Entangled in a membranous web: ER and lipid droplet reorganization during hepatitis C virus infection

Meyers, Nathan L.; Fontaine, Krystal A.; Kumar, G. Renuka; Ott, Mélanie

doi:10.1016/j.ceb.2016.05.003

Cited by 33 publications

(30 citation statements)

References 113 publications

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“…This enveloped, positive strand RNA virus has been intensely studied because it infects well over 100 million people worldwide and can lead to severe liver disease, including liver cirrhosis and liver cancer [130]. After infection, the viral RNA genome is translated into a single polyprotein, which is proteolytically processed into 10 HCV proteins, most of which are associated with the ER [131, 132]. Two of those products, the nucleocapsid core and the non-structural protein NS5A, subsequently associate with LDs.…”

Section: 1 Protein Maturationmentioning

confidence: 99%

“…When DGAT1 is either absent or enzymatically inhibited, cells can still form LDs via another triglyceride-synthesis enzyme, DGAT2, but these do not accumulate core and NS5A and assembly of new infectious viral particles is severely compromised [133, 134]. NS5A accumulates not only on LDs, but also at ER-derived virus-induced structures, so called double-membrane vesicles (DMVs) [131]. DMVs likely represent sites of viral RNA replication, and they require NS5A for their formation [135, 136].…”

Section: 1 Protein Maturationmentioning

confidence: 99%

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Lipid droplet functions beyond energy storage

Welte

Gould

2017

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biolog

442

358

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Lipid droplets are cytoplasmic organelles that store neutral lipids and are critically important for energy metabolism. Their function in energy storage is firmly established and increasingly well characterized. However, emerging evidence indicates that lipid droplets also play important and diverse roles in the cellular handling of lipids and proteins that may not be directly related to energy homeostasis. Lipid handling roles of droplets include the storage of hydrophobic vitamin and signaling precursors, and the management of endoplasmic reticulum and oxidative stress. Roles of lipid droplets in protein handling encompass functions in the maturation, storage, and turnover of cellular and viral polypeptides. Other potential roles of lipid droplets may be connected with their intracellular motility and, in some cases, their nuclear localization. This diversity highlights that lipid droplets are very adaptable organelles, performing different functions in different biological contexts.

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Section: 1 Protein Maturationmentioning

confidence: 99%

Section: 1 Protein Maturationmentioning

confidence: 99%

Lipid droplet functions beyond energy storage

Welte

Gould

2017

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biolog

442

358

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“…The lipid kinase PI4KIII␣ (23,(31)(32)(33)(34) and the protein kinase CKI␣ (18,22,27,28,35) are the two most-studied kinases involved in NS5A hyperphosphorylation. To investigate their roles in S235 and S238 phosphorylation, we measured S235 and S238 phosphorylation in the T7 polymerase-expressing Huh7 cells (T7-Huh7) whose PI4KIII␣ or CKI␣ was knocked down prior to NS3-NS5B expression.…”

Section: S235 Determines Ns5a Hyperphosphorylationmentioning

confidence: 99%

Serine 235 Is the Primary NS5A Hyperphosphorylation Site Responsible for Hepatitis C Virus Replication

Hsu

Pan

et al. 2017

J Virol

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The nonstructural protein 5A (NS5A) of the hepatitis C virus (HCV) is a phosphoprotein with two phosphorylation states: hypo-and hyperphosphorylation. Genetic mutation studies have demonstrated a cluster of serine residues responsible for NS5A hyperphosphorylation and functions in viral replication and assembly; however, the phosphorylation levels and potential interactions among the serine residues are unclear. We used three specific antibodies to measure NS5A phosphorylation at S222, S235, and S238 that were identified in our previous proteomics study. In the HCV (J6/JFH-1)-infected Huh7.5.1 cells, S222 phosphorylation was barely detected, whereas S235 phosphorylation and S238 phosphorylation were always detected in parallel in time and intracellular spaces. S235A mutation eliminated S238 phosphorylation whereas S238A mutation did not affect S235 phosphorylation, indicating that S235 phosphorylation occurs independently of S238 phosphorylation while S238 phosphorylation depends on S235 phosphorylation. In line with this, immunoprecipitation coupled with immunoblotting showed that S235 phosphorylation existed alone without S238 phosphorylation, whereas S238 phosphorylation existed only when S235 was phosphorylated on the same NS5A molecule. S235-phosphorylated NS5A constituted the primary hyperphosphorylated NS5A species. S235A mutation blunted viral replication, whereas S238A mutation did not affect replication. We concluded that S235 is the primary NS5A hyperphosphorylation site required for HCV replication. S238 is likely phosphorylated by casein kinase I␣, which requires a priming phosphorylation at S235. IMPORTANCE It has been known for years that the hepatitis C virus nonstructural protein 5A (NS5A) undergoes transition between two phosphorylation states: hypoand hyperphosphorylation. It is also known that a cluster of serine residues is responsible for NS5A hyperphosphorylation and functions; however, the primary serine residue responsible for NS5A hyperphosphorylation is not clear. Here, we show for the first time that serine 235-phosphorylated NS5A constitutes the primary hyperphosphorylated NS5A species required for viral replication. We also show that NS5A phosphorylation among the serine residues is interdependent and occurs in a directional manner, i.e., phosphorylation at serine 235 leads to phosphorylation at serine 238. Our data provide the first proof-of-principle evidence that NS5A undergoes a sequential phosphorylation cascade.KEYWORDS NS5A, antibody, hepatitis C virus, protein phosphorylation, proteomics H epatitis C virus (HCV) is an enveloped virus with a 9.6-kb single-stranded positivesense RNA genome. It infects about 185 million people worldwide and is a leading cause of liver diseases and related complications (1, 2). The HCV genome encodes a long polyprotein composed of 10 proteins from NH 2 to the COOH terminus: core, E1, E2, p7, NS2, NS3, NS4A, NS4B, NS5A, and NS5B. A complete HCV life cycle requires 3

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“…At the hepatocyte surface, HCV binds to different receptors, including LDLR (low-density lipoprotein receptor) and CLDN1 (Claudin-1), and is transported to the cytoplasm by endocytosis [8]. Once in the endosome, the low pH helps viral uncoating, and the viral genome is free to bind to the endoplasmic reticulum, where a membranous web is formed that helps viral replication [9]. Prior to replication, the viral genome is translated from a 5 internal ribosome entry site (IRES) by cap-independent translation [10].…”

mentioning

confidence: 99%

LncRNAs in HCV Infection and HCV-Related Liver Disease

Unfried¹,

Fortes²

2020

IJMS

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Long non-coding RNAs (lncRNAs) are transcripts with poor coding capacity that may interact with proteins, DNA, or other RNAs to perform structural and regulatory functions. The lncRNA transcriptome changes significantly in most diseases, including cancer and viral infections. In this review, we summarize the functional implications of lncRNA-deregulation after infection with hepatitis C virus (HCV). HCV leads to chronic infection in many patients that may progress to liver cirrhosis and hepatocellular carcinoma (HCC). Most lncRNAs deregulated in infected cells that have been described function to potentiate or block the antiviral response and, therefore, they have a great impact on HCV viral replication. In addition, several lncRNAs upregulated by the infection contribute to viral release. Finally, many lncRNAs have been described as deregulated in HCV-related HCC that function to enhance cell survival, proliferation, and tumor progression by different mechanisms. Interestingly, some HCV-related HCC lncRNAs can be detected in bodily fluids, and there is great hope that they could be used as biomarkers to predict cancer initiation, progression, tumor burden, response to treatment, resistance to therapy, or tumor recurrence. Finally, there is high confidence that lncRNAs could also be used to improve the suboptimal long-term outcomes of current HCC treatment options.

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Entangled in a membranous web: ER and lipid droplet reorganization during hepatitis C virus infection

Cited by 33 publications

References 113 publications

Lipid droplet functions beyond energy storage

Lipid droplet functions beyond energy storage

Serine 235 Is the Primary NS5A Hyperphosphorylation Site Responsible for Hepatitis C Virus Replication

LncRNAs in HCV Infection and HCV-Related Liver Disease

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