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

---

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

Intracellular signaling from the T cell receptor (TCR)zeta/CD3 complex is likely to be mediated by associated protein tyrosine kinases such as p59fyn(T), ZAP-70, and the CD4:p56lck and CD8:p56lck coreceptors. The nature of the signaling cascade initiated by these kinases, their specificities, and downstream targets remain to be elucidated. The TCR-zeta/CD3:p59fyn(T) complex has previously been noted to coprecipitate a 120/130-kD doublet (p120/130). This intracellular protein of unknown identity associates directly with p59fyn(T) within the receptor complex. In this study, we have shown that this interaction with p120/130 is specifically mediated by the SH2 domain (not the fyn-SH3 domain) of p59fyn(T). Further, based on the results of in vitro kinase assays, p120/130 appears to be preferentially associated with p59fyn(T) in T cells, and not with p56lck. Antibody reprecipitation studies identified p120/130 as a previously described 130-kD substrate of pp60v-src whose function and structure is unknown. TCR-zeta/CD3 induced activation of T cells augmented the tyrosine phosphorylation of p120/130 in vivo as detected by antibody and GST:fyn-SH2 fusion proteins. p120/130 represents the first identified p59fyn(T):SH2 binding substrate in T cells, and as such is likely to play a key role in the early events of T cell activation.
...
PMID:T cell receptor zeta/CD3-p59fyn(T)-associated p120/130 binds to the SH2 domain of p59fyn(T). 750 57

Engagement of the T cell antigen receptor (TCR) results in activation of several tyrosine kinases leading to tyrosine phosphorylation of protein substrates and activation of multiple biochemical pathways. TCR-mediated activation of the src-family kinases, Lck and Fyn, results in tyrosine phosphorylation of the TCR zeta and CD3 chains. The site of phosphorylation in these chains is the tyrosine-based activation motif (TAM), a 15-16 amino acid module containing two tyrosine residues. Tyrosine-phosphorylated TAMs serve as targets for binding of the zeta-associated protein (ZAP-70) tyrosine kinase via its tandem SH2 domains. This binding correlates with activation of ZAP-70, a critical event in T cell activation. To further define the structural requirements for ZAP-70 interaction with the TCR, we developed a binding assay using immobilized glutathione S-transferase fusion proteins containing the NH2- and/or COOH-terminal SH2 domains of ZAP-70, and soluble synthetic peptides with the sequence of the cytoplasmic region of the TCR zeta chain (TCR zeta cyt) or individual TCR zeta and CD3 epsilon TAM motifs. Direct binding studies demonstrated that the tandem ZAP-70 SH2 domains bind phosphorylated, but not nonphosphorylated, TCR zeta cyt. The NH2-terminal ZAP-70 SH2 domain also binds to TCR zeta cyt but with 100-fold lower affinity. No binding was observed with the COOH-terminal ZAP-70 SH2 domain. Similar studies demonstrated that the ZAP-70 tandem SH2 domain can bind a TCR zeta 3 TAM peptide in which both tyrosine residues are phosphorylated: Little or no binding was observed with peptides phosphorylated at only one tyrosine residue, or a nonphosphorylated peptide. Binding of the tandem SH2 domains to the other two TCR zeta TAM peptides and to a CD3 epsilon TAM peptide was also observed. All four doubly tyrosine phosphorylated TAM peptides cross-compete with each other for binding to the tandem SH2 domains of ZAP-70. The affinity of these peptides for the tandem SH2 construct demonstrated a hierarchy of TAM zeta 1 > or = TAM zeta 2 > TAM epsilon > or = TAM zeta 3. The results provide further evidence that the ZAP-70 interaction with the TCR requires prior phosphorylation of both tyrosine residues within a TAM motif. Binding of ZAP-70 to phospho-TAMs is notable for the high level of cooperativity between the two SH2 domains, which individually demonstrate low affinity interaction with the ligand. The cooperativity ensures higher affinity for the doubly phosphorylated ligand. Affinity differences of as much as 30-fold indicates a significant specificity of interaction of ZAP-70 SH2 domains for different phospho-TAMs.
...
PMID:ZAP-70 binding specificity to T cell receptor tyrosine-based activation motifs: the tandem SH2 domains of ZAP-70 bind distinct tyrosine-based activation motifs with varying affinity. 752 72

The src family protein tyrosine kinases participate in signaling through cell surface receptors that lack intrinsic tyrosine kinase domains. One of the src family kinases, p59fyn (Fyn), plays an important role in the TCR-mediated signaling. Here we report that Fyn becomes associated with the zeta-associated tyrosine kinase, ZAP-70, in a T cell hybridoma upon stimulation. The association was transient; it occurred as early as 10 s after stimulation and disappeared after 10 min. The two proteins were also associated with each other when coexpressed in COS cells. Coexpression of the zeta-chain was not required for their interaction. Mutational analysis of Fyn and ZAP-70 revealed that their kinase activities were relevant to the association. Deletion of both the SH2 and SH3 domains of Fyn resulted in the decrease of the association with ZAP-70. Consistently, Fyn-SH2 and Fyn-SH3 fused to glutathione S-transferase were able to bind to ZAP-70. These data suggest that multiple sites of Fyn and ZAP-70 are involved in the association. Furthermore, coexpression of the wild-type of both kinases in COS cells enhanced tyrosine phosphorylation of the helix-turn-helix-containing protein, HS1. HS1 was also tyrosine phosphorylated upon TCR stimulation. Thus, we propose that Fyn phosphorylates and activates ZAP-70 and that both kinases cooperate in TCR signaling.
...
PMID:Physical and functional interactions of protein tyrosine kinases, p59fyn and ZAP-70, in T cell signaling. 856 36

cDNAs for three isotypes of inhibitor-2(I-2), I-2 alpha 1, I-2 alpha 2 and I-2 beta were isolated from a rat testis library. I-2 alpha 2 and I-2 beta are new forms. The former is an alternatively spliced form of I-2 alpha 1, encoding a protein with substitution of three amino acids for 14 amino acids of the I-2 alpha 1 protein at the C-terminus. The latter is derived from a different gene and encodes a 126-amino-acid protein having highly conserved regions with the I-2 alpha 1 protein from amino acid positions 22-47 and 111-126. I-2 alpha 2 and I-2 beta are expressed exclusively in the testis, and the expressions of all three forms of I-2 coincide with sperm cell maturation. The half-maximal inhibitory concentration of the GST-I-2 alpha 2 fusion protein on the PP1 gamma 2 catalytic subunit is the same as that of GST-I-2 alpha 1, being 10 nM. However, the half-maximal inhibitory concentration of GST-1-2 beta is 100-fold higher, being 1 microM. GST-I-2 beta showed no competition with GST-I-2 alpha 1. and its biological significance is unknown.
...
PMID:Identification and characterization of three isotypes of protein phosphatase inhibitor-2 and their expression profiles during testis maturation in rats. 902 11

In human T-lymphocytes the Src family protein tyrosine kinase p59(fyn) associates with three phosphoproteins of 43, 55, and 85 kDa (pp43, pp55, and pp85). Employing a GST-Fyn-Src homology 2 (SH2) domain fusion protein pp55 was purified from lysates of Jurkat T-cells. Molecular cloning of the pp55 cDNA reveals that the pp55 gene codes for a so far nondescribed polypeptide of 359 amino acids that comprises a pleckstrin homology domain, a C-terminal SH3 domain, as well as several potential tyrosine phosphorylation sites, among which one fulfills the criteria to bind Src-like SH2 domains with high affinity. Consistent with this observation, pp55 selectively binds to isolated SH2 domains of Lck, Lyn, Src, and Fyn but not to the SH2 domains of ZAP70, Syk, Shc, SLP-76, Grb2, phosphatidylinositol 3-kinase, and c-abl in vitro. Based on these properties the protein was termed SKAP55 (src kinase-associated phosphoprotein of 55 kDa). Northern blot analysis shows that SKAP55 mRNA is preferentially expressed in lymphatic tissues. SKAP55 is detected in resting human T-lymphocytes as a constitutively tyrosine phosphorylated protein that selectively interacts with p59(fyn). These data suggest that SKAP55 represents a novel adaptor protein likely involved in Fyn-mediated signaling in human T-lymphocytes.
...
PMID:Molecular cloning of SKAP55, a novel protein that associates with the protein tyrosine kinase p59fyn in human T-lymphocytes. 919 99

