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Webb NE, Sevareid CM, Sanchez C, Tobin NH, Aldrovandi GM. Natural Variation in HIV-1 Entry Kinetics Map to Specific Residues and Reveal an Interdependence Between Attachment and Fusion. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.25.600587. [PMID: 38979136 PMCID: PMC11230229 DOI: 10.1101/2024.06.25.600587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
HIV-1 entry kinetics reflect the fluid motion of the HIV envelope glycoprotein through at least three major structural configurations that drive virus-cell membrane fusion. The lifetime of each state is an important component of potency for inhibitors that target them. We used the time-of-addition inhibitor assay and a novel analytical strategy to define the kinetics of pre-hairpin exposure (using T20) and co-receptor engagement (via. maraviroc), through a characteristic delay metric, across a variety of naturally occurring HIV Env isolates. Among 257 distinct HIV-1 envelope isolates we found a remarkable breadth of T20 and maraviroc delays ranging from as early as 30 seconds to as late as 60 minutes. The most extreme delays were observed among transmission-linked clade C isolates. We identified four single-residue determinants of late T20 and maraviroc delays that are associated with either receptor engagement or gp41 function. Comparison of these delays with T20 sensitivity suggest co-receptor engagement and fusogenic activity in gp41 act cooperatively but sequentially to drive entry. Our findings support current models of entry where co-receptor engagement drives gp41 eclipse and have strong implications for the design of entry inhibitors and antibodies that target transient entry states. Author Summary The first step of HIV-1 infection is entry, where virus-cell membrane fusion is driven by the HIV-1 envelope glycoprotein through a series of conformational changes. Some of the most broadly active entry inhibitors work by binding conformations that exist only transiently during entry. The lifetimes of these states and the kinetics of entry are important elements of inhibitor activity for which little is known. We demonstrate a remarkable range of kinetics among 257 diverse HIV-1 isolates and find that this phenotype is highly flexible, with multiple single-residue determinants. Examination of the kinetics of two conformational landmarks shed light on novel kinetic features that offer new details about the role of co-receptor engagement and provide a framework to explain entry inhibitor synergy.
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2
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Guizar P, Abdalla AL, Monette A, Davis K, Caballero RE, Niu M, Liu X, Ajibola O, Murooka TT, Liang C, Mouland AJ. An HIV-1 CRISPR-Cas9 membrane trafficking screen reveals a role for PICALM intersecting endolysosomes and immunity. iScience 2024; 27:110131. [PMID: 38957789 PMCID: PMC11217618 DOI: 10.1016/j.isci.2024.110131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 06/12/2023] [Accepted: 05/24/2024] [Indexed: 07/04/2024] Open
Abstract
HIV-1 hijacks host proteins involved in membrane trafficking, endocytosis, and autophagy that are critical for virus replication. Molecular details are lacking but are essential to inform on the development of alternative antiviral strategies. Despite their potential as clinical targets, only a few membrane trafficking proteins have been functionally characterized in HIV-1 replication. To further elucidate roles in HIV-1 replication, we performed a CRISPR-Cas9 screen on 140 membrane trafficking proteins. We identified phosphatidylinositol-binding clathrin assembly protein (PICALM) that influences not only infection dynamics but also CD4+ SupT1 biology. The knockout (KO) of PICALM inhibited viral entry. In CD4+ SupT1 T cells, KO cells exhibited defects in intracellular trafficking and increased abundance of intracellular Gag and significant alterations in autophagy, immune checkpoint PD-1 levels, and differentiation markers. Thus, PICALM modulates a variety of pathways that ultimately affect HIV-1 replication, underscoring the potential of PICALM as a future target to control HIV-1.
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Affiliation(s)
- Paola Guizar
- Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada
- Department of Microbiology and Immunology, McGill University, Montréal, QC H3A 2B4, Canada
| | - Ana Luiza Abdalla
- Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada
- Department of Microbiology and Immunology, McGill University, Montréal, QC H3A 2B4, Canada
| | - Anne Monette
- Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada
| | - Kristin Davis
- Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada
- Department of Microbiology and Immunology, McGill University, Montréal, QC H3A 2B4, Canada
| | - Ramon Edwin Caballero
- Department of Microbiology and Immunology, McGill University, Montréal, QC H3A 2B4, Canada
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montréal, QC H2X 0A9, Canada
| | - Meijuan Niu
- Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada
| | - Xinyun Liu
- Rady Faculty of Health Science, Department of Immunology, University of Manitoba, Winnipeg, MB R3E 0T5, Canada
| | - Oluwaseun Ajibola
- Rady Faculty of Health Science, Department of Immunology, University of Manitoba, Winnipeg, MB R3E 0T5, Canada
| | - Thomas T. Murooka
- Rady Faculty of Health Science, Department of Immunology, University of Manitoba, Winnipeg, MB R3E 0T5, Canada
- Rady Faculty of Health Science, Department of Medical Microbiology and Infectious Disease, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
| | - Chen Liang
- Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada
- Department of Microbiology and Immunology, McGill University, Montréal, QC H3A 2B4, Canada
- Department of Medicine, McGill University, Montréal, QC H4A 3J1, Canada
| | - Andrew J. Mouland
- Lady Davis Institute at the Jewish General Hospital, Montréal, QC H3T 1E2, Canada
- Department of Microbiology and Immunology, McGill University, Montréal, QC H3A 2B4, Canada
- Department of Medicine, McGill University, Montréal, QC H4A 3J1, Canada
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3
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Kruse E, Abdalrahman T, Selhorst P, Franz T. Mathematical model for force and energy of virion-cell interactions during full engulfment in HIV: Impact of virion maturation and host cell morphology. Biomech Model Mechanobiol 2023; 22:1847-1855. [PMID: 37322329 PMCID: PMC10613145 DOI: 10.1007/s10237-023-01736-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 06/04/2023] [Indexed: 06/17/2023]
Abstract
Viral endocytosis involves elastic cell deformation, driven by chemical adhesion energy, and depends on physical interactions between the virion and cell membrane. These interactions are not easy to quantify experimentally. Hence, this study aimed to develop a mathematical model of the interactions of HIV particles with host cells and explore the effects of mechanical and morphological parameters during full virion engulfment. The invagination force and engulfment energy were described as viscoelastic and linear-elastic functions of radius and elastic modulus of virion and cell, ligand-receptor energy density and engulfment depth. The influence of changes in the virion-cell contact geometry representing different immune cells and ultrastructural membrane features and the decrease in virion radius and shedding of gp120 proteins during maturation on invagination force and engulfment energy was investigated. A low invagination force and high ligand-receptor energy are associated with high virion entry ability. The required invagination force was the same for immune cells of different sizes but lower for a local convex geometry of the cell membrane at the virion length scale. This suggests that localized membrane features of immune cells play a role in viral entry ability. The available engulfment energy decreased during virion maturation, indicating the involvement of additional biological or biochemical changes in viral entry. The developed mathematical model offers potential for the mechanobiological assessment of the invagination of enveloped viruses towards improving the prevention and treatment of viral infections.
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Affiliation(s)
- Elizabeth Kruse
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa
| | - Tamer Abdalrahman
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa
| | - Philippe Selhorst
- Division of Virology, Department of Pathology, University of Cape Town, Observatory, South Africa
- Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Observatory, South Africa
- Virology Unit, Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Thomas Franz
- Biomedical Engineering Research Centre, Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory, South Africa.
- Bioengineering Science Research Group, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK.
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4
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Pilz M, Cavelius P, Qoura F, Awad D, Brück T. Lipopeptides development in cosmetics and pharmaceutical applications: A comprehensive review. Biotechnol Adv 2023; 67:108210. [PMID: 37460047 DOI: 10.1016/j.biotechadv.2023.108210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 07/05/2023] [Accepted: 07/09/2023] [Indexed: 07/25/2023]
Abstract
Lipopeptides are surface active, natural products of bacteria, fungi and green-blue algae origin, having diverse structures and functionalities. In analogy, a number of chemical synthesis techniques generated new designer lipopeptides with desirable features and functions. Lipopetides are self-assembly guided, supramolecular compounds which have the capacity of high-density presentation of the functional epitopes at the surface of the nanostructures. This feature contributes to their successful application in several industry sectors, including food, feed, personal care, and pharmaceutics. In this comprehensive review, the novel class of ribosomally synthesized lipopeptides is introduced alongside the more commonly occuring non-ribosomal lipopeptides. We highlight key representatives of the most researched as well as recently described lipopeptide families, with emphasis on structural features, self-assembly and associated functions. The common biological, chemical and hybrid production routes of lipopeptides, including prominent analogues and derivatives are also discussed. Furthermore, genetic engineering strategies aimed at increasing lipopeptide yields, diversity and biological activity are summarized and exemplified. With respect to application, this work mainly details the potential of lipopeptides in personal care and cosmetics industry as cleansing agents, moisturizer, anti-aging/anti-wrinkling, skin whitening and preservative agents as well as the pharmaceutical industry as anitimicrobial agents, vaccines, immunotherapy, and cancer drugs. Given that this review addresses human applications, we conclude on the topic of safety of lipopeptide formulations and their sustainable production.
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Affiliation(s)
- Melania Pilz
- Werner Siemens-Chair of Synthetic Biotechnology, Department of Chemistry, Technical University of Munich (TUM), 85748 Garching, Germany
| | - Philipp Cavelius
- Werner Siemens-Chair of Synthetic Biotechnology, Department of Chemistry, Technical University of Munich (TUM), 85748 Garching, Germany
| | - Farah Qoura
- Werner Siemens-Chair of Synthetic Biotechnology, Department of Chemistry, Technical University of Munich (TUM), 85748 Garching, Germany
| | - Dania Awad
- Werner Siemens-Chair of Synthetic Biotechnology, Department of Chemistry, Technical University of Munich (TUM), 85748 Garching, Germany.
| | - Thomas Brück
- Werner Siemens-Chair of Synthetic Biotechnology, Department of Chemistry, Technical University of Munich (TUM), 85748 Garching, Germany.
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5
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Sharma M, Marin M, Wu H, Prikryl D, Melikyan GB. Human Immunodeficiency Virus 1 Preferentially Fuses with pH-Neutral Endocytic Vesicles in Cell Lines and Human Primary CD4+ T-Cells. ACS NANO 2023; 17:17436-17450. [PMID: 37589658 PMCID: PMC10510587 DOI: 10.1021/acsnano.3c05508] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 08/14/2023] [Indexed: 08/18/2023]
Abstract
Despite extensive efforts, the principal sites of productive HIV-1 entry in different target cells─plasma membrane (PM) vs endosomes─remain controversial. To delineate the site(s) of HIV-1 fusion, we implemented a triple labeling approach that involves tagging pseudoviruses with the fluid-phase viral content marker, iCherry, the viral membrane marker, DiD, and the extraviral pH sensor, ecliptic pHluorin. The viral content marker iCherry is released into the cytoplasm upon virus-cell fusion irrespective of the sites of fusion. In contrast, the extent of dilution of the membrane marker upon fusion with the PM (loss of signal) vs the endosomal membrane (no change in punctate DiD appearance) discriminates between the principal sites of viral fusion. Additionally, ecliptic pHluorin incorporated into the viral membrane reports whether virus fusion occurs in acidic endosomes. Real-time single virus imaging in living HeLa-derived cells, a CD4+ T-cell line, and activated primary human CD4+ T-cells revealed a strong (80-90%) HIV-1 preference for fusion with endosomes. Intriguingly, we observed HIV-1 fusion only with pH-neutral intracellular vesicles and never with acidified endosomes. These endocytic fusion events are likely culminating in productive infection since endocytic inhibitors, such as EIPA, Pitstop2, and Dynasore, as well as a dominant-negative dynamin-2 mutant, inhibited HIV-1 infection in HeLa-derived and primary CD4+ T-cells. Furthermore, the inhibition of endocytosis in HeLa-derived cells promoted hemifusion at the PM but abrogated complete fusion. Collectively, these data reveal that the primary HIV-1 entry pathway in diverse cell types is through fusion with pH-neutral intracellular vesicles.
