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Kislinger G, Fabig G, Wehn A, Rodriguez L, Jiang H, Niemann C, Klymchenko AS, Plesnila N, Misgeld T, Müller-Reichert T, Khalin I, Schifferer M. Combining array tomography with electron tomography provides insights into leakiness of the blood-brain barrier in mouse cortex. eLife 2024; 12:RP90565. [PMID: 39102289 PMCID: PMC11299977 DOI: 10.7554/elife.90565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/06/2024] Open
Abstract
Like other volume electron microscopy approaches, automated tape-collecting ultramicrotomy (ATUM) enables imaging of serial sections deposited on thick plastic tapes by scanning electron microscopy (SEM). ATUM is unique in enabling hierarchical imaging and thus efficient screening for target structures, as needed for correlative light and electron microscopy. However, SEM of sections on tape can only access the section surface, thereby limiting the axial resolution to the typical size of cellular vesicles with an order of magnitude lower than the acquired xy resolution. In contrast, serial-section electron tomography (ET), a transmission electron microscopy-based approach, yields isotropic voxels at full EM resolution, but requires deposition of sections on electron-stable thin and fragile films, thus making screening of large section libraries difficult and prone to section loss. To combine the strength of both approaches, we developed 'ATUM-Tomo, a hybrid method, where sections are first reversibly attached to plastic tape via a dissolvable coating, and after screening detached and transferred to the ET-compatible thin films. As a proof-of-principle, we applied correlative ATUM-Tomo to study ultrastructural features of blood-brain barrier (BBB) leakiness around microthrombi in a mouse model of traumatic brain injury. Microthrombi and associated sites of BBB leakiness were identified by confocal imaging of injected fluorescent and electron-dense nanoparticles, then relocalized by ATUM-SEM, and finally interrogated by correlative ATUM-Tomo. Overall, our new ATUM-Tomo approach will substantially advance ultrastructural analysis of biological phenomena that require cell- and tissue-level contextualization of the finest subcellular textures.
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Affiliation(s)
- Georg Kislinger
- Institute of Neuronal Cell Biology, Technical University MunichMunichGermany
- German Center for Neurodegenerative Diseases (DZNE)MunichGermany
| | - Gunar Fabig
- Experimental Center, Faculty of Medicine Carl Gustav Carus, Technische Universität DresdenDresdenGermany
| | - Antonia Wehn
- Institute for Stroke and Dementia Research (ISD), LMU University Hospital, LMU MunichMunichGermany
- Department of Neurosurgery, University of Munich Medical CenterMunichGermany
| | - Lucia Rodriguez
- Institute of Neuronal Cell Biology, Technical University MunichMunichGermany
- German Center for Neurodegenerative Diseases (DZNE)MunichGermany
| | - Hanyi Jiang
- Institute of Neuronal Cell Biology, Technical University MunichMunichGermany
- German Center for Neurodegenerative Diseases (DZNE)MunichGermany
- Department of Psychiatry and Psychotherapy, University Medicine GreifswaldGreifswaldGermany
| | - Cornelia Niemann
- Institute of Neuronal Cell Biology, Technical University MunichMunichGermany
- German Center for Neurodegenerative Diseases (DZNE)MunichGermany
| | - Andrey S Klymchenko
- Laboratoire de Bioimagerie et Pathologies, Université de StrasbourgIllkirchFrance
| | - Nikolaus Plesnila
- Institute for Stroke and Dementia Research (ISD), LMU University Hospital, LMU MunichMunichGermany
- Munich Cluster of Systems Neurology (SyNergy)MunichGermany
| | - Thomas Misgeld
- Institute of Neuronal Cell Biology, Technical University MunichMunichGermany
- German Center for Neurodegenerative Diseases (DZNE)MunichGermany
- Munich Cluster of Systems Neurology (SyNergy)MunichGermany
| | - Thomas Müller-Reichert
- Experimental Center, Faculty of Medicine Carl Gustav Carus, Technische Universität DresdenDresdenGermany
| | - Igor Khalin
- Institute for Stroke and Dementia Research (ISD), LMU University Hospital, LMU MunichMunichGermany
- Normandie University, UNICAEN, INSERM UMR-S U1237, Physiopathology and Imaging of 19 Neurological Disorders (PhIND), GIP Cyceron, Institute Blood and BrainCaenFrance
| | - Martina Schifferer
- German Center for Neurodegenerative Diseases (DZNE)MunichGermany
- Munich Cluster of Systems Neurology (SyNergy)MunichGermany
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Pillai VN, Ali LM, Prabhu SG, Krishnan A, Tariq S, Mustafa F, Rizvi TA. Expression, purification, and functional characterization of soluble recombinant full-length simian immunodeficiency virus (SIV) Pr55 Gag. Heliyon 2023; 9:e12892. [PMID: 36685375 PMCID: PMC9853374 DOI: 10.1016/j.heliyon.2023.e12892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 12/14/2022] [Accepted: 01/06/2023] [Indexed: 01/11/2023] Open
Abstract
The simian immunodeficiency virus (SIV) precursor polypeptide Pr55Gag drives viral assembly and facilitates specific recognition and packaging of the SIV genomic RNA (gRNA) into viral particles. While several studies have tried to elucidate the role of SIV Pr55Gag by expressing its different components independently, studies using full-length SIV Pr55Gag have not been conducted, primarily due to the unavailability of purified and biologically active full-length SIV Pr55Gag. We successfully expressed soluble, full-length SIV Pr55Gag with His6-tag in bacteria and purified it using affinity and gel filtration chromatography. In the process, we identified within Gag, a second in-frame start codon downstream of a putative Shine-Dalgarno-like sequence resulting in an additional truncated form of Gag. Synonymously mutating this sequence allowed expression of full-length Gag in its native form. The purified Gag assembled into virus-like particles (VLPs) in vitro in the presence of nucleic acids, revealing its biological functionality. In vivo experiments also confirmed formation of functional VLPs, and quantitative reverse transcriptase PCR demonstrated efficient packaging of SIV gRNA by these VLPs. The methodology we employed ensured the availability of >95% pure, biologically active, full-length SIV Pr55Gag which should facilitate future studies to understand protein structure and RNA-protein interactions involved during SIV gRNA packaging.
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Affiliation(s)
- Vineeta N. Pillai
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates
| | - Lizna Mohamed Ali
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates
| | - Suresha G. Prabhu
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates
| | - Anjana Krishnan
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates
| | - Saeed Tariq
- Department of Anatomy, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates
| | - Farah Mustafa
- Department of Biochemistry, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates,Zayed Center for Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates,Corresponding author. Department of Biochemistry, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), P.O. Box 15551, Al Ain, United Arab Emirates.
| | - Tahir A. Rizvi
- Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University, Al Ain, United Arab Emirates,Zayed Center for Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates,Corresponding author. Department of Microbiology & Immunology, College of Medicine and Health Sciences (CMHS), United Arab Emirates University (UAEU), P.O. Box 15551, Al Ain, United Arab Emirates.
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3
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Torii EH, Wünschmann A, Armién AG, Mor SK, Chalupsky E, Kumar R, Willette M. Adenoviral infection in 5 red-tailed hawks and a broad-winged hawk. J Vet Diagn Invest 2022; 34:796-805. [PMID: 35762098 DOI: 10.1177/10406387221105240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Adenoviral infections among raptors are best described in falcons and are characterized most commonly by necrotizing hepatitis and splenitis; only one case has been reported in a hawk. Five red-tailed hawks (Buteo jamaicensis) and a broad-winged hawk (Buteo platypterus) had an adenoviral infection based on history, histopathology, negative-stain electron microscopy, and PCR. All birds had acute onset of illness resulting in death; 3 had evidence of a concurrent bacterial infection. Microscopically, all 6 birds had solitary, pale eosinophilic-to-amphophilic, intranuclear inclusion bodies within presumed hematopoietic cells in bone marrow and macrophages in spleen. Five of the 6 birds had similar inclusions within hepatocytes and Kupffer cells. All but one bird had severe bone marrow necrosis. There was moderate splenic necrosis (3 of 6) and mild-to-marked hepatic necrosis (4 of 6). Negative-stain electron microscopy demonstrated adenoviral particles in bone marrow (5 of 6), liver (1 of 5), and/or spleen (1 of 5). PCR was positive for adenovirus in bone marrow (3 of 5), liver (1 of 3), spleen (4 of 6), and/or intestinal contents (2 of 3). Viral DNA polymerase gene sequences clustered within the Siadenovirus genus. There was 99% nucleotide identity to one another and 90% nucleotide identity with the closest related adenovirus (Harris hawk, EU715130). Our case series expands on the limited knowledge of adenoviral infections in hawks. The splenic and hepatic necrosis, and particularly the hitherto unreported bone marrow necrosis, suggest that adenoviral infection is clinically relevant and potentially fatal in hawks.
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Affiliation(s)
- Emma H Torii
- Minnesota Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, USA
| | - Arno Wünschmann
- Minnesota Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, USA
| | - Anibal G Armién
- California Animal Health & Food Safety Laboratory System, University of California-Davis, Davis, CA, USA
| | - Sunil K Mor
- Minnesota Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, USA
| | - Emma Chalupsky
- The Raptor Center, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, USA
| | - Rahul Kumar
- Minnesota Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, USA
| | - Michelle Willette
- The Raptor Center, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, USA
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Sachse M, Fernández de Castro I, Tenorio R, Risco C. The viral replication organelles within cells studied by electron microscopy. Adv Virus Res 2019; 105:1-33. [PMID: 31522702 PMCID: PMC7112055 DOI: 10.1016/bs.aivir.2019.07.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Transmission electron microscopy (TEM) has been crucial to study viral infections. As a result of recent advances in light and electron microscopy, we are starting to be aware of the variety of structures that viruses assemble inside cells. Viruses often remodel cellular compartments to build their replication factories. Remarkably, viruses are also able to induce new membranes and new organelles. Here we revise the most relevant imaging technologies to study the biogenesis of viral replication organelles. Live cell microscopy, correlative light and electron microscopy, cryo-TEM, and three-dimensional imaging methods are unveiling how viruses manipulate cell organization. In particular, methods for molecular mapping in situ in two and three dimensions are revealing how macromolecular complexes build functional replication complexes inside infected cells. The combination of all these imaging approaches is uncovering the viral life cycle events with a detail never seen before.
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Affiliation(s)
- Martin Sachse
- Unité Technologie et service BioImagerie Ultrastructurale, Institut Pasteur, Paris, France.
| | | | - Raquel Tenorio
- Cell Structure Laboratory, National Center for Biotechnology, CSIC, Madrid, Spain
| | - Cristina Risco
- Cell Structure Laboratory, National Center for Biotechnology, CSIC, Madrid, Spain.
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5
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Contribution of the Cytoplasmic Determinants of Vpu to the Expansion of Virus-Containing Compartments in HIV-1-Infected Macrophages. J Virol 2019; 93:JVI.00020-19. [PMID: 30867316 DOI: 10.1128/jvi.00020-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/09/2019] [Indexed: 12/30/2022] Open
Abstract
HIV-1 infection of macrophages leads to the sequestration of newly formed viruses in intracellular plasma membrane-connected structures termed virus-containing compartments (VCCs), where virions remain infectious and hidden from immune surveillance. The cellular restriction factor bone marrow stromal cell antigen 2 (BST2), which prevents HIV-1 dissemination by tethering budding viral particles at the plasma membrane, can be found in VCCs. The HIV-1 accessory protein Vpu counteracts the restriction factor BST2 by downregulating its expression and removing it from viral budding sites. Numerous studies described these Vpu countermeasures in CD4+ T cells or model cell lines, but the interplay between Vpu and BST2 in VCC formation and HIV-1 production in macrophages is less explored. Here, we show that Vpu expression in HIV-1-infected macrophages enhances viral release. This effect is related to Vpu's ability to circumvent BST2 antiviral activity. We show that in absence of Vpu, BST2 is enriched in VCCs and colocalizes with capsid p24, whereas Vpu expression significantly reduces the presence of BST2 in these compartments. Furthermore, our data reveal that BST2 is dispensable for the formation of VCCs and that Vpu expression impacts the volume of these compartments. This Vpu activity partly depends on BST2 expression and requires the integrity of the Vpu transmembrane domain, the dileucine-like motif E59XXXLV64 and phosphoserines 52 and 56 of Vpu. Altogether, these results highlight that Vpu controls the volume of VCCs and promotes HIV-1 release from infected macrophages.IMPORTANCE HIV-1 infection of macrophages leads to the sequestration of newly formed viruses in virus-containing compartments (VCCs), where virions remain infectious and hidden from immune surveillance. The restriction factor BST2, which prevents HIV-1 dissemination by tethering budding viral particles, can be found in VCCs. The HIV-1 Vpu protein counteracts BST2. This study explores the interplay between Vpu and BST2 in the viral protein functions on HIV-1 release and viral particle sequestration in VCCs in macrophages. The results show that Vpu controls the volume of VCCs and favors viral particle release. These Vpu functions partly depend on Vpu's ability to antagonize BST2. This study highlights that the transmembrane domain of Vpu and two motifs of the Vpu cytoplasmic domain are required for these functions. These motifs were notably involved in the control of the volume of VCCs by Vpu but were dispensable for the prevention of the specific accumulation of BST2 in these structures.
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Schroeder JA. Application of laboratory and digital techniques for visual enhancement during the ultrastructural assessment of cilia. Ultrastruct Pathol 2017; 41:399-407. [DOI: 10.1080/01913123.2017.1363335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Josef A. Schroeder
- Central EM-Lab, Department of Pathology, University Hospital Regensburg, Regensburg, Germany
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Nkwe DO, Pelchen-Matthews A, Burden JJ, Collinson LM, Marsh M. The intracellular plasma membrane-connected compartment in the assembly of HIV-1 in human macrophages. BMC Biol 2016; 14:50. [PMID: 27338237 PMCID: PMC4919869 DOI: 10.1186/s12915-016-0272-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 06/09/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In HIV-infected macrophages, newly formed progeny virus particles accumulate in intracellular plasma membrane-connected compartments (IPMCs). Although the virus is usually seen in these compartments, it is unclear whether HIV assembly is specifically targeted to IPMCs or whether some viruses may also form at the cell surface but are not detected, as particles budding from the latter site will be released into the medium. RESULTS To investigate the fidelity of HIV-1 targeting to IPMCs compared to the cell surface directly, we generated mutants defective in recruitment of the Endosomal Sorting Complexes Required for Transport (ESCRT) proteins required for virus scission. For mutants unable to bind the ESCRT-I component Tsg101, HIV release was inhibited and light and electron microscopy revealed that budding was arrested. When expressed in human monocyte-derived macrophages (MDM), these mutants formed budding-arrested, immature particles at their assembly sites, allowing us to capture virtually all of the virus budding events. A detailed morphological analysis of the distribution of the arrested viruses by immunofluorescence staining and confocal microscopy, and by electron microscopy, demonstrated that HIV assembly in MDMs is targeted primarily to IPMCs, with fewer than 5 % of budding events seen at the cell surface. Morphometric analysis of the relative membrane areas at the cell surface and IPMCs confirmed a large enrichment of virus assembly events in IPMCs. Serial block-face scanning electron microscopy of macrophages infected with a budding-defective HIV mutant revealed high-resolution 3D views of the complex organisation of IPMCs, with in excess of 15,000 associated HIV budding sites, and multiple connections between IPMCs and the cell surface. CONCLUSIONS Using detailed quantitative analysis, we demonstrate that HIV assembly in MDMs is specifically targeted to IPMCs. Furthermore, 3D analysis shows, for the first time, the detailed ultrastructure of an IPMC within a large cell volume, at a resolution that allowed identification of individual virus assembly events, and potential portals through which virus may be released during cell-cell transfer. These studies provide new insights to the organisation of the HIV assembly compartments in macrophages, and show how HIV particles accumulating in these protected sites may function as a virus reservoir.
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Affiliation(s)
- David O. Nkwe
- />MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT UK
- />Present Address: Department of Biology and Biotechnological Sciences, College of Science, Botswana International University of Science and Technology, Private Bag 16, Palapye, Botswana
| | - Annegret Pelchen-Matthews
- />MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT UK
| | - Jemima J. Burden
- />MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT UK
| | - Lucy M. Collinson
- />The Francis Crick Institute, Lincoln’s Inn Fields Laboratories, 44 Lincoln’s Inn Fields, London, WC2A 3LY UK
| | - Mark Marsh
- />MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London, WC1E 6BT UK
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8
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Risco C, de Castro IF, Sanz-Sánchez L, Narayan K, Grandinetti G, Subramaniam S. Three-Dimensional Imaging of Viral Infections. Annu Rev Virol 2014; 1:453-73. [PMID: 26958730 DOI: 10.1146/annurev-virology-031413-085351] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Three-dimensional (3D) imaging technologies are beginning to have significant impact in the field of virology, as they are helping us understand how viruses take control of cells. In this article we review several methodologies for 3D imaging of cells and show how these technologies are contributing to the study of viral infections and the characterization of specialized structures formed in virus-infected cells. We include 3D reconstruction by transmission electron microscopy (TEM) using serial sections, electron tomography, and focused ion beam scanning electron microscopy (FIB-SEM). We summarize from these methods selected contributions to our understanding of viral entry, replication, morphogenesis, egress and propagation, and changes in the spatial architecture of virus-infected cells. In combination with live-cell imaging, correlative microscopy, and new techniques for molecular mapping in situ, the availability of these methods for 3D imaging is expected to provide deeper insights into understanding the structural and dynamic aspects of viral infection.
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Affiliation(s)
- Cristina Risco
- Cell Structure Laboratory, National Center for Biotechnology (CNB-CSIC), Madrid 28049, Spain;
| | | | - Laura Sanz-Sánchez
- Cell Structure Laboratory, National Center for Biotechnology (CNB-CSIC), Madrid 28049, Spain;
| | - Kedar Narayan
- Laboratory of Cell Biology, National Cancer Institute, Bethesda, Maryland 20892;
| | - Giovanna Grandinetti
- Laboratory of Cell Biology, National Cancer Institute, Bethesda, Maryland 20892;
| | - Sriram Subramaniam
- Laboratory of Cell Biology, National Cancer Institute, Bethesda, Maryland 20892;
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Abstract
A mandatory step in the formation of an infectious retroviral particle is the acquisition of its envelope glycoprotein (Env). This step invariably occurs by Env positioning itself in the host membrane at the location of viral budding and being incorporated along with the host membrane into the viral particle. In some ways, this step of the viral life cycle would appear to be imprecise. There is no specific sequence in Env or in the retroviral structural protein, Gag, that is inherently required for the production of an infectious Env-containing particle. Additionally, Env-defective proviruses can efficiently produce infectious particles with any of a number of foreign retroviral Env glycoproteins or even glycoproteins from unrelated viral families, a process termed pseudotyping. However, mounting evidence suggests that Env incorporation is neither passive nor random. Rather, several redundant mechanisms appear to contribute to the carefully controlled process of Env acquisition, many of which are apparently used by a wide variety of enveloped viruses. This review presents and discusses the evidence for these different mechanisms contributing to incorporation.
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Affiliation(s)
- Marc C Johnson
- Department of Molecular Microbiology and Immunology, University of Missouri School of Medicine, Columbia, 65211, USA.
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10
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Abstract
The formation of enveloped virus particles requires that key structural components of the virus, and the viral genomic RNA, are brought together at a cellular membrane system where new particles are assembled. The trafficking events, and the subsequent assembly and release of infectious virus particles, is co-coordinated through interactions between the viral structural proteins and cellular proteins. In the present paper, we consider how these events occur during HIV production in macrophages. In these cells, virus assembly appears to occur on a pre-existing specialized plasma membrane domain that is sequestered within the cells. The events that take place at these intracellular assembly sites may endow the virus with unique biochemical characteristics and allow virus release to be co-ordinated through the formation of infectious synapses.
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11
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Kershaw T, Wavre-Shapton ST, Signoret N, Marsh M. Analysis of chemokine receptor endocytosis and intracellular trafficking. Methods Enzymol 2009; 460:357-77. [PMID: 19446735 DOI: 10.1016/s0076-6879(09)05218-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Chemokine receptors are G protein-coupled receptors (GPCRs) that, through their ability to regulate chemotaxis by responding to small chemoattractant peptides termed chemokines, are involved in the development, maintenance, and functional activities of the immune system. In addition, members of the chemokine receptor family have been implicated in a number of other physiological and pathological processes, including human immunodeficiency virus infection and malaria. These activities are dependent on receptor expression at the cell surface and cellular events that reduce the cell-surface expression of chemokine receptors can abrogate these activities. Moreover, internalization of chemokine receptors by endocytosis is necessary for both receptor degradation and recycling, key regulatory processes that determine cell-surface expression levels. Here we provide detailed methods for the quantitative analysis of CCR5 endocytosis and recycling by flow cytometry, as well as fluorescence and electron microscopic procedures to analyze the endocytosis and intracellular trafficking of CCR5 by immunolabeling of cells or cryosections. In principle, the same approaches can be used for analyzing other chemokine receptors and other GPCR or non-GPCR cell-surface proteins.
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Affiliation(s)
- Tom Kershaw
- Cell Biology Unit, MRC Laboratory for Molecular Cell Biology, and Department of Cell and Developmental Biology, University College London, London, United Kingdom
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Abstract
Viruses are very small and most of them can be seen only by TEM (transmission electron microscopy). TEM has therefore made a major contribution to virology, including the discovery of many viruses, the diagnosis of various viral infections and fundamental investigations of virus-host cell interactions. However, TEM has gradually been replaced by more sensitive methods, such as the PCR. In research, new imaging techniques for fluorescence light microscopy have supplanted TEM, making it possible to study live cells and dynamic interactions between viruses and the cellular machinery. Nevertheless, TEM remains essential for certain aspects of virology. It is very useful for the initial identification of unknown viral agents in particular outbreaks, and is recommended by regulatory agencies for investigation of the viral safety of biological products and/or the cells used to produce them. In research, only TEM has a resolution sufficiently high for discrimination between aggregated viral proteins and structured viral particles. Recent examples of different viral assembly models illustrate the value of TEM for improving our understanding of virus-cell interactions.
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13
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Mori Y, Koike M, Moriishi E, Kawabata A, Tang H, Oyaizu H, Uchiyama Y, Yamanishi K. Human herpesvirus-6 induces MVB formation, and virus egress occurs by an exosomal release pathway. Traffic 2008; 9:1728-42. [PMID: 18637904 PMCID: PMC2613231 DOI: 10.1111/j.1600-0854.2008.00796.x] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The final envelopment of most herpesviruses occurs at Golgi or post-Golgi compartments, such as the trans Golgi network (TGN); however, the final envelopment site of human herpesvirus 6 (HHV-6) is uncertain. In this study, we found novel pathways for HHV-6 assembly and release from T cells that differed, in part, from those of alphaherpesviruses. Electron microscopy showed that late in infection, HHV-6-infected cells were larger than uninfected cells and contained many newly formed multivesicular body (MVB)-like compartments that included small vesicles. These MVBs surrounded the Golgi apparatus. Mature virions were found in the MVBs and MVB fusion with plasma membrane, and the release of mature virions together with small vesicles was observed at the cell surface. Immunoelectron microscopy demonstrated that the MVBs contained CD63, an MVB/late endosome marker, and HHV-6 envelope glycoproteins. The viral glycoproteins also localized to internal vesicles in the MVBs and to secreted vesicles (exosomes). Furthermore, we found virus budding at TGN-associated membranes, which expressed CD63, adaptor protein (AP-1) and TGN46, and CD63 incorporation into virions. Our findings suggest that mature HHV-6 virions are released together with internal vesicles through MVBs by the cellular exosomal pathway. This scenario has significant implications for understanding HHV-6's maturation pathway.
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Affiliation(s)
- Yasuko Mori
- Department of Biomedical Research, Laboratory of Virology and Vaccinology, National Institute of Biomedical Innovation, Ibaraki, Osaka, Japan.
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