title: Scaffolding adaptor protein Gab1 is required for TLR3/4- and RIG-I-mediated production of proinflammatory cytokines and type I IFN in macrophages.
abstract: RIG-I-like helicases and TLRs are critical sensors in the induction of type I IFN and proinflammatory cytokines to initiate innate immunity against invading pathogens. However, the mechanisms for the full activation of TLR and RIG-I-triggered innate response remain to be fully investigated. Grb2-associated binder 1 (Gab1), a member of scaffolding/adaptor proteins, can mediate signal transduction from many receptors, however, whether and how Gab1 is required for TLR and RIG-I-triggered innate responses remain unknown. In this study, we demonstrated that Gab1 significantly enhances TLR4-, TLR3-, and RIG-I-triggered IL-6, IL-1beta, and IFN-alpha/beta production in macrophages. Gab1 knockdown in primary macrophages or Gab1 deficiency in mouse embryonic fibroblasts significantly suppresses TLR3/4- and RIG-I-triggered production of IL-6, IL-1beta, and IFN-alpha/beta. Consistently, Gab1 deficiency impairs vesicular stomatitis virus (VSV) infection-induced IFN-alpha/beta production. In addition to promoting both MyD88- and TLR/IL-1 receptor domain-containing adaptor protein inducing IFN-beta-dependent MAPKs and NF-kappaB activation, Gab1 enhances PI3K/Akt activation by directly binding p85 in TLR signaling and VSV infection. Accordingly, Gab1 inhibits VSV replication and VSV infection-induced cell damage by inducing type I IFNs and IFN-inducible gene expression via PI3K/Akt pathway. Therefore, Gab1 is needed for full activation of TLR3/4- and RIG-I-triggered innate responses by promoting activation of PI3K/Akt, MAPKs, and NF-kappaB pathways.
authors.affiliation: Institute of Immunology, Zhejiang University School of Medicine, Hangzhou, China.
authors.forename: Yuejuan
authors.initials: Y
authors.lastname: Zheng
authors.forename: Huazhang
authors.initials: H
authors.lastname: An
authors.forename: Ming
authors.initials: M
authors.lastname: Yao
authors.forename: Jin
authors.initials: J
authors.lastname: Hou
authors.forename: Yizhi
authors.initials: Y
authors.lastname: Yu
authors.forename: Gensheng
authors.initials: G
authors.lastname: Feng
authors.forename: Xuetao
authors.initials: X
authors.lastname: Cao
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D015153:Blotting, Western; D002469:Cell Separation; D016207:Cytokines; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D015870:Gene Expression; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000276:immunology; D047468:Immunoprecipitation; D007370:Interferon Type I / Q000276:immunology / Q000378:metabolism*; D008264:Macrophages / Q000276:immunology / Q000378:metabolism*; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D020928:Mitogen-Activated Protein Kinases / Q000276:immunology / Q000378:metabolism; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000276:immunology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000276:immunology / Q000378:metabolism; D010750:Phosphoproteins / Q000276:immunology / Q000378:metabolism*; D034622:RNA Interference; D011956:Receptors, Cell Surface; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology; D051196:Toll-Like Receptor 3 / Q000276:immunology / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000276:immunology / Q000378:metabolism*; D014162:Transfection; D000097905:Roundabout Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D016207:Cytokines; D007370:Interferon Type I; D008565:Membrane Proteins; D020928:Mitogen-Activated Protein Kinases; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; C490897:Gab1 protein, mouse; C118348:Robo3 protein, mouse; D000097905:Roundabout Proteins; C519703:TLR3 protein, mouse; C493487:Tlr4 protein, mouse