1
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Stauffer WT, Goodman AZ, Gallay PA. Cyclophilin inhibition as a strategy for the treatment of human disease. Front Pharmacol 2024; 15:1417945. [PMID: 39045055 PMCID: PMC11264201 DOI: 10.3389/fphar.2024.1417945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Accepted: 06/14/2024] [Indexed: 07/25/2024] Open
Abstract
Cyclophilins (Cyps), characterized as peptidyl-prolyl cis-trans isomerases (PPIases), are highly conserved and ubiquitous, playing a crucial role in protein folding and cellular signaling. This review summarizes the biochemical pathways mediated by Cyps, including their involvement in pathological states such as viral replication, inflammation, and cancer progression, to underscore the therapeutic potential of Cyp inhibition. The exploration of Cyp inhibitors (CypI) in this review, particularly non-immunosuppressive cyclosporine A (CsA) derivatives, highlights their significance as therapeutic agents. The structural and functional nuances of CsA derivatives are examined, including their efficacy, mechanism of action, and the balance between therapeutic benefits and off-target effects. The landscape of CypI is evaluated to emphasize the clinical need for targeted approaches to exploit the complex biology of Cyps and to propose future directions for research that may enhance the utility of non-immunosuppressive CsA derivatives in treating diseases where Cyps play a key pathological role.
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Affiliation(s)
| | | | - Philippe A. Gallay
- Department of Immunology & Microbiology, The Scripps Research Institute, La Jolla, CA, United States
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2
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Lu HJ, Koju N, Sheng R. Mammalian integrated stress responses in stressed organelles and their functions. Acta Pharmacol Sin 2024; 45:1095-1114. [PMID: 38267546 PMCID: PMC11130345 DOI: 10.1038/s41401-023-01225-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 12/30/2023] [Indexed: 01/26/2024] Open
Abstract
The integrated stress response (ISR) triggered in response to various cellular stress enables mammalian cells to effectively cope with diverse stressful conditions while maintaining their normal functions. Four kinases (PERK, PKR, GCN2, and HRI) of ISR regulate ISR signaling and intracellular protein translation via mediating the phosphorylation of eukaryotic translation initiation factor 2 α (eIF2α) at Ser51. Early ISR creates an opportunity for cells to repair themselves and restore homeostasis. This effect, however, is reversed in the late stages of ISR. Currently, some studies have shown the non-negligible impact of ISR on diseases such as ischemic diseases, cognitive impairment, metabolic syndrome, cancer, vanishing white matter, etc. Hence, artificial regulation of ISR and its signaling with ISR modulators becomes a promising therapeutic strategy for relieving disease symptoms and improving clinical outcomes. Here, we provide an overview of the essential mechanisms of ISR and describe the ISR-related pathways in organelles including mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes. Meanwhile, the regulatory effects of ISR modulators and their potential application in various diseases are also enumerated.
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Affiliation(s)
- Hao-Jun Lu
- Department of Pharmacology and Laboratory of Aging and Nervous Diseases, Jiangsu Key Laboratory of Neuropsychiatric Diseases, College of Pharmaceutical Sciences of Soochow University, Suzhou, 215123, China
| | - Nirmala Koju
- Department of Pharmacology and Laboratory of Aging and Nervous Diseases, Jiangsu Key Laboratory of Neuropsychiatric Diseases, College of Pharmaceutical Sciences of Soochow University, Suzhou, 215123, China
| | - Rui Sheng
- Department of Pharmacology and Laboratory of Aging and Nervous Diseases, Jiangsu Key Laboratory of Neuropsychiatric Diseases, College of Pharmaceutical Sciences of Soochow University, Suzhou, 215123, China.
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3
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Maneix L, Iakova P, Lee CG, Moree SE, Lu X, Datar GK, Hill CT, Spooner E, King JCK, Sykes DB, Saez B, Di Stefano B, Chen X, Krause DS, Sahin E, Tsai FTF, Goodell MA, Berk BC, Scadden DT, Catic A. Cyclophilin A supports translation of intrinsically disordered proteins and affects haematopoietic stem cell ageing. Nat Cell Biol 2024; 26:593-603. [PMID: 38553595 PMCID: PMC11021199 DOI: 10.1038/s41556-024-01387-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 02/23/2024] [Indexed: 04/11/2024]
Abstract
Loss of protein function is a driving force of ageing. We have identified peptidyl-prolyl isomerase A (PPIA or cyclophilin A) as a dominant chaperone in haematopoietic stem and progenitor cells. Depletion of PPIA accelerates stem cell ageing. We found that proteins with intrinsically disordered regions (IDRs) are frequent PPIA substrates. IDRs facilitate interactions with other proteins or nucleic acids and can trigger liquid-liquid phase separation. Over 20% of PPIA substrates are involved in the formation of supramolecular membrane-less organelles. PPIA affects regulators of stress granules (PABPC1), P-bodies (DDX6) and nucleoli (NPM1) to promote phase separation and increase cellular stress resistance. Haematopoietic stem cell ageing is associated with a post-transcriptional decrease in PPIA expression and reduced translation of IDR-rich proteins. Here we link the chaperone PPIA to the synthesis of intrinsically disordered proteins, which indicates that impaired protein interaction networks and macromolecular condensation may be potential determinants of haematopoietic stem cell ageing.
