Elucidating the role of lipids in positive-sense RNA virus infection.

• Applicant: Professorin Dr. Eva Herker
• Subject Area: Virology
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 416701689

Intracellular pathogens critically depend on host cell metabolic pathways for replication and/or persistent infection. We hypothesize that positive-sense RNA viruses require common lipid metabolic pathways for their replication. Hepatitis C virus (HCV) replication depends on cholesterol ester and triglyceride biosynthesis as well as de novo cholesterol and fatty acid synthesis. The HCV RNA is replicated by RNA replication complexes within ER-derived membrane structures termed the membranous web that is detergent-resistant due to the presence of lipids that are associated with lipid microdomains, namely cholesterol and sphingolipids. Importantly, inhibition of cholesterol and sphingomyelin biosynthesis suppresses viral RNA replication in cells and cholesterol-lowering agents such as statins may be beneficial for therapeutic success. In addition, fatty acid synthase (FASN) enzymatic activity is required for the creation of altered membrane structures in the replication cycle of Flaviviridae family members including HCV, dengue virus (DENV), yellow fever virus (YFV), Usutu virus (USUV), and West Nile virus (WNV). Accordingly, inhibition of FASN leads to a drastic inhibition of viral replication. However, the precise changes in the lipid metabolism of mammalian cells infected with different members of the Flaviviridae family are currently unknown. We recently investigated in-depth the HCV-induced changes in the lipid composition and performed quantitative shotgun lipidomic studies of whole cell extracts and subcellular compartments. Our results indicate that HCV infection reduces the ratio of neutral to membrane lipids. In addition, HCV-infected cells had a higher relative abundance of phosphatidylcholines and triglycerides with longer fatty acyl chains and a striking increased utilization of C18 fatty acids, most prominently oleic acid. Accordingly, depletion of fatty acid elongases and desaturases impaired HCV replication and/or assembly and release of particles. Taken together our preliminary results demonstrate the complex remodeling of the host cell lipid metabolism induced by HCV to enhance both virus replication and progeny production.Here, we propose to perform lipidomic studies of HCV-related viruses such as DENV, YFV, and Zika virus (ZIKV) to compare and contrast the metabolic rewiring by viruses of the Flaviviridae family. These studies will uncover similarities and differences in lipid remodeling that will be probed for their relevance for viral replication. Second, we will study in great mechanistic detail the function of specific fatty acid elongases and desaturases and their enzymatic products in the formation of viral RNA replication vesicles. The final aim will elucidate the role of polyunsaturated fatty acids in virion morphogenesis.

• DFG Programme: Research Grants