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Affiliation(s)
- Manish Sharma
- Department
of Pediatrics, Division of Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia 30322, United States
- Children’s
Healthcare of Atlanta, Atlanta, Georgia 30322, United States
| | - Mariana Marin
- Department
of Pediatrics, Division of Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia 30322, United States
- Children’s
Healthcare of Atlanta, Atlanta, Georgia 30322, United States
| | - Hui Wu
- Department
of Pediatrics, Division of Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia 30322, United States
| | - David Prikryl
- Department
of Pediatrics, Division of Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia 30322, United States
| | - Gregory B. Melikyan
- Department
of Pediatrics, Division of Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia 30322, United States
- Children’s
Healthcare of Atlanta, Atlanta, Georgia 30322, United States
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6
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Santos MF, Rappa G, Karbanová J, Diana P, Cirrincione G, Carbone D, Manna D, Aalam F, Wang D, Vanier C, Corbeil D, Lorico A. HIV-1-induced nuclear invaginations mediated by VAP-A, ORP3, and Rab7 complex explain infection of activated T cells. Nat Commun 2023; 14:4588. [PMID: 37563144 PMCID: PMC10415338 DOI: 10.1038/s41467-023-40227-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 07/19/2023] [Indexed: 08/12/2023] Open
Abstract
The mechanism of human immunodeficiency virus 1 (HIV-1) nuclear entry, required for productive infection, is not fully understood. Here, we report that in HeLa cells and activated CD4+ T cells infected with HIV-1 pseudotyped with VSV-G and native Env protein, respectively, Rab7+ late endosomes containing endocytosed HIV-1 promote the formation of nuclear envelope invaginations (NEIs) by a molecular mechanism involving the VOR complex, composed of the outer nuclear membrane protein VAP-A, hyperphosphorylated ORP3 and Rab7. Silencing VAP-A or ORP3 and drug-mediated impairment of Rab7 binding to ORP3-VAP-A inhibited the nuclear transfer of the HIV-1 components and productive infection. In HIV-1-resistant quiescent CD4+ T cells, ORP3 was not hyperphosphorylated and neither VOR complex nor NEIs were formed. This new cellular pathway and its molecular players are potential therapeutic targets, perhaps shared by other viruses that require nuclear entry to complete their life cycle.
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Affiliation(s)
- Mark F Santos
- Touro University Nevada College of Osteopathic Medicine, Henderson, NV, USA
| | - Germana Rappa
- Touro University Nevada College of Osteopathic Medicine, Henderson, NV, USA
| | - Jana Karbanová
- Biotechnology Center (BIOTEC) and Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, Dresden, Germany
| | - Patrizia Diana
- Department of Biological, Chemical, and Pharmaceutical Sciences and Technologies (STEBICEF), University of Palermo, Palermo, Italy
| | - Girolamo Cirrincione
- Department of Biological, Chemical, and Pharmaceutical Sciences and Technologies (STEBICEF), University of Palermo, Palermo, Italy
| | - Daniela Carbone
- Department of Biological, Chemical, and Pharmaceutical Sciences and Technologies (STEBICEF), University of Palermo, Palermo, Italy
| | - David Manna
- Touro College of Osteopathic Medicine, Middletown, New York, NY, USA
| | - Feryal Aalam
- Touro University Nevada College of Osteopathic Medicine, Henderson, NV, USA
| | - David Wang
- Touro University Nevada College of Osteopathic Medicine, Henderson, NV, USA
| | - Cheryl Vanier
- Touro University Nevada College of Osteopathic Medicine, Henderson, NV, USA
- Imgen Research, LLC, 5495 South Rainbow #201, Las Vegas, NV, USA
| | - Denis Corbeil
- Biotechnology Center (BIOTEC) and Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, Dresden, Germany.
| | - Aurelio Lorico
- Touro University Nevada College of Osteopathic Medicine, Henderson, NV, USA.
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7
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Zhang Y, York J, Brindley MA, Nunberg JH, Melikyan GB. Fusogenic structural changes in arenavirus glycoproteins are associated with viroporin activity. PLoS Pathog 2023; 19:e1011217. [PMID: 37494374 PMCID: PMC10406333 DOI: 10.1371/journal.ppat.1011217] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 08/07/2023] [Accepted: 07/04/2023] [Indexed: 07/28/2023] Open
Abstract
Many enveloped viruses enter host cells by fusing with acidic endosomes. The fusion activity of multiple viral envelope glycoproteins does not generally affect viral membrane permeability. However, fusion induced by the Lassa virus (LASV) glycoprotein complex (GPc) is always preceded by an increase in viral membrane permeability and the ensuing acidification of the virion interior. Here, systematic investigation of this LASV fusion phenotype using single pseudovirus tracking in live cells reveals that the change in membrane barrier function is associated with the fusogenic conformational reorganization of GPc. We show that a small-molecule fusion inhibitor or mutations that impair viral fusion by interfering with GPc refolding into the post-fusion structure prevent the increase in membrane permeability. We find that the increase in virion membrane permeability occurs early during endosomal maturation and is facilitated by virus-cell contact. This increase is observed using diverse arenavirus glycoproteins, whether presented on lentivirus-based pseudoviruses or arenavirus-like particles, and in multiple different cell types. Collectively, these results suggest that conformational changes in GPc triggered by low pH and cell factor binding are responsible for virion membrane permeabilization and acidification of the virion core prior to fusion. We propose that this viroporin-like activity may augment viral fusion and/or post-fusion steps of infection, including ribonucleoprotein release into the cytoplasm.
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Affiliation(s)
- You Zhang
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, United States of America
- Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
| | - Joanne York
- Montana Biotechnology Center, University of Montana, Missoula, Montana, United States of America
| | - Melinda A. Brindley
- Department of Infectious Diseases, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States of America
| | - Jack H. Nunberg
- Montana Biotechnology Center, University of Montana, Missoula, Montana, United States of America
| | - Gregory B. Melikyan
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, United States of America
- Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
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8
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Mao L, Chen Y, Gu J, Zhao Y, Chen Q. Roles and mechanisms of exosomal microRNAs in viral infections. Arch Virol 2023; 168:121. [PMID: 36977948 PMCID: PMC10047465 DOI: 10.1007/s00705-023-05744-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 01/10/2023] [Indexed: 03/30/2023]
Abstract
Exosomes are small extracellular vesicles with a diameter of 30-150 nm that originate from endosomes and fuse with the plasma membrane. They are secreted by almost all kinds of cells and can stably transfer different kinds of cargo from donor to recipient cells, thereby altering cellular functions for assisting cell-to-cell communication. Exosomes derived from virus-infected cells during viral infections are likely to contain different microRNAs (miRNAs) that can be transferred to recipient cells. Exosomes can either promote or suppress viral infections and therefore play a dual role in viral infection. In this review, we summarize the current knowledge about the role of exosomal miRNAs during infection by six important viruses (hepatitis C virus, enterovirus A71, Epstein-Barr virus, human immunodeficiency virus, severe acute respiratory syndrome coronavirus 2, and Zika virus), each of which causes a significant global public health problem. We describe how these exosomal miRNAs, including both donor-cell-derived and virus-encoded miRNAs, modulate the functions of the recipient cell. Lastly, we briefly discuss their potential value for the diagnosis and treatment of viral infections.
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Affiliation(s)
- Lingxiang Mao
- Department of Laboratory Medicine, Affiliated Kunshan Hospital of Jiangsu University, Kunshan, China.
| | - Yiwen Chen
- Department of Laboratory Medicine, Affiliated Kunshan Hospital of Jiangsu University, Kunshan, China
- Department of Immunology, Jiangsu Key Laboratory of Laboratory Medicine, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Jiaqi Gu
- Department of Laboratory Medicine, Nanjing Drum Tower Hospital and Jiangsu Key Laboratory for Molecular Medicine, Nanjing University Medicine School of Medicine, Nanjing, China
| | - Yuxue Zhao
- Department of Laboratory Medicine, Affiliated Kunshan Hospital of Jiangsu University, Kunshan, China
- Department of Immunology, Jiangsu Key Laboratory of Laboratory Medicine, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Qiaoqiao Chen
- Department of Laboratory Medicine, Affiliated Kunshan Hospital of Jiangsu University, Kunshan, China
- Department of Immunology, Jiangsu Key Laboratory of Laboratory Medicine, School of Medicine, Jiangsu University, Zhenjiang, China
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9
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Padilla-Parra S. Time-resolved single virus tracking and spectral imaging to understand HIV-1 entry and fusion. Biol Cell 2023; 115:e2200082. [PMID: 36440600 DOI: 10.1111/boc.202200082] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Revised: 11/02/2022] [Accepted: 11/18/2022] [Indexed: 11/29/2022]
Abstract
Single Virus Tracking (SVT) is a key technique to understand how individual viral particles evolve during the infection cycle. In the case of the human immunodeficiency virus (HIV-1), this technology, which can be employed using a simple and affordable wide-field microscope, has proven to be very useful in the first steps of infection, such as the kinetics of the fusion reaction or the point of fusion within live cells. Here, we describe how SVT in combination with other spectral imaging approaches is a powerful technique to illuminate crucial mechanistic aspects of the HIV-1 fusion reaction. We also stress the role of our laboratory in elucidating a few mechanistic aspects of retroviral fusion employing SVT such as: (i) the role of dynamin, (ii) how metabolism modulates membrane composition and cholesterol and its impact in fusion, (iii) the importance of envelope glycoprotein (Env) intra- and inter-molecular dynamics for neutralization, or (iv) the time-resolved fusion stoichiometry in three characteristic steps for the HIV-1 prefusion step. These observations constitute a good testimony of the complexity of retroviral fusion and show the strength of SVT when applied to live cells and combined with quantitative spectral approaches. Finally, we propose several crucial remaining questions around HIV-1 fusion and how the combined use of these technologies, always in live cells, will be able to shed light into the intricacies of arguably the most important step of the HIV-1 infection cycle.
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Affiliation(s)
- Sergi Padilla-Parra
- Faculty of Life Sciences & Medicine, Department of Infectious Diseases, King's College London, London, UK.,Randall Division of Cell and Molecular Biophysics, King's College London, London, UK
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10
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Negi G, Sharma A, Dey M, Dhanawat G, Parveen N. Membrane attachment and fusion of HIV-1, influenza A, and SARS-CoV-2: resolving the mechanisms with biophysical methods. Biophys Rev 2022; 14:1109-1140. [PMID: 36249860 PMCID: PMC9552142 DOI: 10.1007/s12551-022-00999-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 09/16/2022] [Indexed: 10/31/2022] Open
Abstract
Attachment to and fusion with cell membranes are two major steps in the replication cycle of many human viruses. We focus on these steps for three enveloped viruses, i.e., HIV-1, IAVs, and SARS-CoV-2. Viral spike proteins drive the membrane attachment and fusion of these viruses. Dynamic interactions between the spike proteins and membrane receptors trigger their specific attachment to the plasma membrane of host cells. A single virion on cell membranes can engage in binding with multiple receptors of the same or different types. Such dynamic and multivalent binding of these viruses result in an optimal attachment strength which in turn leads to their cellular entry and membrane fusion. The latter process is driven by conformational changes of the spike proteins which are also class I fusion proteins, providing the energetics of membrane tethering, bending, and fusion. These viruses exploit cellular and membrane factors in regulating the conformation changes and membrane processes. Herein, we describe the major structural and functional features of spike proteins of the enveloped viruses including highlights on their structural dynamics. The review delves into some of the case studies in the literature discussing the findings on multivalent binding, membrane hemifusion, and fusion of these viruses. The focus is on applications of biophysical tools with an emphasis on single-particle methods for evaluating mechanisms of these processes at the molecular and cellular levels.
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Affiliation(s)
- Geetanjali Negi
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Anurag Sharma
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Manorama Dey
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Garvita Dhanawat
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Nagma Parveen
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
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11
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Zhang Y, Carlos de la Torre J, Melikyan GB. Human LAMP1 accelerates Lassa virus fusion and potently promotes fusion pore dilation upon forcing viral fusion with non-endosomal membrane. PLoS Pathog 2022; 18:e1010625. [PMID: 35969633 PMCID: PMC9410554 DOI: 10.1371/journal.ppat.1010625] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 08/25/2022] [Accepted: 08/01/2022] [Indexed: 11/18/2022] Open
Abstract
Lassa virus (LASV) cell entry is mediated by the interaction of the virus glycoprotein complex (GPC) with alpha-dystroglycan at the cell surface followed by binding to LAMP1 in late endosomes. However, LAMP1 is not absolutely required for LASV fusion, as this virus can infect LAMP1-deficient cells. Here, we used LASV GPC pseudoviruses, LASV virus-like particles and recombinant lymphocytic choriomeningitis virus expressing LASV GPC to investigate the role of human LAMP1 (hLAMP1) in LASV fusion with human and avian cells expressing a LAMP1 ortholog that does not support LASV entry. We employed a combination of single virus imaging and virus population-based fusion and infectivity assays to dissect the hLAMP1 requirement for initiation and completion of LASV fusion that culminates in the release of viral ribonucleoprotein into the cytoplasm. Unexpectedly, ectopic expression of hLAMP1 accelerated the kinetics of small fusion pore formation, but only modestly increased productive LASV fusion and infection of human and avian cells. To assess the effects of hLAMP1 in the absence of requisite endosomal host factors, we forced LASV fusion with the plasma membrane by applying low pH. Unlike the conventional LASV entry pathway, ectopic hLAMP1 expression dramatically promoted the initial and full dilation of pores formed through forced fusion at the plasma membrane. We further show that, while the soluble hLAMP1 ectodomain accelerates the kinetics of nascent pore formation, it fails to promote efficient pore dilation, suggesting the hLAMP1 transmembrane domain is involved in this late stage of LASV fusion. These findings reveal a previously unappreciated role of hLAMP1 in promoting dilation of LASV fusion pores, which is difficult to ascertain for endosomal fusion where several co-factors, such as bis(monoacylglycero)phosphate, likely regulate LASV entry. Lassa virus (LASV) enters cells via fusion with acidic endosomes mediated by the viral glycoprotein complex (GPC) interaction with the intracellular receptor LAMP1. However, the requirement for LAMP1 is not absolute, as LASV can infect avian cells expressing a LAMP1 ortholog that does not interact with GPC. To delineate the role of LAMP1 in LASV entry, we developed assays to monitor the formation of nascent fusion pores, as well as their initial and complete dilation to sizes that allow productive infection of avian cells by LASV GPC pseudoviruses. This novel approach provided unprecedented details regarding the dynamics of LASV fusion pores and revealed that ectopic expression of human LAMP1 in avian cells leads to a marked acceleration of fusion but modestly increases the likelihood of complete pore dilation and infection. In contrast, human LAMP1 expression dramatically enhanced the propensity of nascent pores to fully enlarge when LASV fusion with the plasma membrane was forced by exposure to low pH. Thus, whereas the role of LAMP1 in LASV fusion is confounded by an interplay between multiple endosomal factors, the plasma membrane is a suitable target for mechanistic dissection of the roles of host factors in LASV entry.
