Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.25 (triphosphatase)
 1,529 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Regulator of G-protein signaling (RGS) proteins increase the intrinsic guanosine triphosphatase (GTPase) activity of G-protein alpha subunits in vitro, but how specific G-protein-coupled receptor systems are targeted for down-regulation by RGS proteins remains uncharacterized. Here, we describe the GTPase specificity of RGS12 and identify four alternatively spliced forms of human RGS12 mRNA. Two RGS12 isoforms of 6.3 and 5.7 kilobases (kb), encoding both an N-terminal PDZ (PSD-95/Dlg/ZO-1) domain and the RGS domain, are expressed in most tissues, with highest levels observed in testis, ovary, spleen, cerebellum, and caudate nucleus. The 5.7-kb isoform has an alternative 3' end encoding a putative C-terminal PDZ domain docking site. Two smaller isoforms, of 3.1 and 3.7 kb, which lack the PDZ domain and encode the RGS domain with and without the alternative 3' end, respectively, are most abundantly expressed in brain, kidney, thymus, and prostate. In vitro biochemical assays indicate that RGS12 is a GTPase-activating protein for Gi class alpha subunits. Biochemical and interaction trap experiments suggest that the RGS12 N terminus acts as a classical PDZ domain, binding selectively to C-terminal (A/S)-T-X-(L/V) motifs as found within both the interleukin-8 receptor B (CXCR2) and the alternative 3' exon form of RGS12. The presence of an alternatively spliced PDZ domain within RGS12 suggests a mechanism by which RGS proteins may target specific G-protein-coupled receptor systems for desensitization.
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PMID:GTPase activating specificity of RGS12 and binding specificity of an alternatively spliced PDZ (PSD-95/Dlg/ZO-1) domain. 965 75

Proliferation, differentiation, and survival of erythroid progenitor cells are mainly regulated by stem cell factor (SCF) and erythropoietin (Epo). Using normal human progenitors, we analyzed the role of Ca2+-sensitive protein kinase C (PKC) subtypes and of G-protein-coupled receptor ligands on growth factor-dependent DNA synthesis. We show that stimulation of DNA synthesis by the two growth factors requires activation of PKCalpha. Inhibitors of Ca2+-activated PKC subtypes blocked the growth factor-induced 3H-thymidine incorporation. SCF and Epo caused no significant translocation of PKCalpha into the membrane, but treatment of intact cells with either of the two cytokines resulted in enhanced activity of immunoprecipitated cytosolic PKCalpha. Stimulation of PKC with the phorbol ester PMA mimicked the cytokine effect on DNA synthesis. Epo-, SCF-, and PMA-induced thymidine incorporation was potently inhibited by thrombin (half-maximal inhibition with 0.1 U/mL). This effect was mediated via the G-protein-coupled thrombin receptor and the Rho guanosine triphosphatase. Adenosine diphosphate caused a modest Ca2+-dependent stimulation of DNA synthesis in the absence of cytokines and specifically enhanced the effect of SCF. Cyclic 3', 5'-adenosine monophosphate exerted a selective inhibitory effect on Epo-stimulated thymidine incorporation. Our results define PKCalpha as major intermediate effector of cytokine signaling and suggest a role for thrombin in controlling erythroid progenitor proliferation.
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PMID:Erythropoietin- and stem cell factor-induced DNA synthesis in normal human erythroid progenitor cells requires activation of protein kinase Calpha and is strongly inhibited by thrombin. 1038 4

The regulators of G-protein signaling (RGS) proteins accelerate the intrinsic guanosine triphosphatase activity of heterotrimeric G-protein alpha subunits and are thus recognized as key modulators of G-protein-coupled receptor signaling. RGS12 and RGS14 contain not only the hallmark RGS box responsible for GTPase-accelerating activity but also a single G alpha(i/o)-Loco (GoLoco) motif predicted to represent a second G alpha interaction site. Here, we describe functional characterization of the GoLoco motif regions of RGS12 and RGS14. Both regions interact exclusively with G alpha(i1), G alpha(i2), and G alpha(i3) in their GDP-bound forms. In GTP gamma S binding assays, both regions exhibit guanine nucleotide dissociation inhibitor (GDI) activity, inhibiting the rate of exchange of GDP for GTP by G alpha(i1). Both regions also stabilize G alpha(i1) in its GDP-bound form, inhibiting the increase in intrinsic tryptophan fluorescence stimulated by AlF(4)(-). Our results indicate that both RGS12 and RGS14 harbor two distinctly different G alpha interaction sites: a previously recognized N-terminal RGS box possessing G alpha(i/o) GAP activity and a C-terminal GoLoco region exhibiting G alpha(i) GDI activity. The presence of two, independent G alpha interaction sites suggests that RGS12 and RGS14 participate in a complex coordination of G-protein signaling beyond simple G alpha GAP activity.
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PMID:RGS12 and RGS14 GoLoco motifs are G alpha(i) interaction sites with guanine nucleotide dissociation inhibitor Activity. 1138 33