Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.5.1.18 (glutathione S-transferase)
22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The c-kit proto-oncogene encodes a transmembrane tyrosine kinase receptor, which is important for the normal development of hematopoietic cells, melanoblasts, and germ cells. Autophosphorylation of c-kit receptor on tyrosine creates binding sites for cellular src homology 2 (SH2)-containing signaling molecules. The discovery of phosphotyrosine phosphatases that contain SH2 domains suggests roles for these molecules in growth factor signaling pathways. We found that Syp, a phosphotyrosine phosphatase widely expressed in all the tissues in mammals, associates with c-kit receptor after activation with its ligand, steel factor, in the factor-dependent cell line, M07e. Both NH2-terminal and COOH-terminal SH2 domains of Syp, made as glutathione S-transferase fusion proteins, were able to bind to the activated c-kit receptor in vitro. Furthermore, Syp became marginally phosphorylated on tyrosine upon c-kit receptor activation, and tyrosine-phosphorylated Syp was found to be complexed with Grb2 in steel factor-stimulated M07e cells. Direct binding between Syp and Grb2 was also observed in vitro. Last, Ras and Raf interacts in vitro as a result of steel factor-stimulated Ras activation. These results suggest that Syp may be an important signaling component downstream of the c-kit receptor and involved in activation of the Ras signaling pathway in hematopoietic cells.
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PMID:The ubiquitously expressed Syp phosphatase interacts with c-kit and Grb2 in hematopoietic cells. 752 81

The CD45 transmembrane protein-tyrosine phosphatase (PTPase, EC 3.1.3.48) plays an essential role in T-cell activation by activating the Lck and/or Fyn protein-tyrosine kinases. However, numerous experiments have indicated that CD45 may have both stimulatory and inhibitory roles in T-cell activation. Thus, it is unlikely that the two kinases are the sole substrates of the CD45 PTPase. Furthermore, the complex regulation of the alternative splicing of the extracellular domain in various leukocyte lineages also suggests additional roles for the CD45 PTPase. To identify such functions, it is necessary to identify physiologically relevant substrates of the CD45 PTPase other than the two protein-tyrosine kinases. To this end, we searched for high-affinity substrates of the CD45 PTPase among the tyrosine-phosphorylated T-cell proteins by using purified glutathione S-transferase-CD45 fusion molecules. The enzymatically inactive CD45 C828S mutant protein, in which the cysteine residue at the catalytic center was changed to a serine residue, bound tightly to the phosphorylated CD3 zeta chain. This binding was specific to CD45 PTPase, as neither the leukocyte common antigen-related molecule (LAR) PTPase nor the CD45-LAR hybrid PTPases bound the phosphorylated CD3 zeta chain. Furthermore, phosphorylated CD3 zeta chain was preferentially dephosphorylated by the wild-type CD45 PTPase under conditions that did not significantly dephosphorylate other cellular proteins. Thus, the phosphorylated CD3 zeta chain is a specific and high-affinity substrate of the CD45 PTPase. These results suggest that CD45 is involved in the termination of the T-cell response via dephosphorylation of CD3 zeta chain.
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PMID:Specific interaction of the CD45 protein-tyrosine phosphatase with tyrosine-phosphorylated CD3 zeta chain. 752 85

Erythropoietin (Epo) regulates the proliferation and differentiation of erythroid precursors. The phosphorylation of proteins at tyrosine residues is critical in the growth signaling induced by Epo. This mechanism is regulated by the activities of both protein-tyrosine kinases and protein tyrosine phosphatases. The discovery of phosphotyrosine phosphatases that contain SH2 domains suggests roles for these molecules in growth factor signaling pathways. We found that Syp, a phosphotyrosine phosphatase, widely expressed in all tissues in mammals became phosphorylated on tyrosine after stimulation with Epo in M07ER cells engineered to express high levels of human EpoR. Syp was complexed with Grb2 in Epo-stimulated M07ER cells. Direct binding between Syp and Grb2 was also observed in vitro. Furthermore, Syp appeared to bind directly to tyrosine-phosphorylated EpoR in M07ER cells. Both NH2-terminal and COOH-terminal SH2 domains of Syp, made as glutathione S-transferase fusion proteins, were able to bind to the tyrosine-phosphorylated EpoR in vitro. These results suggest that Syp may be an important signaling component downstream of the EpoR and may regulate the proliferation and differentiation of hematopoietic cells.
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PMID:Involvement of SH2-containing phosphotyrosine phosphatase Syp in erythropoietin receptor signal transduction pathways. 753 99

