title: Inhibition of RIG-I-dependent signaling to the interferon pathway during hepatitis C virus expression and restoration of signaling by IKKepsilon.
abstract: Interferon (IFN) is one important effector of the innate immune response, induced by different viral or bacterial components through Toll-like receptor (TLR)-dependent and -independent mechanisms. As part of its pathogenic strategy, hepatitis C virus (HCV) interferes with the innate immune response and induction of IFN-beta via the HCV NS3/4A protease activity which inhibits phosphorylation of IRF-3, a key transcriptional regulator of the IFN response. In the present study, we demonstrate that inhibition by the protease occurs upstream of the noncanonical IKK-related kinases IKKepsilon and TBK-1, which phosphorylate IRF-3, through partial inhibition of the TLR adapter protein TRIF/TICAM1-dependent pathway. Use of TRIF(-/-) mouse embryo fibroblasts however revealed the presence of a TRIF-independent pathway involved in IFN induction that was also inhibited by NS3/4A. Importantly, we show that NS3/4A can strongly inhibit the ability of the recently described RIG-I protein to activate IFN, suggesting that RIG-I is a key factor in the TRIF-independent, NS3/4A-sensitive pathway. Expression of IFN signaling components including IKKepsilon, TBK-1, TRIF, and wild type or constitutively active forms of RIG-I in the HCV replicon cells resulted in IFN-beta promoter transactivation, with IKKepsilon displaying the highest efficiency. Subsequently, overexpression of IKKepsilon resulted in 80% inhibition of both the positive and negative replicative strands of the HCV replicon. The partial restoration of the capacity of the host cell to transcribe IFN-beta indicates that IKKepsilon expression is able to bypass the HCV-mediated inhibition and restore the innate antiviral response.
authors.affiliation: Unité Hépacivirus, Institut Pasteur, 75724 Paris Cedex 15, France.
authors.forename: Adrien
authors.initials: A
authors.lastname: Breiman
authors.forename: Nathalie
authors.initials: N
authors.lastname: Grandvaux
authors.forename: Rongtuan
authors.initials: R
authors.lastname: Lin
authors.forename: Catherine
authors.initials: C
authors.lastname: Ottone
authors.forename: Shizuo
authors.initials: S
authors.lastname: Akira
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Yoneyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Fujita
authors.forename: John
authors.initials: J
authors.lastname: Hiscott
authors.forename: Eliane F
authors.initials: EF
authors.lastname: Meurs
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D004268:DNA-Binding Proteins / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation; D016174:Hepacivirus / Q000276:immunology* / Q000502:physiology*; D006801:Humans; D051550:I-kappa B Kinase; D007113:Immunity, Innate / Q000276:immunology; D050838:Interferon Regulatory Factor-3; D016899:Interferon-beta / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000276:immunology; D051379:Mice; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D020365:RNA Helicases / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000302:isolation & purification; D011956:Receptors, Cell Surface / Q000276:immunology; D011971:Receptors, Immunologic; D012093:Replicon; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051193:Toll-Like Receptors; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D004268:DNA-Binding Proteins; C494232:IRF3 protein, human; D050838:Interferon Regulatory Factor-3; C494233:Irf3 protein, mouse; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; C470409:TICAM1 protein, human; D051193:Toll-Like Receptors; D014157:Transcription Factors; D016899:Interferon-beta; C498588:Tbk1 protein, mouse; D017346:Protein Serine-Threonine Kinases; C403191:TBK1 protein, human; C496559:CHUK protein, human; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; C452820:RIGI protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases