title: Activation of NF-kappaB by FADD, Casper, and caspase-8.
abstract: Fas-associated death domain protein (FADD), caspase-8-related protein (Casper), and caspase-8 are components of the tumor necrosis factor receptor type 1 (TNF-R1) and Fas signaling complexes that are involved in TNF-R1- and Fas-induced apoptosis. Here we show that overexpression of FADD and Casper potently activates NF-kappaB. In the presence of caspase inhibitors, overexpression of caspase-8 also activates NF-kappaB. A caspase-inactive point mutant, caspase-8(C360S), activates NF-kappaB as potently as wild-type caspase-8, suggesting that caspase-8-induced apoptosis and NF-kappaB activation are uncoupled. NF-kappaB activation by FADD and Casper is inhibited by the caspase-specific inhibitors crmA and BD-fmk, suggesting that FADD- and Casper-induced NF-kappaB activation is mediated by caspase-8. FADD, Casper, and caspase-8-induced NF-kappaB activation are inhibited by dominant negative mutants of TRAF2, NIK, IkappaB kinase alpha, and IkappaB kinase beta. A dominant negative mutant of RIP inhibits FADD- and caspase-8-induced but not Casper-induced NF-kappaB activation. A mutant of Casper and the caspase-specific inhibitors crmA and BD-fmk partially inhibit TNF-R1-, TRADD, and TNF-induced NF-kappaB activation, suggesting that FADD, Casper, and caspase-8 function downstream of TRADD and contribute to TNF-R1-induced NF-kappaB activation. Moreover, activation of caspase-8 results in proteolytic processing of NIK, which is inhibited by crmA. When overexpressed, the processed fragments of NIK do not activate NF-kappaB, and the processed C-terminal fragment inhibits TNF-R1-induced NF-kappaB activation. These data indicate that FADD, Casper, and pro-caspase-8 are parts of the TNF-R1-induced NF-kappaB activation pathways, whereas activated caspase-8 can negatively regulate TNF-R1-induced NF-kappaB activation by proteolytically inactivating NIK.
authors.affiliation: Department of Immunology, National Jewish Medical and Research Center, University of Colorado Health Sciences Center, Denver, Colorado 80206, USA.
authors.forename: W H
authors.initials: WH
authors.lastname: Hu
authors.forename: H
authors.initials: H
authors.lastname: Johnson
authors.forename: H B
authors.initials: HB
authors.lastname: Shu
mesh_terms: D015703:Antigens, CD / Q000502:physiology; D017209:Apoptosis; D029681:Arabidopsis Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000502:physiology*; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology*; D044943:Fatty Acid Desaturases / Q000502:physiology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D018124:Receptors, Tumor Necrosis Factor / Q000502:physiology; D047888:Receptors, Tumor Necrosis Factor, Type I; D000097782:NF-kappaB-Inducing Kinase
chemical_list: D015703:Antigens, CD; D029681:Arabidopsis Proteins; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases; D044943:Fatty Acid Desaturases; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D017346:Protein Serine-Threonine Kinases; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D000097782:NF-kappaB-Inducing Kinase; C506386:CFLAR protein, human; C084083:Fad7 protein, Arabidopsis; C505530:CASP8 protein, human; C506433:CASP9 protein, human