title: Hepatitis C virus infection suppresses GLUT2 gene expression via downregulation of hepatocyte nuclear factor 1α.
abstract: Hepatitis C virus (HCV) infection causes not only intrahepatic diseases but also extrahepatic manifestations, including type 2 diabetes. We previously reported that HCV replication suppresses cellular glucose uptake by downregulation of cell surface expression of glucose transporter 2 (GLUT2) (D. Kasai et al., J. Hepatol. 50:883-894, 2009). GLUT2 mRNA levels were decreased in both HCV RNA replicon cells and HCV J6/JFH1-infected cells. To elucidate molecular mechanisms of HCV-induced suppression of GLUT2 gene expression, we analyzed transcriptional regulation of the GLUT2 promoter using a series of GLUT2 promoter-luciferase reporter plasmids. HCV-induced suppression of GLUT2 promoter activity was abrogated when the hepatocyte nuclear factor 1α (HNF-1α)-binding motif was deleted from the GLUT2 promoter. HNF-1α mRNA levels were significantly reduced in HCV J6/JFH1-infected cells. Furthermore, HCV infection remarkably decreased HNF-1α protein levels. We assessed the effects of proteasome inhibitor or lysosomal protease inhibitors on the HCV-induced reduction of HNF-1α protein levels. Treatment of HCV-infected cells with a lysosomal protease inhibitor, but not with a proteasome inhibitor, restored HNF-1α protein levels, suggesting that HCV infection promotes lysosomal degradation of HNF-1α protein. Overexpression of NS5A protein enhanced lysosomal degradation of HNF-1α protein and suppressed GLUT2 promoter activity. Immunoprecipitation analyses revealed that the region from amino acids 1 to 126 of the NS5A domain I physically interacts with HNF-1α protein. Taken together, our results suggest that HCV infection suppresses GLUT2 gene expression via downregulation of HNF-1α expression at transcriptional and posttranslational levels. HCV-induced downregulation of HNF-1α expression may play a crucial role in glucose metabolic disorders caused by HCV.
authors.affiliation: Division of Microbiology, Center for Infectious Diseases, Kobe University Graduate School of Medicine, Chuo-ku, Kobe, Hyogo, Japan.
authors.forename: Chieko
authors.initials: C
authors.lastname: Matsui
authors.forename: Ikuo
authors.initials: I
authors.lastname: Shoji
authors.forename: Shusaku
authors.initials: S
authors.lastname: Kaneda
authors.forename: Imelda Rosalyn
authors.initials: IR
authors.lastname: Sianipar
authors.forename: Lin
authors.initials: L
authors.lastname: Deng
authors.forename: Hak
authors.initials: H
authors.lastname: Hotta
mesh_terms: D000704:Analysis of Variance; D000911:Antibodies, Monoclonal; D045744:Cell Line, Tumor; D017931:DNA Primers / Q000235:genetics; D005786:Gene Expression Regulation / Q000235:genetics*; D005947:Glucose / Q000378:metabolism; D051273:Glucose Transporter Type 2 / Q000235:genetics / Q000378:metabolism*; D006526:Hepatitis C / Q000503:physiopathology*; D051538:Hepatocyte Nuclear Factor 1-alpha / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D008156:Luciferases; D008247:Lysosomes / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D059748:Proteolysis; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017361:Viral Nonstructural Proteins / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase
chemical_list: D000911:Antibodies, Monoclonal; D017931:DNA Primers; D005947:Glucose; D051273:Glucose Transporter Type 2; D051538:Hepatocyte Nuclear Factor 1-alpha; D008156:Luciferases; D017361:Viral Nonstructural Proteins; C495680:SLC2A2 protein, human; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase