Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0079731 (B-cell lymphoma)
 16,671 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In human T cells CD45 is reported to associate with both cell surface and intracellular molecules including CD2, CD4/CD8, CD5, p56lck and p59fyn. In this study the association of molecules with CD45 in murine T lymphocytes was explored using biotinylation, chemical cross-linking, immunoprecipitation and 32P-labelling. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of CD45 monoclonal antibody (mAb) (S-450-15.2) immunoprecipitates from Triton X-100 lysates of murine thymocytes that were surface biotinylated and treated with the chemical cross-linker 3,3'-dithio-bis(sulpho-succinimidylpropionate) (DTSSP) showed that CD45 can be chemically linked to molecules of 25,000-32,000, 42,000 and 60,000-70,000 MW. The CD45 mAb also co-precipitated a prominent 32,000 MW molecule from digitonin lysates of surface biotinylated murine thymocytes, splenocytes and D10 cells, but a weaker association was also detected on splenic B cells and on the murine B-cell lymphoma line A20. The results suggest that in these cells CD45 is associated with a 32,000 MW molecule which is exposed extracellularly. Experiments in which thymocytes were biotinylated after permeabilization with lysolecithin showed that additional molecules of 33,000, 55,000, 60,000 and 90,000 MW, presumably localized intracellularly, also co-precipitated with CD45. Labelling of murine thymocytes or D10 cells with H3(32)PO4 in vivo, and of CD45 immunoprecipitates by in vitro kinase reaction, revealed that the 32,000-33,000 MW molecules are phosphoproteins. The relationship of these molecules with the 30,000-34,000 MW molecules previously reported to associate with CD45 in human T cells is not clear as a number of differences were observed. Firstly, the molecular weight of the CD45-associated 32,000-33,000 MW molecule(s) on murine T cells and B cells is slightly lower than that observed in the human T-cell line Jurkat (34,000 MW). Secondly, phosphoamino acid analysis after in vitro kinase labelling of CD45 immunoprecipitates showed that the murine 32,000-33,000 MW molecules are phosphorylated exclusively on serines. Thirdly, although in vitro phosphorylation of the 32,000-33,000 MW molecules was inhibited by preincubation with either GTP-gamma-S or GDP-beta-S, the 32,000-33,000 MW CD45-associated molecules did not bind 32P-GTP, GDP-agarose, or react with antisera to a consensus sequence of G proteins. The crucial role of CD45 for proper function of the T-cell receptor (TCR), suggests that the CD45-associated 32,000-33,000 MW molecules and kinases also may play a role in the signalling events leading to T-cell activation.
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PMID:Evidence for an association of CD45 with 32,000-33,000 MW phosphoproteins on murine T and B lymphocytes. 783 67

Rituxan, a chimeric anti-CD20 antibody, is the first antibody approved for immunotherapy in non-Hodgkin's B-cell lymphoma and other B-cell lymphoproliferative disorders. Additionally, efficacy of Rituxan treatment has been reported in nonmalignant autoimmune diseases such as rheumatoid arthritis. Crosslinking of CD20 molecules by Rituxan induces therapeutic B-cell depletion. CD20 is a B-lymphocyte specific integral membrane protein, proposed to function as a store-operated calcium channel, which is activated upon receptor-stimulated calcium depletion of intracellular stores. Crosslinking of CD20 by antibodies has been reported to induce a redistribution of CD20 molecules to specialized microdomains at the plasma membrane known as lipid rafts. Here, we report that in the absence of Rituxan, CD20 exhibits a low affinity to lipid rafts. However, binding of Rituxan significantly increases the affinity of CD20 for lipid rafts resulting in its redistribution to a fraction resistant to Triton X-100 solubilization. Furthermore, we demonstrate that disturbing the raft integrity by cholesterol extraction results in dissociation of CD20 from a Triton X-100 resistant fraction followed by complete inhibition of Rituxan-induced calcium entry and apoptosis. The integrity of lipid rafts seems to play a crucial role for CD20-induced caspase activation. These data show, for the first time, that Rituxan-induced translocation of CD20 to lipid rafts is important for increased intracellular Ca(2+) levels and downstream apoptotic signalling.
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PMID:Rituxan (anti-CD20 antibody)-induced translocation of CD20 into lipid rafts is crucial for calcium influx and apoptosis. 1573 Mar 89