Abstract
The proinflammatory cytokine tumor necrosis factor (TNF) alpha signals both cell survival and death. The biological outcome of TNFalpha treatment is determined by the balance between NF-kappaB and Jun kinase (JNK) signaling; NF-kappaB promotes survival, whereas JNK enhances cell death. Critically, identity of a JNK substrate that promotes TNFalpha-induced apoptosis has been outstanding. Here we show that TNFalpha-mediated JNK activation accelerates turnover of the NF-kappaB-induced antiapoptotic protein c-FLIP, an inhibitor of caspase-8. This is not due to direct c-FLIP phosphorylation but depends on JNK-mediated phosphorylation and activation of the E3 ubiquitin ligase Itch, which specifically ubiquitinates c-FLIP and induces its proteasomal degradation. JNK1 or Itch deficiency or treatment with a JNK inhibitor renders mice resistant in three distinct models of TNFalpha-induced acute liver failure, and cells from these mice do not display inducible c-FLIP(L) ubiquitination and degradation. Thus, JNK antagonizes NF-kappaB during TNFalpha signaling by promoting the proteasomal elimination of c-FLIP(L).
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Animals
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Apoptosis / drug effects
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CASP8 and FADD-Like Apoptosis Regulating Protein
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Enzyme Activation
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Female
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Hepatocytes / cytology
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Hepatocytes / drug effects
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Hepatocytes / metabolism
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Intracellular Signaling Peptides and Proteins / metabolism*
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JNK Mitogen-Activated Protein Kinases / metabolism*
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Liver Failure, Acute / etiology
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Liver Failure, Acute / metabolism
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Mice, Mutant Strains
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Models, Biological
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Pregnancy
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Receptors, Tumor Necrosis Factor / metabolism
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Receptors, Tumor Necrosis Factor, Type I
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Signal Transduction
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Tumor Necrosis Factor Decoy Receptors
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Tumor Necrosis Factor-alpha / pharmacology*
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Ubiquitin-Protein Ligases / metabolism*
Substances
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CASP8 and FADD-Like Apoptosis Regulating Protein
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Cflar protein, mouse
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Intracellular Signaling Peptides and Proteins
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Receptors, Tumor Necrosis Factor
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Receptors, Tumor Necrosis Factor, Type I
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Tumor Necrosis Factor Decoy Receptors
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Tumor Necrosis Factor-alpha
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recombinant human tumor necrosis factor-binding protein-1
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Itch protein, mouse
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Ubiquitin-Protein Ligases
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JNK Mitogen-Activated Protein Kinases