title: Targeting cellular squalene synthase, an enzyme essential for cholesterol biosynthesis, is a potential antiviral strategy against hepatitis C virus.
abstract: Hepatitis C virus (HCV) exploits host membrane cholesterol and its metabolism for progeny virus production. Here, we examined the impact of targeting cellular squalene synthase (SQS), the first committed enzyme for cholesterol biosynthesis, on HCV production. By using the HCV JFH-1 strain and human hepatoma Huh-7.5.1-derived cells, we found that the SQS inhibitors YM-53601 and zaragozic acid A decreased viral RNA, protein, and progeny production in HCV-infected cells without affecting cell viability. Similarly, small interfering RNA (siRNA)-mediated knockdown of SQS led to significantly reduced HCV production, confirming the enzyme as an antiviral target. A metabolic labeling study demonstrated that YM-53601 suppressed the biosynthesis of cholesterol and cholesteryl esters at antiviral concentrations. Unlike YM-53601, the cholesterol esterification inhibitor Sandoz 58-035 did not exhibit an antiviral effect, suggesting that biosynthesis of cholesterol is more important than that of cholesteryl esters for HCV production. YM-53601 inhibited transient replication of a JFH-1 subgenomic replicon and entry of JFH-1 pseudoparticles, suggesting that at least suppression of viral RNA replication and entry contributes to the antiviral effect of the drug. Collectively, our findings highlight the importance of the cholesterol biosynthetic pathway in HCV production and implicate SQS as a potential target for antiviral strategies against HCV.
  
  
  OBJECTIVE
  Hepatitis C virus (HCV) is known to be closely associated with host cholesterol and its metabolism throughout the viral life cycle. However, the impact of targeting cholesterol biosynthetic enzymes on HCV production is not fully understood. We found that squalene synthase, the first committed enzyme for cholesterol biosynthesis, is important for HCV production, and we propose this enzyme as a potential anti-HCV target. We provide evidence that synthesis of free cholesterol is more important than that of esterified cholesterol for HCV production, highlighting a marked free cholesterol dependency of HCV production. Our findings also offer a new insight into a role of the intracellular cholesterol pool that is coupled to its biosynthesis in the HCV life cycle.
authors.affiliation: Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Saito
authors.affiliation: Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan Graduate School of Biological Science, Tokyo University of Science, Chiba, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Shirasago
authors.affiliation: Department of Infectious Diseases, Hamamatsu University School of Medicine, Shizuoka, Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Aizaki
authors.affiliation: Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Hanada
authors.affiliation: Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan.
authors.forename: Takaji
authors.initials: T
authors.lastname: Wakita
authors.affiliation: Showa Pharmaceutical University, Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Nishijima
authors.affiliation: Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo, Japan fuka@nih.go.jp.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Fukasawa
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology*; D002460:Cell Line; D002784:Cholesterol / Q000096:biosynthesis*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D013186:Farnesyl-Diphosphate Farnesyltransferase / Q000037:antagonists & inhibitors*; D016174:Hepacivirus / Q000187:drug effects* / Q000502:physiology; D022781:Hepatocytes / Q000201:enzymology / Q000821:virology; D006801:Humans; D011812:Quinuclidines / Q000494:pharmacology*; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D000998:Antiviral Agents; D004791:Enzyme Inhibitors; D011812:Quinuclidines; C414830:YM 53601; D002784:Cholesterol; D013186:Farnesyl-Diphosphate Farnesyltransferase