1. Rituxan (anti-CD20 antibody)-induced translocation of CD20 into lipid rafts is crucial for calcium influx and apoptosis.
- Author
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Janas E, Priest R, Wilde JI, White JH, and Malhotra R
- Subjects
- Antibodies, Monoclonal, Murine-Derived, Antigen-Antibody Reactions, Apoptosis, Biological Transport, Cell Line, Cell Membrane metabolism, Cholesterol metabolism, Humans, Octoxynol, Rituximab, Signal Transduction, Antibodies, Monoclonal pharmacology, Antigens, CD20 immunology, Antineoplastic Agents pharmacology, B-Lymphocytes immunology, Calcium metabolism, Lipids immunology
- Abstract
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.
- Published
- 2005
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