Metabolites that feed upper glycolytic branches support glucose independent human cytomegalovirus replication

Abstract

The broad tissue distribution and cell tropism of human cytomegalovirus indicates that the virus successfully replicates in tissues with various nutrient environments. HCMV requires and reprograms central carbon metabolism for viral replication. However, many studies focus on reprogramming of metabolism in high nutrient conditions that do not recapitulate physiological nutrient environments in the body. In this study, we investigate how HCMV successfully replicates when nutrients are suboptimal. We limited glucose following HCMV infection to determine how glucose supports virus replication and how nutrients potentially present in the physiological environment contribute to successful glucose independent HCMV replication. Glucose is required for HCMV viral genome synthesis, viral protein production and glycosylation, and virus production. However, supplement of glucose-free cultures with uridine, ribose, or UDP-GlcNAc--metabolites that support upper glycolytic branches--resulted in partially restored viral genome synthesis and subsequent partial restoration of viral protein levels. Low levels of virus production were also restored. Supplementing lower glycolysis in glucose-free cultures using pyruvate had no effect on virus replication. These results indicate nutrients that support upper glycolytic branches like the pentose phosphate pathway and hexosamine pathway can compensate for glucose during HCMV replication to support low levels of virus production. More broadly, our findings suggest that HCMV could successfully replicate in diverse metabolic niches, including those in the body with low levels of glucose, through alternative nutrient usage. IMPORTANCEThe metabolic environment is a determinant in the ability of a virus to successfully replicate. HCMV has broad cell tropism and replicates in various tissues that have diverse and/or limiting metabolic environments. We know that HCMV reprograms host central carbon metabolism to support viral replication, but we have little understanding of HCMV replication in diverse metabolic niches as most studies use high nutrient culture media. Here, we show that glucose limitation suppresses virus production through loss of viral genome synthesis and viral protein glycosylation. However, nutrient compensation by uridine, ribose, and UDP-GlcNAc, metabolites that fuel upper glycolytic branches such as the non-oxidative pentose phosphate pathway support low levels of glucose-independent virus production. Our work indicates that metabolite compensation may facilitate HCMV replication in nutrient limited niches in the body.