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Affiliation(s)
- You Zhang
- Department of Pediatrics, Division of Infectious Diseases Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Juan Carlos de la Torre
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Gregory B. Melikyan
- Department of Pediatrics, Division of Infectious Diseases Emory University School of Medicine, Atlanta, Georgia, United States of America
- Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
- * E-mail:
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12
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Intranuclear Positions of HIV-1 Proviruses Are Dynamic and Do Not Correlate with Transcriptional Activity. mBio 2022; 13:e0325621. [PMID: 35012348 PMCID: PMC8749423 DOI: 10.1128/mbio.03256-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The relationship between spatiotemporal distribution of HIV-1 proviruses and their transcriptional activity is not well understood. To elucidate the intranuclear positions of transcriptionally active HIV-1 proviruses, we utilized an RNA fluorescence in situ hybridization assay and RNA stem loops that bind to fluorescently labeled bacterial protein (Bgl-mCherry) to specifically detect HIV-1 transcription sites. Initially, transcriptionally active wild-type proviruses were located closer to the nuclear envelope (NE) than expected by random chance in HeLa (∼1.4 μm) and CEM-SS T cells (∼0.9 μm). Disrupting interactions between HIV-1 capsid and host cleavage and polyadenylation specificity factor (CPSF6) resulted in localization of proviruses to lamina-associated domains (LADs) adjacent to the NE in HeLa cells (∼0.9 - 1.0 μm); however, in CEM-SS T cells, there was little or no shift toward the NE (∼0.9 μm), indicating cell-type differences in the locations of transcriptionally active proviruses. The distance from the NE was not correlated with transcriptional activity, and transcriptionally active proviruses were randomly distributed throughout the HeLa cell after several cell divisions, indicating that the intranuclear locations of the chromosomal sites of integration are dynamic. After nuclear import HIV-1 cores colocalized with nuclear speckles, nuclear domains enriched in pre-mRNA splicing factors, but transcriptionally active proviruses detected 20 h after infection were mostly located outside but near nuclear speckles, suggesting a dynamic relationship between the speckles and integration sites. Overall, these studies establish that the nuclear distribution of HIV-1 proviruses is dynamic and the distance between HIV-1 proviruses and the NE does not correlate with transcriptional activity. IMPORTANCE HIV-1 integrates its genomic DNA into the chromosomes of the infected cell, but how it selects the site of integration and the impact of their location in the 3-dimensional nuclear space is not well understood. Here, we examined the nuclear locations of proviruses 1 and 5 days after infection and found that integration sites are first located near the nuclear envelope but become randomly distributed throughout the nucleus after a few cell divisions, indicating that the locations of the chromosomal sites of integration that harbor transcriptionally active proviruses are dynamic. We also found that the distance from the nuclear envelope to the integration site is cell-type dependent and does not correlate with proviral transcription activity. Finally, we observed that HIV-1 cores were localized to nuclear speckles shortly after nuclear import, but transcriptionally active proviruses were located adjacent to nuclear speckles. Overall, these studies provide insights into HIV-1 integration site selection and their effect on transcription activities.
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13
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HIV-1 entry: Duels between Env and host antiviral transmembrane proteins on the surface of virus particles. Curr Opin Virol 2021; 50:59-68. [PMID: 34390925 DOI: 10.1016/j.coviro.2021.07.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Revised: 07/20/2021] [Accepted: 07/21/2021] [Indexed: 12/18/2022]
Abstract
Human Immunodeficiency Virus type-1 (HIV-1) is the causative agent of AIDS. Its entry step is mediated by the envelope glycoprotein (Env). During the entry process, Env vastly changes its conformation. While non-liganded Env tends to have a closed structure, receptor-binding of Env opens its conformation, which leads to virus-cell membrane fusion. Single-molecule fluorescence resonance energy transfer (smFRET) imaging allows observation of these conformational changes on the virion surface. Nascent HIV-1 particles incorporate multiple host transmembrane proteins, some of which inhibit the entry process. The Env structure or its dynamics may determine the effectiveness of these antiviral mechanisms. Here, we review recent findings about the Env conformation changes on virus particles and inhibition of Env activities by virion-incorporated host transmembrane proteins.
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14
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Tavares LA, Januário YC, daSilva LLP. HIV-1 Hijacking of Host ATPases and GTPases That Control Protein Trafficking. Front Cell Dev Biol 2021; 9:622610. [PMID: 34307340 PMCID: PMC8295591 DOI: 10.3389/fcell.2021.622610] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 06/07/2021] [Indexed: 12/22/2022] Open
Abstract
The human immunodeficiency virus (HIV-1) modifies the host cell environment to ensure efficient and sustained viral replication. Key to these processes is the capacity of the virus to hijack ATPases, GTPases and the associated proteins that control intracellular protein trafficking. The functions of these energy-harnessing enzymes can be seized by HIV-1 to allow the intracellular transport of viral components within the host cell or to change the subcellular distribution of antiviral factors, leading to immune evasion. Here, we summarize how energy-related proteins deviate from their normal functions in host protein trafficking to aid the virus in different phases of its replicative cycle. Recent discoveries regarding the interplay among HIV-1 and host ATPases and GTPases may shed light on potential targets for pharmacological intervention.
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Affiliation(s)
- Lucas A Tavares
- Department of Cell and Molecular Biology, Center for Virology Research, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Yunan C Januário
- Department of Cell and Molecular Biology, Center for Virology Research, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Luis L P daSilva
- Department of Cell and Molecular Biology, Center for Virology Research, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
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15
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Human Defensins Inhibit SARS-CoV-2 Infection by Blocking Viral Entry. Viruses 2021; 13:v13071246. [PMID: 34206990 PMCID: PMC8310277 DOI: 10.3390/v13071246] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 06/17/2021] [Accepted: 06/22/2021] [Indexed: 12/14/2022] Open
Abstract
Innate immunity during acute infection plays a critical role in the disease severity of severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), and is likely to contribute to COVID-19 disease outcomes. Defensins are highly abundant innate immune factors in neutrophils and epithelial cells, including intestinal Paneth cells, and exhibit antimicrobial and immune-modulatory activities. In this study, we investigated the effects of human α- and β-defensins and RC101, a θ-defensin analog, on SARS-CoV-2 infection. We found that human neutrophil peptides (HNPs) 1-3, human defensin (HD) 5 and RC101 exhibited potent antiviral activity against pseudotyped viruses expressing SARS-CoV-2 spike proteins. HNP4 and HD6 had weak anti-SARS-CoV-2 activity, whereas human β-defensins (HBD2, HBD5 and HBD6) had no effect. HNP1, HD5 and RC101 also inhibited infection by replication-competent SARS-CoV-2 viruses and SARS-CoV-2 variants. Pretreatment of cells with HNP1, HD5 or RC101 provided some protection against viral infection. These defensins did not have an effect when provided post-infection, indicating their effect was directed towards viral entry. Indeed, HNP1 inhibited viral fusion but not the binding of the spike receptor-binding domain to hACE2. The anti-SARS-CoV-2 effect of defensins was influenced by the structure of the peptides, as linear unstructured forms of HNP1 and HD5 lost their antiviral function. Pro-HD5, the precursor of HD5, did not block infection by SARS-CoV-2. High virus titers overcame the effect of low levels of HNP1, indicating that defensins act on the virion. HNP1, HD5 and RC101 also blocked viral infection of intestinal and lung epithelial cells. The protective effects of defensins reported here suggest that they may be useful additives to the antivirus arsenal and should be thoroughly studied.
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16
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Carravilla P, Nieva JL, Eggeling C. Fluorescence Microscopy of the HIV-1 Envelope. Viruses 2020; 12:E348. [PMID: 32245254 PMCID: PMC7150788 DOI: 10.3390/v12030348] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Revised: 03/19/2020] [Accepted: 03/20/2020] [Indexed: 12/18/2022] Open
Abstract
Human immunodeficiency virus (HIV) infection constitutes a major health and social issue worldwide. HIV infects cells by fusing its envelope with the target cell plasma membrane. This process is mediated by the viral Env glycoprotein and depends on the envelope lipid composition. Fluorescent microscopy has been employed to investigate the envelope properties, and the processes of viral assembly and fusion, but the application of this technique to the study of HIV is still limited by a number of factors, such as the small size of HIV virions or the difficulty to label the envelope components. Here, we review fluorescence imaging studies of the envelope lipids and proteins, focusing on labelling strategies and model systems.
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Affiliation(s)
- Pablo Carravilla
- Institute of Applied Optics and Biophysics, Friedrich-Schiller-University Jena, Max-Wien Platz 1, 07743 Jena, Germany;
- Leibniz Institute of Photonic Technology, Albert Einstein Strasse 9, 07743 Jena, Germany
- Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain;
- Instituto Biofisika (UPV/EHU, CSIC), University of the Basque Country, E-48940 Leioa, Spain
| | - José L. Nieva
- Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain;
- Instituto Biofisika (UPV/EHU, CSIC), University of the Basque Country, E-48940 Leioa, Spain
| | - Christian Eggeling
- Institute of Applied Optics and Biophysics, Friedrich-Schiller-University Jena, Max-Wien Platz 1, 07743 Jena, Germany;
- Leibniz Institute of Photonic Technology, Albert Einstein Strasse 9, 07743 Jena, Germany
- MRC Weatherall Institute of Molecular Medicine, University of Oxford, Headley Way, Oxford OX3 9DS, UK
- Jena Center for Soft Matter (JCSM), Friedrich-Schiller-University Jena, Philosophenweg 7, 07743 Jena, Germany
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17
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Coomer CA, Carlon-Andres I, Iliopoulou M, Dustin ML, Compeer EB, Compton AA, Padilla-Parra S. Single-cell glycolytic activity regulates membrane tension and HIV-1 fusion. PLoS Pathog 2020; 16:e1008359. [PMID: 32084246 PMCID: PMC7055913 DOI: 10.1371/journal.ppat.1008359] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 03/04/2020] [Accepted: 01/27/2020] [Indexed: 12/21/2022] Open
Abstract
There has been resurgence in determining the role of host metabolism in viral infection yet deciphering how the metabolic state of single cells affects viral entry and fusion remains unknown. Here, we have developed a novel assay multiplexing genetically-encoded biosensors with single virus tracking (SVT) to evaluate the influence of global metabolic processes on the success rate of virus entry in single cells. We found that cells with a lower ATP:ADP ratio prior to virus addition were less permissive to virus fusion and infection. These results indicated a relationship between host metabolic state and the likelihood for virus-cell fusion to occur. SVT revealed that HIV-1 virions were arrested at hemifusion in glycolytically-inactive cells. Interestingly, cells acutely treated with glycolysis inhibitor 2-deoxyglucose (2-DG) become resistant to virus infection and also display less surface membrane cholesterol. Addition of cholesterol in these in glycolytically-inactive cells rescued the virus entry block at hemifusion and enabled completion of HIV-1 fusion. Further investigation with FRET-based membrane tension and membrane order reporters revealed a link between host cell glycolytic activity and host membrane order and tension. Indeed, cells treated with 2-DG possessed lower plasma membrane lipid order and higher tension values, respectively. Our novel imaging approach that combines lifetime imaging (FLIM) and SVT revealed not only changes in plasma membrane tension at the point of viral fusion, but also that HIV is less likely to enter cells at areas of higher membrane tension. We therefore have identified a connection between host cell glycolytic activity and membrane tension that influences HIV-1 fusion in real-time at the single-virus fusion level in live cells.
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Affiliation(s)
- Charles A. Coomer
- Cellular Imaging Group, Wellcome Centre Human Genetics, University of Oxford, Oxford, United Kingdom
- HIV Dynamics and Replication Program, National Cancer Institute, Frederick, Maryland, United States of America
- University of Kentucky, College of Medicine, Lexington, Kentucky, United States of America
- Division of Structural Biology, Wellcome Centre Human Genetics, University of Oxford, United Kingdom
| | - Irene Carlon-Andres
- Cellular Imaging Group, Wellcome Centre Human Genetics, University of Oxford, Oxford, United Kingdom
- Division of Structural Biology, Wellcome Centre Human Genetics, University of Oxford, United Kingdom
| | - Maro Iliopoulou
- Cellular Imaging Group, Wellcome Centre Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Michael L. Dustin
- Kennedy Institute of Rheumatology, University of Oxford, Oxford, United Kingdom
| | - Ewoud B. Compeer
- Kennedy Institute of Rheumatology, University of Oxford, Oxford, United Kingdom
| | - Alex A. Compton
- HIV Dynamics and Replication Program, National Cancer Institute, Frederick, Maryland, United States of America
| | - Sergi Padilla-Parra
- Cellular Imaging Group, Wellcome Centre Human Genetics, University of Oxford, Oxford, United Kingdom
- Division of Structural Biology, Wellcome Centre Human Genetics, University of Oxford, United Kingdom
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18
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Chen YC, Sood C, Francis AC, Melikyan GB, Dickson RM. Facile autofluorescence suppression enabling tracking of single viruses in live cells. J Biol Chem 2019; 294:19111-19118. [PMID: 31694918 DOI: 10.1074/jbc.ra119.010268] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 11/01/2019] [Indexed: 11/06/2022] Open
Abstract
Live cell fluorescence imaging is the method of choice for studying dynamic processes, such as nuclear transport, vesicular trafficking, and virus entry and egress. However, endogenous cellular autofluorescence masks a useful fluorescence signal, limiting the ability to reliably visualize low-abundance fluorescent proteins. Here, we employed synchronously amplified fluorescence image recovery (SAFIRe), which optically alters ground versus photophysical dark state populations within fluorescent proteins to modulate and selectively detect their background-free emission. Using a photoswitchable rsFastLime fluorescent protein combined with a simple illumination and image-processing scheme, we demonstrate the utility of this approach for suppressing undesirable, unmodulatable fluorescence background. Significantly, we adapted this technique to different commercial wide-field and spinning-disk confocal microscopes, obtaining >10-fold improvements in signal to background. SAFIRe allowed visualization of rsFastLime targeted to mitochondria by efficiently suppressing endogenous autofluorescence or overexpressed cytosolic unmodulatable EGFP. Suppression of the overlapping EGFP signal provided a means to perform multiplexed imaging of rsFastLime and spectrally overlapping fluorophores. Importantly, we used SAFIRe to reliably visualize and track single rsFastLime-labeled HIV-1 particles in living cells exhibiting high and uneven autofluorescence signals. Time-lapse SAFIRe imaging can be performed for an extended period of time to visualize HIV-1 entry into cells. SAFIRe should be broadly applicable for imaging live cell dynamics with commercial microscopes, even in strongly autofluorescent cells or cells expressing spectrally overlapping fluorescent proteins.
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Affiliation(s)
- Yen-Cheng Chen
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400.,Department of Pediatrics, Emory School of Medicine, Atlanta, Georgia 30322
| | - Chetan Sood
- Department of Pediatrics, Emory School of Medicine, Atlanta, Georgia 30322
| | - Ashwanth C Francis
- Department of Pediatrics, Emory School of Medicine, Atlanta, Georgia 30322
| | - Gregory B Melikyan
- Department of Pediatrics, Emory School of Medicine, Atlanta, Georgia 30322 .,Children's Healthcare of Atlanta, Atlanta, Georgia 30332
| | - Robert M Dickson
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400
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19
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Wu J, Gu J, Shen L, Fang D, Zou X, Cao Y, Wang S, Mao L. Exosomal MicroRNA-155 Inhibits Enterovirus A71 Infection by Targeting PICALM. Int J Biol Sci 2019; 15:2925-2935. [PMID: 31853228 PMCID: PMC6909958 DOI: 10.7150/ijbs.36388] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 09/18/2019] [Indexed: 12/12/2022] Open
Abstract
Enterovirus A71 (EV-A71) causes hand, foot, and mouth disease (HFMD) that is associated with neurological complications. Researchers have shown that exosomes containing host cellular microRNA (miRNA) can modulate the recipient's cellular response during viral infection. However, it is unclear how exosomal miRNAs regulate this response during EV-A71 infection. In this study, we used an exosomal miRNA chip to show that microRNA-155 (miR-155) was markedly enriched in exosomes after EV-A71 infection. Moreover, exosomal miR-155 efficaciously inhibited EV-A71 infection by targeting phosphatidylinositol clathrin assembly protein (PICALM) in recipient cells. Importantly, we confirmed that exosomal miR-155 reduced EV-A71 infection severity in vivo. Additionally, miR-155 levels in throat swabs from EV-A71-infected patients were higher than in those from healthy individuals. Collectively, our findings provide evidence that exosomal miR-155 plays a role in host-pathogen interactions by mediating EV-A71 infection via the repression of PICALM; these results provide insights into the regulatory mechanisms of viral infection.
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Affiliation(s)
- Jing Wu
- Department of Laboratory Medicine, The Affiliated People's Hospital, Jiangsu University, Zhenjiang, China.,Department of Immunology, Jiangsu Key Laboratory of Laboratory Medicine, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Jiaqi Gu
- Department of Laboratory Medicine, The Affiliated People's Hospital, Jiangsu University, Zhenjiang, China.,Department of Immunology, Jiangsu Key Laboratory of Laboratory Medicine, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Li Shen
- Clinical Laboratory, Zhenjiang Center for Disease Control and Prevention, Jiangsu, China
| | - Daihua Fang
- Clinical Laboratory, Xuzhou Children's Hospital, Xuzhou, China
| | - Xinran Zou
- Department of Laboratory Medicine, The Affiliated People's Hospital, Jiangsu University, Zhenjiang, China.,Department of Immunology, Jiangsu Key Laboratory of Laboratory Medicine, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Yuwen Cao
- Department of Laboratory Medicine, The Affiliated People's Hospital, Jiangsu University, Zhenjiang, China.,Department of Immunology, Jiangsu Key Laboratory of Laboratory Medicine, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Shengjun Wang
- Department of Laboratory Medicine, The Affiliated People's Hospital, Jiangsu University, Zhenjiang, China.,Department of Immunology, Jiangsu Key Laboratory of Laboratory Medicine, School of Medicine, Jiangsu University, Zhenjiang, China
| | - Lingxiang Mao
- Department of Laboratory Medicine, The Affiliated People's Hospital, Jiangsu University, Zhenjiang, China
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20
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Developments in single-molecule and single-particle fluorescence-based approaches for studying viral envelope glycoprotein dynamics and membrane fusion. Adv Virus Res 2019; 104:123-146. [PMID: 31439147 DOI: 10.1016/bs.aivir.2019.05.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Fusion of viral and cellular membranes is an essential step in the entry pathway of all enveloped viruses. This is a dynamic and multistep process, which has been extensively studied, resulting in the endpoints of the reaction being firmly established, and many essential cellular factors identified. What remains is to elucidate the dynamic events that underlie this process, including the order and timing of glycoprotein conformational changes, receptor-binding events, and movement of the glycoprotein on the surface of the virion. Due to the inherently asynchronous nature of these dynamics, there has been an increased focus on the study of single virions and single molecules. These techniques provide researchers the high precision and resolution necessary to bridge the gaps in our understanding of viral membrane fusion. This review highlights the advancement of single-molecule and single-particle fluorescence-based techniques, with a specific focus on how these techniques have been used to study the dynamic nature of the viral fusion pathway.
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21
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Herold N. Overexpression of the Interferon-Inducible Isoform 4 of NCOA7 Dissects the Entry Route of Enveloped Viruses and Demonstrates that HIV Enters Cells via Fusion at the Plasma Membrane. Viruses 2019; 11:v11020121. [PMID: 30700004 PMCID: PMC6410169 DOI: 10.3390/v11020121] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 01/24/2019] [Accepted: 01/27/2019] [Indexed: 11/16/2022] Open
Abstract
The HIV-1 entry-route is a matter of ongoing controversy, and there is evidence for fusion either at the cell surface or from within endosomes. A recent report demonstrated that isoform 4 of nuclear receptor coactivator 7 (NCOA7iso4) interacts with endolysosomal vacuolar-type H+-ATPase (V-ATPase), increasing lytic activity and thereby severely affecting the entry of vesicular stomatitis virus glycoprotein (VSV-G)-mediated, but not HIV-Env-mediated, entry and infection. As basal expression of NCOA7iso4 is low in the absence of type-1 interferons, its overexpression is a novel tool to study viral entry.
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Affiliation(s)
- Nikolas Herold
- Childhood Cancer Research Unit, Department of Women's and Children's Health, Karolinska Institutet, 171 76 Stockholm, Sweden.
- Paediatric Oncology, Theme Women's and Children's Health, Karolinska University Hospital, 171 76 Stockholm, Sweden.
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22
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Eggink D, Bontjer I, de Taeye SW, Langedijk JPM, Berkhout B, Sanders RW. HIV-1 anchor inhibitors and membrane fusion inhibitors target distinct but overlapping steps in virus entry. J Biol Chem 2019; 294:5736-5746. [PMID: 30696772 PMCID: PMC6463712 DOI: 10.1074/jbc.ra119.007360] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 01/25/2019] [Indexed: 12/03/2022] Open
Abstract
HIV-1 entry into cells is mediated by the envelope glycoprotein (Env) and represents an attractive target for therapeutic intervention. Two drugs that inhibit HIV entry are approved for clinical use: the membrane fusion-inhibitor T20 (Fuzeon, enfuvirtide) and the C-C chemokine receptor type 5 (CCR5) blocker maraviroc (Selzentry). Another class of entry inhibitors supposedly target the fusion peptide (FP) and are termed anchor inhibitors. These include the VIRIP peptide and VIRIP derivatives such as VIR165, VIR353, and VIR576. Here, we investigated the mechanism of inhibition by VIR165. We show that substitutions within the FP modulate sensitivity to VIR165, consistent with the FP being the drug target. Our results also revealed that VIR165 acts during an intermediate post-CD4–binding entry step that is overlapping but not identical to the step inhibited by fusion inhibitors such as T20. We found that some but not all resistance mutations to heptad repeat 2 (HR2)-targeting fusion inhibitors can provide cross-resistance to VIR165. In contrast, resistance mutations in the HR1-binding site for the fusion inhibitors did not cause cross-resistance to VIR165. However, Env with mutations located outside this binding site and thought to affect fusion kinetics, exhibited decreased sensitivity to VIR165. Although we found a strong correlation between Env stability and resistance to HR2-based fusion inhibitors, such correlation was not observed for Env stability and VIR165 resistance. We conclude that VIRIP analogs target the FP during an intermediate, post-CD4–binding entry step that overlaps with but is distinct from the step(s) inhibited by HR2-based fusion inhibitors.
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Affiliation(s)
- Dirk Eggink
- From the Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam University Medical Centers (Amsterdam UMC), Location AMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| | - Ilja Bontjer
- From the Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam University Medical Centers (Amsterdam UMC), Location AMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| | - Steven W de Taeye
- From the Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam University Medical Centers (Amsterdam UMC), Location AMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| | | | - Ben Berkhout
- From the Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam University Medical Centers (Amsterdam UMC), Location AMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| | - Rogier W Sanders
- From the Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam University Medical Centers (Amsterdam UMC), Location AMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; the Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York 10065.
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Marin M, Kushnareva Y, Mason CS, Chanda SK, Melikyan GB. HIV-1 Fusion with CD4+ T cells Is Promoted by Proteins Involved in Endocytosis and Intracellular Membrane Trafficking. Viruses 2019; 11:v11020100. [PMID: 30691001 PMCID: PMC6409670 DOI: 10.3390/v11020100] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 01/23/2019] [Indexed: 01/23/2023] Open
Abstract
The HIV-1 entry pathway into permissive cells has been a subject of debate. Accumulating evidence, including our previous single virus tracking results, suggests that HIV-1 can enter different cell types via endocytosis and CD4/coreceptor-dependent fusion with endosomes. However, recent studies that employed indirect techniques to infer the sites of HIV-1 entry into CD4+ T cells have concluded that endocytosis does not contribute to infection. To assess whether HIV-1 enters these cells via endocytosis, we probed the role of intracellular trafficking in HIV-1 entry/fusion by a targeted shRNA screen in a CD4+ T cell line. We performed a screen utilizing a direct virus-cell fusion assay as readout and identified several host proteins involved in endosomal trafficking/maturation, including Rab5A and sorting nexins, as factors regulating HIV-1 fusion and infection. Knockdown of these proteins inhibited HIV-1 fusion irrespective of coreceptor tropism, without altering the CD4 or coreceptor expression, or compromising the virus’ ability to mediate fusion of two adjacent cells initiated by virus-plasma membrane fusion. Ectopic expression of Rab5A in non-permissive cells harboring Rab5A shRNAs partially restored the HIV-cell fusion. Together, these results implicate endocytic machinery in productive HIV-1 entry into CD4+ T cells.
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Affiliation(s)
- Mariana Marin
- Department of Pediatric, Division of Infectious Diseases, Emory University School of Medicine, 2015 Uppergate Drive, Atlanta, GA 30322, USA.
| | - Yulia Kushnareva
- Functional Genomics Center, La Jolla Institute for Allergy and Immunology, 9420 Athena Circle, La Jolla, CA 92037, USA.
| | - Caleb S Mason
- Department of Pediatric, Division of Infectious Diseases, Emory University School of Medicine, 2015 Uppergate Drive, Atlanta, GA 30322, USA.
| | - Sumit K Chanda
- Sanford Burnham Prebys Medical Discovery Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.
| | - Gregory B Melikyan
- Department of Pediatric, Division of Infectious Diseases, Emory University School of Medicine, 2015 Uppergate Drive, Atlanta, GA 30322, USA.
- Children's Healthcare of Atlanta, Atlanta, GA 30322, USA.
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Nathan L, Daniel S. Single Virion Tracking Microscopy for the Study of Virus Entry Processes in Live Cells and Biomimetic Platforms. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1215:13-43. [PMID: 31317494 PMCID: PMC7122913 DOI: 10.1007/978-3-030-14741-9_2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The most widely-used assays for studying viral entry, including infectivity, cofloatation, and cell-cell fusion assays, yield functional information but provide low resolution of individual entry steps. Structural characterization provides high-resolution conformational information, but on its own is unable to address the functional significance of these conformations. Single virion tracking microscopy techniques provide more detail on the intermediate entry steps than infection assays and more functional information than structural methods, bridging the gap between these methods. In addition, single virion approaches also provide dynamic information about the kinetics of entry processes. This chapter reviews single virion tracking techniques and describes how they can be applied to study specific virus entry steps. These techniques provide information complementary to traditional ensemble approaches. Single virion techniques may either probe virion behavior in live cells or in biomimetic platforms. Synthesizing information from ensemble, structural, and single virion techniques ultimately yields a more complete understanding of the viral entry process than can be achieved by any single method alone.
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Affiliation(s)
- Lakshmi Nathan
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA.
| | - Susan Daniel
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, USA.
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25
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Suddala KC, Lee CC, Meraner P, Marin M, Markosyan RM, Desai TM, Cohen FS, Brass AL, Melikyan GB. Interferon-induced transmembrane protein 3 blocks fusion of sensitive but not resistant viruses by partitioning into virus-carrying endosomes. PLoS Pathog 2019; 15:e1007532. [PMID: 30640957 PMCID: PMC6347298 DOI: 10.1371/journal.ppat.1007532] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 01/25/2019] [Accepted: 12/14/2018] [Indexed: 11/19/2022] Open
Abstract
Late endosome-resident interferon-induced transmembrane protein 3 (IFITM3) inhibits fusion of diverse viruses, including Influenza A virus (IAV), by a poorly understood mechanism. Despite the broad antiviral activity of IFITM3, viruses like Lassa virus (LASV), are fully resistant to its inhibitory effects. It is currently unclear whether resistance arises from a highly efficient fusion machinery that is capable of overcoming IFITM3 restriction or the ability to enter from cellular sites devoid of this factor. Here, we constructed and validated a functional IFITM3 tagged with EGFP or other fluorescent proteins. This breakthrough allowed live cell imaging of virus co-trafficking and fusion with endosomal compartments in cells expressing fluorescent IFITM3. Three-color single virus and endosome tracking revealed that sensitive (IAV), but not resistant (LASV), viruses become trapped within IFITM3-positive endosomes where they underwent hemifusion but failed to release their content into the cytoplasm. IAV fusion with IFITM3-containing compartments could be rescued by amphotericin B treatment, which has been previously shown to antagonize the antiviral activity of this protein. By comparison, virtually all LASV particles trafficked and fused with endosomes lacking detectable levels of fluorescent IFITM3, implying that this virus escapes restriction by utilizing endocytic pathways that are distinct from the IAV entry pathways. The importance of virus uptake and transport pathways is further reinforced by the observation that LASV glycoprotein-mediated cell-cell fusion is inhibited by IFITM3 and other members of the IFITM family expressed in target cells. Together, our results strongly support a model according to which IFITM3 accumulation at the sites of virus fusion is a prerequisite for its antiviral activity and that this protein traps viral fusion at a hemifusion stage by preventing the formation of fusion pores. We conclude that the ability to utilize alternative endocytic pathways for entry confers IFITM3-resistance to otherwise sensitive viruses.
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Affiliation(s)
- Krishna C Suddala
- Department of Pediatrics, Emory University, Atlanta, GA, United States of America
| | - Christine C Lee
- Department of Pediatrics, Emory University, Atlanta, GA, United States of America
| | - Paul Meraner
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, United States of America
| | - Mariana Marin
- Department of Pediatrics, Emory University, Atlanta, GA, United States of America
| | - Ruben M Markosyan
- Rush University Medical Center, Department of Physiology and Biophysics, Chicago, IL, United States of America
| | - Tanay M Desai
- Department of Pediatrics, Emory University, Atlanta, GA, United States of America
| | - Fredric S Cohen
- Rush University Medical Center, Department of Physiology and Biophysics, Chicago, IL, United States of America
| | - Abraham L Brass
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, MA, United States of America
- Gastroenterology Division, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, United States of America
| | - Gregory B Melikyan
- Department of Pediatrics, Emory University, Atlanta, GA, United States of America
- Children's Healthcare of Atlanta, Atlanta, GA, United States of America
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26
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Lee WYJ, Fu RM, Liang C, Sloan RD. IFITM proteins inhibit HIV-1 protein synthesis. Sci Rep 2018; 8:14551. [PMID: 30266929 PMCID: PMC6162285 DOI: 10.1038/s41598-018-32785-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 09/11/2018] [Indexed: 01/23/2023] Open
Abstract
Interferon induced transmembrane proteins (IFITMs) inhibit the cellular entry of a broad range of viruses, but it has been suspected that for HIV-1 IFITMs may also inhibit a post-integration replicative step. We show that IFITM expression reduces HIV-1 viral protein synthesis by preferentially excluding viral mRNA transcripts from translation and thereby restricts viral production. Codon-optimization of proviral DNA rescues viral translation, implying that IFITM-mediated restriction requires recognition of viral RNA elements. In addition, we find that expression of the viral accessory protein Nef can help overcome the IFITM-mediated inhibition of virus production. Our studies identify a novel role for IFITMs in inhibiting HIV replication at the level of translation, but show that the effects can be overcome by the lentiviral protein Nef.
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Affiliation(s)
- Wing-Yiu Jason Lee
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, United Kingdom
| | - Rebecca Menhua Fu
- Division of Infection and Pathway Medicine, School of Biomedical Sciences, University of Edinburgh, Edinburgh, EH16 4SB, United Kingdom
| | - Chen Liang
- McGill University AIDS Centre, Lady Davis Institute, Montreal, Quebec, H3T 1E2, Canada
| | - Richard D Sloan
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, United Kingdom.
- Division of Infection and Pathway Medicine, School of Biomedical Sciences, University of Edinburgh, Edinburgh, EH16 4SB, United Kingdom.
- ZJU-UoE Institute, Zhejiang University, Haining, Zhejiang, 314400, P.R. China.
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27
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Song H, DeSantis M, Tian C, Cheng W. Dynasore inhibition on productive infection of HIV-1 in commonly used cell lines is independent of transferrin endocytosis. ACTA ACUST UNITED AC 2018; 2018. [PMID: 31058179 PMCID: PMC6492620 DOI: 10.19185/matters.201805000001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
The route of HIV-1 entry for productive infection in CD4+ host cells is a fundamental question for the molecular understanding of HIV-1 infection and transmission. Although direct fusion has long been thought to be the mode of entry, recent studies have suggested that productive entry of HIV-1 may actually occur through dynamin-dependent endocytosis. In several of these studies, dynasore, a noncompetitive inhibitor of the GTPase activity of dynamin, has been used to support this conclusion. Here we show that dynasore does produce inhibitory effects on the productive infection of HIV-1 in several commonly used cell lines. This effect is present regardless of the methods used to facilitate the infection of HIV-1. However, transferrin uptake remains fully functional in these cell lines upon dynasore treatment. Therefore, the inhibition on HIV-1 infection by dynasore in these cell lines is due to an effect that is independent of transferrin endocytosis. The use of dynasore in probing the role of endocytosis in HIV-1 infection should be corroborated by other methods.
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Affiliation(s)
- Hanna Song
- 428 Church Street, University of Michigan; Pharmaceutical Sciences, Biological Chemistry, University of Michigan
| | - Michael DeSantis
- 428 Church Street, University of Michigan; Pharmaceutical Sciences, Biological Chemistry, University of Michigan
| | - Chunjuan Tian
- 428 Church Street, University of Michigan; Pharmaceutical Sciences, Biological Chemistry, University of Michigan
| | - Wei Cheng
- 428 Church Street, University of Michigan; Pharmaceutical Sciences, Biological Chemistry, University of Michigan
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28
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Live-Cell Imaging of Early Steps of Single HIV-1 Infection. Viruses 2018; 10:v10050275. [PMID: 29783762 PMCID: PMC5977268 DOI: 10.3390/v10050275] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 05/15/2018] [Accepted: 05/18/2018] [Indexed: 01/10/2023] Open
Abstract
Live-cell imaging of single HIV-1 entry offers a unique opportunity to delineate the spatio-temporal regulation of infection. Novel virus labeling and imaging approaches enable the visualization of key steps of HIV-1 entry leading to nuclear import, integration into the host genome, and viral protein expression. Here, we discuss single virus imaging strategies, focusing on live-cell imaging of single virus fusion and productive uncoating that culminates in HIV-1 infection.
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29
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Sood C, Francis AC, Desai TM, Melikyan GB. An improved labeling strategy enables automated detection of single-virus fusion and assessment of HIV-1 protease activity in single virions. J Biol Chem 2017; 292:20196-20207. [PMID: 29046351 PMCID: PMC5724006 DOI: 10.1074/jbc.m117.818088] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 10/12/2017] [Indexed: 11/06/2022] Open
Abstract
Enveloped viruses transfer their genomes into host cells by fusing their membrane to that of the cell. To visualize single-virus fusion in living cells, researchers take advantage of the proteolytic maturation of HIV, type 1 (HIV-1), which can generate free fluorescent proteins within the viral particle. Co-labeling viruses with a content marker and a fluorescently tagged Vpr (a viral core protein) enables detection of single-virus fusions, but a major limitation of this approach is that not all viral particles incorporate both markers. Here we designed a labeling strategy based on the bifunctional mCherry-2xCL-YFP-Vpr construct, in which 2xCL denotes a tandem cleavage site for the viral protease. This bifunctional marker was efficiently cleaved during virus maturation, producing free mCherry and the core-associated YFP-Vpr. A nearly perfect colocalization of these two markers in virions and their fixed 1:1 ratio enabled automated detection of single-particle fusion in both fixed and live cells based on loss of the mCherry signal. Furthermore, a drop in FRET efficiency between YFP and mCherry because of cleavage of the bifunctional marker, which manifested as a marked shift in the normalized YFP/mCherry fluorescence ratio, reliably predicted viral protease activity in single virions. This feature could discriminate between the particles containing free mCherry, and therefore likely representing mature viruses, and immature particles whose fusion cannot be detected. In summary, our new labeling strategy offers several advantages compared with previous approaches, including increased reliability and throughput of detection of viral fusion. We anticipate that our method will have significant utility for studying viral fusion and maturation.
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Affiliation(s)
- Chetan Sood
- Department of Pediatrics, Emory University, Atlanta, Georgia 30322
| | | | - Tanay M Desai
- Department of Pediatrics, Emory University, Atlanta, Georgia 30322
| | - Gregory B Melikyan
- Department of Pediatrics, Emory University, Atlanta, Georgia 30322; Children's Healthcare of Atlanta, Atlanta, Georgia 30322.