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Affiliation(s)
- Laure Maneix
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX, USA
- Stem Cells and Regenerative Medicine Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
- Cell and Gene Therapy Program at the Dan L. Duncan Comprehensive Cancer Center, Houston, TX, USA
| | - Polina Iakova
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX, USA
- Stem Cells and Regenerative Medicine Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
- Cell and Gene Therapy Program at the Dan L. Duncan Comprehensive Cancer Center, Houston, TX, USA
| | - Charles G Lee
- Department of BioSciences, Rice University, Houston, TX, USA
| | - Shannon E Moree
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX, USA
- Stem Cells and Regenerative Medicine Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
- Cell and Gene Therapy Program at the Dan L. Duncan Comprehensive Cancer Center, Houston, TX, USA
| | - Xuan Lu
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
| | - Gandhar K Datar
- Stem Cells and Regenerative Medicine Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
| | - Cedric T Hill
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Eric Spooner
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | - Jordon C K King
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX, USA
- Stem Cells and Regenerative Medicine Center, Baylor College of Medicine, Houston, TX, USA
- Cell and Gene Therapy Program at the Dan L. Duncan Comprehensive Cancer Center, Houston, TX, USA
| | - David B Sykes
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Borja Saez
- Center for Applied Medical Research, Hematology-Oncology Unit, Pamplona, Navarra, Spain
| | - Bruno Di Stefano
- Stem Cells and Regenerative Medicine Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
- Cell and Gene Therapy Program at the Dan L. Duncan Comprehensive Cancer Center, Houston, TX, USA
| | - Xi Chen
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
| | - Daniela S Krause
- Georg-Speyer-Haus, Institute for Tumor Biology and Experimental Therapy, Frankfurt am Main, Germany
| | - Ergun Sahin
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Francis T F Tsai
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
- Department of Biochemistry and Molecular Pharmacology, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Margaret A Goodell
- Stem Cells and Regenerative Medicine Center, Baylor College of Medicine, Houston, TX, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
- Cell and Gene Therapy Program at the Dan L. Duncan Comprehensive Cancer Center, Houston, TX, USA
| | - Bradford C Berk
- Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - David T Scadden
- Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - André Catic
- Huffington Center on Aging, Baylor College of Medicine, Houston, TX, USA.
- Stem Cells and Regenerative Medicine Center, Baylor College of Medicine, Houston, TX, USA.
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA.
- Cell and Gene Therapy Program at the Dan L. Duncan Comprehensive Cancer Center, Houston, TX, USA.
- Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX, USA.
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4
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Zhao X, Zhao X, Di W, Wang C. Inhibitors of Cyclophilin A: Current and Anticipated Pharmaceutical Agents for Inflammatory Diseases and Cancers. Molecules 2024; 29:1235. [PMID: 38542872 PMCID: PMC10974348 DOI: 10.3390/molecules29061235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 03/02/2024] [Accepted: 03/05/2024] [Indexed: 04/07/2024] Open
Abstract
Cyclophilin A, a widely prevalent cellular protein, exhibits peptidyl-prolyl cis-trans isomerase activity. This protein is predominantly located in the cytosol; additionally, it can be secreted by the cells in response to inflammatory stimuli. Cyclophilin A has been identified to be a key player in many of the biological events and is therefore involved in several diseases, including vascular and inflammatory diseases, immune disorders, aging, and cancers. It represents an attractive target for therapeutic intervention with small molecule inhibitors such as cyclosporin A. Recently, a number of novel inhibitors of cyclophilin A have emerged. However, it remains elusive whether and how many cyclophilin A inhibitors function in the inflammatory diseases and cancers. In this review, we discuss current available data about cyclophilin A inhibitors, including cyclosporin A and its derivatives, quinoxaline derivatives, and peptide analogues, and outline the most recent advances in clinical trials of these agents. Inhibitors of cyclophilin A are poised to enhance our comprehension of the molecular mechanisms that underpin inflammatory diseases and cancers associated with cyclophilin A. This advancement will aid in the development of innovative pharmaceutical treatments in the future.
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Affiliation(s)
- Xuemei Zhao
- School of Pharmaceutical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciences, Ji’nan 250000, China; (X.Z.); (W.D.)
| | - Xin Zhao
- School of Pharmaceutical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciences, Ji’nan 250000, China; (X.Z.); (W.D.)
| | - Weihua Di
- School of Pharmaceutical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciences, Ji’nan 250000, China; (X.Z.); (W.D.)
| | - Chang Wang
- School of Pharmaceutical Sciences, Shandong First Medical University & Shandong Academy of Medical Sciences, Ji’nan 250000, China; (X.Z.); (W.D.)
- Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Ji’nan 250000, China
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5
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Mamatis JE, Pellizzari-Delano IE, Gallardo-Flores CE, Colpitts CC. Emerging Roles of Cyclophilin A in Regulating Viral Cloaking. Front Microbiol 2022; 13:828078. [PMID: 35242122 PMCID: PMC8886124 DOI: 10.3389/fmicb.2022.828078] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 01/26/2022] [Indexed: 12/24/2022] Open
Abstract
Cellular cyclophilins (Cyps) such as cyclophilin A (CypA) have emerged as key players at the virus-host interface. As host factors required for the replication of many unrelated viruses, including human immunodeficiency virus (HIV), hepatitis C virus (HCV) and coronaviruses (CoVs), Cyps are attractive targets for antiviral therapy. However, a clear understanding of how these viruses exploit Cyps to promote their replication has yet to be elucidated. Recent findings suggest that CypA contributes to cloaking of viral replication intermediates, an evasion strategy that prevents detection of viral nucleic acid by innate immune sensors. Furthermore, Cyps are emerging to have roles in regulation of cellular antiviral signaling pathways. Recruitment of Cyps by viral proteins may interfere with their ability to regulate these signaling factors. Consistent with disruption of viral cloaking and innate immune evasion, treatment with Cyp inhibitors such as cyclosporine A (CsA) restores antiviral innate immunity and induces expression of a subset of antiviral genes that restrict viral infection, which may help to explain the broad antiviral spectrum of CsA. In this review, we provide an overview of the roles of CypA in viral cloaking and evasion of innate immunity, focusing on the underlying mechanisms and new perspectives for antiviral therapies.
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Affiliation(s)
- John E Mamatis
- Department of Biomedical and Molecular Sciences, Faculty of Health Sciences, Queen's University, Kingston, ON, Canada
| | - Isabella E Pellizzari-Delano
- Department of Biomedical and Molecular Sciences, Faculty of Health Sciences, Queen's University, Kingston, ON, Canada
| | - Carla E Gallardo-Flores
- Department of Biomedical and Molecular Sciences, Faculty of Health Sciences, Queen's University, Kingston, ON, Canada
| | - Che C Colpitts
- Department of Biomedical and Molecular Sciences, Faculty of Health Sciences, Queen's University, Kingston, ON, Canada
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6
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Mitra S, Anand U, Sanyal R, Jha NK, Behl T, Mundhra A, Ghosh A, Radha, Kumar M, Proćków J, Dey A. Neoechinulins: Molecular, cellular, and functional attributes as promising therapeutics against cancer and other human diseases. Biomed Pharmacother 2021; 145:112378. [PMID: 34741824 DOI: 10.1016/j.biopha.2021.112378] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 10/23/2021] [Accepted: 10/25/2021] [Indexed: 12/21/2022] Open
Abstract
Neoechinulins are fungal and plant-derived chemicals extracted from Microsporum sp., Eurotium rubrum, Aspergillus sp., etc. Two analogues of neoechinulin, i.e., A and B, exerted extensive pharmacological properties described in this review. Neoechinulin is an indole alkaloid and has a double bond between C8/C9, which tends to contribute to its cytoprotective nature. Neoechinulin A exhibits protection to PC12 cells against nitrosative stress via increasing NAD(P)H reserve capacity and decreasing cellular GSH levels. It also confers protection via rescuing PC12 cells from rotenone-induced stress by lowering LDH leakage. This compound has great positive potential against neurodegenerative diseases by inhibiting SIN-1 induced cell death in neuronal cells. Together with these, neoechinulin A tends to inhibit Aβ42-induced microglial activation and confers protection against neuroinflammation. Alongside, it also inhibits cervical cancer cells by caspase-dependent apoptosis and via upregulation of apoptosis inducing genes like Bax, it suppresses LPS-induced inflammation in RAW264.7 macrophages and acts as an antidepressant. Whereas, another analogue, Neoechinulin B tends to interfere with the cellular mechanism thereby, inhibiting the entry of influenza A virus and it targets Liver X receptor (LXR) and decreases the infection rate of Hepatitis C. The present review describes the pharmaceutical properties of neoechinulins with notes on their molecular, cellular, and functional basis and their therapeutic properties.
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Affiliation(s)
- Sicon Mitra
- Department of Biotechnology, School of Engineering & Technology, Sharda University, Greater Noida 201310, Uttar Pradesh, India
| | - Uttpal Anand
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | - Rupa Sanyal
- Department of Botany, Bhairab Ganguly College (affiliated to West Bengal State University), Feeder Road, Belghoria, Kolkata 700056, West Bengal, India
| | - Niraj Kumar Jha
- Department of Biotechnology, School of Engineering & Technology, Sharda University, Greater Noida 201310, Uttar Pradesh, India
| | - Tapan Behl
- Chitkara College of Pharmacy, Chitkara University, Punjab 140401, India
| | - Avinash Mundhra
- Department of Botany, Rishi Bankim Chandra College (Affiliated to the West Bengal State University), East Kantalpara, North 24 Parganas, Naihati 743165, West Bengal, India
| | - Arabinda Ghosh
- Department of Botany, Gauhati University, Guwahati, Assam 781014, India
| | - Radha
- School of Biological and Environmental Sciences, Shoolini University of Biotechnology and Management Sciences, Solan, Himachal Pradesh 173229, India
| | - Manoj Kumar
- Chemical and Biochemical Processing Division, ICAR - Central Institute for Research on Cotton Technology, Mumbai 400019, Maharashtra, India
| | - Jarosław Proćków
- Department of Plant Biology, Institute of Environmental Biology, Wrocław University of Environmental and Life Sciences, Kożuchowska 5b, 51-631 Wrocław, Poland.
| | - Abhijit Dey
- Department of Life Sciences, Presidency University, 86/1 College Street, Kolkata, 700073, West Bengal, India.
