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Das PK, Kielian M. Rubella virus assembly requirements and evolutionary relationships with novel rubiviruses. mBio 2024; 15:e0196524. [PMID: 39207105 PMCID: PMC11481484 DOI: 10.1128/mbio.01965-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2024] [Accepted: 08/01/2024] [Indexed: 09/04/2024] Open
Abstract
Rubella virus (RuV) is an enveloped virus that usually causes mild disease in children, but can produce miscarriage or severe congenital birth defects. While in nature RuV only infects humans, the discovery of the related Ruhugu (RuhV) and Rustrela (RusV) viruses highlights the spillover potential of mammalian rubiviruses to humans. RuV buds into the Golgi, but its assembly and exit are not well understood. We identified a potential late domain motif 278PPAY281 at the C-terminus of the RuV E2 envelope protein. Such late domain motifs can promote virus budding by recruiting the cellular ESCRT machinery. An E2 Y281A mutation reduced infectious virus production by >3 logs and inhibited virus particle production. However, RuV was insensitive to inhibition by dominant-negative VPS4, and thus appeared ESCRT-independent. The E2 Y281A mutation did not significantly inhibit the production of the viral structural proteins capsid (Cp), E2, and E1, or dimerization, glycosylation, Golgi transport, and colocalization of E2 and E1. However, E2 Y281A significantly reduced glycoprotein-Cp colocalization and interaction, and inhibited Cp localization to the Golgi. Revertants of the E2 Y281A mutant contained an E2 281V substitution or the second site mutations [E2 N277I + Cp D215A]. These mutations promoted virus growth, particle production, E2/Cp colocalization and Cp-Golgi localization. Both the E2 substitutions 281V and 277I were found at the corresponding positions in the RuhV E2 protein. Taken together, our data identify a key interaction of the RuV E2 endodomain with the Cp during RuV biogenesis, and support the close evolutionary relationship between human and animal rubiviruses. IMPORTANCE Rubella virus (RuV) is an enveloped virus that only infects humans, where transplacental infection can cause miscarriage or congenital birth defects. We identified a potential late domain, 278PPAY281, at the C terminus of the E2 envelope protein. However, rather than this domain recruiting the cellular ESCRT machinery as predicted, our data indicate that E2 Y281 promotes a critical interaction of the E2 endodomain with the capsid protein, leading to capsid's localization to the Golgi where virus budding occurs. Revertant analysis demonstrated that two substitutions on the E2 protein could partially rescue virus growth and Cp-Golgi localization. Both residues were found at the corresponding positions in Ruhugu virus E2, supporting the close evolutionary relationship between RuV and Ruhugu virus, a recently discovered rubivirus from bats.
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Affiliation(s)
- Pratyush Kumar Das
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Margaret Kielian
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, USA
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2
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Das PK, Gonzalez PA, Jangra RK, Yin P, Kielian M. A single-point mutation in the rubella virus E1 glycoprotein promotes rescue of recombinant vesicular stomatitis virus. mBio 2024; 15:e0237323. [PMID: 38334805 PMCID: PMC10936182 DOI: 10.1128/mbio.02373-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 01/10/2024] [Indexed: 02/10/2024] Open
Abstract
Rubella virus (RuV) is an enveloped plus-sense RNA virus and a member of the Rubivirus genus. RuV infection in pregnant women can lead to miscarriage or an array of severe birth defects known as congenital rubella syndrome. Novel rubiviruses were recently discovered in various mammals, highlighting the spillover potential of other rubiviruses to humans. Many features of the rubivirus infection cycle remain unexplored. To promote the study of rubivirus biology, here, we generated replication-competent recombinant VSV-RuV (rVSV-RuV) encoding the RuV transmembrane glycoproteins E2 and E1. Sequencing of rVSV-RuV showed that the RuV glycoproteins acquired a single-point mutation W448R in the E1 transmembrane domain. The E1 W448R mutation did not detectably alter the intracellular expression, processing, glycosylation, colocalization, or dimerization of the E2 and E1 glycoproteins. Nonetheless, the mutation enhanced the incorporation of RuV E2/E1 into VSV particles, which bud from the plasma membrane rather than the RuV budding site in the Golgi. Neutralization by E1 antibodies, calcium dependence, and cell tropism were comparable between WT-RuV and either rVSV-RuV or RuV containing the E1 W448R mutation. However, the E1 W448R mutation strongly shifted the threshold for the acid pH-triggered virus fusion reaction, from pH 6.2 for the WT RuV to pH 5.5 for the mutant. These results suggest that the increased resistance of the mutant RuV E1 to acidic pH promotes the ability of viral envelope proteins to generate infectious rVSV and provide insights into the regulation of RuV fusion during virus entry and exit.IMPORTANCERubella virus (RuV) infection in pregnant women can cause miscarriage or severe fetal birth defects. While a highly effective vaccine has been developed, RuV cases are still a significant problem in areas with inadequate vaccine coverage. In addition, related viruses have recently been discovered in mammals, such as bats and mice, leading to concerns about potential virus spillover to humans. To facilitate studies of RuV biology, here, we generated and characterized a replication-competent vesicular stomatitis virus encoding the RuV glycoproteins (rVSV-RuV). Sequence analysis of rVSV-RuV identified a single-point mutation in the transmembrane region of the E1 glycoprotein. While the overall properties of rVSV-RuV are similar to those of WT-RuV, the mutation caused a marked shift in the pH dependence of virus membrane fusion. Together, our studies of rVSV-RuV and the identified W448R mutation expand our understanding of rubivirus biology and provide new tools for its study.
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Affiliation(s)
- Pratyush Kumar Das
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, USA
| | | | - Rohit K. Jangra
- Department of Microbiology and Immunology, Louisiana State University Health Science Center-Shreveport, Shreveport, Louisiana, USA
| | - Peiqi Yin
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Margaret Kielian
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, USA
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3
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Sengupta R, Mihelc EM, Angel S, Lanman JK, Kuhn RJ, Stahelin RV. Contribution of the Golgi apparatus in morphogenesis of a virus-induced cytopathic vacuolar system. Life Sci Alliance 2022; 5:5/10/e202000887. [PMID: 36137747 PMCID: PMC9500387 DOI: 10.26508/lsa.202000887] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 09/07/2022] [Accepted: 09/08/2022] [Indexed: 11/24/2022] Open
Abstract
Electron tomography reveals four classes of cytopathic vesicles-II (CPV-II) stemming from the host Golgi apparatus after Venezuelan equine encephalitis virus infection. The Golgi apparatus (GA) in mammalian cells is pericentrosomally anchored and exhibits a stacked architecture. During infections by members of the alphavirus genus, the host cell GA is thought to give rise to distinct mobile pleomorphic vacuoles known as CPV-II (cytopathic vesicle-II) via unknown morphological steps. To dissect this, we adopted a phased electron tomography approach to image multiple overlapping volumes of a cell infected with Venezuelan equine encephalitis virus (VEEV) and complemented it with localization of a peroxidase-tagged Golgi marker. Analysis of the tomograms revealed a pattern of progressive cisternal bending into double-lamellar vesicles as a central process underpinning the biogenesis and the morphological complexity of this vacuolar system. Here, we propose a model for the conversion of the GA to CPV-II that reveals a unique pathway of intracellular virus envelopment. Our results have implications for alphavirus-induced displacement of Golgi cisternae to the plasma membrane to aid viral egress operating late in the infection cycle.
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Affiliation(s)
- Ranjan Sengupta
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA .,Department of Biological Sciences, Purdue University, West Lafayette, IN, USA.,The Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, USA
| | - Elaine M Mihelc
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Stephanie Angel
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA.,Department of Biological Sciences, Purdue University, West Lafayette, IN, USA.,The Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, USA
| | - Jason K Lanman
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Richard J Kuhn
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA.,The Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, USA
| | - Robert V Stahelin
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA .,The Purdue Institute of Inflammation, Immunology and Infectious Disease, Purdue University, West Lafayette, IN, USA
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4
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A filamentous archaeal virus is enveloped inside the cell and released through pyramidal portals. Proc Natl Acad Sci U S A 2021; 118:2105540118. [PMID: 34341107 DOI: 10.1073/pnas.2105540118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The majority of viruses infecting hyperthermophilic archaea display unique virion architectures and are evolutionarily unrelated to viruses of bacteria and eukaryotes. The lack of relationships to other known viruses suggests that the mechanisms of virus-host interaction in Archaea are also likely to be distinct. To gain insights into archaeal virus-host interactions, we studied the life cycle of the enveloped, ∼2-μm-long Sulfolobus islandicus filamentous virus (SIFV), a member of the family Lipothrixviridae infecting a hyperthermophilic and acidophilic archaeon Saccharolobus islandicus LAL14/1. Using dual-axis electron tomography and convolutional neural network analysis, we characterize the life cycle of SIFV and show that the virions, which are nearly two times longer than the host cell diameter, are assembled in the cell cytoplasm, forming twisted virion bundles organized on a nonperfect hexagonal lattice. Remarkably, our results indicate that envelopment of the helical nucleocapsids takes place inside the cell rather than by budding as in the case of most other known enveloped viruses. The mature virions are released from the cell through large (up to 220 nm in diameter), six-sided pyramidal portals, which are built from multiple copies of a single 89-amino-acid-long viral protein gp43. The overexpression of this protein in Escherichia coli leads to pyramid formation in the bacterial membrane. Collectively, our results provide insights into the assembly and release of enveloped filamentous viruses and illuminate the evolution of virus-host interactions in Archaea.
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Abstract
Rubella virus (RUBV), a rubivirus, is an airborne human pathogen that generally causes mild measles-like symptoms in children or adults. However, RUBV infection of pregnant women can result in miscarriage or congenital rubella syndrome (CRS), a collection of long-term birth defects including incomplete organ development and mental retardation. Worldwide vaccination campaigns have significantly reduced the number of RUBV infections, but RUBV continues to be a problem in countries with low vaccination coverage. Further, the recent discovery of pathogenic rubiviruses in other mammals emphasizes the spillover potential of rubella-related viruses to humans. In the last decade, our understanding of RUBV has been significantly increased by virological, biochemical, and structural studies, providing a platform to begin understanding the life cycle of RUBV at the molecular level. This review concentrates on recent work on RUBV, focusing on the virion, its structural components, and its entry, fusion, and assembly mechanisms. Important features of RUBV are compared with those of viruses from other families. We also use comparative genomics, manual curation, and protein homology modeling to highlight distinct features of RUBV that are evolutionarily conserved in the non-human rubiviruses. Since rubella-like viruses may potentially have higher pathogenicity and transmissibility to humans, we also propose a framework for utilizing RUBV as a model to study its more pathogenic cousins.
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Hernandez-Gonzalez M, Larocque G, Way M. Viral use and subversion of membrane organization and trafficking. J Cell Sci 2021; 134:jcs252676. [PMID: 33664154 PMCID: PMC7610647 DOI: 10.1242/jcs.252676] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Membrane trafficking is an essential cellular process conserved across all eukaryotes, which regulates the uptake or release of macromolecules from cells, the composition of cellular membranes and organelle biogenesis. It influences numerous aspects of cellular organisation, dynamics and homeostasis, including nutrition, signalling and cell architecture. Not surprisingly, malfunction of membrane trafficking is linked to many serious genetic, metabolic and neurological disorders. It is also often hijacked during viral infection, enabling viruses to accomplish many of the main stages of their replication cycle, including entry into and egress from cells. The appropriation of membrane trafficking by viruses has been studied since the birth of cell biology and has helped elucidate how this integral cellular process functions. In this Review, we discuss some of the different strategies viruses use to manipulate and take over the membrane compartments of their hosts to promote their replication, assembly and egress.
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Affiliation(s)
- Miguel Hernandez-Gonzalez
- Cellular Signalling and Cytoskeletal Function Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Gabrielle Larocque
- Cellular Signalling and Cytoskeletal Function Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Michael Way
- Cellular Signalling and Cytoskeletal Function Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
- Department of Infectious Disease, Imperial College, London W2 1PG, UK
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7
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Vaccinia Virus Glycoproteins A33, A34, and B5 Form a Complex for Efficient Endoplasmic Reticulum to trans-Golgi Network Transport. J Virol 2020; 94:JVI.02155-19. [PMID: 31941777 DOI: 10.1128/jvi.02155-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 12/23/2019] [Indexed: 01/10/2023] Open
Abstract
Orthopoxviruses produce two, antigenically distinct, infectious enveloped virions termed intracellular mature virions and extracellular virions. Extracellular virions are required for cell-to-cell spread and pathogenesis. Specific to the extracellular virion membrane, glycoproteins A33, A34, and B5 are highly conserved among orthopoxviruses and have roles during extracellular virion formation and subsequent infection. B5 is dependent on an interaction with either A33 or A34 for localization to the site of intracellular envelopment and incorporation into the envelope of released extracellular virions. In this report we show that an interaction between A33 and A34 can be detected in infected cells. Furthermore, we show that a three-protein complex between A33, A34, and B5 forms in the endoplasmic reticulum (ER) that disassociates post ER export. Finally, immunofluorescence reveals that coexpression of all three glycoproteins results in their localization to a juxtanuclear region that is presumably the site of intracellular envelopment. These results demonstrate the existence of two previously unidentified interactions: one between A33 and A34 and another simultaneous interaction between all three of the glycoproteins. Furthermore, these results indicate that interactions among A33, A34, and B5 are vital for proper intracellular trafficking and subcellular localization.IMPORTANCE The secondary intracellular envelopment of poxviruses at the trans-Golgi network to release infectious extracellular virus (EV) is essential for their spread and pathogenesis. Viral glycoproteins A33, A34, and B5 are critical for the efficient production of infectious EV and interactions among these proteins are important for their localization and incorporation into the outer extracellular virion membrane. We have uncovered a novel interaction between glycoproteins A33 and A34. Furthermore, we show that B5 can interact with the A33-A34 complex. Our analysis indicates that the three-protein complex has a role in ER exit and proper localization of the three glycoproteins to the intracellular site of wrapping. These results show that a complex set of interactions occur in the secretory pathway of infected cells to ensure proper glycoprotein trafficking and envelope content, which is important for the release of infectious poxvirus virions.
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Abstract
The Golgi apparatus is a central intracellular membrane-bound organelle with key functions in trafficking, processing, and sorting of newly synthesized membrane and secretory proteins and lipids. To best perform these functions, Golgi membranes form a unique stacked structure. The Golgi structure is dynamic but tightly regulated; it undergoes rapid disassembly and reassembly during the cell cycle of mammalian cells and is disrupted under certain stress and pathological conditions. In the past decade, significant amount of effort has been made to reveal the molecular mechanisms that regulate the Golgi membrane architecture and function. Here we review the major discoveries in the mechanisms of Golgi structure formation, regulation, and alteration in relation to its functions in physiological and pathological conditions to further our understanding of Golgi structure and function in health and diseases.
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Affiliation(s)
- Jie Li
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Erpan Ahat
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Yanzhuang Wang
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
- Department of Neurology, University of Michigan School of Medicine, Ann Arbor, MI, USA.
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Glingston RS, Deb R, Kumar S, Nagotu S. Organelle dynamics and viral infections: at cross roads. Microbes Infect 2018; 21:20-32. [PMID: 29953921 PMCID: PMC7110583 DOI: 10.1016/j.micinf.2018.06.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 06/14/2018] [Accepted: 06/15/2018] [Indexed: 01/12/2023]
Abstract
Viruses are obligate intracellular parasites of the host cells. A commonly accepted view is the requirement of internal membranous structures for various aspects of viral life cycle. Organelles enable favourable intracellular environment for several viruses. However, studies reporting organelle dynamics upon viral infections are scant. In this review, we aim to summarize and highlight modulations caused to various organelles upon viral infection or expression of its proteins.
