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Sakin V, Paci G, Lemke EA, Müller B. Labeling of virus components for advanced, quantitative imaging analyses. FEBS Lett 2016; 590:1896-914. [PMID: 26987299 DOI: 10.1002/1873-3468.12131] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 03/08/2016] [Accepted: 03/09/2016] [Indexed: 12/31/2022]
Abstract
In recent years, investigation of virus-cell interactions has moved from ensemble measurements to imaging analyses at the single-particle level. Advanced fluorescence microscopy techniques provide single-molecule sensitivity and subdiffraction spatial resolution, allowing observation of subviral details and individual replication events to obtain detailed quantitative information. To exploit the full potential of these techniques, virologists need to employ novel labeling strategies, taking into account specific constraints imposed by viruses, as well as unique requirements of microscopic methods. Here, we compare strengths and limitations of various labeling methods, exemplify virological questions that were successfully addressed, and discuss challenges and future potential of novel approaches in virus imaging.
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Affiliation(s)
- Volkan Sakin
- Department of Infectious Diseases, Virology, University Hospital Heidelberg, Germany
| | - Giulia Paci
- Structural and Computational Biology Unit, Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Edward A Lemke
- Structural and Computational Biology Unit, Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Barbara Müller
- Department of Infectious Diseases, Virology, University Hospital Heidelberg, Germany
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Yu KL, Lee SH, Lee ES, You JC. HIV-1 nucleocapsid protein localizes efficiently to the nucleus and nucleolus. Virology 2016; 492:204-12. [PMID: 26967976 DOI: 10.1016/j.virol.2016.03.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 03/01/2016] [Accepted: 03/02/2016] [Indexed: 10/22/2022]
Abstract
The HIV-1 nucleocapsid (NC) is an essential viral protein containing two highly conserved retroviral-type zinc finger (ZF) motifs, which functions in multiple stages of the HIV-1 life cycle. Although a number of functions for NC either in its mature form or as a domain of Gag have been revealed, little is known about the intracellular localization of NC and, moreover, its role in Gag protein trafficking. Here, we have investigated various forms of HIV-1 NC protein for its cellular localization and found that the NC has a strong nuclear and nucleolar localization activity. The linker region, composed of a stretch of basic amino acids between the two ZF motifs, was necessary and sufficient for the activity.
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Affiliation(s)
- Kyung Lee Yu
- National Research Laboratory of Molecular Virology, Department of Pathology, School of Medicine, The Catholic University of Korea, Seocho-gu Banpo-dong 505, Seoul 137-701, Republic of Korea
| | - Sun Hee Lee
- National Research Laboratory of Molecular Virology, Department of Pathology, School of Medicine, The Catholic University of Korea, Seocho-gu Banpo-dong 505, Seoul 137-701, Republic of Korea
| | - Eun Soo Lee
- National Research Laboratory of Molecular Virology, Department of Pathology, School of Medicine, The Catholic University of Korea, Seocho-gu Banpo-dong 505, Seoul 137-701, Republic of Korea
| | - Ji Chang You
- National Research Laboratory of Molecular Virology, Department of Pathology, School of Medicine, The Catholic University of Korea, Seocho-gu Banpo-dong 505, Seoul 137-701, Republic of Korea.
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Optimized production of HIV-1 virus-like particles by transient transfection in CAP-T cells. Appl Microbiol Biotechnol 2015; 100:3935-47. [PMID: 26685677 DOI: 10.1007/s00253-015-7213-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Revised: 11/26/2015] [Accepted: 12/01/2015] [Indexed: 02/07/2023]
Abstract
HIV-1 virus-like particles (VLPs) have great potential as new-generation vaccines. The novel CAP-T cell line is used for the first time to produce Gag-GFP HIV-1 VLPs by means of polyethylenimine (PEI)-mediated transient transfection. CAP-T cells are adapted to grow to high cell densities in serum-free medium, and are able to express complex recombinant proteins with human post-translational modifications. Furthermore, this cell line is easily transfected with PEI, which offers the flexibility to rapidly generate and screen a number of candidates in preclinical studies. Transient transfection optimization of CAP-T cells has been performed systematically in this work. It is determined that for optimal production, cells need to be growing at mid-exponential phase, Protein Expression Medium (PEM) medium has to be added post-transfection, and cells can be transfected by independent addition of DNA and PEI with no prior complexation. A Box-Behnken experimental design is used to optimize cell density at time of transfection, DNA/cell and PEI/cell ratios. The optimal conditions determined are transfection at a density of 3.3E + 06 cells/mL with 0.5 pg of DNA/cell and 3 pg of PEI/cell. Using the optimized protocol, 6 × 10(10) VLP/mL are obtained, demonstrating that CAP-T is a highly efficient cell line for the production of HIV-1 VLPs and potentially other complex viral-based biotherapeutics.
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Huang F, Zhang J, Zhang Y, Geng G, Liang J, Li Y, Chen J, Liu C, Zhang H. RNA helicase MOV10 functions as a co-factor of HIV-1 Rev to facilitate Rev/RRE-dependent nuclear export of viral mRNAs. Virology 2015; 486:15-26. [PMID: 26379090 DOI: 10.1016/j.virol.2015.08.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 08/20/2015] [Accepted: 08/25/2015] [Indexed: 12/25/2022]
Abstract
Human immunodeficiency virus type 1 (HIV-1) exploits multiple host factors during its replication. The REV/RRE-dependent nuclear export of unspliced/partially spliced viral transcripts needs the assistance of host proteins. Recent studies have shown that MOV10 overexpression inhibited HIV-1 replication at various steps. However, the endogenous MOV10 was required in certain step(s) of HIV-1 replication. In this report, we found that MOV10 potently enhances the nuclear export of viral mRNAs and subsequently increases the expression of Gag protein and other late products through affecting the Rev/RRE axis. The co-immunoprecipitation analysis indicated that MOV10 interacts with Rev in an RNA-independent manner. The DEAG-box of MOV10 was required for the enhancement of Rev/RRE-dependent nuclear export and the DEAG-box mutant showed a dominant-negative activity. Our data propose that HIV-1 utilizes the anti-viral factor MOV10 to function as a co-factor of Rev and demonstrate the complicated effects of MOV10 on HIV-1 life cycle.
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Affiliation(s)
- Feng Huang
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Junsong Zhang
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Yijun Zhang
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Guannan Geng
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Juanran Liang
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Yingniang Li
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Jingliang Chen
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Chao Liu
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China.
| | - Hui Zhang
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Key Laboratory of Tropical Disease Control of Ministry of Education, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
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Cervera L, Fuenmayor J, González-Domínguez I, Gutiérrez-Granados S, Segura MM, Gòdia F. Selection and optimization of transfection enhancer additives for increased virus-like particle production in HEK293 suspension cell cultures. Appl Microbiol Biotechnol 2015; 99:9935-49. [PMID: 26278533 DOI: 10.1007/s00253-015-6842-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Revised: 07/08/2015] [Accepted: 07/11/2015] [Indexed: 01/09/2023]
Abstract
The manufacturing of biopharmaceuticals in mammalian cells typically relies on the use of stable producer cell lines. However, in recent years, transient gene expression has emerged as a suitable technology for rapid production of biopharmaceuticals. Transient gene expression is particularly well suited for early developmental phases, where several potential therapeutic targets need to be produced and tested in vivo. As a relatively new bioprocessing modality, a number of opportunities exist for improving cell culture productivity upon transient transfection. For instance, several compounds have shown positive effects on transient gene expression. These transfection enhancers either facilitate entry of PEI/DNA transfection complexes into the cell or nucleus or increase levels of gene expression. In this work, the potential of combining transfection enhancers to increase Gag-based virus-like particle production levels upon transfection of suspension-growing HEK 293 cells is evaluated. Using Plackett-Burman design of experiments, it is first tested the effect of eight transfection enhancers: trichostatin A, valproic acid, sodium butyrate, dimethyl sulfoxide (DMSO), lithium acetate, caffeine, hydroxyurea, and nocodazole. An optimal combination of compounds exhibiting the highest effect on gene expression levels was subsequently identified using a surface response experimental design. The optimal consisted on the addition of 20 mM lithium acetate, 3.36 mM valproic acid, and 5.04 mM caffeine which increased VLP production levels 3.8-fold, while maintaining cell culture viability at 94%.
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Affiliation(s)
- Laura Cervera
- Grup d'Enginyeria Cellular i Bioprocés, Escola d'Enginyeria, Universitat Autònoma de Barcelona, Campus de Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain.
| | - Javier Fuenmayor
- Grup d'Enginyeria Cellular i Bioprocés, Escola d'Enginyeria, Universitat Autònoma de Barcelona, Campus de Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain
| | - Irene González-Domínguez
- Grup d'Enginyeria Cellular i Bioprocés, Escola d'Enginyeria, Universitat Autònoma de Barcelona, Campus de Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain
| | - Sonia Gutiérrez-Granados
- Grup d'Enginyeria Cellular i Bioprocés, Escola d'Enginyeria, Universitat Autònoma de Barcelona, Campus de Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain
| | - Maria Mercedes Segura
- Bluebird Bio Pharmaceutical Sciences, Process Development Group, 150 2nd Street, Cambridge, MA, 02141, USA
| | - Francesc Gòdia
- Grup d'Enginyeria Cellular i Bioprocés, Escola d'Enginyeria, Universitat Autònoma de Barcelona, Campus de Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain
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56
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Super-resolution imaging of ESCRT-proteins at HIV-1 assembly sites. PLoS Pathog 2015; 11:e1004677. [PMID: 25710462 PMCID: PMC4339578 DOI: 10.1371/journal.ppat.1004677] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 01/12/2015] [Indexed: 11/19/2022] Open
Abstract
The cellular endosomal sorting complex required for transport (ESCRT) machinery is involved in membrane budding processes, such as multivesicular biogenesis and cytokinesis. In HIV-infected cells, HIV-1 hijacks the ESCRT machinery to drive HIV release. Early in the HIV-1 assembly process, the ESCRT-I protein Tsg101 and the ESCRT-related protein ALIX are recruited to the assembly site. Further downstream, components such as the ESCRT-III proteins CHMP4 and CHMP2 form transient membrane associated lattices, which are involved in virus-host membrane fission. Although various geometries of ESCRT-III assemblies could be observed, the actual membrane constriction and fission mechanism is not fully understood. Fission might be driven from inside the HIV-1 budding neck by narrowing the membranes from the outside by larger lattices surrounding the neck, or from within the bud. Here, we use super-resolution fluorescence microscopy to elucidate the size and structure of the ESCRT components Tsg101, ALIX, CHMP4B and CHMP2A during HIV-1 budding below the diffraction limit. To avoid the deleterious effects of using fusion proteins attached to ESCRT components, we performed measurements on the endogenous protein or, in the case of CHMP4B, constructs modified with the small HA tag. Due to the transient nature of the ESCRT interactions, the fraction of HIV-1 assembly sites with colocalizing ESCRT complexes was low (1.5%-3.4%). All colocalizing ESCRT clusters exhibited closed, circular structures with an average size (full-width at half-maximum) between 45 and 60 nm or a diameter (determined using a Ripley's L-function analysis) of roughly 60 to 100 nm. The size distributions for colocalizing clusters were narrower than for non-colocalizing clusters, and significantly smaller than the HIV-1 bud. Hence, our results support a membrane scission process driven by ESCRT protein assemblies inside a confined structure, such as the bud neck, rather than by large lattices around the neck or in the bud lumen. In the case of ALIX, a cloud of individual molecules surrounding the central clusters was often observed, which we attribute to ALIX molecules incorporated into the nascent HIV-1 Gag shell. Experiments performed using YFP-tagged Tsg101 led to an over 10-fold increase in ESCRT structures colocalizing with HIV-1 budding sites indicating an influence of the fusion protein tag on the function of the ESCRT protein.
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57
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Döring T, Prange R. Rab33B and its autophagic Atg5/12/16L1 effector assist in hepatitis B virus naked capsid formation and release. Cell Microbiol 2015; 17:747-64. [PMID: 25439980 DOI: 10.1111/cmi.12398] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 11/21/2014] [Accepted: 11/26/2014] [Indexed: 12/22/2022]
Abstract
Hepatitis B virus morphogenesis is accompanied by the production and release of non-enveloped capsids/nucleocapsids. Capsid particles are formed inside the cell cytosol by multimerization of core protein subunits and ultimately exported in an uncommon coatless state. Here, we investigated potential roles of Rab GTPases in capsid formation and trafficking by using RNA interference and overexpression studies. Naked capsid release does not require functions of the endosome-associated Rab5, Rab7 and Rab27 proteins, but depends on functional Rab33B, a GTPase participating in autophagosome formation via interaction with the Atg5-Atg12/Atg16L1 complex. During capsid formation, Rab33B acts in conjunction with its effector, as silencing of Atg5, Atg12 and Atg16L1 also impaired capsid egress. Analysis of capsid maturation steps revealed that Rab33B and Atg5/12/16L1 are required for proper particle assembly and/or stability. In support, the capsid protein was found to interact with Atg5 and colocalize with Atg5/12/16L1, implicating that autophagy pathway functions are involved in capsid biogenesis. However, a complete and functional autophagy pathway is dispensable for capsid release, as judged by knockdown analysis of Atg8/LC3 family members and pharmaceutical ablation of canonical autophagy. Experiments aimed at analysing the capsid release-stimulating activity of the Alix protein provide further evidence for a link between capsid formation and autophagy.
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Affiliation(s)
- Tatjana Döring
- Department of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, D-55101, Germany
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58
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Cervera L, Gutiérrez-Granados S, Berrow NS, Segura MM, Gòdia F. Extended gene expression by medium exchange and repeated transient transfection for recombinant protein production enhancement. Biotechnol Bioeng 2015; 112:934-46. [PMID: 25421734 DOI: 10.1002/bit.25503] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 11/11/2014] [Accepted: 11/18/2014] [Indexed: 11/07/2022]
Abstract
Production of recombinant products in mammalian cell cultures can be achieved by stable gene expression (SGE) or transient gene expression (TGE). The former is based on the integration of a plasmid DNA into the host cell genome allowing continuous gene expression. The latter is based on episomal plasmid DNA expression. Conventional TGE is limited to a short production period of usually about 96 h, therefore limiting productivity. A novel gene expression approach termed extended gene expression (EGE) is explored in this study. The aim of EGE is to prolong the production period by the combination of medium exchange and repeated transfection of cell cultures with plasmid DNA to improve overall protein production. The benefit of this methodology was evaluated for the production of three model recombinant products: intracellular GFP, secreted GFP, and a Gag-GFP virus-like particles (VLPs). Productions were carried out in HEK 293 cell suspension cultures grown in animal-derived component free media using polyethylenimine (PEI) as transfection reagent. Transfections were repeated throughout the production process using different plasmid DNA concentrations, intervals of time, and culture feeding conditions in order to identify the best approach to achieve sustained high-level gene expression. Using this novel EGE strategy, the production period was prolonged between 192 and 240 h with a 4-12-fold increase in production levels, depending on the product type considered.
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Affiliation(s)
- Laura Cervera
- Grup d'Enginyeria Cellular i Tissular, Escola d'Enginyeria, Universitat Autònoma de Barcelona, Campus de Bellaterra, Cerdanyola del Vallès, 08193, Barcelona, Spain
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59
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Richert L, Didier P, de Rocquigny H, Mély Y. Monitoring HIV-1 Protein Oligomerization by FLIM FRET Microscopy. SPRINGER SERIES IN CHEMICAL PHYSICS 2015. [DOI: 10.1007/978-3-319-14929-5_8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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60
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A Quantitative Approach to Evaluate the Impact of Fluorescent Labeling on Membrane-Bound HIV-Gag Assembly by Titration of Unlabeled Proteins. PLoS One 2014; 9:e115095. [PMID: 25493438 PMCID: PMC4262470 DOI: 10.1371/journal.pone.0115095] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Accepted: 11/18/2014] [Indexed: 11/19/2022] Open
Abstract
The assembly process of the human immunodeficiency virus 1 (HIV-1) is driven by the viral polyprotein Gag. Fluorescence imaging of Gag protein fusions is widely performed and has revealed important information on viral assembly. Gag fusion proteins are commonly co-transfected with an unlabeled form of Gag to prevent labeling artifacts such as morphological defects and decreased infectivity. Although viral assembly is widely studied on individual cells, the efficiency of the co-transfection rescue has never been tested at the single cell level. Here, we first develop a methodology to quantify levels of unlabeled to labeled Gag in single cells using a fluorescent reporter protein for unlabeled Gag and fluorescence correlation spectroscopy. Using super-resolution imaging based on photoactivated localization microscopy (PALM) combined with molecular counting we then study the nanoscale morphology of Gag clusters as a function of unlabeled to labeled Gag ratios in single cells. We show that for a given co-transfection ratio, individual cells express a wide range of protein ratios, necessitating a quantitative read-out for the expression of unlabeled Gag. Further, we show that monomerically labeled Gag assembles into membrane-bound clusters that are morphologically indistinguishable from mixtures of unlabeled and labeled Gag.
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61
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Inlora J, Collins DR, Trubin ME, Chung JYJ, Ono A. Membrane binding and subcellular localization of retroviral Gag proteins are differentially regulated by MA interactions with phosphatidylinositol-(4,5)-bisphosphate and RNA. mBio 2014; 5:e02202. [PMID: 25491356 PMCID: PMC4324246 DOI: 10.1128/mbio.02202-14] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 11/07/2014] [Indexed: 01/29/2023] Open
Abstract
UNLABELLED The matrix (MA) domain of HIV-1 mediates proper Gag localization and membrane binding via interaction with a plasma-membrane (PM)-specific acidic phospholipid, phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2]. HIV-1 MA also interacts with RNA, which prevents Gag from binding to membranes containing phosphatidylserine, a prevalent cellular acidic phospholipid. These results suggest that the MA-bound RNA promotes PM-specific localization of HIV-1 Gag by blocking nonspecific interactions with cellular membranes that do not contain PI(4,5)P2. To examine whether PI(4,5)P2 dependence and RNA-mediated inhibition collectively determine MA phenotypes across a broad range of retroviruses and elucidate the significance of their interrelationships, we compared a panel of Gag-leucine zipper constructs (GagLZ) containing MA of different retroviruses. We found that in vitro membrane binding of GagLZ via HIV-1 MA and Rous sarcoma virus (RSV) MA is both PI(4,5)P2 dependent and susceptible to RNA-mediated inhibition. The PM-specific localization and virus-like particle (VLP) release of these GagLZ proteins are severely impaired by overexpression of a PI(4,5)P2-depleting enzyme, polyphosphoinositide 5-phosphatase IV (5ptaseIV). In contrast, membrane binding of GagLZ constructs that contain human T-lymphotropic virus type 1 (HTLV-1) MA, murine leukemia virus (MLV) MA, and human endogenous retrovirus K (HERV-K) MA is PI(4,5)P2 independent and not blocked by RNA. The PM localization and VLP release of these GagLZ chimeras were much less sensitive to 5ptaseIV expression. Notably, single amino acid substitutions that confer a large basic patch rendered HTLV-1 MA susceptible to the RNA-mediated block, suggesting that RNA readily blocks MA containing a large basic patch, such as HIV-1 and RSV MA. Further analyses of these MA mutants suggest a possibility that HIV-1 and RSV MA acquired PI(4,5)P2 dependence to alleviate the membrane binding block imposed by RNA. IMPORTANCE MA basic residues in the HIV-1 structural protein Gag interact with phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2] and RNA. RNA inhibits HIV-1 MA binding to non-PI(4,5)P2 acidic lipids. This inhibition may promote PM specificity of Gag membrane binding, an early essential step in virus assembly. However, whether and how relationships between these interactions have developed among retroviruses are poorly understood. In this study, by comparing diverse retroviral MA domains, we elucidated a strong correlation among PI(4,5)P2 dependence, susceptibility to RNA-mediated inhibition, and cellular behaviors of Gag. Mutagenesis analyses suggest that a large basic patch on MA is sufficient to confer susceptibility to RNA-mediated inhibition but not for PI(4,5)P2-dependent membrane binding. Our findings highlight RNA's role as a general blocker of large basic patches and suggest a possibility that some retroviruses, including HIV-1, have evolved to bind PI(4,5)P2, while others have adopted smaller basic patches on their MA domains, to overcome the RNA-mediated restriction of membrane binding.
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Affiliation(s)
- Jingga Inlora
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - David R Collins
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Marc E Trubin
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Ji Yeon J Chung
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Akira Ono
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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The ubiquitin ligases RNF8 and RNF168 display rapid but distinct dynamics at DNA repair foci in living cells. Int J Biochem Cell Biol 2014; 57:27-34. [PMID: 25304081 DOI: 10.1016/j.biocel.2014.09.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 09/25/2014] [Accepted: 09/30/2014] [Indexed: 01/15/2023]
Abstract
Rapid assembly of DNA damage response (DDR) proteins at nuclear "repair" foci is a hallmark response of ionizing radiation (IR)-treated cells. The ubiquitin E3 ligases RNF8 and RNF168 are critical for foci formation, and here we aim to determine their dynamic mobility and abundance at individual foci in living cells. To this end, YFP-tagged RNF8 and RNF168 were expressed at physiological levels in MCF-7 cells, then analyzed by fluorescence recovery after photobleaching (FRAP) assays, nuclear retention measurement, and virus-like particles (VLPs)-based quantification. The results showed that RNF8 and RNF168 were both highly dynamic at IR-induced foci. Intriguingly, RNF8 displayed remarkably faster in vivo association/dissociation rates than RNF168, and RNF8-positive IR-foci were less resistant to detergent extraction. In addition, copy number assay revealed that RNF168 was two-fold more abundant than RNF8 at foci. Collectively, we show for the first time that RNF8 moves on-and-off nuclear DNA repair foci more than six-fold as quickly as RNF168. The faster kinetics of RNF8 recruitment explains why RNF8 is generally observed at DNA-breaks prior to RNF168. Moreover, our finding that RNF8 is less abundant than RNF168 identifies RNF8 as a rate-limiting determinant of focal repair complex assembly.
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63
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Lachambre S, Chopard C, Beaumelle B. Preliminary characterisation of nanotubes connecting T-cells and their use by HIV-1. Biol Cell 2014; 106:394-404. [DOI: 10.1111/boc.201400037] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 08/07/2014] [Indexed: 01/06/2023]
Affiliation(s)
- Simon Lachambre
- CPBS, UMR 5236 CNRS-Université de Montpellier; Route de Mende; Montpellier 34293 France
| | - Christophe Chopard
- CPBS, UMR 5236 CNRS-Université de Montpellier; Route de Mende; Montpellier 34293 France
| | - Bruno Beaumelle
- CPBS, UMR 5236 CNRS-Université de Montpellier; Route de Mende; Montpellier 34293 France
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64
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Sanford B, Li Y, Maly CJ, Madson CJ, Chen H, Zhou Y, Belshan M. Deletions in the fifth alpha helix of HIV-1 matrix block virus release. Virology 2014; 468-470:293-302. [PMID: 25217711 DOI: 10.1016/j.virol.2014.08.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 06/15/2014] [Accepted: 08/18/2014] [Indexed: 12/20/2022]
Abstract
The matrix (MA) protein of HIV-1 is the N-terminal component of the Gag structural protein and is critical for the early and late stages of viral replication. MA contains five α-helices (α1-α5). Deletions in the N-terminus of α5 as small as three amino acids impaired virus release. Electron microscopy of one deletion mutant (MA∆96-120) showed that its particles were tethered to the surface of cells by membranous stalks. Immunoblots indicated all mutants were processed completely, but mutants with large deletions had alternative processing intermediates. Consistent with the EM data, MA∆96-120 retained membrane association and multimerization capability. Co-expression of this mutant inhibited wild type particle release. Alanine scanning mutation in this region did not affect virus release, although the progeny virions were poorly infectious. Combined, these data demonstrate that structural ablation of the α5 of MA inhibits virus release.
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Affiliation(s)
- Bridget Sanford
- Department of Medical Microbiology and Immunology, Creighton University, 2500 California Plaza, Omaha, NE 68178, USA
| | - Yan Li
- Department of Medical Microbiology and Immunology, Creighton University, 2500 California Plaza, Omaha, NE 68178, USA
| | - Connor J Maly
- Department of Medical Microbiology and Immunology, Creighton University, 2500 California Plaza, Omaha, NE 68178, USA
| | - Christian J Madson
- Department of Medical Microbiology and Immunology, Creighton University, 2500 California Plaza, Omaha, NE 68178, USA
| | - Han Chen
- Center for Biotechnology, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - You Zhou
- Center for Biotechnology, University of Nebraska-Lincoln, Lincoln, NE, USA; Nebraska Center for Virology, Lincoln, NE, USA
| | - Michael Belshan
- Department of Medical Microbiology and Immunology, Creighton University, 2500 California Plaza, Omaha, NE 68178, USA; Nebraska Center for Virology, Lincoln, NE, USA.
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Role of the nucleocapsid region in HIV-1 Gag assembly as investigated by quantitative fluorescence-based microscopy. Virus Res 2014; 193:78-88. [PMID: 25016037 DOI: 10.1016/j.virusres.2014.06.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Revised: 06/17/2014] [Accepted: 06/17/2014] [Indexed: 11/19/2022]
Abstract
The Gag precursor of HIV-1, formed of the four proteic regions matrix (MA), capsid (CA), nucleocapsid (NC) and p6, orchestrates virus morphogenesis. This complex process relies on three major interactions, NC-RNA acting as a scaffold, CA-CA and MA-membrane that targets assembly to the plasma membrane (PM). The characterization of the molecular mechanism of retroviral assembly has extensively benefited from biochemical studies and more recently an important step forward was achieved with the use of fluorescence-based techniques and fluorescently labeled viral proteins. In this review, we summarize the findings obtained with such techniques, notably quantitative-based approaches, which highlight the role of the NC region in Gag assembly.
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Müller B, Anders M, Reinstein J. In vitro analysis of human immunodeficiency virus particle dissociation: gag proteolytic processing influences dissociation kinetics. PLoS One 2014; 9:e99504. [PMID: 24915417 PMCID: PMC4051761 DOI: 10.1371/journal.pone.0099504] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 05/15/2014] [Indexed: 11/18/2022] Open
Abstract
Human immunodeficiency virus particles undergo a step of proteolytic maturation, in which the main structural polyprotein Gag is cleaved into its mature subunits matrix (MA), capsid (CA), nucleocapsid (NC) and p6. Gag proteolytic processing is accompanied by a dramatic structural rearrangement within the virion, which is necessary for virus infectivity and has been proposed to proceed through a sequence of dissociation and reformation of the capsid lattice. Morphological maturation appears to be tightly regulated, with sequential cleavage events and two small spacer peptides within Gag playing important roles by regulating the disassembly of the immature capsid layer and formation of the mature capsid lattice. In order to measure the influence of individual Gag domains on lattice stability, we established Förster's resonance energy transfer (FRET) reporter virions and employed rapid kinetic FRET and light scatter measurements. This approach allowed us to measure dissociation properties of HIV-1 particles assembled in eukaryotic cells containing Gag proteins in different states of proteolytic processing. While the complex dissociation behavior of the particles prevented an assignment of kinetic rate constants to individual dissociation steps, our analyses revealed characteristic differences in the dissociation properties of the MA layer dependent on the presence of additional domains. The most striking effect observed here was a pronounced stabilization of the MA-CA layer mediated by the presence of the 14 amino acid long spacer peptide SP1 at the CA C-terminus, underlining the crucial role of this peptide for the resolution of the immature particle architecture.
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Affiliation(s)
- Barbara Müller
- Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
- * E-mail:
| | - Maria Anders
- Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
| | - Jochen Reinstein
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Heidelberg, Germany
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Proteome analysis of the HIV-1 Gag interactome. Virology 2014; 460-461:194-206. [PMID: 25010285 DOI: 10.1016/j.virol.2014.04.038] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 02/06/2014] [Accepted: 04/19/2014] [Indexed: 11/22/2022]
Abstract
Human immunodeficiency virus Gag drives assembly of virions in infected cells and interacts with host factors which facilitate or restrict viral replication. Although several Gag-binding proteins have been characterized, understanding of virus-host interactions remains incomplete. In a series of six affinity purification screens, we have identified protein candidates for interaction with HIV-1 Gag. Proteins previously found in virions or identified in siRNA screens for host factors influencing HIV-1 replication were recovered. Helicases, translation factors, cytoskeletal and motor proteins, factors involved in RNA degradation and RNA interference were enriched in the interaction data. Cellular networks of cytoskeleton, SR proteins and tRNA synthetases were identified. Most prominently, components of cytoplasmic RNA transport granules were co-purified with Gag. This study provides a survey of known Gag-host interactions and identifies novel Gag binding candidates. These factors are associated with distinct molecular functions and cellular pathways relevant in host-pathogen interactions.
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Cashikar AG, Shim S, Roth R, Maldazys MR, Heuser JE, Hanson PI. Structure of cellular ESCRT-III spirals and their relationship to HIV budding. eLife 2014; 3. [PMID: 24878737 PMCID: PMC4073282 DOI: 10.7554/elife.02184] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 05/27/2014] [Indexed: 12/23/2022] Open
Abstract
The ESCRT machinery along with the AAA+ ATPase Vps4 drive membrane scission for trafficking into multivesicular bodies in the endocytic pathway and for the topologically related processes of viral budding and cytokinesis, but how they accomplish this remains unclear. Using deep-etch electron microscopy, we find that endogenous ESCRT-III filaments stabilized by depleting cells of Vps4 create uniform membrane-deforming conical spirals which are assemblies of specific ESCRT-III heteropolymers. To explore functional roles for ESCRT-III filaments, we examine HIV-1 Gag-mediated budding of virus-like particles and find that depleting Vps4 traps ESCRT-III filaments around nascent Gag assemblies. Interpolating between the observed structures suggests a new role for Vps4 in separating ESCRT-III from Gag or other cargo to allow centripetal growth of a neck constricting ESCRT-III spiral. DOI:http://dx.doi.org/10.7554/eLife.02184.001 Cells contain compartments called organelles that are enclosed within membranes similar to the plasma membrane that surrounds the cell itself. Cells police the proteins on their membranes and move old or damaged proteins into a type of organelle called an endosome. This involves the membrane folding in on itself to form a multivesicular body. The multivesicular bodies deliver their contents to organelles called lysosomes where the old proteins are destroyed. Although it is known that over 30 proteins are involved in the formation of multivesicular bodies, many aspects of how they operate are not well understood. Moreover, disruptions to this process contribute to a large number of diseases including forms of cancer and neurodegeneration. Importantly, the same proteins are hijacked by viruses such as HIV to help them escape from the cells they have infected. Most of the proteins involved in forming multivesicular bodies are part of the ESCRT (Endosomal Sorting Complex Required for Transport) system of proteins. A special set of these proteins—ESCRT-III—is thought to cut the membrane to release vesicles and viruses, as well as helping the membrane to deform. Previously, researchers have been unsure how the ESCRT-III complex works because it has a short lifespan and is too small to see on cellular membranes using standard techniques. Now Cashikar, Shim et al. have used a technique called deep-etch electron microscopy in combination with gene knockdown strategies to reveal the structure of the ESCRT-III complex inside cells. A protein called Vps4 is known to recycle ESCRT-III complexes, so Cashikar, Shim et al. studied cells in which the levels of Vps4 had been depleted in order to increase the lifespan of ESCRT-III complexes. In these cells filaments made of ESCRT-III complexes tended to form conical spirals that matched the size and shape of the vesicles and viruses ESCRT-III is thought to produce. ESCRT-III filaments also accumulated as rings around the molecules destined for incorporation into a vesicle or virus. This indicated a new role for Vps4: it separates ESCRT-III from the contents of the vesicle, leaving it free to form a spiral that drives release of the vesicle or virus from the cell. The next challenge will be to test the predictions of this model using techniques that can capture individual vesicle formation events in real time. Understanding the function of ESCRT-III in greater detail may suggest ways to manipulate this pathway to limit the replication of viruses or the degradation of membrane proteins. DOI:http://dx.doi.org/10.7554/eLife.02184.002
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Affiliation(s)
- Anil G Cashikar
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
| | - Soomin Shim
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
| | - Robyn Roth
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
| | - Michael R Maldazys
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
| | - John E Heuser
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
| | - Phyllis I Hanson
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
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Nityanandam R, Serra-Moreno R. BCA2/Rabring7 targets HIV-1 Gag for lysosomal degradation in a tetherin-independent manner. PLoS Pathog 2014; 10:e1004151. [PMID: 24852021 PMCID: PMC4031200 DOI: 10.1371/journal.ppat.1004151] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2014] [Accepted: 04/14/2014] [Indexed: 12/04/2022] Open
Abstract
BCA2 (Rabring7, RNF115 or ZNF364) is a RING-finger E3 ubiquitin ligase that was identified as a co-factor in the restriction imposed by tetherin/BST2 on HIV-1. Contrary to the current model, in which BCA2 lacks antiviral activity in the absence of tetherin, we found that BCA2 possesses tetherin-independent antiviral activity. Here we show that the N-terminus of BCA2 physically interacts with the Matrix region of HIV-1 and other retroviral Gag proteins and promotes their ubiquitination, redistribution to endo-lysosomal compartments and, ultimately, lysosomal degradation. The targeted depletion of BCA2 in tetherin-expressing and tetherin-deficient cells results in a significant increase in virus release and replication, indicating that endogenous BCA2 possesses antiviral activity. Therefore, these results indicate that BCA2 functions as an antiviral factor that targets HIV-1 Gag for degradation, impairing virus assembly and release. Tetherin (also known as BST2, CD317 or HM1.24) is an interferon-inducible cellular factor that interferes with the release of enveloped viruses from infected cells. A recent study identified BCA2 (Breast Cancer-Associated gene 2, also known as RNF115, ZNF364 or Rabring7), a RING-finger E3 ubiquitin ligase, as a co-factor in the tetherin-mediated restriction of HIV-1. According to this model, BCA2 interacts with sequences in the N-terminus of tetherin to promote the internalization and lysosomal degradation of tethered HIV-1 particles, with no apparent antiviral activity in cells not expressing tetherin. However, here we show for the first time that BCA2 inhibits virus production for HIV-1 and other retroviruses in a tetherin-independent manner by reducing the cellular levels of Gag – the precursor of the structural proteins Matrix, Capsid, Nucleocapsid and p6. Hence, contrary to its reported role as a tetherin co-factor, BCA2 functions as a tetherin-independent antiviral factor that impairs virus assembly and release.
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Affiliation(s)
- Ramya Nityanandam
- Division of Immunology, New England Primate Research Center, Harvard Medical School, Southborough, Massachusetts, United States of America
| | - Ruth Serra-Moreno
- Division of Immunology, New England Primate Research Center, Harvard Medical School, Southborough, Massachusetts, United States of America
- * E-mail:
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Ehrlich LS, Medina GN, Photiadis S, Whittredge PB, Watanabe S, Taraska JW, Carter CA. Tsg101 regulates PI(4,5)P2/Ca(2+) signaling for HIV-1 Gag assembly. Front Microbiol 2014; 5:234. [PMID: 24904548 PMCID: PMC4033031 DOI: 10.3389/fmicb.2014.00234] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Accepted: 04/30/2014] [Indexed: 11/13/2022] Open
Abstract
Our previous studies identified the 1,4,5-inositol trisphosphate receptor (IP3R), a channel mediating release of Ca2+ from ER stores, as a cellular factor differentially associated with HIV-1 Gag that might facilitate ESCRT function in virus budding. Channel opening requires activation that is initiated by binding of 1,4,5-triphosphate (IP3), a product of phospholipase C (PLC)-mediated PI(4,5)P2 hydrolysis. The store emptying that follows stimulates store refilling which requires intact PI(4,5)P2. Raising cytosolic Ca2+ promotes viral particle production and our studies indicate that IP3R and the ER Ca2+ store are the physiological providers of Ca2+ for Gag assembly and release. Here, we show that Gag modulates ER store gating and refilling. Cells expressing Gag exhibited a higher cytosolic Ca2+ level originating from the ER store than control cells, suggesting that Gag induced release of store Ca2+. This property required the PTAP motif in Gag that recruits Tsg101, an ESCRT-1 component. Consistent with cytosolic Ca2+ elevation, Gag accumulation at the plasma membrane was found to require continuous IP3R activation. Like other IP3R channel modulators, Gag was detected in physical proximity to the ER and to endogenous IP3R, as indicated respectively by total internal reflection fluorescence (TIRF) and immunoelectron microscopy (IEM) or indirect immunofluorescence. Reciprocal co-immunoprecipitation suggested that Gag and IP3R proximity is favored when the PTAP motif in Gag is intact. Gag expression was also accompanied by increased PI(4,5)P2 accumulation at the plasma membrane, a condition favoring store refilling capacity. Supporting this notion, Gag particle production was impervious to treatment with 2-aminoethoxydiphenyl borate, an inhibitor of a refilling coupling interaction. In contrast, particle production by a Gag mutant lacking the PTAP motif was reduced. We conclude that a functional PTAP L domain, and by inference Tsg101 binding, confers Gag with an ability to modulate both ER store Ca2+ release and ER store refilling.
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Affiliation(s)
- Lorna S Ehrlich
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Gisselle N Medina
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Sara Photiadis
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Paul B Whittredge
- Laboratory of Molecular Biophysics, National Heart Lung and Blood Institute, National Institutes of Health Bethesda, MD, USA
| | - Susan Watanabe
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
| | - Justin W Taraska
- Laboratory of Molecular Biophysics, National Heart Lung and Blood Institute, National Institutes of Health Bethesda, MD, USA
| | - Carol A Carter
- Molecular Genetics and Microbiology, Stony Brook University Stony Brook, NY, USA
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Cai Y, Bak RO, Mikkelsen JG. Targeted genome editing by lentiviral protein transduction of zinc-finger and TAL-effector nucleases. eLife 2014; 3:e01911. [PMID: 24843011 PMCID: PMC3996624 DOI: 10.7554/elife.01911] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Future therapeutic use of engineered site-directed nucleases, like zinc-finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs), relies on safe and effective means of delivering nucleases to cells. In this study, we adapt lentiviral vectors as carriers of designer nuclease proteins, providing efficient targeted gene disruption in vector-treated cell lines and primary cells. By co-packaging pairs of ZFN proteins with donor RNA in ‘all-in-one’ lentiviral particles, we co-deliver ZFN proteins and the donor template for homology-directed repair leading to targeted DNA insertion and gene correction. Comparative studies of ZFN activity in a predetermined target locus and a known nearby off-target locus demonstrate reduced off-target activity after ZFN protein transduction relative to conventional delivery approaches. Additionally, TALEN proteins are added to the repertoire of custom-designed nucleases that can be delivered by protein transduction. Altogether, our findings generate a new platform for genome engineering based on efficient and potentially safer delivery of programmable nucleases. DOI:http://dx.doi.org/10.7554/eLife.01911.001 Altering the genetic code of a living organism to produce certain desirable outcomes is the goal of genetic engineering. The field builds on a long history of human attempts to alter genetics, from selective breeding of crops and livestock to genetically modified organisms and gene therapies. Researchers routinely use gene editing to create ‘knock-out’ mice in which a particular gene is turned off: the researchers can learn more about the function of this gene by watching what happens when it is absent. As gene editing techniques have grown more sophisticated, they have become an increasingly promising tool for treating diseases that are caused by gene mutations. The aim of this work is to replace faulty genes with genes that work properly. However, it has been difficult to adapt genetic engineering techniques so that they can be used safely in humans. Scientists have created customized enzymes called nucleases that can remove specific genes, but it has been a challenge to get these nucleases into cells in the first place. A virus can be used to deliver the genes that encode these nucleases into the DNA of a cell, but this approach can lead to the production of too many nucleases and to the removal of more genes than intended. Now Cai et al. have developed a ‘hit-and-run’ method for getting the nucleases into cells and making them active only for a short period of time. This method involves using a virus to deliver two different nucleases to a cell. Once inside the cell, the viruses released the nucleases, which were able to remove up to one-quarter of their gene targets, with relatively few errors, in the time that they were active. Next, Cai et al. added gene patches—new genes to replace those removed by the nucleases—to the viruses. This ‘cut and patch’ strategy was successful in up to 8% of the treated cells. The results also suggest that this approach is safer than other gene-editing techniques. DOI:http://dx.doi.org/10.7554/eLife.01911.002
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Affiliation(s)
- Yujia Cai
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Rasmus O Bak
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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Abstract
UNLABELLED We recently demonstrated that a soluble protein, Gas6, can facilitate viral entry by bridging viral envelope phosphatidylserine to Axl, a receptor tyrosine kinase expressed on target cells. The interaction between phosphatidylserine, Gas6, and Axl was originally shown to be a molecular mechanism through which phagocytes recognize phosphatidylserine exposed on dead cells. Since our initial report, several groups have confirmed that Axl/Gas6, as well as other phosphatidylserine receptors, facilitate entry of dengue, West Nile, and Ebola viruses. Virus binding by viral envelope phosphatidylserine is now a viral entry mechanism generalized to many families of viruses. In addition to Axl/Gas6, various molecules are known to recognize phosphatidylserine; however, the effects of these molecules on virus binding and entry have not been comprehensively evaluated and compared. In this study, we examined most of the known human phosphatidylserine-recognizing molecules, including MFG-E8, TIM-1, -3, and -4, CD300a, BAI1, and stabilin-1 and -2, for their abilities to facilitate virus binding and infection. Using pseudotyped lentiviral vectors, we found that a soluble phosphatidylserine-binding protein, MFG-E8, enhances transduction. Cell surface receptors TIM-1 and -4 also enhance virus binding/transduction. The extent of enhancement by these molecules varies, depending on the type of pseudotyping envelope proteins. Mutated MFG-E8, which binds viral envelope phosphatidylserine without bridging virus to cells, but, surprisingly, not annexin V, which has been used to block phagocytosis of dead cells by concealing phosphatidylserine, efficiently blocks these phosphatidylserine-dependent viral entry mechanisms. These results provide insight into understanding the role of viral envelope phosphatidylserine in viral infection. IMPORTANCE Envelope phosphatidylserine has previously been shown to be important for replication of various envelope viruses, but details of this mechanism(s) were unclear. We were the first to report that a bifunctional serum protein, Gas6, bridges envelope phosphatidylserine to a cell surface receptor, Axl. Recent studies demonstrated that many envelope viruses, including vaccinia, dengue, West Nile, and Ebola viruses, utilize Axl/Gas6 to facilitate their entry, suggesting that the phosphatidylserine-mediated viral entry mechanism can be shared by various enveloped viruses. In addition to Axl/Gas6, various molecules are known to recognize phosphatidylserine; however, the effects of these molecules on virus binding and entry have not been comprehensively evaluated and compared. In this study, we examined most human phosphatidylserine-recognizing molecules for their abilities to facilitate viral infection. The results provide insights into the role(s) of envelope phosphatidylserine in viral infection, which can be applicable to the development of novel antiviral reagents that block phosphatidylserine-mediated viral entry.
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Abstract
Assembly, release and maturation of HIV-1 particles comprise a highly dynamic sequence of events, characterized by a series of dramatic rearrangements of the viral structural proteins and overall virion architecture. HIV-1 morphogenesis is a relatively rapid and asynchronous process, showing high variability between cells and individual virions. Therefore, bulk biochemical methods are not ideally suited to study specific aspects of this process in detail. In contrast, imaging represents a direct approach to analyze individual particles and events. While live-cell imaging can reveal the dynamics of intracellular events with high temporal resolution, it falls short in revealing ultra-structural details. Thus, live-cell fluorescence microscopy and electron microscopy (EM) can complement each other to gain insight into both the dynamics of assembly and the structures detected at HIV-1 assembly sites. In this chapter we describe microscopic setups, tools, and methods for live-cell fluorescence microscopy as well as for different EM techniques, which have been successfully used by us and others to study HIV-1 assembly at the host cell plasma membrane. These methods can be used in a complementary manner to investigate the effects of cellular factors, mutations in the viral genome or antiviral drugs on dynamic and structural aspects of HIV-1 morphogenesis.
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Affiliation(s)
- Barbara Müller
- Department of Infectious Diseases, University Hospital Heidelberg, Heidelberg, Germany
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Watanabe SM, Chen MH, Khan M, Ehrlich L, Kemal KS, Weiser B, Shi B, Chen C, Powell M, Anastos K, Burger H, Carter CA. The S40 residue in HIV-1 Gag p6 impacts local and distal budding determinants, revealing additional late domain activities. Retrovirology 2013; 10:143. [PMID: 24257210 PMCID: PMC3907034 DOI: 10.1186/1742-4690-10-143] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 11/11/2013] [Indexed: 12/11/2022] Open
Abstract
Background HIV-1 budding is directed primarily by two motifs in Gag p6 designated as late domain-1 and −2 that recruit ESCRT machinery by binding Tsg101 and Alix, respectively, and by poorly characterized determinants in the capsid (CA) domain. Here, we report that a conserved Gag p6 residue, S40, impacts budding mediated by all of these determinants. Results Whereas budding normally results in formation of single spherical particles ~100 nm in diameter and containing a characteristic electron-dense conical core, the substitution of Phe for S40, a change that does not alter the amino acids encoded in the overlapping pol reading frame, resulted in defective CA-SP1 cleavage, formation of strings of tethered particles or filopodia-like membrane protrusions containing Gag, and diminished infectious particle formation. The S40F-mediated release defects were exacerbated when the viral-encoded protease (PR) was inactivated or when L domain-1 function was disrupted or when budding was almost completely obliterated by the disruption of both L domain-1 and −2. S40F mutation also resulted in stronger Gag-Alix interaction, as detected by yeast 2-hybrid assay. Reducing Alix binding by mutational disruption of contact residues restored single particle release, implicating the perturbed Gag-Alix interaction in the aberrant budding events. Interestingly, introduction of S40F partially rescued the negative effects on budding of CA NTD mutations EE75,76AA and P99A, which both prevent membrane curvature and therefore block budding at an early stage. Conclusions The results indicate that the S40 residue is a novel determinant of HIV-1 egress that is most likely involved in regulation of a critical assembly event required for budding in the Tsg101-, Alix-, Nedd4- and CA N-terminal domain affected pathways.
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Affiliation(s)
- Susan M Watanabe
- Department of Molecular Genetics & Microbiology, Stony Brook University, Life Sciences Bldg, Rm 248, Stony Brook, NY 11794-5222, USA.
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Gutiérrez-Granados S, Cervera L, Gòdia F, Carrillo J, Segura MM. Development and validation of a quantitation assay for fluorescently tagged HIV-1 virus-like particles. J Virol Methods 2013; 193:85-95. [DOI: 10.1016/j.jviromet.2013.05.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Revised: 04/24/2013] [Accepted: 05/08/2013] [Indexed: 02/03/2023]
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Müller B, Heilemann M. Shedding new light on viruses: super-resolution microscopy for studying human immunodeficiency virus. Trends Microbiol 2013; 21:522-33. [PMID: 23916730 DOI: 10.1016/j.tim.2013.06.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 06/20/2013] [Accepted: 06/27/2013] [Indexed: 01/09/2023]
Abstract
For more than 70 years electron microscopy (EM) techniques have played an important role in investigating structures of enveloped viruses. By contrast, use of fluorescence microscopy (FM) methods for this purpose was limited by the fact that the size of virus particles is generally around or below the diffraction limit of light microscopy. Various super-resolution (SR) fluorescence imaging techniques developed over the past two decades bypass the diffraction limit of light microscopy, allowing visualization of subviral details and bridging the gap between conventional FM and EM methods. We summarize here findings on human immunodeficiency virus (HIV-1) obtained using SR-FM techniques. Although the number of published studies is currently limited and some of the pioneering analyses also covered methodological or descriptive aspects, recent publications clearly indicate the potential to approach open questions in HIV-1 replication from a new angle.
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Affiliation(s)
- Barbara Müller
- Department of Infectious Diseases, Virology, University of Heidelberg, Germany.
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Sette P, Nagashima K, Piper RC, Bouamr F. Ubiquitin conjugation to Gag is essential for ESCRT-mediated HIV-1 budding. Retrovirology 2013; 10:79. [PMID: 23895345 PMCID: PMC3751857 DOI: 10.1186/1742-4690-10-79] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 07/24/2013] [Indexed: 01/05/2023] Open
Abstract
Background HIV-1 relies on the host ESCRTs for release from cells. HIV-1 Gag engages ESCRTs by directly binding TSG101 or Alix. ESCRTs also sort ubiquitinated membrane proteins through endosomes to facilitate their lysosomal degradation. The ability of ESCRTs to recognize and process ubiquitinated proteins suggests that ESCRT-dependent viral release may also be controlled by ubiquitination. Although both Gag and ESCRTs undergo some level of ubiquitination, definitive demonstration that ubiquitin is required for viral release is lacking. Here we suppress ubiquitination at viral budding sites by fusing the catalytic domain of the Herpes Simplex UL36 deubiquitinating enzyme (DUb) onto TSG101, Alix, or Gag. Results Expressing DUb-TSG101 suppressed Alix-independent HIV-1 release and viral particles remained tethered to the cell surface. DUb-TSG101 had no effect on budding of MoMLV or EIAV, two retroviruses that rely on the ESCRT machinery for exit. Alix-dependent virus release such as EIAV’s, and HIV-1 lacking access to TSG101, was instead dramatically blocked by co-expressing DUb-Alix. Finally, Gag-DUb was unable to support virus release and dominantly interfered with release of wild type HIV-1. Fusion of UL36 did not effect interactions with Alix, TSG101, or Gag and all of the inhibitory effects of UL36 fusion were abolished when its catalytic activity was ablated. Accordingly, Alix, TSG101 and Gag fused to inactive UL36 functionally replaced their unfused counterparts. Interestingly, coexpression of the Nedd4-2s ubiquitin ligase suppressed the ability of DUb-TSG101 to inhibit HIV-1 release while also restoring detectable Gag ubiquitination at the membrane. Similarly, incorporation of Gag-Ub fusion proteins into virions lifted DUb-ESCRT inhibitory effect. In contrast, Nedd4-2s did not suppress the inhibition mediated by Gag-DUb despite restoring robust ubiquitination of TSG101/ESCRT-I at virus budding sites. Conclusions These studies demonstrate a necessary and natural role for ubiquitin in ESCRT-dependent viral release and indicate a critical role for ubiquitination of Gag rather than ubiquitination of ESCRTs themselves.
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Affiliation(s)
- Paola Sette
- Viral Budding Unit, Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 4 Center Dr, Bethesda, MD 20894, USA
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Bohl CR, Abrahamyan LG, Wood C. Human Ubc9 is involved in intracellular HIV-1 Env stability after trafficking out of the trans-Golgi network in a Gag dependent manner. PLoS One 2013; 8:e69359. [PMID: 23861967 PMCID: PMC3704627 DOI: 10.1371/journal.pone.0069359] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 06/07/2013] [Indexed: 01/03/2023] Open
Abstract
The cellular E2 Sumo conjugase, Ubc9 interacts with HIV-1 Gag, and is important for the assembly of infectious HIV-1 virions. In the previous study we demonstrated that in the absence of Ubc9, a defect in virion assembly was associated with decreased levels of mature intracellular Envelope (Env) that affected Env incorporation into virions and virion infectivity. We have further characterized the effect of Ubc9 knockdown on HIV Env processing and assembly. We found that gp160 stability in the endoplasmic reticulum (ER) and its trafficking to the trans-Golgi network (TGN) were unaffected, indicating that the decreased intracellular mature Env levels in Ubc9-depleted cells were due to a selective degradation of mature Env gp120 after cleavage from gp160 and trafficked out of the TGN. Decreased levels of Gag and mature Env were found to be associated with the plasma membrane and lipid rafts, which suggest that these viral proteins were not trafficked correctly to the assembly site. Intracellular gp120 were partially rescued when treated with a combination of lysosome inhibitors. Taken together our results suggest that in the absence of Ubc9, gp120 is preferentially degraded in the lysosomes likely before trafficking to assembly sites leading to the production of defective virions. This study provides further insight in the processing and packaging of the HIV-1 gp120 into mature HIV-1 virions.
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Affiliation(s)
- Christopher R. Bohl
- Nebraska Center for Virology and the School of Biological Sciences, University of Nebraska, Lincoln, Lincoln, Nebraska, United States of America
| | - Levon G. Abrahamyan
- Nebraska Center for Virology and the School of Biological Sciences, University of Nebraska, Lincoln, Lincoln, Nebraska, United States of America
| | - Charles Wood
- Nebraska Center for Virology and the School of Biological Sciences, University of Nebraska, Lincoln, Lincoln, Nebraska, United States of America
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79
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Fluorosomes: fluorescent virus-like nanoparticles that represent a convenient tool to visualize receptor-ligand interactions. SENSORS 2013; 13:8722-49. [PMID: 23881135 PMCID: PMC3758619 DOI: 10.3390/s130708722] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 06/28/2013] [Accepted: 07/05/2013] [Indexed: 01/03/2023]
Abstract
Viruses are the smallest life forms and parasitize on many eukaryotic organisms, including humans. Consequently, the study of viruses and viral diseases has had an enormous impact on diverse fields of biology and medicine. Due to their often pathogenic properties, viruses have not only had a strong impact on the development of immune cells but also on shaping entire immune mechanisms in their hosts. In order to better characterize virus-specific surface receptors, pathways of virus entry and the mechanisms of virus assembly, diverse methods to visualize virus particles themselves have been developed in the past decades. Apart from characterization of virus-specific mechanisms, fluorescent virus particles also serve as valuable platforms to study receptor-ligand interactions. Along those lines the authors have developed non-infectious virus-like nanoparticles (VNP), which can be decorated with immune receptors of choice and used for probing receptor-ligand interactions, an especially interesting application in the field of basic but also applied immunology research. To be able to better trace receptor-decorated VNP the authors have developed technology to introduce fluorescent proteins into such particles and henceforth termed them fluorosomes (FS). Since VNP are assembled in a simple expression system relying on HEK-293 cells, gene-products of interest can be assembled in a simple and straightforward fashion—one of the reasons why the authors like to call fluorosomes ‘the poor-man's staining tool’. Within this review article an overview on virus particle assembly, chemical and recombinant methods of virus particle labeling and examples on how FS can be applied as sensors to monitor receptor-ligand interactions on leukocytes are given.
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80
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Cervera L, Gutiérrez-Granados S, Martínez M, Blanco J, Gòdia F, Segura MM. Generation of HIV-1 Gag VLPs by transient transfection of HEK 293 suspension cell cultures using an optimized animal-derived component free medium. J Biotechnol 2013; 166:152-65. [DOI: 10.1016/j.jbiotec.2013.05.001] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Revised: 04/29/2013] [Accepted: 05/02/2013] [Indexed: 01/08/2023]
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81
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Abbas W, Herbein G. Plasma membrane signaling in HIV-1 infection. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:1132-42. [PMID: 23806647 DOI: 10.1016/j.bbamem.2013.06.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Revised: 06/12/2013] [Accepted: 06/16/2013] [Indexed: 10/26/2022]
Abstract
Plasma membrane is a multifunctional structure that acts as the initial barrier against infection by intracellular pathogens. The productive HIV-1 infection depends upon the initial interaction of virus and host plasma membrane. Immune cells such as CD4+ T cells and macrophages contain essential cell surface receptors and molecules such as CD4, CXCR4, CCR5 and lipid raft components that facilitate HIV-1 entry. From plasma membrane HIV-1 activates signaling pathways that prepare the grounds for viral replication. Through viral proteins HIV-1 hijacks host plasma membrane receptors such as Fas, TNFRs and DR4/DR5, which results in immune evasion and apoptosis both in infected and uninfected bystander cells. These events are hallmark in HIV-1 pathogenesis that leads towards AIDS. The interplay between HIV-1 and plasma membrane signaling has much to offer in terms of viral fitness and pathogenicity, and a better understanding of this interplay may lead to development of new therapeutic approaches. This article is part of a Special Issue entitled: Viral Membrane Proteins - Channels for Cellular Networking.
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Affiliation(s)
- Wasim Abbas
- Department of Virology, EA 4266 "Pathogens & Inflammation", SFR FED4234, University of Franche-Comte, CHRU Besançon, F-25030 Besançon, France.
| | - Georges Herbein
- Department of Virology, EA 4266 "Pathogens & Inflammation", SFR FED4234, University of Franche-Comte, CHRU Besançon, F-25030 Besançon, France.
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82
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Chukkapalli V, Inlora J, Todd GC, Ono A. Evidence in support of RNA-mediated inhibition of phosphatidylserine-dependent HIV-1 Gag membrane binding in cells. J Virol 2013; 87:7155-9. [PMID: 23552424 PMCID: PMC3676091 DOI: 10.1128/jvi.00075-13] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 03/27/2013] [Indexed: 12/11/2022] Open
Abstract
The matrix domain promotes plasma-membrane-specific binding of HIV-1 Gag through interaction with an acidic lipid phosphatidylinositol-(4,5)-bisphosphate. In in vitro systems, matrix-bound RNA suppresses Gag interactions with phosphatidylserine, an acidic lipid prevalent in various cytoplasmic membranes, thereby enhancing the lipid specificity of the matrix domain. Here we provide in vitro and cell-based evidence supporting the idea that this RNA-mediated suppression occurs in cells and hence is a physiologically relevant mechanism that prevents Gag from binding promiscuously to phosphatidylserine-containing membranes.
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Affiliation(s)
- Vineela Chukkapalli
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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83
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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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84
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Dai L, Lidie KB, Chen Q, Adelsberger JW, Zheng X, Huang D, Yang J, Lempicki RA, Rehman T, Dewar RL, Wang Y, Hornung RL, Canizales KA, Lockett SJ, Lane HC, Imamichi T. IL-27 inhibits HIV-1 infection in human macrophages by down-regulating host factor SPTBN1 during monocyte to macrophage differentiation. J Exp Med 2013; 210:517-34. [PMID: 23460728 PMCID: PMC3600911 DOI: 10.1084/jem.20120572] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 01/31/2013] [Indexed: 02/06/2023] Open
Abstract
The susceptibility of macrophages to HIV-1 infection is modulated during monocyte differentiation. IL-27 is an anti-HIV cytokine that also modulates monocyte activation. In this study, we present new evidence that IL-27 promotes monocyte differentiation into macrophages that are nonpermissive for HIV-1 infection. Although IL-27 treatment does not affect expression of macrophage differentiation markers or macrophage biological functions, it confers HIV resistance by down-regulating spectrin β nonerythrocyte 1 (SPTBN1), a required host factor for HIV-1 infection. IL-27 down-regulates SPTBN1 through a TAK-1-mediated MAPK signaling pathway. Knockdown of SPTBN1 strongly inhibits HIV-1 infection of macrophages; conversely, overexpression of SPTBN1 markedly increases HIV susceptibility of IL-27-treated macrophages. Moreover, we demonstrate that SPTBN1 associates with HIV-1 gag proteins. Collectively, our results underscore the ability of IL-27 to protect macrophages from HIV-1 infection by down-regulating SPTBN1, thus indicating that SPTBN1 is an important host target to reduce HIV-1 replication in one major element of the viral reservoir.
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Affiliation(s)
- Lue Dai
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Kristy B. Lidie
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Qian Chen
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Joseph W. Adelsberger
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Xin Zheng
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - DaWei Huang
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Jun Yang
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Richard A. Lempicki
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Tauseef Rehman
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Robin L. Dewar
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Yanmei Wang
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Ronald L. Hornung
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Kelsey A. Canizales
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Stephen J. Lockett
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - H. Clifford Lane
- Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Tomozumi Imamichi
- Applied and Developmental Directorate and Advanced Technology Program Directorate, Science Applications International Corporation-Frederick, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702
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85
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Super-resolution microscopy reveals specific recruitment of HIV-1 envelope proteins to viral assembly sites dependent on the envelope C-terminal tail. PLoS Pathog 2013; 9:e1003198. [PMID: 23468635 PMCID: PMC3585150 DOI: 10.1371/journal.ppat.1003198] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2012] [Accepted: 01/03/2013] [Indexed: 12/13/2022] Open
Abstract
The inner structural Gag proteins and the envelope (Env) glycoproteins of human immunodeficiency virus (HIV-1) traffic independently to the plasma membrane, where they assemble the nascent virion. HIV-1 carries a relatively low number of glycoproteins in its membrane, and the mechanism of Env recruitment and virus incorporation is incompletely understood. We employed dual-color super-resolution microscopy visualizing Gag assembly sites and HIV-1 Env proteins in virus-producing and in Env expressing cells. Distinctive HIV-1 Gag assembly sites were readily detected and were associated with Env clusters that always extended beyond the actual Gag assembly site and often showed enrichment at the periphery and surrounding the assembly site. Formation of these Env clusters depended on the presence of other HIV-1 proteins and on the long cytoplasmic tail (CT) of Env. CT deletion, a matrix mutation affecting Env incorporation or Env expression in the absence of other HIV-1 proteins led to much smaller Env clusters, which were not enriched at viral assembly sites. These results show that Env is recruited to HIV-1 assembly sites in a CT-dependent manner, while Env(ΔCT) appears to be randomly incorporated. The observed Env accumulation surrounding Gag assemblies, with a lower density on the actual bud, could facilitate viral spread in vivo. Keeping Env molecules on the nascent virus low may be important for escape from the humoral immune response, while cell-cell contacts mediated by surrounding Env molecules could promote HIV-1 transmission through the virological synapse.
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86
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Schiralli Lester GM, Akiyama H, Evans E, Singh J, Gummuluru S, Henderson AJ. Interleukin 2-inducible T cell kinase (ITK) facilitates efficient egress of HIV-1 by coordinating Gag distribution and actin organization. Virology 2013; 436:235-43. [PMID: 23260110 PMCID: PMC3598624 DOI: 10.1016/j.virol.2012.11.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 08/18/2012] [Accepted: 11/25/2012] [Indexed: 12/18/2022]
Abstract
Interleukin 2-inducible T cell kinase (ITK) influences T cell signaling by coordinating actin polymerization and polarization as well as recruitment of kinases and adapter proteins. ITK regulates multiple steps of HIV-1 replication, including virion assembly and release. Fluorescent microscopy was used to examine the functional interactions between ITK and HIV-1 Gag during viral particle release. ITK and Gag colocalized at the plasma membrane and were concentrated at sites of F-actin accumulation and membrane lipid rafts in HIV-1 infected T cells. There was polarized staining of ITK, Gag, and actin towards sites of T cell conjugates. Small molecule inhibitors of ITK disrupted F-actin capping, perturbed Gag-ITK colocalization, inhibited virus like particle release, and reduced HIV replication in primary human CD4+ T cells. These data provide insight as to how ITK influences HIV-1 replication and suggest that targeting host factors that regulate HIV-1 egress provides an innovative strategy for controlling HIV infection.
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Affiliation(s)
- Gillian M. Schiralli Lester
- Department of Medicine, Section of Infectious Diseases, Boston University School of Medicine, 650 Albany Street, EBRC 648, Boston, MA 02118, United States
| | - Hisashi Akiyama
- Department of Microbiology, Boston University School of Medicine, Boston, MA, United States
| | - Erica Evans
- Celgene Avilomics Research, Bedford, MA, United States
| | | | - Suryaram Gummuluru
- Department of Microbiology, Boston University School of Medicine, Boston, MA, United States
| | - Andrew J. Henderson
- Department of Medicine, Section of Infectious Diseases, Boston University School of Medicine, 650 Albany Street, EBRC 648, Boston, MA 02118, United States
- Department of Microbiology, Boston University School of Medicine, Boston, MA, United States
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87
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Zentner I, Sierra LJ, Fraser AK, Maciunas L, Mankowski MK, Vinnik A, Fedichev P, Ptak RG, Martín-García J, Cocklin S. Identification of a small-molecule inhibitor of HIV-1 assembly that targets the phosphatidylinositol (4,5)-bisphosphate binding site of the HIV-1 matrix protein. ChemMedChem 2013; 8:426-32. [PMID: 23361947 DOI: 10.1002/cmdc.201200577] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2012] [Indexed: 12/22/2022]
Abstract
The development of drug resistance remains a critical problem for current HIV-1 antiviral therapies, creating a need for new inhibitors of HIV-1 replication. We previously reported on a novel anti-HIV-1 compound, N(2)-(phenoxyacetyl)-N-[4-(1-piperidinylcarbonyl)benzyl]glycinamide (14), that binds to the highly conserved phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P(2)) binding pocket of the HIV-1 matrix (MA) protein. In this study, we re-evaluate the hits from the virtual screen used to identify compound 14 and test them directly in an HIV-1 replication assay using primary human peripheral blood mononuclear cells. This study resulted in the identification of three new compounds with antiviral activity; 2-(4-{[3-(4-fluorophenyl)-1,2,4-oxadiazol-5-yl]methyl})-1-piperazinyl)-N-(4-methylphenyl)acetamide (7), 3-(2-ethoxyphenyl)-5-[[4-(4-nitrophenyl)piperazin-1-yl]methyl]-1,2,4-oxadiazole (17), and N-[4-ethoxy-3-(1-piperidinylsulfonyl)phenyl]-2-(imidazo[2,1-b][1,3]thiazol-6-yl)acetamide (18), with compound 7 being the most potent of these hits. Mechanistic studies on 7 demonstrated that it directly interacts with and functions through HIV-1 MA. In accordance with our drug target, compound 7 competes with PI(4,5)P(2) for MA binding and, as a result, diminishes the production of new virus. Mutation of residues within the PI(4,5)P(2) binding site of MA decreased the antiviral effect of compound 7. Additionally, compound 7 displays a broadly neutralizing anti-HIV activity, with IC(50) values of 7.5-15.6 μM for the group M isolates tested. Taken together, these results point towards a novel chemical probe that can be used to more closely study the biological role of MA and could, through further optimization, lead to a new class of anti-HIV-1 therapeutics.
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Affiliation(s)
- Isaac Zentner
- Department of Biochemistry & Molecular Biology, Drexel University College of Medicine, 245 North 15th Street, Philadelphia, PA 19102, USA
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88
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Alterations in the MA and NC domains modulate phosphoinositide-dependent plasma membrane localization of the Rous sarcoma virus Gag protein. J Virol 2013; 87:3609-15. [PMID: 23325682 DOI: 10.1128/jvi.03059-12] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Retroviral Gag proteins direct virus particle assembly from the plasma membrane (PM). Phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P(2)] plays a role in PM targeting of several retroviral Gag proteins. Here we report that depletion of intracellular PI(4,5)P(2) and phosphatidylinositol-(3,4,5)-triphosphate [PI(3,4,5)P(3)] levels impaired Rous sarcoma virus (RSV) Gag PM localization. Gag mutants deficient in nuclear trafficking were less sensitive to reduction of intracellular PI(4,5)P(2) and PI(3,4,5)P(3), suggesting a possible connection between Gag nuclear trafficking and phosphoinositide-dependent PM targeting.
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89
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Margine I, Martinez-Gil L, Chou YY, Krammer F. Residual baculovirus in insect cell-derived influenza virus-like particle preparations enhances immunogenicity. PLoS One 2012; 7:e51559. [PMID: 23236516 PMCID: PMC3517492 DOI: 10.1371/journal.pone.0051559] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 11/05/2012] [Indexed: 12/22/2022] Open
Abstract
Influenza virus-like particles are currently evaluated in clinical trials as vaccine candidates for influenza viruses. Most commonly they are produced in baculovirus- or mammalian- expression systems. Here we used different vaccination schemes in order to systematically compare virus-like particle preparations generated in the two systems. Our work shows significant differences in immunogenicity between the two, and indicates superior and broader immune responses induced by the baculovirus-derived constructs. We demonstrate that these differences critically influence protection and survival in a mouse model of influenza virus infection. Finally, we show that the enhanced immunogenicity of the baculovirus-derived virus-like particles is caused by contamination with residual baculovirus which activates the innate immune response at the site of inoculation.
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Affiliation(s)
- Irina Margine
- Department of Microbiology, Mount Sinai School of Medicine, New York, New York, United States of America
- Graduate School of Biological Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Luis Martinez-Gil
- Department of Microbiology, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Yi-ying Chou
- Department of Microbiology, Mount Sinai School of Medicine, New York, New York, United States of America
- Graduate School of Biological Sciences, Mount Sinai School of Medicine, New York, New York, United States of America
| | - Florian Krammer
- Department of Microbiology, Mount Sinai School of Medicine, New York, New York, United States of America
- * E-mail:
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90
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Zentner I, Sierra LJ, Maciunas L, Vinnik A, Fedichev P, Mankowski MK, Ptak RG, Martín-García J, Cocklin S. Discovery of a small-molecule antiviral targeting the HIV-1 matrix protein. Bioorg Med Chem Lett 2012; 23:1132-5. [PMID: 23305922 DOI: 10.1016/j.bmcl.2012.11.041] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Revised: 11/07/2012] [Accepted: 11/12/2012] [Indexed: 01/03/2023]
Abstract
Due to the emergence of drug-resistant strains and the cumulative toxicities associated with current therapies, demand remains for new inhibitors of HIV-1 replication. The HIV-1 matrix (MA) protein is an essential viral component with established roles in the assembly of the virus. Using virtual and surface plasmon resonance (SPR)-based screening, we describe the identification of the first small molecule to bind to the HIV-1 MA protein and to possess broad range anti-HIV properties.
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Affiliation(s)
- Isaac Zentner
- Department of Biochemistry & Molecular Biology, Drexel University College of Medicine, 245 N. 15th Street, Philadelphia, PA 19102, USA
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91
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Chojnacki J, Müller B. Investigation of HIV-1 assembly and release using modern fluorescence imaging techniques. Traffic 2012; 14:15-24. [PMID: 22957540 DOI: 10.1111/tra.12006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 09/04/2012] [Accepted: 09/07/2012] [Indexed: 12/17/2022]
Abstract
The replication of HIV-1, like that of all viruses, is intimately connected with cellular structures and pathways. For many years, bulk biochemical and cell biological methods were the main approaches employed to investigate interactions between HIV-1 and its host cell. However, during the past decade advancements in fluorescence imaging technologies opened new possibilities for the direct visualization of individual steps occurring throughout the viral replication cycle. Electron microscopy (EM) methods, which have traditionally been employed for the study of viruses, are complemented by fluorescence microscopy (FM) techniques that allow us to follow the dynamics of virus-cell interaction. Subdiffraction fluorescence microscopy, as well as correlative EM/FM approaches, are narrowing the fundamental gap between the high structural resolution provided by EM and the high temporal resolution and throughput accomplished by FM. The application of modern microscopy to the study of HIV-1-host cell interactions has provided insights into the biology of the virus which could not easily, or not at all, have been gained by other methods. Here, we review how modern fluorescence imaging techniques enhanced our knowledge of the dynamic and structural changes involved in HIV-1 particle formation.
