Cytokine induction of Fas gene expression in insulin-producing cells requires the transcription factors NF-kappaB and C/EBP.
Fas-mediated cell death may play a role in the autoimmune destruction of pancreatic beta-cells in type 1 diabetes. beta-Cells do not express Fas under physiological conditions, but Fas mRNA and protein are induced in cytokine-exposed mouse and human islets, rendering the beta-cells susceptible to Fas ligand-induced apoptosis. The aim of the present study was to investigate the molecular regulation of Fas by cytokines in rat beta-cells and in insulin-producing RINm5F cells. Fas mRNA expression was increased 15-fold in fluorescence-activated cell sorting-purified rat beta-cells exposed to interleukin (IL)-1beta, whereas gamma-interferon had no effect. Transfection experiments of rat Fas promoter-luciferase reporter constructs into purified rat beta-cells and RINm5F insulinoma cells identified an IL-1beta-responsive region between nucleotides -223 and -54. Inactivation of two adjacent NF-kappaB and C/EBP sites in this region abolished IL-1beta-induced Fas promoter activity in RINm5F cells. Binding of NF-kappaB and C/EBP factors to their respective sites was confirmed by gel shift assays. In cotransfection experiments, NF-kappaB p65 transactivated the Fas promoter. NF-kappaB p50 and C/EBPbeta overexpression had no effect by themselves on the Fas promoter activity, but when cotransfected with p65, each factor inhibited transactivation by p65. These results suggest a critical role for NF-kappaB and C/EBP factors in cytokine-regulation of Fas expression in insulin-producing cells.
Darville
M I
MI
Gene Expression Unit, Diabetes Research Center, Vrije Universiteit Brussel, Brussels, Belgium. mdarv@mebo.vub.ac.be
Eizirik
D L
DL
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000378:metabolism*; D016207:Cytokines / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D007328:Insulin / Q000096:biosynthesis*; D007340:Insulinoma; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology*; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D010190:Pancreatic Neoplasms; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis / Q000187:drug effects / Q000276:immunology; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000276:immunology; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000276:immunology*
D022782:CCAAT-Enhancer-Binding Protein-beta; D016207:Cytokines; D007328:Insulin; D007375:Interleukin-1; D016328:NF-kappa B; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014157:Transcription Factors; D019014:fas Receptor; D007371:Interferon-gamma; D015056:1-Methyl-3-isobutylxanthine