Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Aggregation of the high affinity IgE receptors (Fc epsilon RI) on rat basophilic leukemia RBL-2H3 cells results in protein tyrosine phosphorylations. Previously we reported that there is prominent tyrosine phosphorylation of approximately 72-kDa proteins (pp72) and that the tyrosine kinase p72syk is one component of pp72. Here we studied further the relationship of p72syk to pp72. The aggregation of Fc epsilon RI induced the activation of p72syk which was parallel to its tyrosine phosphorylation. By in vitro kinase assay of immune complexes purified with anti-phosphotyrosine antibodies, p72syk was the major pp72 tyrosine kinase. However, by immunoblotting with anti-phosphotyrosine antibodies, p72syk was a minor component of pp72. The heterogeneous nature of pp72 was indicated by different studies. Under optimum conditions of one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis, pp72 consisted of a heterogeneous group of 69-, 71-, and 72-kDa tyrosine-phosphorylated proteins. There were differences in the tyrosine phosphorylation of these proteins in cells activated in the absence of extracellular calcium or when stimulation was with the calcium ionophore A23187 or with phorbol myristate acetate. One of the proteins migrating at 69 kDa was p72syk. By two-dimensional gel electrophoresis pp72 was found to consist of multiple tyrosine-phosphorylated protens including 71-80-kDa proteins that associate with p53/56lyn. A 75-kDa tyrosine-phosphorylated protein, different from pp72, was identified as p75HS1 (SPY75). These results demonstrate the heterogeneous nature of the pp72 and that p72syk is activated after Fc epsilon RI aggregation.
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PMID:Activation of protein tyrosine kinase p72syk by Fc epsilon RI aggregation in rat basophilic leukemia cells. p72syk is a minor component but the major protein tyrosine kinase of pp72. 751 87

Aggregation of the receptor with high affinity for IgE (Fc epsilon RI) on the surface of mast cells and basophils stimulates phosphorylation of protein tyrosines, a process in which p53/56lyn kinase has been implicated. We measured the association between Fc epsilon RI and the kinase, using chemical crosslinking to stabilize their interaction. In the rat basophilic leukemia mast cell line, 3-4%, and at most 20%, of Fc epsilon RI appear to be associated with the kinase prior to aggregation, even though there is an excess of total cell lyn kinase. Aggregating the Fc epsilon RI causes three to four times more of the kinase to associate with receptors, a process requiring a prior phosphorylation step. In an in vitro assay, the lyn associated with the aggregated receptors becomes disproportionately more phosphorylated than would be predicted from the amount of lyn associated with the receptors. These and other data are consistent with a model in which aggregation of the receptor leads to its transphosphorylation by constitutively associated lyn kinase. We propose that additional molecules of this kinase are thereby recruited and that this markedly enhances transphosphorylation of tyrosine on the receptor and associated proteins, thereby initiating a cascade of further biochemical changes. This model is also consistent with data on receptors such as the clonotypic receptors on B and T lymphocytes, which share structural and functional features with Fc epsilon RI.
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PMID:Aggregation of the high-affinity IgE receptor and enhanced activity of p53/56lyn protein-tyrosine kinase. 752 94

Aggregation of the high-affinity receptors for IgE (Fc epsilon RI) on mast cells activates nonreceptor kinases and other enzymes, thereby initiating a complex biochemical cascade. We have employed a chemical cross-linker in order to stabilize the association of Fc epsilon RI with other cellular proteins that are involved in the early events. We reacted the water-soluble, membrane-impermeant chemical cross-linker 3,3'-dithiobis(sulfosuccinimidyl propionate) (DTSSP) with permeabilized rat mucosal mast cells of the RBL line and analyzed immunoprecipitates of the receptor in detergent lysates of cells that had biosynthetically incorporated [35S]cysteine. Gel electrophoresis revealed substantial amounts of nonreceptor components only when the cells had been reacted with DTSSP. Receptors isolated from cells whose receptor-bound IgE had been aggregated with antigen prior to cross-linking yielded a similar pattern of 35S-labeled proteins. However, when the cells had also been exposed to [gamma-32P]ATP, the proteins associated with the cross-linked, aggregated receptors revealed enhanced incorporation of 32P compared to those associated with cross-linked, unaggregated receptors. A variety of antibodies were used to try to identify the associated proteins. Of those tested for, two, the src-like kinase p53/56lyn and the delta isoform of protein kinase C, were associated with the cross-linked Fc epsilon RI in amounts much greater than could be accounted for by nonspecific cross-linking.
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PMID:Chemical cross-linking of IgE-receptor complexes in RBL-2H3 cells. 753 96