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Affiliation(s)
- R Sahaya Glingston
- Organelle Biology and Cellular Ageing Lab, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India
| | - Rachayeeta Deb
- Organelle Biology and Cellular Ageing Lab, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India
| | - Sachin Kumar
- Viral Immunology Lab, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India.
| | - Shirisha Nagotu
- Organelle Biology and Cellular Ageing Lab, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India.
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Mangala Prasad V, Klose T, Rossmann MG. Assembly, maturation and three-dimensional helical structure of the teratogenic rubella virus. PLoS Pathog 2017; 13:e1006377. [PMID: 28575072 PMCID: PMC5470745 DOI: 10.1371/journal.ppat.1006377] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 06/14/2017] [Accepted: 04/25/2017] [Indexed: 01/24/2023] Open
Abstract
Viral infections during pregnancy are a significant cause of infant morbidity and mortality. Of these, rubella virus infection is a well-substantiated example that leads to miscarriages or severe fetal defects. However, structural information about the rubella virus has been lacking due to the pleomorphic nature of the virions. Here we report a helical structure of rubella virions using cryo-electron tomography. Sub-tomogram averaging of the surface spikes established the relative positions of the viral glycoproteins, which differed from the earlier icosahedral models of the virus. Tomographic analyses of in vitro assembled nucleocapsids and virions provide a template for viral assembly. Comparisons of immature and mature virions show large rearrangements in the glycoproteins that may be essential for forming the infectious virions. These results present the first known example of a helical membrane-enveloped virus, while also providing a structural basis for its assembly and maturation pathway. Rubella virus (RV) causes serious fetal defects when contracted during pregnancy. Despite its medical importance, due to the irregular shapes and different sizes of the virions, the RV structure has remained unknown. Using cryo-electron tomography, we have determined the RV structure, which shows a unique, helical outer surface. Subsequent local averaging of the RV surface spikes has established the conformations of its immunogenic glycoproteins. In vitro assembly studies on the virus capsid protein have provided insights into the interactions necessary for virus assembly. Comparisons between mature and immature RV show large conformational changes in the virion structure that are essential for virus maturation. These results help to gain a structural understanding of RV pathogenicity, which may also be relevant to other teratogenic viruses.
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Affiliation(s)
- Vidya Mangala Prasad
- Department of Biological Sciences, 240 S. Martin Jischke Drive, Purdue University, West Lafayette, IN, United States of America
| | - Thomas Klose
- Department of Biological Sciences, 240 S. Martin Jischke Drive, Purdue University, West Lafayette, IN, United States of America
| | - Michael G. Rossmann
- Department of Biological Sciences, 240 S. Martin Jischke Drive, Purdue University, West Lafayette, IN, United States of America
- * E-mail:
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11
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Antiviral activity of hemolymph of Podalia against rubella virus. Cytotechnology 2016; 69:31-37. [PMID: 27896559 DOI: 10.1007/s10616-016-0035-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 10/26/2016] [Indexed: 10/20/2022] Open
Abstract
Many active principles produced by animals, plants and microorganisms have been employed in the development of new drugs for the treatment of human diseases. Among animals known to produce pharmacologically active molecules that interfere in human cell physiology. Rubella virus (genus Rubivirus, family Togaviridae) is a single stranded RNA virus of positive genome polarity. Rubella virus infection of susceptible women during the first trimester of pregnancy often results in long-term virus persistence in the fetus causing multiple organ abnormalities. Potent antiviral activity against rubella virus (RV) has been observed in the hemolymph of Podalia sp. (Lepidoptera: Megalopygidae). This study evaluated the effect of hemolymph on RV infected Statens Serum Institute Rabbit Cornea (SIRC) cells. Results of cell viability and cell proliferation assays indicated that hemolymph was not toxic to cultured SIRC cells. Viral binding assay, antiviral assay, PCR, real-time PCR, and transmission electron microscopy were used to demonstrate that hemolymph in post-treatment could inhibit the production of infectious RV particles. Specifically, hemolymph was found to inhibit RV adsorption to the SIRC cells.
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de Armas-Rillo L, Valera MS, Marrero-Hernández S, Valenzuela-Fernández A. Membrane dynamics associated with viral infection. Rev Med Virol 2016; 26:146-60. [PMID: 26817660 PMCID: PMC5066672 DOI: 10.1002/rmv.1872] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 12/14/2015] [Accepted: 12/16/2015] [Indexed: 12/15/2022]
Abstract
Viral replication and spreading are fundamental events in the viral life cycle, accounting for the assembly and egression of nascent virions, events that are directly associated with viral pathogenesis in target hosts. These processes occur in cellular compartments that are modified by specialized viral proteins, causing a rearrangement of different cell membranes in infected cells and affecting the ER, mitochondria, Golgi apparatus, vesicles and endosomes, as well as processes such as autophagic membrane flux. In fact, the activation or inhibition of membrane trafficking and other related activities are fundamental to ensure the adequate replication and spreading of certain viruses. In this review, data will be presented that support the key role of membrane dynamics in the viral cycle, especially in terms of the assembly, egression and infection processes. By defining how viruses orchestrate these events it will be possible to understand how they successfully complete their route of infection, establishing viral pathogenesis and provoking disease. © 2015 The Authors Reviews in Medical Virology Published by John Wiley & Sons, Ltd.
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Affiliation(s)
- Laura de Armas-Rillo
- Laboratorio de Inmunología Celular y Viral, Unidad de Virología IUETSPC, Unidad de Farmacología, Sección de Medicina, Facultad de Ciencias de la Salud, Universidad de La Laguna (ULL), Tenerife, Spain
| | - María-Soledad Valera
- Laboratorio de Inmunología Celular y Viral, Unidad de Virología IUETSPC, Unidad de Farmacología, Sección de Medicina, Facultad de Ciencias de la Salud, Universidad de La Laguna (ULL), Tenerife, Spain
| | - Sara Marrero-Hernández
- Laboratorio de Inmunología Celular y Viral, Unidad de Virología IUETSPC, Unidad de Farmacología, Sección de Medicina, Facultad de Ciencias de la Salud, Universidad de La Laguna (ULL), Tenerife, Spain
| | - Agustín Valenzuela-Fernández
- Laboratorio de Inmunología Celular y Viral, Unidad de Virología IUETSPC, Unidad de Farmacología, Sección de Medicina, Facultad de Ciencias de la Salud, Universidad de La Laguna (ULL), Tenerife, Spain
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13
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Ooi YS, Dubé M, Kielian M. BST2/tetherin inhibition of alphavirus exit. Viruses 2015; 7:2147-67. [PMID: 25912717 PMCID: PMC4411694 DOI: 10.3390/v7042147] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 04/08/2015] [Accepted: 04/17/2015] [Indexed: 11/29/2022] Open
Abstract
Alphaviruses such as chikungunya virus (CHIKV) and Semliki Forest virus (SFV) are small enveloped RNA viruses that bud from the plasma membrane. Tetherin/BST2 is an interferon-induced host membrane protein that inhibits the release of many enveloped viruses via direct tethering of budded particles to the cell surface. Alphaviruses have highly organized structures and exclude host membrane proteins from the site of budding, suggesting that their release might be insensitive to tetherin inhibition. Here, we demonstrated that exogenously-expressed tetherin efficiently inhibited the release of SFV and CHIKV particles from host cells without affecting virus entry and infection. Alphavirus release was also inhibited by the endogenous levels of tetherin in HeLa cells. While rubella virus (RuV) and dengue virus (DENV) have structural similarities to alphaviruses, tetherin inhibited the release of RuV but not DENV. We found that two recently identified tetherin isoforms differing in length at the N-terminus exhibited distinct capabilities in restricting alphavirus release. SFV exit was efficiently inhibited by the long isoform but not the short isoform of tetherin, while both isoforms inhibited vesicular stomatitis virus exit. Thus, in spite of the organized structure of the virus particle, tetherin specifically blocks alphavirus release and shows an interesting isoform requirement.
