Viruses are defined as obligate intracellular parasites that rely entirely on host cell metabolic machinery during replication. The viral replication causes various alterations in cellular metabolic pathways to provide energy and macromolecules required for the production of viral progeny. Alterations in virus-infected cells often resemble those occurring in cancer cells as both are characterized by a high rate of anabolic reactions.
Over the last few decades, there have been published many studies investigating the virus-host interactions in cells infected with both RNA and DNA viruses. However, not much is known about this kind of interaction in the case of the Arenaviridae family, which comprises dangerous pathogens causing hemorrhagic fever, such as the Lassa, Junín, and Machupo virus. Our research focuses on the alterations in cells infected with lymphocytic choriomeningitis virus (LCMV), a prototypic arenavirus. Since lipids play an important role during infection with almost all viruses, we chose to analyze the impact of LCMV infection on lipid metabolism. The first objective was to analyze the gene expression of genes encoding lipogenic enzymes in mock and LCMV-infected cells. Then, we used pharmacological inhibitors to inhibit two of the analyzed enzymes and examined the impact they had on the production of new virions. Lastly, we investigated the mechanisms responsible for regulating the observed changes.
The transcriptional analysis revealed that LCMV infection increases the expression of genes coding for lipogenic enzymes at later stages of infection. This suggests that lipids may play a role during the LCMV life cycle. When we pharmacologically inhibited acetyl-CoA carboxylase (ACC), a rate-limiting enzyme catalyzing fatty acid synthesis, we observed a 20-fold reduction in LCMV titer. Additionally, inhibition of fatty acid synthase (FASN) showed similar results, which highlights the importance of de novo synthesized fatty acids during the synthesis of new LCMV infectious virions. The analysis of regulation on the transcriptional level showed that the expression of genes encoding lipogenic enzymes is at least partially regulated by sterol regulated element-binding protein (SREBP) as we observed an increase in its activity at later stages of the infection. Furthermore, we discovered that LCMV regulates ACC activity by impairing AMP-activated protein kinase (AMPK) phosphorylation.
Our results shed light on the importance of lipids, particularly fatty acids, during LCMV replication in human cells. Fatty acids have many roles, such as posttranslational modifications, energy storage, and phospholipid membrane synthesis. Therefore, it is important to conduct further analysis and acquire a more detailed understanding of the requirements for the completion of the arenavirus life cycle.
This project was supported by VEGA 2/0030/19 grant.