Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The noncatalytic domain of Ras-GAP can affect signaling through G protein-coupled receptors by a poorly understood mechanism. 2. In this study, fusion proteins containing elements of the noncatalytic domain of ras-GAP were examined for their ability to bind beta gamma subunits of heterotrimeric G proteins and phosphotyrosine-containing polypeptides. 3. Our results demonstrate that purified beta gamma dimers associated with bacterially expressed GAP proteins and that this association does not require SH2 or SH3 domains but is dependent on the presence of the GAP pleckstrin-homology (PH) domain. In contrast, only the SH2 domains are necessary for binding to tyrosine phosphorylated proteins. 4. These findings raise the possibility that heterotrimeric G proteins might affect functioning of ras-like proteins through beta gamma subunits acting on their regulatory molecules.
Cell Mol Neurobiol 1996 Feb
PMID:The PH domain of Ras-GAP is sufficient for in vitro binding to beta gamma subunits of heterotrimeric G proteins. 871 59

We previously described IQGAP1 as a human protein related to a putative Ras GTPase-activating protein (RasGAP) from the fission yeast Schizosaccharomyces pombe. Here we report the identification of a liver-specific human protein that is 62% identical to IQGAP1. Like IQGAP1, the novel IQGAP2 protein harbors an N-terminal calponin homology motif which functions as an F-actin binding domain in members of the spectrin, filamin, and fimbrin families. Both IQGAPs also harbor several copies of a novel 50- to 55-amino-acid repeat, a single WW domain, and four IQ motifs and have 25% sequence identity with almost the entire S. pombe sar1 RasGAP homolog. As predicted by the presence of IQ motifs, IQGAP2 binds calmodulin. However, neither full-length nor truncated IQGAP2 stimulated the GTPase activity of Ras or its close relatives. Instead, IQGAP2 binds Cdc42 and Racl but not RhoA. This interaction involves the C-terminal half of IQGAP2 and appears to be independent of the nucleotide binding status of the GTPases. Although IQGAP2 shows no GAP activity towards Cdc42 and Rac1, the protein did inhibit both the intrinsic and RhoGAP-stimulated GTP hydrolysis rates of Cdc42 and Rac1, suggesting an alternative mechanism via which IQGAPs might modulate signaling by these GTPases. Since IQGAPs harbor a potential actin binding domain, they could play roles in the Cdc42 and Rac1 controlled generation of specific actin structures.
Mol Cell Biol 1996 Sep
PMID:The Ras GTPase-activating-protein-related human protein IQGAP2 harbors a potential actin binding domain and interacts with calmodulin and Rho family GTPases. 875 46

Granule cells in the adult rat hippocampus do not constitutively express the growth-related axonal protein F1 (a.k.a. B-50, GAP-43, neuromodulin, pp46), yet kainic acid (KA) can induce extensive growth of granule cell axons, the mossy fibers, into the supragranular layer. Does this KA-induced growth occur in the absence of protein F1/GAP-43? Using quantitative in situ hybridization, we found that 16-24 h after KA (10 mg/kg, s.c.) F1/GAP-43 mRNA was in fact induced in granule cells and remained elevated above control levels for at least 20 days. The induction of F1/GAP-43 mRNA in granule cells was blocked either by MK-801 or pentobarbital pretreatment. If pentobarbitol was given 55 min, but not 90 min, after KA, F1/GAP-43 mRNA was also blocked. Since induction of F1/GAP-43 occurred when pentobarbitol was given 90 min after KA, a 35 min window of activation is required, beyond the initial 55 min, for F1/GAP-43 mRNA induction. As both MK-801 and pentobarbital blocked behavioral seizures their anti-convulsant action may be important for blocking F1/GAP-43 mRNA induction. Mossy fiber sprouting observed 30 days after KA was also blocked when either MK-801 or pentobarbital was given prior to KA. These results are consistent with the proposal that protein F1/GAP-43 promotes axonal growth in the adult brain in an input-dependent manner, and may also be of clinical relevance to the molecular mechanisms underlying structural remodeling in epilepsy.
Brain Res Mol Brain Res 1995 Oct
PMID:NMDA receptor blockade prevents kainate induction of protein F1/GAP-43 mRNA in hippocampal granule cells and subsequent mossy fiber sprouting in the rat. 877 42