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Affiliation(s)
- Yaw Shin Ooi
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA.
| | - Mathieu Dubé
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA.
| | - Margaret Kielian
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA.
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14
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Zhang L, Ren X, Chen Y, Gao Y, Wang N, Lu Z, Gao L, Qin L, Wang Y, Gao H, Li K, Jiang L, Cui H, Liu C, Zhang Y, Qi X, Wang X. Chondroitin sulfate N-acetylgalactosaminyltransferase-2 contributes to the replication of infectious bursal disease virus via interaction with the capsid protein VP2. Viruses 2015; 7:1474-91. [PMID: 25807054 PMCID: PMC4379581 DOI: 10.3390/v7031474] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 03/13/2015] [Accepted: 03/16/2015] [Indexed: 01/11/2023] Open
Abstract
Infectious bursal disease virus (IBDV) is a birnavirus that causes a highly contagious immunosuppressive disease in young chickens. The capsid protein VP2 of IBDV plays multiple roles in its life cycle. To more comprehensively understand the functions of VP2 involved in the communication between virus and host, we used yeast two-hybrid screening to identify the cellular factors that interact with this protein. We found that chondroitin sulfate N-acetylgalactosaminyltransferase-2 (CSGalNAcT2), a typical type II transmembrane protein located in Golgi apparatus, could interact with VP2, and we confirmed this interaction by co-immunoprecipitation and confocal laser scanning microscopy assays. Additionally, up-regulation of CSGalNAcT2 during IBDV infection was observed. Overexpression and siRNA-mediated knockdown of CSGalNAcT2 assays suggested that CSGalNAcT2 promoted IBDV replication. Moreover, this enhancing effect of CSGalNAcT2 could be inhibited by Brefeldin A, which is a Golgi-disturbing agent. This indicated that the integrity of Golgi apparatus structure was involved in the function of CSGalNAcT2. Taken together, we concluded that CSGalNAcT2, located in the Golgi apparatus, contributed to the replication of IBDV via interaction with VP2.
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Affiliation(s)
- Lizhou Zhang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Xiangang Ren
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Yuming Chen
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Yulong Gao
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Nian Wang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Zhen Lu
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Li Gao
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Liting Qin
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Yongqiang Wang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Honglei Gao
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Kai Li
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Lili Jiang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Hongyu Cui
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Changjun Liu
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Yanping Zhang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Xiaole Qi
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
| | - Xiaomei Wang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, the Chinese Academy of Agricultural Sciences, Harbin 150001, China.
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Disease and Zoonoses, Yangzhou 225009, China.
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Dubé M, Rey FA, Kielian M. Rubella virus: first calcium-requiring viral fusion protein. PLoS Pathog 2014; 10:e1004530. [PMID: 25474548 PMCID: PMC4256232 DOI: 10.1371/journal.ppat.1004530] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 10/20/2014] [Indexed: 12/22/2022] Open
Abstract
Rubella virus (RuV) infection of pregnant women can cause fetal death, miscarriage, or severe fetal malformations, and remains a significant health problem in much of the underdeveloped world. RuV is a small enveloped RNA virus that infects target cells by receptor-mediated endocytosis and low pH-dependent membrane fusion. The structure of the RuV E1 fusion protein was recently solved in its postfusion conformation. RuV E1 is a member of the class II fusion proteins and is structurally related to the alphavirus and flavivirus fusion proteins. Unlike the other known class II fusion proteins, however, RuV E1 contains two fusion loops, with a metal ion complexed between them by the polar residues N88 and D136. Here we demonstrated that RuV infection specifically requires Ca2+ during virus entry. Other tested cations did not substitute. Ca2+ was not required for virus binding to cell surface receptors, endocytic uptake, or formation of the low pH-dependent E1 homotrimer. However, Ca2+ was required for low pH-triggered E1 liposome insertion, virus fusion and infection. Alanine substitution of N88 or D136 was lethal. While the mutant viruses were efficiently assembled and endocytosed by host cells, E1-membrane insertion and fusion were specifically blocked. Together our data indicate that RuV E1 is the first example of a Ca2+-dependent viral fusion protein and has a unique membrane interaction mechanism. Rubella virus (RuV) is a small enveloped RNA virus causing mild disease in children. However, infection of pregnant women can produce fetal death or congenital rubella syndrome, a constellation of severe birth defects including cataracts, hearing loss, heart disease and developmental delays. While vaccination has greatly reduced disease in the developed world, rubella remains prevalent in developing countries and other undervaccinated populations. RuV infects cells by endocytic uptake and a low pH-triggered membrane fusion reaction mediated by the viral E1 protein. The postfusion structure of E1 revealed a metal ion complexed at the membrane-interacting tip of the protein. Here we demonstrated that RuV infection and fusion are completely dependent on calcium, which could not be replaced functionally by any other metal that was tested. In the absence of calcium, RuV entry and low pH-conformational changes were unchanged, but E1's interaction with the target membrane was specifically blocked. Mutations of the calcium-binding residues in E1 caused a similar inhibition of E1 membrane interaction, fusion and infection. Thus, RuV E1 is the first known example of a calcium-dependent virus fusion protein.
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Affiliation(s)
- Mathieu Dubé
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Felix A. Rey
- Unité de Virologie Structurale, Institut Pasteur and CNRS UMR 3569, Paris, France
| | - Margaret Kielian
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail:
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16
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Barroso-González J, García-Expósito L, Puigdomènech I, de Armas-Rillo L, Machado JD, Blanco J, Valenzuela-Fernández A. Viral infection. Commun Integr Biol 2014. [DOI: 10.4161/cib.16716] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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17
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Membranous replication factories induced by plus-strand RNA viruses. Viruses 2014; 6:2826-57. [PMID: 25054883 PMCID: PMC4113795 DOI: 10.3390/v6072826] [Citation(s) in RCA: 200] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 06/02/2014] [Accepted: 06/24/2014] [Indexed: 12/13/2022] Open
Abstract
In this review, we summarize the current knowledge about the membranous replication factories of members of plus-strand (+) RNA viruses. We discuss primarily the architecture of these complex membrane rearrangements, because this topic emerged in the last few years as electron tomography has become more widely available. A general denominator is that two “morphotypes” of membrane alterations can be found that are exemplified by flaviviruses and hepaciviruses: membrane invaginations towards the lumen of the endoplasmatic reticulum (ER) and double membrane vesicles, representing extrusions also originating from the ER, respectively. We hypothesize that either morphotype might reflect common pathways and principles that are used by these viruses to form their membranous replication compartments.
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18
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Delgui LR, Rodríguez JF, Colombo MI. The endosomal pathway and the Golgi complex are involved in the infectious bursal disease virus life cycle. J Virol 2013; 87:8993-9007. [PMID: 23741000 PMCID: PMC3754037 DOI: 10.1128/jvi.03152-12] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 05/30/2013] [Indexed: 12/22/2022] Open
Abstract
Infectious bursal disease virus (IBDV), a double-stranded RNA virus belonging to the Birnaviridae family, causes immunosuppression in chickens. In this study, we defined the localization of IBDV replication complexes based on colocalization analysis of VP3, the major protein component of IBDV ribonucleoproteins (RNPs). Our results indicate that VP3 localizes to vesicular structures bearing features of early and late endocytic compartments located in the juxtanuclear region. Interfering with the endocytic pathway with a dominant negative version of Rab5 after the internalization step leads to a reduction in virus titer. Triple-immunostaining studies between VP3, the viral RNA-dependent RNA polymerase VP1, and viral double-stranded RNA (dsRNA) showed a well-defined colocalization, indicating that the three critical components of the RNPs colocalize in the same structure, likely representing replication complexes. Interestingly, recombinant expressed VP3 also localizes to endosomes. Employing Golgi markers, we found that VP3-containing vesicles were closely associated with this organelle. Depolymerization of microtubules with nocodazole caused a profound change in VP3 localization, showing a punctate distribution scattered throughout the cytoplasm. However, these VP3-positive structures remained associated with Golgi ministacks. Similarly, brefeldin A (BFA) treatment led to a punctate distribution of VP3, scattered throughout the cytoplasm of infected cells. In addition, analysis of intra- and extracellular viral infective particles after BFA treatment of avian cells suggested a role for the Golgi complex in viral assembly. These results constitute the first study elucidating the localization of IBDV replication complexes (i.e., in endocytic compartments) and establishing a role for the Golgi apparatus in the assembly step of a birnavirus.
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Affiliation(s)
- Laura R. Delgui
- Laboratorio de Biología Celular y Molecular, Instituto de Histología y Embriología de Mendoza, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo-CONICET, Mendoza, Argentina
- Instituto de Ciencias Básicas, Universidad Nacional de Cuyo, Mendoza, Argentina
| | - José F. Rodríguez
- Departamento de Biología Molecular y Celular, Centro Nacional de Biotecnología (CSIC), Madrid, Spain
| | - María I. Colombo
- Laboratorio de Biología Celular y Molecular, Instituto de Histología y Embriología de Mendoza, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo-CONICET, Mendoza, Argentina
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19
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Abstract
In mammalian cells, the Golgi complex has an elaborate structure consisting of stacked, flattened cisternal membranes collected into a ribbon in the center of the cell. Amazingly, the flattened cisternae can rapidly dilate to accommodate large cargo as it traffics through the organelle. The mechanism by which this occurs is unknown. Exocytosis of large cargo is essential for many physiological processes, including collagen and lipoprotein secretion, and defects in the process lead to disease. In addition, enveloped viruses that bud into the endoplasmic reticulum or Golgi complex must also be transported through Golgi cisternae for secretion from the infected cell. This review summarizes our understanding of intra-Golgi transport of large cargo, and outlines current questions open for experimentation.
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Affiliation(s)
- Carolyn E Machamer
- Department of Cell Biology, Johns Hopkins University School of Medicine, 725 N. Wolfe St., Baltimore, MD 20205, USA.
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20
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Virnik K, Ni Y, Berkower I. Enhanced expression of HIV and SIV vaccine antigens in the structural gene region of live attenuated rubella viral vectors and their incorporation into virions. Vaccine 2013; 31:2119-25. [PMID: 23474312 DOI: 10.1016/j.vaccine.2013.02.055] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 01/31/2013] [Accepted: 02/25/2013] [Indexed: 10/27/2022]
Abstract
Despite the urgent need for an HIV vaccine, its development has been hindered by virus variability, weak immunogenicity of conserved epitopes, and limited durability of the immune response. For other viruses, difficulties with immunogenicity were overcome by developing live attenuated vaccine strains. However, there is no reliable method of attenuation for HIV, and an attenuated strain would risk reversion to wild type. We have developed rubella viral vectors, based on the live attenuated vaccine strain RA27/3, which are capable of expressing important HIV and SIV vaccine antigens. The rubella vaccine strain has demonstrated safety, immunogenicity, and long lasting protection in millions of children. Rubella vectors combine the growth and immunogenicity of live rubella vaccine with the antigenicity of HIV or SIV inserts. This is the first report showing that live attenuated rubella vectors can stably express HIV and SIV vaccine antigens at an insertion site located within the structural gene region. Unlike the Not I site described previously, the new site accommodates a broader range of vaccine antigens without interfering with essential viral functions. In addition, antigens expressed at the structural site were controlled by the strong subgenomic promoter, resulting in higher levels and longer duration of antigen expression. The inserts were expressed as part of the structural polyprotein, processed to free antigen, and incorporated into rubella virions. The rubella vaccine strain readily infects rhesus macaques, and these animals will be the model of choice for testing vector growth in vivo and immunogenicity.
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Affiliation(s)
- Konstantin Virnik
- Lab of Immunoregulation, Division of Viral Products, Office of Vaccines, Center for Biologics, FDA, Bldg 29, Room 523, NIH Campus, Bethesda, MD 20892, United States
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21
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Abstract
Rubella virus is the only member of the Rubivirus genus within the Togaviridae family and is the causative agent of the childhood disease known as rubella or German measles. Here, we report the use of cryo-electron tomography to examine the three-dimensional structure of rubella virions and compare their structure to that of Ross River virus, a togavirus belonging the genus Alphavirus. The ectodomains of the rubella virus glycoproteins, E1 and E2, are shown to be organized into extended rows of density, separated by 9 nm on the viral surface. We also show that the rubella virus nucleocapsid structure often forms a roughly spherical shell which lacks high density at its center. While many rubella virions are approximately spherical and have dimensions similar to that of the icosahedral Ross River virus, the present results indicate that rubella exhibits a large degree of pleomorphy. In addition, we used rotation function calculations and other analyses to show that approximately spherical rubella virions lack the icosahedral organization which characterizes Ross River and other alphaviruses. The present results indicate that the assembly mechanism of rubella virus, which has previously been shown to differ from that of the alphavirus assembly pathway, leads to an organization of the rubella virus structural proteins that is different from that of alphaviruses.
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22
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Claus C, Tzeng WP, Liebert UG, Frey TK. Rubella virus-like replicon particles: analysis of encapsidation determinants and non-structural roles of capsid protein in early post-entry replication. J Gen Virol 2011; 93:516-525. [PMID: 22113006 DOI: 10.1099/vir.0.038984-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Rubella virus (RUBV) contains a plus-strand RNA genome with two ORFs, one encoding the non-structural replicase proteins (NS-ORF) and the second encoding the virion structural proteins (SP-ORF). This study describes development and use of a trans-encapsidation system for the assembly of infectious RUBV-like replicon particles (VRPs) containing RUBV replicons (self replicating genomes with the SP-ORF replaced with a reporter gene). First, this system was used to map signals within the RUBV genome that mediate packaging of viral RNA. Mutations within a proposed packaging signal did not significantly affect relative packaging efficiency. The insertion of various fragments derived from the RUBV genome into Sindbis virus replicons revealed that there are several regions within the RUBV genome capable of enhancing encapsidation of heterologous replicon RNAs. Secondly, the trans-encapsidation system was used to analyse the effect of alterations within the capsid protein (CP) on release of VRPs and subsequent initiation of replication in newly infected cells. Deletion of the N-terminal eight amino acids of the CP reduced VRP titre significantly, which could be partially complemented by native CP provided in trans, indicating that this mutation affected an entry or post-entry event in the replication cycle. To test this hypothesis, the trans-encapsidation system was used to demonstrate the rescue of a lethal deletion within P150, one of the virus replicase proteins, by CP contained within the virus particle. This novel finding substantiated the functional role of CP in early post-entry replication.
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Affiliation(s)
- Claudia Claus
- Institute of Virology, University of Leipzig, Leipzig, Germany
| | - Wen-Pin Tzeng
- Department of Biology, Georgia State University, Atlanta, GA, USA
| | - U G Liebert
- Institute of Virology, University of Leipzig, Leipzig, Germany
| | - Teryl K Frey
- Department of Biology, Georgia State University, Atlanta, GA, USA
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23
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Abstract
A number of viruses transport their genomic material from cell to cell enclosed within a lipid bilayer that is in turn encased within a symmetric protein shell. This review focuses in a group of RNA viruses that have this type of virions. This group includes several of important human pathogenic viruses, such as the hepatitis C virus, dengue virus, chikungunya virus, rubella virus and the bunyaviruses. The best studied are the flaviviruses and the alphaviruses, which have a β-sheet rich class II viral fusion protein used for entry into susceptible cells. We extend here the class II concept to encompass symmetric viruses in which the envelope proteins are derived from a precursor polyprotein containing two transmembrane glycoproteins arranged in tandem. The first glycoprotein acts as chaperone for the folding of the second one, which carries the membrane fusion function. Since the bunyaviruses, included here, are very similar to the class I arenaviruses in other respects, this analysis highlights the patchwork nature of the various viral functional modules acting at different stages of the virus cycle, which appear assembled from genes of different origins.
