HCMV infection dramatically alters glucose and glutamine metabolism. The hypothesis of this proposal is that HCMV induces adipocyte-like differentiation in infected cells in order to allow glucose to be used synthetically for the production of fatty acids and lipids which are known to be essential for HCMV replication. This requires the activation of lipogenic genes, increased glucose and glutamine uptake and the use of glutamine to maintain the tricarboxylic acid (TCA) cycle. Our data show that glutamine is essential for maintenance of the TCA cycle during HCMV infection. This is done in a manner that is very similar to many tumor cells in which glucose is used synthetically and glutamine must be used to maintain the TCA cycle. In tumor cells the program for this use of glutamine is activated by c-Myc; our preliminary data suggest that this is also the case in HCMV infected cells. Adipocyte differentiation and the activation of lipogenic genes have previously been shown to be mediated by PKR-like endoplasmic reticulum kinase (PERK), an ER-resident sensor that is activated by endoplasmic reticulum stress, specifically the unfolded protein response (UPR). Our published and preliminary studies of HCMV-mediated effects on the UPR suggest that PERK is activated by HCMV infection and induces an adipocyte-like differentiation program.
The specific aims are: 1) Determine the role of PERK in the induction of lipid biosynthesis and adipocyte-like differentiation in HCMV infected human fibroblasts. 2) Determine the role of c-Myc in the induction of glutamine utilization for the maintenance of the TCA cycle in infected cells. 3) Use murine cytomegalovirus (MCMV) to further assess the roles of PERK and c-Myc in inducing lipid biogenesis and the utilization of glutamine to maintain the TCA cycle. Here we will expand the studies using MCMV with the many mouse embryo fibroblast lines with genes of interest for Aims 1 and 2 knocked out or conditionally knocked out. This approach not only provides a means to verify the studies with HCMV, but also a means to address questions that would be more difficult, or impossible, in the human system. Accomplishing the aims will shift current research toward the concept that viruses like HCMV must dramatically alter cellular metabolism and that they accomplish this by integrating mechanisms for manipulating cellular signaling and stress responses.
In order to better understand the molecular pathogenesis of human cytomegalovirus (HCMV) it is essential to determine the means by which the virus alters key cellular functions such as cellular metabolism. Such understanding will elucidate new aspects of HCMV virology and pathogenesis, help clarify HCMVs potential role in transformation and will highlight new targets for therapeutic intervention in HCMV disease.
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