title: Hepatitis C virus nonstructural protein 5A inhibits thapsigargin-induced apoptosis.
abstract: BACKGROUND
  We previously reported that the hepatitis C virus (HCV) nonstructural protein 5A (NS5A) down-regulates TLR4 signaling and lipopolysaccharide-induced apoptosis of hepatocytes. There have been several reports regarding the association between HCV infection and endoplasmic reticulum (ER) stress. Here, we examined the regulation of HCV NS5A on the apoptosis of hepatocytes induced by thapsigargin, an inducer of ER stress.
  
  
  METHODS
  The apoptotic response to thapsigargin and the expression of molecules involved in human hepatocyte apoptotic pathways were examined in the presence or absence of HCV NS5A expression.
  
  
  RESULTS
  HCV JFH1 infection induced ER stress in the Huh7 cell line. HCV NS5A protected HepG2 cells against thapsigargin-induced apoptosis, the effect of which was linked to the enhanced expression of the 78-kDa glucose-regulated protein/immunoglobulin heavy-chain binding protein (GRP78). Consistent with a conferred pro-survival advantage, HCV NS5A reduced poly(adenosine diphosphate-ribose) polymerase cleavage and activation of caspases-3, -7 and -9, and Bax expression, while increasing the expressions of the anti-apoptotic molecules XIAP and c-FLIP. HCV NS5A weakly interacts with GRP78 and enhances GRP78 expression in hepatocytes.
  
  
  CONCLUSIONS
  HCV NS5A enhances GRP78 expression, resulting in the inhibition of apoptotic properties, and inhibits thapsigargin-induced apoptotic pathways in human hepatocytes, suggesting that disruption of ER stress-mediated apoptosis may have a role in the pathogenesis of HCV infection. Thus, HCV NS5A might engender the survival of HCV-infected hepatocytes contributing to the establishment of persistent infection.
authors.affiliation: Department of Gastroenterology and Nephrology, Chiba University, Graduate School of Medicine, Chiba, Japan.
authors.forename: Xia
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Department of Gastroenterology and Nephrology, Chiba University, Graduate School of Medicine, Chiba, Japan.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Kanda
authors.affiliation: Department of Gastroenterology and Nephrology, Chiba University, Graduate School of Medicine, Chiba, Japan.
authors.forename: Shuang
authors.initials: S
authors.lastname: Wu
authors.affiliation: Department of Molecular Virology, Chiba University, Graduate School of Medicine, Chiba, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Nakamoto
authors.affiliation: Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Takaji
authors.initials: T
authors.lastname: Wakita
authors.affiliation: Department of Molecular Virology, Chiba University, Graduate School of Medicine, Chiba, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shirasawa
authors.affiliation: Department of Gastroenterology and Nephrology, Chiba University, Graduate School of Medicine, Chiba, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Yokosuka
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects*; D001483:Base Sequence; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002460:Cell Line; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D056945:Hep G2 Cells; D016174:Hepacivirus / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase
chemical_list: D053148:Caspase 3; D053179:Caspase 7; D053453:Caspase 9; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D011065:Poly(ADP-ribose) Polymerases; D034741:RNA, Small Interfering; D019284:Thapsigargin; D017361:Viral Nonstructural Proteins; D051028:bcl-2-Associated X Protein; C000717247:HSPA5 protein, human; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase