11 results on '"Ronik Khachatoorian"'
Search Results
2. Allosteric heat shock protein 70 inhibitors block hepatitis C virus assembly
- Author
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Asim Dasgupta, Christopher Sundberg, Samuel W. French, Ekambaram Ganapathy, Vaithilingaraja Arumugaswami, Rana Riahi, Piotr Ruchala, Nicole M. Wheatley, Hao Shao, Ronik Khachatoorian, Jason E. Gestwicki, and Chun-Ling Jung
- Subjects
0301 basic medicine ,Microbiology (medical) ,Cell Survival ,Viral protein ,viruses ,Hepacivirus ,Biology ,medicine.disease_cause ,Antiviral Agents ,Article ,Virus ,Cell Line ,03 medical and health sciences ,Viral entry ,medicine ,Viral structural protein ,Humans ,HSP70 Heat-Shock Proteins ,Pharmacology (medical) ,Enzyme Inhibitors ,NS5A ,Virus Assembly ,Viral translation ,HSC70 Heat-Shock Proteins ,General Medicine ,Virology ,Internal ribosome entry site ,030104 developmental biology ,Infectious Diseases ,Virion assembly ,Hepatocytes - Abstract
The human molecular chaperones heat shock protein 70 (Hsp70) and heat shock cognate protein 70 (Hsc70) bind to the hepatitis C viral nonstructural protein 5A (NS5A) and regulate its activity. Specifically, Hsp70 is involved in NS5A-augmented internal ribosomal entry site (IRES)-mediated translation of the viral genome, whilst Hsc70 appears to be primarily important for intracellular infectious virion assembly. To better understand the importance of these two chaperones in the viral life cycle, infected human cells were treated with allosteric Hsp70/Hsc70 inhibitors (AHIs). Treatment with AHIs significantly reduced the production of intracellular virus at concentrations that were non-toxic to human hepatoma Huh7.5 cells. The supernatant of treated cultures was then used to infect naïve cells, revealing that AHIs also lowered levels of secreted virus. In contrast to their effects on virion assembly, AHIs did not impact the stability of NS5A or viral protein translation in IRES assays. These results suggest that Hsc70 plays a particularly important and sensitive role in virion assembly. Indeed, it was found that combination of AHIs with a peptide-based viral translation inhibitor exhibited additive antiviral activity. Together these results suggest that the host Hsc70 is a new antiviral target and that its inhibitors utilise a new mechanism of action.
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- 2016
3. Oncoprotein Stathmin Modulates Sensitivity to Apoptosis in Hepatocellular Carcinoma Cells During Hepatitis C Viral Replication
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Ronik Khachatoorian, Asim Dasgupta, Nikita Patel, Lisa Liu, Peter Cho, Vaithilingaraja Arumugaswami, Samuel Wheeler French, Chae Yeon Kim, Nu T. Lu, James Q. Vu, Natalie M. Liu, Darshil Patel, Clara E. Magyar, and Ekambaram Ganapathy
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0301 basic medicine ,Liver Cancer ,Hepatitis C virus ,viruses ,Chronic Liver Disease and Cirrhosis ,Stathmin ,macromolecular substances ,Biology ,medicine.disease_cause ,Biochemistry ,Virus ,Hepatitis ,03 medical and health sciences ,0302 clinical medicine ,Rare Diseases ,Hepatitis - C ,medicine ,2.1 Biological and endogenous factors ,Replicon ,lcsh:QH573-671 ,Aetiology ,Original Research ,Cancer ,Gene knockdown ,STMN1 ,Cell growth ,lcsh:Cytology ,phosphorylation ,Liver Disease ,apoptosis ,Cell Biology ,hepatocellular carcinoma ,biochemical phenomena, metabolism, and nutrition ,medicine.disease ,digestive system diseases ,3. Good health ,030104 developmental biology ,Emerging Infectious Diseases ,Infectious Diseases ,Good Health and Well Being ,Apoptosis ,030220 oncology & carcinogenesis ,Hepatocellular carcinoma ,Cancer research ,biology.protein ,Digestive Diseases ,Infection ,microtubule - Abstract
Patients with chronic hepatitis C virus (HCV) infection risk complications of cirrhosis, liver failure, and hepatocellular carcinoma (HCC). Previously, our proteomic examination of hepatocytes carrying a HCV-replicon revealed that deregulation of cytoskeletal dynamics may be a potential mechanism of viral-induced HCC growth. Here, we demonstrate the effect of HCV replication on the microtubule regulator stathmin (STMN1) in HCC cells. We further explore how the altered activity or synthesis of stathmin affects cellular proliferation and sensitivity to apoptosis in control HCC cells (Huh7.5) and experimental HCV-replicon harboring HCC cells (R-Huh7.5). The HCV-replicon harboring HCC cells (R-Huh 7.5) lack viral structural genes/proteins for acute infectivity and thus is the standard model for in vitro chronic infection study. Knockdown of endogenous stathmin reduced sensitivity to apoptosis in replicon cells. Meanwhile, constitutively active stathmin increased sensitivity to apoptosis in replicon cells. In addition, overexpression of constitutively active stathmin reduced cell proliferation in both control and replicon cells. These findings implicate, for the first time, a novel role for stathmin in viral replication–related apoptosis. Stathmin’s potential role in HCV replication and HCC make it a candidate for the future study of viral-induced malignancies.
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- 2018
4. Chaperones in hepatitis C virus infection
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Samuel W. French and Ronik Khachatoorian
- Subjects
0301 basic medicine ,Hepatitis C virus ,viruses ,Chronic Liver Disease and Cirrhosis ,Protein degradation ,medicine.disease_cause ,2.2 Factors relating to physical environment ,Virus ,Hepatitis ,03 medical and health sciences ,Flaviviridae ,Hepatitis - C ,Viral life cycle ,Chaperones ,Genetics ,medicine ,2.1 Biological and endogenous factors ,Topic Highlight ,Heat shock proteins ,Hepatology ,biology ,Liver Disease ,RNA virus ,Hepatitis C ,biology.organism_classification ,medicine.disease ,Virology ,digestive system diseases ,NS2-3 protease ,Infectious Diseases ,Emerging Infectious Diseases ,030104 developmental biology ,HIV/AIDS ,Digestive Diseases ,Infection - Abstract
© The Author(s) 2016. The hepatitis C virus (HCV) infects approximately 3% of the world population or more than 185 million people worldwide. Each year, an estimated 350000-500000 deaths occur worldwide due to HCV-associated diseases including cirrhosis and hepatocellular carcinoma. HCV is the most common indication for liver transplantation in patients with cirrhosis worldwide. HCV is an enveloped RNA virus classified in the genus Hepacivirus in the Flaviviridae family. The HCV viral life cycle in a cell can be divided into six phases: (1) binding and internalization; (2) cytoplasmic release and uncoating; (3) viral polyprotein translation and processing; (4) RNA genome replication; (5) encapsidation (packaging) and assembly; and (6) virus morphogenesis (maturation) and secretion. Many host factors are involved in the HCV life cycle. Chaperones are an important group of host cytoprotective molecules that coordinate numerous cellular processes including protein folding, multimeric protein assembly, protein trafficking, and protein degradation. All phases of the viral life cycle require chaperone activity and the interaction of viral proteins with chaperones. This review will present our current knowledge and understanding of the role of chaperones in the HCV life cycle. Analysis of chaperones in HCV infection will provide further insights into viral/host interactions and potential therapeutic targets for both HCV and other viruses.
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- 2016
5. The Allosteric Heat Shock Protein Inhibitor YM‐01 Protects Against Alcohol‐Induced Growth Arrest
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Harsh Patel, Samuel W. French, Ekambaram Ganapathy, Vaithilingaraja Arumugaswami, and Ronik Khachatoorian
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Liver injury ,chemistry.chemical_classification ,Reactive oxygen species ,biology ,Allosteric regulation ,Cytochrome P450 ,CYP2E1 ,Heat Shock Protein Inhibitor ,Pharmacology ,medicine.disease ,medicine.disease_cause ,Biochemistry ,Pathogenesis ,chemistry ,Genetics ,biology.protein ,medicine ,Molecular Biology ,Oxidative stress ,Biotechnology - Abstract
Background: Oxidative stress is implicated in the pathogenesis of alcohol-induced liver injury. This is, in part, mediated by the cytochrome P450 CYP2E1 which contributes to reactive oxygen species...
- Published
- 2015
6. The heat shock protein 70 family members HSC70 and HSP70 play distinct roles in the hepatitis C viral life cycle (144.1)
- Author
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Christopher Sundberg, Asim Dasgupta, Ekambaram Ganapathy, Chun-Ling Jung, Ronik Khachatoorian, Yasaman Ahmadieh, Nicole M. Wheatley, Samuel W. French, Santanu Raychaudhuri, and Vaithilingaraja Arumugaswami
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Gene knockdown ,animal structures ,Viral protein ,viruses ,macromolecular substances ,Biology ,medicine.disease_cause ,Biochemistry ,Virology ,Cell biology ,Hsp70 ,Viral life cycle ,Virion assembly ,Heat shock protein ,embryonic structures ,Genetics ,medicine ,Protein biosynthesis ,NS5A ,Molecular Biology ,Biotechnology - Abstract
We have previously identified HSC70 in complex with viral NS5A along with other heat shock proteins. HSC70 has been reported to modulate HCV infectivity. Here, we further analyze the NS5A/HSC70 interaction biochemically and investigate the role of HSC70 in viral life cycle. We demonstrate that HSC70 knockdown significantly affects virus production with no cytotoxicity. We observed that HSC70 knockdown did not affect viral RNA replication and protein production. In fact, we found a slight, but statistically significant increase in viral RNA and protein levels likely caused by compensatory upregulation of HSP70, which we have previously shown to be required for viral protein production. NS5A-augmented IRES-mediated translation was also not inhibited by HSC70 knockdown and, rather, slightly increased. In contrast, we discovered that intracellular infectious virion assembly was significantly impaired by HSC70 knockdown. We also discovered that both HSC70 nucleotide binding and substrate binding domains direct...
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- 2014
7. Quercetin: bioflavonoids as part of interferon-free hepatitis C therapy?
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Nu Lu, Samuel W. French, and Ronik Khachatoorian
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Microbiology (medical) ,Naringenin ,Hepatitis C virus ,Hepacivirus ,Pharmacology ,medicine.disease_cause ,Microbiology ,chemistry.chemical_compound ,Virology ,Heat shock protein ,medicine ,Humans ,HSP70 Heat-Shock Proteins ,NS5A ,Randomized Controlled Trials as Topic ,Flavonoids ,business.industry ,Interferon free ,virus diseases ,Hepatitis C ,medicine.disease ,digestive system diseases ,Internal ribosome entry site ,Infectious Diseases ,chemistry ,Quercetin ,Interferons ,business - Abstract
HCV affects more than 170 million people worldwide, including 3.2 million Americans. It accounts for more than 350,000 deaths globally each year [101,102]. Although some HCV-infected patients spont...
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- 2012
8. A cell permeable hairpin peptide inhibits hepatitis C viral NS5A‐mediated translation and virus production
- Author
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Ronik Khachatoorian, Santanu Raychaudhuri, Eden M. Maloney, Asim Dasgupta, Vaithilingaraja Arumugaswami, Samuel Wheeler French, Edna Miao, and Piotr Ruchala
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chemistry.chemical_classification ,Hepatitis c viral ,Chemistry ,Cell ,Translation (biology) ,Peptide ,Biochemistry ,Virology ,Molecular biology ,Virus ,medicine.anatomical_structure ,Genetics ,medicine ,NS5A ,Molecular Biology ,Biotechnology - Published
- 2012
9. A Cell-Permeable Hairpin Peptide Inhibits Hepatitis C Viral Nonstructural Protein 5A Mediated Translation and Virus Production
- Author
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Asim Dasgupta, Edna Miao, Ronik Khachatoorian, Eden M. Maloney, Piotr Ruchala, Samuel W. French, Santanu Raychaudhuri, and Vaithilingaraja Arumugaswami
- Subjects
Viral protein ,viruses ,Biology ,Viral Nonstructural Proteins ,medicine.disease_cause ,Virus Replication ,Ribosome ,Article ,Protein structure ,medicine ,Protein biosynthesis ,Humans ,HSP70 Heat-Shock Proteins ,NS5A ,Cells, Cultured ,Binding Sites ,Hepatology ,virus diseases ,Translation (biology) ,biochemical phenomena, metabolism, and nutrition ,Molecular biology ,digestive system diseases ,Peptide Fragments ,Protein Structure, Tertiary ,Internal ribosome entry site ,Viral replication ,Drug Design ,Protein Biosynthesis ,Ribosomes - Abstract
NS5A is a key regulator of the hepatitis C virus (HCV) life cycle including RNA replication, assembly, and translation. We and others have shown that NS5A augments HCV internal ribosomal entry site (IRES)-mediated translation. Furthermore, Quercetin treatment and heat shock protein (HSP) 70 knockdown inhibit the NS5A-driven augmentation of IRES-mediated translation and infectious virus production. We have also coimmunoprecipitated HSP70 with NS5A and demonstrated cellular colocalization, leading to the hypothesis that the NS5A/HSP70 complex formation is important for IRES-mediated translation. Here, we have identified the NS5A region responsible for complex formation through in vitro deletion analyses. Deletion of NS5A domains II and III failed to reduce HSP70 binding, whereas domain I deletion eliminated complex formation. NS5A domain I alone also bound HSP70. Deletion mapping of domain I identified the C-terminal 34 amino acids (C34) as the interaction site. Furthermore, addition of C34 to domains II and III restored complex formation. C34 expression significantly reduced intracellular viral protein levels, in contrast to same-size control peptides from other NS5A domains. C34 also competitively inhibited NS5A-augmented IRES-mediated translation, whereas controls did not. Triple-alanine scan mutagenesis determined that an exposed beta-sheet hairpin in C34 was primarily responsible for NS5A-augmented IRES-mediated translation. Moreover, treatment with a 10–amino acid peptide derivative of C34 suppressed NS5A-augmented IRES-mediated translation and significantly inhibited intracellular viral protein synthesis, with no associated cytotoxicity. Conclusion: These results support the hypothesis that the NS5A/HSP70 complex augments viral IRES-mediated translation, identify a sequence-specific hairpin element in NS5A responsible for complex formation, and demonstrate the functional significance of C34 hairpin–mediated NS5A/HSP70 interaction. Identification of this element may allow for further interrogation of NS5A-mediated IRES activity, sequence-specific HSP recognition, and rational drug design. (HEPATOLOGY 2012;55:1662–1672)
- Published
- 2012
10. Divergent antiviral effects of bioflavonoids on the hepatitis C virus life cycle
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Julie Wang, George K. Yeh, Samuel W. French, Eden M. Maloney, Santanu Raychaudhuri, Vaithilingaraja Arumugaswami, Ronik Khachatoorian, and Asim Dasgupta
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Naringenin ,viruses ,Hepacivirus ,Microbial Sensitivity Tests ,Viral Nonstructural Proteins ,Biology ,NS5A ,Antiviral Agents ,Catechin ,Article ,Cell Line ,Viral Proteins ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Interferon ,IRES ,Virology ,medicine ,Humans ,HSP70 Heat-Shock Proteins ,heterocyclic compounds ,HSP70 ,030304 developmental biology ,Flavonoids ,0303 health sciences ,Virus Assembly ,Viral translation ,food and beverages ,Molecular biology ,3. Good health ,Internal ribosome entry site ,HEK293 Cells ,chemistry ,Virion assembly ,Protein Biosynthesis ,030220 oncology & carcinogenesis ,Flavanones ,HCV ,Quercetin ,Bioflavonoid ,medicine.drug - Abstract
We have previously demonstrated that quercetin, a bioflavonoid, blocks hepatitis C virus (HCV) proliferation by inhibiting NS5A-driven internal ribosomal entry site (IRES)-mediated translation of the viral genome. Here, we investigate the mechanisms of antiviral activity of quercetin and six additional bioflavonoids. We demonstrate that catechin, naringenin, and quercetin possess significant antiviral activity, with no associated cytotoxicity. Infectious virion secretion was not significantly altered by these bioflavonoids. Catechin and naringenin demonstrated stronger inhibition of infectious virion assembly compared to quercetin. Quercetin markedly blocked viral translation whereas catechin and naringenin demonstrated mild activity. Similarly quercetin completely blocked NS5A-augmented IRES-mediated translation in an IRES reporter assay, whereas catechin and naringenin had only a mild effect. Moreover, quercetin differentially inhibited HSP70 induction compared to catechin and naringenin. Thus, the antiviral activity of these bioflavonoids is mediated through different mechanisms. Therefore combination of these bioflavonoids may act synergistically against HCV.
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11. The NS5A-binding heat shock proteins HSC70 and HSP70 play distinct roles in the hepatitis C viral life cycle
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Samuel W. French, Ronik Khachatoorian, Vaithilingaraja Arumugaswami, Chun-Ling Jung, Asim Dasgupta, Yasaman Ahmadieh, Santanu Raychaudhuri, Christopher Sundberg, Ekambaram Ganapathy, and Nicole M. Wheatley
- Subjects
animal structures ,HSC70 ,Viral protein ,viruses ,Assembly ,Plasma protein binding ,Hepacivirus ,macromolecular substances ,Biology ,Viral Nonstructural Proteins ,medicine.disease_cause ,Virus Replication ,NS5A ,Article ,Viral life cycle ,IRES ,Virology ,Heat shock protein ,medicine ,Medicine and Health Sciences ,Humans ,Immunoprecipitation ,HSP70 Heat-Shock Proteins ,HSP70 ,Gene knockdown ,Microscopy, Confocal ,Virus Assembly ,Molecular biology ,3. Good health ,Hsp70 ,Viral replication ,Virion assembly ,Host-Pathogen Interactions ,embryonic structures ,HCV ,Protein Binding - Abstract
We previously identified HSP70 and HSC70 in complex with NS5A in a proteomic screen. Here, coimmunoprecipitation studies confirmed NS5A/HSC70 complex formation during infection, and immunofluorescence studies showed NS5A and HSC70 to colocalize. Unlike HSP70, HSC70 knockdown did not decrease viral protein levels. Rather, intracellular infectious virion assembly was significantly impaired by HSC70 knockdown. We also discovered that both HSC70 nucleotide binding and substrate binding domains directly bind NS5A whereas only the HSP70 nucleotide binding domain does. Knockdown of both HSC70 and HSP70 demonstrated an additive reduction in virus production. This data suggests that HSC70 and HSP70 play discrete roles in the viral life cycle. Investigation of these different functions may facilitate developing of novel strategies that target host proteins to treat HCV infection.
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