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7
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Gallardo-Flores CE, Colpitts CC. Cyclophilins and Their Roles in Hepatitis C Virus and Flavivirus Infections: Perspectives for Novel Antiviral Approaches. Pathogens 2021; 10:902. [PMID: 34358052 PMCID: PMC8308494 DOI: 10.3390/pathogens10070902] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 07/07/2021] [Accepted: 07/15/2021] [Indexed: 12/19/2022] Open
Abstract
Cyclophilins are cellular peptidyl-prolyl isomerases that play an important role in viral infections, with demonstrated roles in the replication of hepatitis C virus (HCV) and other viruses in the Flaviviridae family, such as dengue virus (DENV) and yellow fever virus (YFV). Here, we discuss the roles of cyclophilins in HCV infection and provide a comprehensive overview of the mechanisms underlying the requirement for cyclophilins during HCV replication. Notably, cyclophilin inhibitor therapy has been demonstrated to be effective in reducing HCV replication in chronically infected patients. While the roles of cyclophilins are relatively well-understood for HCV infection, cyclophilins are more recently emerging as host factors for flavivirus infection as well, providing potential new therapeutic avenues for these viral infections which currently lack antiviral therapies. However, further studies are required to elucidate the roles of cyclophilins in flavivirus replication. Here, we review the current knowledge of the role of cyclophilins in HCV infection to provide a conceptual framework to understand how cyclophilins may contribute to other viral infections, such as DENV and YFV. Improved understanding of the roles of cyclophilins in viral infection may open perspectives for the development of cyclophilin inhibitors as effective antiviral therapeutics for HCV and related viruses.
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Affiliation(s)
| | - Che C. Colpitts
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L 3N6, Canada;
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8
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Roca Suarez AA, Testoni B, Baumert TF, Lupberger J. Nucleic Acid-Induced Signaling in Chronic Viral Liver Disease. Front Immunol 2021; 11:624034. [PMID: 33613561 PMCID: PMC7892431 DOI: 10.3389/fimmu.2020.624034] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 12/21/2020] [Indexed: 12/12/2022] Open
Abstract
A hallmark for the development and progression of chronic liver diseases is the persistent dysregulation of signaling pathways related to inflammatory responses, which eventually promotes the development of hepatic fibrosis, cirrhosis and hepatocellular carcinoma (HCC). The two major etiological agents associated with these complications in immunocompetent patients are hepatitis B virus (HBV) and hepatitis C virus (HCV), accounting for almost 1.4 million liver disease-associated deaths worldwide. Although both differ significantly from the point of their genomes and viral life cycles, they exert not only individual but also common strategies to divert innate antiviral defenses. Multiple virus-modulated pathways implicated in stress and inflammation illustrate how chronic viral hepatitis persistently tweaks host signaling processes with important consequences for liver pathogenesis. The following review aims to summarize the molecular events implicated in the sensing of viral nucleic acids, the mechanisms employed by HBV and HCV to counter these measures and how the dysregulation of these cellular pathways drives the development of chronic liver disease and the progression toward HCC.
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MESH Headings
- Carcinoma, Hepatocellular/immunology
- Carcinoma, Hepatocellular/mortality
- Carcinoma, Hepatocellular/pathology
- DNA, Viral/immunology
- Hepacivirus/immunology
- Hepatitis B virus/immunology
- Hepatitis B, Chronic/immunology
- Hepatitis B, Chronic/mortality
- Hepatitis B, Chronic/pathology
- Hepatitis C, Chronic/immunology
- Hepatitis C, Chronic/mortality
- Hepatitis C, Chronic/pathology
- Humans
- Liver Neoplasms/immunology
- Liver Neoplasms/mortality
- Liver Neoplasms/pathology
- RNA, Viral/immunology
- Signal Transduction/immunology
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Affiliation(s)
- Armando Andres Roca Suarez
- INSERM, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
- INSERM U1052, CNRS UMR-5286, Cancer Research Center of Lyon (CRCL), Lyon, France
- University of Lyon, Université Claude-Bernard (UCBL), Lyon, France
| | - Barbara Testoni
- INSERM U1052, CNRS UMR-5286, Cancer Research Center of Lyon (CRCL), Lyon, France
- University of Lyon, Université Claude-Bernard (UCBL), Lyon, France
| | - Thomas F. Baumert
- INSERM, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
- Institut Hospitalo-Universitaire, Pôle Hépato-digestif, Nouvel Hôpital Civil, Strasbourg, France
- Institut Universitaire de France (IUF), Paris, France
| | - Joachim Lupberger
- INSERM, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, Strasbourg, France
- Université de Strasbourg, Strasbourg, France
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9
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ISGylation of Hepatitis C Virus NS5A Protein Promotes Viral RNA Replication via Recruitment of Cyclophilin A. J Virol 2020; 94:JVI.00532-20. [PMID: 32727878 DOI: 10.1128/jvi.00532-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 07/24/2020] [Indexed: 12/14/2022] Open
Abstract
Interferon-stimulated gene 15 (ISG15) is a ubiquitin-like protein that is covalently conjugated to many substrate proteins in order to modulate their functions; this conjugation is called ISGylation. Several groups reported that the ISGylation of hepatitis C virus (HCV) NS5A protein affects HCV replication. However, the ISG15 conjugation sites on NS5A are not well determined, and it is unclear whether the role of NS5A ISGylation in HCV replication is proviral or antiviral. Here, we investigated the role of NS5A ISGylation in HCV replication by using HCV RNA replicons that encode a mutation at each lysine (Lys) residue of the NS5A protein. Immunoblot analyses revealed that 5 Lys residues (K44, K68, K166, K215, and K308) of the 14 Lys residues within NS5A (genotype 1b, Con1) have the potential to accept ISGylation. We tested the NS5A ISGylation among different HCV genotypes and observed that the NS5A proteins of all of the HCV genotypes accept ISGylation at multiple Lys residues. Using an HCV luciferase reporter replicon assay revealed that residue K308 of NS5A is important for HCV (1b, Con1) RNA replication. We observed that K308, one of the Lys residues for NS5A ISGylation, is located within the binding region of cyclophilin A (CypA), which is the critical host factor for HCV replication. We obtained evidence derived from all of the HCV genotypes suggesting that NS5A ISGylation enhances the interaction between NS5A and CypA. Taken together, these results suggest that NS5A ISGylation functions as a proviral factor and promotes HCV replication via the recruitment of CypA.IMPORTANCE Host cells have evolved host defense machinery (such as innate immunity) to eliminate viral infections. Viruses have evolved several counteracting strategies for achieving an immune escape from host defense machinery, including type I interferons (IFNs) and inflammatory cytokines. ISG15 is an IFN-inducible ubiquitin-like protein that is covalently conjugated to the viral protein via specific Lys residues and suppresses viral functions and viral propagation. Here, we demonstrate that HCV NS5A protein accepts ISG15 conjugation at specific Lys residues and that the HERC5 E3 ligase specifically promotes NS5A ISGylation. We obtained evidence suggesting that NS5A ISGylation facilitates the recruitment of CypA, which is the critical host factor for HCV replication, thereby promoting HCV replication. These findings indicate that E3 ligase HERC5 is a potential therapeutic target for HCV infection. We propose that HCV hijacks an intracellular ISG15 function to escape the host defense machinery in order to establish a persistent infection.
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10
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Colpitts CC, Ridewood S, Schneiderman B, Warne J, Tabata K, Ng CF, Bartenschlager R, Selwood DL, Towers GJ. Hepatitis C virus exploits cyclophilin A to evade PKR. eLife 2020; 9:e52237. [PMID: 32539931 PMCID: PMC7297535 DOI: 10.7554/elife.52237] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 05/28/2020] [Indexed: 12/12/2022] Open
Abstract
Counteracting innate immunity is essential for successful viral replication. Host cyclophilins (Cyps) have been implicated in viral evasion of host antiviral responses, although the mechanisms are still unclear. Here, we show that hepatitis C virus (HCV) co-opts the host protein CypA to aid evasion of antiviral responses dependent on the effector protein kinase R (PKR). Pharmacological inhibition of CypA rescues PKR from antagonism by HCV NS5A, leading to activation of an interferon regulatory factor-1 (IRF1)-driven cell intrinsic antiviral program that inhibits viral replication. These findings further the understanding of the complexity of Cyp-virus interactions, provide mechanistic insight into the remarkably broad antiviral spectrum of Cyp inhibitors, and uncover novel aspects of PKR activity and regulation. Collectively, our study identifies a novel antiviral mechanism that harnesses cellular antiviral immunity to suppress viral replication.
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Affiliation(s)
- Che C Colpitts
- Department of Biomedical and Molecular Sciences, Queen’s UniversityKingstonCanada
- Division of Infection and Immunity, University College LondonLondonUnited Kingdom
| | - Sophie Ridewood
- Division of Infection and Immunity, University College LondonLondonUnited Kingdom
| | - Bethany Schneiderman
- Division of Infection and Immunity, University College LondonLondonUnited Kingdom
| | - Justin Warne
- Wolfson Institute for Biomedical Research, UCLLondonUnited Kingdom
| | - Keisuke Tabata
- Department of Infectious Diseases, Molecular Virology, Heidelberg UniversityHeidelbergGermany
| | - Caitlin F Ng
- Division of Infection and Immunity, University College LondonLondonUnited Kingdom
| | - Ralf Bartenschlager
- Department of Infectious Diseases, Molecular Virology, Heidelberg UniversityHeidelbergGermany
- Division Virus-Associated Carcinogenesis, German Cancer Research CenterHeidelbergGermany
- German Center for Infection Research (DZIF), Heidelberg Partner SiteHeidelbergGermany
| | - David L Selwood
- Department of Medicine, Imperial College LondonLondonUnited Kingdom
| | - Greg J Towers
- Division of Infection and Immunity, University College LondonLondonUnited Kingdom
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11
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Stanciu C, Trifan A, Muzica C, Sfarti C. Efficacy and safety of alisporivir for the treatment of hepatitis C infection. Expert Opin Pharmacother 2019; 20:379-384. [PMID: 30576256 DOI: 10.1080/14656566.2018.1560424] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Alisporivir (ALV) (previously known as Debio 025) is a potent, pangenotypic host-targeting antiviral oral agent acting on cyclophilin A, which is necessary for HCV replication. Areas covered: This article reviews the therapeutic efficacy and safety of ALV for the treatment of HCV infection. Expert opinion: Direct-acting antivirals (DAAs) have revolutionized the HCV antiviral treatment paradigm with success rates well above 95% for all HCV genotypes. However, challenges still remain in certain patient populations such as those who have developed resistance and have experienced multi-DAA failure. To cure HCV infection, a treatment regimen must combine antiviral potency and a high barrier to resistance. ALV fulfills this need as shown by the studies evaluating its clinical efficacy. Nevertheless, ALV missed the chance to be included in the HCV treatment armamentarium after the FDA halted clinical studies following reports of serious side effects (three cases of pancreatitis, one lethal). However, it is possible that ALV could still be considered for HCV-infected non-cirrhotic patients that are infected with a multiresistant virus or with HCV genotype 3, although it must be said that the drug industry would be reluctant to invest in new antivirals if the current clinical need is effectively met.