Syp (SH-PTP2) was recently identified as a phosphotyrosine phosphatase containing two SH2 domains within its primary structure. In response to appropriate growth factor stimulation, Syp becomes phosphorylated on tyrosine residues and associates with insulin receptor substrate 1 (IRS-1) and/or the corresponding growth factor receptor via its SH2 domains, leading to increased Syp activity. To assess the importance of Syp in mitogenic signaling, we microinjected mammalian fibroblasts with several reagents designed to interfere with Syp SH2/phosphotyrosine interaction in vivo. Insulin-, insulin-like growth factor-1-, and epidermal growth factor-stimulated DNA synthesis, indicated by bromodeoxyuridine (BrdUrd) incorporation, was dramatically decreased following microinjection of a Syp antibody (Ab) (65-85%) or a Syp GST-SH2 fusion protein (approximately 90%) in comparison with cells microinjected with control IgG or glutathione S-transferase (GST), respectively. In addition, microinjection of an IRS-1-derived phosphonopeptide, which inhibits in vitro binding of Syp-SH2 to IRS-1 with an ED50 value of approximately 23 microM, also decreased BrdUrd incorporation in vivo by approximately 50-75%. Microinjection of the Syp Ab, Syp GST-SH2 fusion protein, or the phosphonopeptide had no effect on serum-stimulated BrdUrd incorporation. In conclusion, disruption of Syp function in living cells inhibited cell cycle progression in response to growth factor stimulation, indicating that Syp is a critical positive regulator of mitogenic signal transduction.
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PMID:Syp (SH-PTP2) is a positive mediator of growth factor-stimulated mitogenic signal transduction. 806 47

The receptor-like protein tyrosine phosphatase, PTPmu, displays structural similarity to cell-cell adhesion molecules of the immunoglobulin superfamily. We have investigated the ability of human PTPmu to function in such a capacity. Expression of PTPmu, with or without the PTPase domains, by recombinant baculovirus infection of Sf9 cells induced their aggregation. However, neither a chimeric form of PTPmu, containing the extracellular and transmembrane segments of the EGF receptor and the intracellular segment of PTPmu, nor the intracellular segment of PTPmu expressed as a soluble protein induced aggregation. PTPmu mediates aggregation via a homophilic mechanism, as judged by lack of incorporation of uninfected Sf9 cells into aggregates of PTPmu-expressing cells. Homophilic binding has been demonstrated between PTPmu-coated fluorescent beads (Covaspheres) and endogenously expressed PTPmu on MvLu cells. Additionally the PTPmu-coated beads specifically bound to a bacterially expressed glutathione-S-transferase fusion protein containing the extracellular segment of PTPmu (GST/PTPmu) adsorbed to petri dishes. Covaspheres coated with the GST/PTPmu fusion protein aggregated in vitro and also bound to PTPmu expressed endogenously on MvLu cells. These results suggest that the ligand for this transmembrane PTPase is another PTPmu molecule on an adjacent cell. Thus homophilic binding interactions may be an important component of the function of PTPmu in vivo.
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PMID:Homophilic binding of PTP mu, a receptor-type protein tyrosine phosphatase, can mediate cell-cell aggregation. 839 72

