PROJECT SUMMARY Human cytomegalovirus (HCMV) is a herpesvirus that causes disease and death in theimmunocompromised and is a leading cause of congenital disabilities. HCMV replication requires lipids.Since HCMV does not encode a metabolic network virus replication depends on host lipid metabolism.However little is known about how HCMV reprograms host metabolism to ensure lipids required for virusreplication are made. Our overall goal is to understand the virus-host interactions that regulate lipid synthesisessential for HCMV replication. Recently we showed that HCMV infection results in an increase in lipidsynthesis and a rise in lipid abundances. Here we demonstrate that HCMV infection induces the synthesis ofat least 20 previously undescribed lipids unique to infected cells. Most of these unique lipids are phospholipidswith very long-chain fatty acid tails (PL-VLCFAs). The PL-VLCFAs discussed in this application areunderstudied in general and unstudied in HCMV biology beyond our work. While shorter FA tails have beenwell-studied we know little about lipids with VLCFAs tails that are as long as those we observe in HCMVinfection including how they will behave in a biological membrane. The molecular mechanisms underlying thisHCMV-induced expansion in the host lipidome and the functional roles of the newly generated lipids arelargely unknown. We discovered that HCMV pUL37x1 and pUL38 proteins promote PL-VLCFA synthesis laying thefoundation for understanding the mechanisms by which HCMV reprograms lipid synthesis. pUL37x1 andpUL38 induce Ca2+ and mTOR signaling respectively. We have preliminary data suggesting that stressresponses related to these signaling pathways contribute to HCMV remodeling of lipids. We hypothesize thatpUL37x1 and pUL38 use Ca2+ and mTOR signaling to promote the synthesis of PC-VLCFAs required forHCMV replication. We will test this hypothesis by determining the mechanisms by which pUL37x1 and pUL38promote synthesis of PL-VLCFAs (Aim 1) and defining the PL-VLCFA synthesis enzymes required for HCMVreplication and the role of PL-VLCFAs in infection (Aim 2). These studies will determine the mechanisms bywhich HCMV interacts with the host to create a unique lipid environment advancing our knowledge of HCMVreprogramming of metabolism. Furthermore these studies will define the biological functions of PC-VLCFAsin HCMV replication and further our understanding of lipids required for HCMV infection. Determining themechanisms involved in HCMV-induced reprogramming of lipid metabolism and functions of PC-VLCFAs willadvance knowledge in HCMV biology needed to identify new targets for treating infection.