title: c-FLIP protects mature T lymphocytes from TCR-mediated killing.
abstract: Although c-FLIP has been identified as an important player in the extrinsic (death receptor-induced) apoptosis pathway, its endogenous function in mature T lymphocytes remains undefined. c-FLIP may inhibit or promote T cell death as previous data demonstrate that the c-FLIP(L) isoform can promote or inhibit caspase 8 activation while the c-FLIP(S) isoform promotes or inhibits T cell death when overexpressed. Although the c-FLIP(R) isoform inhibits cell death in cell lines, its function in T cells remains unknown. To investigate the function of c-FLIP in mature T cells, we have generated several genetic mouse models with c-FLIP or its individual isoforms deleted in mature T cells. Surprisingly, we found that c-FLIP protects mature T cells not only from apoptosis induced by the death receptors Fas and TNFR but also from TCR-mediated and spontaneous apoptosis. Thus, c-FLIP plays an essential role in protecting mature T cells from a death signal induced through the TCR itself and is required for naive T cell survival. Our results demonstrate that c-FLIP functions beyond the extrinsic death pathway.
authors.affiliation: Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Nu
authors.initials: N
authors.lastname: Zhang
authors.forename: Kaycie
authors.initials: K
authors.lastname: Hopkins
authors.forename: You-Wen
authors.initials: YW
authors.lastname: He
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000276:immunology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000235:genetics / Q000276:immunology*; D053181:Caspase 8 / Q000235:genetics / Q000276:immunology; D051379:Mice; D008822:Mice, Transgenic; D018448:Models, Immunological; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D019014:fas Receptor / Q000235:genetics / Q000276:immunology
chemical_list: D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506387:Cflar protein, mouse; C491899:Fas protein, mouse; D020033:Protein Isoforms; D011948:Receptors, Antigen, T-Cell; D019014:fas Receptor; C505526:Casp8 protein, mouse; D053181:Caspase 8