title: Ebola virus protein VP35 impairs the function of interferon regulatory factor-activating kinases IKKepsilon and TBK-1.
abstract: The Ebola virus (EBOV) VP35 protein antagonizes the early antiviral alpha/beta interferon (IFN-alpha/beta) response. We previously demonstrated that VP35 inhibits the virus-induced activation of the IFN-beta promoter by blocking the phosphorylation of IFN-regulatory factor 3 (IRF-3), a transcription factor that is crucial for the induction of IFN-alpha/beta expression. Furthermore, VP35 blocks IFN-beta promoter activation induced by any of several components of the retinoic acid-inducible gene I (RIG-I)/melanoma differentiation-associated gene 5 (MDA-5)-activated signaling pathways including RIG-I, IFN-beta promoter stimulator 1 (IPS-1), TANK-binding kinase 1 (TBK-1), and IkappaB kinase epsilon (IKKepsilon). These results suggested that VP35 may target the IRF kinases TBK-1 and IKKepsilon. Coimmunoprecipitation experiments now demonstrate physical interactions of VP35 with IKKepsilon and TBK-1, and the use of an IKKepsilon deletion construct further demonstrates that the amino-terminal kinase domain of IKKepsilon is sufficient for interactions with either IRF-3 or VP35. In vitro, either IKKepsilon or TBK-1 phosphorylates not only IRF-3 but also VP35. Moreover, VP35 overexpression impairs IKKepsilon-IRF-3, IKKepsilon-IRF-7, and IKKepsilon-IPS-1 interactions. Finally, lysates from cells overexpressing IKKepsilon contain kinase activity that can phosphorylate IRF-3 in vitro. When VP35 is expressed in the IKKepsilon-expressing cells, this kinase activity is suppressed. These data suggest that VP35 exerts its IFN-antagonist function, at least in part, by blocking necessary interactions between the kinases IKKepsilon and TBK-1 and their normal interaction partners, including their substrates, IRF-3 and IRF-7.
authors.affiliation: Department of Microbiology, Mount Sinai School of Medicine, New York, New York 10029, USA.
authors.forename: Kathleen C
authors.initials: KC
authors.lastname: Prins
authors.forename: Washington B
authors.initials: WB
authors.lastname: Cárdenas
authors.forename: Christopher F
authors.initials: CF
authors.lastname: Basler
mesh_terms: D002460:Cell Line; D029043:Ebolavirus / Q000276:immunology*; D006801:Humans; D051550:I-kappa B Kinase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017384:Sequence Deletion; D054334:Viral Regulatory and Accessory Proteins / Q000378:metabolism*
chemical_list: D050838:Interferon Regulatory Factor-3; C080980:VP35 protein, filovirus; D054334:Viral Regulatory and Accessory Proteins; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human; D051550:I-kappa B Kinase