101
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Sabo Y, Walsh D, Barry DS, Tinaztepe S, de los Santos K, Goff SP, Gundersen GG, Naghavi MH. HIV-1 induces the formation of stable microtubules to enhance early infection. Cell Host Microbe 2013; 14:535-46. [PMID: 24237699 PMCID: PMC3855456 DOI: 10.1016/j.chom.2013.10.012] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 08/27/2013] [Accepted: 10/22/2013] [Indexed: 02/05/2023]
Abstract
Stable microtubule (MT) subsets form distinct networks from dynamic MTs and acquire distinguishing posttranslational modifications, notably detyrosination and acetylation. Acting as specialized tracks for vesicle and macromolecular transport, their formation is regulated by the end-binding protein EB1, which recruits proteins that stabilize MTs. We show that HIV-1 induces the formation of acetylated and detyrosinated stable MTs early in infection. Although the MT depolymerizing agent nocodazole affected dynamic MTs, HIV-1 particles localized to nocodazole-resistant stable MTs, and infection was minimally affected. EB1 depletion or expression of an EB1 carboxy-terminal fragment that acts as a dominant-negative inhibitor of MT stabilization prevented HIV-1-induced stable MT formation and suppressed early viral infection. Furthermore, we show that the HIV-1 matrix protein targets the EB1-binding protein Kif4 to induce MT stabilization. Our findings illustrate how specialized MT-binding proteins mediate MT stabilization by HIV-1 and the importance of stable MT subsets in viral infection.
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Affiliation(s)
- Yosef Sabo
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Derek Walsh
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA
| | - Denis S. Barry
- Centre for Research in Infectious Diseases, University College Dublin, Dublin 4, Ireland
| | - Sedef Tinaztepe
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
- Department of Genetics and Development, Columbia University, New York, NY 10032, USA
| | - Kenia de los Santos
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Stephen P. Goff
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Gregg G. Gundersen
- Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA
| | - Mojgan H. Naghavi
- Department of Biochemistry and Molecular Biophysics, Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
- Centre for Research in Infectious Diseases, University College Dublin, Dublin 4, Ireland
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102
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Abstract
Apolipoprotein L1 (APOL1) is a major component of the human innate immune response against African trypanosomes. Although the mechanism of the trypanolytic activity of circulating APOL1 has been recently clarified, the intracellular function(s) of APOL1 in human cells remains poorly defined. Like that of many genes linked to host immunity, APOL1 expression is induced by proinflammatory cytokines gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α). Additionally, IFN-γ-polarized macrophages that potently restrict HIV-1 replication express APOL1, which suggests that APOL1 may contribute to HIV-1 suppression. Here, we report that APOL1 inhibits HIV-1 replication by multiple mechanisms. We found that APOL1 protein targeted HIV-1 Gag for degradation by the endolysosomal pathway. Interestingly, we found that APOL1 stimulated both endocytosis and lysosomal biogenesis by promoting nuclear localization of transcription factor EB (TFEB) and expression of TFEB target genes. Moreover, we demonstrated that APOL1 depletes cellular viral accessory protein Vif, which counteracts the host restriction factor APOBEC3G, via a pathway involving degradation of Vif in lysosomes and by secretion of Vif in microvesicles. As a result of Vif depletion by APOL1, APOBEC3G was not degraded and reduced infectivity of progeny virions. In support of this model, we also showed that endogenous expression of APOL1 in differentiated U937 monocytic cells stimulated with IFN-γ resulted in a reduced production of virus particles. This finding supports the hypothesis that induction of APOL1 contributes to HIV-1 suppression in differentiated monocytes. Deciphering the precise mechanism of APOL1-mediated HIV-1 restriction may facilitate the design of unique therapeutics to target HIV-1 replication.
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103
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MX2 is an interferon-induced inhibitor of HIV-1 infection. Nature 2013; 502:563-6. [PMID: 24121441 DOI: 10.1038/nature12653] [Citation(s) in RCA: 379] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Accepted: 09/12/2013] [Indexed: 12/24/2022]
Abstract
HIV-1 replication can be inhibited by type I interferon (IFN), and the expression of a number of gene products with anti-HIV-1 activity is induced by type I IFN. However, none of the known antiretroviral proteins can account for the ability of type I IFN to inhibit early, preintegration phases of the HIV-1 replication cycle in human cells. Here, by comparing gene expression profiles in cell lines that differ in their ability to support the inhibitory action of IFN-α at early steps of the HIV-1 replication cycle, we identify myxovirus resistance 2 (MX2) as an interferon-induced inhibitor of HIV-1 infection. Expression of MX2 reduces permissiveness to a variety of lentiviruses, whereas depletion of MX2 using RNA interference reduces the anti-HIV-1 potency of IFN-α. HIV-1 reverse transcription proceeds normally in MX2-expressing cells, but 2-long terminal repeat circular forms of HIV-1 DNA are less abundant, suggesting that MX2 inhibits HIV-1 nuclear import, or destabilizes nuclear HIV-1 DNA. Consistent with this notion, mutations in the HIV-1 capsid protein that are known, or suspected, to alter the nuclear import pathways used by HIV-1 confer resistance to MX2, whereas preventing cell division increases MX2 potency. Overall, these findings indicate that MX2 is an effector of the anti-HIV-1 activity of type-I IFN, and suggest that MX2 inhibits HIV-1 infection by inhibiting capsid-dependent nuclear import of subviral complexes.
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104
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Gaudin R, de Alencar BC, Arhel N, Benaroch P. HIV trafficking in host cells: motors wanted! Trends Cell Biol 2013; 23:652-62. [PMID: 24119663 DOI: 10.1016/j.tcb.2013.09.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 09/05/2013] [Accepted: 09/09/2013] [Indexed: 11/16/2022]
Abstract
Throughout the viral replication cycle, viral proteins, complexes, and particles need to be transported within host cells. These transport events are dependent on the host cell cytoskeleton and molecular motors. However, the mechanisms by which virus is trafficked along cytoskeleton filaments and how molecular motors are recruited and regulated to guarantee successful integration of the viral genome and production of new viruses has only recently begun to be understood. Recent studies on HIV have identified specific molecular motors involved in the trafficking of these viral particles. Here we review recent literature on the transport of HIV components in the cell, provide evidence for the identity and role of molecular motors in this process, and highlight how these trafficking events may be related to those occurring with other viruses.
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Affiliation(s)
- Raphaël Gaudin
- Institut Curie, Centre de Recherche, 26 rue d'Ulm, 75248 Paris Cedex 05, France; INSERM, U932, 26 rue d'Ulm, 75248 Paris Cedex 05, France
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105
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Effect of multimerization on membrane association of Rous sarcoma virus and HIV-1 matrix domain proteins. J Virol 2013; 87:13598-608. [PMID: 24109216 DOI: 10.1128/jvi.01659-13] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In most retroviruses, plasma membrane (PM) association of the Gag structural protein is a critical step in viral assembly, relying in part on interaction between the highly basic Gag MA domain and the negatively charged inner leaflet of the PM. Assembly is thought to begin with Gag dimerization followed by multimerization, resulting in a hexameric lattice. To directly address the role of multimerization in membrane binding, we fused the MA domains of Rous sarcoma virus (RSV) and HIV-1 to the chemically inducible dimerization domain FK506-binding protein (FKBP) or to the hexameric protein CcmK4 from cyanobacteria. The cellular localization of the resulting green fluorescent protein (GFP)-tagged chimeric proteins was examined by fluorescence imaging, and the association of the proteins with liposomes was quantified by flotation in sucrose gradients, following synthesis in a reticulocyte extract or as purified proteins. Four lipid compositions were tested, representative of liposomes commonly reported in flotation experiments. By themselves, GFP-tagged RSV and HIV-1 MA proteins were largely cytoplasmic, but both hexamerized proteins were highly concentrated at the PM. Dimerization led to partial PM localization for HIV-1 MA. These in vivo effects of multimerization were reproduced in vitro. In flotation analyses, the intact RSV and HIV-1 Gag proteins were more similar to multimerized MA than to monomeric MA. RNA is reported to compete with acidic liposomes for HIV-1 Gag binding, and thus we also examined the effects of RNase treatment or tRNA addition on flotation. tRNA competed with liposomes in the case of some but not all lipid compositions and ionic strengths. Taken together, our results further underpin the model that multimerization is critical for PM association of retroviral Gag proteins. In addition, they suggest that the modulation of membrane binding by RNA, as previously reported for HIV-1, may not hold for RSV.
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106
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Cornall A, Mak J, Greenway A, Tachedjian G. HIV-1 infection of T cells and macrophages are differentially modulated by virion-associated Hck: a Nef-dependent phenomenon. Viruses 2013; 5:2235-52. [PMID: 24051604 PMCID: PMC3798898 DOI: 10.3390/v5092235] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Revised: 09/01/2013] [Accepted: 09/12/2013] [Indexed: 12/18/2022] Open
Abstract
The proline repeat motif (PxxP) of Nef is required for interaction with the SH3 domains of macrophage-specific Src kinase Hck. However, the implication of this interaction for viral replication and infectivity in macrophages and T lymphocytes remains unclear. Experiments in HIV-1 infected macrophages confirmed the presence of a Nef:Hck complex which was dependent on the Nef proline repeat motif. The proline repeat motif of Nef also enhanced both HIV-1 infection and replication in macrophages, and was required for incorporation of Hck into viral particles. Unexpectedly, wild-type Hck inhibited infection of macrophages, but Hck was shown to enhance infection of primary T lymphocytes. These results indicate that the interaction between Nef and Hck is important for Nef-dependent modulation of viral infectivity. Hck-dependent enhancement of HIV-1 infection of T cells suggests that Nef-Hck interaction may contribute to the spread of HIV-1 infection from macrophages to T cells by modulating events in the producer cell, virion and target cell.
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Affiliation(s)
- Alyssa Cornall
- Centre for Biomedical Research, Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne 3004, Victoria, Australia; E-Mails: (A.C.); (A.G.)
- Regional HPV Labnet Reference Laboratory, Department of Microbiology and Infectious Diseases, The Royal Women’s Hospital, Parkville 3052, Victoria, Australia
- Murdoch Children’s Research Institute, Parkville 3052, Victoria, Australia
| | - Johnson Mak
- School of Medicine, Faculty of Health, Deakin University, Geelong 3220, Victoria, Australia; E-Mail:
- Commonwealth Scientific and Industrial Research Organisation, Livestock Industries, Australian Animal Health Laboratory, Geelong 3220, Victoria, Australia
| | - Alison Greenway
- Centre for Biomedical Research, Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne 3004, Victoria, Australia; E-Mails: (A.C.); (A.G.)
| | - Gilda Tachedjian
- Centre for Biomedical Research, Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne 3004, Victoria, Australia; E-Mails: (A.C.); (A.G.)
- Department of Microbiology, Monash University, Clayton 3168, Victoria, Australia
- Department of Infectious Diseases, Monash University, Melbourne 3004, Victoria, Australia
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +61-3-9282-2256; Fax: +61-3-9282-2100
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107
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Mlcochova P, Pelchen-Matthews A, Marsh M. Organization and regulation of intracellular plasma membrane-connected HIV-1 assembly compartments in macrophages. BMC Biol 2013; 11:89. [PMID: 23915020 PMCID: PMC3751737 DOI: 10.1186/1741-7007-11-89] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 07/26/2013] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND In HIV-1-infected human monocyte-derived macrophages (MDMs), virus particles assemble primarily on intracellularly sequestered plasma membrane domains termed intracellular plasma membrane-connected compartments (IPMCs). Despite their clear role in virus formation, little is known of the organization, composition, dynamics or function of these compartments. RESULTS We have used amphipathic membrane dyes to reveal the complex three-dimensional structure of IPMCs in whole MDMs and to visualize connections between IPMCs and the cell surface. The observation of similar IPMC structures in both infected and uninfected cells indicates that these compartments are not induced by virus infection, but are present constitutively in MDMs. By expressing a phospholipase Cδ pleckstrin homology domain linked to green fluorescent protein, we demonstrate that IPMCs contain phosphatidylinositol 4,5-bisphosphate. Live cell imaging of cells expressing this probe shows that IPMCs are dynamic, but relatively stable, sub-domains of the plasma membrane. As recent electron microscopy studies indicated that portions of IPMCs are coated with β2 integrin-containing focal adhesion-like complexes linked to actin, we investigated whether the actin cytoskeleton is required for the organization of IPMCs. In MDMs treated with the actin polymerization inhibitor latrunculin, the normally compact IPMCs dispersed into smaller structures that remained connected to the plasma membrane. Moreover, latrunculin enhanced the release of preformed, mature HIV-1 particles from infected MDMs. CONCLUSIONS IPMCs are constitutive features of MDMs that are continuous with the plasma membrane and are used as unique sites for the assembly of new virions following infection by HIV-1. A functionally intact actin cytoskeleton is required to maintain the organization of the IPMCs and, in HIV-1-infected cells, perturbation of the actin cytoskeleton influences both the organization of the compartment and the release of sequestered virus.
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Affiliation(s)
- Petra Mlcochova
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Annegret Pelchen-Matthews
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Mark Marsh
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
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108
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Malbec M, Sourisseau M, Guivel-Benhassine F, Porrot F, Blanchet F, Schwartz O, Casartelli N. HIV-1 Nef promotes the localization of Gag to the cell membrane and facilitates viral cell-to-cell transfer. Retrovirology 2013; 10:80. [PMID: 23899341 PMCID: PMC3734038 DOI: 10.1186/1742-4690-10-80] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 07/26/2013] [Indexed: 11/16/2022] Open
Abstract
Background Newly synthesized HIV-1 particles assemble at the plasma membrane of infected cells, before being released as free virions or being transferred through direct cell-to-cell contacts to neighboring cells. Localization of HIV-1 Gag precursor at the cell membrane is necessary and sufficient to trigger viral assembly, whereas the GagPol precursor is additionally required to generate a fully matured virion. HIV-1 Nef is an accessory protein that optimizes viral replication through partly defined mechanisms. Whether Nef modulates Gag and/or GagPol localization and assembly at the membrane and facilitates viral cell-to-cell transfer has not been extensively characterized so far. Results We report that Nef increases the total amount of Gag proteins present in infected cells, and promotes Gag localization at the cell membrane. Moreover, the processing of p55 into p24 is improved in the presence of Nef. We also examined the effect of Nef during HIV-1 cell-to-cell transfer. We show that without Nef, viral transfer through direct contacts between infected cells and target cells is impaired. With a nef-deleted virus, the number of HIV-1 positive target cells after a short 2h co-culture is reduced, and viral material transferred to uninfected cells is less matured. At later time points, this defect is associated with a reduction in the productive infection of new target cells. Conclusions Our results highlight a previously unappreciated role of Nef during the viral replication cycle. Nef promotes HIV-1 Gag membrane localization and processing, and facilitates viral cell-to-cell transfer.
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Affiliation(s)
- Marine Malbec
- Département de Virologie, Institut Pasteur, Unité Virus et Immunité, 28 rue du Docteur Roux, Paris F-75015, France
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109
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Sundquist WI, Kräusslich HG. HIV-1 assembly, budding, and maturation. Cold Spring Harb Perspect Med 2013; 2:a006924. [PMID: 22762019 DOI: 10.1101/cshperspect.a006924] [Citation(s) in RCA: 517] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A defining property of retroviruses is their ability to assemble into particles that can leave producer cells and spread infection to susceptible cells and hosts. Virion morphogenesis can be divided into three stages: assembly, wherein the virion is created and essential components are packaged; budding, wherein the virion crosses the plasma membrane and obtains its lipid envelope; and maturation, wherein the virion changes structure and becomes infectious. All of these stages are coordinated by the Gag polyprotein and its proteolytic maturation products, which function as the major structural proteins of the virus. Here, we review our current understanding of the mechanisms of HIV-1 assembly, budding, and maturation, starting with a general overview and then providing detailed descriptions of each of the different stages of virion morphogenesis.
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Affiliation(s)
- Wesley I Sundquist
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah, USA.
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110
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Dynamics of HIV-containing compartments in macrophages reveal sequestration of virions and transient surface connections. PLoS One 2013; 8:e69450. [PMID: 23922713 PMCID: PMC3726685 DOI: 10.1371/journal.pone.0069450] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 06/09/2013] [Indexed: 11/19/2022] Open
Abstract
During HIV pathogenesis, infected macrophages behave as “viral reservoirs” that accumulate and retain virions within dedicated internal Virus-Containing Compartments (VCCs). The nature of VCCs remains ill characterized and controversial. Using wild-type HIV-1 and a replication-competent HIV-1 carrying GFP internal to the Gag precursor, we analyzed the biogenesis and evolution of VCCs in primary human macrophages. VCCs appear roughly 14 hours after viral protein synthesis is detected, initially contain few motile viral particles, and then mature to fill up with virions that become packed and immobile. The amount of intracellular Gag, the proportion of dense VCCs, and the density of viral particles in their lumen increased with time post-infection. In contrast, the secretion of virions, their infectivity and their transmission to T cells decreased overtime, suggesting that HIV-infected macrophages tend to pack and retain newly formed virions into dense compartments. A minor proportion of VCCs remains connected to the plasma membrane overtime. Surprisingly, live cell imaging combined with correlative light and electron microscopy revealed that such connections can be transient, highlighting their dynamic nature. Together, our results shed light on the late phases of the HIV-1 cycle and reveal some of its macrophage specific features.
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111
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Abstract
Lentiviruses are characterized by their ability to infect resting cells, such as CD4 T cells, macrophages and dendritic cells (DC). Cells of myeloid lineage, which herein we include including monocytes, macrophages, and dendritic cells, play a pivotal role in HIV infection by not only promoting transmission and spread but also serving as viral reservoirs. However, the recent discovery of the HIV restriction factor SAMHD1 within myeloid cells has again led us to question the role of this lineage both in HIV transmission and pathogenesis. Herein we will summarize what the potential role of myeloid cells in HIV pathogenesis is and how recent observations have or haven't reshaped this view. Finally we highlight the idea that cells of myeloid lineage are quality rather than quantity HIV substrates. Thus, whilst is may indeed be difficult for a lentivirus like HIV to infect a resting cell like a macrophage and/or Dendritic cell, there are significant benefits in doing so, even at low frequency.
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Affiliation(s)
- Anupriya Aggarwal
- Laboratory of HIV Biology, Immunovirology and Pathogenesis Program, The Kirby Institute, University of New South Wales, Kensington, NSW, 2010, Australia
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112
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Iordanskiy S, Santos S, Bukrinsky M. Nature, nurture and HIV: The effect of producer cell on viral physiology. Virology 2013; 443:208-13. [PMID: 23747196 DOI: 10.1016/j.virol.2013.05.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 04/23/2013] [Accepted: 05/15/2013] [Indexed: 01/13/2023]
Abstract
Macrophages and CD4-positive T lymphocytes are the major targets and producers of HIV-1. While the molecular details underlying HIV replication in macrophages and T cells become better understood, it remains unclear whether viruses produced by these target cells differ in their biological properties. Recent reports suggest that HIV virions incorporate a large number of producer cell proteins and lipids which have an effect on subsequent viral replication in newly infected cells. The identity and abundance of these incorporated factors varies between different types of producer cells, suggesting that they may influence the replication capacity and pathogenic activity of the virions produced by T cells and macrophages.
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Affiliation(s)
- Sergey Iordanskiy
- Department of Microbiology, Immunology and Tropical Medicine, School of Medicine and Health Sciences, George Washington University, 2300 I Street NW, Ross Hall, Washington, DC 20037, USA.
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113
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Tan J, Sattentau QJ. The HIV-1-containing macrophage compartment: a perfect cellular niche? Trends Microbiol 2013; 21:405-12. [PMID: 23735804 DOI: 10.1016/j.tim.2013.05.001] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 04/29/2013] [Accepted: 05/06/2013] [Indexed: 12/15/2022]
Abstract
Macrophages are a major target of HIV-1 infection and are believed to act as viral reservoirs and mediators of HIV-1-associated neurological damage. These pathological roles may be associated with the ability of the virus to assemble and accumulate in apparently intracellular compartments in macrophages. These so-called virus-containing compartments were initially thought to be late endosomes or multivesicular bodies, but it has since been shown that they are distinct structures that have complex three-dimensional morphology, a unique set of protein markers, and features such as a near-neutral pH and frequent connections to the extracellular milieu. These features appear to protect HIV-1 from hostile elements both within and outside the cell. This review discusses the cellular and molecular characteristics of HIV-1-containing compartments in macrophages and how they offer a safe haven for the virus, with important consequences for pathogenesis.
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Affiliation(s)
- Joshua Tan
- The Sir William Dunn School of Pathology, The University of Oxford, Oxford OX13RE, UK
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114
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Santos da Silva E, Mulinge M, Perez Bercoff D. The frantic play of the concealed HIV envelope cytoplasmic tail. Retrovirology 2013; 10:54. [PMID: 23705972 PMCID: PMC3686653 DOI: 10.1186/1742-4690-10-54] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 05/01/2013] [Indexed: 11/18/2022] Open
Abstract
Lentiviruses have unusually long envelope (Env) cytoplasmic tails, longer than those of other retroviruses. Whereas the Env ectodomain has received much attention, the gp41 cytoplasmic tail (gp41-CT) is one of the least studied parts of the virus. It displays relatively high conservation compared to the rest of Env. It has been long established that the gp41-CT interacts with the Gag precursor protein to ensure Env incorporation into the virion. The gp41-CT contains distinct motifs and domains that mediate both intensive Env intracellular trafficking and interactions with numerous cellular and viral proteins, optimizing viral infectivity. Although they are not fully understood, a multiplicity of interactions between the gp41-CT and cellular factors have been described over the last decade; these interactions illustrate how Env expression and incorporation into virions is a finely tuned process that has evolved to best exploit the host system with minimized genetic information. This review addresses the structure and topology of the gp41-CT of lentiviruses (mainly HIV and SIV), their domains and believed functions. It also considers the cellular and viral proteins that have been described to interact with the gp41-CT, with a particular focus on subtype-related polymorphisms.
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115
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McNatt MW, Zang T, Bieniasz PD. Vpu binds directly to tetherin and displaces it from nascent virions. PLoS Pathog 2013; 9:e1003299. [PMID: 23633949 PMCID: PMC3635990 DOI: 10.1371/journal.ppat.1003299] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Accepted: 02/25/2013] [Indexed: 12/27/2022] Open
Abstract
Tetherin (Bst2/CD317/HM1.24) is an interferon-induced antiviral host protein that inhibits the release of many enveloped viruses by tethering virions to the cell surface. The HIV-1 accessory protein, Vpu, antagonizes Tetherin through a variety of proposed mechanisms, including surface downregulation and degradation. Previous studies have demonstrated that mutation of the transmembrane domains (TMD) of both Vpu and Tetherin affect antagonism, but it is not known whether Vpu and Tetherin bind directly to each other. Here, we use cysteine-scanning mutagenesis coupled with oxidation-induced cross-linking to demonstrate that Vpu and Tetherin TMDs bind directly to each other in the membranes of living cells and to map TMD residues that contact each other. We also reveal a property of Vpu, namely the ability to displace Tetherin from sites of viral assembly, which enables Vpu to exhibit residual Tetherin antagonist activity in the absence of surface downregulation or degradation. Elements in the cytoplasmic tail domain (CTD) of Vpu mediate this displacement activity, as shown by experiments in which Vpu CTD fragments were directly attached to Tetherin in the absence of the TMD. In particular, the C-terminal α-helix (H2) of Vpu CTD is sufficient to remove Tetherin from sites of viral assembly and is necessary for full Tetherin antagonist activity. Overall, these data demonstrate that Vpu and Tetherin interact directly via their transmembrane domains enabling activities present in the CTD of Vpu to remove Tetherin from sites of viral assembly.
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Affiliation(s)
- Matthew W. McNatt
- Howard Hughes Medical Institute, Aaron Diamond AIDS Research Center and Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
| | - Trinity Zang
- Howard Hughes Medical Institute, Aaron Diamond AIDS Research Center and Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
| | - Paul D. Bieniasz
- Howard Hughes Medical Institute, Aaron Diamond AIDS Research Center and Laboratory of Retrovirology, The Rockefeller University, New York, New York, United States of America
- * E-mail:
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116
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Basic residues in the matrix domain and multimerization target murine leukemia virus Gag to the virological synapse. J Virol 2013; 87:7113-26. [PMID: 23616653 DOI: 10.1128/jvi.03263-12] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Murine leukemia virus (MLV) can efficiently spread in tissue cultures by polarizing assembly to virological synapses. The viral envelope glycoprotein (Env) establishes cell-cell contacts and subsequently recruits Gag by a process that depends on its cytoplasmic tail. MLV Gag is recruited to virological synapses through the matrix domain (MA) (J. Jin, F. Li, and W. Mothes, J. Virol. 85:7672-7682, 2011). However, how MA targets Gag to sites of cell-cell contact remains unknown. Here we report that basic residues within MA are critical for directing MLV Gag to virological synapses. Alternative membrane targeting domains (MTDs) containing multiple basic residues can efficiently substitute MA to direct polarized assembly. Similarly, mutations in the polybasic cluster of MA that disrupt Gag polarization can be rescued by N-terminal addition of MTDs containing basic residues. MTDs containing basic residues alone fail to be targeted to the virological synapse. Systematic deletion experiments reveal that domains within Gag known to mediate Gag multimerization are also required. Thus, our data predict the existence of a specific "acidic" interface at virological synapses that mediates the recruitment of MLV Gag via the basic cluster of MA and Gag multimerization.
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117
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Hütter S, Zurnic I, Lindemann D. Foamy virus budding and release. Viruses 2013; 5:1075-98. [PMID: 23575110 PMCID: PMC3705266 DOI: 10.3390/v5041075] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/25/2013] [Accepted: 03/29/2013] [Indexed: 12/21/2022] Open
Abstract
Like all other viruses, a successful egress of functional particles from infected cells is a prerequisite for foamy virus (FV) spread within the host. The budding process of FVs involves steps, which are shared by other retroviruses, such as interaction of the capsid protein with components of cellular vacuolar protein sorting (Vps) machinery via late domains identified in some FV capsid proteins. Additionally, there are features of the FV budding strategy quite unique to the spumaretroviruses. This includes secretion of non-infectious subviral particles and a strict dependence on capsid-glycoprotein interaction for release of infectious virions from the cells. Virus-like particle release is not possible since FV capsid proteins lack a membrane-targeting signal. It is noteworthy that in experimental systems, the important capsid-glycoprotein interaction could be bypassed by fusing heterologous membrane-targeting signals to the capsid protein, thus enabling glycoprotein-independent egress. Aside from that, other systems have been developed to enable envelopment of FV capsids by heterologous Env proteins. In this review article, we will summarize the current knowledge on FV budding, the viral components and their domains involved as well as alternative and artificial ways to promote budding of FV particle structures, a feature important for alteration of target tissue tropism of FV-based gene transfer systems.
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Affiliation(s)
- Sylvia Hütter
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, Dresden 01307, Germany; E-Mails: (S.H); (I.Z.)
- DFG-Center for Regenerative Therapies Dresden (CRTD)—Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, Dresden 01307, Germany
| | - Irena Zurnic
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, Dresden 01307, Germany; E-Mails: (S.H); (I.Z.)
- DFG-Center for Regenerative Therapies Dresden (CRTD)—Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, Dresden 01307, Germany
| | - Dirk Lindemann
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, Dresden 01307, Germany; E-Mails: (S.H); (I.Z.)
- DFG-Center for Regenerative Therapies Dresden (CRTD)—Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, Dresden 01307, Germany
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +49-351458-6210; Fax: +49-351-458-6310
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118
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Lin J, Hoppe AD. Uniform total internal reflection fluorescence illumination enables live cell fluorescence resonance energy transfer microscopy. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2013; 19:350-9. [PMID: 23472941 DOI: 10.1017/s1431927612014420] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Fluorescence resonance energy transfer (FRET) microscopy is a powerful technique to quantify dynamic protein-protein interactions in live cells. Total internal reflection fluorescence (TIRF) microscopy can selectively excite molecules within about 150 nm of the glass-cell interface. Recently, these two approaches were combined to enable high-resolution FRET imaging on the adherent surface of living cells. Here, we show that interference fringing of the coherent laser excitation used in TIRF creates lateral heterogeneities that impair quantitative TIRF-FRET measurements. We overcome this limitation by using a two-dimensional scan head to rotate laser beams for donor and acceptor excitation around the back focal plane of a high numerical aperture objective. By setting different radii for the circles traced out by each laser in the back focal plane, the penetration depth was corrected for different wavelengths. These modifications quell spatial variations in illumination and permit calibration for quantitative TIRF-FRET microscopy. The capability of TIRF-FRET was demonstrated by imaging assembled cyan and yellow fluorescent protein-tagged HIV-Gag molecules in single virions on the surfaces of living cells. These interactions are shown to be distinct from crowding of HIV-Gag in lipid rafts.
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Affiliation(s)
- Jia Lin
- Department of Chemistry and Biochemistry, South Dakota State University, Brookings, SD 57007, USA
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119
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Wilson SJ, Schoggins JW, Zang T, Kutluay SB, Jouvenet N, Alim MA, Bitzegeio J, Rice CM, Bieniasz PD. Inhibition of HIV-1 particle assembly by 2',3'-cyclic-nucleotide 3'-phosphodiesterase. Cell Host Microbe 2013; 12:585-97. [PMID: 23084924 DOI: 10.1016/j.chom.2012.08.012] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 07/16/2012] [Accepted: 08/31/2012] [Indexed: 10/27/2022]
Abstract
The expression of hundreds of interferon-stimulated genes (ISGs) causes the cellular "antiviral state" in which the replication of many viruses, including HIV-1, is attenuated. We conducted a screen for ISGs that inhibit HIV-1 virion production and found that 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNP), a membrane-associated protein with unknown function in mammals has this property. CNP binds to the structural protein Gag and blocks HIV-1 particle assembly after Gag and viral RNA have associated with the plasma membrane. Several primate lentiviruses are CNP-sensitive, and CNP sensitivity/resistance is determined by a single, naturally dimorphic, codon (E/K40) in the matrix domain of Gag. Like other antiretroviral proteins, CNP displays interspecies variation in antiviral activity. Mice encode an inactive CNP variant and a single amino acid difference in murine versus human CNP determines Gag binding and antiviral activity. Some cell types express high levels of CNP and we speculate that CNP evolved to restrict lentivirus replication therein.
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Affiliation(s)
- Sam J Wilson
- Aaron Diamond AIDS Research Center, The Rockefeller University, New York, NY 10016, USA
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120
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Trio engagement via plasma membrane phospholipids and the myristoyl moiety governs HIV-1 matrix binding to bilayers. Proc Natl Acad Sci U S A 2013; 110:3525-30. [PMID: 23401539 DOI: 10.1073/pnas.1216655110] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Localization of the HIV type-1 (HIV-1) Gag protein on the plasma membrane (PM) for virus assembly is mediated by specific interactions between the N-terminal myristoylated matrix (MA) domain and phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P(2)]. The PM bilayer is highly asymmetric, and this asymmetry is considered crucial in cell function. In a typical mammalian cell, the inner leaflet of the PM is enriched in phosphatidylserine (PS) and phosphatidylethanolamine (PE) and contains minor populations of phosphatidylcholine (PC) and PI(4,5)P(2). There is strong evidence that efficient binding of HIV-1 Gag to membranes is sensitive not only to lipid composition and net negative charge, but also to the hydrophobic character of the acyl chains. Here, we show that PS, PE, and PC interact directly with MA via a region that is distinct from the PI(4,5)P(2) binding site. Our NMR data also show that the myristoyl group is readily exposed when MA is bound to micelles or bicelles. Strikingly, our structural data reveal a unique binding mode by which the 2'-acyl chain of PS, PE, and PC lipids is buried in a hydrophobic pocket whereas the 1'-acyl chain is exposed. Sphingomyelin, a major lipid localized exclusively on the outer layer of the PM, does not bind to MA. Our findings led us to propose a trio engagement model by which HIV-1 Gag is anchored to the PM via the 1'-acyl chains of PI(4,5)P(2) and PS/PE/PC and the myristoyl group, which collectively bracket a basic patch projecting toward the polar leaflet of the membrane.
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121
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Abstract
Proteins bud from cells in small single-membraned vesicles (~50–250 nm) that have the same topology as the cell. Known variously as exosomes and microvesicles (EMVs), these extracellular organelles are enriched for specific proteins, lipids, carbohydrates and nucleic acids. EMV biogenesis plays critical roles in protein quality control and cell polarity, and, once released, EMVs can transmit signals and molecules to neighbouring cells via a non-viral pathway of intercellular vesicle traffic. In the present paper, we discuss the cis-acting targeting signals that target proteins to EMVs and mediate protein budding from the cell.
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122
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Efavirenz enhances HIV-1 gag processing at the plasma membrane through Gag-Pol dimerization. J Virol 2013; 87:3348-60. [PMID: 23302874 DOI: 10.1128/jvi.02306-12] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Efavirenz (EFV), a nonnucleoside reverse transcriptase (RT) inhibitor, also inhibits HIV-1 particle release through enhanced Gag/Gag-Pol processing by protease (PR). To better understand the mechanisms of the EFV-mediated enhancement of Gag processing, we examined the intracellular localization of Gag/Gag-Pol processing products and their precursors. Confocal microscopy revealed that in the presence of EFV, the N-terminal p17 matrix (p17MA) fragment was uniformly distributed at the plasma membrane (PM) but the central p24 capsid (p24CA) and the Pol-encoded RT antigens were diffusely distributed in the cytoplasm, and all of the above were observed in puncta at the PM in the absence of EFV. EFV did not impair PM targeting of Gag/Gag-Pol precursors. Membrane flotation analysis confirmed these findings. Such uniform distribution of p17MA at the PM was not seen by overexpression of Gag-Pol and was suppressed when EFV-resistant HIV-1 was used. Forster's fluorescence resonance energy transfer assay revealed that Gag-Pol precursor dimerization occurred mainly at the PM and that EFV induced a significant increase of the Gag-Pol dimerization at the PM. Gag-Pol dimerization was not enhanced when HIV-1 contained the EFV resistance mutation in RT. Bacterial two-hybrid assay showed that EFV enhanced the dimerization of PR-RT fragments and restored the dimerization impaired by the dimerization-defective mutation in the RT tryptophan repeat motif but not that impaired by the mutation at the PR dimer interface. Collectively, our data indicate that EFV enhances Gag-Pol precursor dimerization, likely after PM targeting but before complete particle assembly, resulting in uniform distribution of p17MA to and dissociation of p24CA and RT from the PM.
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123
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Finzi A, Perlman M, Bourgeois-Daigneault MC, Thibodeau J, Cohen ÉA. Major histocompatibility complex class-II molecules promote targeting of human immunodeficiency virus type 1 virions in late endosomes by enhancing internalization of nascent particles from the plasma membrane. Cell Microbiol 2012; 15:809-22. [PMID: 23170932 DOI: 10.1111/cmi.12074] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 11/08/2012] [Accepted: 11/14/2012] [Indexed: 12/15/2022]
Abstract
Productive assembly of human immunodeficiency virus type 1 (HIV-1) takes place, primarily, at the plasma membrane. However, depending on the cell types, a significant proportion of nascent virus particles are internalized and routed to late endosomes. We previously reported that expression of human leucocyte antigen (HLA)-DR promoted a redistribution of Gag in late endosomes and an increased detection of mature virions in these compartments in HeLa and human embryonic kidney 293T model cell lines. Although this redistribution of Gag resulted in a marked decrease of HIV-1 release, the underlying mechanism remained undefined. Here, we provide evidence that expression of HLA-DR at the cell surface induces a redistribution of mature Gag products into late endosomes by enhancing nascent HIV-1 particle internalization from the plasma membrane through a process that relies on the presence of intact HLA-DR α and β-chain cytosolic tails. These findings raise the possibility that major histocompatibility complex class-II molecules might influence endocytic events at the plasma membrane and as a result promote endocytosis of progeny HIV-1 particles.
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Affiliation(s)
- Andrés Finzi
- Laboratory of Human Retrovirology, Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec, Canada
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124
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Jouvenet N. Dynamics of ESCRT proteins. Cell Mol Life Sci 2012; 69:4121-33. [PMID: 22669260 PMCID: PMC11114710 DOI: 10.1007/s00018-012-1035-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2012] [Revised: 05/11/2012] [Accepted: 05/16/2012] [Indexed: 10/28/2022]
Abstract
Proteins of the ESCRT (endosomal sorting complex required for transport) complex function in membrane fission processes, such as multivesicular body (MVBs) formation, the terminal stages of cytokinesis, and separation of enveloped viruses from the plasma membrane. In mammalian cells, the machinery consists of a network of more than 20 proteins, organized into three complexes (ESCRT-I, -II, and -III), and other associated proteins such as the ATPase vacuolar protein sorting 4 (Vps4). Early biochemical studies of MVBs biogenesis in yeast support a model of sequential recruitment of ESCRT complexes on membranes. Live-cell imaging of ESCRT protein dynamics during viral budding and cytokinesis now reveal that this long-standing model of sequential assembly and disassembly holds true in mammalian cells.
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125
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Helma J, Schmidthals K, Lux V, Nüske S, Scholz AM, Kräusslich HG, Rothbauer U, Leonhardt H. Direct and dynamic detection of HIV-1 in living cells. PLoS One 2012; 7:e50026. [PMID: 23209635 PMCID: PMC3509150 DOI: 10.1371/journal.pone.0050026] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Accepted: 10/15/2012] [Indexed: 12/22/2022] Open
Abstract
In basic and applied HIV research, reliable detection of viral components is crucial to monitor progression of infection. While it is routine to detect structural viral proteins in vitro for diagnostic purposes, it previously remained impossible to directly and dynamically visualize HIV in living cells without genetic modification of the virus. Here, we describe a novel fluorescent biosensor to dynamically trace HIV-1 morphogenesis in living cells. We generated a camelid single domain antibody that specifically binds the HIV-1 capsid protein (CA) at subnanomolar affinity and fused it to fluorescent proteins. The resulting fluorescent chromobody specifically recognizes the CA-harbouring HIV-1 Gag precursor protein in living cells and is applicable in various advanced light microscopy systems. Confocal live cell microscopy and super-resolution microscopy allowed detection and dynamic tracing of individual virion assemblies at the plasma membrane. The analysis of subcellular binding kinetics showed cytoplasmic antigen recognition and incorporation into virion assembly sites. Finally, we demonstrate the use of this new reporter in automated image analysis, providing a robust tool for cell-based HIV research.
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Affiliation(s)
- Jonas Helma
- Department of Biology II, Ludwig Maximilians University Munich, Planegg-Martinsried, Germany
- Center for Integrated Protein Science, Munich, Germany
| | - Katrin Schmidthals
- Department of Biology II, Ludwig Maximilians University Munich, Planegg-Martinsried, Germany
- ChromoTek GmbH, Planegg-Martinsried, Germany
| | - Vanda Lux
- Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
| | - Stefan Nüske
- Livestock Center of the Faculty of Veterinary Medicine, Ludwig Maximilians University Munich, Oberschleissheim, Germany
| | - Armin M. Scholz
- Livestock Center of the Faculty of Veterinary Medicine, Ludwig Maximilians University Munich, Oberschleissheim, Germany
| | - Hans-Georg Kräusslich
- Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
| | - Ulrich Rothbauer
- Department of Biology II, Ludwig Maximilians University Munich, Planegg-Martinsried, Germany
- ChromoTek GmbH, Planegg-Martinsried, Germany
- * E-mail: (UR); (HL)
| | - Heinrich Leonhardt
- Department of Biology II, Ludwig Maximilians University Munich, Planegg-Martinsried, Germany
- Center for Integrated Protein Science, Munich, Germany
- * E-mail: (UR); (HL)
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126
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Alfadhli A, McNett H, Eccles J, Tsagli S, Noviello C, Sloan R, López CS, Peyton DH, Barklis E. Analysis of small molecule ligands targeting the HIV-1 matrix protein-RNA binding site. J Biol Chem 2012; 288:666-76. [PMID: 23135280 DOI: 10.1074/jbc.m112.399865] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The matrix domain (MA) of the HIV-1 precursor Gag (PrGag) protein directs PrGag proteins to assembly sites at the plasma membrane by virtue of its affinity to the phospholipid, phosphatidylinositol-4,5-bisphosphate (PI(4,5)P(2)). MA also binds to RNA at a site that overlaps its PI(4,5)P(2) site, suggesting that RNA binding may protect MA from associating with inappropriate cellular membranes prior to PrGag delivery to the PM. Based on this, we have developed an assay in which small molecule competitors to MA-RNA binding can be characterized, with the assumption that such compounds might interfere with essential MA functions and help elucidate additional features of MA binding. Following this approach, we have identified four compounds, including three thiadiazolanes, that compete with RNA for MA binding. We also have identified MA residues involved in thiadiazolane binding and found that they overlap the MA PI(4,5)P(2) and RNA sites. Cell culture studies demonstrated that thiadiazolanes inhibit HIV-1 replication but are associated with significant levels of toxicity. Nevertheless, these observations provide new insights into MA binding and pave the way for the development of antivirals that target the HIV-1 matrix domain.
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Affiliation(s)
- Ayna Alfadhli
- Vollum Institute and Department of Microbiology, Oregon Health and Science University, Portland, Oregon 97201-3098, USA
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127
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Hollinshead M, Johns HL, Sayers CL, Gonzalez-Lopez C, Smith GL, Elliott G. Endocytic tubules regulated by Rab GTPases 5 and 11 are used for envelopment of herpes simplex virus. EMBO J 2012; 31:4204-20. [PMID: 22990238 PMCID: PMC3492727 DOI: 10.1038/emboj.2012.262] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Accepted: 08/24/2012] [Indexed: 02/08/2023] Open
Abstract
Enveloped viruses employ diverse and complex strategies for wrapping at cellular membranes, many of which are poorly understood. Here, an ultrastructural study of herpes simplex virus 1 (HSV1)-infected cells revealed envelopment in tubular membranes. These tubules were labelled by the fluid phase marker horseradish peroxidase (HRP), and were observed to wrap capsids as early as 2 min after HRP addition, indicating that the envelope had recently cycled from the cell surface. Consistent with this, capsids did not colocalise with either the trans-Golgi network marker TGN46 or late endosomal markers, but showed coincidence with the transferrin receptor. Virus glycoproteins were retrieved from the plasma membrane (PM) to label wrapping capsids, a process that was dependent on both dynamin and Rab5. Combined depletion of Rab5 and Rab11 reduced virus yield to <1%, resulting in aberrant localisation of capsids. These results suggest that endocytosis from the PM into endocytic tubules provides the main source of membrane for HSV1, and reveal a new mechanism for virus exploitation of the endocytic pathway.
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Affiliation(s)
- Michael Hollinshead
- Section of Virology, Faculty of Medicine, Imperial College London, London, UK
| | - Helen L Johns
- Section of Virology, Faculty of Medicine, Imperial College London, London, UK
| | - Charlotte L Sayers
- Section of Virology, Faculty of Medicine, Imperial College London, London, UK
| | | | - Geoffrey L Smith
- Section of Virology, Faculty of Medicine, Imperial College London, London, UK
| | - Gillian Elliott
- Section of Virology, Faculty of Medicine, Imperial College London, London, UK
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128
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Haraguchi H, Noda T, Kawaoka Y, Morikawa Y. A large extension to HIV-1 Gag, like Pol, has negative impacts on virion assembly. PLoS One 2012; 7:e47828. [PMID: 23110110 PMCID: PMC3479142 DOI: 10.1371/journal.pone.0047828] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 09/17/2012] [Indexed: 01/08/2023] Open
Abstract
The GagPol protein of HIV-1 harbors viral enzymes, such as protease (PR), reverse transcriptase, and integrase, that are all crucial for virion infectivity. Previous studies have suggested that expression of GagPol alone does not produce viral particles and that the budding defect is caused by the presence of the Pol region. However, it has remained unknown why GagPol fails to produce viral particles. We show here that HIV-1 GagPol is incapable of membrane binding and subsequent particle assembly. Our confocal data indicated that, despite full N-myristoylation, GagPol protein failed to target plasma membrane with diffuse distribution in the cytoplasm. Membrane flotation analysis confirmed these findings. Progressive C-terminal truncation of GagPol to give GagPR allowed for plasma membrane targeting but still not for particle production. Conversely, the C-terminal addition of a noncognate protein, such as ß-galactosidase or 4 tandem GFP, to Gag impaired the membrane affinity, indicating that the Pol region, a large extension to Gag, inhibits membrane binding in the context of GagPol. The addition of the 10 N-terminal amino acids of Fyn kinase [Fyn(10)], a tight membrane-binding signal, conferred plasma membrane targeting on GagPol, but the Fyn(10)GagPol did not produce viral particles. The defect in particle budding was not rescued by the introduction of the PTAP motif, which is responsible for a late stage of viral particle budding. Rather, electron microscopy suggested that the budding defect of GagPR occurred at an early stage of particle morphogenesis. Our data, which were consistent with previous observations, demonstrate the defects of GagPol in membrane binding and particle assembly.
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Affiliation(s)
- Hiyori Haraguchi
- Kitasato Institute for Life Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Takeshi Noda
- Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Yoshihiro Kawaoka
- Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
- ERATO Infection-Induced Host Responses Project, Japan Science and Technology Agency, Saitama, Japan
- Influenza Research Institute, Department of Pathological Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Yuko Morikawa
- Kitasato Institute for Life Sciences, Kitasato University, Minato-ku, Tokyo, Japan
- * E-mail:
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129
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Gaudin R, de Alencar BC, Jouve M, Bèrre S, Le Bouder E, Schindler M, Varthaman A, Gobert FX, Benaroch P. Critical role for the kinesin KIF3A in the HIV life cycle in primary human macrophages. ACTA ACUST UNITED AC 2012; 199:467-79. [PMID: 23091068 PMCID: PMC3483138 DOI: 10.1083/jcb.201201144] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Macrophages are long-lived target cells for HIV infection and are considered viral reservoirs. HIV assembly in macrophages occurs in virus-containing compartments (VCCs) in which virions accumulate and are stored. The regulation of the trafficking and release of these VCCs remains unknown. Using high resolution light and electron microscopy of HIV-1-infected primary human macrophages, we show that the spatial distribution of VCCs depended on the microtubule network and that VCC-limiting membrane was closely associated with KIF3A+ microtubules. Silencing KIF3A strongly decreased virus release from HIV-1-infected macrophages, leading to VCC accumulation intracellularly. Time-lapse microscopy further suggested that VCCs and associated KIF3A move together along microtubules. Importantly, KIF3A does not play a role in HIV release from T cells that do not possess VCCs. These results reveal that HIV-1 requires the molecular motor KIF3 to complete its cycle in primary macrophages. Targeting this step may lead to novel strategies to eliminate this viral reservoir.
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Affiliation(s)
- Raphaël Gaudin
- Institut Curie, Centre de Recherche, Paris, F-75248 France
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130
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Abstract
Viruses have a limited number of genes but a complex life cycle and have evolved to utilize numerous host factors to complete their replication. The assembly and budding process of enveloped viruses utilizes numerous cellular factors to facilitate transport from one membrane bound compartment to the other. The host SNARE proteins are widely involved in late stages of vesicular mediated transport by catalyzing the docking and fusion of apposing membranes in the vesicle and target compartment. By generalized disruption of the SNARE sorting machinery, we recently demonstrated a role for these proteins in HIV-1 assembly by affecting Gag localization to the plasma membrane. Whether the observed phenomenon is specifically due to SNARE disruption or generalized disturbance of the cell sorting machinery and the involvement of specific “v” vs. “t” SNAREs in this phenomenon remains to be elucidated.
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Affiliation(s)
- Himanshu Garg
- Center of Excellence for Infectious Diseases; Department of Biomedical Sciences; Paul L. Foster School of Medicine; Texas Tech University Health Sciences Center; El Paso, TX USA
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131
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Chu H, Wang JJ, Qi M, Yoon JJ, Chen X, Wen X, Hammonds J, Ding L, Spearman P. Tetherin/BST-2 is essential for the formation of the intracellular virus-containing compartment in HIV-infected macrophages. Cell Host Microbe 2012; 12:360-72. [PMID: 22980332 PMCID: PMC3444820 DOI: 10.1016/j.chom.2012.07.011] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2011] [Revised: 05/06/2012] [Accepted: 07/19/2012] [Indexed: 11/16/2022]
Abstract
HIV-1 assembly and release occur at the plasma membrane in T lymphocytes, while intracellular sites of virus assembly or accumulation are apparent in macrophages. The host protein tetherin (BST-2) inhibits HIV release from the plasma membrane by retaining viral particles at the cell surface, but the role of tetherin at intracellular HIV assembly sites is unclear. We determined that tetherin is significantly upregulated upon macrophage infection and localizes to an intracellular virus-containing compartment (VCC). Tetherin localized at the virus-VCC membrane interface, suggesting that tetherin physically tethers virions in VCCs. Tetherin knockdown diminished and redistributed VCCs within macrophages and promoted HIV release and cell-cell transmission. The HIV Vpu protein, which downregulates tetherin from the plasma membrane, did not fully overcome tetherin-mediated restriction of particle release in macrophages. Thus, tetherin is essential for VCC formation and may account for morphologic differences in the apparent HIV assembly sites in macrophages versus T cells.
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Affiliation(s)
- Hin Chu
- Emory University Department of Pediatrics and Children’s Healthcare of Atlanta, Atlanta, GA 30322; USA
| | - Jaang-Jiun Wang
- Emory University Department of Pediatrics and Children’s Healthcare of Atlanta, Atlanta, GA 30322; USA
| | - Mingli Qi
- Emory University Department of Pediatrics and Children’s Healthcare of Atlanta, Atlanta, GA 30322; USA
| | - Jeong-Joong Yoon
- Emory University Department of Pediatrics and Children’s Healthcare of Atlanta, Atlanta, GA 30322; USA
| | - Xuemin Chen
- Emory University Department of Pediatrics and Children’s Healthcare of Atlanta, Atlanta, GA 30322; USA
| | - Xiaoyun Wen
- Emory University Department of Pediatrics and Children’s Healthcare of Atlanta, Atlanta, GA 30322; USA
| | - Jason Hammonds
- Emory University Department of Pediatrics and Children’s Healthcare of Atlanta, Atlanta, GA 30322; USA
| | - Lingmei Ding
- Emory University Department of Pediatrics and Children’s Healthcare of Atlanta, Atlanta, GA 30322; USA
| | - Paul Spearman
- Emory University Department of Pediatrics and Children’s Healthcare of Atlanta, Atlanta, GA 30322; USA
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132
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Gunzenhäuser J, Olivier N, Pengo T, Manley S. Quantitative super-resolution imaging reveals protein stoichiometry and nanoscale morphology of assembling HIV-Gag virions. NANO LETTERS 2012; 12:4705-4710. [PMID: 22906128 DOI: 10.1021/nl3021076] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The HIV structural protein Gag assembles to form spherical particles of radius ∼70 nm. During the assembly process, the number of Gag proteins increases over several orders of magnitude from a few at nucleation to thousands at completion. The challenge in studying protein assembly lies in the fact that current methods such as standard fluorescence or electron microscopy techniques cannot access all stages of the assembly process in a cellular context. Here, we demonstrate an approach using super-resolution fluorescence imaging that permits quantitative morphological and molecular counting analysis over a wide range of protein cluster sizes. We applied this technique to the analysis of hundreds of HIV-Gag clusters at the cellular plasma membrane, thus elucidating how different fluorescent labels can change the assembly of virions.
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Affiliation(s)
- Julia Gunzenhäuser
- Laboratory of Experimental Biophysics, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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133
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Malkusch S, Muranyi W, Müller B, Kräusslich HG, Heilemann M. Single-molecule coordinate-based analysis of the morphology of HIV-1 assembly sites with near-molecular spatial resolution. Histochem Cell Biol 2012; 139:173-9. [DOI: 10.1007/s00418-012-1014-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/31/2012] [Indexed: 01/08/2023]
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134
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Kemler I, Saenz D, Poeschla E. Feline immunodeficiency virus Gag is a nuclear shuttling protein. J Virol 2012; 86:8402-11. [PMID: 22623802 PMCID: PMC3421727 DOI: 10.1128/jvi.00692-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 05/16/2012] [Indexed: 02/03/2023] Open
Abstract
Lentiviral genomic RNAs are encapsidated by the viral Gag protein during virion assembly. The intracellular location of the initial Gag-RNA interaction is unknown. We previously observed feline immunodeficiency virus (FIV) Gag accumulating at the nuclear envelope during live-cell imaging, which suggested that trafficking of human immunodeficiency virus type 1 (HIV-1) and FIV Gag may differ. Here we analyzed the nucleocytoplasmic transport properties of both Gag proteins. We discovered that inhibition of the CRM1 nuclear export pathway with leptomycin B causes FIV Gag but not HIV-1 Gag to accumulate in the nucleus. Virtually all FIV Gag rapidly became intranuclear when the CRM1 export pathway was blocked, implying that most if not all FIV Gag normally undergoes nuclear cycling. In FIV-infected feline cells, some intranuclear Gag was detected in the steady state without leptomycin B treatment. When expressed individually, the FIV matrix (MA), capsid (CA), and nucleocapsid-p2 (NC-p2) domains were not capable of mediating leptomycin B-sensitive nuclear export of a fluorescent protein. In contrast, CA-NC-p2 did mediate nuclear export, with MA being dispensable. We conclude that HIV-1 and FIV Gag differ strikingly in a key intracellular trafficking property. FIV Gag is a nuclear shuttling protein that utilizes the CRM1 nuclear export pathway, while HIV-1 Gag is excluded from the nucleus. These findings expand the spectrum of lentiviral Gag behaviors and raise the possibility that FIV genome encapsidation may initiate in the nucleus.
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Affiliation(s)
| | | | - Eric Poeschla
- Department of Molecular Medicine
- Division of Infectious Diseases, Mayo Clinic College of Medicine, Rochester, Minnesota, USA
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135
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Extracellular vesicles and their convergence with viral pathways. Adv Virol 2012; 2012:767694. [PMID: 22888349 PMCID: PMC3410301 DOI: 10.1155/2012/767694] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 06/06/2012] [Indexed: 01/01/2023] Open
Abstract
Extracellular vesicles (microvesicles), such as exosomes and shed microvesicles, contain a variety of molecules including proteins, lipids, and nucleic acids. Microvesicles appear mostly to originate from multivesicular bodies or to bud from the plasma membrane. Here, we review the convergence of microvesicle biogenesis and aspects of viral assembly and release pathways. Herpesviruses and retroviruses, amongst others, recruit several elements from the microvesicle biogenesis pathways for functional virus release. In addition, noninfectious pleiotropic virus-like vesicles can be released, containing viral and cellular components. We highlight the heterogeneity of microvesicle function during viral infection, addressing microvesicles that can either block or enhance infection, or cause immune dysregulation through bystander action in the immune system. Finally, endogenous retrovirus and retrotransposon elements deposited in our genomes millions of years ago can be released from cells within microvesicles, suggestive of a viral origin of the microvesicle system or perhaps of an evolutionary conserved system of virus-vesicle codependence. More research is needed to further elucidate the complex function of the various microvesicles produced during viral infection, possibly revealing new therapeutic intervention strategies.
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136
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Hogue IB, Llewellyn GN, Ono A. Dynamic Association between HIV-1 Gag and Membrane Domains. Mol Biol Int 2012; 2012:979765. [PMID: 22830021 PMCID: PMC3399408 DOI: 10.1155/2012/979765] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Accepted: 06/01/2012] [Indexed: 12/18/2022] Open
Abstract
HIV-1 particle assembly is driven by the structural protein Gag. Gag binds to and multimerizes on the inner leaflet of the plasma membrane, eventually resulting in formation of spherical particles. During virus spread among T cells, Gag accumulates to the plasma membrane domain that, together with target cell membrane, forms a cell junction known as the virological synapse. While Gag association with plasma membrane microdomains has been implicated in virus assembly and cell-to-cell transmission, recent studies suggest that, rather than merely accumulating to pre-existing microdomains, Gag plays an active role in reorganizing the microdomains via its multimerization activity. In this paper, we will discuss this emerging view of Gag microdomain interactions. Relationships between Gag multimerization and microdomain association will be further discussed in the context of Gag localization to T-cell uropods and virological synapses.
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Affiliation(s)
- Ian B. Hogue
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - G. Nicholas Llewellyn
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Molecular Microbiology and Immunology, University of Southern California, Los Angeles, CA 90033, USA
| | - Akira Ono
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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137
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Caveolin-1 suppresses human immunodeficiency virus-1 replication by inhibiting acetylation of NF-κB. Virology 2012; 432:110-9. [PMID: 22748181 DOI: 10.1016/j.virol.2012.05.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 03/24/2012] [Accepted: 05/22/2012] [Indexed: 12/22/2022]
Abstract
Caveolin-1 is an integral membrane protein primarily responsible for the formation of membrane structures known as caveolae. Caveolae are specialized lipid rafts involved in protein trafficking, cholesterol homeostasis, and a number of signaling functions. It has been demonstrated that caveolin-1 suppresses HIV-1 protein expression. We found that co-transfecting cells with HIV-1 and caveolin-1 constructs, results in a marked decrease in the level of HIV-1 transcription relative to cells transfected with HIV-1 DNA alone. Correspondingly, reduction of endogenous caveolin-1 expression by siRNA-mediated silencing resulted in an enhancement of HIV-1 replication. Further, we observed a loss of caveolin-mediated suppression of HIV-1 transcription in promoter studies with reporters containing mutations in the NF-κB binding site. Our analysis of the posttranslational modification status of the p65 subunit of NF-κB demonstrates hypoacetylation of p65 in the presence of caveolin-1. Since hypoacetylated p65 has been shown to inhibit transcription, we conclude that caveolin-1 inhibits HIV-1 transcription through a NF-κB-dependent mechanism.
