Regulation of CD95 (Fas) ligand expression by TCR-mediated signaling events.
Stimulation of mature peripheral T cells by TCR engagement results in activation of signals that drive induction of cytokine gene expression and clonal expansion. However, under some conditions, engagement of the TCR leads instead to apoptosis. Recent studies demonstrate that TCR-stimulated apoptosis requires expression of CD95 ligand on activated T cells followed by an interaction between CD95 ligand and the CD95 receptor also expressed on this population. The experiments reported in this study were designed to address the signaling events triggered by TCR engagement that are important for regulating CD95 ligand gene expression. To approach this, we generated a luciferase reporter construct containing elements of the CD95 ligand promoter. Using a previously described mutant of the Jurkat T cell line, we show that proximal signaling events dependent on the presence of the CD45 tyrosine phosphatase are required for TCR-stimulated CD95 ligand expression. Transient transfection studies demonstrate further that TCR-stimulated activation of the Ras signaling pathway is required for optimal activation of CD95 ligand. Next, in an effort to determine critical transcription factors that regulate CD95 ligand expression, we demonstrate a cyclosporin A-sensitive nuclear factor-AT response element in the promoter region of this gene that is critical for optimal CD95 ligand reporter activity in stimulated T cells. Together, these studies begin a dissection of the biochemical events that lead to expression of CD95 ligand, a required step for TCR-induced apoptosis.
Latinis
K M
KM
Interdisciplinary Graduate Program in Immunology, University of Iowa, Iowa City 52242, USA.
Carr
L L
LL
Peterson
E J
EJ
Norian
L A
LA
Eliason
S L
SL
Koretzky
G A
GA
D004268:DNA-Binding Proteins / Q000502:physiology; D053222:Fas Ligand Protein; D005786:Gene Expression Regulation; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D017493:Leukocyte Common Antigens / Q000502:physiology; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000235:genetics*; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000502:physiology; D011994:Recombinant Proteins; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D007476:Ionophores; D008562:Membrane Glycoproteins; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D015759:Ionomycin; D011505:Protein-Tyrosine Kinases; D017493:Leukocyte Common Antigens; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D013755:Tetradecanoylphorbol Acetate