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Affiliation(s)
- Carol Stanciu
- a Department of Gastroenterology , Grigore T. Popa University of Medicine and Pharmacy , Iasi , Romania
- b Department of Gastroenterology , St. Spiridon, Emergency Clinical Hospital , Iasi , Romania
| | - Anca Trifan
- a Department of Gastroenterology , Grigore T. Popa University of Medicine and Pharmacy , Iasi , Romania
- b Department of Gastroenterology , St. Spiridon, Emergency Clinical Hospital , Iasi , Romania
| | - Cristina Muzica
- b Department of Gastroenterology , St. Spiridon, Emergency Clinical Hospital , Iasi , Romania
| | - Catalin Sfarti
- a Department of Gastroenterology , Grigore T. Popa University of Medicine and Pharmacy , Iasi , Romania
- b Department of Gastroenterology , St. Spiridon, Emergency Clinical Hospital , Iasi , Romania
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Crouchet E, Wrensch F, Schuster C, Zeisel MB, Baumert TF. Host-targeting therapies for hepatitis C virus infection: current developments and future applications. Therap Adv Gastroenterol 2018; 11:1756284818759483. [PMID: 29619090 PMCID: PMC5871046 DOI: 10.1177/1756284818759483] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 01/15/2018] [Indexed: 02/04/2023] Open
Abstract
Chronic hepatitis C virus (HCV) infection is a leading cause of chronic liver diseases and hepatocellular carcinoma (HCC) worldwide. In the past few years, anti-HCV therapies have undergone a revolution with the approval of multiple direct-acting antivirals (DAAs), which enable interferon-free treatments with considerable improvement of sustained virologic response in patients. Today, DAAs have become the standard of care for HCV therapy. However, several limitations remain, which include access to therapy, treatment failure in a subset of patients and persistent risk of HCC development following cure in patients with advanced fibrosis. By targeting conserved host proteins involved in the HCV life cycle, host-targeting agents (HTAs) offer opportunities for pan-genotypic antiviral approaches with a high barrier to drug resistance. Moreover, when applied in combination with DAAs, HTAs could improve the management of difficult-to-treat patients by acting through a complementary mechanism of action. In this review, we summarize the different HTAs evaluated in preclinical and clinical development and discuss their potential role for anti-HCV therapies.
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Affiliation(s)
- Emilie Crouchet
- Institut National de la Santé et de la Recherche Médicale (Inserm), U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, Strasbourg, France Université de Strasbourg, Strasbourg, France
| | - Florian Wrensch
- Institut National de la Santé et de la Recherche Médicale (Inserm), U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, Strasbourg, France Université de Strasbourg, Strasbourg, France
| | - Catherine Schuster
- Institut National de la Santé et de la Recherche Médicale (Inserm), U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, Strasbourg, France Université de Strasbourg, Strasbourg, France
| | - Mirjam B. Zeisel
- Institut National de la Santé et de la Recherche Médicale (Inserm), U1110, Institut de Recherche sur les Maladies Virales et Hépatiques, Strasbourg, France Université de Strasbourg, Strasbourg, France Inserm U1052, CNRS UMR 5286, Cancer Research Center of Lyon (CRCL), Université de Lyon (UCBL), Lyon, France
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Immunoproteasome induction is suppressed in hepatitis C virus-infected cells in a protein kinase R-dependent manner. Exp Mol Med 2016; 48:e270. [PMID: 27833096 PMCID: PMC5133375 DOI: 10.1038/emm.2016.98] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 06/11/2016] [Indexed: 02/08/2023] Open
Abstract
By changing the relative abundance of generated antigenic peptides through alterations in the proteolytic activity, interferon (IFN)-γ-induced immunoproteasomes influence the outcome of CD8+ cytotoxic T lymphocyte responses. In the present study, we investigated the effects of hepatitis C virus (HCV) infection on IFN-γ-induced immunoproteasome expression using a HCV infection cell culture system. We found that, although IFN-γ induced the transcriptional expression of mRNAs encoding the β1i/LMP2, β2i/MECL-1 and β5i/LMP7 immunoproteasome subunits, the formation of immunoproteasomes was significantly suppressed in HCV-infected cells. This finding indicated that immunoproteasome induction was impaired at the translational or posttranslational level by HCV infection. Gene silencing studies showed that the suppression of immunoproteasome induction is essentially dependent on protein kinase R (PKR). Indeed, the generation of a strictly immunoproteasome-dependent cytotoxic T lymphocyte epitope was impaired in in vitro processing experiments using isolated 20S proteasomes from HCV-infected cells and was restored by the silencing of PKR expression. In conclusion, our data point to a novel mechanism of immune regulation by HCV that affects the antigen-processing machinery through the PKR-mediated suppression of immunoproteasome induction in infected cells.
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Fungus-Derived Neoechinulin B as a Novel Antagonist of Liver X Receptor, Identified by Chemical Genetics Using a Hepatitis C Virus Cell Culture System. J Virol 2016; 90:9058-74. [PMID: 27489280 DOI: 10.1128/jvi.00856-16] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 07/20/2016] [Indexed: 12/13/2022] Open
Abstract
UNLABELLED Cell culture systems reproducing virus replication can serve as unique models for the discovery of novel bioactive molecules. Here, using a hepatitis C virus (HCV) cell culture system, we identified neoechinulin B (NeoB), a fungus-derived compound, as an inhibitor of the liver X receptor (LXR). NeoB was initially identified by chemical screening as a compound that impeded the production of infectious HCV. Genome-wide transcriptome analysis and reporter assays revealed that NeoB specifically inhibits LXR-mediated transcription. NeoB was also shown to interact directly with LXRs. Analysis of structural analogs suggested that the molecular interaction of NeoB with LXR correlated with the capacity to inactivate LXR-mediated transcription and to modulate lipid metabolism in hepatocytes. Our data strongly suggested that NeoB is a novel LXR antagonist. Analysis using NeoB as a bioprobe revealed that LXRs support HCV replication: LXR inactivation resulted in dispersion of double-membrane vesicles, putative viral replication sites. Indeed, cells treated with NeoB showed decreased replicative permissiveness for poliovirus, which also replicates in double-membrane vesicles, but not for dengue virus, which replicates via a distinct membrane compartment. Together, our data suggest that LXR-mediated transcription regulates the formation of virus-associated membrane compartments. Significantly, inhibition of LXRs by NeoB enhanced the activity of all known classes of anti-HCV agents, and NeoB showed especially strong synergy when combined with interferon or an HCV NS5A inhibitor. Thus, our chemical genetics analysis demonstrates the utility of the HCV cell culture system for identifying novel bioactive molecules and characterizing the virus-host interaction machinery. IMPORTANCE Hepatitis C virus (HCV) is highly dependent on host factors for efficient replication. In the present study, we used an HCV cell culture system to screen an uncharacterized chemical library. Our results identified neoechinulin B (NeoB) as a novel inhibitor of the liver X receptor (LXR). NeoB inhibited the induction of LXR-regulated genes and altered lipid metabolism. Intriguingly, our results indicated that LXRs are critical to the process of HCV replication: LXR inactivation by NeoB disrupted double-membrane vesicles, putative sites of viral replication. Moreover, NeoB augmented the antiviral activity of all known classes of currently approved anti-HCV agents without increasing cytotoxicity. Thus, our strategy directly links the identification of novel bioactive compounds to basic virology and the development of new antiviral agents.
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Valadão ALC, Aguiar RS, de Arruda LB. Interplay between Inflammation and Cellular Stress Triggered by Flaviviridae Viruses. Front Microbiol 2016; 7:1233. [PMID: 27610098 PMCID: PMC4996823 DOI: 10.3389/fmicb.2016.01233] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 07/25/2016] [Indexed: 12/15/2022] Open
Abstract
The Flaviviridae family comprises several human pathogens, including Dengue, Zika, Yellow Fever, West Nile, Japanese Encephalitis viruses, and Hepatitis C Virus. Those are enveloped, single-stranded positive sense RNA viruses, which replicate mostly in intracellular compartments associated to endoplasmic reticulum (ER) and Golgi complex. Virus replication results in abundant viral RNAs and proteins, which are recognized by cellular mechanisms evolved to prevent virus infection, resulting in inflammation and stress responses. Virus RNA molecules are sensed by Toll-like receptors (TLRs), RIG-I-like receptors (RIG-I and MDA5) and RNA-dependent protein kinases (PKR), inducing the production of inflammatory mediators and interferons. Simultaneously, the synthesis of virus RNA and proteins are distinguished in different compartments such as mitochondria, ER and cytoplasmic granules, triggering intracellular stress pathways, including oxidative stress, unfolded protein response pathway, and stress granules assembly. Here, we review the new findings that connect the inflammatory pathways to cellular stress sensors and the strategies of Flaviviridae members to counteract these cellular mechanisms and escape immune response.
