title: Act1, a U-box E3 ubiquitin ligase for IL-17 signaling.
abstract: Interleukin-17 (IL-17), a proinflammatory cytokine mainly produced by cells of the T helper 17 (T(H)17) lineage, is required for host defense against bacterial and fungal infections and plays a critical role in the pathogenesis of inflammatory and autoimmune diseases. Act1 is an essential adaptor molecule in IL-17-mediated signaling and is recruited to the IL-17 receptor (IL-17R) upon IL-17 stimulation through an interaction between its SEFIR domain and that of the IL-17R. Here, we report that Act1 is a U-box E3 ubiquitin ligase and that its activity is essential for IL-17-mediated signaling pathways. Through the use of the Ubc13-Uev1A E2 complex, Act1 mediated the lysine-63-linked ubiquitination of tumor necrosis factor receptor-associated factor 6 (TRAF6), a component of IL-17-mediated signaling. Deletion and point mutations of the Act1 U-box abolished Act1-mediated ubiquitination of TRAF6 and impaired the ability of Act1 to restore IL-17-dependent signaling and expression of target genes in Act1(-/-) mouse embryonic fibroblasts. We also showed that the lysine-124 residue of TRAF6 was critical for efficient Act1-mediated ubiquitination of TRAF6 and for the ability of TRAF6 to mediate IL-17-induced activation of nuclear factor kappaB. Thus, we propose that Act1 mediates IL-17-induced signaling pathways through its E3 ubiquitin ligase activity and that TRAF6 is a critical substrate of Act1, which indicates the importance of protein ubiquitination in the IL-17-dependent inflammatory response.
authors.affiliation: Department of Immunology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44915, USA.
authors.forename: Caini
authors.initials: C
authors.lastname: Liu
authors.forename: Wen
authors.initials: W
authors.lastname: Qian
authors.forename: Youcun
authors.initials: Y
authors.lastname: Qian
authors.forename: Natalia V
authors.initials: NV
authors.lastname: Giltiay
authors.forename: Yi
authors.initials: Y
authors.lastname: Lu
authors.forename: Shadi
authors.initials: S
authors.lastname: Swaidani
authors.forename: Saurav
authors.initials: S
authors.lastname: Misra
authors.forename: Li
authors.initials: L
authors.lastname: Deng
authors.forename: Zhijian J
authors.initials: ZJ
authors.lastname: Chen
authors.forename: Xiaoxia
authors.initials: X
authors.lastname: Li
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D016207:Cytokines / Q000378:metabolism; D006801:Humans; D020381:Interleukin-17 / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009154:Mutation; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D016207:Cytokines; D020381:Interleukin-17; D048029:TNF Receptor-Associated Factor 6; C414202:TRAF3IP2 protein, human; C515963:Traf3ip2 protein, mouse; D047988:Tumor Necrosis Factor Receptor-Associated Peptides and Proteins; D044767:Ubiquitin-Protein Ligases