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138
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Smyth RP, Davenport MP, Mak J. The origin of genetic diversity in HIV-1. Virus Res 2012; 169:415-29. [PMID: 22728444 DOI: 10.1016/j.virusres.2012.06.015] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2012] [Revised: 06/10/2012] [Accepted: 06/12/2012] [Indexed: 10/28/2022]
Abstract
One of the hallmarks of HIV infection is the rapid development of a genetically complex population (quasispecies) from an initially limited number of infectious particles. Genetic diversity remains one of the major obstacles to eradication of HIV. The viral quasispecies can respond rapidly to selective pressures, such as that imposed by the immune system and antiretroviral therapy, and frustrates vaccine design efforts. Two unique features of retroviral replication are responsible for the unprecedented variation generated during infection. First, mutations are frequently introduced into the viral genome by the error prone viral reverse transcriptase and through the actions of host cellular factors, such as the APOBEC family of nucleic acid editing enzymes. Second, the HIV reverse transcriptase can utilize both copies of the co-packaged viral genome in a process termed retroviral recombination. When the co-packaged viral genomes are genetically different, retroviral recombination can lead to the shuffling of mutations between viral genomes in the quasispecies. This review outlines the stages of the retroviral life cycle where genetic variation is introduced, focusing on the principal mechanisms of mutation and recombination. Understanding the mechanistic origin of genetic diversity is essential to combating HIV.
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Affiliation(s)
- Redmond P Smyth
- Centre for Virology, Burnet Institute, 85 Commercial Road, Melbourne, Victoria 3004, Australia
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139
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Abstract
Many studies have documented how extensively HIV-1 and related viruses interact with host cells. Virus-host interactions are of two conceptual types. First, viruses have evolved to make use of numerous host-cell functions to facilitate their own replication. Second, hosts have evolved a number of activities to inhibit virus replication. Understanding the scope and details of HIV-host interactions has been an extraordinary rich scientific endeavor, and in addition to their biomedical importance, studies in this area have established HIV as a model system in virology. Here, I present an overview of how HIV-1 interacts with some key host cell factors during its replication cycle.
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140
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Kyere SK, Mercredi PY, Dong X, Spearman P, Summers MF. The HIV-1 matrix protein does not interact directly with the protein interactive domain of AP-3δ. Virus Res 2012; 169:411-4. [PMID: 22705971 DOI: 10.1016/j.virusres.2012.06.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 06/06/2012] [Accepted: 06/06/2012] [Indexed: 11/19/2022]
Abstract
During the late phase of the Human Immunodeficiency Virus Type-1 (HIV-1) replication cycle, viral Gag proteins and the intact RNA genome are trafficked to specific sub-cellular membranes where virus assembly and budding occurs. Targeting to the plasma membranes of T cells and macrophages is mediated by interactions between the N-terminal matrix (MA) domain of Gag and cellular phosphatidylinositol-4,5-bisphosphate [PI(4,5)P(2)] molecules. However, in macrophages and dendritic cells, a subset of Gag proteins appears to be targeted to tetraspanin enriched viral compartments, a process that appears to be mediated by MA interactions with the Delta subunit of the cellular Adaptor Protein AP-3 (AP-3δ). We cloned, overexpressed and purified the protein interactive domain of AP-3δ and probed for MA binding by NMR. Unexpectedly, no evidence of binding was observed in these in vitro experiments, even at relatively high protein concentrations (200μM), suggesting that AP-3δ plays an alternative role in HIV-1 assembly.
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Affiliation(s)
- Sampson K Kyere
- Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
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141
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HIV Assembly and Budding: Ca(2+) Signaling and Non-ESCRT Proteins Set the Stage. Mol Biol Int 2012; 2012:851670. [PMID: 22761998 PMCID: PMC3384956 DOI: 10.1155/2012/851670] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 03/26/2012] [Indexed: 12/16/2022] Open
Abstract
More than a decade has elapsed since the link between the endosomal sorting complex required for transport (ESCRT) machinery and HIV-1 protein trafficking and budding was first identified. L domains in HIV-1 Gag mediate recruitment of ESCRT which function in bud abscission releasing the viral particle from the host cell. Beyond virus budding, the ESCRT machinery is also involved in the endocytic pathway, cytokinesis, and autophagy. In the past few years, the number of non-ESCRT host proteins shown to be required in the assembly process has also grown. In this paper, we highlight the role of recently identified cellular factors that link ESCRT machinery to calcium signaling machinery and we suggest that this liaison contributes to setting the stage for productive ESCRT recruitment and mediation of abscission. Parallel paradigms for non-ESCRT roles in virus budding and cytokinesis will be discussed.
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142
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Chu H, Wang JJ, Qi M, Yoon JJ, Wen X, Chen X, Ding L, Spearman P. The intracellular virus-containing compartments in primary human macrophages are largely inaccessible to antibodies and small molecules. PLoS One 2012; 7:e35297. [PMID: 22567100 PMCID: PMC3342280 DOI: 10.1371/journal.pone.0035297] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Accepted: 03/14/2012] [Indexed: 12/29/2022] Open
Abstract
HIV-1 assembly and release occurs at the plasma membrane of human T lymphocytes and model epithelial cell lines, whereas in macrophages intracellular sites of virus assembly or accumulation predominate. The origin of the intracellular virus-containing compartment (VCC) has been controversial. This compartment is enriched in markers of the multivesicular body, and has been described as a modified endosomal compartment. Several studies of this compartment have revealed the presence of small channels connecting to the plasma membrane, suggesting that instead of an endosomal origin the compartment is a modified plasma membrane compartment. If the compartment is accessible to the external environment, this would have important implications for antiviral immune responses and antiviral therapy. We performed a series of experiments designed to determine if the VCC in macrophages was open to the external environment and accessible to antibodies and small molecules. The majority of VCCs were found to be inaccessible to exogenously-applied antibodies to tetraspanins in the absence of membrane permeabilization, while tetraspanin staining was readily observed following membrane permeabilization. Cationized ferritin was utilized to stain the plasma membrane, and revealed that the majority of virus-containing compartments were inaccessible to ferritin. Low molecular weight dextrans could access only a very small percentage of VCCs, and these tended to be more peripheral compartments. We conclude that the VCCs in monocyte-derived human macrophages are heterogeneous, but the majority of VCCs are closed to the external environment.
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Affiliation(s)
- Hin Chu
- Department of Pediatrics, Emory University and Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
| | - Jaang-Jiun Wang
- Department of Pediatrics, Emory University and Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
| | - Mingli Qi
- Department of Pediatrics, Emory University and Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
| | - Jeong-Joong Yoon
- Department of Pediatrics, Emory University and Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
| | - Xiaoyun Wen
- Department of Pediatrics, Emory University and Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
| | - Xuemin Chen
- Department of Pediatrics, Emory University and Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
| | - Lingmei Ding
- Department of Pediatrics, Emory University and Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
| | - Paul Spearman
- Department of Pediatrics, Emory University and Children’s Healthcare of Atlanta, Atlanta, Georgia, United States of America
- * E-mail:
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143
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Ghanam RH, Samal AB, Fernandez TF, Saad JS. Role of the HIV-1 Matrix Protein in Gag Intracellular Trafficking and Targeting to the Plasma Membrane for Virus Assembly. Front Microbiol 2012; 3:55. [PMID: 22363329 PMCID: PMC3281212 DOI: 10.3389/fmicb.2012.00055] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Accepted: 02/01/2012] [Indexed: 11/13/2022] Open
Abstract
Human immunodeficiency virus type-1 (HIV-1) encodes a polypeptide called Gag that is able to form virus-like particles in vitro in the absence of any cellular or viral constituents. During the late phase of the HIV-1 infection, Gag polyproteins are transported to the plasma membrane (PM) for assembly. In the past two decades, in vivo, in vitro, and structural studies have shown that Gag trafficking and targeting to the PM are orchestrated events that are dependent on multiple factors including cellular proteins and specific membrane lipids. The matrix (MA) domain of Gag has been the focus of these studies as it appears to be engaged in multiple intracellular interactions that are suggested to be critical for virus assembly and replication. The interaction between Gag and the PM is perhaps the most understood. It is now established that the ultimate localization of Gag on punctate sites on the PM is mediated by specific interactions between the MA domain of Gag and phosphatidylinositol-4,5-bisphosphate [PI(4,5)P(2)], a minor lipid localized on the inner leaflet of the PM. Structure-based studies revealed that binding of PI(4,5)P(2) to MA induces minor conformational changes, leading to exposure of the myristyl (myr) group. Exposure of the myr group is also triggered by binding of calmodulin, enhanced by factors that promote protein self-association like the capsid domain of Gag, and is modulated by pH. Despite the steady progress in defining both the viral and cellular determinants of retroviral assembly and release, Gag's intracellular interactions and trafficking to its assembly sites in the infected cell are poorly understood. In this review, we summarize the current understanding of the structural and functional role of MA in HIV replication.
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Affiliation(s)
- Ruba H Ghanam
- Department of Microbiology, University of Alabama at Birmingham Birmingham, AL, USA
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144
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Dordor A, Poudevigne E, Göttlinger H, Weissenhorn W. Essential and supporting host cell factors for HIV-1 budding. Future Microbiol 2012; 6:1159-70. [PMID: 22004035 DOI: 10.2217/fmb.11.100] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
HIV-1 employs its structural proteins to orchestrate assembly and budding at the plasma membrane of host cells. The Gag polyprotein is sufficient to form virus-like particles in the absence of other viral proteins and provides a platform to interact with numerous cellular factors that regulate Gag trafficking to the site of assembly and budding. Notably endosomal sorting complexes required for transport have attained much attention over the last decade because of their essential role in virion release. Here we review recent advances in understanding the role of host cell factors recruited by Gag during HIV-1 assembly and budding.
