title: The AMPK-related kinase SNARK regulates hepatitis C virus replication and pathogenesis through enhancement of TGF-β signaling.
abstract: OBJECTIVE
  Hepatitis C virus (HCV) is a major cause of chronic liver disease worldwide. The biological and therapeutic importance of host cellular cofactors for viral replication has been recently appreciated. Here we examined the roles of SNF1/AMP kinase-related kinase (SNARK) in HCV replication and pathogenesis.
  
  
  METHODS
  The JFH1 infection system and the full-length HCV replicon OR6 cell line were used. Gene expression was knocked down by siRNAs. SNARK mutants were created by site-directed mutagenesis. Intracellular mRNA levels were measured by qRT-PCR. Endogenous and overexpressed proteins were detected by Western blot analysis and immunofluorescence. Transforming growth factor (TGF)-β signaling was monitored by a luciferase reporter construct. Liver biopsy samples from HCV-infected patients were analyzed for SNARK expression.
  
  
  RESULTS
  Knockdown of SNARK impaired viral replication, which was rescued by wild type SNARK but not by unphosphorylated or kinase-deficient mutants. Knockdown and overexpression studies demonstrated that SNARK promoted TGF-β signaling in a manner dependent on both its phosphorylation and kinase activity. In turn, chronic HCV replication upregulated the expression of SNARK in patients. Further, the SNARK kinase inhibitor metformin suppressed both HCV replication and SNARK-mediated enhancement of TGF-β signaling.
  
  
  CONCLUSIONS
  Thus reciprocal regulation between HCV and SNARK promotes TGF-β signaling, a major driver of hepatic fibrogenesis. These findings suggest that SNARK will be an attractive target for the design of novel host-directed antiviral and antifibrotic drugs.
authors.affiliation: Gastrointestinal Unit, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA; The Advanced Clinical Research Center, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan; Japan Society for the Promotion of Science, Tokyo 102-8472, Japan.
authors.forename: Kaku
authors.initials: K
authors.lastname: Goto
authors.forename: Wenyu
authors.initials: W
authors.lastname: Lin
authors.forename: Leiliang
authors.initials: L
authors.lastname: Zhang
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Jilg
authors.forename: Run-Xuan
authors.initials: RX
authors.lastname: Shao
authors.forename: Esperance A K
authors.initials: EA
authors.lastname: Schaefer
authors.forename: Hong
authors.initials: H
authors.lastname: Zhao
authors.forename: Dahlene N
authors.initials: DN
authors.lastname: Fusco
authors.forename: Lee F
authors.initials: LF
authors.lastname: Peng
authors.forename: Naoya
authors.initials: N
authors.lastname: Kato
authors.forename: Raymond T
authors.initials: RT
authors.lastname: Chung
mesh_terms: D001706:Biopsy; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects; D016174:Hepacivirus / Q000502:physiology*; D006526:Hepatitis C / Q000209:etiology* / Q000503:physiopathology; D006801:Humans; D008099:Liver / Q000473:pathology / Q000821:virology; D008687:Metformin / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000502:physiology*; D014779:Virus Replication / Q000502:physiology*
chemical_list: D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D016212:Transforming Growth Factor beta; D008687:Metformin; C486061:NUAK2 protein, human; D017346:Protein Serine-Threonine Kinases
keywords: CsA; Fibrosis; HCC; HCV; HTAs; JFH1; Japanese fulminant hepatitis 1; Kinase; Metformin; NUAK2; SMAD; SNARK; SVR; TGF-beta; TGF-β; cyclosporin A; hepatocellular carcinoma; host-targeting antivirals; sucrose-non-fermenting protein kinase 1/AMP-activated protein kinase-related protein kinase; sustained virological response; transforming growth factor beta