title: Human subtilase SKI-1/S1P is a master regulator of the HCV Lifecycle and a potential host cell target for developing indirect-acting antiviral agents.
abstract: HCV infection is a major risk factor for liver cancer and liver transplantation worldwide. Overstimulation of host lipid metabolism in the liver by HCV-encoded proteins during viral infection creates a favorable environment for virus propagation and pathogenesis. In this study, we hypothesize that targeting cellular enzymes acting as master regulators of lipid homeostasis could represent a powerful approach to developing a novel class of broad-spectrum antivirals against infection associated with human Flaviviridae viruses such as hepatitis C virus (HCV), whose assembly and pathogenesis depend on interaction with lipid droplets (LDs). One such master regulator of cholesterol metabolic pathways is the host subtilisin/kexin-isozyme-1 (SKI-1)--or site-1 protease (S1P). SKI-1/S1P plays a critical role in the proteolytic activation of sterol regulatory element binding proteins (SREBPs), which control expression of the key enzymes of cholesterol and fatty-acid biosynthesis. Here we report the development of a SKI-1/S1P-specific protein-based inhibitor and its application to blocking the SREBP signaling cascade. We demonstrate that SKI-1/S1P inhibition effectively blocks HCV from establishing infection in hepatoma cells. The inhibitory mechanism is associated with a dramatic reduction in the abundance of neutral lipids, LDs, and the LD marker: adipose differentiation-related protein (ADRP)/perilipin 2. Reduction of LD formation inhibits virus assembly from infected cells. Importantly, we confirm that SKI-1/S1P is a key host factor for HCV infection by using a specific active, site-directed, small-molecule inhibitor of SKI-1/S1P: PF-429242. Our studies identify SKI-1/S1P as both a novel regulator of the HCV lifecycle and as a potential host-directed therapeutic target against HCV infection and liver steatosis. With identification of an increasing number of human viruses that use host LDs for infection, our results suggest that SKI-1/S1P inhibitors may allow development of novel broad-spectrum biopharmaceuticals that could lead to novel indirect-acting antiviral options with the current standard of care.
authors.affiliation: Department of Microbiology and Immunology, Life Sciences Centre, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Andrea D
authors.initials: AD
authors.lastname: Olmstead
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Knecht
authors.forename: Ina
authors.initials: I
authors.lastname: Lazarov
authors.forename: Surjit B
authors.initials: SB
authors.lastname: Dixit
authors.forename: François
authors.initials: F
authors.lastname: Jean
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology* / Q000627:therapeutic use; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000096:biosynthesis / Q000235:genetics; D015195:Drug Design; D005227:Fatty Acids / Q000096:biosynthesis / Q000235:genetics; D005234:Fatty Liver / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D016174:Hepacivirus / Q000502:physiology*; D006526:Hepatitis C / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D000070780:Perilipin-2; D043484:Proprotein Convertases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D059748:Proteolysis / Q000187:drug effects; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D051779:Sterol Regulatory Element Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019065:Virus Assembly / Q000187:drug effects* / Q000502:physiology
chemical_list: D000998:Antiviral Agents; D005227:Fatty Acids; D008565:Membrane Proteins; C000602982:PLIN2 protein, human; D000070780:Perilipin-2; D011480:Protease Inhibitors; D051779:Sterol Regulatory Element Binding Proteins; D002784:Cholesterol; D043484:Proprotein Convertases; D012697:Serine Endopeptidases; C115575:membrane-bound transcription factor peptidase, site 1