title: Hepatitis C virus (HCV) constitutively activates STAT-3 via oxidative stress: role of STAT-3 in HCV replication.
abstract: The hepatitis C virus (HCV) causes chronic hepatitis, which often results in liver cirrhosis and hepatocellular carcinoma. We have previously shown that HCV nonstructural proteins induce activation of STAT-3 via oxidative stress and Ca2+ signaling (G. Gong, G. Waris, R. Tanveer, and A. Siddiqui, Proc. Natl. Acad. Sci. USA 98:9599-9604, 2001). In this study, we focus on the signaling pathway leading to STAT-3 activation in response to oxidative stress induced by HCV translation and replication activities. Here, we demonstrate the constitutive activation of STAT-3 in HCV replicon-expressing cells. The HCV-induced STAT-3 activation was inhibited in the presence of antioxidant (pyrrolidine dithiocarbamate) and Ca2+ chelators (BAPTA-AM and TMB-8). Previous studies have shown that maximum STAT-3 transactivation requires Ser727 phosphorylation in addition to tyrosine phosphorylation. Using a series of inhibitors and dominant negative mutants, we show that HCV-induced activation of STAT-3 is mediated by oxidative stress and influenced by the activation of cellular kinases, including p38 mitogen-activated protein kinase, JNK, JAK-2, and Src. Our results also suggest a potential role of STAT-3 in HCV RNA replication. We also observed the constitutive activation of STAT-3 in the liver biopsy of an HCV-infected patient. These studies provide an insight into the mechanisms by which HCV induces intracellular events relevant to liver pathogenesis associated with the viral infection.
authors.affiliation: Department of Microbiology and Program in Molecular Biology, University of Colorado HSC, 4200 East Ninth Ave., Denver, CO 80262, USA.
authors.forename: Gulam
authors.initials: G
authors.lastname: Waris
authors.forename: James
authors.initials: J
authors.lastname: Turkson
authors.forename: Tarek
authors.initials: T
authors.lastname: Hassanein
authors.forename: Aleem
authors.initials: A
authors.lastname: Siddiqui
mesh_terms: D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D016174:Hepacivirus / Q000472:pathogenicity* / Q000502:physiology; D019698:Hepatitis C, Chronic / Q000821:virology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D053614:Janus Kinase 2; D008099:Liver / Q000378:metabolism / Q000821:virology; D018384:Oxidative Stress; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D012093:Replicon; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism*; D014779:Virus Replication; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases