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Viperin regulates cellular lipid metabolism during human cytomegalovirus infection.

ABSTRACT: Human cytomegalovirus (HCMV) has been shown to induce increased lipogenesis in infected cells, and this is believed to be required for proper virion envelopment. We show here that this increase is a consequence of the virus-induced redistribution of the host protein viperin to mitochondria and its capacity to interact with and block the function of the mitochondrial trifunctional protein (TFP), the enzyme that mediates fatty acid-?-oxidation. The resulting decrease in cellular ATP levels activates the enzyme AMP-activated protein kinase (AMPK), which induces expression of the glucose transporter GLUT4, resulting in increased glucose import and translocation to the nucleus of the glucose-regulated transcription factor ChREBP. This induces increased transcription of genes encoding lipogenic enzymes, increased lipid synthesis and lipid droplet accumulation, and generation of the viral envelope. Viperin-dependent lipogenesis is required for optimal production of infectious virus. We show that all of these metabolic outcomes can be replicated by direct targeting of viperin to mitochondria in the absence of HCMV infection, and that the motif responsible for Fe-S cluster binding by viperin is essential. The data indicate that viperin is the major effector underlying the ability of HCMV to regulate cellular lipid metabolism.

SUBMITTER: Seo JY

PROVIDER: S-EPMC3731232 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Viperin regulates cellular lipid metabolism during human cytomegalovirus infection.

Seo Jun-Young JY Cresswell Peter P

PLoS pathogens 20130801 8

Human cytomegalovirus (HCMV) has been shown to induce increased lipogenesis in infected cells, and this is believed to be required for proper virion envelopment. We show here that this increase is a consequence of the virus-induced redistribution of the host protein viperin to mitochondria and its capacity to interact with and block the function of the mitochondrial trifunctional protein (TFP), the enzyme that mediates fatty acid-β-oxidation. The resulting decrease in cellular ATP levels activat ...[more]

PMID: 23935494

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Project description:Human cytomegalovirus (HCMV) is a common cause of morbidity and mortality in immunocompromised and immunosuppressed individuals. During infection, HCMV is known to employ host transcription factors to facilitate viral gene expression. To further understand the previously observed delayed viral replication and protein expression in p53 knockout cells, we conducted microarray analyses on p53+/+ and p53-/- immortalized fibroblast cell lines. At 12 hpi, applying the significance criteria defined above, no genes showed a significant difference in any of the comparisons. At 24 hpi, we found 19 genes to be significantly different in the THF versus p53-/- comparison and 14 genes to be significantly different in the HFF versus p53-/- comparison. Eleven genes were shared between HFF and THF cells when compared to p53-/- cells (UL30, UL54, UL63, UL65, UL69, UL75, UL110, UL122, IRL4, IRS1, TRS1, shown in bold in Table 1). Eight genes were unique in the THF versus p53-/- comparison (UL48, UL68, UL84, UL100, UL106, UL109, UL111, RL5A), and three genes in the HFF versus p53-/- cell comparison (UL14, UL16, US2). When comparing HFF and THF cells, only US2 showed a significant difference. The ratio (HFF versus p53-/- divided by THF versus p53-/-) of the expression levels of the eleven shared genes from the HFF versus p53-/- and THF versus p53-/- comparisons was an averaged 1.2, indicating that, with the exception of US2, these two cell lines behaved similarly with respect to p53-driven viral gene expression. Keywords: time course, virus, cytomegalo, hhv5, infection, p53 Each slide consisted of 4 arrays. Each array consisted of 305 control features, 1265 cellular gene features and 670 viral gene features. The study was performed on 6 slides (HFF-THF, HFF-p53-/-, THF-p53-/- at 12 and 24 hpi). 3 arrays per slide were hybridized with 3 biological replicates of labelled RNA, the 4th array was hybridized with an equimolar mixture of the 3 biological replicate samples. This array was used for control purposes only, and the results were not used for downstream calculations. Each slide was stripped and reprobed two times to provide 3 technical replicates of each sample. As our experiments concentrated on viral genes and their expression, cellular genes were not further analyzed in this study.

Project description: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.

Dataset Information

Viperin regulates cellular lipid metabolism during human cytomegalovirus infection.

Publications

Viperin regulates cellular lipid metabolism during human cytomegalovirus infection.

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