Fas aggregation does not correlate with Fas-mediated apoptosis.
Cross-linking of cell surface Fas molecules by Fas ligand or by agonistic anti-Fas Abs induces cell death by apoptosis. We found that a serine protease inhibitor, N-tosyl-L-lysine chloromethyl ketone (TLCK), dramatically enhances Fas-mediated apoptosis in the human T cell line Jurkat and in various B cell lines resistant to Fas-mediated apoptosis. The enhancing effect of TLCK is specific to Fas-induced cell death, with no effect seen on TNF-alpha or TNF-related apoptosis-inducing ligand-induced apoptosis. TLCK treatment had no effect on Fas expression levels on the cell surface, and neither promoted death-inducing signaling complex formation nor decreased expression levels of cellular inhibitors of apoptosis (FLICE inhibitory protein, X chromosome-linked inhibitor of apoptosis, and Bcl-2). Activation of the Fas-mediated apoptotic pathway by anti-Fas Ab is accompanied by aggregation of Fas molecules to form oligomers that are stable to boiling in SDS and beta-ME. Fas aggregation is often considered to be required for Fas-mediated apoptosis. However, sensitization of cells to Fas-mediated apoptosis by TLCK or other agents (cycloheximide, protein kinase C inhibitors) causes less Fas aggregation during the apoptotic process compared with that in nonsensitized cells. These results show that Fas aggregation and Fas-mediated apoptosis are not directly correlated and may even be inversely correlated.
Lee
Y
Y
Laboratory of Immunology, Division of Therapeutic Proteins, Food and Drug Administration, Center for Biologics and Evaluation and Research, Bethesda, MD 20892, USA. wicknery@ninds.nih.gov
Shacter
E
E
D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D058846:Antibodies, Monoclonal, Murine-Derived; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000096:biosynthesis; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000096:biosynthesis; D002461:Cell Line, Transformed; D003513:Cycloheximide / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000187:drug effects; D009363:Neoplasm Proteins / Q000096:biosynthesis; D014176:Protein Biosynthesis; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D014107:Tosyllysine Chloromethyl Ketone / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D051636:X-Linked Inhibitor of Apoptosis Protein; D019014:fas Receptor / Q000096:biosynthesis / Q000276:immunology* / Q000378:metabolism*
D000276:Adjuvants, Immunologic; D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; D061945:Caspase Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D015842:Serine Proteinase Inhibitors; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C411023:anti-Fas monoclonal antibody; D019014:fas Receptor; C030193:immunosuppressive acidic protein; D014107:Tosyllysine Chloromethyl Ketone; D003513:Cycloheximide; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases