title: Distinct requirements for activation-induced cell surface expression of preformed Fas/CD95 ligand and cytolytic granule markers in T cells.
abstract: Fas (CD95/Apo-1) ligand is a potent inducer of apoptosis and one of the major killing effector mechanisms of cytotoxic T cells. Thus, Fas ligand activity has to be tightly regulated, involving various transcriptional and post-transcriptional processes. For example, preformed Fas ligand is stored in secretory lysosomes of activated T cells, and rapidly released by degranulation upon reactivation. In this study, we analyzed the minimal requirements for activation-induced degranulation of Fas ligand. T cell receptor activation can be mimicked by calcium ionophore and phorbol ester. Unexpectedly, we found that stimulation with phorbol ester alone is sufficient to trigger Fas ligand release, whereas calcium ionophore is neither sufficient nor necessary. The relevance of this process was confirmed in primary CD4(+) and CD8(+) T cells and NK cells. Although the activation of protein kinase(s) was absolutely required for Fas ligand degranulation, protein kinase C or A were not involved. Previous reports have shown that preformed Fas ligand co-localizes with other markers of cytolytic granules. We found, however, that the activation-induced degranulation of Fas ligand has distinct requirements and involves different mechanisms than those of the granule markers CD63 and CD107a/Lamp-1. We conclude that activation-induced degranulation of Fas ligand in cytotoxic lymphocytes is differently regulated than other classical cytotoxic granule proteins.
authors.affiliation: Division of Immunopathology, Institute of Pathology, University of Bern, Bern, Switzerland.
authors.forename: D
authors.initials: D
authors.lastname: Kassahn
authors.forename: U
authors.initials: U
authors.lastname: Nachbur
authors.forename: S
authors.initials: S
authors.lastname: Conus
authors.forename: O
authors.initials: O
authors.lastname: Micheau
authors.forename: P
authors.initials: P
authors.lastname: Schneider
authors.forename: H-U
authors.initials: HU
authors.lastname: Simon
authors.forename: T
authors.initials: T
authors.lastname: Brunner
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis*; D017209:Apoptosis / Q000502:physiology; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism*; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism*; D015550:Cell Degranulation / Q000187:drug effects / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D053222:Fas Ligand Protein / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D019169:Jurkat Cells; D007694:Killer Cells, Natural / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects / Q000502:physiology; D051907:Lysosomal Membrane Proteins / Q000096:biosynthesis*; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D051379:Mice; D010703:Phorbol Esters / Q000494:pharmacology; D010980:Platelet Membrane Glycoproteins; D011494:Protein Kinases / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism*; D060149:Tetraspanin 30; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D015703:Antigens, CD; D053222:Fas Ligand Protein; D007476:Ionophores; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D010703:Phorbol Esters; D010980:Platelet Membrane Glycoproteins; D011494:Protein Kinases; D060149:Tetraspanin 30; C554586:CD63 protein, human; C554587:Cd63 protein, mouse; C489116:LAMP1 protein, human; D052118:Lysosomal-Associated Membrane Protein 1; C052255:Lamp1 protein, mouse