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30
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Dynamin-2 Stabilizes the HIV-1 Fusion Pore with a Low Oligomeric State. Cell Rep 2017; 18:443-453. [PMID: 28076788 PMCID: PMC5263234 DOI: 10.1016/j.celrep.2016.12.032] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/14/2016] [Accepted: 12/12/2016] [Indexed: 11/22/2022] Open
Abstract
One of the key research areas surrounding HIV-1 concerns the regulation of the fusion event that occurs between the virus particle and the host cell during entry. Even if it is universally accepted that the large GTPase dynamin-2 is important during HIV-1 entry, its exact role during the first steps of HIV-1 infection is not well characterized. Here, we have utilized a multidisciplinary approach to study the DNM2 role during fusion of HIV-1 in primary resting CD4 T and TZM-bl cells. We have combined advanced light microscopy and functional cell-based assays to experimentally assess the role of dynamin-2 during these processes. Overall, our data suggest that dynamin-2, as a tetramer, might help to establish hemi-fusion and stabilizes the pore during HIV-1 fusion. DNM2 is crucial for HIV-1 fusion in T Cells and reporter cells DNM2 is not necessarily linked with endocytosis DNM2 tetramer stabilizes the HIV-1 fusion pore
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31
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Giroud C, Du Y, Marin M, Min Q, Jui NT, Fu H, Melikyan GB. Screening and Functional Profiling of Small-Molecule HIV-1 Entry and Fusion Inhibitors. Assay Drug Dev Technol 2017; 15:53-63. [PMID: 28322598 DOI: 10.1089/adt.2017.777] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
HIV-1 entry and fusion with target cells is an important target for antiviral therapy. However, a few currently approved treatments are not effective as monotherapy due to the emergence of drug resistance. This consideration has fueled efforts to develop new bioavailable inhibitors targeting different steps of the HIV-1 entry process. Here, a high-throughput screen was performed of a large library of 100,000 small molecules for HIV-1 entry/fusion inhibitors, using a direct virus-cell fusion assay in a 384 half-well format. Positive hits were validated using a panel of functional assays, including HIV-1 specificity, cytotoxicity, and single-cycle infectivity assays. One compound-4-(2,5-dimethyl-pyrrol-1-yl)-2-hydroxy-benzoic acid (DPHB)-that selectively inhibited HIV-1 fusion was further characterized. Functional experiments revealed that DPHB caused irreversible inactivation of HIV-1 Env on cell-free virions and that this effect was related to binding to the third variable loop (V3) of the gp120 subunit of HIV-1 Env. Moreover, DPHB selectively inhibited HIV-1 strains that use CXCR4 or both CXCR4 and CCR5 co-receptors for entry, but not strains exclusively using CCR5. This selectivity was mapped to the gp120 V3 loop using chimeric Env glycoproteins. However, it was found that pure DPHB was not active against HIV-1 and that its degradation products (most likely polyanions) were responsible for inhibition of viral fusion. These findings highlight the importance of post-screening validation of positive hits and are in line with previous reports of the broad antiviral activity of polyanions.
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Affiliation(s)
- Charline Giroud
- 1 Department of Pediatrics Infectious Diseases, Emory University School of Medicine , Atlanta, Georgia
| | - Yuhong Du
- 2 Department of Pharmacology, Emory University School of Medicine , Atlanta, Georgia .,3 Emory Chemical Biology Discovery Center, Emory University School of Medicine , Atlanta, Georgia
| | - Mariana Marin
- 1 Department of Pediatrics Infectious Diseases, Emory University School of Medicine , Atlanta, Georgia
| | - Qui Min
- 2 Department of Pharmacology, Emory University School of Medicine , Atlanta, Georgia .,3 Emory Chemical Biology Discovery Center, Emory University School of Medicine , Atlanta, Georgia
| | - Nathan T Jui
- 4 Department of Chemistry, Emory University , Atlanta, Georgia
| | - Haian Fu
- 2 Department of Pharmacology, Emory University School of Medicine , Atlanta, Georgia .,3 Emory Chemical Biology Discovery Center, Emory University School of Medicine , Atlanta, Georgia .,5 Department of Hematology and Medical Oncology, Winship Cancer Institute , Atlanta, Georgia
| | - Gregory B Melikyan
- 1 Department of Pediatrics Infectious Diseases, Emory University School of Medicine , Atlanta, Georgia .,6 Children's Healthcare of Atlanta , Atlanta, Georgia
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32
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HIV Fusion in Dendritic Cells Occurs Mainly at the Surface and Is Limited by Low CD4 Levels. J Virol 2017; 91:JVI.01248-17. [PMID: 28814521 DOI: 10.1128/jvi.01248-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 08/10/2017] [Indexed: 01/06/2023] Open
Abstract
HIV-1 poorly infects monocyte-derived dendritic cells (MDDCs). This is in large part due to SAMHD1, which restricts viral reverse transcription. Pseudotyping HIV-1 with vesicular stomatitis virus G protein (VSV-G) strongly enhances infection, suggesting that earlier steps of viral replication, including fusion, are also inefficient in MDDCs. The site of HIV-1 fusion remains controversial and may depend on the cell type, with reports indicating that it occurs at the plasma membrane or, conversely, in an endocytic compartment. Here, we examined the pathways of HIV-1 entry in MDDCs. Using a combination of temperature shift and fusion inhibitors, we show that HIV-1 fusion mainly occurs at the cell surface. We then asked whether surface levels or intracellular localization of CD4 modulates HIV-1 entry. Increasing CD4 levels strongly enhanced fusion and infection with various HIV-1 isolates, including reference and transmitted/founder strains, but not with BaL, which uses low CD4 levels for entry. Overexpressing coreceptors did not facilitate viral infection. To further study the localization of fusion events, we generated CD4 mutants carrying heterologous cytoplasmic tails (LAMP1 or Toll-like receptor 7 [TLR7]) to redirect the molecule to intracellular compartments. The intracellular CD4 mutants did not facilitate HIV-1 fusion and replication in MDDCs. Fusion of an HIV-2 isolate with MDDCs was also enhanced by increasing surface CD4 levels. Our results demonstrate that MDDCs are inefficiently infected by various HIV-1 and HIV-2 strains, in part because of low CD4 levels. In these cells, viral fusion occurs mainly at the surface, and probably not after internalization.IMPORTANCE Dendritic cells (DCs) are professional antigen-presenting cells inducing innate and adaptive immune responses. DCs express the HIV receptor CD4 and are potential target cells for HIV. There is debate about the sensitivity of DCs to productive HIV-1 and HIV-2 infection. The fusion step of the viral replication cycle is inefficient in DCs, and the underlying mechanisms are poorly characterized. We show that increasing the levels of CD4 at the plasma membrane allows more HIV fusion and productive infection in DCs. We further demonstrate that HIV fusion occurs mainly at the cell surface and not in an intracellular compartment. Our results help us understand why DCs are poorly sensitive to HIV infection.
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33
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Jakobsdottir GM, Iliopoulou M, Nolan R, Alvarez L, Compton AA, Padilla-Parra S. On the Whereabouts of HIV-1 Cellular Entry and Its Fusion Ports. Trends Mol Med 2017; 23:932-944. [PMID: 28899754 DOI: 10.1016/j.molmed.2017.08.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 08/12/2017] [Accepted: 08/14/2017] [Indexed: 01/06/2023]
Abstract
HIV-1 disseminates to diverse tissues through different cell types and establishes long-lived reservoirs. The exact cellular compartment where fusion occurs differs depending on the cell type and mode of viral transmission. This implies that HIV-1 may modulate a number of common host cell factors in different cell types. In this review, we evaluate recent advances on the host cell factors that play an important role in HIV-1 entry and fusion. New insights from restriction factors inhibiting virus-cell fusion in vitro may contribute to the development of future therapeutic interventions. Collectively, novel findings underline the need for potent, host-directed therapies that disrupt the earliest stages of the virus life cycle and preclude the emergence of resistant viral variants.
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Affiliation(s)
- G Maria Jakobsdottir
- Wellcome Trust Centre for Human Genetics, Cellular Imaging, University of Oxford, Oxford, UK
| | - Maro Iliopoulou
- Wellcome Trust Centre for Human Genetics, Cellular Imaging, University of Oxford, Oxford, UK
| | - Rory Nolan
- Wellcome Trust Centre for Human Genetics, Cellular Imaging, University of Oxford, Oxford, UK
| | - Luis Alvarez
- Wellcome Trust Centre for Human Genetics, Cellular Imaging, University of Oxford, Oxford, UK
| | - Alex A Compton
- HIV Dynamics and Replication Program, National Cancer Institute, Frederick, MD 21702, USA
| | - Sergi Padilla-Parra
- Wellcome Trust Centre for Human Genetics, Cellular Imaging, University of Oxford, Oxford, UK; Division of Structural Biology, University of Oxford,The Henry Wellcome Building for Genomic Medicine, Headington, Oxford OX3 7BN, UK.
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34
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Abstract
CCR5 (R5)-tropic, but not CXCR4 (X4)-tropic, HIV-1 is associated with primary HIV-1 infection and transmission. Recent studies have shown that IFN-induced transmembrane (IFITM) proteins, including IFITM1, IFITM2, and IFITM3, restrict a broad range of viruses. Here, we demonstrate that an IFITM2 isoform (Δ20 IFITM2) lacking 20 amino acids at the N terminus differentially restricts X4 and R5 HIV-1. Δ20 IFITM2 suppresses replication of X4 HIV-1 strains by inhibiting their entry. High levels of Δ20 IFITM2 expression could be detected in CD4+ T cells and in monocytes. Infection of X4 viruses in monocyte-derived macrophages and dendritic cells is enhanced upon depletion of IFITM2 isoforms. Furthermore, we also show that coreceptor use is the determining factor for differential HIV-1 restriction of Δ20 IFITM2. When we replace the C terminus of CCR5 with the C terminus of CXCR4, R5 viruses become more susceptible to Δ20 IFITM2-mediated restriction. In contrast to previous studies, our research reveals that neither X4 nor R5 HIV-1 is suppressed by IFITM2 and IFITM3. The multifactor gatekeeping model has been proposed to explain restriction of X4 viruses in the early stage of HIV-1 diseases. Our findings indicate that Δ20 IFITM2 may serve as a major contributor to this gatekeeping mechanism.
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35
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RNA-Associated Early-Stage Antiviral Factor Is a Major Component of Lv2 Restriction. J Virol 2017; 91:JVI.01228-16. [PMID: 28275184 DOI: 10.1128/jvi.01228-16] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 02/21/2017] [Indexed: 01/06/2023] Open
Abstract
Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) replication in human cells is restricted at early postentry steps by host inhibitory factors. We previously described and characterized an early-phase restriction of HIV-1 and -2 replication in human cell lines, primary macrophages, and peripheral blood mononuclear cells. The restriction was termed lentiviral restriction 2 (Lv2). The viral determinants of Lv2 susceptibility mapped to the HIV-2 envelope (Env) and capsid (CA). We subsequently reported a whole-genome small interfering RNA screening for factors involved in HIV that identified RNA-associated early-stage antiviral factor (REAF). Using HIV-2 chimeras of susceptible and nonsusceptible viruses, we show here that REAF is a major component of the previously described Lv2 restriction. Further studies of the viral CA demonstrate that the CA mutation I73V (previously called I207V), a potent determinant for HIV-2, is a weak determinant of susceptibility for HIV-1. More potent CA determinants for HIV-1 REAF restriction were identified at P38A, N74D, G89V, and G94D. These results firmly establish that in HIV-1, CA is a strong determinant of susceptibility to Lv2/REAF. Similar to HIV-2, HIV-1 Env can rescue sensitive CAs from restriction. We conclude that REAF is a major component of the previously described Lv2 restriction.IMPORTANCE Measures taken by the host cell to combat infection drive the evolution of pathogens to counteract or sidestep them. The study of such virus-host conflicts can point to possible weaknesses in the arsenal of viruses and may lead to the rational design of antiviral agents. Here we describe our discovery that the host restriction factor REAF fulfills the same criteria previously used to describe lentiviral restriction (Lv2). We show that, like the HIV-2 CA, the CA of HIV-1 is a strong determinant of Lv2/REAF susceptibility. We illustrate how HIV counteracts Lv2/REAF by using an envelope with alternative routes of entry into cells.
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36
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Takechi-Haraya Y, Aki K, Tohyama Y, Harano Y, Kawakami T, Saito H, Okamura E. Glycosaminoglycan Binding and Non-Endocytic Membrane Translocation of Cell-Permeable Octaarginine Monitored by Real-Time In-Cell NMR Spectroscopy. Pharmaceuticals (Basel) 2017; 10:ph10020042. [PMID: 28420127 PMCID: PMC5490399 DOI: 10.3390/ph10020042] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 03/27/2017] [Accepted: 04/12/2017] [Indexed: 12/13/2022] Open
Abstract
Glycosaminoglycans (GAGs), which are covalently-linked membrane proteins at the cell surface have recently been suggested to involve in not only endocytic cellular uptake but also non-endocytic direct cell membrane translocation of arginine-rich cell-penetrating peptides (CPPs). However, in-situ comprehensive observation and the quantitative analysis of the direct membrane translocation processes are challenging, and the mechanism therefore remains still unresolved. In this work, real-time in-cell NMR spectroscopy was applied to investigate the direct membrane translocation of octaarginine (R8) into living cells. By introducing 4-trifluoromethyl-l-phenylalanine to the N terminus of R8, the non-endocytic membrane translocation of 19F-labeled R8 (19F-R8) into a human myeloid leukemia cell line was observed at 4 °C with a time resolution in the order of minutes. 19F NMR successfully detected real-time R8 translocation: the binding to anionic GAGs at the cell surface, followed by the penetration into the cell membrane, and the entry into cytosol across the membrane. The NMR concentration analysis enabled quantification of how much of R8 was staying in the respective translocation processes with time in situ. Taken together, our in-cell NMR results provide the physicochemical rationale for spontaneous penetration of CPPs in cell membranes.
