title: Limited suppression of the interferon-beta production by hepatitis C virus serine protease in cultured human hepatocytes.
abstract: Toll-like receptors and RNA helicase family members [retinoic acid-inducible gene I (RIG-I) and melanoma differentiation associated gene-5 (MDA5)] play important roles in the induction of interferon-beta as a major event in innate immune responses after virus infection. TRIF (adaptor protein of Toll-like receptor 3)-mediated and Cardif (adaptor protein of RIG-I or MDA5)-mediated signaling pathways contribute rapid induction of interferon-beta through the activation of interferon regulatory factor-3 (IRF-3). Previously, it has been reported that the hepatitis C virus NS3-4A serine protease blocks virus-induced activation of IRF-3 in the human hepatoma cell line HuH-7, and that NS3-4A cleaves TRIF and Cardif molecules, resulting in the interruption of antiviral signaling pathways. On the other hand, it has recently been reported that non-neoplastic human hepatocyte PH5CH8 cells retain robust TRIF- and Cardif-mediated pathways, unlike HuH-7 cells, which lack a TRIF-mediated pathway. In the present study, we further investigated the effect of NS3-4A on antiviral signaling pathways. Although we confirmed that PH5CH8 cells were much more effective than HuH-7 cells for the induction of interferon-beta, we obtained the unexpected result that NS3-4A could not suppress the interferon-beta production induced by the TRIF-mediated pathway, although it suppressed the Cardif-mediated pathway by cleaving Cardif at the Cys508 residue. Using PH5CH8, HeLa, and HuH-7-derived cells, we further showed that NS3-4A could not cleave TRIF, in disagreement with a previous report describing the cleavage of TRIF by NS3-4A. Taken together, our findings suggest that the blocking of the interferon production by NS3-4A is not sufficient in HCV-infected hepatocyte cells.
authors.affiliation: Department of Molecular Biology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Japan.
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Dansako
authors.forename: Masanori
authors.initials: M
authors.lastname: Ikeda
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kato
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007369:Interferon Inducers / Q000494:pharmacology; D050838:Interferon Regulatory Factor-3 / Q000235:genetics / Q000378:metabolism; D016899:Interferon-beta / Q000235:genetics / Q000378:metabolism*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D011070:Poly I-C / Q000494:pharmacology; D016133:Polymerase Chain Reaction / Q000379:methods; D034622:RNA Interference; D011971:Receptors, Immunologic; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D051196:Toll-Like Receptor 3 / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D043583:Nucleoside-Triphosphatase; D000085242:Viral Proteases
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D049452:Green Fluorescent Proteins; D007369:Interferon Inducers; D050838:Interferon Regulatory Factor-3; D016899:Interferon-beta; D008156:Luciferases; D011070:Poly I-C; D011971:Receptors, Immunologic; D011993:Recombinant Fusion Proteins; D012697:Serine Endopeptidases; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D017361:Viral Nonstructural Proteins; C494232:IRF3 protein, human; C084422:NS3 protein, hepatitis C virus; D043583:Nucleoside-Triphosphatase; D000085242:Viral Proteases; C470409:TICAM1 protein, human; C495345:TLR4 protein, human; C452820:RIGI protein, human