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Affiliation(s)
- Marie-Christine Vaney
- Institut Pasteur, Département de Virologie, Unité de Virologie Structurale, F-75724 Paris Cedex 15, France
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24
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Barroso-González J, García-Expósito L, Puigdomènech I, de Armas-Rillo L, Machado JD, Blanco J, Valenzuela-Fernández A. Viral infection: Moving through complex and dynamic cell-membrane structures. Commun Integr Biol 2011; 4:398-408. [PMID: 21966556 DOI: 10.4161/cib.4.4.16716] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Accepted: 05/31/2011] [Indexed: 01/19/2023] Open
Abstract
Viruses have developed different survival strategies in host cells by crossing cell-membrane compartments, during different steps of their viral life cycle. In fact, the non-regenerative viral membrane of enveloped viruses needs to encounter the dynamic cell-host membrane, during early steps of the infection process, in which both membranes fuse, either at cell-surface or in an endocytic compartment, to promote viral entry and infection. Once inside the cell, many viruses accomplish their replication process through exploiting or modulating membrane traffic, and generating specialized compartments to assure viral replication, viral budding and spreading, which also serve to evade the immune responses against the pathogen. In this review, we have attempted to present some data that highlight the importance of membrane dynamics during viral entry and replicative processes, in order to understand how viruses use and move through different complex and dynamic cell-membrane structures and how they use them to persist.
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Affiliation(s)
- Jonathan Barroso-González
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - Laura García-Expósito
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - Isabel Puigdomènech
- Fundació irsiCaixa-HIVACAT; Institut de Recerca en Ciències de la Salut Germans Trias i Pujol (IGTP); Hospital Germans Trias i Pujol; Universitat Autònoma de Barcelona; Barcelona, Catalonia Spain
| | - Laura de Armas-Rillo
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - José-David Machado
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
| | - Julià Blanco
- Fundació irsiCaixa-HIVACAT; Institut de Recerca en Ciències de la Salut Germans Trias i Pujol (IGTP); Hospital Germans Trias i Pujol; Universitat Autònoma de Barcelona; Barcelona, Catalonia Spain
| | - Agustín Valenzuela-Fernández
- Laboratorio de Inmunología Celular y Viral; Laboratorio de Neurosecreción; Unidad de Farmacología; Departamento de Medicina Física y Farmacología; Facultad de Medicina; Instituto de Tecnologías Biomédicas (ITB); Universidad de La Laguna (ULL)
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25
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Concentration and purification of rubella virus using monolithic chromatographic support. J Chromatogr B Analyt Technol Biomed Life Sci 2011; 879:981-6. [DOI: 10.1016/j.jchromb.2011.03.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 02/22/2011] [Accepted: 03/06/2011] [Indexed: 11/19/2022]
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26
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27
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Fontana J, López-Iglesias C, Tzeng WP, Frey TK, Fernández JJ, Risco C. Three-dimensional structure of Rubella virus factories. Virology 2010; 405:579-91. [PMID: 20655079 PMCID: PMC7111912 DOI: 10.1016/j.virol.2010.06.043] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 06/07/2010] [Accepted: 06/24/2010] [Indexed: 12/14/2022]
Abstract
Viral factories are complex structures in the infected cell where viruses compartmentalize their life cycle. Rubella virus (RUBV) assembles factories by recruitment of rough endoplasmic reticulum (RER), mitochondria and Golgi around modified lysosomes known as cytopathic vacuoles or CPVs. These organelles contain active replication complexes that transfer replicated RNA to assembly sites in Golgi membranes. We have studied the structure of RUBV factory in three dimensions by electron tomography and freeze-fracture. CPVs contain stacked membranes, rigid sheets, small vesicles and large vacuoles. These membranes are interconnected and in communication with the endocytic pathway since they incorporate endocytosed BSA-gold. RER and CPVs are coupled through protein bridges and closely apposed membranes. Golgi vesicles attach to the CPVs but no tight contacts with mitochondria were detected. Immunogold labelling confirmed that the mitochondrial protein p32 is an abundant component around and inside CPVs where it could play important roles in factory activities.
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Affiliation(s)
- Juan Fontana
- Cell Structure Lab, Centro Nacional de Biotecnología, CSIC, Darwin, Madrid, Spain
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28
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Ulasli M, Verheije MH, de Haan CAM, Reggiori F. Qualitative and quantitative ultrastructural analysis of the membrane rearrangements induced by coronavirus. Cell Microbiol 2010; 12:844-61. [PMID: 20088951 PMCID: PMC7159092 DOI: 10.1111/j.1462-5822.2010.01437.x] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Coronaviruses (CoV) are enveloped positive‐strand RNA viruses that induce different membrane rearrangements in infected cells in order to efficiently replicate and assemble. The origin, the protein composition and the function of these structures are not well established. To shed further light on these structures, we have performed a time‐course experiment in which the mouse hepatitis virus (MHV)‐induced membrane rearrangements were examined qualitatively and quantitatively by (immuno)‐electron microscopy. With our approach we were able to confirm the appearance of 6, previously reported, membranous structures during the course of a complete infection cycle. These structures include the well‐characterized double‐membrane vesicles (DMVs), convoluted membranes (CMs) and virions but also the more enigmatic large virion‐containing vacuoles (LVCVs), tubular bodies (TBs) and cubic membrane structures (CMSs). We have characterized the LVCVs, TBs and CMSs, and found that the CoV‐induced structures appear in a strict order. By combining these data with quantitative analyses on viral RNA, protein synthesis and virion release, this study generates an integrated molecular and ultrastructural overview of CoV infection. In particular, it provides insights in the role of each CoV‐induced structure and reveals that LVCVs are ERGIC/Golgi compartments that expand to accommodate an increasing production of viral particles.
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Affiliation(s)
- Mustafa Ulasli
- Department of Cell Biology and Institute of Biomembranes, University Medical Centre Utrecht, The Netherlands
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29
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Rodriguez-Cariñg C, SegalÉS J. Ultrastructural Findings in Lymph Nodes from Pigs Suffering from Naturally Occurring Postweaning Multisystemic Wasting Syndrome. Vet Pathol 2009; 46:729-35. [DOI: 10.1354/vp.08-vp-0141-r-fl] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The aims of this study were to evaluate ultrastructural lesions in lymph nodes from postweaning multisystemic wasting syndrome (PMWS)-affected pigs and to correlate these alterations with detection of viral-like particles (VLPs). Samples of lymph nodes were taken from 4 PMWS-affected pigs and 2 healthy animals and processed by transmission electron microscopy. Significant ultrastructural alterations were only noted in PMWS-affected pigs, mainly in histiocytes and rarely in other cell types. Histiocytes showed severe swelling and proliferation of mitochondria, and proliferation and dilation of rough endoplasmic reticulum and Golgi complex. Infected histiocytes contained large numbers of intracytoplasmic inclusion (ICI) bodies with VLPs; some histiocytes also had intranuclear inclusions (INIs). Small inclusions were surrounded by double membrane, with a granular appearance or containing paracrystalline arrays; icosahedral VLPs were 8–17 nm in diameter. Large ICIs were double-membrane bounded or not and contained VLPs usually forming paracrystalline arrays. ICIs were often found next to mitochondria with severe swelling, and also inside them. INIs were not surrounded by membranes and contained virions of 10–13 nm diameter. Lymphocyte depletion was a striking finding of lymph nodes from PMWS-affected pigs. The inclusion bodies containing VLPs referred to in the present study should be classified as viral factories, suggesting that viral replication is probably a frequent event in macrophages, in which mitochondria might play a role.
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Affiliation(s)
- C. Rodriguez-Cariñg
- Departament de Sanitat i Anatomia Animals, Centre de Recerca en Sanitat Animal (CReSA), UAB-IRTA, Campus de la Universitat Autonoma de Barcelona, Bellaterra, Barcelona, Spain
| | - J. SegalÉS
- Departament de Sanitat i Anatomia Animals, Centre de Recerca en Sanitat Animal (CReSA), UAB-IRTA, Campus de la Universitat Autonoma de Barcelona, Bellaterra, Barcelona, Spain
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30
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Meckes DG, Wills JW. Dynamic interactions of the UL16 tegument protein with the capsid of herpes simplex virus. J Virol 2007; 81:13028-36. [PMID: 17855514 PMCID: PMC2169088 DOI: 10.1128/jvi.01306-07] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The UL16 tegument protein of herpes simplex virus is conserved throughout the herpesvirus family. It has been reported to be capsid associated and may be involved in budding by providing an interaction with the membrane-bound UL11 protein. UL16 has been shown to be present in all the major locations that capsids are found (i.e., the nucleus, cytoplasm, and virions), but whether it is actually capsid associated in each of these has not been reported. Therefore, capsids were purified from each compartment, and it was found that UL16 was present on cytoplasmic but not nuclear capsids. In extracellular virions, the majority of UL16 (87%) was once again not capsid associated, which suggests that the interaction is transient during egress. Because herpes simplex virus (HSV) buds into the acidic compartment of the trans-Golgi network (TGN), the effect of pH on the interaction was examined. The amount of capsid-associated UL16 dramatically increased when extracellular virions were exposed to mildly acidic medium (pH 5.0 to 5.5), and this association was fully reversible. After budding into the TGN, capsid and tegument proteins also encounter an oxidizing environment, which is conducive to disulfide bond formation. UL16 contains 20 cysteines, including five that are conserved within a putative zinc finger. Any free cysteines that are involved in the capsid interaction or release mechanism of UL16 would be expected to be modified by N-ethylmaleimide, and, consistent with this, the amount of capsid-associated UL16 dramatically increased when virions were incubated with this compound. Taken together, these data suggest a transient interaction between UL16 and capsids, possibly modified in the acidic compartment of secretory vesicles and requiring a release mechanism that involves cysteines.
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Affiliation(s)
- David G Meckes
- Department of Microbiology and Immunology, The Pennsylvania State University College of Medicine, 500 University Drive, P.O. Box 850, Hershey, PA 17036, USA
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Claus C, Tzeng WP, Liebert UG, Frey TK. Analysis of the selective advantage conferred by a C-E1 fusion protein synthesized by rubella virus DI RNAs. Virology 2007; 369:19-34. [PMID: 17698161 PMCID: PMC2694055 DOI: 10.1016/j.virol.2007.06.047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Revised: 02/01/2007] [Accepted: 06/19/2007] [Indexed: 11/17/2022]
Abstract
During serial passaging of rubella virus (RUB) in cell culture, the dominant species of defective-interfering RNA (DI) generated contains an in-frame deletion between the capsid protein (C) gene and E1 glycoprotein gene resulting in production of a C-E1 fusion protein that is necessary for the maintenance of the DI [Tzeng, W.P., Frey, T.K. (2006). C-E1 fusion protein synthesized by rubella virus DI RNAs maintained during serial passage. Virology 356 198-207.]. A BHK cell line stably expressing the RUB structural proteins was established which was used to package DIs into virus particles following transfection with in vitro transcripts from DI infectious cDNA constructs. Packaging of a DI encoding an in-frame C-GFP-E1 reporter fusion protein corresponding to the C-E1 fusion protein expressed in a native DI was only marginally more efficient than packaging of a DI encoding GFP, indicating that the C-E1 fusion protein did not function by enhancing packaging. However, infection with the DI encoding the C-GFP-E1 fusion protein (in the absence of wt RUB helper virus) resulted in formation of clusters of GFP-positive cells and the percentage of GFP-positive cells in the culture following infection remained relatively constant. In contrast, a DI encoding GFP did not form GFP-positive clusters and the percentage of GFP-positive cells declined by roughly half from 2 to 4 days post-infection. Cluster formation and sustaining the percentage of infected (GFP-positive) cells required the C part of the fusion protein, including the downstream but not the upstream of two arginine clusters (both of which are associated with RNA binding and association with mitochondrial p32 protein) and the E1 part through the transmembrane sequence, but not the C-terminal cytoplasmic tail. Among a collection of mutant DI constructs, cluster formation and sustaining infected cell percentage correlated with maintenance during serial passage with wt RUB. We hypothesize that cluster formation and sustaining infected cell percentage increase the likelihood of co-infection by a DI and wt RUB during serial passage thus enhancing maintenance of the DI. Cluster formation and sustaining infected cell percentage were found to be due to a combination of attenuated cytopathogenicity of DIs that express the C-E1 fusion protein and cell-to-cell movement of the DI. In infected cells, the C-GFP-E1 fusion protein was localized to potentially novel vesicular structures that appear to originate from ER-Golgi transport vacuoles. This species of DI expressing a C-E1 fusion protein that exhibits attenuated cytopathogenicity and the ability to increase the number of infected cells through cell-to-cell movement could be the basis for development of an attractive vaccine vector.
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Affiliation(s)
- Claudia Claus
- Institute of Virology, University of Leipzig, Leipzig, Germany
| | - Wen-Pin Tzeng
- Department of Biology, Georgia State University, Atlanta GA
| | | | - Teryl K. Frey
- Department of Biology, Georgia State University, Atlanta GA
- Corresponding author: Department of Biology, Georgia State University, 24 Peachtree Center Ave., Atlanta GA 30303; Tel: (404) 413-5392; FAX: (404) 413-5301;
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Claus C, Hofmann J, Überla K, Liebert UG. Rubella virus pseudotypes and a cell-cell fusion assay as tools for functional analysis of the rubella virus E2 and E1 envelope glycoproteins. J Gen Virol 2006; 87:3029-3037. [PMID: 16963762 DOI: 10.1099/vir.0.82035-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The rubivirus Rubella virus contains the two envelope glycoproteins E2 and E1 as a heterodimeric spike complex embedded in its lipid envelope. The functions of both proteins, especially of E2, in the process of viral entry are still not entirely understood. In order to dissect E2 and E1 entry functions from post-entry steps, pseudotypes of lentiviral vectors based on Simian immunodeficiency virus were used. C-terminally modified E2 and E1 variants successfully pseudotyped lentiviral vector particles. This is the first report to show that not only E1, but also E2, is able to mediate infectious viral entry. Furthermore, a cell-cell fusion assay was used to further clarify membrane-fusion activities of E2 and E1 as one of the early steps of infection. It was demonstrated that the capsid protein, when coexpressed in cis, enhances the degree of E2- and E1-mediated cell-cell fusion.
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Affiliation(s)
- Claudia Claus
- Institute of Virology, University of Leipzig, Johannisallee 30, 04103 Leipzig, Germany
| | - Jörg Hofmann
- Institute of Virology, University of Leipzig, Johannisallee 30, 04103 Leipzig, Germany
| | - Klaus Überla
- Department of Molecular and Medical Virology, Ruhr University Bochum, Bochum, Germany
| | - U G Liebert
- Institute of Virology, University of Leipzig, Johannisallee 30, 04103 Leipzig, Germany
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Shi X, Kohl A, Léonard VHJ, Li P, McLees A, Elliott RM. Requirement of the N-terminal region of orthobunyavirus nonstructural protein NSm for virus assembly and morphogenesis. J Virol 2006; 80:8089-99. [PMID: 16873265 PMCID: PMC1563826 DOI: 10.1128/jvi.00579-06] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The nonstructural protein NSm of Bunyamwera virus (BUNV), the prototype of the Bunyaviridae family, is encoded by the M segment in a polyprotein precursor, along with the virion glycoproteins, in the order Gn-NSm-Gc. As little is known of its function, we examined the intracellular localization, membrane integrality, and topology of NSm and its role in virus replication. We confirmed that NSm is an integral membrane protein and that it localizes in the Golgi complex, together with Gn and Gc. Coimmunoprecipitation assays and yeast two-hybrid analysis demonstrated that NSm was able to interact with other viral proteins. NSm is predicted to contain three hydrophobic (I, III, and V) and two nonhydrophobic (II and IV) domains. The N-terminal nonhydrophobic domain II was found in the lumen of an intracellular compartment. A novel BUNV assembly assay was developed to monitor the formation of infectious virus-like-particles (VLPs). Using this assay, we showed that deletions of either the complete NSm coding region or domains I, II, and V individually seriously compromised VLP production. Consistently, we were unable to rescue viable viruses by reverse genetics from cDNA constructs that contained the same deletions. However, we could generate mutant BUNV with deletions in NSm domains III and IV and also a recombinant virus with the green fluorescent protein open reading frame inserted into NSm domain IV. The mutant viruses displayed differences in their growth properties. Overall, our data showed that the N-terminal region of NSm, which includes domain I and part of domain II, is required for virus assembly and that the C-terminal hydrophobic domain V may function as an internal signal sequence for the Gc glycoprotein.
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Affiliation(s)
- Xiaohong Shi
- Centre for Biomolecular Sciences, School of Biology, University of St Andrews, North Haugh, St Andrews KY16 9ST, Scotland, United Kingdom
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Yu SF, Eastman SW, Linial ML. Foamy virus capsid assembly occurs at a pericentriolar region through a cytoplasmic targeting/retention signal in Gag. Traffic 2006; 7:966-77. [PMID: 16749903 PMCID: PMC7488586 DOI: 10.1111/j.1600-0854.2006.00448.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Foamy viruses (FV) are unusual retroviruses that differ in many aspects of their life cycle from the orthoretroviruses such as human immunodeficiency virus. Similar to Mason-Pfizer monkey virus (MPMV), FV assemble into capsids intracellularly. The capsids are then transported to a cellular membrane for acquisition of envelope (Env) glycoproteins and budding. However, unlike MPMV, budding of FV is dependent upon the presence of Env. Previous work suggested that FV Env proteins are localized to the endoplasmic reticulum (ER) where budding takes place. However, very little was known about the details of FV assembly. We have used immunofluorescence and electron microscopy to visualize the intracellular location of FV assembly and budding. We have found that, as in the case of MPMV, FV capsids assemble at a pericentriolar site in the cytoplasm. Surprisingly, FV Env is mostly absent from this site and, contrary to expectations, FV capsid structural protein (Gag) is absent from the ER. Gag and Env only co-localize at the trans-Golgi network, suggesting that Env-Gag interactions that are required for viral egress from the cell, occurs at this site. Finally, inhibitor studies suggest an important role of microtubule networks for foamy viral assembly and budding.
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Affiliation(s)
- Shuyuarn F Yu
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
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Novoa RR, Calderita G, Cabezas P, Elliott RM, Risco C. Key Golgi factors for structural and functional maturation of bunyamwera virus. J Virol 2005; 79:10852-63. [PMID: 16103138 PMCID: PMC1193595 DOI: 10.1128/jvi.79.17.10852-10863.2005] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Several complex enveloped viruses assemble in the membranes of the secretory pathway, such as the Golgi apparatus. Among them, bunyaviruses form immature viral particles that change their structure in a trans-Golgi-dependent manner. To identify key Golgi factors for viral structural maturation, we have purified and characterized the three viral forms assembled in infected cells, two intracellular intermediates and the extracellular mature virion. The first viral form is a pleomorphic structure with fully endo-beta-N-acetylglucosaminidase H (Endo-H)-sensitive, nonsialylated glycoproteins. The second viral intermediate is a structure with hexagonal and pentagonal contours and partially Endo-H-resistant glycoproteins. Sialic acid is incorporated into the small glycoprotein of this second viral form. Growing the virus in glycosylation-deficient cells confirmed that acquisition of Endo-H resistance but not sialylation is critical for the trans-Golgi-dependent structural maturation and release of mature viruses. Conformational changes in viral glycoproteins triggered by changes in sugar composition would then induce the assembly of a compact viral particle of angular contours. These structures would be competent for the second maturation step, taking place during exit from cells, that originates fully infectious virions.
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Affiliation(s)
- Reyes R Novoa
- Department of Structure of Macromolecules, Centro Nacional de Biotecnología, CSIC, Cantoblanco, Madrid, Spain
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Novoa RR, Calderita G, Arranz R, Fontana J, Granzow H, Risco C. Virus factories: associations of cell organelles for viral replication and morphogenesis. Biol Cell 2005; 97:147-72. [PMID: 15656780 PMCID: PMC7161905 DOI: 10.1042/bc20040058] [Citation(s) in RCA: 349] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2004] [Accepted: 07/06/2004] [Indexed: 12/13/2022]
Abstract
Genome replication and assembly of viruses often takes place in specific intracellular compartments where viral components concentrate, thereby increasing the efficiency of the processes. For a number of viruses the formation of 'factories' has been described, which consist of perinuclear or cytoplasmic foci that mostly exclude host proteins and organelles but recruit specific cell organelles, building a unique structure. The formation of the viral factory involves a number of complex interactions and signalling events between viral and cell factors. Mitochondria, cytoplasmic membranes and cytoskeletal components frequently participate in the formation of viral factories, supplying basic and common needs for key steps in the viral replication cycle.
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Affiliation(s)
- Reyes R Novoa
- Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma, Cantoblanco, 28049 Madrid, Spain
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Fontana J, Tzeng WP, Calderita G, Fraile-Ramos A, Frey TK, Risco C. Structural maturation of rubella virus in the Golgi complex. Virology 2003; 9:875-90. [PMID: 17087733 PMCID: PMC7162162 DOI: 10.1111/j.1462-5822.2006.00837.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Rubella virus (RUB) assembles its replication complexes (RCs) in modified organelles of endo‐lysosomal origin, known as cytopathic vacuoles (CPVs). These peculiar structures are key elements of RUB factories, where rough endoplasmic reticulum, mitochondria, and Golgi are recruited. Bicistronic RUB replicons expressing an antibiotic resistance gene either in the presence or the absence of the RUB capsid (C) gene were used to study the structure of RCs in transfected cells. Confocal microscopy showed that the RUB replicase components P90 and P150 localized to CPVs, as did double‐stranded RNA (dsRNA), a marker for RNA synthesis. Electron microscopy (EM) showed that replicons generated CPVs containing small vesicles and large vacuoles, similar to CPVs from RUB‐infected cells and that the replicase proteins were sufficient for organelle recruitment. Some of these CPVs contained straight membranes. When cross‐sectioned, these rigid membranes appeared to be sheets of closely packed proteins. Immuno‐EM revealed that these sheets, apparently in contact with the cytosol, contained both P150 and P90, as well as dsRNA, and thus could be two‐dimensional arrays of functional viral replicases. Labelling of dsRNA after streptolysin‐O permeabilization showed that replication of viral genome takes place on the cytoplasmic side of CPVs. When present, C accumulated around CPVs. Mitochondrial protein P32 was detected within modified CPVs, the first demonstration of involvement of this protein, which interacts with C, with RCs.
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Affiliation(s)
- Juan Fontana
- Department of Structure of Macromolecules, Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma, Cantoblanco, 28049 Madrid, Spain
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