title: Poxviral protein A52 stimulates p38 mitogen-activated protein kinase (MAPK) activation by causing tumor necrosis factor receptor-associated factor 6 (TRAF6) self-association leading to transforming growth factor β-activated kinase 1 (TAK1) recruitment.
abstract: Vaccinia virus encodes a number of proteins that inhibit and manipulate innate immune signaling pathways that also have a role in virulence. These include A52, a protein shown to inhibit IL-1- and Toll-like receptor-stimulated NFκB activation, via interaction with interleukin-1 receptor-associated kinase 2 (IRAK2). Interestingly, A52 was also found to activate p38 MAPK and thus enhance Toll-like receptor-dependent IL-10 induction, which was TRAF6-dependent, but the manner in which A52 manipulates TRAF6 to stimulate p38 activation was unclear. Here, we show that A52 has a non-canonical TRAF6-binding motif that is essential for TRAF6 binding and p38 activation but dispensable for NFκB inhibition and IRAK2 interaction. Wild-type A52, but not a mutant defective in p38 activation and TRAF6 binding (F154A), caused TRAF6 oligomerization and subsequent TRAF6-TAK1 association. The crystal structure of A52 shows that it adopts a Bcl2-like fold and exists as a dimer in solution. Residue Met-65 was identified as being located in the A52 dimer interface, and consistent with that, A52-M65E was impaired in its ability to dimerize. A52-M65E although capable of interacting with TRAF6, was unable to cause either TRAF6 self-association, induce the TRAF6-TAK1 association, or activate p38 MAPK. The results suggest that an A52 dimer causes TRAF6 self-association, leading to TAK1 recruitment and p38 activation. This reveals a molecular mechanism whereby poxviruses manipulate TRAF6 to activate MAPKs (which can be proviral) without stimulating antiviral NFκB activation.
authors.affiliation: Immunology Research Centre, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Julianne
authors.initials: J
authors.lastname: Stack
authors.affiliation: Immunology Research Centre, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Tara P
authors.initials: TP
authors.lastname: Hurst
authors.affiliation: Immunology Research Centre, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Sinead M
authors.initials: SM
authors.lastname: Flannery
authors.affiliation: Immunology Research Centre, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Kiva
authors.initials: K
authors.lastname: Brennan
authors.affiliation: Immunology Research Centre, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Rupp
authors.affiliation: Immunology Research Centre, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Shun-Ichiro
authors.initials: SI
authors.lastname: Oda
authors.affiliation: Immunology Research Centre, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Amir R
authors.initials: AR
authors.lastname: Khan
authors.affiliation: Immunology Research Centre, School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland. Electronic address: agbowie@tcd.ie.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Bowie
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D004789:Enzyme Activation; D057809:HEK293 Cells; D006801:Humans; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics / Q000378:metabolism; D016753:Interleukin-10 / Q000235:genetics / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D020125:Mutation, Missense; D011485:Protein Binding; D055503:Protein Multimerization; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism*; D014615:Vaccinia / Q000235:genetics / Q000378:metabolism*; D014616:Vaccinia virus / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000099151:MAP Kinase Kinase Kinase 7
chemical_list: D053592:Interleukin-1 Receptor-Associated Kinases; D016753:Interleukin-10; D020930:MAP Kinase Kinase Kinases; D048029:TNF Receptor-Associated Factor 6; D014764:Viral Proteins; D048051:p38 Mitogen-Activated Protein Kinases; D000099151:MAP Kinase Kinase Kinase 7; C556062:IL10 protein, mouse
keywords: NF-kappa B (NF-KB); Pox Viruses; Signal Transduction; TRAF6; Viral Protein; p38 MAPK