title: Bruton's tyrosine kinase phosphorylates Toll-like receptor 3 to initiate antiviral response.
abstract: Toll-like receptor 3 (TLR3) mediates antiviral response by recognizing double-stranded RNA. Its cytoplasmic domain is tyrosine phosphorylated upon ligand binding and initiates downstream signaling via the adapter TIR-containing adaptor inducing interferon-β (TRIF). However, the kinase responsible for TLR3 phosphorylation remains unknown. We show here that Bruton's tyrosine kinase (BTK)-deficient macrophages failed to secrete inflammatory cytokines and IFN-β upon TLR3 stimulation and were impaired in clearing intracellular dengue virus infection. Mutant mice were also less susceptible to d-galactosamine/p(I:C)-induced sepsis. In the absence of BTK, TLR3-induced phosphoinositide 3-kinase (PI3K), AKT and MAPK signaling and activation of NFκB, IRF3, and AP-1 transcription factors were all defective. We demonstrate that BTK directly phosphorylates TLR3 and in particular the critical Tyr759 residue. BTK point mutations that abrogate or led to constitutive kinase activity have opposite effects on TLR3 phosphorylation. Loss of BTK also compromises the formation of the downstream TRIF/receptor-interacting protein 1 (RIP1)/TBK1 complex. Thus, BTK plays a critical role in initiating TLR3 signaling.
authors.affiliation: Immunology Group, Bioprocessing Technology Institute,  Agency for Science, Technology and Research (ASTAR),  Republic of Singapore 138668.
authors.forename: Koon-Guan
authors.initials: KG
authors.lastname: Lee
authors.forename: Shengli
authors.initials: S
authors.lastname: Xu
authors.forename: Zi-Han
authors.initials: ZH
authors.lastname: Kang
authors.forename: Jianxin
authors.initials: J
authors.lastname: Huo
authors.forename: Mei
authors.initials: M
authors.lastname: Huang
authors.forename: Dingxiang
authors.initials: D
authors.lastname: Liu
authors.forename: Osamu
authors.initials: O
authors.lastname: Takeuchi
authors.forename: Shizuo
authors.initials: S
authors.lastname: Akira
authors.forename: Kong-Peng
authors.initials: KP
authors.lastname: Lam
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D000998:Antiviral Agents / Q000276:immunology*; D016207:Cytokines / Q000096:biosynthesis; D003716:Dengue Virus / Q000276:immunology* / Q000502:physiology; D004789:Enzyme Activation; D020690:GTPase-Activating Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D016899:Interferon-beta / Q000096:biosynthesis; D020935:MAP Kinase Signaling System; D008262:Macrophage Activation; D008264:Macrophages / Q000201:enzymology / Q000821:virology; D051379:Mice; D008810:Mice, Inbred C57BL; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000172:deficiency / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051196:Toll-Like Receptor 3 / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014779:Virus Replication
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D000077329:Agammaglobulinaemia Tyrosine Kinase; D000998:Antiviral Agents; D016207:Cytokines; D020690:GTPase-Activating Proteins; D016899:Interferon-beta; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D051057:Proto-Oncogene Proteins c-akt; D051196:Toll-Like Receptor 3; D014157:Transcription Factors; C490620:Ralbp1 protein, mouse; C476286:Ticam1 protein, mouse; C519703:TLR3 protein, mouse; C498588:Tbk1 protein, mouse; C000625949:BTK protein, human; C000625951:Btk protein, mouse