N-terminal fragment of c-FLIP(L) processed by caspase 8 specifically interacts with TRAF2 and induces activation of the NF-kappaB signaling pathway.
Caspase 8 is required not only for death receptor-mediated apoptosis but also for lymphocyte activation in the immune system. FLIP(L), the long-splice form of c-FLIP, is one of the specific substrates for caspase 8, and increased expression of FLIP(L) promotes activation of the NF-kappaB signaling pathway. The synthetic caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (zVAD-fmk) markedly blocked NF-kappaB activation induced by overexpression of FLIP(L). FLIP(L) is specifically processed by caspase 8 into N-terminal FLIP(p43) and C-terminal FLIP(p12). Only FLIP(p43) was able to induce NF-kappaB activation as efficiently as FLIP(L), and FLIP(p43)-induced NF-kappaB activation became insensitive to zVAD-fmk. In caspase 8-deficient cells, FLIP(p43) provoked NF-kappaB activation only when procaspase 8 or caspase 8(p43) was complemented. FLIP(p43)-induced NF-kappaB activation was profoundly blocked by the dominant-negative TRAF2. Moreover, endogenous TRAF2 interacted specifically with FLIP(p43), and the formation of the FLIP(p43)-caspase 8-TRAF2 tertiary complex was a prerequisite to induction of NF-kappaB activation. zVAD-fmk prevented the recruitment of TRAF2 into the death-inducing signaling complex. Thus, our present results demonstrate that FLIP(p43) processed by caspase 8 specifically interacts with TRAF2 and subsequently induces activation of the NF-kappaB signaling pathway.
Kataoka
Takao
T
Division of Bioinformatics, Center for Biological Resources and Informatics, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501, Japan. tkataoka@bio.titech.ac.jp
Tschopp
Jürg
J
D000590:Amino Acid Chloromethyl Ketones / Q000378:metabolism; D000818:Animals; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D019281:Dimerization; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D047992:TNF Receptor-Associated Factor 2
D000590:Amino Acid Chloromethyl Ketones; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; C506387:Cflar protein, mouse; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D010446:Peptide Fragments; D011506:Proteins; D047992:TNF Receptor-Associated Factor 2; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C505530:CASP8 protein, human; C505526:Casp8 protein, mouse; D053181:Caspase 8; D020169:Caspases