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Three-Dimensional Structural Characterization of HIV-1 Tethered to Human Cells. J Virol 2015; 90:1507-21. [PMID: 26582000 DOI: 10.1128/jvi.01880-15] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 11/14/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Tetherin (BST2, CD317, or HM1.24) is a host cellular restriction factor that prevents the release of enveloped viruses by mechanically linking virions to the plasma membrane. The precise arrangement of tetherin molecules at the plasma membrane site of HIV-1 assembly, budding, and restriction is not well understood. To gain insight into the biophysical mechanism underlying tetherin-mediated restriction of HIV-1, we utilized cryo-electron tomography (cryo-ET) to directly visualize HIV-1 virus-like particles (VLPs) and virions tethered to human cells in three dimensions (3D). Rod-like densities that we refer to as tethers were seen connecting HIV-1 virions to each other and to the plasma membrane. Native immunogold labeling showed tetherin molecules located on HIV-1 VLPs and virions in positions similar to those of the densities observed by cryo-ET. The location of the tethers with respect to the ordered immature Gag lattice or mature conical core was random. However, tethers were not uniformly distributed on the viral membrane but rather formed clusters at sites of contact with the cell or other virions. Chains of tethered HIV-1 virions often were arranged in a linear fashion, primarily as single chains and, to a lesser degree, as branched chains. Distance measurements support the extended tetherin model, in which the coiled-coil ectodomains are oriented perpendicular with respect to the viral and plasma membranes. IMPORTANCE Tetherin is a cellular factor that restricts HIV-1 release by directly cross-linking the virus to the host cell plasma membrane. We used cryo-electron tomography to visualize HIV-1 tethered to human cells in 3D. We determined that tetherin-restricted HIV-1 virions were physically connected to each other or to the plasma membrane by filamentous tethers that resembled rods ∼15 nm in length, which is consistent with the extended tetherin model. In addition, we found the position of the tethers to be arbitrary relative to the ordered immature Gag lattice or the mature conical cores. However, when present as multiple copies, the tethers clustered at the interface between virions. Tethered HIV-1 virions were arranged in a linear fashion, with the majority as single chains. This study advances our understanding of tetherin-mediated HIV-1 restriction by defining the spatial arrangement and orientation of tetherin molecules at sites of HIV-1 restriction.
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Londrigan SL, Tate MD, Job ER, Moffat JM, Wakim LM, Gonelli CA, Purcell DFJ, Brooks AG, Villadangos JA, Reading PC, Mintern JD. Endogenous Murine BST-2/Tetherin Is Not a Major Restriction Factor of Influenza A Virus Infection. PLoS One 2015; 10:e0142925. [PMID: 26566124 PMCID: PMC4643895 DOI: 10.1371/journal.pone.0142925] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 10/28/2015] [Indexed: 01/23/2023] Open
Abstract
BST-2 (tetherin, CD317, HM1.24) restricts virus growth by tethering enveloped viruses to the cell surface. The role of BST-2 during influenza A virus infection (IAV) is controversial. Here, we assessed the capacity of endogenous BST-2 to restrict IAV in primary murine cells. IAV infection increased BST-2 surface expression by primary macrophages, but not alveolar epithelial cells (AEC). BST-2-deficient AEC and macrophages displayed no difference in susceptibility to IAV infection relative to wild type cells. Furthermore, BST-2 played little role in infectious IAV release from either AEC or macrophages. To examine BST-2 during IAV infection in vivo, we infected BST-2-deficient mice. No difference in weight loss or in viral loads in the lungs and/or nasal tissues were detected between BST-2-deficient and wild type animals. This study rules out a major role for endogenous BST-2 in modulating IAV in the mouse model of infection.
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Affiliation(s)
- Sarah L. Londrigan
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Michelle D. Tate
- Centre for Innate Immunity and Infectious Diseases, MIMR-PHI Institute of Medical Research, Clayton, Victoria, 3168, Australia
- Monash University, Clayton, Victoria, 3168, Australia
| | - Emma R. Job
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Jessica M. Moffat
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Linda M. Wakim
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Christopher A. Gonelli
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Damien F. J. Purcell
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Andrew G. Brooks
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Jose A. Villadangos
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria, 3010, Australia
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Bio21 Molecular Science and Biotechnology Institute, 30 Flemington Rd, Parkville, Victoria, 3010, Australia
| | - Patrick C. Reading
- Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, The University of Melbourne, Parkville, Victoria, 3010, Australia
- WHO Collaborating Centre for Reference and Research on Influenza, Victorian Infectious Diseases Reference Laboratory, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, 3000, Australia
| | - Justine D. Mintern
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Bio21 Molecular Science and Biotechnology Institute, 30 Flemington Rd, Parkville, Victoria, 3010, Australia
- * E-mail:
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Rhein BA, Powers LS, Rogers K, Anantpadma M, Singh BK, Sakurai Y, Bair T, Miller-Hunt C, Sinn P, Davey RA, Monick MM, Maury W. Interferon-γ Inhibits Ebola Virus Infection. PLoS Pathog 2015; 11:e1005263. [PMID: 26562011 PMCID: PMC4643030 DOI: 10.1371/journal.ppat.1005263] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2015] [Accepted: 10/19/2015] [Indexed: 12/31/2022] Open
Abstract
Ebola virus outbreaks, such as the 2014 Makona epidemic in West Africa, are episodic and deadly. Filovirus antivirals are currently not clinically available. Our findings suggest interferon gamma, an FDA-approved drug, may serve as a novel and effective prophylactic or treatment option. Using mouse-adapted Ebola virus, we found that murine interferon gamma administered 24 hours before or after infection robustly protects lethally-challenged mice and reduces morbidity and serum viral titers. Furthermore, we demonstrated that interferon gamma profoundly inhibits Ebola virus infection of macrophages, an early cellular target of infection. As early as six hours following in vitro infection, Ebola virus RNA levels in interferon gamma-treated macrophages were lower than in infected, untreated cells. Addition of the protein synthesis inhibitor, cycloheximide, to interferon gamma-treated macrophages did not further reduce viral RNA levels, suggesting that interferon gamma blocks life cycle events that require protein synthesis such as virus replication. Microarray studies with interferon gamma-treated human macrophages identified more than 160 interferon-stimulated genes. Ectopic expression of a select group of these genes inhibited Ebola virus infection. These studies provide new potential avenues for antiviral targeting as these genes that have not previously appreciated to inhibit negative strand RNA viruses and specifically Ebola virus infection. As treatment of interferon gamma robustly protects mice from lethal Ebola virus infection, we propose that interferon gamma should be further evaluated for its efficacy as a prophylactic and/or therapeutic strategy against filoviruses. Use of this FDA-approved drug could rapidly be deployed during future outbreaks. Filovirus outbreaks occur sporadically, but with increasing frequency. With no current approved filovirus therapeutics, the 2014 Makona Ebola virus epidemic in Guinea, Sierra Leone and Liberia emphasizes the need for effective treatments against this highly pathogenic family of viruses. The use of this FDA-approved drug to inhibit Ebola virus infection would allow rapid implementation of a novel antiviral therapy for future crises. Interferon gamma elicits an antiviral state in antigen-presenting cells and stimulates cellular immune responses. We demonstrate that interferon gamma profoundly inhibits Ebola virus infection of macrophages, which are early cellular targets of Ebola virus. We also identify novel interferon gamma-stimulated genes in human macrophage populations that have not been previously appreciated to inhibit filoviruses or other negative strand RNA viruses. Finally and most importantly, we show that interferon gamma given 24 hours prior to or after virus infection protects mice from lethal Ebola virus challenge, suggesting that this drug may serve as an effective prophylactic and/or therapeutic strategy against this deadly virus.
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Affiliation(s)
- Bethany A. Rhein
- Department of Microbiology, The University of Iowa, Iowa City, Iowa, United States of America
| | - Linda S. Powers
- Department of Internal Medicine, The University of Iowa, Iowa City, Iowa, United States of America
| | - Kai Rogers
- Department of Microbiology, The University of Iowa, Iowa City, Iowa, United States of America
| | - Manu Anantpadma
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, Texas, United States of America
| | - Brajesh K. Singh
- Department of Pediatrics, The University of Iowa, Iowa City, Iowa, United States of America
| | - Yasuteru Sakurai
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, Texas, United States of America
| | - Thomas Bair
- Iowa Institute for Human Genetics, The University of Iowa, Iowa City, Iowa, United States of America
| | - Catherine Miller-Hunt
- Department of Microbiology, The University of Iowa, Iowa City, Iowa, United States of America
| | - Patrick Sinn
- Department of Pediatrics, The University of Iowa, Iowa City, Iowa, United States of America
| | - Robert A. Davey
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, Texas, United States of America
| | - Martha M. Monick
- Department of Internal Medicine, The University of Iowa, Iowa City, Iowa, United States of America
| | - Wendy Maury
- Department of Microbiology, The University of Iowa, Iowa City, Iowa, United States of America
- * E-mail:
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104
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Mussil B, Javed A, Töpfer K, Sauermann U, Sopper S. Increased BST2 expression during simian immunodeficiency virus infection is not a determinant of disease progression in rhesus monkeys. Retrovirology 2015; 12:92. [PMID: 26554913 PMCID: PMC4641394 DOI: 10.1186/s12977-015-0219-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 10/23/2015] [Indexed: 12/21/2022] Open
Abstract
Background Bone marrow stromal cell antigen 2 (BST2), also known as tetherin, HM1.24 or CD317 represents a type 2 integral membrane protein, which has been described to restrict the production of some enveloped viruses by inhibiting the virus release from the cell surface. This innate antiviral mechanism is counteracted by the HIV-1 viral factor Vpu, targeting BST2 for cellular degradation. Since antiviral BST2 activity has been mainly confirmed by in vitro data, we investigated its role in vivo on the disease progression using the SIV/macaque model for AIDS. We determined BST2 expression in PBMC and leukocyte subsets of uninfected and SIV-infected rhesus macaques by real-time PCR and flow cytometry and correlated it with disease progression and viral load. Results Compared to pre-infection levels, we found increased BST2 expression in PBMC, purified CD4+ lymphocytes and CD14+ monocytes of SIV-infected animals, which correlated with viral load. Highest BST2 levels were found in progressors and lowest levels comparable to uninfected macaques were observed in long-term non-progressors (LTNPs). During acute viremia, BST2 mRNA increased in parallel with MX1, a prototype interferon-stimulated gene. This association was maintained during the whole disease course. Conclusion The detected relationship between BST2 expression and viral load as well as with MX1 indicate a common regulation by the interferon response and suggest rather limited influence of BST2 in vivo on the disease outcome. Electronic supplementary material The online version of this article (doi:10.1186/s12977-015-0219-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Bianka Mussil
- Unit of Infection Models, German Primate Centre, Goettingen, Germany.
| | - Aneela Javed
- Unit of Infection Models, German Primate Centre, Goettingen, Germany. .,Department of Healthcare Biotechnology, Atta-ur-Rahman School of Applied Biosciences (ASAB), National University of Science and Technology (NUST), H12, Islamabad, Pakistan.
| | - Katharina Töpfer
- Unit of Infection Models, German Primate Centre, Goettingen, Germany.
| | - Ulrike Sauermann
- Unit of Infection Models, German Primate Centre, Goettingen, Germany.
| | - Sieghart Sopper
- Department of Hematology and Oncology, Medical University Innsbruck, ZVG 7G5 009A, Anichstr. 35, 6020, Innsbruck, Austria. .,Tyrolean Cancer Research Institute, Innsbruck, Austria.
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105
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HIV-1 Adapts To Replicate in Cells Expressing Common Marmoset APOBEC3G and BST2. J Virol 2015; 90:725-40. [PMID: 26512082 DOI: 10.1128/jvi.02431-15] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 10/16/2015] [Indexed: 12/11/2022] Open
Abstract
UNLABELLED Previous studies have shown that a major block to HIV-1 replication in common marmosets operates at the level of viral entry and that this block can be overcome by adaptation of the virus in tissue-cultured cells. However, our current studies indicate that HIV-1 encounters additional postentry blocks in common marmoset peripheral blood mononuclear cells. Here, we show that the common marmoset APOBEC3G (A3G) and BST2 proteins block HIV-1 in cell cultures. Using a directed-evolution method that takes advantage of the natural ability of HIV-1 to mutate during replication, we have been able to overcome these blocks in tissue-cultured cells. In the adapted viruses, specific changes were observed in gag, vif, env, and nef. The contribution of these changes to virus replication in the presence of the A3G and BST2 restriction factors was studied. We found that certain amino acid changes in Vif and Env that arise during adaptation to marmoset A3G and BST2 allow the virus to replicate in the presence of these restriction factors. The changes in Vif reduce expression levels and encapsidation of marmoset APOBEC3G, while the changes in Env increase viral fitness and discretely favor cell-to-cell transmission of the virus, allowing viral escape from these restriction factors. IMPORTANCE HIV-1 can infect only humans and chimpanzees. The main reason for this narrow tropism is the presence in many species of dominant-acting factors, known as restriction factors, that block viral replication in a species-specific way. We have been exploring the blocks to HIV-1 in common marmosets, with the ultimate goal of developing a new animal model of HIV-1 infection in these monkeys. In this study, we observed that common marmoset APOBEC3G and BST2, two known restriction factors, are able to block HIV-1 in cell cultures. We have adapted HIV-1 to replicate in the presence of these restriction factors and have characterized the mechanisms of escape. These studies can help in the development of a novel animal model for in vivo infection of marmosets with HIV-1-like viruses.
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106
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Sasset L, Petris G, Cesaratto F, Burrone OR. The VCP/p97 and YOD1 Proteins Have Different Substrate-dependent Activities in Endoplasmic Reticulum-associated Degradation (ERAD). J Biol Chem 2015; 290:28175-28188. [PMID: 26463207 DOI: 10.1074/jbc.m115.656660] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2015] [Indexed: 11/06/2022] Open
Abstract
Endoplasmic reticulum-associated degradation (ERAD) is an essential quality control mechanism of the folding state of proteins in the secretory pathway that targets unfolded/misfolded polypeptides for proteasomal degradation. The cytosolic p97/valosin-containing protein is an essential ATPase for degradation of ERAD substrates. It has been considered necessary during retro-translocation to extract proteins from the endoplasmic reticulum that are otherwise supposed to accumulate in the endoplasmic reticulum lumen. The activity of the p97-associated deubiquitinylase YOD1 is also required for substrate disposal. We used the in vivo biotinylation retro-translocation assay in mammalian cells under conditions of impaired p97 or YOD1 activity to directly discriminate their requirements and diverse functions in ERAD. Using different ERAD substrates, we found that both proteins participate in two distinct retro-translocation steps. For CD4 and MHC-Iα, which are induced to degradation by the HIV-1 protein Vpu and by the CMV immunoevasins US2 and US11, respectively, p97 and YOD1 have a retro-translocation-triggering role. In contrast, for three other spontaneous ERAD model substrates (NS1, NHK-α1AT, and BST-2/Tetherin), p97 and YOD1 are required in the downstream events of substrate deglycosylation and proteasomal degradation.
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Affiliation(s)
- Linda Sasset
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy
| | - Gianluca Petris
- CIBIO, University of Trento, Via delle Regole 101, 38123 Mattarello, Italy.
| | - Francesca Cesaratto
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy
| | - Oscar R Burrone
- International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy
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107
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Messaoudi I, Amarasinghe GK, Basler CF. Filovirus pathogenesis and immune evasion: insights from Ebola virus and Marburg virus. Nat Rev Microbiol 2015; 13:663-76. [PMID: 26439085 DOI: 10.1038/nrmicro3524] [Citation(s) in RCA: 171] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Ebola viruses and Marburg viruses, members of the filovirus family, are zoonotic pathogens that cause severe disease in people, as highlighted by the latest Ebola virus epidemic in West Africa. Filovirus disease is characterized by uncontrolled virus replication and the activation of host responses that contribute to pathogenesis. Underlying these phenomena is the potent suppression of host innate antiviral responses, particularly the type I interferon response, by viral proteins, which allows high levels of viral replication. In this Review, we describe the mechanisms used by filoviruses to block host innate immunity and discuss the links between immune evasion and filovirus pathogenesis.
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Affiliation(s)
- Ilhem Messaoudi
- School of Medicine, University of California Riverside, Riverside, California 92521, USA
| | - Gaya K Amarasinghe
- The Division of Biology &Biomedical Sciences, Washington University in St. Louis, St. Louis, Missouri 63110, USA
| | - Christopher F Basler
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York 10029, USA
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108
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The KT Jeang Retrovirology prize 2015: Paul Bieniasz. Retrovirology 2015; 12:84. [PMID: 26438335 PMCID: PMC4595249 DOI: 10.1186/s12977-015-0208-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 09/18/2015] [Indexed: 11/13/2022] Open
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109
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Koutsoudakis G, Romero-Brey I, Berger C, Pérez-Vilaró G, Monteiro Perin P, Vondran FWR, Kalesse M, Harmrolfs K, Müller R, Martinez JP, Pietschmann T, Bartenschlager R, Brönstrup M, Meyerhans A, Díez J. Soraphen A: A broad-spectrum antiviral natural product with potent anti-hepatitis C virus activity. J Hepatol 2015; 63:813-21. [PMID: 26070407 DOI: 10.1016/j.jhep.2015.06.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 05/28/2015] [Accepted: 06/01/2015] [Indexed: 02/07/2023]
Abstract
BACKGROUND & AIMS Soraphen A (SorA) is a myxobacterial metabolite that inhibits the acetyl-CoA carboxylase, a key enzyme in lipid biosynthesis. We have previously identified SorA to efficiently inhibit the human immunodeficiency virus (HIV). The aim of the present study was to evaluate the capacity of SorA and analogues to inhibit hepatitis C virus (HCV) infection. METHODS SorA inhibition capacity was evaluated in vitro using cell culture derived HCV, HCV pseudoparticles and subgenomic replicons. Infection studies were performed in the hepatoma cell line HuH7/Scr and in primary human hepatocytes. The effects of SorA on membranous web formation were analysed by electron microscopy. RESULTS SorA potently inhibits HCV infection at nanomolar concentrations. Obtained EC50 values were 0.70 nM with a HCV reporter genome, 2.30 nM with wild-type HCV and 2.52 nM with subgenomic HCV replicons. SorA neither inhibited HCV RNA translation nor HCV entry, as demonstrated with subgenomic HCV replicons and HCV pseudoparticles, suggesting an effect on HCV replication. Consistent with this, evidence was obtained that SorA interferes with formation of the membranous web, the site of HCV replication. Finally, a series of natural and synthetic SorA analogues helped to establish a first structure-activity relationship. CONCLUSIONS SorA has a very potent anti-HCV activity. Since it also interferes with the membranous web formation, SorA is an excellent tool to unravel the mechanism of HCV replication.
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Affiliation(s)
- George Koutsoudakis
- Molecular Virology Group, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
| | - Inés Romero-Brey
- Department of Infectious Diseases, Molecular Virology, Heidelberg University, Heidelberg, Germany
| | - Carola Berger
- Department of Infectious Diseases, Molecular Virology, Heidelberg University, Heidelberg, Germany
| | - Gemma Pérez-Vilaró
- Molecular Virology Group, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
| | - Paula Monteiro Perin
- TWINCORE - Institute of Experimental Virology, Centre for Experimental and Clinical Infection Research, Hannover, Germany; German Centre for Infection Research (DZIF), partner site Hannover-Braunschweig, Germany
| | - Florian Wolfgang Rudolf Vondran
- German Centre for Infection Research (DZIF), partner site Hannover-Braunschweig, Germany; ReMediES, Department of General, Visceral and Transplantation Surgery, German Centre for Infection Research Hannover Medical School, Hannover, Germany
| | - Markus Kalesse
- Department of Chemical Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Kirsten Harmrolfs
- Helmholtz Institut für Pharmazeutische Forschung Saarland, Saarbrücken, Germany
| | - Rolf Müller
- Helmholtz Institut für Pharmazeutische Forschung Saarland, Saarbrücken, Germany
| | - Javier P Martinez
- Infection Biology Group, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain
| | - Thomas Pietschmann
- TWINCORE - Institute of Experimental Virology, Centre for Experimental and Clinical Infection Research, Hannover, Germany; German Centre for Infection Research (DZIF), partner site Hannover-Braunschweig, Germany
| | - Ralf Bartenschlager
- Department of Infectious Diseases, Molecular Virology, Heidelberg University, Heidelberg, Germany; German Centre for Infection Research (DZIF), partner site Heidelberg, Germany
| | - Mark Brönstrup
- Department of Chemical Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Andreas Meyerhans
- Infection Biology Group, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
| | - Juana Díez
- Molecular Virology Group, Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona, Spain.
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110
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Yi H, Strauss JD, Ke Z, Alonas E, Dillard RS, Hampton CM, Lamb KM, Hammonds JE, Santangelo PJ, Spearman PW, Wright ER. Native immunogold labeling of cell surface proteins and viral glycoproteins for cryo-electron microscopy and cryo-electron tomography applications. J Histochem Cytochem 2015; 63:780-92. [PMID: 26069287 PMCID: PMC4823802 DOI: 10.1369/0022155415593323] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 05/29/2015] [Indexed: 11/22/2022] Open
Abstract
Numerous methods have been developed for immunogold labeling of thick, cryo-preserved biological specimens. However, most of the methods are permutations of chemical fixation and sample sectioning, which select and isolate the immunolabeled region of interest. We describe a method for combining immunogold labeling with cryo-electron microscopy (cryo-EM) and cryo-electron tomography (cryo-ET) of the surface proteins of intact mammalian cells or the surface glycoproteins of assembling and budding viruses in the context of virus-infected mammalian cells cultured on EM grids. In this method, the cells were maintained in culture media at physiologically relevant temperatures while sequentially incubated with the primary and secondary antibodies. Subsequently, the immunogold-labeled specimens were vitrified and observed under cryo-conditions in the transmission electron microscope. Cryo-EM and cryo-ET examination of the immunogold-labeled cells revealed the association of immunogold particles with the target antigens. Additionally, the cellular structure was unaltered by pre-immunolabeling chemical fixation and retained well-preserved plasma membranes, cytoskeletal elements, and macromolecular complexes. We think this technique will be of interest to cell biologists for cryo-EM and conventional studies of native cells and pathogen-infected cells.
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Affiliation(s)
- Hong Yi
- Robert P. Apkarian Integrated Electron Microscopy Core, Emory University, Atlanta, Georgia (HY, ERW)
| | - Joshua D Strauss
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, Georgia (JDS, RSD, CMH, KML, JEH, PWS, ERW)
| | - Zunlong Ke
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia (ZK)
| | - Eric Alonas
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia (EA, PJS)
| | - Rebecca S Dillard
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, Georgia (JDS, RSD, CMH, KML, JEH, PWS, ERW)
| | - Cheri M Hampton
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, Georgia (JDS, RSD, CMH, KML, JEH, PWS, ERW)
| | - Kristen M Lamb
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, Georgia (JDS, RSD, CMH, KML, JEH, PWS, ERW)
| | - Jason E Hammonds
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, Georgia (JDS, RSD, CMH, KML, JEH, PWS, ERW)
| | - Philip J Santangelo
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia (EA, PJS)
| | - Paul W Spearman
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, Georgia (JDS, RSD, CMH, KML, JEH, PWS, ERW)
| | - Elizabeth R Wright
- Robert P. Apkarian Integrated Electron Microscopy Core, Emory University, Atlanta, Georgia (HY, ERW)
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, Georgia (JDS, RSD, CMH, KML, JEH, PWS, ERW)
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111
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Early Vertebrate Evolution of the Host Restriction Factor Tetherin. J Virol 2015; 89:12154-65. [PMID: 26401043 DOI: 10.1128/jvi.02149-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 09/17/2015] [Indexed: 01/07/2023] Open
Abstract
UNLABELLED Tetherin is an interferon-inducible restriction factor targeting a broad range of enveloped viruses. Its antiviral activity depends on an unusual topology comprising an N-terminal transmembrane domain (TMD) followed by an extracellular coiled-coil region and a C-terminal glycosylphosphatidylinositol (GPI) anchor. One of the two membrane anchors is inserted into assembling virions, while the other remains in the plasma membrane of the infected cell. Thus, tetherin entraps budding viruses by physically bridging viral and cellular membranes. Although tetherin restricts the release of a large variety of diverse human and animal viruses, only mammalian orthologs have been described to date. Here, we examined the evolutionary origin of this protein and demonstrate that tetherin orthologs are also found in fish, reptiles, and birds. Notably, alligator tetherin efficiently blocks the release of retroviral particles. Thus, tetherin emerged early during vertebrate evolution and acquired its antiviral activity before the mammal/reptile divergence. Although there is only limited sequence homology, all orthologs share the typical topology. Two unrelated proteins of the slime mold Dictyostelium discoideum also adopt a tetherin-like configuration with an N-terminal TMD and a C-terminal GPI anchor. However, these proteins showed no evidence for convergent evolution and failed to inhibit virion release. In summary, our findings demonstrate that tetherin emerged at least 450 million years ago and is more widespread than previously anticipated. The early evolution of antiviral activity together with the high topology conservation but low sequence homology suggests that restriction of virus release is the primary function of tetherin. IMPORTANCE The continuous arms race with viruses has driven the evolution of a variety of cell-intrinsic immunity factors that inhibit different steps of the viral replication cycle. One of these restriction factors, tetherin, inhibits the release of newly formed progeny virions from infected cells. Although tetherin targets a broad range of enveloped viruses, including retro-, filo-, herpes-, and arenaviruses, the evolutionary origin of this restriction factor and its antiviral activity remained obscure. Here, we examined diverse vertebrate genomes for genes encoding cellular proteins that share with tetherin the highly unusual combination of an N-terminal transmembrane domain and a C-terminal glycosylphosphatidylinositol anchor. We show that tetherin orthologs are found in fish, reptiles, and birds and demonstrate that alligator tetherin efficiently inhibits the release of retroviral particles. Our findings identify tetherin as an evolutionarily ancient restriction factor and provide new important insights into the continuous arms race between viruses and their hosts.
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Wang W, Wang J, Qu M, Li X, Zhang J, Zhang H, Wu J, Yu B, Wu H, Kong W, Yu X. Viral Restriction Activity of Feline BST2 Is Independent of Its N-Glycosylation and Induction of NF-κB Activation. PLoS One 2015; 10:e0138190. [PMID: 26379128 PMCID: PMC4574558 DOI: 10.1371/journal.pone.0138190] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 08/26/2015] [Indexed: 11/18/2022] Open
Abstract
BST2 (CD317, tetherin, HM1.24) is an interferon-inducible transmembrane protein which can directly inhibit the release of enveloped virus particles from infected cells, and its anti-viral activity is reported to be related to the specific topological arrangement of its four structural domains. The N-terminal cytoplasmic tail of feline BST2 (fBST2) is characterized by a shorter N-terminal region compared to those of other known homologs. In this study, we investigated the functional impact of modifying the cytoplasmic tail region of fBST2 and its molecular mechanism. The fBST2 protein with the addition of a peptide at the N-terminus retained anti-release activity against human immunodeficiency virus type-1 and pseudovirus based on feline immunodeficiency virus at a weaker level compared with the wild-type fBST2. However, the fBST2 protein with addition of a peptide internally in the ectodomain proximal to the GPI anchor still retained its anti-viral activity well. Notably, the N-glycosylation state and the cell surface level of the N-terminally modified variants were unlike those of the wild-type protein, while no difference was observed in their intracellular localizations. However, in contrast to human BST2, the wild-type fBST2 did not show the ability to activate NF-κB. Consistent with previous reports, our findings showed that adding a peptide in the cytoplasmic tail region of fBST2 may influence its anti-viral activity. The shorter N-terminal cytoplasmic region of fBST2 compared with human BST2 did not apparently affect its anti-viral activity, which is independent of its N-glycosylation and ability to activate NF-κB.
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Affiliation(s)
- Weiran Wang
- National Engineering Laboratory for AIDS Vaccine, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
| | - Jiawen Wang
- National Engineering Laboratory for AIDS Vaccine, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
- Center for New Medicine Research, Changchun University of Chinese Medicine, Changchun, Jilin Province, People’s Republic of China
| | - Meng Qu
- National Engineering Laboratory for AIDS Vaccine, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
| | - Xiaojun Li
- National Engineering Laboratory for AIDS Vaccine, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
| | - Jingyao Zhang
- National Engineering Laboratory for AIDS Vaccine, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
| | - Haihong Zhang
- National Engineering Laboratory for AIDS Vaccine, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
| | - Jiaxin Wu
- National Engineering Laboratory for AIDS Vaccine, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
| | - Bin Yu
- National Engineering Laboratory for AIDS Vaccine, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
| | - Hui Wu
- National Engineering Laboratory for AIDS Vaccine, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
| | - Wei Kong
- National Engineering Laboratory for AIDS Vaccine, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
- Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
- * E-mail: (WK); (XHY)
| | - Xianghui Yu
- National Engineering Laboratory for AIDS Vaccine, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
- Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, School of Life Science, Jilin University, Changchun, Jilin Province, People’s Republic of China
- * E-mail: (WK); (XHY)
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113
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Exline CM, Yang SJ, Haworth KG, Rengarajan S, Lopez LA, Droniou ME, Seclen E, Cannon PM. Determinants in HIV-2 Env and tetherin required for functional interaction. Retrovirology 2015; 12:67. [PMID: 26248668 PMCID: PMC4528709 DOI: 10.1186/s12977-015-0194-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 07/23/2015] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND The interferon-inducible factor BST-2/tetherin blocks the release of nascent virions from the surface of infected cells for certain enveloped virus families. The primate lentiviruses have evolved several counteracting mechanisms which, in the case of HIV-2, is a function of its Env protein. We sought to further understand the features of the Env protein and tetherin that are important for this interaction, and to evaluate the selective pressure on HIV-2 to maintain such an activity. RESULTS By examining Env mutants with changes in the ectodomain of the protein (virus ROD14) or the cytoplasmic tail (substitution Y707A) that render the proteins unable to counteract tetherin, we determined that an interaction between Env and tetherin is important for this activity. Furthermore, this Env-tetherin interaction required an alanine face in the tetherin ectodomain, although insertion of this domain into an artificial tetherin-like protein was not sufficient to confer sensitivity to the HIV-2 Env. The replication of virus carrying the ROD14 substitutions was significantly slower than the matched wild-type virus, but it acquired second-site mutations during passaging in the cytoplasmic tail of Env which restored the ability of the protein to both bind to and counteract tetherin. CONCLUSIONS These results shed light on the interaction between HIV-2 and tetherin, suggesting a physical interaction that maps to the ectodomains of both proteins and indicating a strong selection pressure to maintain an anti-tetherin activity in the HIV-2 Env.
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Affiliation(s)
- Colin M Exline
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, 2011 Zonal Avenue, HMR 502, Los Angeles, CA, 90033, USA.
| | - Su Jung Yang
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, 2011 Zonal Avenue, HMR 502, Los Angeles, CA, 90033, USA.
| | - Kevin G Haworth
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, 2011 Zonal Avenue, HMR 502, Los Angeles, CA, 90033, USA.
| | - Srinivas Rengarajan
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, 2011 Zonal Avenue, HMR 502, Los Angeles, CA, 90033, USA.
| | - Lisa A Lopez
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, 2011 Zonal Avenue, HMR 502, Los Angeles, CA, 90033, USA.
| | - Magali E Droniou
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, 2011 Zonal Avenue, HMR 502, Los Angeles, CA, 90033, USA.
| | - Eduardo Seclen
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, 2011 Zonal Avenue, HMR 502, Los Angeles, CA, 90033, USA.
| | - Paula M Cannon
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, 2011 Zonal Avenue, HMR 502, Los Angeles, CA, 90033, USA.
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114
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Lv M, Zhang B, Shi Y, Han Z, Zhang Y, Zhou Y, Zhang W, Niu J, Yu XF. Identification of BST-2/tetherin-induced hepatitis B virus restriction and hepatocyte-specific BST-2 inactivation. Sci Rep 2015; 5:11736. [PMID: 26119070 PMCID: PMC4484258 DOI: 10.1038/srep11736] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 05/05/2015] [Indexed: 12/25/2022] Open
Abstract
BST-2/tetherin is an interferon-inducible antiviral protein that blocks the release of various enveloped viruses, including HIV-1. Hepatitis B virus (HBV), a major cause of liver disease, belongs to the Hepadnaviridae family of enveloped DNA viruses. Whether BST-2 regulates HBV production is largely unknown. In this report, we have demonstrated that HBV particle release is modulated by BST-2 in a cell type-dependent fashion. In HEK293T cells, ectopically expressed or interferon-induced BST-2 strongly inhibited HBV release. BST-2 co-localized with HBV surface protein at multivesicular bodies (MVBs) and physically interacted with HBV particles. However, exogenous BST-2-induced HBV restriction was weak in Huh-7 hepatoma cells, and the interferon-induced anti-HBV effect was independent of BST-2 induction in hepatic L02 cells. Notably, HBV could promote HIV-1 ΔVpu virus release from BST-2-positive HepG2 hepatoma cells but not HeLa cells, whereas Vpu failed to efficiently inhibit BST-2-induced HBV restriction. HBx exhibited an enhanced interaction and co-localization with BST-2 in hepatocytes. These observations indicate that BST-2 restricts HBV production at intracellular MVBs but is inactivated by HBV through a novel mechanism requiring hepatocyte-specific cellular co-factors or a hepatocyte-specific environment. Further understanding of BST-2-induced HBV restriction may provide new therapeutic targets for future HBV treatments.
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Affiliation(s)
- Mingyu Lv
- 1] Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China [2] Department of Hepatology, First Hospital of Jilin University, Changchun, P. R. China
| | - Biao Zhang
- 1] Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China [2] School of Pharmaceutical Sciences, Jilin University, Changchun, P. R. China
| | - Ying Shi
- Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China
| | - Zhu Han
- Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China
| | - Yan Zhang
- School of Life Sciences, Jilin University, Changchun, P. R. China
| | - Yulai Zhou
- School of Pharmaceutical Sciences, Jilin University, Changchun, P. R. China
| | - Wenyan Zhang
- Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China
| | - Junqi Niu
- Department of Hepatology, First Hospital of Jilin University, Changchun, P. R. China
| | - Xiao-Fang Yu
- 1] Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, P. R. China [2] Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
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115
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The Interferon-Inducible Protein Tetherin Inhibits Hepatitis B Virus Virion Secretion. J Virol 2015; 89:9200-12. [PMID: 26109732 DOI: 10.1128/jvi.00933-15] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 06/18/2015] [Indexed: 12/17/2022] Open
Abstract
UNLABELLED Interferon alpha (IFN-α) is an approved medication for chronic hepatitis B therapy. Besides acting as an immunomodulator, IFN-α elicits a pleiotropic antiviral state in hepatitis B virus (HBV)-infected hepatocytes, but whether or not IFN-α impedes the late steps of the HBV life cycle, such as HBV secretion, remains elusive. Here we report that IFN-α treatment of HepAD38 cells with established HBV replication selectively reduced HBV virion release without altering intracellular viral replication or the secretion of HBV subviral particles and nonenveloped capsids. In search of the interferon-stimulated gene(s) that is responsible for the reduction of HBV virion release, we found that tetherin, a broad-spectrum antiviral transmembrane protein that inhibits the egress of a variety of enveloped viruses, was highly induced by IFN-α in HepAD38 cells and in primary human hepatocytes. We further demonstrated that the expression of full-length tetherin, but not the C-terminal glycosylphosphatidylinositol (GPI) anchor-truncated form, inhibited HBV virion egress from HepAD38 cells. In addition, GPI anchor-truncated tetherin exhibited a dominant-negative effect and was incorporated into the liberated virions. We also found colocalization of tetherin and HBV L protein at the intracellular multivesicular body, where the budding of HBV virions takes place. In line with this, electron microscopy demonstrated that HBV virions were tethered in the lumen of the cisterna membrane under tetherin expression. Finally, knockdown of tetherin or overexpression of dominant negative tetherin attenuated the IFN-α-mediated reduction of HBV virion release. Taken together, our study suggests that IFN-α inhibits HBV virion egress from hepatocytes through the induction of tetherin. IMPORTANCE Tetherin is a host restriction factor that blocks the egress of a variety of enveloped viruses through tethering the budding virions on the cell surface with its membrane anchor domains. Here we report that interferon directly and selectively inhibits the secretion of HBV virions, but not subviral particles or nonenveloped capsids, through the induction of tetherin in hepatocyte-derived cells. The antiviral function of tetherin requires the carboxyl-terminal GPI anchor, while the GPI anchor deletion mutant exhibits dominant negative activity and attaches to liberated HBV virions. Consistent with the fact that HBV is an intracellular budding virus, microscopy analyses demonstrated that the tethering of HBV virions occurs in the intracellular cisterna and that tetherin colocalizes with HBV virions on the multivesicular body, which is the HBV virion budding site. Our study not only expands the antiviral spectrum of tetherin but also sheds light on the mechanisms of interferon-elicited anti-HBV responses.
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116
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Falasca L, Agrati C, Petrosillo N, Di Caro A, Capobianchi MR, Ippolito G, Piacentini M. Molecular mechanisms of Ebola virus pathogenesis: focus on cell death. Cell Death Differ 2015; 22:1250-9. [PMID: 26024394 PMCID: PMC4495366 DOI: 10.1038/cdd.2015.67] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 03/31/2015] [Accepted: 04/20/2015] [Indexed: 12/28/2022] Open
Abstract
Ebola virus (EBOV) belongs to the Filoviridae family and is responsible for a severe disease characterized by the sudden onset of fever and malaise accompanied by other non-specific signs and symptoms; in 30–50% of cases hemorrhagic symptoms are present. Multiorgan dysfunction occurs in severe forms with a mortality up to 90%. The EBOV first attacks macrophages and dendritic immune cells. The innate immune reaction is characterized by a cytokine storm, with secretion of numerous pro-inflammatory cytokines, which induces a huge number of contradictory signals and hurts the immune cells, as well as other tissues. Other highly pathogenic viruses also trigger cytokine storms, but Filoviruses are thought to be particularly lethal because they affect a wide array of tissues. In addition to the immune system, EBOV attacks the spleen and kidneys, where it kills cells that help the body to regulate its fluid and chemical balance and that make proteins that help the blood to clot. In addition, EBOV causes liver, lungs and kidneys to shut down their functions and the blood vessels to leak fluid into surrounding tissues. In this review, we analyze the molecular mechanisms at the basis of Ebola pathogenesis with a particular focus on the cell death pathways induced by the virus. We also discuss how the treatment of the infection can benefit from the recent experience of blocking/modulating cell death in human degenerative diseases.
