The p97-UBXD8 complex regulates ER-Mitochondria contact sites by altering membrane lipid saturation and composition

The intimate association between the endoplasmic reticulum (ER) and mitochondrial membranes at ER-Mitochondria contact sites (ERMCS) is a platform for critical cellular processes, particularly lipid synthesis. How contacts are remodeled and the impact of altered contacts on lipid metabolism remains poorly understood. We show that the p97 AAA-ATPase and its adaptor ubiquitin-X domain adaptor 8 (UBXD8) regulate ERMCS. The p97-UBXD8 complex localizes to contacts and its loss increases contacts in a manner that is dependent on p97 catalytic activity. Quantitative proteomics and lipidomics of ERMCS demonstrates alterations in proteins regulating lipid metabolism and a significant change in membrane lipid saturation upon UBXD8 deletion. Loss of p97-UBXD8 increased membrane lipid saturation via SREBP1 and the lipid desaturase SCD1. Aberrant contacts can be rescued by unsaturated fatty acids or overexpression of SCD1. We find that the SREBP1-SCD1 pathway is negatively impacted in the brains of mice with p97 mutations that cause neurodegeneration. We propose that contacts are exquisitely sensitive to alterations to membrane lipid composition and saturation

Human Cytomegalovirus Regulates Host Lipid Metabolism

No virus encodes a metabolic network. Thus, they must rely on host cell machinery to acquire energy and building blocks necessary for replication. Viral infection, including human cytomegalovirus (HCMV), induces the synthesis of fatty acid and lipid synthesis for incorporation of lipids into virion membrane. Lipids with very-long-chain fatty acids (VLCFAs) are abundant in HCMV-infected cells. However, little is known regarding the mechanism by which HCMV induces the synthesis of lipids with VLCFA tails and the functional role of these lipids. I hypothesize that HCMV viral protein pUL37x1 uses a host stress response to regulate fatty acid and lipid metabolism. This dissertation will test this hypothesis from three perspectives: a) How does HCMV viral protein pUL37x1 remodel host lipid metabolism; b) How HCMV uses host stress response to manipulate and balance lipids with VLCFA tails and c) What is the role of human fatty acid elongase 5 (ELOVL5) in virally induced changes in the abundance of lipids with polyunsaturated fatty acid (PUFA) tails. I found that HCMV pUL37x1-induction of phospholipids with saturated/monounsaturated (SFA/MUFA) VLCFAs requires ELOVL7 and PERK (an ER stress sensor protein). Loss of PERK leads to an accumulation of polyunsaturated fatty acid (PUFAs) suggesting a role of PERK in balancing the pool of lipids with SFA/MUFA and PUFA tails by differentially regulating ELOVL7 and ELOVL5 during infection. Finally, HCMV induction of lipids with PUFA VLCFAs requires ELOVL5. This dissertation provides an overview of mechanisms that HCMV remodeling of host lipid metabolism and the functional role of lipids in virus replication

Human Cytomegalovirus pUL37x1 Is Important for Remodeling of Host Lipid Metabolism

Human cytomegalovirus (HCMV) replication requires host metabolism. Infection alters the activity in multiple metabolic pathways, including increasing fatty acid elongation and lipid synthesis. The virus-host interactions regulating the metabolic changes associated with replication are essential for infection. While multiple host factors, including kinases and transcription factors, important for metabolic changes that occur following HCMV infection have been identified, little is known about the viral factors required to alter metabolism. In this study, we tested the hypothesis that pUL37x1 is important for the metabolic remodeling that is necessary for HCMV replication using a combination of metabolomics, lipidomics, and metabolic tracers to measure fatty acid elongation. We observed that fibroblast cells infected with wild-type (WT) HCMV had levels of metabolites similar to those in cells infected with a mutant virus lacking the UL37x1 gene, subUL37x1. However, we found that relative to WT-infected cells, subUL37x1-infected cells had reduced levels of two host proteins that were previously demonstrated to be important for lipid metabolism during HCMV infection: fatty acid elongase 7 (ELOVL7) and the endoplasmic reticulum (ER) stress-related kinase PERK. Moreover, we observed that HCMV infection results in an increase in phospholipids with very-long-chain fatty acid tails (PL-VLCFAs) that contain 26 or more carbons in one of their two tails. The levels of many PL-VLCFAs were lower in subUL37x1-infected cells than in WT-infected cells. Overall, we conclude that although pUL37x1 is not necessary for network-wide metabolic changes associated with HCMV infection, it is important for the remodeling of a subset of metabolic changes that occur during infection.IMPORTANCE Human cytomegalovirus (HCMV) is a common pathogen that asymptomatically infects most people and establishes a lifelong infection. However, HCMV can cause end-organ disease that results in death in the immunosuppressed and is a leading cause of birth defects. HCMV infection depends on host metabolism, including lipid metabolism. However, the viral mechanisms for remodeling of metabolism are poorly understood. In this study, we demonstrate that the viral UL37x1 protein (pUL37x1) is important for infection-associated increases in lipid metabolism, including fatty acid elongation to produce very-long-chain fatty acids (VLCFAs). Furthermore, we found that HCMV infection results in a significant increase in phospholipids, particularly those with VLCFA tails (PL-VLCFAs). We found that pUL37x1 was important for the high levels of fatty acid elongation and PL-VLCFA accumulation that occur in HCMV-infected cells. Our findings identify a viral protein that is important for changes in lipid metabolism that occur following HCMV infection.Arizona Biomedical Research Commission [ADHS18-198868]; BIO5 Institute, the Department of Immunobiology, University of Arizona College of Medicine-Tucson; University of Arizona Health Sciences6 month embargo; published online: 15 October 2019This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Observation of A -site antiferromagnetic and B -site ferrimagnetic orderings in the quadruple perovskite oxide CaCu3_{3}Co2_{2}Re2_{2}O12_{12}

A quadruple perovskite oxide CCaCu$_{3}$Co$_{2}$Re$_{2}$O$_{12}$ was synthesized by high-pressure annealing. This compound crystallizes in an A- and B-site ordered quadruple perovskite structure with space group Pn−3. The charge combination is determined to be CaCu$^{2+}_3$Co$^{2+}_2$Re$^{6+}_2$O$_{12}$ by bond valence sum analysis and x-ray absorption spectroscopy. In contrast to other isostructural ACu$_3$B$_{2}$B′$_{2}$O$_{12}$ compounds with a single magnetic transition, a long-range antiferromagnetic phase transition originating from the A′-site Cu$^{2+}$ sublattice is found to occur at T$_N ≈$ 28K. Subsequently, the spin coupling between the B-site Co$^{2+}$ and B′-site Re$^{6+}$ ions contributes to a ferrimagnetic transition around T$_C ≈$ 20K. Strong electrical insulating behavior is identified by optical measurement with an energy gap of approximately 3.75 eV. The mechanisms of the spin interactions are discussed in detail