Manipulation of lipid metabolism in (+)RNA virus replication

All (+) RNA viruses modify cytoplasmic membranes, such as the endoplasmic reticulum (ER) to establish replication compartments (RCs). These RCs are thought to form a platform for membrane- associated replicases, in addition to protecting the viral RNAs from cytosolic RIG-I-like receptors that trigger innate immune signaling and RNA-degradation machinery. We and others have shown that a key component in the viral mechanism of RC formation is the modulation of RC membrane lipid composition. We previously published that at least 3 (+) RNA virus families (Bromoviridae, Picornaviridae, and Flaviviridae) share the property of stimulating phosphatidyl choline (PC) accumulation at RCs. This suggests that understanding viral modulation of PC synthesis may have broad implication as a conserved mechanism in RC formation. We have extended this observation to gain significant mechanistic insight into this process. The specific aims are: Aim 1. Define the contribution of PC synthesis for viral replication. We hypothesize the activation of PC synthesis aids the formation of viral RCs and may also impact virion infectivity via altered ER lipid composition. Aim 2. Define the mechanism by which HCV modulates PC synthesis. Aim 3. Define the significance of the ASCL enzymes in HCV replication. ASCLs localize to RCs and are required for HCV replication. We hypothesize that a viral protein recruits them to RCs and that they are required to provide the long chain fatty acids for phospholipids, such as PI and PC.