title: Cyclosporine-insensitive partial signaling and multiple roles of Ca2+ in Fas ligand-induced lysis.
abstract: The induction of Fas ligand (FasL) mRNA expression and FasL-mediated cytotoxicity in CD8+ CTL is a rapid and transient response to activation via the TCR. This response can also be initiated by pharmacologic activation of two major TCR signaling pathways using phorbol ester (PMA) and calcium ionophore (ionomycin). In these experiments using CD8+ alloreactive cell lines, we demonstrate that induction of FasL mRNA can occur in response to either PMA or ionomycin independently. However, only the ionomycin pathway is sensitive to inhibition by cyclosporine A. Both pathways are blocked by genistein, a general protein tyrosine kinase inhibitor. The magnitude of induction of FasL mRNA is not proportional to the manifested FasL-dependent cytotoxicity. We also found a calcium requirement for cytotoxicity that is unrelated to FasL mRNA induction. In addition to the positive effects of constitutive and induced calcium levels on FasL-mediated cytotoxicity, calcium may play a role in the rapid down-regulation of the response. We also present data suggesting that CD2 and LFA-1 contribute to FasL-mediated cytotoxicity. Together these results suggest pathways by which partial TCR activation could, among the many activation-induced functions of a T cell, selectively lead to the induction of FasL-mediated cytotoxicity that can be regulated by lineage/ activation-dependent accessory molecules on the target.
authors.affiliation: Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Rogers
authors.forename: A R
authors.initials: AR
authors.lastname: Thilenius
authors.forename: J H
authors.initials: JH
authors.lastname: Russell
mesh_terms: D000818:Animals; D018801:CD2 Antigens / Q000378:metabolism; D002118:Calcium / Q000502:physiology*; D002460:Cell Line; D016572:Cyclosporine / Q000494:pharmacology*; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D053222:Fas Ligand Protein; D007166:Immunosuppressive Agents / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D008024:Ligands; D008213:Lymphocyte Activation / Q000187:drug effects; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000276:immunology / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D019463:Mice, Inbred MRL lpr; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000276:immunology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology; D019014:fas Receptor / Q000378:metabolism / Q000502:physiology*
chemical_list: D018801:CD2 Antigens; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D007166:Immunosuppressive Agents; D008024:Ligands; D016169:Lymphocyte Function-Associated Antigen-1; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D019014:fas Receptor; D015759:Ionomycin; D016572:Cyclosporine; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium