title: Homo-oligomerization is essential for Toll/interleukin-1 receptor domain-containing adaptor molecule-1-mediated NF-kappaB and interferon regulatory factor-3 activation.
abstract: Toll-IL-1 receptor (TIR) domain-containing adaptor molecule-1 (TICAM-1, also named TIR domain-containing adaptor-inducing interferon (IFN)-beta or TRIF)) is a signaling adaptor of Toll-like receptor (TLR) 3/4 that activates the transcription factors, interferon regulatory factor-3 (IRF-3) and NF-kappaB leading to inducing IFN-beta production. The mechanisms by which TICAM-1 is activated by TLR3/4 to serve as a signaling platform are unknown. In this study, we show that homo-oligomerization of TICAM-1 is critical for TICAM-1-mediated activation of NF-kappaB and IRF-3. Both TIR and C-terminal domain of TICAM-1 mediated TICAM-1 oligomerization. Pro(434) located in the TIR domain and the C-terminal region, with the exception of the RIP homotypic-interacting motif, were determinants of TICAM-1 oligomerization. Mutation of TIR domain (P434H) or deletion of C-terminal domain greatly reduced TICAM-1-mediated NF-kappaB and IFN-beta promoter activation. TICAM-1 oligomerization at either the TIR domain or the C-terminal region resulted in recruitment of tumor necrosis factor receptor-associated factor 3, a downstream signaling molecule essential for TICAM-1-mediated IRF-3 activation, but not recruitment of the IRF-3 kinase complex, NF-kappaB-activating kinase-associated protein 1 and TANK-binding kinase 1. In addition, RIP homotypic-interacting motif mutant, which possesses two oligomerization motifs but not the RIP1 binding motif, also failed to recruit NF-kappaB-activating kinase-associated protein 1 and TANK-binding kinase 1. Thus, full activation and formation of TICAM-1 signalosomes requires oligomerization induced at two different sites and RIP1 binding.
authors.affiliation: Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Funami
authors.forename: Miwa
authors.initials: M
authors.lastname: Sasai
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Oshiumi
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Seya
authors.forename: Misako
authors.initials: M
authors.lastname: Matsumoto
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry*; D020816:Amino Acid Motifs; D001665:Binding Sites; D002460:Cell Line; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism*; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: C119724:AGFG1 protein, human; D033942:Adaptor Proteins, Vesicular Transport; D050838:Interferon Regulatory Factor-3; D016328:NF-kappa B; D028861:Nuclear Pore Complex Proteins; D016601:RNA-Binding Proteins; C470409:TICAM1 protein, human