Human Cytomegalovirus pUL37x1 Is Important for Remodeling of Host Lipid Metabolism

Abstract

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.

Nitric Oxide Circumvents Virus-Mediated Metabolic Regulation during Human Cytomegalovirus Infection

“…Liu et al ( 54 ) have defined the lipid composition of the viral particle and postulate that fatty acids and lipids synthesized during infection are the major contributor to the lipid composition of the viral particle ( 54 ). HCMV does remodel the host lipidome, which is partially mediated by expression of HCMV UL37x1 ( 72 ). We detected changes in host cell lipids at 24 hpi between vehicle- and nitric oxide-treated fibroblasts ( Fig.…”

Hypoxia-inducible factor 1α (HIF1α) Suppresses Virus Replication in Human Cytomegalovirus Infection by Limiting Kynurenine Synthesis

“…Infection alters activity in many pathways in the host metabolic network, such as increasing glycolysis and the flow of carbons into lipid synthesis to support virus replication (2)(3)(4)(5)(6)(7)(8).…”

Shear-Mediated Platelet Activation is Accompanied by Unique Alterations of Platelet Lipid Profile

“…Lipids were separated using a Kinetex 2.6 µm C18 column (Phenomenex 00F-4462-AN) at 60 ˚C on a Vanquish UHPLC system (Thermo Scientific). UHPLC was performed using two solvents: solvent A (40:60 water:methanol plus 10 mM ammonium formate and 0.1% formic acid) and solvent B (10:90 methanol:isopropanol plus 10 mM ammonium formate and 0.1% formic acid) at 0.25 ml/min flow rate using conditions previously described [44]. Between each sample, the column was briefly washed and re-equilibrated.…”

“…All lipids were measured using a Q-Exactive Plus mass spectrometer operating in a data-dependent Full MS/dd-MS2 TopN mode using heated electrospray ionization, as previously described. [44] Spectra were collected over a 200-1600 m/z mass range. MS1 scans were collected using a resolution setting of 70,000 or 120,000.…”