Acetyl-CoA carboxylase is important for lymphocytic choriomeningitis virus replication in A549 cells

Due to their parasitic nature, viruses are entirely dependent on the host cell's metabolic machinery, which provides building blocks and energy for newly synthesized virions during viral replication. After entry into the cell, viruses induce alterations in cellular metabolism to support their replication, which is a high energy-demanding process. Studies on viruses belonging to various families showed that every virus induces different changes, therefore, needs to be studied individually. Virus-host metabolic interactions in the case of lymphocytic choriomeningitis virus (LCMV) remain an unexplored field. LCMV is the prototypic member of the Arenaviridae family, which comprises viral hemorrhagic fever-causing pathogens such as Lassa, Junín, Machupo, and Guanarito viruses. As lipids play an important role during infection with various viruses, our research focuses on the impact of LCMV on the lipid metabolism of host cells. Specifically, this study explores the importance of acetyl-CoA carboxylase (ACC), a rate-limiting enzyme of fatty acid synthesis, during LCMV replication. ACC catalyzes the conversion of citrate-derived acetyl-CoA to malonyl-CoA, both of which are used to yield palmitate in the next step. Palmitate is the simplest fatty acid that can undergo elongation and form more complex lipids, which play important roles during the viral life cycle, such as energy storage, phospholipid membrane building blocks, posttranslational protein modification, etc. Our previous results showed that LCMV infection increases ACC expression in MRC-5 cells, as well as that pharmacological inhibition of this enzyme causes a 95% decrease in LCMV propagation, showing that ACC activity is needed during LCMV replication. To confirm these results on the genetic level, we used CRICPR/Cas9 system to delete the ACC gene in A549 cells as MRC-5 cells did not survive ACC knockout. First, we analyzed ACC on the transcriptional level in A549 cells to verify whether LCMV infection also affects ACC expression in this cell line. Since we observed an increase in ACC expression in LCMV-infected A549 cells, we further analyzed ACC activity. One of the ways of regulating ACC is by phosphorylation, which inhibits its activity, therefore, we performed protein analysis of total ACC and phosphorylated ACC (p-ACC) levels in A549 cells infected with LCMV. Levels of p-ACC in LCMV-infected cells were decreased at 6, 8, 24, 36, 48, and 60 hours post-infection compared to mock-infected cells, confirming that LCMV requires ACC activity at different stages of infection. Finally, the CRISPR/Cas9-mediated ACC knockout inhibited the propagation of LCMV in A549 cells by ~75%, confirming that ACC-catalyzed reactions are needed for successful LCMV replication. In addition to prior findings from MRC-5 cells, the results acquired during this study revealed the requirement for ACC in another cell line, demonstrating that lipid synthesis is needed for LCMV replication. Host-targeted antiviral drugs are an alternative approach to treating viral infections as virus-targeted antivirals often cause rapid generation of drug-resistant viruses. To date, there are no FDA-approved antiviral drugs available for treating infections caused by arenaviruses. Our results suggest that antiviral drugs targeting components of cellular lipid metabolism may represent a candidate for treating arenavirus infections.