Membrane and lipidome dynamics during enterovirus infection

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Summary/Abstract Enterovirus infections are a significant public health burden worldwide. Nearly 15 million enterovirus infections occur each year. While infection predominantly elicits mild-symptom disease, some enterovirus strains may confer severe respiratory and neurological illnesses with higher morbidity in children. There are no current antiviral therapeutics to thwart enteroviral infections. All positive-strand RNA viruses, even non-enveloped poliovirus (PV)-like enteroviruses, require host membranes for multiplication. These viruses remodel the host lipidome to create virus-induced membranes with unique phospholipid composition, thereby conferring unique biochemical and biophysical properties upon these membranes that enable distinct biological functions. PV- related enteroviruses and likely many other viruses fall into this category. Remarkably, during PV infection, translation of the infecting RNA is sufficient to induce cellular transformations before genome replication or host transcription is engaged. This observation suggests that post-transcriptional and/or post-translational mechanisms exist in the mammalian cell cytoplasm to reprogram phospholipid biosynthesis and membrane biogenesis minutes after infection and that “hubs,” which can be co-opted by PV, control these mechanisms. Our research aims to illuminate mechanisms regulating membrane biogenesis, function, and trafficking in cells by understanding how PV co-opts these mechanisms. PV 3CD induces multiple phospholipids during infection. To investigate the mechanism, we expressed a tagged 3CD in HeLa cells and exploited the tag to isolate 3CD- associated proteins. We identified 3CD-associated proteins using mass spectrometry. We combined our data with genetic screens and published data on known interactions to arrive at a hypothetical model for lipid induction. By evaluating proteins with two or three degrees of separation from interactions discovered empirically, c-Fos appeared. Studies have demonstrated a direct role of c-Fos in activating enzymes that perform rate-limiting steps in phospholipid biosynthesis and membrane biogenesis. We hypothesize that PV modulates c-Fos to form PV-induced membranes of unique phospholipid composition by exploiting multiple lipid biosynthetic pathways. Thus Aim 1 will evaluate PV-mediated c-Fos modulation for the induction of phospholipid biosynthesis and membrane biogenesis. Furthermore, our preliminary data evaluating the lipidome of PV-infected cells shows the induction of very long-chain fatty acids synthesis. Only one isoform in the Elongation of Very Long-Chain Fatty Acids family of enzymes (ELOVL4) produces these fatty acids. We hypothesize that PV viral factors hijack cellular pathways (namely ELOVL4) to produce long fatty acids that stabilize virus-containing vesicles during infection. Thus Aim 2 will characterize the dynamics, mechanisms, and functions of host-lipidome remodeling during PV infection. These studies will not only elucidate pathways governing membrane dynamics during viral infection but also provide insight into how these pathways are regulated during normal cellular physiology—presenting attractive target candidates for developing antivirals.