Engagement of the T cell antigen receptor initiates signal transduction involving tyrosine phosphorylation of multiple effector molecules and the formation of multimolecular complexes at the receptor site. Adapter proteins that possess SH2 and SH3 protein-protein interaction domains are implicated in the assembly of cell activation-induced signaling complexes. We found that Crk adapter proteins undergo activation-induced interaction with the zeta-chain associated protein (ZAP-70) tyrosine kinase in the human T cell line, Jurkat. Incubation of various glutathione S-transferase fusion proteins with a lysate of activated Jurkat cells resulted in selective association of ZAP-70 with Crk, but not Grb2 or Nck, adapter proteins. In addition, tyrosine-phosphorylated ZAP-70 co-immunoprecipitated with Crk from a lysate of activated Jurkat cells, and ZAP-70 association with GST-Crk was observed in a lysate of activated human peripheral blood T cells. Association between the two molecules was mediated by direct physical interaction and involved the Crk-SH2 domain and phosphotyrosyl-containing sequences on ZAP-70. The association required intact Lck, considered to be an upstream regulator of ZAP-70, because it could not take place in activated JCaM1 cells, which express normal levels of ZAP-70 but are devoid of Lck. Finally, glutathione S-transferase-Crk fusion proteins were found to interact predominantly with membrane-residing tyrosine-phosphorylated ZAP-70 that exhibited autophosphorylation activity as well as phosphorylation of an exogenous substrate, CFB3. These findings suggest that Crk adapter proteins play a role in the early activation events of T lymphocytes, apparently, by direct interaction with, and regulation of, the membrane-residing ZAP-70 protein tyrosine kinase.
...
PMID:T cell activation stimulates the association of enzymatically active tyrosine-phosphorylated ZAP-70 with the Crk adapter proteins. 1041 55

The tyrosine phosphatase SHP-1 functions as a negative regulator in hematopoietic cell development, proliferation, and receptor-mediated cellular activation. In Jurkat T cells, a major 68-kDa band and a minor 70-kDa band were immunoprecipitated by a monoclonal antibody against the SHP-1 protein-tyrosine phosphatase domain, while an antibody against the SHP-1 C-terminal 19 amino acids recognized only the 68-kDa SHP-1. The SDS-gel-purified 70-kDa protein was subjected to tryptic mapping and microsequencing, which was followed by molecular cloning. It revealed that the 70-kDa protein, termed SHP-1L, is a C-terminal alternatively spliced form of SHP-1. SHP-1L is 29 amino acids longer than SHP-1, and its 66 C-terminal amino acids are different from SHP-1. The C terminus of SHP-1L contains a proline-rich motif PVPGPPVLSP, a potential Src homology 3 domain-binding site. In contrast to SHP-1, tyrosine phosphorylation of SHP-1L is not detected upon stimulation in Jurkat T cells. This is apparently due to the lack of a single in vivo tyrosine phosphorylation site, which only exists in the C terminus of SHP-1 (Y564). COS cell-expressed glutathione S-transferase-SHP-1L can dephosphorylate tyrosine-phosphorylated ZAP70. At pH 7.4, SHP-1L was shown to be more active than SHP-1 in the dephosphorylation of ZAP70. At pH 5.4, SHP-1L and SHP-1 exhibited similar catalytic activity. It is likely that these two isoforms play different roles in the regulation of hematopoietic cell signal transduction.
...
PMID:Human 70-kDa SHP-1L differs from 68-kDa SHP-1 in its C-terminal structure and catalytic activity. 1049 87