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Affiliation(s)
- Aurelien Dordor
- Unit of Virus Host Cell Interactions UMI 3265 Université Joseph Fourier-EMBL-CNRS, 6 rue Jules Horowitz 38042 Grenoble Cedex 9, France
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145
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HIV cell-to-cell transmission requires the production of infectious virus particles and does not proceed through env-mediated fusion pores. J Virol 2012; 86:3924-33. [PMID: 22258237 DOI: 10.1128/jvi.06478-11] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Direct cell-to-cell transmission of human immunodeficiency virus (HIV) is a more potent and efficient means of virus propagation than infection by cell-free virus particles. The aim of this study was to determine whether cell-to-cell transmission requires the assembly of enveloped virus particles or whether nucleic acids with replication potential could translocate directly from donor to target cells through envelope glycoprotein (Env)-induced fusion pores. To this end, we characterized the transmission properties of viruses carrying mutations in the matrix protein (MA) that affect the incorporation of Env into virus particles but do not interfere with Env-mediated cell-cell fusion. By use of cell-free virus, the infectivity of MA mutant viruses was below the detection threshold both in single-cycle and in multiple-cycle assays. Truncation of the cytoplasmic tail (CT) of Env restored the incorporation of Env into MA mutant viruses and rescued their cell-free infectivity to different extents. In cell-to-cell transmission assays, MA mutations prevented HIV transmission from donor to target cells, despite efficient Env-dependent membrane fusion. HIV transmission was blocked at the level of virus core translocation into the cytosol of target cells. As in cell-free assays, rescue of Env incorporation by truncation of the Env CT restored the virus core translocation and cell-to-cell infectivity of MA mutant viruses. These data show that HIV cell-to-cell transmission requires the assembly of enveloped virus particles. The increased efficiency of this infection route may thus be attributed to the high local concentrations of virus particles at sites of cellular contacts rather than to a qualitatively different transmission process.
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146
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Cohen S, Etingov I, Panté N. Effect of viral infection on the nuclear envelope and nuclear pore complex. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 299:117-59. [PMID: 22959302 DOI: 10.1016/b978-0-12-394310-1.00003-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The nuclear envelope (NE) is a vital structure that separates the nucleus from the cytoplasm. Because the NE is such a critical cellular barrier, many viral pathogens have evolved to modulate its permeability. They do this either by breaching the NE or by disrupting the integrity and functionality of the nuclear pore complex (NPC). Viruses modulate NE permeability for different reasons. Some viruses disrupt NE to deliver the viral genome into the nucleus for replication, while others cause NE disruption during nuclear egress of newly assembled capsids. Yet, other viruses modulate NE permeability and affect the compartmentalization of host proteins or block the nuclear transport of host proteins involved in the host antiviral response. Recent scientific advances demonstrated that other viruses use proteins of the NPC for viral assembly or disassembly. Here we review the ways in which various viruses affect NE and NPC during infection.
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Affiliation(s)
- Sarah Cohen
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
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147
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Abstract
In macrophages, HIV-1 accumulates in intracellular vesicles designated virus-containing compartments (VCCs). These might play an important role in the constitution of macrophages as viral reservoirs and allow HIV-1 to evade the immune system by sequestration in an internal niche, which is difficult to access from the exterior. However, until now, evidence of whether internal virus accumulations are protected from the host's humoral immune response is still lacking. In order to be able to study the formation and antibody accessibility of VCCs, we generated HIV-1 with green fluorescent protein (GFP)-tagged Gag replicating in primary macrophages. Live-cell observations revealed faint initial cytosolic Gag expression and subsequent large intracellular Gag accumulations which stayed stable over days. Taking advantage of the opportunity to study the accessibility of intracellular VCCs via the cell surface, we demonstrate that macrophage internal HIV-1-containing compartments cannot be targeted by neutralizing antibodies. Furthermore, HIV-1 was efficiently transferred from antibody-treated macrophages to T cells. Three-dimensional reconstruction of electron microscopic slices revealed that Gag accumulations correspond to viral particles within enclosed compartments and convoluted membranes. Thus, although some VCCs were connected to the plasma membrane, the complex membrane architecture of the HIV-1-containing compartment might shield viral particles from neutralizing antibodies. In sum, our study provides evidence that HIV-1 is sequestered into a macrophage internal membranous web, posing an obstacle for the elimination of this viral reservoir.
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148
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Pelchen-Matthews A, Giese S, Mlčochová P, Turner J, Marsh M. β2 integrin adhesion complexes maintain the integrity of HIV-1 assembly compartments in primary macrophages. Traffic 2011; 13:273-91. [PMID: 22017400 DOI: 10.1111/j.1600-0854.2011.01306.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Revised: 10/19/2011] [Accepted: 10/19/2011] [Indexed: 11/30/2022]
Abstract
In human monocyte-derived macrophages (MDM), human immunodeficiency virus type 1 (HIV-1) assembly takes place primarily on complex intracellular plasma membrane domains connected to the cell surface by closely apposed membrane sheets or narrow channels. Some of the membranes associated with these compartments are decorated by thick (≈30 nm), electron-dense, cytoplasmic coats. Here we show by immunolabelling of ultrathin cryosections that the β2 integrin CD18, together with the αM and αX integrins (CD11b and CD11c), is clustered at these coated domains, and that the coats themselves contain the cytoskeletal linker proteins talin, vinculin and paxillin that connect the integrin complexes to the actin cytoskeleton. Intracellular plasma membrane-connected compartments (IPMC) with CD18-containing focal adhesion-like coats are also present in uninfected MDM. These compartments become more prominent as the cells mature in tissue culture and their appearance correlates with increased expression of CD18, CD11b/c and paxillin. Depletion of CD18 by RNA interference leads to parallel down-regulation of CD11b and CD11c, as well as of paxillin, and the disappearance of the adhesion-like coats. In addition, CD18 knockdown alters the appearance of virus-containing IPMC in HIV-infected MDM, indicating that the β2 integrin/focal adhesion-like coat structures are involved in the organization of these compartments.
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Affiliation(s)
- Annegret Pelchen-Matthews
- Cell Biology Unit, Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, WC1E 6BT, UK
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149
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Inhibition or deficiency of cathepsin B leads defects in HIV-1 Gag pseudoparticle release in macrophages and HEK293T cells. Antiviral Res 2011; 93:175-84. [PMID: 22138708 DOI: 10.1016/j.antiviral.2011.11.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 10/11/2011] [Accepted: 11/17/2011] [Indexed: 11/23/2022]
Abstract
Human immunodeficiency virus type 1 (HIV-1) egresses from infected cells through utilizing the host membrane budding mechanisms. Assembly of HIV-1 Gag particles occurs on membranes where the Gag multimers subsequently bud off and form enveloped viral particles. In certain cell types such as macrophages, HIV-1 Gag particles have shown to be released into intracellular virus containing compartments (VCC) such as late endosomes, multivesicular bodies (MVBs) or invaginated plasma membrane pockets. Here, we showed that macrophages or HEK293T cells treated with the cathepsin B (CTSB)-specific inhibitor CA-074Me or cells deficient in CTSB failed to release HIV-1 Gag pseudoparticles into the extracellular environment. Based on immunofluorescence and electron microscopy, these cells retained the pseudoparticles in heterogeneous intracellular VCC. CA-074Me was also able to inhibit propagation of two enveloped viruses, herpes simplex virus and influenza A virus, but not non-enveloped enterovirus. These results suggest that CTSB is required for the efficient release of HIV-1 Gag pseudoparticles and targeting CTSB can be a new therapeutic strategy for inhibiting egress of HIV-1 and other enveloped viruses.
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150
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Lehmann M, Nikolic DS, Piguet V. How HIV-1 takes advantage of the cytoskeleton during replication and cell-to-cell transmission. Viruses 2011; 3:1757-76. [PMID: 21994805 PMCID: PMC3187690 DOI: 10.3390/v3091757] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 08/26/2011] [Accepted: 08/30/2011] [Indexed: 12/29/2022] Open
Abstract
Human immunodeficiency virus 1 (HIV-1) infects T cells, macrophages and dendritic cells and can manipulate their cytoskeleton structures at multiple steps during its replication cycle. Based on pharmacological and genetic targeting of cytoskeleton modulators, new imaging approaches and primary cell culture models, important roles for actin and microtubules during entry and cell-to-cell transfer have been established. Virological synapses and actin-containing membrane extensions can mediate HIV-1 transfer from dendritic cells or macrophage cells to T cells and between T cells. We will review the role of the cytoskeleton in HIV-1 entry, cellular trafficking and cell-to-cell transfer between primary cells.
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Affiliation(s)
- Martin Lehmann
- Department of Microbiology and Molecular Medicine, University Hospital and Medical School of Geneva, Geneva 1211, Switzerland; E-Mails: (M.L.); (D.S.N)
- Department of Dermatology and Venereology, University Hospital and Medical School of Geneva, Geneva 1211, Switzerland
| | - Damjan S. Nikolic
- Department of Microbiology and Molecular Medicine, University Hospital and Medical School of Geneva, Geneva 1211, Switzerland; E-Mails: (M.L.); (D.S.N)
- Department of Dermatology and Venereology, University Hospital and Medical School of Geneva, Geneva 1211, Switzerland
| | - Vincent Piguet
- Department of Microbiology and Molecular Medicine, University Hospital and Medical School of Geneva, Geneva 1211, Switzerland; E-Mails: (M.L.); (D.S.N)
- Department of Dermatology and Venereology, University Hospital and Medical School of Geneva, Geneva 1211, Switzerland
- Department of Dermatology and Wound Healing, Cardiff University School of Medicine and University Hospital of Wales, Cardiff, Wales, CF144XN, UK
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +44-(0)-29-20-744721; Fax: +44-(0)-29-20-744312
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