We have investigated the roles of the phosphotyrosine phosphatase Syp (also called SH-PTP2), phospholipase C (PLC) gamma1, rasGTPase Activating Protein (rasGAP) and the adapter molecules Nck and Shc in the mitogenic response induced by PDGF in fibroblasts. Two separate approaches were used to inhibit the biological activity of these signalling proteins in vivo. Either glutathione S-transferase (GST) fusion proteins containing the SH2 domains of these proteins, or antibodies specific for these polypeptides, were microinjected into cells. GST-SH2 fusion proteins are expected to act as dominant inhibitors by competing for physiological SH2-mediated interactions, while microinjected antibodies can directly block protein functions. Inhibition of PLCgamma, Syp, Shc and Nck signals blocked PDGF-stimulated cells in G1 showing a requirement for these proteins for S-phase entry. Inhibition of rasGAP, in contrast, had no effect on S-phase entry. We next examined which of these signals were required for PDGF-induced cFos expression, a Ras-dependent event important for signalling. By using the same approaches with cells expressing beta-galactosidase under the control of a c-fos promoter, we showed that PLCgamma, Syp and Shc were necessary for ligand-induced cFos expression whereas Nck and phosphatidylinositol 3-kinase alpha were not. From these results we concluded that PDGF generates Ras-dependent and Ras-independent pathways important for DNA synthesis.
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PMID:Requirement of phospholipase C gamma, the tyrosine phosphatase Syp and the adaptor proteins Shc and Nck for PDGF-induced DNA synthesis: evidence for the existence of Ras-dependent and Ras-independent pathways. 889 Jan 67

BCR-ABL is a chimeric oncoprotein that exhibits deregulated tyrosine kinase activity and is implicated in the pathogenesis of Philadelphia chromosome (Ph1)-positive leukemia. We have previously shown SH2-containing phosphotyrosine phosphatase SHP-2 forms stable complexes with BCR-ABL and Grb2 in BCR-ABL-transformed cells (Tauchi, T., Feng, G. S., Shen, R., Song, H. Y., Donner, D., Pawson, T., and Broxmeyer, H. E. (1994) J. Biol. Chem. 269, 15381-15387). To elucidate the structural requirement of BCR-ABL for the interactions with SH2-containing signaling molecules, we examined a series of BCR-ABL mutants which include the Grb2 binding site-deleted BCR-ABL (1-63 BCR/ABL), the tetramerization domain-deleted BCR-ABL (64-509 BCR/ABL), and the SH2 domain-deleted BCR-ABL (BCR/ABL deltaSH2). These BCR-ABL mutants were previously shown to reduce the transforming activity in fibroblasts. We found that the tetramerization domain-deleted BCR-ABL did not induce the tyrosine phosphorylation of SHP-2 and the interactions of BCR-ABL, SHP-2, and Grb2. In vitro kinase assays have also shown that the tetramerization domain-deleted BCR-ABL mutant did not phosphorylate GST-SHP-2 in vitro. SHP-2 was co-immunoprecipitated with phosphatidylinositol 3-kinase in BCR/ABL p210-transformed cells; however, this interaction was not observed in the tetramerization domain-deleted BCR-ABL mutant. Therefore the tetramerization domain of BCR-ABL is essential for interactions of these downstream molecules.
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PMID:A coiled-coil tetramerization domain of BCR-ABL is essential for the interactions of SH2-containing signal transduction molecules. 899 49

