Hepatitis C virus infection suppresses GLUT2 gene expression via downregulation of hepatocyte nuclear factor 1α

J Virol. 2012 Dec;86(23):12903-11. doi: 10.1128/JVI.01418-12. Epub 2012 Sep 19.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Antibodies, Monoclonal
  • Cell Line, Tumor
  • DNA Primers / genetics
  • Gene Expression Regulation / genetics*
  • Glucose / metabolism
  • Glucose Transporter Type 2 / genetics
  • Glucose Transporter Type 2 / metabolism*
  • Hepatitis C / physiopathology*
  • Hepatocyte Nuclear Factor 1-alpha / metabolism*
  • Humans
  • Immunoblotting
  • Immunoprecipitation
  • Luciferases
  • Lysosomes / metabolism
  • Plasmids / genetics
  • Promoter Regions, Genetic / genetics
  • Proteolysis
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • Viral Nonstructural Proteins / metabolism

Substances

  • Antibodies, Monoclonal
  • DNA Primers
  • Glucose Transporter Type 2
  • Hepatocyte Nuclear Factor 1-alpha
  • SLC2A2 protein, human
  • Viral Nonstructural Proteins
  • Luciferases
  • NS-5 protein, hepatitis C virus
  • Glucose