Increased phosphoenolpyruvate carboxykinase gene expression and steatosis during hepatitis C virus subgenome replication: role of nonstructural component 5A and CCAAT/enhancer-binding protein β

J Biol Chem. 2012 Oct 26;287(44):37340-51. doi: 10.1074/jbc.M112.384743. Epub 2012 Sep 6.

Abstract

Chronic hepatitis C virus (HCV) infection greatly increases the risk for type 2 diabetes and nonalcoholic steatohepatitis; however, the pathogenic mechanisms remain incompletely understood. Here we report gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) transcription and associated transcription factors are dramatically up-regulated in Huh.8 cells, which stably express an HCV subgenome replicon. HCV increased activation of cAMP response element-binding protein (CREB), CCAAT/enhancer-binding protein (C/EBPβ), forkhead box protein O1 (FOXO1), and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and involved activation of the cAMP response element in the PEPCK promoter. Infection with dominant-negative CREB or C/EBPβ-shRNA significantly reduced or normalized PEPCK expression, with no change in PGC-1α or FOXO1 levels. Notably, expression of HCV nonstructural component NS5A in Huh7 or primary hepatocytes stimulated PEPCK gene expression and glucose output in HepG2 cells, whereas a deletion in NS5A reduced PEPCK expression and lowered cellular lipids but was without effect on insulin resistance, as demonstrated by the inability of insulin to stimulate mobilization of a pool of insulin-responsive vesicles to the plasma membrane. HCV-replicating cells demonstrated increases in cellular lipids with insulin resistance at the level of the insulin receptor, increased insulin receptor substrate 1 (Ser-312), and decreased Akt (Ser-473) activation in response to insulin. C/EBPβ-RNAi normalized lipogenic genes sterol regulatory element-binding protein-1c, peroxisome proliferator-activated receptor γ, and liver X receptor α but was unable to reduce accumulation of triglycerides in Huh.8 cells or reverse the increase in ApoB expression, suggesting a role for increased lipid retention in steatotic hepatocytes. Collectively, these data reveal an important role of NS5A, C/EBPβ, and pCREB in promoting HCV-induced gluconeogenic gene expression and suggest that increased C/EBPβ and NS5A may be essential components leading to increased gluconeogenesis associated with HCV infection.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CCAAT-Enhancer-Binding Protein-beta / genetics
  • CCAAT-Enhancer-Binding Protein-beta / metabolism
  • CCAAT-Enhancer-Binding Protein-beta / physiology*
  • Cell Line, Tumor
  • Cyclic AMP Response Element-Binding Protein / metabolism
  • Diabetes Mellitus, Type 2 / virology
  • Enzyme Induction
  • Fatty Liver / enzymology
  • Fatty Liver / virology*
  • Forkhead Box Protein O1
  • Forkhead Transcription Factors / genetics
  • Forkhead Transcription Factors / metabolism
  • Genes, Reporter
  • Genome, Viral*
  • Gluconeogenesis / genetics
  • Glucose / metabolism
  • Glucose-6-Phosphatase / genetics
  • Glucose-6-Phosphatase / metabolism
  • Hepacivirus / genetics*
  • Hepacivirus / physiology
  • Humans
  • Insulin / physiology
  • Lipid Metabolism / genetics
  • Luciferases / biosynthesis
  • Luciferases / genetics
  • Phosphoenolpyruvate Carboxykinase (GTP) / genetics*
  • Phosphoenolpyruvate Carboxykinase (GTP) / metabolism
  • Promoter Regions, Genetic
  • Rats
  • Secretory Vesicles / metabolism
  • Signal Transduction
  • Viral Nonstructural Proteins / physiology*
  • Virus Replication

Substances

  • CCAAT-Enhancer-Binding Protein-beta
  • CEBPB protein, human
  • CREB1 protein, human
  • Cyclic AMP Response Element-Binding Protein
  • FOXO1 protein, human
  • Forkhead Box Protein O1
  • Forkhead Transcription Factors
  • Insulin
  • Viral Nonstructural Proteins
  • Luciferases
  • NS-5 protein, hepatitis C virus
  • Glucose-6-Phosphatase
  • Phosphoenolpyruvate Carboxykinase (GTP)
  • Glucose