Detergent-resistant plasma membrane structures, such as caveolae, have been implicated in signalling, transport, and vesicle trafficking functions. Using sucrose gradient ultracentrifugation, we have isolated low-density, Triton X-100-insoluble membrane domains from RBL-2H3 mucosal mast cells that contain several markers common to caveolae, including a src-family tyrosine kinase, p53/56lyn. Aggregation of Fc epsilon RI, the high-affinity IgE receptor, causes a significant increase in the amount of p53/56lyn associated with these low-density membrane domains. Under our standard conditions for lysis, IgE-Fc epsilon RI fractionates with the majority of the solubilized proteins, whereas aggregated receptor complexes are found at a higher density in the gradient. Stimulated translocation of p53/56lyn is accompanied by increased tyrosine phosphorylation of several proteins in the low-density membrane domains as well as enhanced in vitro tyrosine kinase activity toward these proteins and an exogenous substrate. With a lower detergent-to-cell ratio during lysis, significant Fc epsilon RI remains associated with these membrane domains, consistent with the ability to coimmunoprecipitate tyrosine kinase activity with Fc epsilon RI under similar lysis conditions [Pribluda, V. S., Pribluda, C. & Metzger, H. (1994) Proc. Natl. Acad. Sci. USA 91, 11246-11250]. These results indicate that specialized membrane domains may be directly involved in the coupling of receptor aggregation to the activation of signaling events.
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PMID:Fc epsilon RI-mediated recruitment of p53/56lyn to detergent-resistant membrane domains accompanies cellular signaling. 756 1

We have investigated the isotypic and IgG subclass profile of the antibody response to HTLV-I structural proteins (gag and env) in patients with HTLV-I-associated myelopathy (HAM; n = 20), adult T-cell leukemia (ATL; n = 15), and HTLV-I-positive asymptomatic carriers (ASY; n = 21). IgG, IgM, and IgA were the predominant antibody responses in all HTLV-I-infected individuals; minimal IgE response was detectable in the HAM and ATL groups. Among the IgG subclasses, IgG1 was the most predominant antibody detected in responses to HTLV-I antigens, followed by IgG3 and IgG2; IgG4 could not be detected in any patient group. Levels of both IgG1 and IgG3 were significantly higher in patients with HAM, when compared to ATL and ASY (P < 0.01 for both comparisons). In addition, Ig isotypes and IgG subclass antibody in patient sera reactive with purified viral proteins and several immunodominant epitopes, represented by synthetic peptides, Gag-1a102-117, Env-1(191-214), Env-5(242-257), and recombinant proteins, MTA-1(162-209) and r21e303-440, were examined to delineate specific epitopes responsible for inducing the host immune responses of each isotype and subclass to the structural proteins of HTLV-I. IgG, IgM, and IgA responses were directed against both the gag and env gene products. Among IgG subclasses, the IgG1 and IgG3 responses were directed against both the gag (p53, p24, p19, and Gag-1a) and env (recombinant MTA-1, r21e, and synthetic Env-1, Env-5) proteins; IgG2 responses were mainly restricted to gag proteins. The frequency profile of HTLV-I-specific antigen recognition in all four IgG subclasses were similar in all of the clinical groups. These results further define the fine specificity of anti-HTLV-I immune reaction for understanding the mechanism of pathogenesis in these individuals and suggest that factors other than the humoral immune responses may be associated with the clinical manifestation of the disease.
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PMID:Isotypic and IgG subclass restriction of the humoral immune responses to human T-lymphotropic virus type-I. 768 Mar

