Gel filtration experiments show that the Ras x RGS-RBD complex is a monomer. The results are compared to a recently determined structure of a similar complex using a Ras mutant (Huang et al., 1998) and are discussed in relation to partial loss-of-function mutations and the specificity of Ras versus Rap binding.

Lifetime regulation of G protein-effector complex: emerging importance of RGS proteins.

Arshavsky VY, PughENJ r
Neuron. 1998; 20: 11-4

Mammalian RGS proteins: barbarians at the gate.

Berman DM, Gilman AG
J Biol Chem. 1998; 273: 1269-72

Oligophrenin-1 encodes a rhoGAP protein involved in X-linked mental retardation.

Billuart P, Bienvenu T, Ronce N, desPortes V, Vinet MC, Zemni R, RoestCrollius H, Carrie A, Fauchereau F, Cherry M, Briault S, Hamel B, Fryns JP, Beldjord C, Kahn A, Moraine C, Chelly J
Nature. 1998; 392: 923-6

Primary or nonspecific X-linked mental retardation (MRX) is a heterogeneous condition in which affected patients do not have any distinctive clinical or biochemical features in common apart from cognitive impairment. Although it is present in approximately 0.15-0.3% of males, most of the genetic defects associated with MRX, which may involve more than ten different genes, remain unknown. Here we report the characterization of a new gene on the long arm of the X-chromosome (position Xq12) and the identification in unrelated individuals of different mutations that are predicted to cause a loss of function. This gene is highly expressed in fetal brain and encodes a protein of relative molecular mass 91K, named oligophrenin-1, which contains a domain typical of a Rho-GTPase-activating protein (rhoGAP). By enhancing their GTPase activity, GAP proteins inactivate small Rho and Ras proteins, so inactivation of rhoGAP proteins might cause constitutive activation of their GTPase targets. Such activation is known to affect cell migration and outgrowth of axons and dendrites in vivo. Our results demonstrate an association between cognitive impairment and a defect in a signalling pathway that depends on a Ras-like GTPase.

A G protein gamma subunit-like domain shared between RGS11 and other RGS proteins specifies binding to Gbeta5 subunits.

Snow BE, Krumins AM, Brothers GM, Lee SF, Wall MA, Chung S, Mangion J, Arya S, Gilman AG, Siderovski DP
Proc Natl Acad Sci U S A. 1998; 95: 13307-12

Regulators of G protein signaling (RGS) proteins act as GTPase-activating proteins (GAPs) toward the alpha subunits of heterotrimeric, signal-transducing G proteins. RGS11 contains a G protein gamma subunit-like (GGL) domain between its Dishevelled/Egl-10/Pleckstrin and RGS domains. GGL domains are also found in RGS6, RGS7, RGS9, and the Caenorhabditis elegans protein EGL-10. Coexpression of RGS11 with different Gbeta subunits reveals specific interaction between RGS11 and Gbeta5. The expression of mRNA for RGS11 and Gbeta5 in human tissues overlaps. The Gbeta5/RGS11 heterodimer acts as a GAP on Galphao, apparently selectively. RGS proteins that contain GGL domains appear to act as GAPs for Galpha proteins and form complexes with specific Gbeta subunits, adding to the combinatorial complexity of G protein-mediated signaling pathways.

Molecular characterization of the GTPase-activating domain of ADP-ribosylation factor domain protein 1 (ARD1).

Vitale N, Moss J, Vaughan M
J Biol Chem. 1998; 273: 2553-60

ADP-ribosylation factors (ARFs) are approximately 20-kDa guanine nucleotide-binding proteins recognized as critical components in intracellular vesicular transport and phospholipase D activation. Both guanine nucleotide-exchange proteins and GTPase-activating proteins (GAPs) for ARFs have been cloned recently. A zinc finger motif near the amino terminus of the ARF1 GAP was required for stimulation of GTP hydrolysis. ARD1 is an ARF family member that differs from other ARFs by the presence of a 46-kDa amino-terminal extension. We had reported that the ARF domain of ARD1 binds specifically GDP and GTP and that the amino-terminal extension acts as a GAP for the ARF domain of ARD1 but not for ARF proteins. The GAP domain of ARD1, synthesized in Escherichia coli, stimulated hydrolysis of GTP bound to the ARF domain of ARD1. Using ARD1 truncations, it appears that amino acids 101-190 are critical for GAP activity, whereas residues 190-333 are involved in physical interaction between the two domains of ARD1 and are required for GTP hydrolysis. The GAP function of the amino-terminal extension of ARD1 required two arginines, an intact zinc finger motif, and a group of residues which resembles a sequence present in Rho/Rac GAPs. Interaction between the two domains of ARD1 required two negatively charged residues (Asp427 and Glu428) located in the effector region of the ARF domain and two basic amino acids (Arg249 and Lys250) found in the amino-terminal extension. The GAP domain of ARD1 thus is similar to ARF GAPs but differs from other GAPs in its covalent association with the GTP-binding domain.