A 592-amino acid segment of the regulatory domain of the neuronal type-I inositol 1,4,5-trisphosphate receptor (IP(3)R) isoform (type-I long, amino acids1314-1905) and the corresponding 552-amino acid alternatively spliced form present in peripheral tissues (type-I short, amino acids 1693-1733 deleted) were expressed as glutathione S-transferase fusion proteins. These domains encompass a putative calmodulin (CaM) binding domain and two protein kinase A phosphorylation sites. Both long and short fusion proteins retained the ability to bind CaM in a Ca(2+)-dependent manner as measured by CaM-Sepharose chromatography or a dansyl-CaM fluorescence assay. Both assays indicated that the short fusion protein bound twice the amount of CaM than the long form at saturating concentrations of CaM. In addition, the binding of the short form to CaM-Sepharose was inhibited by phosphorylation with protein kinase A, whereas the binding of the long form was unaffected. Full-length cDNAs encoding type-I long, type-I short, and type-III IP(3)R isoforms were expressed in COS cells, and the Ca(2+) sensitivity of [(3)H]IP(3) binding to permeabilized cells was measured. The type-I long isoform was more sensitive to Ca(2+) inhibition (IC(50) = 0.55 microM) than the type-I short (IC(50) = 5.7 microM) or the type-III isoform (IC(50) = 3 microM). In agreement with studies on the fusion proteins, the full-length type-I short bound more CaM-Sepharose, and this binding was inhibited to a greater extent by protein kinase A phosphorylation than the type-I long IP(3)R. Although type-III IP(3)Rs did not bind directly to CaM-Sepharose, hetero-oligomers of type-I/III IP(3)Rs retained the ability to interact with CaM. We conclude that the deletion of the SII splice site in the type-I IP(3)R results in the differential regulation of the alternatively spliced isoforms by Ca(2+), CaM, and protein kinase A.
...
PMID:The interaction of calmodulin with alternatively spliced isoforms of the type-I inositol trisphosphate receptor. 1064 79

Aggregation of the high affinity IgE receptors (FcepsilonRI) on basophils and mast cells, members of the immune receptor family, initiates a cascade of events that results in the release of inflammatory mediators. This pathway involves the activation of several protein-tyrosine kinases, including Lyn, Syk, Btk, and Fak that induce the tyrosine phosphorylation of various proteins. The linker for activation of T cells (LAT), was originally found as a ZAP-70 tyrosine kinase substrate that linked T cell receptors to cellular activation, and was expressed in T cells, NK cells and mast cells. Here we show that LAT expressed in the RBL-2H3 rat mast cell line is tyrosine-phosphorylated after aggregation of FcepsilonRI. The tyrosine phosphorylation of the LAT was dramatically enhanced after receptor aggregation. Furthermore, a tyrosine-phosphorylated 80-kDa protein associated with LAT transiently after receptor aggregation. GST fusion proteins containing parts of PLCgamma or PI3 kinase can bind LAT. These results suggest that LAT plays an important role not only in T cell, but also in mast cell activation, and that the association among these signaling molecules is critical for FcepsilonRI-mediated intracellular signal transduction in mast cells.
...
PMID:Tyrosine phosphorylation of the linker for activator of T cells in mast cells by stimulation with the high affinity IgE receptor. 1113 36

The Crk adapter proteins are assumed to play a role in T lymphocyte activation because of their induced association with tyrosine-phosphorylated proteins, such as ZAP-70 and Cbl, and with the phosphatidylinositol 3kinase regulatory subunit, p85, following engagement of the T cell antigen receptor. Although the exact mechanism of interaction between these molecules has not been fully defined, it has been generally accepted that Crk, ZAP-70, and p85 interact with tyrosine-phosphorylated Cbl, which serves as a major scaffold protein in activated T lymphocytes. Our present results demonstrate a cell activation-dependent reciprocal co-immunoprecipitation of CrkII and p85 from lysates of Jurkat T cells and a direct binding of CrkII to p85 in an overlay assay. The use of bead-immobilized GST fusion proteins indicated a complex mechanism of interaction between CrkII and p85 involving two distinct and mutually independent regions in each molecule. A relatively high affinity binding of the CrkII-SH3(N) domain to p85 and the p85-proline-B cell receptor-proline (PBP) region to CrkII was observed in lysates of either resting or activated T cells. Direct physical interaction between the CrkII-SH3(N) and the p85-PBP domain was demonstrated using recombinant fusion proteins and was further substantiated by binding competition studies. In addition, immobilized fusion proteins possessing the CrkII-SH2 and p85-SH3 domains were found to pull down p85 and CrkII, respectively, but only from lysates of activated T cells. Nevertheless, the GST-CrkII-SH2 fusion protein was unable to mediate direct association with p85 from lysates of either resting or activated T cells. Our results support a model in which T cell activation dependent conformational changes in CrkII and/or p85 promote an initial direct or indirect low affinity interaction between the two molecules, which is then stabilized by a secondary high affinity interaction mediated by direct binding of the CrkII-SH3(N) to the p85-PBP domain.
...
PMID:T cell activation induces direct binding of the Crk adapter protein to the regulatory subunit of phosphatidylinositol 3-kinase (p85) via a complex mechanism involving the Cbl protein. 1141 12


1 2 Next >>

---