The Rela(p65) subunit of NF-kappaB is essential for inhibiting double-stranded RNA-induced cytotoxicity.
Double-stranded RNA (dsRNA) molecules generated during virus infection can initiate a host antiviral response to limit further infection. Such a response involves induction of antiviral gene expression by the dsRNA-activated protein kinase (PKR) and the NF-kappaB transcription factor. In addition, dsRNA can also induce apoptosis by an incompletely understood mechanism that may serve to further limit viral replication. Here we demonstrate a novel role for the RelA subunit of NF-kappaB in inhibiting dsRNA-induced cell death. dsRNA treatment resulted in caspase 3 activation and apoptotic morphological transformations in mouse embryonic fibroblasts (MEFs) derived from RelA-/- mice but not from RelA+/+ mice. Such dsRNA-induced killing could be inhibited by expression of either a dominant-negative mutant of PKR or wild-type RelA. Interestingly, caspase 3 activated following dsRNA treatment of RelA-/- MEFs was essential for apoptotic nuclear changes but dispensable for cytotoxicity. A broader specificity caspase inhibitor was also unable to inhibit dsRNA-induced cytotoxicity, suggesting that caspase activation is not essential for the induction of cell death by dsRNA in MEFs. However, combined inhibition of caspase 3 and reactive oxygen species production resulted in complete inhibition of dsRNA-induced cytotoxicity. These results demonstrate an essential role for NF-kappaB in protecting cells from dsRNA-induced apoptosis and suggest that NF-kappaB may inhibit both caspase-dependent and reactive oxygen species-dependent cytotoxic pathways.
Li
M
M
Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
Shillinglaw
W
W
Henzel
W J
WJ
Beg
A A
AA
D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003609:Dactinomycin / Q000494:pharmacology; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D008099:Liver / Q000196:embryology; D008264:Macrophages / Q000166:cytology / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000737:chemistry* / Q000378:metabolism*; D021122:Protein Subunits; D012330:RNA, Double-Stranded / Q000502:physiology* / Q000633:toxicity*; D017382:Reactive Oxygen Species / Q000502:physiology; D051996:Transcription Factor RelA; D019892:eIF-2 Kinase / Q000378:metabolism*
D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; D016328:NF-kappa B; D021122:Protein Subunits; D012330:RNA, Double-Stranded; D017382:Reactive Oxygen Species; D051996:Transcription Factor RelA; D003609:Dactinomycin; D019892:eIF-2 Kinase; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases