scholarly journals microRNA-99a Restricts Replication of Hepatitis C Virus by Targeting mTOR and De Novo Lipogenesis

Viruses ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 696 ◽  
Author(s):  
Eun Byul Lee ◽  
Pil Soo Sung ◽  
Jung-Hee Kim ◽  
Dong Jun Park ◽  
Wonhee Hur ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Lipid Accumulation ◽  
De Novo ◽  
Regulatory Element ◽  
Mammalian Target Of Rapamycin ◽  
De Novo Lipogenesis ◽  
Hcv Rna ◽  
Intracellular Lipid ◽  
Intracellular Lipid Accumulation

In this study, we investigated the role of microRNA-99a (miR-99a) in hepatitis C virus (HCV) replication and lipogenesis in hepatocytes. Cell-culture-derived HCV (HCVcc) infection caused down-regulation of miR-99a in Huh-7 cells, and the relative levels of miR-99a were significantly lower in the sera of the HCV-infected patients than in those of healthy controls. Transfection of miR-99a-5p mimics resulted in a decrease in the intracellular and secreted HCV RNA levels. It also caused a decreased mammalian target of rapamycin (mTOR) protein level and phosphorylation of its downstream targets in HCV-replicating cells. Sterol regulatory element binding protein (SREBP)-1c expression and intracellular lipid accumulation decreased when either miR-99a-5p mimics or si-mTOR was transfected in oleic acid-treated Huh-7 cells. Overexpression of mTOR rescued HCV RNA replication and lipid droplet accumulation in miR-99a-5p mimics-transfected HCV replicon cells. Our data demonstrated that miR-99a ameliorates intracellular lipid accumulation by regulating mTOR/SREBP-1c and causes inefficient replication and packaging of intracellular HCV.

scholarly journals Effect of Cell Growth on Hepatitis C Virus (HCV) Replication and a Mechanism of Cell Confluence-Based Inhibition of HCV RNA and Protein Expression

2006 ◽  
Vol 80 (3) ◽  
pp. 1181-1190 ◽  
Author(s):  
Heather B. Nelson ◽  
Hengli Tang
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Cell Growth ◽  
De Novo ◽  
Physiological State ◽  
Inhibitory Effect ◽  
Cell Number ◽  
Serum Starvation ◽  
Hcv Rna ◽  
Cell Growth Arrest

ABSTRACT An intimate relationship between hepatitis C virus (HCV) replication and the physiological state of the host liver cells has been reported. In particular, a highly reproducible and reversible inhibitory effect of high cell density on HCV replication was observed: high levels of HCV RNA and protein can be detected in actively growing cells but decline sharply when the replicon cells reach confluence. Arrested cell growth of confluent cells has been proposed to be responsible for the inhibitory effect. Indeed, other means of arresting cell growth have also been shown to inhibit HCV replication. Here, we report a detailed study of the effect of cell growth and confluence on HCV replication using a flow cytometry-based assay that is not biased against cytostasis and reduced cell number. Although we readily reproduced the inhibitory effect of cell confluence on HCV replication, we found no evidence of inhibition by serum starvation, which arrested cell growth as expected. In addition, we observed no inhibitory effect by agents that perturb the cell cycle. Instead, our results suggest that the reduced intracellular pools of nucleosides account for the suppression of HCV expression in confluent cells, possibly through the shutoff of the de novo nucleoside biosynthetic pathway when cells become confluent. Adding exogenous uridine and cytidine to the culture medium restored HCV replication and expression in confluent cells. These results suggest that cell growth arrest is not sufficient for HCV replicon inhibition and reveal a mechanism for HCV RNA inhibition by cell confluence.

Regulation of the SREBP transcription factors by mTORC1

2011 ◽  
Vol 39 (2) ◽  
pp. 495-499 ◽  
Author(s):  
Caroline A. Lewis ◽  
Beatrice Griffiths ◽  
Claudio R. Santos ◽  
Mario Pende ◽  
Almut Schulze
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Synthase ◽  
Target Genes ◽  
De Novo ◽  
Regulatory Element ◽  
Cholesterol Biosynthesis ◽  
Mammalian Target Of Rapamycin ◽  
Lipid Biosynthesis ◽  
De Novo Lipogenesis ◽  
Genes Encoding

In recent years several reports have linked mTORC1 (mammalian target of rapamycin complex 1) to lipogenesis via the SREBPs (sterol-regulatory-element-binding proteins). SREBPs regulate the expression of genes encoding enzymes required for fatty acid and cholesterol biosynthesis. Lipid metabolism is perturbed in some diseases and SREBP target genes, such as FASN (fatty acid synthase), have been shown to be up-regulated in some cancers. We have previously shown that mTORC1 plays a role in SREBP activation and Akt/PKB (protein kinase B)-dependent de novo lipogenesis. Our findings suggest that mTORC1 plays a crucial role in the activation of SREBP and that the activation of lipid biosynthesis through the induction of SREBP could be part of a regulatory pathway that co-ordinates protein and lipid biosynthesis during cell growth. In the present paper, we discuss the increasing amount of data supporting the potential mechanisms of mTORC1-dependent activation of SREBP as well as the implications of this signalling pathway in cancer.

scholarly journals De novo lipogenesis is elicited dramatically in human hepatocellular carcinoma especially in hepatitis C virus‐induced hepatocellular carcinoma

MedComm ◽  
2020 ◽  
Vol 1 (2) ◽  
pp. 178-187
Author(s):  
Shaojian Li ◽  
Ruonan Liu ◽  
Qinling Pan ◽  
Genshu Wang ◽  
Daorou Cheng ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
De Novo ◽  
Human Hepatocellular Carcinoma ◽  
De Novo Lipogenesis

scholarly journals Cross-Genotypic Examination of Hepatitis C Virus Polymerase Inhibitors Reveals a Novel Mechanism of Action for Thumb Binders

2014 ◽  
Vol 58 (12) ◽  
pp. 7215-7224 ◽  
Author(s):  
Auda A. Eltahla ◽  
Enoch Tay ◽  
Mark W. Douglas ◽  
Peter A. White
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
De Novo ◽  
Hcv Rna ◽  
Amino Acid Residues ◽  
Recombinant Enzymes ◽  
Polymerase Inhibitors ◽  
Binding Pockets ◽  
Direct Acting

ABSTRACTDirect-acting antivirals (DAAs) targeting proteins encoded by the hepatitis C virus (HCV) genome have great potential for the treatment of HCV infections. However, the efficacy of DAAs designed to target genotype 1 (G1) HCV against non-G1 viruses has not been characterized fully. In this study, we investigated the inhibitory activities of nonnucleoside inhibitors (NNIs) against the HCV RNA-dependent RNA polymerase (RdRp). We examined the ability of six NNIs to inhibit G1b, G2a, and G3a subgenomic replicons in cell culture, as well asin vitrotranscription by G1b and G3a recombinant RdRps. Of the six G1 NNIs, only the palm II binder nesbuvir demonstrated activity against G1, G2, and G3 HCV, in both replicon and recombinant enzyme models. The thumb I binder JTK-109 also inhibited G1b and G3a replicons and recombinant enzymes but was 41-fold less active against the G2a replicon. The four other NNIs, which included a palm I binder (setrobuvir), two thumb II binders (lomibuvir and filibuvir), and a palm β-hairpin binder (tegobuvir), all showed at least 40-fold decreases in potency against G2a and G3a replicons and the G3a enzyme. This antiviral resistance was largely conferred by naturally occurring amino acid residues in the G2a and G3a RdRps that are associated with G1 resistance. Lomibuvir and filibuvir (thumb II binders) inhibited primer-dependent but notde novoactivity of the G1b polymerase. Surprisingly, these compounds instead specifically enhanced thede novoactivity at concentrations of ≥100 nM. These findings highlight a potential differential mode of RdRp inhibition for HCV NNIs, depending on their prospective binding pockets, and also demonstrate a surprising enhancement ofde novoactivity for thumb RdRp binders. These results also provide a better understanding of the antiviral coverage for these polymerase inhibitors, which will likely be used in future combinational interferon-free therapies.

scholarly journals Prolactin Regulatory Element Binding Protein Is Involved in Hepatitis C Virus Replication by Interaction with NS4B

2016 ◽  
Vol 90 (6) ◽  
pp. 3093-3111 ◽  
Author(s):  
Lingbao Kong ◽  
Akira Fujimoto ◽  
Mariko Nakamura ◽  
Haruyo Aoyagi ◽  
Mami Matsuda ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Affinity Purification ◽  
Regulatory Element ◽  
Proteome Analysis ◽  
Hcv Rna ◽  
Double Stranded Rna ◽  
Replication Complex ◽  
Interfering Rna ◽  
Replication Compartment

ABSTRACTIt has been proposed that the hepatitis C virus (HCV) NS4B protein triggers the membranous HCV replication compartment, but the underlying molecular mechanism is not fully understood. Here, we screened for NS4B-associated membrane proteins by tandem affinity purification and proteome analysis and identified 202 host proteins. Subsequent screening of replicon cells with small interfering RNA identified prolactin regulatory element binding (PREB) to be a novel HCV host cofactor. The interaction between PREB and NS4B was confirmed by immunoprecipitation, immunofluorescence, and proximity ligation assays. PREB colocalized with double-stranded RNA and the newly synthesized HCV RNA labeled with bromouridine triphosphate in HCV replicon cells. Furthermore, PREB shifted to detergent-resistant membranes (DRMs), where HCV replication complexes reside, in the presence of NS4B expression in Huh7 cells. However, a PREB mutant lacking the NS4B-binding region (PREBd3) could not colocalize with double-stranded RNA and did not shift to the DRM in the presence of NS4B. These results indicate that PREB locates at the HCV replication complex by interacting with NS4B. PREB silencing inhibited the formation of the membranous HCV replication compartment and increased the protease and nuclease sensitivity of HCV replicase proteins and RNA in DRMs, respectively. Collectively, these data indicate that PREB promotes HCV RNA replication by participating in the formation of the membranous replication compartment and by maintaining its proper structure by interacting with NS4B. Furthermore, PREB was induced by HCV infectionin vitroandin vivo. Our findings provide new insights into HCV host cofactors.IMPORTANCEThe hepatitis C virus (HCV) protein NS4B can induce alteration of the endoplasmic reticulum and the formation of a membranous web structure, which provides a platform for the HCV replication complex. The molecular mechanism by which NS4B induces the membranous HCV replication compartment is not understood. We screened for NS4B-associated membrane proteins by tandem affinity purification and proteome analysis, followed by screening with small interfering RNA. We identified prolactin regulatory element binding (PREB) to be a novel HCV host cofactor. PREB is induced by HCV infection and recruited into the replication complex by interaction with NS4B. Recruited PREB promotes HCV RNA replication by participating in the formation of the membranous HCV replication compartment. To our knowledge, the effect of NS4B-binding protein on the formation of the membranous HCV replication compartment is newly described in this report. Our findings are expected to provide new insights into HCV host cofactors.

scholarly journals Zanthoxylum ailanthoides Suppresses Oleic Acid-Induced Lipid Accumulation through an Activation of LKB1/AMPK Pathway in HepG2 Cells

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Eun-Bin Kwon ◽  
Myung-Ji Kang ◽  
Soo-Yeon Kim ◽  
Yong-Moon Lee ◽  
Mi-Kyeong Lee ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Lipid Accumulation ◽  
Hepg2 Cells ◽  
Methanol Extract ◽  
De Novo ◽  
Oxygen Species ◽  
Gene Expressions ◽  
Intracellular Lipid ◽  
Ampk Signaling ◽  
Intracellular Lipid Accumulation

Zanthoxylum ailanthoides (ZA) has been used as folk medicines in East Asian and recently reported to have several bioactivity; however, the studies of ZA on the regulation of triacylglycerol (TG) biosynthesis have not been elucidated yet. In this study, we examined whether the methanol extract of ZA (ZA-M) could reduce oleic acid- (OA-) induced intracellular lipid accumulation and confirmed its mode of action in HepG2 cells. ZA-M was shown to promote the phosphorylation of AMPK and its upstream LKB1, followed by reduction of lipogenic gene expressions. As a result, treatment of ZA-M blocked de novo TG biosynthesis and subsequently mitigated intracellular neutral lipid accumulation in HepG2 cells. ZA-M also inhibited OA-induced production of reactive oxygen species (ROS) and TNF-α, suggesting that ZA-M possess the anti-inflammatory feature in fatty acid over accumulated condition. Taken together, these results suggest that ZA-M attenuates OA-induced lipid accumulation and inflammation through the activation of LKB1/AMPK signaling pathway in HepG2 cells.

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