title: MDA5 plays a critical role in interferon response during hepatitis C virus infection.
abstract: OBJECTIVE
  Hepatitis C virus (HCV) is a human pathogen that can evade host immunity to cause persistent infection, leading to liver cirrhosis and hepatocellular carcinoma. The transfected 3'UTR of HCV genomic RNA can be recognized by host protein RIG-I to activate interferon production in hepatocytes. However, it is difficult to demonstrate the RIG-I mediated sensing of HCV genomic RNA in the context of HCV infection because HCV-encoded NS3-4A protease can inactivate MAVS, a critical adaptor protein in interferon signaling. Our aim was to identify the viral sensor that triggers interferon response in hepatocytes during HCV infection.
  
  
  METHODS
  We generated a hepatic cell line that stably expressed mutant MAVS resistant to the NS3-4A cleavage. This cell line allowed us to investigate the interferon signaling pathway in the context of HCV infection. By using the knockdown and knockout technology together with biochemical approaches, we were able to identify the actual viral sensor in hepatocytes during HCV infection.
  
  
  RESULTS
  We showed that HCV infection induced robust interferon response in the cells expressing MAVS resistant to the NS3-4A cleavage. Unexpectedly, the interaction between HCV's 3'UTR and RIG-I seemed to play a minor role in this activation, while another helicase MDA5 played a more important role in sensing HCV infection to trigger interferon response.
  
  
  CONCLUSIONS
  Our data demonstrate that MDA5 recognizes HCV to initiate host innate immune response during HCV infection. This study provides insight into how host senses HCV to initiate innate immunity during HCV infection.
authors.affiliation: Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Xuezhi
authors.initials: X
authors.lastname: Cao
authors.affiliation: Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ding
authors.affiliation: Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Lu
authors.affiliation: Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Wanyin
authors.initials: W
authors.lastname: Tao
authors.affiliation: Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Huang
authors.affiliation: Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China; Department of Hepatology, First Hospital of Jilin University, Changchun, Jilin 130021, China.
authors.forename: Junqi
authors.initials: J
authors.lastname: Niu
authors.affiliation: Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China; Baylor Institute for Immunology Research, 3434 Live Oak, Dallas, TX 75204, USA.
authors.forename: Yong-Jun
authors.initials: YJ
authors.lastname: Liu
authors.affiliation: Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China. Electronic address: jzhong@sibs.ac.cn.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhong
mesh_terms: D020413:3' Untranslated Regions / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D002460:Cell Line; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000276:immunology* / Q000378:metabolism*; D016174:Hepacivirus / Q000235:genetics*; D019698:Hepatitis C, Chronic / Q000276:immunology / Q000821:virology; D022781:Hepatocytes / Q000276:immunology / Q000378:metabolism; D054884:Host-Pathogen Interactions; D006801:Humans; D007113:Immunity, Innate; D050835:Interferon Regulatory Factors / Q000378:metabolism; D000072640:Interferon-Induced Helicase, IFIH1; D007372:Interferons / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D011971:Receptors, Immunologic; D012697:Serine Endopeptidases / Q000378:metabolism; D015398:Signal Transduction; D017361:Viral Nonstructural Proteins / Q000378:metabolism*; D043583:Nucleoside-Triphosphatase; D000085242:Viral Proteases
chemical_list: D020413:3' Untranslated Regions; D048868:Adaptor Proteins, Signal Transducing; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D050835:Interferon Regulatory Factors; D000072640:Interferon-Induced Helicase, IFIH1; D007372:Interferons; D018160:Receptors, Cytoplasmic and Nuclear; D011971:Receptors, Immunologic; D012697:Serine Endopeptidases; D017361:Viral Nonstructural Proteins; C505371:MAVS protein, human; C084422:NS3 protein, hepatitis C virus; D043583:Nucleoside-Triphosphatase; D000085242:Viral Proteases; C452820:RIGI protein, human; C452815:IFIH1 protein, human
keywords: HCV; Innate immunity; Interferon; MDA5