A new family of G-protein regulators - the RGS proteins.

Koelle MR
Curr Opin Cell Biol. 1997; 9: 143-7

Genetic experiments have recently been used to identify a family of 'regulator of G-protein signaling' (RGS) proteins, which downregulate signaling by heterotrimeric G proteins. The first biochemical studies of RGS proteins have shown that they accelerate the GTPase activities of G-protein alpha subunits, thus driving G proteins into their inactive GDP-bound forms. The physiological significance of the large number of different RGS proteins remains to be explored.

A novel GTPase-activating protein for Rho interacts with a PDZ domain of the protein-tyrosine phosphatase PTPL1.

Saras J, Franzen P, Aspenstrom P, Hellman U, Gonez LJ, Heldin CH
J Biol Chem. 1997; 272: 24333-8

PTPL1 is an intracellular protein-tyrosine phosphatase that contains five PDZ domains. Here, we present the cloning of a novel 150-kDa protein, the four most C-terminal amino acid residues of which specifically interact with the fourth PDZ domain of PTPL1. The molecule contains a GTPase-activating protein (GAP) domain, a cysteine-rich, putative Zn2+- and diacylglycerol-binding domain, and a region of sequence homology to the product of the Caenorhabditis elegans gene ZK669.1a. The GAP domain is active on Rho, Rac, and Cdc42 in vitro but with a clear preference for Rho; we refer to the molecule as PTPL1-associated RhoGAP 1, PARG1. Rho is inactivated by GAPs, and protein-tyrosine phosphorylation has been implicated in Rho signaling. Therefore, a complex between PTPL1 and PARG1 may function as a powerful negative regulator of Rho signaling, acting both on Rho itself and on tyrosine phosphorylated components in the Rho signal transduction pathway.

Structure of RGS4 bound to AlF4--activated G(i alpha1): stabilization of the transition state for GTP hydrolysis.

Tesmer JJ, Berman DM, Gilman AG, Sprang SR
Cell. 1997; 89: 251-61

RGS proteins are GTPase activators for heterotrimeric G proteins. We report here the 2.8 A resolution crystal structure of the RGS protein RGS4 complexed with G(i alpha1)-Mg2+-GDP-AlF4 . Only the core domain of RGS4 is visible in the crystal. The core domain binds to the three switch regions of G(i alpha1), but does not contribute catalytic residues that directly interact with either GDP or AlF4-. Therefore, RGS4 appears to catalyze rapid hydrolysis of GTP primarily by stabilizing the switch regions of G(i alpha1), although the conserved Asn-128 from RGS4 could also play a catalytic role by interacting with the hydrolytic water molecule or the side chain of Gln-204. The binding site for RGS4 on G(i alpha1) is also consistent with the activity of RGS proteins as antagonists of G(alpha) effectors.

The interaction of Ras with GTPase-activating proteins.

Wittinghofer A, Scheffzek K, Ahmadian MR
FEBS Lett. 1997; 410: 63-7

Ras plays a major role as a molecular switch in many signal transduction pathways which lead to cell growth and differentiation. The GTPase reaction of Ras is of central importance in the function of the switch since it terminates Ras-effector interactions. GTPase-activating proteins (GAPs) accelerate the very slow intrinsic hydrolysis reaction of the GTP-bound Ras by several orders of magnitude and thereby act as presumably negative regulators of Ras action. The GTP hydrolysis of oncogenic mutants of Ras remains unaltered. In this review we discuss recent biochemical and structural findings relating to the mechanism of GAP action, which strengthen the hypothesis that GAP accelerates the actual cleavage step by stabilizing the transition state of the phosphoryl transfer reaction.

GAIP and RGS4 are GTPase-activating proteins for the Gi subfamily of G protein alpha subunits.

Berman DM, Wilkie TM, Gilman AG
Cell. 1996; 86: 445-52

A novel class of regulators of G protein signaling (RGS) proteins has been identified recently. Genetic evidence suggests that RGS proteins inhibit G protein-mediated signaling at the level of the receptor-G protein interaction or the G protein alpha subunit itself. We have found that two RGS family members, GAIP and RGS4, are GTPase-activating proteins (GAPs), accelerating the rate of GTP hydrolysis by Gi alpha 1 at least 40-fold. All Gi subfamily members assayed were substrates for these GAPs; Gs alpha was not. RGS4 activates the GTPase activity of certain Gi alpha 1 mutants (e.g., R178C), but not others (e.g., Q204L). The GAP activity of RGS proteins is consistent with their proposed role as negative regulators of G protein-mediated signaling.

RGS family members: GTPase-activating proteins for heterotrimeric G-protein alpha-subunits.

Watson N, Linder ME, Druey KM, Kehrl JH, Blumer KJ
Nature. 1996; 383: 172-5

Signaling pathways using heterotrimeric guanine-nucleotide-binding-proteins (G proteins) trigger physiological responses elicited by hormones, neurotransmitters and sensory stimuli. GTP binding activates G proteins by dissociating G alpha from G beta gamma subunits, and GTP hydrolysis by G alpha subunits deactivates G proteins by allowing heterotrimers to reform. However, deactivation of G-protein signalling pathways in vivo can occur 10- to 100-fold faster than the rate of GTP hydrolysis of G alpha subunits in vitro, suggesting that GTPase-activating proteins (GAPs) deactivate G alpha subunits. Here we report that RGS (for regulator of G-protein signalling) proteins are GAPs for G alpha subunits. RGS1, RGS4 and GAIP (for G alpha-interacting protein) bind specifically and tightly to G alphai and G alpha0 in cell membranes treated with GDP and AlF4(-), and are GAPs for G alphai, G alpha0 and transducin alpha-subunits, but not for G alphas. Thus, these RGS proteins are likely to regulate a subset of the G-protein signalling pathways in mammalian cells. Our results provide insight into the mechanisms that govern the duration and specificity of physiological responses elicited by G-protein-mediated signalling pathways.

GAIP, a protein that specifically interacts with the trimeric G protein G alpha i3, is a member of a protein family with a highly conserved core domain.

DeVries L, Mousli M, Wurmser A, Farquhar MG
Proc Natl Acad Sci U S A. 1995; 92: 11916-20

Using the yeast two-hybrid system we have identified a human protein, GAIP (G Alpha Interacting Protein), that specifically interacts with the heterotrimeric GTP-binding protein G alpha i3. Interaction was verified by specific binding of in vitro-translated G alpha i3 with a GAIP-glutathione S-transferase fusion protein. GAIP is a small protein (217 amino acids, 24 kDa) that contains two potential phosphorylation sites for protein kinase C and seven for casein kinase 2. GAIP shows high homology to two previously identified human proteins, GOS8 and 1R20, two Caenorhabditis elegans proteins, CO5B5.7 and C29H12.3, and the FLBA gene product in Aspergillus nidulans--all of unknown function. Significant homology was also found to the SST2 gene product in Saccharomyces cerevisiae that is known to interact with a yeast G alpha subunit (Gpa1). A highly conserved core domain of 125 amino acids characterizes this family of proteins. Analysis of deletion mutants demonstrated that the core domain is the site of GAIP's interaction with G alpha i3. GAIP is likely to be an early inducible phosphoprotein, as its cDNA contains the TTTTGT sequence characteristic of early response genes in its 3'-untranslated region. By Northern analysis GAIP's 1.6-kb mRNA is most abundant in lung, heart, placenta, and liver and is very low in brain, skeletal muscle, pancreas, and kidney. GAIP appears to interact exclusively with G alpha i3, as it did not interact with G alpha i2 and G alpha q. The fact that GAIP and Sst2 interact with G alpha subunits and share a common domain suggests that other members of the GAIP family also interact with G alpha subunits through the 125-amino-acid core domain.

Inhibition of G-protein signaling by dominant gain-of-function mutations in Sst2p, a pheromone desensitization factor in Saccharomyces cerevisiae.

Dohlman HG, Apaniesk D, Chen Y, Song J, Nusskern D
Mol Cell Biol. 1995; 15: 3635-43

Genetic analysis of cell-cell signaling in Saccharomyces cerevisiae has led to the identification of a novel factor, known as Sst2p, that promotes recovery after pheromone-induced growth arrest (R. K. Chan and C. A. Otte, Mol. Cell. Biol. 2:11-20, 1982). Loss-of-function mutations lead to increased pheromone sensitivity, but this phenotype is partially suppressed by overexpression of the G protein alpha subunit gene (GPA1). Suppression is allele specific, however, suggesting that there is direct interaction between the two gene products. To test this model directly, we isolated and characterized several dominant gain-of-function mutants of SST2. These mutations block the normal pheromone response, including a loss of pheromone-stimulated gene transcription, cell cycle growth arrest, and G protein myristoylation. Although the SST2 mutations confer a pheromone-resistant phenotype, they do not prevent downstream activation by overexpression of G beta (STE4), a constitutively active G beta mutation (STE4Hpl), or a disruption of GPA1. None of the SST2 alleles affects the expression or stability of G alpha. These results point to the G protein alpha subunit as being the direct target of Sst2p action and underscore the importance of this novel desensitization factor in G-protein-mediated signaling.