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Affiliation(s)
- Yuki Takechi-Haraya
- Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, 7-2-1 Kamiohno, Himeji 670-8524, Japan.
| | - Kenzo Aki
- Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, 7-2-1 Kamiohno, Himeji 670-8524, Japan.
| | - Yumi Tohyama
- Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, 7-2-1 Kamiohno, Himeji 670-8524, Japan.
| | - Yuichi Harano
- Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, 7-2-1 Kamiohno, Himeji 670-8524, Japan.
| | - Toru Kawakami
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Hiroyuki Saito
- Department of Biophysical Chemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan.
| | - Emiko Okamura
- Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, 7-2-1 Kamiohno, Himeji 670-8524, Japan.
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Aggarwal A, Hitchen TL, Ootes L, McAllery S, Wong A, Nguyen K, McCluskey A, Robinson PJ, Turville SG. HIV infection is influenced by dynamin at 3 independent points in the viral life cycle. Traffic 2017; 18:392-410. [PMID: 28321960 DOI: 10.1111/tra.12481] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 03/16/2017] [Accepted: 03/16/2017] [Indexed: 12/19/2022]
Abstract
CD4 T cells are important cellular targets for HIV-1, yet the primary site of HIV fusion remains unresolved. Candidate fusion sites are either the plasma membrane or from within endosomes. One area of investigation compounding the controversy of this field, is the role of the protein dynamin in the HIV life cycle. To understand the role of dynamin in primary CD4 T cells we combined dynamin inhibition with a series of complementary assays based on single particle tracking, HIV fusion, detection of HIV DNA products and active viral transcription. We identify 3 levels of dynamin influence on the HIV life cycle. Firstly, dynamin influences productive infection by preventing cell cycle progression. Secondly, dynamin influences endocytosis rates and increases the probability of endosomal fusion. Finally, we provide evidence in resting CD4 T cells that dynamin directly regulates the HIV fusion reaction at the plasma membrane. We confirm this latter observation using 2 divergent dynamin modulating compounds, one that enhances dynamin conformations associated with dynamin ring formation (ryngo-1-23) and the other that preferentially targets dynamin conformations that appear in helices (dyngo-4a). This in-depth understanding of dynamin's roles in HIV infection clarifies recent controversies and furthermore provides evidence for dynamin regulation specifically in the HIV fusion reaction.
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Affiliation(s)
- Anupriya Aggarwal
- The Kirby Institute, University of New South Wales, New South Wales, Australia
| | - Tina L Hitchen
- The Kirby Institute, University of New South Wales, New South Wales, Australia
| | - Lars Ootes
- The Kirby Institute, University of New South Wales, New South Wales, Australia
| | - Samantha McAllery
- The Kirby Institute, University of New South Wales, New South Wales, Australia
| | - Andrew Wong
- The Kirby Institute, University of New South Wales, New South Wales, Australia
| | - Khanh Nguyen
- The Kirby Institute, University of New South Wales, New South Wales, Australia
| | - Adam McCluskey
- Centre for Chemical Biology, Chemistry, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, Australia
| | - Phillip J Robinson
- Children's Medical Research Institute, The University of Sydney, New South Wales, Australia
| | - Stuart G Turville
- The Kirby Institute, University of New South Wales, New South Wales, Australia
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Desai TM, Marin M, Mason C, Melikyan GB. pH regulation in early endosomes and interferon-inducible transmembrane proteins control avian retrovirus fusion. J Biol Chem 2017; 292:7817-7827. [PMID: 28341742 DOI: 10.1074/jbc.m117.783878] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 03/22/2017] [Indexed: 01/09/2023] Open
Abstract
Enveloped viruses infect host cells by fusing their membranes with those of the host cell, a process mediated by viral glycoproteins upon binding to cognate host receptors or entering into acidic intracellular compartments. Whereas the effect of receptor density on viral infection has been well studied, the role of cell type-specific factors/processes, such as pH regulation, has not been characterized in sufficient detail. Here, we examined the effects of cell-extrinsic factors (buffer environment) and cell-intrinsic factors (interferon-inducible transmembrane proteins, IFITMs), on the pH regulation in early endosomes and on the efficiency of acid-dependent fusion of the avian sarcoma and leukosis virus (ASLV), with endosomes. First, we found that a modest elevation of external pH can raise the pH in early endosomes in a cell type-dependent manner and thereby delay the acid-induced fusion of endocytosed ASLV. Second, we observed a cell type-dependent delay between the low pH-dependent and temperature-dependent steps of viral fusion, consistent with the delayed enlargement of the fusion pore. Third, ectopic expression of IFITMs, known to potently block influenza virus fusion with late compartments, was found to only partially inhibit ASLV fusion with early endosomes. Interestingly, IFITM expression promoted virus uptake and the acidification of endosomal compartments, resulting in an accelerated fusion rate when driven by the glycosylphosphatidylinositol-anchored, but not by the transmembrane isoform of the ASLV receptor. Collectively, these results highlight the role of cell-extrinsic and cell-intrinsic factors in regulating the efficiency and kinetics of virus entry and fusion with target cells.
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Affiliation(s)
- Tanay M Desai
- From the Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia 30322 and
| | - Mariana Marin
- From the Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia 30322 and
| | - Caleb Mason
- From the Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia 30322 and
| | - Gregory B Melikyan
- From the Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia 30322 and .,the Children's Healthcare of Atlanta, Atlanta, Georgia 300322
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Sood C, Marin M, Chande A, Pizzato M, Melikyan GB. SERINC5 protein inhibits HIV-1 fusion pore formation by promoting functional inactivation of envelope glycoproteins. J Biol Chem 2017; 292:6014-6026. [PMID: 28179429 DOI: 10.1074/jbc.m117.777714] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 02/07/2017] [Indexed: 12/24/2022] Open
Abstract
The host proteins, SERINC3 and SERINC5, have been recently shown to incorporate into HIV-1 particles and compromise their ability to fuse with target cells, an effect that is antagonized by the viral Nef protein. Envelope (Env) glycoproteins from different HIV-1 isolates exhibit a broad range of sensitivity to SERINC-mediated restriction, and the mechanism by which SERINCs interfere with HIV-1 fusion remains unclear. Here, we show that incorporation of SERINC5 into virions in the absence of Nef inhibits the formation of small fusion pores between viruses and cells. Strikingly, we found that SERINC5 promotes spontaneous functional inactivation of sensitive but not resistant Env glycoproteins. Although SERINC5-Env interaction was not detected by co-immunoprecipitation, incorporation of this protein enhanced the exposure of the conserved gp41 domains and sensitized the virus to neutralizing antibodies and gp41-derived inhibitory peptides. These results imply that SERINC5 restricts HIV-1 fusion at a step prior to small pore formation by selectively inactivating sensitive Env glycoproteins, likely through altering their conformation. The increased HIV-1 sensitivity to anti-gp41 antibodies and peptides suggests that SER5 also delays refolding of the remaining fusion-competent Env trimers.
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Affiliation(s)
- Chetan Sood
- From the Department of Pediatrics, Emory University, Atlanta, Georgia 30322 and
| | - Mariana Marin
- From the Department of Pediatrics, Emory University, Atlanta, Georgia 30322 and
| | - Ajit Chande
- the Centre for Integrative Biology, University of Trento, 38123 Trento, Italy
| | - Massimo Pizzato
- the Centre for Integrative Biology, University of Trento, 38123 Trento, Italy
| | - Gregory B Melikyan
- From the Department of Pediatrics, Emory University, Atlanta, Georgia 30322 and
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Jones DM, Padilla-Parra S. The β-Lactamase Assay: Harnessing a FRET Biosensor to Analyse Viral Fusion Mechanisms. SENSORS 2016; 16:s16070950. [PMID: 27347948 PMCID: PMC4970004 DOI: 10.3390/s16070950] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 06/08/2016] [Accepted: 06/20/2016] [Indexed: 02/06/2023]
Abstract
The β-lactamase (BlaM) assay was first revealed in 1998 and was demonstrated to be a robust Förster resonance energy transfer (FRET)-based reporter system that was compatible with a range of commonly-used cell lines. Today, the BlaM assay is available commercially as a kit and can be utilised readily and inexpensively for an array of experimental procedures that require a fluorescence-based readout. One frequent application of the BlaM assay is the measurement of viral fusion—the moment at which the genetic material harboured within virus particles is released into the cytosol following successful entry. The flexibility of the system permits evaluation of not only total fusion levels, but also the kinetics of fusion. However, significant variation exists in the scientific literature regarding the methodology by which the assay is applied to viral fusion analysis, making comparison between results difficult. In this review we draw attention to the disparity of these methodologies and examine the advantages and disadvantages of each approach. Successful strategies shown to render viruses compatible with BlaM-based analyses are also discussed.
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Affiliation(s)
- Daniel M Jones
- Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK.
| | - Sergi Padilla-Parra
- Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford, OX3 7BN, UK.
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Sood C, Marin M, Mason CS, Melikyan GB. Visualization of Content Release from Cell Surface-Attached Single HIV-1 Particles Carrying an Extra-Viral Fluorescent pH-Sensor. PLoS One 2016; 11:e0148944. [PMID: 26863211 PMCID: PMC4749635 DOI: 10.1371/journal.pone.0148944] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 01/23/2016] [Indexed: 11/18/2022] Open
Abstract
HIV-1 fusion leading to productive entry has long been thought to occur at the plasma membrane. However, our previous single virus imaging data imply that, after Env engagement of CD4 and coreceptors at the cell surface, the virus enters into and fuses with intracellular compartments. We were unable to reliably detect viral fusion at the plasma membrane. Here, we implement a novel virus labeling strategy that biases towards detection of virus fusion that occurs in a pH-neutral environment-at the plasma membrane or, possibly, in early pH-neutral vesicles. Virus particles are co-labeled with an intra-viral content marker, which is released upon fusion, and an extra-viral pH sensor consisting of ecliptic pHluorin fused to the transmembrane domain of ICAM-1. This sensor fully quenches upon virus trafficking to a mildly acidic compartment, thus precluding subsequent detection of viral content release. As an interesting secondary observation, the incorporation of the pH-sensor revealed that HIV-1 particles occasionally shuttle between neutral and acidic compartments in target cells expressing CD4, suggesting a small fraction of viral particles is recycled to the plasma membrane and re-internalized. By imaging viruses bound to living cells, we found that HIV-1 content release in neutral-pH environment was a rare event (~0.4% particles). Surprisingly, viral content release was not significantly reduced by fusion inhibitors, implying that content release was due to spontaneous formation of viral membrane defects occurring at the cell surface. We did not measure a significant occurrence of HIV-1 fusion at neutral pH above this defect-mediated background loss of content, suggesting that the pH sensor may destabilize the membrane of the HIV-1 pseudovirus and, thus, preclude reliable detection of single virus fusion events at neutral pH.
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Affiliation(s)
- Chetan Sood
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Mariana Marin
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Caleb S. Mason
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Gregory B. Melikyan
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia, United States of America
- Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
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Asati A, Kachurina O, Karol A, Dhir V, Nguyen M, Parkhill R, Kouiavskaia D, Chumakov K, Warren W, Kachurin A. Fluorescence Adherence Inhibition Assay: A Novel Functional Assessment of Blocking Virus Attachment by Vaccine-Induced Antibodies. PLoS One 2016; 11:e0144261. [PMID: 26863313 PMCID: PMC4749260 DOI: 10.1371/journal.pone.0144261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 11/16/2015] [Indexed: 11/18/2022] Open
Abstract
Neutralizing antibodies induced by vaccination or natural infection play a critically important role in protection against the viral diseases. In general, neutralization of the viral infection occurs via two major pathways: pre- and post-attachment modes, the first being the most important for such infections as influenza and polio, the latter being significant for filoviruses. Neutralizing capacity of antibodies is typically evaluated by virus neutralization assays that assess reduction of viral infectivity to the target cells in the presence of functional antibodies. Plaque reduction neutralization test, microneutralization and immunofluorescent assays are often used as gold standard virus neutralization assays. However, these methods are associated with several important prerequisites such as use of live virus requiring safety precautions, tedious evaluation procedure and long assessment time. Hence, there is a need for a robust, inexpensive high throughput functional assay that can be performed rapidly using inactivated virus, without extensive safety precautions. Herein, we report a novel high throughput Fluorescence Adherence Inhibition assay (fADI) using inactivated virus labeled with fluorescent secondary antibodies virus and Vero cells or erythrocytes as targets. It requires only few hours to assess pre-attachment neutralizing capacity of donor sera. fADI assay was tested successfully on donors immunized with polio, yellow fever and influenza vaccines. To further simplify and improve the throughput of the assay, we have developed a mathematical approach for calculating the 50% titers from a single sample dilution, without the need to analyze multi-point titration curves. Assessment of pre- and post-vaccination human sera from subjects immunized with IPOL®, YF-VAX® and 2013-2014 Fluzone® vaccines demonstrated high efficiency of the assay. The results correlated very well with microneutralization assay performed independently by the FDA Center of Biologics Evaluation and Research, with plaque reduction neutralization test performed by Focus Diagnostics, and with hemaglutination inhibition assay performed in-house at Sanofi Pasteur. Taken together, fADI assay appears to be a useful high throughput functional immunoassay for assessment of antibody-related neutralization of the viral infections for which pre-attachment neutralization pathway is predominant, such as polio, influenza, yellow fever and dengue.