Thy-1 is a surface glycoprotein that is attached to the plasma membrane by a glycosyl-phosphatidyl-inositol anchor. Crosslinking of Thy-1 in rat mast cells and basophilic leukemia cells (RBL-2H3) induces cell activation including histamine release and tyrosine phosphorylation of several proteins. Here we show that glycosyl-phosphatidylinositol-linked Thy-1 forms noncovalent complexes with src-related protein-tyrosine kinase p53/p56lyn and other protein-tyrosine kinases and/or their substrates. These complexes are resistant to solubilization by a nonionic detergent, sedimentable at 200,000 x g, and very large ( > 10 MDa) as determined by gel chromatography. Activation of RBL-2H3 cells by crosslinking of the high-affinity IgE receptors resulted in decreased recovery of the complexes. The combined data indicate the existence of large detergent-resistant domains in the surface membrane of mast cells that may play an important role in their activation.
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PMID:Thy-1 glycoprotein and src-like protein-tyrosine kinase p53/p56lyn are associated in large detergent-resistant complexes in rat basophilic leukemia cells. 768 13

The monoclonal antibody AA4 (mAb AA4) recognizes novel alpha-galactosyl derivatives of GD1b on rat basophilic leukemia (RBL-2H3) cells. The binding of mAb AA4 induced protein tyrosine phosphorylations without histamine release. Several of the same proteins including Fc epsilon RI beta, Fc epsilon RI gamma, p72syk, and phospholipase C-gamma 1 were tyrosine-phosphorylated by mAb AA4 binding and by the activation of the high affinity IgE receptor, Fc epsilon RI. There was also activation of the p53/56lyn and p72syk protein-tyrosine kinases, but compared to direct Fc epsilon RI activation, mAb AA4 did not result in increased tyrosine phosphorylation of pp105-115 or pp125FAK, and the receptor subunits (Fc epsilon RI beta and Fc epsilon RI gamma) were more heavily phosphorylated. Furthermore, the time course of the phosphorylations with mAb AA4 was slower than that induced by Fc epsilon RI aggregation. By immunofluorescence, the tyrosine-phosphorylated proteins after mAb AA4 stimulation were localized in patches at the cell membrane and in areas of cell-cell contact, whereas after Fc epsilon RI activation, there was a reticular cytoplasmic pattern. There were no protein tyrosine phosphorylations either when Fc epsilon RI was saturated with IgE or when F(ab')2 fragments of mAb AA4 were used, although the F(ab')2 fragments still induced morphological changes. There was also coprecipitation of the beta and gamma subunits of Fc epsilon RI with the anti-ganglioside antibody. These data strongly suggest the involvement of Fc epsilon RI in the antiganglioside-induced protein tyrosine phosphorylations. Moreover, phosphorylations of these proteins including the beta and gamma chains of Fc epsilon RI and activation of p53/56lyn and p72syk did not result in histamine release.
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PMID:The anti-ganglioside monoclonal antibody AA4 induces protein tyrosine phosphorylations, but not degranulation, in rat basophilic leukemia cells. 803 15

The monoclonal antibody (mAb) AA4 recognizes two alpha-galactosyl derivatives of the GD1b ganglioside on rat mast cells and on the rat basophilic leukemia RBL-2H3 cultured cell line. Here we demonstrate that mAb AA4 coprecipitated both protein tyrosine and serine kinases. In contrast, a monoclonal antibody to the GD3 ganglioside did not coprecipitate any kinase activity. In kinase assays of mAb AA4 immunoprecipitates there were phosphorylated proteins of 71-80, 53/56, and 41/42 kDa. All proteins were phosphorylated on tyrosine, whereas the 71-80- and 41/42-kDa proteins were also phosphorylated on serine residues. The precipitation of these proteins by mAb AA4 correlated with the presence of the alpha-galactosyl derivatives of GD1b. The 53/56-kDa proteins were identified as the Src-related tyrosine kinase p53/56lyn. The presence of p53/56lyn in the mAb AA4 immunoprecipitates was specific and was observed when several different detergents were used. The same 71-80-kDa tyrosine-phosphorylated proteins were immunoprecipitated by mAb AA4 and anti-Lyn antibodies and may play a role in the interaction of p53/56lyn with the gangliosides. Although there is a weak association of the high affinity IgE receptor with these gangliosides, the coprecipitation of p53/56lyn with mAb AA4 was not secondary to the association of this kinase with receptor. These complexes of gangliosides and several proteins that include p53/56lyn, a serine kinase, and the high affinity IgE receptor could play an important role in receptor-mediated signal transduction.
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PMID:Src family tyrosine kinase p53/56lyn, a serine kinase and Fc epsilon RI associate with alpha-galactosyl derivatives of ganglioside GD1b in rat basophilic leukemia RBL-2H3 cells. 810 8

Aggregation of the high affinity IgE receptors on rat basophilic leukemia (RBL-2H3) cells results in protein tyrosine phosphorylation although the receptor has no intrinsic enzymatic activity. The Src related protein tyrosine kinase p53/56lyn present in RBL-2H3 cells could play a role in this reaction. Here we have isolated the cDNA for rat Lyn and found it to be very homologous at the amino acid level to both the human and mouse proteins. A bacterially expressed maltose binding protein-Lyn (MBP-Lyn) fusion protein was already tyrosine phosphorylated and had tyrosine kinase activity. In a filter-binding assay, MBP-Lyn fusion protein (at 0.1 microM) specifically bound to several proteins of RBL-2H3 cells. In lysates of IgE receptor-activated cells, there was increased binding of MBP-Lyn to 65, 72, 78 and 110 kDa tyrosine phosphorylated proteins. The 72, 78 and 110 kDa tyrosine phosphorylated proteins were precipitated by a fusion protein containing the Lyn Src Homology 2 (SH2) domain. The 72 kDa Lyn binding protein was different from p72syk. Furthermore, paxillin, a cytoskeletal protein, was identified as one of the Lyn binding proteins. Thus Fc epsilon RI mediated signal transduction in RBL-2H3 cells may result from the interaction of p53/56lyn with paxillin, pp72, pp110 and other proteins.
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PMID:Src family tyrosine kinase Lyn binds several proteins including paxillin in rat basophilic leukemia cells. 819 Jan 27

Cells of the mucosal mast cell line, RBL-2H3, are normally stimulated to degranulate after aggregation of high affinity receptors for IgE (Fc epsilon RI) by soluble cross-linking ligands. This cellular degranulation process requires sustained elevation of cytoplasmic Ca2+. In this study, we investigated the response of RBL-2H3 cells to 6-micron beads coated with IgE-specific ligands. These ligand-coated beads cause only small, transient Ca2+ responses, even though the same ligands added in soluble form cause larger, more sustained Ca2+ responses. The ligand-coated 6-micron beads also fail to stimulate significant degranulation of RBL-2H3 cells, whereas much larger ligand-coated Sepharose beads stimulate ample degranulation. Confocal fluorescence microscopy shows that the 6-micron beads (but not the Sepharose beads) are phagocytosed by RBL-2H3 cells and that, beginning with the initial stages of bead engulfment, there is exclusion of many plasma membrane components from the 6-micron bead/cell interface, including p53/56lyn and several other markers for detergent-resistant membrane domains, as well as an integrin and unliganded IgE-Fc epsilon RI. The fluorescent lipid probe DiIC16 is a marker for the membrane domains that is excluded from the cell/bead interface, whereas a structural analogue, fast DiI, which differs from DiIC16 by the presence of unsaturated acyl chains, is not substantially excluded from the interface. None of these components are excluded from the interface of RBL-2H3 cells and the large Sepharose beads. Additional confocal microscopy analysis indicates that microfilaments are involved in the exclusion of plasma membrane components from the cell/bead interface. These results suggest that initiation of phagocytosis diverts normal signaling pathways in a cytoskeleton-driven membrane clearance process that alters the physiological response of the cells.
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PMID:Fc epsilon RI-mediated association of 6-micron beads with RBL-2H3 mast cells results in exclusion of signaling proteins from the forming phagosome and abrogation of normal downstream signaling. 883 Jul 72


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