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Affiliation(s)
- L Falasca
- National Institute for Infectious Diseases, Lazzaro Spallanzani, Rome, Italy
| | - C Agrati
- National Institute for Infectious Diseases, Lazzaro Spallanzani, Rome, Italy
| | - N Petrosillo
- National Institute for Infectious Diseases, Lazzaro Spallanzani, Rome, Italy
| | - A Di Caro
- National Institute for Infectious Diseases, Lazzaro Spallanzani, Rome, Italy
| | - M R Capobianchi
- National Institute for Infectious Diseases, Lazzaro Spallanzani, Rome, Italy
| | - G Ippolito
- National Institute for Infectious Diseases, Lazzaro Spallanzani, Rome, Italy
| | - M Piacentini
- 1] National Institute for Infectious Diseases, Lazzaro Spallanzani, Rome, Italy [2] Department of Biology, University of Rome Tor Vergata, Rome, Italy
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117
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Basler CF. Innate immune evasion by filoviruses. Virology 2015; 479-480:122-30. [DOI: 10.1016/j.virol.2015.03.030] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 03/17/2015] [Indexed: 01/07/2023]
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118
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Human Pirh2 is a novel inhibitor of prototype foamy virus replication. Viruses 2015; 7:1668-84. [PMID: 25848801 PMCID: PMC4411673 DOI: 10.3390/v7041668] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 02/02/2015] [Accepted: 03/25/2015] [Indexed: 12/11/2022] Open
Abstract
Prototype foamy virus (PFV) is a member of the unconventional and nonpathogenic retroviruses. PFV causes lifelong chronic infections, which are partially attributable to a number of host cell factors that restrict viral replication. Herein, we identified human p53-induced RING-H2 protein (Pirh2) as a novel inhibitor of prototype foamy virus. Overexpression of Pirh2 decreased the replication of PFV, whereas knockdown of Pirh2 with specific siRNA increased PFV replication. Dual-luciferase assays and coimmunoprecipitation demonstrated that Pirh2 negatively influences the Tas-dependent transcriptional activation of the PFV long terminal repeat (LTR) and internal promoter (IP) by interacting with the transactivator Tas and down-regulating its expression. In addition, the viral inhibitory function of Pirh2 is N-terminal and RING domain dependent. Together, these results indicated that Pirh2 suppresses PFV replication by negatively impacting its transactivator Tas and the transcription of two viral promoters, which may contribute to the latency of PFV infection.
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119
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Gustin JK, Bai Y, Moses AV, Douglas JL. Ebola Virus Glycoprotein Promotes Enhanced Viral Egress by Preventing Ebola VP40 From Associating With the Host Restriction Factor BST2/Tetherin. J Infect Dis 2015; 212 Suppl 2:S181-90. [PMID: 25821226 DOI: 10.1093/infdis/jiv125] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND BST2/tetherin is an innate immune molecule with the unique ability to restrict the egress of human immunodeficiency virus (HIV) and other enveloped viruses, including Ebola virus (EBOV). Coincident with this discovery was the finding that the HIV Vpu protein down-regulates BST2 from the cell surface, thereby promoting viral release. Evidence suggests that the EBOV envelope glycoprotein (GP) also counteracts BST2, although the mechanism is unclear. RESULTS We find that total levels of BST2 remain unchanged in the presence of GP, whereas surface BST2 is significantly reduced. GP is known to sterically mask surface receptors via its mucin domain. Our evaluation of mutant GP molecules indicate that masking of BST2 by GP is probably responsible for the apparent surface BST2 down-regulation; however, this masking does not explain the observed virus-like particle egress enhancement. We discovered that VP40 coimmunoprecipitates and colocalizes with BST2 in the absence but not in the presence of GP. CONCLUSIONS These results suggest that GP may overcome the BST2 restriction by blocking an interaction between VP40 and BST2. Furthermore, we have observed that GP may enhance BST2 incorporation into virus-like particles. Understanding this novel EBOV immune evasion strategy will provide valuable insights into the pathogenicity of this deadly pathogen.
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Affiliation(s)
- Jean K Gustin
- Vaccine and Gene Therapy Institute, Oregon Health & Science University, Beaverton
| | - Ying Bai
- Vaccine and Gene Therapy Institute, Oregon Health & Science University, Beaverton
| | - Ashlee V Moses
- Vaccine and Gene Therapy Institute, Oregon Health & Science University, Beaverton
| | - Janet L Douglas
- Vaccine and Gene Therapy Institute, Oregon Health & Science University, Beaverton
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120
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Kajihara M, Takada A. Host Cell Factors Involved in Filovirus Infection. CURRENT TROPICAL MEDICINE REPORTS 2015. [DOI: 10.1007/s40475-015-0039-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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121
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Gong S, Osei ES, Kaplan D, Chen YH, Meyerson H. CD317 is over-expressed in B-cell chronic lymphocytic leukemia, but not B-cell acute lymphoblastic leukemia. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2015; 8:1613-1621. [PMID: 25973046 PMCID: PMC4396245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Accepted: 01/28/2015] [Indexed: 06/04/2023]
Abstract
CD317 was first identified as a multiple myeloma-associated antigen. Here we report the expression of CD317 in normal B cells and B-cell malignancies. In normal bone marrow, CD317 demonstrates a biphasic expression pattern, with higher expression on stage 1 and stage 3 hematogones, but not on stage 2 hematogones. CD317 is over-expressed in B-cell chronic lymphocytic leukemia, and appears associated with negative CD38 expression. Moreover, CD317 is barely detectable in B-cell acute lymphoblastic leukemia. Our results suggest that CD317 expression might be of prognostic significance for B-CLL, and CD317 could be used as a new marker for minimal residual disease detection in B-ALL.
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Affiliation(s)
- Shunyou Gong
- Department of Pathology, University Hospitals Case Medical Center, Case Western Reserve UniversityCleveland 44106, Ohio, USA
- Department of Pathology and Laboratory Medicine, University of PennsylvaniaPhiladelphia 19104, PA, USA
| | - Ebenezer S Osei
- Department of Pathology, University Hospitals Case Medical Center, Case Western Reserve UniversityCleveland 44106, Ohio, USA
| | - David Kaplan
- Department of Pathology, University Hospitals Case Medical Center, Case Western Reserve UniversityCleveland 44106, Ohio, USA
| | - Youhai H Chen
- Department of Pathology and Laboratory Medicine, University of PennsylvaniaPhiladelphia 19104, PA, USA
| | - Howard Meyerson
- Department of Pathology, University Hospitals Case Medical Center, Case Western Reserve UniversityCleveland 44106, Ohio, USA
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Abstract
UNLABELLED In 2001-2002, six of seven Japanese macaques (Macaca fuscata) died after developing hemorrhagic syndrome at the Kyoto University Primate Research Institute (KUPRI). While the cause of death was unknown at the time, we detected simian retrovirus 4 (SRV-4) in samples obtained from a similar outbreak in 2008-2011, during which 42 of 43 Japanese macaques died after exhibiting hemorrhagic syndrome. In this study, we isolated SRV-4 strain PRI-172 from a Japanese macaque showing severe thrombocytopenia. When inoculated into four Japanese macaques, the isolate induced severe thrombocytopenia in all within 37 days. We then constructed an infectious molecular clone of strain PRI-172, termed pSR415, and inoculated the clone-derived virus into two Japanese macaques. These animals also developed severe thrombocytopenia in just 31 days after inoculation, and the virus was reisolated from blood, bone marrow, and stool. At necropsy, we observed bleeding from the gingivae and subcutaneous bleeding in all animals. SRV-4 infected a variety of tissues, especially in digestive organs, including colon and stomach, as determined by real-time reverse transcription-PCR (RT-PCR) and immunohistochemical staining. Furthermore, we identified the SRV-4 receptor as ASCT2, a neutral amino acid transporter. ASCT2 mRNA was expressed in a variety of tissues, and the distribution of SRV-4 proviruses in infected Japanese macaques correlated well with the expression levels of ASCT2 mRNA. From these results, we conclude that the causative agent of hemorrhagic syndrome in KUPRI Japanese macaques was SRV-4, and its receptor is ASCT2. IMPORTANCE During two separate outbreaks at the KUPRI, in 2001-2002 and 2008-2011, 96% of Japanese macaques (JM) that developed an unknown hemorrhagic syndrome died. Here, we isolated SRV-4 from a JM developing thrombocytopenia. The SRV-4 isolate and a molecularly cloned SRV-4 induced severe thrombocytopenia in virus-inoculated JMs within 37 days. At necropsy, we observed bleeding from gingivae and subcutaneous bleeding in all affected JMs and reisolated SRV-4 from blood, bone marrow, and stool. The distribution of SRV-4 proviruses in tissues correlated with the mRNA expression levels of ASCT2, which we identified as the SRV-4 receptor. From these results, we conclude that SRV-4 was the causative agent of hemorrhagic syndrome in JMs in KUPRI.
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Armezzani A, Varela M, Spencer TE, Palmarini M, Arnaud F. "Ménage à Trois": the evolutionary interplay between JSRV, enJSRVs and domestic sheep. Viruses 2014; 6:4926-45. [PMID: 25502326 PMCID: PMC4276937 DOI: 10.3390/v6124926] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 11/24/2014] [Accepted: 12/02/2014] [Indexed: 12/03/2022] Open
Abstract
Sheep betaretroviruses represent a fascinating model to study the complex evolutionary interplay between host and pathogen in natural settings. In infected sheep, the exogenous and pathogenic Jaagsiekte sheep retrovirus (JSRV) coexists with a variety of highly related endogenous JSRVs, referred to as enJSRVs. During evolution, some of them were co-opted by the host as they fulfilled important biological functions, including placental development and protection against related exogenous retroviruses. In particular, two enJSRV loci, enJS56A1 and enJSRV-20, were positively selected during sheep domestication due to their ability to interfere with the replication of related competent retroviruses. Interestingly, viruses escaping these transdominant enJSRVs have recently emerged, probably less than 200 years ago. Overall, these findings suggest that in sheep the process of endogenization is still ongoing and, therefore, the evolutionary interplay between endogenous and exogenous sheep betaretroviruses and their host has not yet reached an equilibrium.
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Affiliation(s)
- Alessia Armezzani
- MRC-University of Glasgow Centre for Virus Research, 464 Bearsden Road, Glasgow G61-1QH, UK.
| | - Mariana Varela
- MRC-University of Glasgow Centre for Virus Research, 464 Bearsden Road, Glasgow G61-1QH, UK.
| | - Thomas E Spencer
- Department of Animal Sciences and Center for Reproductive Biology, Washington State University, PO Box 646310 Pullman, Washington, DC, USA.
| | - Massimo Palmarini
- MRC-University of Glasgow Centre for Virus Research, 464 Bearsden Road, Glasgow G61-1QH, UK.
| | - Frédérick Arnaud
- UMR754, Université Claude Bernard Lyon 1, Institut National de la Recherche Agronomique, Ecole Pratique des Hautes Etudes, SFR BioSciences Gerland, 50 avenue Tony Garnier, 69007 Lyon, France.
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Tedbury PR, Freed EO. The cytoplasmic tail of retroviral envelope glycoproteins. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 129:253-84. [PMID: 25595807 DOI: 10.1016/bs.pmbts.2014.10.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Retroviruses comprise a large, diverse group that infects a broad range of host organisms. Pathogenicity varies widely; the human immunodeficiency virus is the causative agent of acquired immunodeficiency syndrome, one of the world's leading infectious causes of death, while many nonhuman retroviruses cause cancer in the host. Retroviruses have been studied intensively, and great strides have been made in understanding aspects of retroviral biology. While the principal functions of the viral structural proteins are well understood, there remain many incompletely characterized domains. One of these is the cytoplasmic tail (CT) of the envelope glycoprotein. Several functions of the CT are highly conserved, whereas other properties are unique to a specific retrovirus. For example, the lentiviruses encode envelope glycoproteins with particularly large cytoplasmic domains. The functions of the long lentiviral envelope CT are still being deciphered. The reported functions of retroviral envelope CTs are discussed in this chapter.
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Affiliation(s)
- Philip R Tedbury
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Eric O Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA.
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125
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Liu Y, Luo S, He S, Zhang M, Wang P, Li C, Huang W, Hu B, Griffin GE, Shattock RJ, Hu Q. Tetherin restricts HSV-2 release and is counteracted by multiple viral glycoproteins. Virology 2014; 475:96-109. [PMID: 25462350 DOI: 10.1016/j.virol.2014.11.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 02/09/2014] [Accepted: 11/04/2014] [Indexed: 01/08/2023]
Abstract
Tetherin has been defined as a restriction factor of HIV-1 and several other enveloped viruses. However, the significance of tetherin in viral infection remains to be further addressed. Here, we investigated whether tetherin plays a role in HSV-2 infection. Our study revealed that overexpression of tetherin restricted the release of HSV-2 into the extracellular medium, while knockdown of tetherin by siRNA enhanced its release. We further demonstrated that HSV-2 infection and viral glycoproteins gB, gD, gH and gL but not gM significantly downregulated the endogenous expression of tetherin. Additional study indicated that tetherin likely physically interacted with gB, gD, gH and gL. This is the first time that tetherin has been shown to be counteracted by multiple viral components of a virus. Our findings inform the complexity of HSV-2-host interactions, providing basis for understanding the role of tetherin as a viral restriction factor and the mechanisms underlying viral countermeasures.
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Affiliation(s)
- Yalan Liu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Sukun Luo
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Siyi He
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Mudan Zhang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ping Wang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chang Li
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wenjie Huang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Bodan Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - George E Griffin
- Institute for Infection and Immunity, St George's University of London, London SW17 0RE, UK
| | - Robin J Shattock
- Section of Infectious Diseases, Faculty of Medicine, Imperial College London, St. Mary's Campus, London W2 1PG, UK
| | - Qinxue Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China; Institute for Infection and Immunity, St George's University of London, London SW17 0RE, UK.
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126
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Waheed AA, Kuruppu ND, Felton KL, D’Souza D, Freed EO. In COS cells Vpu can both stabilize tetherin expression and counteract its antiviral activity. PLoS One 2014; 9:e111628. [PMID: 25360760 PMCID: PMC4216104 DOI: 10.1371/journal.pone.0111628] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 10/03/2014] [Indexed: 01/12/2023] Open
Abstract
The interferon-inducible cellular protein tetherin (CD317/BST-2) inhibits the release of a broad range of enveloped viruses. The HIV-1 accessory protein Vpu enhances virus particle release by counteracting this host restriction factor. While the antagonism of human tetherin by Vpu has been associated with both proteasomal and lysosomal degradation, the link between Vpu-mediated tetherin degradation and the ability of Vpu to counteract the antiviral activity of tetherin remains poorly understood. Here, we show that human tetherin is expressed at low levels in African green monkey kidney (COS) cells. However, Vpu markedly increases tetherin expression in this cell line, apparently by sequestering it in an internal compartment that bears lysosomal markers. This stabilization of tetherin by Vpu requires the transmembrane sequence of human tetherin. Although Vpu stabilizes human tetherin in COS cells, it still counteracts the ability of tetherin to suppress virus release. The enhancement of virus release by Vpu in COS cells is associated with a modest reduction in cell-surface tetherin expression, even though the overall expression of tetherin is higher in the presence of Vpu. This study demonstrates that COS cells provide a model system in which Vpu-mediated enhancement of HIV-1 release is uncoupled from Vpu-mediated tetherin degradation.
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Affiliation(s)
- Abdul A. Waheed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
- * E-mail:
| | - Nishani D. Kuruppu
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
| | - Kathryn L. Felton
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
| | - Darren D’Souza
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
| | - Eric O. Freed
- Virus-Cell Interaction Section, HIV Drug Resistance Program, NCI-Frederick, Frederick, Maryland, United States of America
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Lv M, Wang J, Zhang J, Zhang B, Wang X, Zhu Y, Zuo T, Liu D, Li X, Wu J, Zhang H, Yu B, Wu H, Zhao X, Kong W, Yu X. Epitope tags beside the N-terminal cytoplasmic tail of human BST-2 alter its intracellular trafficking and HIV-1 restriction. PLoS One 2014; 9:e111422. [PMID: 25347789 PMCID: PMC4210262 DOI: 10.1371/journal.pone.0111422] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 09/25/2014] [Indexed: 12/02/2022] Open
Abstract
BST-2 blocks the particle release of various enveloped viruses including HIV-1, and this antiviral activity is dependent on the topological arrangement of its four structural domains. Several functions of the cytoplasmic tail (CT) of BST-2 have been previously discussed, but the exact role of this domain remains to be clearly defined. In this study, we investigated the impact of truncation and commonly-used tags addition into the CT region of human BST-2 on its intracellular trafficking and signaling as well as its anti-HIV-1 function. The CT-truncated BST-2 exhibited potent inhibition on Vpu-defective HIV-1 and even wild-type HIV-1. However, the N-terminal HA-tagged CT-truncated BST-2 retained little antiviral activity and dramatically differed from its original protein in the cell surface level and intracellular localization. Further, we showed that the replacement of the CT domain with a hydrophobic tag altered BST-2 function possibly by preventing its normal vesicular trafficking. Notably, we demonstrated that a positive charged motif “KRXK” in the conjunctive region between the cytotail and the transmembrane domain which is conserved in primate BST-2 is important for the protein trafficking and the antiviral function. These results suggest that although the CT of BST-2 is not essential for its antiviral activity, the composition of residues in this region may play important roles in its normal trafficking which subsequently affected its function. These observations provide additional implications for the structure-function model of BST-2.
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Affiliation(s)
- Mingyu Lv
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Jiawen Wang
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
- Center for New Medicine Research, Changchun University of Chinese Medicine, Changchun, P.R. China
| | - Jingyao Zhang
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Biao Zhang
- School of Pharmaceutical Sciences, Jilin University, Changchun, P.R. China
| | - Xiaodan Wang
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Yingzi Zhu
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Tao Zuo
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Donglai Liu
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Xiaojun Li
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Jiaxin Wu
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Haihong Zhang
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Bin Yu
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Hui Wu
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Xinghong Zhao
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
| | - Wei Kong
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
- * E-mail: (WK); (XY)
| | - Xianghui Yu
- National Engineering Laboratory for AIDS Vaccine, School of Life Sciences, Jilin University, Changchun, P.R. China
- * E-mail: (WK); (XY)
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128
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The sheep tetherin paralog oBST2B blocks envelope glycoprotein incorporation into nascent retroviral virions. J Virol 2014; 89:535-44. [PMID: 25339764 DOI: 10.1128/jvi.02751-14] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
UNLABELLED Bone marrow stromal cell antigen 2 (BST2) is a cellular restriction factor with a broad antiviral activity. In sheep, the BST2 gene is duplicated into two paralogs termed oBST2A and oBST2B. oBST2A impedes viral exit of the Jaagsiekte sheep retroviruses (JSRV), most probably by retaining virions at the cell membrane, similar to the "tethering" mechanism exerted by human BST2. In this study, we provide evidence that unlike oBST2A, oBST2B is limited to the Golgi apparatus and disrupts JSRV envelope (Env) trafficking by sequestering it. In turn, oBST2B leads to a reduction in Env incorporation into viral particles, which ultimately results in the release of virions that are less infectious. Furthermore, the activity of oBST2B does not seem to be restricted to retroviruses, as it also acts on vesicular stomatitis virus glycoproteins. Therefore, we suggest that oBST2B exerts antiviral activity using a mechanism distinct from the classical tethering restriction observed for oBST2A. IMPORTANCE BST2 is a powerful cellular restriction factor against a wide range of enveloped viruses. Sheep possess two paralogs of the BST2 gene called oBST2A and oBST2B. JSRV, the causative agent of a transmissible lung cancer of sheep, is known to be restricted by oBST2A. In this study, we show that unlike oBST2A, oBST2B impairs the normal cellular trafficking of JSRV envelope glycoproteins by sequestering them within the Golgi apparatus. We also show that oBST2B decreases the incorporation of envelope glycoprotein into JSRV viral particles, which in turn reduces virion infectivity. In conclusion, oBST2B exerts a novel antiviral activity that is distinct from those of BST2 proteins of other species.
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The VP40 protein of Marburg virus exhibits impaired budding and increased sensitivity to human tetherin following mouse adaptation. J Virol 2014; 88:14440-50. [PMID: 25297995 DOI: 10.1128/jvi.02069-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
UNLABELLED The Marburg virus VP40 protein is a viral matrix protein that spontaneously buds from cells. It also functions as an interferon (IFN) signaling antagonist by targeting Janus kinase 1 (JAK1). A previous study demonstrated that the VP40 protein of the Ravn strain of Marburg virus (Ravn virus [RAVV]) failed to block IFN signaling in mouse cells, whereas the mouse-adapted RAVV (maRAVV) VP40 acquired the ability to inhibit IFN responses in mouse cells. The increased IFN antagonist function of maRAVV VP40 mapped to residues 57 and 165, which were mutated during the mouse adaptation process. In the present study, we demonstrate that maRAVV VP40 lost the capacity to efficiently bud from human cell lines, despite the fact that both parental and maRAVV VP40s bud efficiently from mouse cell lines. The impaired budding in human cells corresponds with the appearance of protrusions on the surface of maRAVV VP40-expressing Huh7 cells and with an increased sensitivity of maRAVV VP40 to restriction by human tetherin but not mouse tetherin. However, transfer of the human tetherin cytoplasmic tail to mouse tetherin restored restriction of maRAVV VP40. Residues 57 and 165 were demonstrated to contribute to the failure of maRAVV VP40 to bud from human cells, and residue 57 was demonstrated to alter VP40 oligomerization, as assessed by coprecipitation assay, and to determine sensitivity to human tetherin. This suggests that RAVV VP40 acquired, during adaptation to mice, changes in its oligomerization potential that enhanced IFN antagonist function. However, this new capacity impaired RAVV VP40 budding from human cells. IMPORTANCE Filoviruses, which include Marburg viruses and Ebola viruses, are zoonotic pathogens that cause severe disease in humans and nonhuman primates but do not cause similar disease in wild-type laboratory strains of mice unless first adapted to these animals. Although mouse adaptation has been used as a method to develop small animal models of pathogenesis, the molecular determinants associated with filovirus mouse adaptation are poorly understood. Our study demonstrates how genetic changes that accrued during mouse adaptation of the Ravn strain of Marburg virus have impacted the budding function of the viral VP40 matrix protein. Strikingly, we find impairment of mouse-adapted VP40 budding function in human but not mouse cell lines, and we correlate the impairment with an increased sensitivity of VP40 to restriction by human but not mouse tetherin and with changes in VP40 oligomerization. These data suggest that there are functional costs associated with filovirus adaptation to new hosts and implicate tetherin as a filovirus host restriction factor.
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130
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The HERV-K human endogenous retrovirus envelope protein antagonizes Tetherin antiviral activity. J Virol 2014; 88:13626-37. [PMID: 25210194 DOI: 10.1128/jvi.02234-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Endogenous retroviruses are the remnants of past retroviral infections that are scattered within mammalian genomes. In humans, most of these elements are old degenerate sequences that have lost their coding properties. The HERV-K(HML2) family is an exception: it recently amplified in the human genome and corresponds to the most active proviruses, with some intact open reading frames and the potential to encode viral particles. Here, using a reconstructed consensus element, we show that HERV-K(HML2) proviruses are able to inhibit Tetherin, a cellular restriction factor that is active against most enveloped viruses and acts by keeping the viral particles attached to the cell surface. More precisely, we identify the Envelope protein (Env) as the viral effector active against Tetherin. Through immunoprecipitation experiments, we show that the recognition of Tetherin is mediated by the surface subunit of Env. Similar to Ebola glycoprotein, HERV-K(HML2) Env does not mediate Tetherin degradation or cell surface removal; therefore, it uses a yet-undescribed mechanism to inactivate Tetherin. We also assessed all natural complete alleles of endogenous HERV-K(HML2) Env described to date for their ability to inhibit Tetherin and found that two of them (out of six) can block Tetherin restriction. However, due to their recent amplification, HERV-K(HML2) elements are extremely polymorphic in the human population, and it is likely that individuals will not all possess the same anti-Tetherin potential. Because of Tetherin's role as a restriction factor capable of inducing innate immune responses, this could have functional consequences for individual responses to infection. IMPORTANCE Tetherin, a cellular protein initially characterized for its role against HIV-1, has been proven to counteract numerous enveloped viruses. It blocks the release of viral particles from producer cells, keeping them tethered to the cell surface. Several viruses have developed strategies to inhibit Tetherin activity, allowing them to efficiently infect and replicate in their host. Here, we show that human HERV-K(HML2) elements, the remnants of an ancient retroviral infection, possess an anti-Tetherin activity which is mediated by the envelope protein. It is likely that this activity was an important factor that contributed to the recent, human-specific amplification of this family of elements. Also, due to their recent amplification, HERV-K(HML2) elements are highly polymorphic in the human population. Since Tetherin is a mediator of innate immunity, interindividual variations among HERV-K(HML2) Env genes may result in differences in immune responses to infection.
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131
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Abe M, Fukuma A, Yoshikawa R, Miyazawa T, Yasuda J. Inhibition of budding/release of porcine endogenous retrovirus. Microbiol Immunol 2014; 58:432-8. [DOI: 10.1111/1348-0421.12166] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2014] [Revised: 05/21/2014] [Accepted: 06/06/2014] [Indexed: 01/14/2023]
Affiliation(s)
- Masumi Abe
- Fifth Biology Section for Microbiology; First Department of Forensic Science; National Research Institute of Police Science; Kashiwa 277-0882
| | - Aiko Fukuma
- Fifth Biology Section for Microbiology; First Department of Forensic Science; National Research Institute of Police Science; Kashiwa 277-0882
- Department of Emerging Infectious Diseases; Institute of Tropical Medicine (NEKKEN); Nagasaki University; Nagasaki 852-8523
| | - Rokusuke Yoshikawa
- Laboratory of Signal Transduction; Department of Cell Biology; Institute for Virus Research; Kyoto University; Kyoto 606-8507 Japan
| | - Takayuki Miyazawa
- Laboratory of Signal Transduction; Department of Cell Biology; Institute for Virus Research; Kyoto University; Kyoto 606-8507 Japan
| | - Jiro Yasuda
- Fifth Biology Section for Microbiology; First Department of Forensic Science; National Research Institute of Police Science; Kashiwa 277-0882
- Department of Emerging Infectious Diseases; Institute of Tropical Medicine (NEKKEN); Nagasaki University; Nagasaki 852-8523
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Narkpuk J, Wanitchang A, Kramyu J, Frantz PN, Jongkaewwattana A, Teeravechyan S. An unconventional BST-2 function: down-regulation of transient protein expression. Biochem Biophys Res Commun 2014; 450:1469-74. [PMID: 25019996 DOI: 10.1016/j.bbrc.2014.07.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 07/03/2014] [Indexed: 11/17/2022]
Abstract
While viral inhibition by tethering of budding virions to host cell membranes has been focused upon as one of the main functions of BST-2/tetherin, BST-2 is thought to possess other functions as well. Overexpression of BST-2 was found here to down-regulate transient protein expression. Removal of the N- and C-terminal regions of BST-2, previously described to be involved in signal transduction, reduced the impact of BST-2. These results suggest that BST-2-mediated signaling may play a role in regulating the levels of transiently expressed proteins, highlighting a new function for BST-2 that may also have implications for viral inhibition.
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Affiliation(s)
- Jaraspim Narkpuk
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park, Phaholyothin Rd, Klong 1, Klong Luang, Pathumthani 12120, Thailand
| | - Asawin Wanitchang
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park, Phaholyothin Rd, Klong 1, Klong Luang, Pathumthani 12120, Thailand
| | - Jarin Kramyu
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park, Phaholyothin Rd, Klong 1, Klong Luang, Pathumthani 12120, Thailand
| | - Phanramphoei Namprachan Frantz
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park, Phaholyothin Rd, Klong 1, Klong Luang, Pathumthani 12120, Thailand
| | - Anan Jongkaewwattana
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park, Phaholyothin Rd, Klong 1, Klong Luang, Pathumthani 12120, Thailand
| | - Samaporn Teeravechyan
- Virology and Cell Technology Laboratory, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, 113 Thailand Science Park, Phaholyothin Rd, Klong 1, Klong Luang, Pathumthani 12120, Thailand.
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Maturation and vesicle-mediated egress of primate gammaherpesvirus rhesus monkey rhadinovirus require inner tegument protein ORF52. J Virol 2014; 88:9111-28. [PMID: 24899183 DOI: 10.1128/jvi.01502-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
UNLABELLED The tegument layer of herpesviruses comprises a collection of proteins that is unique to each viral species. In rhesus monkey rhadinovirus (RRV), a close relative of the human oncogenic pathogen Kaposi's sarcoma-associated herpesvirus, ORF52 is a highly abundant tegument protein tightly associated with the capsid. We now report that ORF52 knockdown during RRV infection of rhesus fibroblasts led to a greater than 300-fold reduction in the viral titer by 48 h but had little effect on the number of released particles and caused only modest reductions in the levels of intracellular viral genomic DNA and no appreciable change in viral DNA packaging into capsids. These data suggested that the lack of ORF52 resulted in the production and release of defective particles. In support of this interpretation, transmission electron microscopy (TEM) revealed that without ORF52, capsid-like particles accumulated in the cytoplasm and were unable to enter egress vesicles, where final tegumentation and envelopment normally occur. TEM also demonstrated defective particles in the medium that closely resembled the accumulating intracellular particles, having neither a full tegument nor an envelope. The disruption in tegument formation from ORF52 suppression, therefore, prevented the incorporation of ORF45, restricting its subcellular localization to the nucleus and appearing, by confocal microscopy, to inhibit particle transport toward the periphery. Ectopic expression of small interfering RNA (siRNA)-resistant ORF52 was able to partially rescue all of these phenotypic changes. In sum, our results indicate that efficient egress of maturing virions and, in agreement with studies on murine gammaherpesvirus 68 (MHV-68), complete tegumentation and secondary envelopment are dependent on intact ORF52. IMPORTANCE The tegument, or middle layer, of herpesviruses comprises both viral and cellular proteins that play key roles in the viral life cycle. A subset of these proteins is present only within members of one of the three subfamilies (alphaherpesviruses, betaherpesviruses, or gammaherpesviruses) of Herpesviridae. In this report, we show that the gammaherpesvirus-specific tegument protein ORF52 is critical for maturation of RRV, the closest relative of Kaposi's sarcoma-associated herpesvirus (KSHV) (a human cancer-causing pathogen) that has undergone this type of analysis. Without ORF52, the nascent subviral particles are essentially stuck in maturation limbo, unable to acquire the tegument or outer (envelope) layers. This greatly attenuates infectivity. Our data, together with earlier work on a murine homolog, as well as a more distantly related human homolog, provide a more complete understanding of how early protein interactions involving virus-encoded tegument proteins are critical for virus assembly and are also, therefore, potentially attractive therapeutic targets.
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Nityanandam R, Serra-Moreno R. BCA2/Rabring7 targets HIV-1 Gag for lysosomal degradation in a tetherin-independent manner. PLoS Pathog 2014; 10:e1004151. [PMID: 24852021 PMCID: PMC4031200 DOI: 10.1371/journal.ppat.1004151] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2014] [Accepted: 04/14/2014] [Indexed: 12/04/2022] Open
Abstract
BCA2 (Rabring7, RNF115 or ZNF364) is a RING-finger E3 ubiquitin ligase that was identified as a co-factor in the restriction imposed by tetherin/BST2 on HIV-1. Contrary to the current model, in which BCA2 lacks antiviral activity in the absence of tetherin, we found that BCA2 possesses tetherin-independent antiviral activity. Here we show that the N-terminus of BCA2 physically interacts with the Matrix region of HIV-1 and other retroviral Gag proteins and promotes their ubiquitination, redistribution to endo-lysosomal compartments and, ultimately, lysosomal degradation. The targeted depletion of BCA2 in tetherin-expressing and tetherin-deficient cells results in a significant increase in virus release and replication, indicating that endogenous BCA2 possesses antiviral activity. Therefore, these results indicate that BCA2 functions as an antiviral factor that targets HIV-1 Gag for degradation, impairing virus assembly and release. Tetherin (also known as BST2, CD317 or HM1.24) is an interferon-inducible cellular factor that interferes with the release of enveloped viruses from infected cells. A recent study identified BCA2 (Breast Cancer-Associated gene 2, also known as RNF115, ZNF364 or Rabring7), a RING-finger E3 ubiquitin ligase, as a co-factor in the tetherin-mediated restriction of HIV-1. According to this model, BCA2 interacts with sequences in the N-terminus of tetherin to promote the internalization and lysosomal degradation of tethered HIV-1 particles, with no apparent antiviral activity in cells not expressing tetherin. However, here we show for the first time that BCA2 inhibits virus production for HIV-1 and other retroviruses in a tetherin-independent manner by reducing the cellular levels of Gag – the precursor of the structural proteins Matrix, Capsid, Nucleocapsid and p6. Hence, contrary to its reported role as a tetherin co-factor, BCA2 functions as a tetherin-independent antiviral factor that impairs virus assembly and release.
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Affiliation(s)
- Ramya Nityanandam
- Division of Immunology, New England Primate Research Center, Harvard Medical School, Southborough, Massachusetts, United States of America
| | - Ruth Serra-Moreno
- Division of Immunology, New England Primate Research Center, Harvard Medical School, Southborough, Massachusetts, United States of America
- * E-mail:
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Arias JF, Heyer LN, von Bredow B, Weisgrau KL, Moldt B, Burton DR, Rakasz EG, Evans DT. Tetherin antagonism by Vpu protects HIV-infected cells from antibody-dependent cell-mediated cytotoxicity. Proc Natl Acad Sci U S A 2014; 111:6425-30. [PMID: 24733916 PMCID: PMC4035966 DOI: 10.1073/pnas.1321507111] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Tetherin is an IFN-inducible transmembrane protein that inhibits the detachment of enveloped viruses from infected cells. HIV-1 overcomes this restriction factor by expressing HIV-1 viral protein U (Vpu), which down-regulates and degrades tetherin. We report that mutations in Vpu that impair tetherin antagonism increase the susceptibility of HIV-infected cells to antibody-dependent cell-mediated cytotoxicity (ADCC), and conversely that RNAi knockdown of tetherin, but not other cellular proteins down-modulated by Vpu, decreases the susceptibility of HIV-infected cells to ADCC. These results reveal that Vpu protects HIV-infected cells from ADCC as a function of its ability to counteract tetherin. By serving as link between innate and adaptive immunity, the antiviral activity of tetherin may be augmented by virus-specific antibodies, and hence much greater than previously appreciated.
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Affiliation(s)
- Juan F. Arias
- Department of Microbiology and Immunobiology, New England Primate Research Center, Harvard Medical School, Southborough, MA 01772
| | - Lisa N. Heyer
- Department of Microbiology and Immunobiology, New England Primate Research Center, Harvard Medical School, Southborough, MA 01772
| | - Benjamin von Bredow
- Department of Microbiology and Immunobiology, New England Primate Research Center, Harvard Medical School, Southborough, MA 01772
| | - Kim L. Weisgrau
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI 53715
| | - Brian Moldt
- Department of Immunology and Microbial Science, International AIDS Vaccine Initiative Neutralizing Antibody Center and Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, CA 92037; and
| | - Dennis R. Burton
- Department of Immunology and Microbial Science, International AIDS Vaccine Initiative Neutralizing Antibody Center and Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, CA 92037; and
- Ragon Institute of MGH, MIT and Harvard, Cambridge, MA 02139
| | - Eva G. Rakasz
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI 53715
| | - David T. Evans
- Department of Microbiology and Immunobiology, New England Primate Research Center, Harvard Medical School, Southborough, MA 01772
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136
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Jia X, Weber E, Tokarev A, Lewinski M, Rizk M, Suarez M, Guatelli J, Xiong Y. Structural basis of HIV-1 Vpu-mediated BST2 antagonism via hijacking of the clathrin adaptor protein complex 1. eLife 2014; 3:e02362. [PMID: 24843023 PMCID: PMC4018625 DOI: 10.7554/elife.02362] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
BST2/tetherin, an antiviral restriction factor, inhibits the release of enveloped viruses from the cell surface. Human immunodeficiency virus-1 (HIV-1) antagonizes BST2 through viral protein u (Vpu), which downregulates BST2 from the cell surface. We report the crystal structure of a protein complex containing Vpu and BST2 cytoplasmic domains and the core of the clathrin adaptor protein complex 1 (AP1). This, together with our biochemical and functional validations, reveals how Vpu hijacks the AP1-dependent membrane trafficking pathways to mistraffick BST2. Vpu mimics a canonical acidic dileucine-sorting motif to bind AP1 in the cytosol, while simultaneously interacting with BST2 in the membrane. These interactions enable Vpu to build on an intrinsic interaction between BST2 and AP1, presumably causing the observed retention of BST2 in juxtanuclear endosomes and stimulating its degradation in lysosomes. The ability of Vpu to hijack AP-dependent trafficking pathways suggests a potential common theme for Vpu-mediated downregulation of host proteins. DOI:http://dx.doi.org/10.7554/eLife.02362.001 HIV is a retrovirus that attacks the immune system, making the body increasingly susceptible to opportunistic infections and disease and eventually leading to AIDS. While antiretroviral drugs have allowed people with AIDS to live longer, there is no cure or vaccine for HIV. Two types of HIV exist, with HIV-1 being much more common and pathogenic than HIV-2. Like other ‘complex’ retroviruses, the HIV-1 genome contains genes that encode various proteins that allow the virus to disrupt the immune response of the host it is attacking. Viral protein u is a protein encoded by HIV-1 (but not HIV-2) that counteracts an antiviral protein called BST2 in the host. BST2, which is part of the host's innate immune response, prevents newly formed viruses from leaving the surface of infected cells. By counteracting BST2, viral protein u allows the virus to spread in the host more efficiently. Like many proteins, newly produced BST2 is packaged inside structures called vesicles in a part of the cell called the trans-Golgi network, and then sent to its destination. Complexes formed by various proteins make sure that the vesicles take their cargo to their correct destinations within the cell. Two adaptor protein complexes—known as AP1 and AP2—are thought to be involved the transport of BST2. However, it is not known how viral protein u stops BST2 from reaching the cell surface, or how it decreases the amount of BST2 in the cell as a whole. Jia et al. show how viral protein u and BST2 jointly interact with AP1. This interaction leads to the mistrafficking and degradation of BST2 and the counteraction of its antiviral activity. DOI:http://dx.doi.org/10.7554/eLife.02362.002
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Affiliation(s)
- Xiaofei Jia
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Erin Weber
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
| | - Andrey Tokarev
- Department of Medicine, University of California San Diego, La Jolla, United States The VA San Diego Healthcare System, San Diego, United States
| | - Mary Lewinski
- Department of Medicine, University of California San Diego, La Jolla, United States The VA San Diego Healthcare System, San Diego, United States
| | - Maryan Rizk
- Department of Medicine, University of California San Diego, La Jolla, United States The VA San Diego Healthcare System, San Diego, United States
| | - Marissa Suarez
- Department of Medicine, University of California San Diego, La Jolla, United States The VA San Diego Healthcare System, San Diego, United States
| | - John Guatelli
- Department of Medicine, University of California San Diego, La Jolla, United States The VA San Diego Healthcare System, San Diego, United States
| | - Yong Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States
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137
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Sauter D. Counteraction of the multifunctional restriction factor tetherin. Front Microbiol 2014; 5:163. [PMID: 24782851 PMCID: PMC3989765 DOI: 10.3389/fmicb.2014.00163] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 03/26/2014] [Indexed: 01/28/2023] Open
Abstract
The interferon-inducible restriction factor tetherin (also known as CD317, BST-2 or HM1.24) has emerged as a key component of the antiviral immune response. Initially, tetherin was shown to restrict replication of various enveloped viruses by inhibiting the release of budding virions from infected cells. More recently, it has become clear that tetherin also acts as a pattern recognition receptor inducing NF-κB-dependent proinflammatory gene expression in virus infected cells. Whereas the ability to restrict virion release is highly conserved among mammalian tetherin orthologs and thus probably an ancient function of this protein, innate sensing seems to be an evolutionarily recent activity. The potent and broad antiviral activity of tetherin is reflected by the fact that many viruses evolved means to counteract this restriction factor. A continuous arms race with viruses has apparently driven the evolution of different isoforms of tetherin with different functional properties. Interestingly, tetherin has also been implicated in cellular processes that are unrelated to immunity, such as the organization of the apical actin network and membrane microdomains or stabilization of the Golgi apparatus. In this review, I summarize our current knowledge of the different functions of tetherin and describe the molecular strategies that viruses have evolved to antagonize or evade this multifunctional host restriction factor.
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Affiliation(s)
- Daniel Sauter
- Institute of Molecular Virology, Ulm University Medical Center Ulm, Germany
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138
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Durbin RK, Kotenko SV, Durbin JE. Interferon induction and function at the mucosal surface. Immunol Rev 2014; 255:25-39. [PMID: 23947345 DOI: 10.1111/imr.12101] [Citation(s) in RCA: 168] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Interferons (IFNs) are produced in response to virus infection and induce an antiviral state in virtually all cell types. In addition to upregulating the transcription of genes that inhibit virus replication, type I (or -α/β) IFNs also act to orchestrate the adaptive immune response to virus infection. Recently a new family of antiviral cytokines, the type III (or -λ) IFNs, has been identified that activate the same antiviral pathways via a distinct receptor. Although the identical transcription factor, IFN-stimulated gene factor 3 is activated by either IFN-α/β or IFN-λ signaling, differences in the induction and action of these two cytokine families are beginning to be appreciated. In this article, we review this emerging body of literature on the differing roles these cytokines play in host defense of the mucosal surface. Although many viruses enter the body through the respiratory and gastrointestinal tracts, we have focused the discussion on influenza A virus, respiratory syncytial virus, and rotavirus, three ubiquitous human pathogens that target the epithelial lining and are associated with a major disease burden.
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Affiliation(s)
- Russell K Durbin
- Department of Pathology, New York University School of Medicine, New York, NY 10016, USA
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139
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ROCK1 and LIM kinase modulate retrovirus particle release and cell-cell transmission events. J Virol 2014; 88:6906-21. [PMID: 24696479 DOI: 10.1128/jvi.00023-14] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
UNLABELLED The assembly and release of retroviruses from the host cells require dynamic interactions between viral structural proteins and a variety of cellular factors. It has been long speculated that the actin cytoskeleton is involved in retrovirus production, and actin and actin-related proteins are enriched in HIV-1 virions. However, the specific role of actin in retrovirus assembly and release remains unknown. Here we identified LIM kinase 1 (LIMK1) as a cellular factor regulating HIV-1 and Mason-Pfizer monkey virus (M-PMV) particle release. Depletion of LIMK1 reduced not only particle output but also virus cell-cell transmission and was rescued by LIMK1 replenishment. Depletion of the upstream LIMK1 regulator ROCK1 inhibited particle release, as did a competitive peptide inhibitor of LIMK1 activity that prevented cofilin phosphorylation. Disruption of either ROCK1 or LIMK1 led to enhanced particle accumulation on the plasma membrane as revealed by total internal reflection fluorescence microscopy (TIRFM). Electron microscopy demonstrated a block to particle release, with clusters of fully mature particles on the surface of the cells. Our studies support a model in which ROCK1- and LIMK1-regulated phosphorylation of cofilin and subsequent local disruption of dynamic actin turnover play a role in retrovirus release from host cells and in cell-cell transmission events. IMPORTANCE Viruses often interact with the cellular cytoskeletal machinery in order to deliver their components to the site of assembly and budding. This study indicates that a key regulator of actin dynamics at the plasma membrane, LIM kinase, is important for the release of viral particles for HIV as well as for particle release by a distantly related retrovirus, Mason-Pfizer monkey virus. Moreover, disruption of LIM kinase greatly diminished the spread of HIV from cell to cell. These findings suggest that LIM kinase and its dynamic modulation of the actin cytoskeleton in the cell may be an important host factor for the production, release, and transmission of retroviruses.
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140
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141
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HIV-1 Vpu antagonism of tetherin inhibits antibody-dependent cellular cytotoxic responses by natural killer cells. J Virol 2014; 88:6031-46. [PMID: 24623433 DOI: 10.1128/jvi.00449-14] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
UNLABELLED The type I interferon-inducible factor tetherin retains virus particles on the surfaces of cells infected with vpu-deficient human immunodeficiency virus type 1 (HIV-1). While this mechanism inhibits cell-free viral spread, the immunological implications of tethered virus have not been investigated. We found that surface tetherin expression increased the antibody opsonization of vpu-deficient HIV-infected cells. The absence of Vpu also stimulated NK cell-activating FcγRIIIa signaling and enhanced NK cell degranulation and NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC). The deletion of vpu in HIV-1-infected primary CD4(+) T cells enhanced the levels of antibody binding and Fc receptor signaling mediated by HIV-positive-patient-derived antibodies. The magnitudes of antibody binding and Fc signaling were both highly correlated to the levels of tetherin on the surfaces of infected primary CD4 T cells. The affinity of antibody binding to FcγRIIIa was also found to be critical in mediating efficient Fc activation. These studies implicate Vpu antagonism of tetherin as an ADCC evasion mechanism that prevents antibody-mediated clearance of virally infected cells. IMPORTANCE The ability of the HIV-1 accessory factor to antagonize tetherin has been considered to primarily function by limiting the spread of virus by preventing the release of cell-free virus. This study supports the hypothesis that a major function of Vpu is to decrease the recognition of infected cells by anti-HIV antibodies at the cell surface, thereby reducing recognition by antibody-dependent clearance by natural killer cells.
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142
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Differential sensitivities of tetherin isoforms to counteraction by primate lentiviruses. J Virol 2014; 88:5845-58. [PMID: 24623426 DOI: 10.1128/jvi.03818-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
UNLABELLED The mammalian antiviral membrane protein tetherin (BST2/CD317) can be expressed as two isoforms derived from differential translational initiation. The shorter isoform of the human protein (S-tetherin) lacks the first 12 amino acids of the longer (L-tetherin) cytoplasmic tail, which includes a tyrosine motif that acts as both an endocytic recycling signal and a determinant of virus-induced NF-κB activation. S-tetherin is also reported to be less sensitive to the prototypic viral antagonist human immunodeficiency virus type 1 (HIV-1) Vpu. Here we analyzed the relative sensitivities of L- and S-tetherins to primate lentiviral countermeasures. We show that the reduced sensitivity of S-tetherin to HIV-1 Vpu is a feature of all group M proteins, including those of transmitted founder viruses, primarily because it cannot be targeted for endosomal degradation owing to the truncation of its cytoplasmic tail. In contrast, both isoforms of the human and rhesus macaque tetherins display the same sensitivity to nondegradative lentiviral countermeasures of HIV-2 and SIVmac, respectively. Surprisingly, however, the Vpu proteins encoded by simian immunodeficiency viruses (SIVs) of African guenons, as well as that from recently isolated highly pathogenic HIV-1 group N, do not discriminate between tetherin isoforms. Together, these data suggest that the group M HIV-1 Vpu primarily adapted to target L-tetherin upon zoonotic transmission from chimpanzees, and further, we speculate that functions specifically associated with this isoform, such as proinflammatory signaling, play key roles in human tetherin's antiviral function in vivo. IMPORTANCE The ability of HIV-1 and related viruses to counteract a host antiviral protein, tetherin, is strictly maintained. The adaptation of the HIV-1 Vpu protein to counteract human tetherin is thought to have been one of the key events in the establishment of the HIV/AIDS pandemic. Recent evidence shows that tetherin is expressed as two isoforms and that Vpu preferentially targets the longer form. Here we show that unlike other virus-encoded countermeasures, such as those from primate viruses related to HIV-1, the enhanced ability to counteract the long tetherin isoform is conserved among HIV-1 strains that make up the majority of the human pandemic. This correlates with the ability of Vpu to induce long tetherin degradation. We speculate that functions associated with the human version of this isoform, such as an inflammatory signaling capacity, selected for Vpu's enhanced targeting of long tetherin during its adaptation to humans.
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143
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Skelton MM, Kampira EE, Wonkam AA, Mhandire KK, Kumwenda JJ, Duri KK, Dandara CC. Frequency variation among sub-Saharan populations in virus restriction gene, BST-2 proximal promoter polymorphisms: implications for HIV-1 prevalence differences among African countries. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2014; 18:461-71. [PMID: 24601767 DOI: 10.1089/omi.2013.0127] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The present study reports promoter variants in four sub-Saharan African populations that may affect BST-2 gene regulation. Recently, an in/del within the BST-2 promoter has been associated with HIV-1 disease progression in a Spanish cohort. Hence, we sequenced the proximal promoter region of the BST-2 gene in 581 individuals from South Africa, Zimbabwe, Malawi, and Cameroon. Seven SNPs were identified: rs28413176 (+26i6/Δ6); rs28413175 (-160i1/Δ1), -187A>G (nucleotide position -17516614); rs28413174 (-193G>A); rs73921425 (-199G>A); rs12609479 (-201C>T); and rs112492472 (-225C>T). The -199A and -225T alleles showed interesting trends across the sub-Saharan continent. Using predictive bioinformatics tools, we show that allelic variation at -199 and -201 potentially affect key transcription factor binding sites including bHLH, c-Myb, and E47. Importantly, data available from the ENCODE study gave further credence to our hypothesis of transcriptional regulation of BST-2 by a bHLH TF such as Mxi1. The possible repressive transcriptional effect of Mxi1 combined with the allelic frequency trend seen at -199 between African populations overlays well with current HIV-1 prevalence data, and may be a contributing factor to this phenomenon. The differences in HIV-1 prevalence in African countries could be, in part, due to distribution of genetic variants that affect susceptibility to HIV-1. Our findings therefore have substantive value for the design of future diagnostics for global health oriented diagnostics for HIV-1 susceptibility, and rational therapeutics on the critical path to personalized medicine in the African continent. As HIV-1 epidemiology vastly impacts human populations around the world, the population genomics strategy we have utilized herein can have value for other global regions as well.
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Affiliation(s)
- Michelle M Skelton
- 1 Division of Human Genetics, Faculty of Health Sciences, University of Cape Town , Observatory, Cape Town, South Africa
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144
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Feline immunodeficiency virus envelope glycoproteins antagonize tetherin through a distinctive mechanism that requires virion incorporation. J Virol 2014; 88:3255-72. [PMID: 24390322 DOI: 10.1128/jvi.03814-13] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
UNLABELLED BST2/tetherin inhibits the release of enveloped viruses from cells. Primate lentiviruses have evolved specific antagonists (Vpu, Nef, and Env). Here we characterized tetherin proteins of species representing both branches of the order Carnivora. Comparison of tiger and cat (Feliformia) to dog and ferret (Caniformia) genes demonstrated that the tiger and cat share a start codon mutation that truncated most of the tetherin cytoplasmic tail early in the Feliformia lineage (19 of 27 amino acids, including the dual tyrosine motif). Alpha interferon (IFN-α) induced tetherin and blocked feline immunodeficiency virus (FIV) replication in lymphoid and nonlymphoid feline cells. Budding of bald FIV and HIV particles was blocked by carnivore tetherins. However, infectious FIV particles were resistant, and spreading FIV replication was uninhibited. Antagonism mapped to the envelope glycoprotein (Env), which rescued FIV from carnivore tetherin restriction when expressed in trans but, in contrast to known antagonists, did not rescue noncognate particles. Also unlike the primate lentiviral antagonists, but similar to the Ebola virus glycoprotein, FIV Env did not reduce intracellular or cell surface tetherin levels. Furthermore, FIV-enveloped FIV particles actually required tetherin for optimal release from cells. The results show that FIV Envs mediate a distinctive tetherin evasion. Well adapted to a phylogenetically ancient tetherin tail truncation in the Felidae, it requires functional virion incorporation of Env, and it shields the budding particle without downregulating plasma membrane tetherin. Moreover, FIV has evolved dependence on this protein: particles containing FIV Env need tetherin for optimal release from the cell, while Env(-) particles do not. IMPORTANCE HIV-1 antagonizes the restriction factor tetherin with the accessory protein Vpu, while HIV-2 and the filovirus Ebola use their envelope (Env) glycoproteins for this purpose. It turns out that the FIV tetherin antagonist is also its Env protein, but the mechanism is distinctive. Unlike other tetherin antagonists, FIV Env cannot act in trans to rescue vpu-deficient HIV-1. It must be incorporated specifically into FIV virions to be active. Also unlike other retroviral antagonists, but similar to Ebola virus Env, it does not act by downregulating or degrading tetherin. FIV Env might exclude tetherin locally or direct assembly to tetherin-negative membrane domains. Other distinctive features are apparent, including evidence that this virus evolved an equilibrium in which tetherin is both restriction factor and cofactor, as FIV requires tetherin for optimal particle release.
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145
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Leyva-Grado VH, Hai R, Fernandes F, Belicha-Villanueva A, Carter C, Yondola MA. Modulation of an ectodomain motif in the influenza A virus neuraminidase alters tetherin sensitivity and results in virus attenuation in vivo. J Mol Biol 2013; 426:1308-21. [PMID: 24380762 DOI: 10.1016/j.jmb.2013.12.023] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 12/19/2013] [Accepted: 12/19/2013] [Indexed: 11/19/2022]
Abstract
We previously demonstrated that ectodomain residue Asp286 in N2 neuraminidase (NA; Asp268 in N1 NA) present in budding-capable NA proteins contributes to productive NA plasma membrane transport partly by mediating escape from tetherin restriction [Yondola MA, Fernandes F, Belicha-Villanueva A, Uccelini M, Gao Q, Carter C, et al. (2011). Budding capability of the influenza virus neuraminidase can be modulated by tetherin. J Virol, 85, 2480-2491]. Budding-incapable NA proteins contain a G at this position and either co-expression of human immunodeficiency virus type 1 vpu or siRNA-mediated depletion of tetherin rescued budding capabilities in these proteins [Yondola MA, Fernandes F, Belicha-Villanueva A, Uccelini M, Gao Q, Carter C, et al. (2011). Budding capability of the influenza virus neuraminidase can be modulated by tetherin. J Virol, 85, 2480-2491]. Furthermore, replacement of D286 with G in budding-capable NA proteins caused loss of function, preventing release of NA virus-like particles (VLPs). Here, we show that mutation of this residue specifically modulates the ability of NA to escape tetherin restriction at the plasma membrane and results in virus attenuation in vivo. Based on immunogold electron microscopy and co-immunoprecipitation assays, both NAD286-containing and NAD286G-containing proteins associated with tetherin in the endoplasmic reticulum (ER). However, the NAD286G loss-of-function mutant also associated with the host factor outside the ER and in plasma-membrane-localized VLPs as visualized using immunogold electron microscopy. We conclude that the presence of aspartate at residue 286 liberates NA from tetherin-dependent restriction upon exit from the ER compartment thus preventing restriction at the plasma membrane. Underscoring the importance of these observations, knockdown of tetherin resulted in a 1-1.5 log increase in influenza virus growth. Additionally, the loss-of-function mutation conferred attenuation in a mouse model of influenza infection as evidenced by a 5-fold increase in LD50 and increases in either percent survival or time to death dependent on the administered dose in vivo.
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Affiliation(s)
| | - Rong Hai
- Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | | | | | - Carol Carter
- Stony Brook University, Stony Brook, NY 11790, USA
| | - Mark A Yondola
- Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA.
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146
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Boasso A. Type I Interferon at the Interface of Antiviral Immunity and Immune Regulation: The Curious Case of HIV-1. SCIENTIFICA 2013; 2013:580968. [PMID: 24455433 PMCID: PMC3885208 DOI: 10.1155/2013/580968] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 12/10/2013] [Indexed: 06/03/2023]
Abstract
Type I interferon (IFN-I) play a critical role in the innate immune response against viral infections. They actively participate in antiviral immunity by inducing molecular mechanisms of viral restriction and by limiting the spread of the infection, but they also orchestrate the initial phases of the adaptive immune response and influence the quality of T cell immunity. During infection with the human immunodeficiency virus type 1 (HIV-1), the production of and response to IFN-I may be severely altered by the lymphotropic nature of the virus. In this review I consider the different aspects of virus sensing, IFN-I production, signalling, and effects on target cells, with a particular focus on the alterations observed following HIV-1 infection.
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Affiliation(s)
- Adriano Boasso
- Immunology Section, Chelsea and Westminster Hospital, 369 Fulham Road, London SW10 9NH, UK
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147
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Wang SM, Huang KJ, Wang CT. BST2/CD317 counteracts human coronavirus 229E productive infection by tethering virions at the cell surface. Virology 2013; 449:287-96. [PMID: 24418563 PMCID: PMC7111910 DOI: 10.1016/j.virol.2013.11.030] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 09/09/2013] [Accepted: 11/20/2013] [Indexed: 12/24/2022]
Abstract
Bone marrow stromal antigen 2 (BST2), an interferon-inducible antiviral factor, has been shown to block the release of various enveloped viruses from cells. It has also been identified as an innate immune system component. Most enveloped viruses subject to BST2 restriction bud at the plasma membrane. Here we report our findings that (a) the production of human coronavirus 229E (HCoV-229E) progeny viruses, whose budding occurs at the ER-Golgi intermediate compartment (ERGIC), markedly decreases in the presence of BST2; and (b) BST2 knockdown expression results in enhanced HCoV-229E virion production. Electron microscopy analyses indicate that HCoV-229E virions are tethered to cell surfaces or intracellular membranes by BST2. Our results suggest that BST2 exerts a broad blocking effect against enveloped virus release, regardless of whether budding occurs at the plasma membrane or intracellular compartments.
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Affiliation(s)
- Shiu-Mei Wang
- Department of Medical Research and Education, Taipei Veterans General Hospital and Institute of Clinical Medicine, Taipei 11217, Taiwan; Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan
| | - Kuo-Jung Huang
- Department of Medical Research and Education, Taipei Veterans General Hospital and Institute of Clinical Medicine, Taipei 11217, Taiwan
| | - Chin-Tien Wang
- Department of Medical Research and Education, Taipei Veterans General Hospital and Institute of Clinical Medicine, Taipei 11217, Taiwan; Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan.
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148
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Dewannieux M, Heidmann T. Endogenous retroviruses: acquisition, amplification and taming of genome invaders. Curr Opin Virol 2013; 3:646-56. [DOI: 10.1016/j.coviro.2013.08.005] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 08/13/2013] [Accepted: 08/14/2013] [Indexed: 12/12/2022]
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149
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Rahmberg AR, Neidermyer WJ, Breed MW, Alvarez X, Midkiff CC, Piatak M, Lifson JD, Evans DT. Tetherin upregulation in simian immunodeficiency virus-infected macaques. J Virol 2013; 87:13917-21. [PMID: 24109219 PMCID: PMC3838227 DOI: 10.1128/jvi.01757-13] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 10/02/2013] [Indexed: 11/20/2022] Open
Abstract
Here we show that simian immunodeficiency virus (SIV) infection of rhesus macaques results in rapid upregulation of tetherin (BST-2 or CD317) on peripheral blood lymphocytes, including the CD4(+) CCR5(+) T cell targets of virus infection, with a peak of induction that coincides with peak alpha interferon (IFN-α) levels in plasma, and that tetherin remains above baseline levels throughout chronic infection. These observations are consistent with a role for tetherin in innate immunity to immunodeficiency virus infection.
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Affiliation(s)
- Andrew R. Rahmberg
- Department of Microbiology and Immunobiology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts, USA
| | - William J. Neidermyer
- Department of Microbiology and Immunobiology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts, USA
| | - Matthew W. Breed
- Division of Comparative Pathology, Tulane National Primate Research Center, Covington, Louisiana, USA
| | - Xavier Alvarez
- Division of Comparative Pathology, Tulane National Primate Research Center, Covington, Louisiana, USA
| | - Cecily C. Midkiff
- Division of Comparative Pathology, Tulane National Primate Research Center, Covington, Louisiana, USA
| | - Michael Piatak
- SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland, USA
| | - Jeffrey D. Lifson
- SAIC—Frederick, National Cancer Institute at Frederick, Frederick, Maryland, USA
| | - David T. Evans
- Department of Microbiology and Immunobiology, Harvard Medical School, New England Primate Research Center, Southborough, Massachusetts, USA
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Cachat A, Chevalier SA, Alais S, Ko NL, Ratner L, Journo C, Dutartre H, Mahieux R. Alpha interferon restricts human T-lymphotropic virus type 1 and 2 de novo infection through PKR activation. J Virol 2013; 87:13386-96. [PMID: 24089560 PMCID: PMC3838277 DOI: 10.1128/jvi.02758-13] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 09/25/2013] [Indexed: 01/24/2023] Open
Abstract
Type I interferon (IFN-I) inhibits the replication of different viruses. However, the effect of IFN-I on the human T-lymphotropic virus type 1 (HTLV-1) viral cycle is controversial. Here, we investigated the consequences of IFN-α addition for different steps of HTLV-1 and HTLV-2 infection. We first show that alpha interferon (IFN-α) efficiently impairs HTLV-1 and HTLV-2 de novo infection in a T cell line and in primary lymphocytes. Using pseudotyped viruses expressing HTLV-1 envelope, we then show that cell-free infection is insensitive to IFN-α, demonstrating that the cytokine does not affect the early stages of the viral cycle. In contrast, intracellular levels of Gag, Env, or Tax protein are affected by IFN-α treatment in T cells, primary lymphocytes, or 293T cells transfected with HTLV-1 or HTLV-2 molecular clones, demonstrating that IFN-α acts during the late stages of infection. We show that IFN-α does not affect Tax-mediated transcription and acts at a posttranscriptional level. Using either small interfering RNA (siRNA) directed against PKR or a PKR inhibitor, we demonstrate that PKR, whose expression is induced by interferon, plays a major role in IFN-α-induced HTLV-1/2 inhibition. These results indicate that IFN-α has a strong repressive effect on the HTLV-1 and HTLV-2 viral cycle during de novo infection of cells that are natural targets of the viruses.
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Affiliation(s)
- Anne Cachat
- Equipe Oncogenèse Rétrovirale
- Equipe Labelisée Ligue Nationale Contre le Cancer
- International Center for Research in Infectiology, INSERM U1111-CNRS UMR5308
- Ecole Normale Supérieure de Lyon
- Université Lyon 1, LabEx ECOFECT-Eco-Evolutionary Dynamics of Infectious Diseases, Lyon, France
| | - Sébastien Alain Chevalier
- Equipe Oncogenèse Rétrovirale
- Equipe Labelisée Ligue Nationale Contre le Cancer
- International Center for Research in Infectiology, INSERM U1111-CNRS UMR5308
- Ecole Normale Supérieure de Lyon
- Université Lyon 1, LabEx ECOFECT-Eco-Evolutionary Dynamics of Infectious Diseases, Lyon, France
| | - Sandrine Alais
- Equipe Oncogenèse Rétrovirale
- Equipe Labelisée Ligue Nationale Contre le Cancer
- International Center for Research in Infectiology, INSERM U1111-CNRS UMR5308
- Ecole Normale Supérieure de Lyon
- Université Lyon 1, LabEx ECOFECT-Eco-Evolutionary Dynamics of Infectious Diseases, Lyon, France
| | - Nga Ling Ko
- Unité d'Épidémiologie et Physiopathoglogie des Virus Oncogenes, Institut Pasteur, Paris, France
| | - Lee Ratner
- Division of Molecular Oncology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Chloé Journo
- Equipe Oncogenèse Rétrovirale
- Equipe Labelisée Ligue Nationale Contre le Cancer
- International Center for Research in Infectiology, INSERM U1111-CNRS UMR5308
- Ecole Normale Supérieure de Lyon
- Université Lyon 1, LabEx ECOFECT-Eco-Evolutionary Dynamics of Infectious Diseases, Lyon, France
| | - Hélène Dutartre
- Equipe Oncogenèse Rétrovirale
- Equipe Labelisée Ligue Nationale Contre le Cancer
- International Center for Research in Infectiology, INSERM U1111-CNRS UMR5308
- Ecole Normale Supérieure de Lyon
- Université Lyon 1, LabEx ECOFECT-Eco-Evolutionary Dynamics of Infectious Diseases, Lyon, France
| | - Renaud Mahieux
- Equipe Oncogenèse Rétrovirale
- Equipe Labelisée Ligue Nationale Contre le Cancer
- International Center for Research in Infectiology, INSERM U1111-CNRS UMR5308
- Ecole Normale Supérieure de Lyon
- Université Lyon 1, LabEx ECOFECT-Eco-Evolutionary Dynamics of Infectious Diseases, Lyon, France
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