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Affiliation(s)
- Jakub Chojnacki
- Department of Infectious Diseases, Virology, University Hospital of Heidelberg, Heidelberg, Germany
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92
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NC-mediated nucleolar localization of retroviral gag proteins. Virus Res 2012; 171:304-18. [PMID: 23036987 DOI: 10.1016/j.virusres.2012.09.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 08/13/2012] [Accepted: 09/22/2012] [Indexed: 11/21/2022]
Abstract
The assembly and release of retrovirus particles from the cell membrane is directed by the Gag polyprotein. The Gag protein of Rous sarcoma virus (RSV) traffics through the nucleus prior to plasma membrane localization. We previously reported that nuclear localization of RSV Gag is linked to efficient packaging of viral genomic RNA, however the intranuclear activities of RSV Gag are not well understood. To gain insight into the properties of the RSV Gag protein within the nucleus, we examined the subnuclear localization and dynamic trafficking of RSV Gag. Restriction of RSV Gag to the nucleus by mutating its nuclear export signal (NES) in the p10 domain or interfering with CRM1-mediated nuclear export of Gag by leptomycin B (LMB) treatment led to the accumulation of Gag in nucleoli and discrete nucleoplasmic foci. Retention of RSV Gag in nucleoli was reduced with cis-expression of the 5' untranslated RU5 region of the viral RNA genome, suggesting the psi (Ψ) packaging signal may alter the subnuclear localization of Gag. Fluorescence recovery after photobleaching (FRAP) demonstrated that the nucleolar fraction of Gag was highly mobile, indicating that there was rapid exchange with Gag proteins in the nucleoplasm. RSV Gag is targeted to nucleoli by a nucleolar localization signal (NoLS) in the NC domain, and similarly, the human immunodeficiency virus type 1 (HIV-1) NC protein also contains an NoLS consisting of basic residues. Interestingly, co-expression of HIV-1 NC or Rev with HIV-1 Gag resulted in accumulation of Gag in nucleoli. Moreover, a subpopulation of HIV-1 Gag was detected in the nucleoli of HeLa cells stably expressing the entire HIV-1 genome in a Rev-dependent fashion. These findings suggest that the RSV and HIV-1 Gag proteins undergo nucleolar trafficking in the setting of viral infection.
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93
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Taha AY, Basselin M, Ramadan E, Modi HR, Rapoport SI, Cheon Y. Altered lipid concentrations of liver, heart and plasma but not brain in HIV-1 transgenic rats. Prostaglandins Leukot Essent Fatty Acids 2012; 87:91-101. [PMID: 22939288 PMCID: PMC3467364 DOI: 10.1016/j.plefa.2012.07.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2012] [Revised: 07/17/2012] [Accepted: 07/18/2012] [Indexed: 12/15/2022]
Abstract
Disturbed lipid metabolism has been reported in antiretroviral-naive HIV-1-infected patients suggesting a direct effect of the virus on lipid metabolism. To test that the HIV-1 virus alone could alter lipid concentrations, we measured these concentrations in an HIV-1 transgenic (Tg) rat model of human HIV-1 infection, which demonstrates peripheral and central pathology by 7-9 months of age. Concentrations were measured in high-energy microwaved heart, brain and liver from 7-9 month-old HIV-1 Tg and wildtype rats, and in plasma from non-microwaved rats. Plasma triglycerides and liver cholesteryl ester and total cholesterol concentrations were significantly higher in HIV-1 Tg rats than controls. Heart and plasma fatty acid concentrations reflected concentration differences in liver, which showed higher n-3 and n-6 polyunsaturated fatty acid (PUFA) concentrations in multiple lipid compartments. Fatty acid concentrations were increased or decreased in heart and liver phospholipid subfractions. Brain fatty acid concentrations differed significantly between the groups for minor fatty acids such as linoleic acid and n-3 docosapentaenoic acid. The profound changes in heart, plasma and liver lipid concentrations suggest a direct effect of chronic exposure to the HIV-1 virus on peripheral lipid (including PUFA) metabolism.
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Affiliation(s)
- Ameer Y Taha
- Brain Physiology and Metabolism Section, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA.
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94
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Mok MT, Henderson BR. The in vivo dynamic interplay of MDC1 and 53BP1 at DNA damage-induced nuclear foci. Int J Biochem Cell Biol 2012; 44:1398-409. [DOI: 10.1016/j.biocel.2012.05.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 05/28/2012] [Accepted: 05/29/2012] [Indexed: 11/16/2022]
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95
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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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96
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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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97
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Baumgärtel V, Müller B, Lamb DC. Quantitative live-cell imaging of human immunodeficiency virus (HIV-1) assembly. Viruses 2012; 4:777-99. [PMID: 22754649 PMCID: PMC3386619 DOI: 10.3390/v4050777] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2012] [Accepted: 04/24/2012] [Indexed: 11/16/2022] Open
Abstract
Advances in fluorescence methodologies make it possible to investigate biological systems in unprecedented detail. Over the last few years, quantitative live-cell imaging has increasingly been used to study the dynamic interactions of viruses with cells and is expected to become even more indispensable in the future. Here, we describe different fluorescence labeling strategies that have been used to label HIV-1 for live cell imaging and the fluorescence based methods used to visualize individual aspects of virus-cell interactions. This review presents an overview of experimental methods and recent experiments that have employed quantitative microscopy in order to elucidate the dynamics of late stages in the HIV-1 replication cycle. This includes cytosolic interactions of the main structural protein, Gag, with itself and the viral RNA genome, the recruitment of Gag and RNA to the plasma membrane, virion assembly at the membrane and the recruitment of cellular proteins involved in HIV-1 release to the nascent budding site.
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Affiliation(s)
- Viola Baumgärtel
- Department of Chemistry, Center for NanoScience (CeNS) and Center for Integrated Protein Science, Munich (CIPSM), Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, D-81377 München, Germany;
| | - Barbara Müller
- Department of Infectious Diseases, Virology, University Hospital Heidelberg, Im Neuenheimer Feld 324, D-69120 Heidelberg, Germany
- Authors to whom correspondence should be addressed; (B.M.); (D.C.L.); Tel.: +49-6221-56-1325 (B.M.); +49-89-2180-77564 (D.C.L.); Fax: +49-6221-56-5003 (B.M.); +49-89-2180-77560 (D.C.L.)
| | - Don C. Lamb
- Department of Chemistry, Center for NanoScience (CeNS) and Center for Integrated Protein Science, Munich (CIPSM), Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, D-81377 München, Germany;
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61820, USA
- Authors to whom correspondence should be addressed; (B.M.); (D.C.L.); Tel.: +49-6221-56-1325 (B.M.); +49-89-2180-77564 (D.C.L.); Fax: +49-6221-56-5003 (B.M.); +49-89-2180-77560 (D.C.L.)
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98
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Mok MT, Henderson BR. The In Vivo Dynamic Organization of BRCA1-A Complex Proteins at DNA Damage-Induced Nuclear Foci. Traffic 2012; 13:800-14. [DOI: 10.1111/j.1600-0854.2012.01355.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 03/13/2012] [Accepted: 03/15/2012] [Indexed: 12/01/2022]
Affiliation(s)
- Myth T.S. Mok
- Westmead Institute for Cancer Research; The University of Sydney, Westmead Millennium Institute at Westmead Hospital; Westmead; NSW; 2145; Australia
| | - Beric R. Henderson
- Westmead Institute for Cancer Research; The University of Sydney, Westmead Millennium Institute at Westmead Hospital; Westmead; NSW; 2145; Australia
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99
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Ganser-Pornillos BK, Yeager M, Pornillos O. Assembly and architecture of HIV. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 726:441-65. [PMID: 22297526 DOI: 10.1007/978-1-4614-0980-9_20] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
HIV forms spherical, membrane-enveloped, pleomorphic virions, 1,000-1,500 Å in diameter, which contain two copies of its single-stranded, positive-sense RNA genome. Virus particles initially bud from host cells in a noninfectious or immature form, in which the genome is further encapsulated inside a spherical protein shell composed of around 2,500 copies of the virally encoded Gag polyprotein. The Gag molecules are radially arranged, adherent to the inner leaflet of the viral membrane, and closely associated as a hexagonal, paracrystalline lattice. Gag comprises three major structural domains called MA, CA, and NC. For immature virions to become infectious, they must undergo a maturation process that is initiated by proteolytic processing of Gag by the viral protease. The new Gag-derived proteins undergo dramatic rearrangements to form the mature virus. The mature MA protein forms a "matrix" layer and remains attached to the viral envelope, NC condenses with the genome, and approximately 1,500 copies of CA assemble into a new cone-shaped protein shell, called the mature capsid, which surrounds the genomic ribonucleoprotein complex. The HIV capsid conforms to the mathematical principles of a fullerene shell, in which the CA subunits form about 250 CA hexamers arrayed on a variably curved hexagonal lattice, which is closed by incorporation of exactly 12 pentamers, seven pentamers at the wide end and five at the narrow end of the cone. This chapter describes our current understanding of HIV's virion architecture and its dynamic transformations: the process of virion assembly as orchestrated by Gag, the architecture of the immature virion, the virus maturation process, and the structure of the mature capsid.
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Affiliation(s)
- Barbie K Ganser-Pornillos
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
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100
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Baluyot MF, Grosse SA, Lyddon TD, Janaka SK, Johnson MC. CRM1-dependent trafficking of retroviral Gag proteins revisited. J Virol 2012; 86:4696-700. [PMID: 22318151 PMCID: PMC3318649 DOI: 10.1128/jvi.07199-11] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2011] [Accepted: 01/27/2012] [Indexed: 11/20/2022] Open
Abstract
We analyzed the nuclear trafficking ability of Gag proteins from six retroviral genera. Contrary to a previous report, human immunodeficiency virus type 1 (HIV-1) Gag showed no propensity to cycle through the nucleus. The only Gag protein that displayed CRM1-dependent nuclear cycling was that of Rous sarcoma virus (RSV). Surprisingly, this cycling could be eliminated without compromising infectivity by replacing the RSV Gag N-terminal matrix (MA) domain with HIV MA.
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Affiliation(s)
| | - Sarah A. Grosse
- Rosalind Franklin University of Medicine and Science, Chicago, Illinois, USA
| | - Terri D. Lyddon
- Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri, Columbia, Missouri, USA
| | - Sanath K. Janaka
- Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri, Columbia, Missouri, USA
| | - Marc C. Johnson
- Molecular Microbiology and Immunology, Christopher S. Bond Life Science Center, University of Missouri, Columbia, Missouri, USA
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