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Affiliation(s)
- Atul Asati
- Sanofi Pasteur VaxDesign Campus, 2501 Discovery Dr. Suite 3000, Orlando, Florida 32826, United States of America
| | - Olga Kachurina
- Sanofi Pasteur VaxDesign Campus, 2501 Discovery Dr. Suite 3000, Orlando, Florida 32826, United States of America
| | - Alex Karol
- Sanofi Pasteur VaxDesign Campus, 2501 Discovery Dr. Suite 3000, Orlando, Florida 32826, United States of America
| | - Vipra Dhir
- Sanofi Pasteur VaxDesign Campus, 2501 Discovery Dr. Suite 3000, Orlando, Florida 32826, United States of America
| | - Michael Nguyen
- Sanofi Pasteur VaxDesign Campus, 2501 Discovery Dr. Suite 3000, Orlando, Florida 32826, United States of America
| | - Robert Parkhill
- Sanofi Pasteur VaxDesign Campus, 2501 Discovery Dr. Suite 3000, Orlando, Florida 32826, United States of America
| | - Diana Kouiavskaia
- U. S. Food and Drug Administration, Center for Biologics Evaluation and Research, 10903 New Hampshire Avenue, Silver Spring, MD 20993, United States of America
| | - Konstantin Chumakov
- U. S. Food and Drug Administration, Center for Biologics Evaluation and Research, 10903 New Hampshire Avenue, Silver Spring, MD 20993, United States of America
| | - William Warren
- Sanofi Pasteur VaxDesign Campus, 2501 Discovery Dr. Suite 3000, Orlando, Florida 32826, United States of America
| | - Anatoly Kachurin
- Sanofi Pasteur VaxDesign Campus, 2501 Discovery Dr. Suite 3000, Orlando, Florida 32826, United States of America
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Latinovic OS, Medina-Moreno S, Schneider K, Gohain N, Zapata J, Pazgier M, Reitz M, Bryant J, Redfield RR. Full Length Single Chain Fc Protein (FLSC IgG1) as a Potent Antiviral Therapy Candidate: Implications for In Vivo Studies. AIDS Res Hum Retroviruses 2016; 32:178-86. [PMID: 26059995 DOI: 10.1089/aid.2015.0020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We have previously shown that FLSC, a chimeric protein containing HIV-1BAL gp120 and the D1 and D2 domains of human CD4, blocks the binding and entry of HIV-1 into target cells by occluding CCR5, the major HIV-1 coreceptor. In an effort to improve the antiviral potential of FLSC, we fused it with the hinge-CH2-CH3 region of human IgG1. The IgG moiety should increase both the affinity and stability in vivo of FLSC, due to the resultant bivalency and an extended serum half-life, thereby increasing its antiviral potency. We previously showed that (FLSC) IgG1 indeed had greater antiviral activity against T cell infections. Here we extend these results to macrophages, for which (FLSC) IgG1 has a more potent antiviral activity than FLSC alone, due in part to its higher binding affinity for CCR5. We also test both compounds in a relevant humanized mouse model and show that, as anticipated, the IgG1 moiety confers a greatly extended half-life. These data, taken together with previous results, suggest potential clinical utility for (FLSC) IgG1 and support further developmental work toward eventual clinical trials.
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Affiliation(s)
- Olga S. Latinovic
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Sandra Medina-Moreno
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Kate Schneider
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Neelakshi Gohain
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Juan Zapata
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Marzena Pazgier
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Marvin Reitz
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland
- School of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Joseph Bryant
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland
- Department of Pathology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Robert R. Redfield
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland
- School of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
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44
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Desai TM, Marin M, Sood C, Shi J, Nawaz F, Aiken C, Melikyan GB. Fluorescent protein-tagged Vpr dissociates from HIV-1 core after viral fusion and rapidly enters the cell nucleus. Retrovirology 2015; 12:88. [PMID: 26511606 PMCID: PMC4625717 DOI: 10.1186/s12977-015-0215-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 10/16/2015] [Indexed: 02/06/2023] Open
Abstract
Background HIV-1 Vpr is recruited into virions during assembly and appears to remain associated with the viral core after the reverse transcription and uncoating steps of entry. This feature has prompted the use of fluorescently labeled Vpr to visualize viral particles and to follow trafficking of post-fusion HIV-1 cores in the cytoplasm. Results Here, we tracked single pseudovirus entry and fusion and observed that fluorescently tagged Vpr gradually dissociates from post-fusion viral cores over the course of several minutes and accumulates in the nucleus. Kinetics measurements showed that fluorescent Vpr released from the cores very rapidly entered the cell nucleus. More than 10,000 Vpr molecules can be delivered into the cell nucleus within 45 min of infection by HIV-1 particles pseudotyped with the avian sarcoma and leukosis virus envelope glycoprotein. The fraction of Vpr from cell-bound viruses that accumulated in the nucleus was proportional to the extent of virus-cell fusion and was fully blocked by viral fusion inhibitors. Entry of virus-derived Vpr into the nucleus occurred independently of envelope glycoproteins or target cells. Fluorescence correlation spectroscopy revealed two forms of nuclear Vpr—monomers and very large complexes, likely involving host factors. The kinetics of viral Vpr entering the nucleus after fusion was not affected by point mutations in the capsid protein that alter the stability of the viral core. Conclusions The independence of Vpr shedding of capsid stability and its relatively rapid dissociation from post-fusion cores suggest that this process may precede capsid uncoating, which appears to occur on a slower time scale. Our results thus demonstrate that a bulk of fluorescently labeled Vpr incorporated into HIV-1 particles is released shortly after fusion. Future studies will address the question whether the quick and efficient nuclear delivery of Vpr derived from incoming viruses can regulate subsequent steps of HIV-1 infection. Electronic supplementary material The online version of this article (doi:10.1186/s12977-015-0215-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Tanay M Desai
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, GA, USA.
| | - Mariana Marin
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, GA, USA.
| | - Chetan Sood
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, GA, USA.
| | - Jiong Shi
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN, 37232, USA.
| | - Fatima Nawaz
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN, 37232, USA.
| | - Christopher Aiken
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN, 37232, USA.
| | - Gregory B Melikyan
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, GA, USA. .,Children's Healthcare of Atlanta, Atlanta, GA, USA.
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Ebolavirus Glycoprotein Directs Fusion through NPC1+ Endolysosomes. J Virol 2015; 90:605-10. [PMID: 26468524 PMCID: PMC4702577 DOI: 10.1128/jvi.01828-15] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2015] [Accepted: 10/06/2015] [Indexed: 12/31/2022] Open
Abstract
Ebolavirus, a deadly hemorrhagic fever virus, was thought to enter cells through endolysosomes harboring its glycoprotein receptor, Niemann-Pick C1. However, an alternate model was recently proposed in which ebolavirus enters through a later NPC1-negative endosome that contains two-pore Ca(2+) channel 2 (TPC2), a newly identified ebolavirus entry factor. Here, using live cell imaging, we obtained evidence that in contrast to the new model, ebolavirus enters cells through endolysosomes that contain both NPC1 and TPC2.
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46
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Jones DM, Padilla-Parra S. Imaging real-time HIV-1 virion fusion with FRET-based biosensors. Sci Rep 2015; 5:13449. [PMID: 26300212 PMCID: PMC4547133 DOI: 10.1038/srep13449] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 07/28/2015] [Indexed: 11/08/2022] Open
Abstract
We have produced a novel, simple and rapid method utilising genetically encodable FRET-based biosensors to permit the detection of HIV-1 virion fusion in living cells. These biosensors show high sensitivity both spatially and temporally, and allow the real-time recovery of HIV-1 fusion kinetics in both single cells and cell populations simultaneously.
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Affiliation(s)
- Daniel M. Jones
- Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford OX3 7BN, UK
| | - Sergi Padilla-Parra
- Division of Structural Biology, University of Oxford, The Henry Wellcome Building for Genomic Medicine, Headington, Oxford OX3 7BN, UK
- Cellular Imaging Core, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
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47
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P2X1 Receptor Antagonists Inhibit HIV-1 Fusion by Blocking Virus-Coreceptor Interactions. J Virol 2015; 89:9368-82. [PMID: 26136569 DOI: 10.1128/jvi.01178-15] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 06/23/2015] [Indexed: 01/03/2023] Open
Abstract
UNLABELLED HIV-1 Env glycoprotein-mediated fusion is initiated upon sequential binding of Env to CD4 and the coreceptor CXCR4 or CCR5. Whereas these interactions are thought to be necessary and sufficient to promote HIV-1 fusion, other host factors can modulate this process. Previous studies reported potent inhibition of HIV-1 fusion by selective P2X1 receptor antagonists, including NF279, and suggested that these receptors play a role in HIV-1 entry. Here we investigated the mechanism of antiviral activity of NF279 and found that this compound does not inhibit HIV-1 fusion by preventing the activation of P2X1 channels but effectively blocks the binding of the virus to CXCR4 or CCR5. The notion of an off-target effect of NF279 on HIV-1 fusion is supported by the lack of detectable expression of P2X1 receptors in cells used in fusion experiments and by the fact that the addition of ATP or the enzymatic depletion of ATP in culture medium does not modulate viral fusion. Importantly, NF279 fails to inhibit HIV-1 fusion with cell lines and primary macrophages when added at an intermediate stage downstream of Env-CD4-coreceptor engagement. Conversely, in the presence of NF279, HIV-1 fusion is arrested downstream of CD4 binding but prior to coreceptor engagement. NF279 also antagonizes the signaling function of CCR5, CXCR4, and another chemokine receptor, as evidenced by the suppression of calcium responses elicited by specific ligands and by recombinant gp120. Collectively, our results demonstrate that NF279 is a dual HIV-1 coreceptor inhibitor that interferes with the functional engagement of CCR5 and CXCR4 by Env. IMPORTANCE Inhibition of P2X receptor activity suppresses HIV-1 fusion and replication, suggesting that P2X signaling is involved in HIV-1 entry. However, mechanistic experiments conducted in this study imply that P2X1 receptor is not expressed in target cells or involved in viral fusion. Instead, we found that inhibition of HIV-1 fusion by a specific P2X1 receptor antagonist, NF279, is due to the blocking of virus interactions with both the CXCR4 and CCR5 coreceptors. The ability of NF279 to abrogate cellular calcium signaling induced by the respective chemokines showed that this compound acts as a dual-coreceptor antagonist. P2X1 receptor antagonists could thus represent a new class of dual-coreceptor inhibitors with a structure and a mechanism of action that are distinct from those of known HIV-1 coreceptor antagonists.
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48
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Reply to "Can HIV-1 entry sites be deduced by comparing bulk endocytosis to functional readouts for viral fusion?". J Virol 2015; 89:2986-7. [PMID: 25657215 DOI: 10.1128/jvi.03376-14] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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49
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Can HIV-1 entry sites be deduced by comparing bulk endocytosis to functional readouts for viral fusion? J Virol 2015; 89:2985. [PMID: 25657214 DOI: 10.1128/jvi.03352-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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50
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Marin M, Du Y, Giroud C, Kim JH, Qui M, Fu H, Melikyan GB. High-Throughput HIV-Cell Fusion Assay for Discovery of Virus Entry Inhibitors. Assay Drug Dev Technol 2015; 13:155-66. [PMID: 25871547 DOI: 10.1089/adt.2015.639] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
HIV-1 initiates infection by merging its envelope membrane with the target cell membrane, a process that is mediated by the viral Env glycoprotein following its sequential binding to CD4 and coreceptors, CXCR4 or CCR5. Although HIV-1 fusion has been a target for antiviral therapy, the virus has developed resistance to drugs blocking the CCR5 binding or Env refolding steps of this process. This highlights the need for novel inhibitors. Here, we adapted and optimized an enzymatic HIV-cell fusion assay, which reports the transfer of virus-encapsulated β-lactamase into the cytoplasm, to high-throughput screening (HTS) with a 384-well format. The assay was robustly performed in HTS format and was validated by the pilot screen of a small library of pharmacologically active compounds. Several hits identified by screening included a prominent cluster of purinergic receptor antagonists. Functional studies demonstrated that P2X1 receptor antagonists selectively inhibited HIV-1 fusion without affecting the fusion activity of an unrelated virus that enters cells through an endocytic route. The inhibition of HIV-cell fusion by P2X1 antagonists was not through downmodulation of the cell surface expression of CD4 or coreceptors, thus implicating P2X1 receptor in the HIV-1 fusion step. The ability of these antagonists to inhibit viruses regardless of their coreceptor (CXCR4 or CCR5) preference indicates that fusion is blocked at a late step downstream of coreceptor binding. A future large-scale screening campaign for HIV-1 fusion inhibitors, using the above functional readout, will likely reveal novel classes of inhibitors and suggest potential targets for antiviral therapy.
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Affiliation(s)
- Mariana Marin
- 1 Division of Pediatric Infectious Diseases, Emory University Children's Center , Atlanta, Georgia
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