Nuclear factor-kappaB regulates beta-cell death: a critical role for A20 in beta-cell protection.
Apoptotic beta-cell death is central to the pathogenesis of type 1 diabetes and may be important in islet graft rejection. Despite this, genetic control of beta-cell apoptosis is only poorly understood. We report that inhibition of gene transcription sensitized beta-cells to tumor necrosis factor (TNF)-alpha-induced apoptosis, indicating the presence of a regulated antiapoptotic response. Using oligonucleotide microarrays and real-time PCR, we identified TNFAIP3/A20 as the most highly regulated antiapoptotic gene expressed in cytokine-stimulated human and mouse islets. Cytokine induction of A20 mRNA in primary islets and insulinoma cells was rapid and observed within 1 h, consistent with A20 being an immediate early response gene in beta-cells. Regulation of A20 was nuclear factor-kappaB (NF-kappaB)-dependent, two NF-kappaB sites within the A20 promoter were found to be necessary and sufficient for A20 expression in beta-cells. Activation of NF-kappaB by TNF receptor-associated factor (TRAF) 2, TRAF6, NF-kappaB-inducing kinase, or protein kinase D, which transduce signals downstream of Toll-like receptors, TNF receptors, and free radicals, respectively, were all potent activators of the A20 promoter. Moreover, A20 expression was induced in transplanted islets in vivo. Finally, A20 expression was sufficient to protect beta-cells from TNF-induced apoptosis. These data demonstrate that A20 is the cardinal antiapoptotic gene in beta-cells. Further, A20 expression is NF-kappaB dependent, thus linking islet proinflammatory gene responses with protection from apoptosis.
Liuwantara
David
D
Arthritis and Inflammation Program, Garvan Institute of Medical Research, Darlinghurst, NSW 2010, Australia.
Elliot
Mark
M
Smith
Mariya W
MW
Yam
Andrew O
AO
Walters
Stacy N
SN
Marino
Eliana
E
McShea
Andy
A
Grey
Shane T
ST
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D003546:Cysteine Endopeptidases; D004268:DNA-Binding Proteins; D020869:Gene Expression Profiling; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology* / Q000187:drug effects; D007375:Interleukin-1; D047908:Intracellular Signaling Peptides and Proteins; D007515:Islets of Langerhans / Q000166:cytology; D051379:Mice; D008807:Mice, Inbred BALB C; D016688:Mice, Inbred NOD; D016328:NF-kappa B / Q000502:physiology*; D009687:Nuclear Proteins; D020411:Oligonucleotide Array Sequence Analysis; D011493:Protein Kinase C / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000502:physiology*; D015398:Signal Transduction; D047992:TNF Receptor-Associated Factor 2 / Q000494:pharmacology; D048029:TNF Receptor-Associated Factor 6 / Q000494:pharmacology; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D000097782:NF-kappaB-Inducing Kinase
D003546:Cysteine Endopeptidases; D004268:DNA-Binding Proteins; D007375:Interleukin-1; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D009687:Nuclear Proteins; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D047992:TNF Receptor-Associated Factor 2; D048029:TNF Receptor-Associated Factor 6; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D000097782:NF-kappaB-Inducing Kinase; C089212:protein kinase D; C076529:TNFAIP3 protein, human; C513261:Tnfaip3 protein, mouse