BCR-ABL is a chimeric oncoprotein that exhibits deregulated tyrosine kinase activity and is implicated in the pathogenesis of Philadelphia chromosome (ph1)-positive leukemia. We have previously shown SH2-containing phosphotyrosine phosphatase SHP-2 forms stable complexes with BCR-ABL and Grb2 in BCR-ABL transformed cells (T., Tauchi, et al. J. Biol. Chem. 269, 15381, 1994). To elucidate the structural requirement of BCR-ABL for the interactions with SH2-containing signaling molecules, we examined a series of BCR-ABL mutants which include the Grb2 binding site deleted BCR-ABL (1-63 BCR/ABL), the tetramerization domain deleted BCR-ABL (64-509 BCR/ABL), and the SH2 domain deleted BCR-ABL (BCR/ABL delta SH2). These BCR-ABL mutants were previously shown to reduce the transforming activity in fibroblasts. We found that the tetramerization domain deleted BCR-ABL did not induce the tyrosine phosphorylation of SHP-2 and the interactions of BCR-ABL, SHP-2, and Grb2. In vitro kinase assays have also shown the tetramerization domain deleted BCR-ABL mutant did not phosphorylate GST-SHP-2 in vitro. SHP-2 was co-immunoprecipitated with P13Kinase in BCR/ABL p210 transformed cells, however this interaction was not observed in the tetramerization domain deleted BCR-ABL mutant. Therefore the tetramerization domain of BCR-ABL is essential for interactions of these downstream molecules.
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PMID:A coiled-coil tetramerization domain of BCR-ABL is essential for the interactions of SH2-containing signal transduction molecules. 918 66

Disodium aurothiomalate (AuTM) has been used successfully in the treatment of various autoimmune and inflammatory disorders; however, the molecular target(s) for this agent remains unknown. The aim of this study was to investigate whether the activity of CD45, a protein-tyrosine phosphatase (PTP, EC 3.1.3.48) essential for antigen-receptor-mediated lymphocyte signaling, was modified by AuTM exposure. The effects of AuTM on the activities of CD45 and other PTPs were monitored in vitro by a continuous assay using the substrate fluorescein diphosphate. In addition, the inhibition of PTP1B by AuTM was determined using a novel binding assay that employed an optical biosensor (BIAcore). The experimental results are summarized here: AuTM inhibited CD45 activity with an IC50 of 1.2 +/- 0.1 microM, and inhibition was competitive with substrate. The effect of AuTM, however, was not restricted to CD45, as the cytoplasmic PTP (PTP1B) was also inhibited, with an IC50 of 3.6 +/- 0.2 microM. AuTM also blocked the binding of GST-PTP1B to an immobilized active site inhibitor: a non-hydrolyzable difluorophosphonomethyl phenylalanine-containing biotinylated hexapeptide. AuTM-inhibited CD45 could be reactivated by the addition of excess dithiothreitol. These findings indicate that AuTM may interact with the essential active site cysteine residue involved in the catalytic mechanism of PTPs. Thus, it is possible that some of the cellular effects of gold result from the inhibition of these important cell signaling molecules.
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PMID:Mechanism of inhibition of protein-tyrosine phosphatases by disodium aurothiomalate. 931 Mar 47

The SH2 domain of c-Fgr (class 1A) has been expressed in E. coli as GST fusion protein and tested for its ability to prevent the dephosphorylation of a variety of phosphotyrosyl (poly)peptides by three distinct protein tyrosine phosphatases (TC-PTPase, YOP, and Low Mr PTPase). Dephosphorylation of HS1 protein and of a derived phosphopeptide, HS1 (388-402), exhibiting the motif selected by class 1A SH2 domains is inhibited in a dose dependent manner with full inhibition promoted by a 2- to 3-molar excess of GST/SH2 domain irrespective of either the nature or the amount of phosphatase used. The IC50 values for inhibition of these and other phosphotyrosyl substrates roughly correlates with their expected affinity for class 1A SH2 domain. Inhibition is partially reversed by the addition of D-myo-inositol 1,4,5-triphosphate, which competes for the binding to the SH2 domains. Our data on one side show that additional mechanism(s) besides mere competition must assist PTPases to dissociate SH2-PTyr complexes and on the other suggest a role for SH2 domains in protecting phosphotyrosyl residues from premature dephosphorylation.
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PMID:Src homology-2 domains protect phosphotyrosyl residues against enzymatic dephosphorylation. 950 Sep 84


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