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Affiliation(s)
- Ana L C Valadão
- Departamento de Genética, Instituto de Biologia, Universidade Federal do Rio de Janeiro Rio de Janeiro, Brazil
| | - Renato S Aguiar
- Departamento de Genética, Instituto de Biologia, Universidade Federal do Rio de Janeiro Rio de Janeiro, Brazil
| | - Luciana B de Arruda
- Departamento de Virologia, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro Rio de Janeiro, Brazil
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16
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Mouse Systems to Model Hepatitis C Virus Treatment and Associated Resistance. Viruses 2016; 8:v8060176. [PMID: 27338446 PMCID: PMC4926196 DOI: 10.3390/v8060176] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 05/12/2016] [Accepted: 06/16/2016] [Indexed: 12/15/2022] Open
Abstract
While addition of the first-approved protease inhibitors (PIs), telaprevir and boceprevir, to pegylated interferon (PEG-IFN) and ribavirin (RBV) combination therapy significantly increased sustained virologic response (SVR) rates, PI-based triple therapy for the treatment of chronic hepatitis C virus (HCV) infection was prone to the emergence of resistant viral variants. Meanwhile, multiple direct acting antiviral agents (DAAs) targeting either the HCV NS3/4A protease, NS5A or NS5B polymerase have been approved and these have varying potencies and distinct propensities to provoke resistance. The pre-clinical in vivo assessment of drug efficacy and resistant variant emergence underwent a great evolution over the last decade. This field had long been hampered by the lack of suitable small animal models that robustly support the entire HCV life cycle. In particular, chimeric mice with humanized livers (humanized mice) and chimpanzees have been instrumental for studying HCV inhibitors and the evolution of drug resistance. In this review, we present the different in vivo HCV infection models and discuss their applicability to assess HCV therapy response and emergence of resistant variants.
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Khachatoorian R, French SW. Chaperones in hepatitis C virus infection. World J Hepatol 2016; 8:9-35. [PMID: 26783419 PMCID: PMC4705456 DOI: 10.4254/wjh.v8.i1.9] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 10/01/2015] [Accepted: 12/18/2015] [Indexed: 02/06/2023] Open
Abstract
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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Stress granules regulate double-stranded RNA-dependent protein kinase activation through a complex containing G3BP1 and Caprin1. mBio 2015; 6:e02486. [PMID: 25784705 PMCID: PMC4453520 DOI: 10.1128/mbio.02486-14] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Stress granules (SGs) are dynamic cytoplasmic repositories containing translationally silenced mRNAs that assemble upon cellular stress. We recently reported that the SG nucleating protein G3BP1 promotes antiviral activity and is essential in double-stranded RNA-dependent protein kinase (PKR) recruitment to stress granules, thereby driving phosphorylation of the α subunit of eukaryotic initiation factor 2 (eIF2α). Here, we delineate the mechanism for SG-dependent PKR activation. We show that G3BP1 and inactive PKR directly interact with each other, dependent on both the NTF2-like and PXXP domains of G3BP1. The G3BP1-interacting protein Caprin1 also directly interacts with PKR, regulates efficient PKR activation at the stress granule, and is also integral for the release of active PKR into the cytoplasm to engage in substrate recognition. The G3BP1-Caprin1-PKR complex represents a new mode of PKR activation and is important for antiviral activity of G3BP1 and PKR during infection with mengovirus. Our data links stress responses and their resultant SGs with innate immune activation through PKR without a requirement for foreign double-stranded RNA (dsRNA) pattern recognition. Our previous work indicates that stress granules have antiviral activity and mediate innate immunity through functions of G3BP1; however, the mechanistic details of these functions were not resolved. We show that much of the antiviral activity of stress granules is contingent on the function of PKR in a complex with G3BP1 and Caprin1. The PKR-G3BP1-Caprin1 complex undergoes dynamic transitioning within and outside stress granules to accomplish PKR activation and translational repression. This mechanism appears to function distinctly from canonical pattern recognition of double-stranded RNA by PKR. Therefore, this mechanism bridges the stress response with innate immunity, allowing the cell to respond to many cellular stressors and amplify the pathogen pattern recognition systems of innate immunity.
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Ross-Thriepland D, Harris M. Hepatitis C virus NS5A: enigmatic but still promiscuous 10 years on! J Gen Virol 2014; 96:727-738. [PMID: 25481754 DOI: 10.1099/jgv.0.000009] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Since one of us co-authored a review on NS5A a decade ago, the hepatitis C virus (HCV) field has changed dramatically, primarily due to the advent of the JFH-1 cell culture infectious clone, which allowed the study of all aspects of the virus life cycle from entry to exit. This review will describe advances in our understanding of NS5A biology over the past decade, highlighting how the JFH-1 system has allowed us to determine that NS5A is essential not only in genome replication but also in the assembly of infectious virions. We shall review the recent structural insights - NS5A is predicted to comprise three domains; X-ray crystallography has revealed the structure of domain I but there is a lack of detailed structural information about the other two domains, which are predicted to be largely unstructured. Recent insights into the phosphorylation of NS5A will be discussed, and we shall highlight a few pertinent examples from the ever-expanding list of NS5A-binding partners identified over the past decade. Lastly, we shall review the literature showing that NS5A is a potential target for a new class of highly potent small molecules that function to inhibit virus replication. These direct-acting antivirals (DAAs) are now either licensed, or in the late stages of approval for clinical use both in the USA and in the UK/Europe. In combination with other DAAs targeting the viral protease (NS3) and polymerase (NS5B), they are revolutionizing treatment for HCV infection.
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Affiliation(s)
- Douglas Ross-Thriepland
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Mark Harris
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
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