Kaposi sarcoma herpesvirus vFLIP induces lipid droplet formation in Tert-immortalized microvascular endothelial cells via NF-κB activation
Kaposi sarcoma herpesvirus (KSHV) is the etiologic agent of Kaposi sarcoma (KS) and preferentially establishes a latent infection state in both the characteristic spindle cells of the KS tumor and cultured endothelial cells. KSHV has been described to broadly alter cellular metabolism during latent infection of endothelial cells. In Tert-immortalized microvascular endothelial (TIME) cells, our lab has shown that latent infection increases the abundance of long chain fatty acids in the cell, as well as formation of lipid droplets, which is dependent on viral gene expression. Here, we show that acyl-CoA synthetase activity, crucial for lipid droplet formation, is essential for cell survival during latent infection of TIME cells. Expression of the major genetic locus expressed during KSHV latency is sufficient to induce lipid droplet formation. Virus mutants lacking expression of the latent viral gene vFLIP, or the expression of the latent viral microRNAs, do not induce lipid droplet formation. Expression of vFLIP in isolation is sufficient to induce lipid droplet formation and sensitivity to ACSL inhibition, but a mutant version of vFLIP with decreased NF-{kappa}B signaling capacity is unable to increase lipid droplet formation to the same degree as its wild-type counterpart. Lipid droplet formation is also limited in the context of co-expression with a mutant version of I{kappa}B resistant to degradation. We conclude that vFLIP drives the increase in lipid droplet formation observed during latent KSHV infection, in an NF-{kappa}B signaling dependent fashion and that ACSL function is important for the survival of latently infected endothelial cells.