title: Ethanol and hepatitis C virus suppress peptide-MHC class I presentation in hepatocytes by altering proteasome function.
abstract: BACKGROUND
  Previously, we reported that exposure of hepatitis C virus (HCV) core-expressing ethanol (EtOH)-metabolizing cells to EtOH significantly suppresses proteasome activity which exists as 26S (20S and 19S) and as an unassociated 20S particle. The replacement of the constitutive proteasomal subunits with immunoproteasome (IPR) favors antigen processing. Here, we examined the effects of EtOH consumption by HCV core transgenic mice on proteasome activity in hepatocytic lysates and in partially purified 26S proteasome and the impact of these changes on antigen presentation.
  
  
  METHODS
  HCV (-)  and HCV (+)  core transgenic mice were fed chow diet with or without 20% (v/v) EtOH in water for 4 weeks. Following the feeding regimen, hepatocytes were isolated and examined for chymotrypsin-like proteasome activity, oxidative stress, and the presentation of SIINFEKL-H2Kb complex. Additionally, the constitutive proteasome and IPR were purified for further analysis and identification of proteasome-interacting proteins (PIPs).
  
  
  RESULTS
  EtOH significantly decreased proteasome activity in hepatocytes of HCV (+)  mice, and this finding correlated with oxidative stress and dysregulated methylation reactions. In isolated 26S proteasome, EtOH suppressed proteasome activity equally in HCV (+)  and HCV (-)  mice. EtOH feeding caused proteasome instability and lowered the content of both constitutive and IPR subunits in the 20S proteasome. In addition, the level of other PIPs, PA28 and UCHL5, were also suppressed after EtOH exposure. Furthermore, in EtOH-fed mice and, especially, in HCV (+)  mice, the presentation of SIINFEKL-H2Kb complex in hepatocytes was also decreased.
  
  
  CONCLUSIONS
  Proteasomal dysfunction induced by EtOH feeding and exacerbated by the presence of HCV structural proteins led to suppression of SIINFEKL-H2Kb presentation in hepatocytes.
authors.affiliation: Research Service, Veterans Affairs Nebraska-Western Iowa Health Care System, Omaha, Nebraska 68105, USA. nosna@unmc.edu
authors.forename: Natalia A
authors.initials: NA
authors.lastname: Osna
authors.forename: Fawzia
authors.initials: F
authors.lastname: Bardag-Gorce
authors.forename: Ronda L
authors.initials: RL
authors.lastname: White
authors.forename: Steven A
authors.initials: SA
authors.lastname: Weinman
authors.forename: Terrence M
authors.initials: TM
authors.lastname: Donohue
authors.forename: Kusum K
authors.initials: KK
authors.lastname: Kharbanda
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000187:drug effects; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D005805:Genes, MHC Class I / Q000187:drug effects*; D016174:Hepacivirus / Q000378:metabolism; D006526:Hepatitis C / Q000378:metabolism*; D022781:Hepatocytes / Q000187:drug effects* / Q000821:virology; D008297:Male; D008745:Methylation / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018384:Oxidative Stress / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000431:Ethanol; D046988:Proteasome Endopeptidase Complex