title: Regulation of Fas-mediated immune homeostasis by an activation-induced protein, Cyclon.
abstract: Activation-induced cell death (AICD) plays an essential role in the contraction of activated T cells after eradication of pathogen. Fas (APO-1/CD95) is one of the key cell surface proteins that mediate AICD in CD4(+) and CD8(+) T cells. Despite its prime importance in cell death, regulation of Fas expression in T cells is poorly understood. Here we show that Cyclon, a newly identified cytokine-inducible protein, is induced in T cells on T-cell receptor ligation and important for immune homeostasis. Transgenic expression of Cyclon ameliorated autoimmune phenotype in mice lacking subunits of IL-2R. Transgenic expression of Cyclon markedly enhanced AICD through increased expression of Fas whose expression is essential for Cyclon action. Finally, we demonstrated that activated but not resting CD4(+) T cells with targeted deletion of a Cyclon allele show reduced AICD and expression of Fas, indicating a critical role of Cyclon in Fas expression in activated T cells. We think that our data provide insight into expression regulation of Fas in T cells.
authors.affiliation: Department of Pathology, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY, USA.
authors.forename: Shella
authors.initials: S
authors.lastname: Saint Fleur
authors.forename: Akemi
authors.initials: A
authors.lastname: Hoshino
authors.forename: Kimie
authors.initials: K
authors.lastname: Kondo
authors.forename: Takeshi
authors.initials: T
authors.lastname: Egawa
authors.forename: Hodaka
authors.initials: H
authors.lastname: Fujii
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D016923:Cell Death / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation / Q000235:genetics / Q000276:immunology*; D055785:Gene Knockdown Techniques; D006706:Homeostasis / Q000235:genetics / Q000276:immunology*; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015375:Receptors, Interleukin-2 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D019014:fas Receptor / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*
chemical_list: C491899:Fas protein, mouse; D009687:Nuclear Proteins; D011948:Receptors, Antigen, T-Cell; D015375:Receptors, Interleukin-2; C543748:cyclon protein, mouse; D019014:fas Receptor