We have studied both the expression and the interactions of focal adhesion kinase (FAK) during brain development. We have discovered that during different periods of development, FAK apparently has different properties. During the early stage of neurogenesis, FAK is phosphorylated, shows multiple isoforms, and interacts with the proto-oncogenes, src, fyn, and lyn. At this stage, FAK also interacts with both the N- and C-terminal SH2 domains of GAP, a negative regulator of the ras pathway. During later embryonic development, none of these protein interactions are apparent even though FAK is still predominantly phosphorylated. By adulthood FAK is largely unphosphorylated and migrates as a single protein species on SDS--PAGE. We discuss these results in terms of the dynamic cell movements that occur during embryonic brain development.
Mol Cell Neurosci 1996 May
PMID:The regulation of the expression, phosphorylation, and protein associations of pp125FAK during rat brain development. 881 64

We describe in vitro tyrosine phosphorylation of the C-terminal 334 amino acids of ras-GTPase-activating protein (ras-GAP)1 that contains the activity domain for ras interaction. To date, there have been no other phosphorylation sites determined than the reported in N-terminal domain of ras-GAP Tyr-460, which is considered to be the major phosphorylation site of ras-GAP. In our assays some differences of the kinetic parameters were observed when the reaction was catalyzed by EGF-R compared to p60c-src. Enzyme specific regulation of activity is associated with autophosphorylation which leads to reduced (in case of EGF-R) or increased (in case of p60c-src) phosphorylation of the C-terminal 334 amino acids of ras-GAP (GAP334). Because of the characteristics of these investigated reactions the phosphorylation of GAP334 seems to be-independent from the presence of SH2 or SH3 domains-triggered off by complex mechanisms different from those regulating the phosphorylation at Tyr-460.
Biochem Mol Biol Int 1996 Jun
PMID:Characterization of the C-terminal domain of ras-GTPase-activating protein (ras-GAP) as substrate for epidermal growth factor receptor and p60c-src kinase. 882 16

Although the Ras-related protein TC21/R-Ras2 has only 55% amino acid identity with Ras proteins, mutated forms of TC21 exhibit the same potent transforming activity as constitutively activated forms of Ras. Therefore, like Ras, TC21 may activate signaling pathways that control normal cell growth and differentiation. To address this possibility, we determined if regulators and effectors of Ras are also important for controlling TC21 activity. First, we determined that Ras guanine nucleotide exchange factors (SOS1 and RasGRF/CDC25) synergistically enhanced wild-type TC21 activity in vivo and that Ras GTPase-activating proteins (GAPs; p120-GAP and NF1-GAP) stimulated wild-type TC21 GTP hydrolysis in vitro. Thus, extracellular signals that activate Ras via SOS1 activation may cause coordinate activation of Ras and TC21. Second, we determined if Raf kinases were effectors for TC21 transformation. Unexpectedly, yeast two-hybrid binding analyses showed that although both Ras and TC21 could interact with the isolated Ras-binding domain of Raf-1, only Ras interacted with full-length Raf-1, A-Raf, or B-Raf. Consistent with this observation, we found that Ras- but not TC21-transformed NIH 3T3 cells possessed constitutively elevated Raf-1 and B-Raf kinase activity. Thus, Raf kinases are effectors for Ras, but not TC21, signaling and transformation. We conclude that common upstream signals cause activation of Ras and TC21, but activated TC21 controls cell growth via distinct Raf-independent downstream signaling pathways.
Mol Cell Biol 1996 Nov
PMID:TC21 causes transformation by Raf-independent signaling pathways. 888 43

GTP and ATP hydrolysing proteins have an absolute requirement for a divalent cation, which is usually Mg2+, as a cofactor in the enzymatic reaction. Other phosphoryl transfer enzymes employ more than one divalent ion for the enzymatic reaction. It is shown here for p21ras, a well studied example of GTP hydrolysing proteins, that the GTP-hydrolysis rate is significantly faster if Mg2+ is replaced by Mn2+, both in the presence or absence of its GTPase-activating protein Ras-GAP. This effect is not due to a different stoichiometry of metal ion binding, since one metal ion is sufficient for full enzymatic activity. To determine the role of the metal ion, the crystal structure of p21(G12P). GppCp complexed with Mn2+ was determined and shown to be very similar to the corresponding p21(G12P). GppCp.Mg2+ structure. Especially the coordination sphere around the metal ions is very similar, and no second metal ion binding site could be detected, consistent with the assumption that one metal ion is sufficient for GTP hydrolysis. In order to explain the biochemical differences, we analysed the GTPase reaction mechanism with a linear free energy relationships approach. The result suggests that the reaction mechanism is not changed with Mn2+ but that the transition metal ion Mn2+ shifts the pKa of the gamma-phosphate by almost half a unit and increases the reaction rate due to an increase in the basicity of GTP acting as the general base. This suggests that the intrinsic GTPase reaction could be an attractive target for anti-cancer drug design. By using Rap1A and Ran, we show that the acceleration of the GTPase by Mn2+ appears to be a general phenomenon of GTP-binding proteins.
J Mol Biol 1997 Mar 07
PMID:The role of the metal ion in the p21ras catalysed GTP-hydrolysis: Mn2+ versus Mg2+. 910 73

To address whether Ras can be activated by insulin in the PC12 cell line, proteins interacting with insulin receptor and IRS-1 molecules and their tyrosine phosphorylation were analyzed by immunoblotting following immunoprecipitation with antibodies. Tyrosine phosphorylation of the insulin receptor and IRS-1 was increased by insulin. Grb2 and Ras-GAP appeared in the immunoprecipitates by anti-insulin receptor and anti-IRS-1 from insulin-treated cells. In addition, PI 3-kinase was activated by insulin treatment in this cell line and Grb2, Ras-GAP, and MAP kinase were coprecipitated with Ras from both insulin-treated and NGF-treated cells. Analysis of MAP kinases from insulin-treated cells revealed that insulin, like NGF, increased tyrosine phosphorylation. However, activation of the MAP kinase by NGF lasted longer than activation by insulin. These results indicate that Ras can be activated by insulin in the PC12 cell line and that Ras activation is neither an accurate nor a plausible method of discriminating signals between proliferation and differentiation.
Mol Cells 1997 Jun 30
PMID:Insulin activates Ras in the PC12 cell line. 926 35

We report the identification and characterization of a novel 124-kDa Ran binding protein, RanBP5. This protein is related to importin-beta, the key mediator of nuclear localization signal (NLS)-dependent nuclear transport. RanBP5 was identified by two independent methods: it was isolated from HeLa cells by using its interaction with RanGTP in an overlay assay to monitor enrichment, and it was also found by the yeast two-hybrid selection method with RanBP1 as bait. RanBP5 binds to RanBP1 as part of a trimeric RanBP1-Ran-RanBP5 complex. Like importin-beta, RanBP5 strongly binds the GTP-bound form of Ran, stabilizing it against both intrinsic and RanGAP1-induced GTP hydrolysis and also against nucleotide exchange. The GAP resistance of the RanBP5-RanGTP complex can be relieved by RanBP1, which might reflect an in vivo role for RanBP1. RanBP5 is a predominantly cytoplasmic protein that can bind to nuclear pore complexes. We propose that RanBP5 is a mediator of a nucleocytoplasmic transport pathway that is distinct from the importin-alpha-dependent import of proteins with a classical NLS.
Mol Cell Biol 1997 Sep
PMID:Ran-binding protein 5 (RanBP5) is related to the nuclear transport factor importin-beta but interacts differently with RanBP1. 927 86

Tuberous sclerosis is an autosomal dominant trait in which the dysregulation of cellular proliferation and differentiation results in the development of hamartomatous growths in many organs. The TSC2 gene is one of two genes determining tuberous sclerosis. Inactivating germline mutations of TSC2 in patients with tuberous sclerosis and somatic loss of heterozygosity at the TSC2 locus in the associated hamartomas indicate that TSC2 functions as a tumour suppressor gene and that loss of function is critical to expression of the tuberous sclerosis phenotype. The TSC2 product, tuberin, has a region of homology with the GTPase activating protein rap1GAP and stimulates the GTPase activity of rap1a and rab5a in vitro. Here we show that the region of homology between tuberin and human rap1GAP and the murine GAP mSpa1 is more extensive than previously reported and spans approximately 160 amino acid residues encoded within exons 34-38 of the TSC2 gene. Single strand conformation polymorphism analysis of these exons in 173 unrelated patients with tuberous sclerosis and direct sequencing of variant conformers together with study of additional family members enabled characterisation of disease associated mutations in 14 cases. Missense mutations, which occurred in exons 36, 37 and 38 were identified in eight cases, four of whom shared the same recurrent change P1675L. Each of the five different missense mutations identified was shown to occur de novo in at least one sporadic case of tuberous sclerosis. The high proportion of missense mutations detected in the region of the TSC2 gene encoding the GAP-related domain supports its key role in the regulation of cellular growth.
Hum Mol Genet 1997 Oct
PMID:The GAP-related domain of tuberin, the product of the TSC2 gene, is a target for missense mutations in tuberous sclerosis. 930 81


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