The hepatitis C virus (HCV) epidemic is a global health problem and affects ~170 million people worldwide. In ~80% of cases, viral infection becomes chronic, rendering HCV a leading cause of liver-related morbidity and mortality. A common symptom of chronic HCV infection is steatosis, the abnormal accumulation of lipid droplets in the liver. Steatosis is observed in ~55% of chronically HCV-infected patients and represents an important risk factor for the development of liver fibrosis and cancer. The viral nucleocapsid core expressed in livers of transgenic mice recapitulates this condition; core itself also localizes to the surface of lipid droplets (LDs), a process critical for the assembly of progeny virions at membranes in close proximity to LDs. We recently identified the triglyceride-synthesizing enzyme DGAT1 as a novel host factor for HCV assembly (Herker et al, Nat. Med. 2010). In cells lacking DGAT1 or treated with a DGAT1 inhibitor, core cannot localize to LDs and cannot recruit viral RNA to neighboring endoplasmic reticulum membranes for encapsidation. As a consequence, HCV particle production is severely impaired. We recently published three additional studies that demonstrate 1) that a second HCV protein, NS5A, interacts with DGAT1 and requires DGAT1 for LD localization (Camus et al, J. Biol. Chem. 2013), 2) that core at the surface of LDs decreases the lipolysis of these LDs, thereby causing steatosis (Harris, Herker et al, J. Biol. Chem. 2012), and 3) that LDs play a larger role in HCV infection with a new involvement in HCV RNA replication via a new interaction between the LD- associated protein TIP47 and NS5A (Vogt et al, PLoS Pathog. 2013). We seek to study in molecular detail the role of LDs as critical host organelles in the HCV lifecycle. We propose three experiments. 1) To define the role of DGAT1 in recruiting HCV proteins to LDs. We will test the hypothesis that a tripartite complex of DGAT1, NS5A and core has evolved to co-recruit core and NS5A to DGAT1-generated LDs. We will also determine if NS5A and core are new protein targets for the acyltransferase activity of DGAT1. 2) To determine how the HCV core protein inhibits lipolysis. We will test whether core at the surface of LDs interferes with the recruitment or activity of the triglyceride lipases ATGL/PNPLA2 and PNPLA3, thus inhibiting lipolysis. Because patients infected with different HCV genotypes are at different risks to develop steatosis, we will compare anti-lipolytic activities of core proteins from different viral genotypes. 3) To explore how the NS5A-TIP47 interaction regulates HCV RNA replication. We will determine if LDs serve a dual role in HCV infection: one as membrane and energy sources for HCV RNA replication and another as assembly platforms. We will determine whether binding of NS5A to TIP47 plays an important role in this process. Collectively, our proposed studies will bring new molecular insight into the role of LDs in the HCV lifecycle and may uncover potential novel therapeutic strategies to treat chronic HCV disease.

Public Health Relevance

We seek to identify and characterize novel regulatory mechanisms controlling Hepatitis C Virus (HCV) infection that might be exploited as new therapeutic targets. Our proposed studies characterize the role of lipid droplets in the HCV life cycle. These studies are directly relevant to HCV pathogenesis and may contribute to the development of novel antiviral drugs that will address public need.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Koshy, Rajen
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J. David Gladstone Institutes
San Francisco
United States
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Fontaine, Krystal A; Leon, Kristoffer E; Khalid, Mir M et al. (2018) The Cellular NMD Pathway Restricts Zika Virus Infection and Is Targeted by the Viral Capsid Protein. MBio 9:
Meyers, Nathan L; Fontaine, Krystal A; Kumar, G Renuka et al. (2016) Entangled in a membranous web: ER and lipid droplet reorganization during hepatitis C virus infection. Curr Opin Cell Biol 41:117-24
Khan, Shahzada; Woodruff, Erik M; Trapecar, Martin et al. (2016) Dampened antiviral immunity to intravaginal exposure to RNA viral pathogens allows enhanced viral replication. J Exp Med 213:2913-2929
Ramage, Holly R; Kumar, G Renuka; Verschueren, Erik et al. (2015) A combined proteomics/genomics approach links hepatitis C virus infection with nonsense-mediated mRNA decay. Mol Cell 57:329-340
Camus, Gregory; Schweiger, Martina; Herker, Eva et al. (2014) The hepatitis C virus core protein inhibits adipose triglyceride lipase (ATGL)-mediated lipid mobilization and enhances the ATGL interaction with comparative gene identification 58 (CGI-58) and lipid droplets. J Biol Chem 289:35770-80