title: Functional characterization of domains of IPS-1 using an inducible oligomerization system.
abstract: The innate immune system recognizes viral nucleic acids and stimulates cellular antiviral responses. Intracellular detection of viral RNA is mediated by the Retinoic acid inducible gene (RIG)-I Like Receptor (RLR), leading to production of type I interferon (IFN) and pro-inflammatory cytokines. Once cells are infected with a virus, RIG-I and MDA5 bind to viral RNA and undergo conformational change to transmit a signal through direct interaction with downstream CARD-containing adaptor protein, IFN-β promoter stimulator-1 (IPS-1, also referred as MAVS/VISA/Cardif). IPS-1 is composed of N-terminal Caspase Activation and Recruitment Domain (CARD), proline-rich domain, intermediate domain, and C-terminal transmembrane (TM) domain. The TM domain of IPS-1 anchors it to the mitochondrial outer membrane. It has been hypothesized that activated RLR triggers the accumulation of IPS-1, which forms oligomer as a scaffold for downstream signal proteins. However, the exact mechanisms of IPS-1-mediated signaling remain controversial. In this study, to reveal the details of IPS-1 signaling, we used an artificial oligomerization system to induce oligomerization of IPS-1 in cells. Artificial oligomerization of IPS-1 activated antiviral signaling without a viral infection. Using this system, we investigated the domain-requirement of IPS-1 for its signaling. We discovered that artificial oligomerization of IPS-1 could overcome the requirement of CARD and the TM domain. Moreover, from deletion- and point-mutant analyses, the C-terminal Tumor necrosis factor Receptor-Associated Factor (TRAF) binding motif of IPS-1 (aa. 453-460) present in the intermediate domain is critical for downstream signal transduction. Our results suggest that IPS-1 oligomerization is essential for the formation of a multiprotein signaling complex and enables downstream activation of transcription factors, Interferon Regulatory Factor 3 (IRF3) and Nuclear Factor-κB (NF-κB), leading to type I IFN and pro-inflammatory cytokine production.
authors: Laboratory of Molecular Genetics, Institute for Virus Research, Kyoto University, Kyoto, Japan.
authors: Shiori
authors: S
authors: Takamatsu
authors: Kazuhide
authors: K
authors: Onoguchi
authors: Koji
authors: K
authors: Onomoto
authors: Ryo
authors: R
authors: Narita
authors: Kiyohiro
authors: K
authors: Takahasi
authors: Fumiyoshi
authors: F
authors: Ishidate
authors: Takahiro K
authors: TK
authors: Fujiwara
authors: Mitsutoshi
authors: M
authors: Yoneyama
authors: Hiroki
authors: H
authors: Kato
authors: Takashi
authors: T
authors: Fujita
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000235:genetics* / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000821:virology; D005786:Gene Expression Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000235:genetics / Q000378:metabolism; D007370:Interferon Type I / Q000096:biosynthesis / Q000276:immunology; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009522:Newcastle disease virus / Q000254:growth & development; D009842:Oligopeptides / Q000494:pharmacology; D054730:Protein Interaction Domains and Motifs / Q000235:genetics*; D055503:Protein Multimerization / Q000187:drug effects; D017434:Protein Structure, Tertiary; D011971:Receptors, Immunologic; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; D007370:Interferon Type I; C505371:MAVS protein, human; D016328:NF-kappa B; D009842:Oligopeptides; D011971:Receptors, Immunologic; C452820:RIGI protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases