HCV NS5A inhibits interferon-α signaling through suppression of STAT1 phosphorylation in hepatocyte-derived cell lines

Lan, Keng‐Hsin; Lan, Keng‐Li; Lee, Wei-Ping; Sheu, Meei-Ling; Chen, Ming‐Yuan; Lee, Yung-Lu; Yen, Sang‐Hue; Chang, Full‐Young; Lee, Shou‐Dong

doi:10.1016/j.jhep.2006.11.013

Cited by 50 publications

(41 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Stat-1 phosphorylation is suppressed in hepatocytes from patients with HCV infections (26) and in cells expressing HCV NS5A (17). IFN-␥-induced C4 activation requires functional Stat-1.…”

Section: Discussionmentioning

confidence: 98%

See 1 more Smart Citation

Transcriptional Repression of C4 Complement by Hepatitis C Virus Proteins

Banerjee

Mazumdar

Meyer

et al. 2011

J Virol

View full text Add to dashboard Cite

The fourth component of human complement (C4) plays an important role in innate immune function. C4 activity has been observed to be significantly lower in patients with chronic hepatitis C virus (HCV) infections, although the mechanism remains unknown. In this study, we have examined the mechanisms of C4 regulation by HCV. Liver biopsy specimens from patients with chronic HCV infections displayed significantly lower C4 mRNA levels than liver tissue samples from patients with unrelated liver disease. Further, C4 mRNA levels of the two isoforms (C4A and C4B) were significantly reduced in hepatocytes transfected with RNA from HCV genotype 1a or 2a. Subsequently, a significant C4 regulatory role of HCV core or NS5A upon C4 promoter activity was observed. HCV core or NS5A transgenic mice displayed a reduction in C4 mRNA. Gamma interferon (IFN-␥)-induced C4 promoter activation was also impaired in the presence of HCV proteins. We further demonstrated that HCV core reduced the expression of upstream stimulating factor 1 (USF-1), a transcription factor important for basal C4 expression. On the other hand, the expression of interferon regulatory factor 1 (IRF-1), which is important for IFN-␥-induced C4 expression, was inhibited by hepatocytes expressing HCV NS5A. These results underscore the roles of HCV proteins in innate immune regulation in establishing a chronic infection.The complement system is a set of biochemical pathways that helps to clear pathogens from an organism as part of the innate and acquired immunity programs. Activation of the complement system triggers a wide range of cellular responses ranging from apoptosis to opsonization (27). The complement system plays a critical role in the pathogenesis of a variety of chronic human diseases. Viruses have been shown to attenuate complement activation. Recently, the nonstructural protein (NS1) from flaviviruses (dengue fever virus, West Nile virus, and yellow fever virus) has been reported to attenuate complement activation by interacting with several complement components (1,8). Results from another study suggest that the complement system is also involved in the pathogenesis of a variety of liver disorders, including liver injury and repair, fibrosis, viral hepatitis, alcoholic liver disease, and liver ischemia/reperfusion injury (24). The fourth component of the complement system, C4, plays a vital role in mounting a proper immune response against infection (35). Chronic hepatitis C virus (HCV) infection is a leading cause of progressive liver disease. The mechanisms responsible for HCV persistence are not well understood, although the interactions between HCV and host cells appear to play an important role. Dumestre-Perard et al. (11) reported in a study of a large cohort that in patients with chronic HCV infections, the blood level of specific complement components is depleted, and C4 activity is significantly lower. A decrease in specific C4 activity was reported among relapsers compared with sustained responders, before and during therapy, suggesting it...

show abstract

“…Stat-1 phosphorylation is suppressed in hepatocytes from patients with HCV infections (26) and in cells expressing HCV NS5A (17). IFN-␥-induced C4 activation requires functional Stat-1.…”

Section: Discussionmentioning

confidence: 98%

“…Since the phosphorylation of Stat-1 and expression of IRF-1 are inhibited by HCV infection and by the presence of NS5A protein (17,26), we examined the effect of IFN-␥ on C4 promoter activation in Huh7 cells in which IRF-1 had been knocked down. To do this, siRNA directed against IRF-1 was transfected into Huh7 cells.…”

mentioning

confidence: 99%

Transcriptional Repression of C4 Complement by Hepatitis C Virus Proteins

Banerjee

Mazumdar

Meyer

et al. 2011

J Virol

View full text Add to dashboard Cite

show abstract

“…In our study, substitutions N248H and E269K found in the "medium" lineage at p45 and S272P in the "low" lineage (mixed at p45 and dominant by p100) are located within the ISDR. Studies on the mechanisms by which NS5A counteracts IFN-␣ activity have not given conclusive results (91,(93)(94)(95)112).…”

Section: Discussionmentioning

confidence: 99%

Response of Hepatitis C Virus to Long-Term Passage in the Presence of Alpha Interferon: Multiple Mutations and a Common Phenotype

Perales

Beach

Gallego

et al. 2013

J Virol

172

View full text Add to dashboard Cite

H epatitis C virus (HCV) infects an estimated 180 million people worldwide, and about 75% of newly infected patients progress toward a chronic infection, which constitutes a risk for severe liver diseases such as cirrhosis and hepatocarcinoma (1-4). HCV is a hepacivirus in the Flaviviridae family characterized by the error-prone replication and quasispecies dynamics typical of RNA viruses (2,(5)(6)(7). No vaccine is available to prevent HCV infections or disease, and the current standard of care treatment consists of the combination of pegylated alpha interferon (IFN-␣) and the purine nucleoside analogue ribavirin (1-␤-D-ribofuranosyl-1-H-1,2,4-triazole-3-carboxamide) (8-10). Type I interferons (IFNs) such as IFN-␣ are members of a family of cytokines that constitute key components of the innate immune response to viruses, and their induction results in an antiviral state of the cell and suppression of viral replication (11)(12)(13)(14). Ribavirin is currently used to treat a number of human viral infections, and it can display multiple mechanisms of action, including enhancement of Th1 antiviral immune responses, upregulation of IFN-stimulated genes (ISGs), depletion of GTP pools, or viral RNA mutagenesis (see reviews in references 15, 16 and 17). However, on average only about 60% of the chronically infected patients show a sustained virological response to treatment with IFN-␣ plus ribavirin that results in virus clearance (18-21). The molecular and physiological bases of the therapeutic activity of the current combination treatment with IFN-␣ plus ribavirin are poorly understood. It might be possible to establish new treatment protocols based on recently developed directly acting antiviral agents (DAAs), with or without .Highly variable viruses exploit a number of strategies to counteract selective constraints intended to prevent their replication (reviewed in reference 7). Mutations that confer resistance to DAAs generally map in the target protein or in a protein that interacts with the target (28-30). However, the complexity of the cellular IFN response pathway is expected to require greater diversity of viral resistance mutations. Current evidence suggests that the response of HCV to IFN-␣-based therapy is influenced by several host (i.e., interleukin-28B [IL-28B] gene polymorphisms) and viral genetic (i.e., viral genotype and population complexity) factors (31-37).The advent of cell culture systems for sustained replication of HCV offers new prospects to approach the evolutionary dynamics of HCV and the host cell-virus relationship, including the anti-HCV activity of IFN-␣. Using these systems, Garaigorta and Chisari documented that HCV-induced protein kinase R (PKR) phosphorylation inhibited translation of IFN-stimulated genes (ISGs) in infected hepatocytes (38). Here we describe the adaptation of the HCV replication system of genotype 2a (39-41) to perform serial passages of HCV in the Huh-7.5 hepatocyte cell line with sustained, efficient viral replication for at least 100 serial passages. This cell ...

show abstract

“…It might be one of the HCV NS5A related molecular mechanism in interferon resistance. Interestingly, almost in the same time, Lan also reported the similar result that HCV NS5A protein inhibited IFN-induced STAT1 phosphorylation and nuclear translocation in three heptocyte-derived cell lines, and found HCV NS5A protein could interact with the N-terminal of STAT1, which would be the molecular mechanism by which HCV NS5A inhibits STAT1 phosphorylation [25] . They used full-length HCV and HCV subgenomic constructs to transiently transfect Huh-T7 cells.…”

Section: Discussionmentioning

confidence: 69%

Hepatitis C Virus non-structural 5A abrogates signal transducer and activator of transcription-1 nucleartranslocation induced by IFN-α through dephosphorylation

Gong

Cao²,

Jiang³

et al. 2007

WJG

View full text Add to dashboard Cite

AIM:To study the effect of Hepatitis C virus nonstructural 5A (HCV NS5A) on IFNα induced signal transducer and activator of transcription-1 (STAT1) phosphorylation and nuclear translocation. METHODS:Expression of STAT1 Tyr701 phosphorylation at different time points was confirmed by Western blot, and the time point when p-STAT1 expressed most, was taken as the IFN induction time for further studies. Immunocytochemistry was used to confirm the successful transient transfection of NS5A expression plasmid. Immunofluorescene was performed to observe if there was any difference in IFNα-induced STAT1 phosphorylation and nuclear translocation between HCV NS5A-expressed and non-HCV NS5A-expressed cells. Western blot was used to compare the phosphorylated STAT1 protein of the cells. RESULTS:Expression of HCV NS5A was found in the cytoplasm of P CNS5A-transfected Huh7 cells, but not in the PRC/ CMV transfected or non-transfected cells. STAT1 Tyr701 phosphorylation was found strongest in 30 min of IFN induction. STAT1 phosphorylation and nuclear import were much less in the presence of HCV NS5A protein in contrast to P RC/CMV-transfected and non-transfected cells under fluorescent microscopy, which was further confirmed by Western blot.CONCLUSION: HCV NS5A expression plasmid is successfully transfected into Huh7 cells and HCV NS5A protein is expressed in the cytoplasm of the cells. IFN-α is able to induce STAT1 phosphrylation and nuclear translocation, and this effect is inhibited by HCV NS5A protein, which might be another possible resistance mechanism to interferon alpha therapy.

show abstract

HCV NS5A inhibits interferon-α signaling through suppression of STAT1 phosphorylation in hepatocyte-derived cell lines

Cited by 50 publications

References 38 publications

Transcriptional Repression of C4 Complement by Hepatitis C Virus Proteins

Transcriptional Repression of C4 Complement by Hepatitis C Virus Proteins

Response of Hepatitis C Virus to Long-Term Passage in the Presence of Alpha Interferon: Multiple Mutations and a Common Phenotype

Hepatitis C Virus non-structural 5A abrogates signal transducer and activator of transcription-1 nucleartranslocation induced by IFN-α through dephosphorylation

Contact Info

Product

Resources

About