title: Nonstructural 5A protein of hepatitis C virus modulates tumor necrosis factor alpha-stimulated nuclear factor kappa B activation.
abstract: The hepatitis C virus nonstructural protein 5A (NS5A) is a multifunctional phosphoprotein that leads to pleiotropic responses, in part by regulating cell growth and cellular signaling pathways. Here we show that overexpression of NS5A inhibits tumor necrosis factor (TNF)-alpha-induced nuclear factor kappaB (NF-kappaB) activation in HEK293 cells, as determined by luciferase reporter gene expression and by electrophoretic mobility shift assay. When overexpressed, NS5A cannot inhibit the recruitment of TNF receptor-associated factor 2 (TRAF2) and IkappaB kinase (IKK)beta into the TNF receptor 1-TNF receptor-associated death domain complex. In contrast, NS5A is a part of the TNF receptor 1 signaling complex. NF-kappaB activation by TNF receptor-associated death domain and TRAF2 was inhibited by NS5A, whereas MEKK1 and IKKbeta-dependent NF-kappaB activation was not affected, suggesting that NS5A may inhibit NF-kappaB activation signaled by TRAF2. Coimmunoprecipitation and colocalization of NS5A and TRAF2 expressed in vivo provide compelling evidence that NS5A directly interacts with TRAF2. This interaction was mapped to the middle one-third (amino acids 148-301) of NS5A and the TRAF domain of TRAF2. Our findings suggest a possible molecular mechanism that could explain the ability of NS5A to negatively regulate TNF-alpha-induced NF-kappaB activation.
authors.affiliation: Institute of Environment and Life Science, The Hallym Academy of Sciences, Hallym University, 1 Ockcheon-dong, Chuncheon 200-702, Korea.
authors.forename: Kyu-Jin
authors.initials: KJ
authors.lastname: Park
authors.forename: Soo-Ho
authors.initials: SH
authors.lastname: Choi
authors.forename: Soo Young
authors.initials: SY
authors.lastname: Lee
authors.forename: Soon B
authors.initials: SB
authors.lastname: Hwang
authors.forename: Michael M C
authors.initials: MM
authors.lastname: Lai
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D024202:Electrophoretic Mobility Shift Assay; D006801:Humans; D051550:I-kappa B Kinase; D048728:MAP Kinase Kinase Kinase 1; D018613:Microscopy, Confocal; D016328:NF-kappa B / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000037:antagonists & inhibitors; D047992:TNF Receptor-Associated Factor 2; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D017361:Viral Nonstructural Proteins / Q000502:physiology*; D012324:RNA-Dependent RNA Polymerase
chemical_list: D017931:DNA Primers; D051550:I-kappa B Kinase; D048728:MAP Kinase Kinase Kinase 1; D016328:NF-kappa B; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D047992:TNF Receptor-Associated Factor 2; D014409:Tumor Necrosis Factor-alpha; D017361:Viral Nonstructural Proteins; C496559:CHUK protein, human; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C482576:MAP3K1 protein, human; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase