title: NF-kappaB suppression by the deubiquitinating enzyme Cezanne: a novel negative feedback loop in pro-inflammatory signaling.
abstract: Transcription factors belonging to the NF-kappaB family regulate inflammation by inducing pro-inflammatory molecules (e.g. interleukin (IL)-8) in response to cytokines (e.g. tumor necrosis factor (TNF) alpha, IL-1) or other stimuli. Several negative regulators of NF-kappaB, including the ubiquitin-editing enzyme A20, participate in the resolution of inflammatory responses. We report that Cezanne, a member of the A20 family of the deubiquitinating cysteine proteases, can be induced by TNFalpha in cultured cells. Silencing of endogenous Cezanne using small interfering RNA led to elevated NF-kappaB luciferase reporter gene activity and enhanced expression of IL-8 transcripts in TNFalpha-treated cells. Thus we conclude that endogenous Cezanne can attenuate NF-kappaB activation and the induction of pro-inflammatory transcripts in response to TNF receptor (TNFR) signaling. Overexpression studies revealed that Cezanne suppressed NF-kappaB nuclear translocation and transcriptional activity by targeting the TNFR signaling pathway at the level of the IkappaB kinase complex or upstream from it. These effects were not observed in a form of Cezanne that was mutated at the catalytic cysteine residue (Cys209), indicating that the deubiquitinating activity of Cezanne is essential for NF-kappaB regulation. Finally, we demonstrate that Cezanne can be recruited to activated TNFRs where it suppresses the build-up of polyubiquitinated RIP1 signal adapter proteins. Thus we conclude that Cezanne forms a novel negative feedback loop in pro-inflammatory signaling and that it suppresses NF-kappaB activation by targeting RIP1 signaling intermediaries for deubiquitination.
authors.affiliation: British Heart Foundation Cardiovascular Sciences Unit, National Heart and Lung Institute, Imperial College London, London W12 ONN, United Kingdom.
authors.forename: Karine
authors.initials: K
authors.lastname: Enesa
authors.forename: Mustafa
authors.initials: M
authors.lastname: Zakkar
authors.forename: Hera
authors.initials: H
authors.lastname: Chaudhury
authors.forename: Le A
authors.initials: le A
authors.lastname: Luong
authors.forename: Lesley
authors.initials: L
authors.lastname: Rawlinson
authors.forename: Justin C
authors.initials: JC
authors.lastname: Mason
authors.forename: Dorian O
authors.initials: DO
authors.lastname: Haskard
authors.forename: Jonathan L E
authors.initials: JL
authors.lastname: Dean
authors.forename: Paul C
authors.initials: PC
authors.lastname: Evans
mesh_terms: D004268:DNA-Binding Proteins; D010450:Endopeptidases / Q000378:metabolism*; D042783:Endothelial Cells / Q000166:cytology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007249:Inflammation; D016209:Interleukin-8 / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008239:Lysine / Q000737:chemistry; D008954:Models, Biological; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D015398:Signal Transduction; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: C119724:AGFG1 protein, human; D004268:DNA-Binding Proteins; D016209:Interleukin-8; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D018124:Receptors, Tumor Necrosis Factor; D025801:Ubiquitin; D010450:Endopeptidases; C476458:OTUD7B protein, human; C076529:TNFAIP3 protein, human; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D008239:Lysine