title: Akt contributes to activation of the TRIF-dependent signaling pathways of TLRs by interacting with TANK-binding kinase 1.
abstract: Toll/IL-1R domain-containing adaptor inducing IFN-β (TRIF) is an adaptor molecule that is recruited to TLR3 and -4 upon agonist stimulation and triggers activation of IFN regulatory factor 3 (IRF3) and expression of type 1 IFNs, which are critical for cellular antiviral responses. We show that Akt is a downstream molecule of TRIF/TANK-binding kinase 1 (TBK1) and plays an important role in the activation of IRF3 by TLR3 and -4 agonists. Blockade of Akt by a dominant-negative mutant or by short interfering RNA decreased IRF3 activation and IFN-β expression induced by polyinosinic:polycytidylic acid [poly(I:C)], LPS, TRIF, and TBK1. Association of endogenous TBK1 and Akt was observed in macrophages when stimulated with poly(I:C) and LPS. In vitro kinase assays combined with reversed-phase liquid chromatography mass spectrometry analysis showed that TBK1 enhanced phosphorylation of Akt on Ser(473), whereas knockdown of TBK1 expression by short interfering RNA in macrophages decreased poly(I:C)- and LPS-induced Akt phosphorylation. Embryonic fibroblasts derived from TBK1 knockout mice also showed impaired Akt phosphorylation in response to poly(I:C) and LPS. To our knowledge, our results demonstrate a new regulatory mechanism for Akt activation mediated by TBK1 and a novel role of Akt in TLR-mediated immune responses.
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Korea.
authors.forename: Sun Myung
authors.initials: SM
authors.lastname: Joung
authors.forename: Zee-Yong
authors.initials: ZY
authors.lastname: Park
authors.forename: Shilpa
authors.initials: S
authors.lastname: Rani
authors.forename: Osamu
authors.initials: O
authors.lastname: Takeuchi
authors.forename: Shizuo
authors.initials: S
authors.lastname: Akira
authors.forename: Joo Young
authors.initials: JY
authors.lastname: Lee
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002460:Cell Line; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010766:Phosphorylation / Q000235:genetics / Q000276:immunology; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000378:metabolism* / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism* / Q000502:physiology; D020239:Receptor Cross-Talk / Q000276:immunology; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D051196:Toll-Like Receptor 3 / Q000819:agonists; D051197:Toll-Like Receptor 4 / Q000819:agonists; D051193:Toll-Like Receptors / Q000378:metabolism / Q000502:physiology*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; C476286:Ticam1 protein, mouse; C495344:TLR3 protein, human; C519703:TLR3 protein, mouse; C495345:TLR4 protein, human; C493487:Tlr4 protein, mouse; C498588:Tbk1 protein, mouse; C494918:AKT1 protein, human