NF-kappaB inducers upregulate cFLIP, a cycloheximide-sensitive inhibitor of death receptor signaling.
The caspase 8 homologue FLICE-inhibitory protein (cFLIP) is a potent negative regulator of death receptor-induced apoptosis. We found that cFLIP can be upregulated in some cell lines under critical involvement of the NF-kappaB pathway, but NF-kappaB activation was clearly not sufficient for cFLIP induction in all cell lines. Treatment of SV80 cells with the proteasome inhibitor N-benzoyloxycarbonyl (Z)-Leu-Leu-leucinal (MG-132) or geldanamycin, a drug interfering with tumor necrosis factor (TNF)-induced NF-kappaB activation, inhibited TNF-induced upregulation of cFLIP. Overexpression of a nondegradable IkappaBalpha mutant (IkappaBalpha-SR) or lack of IkappaB kinase gamma expression completely prevented phorbol myristate acetate-induced upregulation of cFLIP mRNA in Jurkat cells. These data point to an important role for NF-kappaB in the regulation of the cFLIP gene. SV80 cells normally show resistance to TNF-related apoptosis-inducing ligand (TRAIL) and TNF, as apoptosis can be induced only in the presence of low concentrations of cycloheximide (CHX). However, overexpression of IkappaBalpha-SR rendered SV80 cells sensitive to TRAIL-induced apoptosis in the absence of CHX, and cFLIP expression was able to reverse the proapoptotic effect of NF-kappaB inhibition. Western blot analysis further revealed that cFLIP, but not TRAF1, A20, and cIAP2, expression levels rapidly decrease upon CHX treatment. In conclusion, these data suggest a key role for cFLIP in the antiapoptotic response of NF-kappaB activation.
Kreuz
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S
Institute of Cell Biology and Immunology, University of Stuttgart, 70569 Stuttgart, Germany.
Siegmund
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D
Scheurich
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P
Wajant
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H
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis; D016227:Benzoquinones; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D019013:CD40 Antigens / Q000276:immunology; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins; D007375:Interleukin-1 / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D047029:Lactams, Macrocyclic; D007976:Leupeptins / Q000494:pharmacology; D009154:Mutation; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D011809:Quinones / Q000494:pharmacology; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation
D000911:Antibodies, Monoclonal; D016227:Benzoquinones; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D019013:CD40 Antigens; C506386:CFLAR protein, human; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D007375:Interleukin-1; D047908:Intracellular Signaling Peptides and Proteins; D047029:Lactams, Macrocyclic; D007976:Leupeptins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D011809:Quinones; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; C505639:TNFRSF10B protein, human; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D003513:Cycloheximide; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C001277:geldanamycin