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Human Subtilisin Kexin Isozyme-1 (SKI-1)/Site-1 Protease (S1P) regulates cytoplasmic lipid droplet abundance: A potential target for indirect-acting anti-dengue virus agents.

ABSTRACT: Viral hijacking and manipulation of host-cell biosynthetic pathways by human enveloped viruses are shared molecular events essential for the viral lifecycle. For Flaviviridae members such as hepatitis C virus and dengue virus (DENV), one of the key subsets of cellular pathways that undergo manipulation is the lipid metabolic pathways, underlining the importance of cellular lipids and, in particular, lipid droplets (LDs) in viral infection. Here, we hypothesize that targeting cellular enzymes that act as key regulators of lipid homeostasis and LD formation could represent a powerful approach to developing a novel class of broad-spectrum antivirals against infection associated with all DENV serotypes (1-4) circulating around the world. Using PF-429242, an active-site-directed inhibitor of SKI-1/S1P, we demonstrate that inhibition of SKI-1/S1P enzymatic activity in human hepatoma Huh-7.5.1 cells results in a robust reduction of the LD numbers and LD-positive areas and provides a means of effectively inhibiting infection by DENV (1-4). Pre-treatment of Huh-7.5.1 cells with PF-429242 results in a dose-dependent inhibition of DENV infection [median inhibitory dose (EC50) = 1.2 microM; median cytotoxic dose (CC50) = 81 microM; selectivity index (SI) = 68)] and a ~3-log decrease in DENV-2 titer with 20 microM of PF-429242. Post-treatment of DENV-2 infected Huh-7.5.1 cells with PF-429242 does not affect viral RNA abundance, but it does compromise the assembly and/or release of infectious virus particles. PF-429242 antiviral activity is reversed by exogenous oleic acid, which acts as an inducer of LD formation in PF-429242-treated and non-treated control cells. Collectively, our results demonstrate that human SKI-1/S1P is a potential target for indirect-acting pan-serotypic anti-DENV agents and reveal new therapeutic opportunities associated with the use of lipid-modulating drugs for controlling DENV infection.

SUBMITTER: Hyrina A

PROVIDER: S-EPMC5365115 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Human Subtilisin Kexin Isozyme-1 (SKI-1)/Site-1 Protease (S1P) regulates cytoplasmic lipid droplet abundance: A potential target for indirect-acting anti-dengue virus agents.

Hyrina Anastasia A Meng Fanrui F McArthur Steven J SJ Eivemark Sharlene S Nabi Ivan R IR Jean François F

PloS one 20170324 3

Viral hijacking and manipulation of host-cell biosynthetic pathways by human enveloped viruses are shared molecular events essential for the viral lifecycle. For Flaviviridae members such as hepatitis C virus and dengue virus (DENV), one of the key subsets of cellular pathways that undergo manipulation is the lipid metabolic pathways, underlining the importance of cellular lipids and, in particular, lipid droplets (LDs) in viral infection. Here, we hypothesize that targeting cellular enzymes tha ...[more]

PMID: 28339489

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Project description: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.

Dataset Information

Human Subtilisin Kexin Isozyme-1 (SKI-1)/Site-1 Protease (S1P) regulates cytoplasmic lipid droplet abundance: A potential target for indirect-acting anti-dengue virus agents.

Publications

Human Subtilisin Kexin Isozyme-1 (SKI-1)/Site-1 Protease (S1P) regulates cytoplasmic lipid droplet abundance: A potential target for indirect-acting anti-dengue virus agents.

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