title: Arenavirus nucleoprotein targets interferon regulatory factor-activating kinase IKKε.
abstract: Arenaviruses perturb innate antiviral defense by blocking induction of type I interferon (IFN) production. Accordingly, the arenavirus nucleoprotein (NP) was shown to block activation and nuclear translocation of interferon regulatory factor 3 (IRF3) in response to virus infection. Here, we sought to identify cellular factors involved in innate antiviral signaling targeted by arenavirus NP. Consistent with previous studies, infection with the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) prevented phosphorylation of IRF3 in response to infection with Sendai virus, a strong inducer of the retinoic acid-inducible gene I (RIG-I)/mitochondrial antiviral signaling (MAVS) pathway of innate antiviral signaling. Using a combination of coimmunoprecipitation and confocal microscopy, we found that LCMV NP associates with the IκB kinase (IKK)-related kinase IKKε but that, rather unexpectedly, LCMV NP did not bind to the closely related TANK-binding kinase 1 (TBK-1). The NP-IKKε interaction was highly conserved among arenaviruses from different clades. In LCMV-infected cells, IKKε colocalized with NP but not with MAVS located on the outer membrane of mitochondria. LCMV NP bound the kinase domain (KD) of IKKε (IKBKE) and blocked its autocatalytic activity and its ability to phosphorylate IRF3, without undergoing phosphorylation. Together, our data identify IKKε as a novel target of arenavirus NP. Engagement of NP seems to sequester IKKε in an inactive complex. Considering the important functions of IKKε in innate antiviral immunity and other cellular processes, the NP-IKKε interaction likely plays a crucial role in arenavirus-host interaction.
authors.affiliation: Institute of Microbiology University Hospital Center and University of Lausanne, Lausanne, Switzerland.
authors.forename: Christelle
authors.initials: C
authors.lastname: Pythoud
authors.forename: W W Shanaka I
authors.initials: WW
authors.lastname: Rodrigo
authors.forename: Giulia
authors.initials: G
authors.lastname: Pasqual
authors.forename: Sylvia
authors.initials: S
authors.lastname: Rothenberger
authors.forename: Luis
authors.initials: L
authors.lastname: Martínez-Sobrido
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: de la Torre
authors.forename: Stefan
authors.initials: S
authors.lastname: Kunz
mesh_terms: D045744:Cell Line, Tumor; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D007113:Immunity, Innate / Q000235:genetics; D050838:Interferon Regulatory Factor-3 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008216:Lymphocytic Choriomeningitis / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008217:Lymphocytic choriomeningitis virus / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000276:immunology / Q000378:metabolism; D046912:Multiprotein Complexes / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D019590:Nucleocapsid Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation / Q000235:genetics / Q000276:immunology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011971:Receptors, Immunologic; D029082:Sendai virus / Q000235:genetics / Q000276:immunology / Q000378:metabolism
chemical_list: C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; D046912:Multiprotein Complexes; D019590:Nucleocapsid Proteins; D011971:Receptors, Immunologic; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human; D051550:I-kappa B Kinase; C452820:RIGI protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases