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Butnariu AB, Look A, Grillo M, Tabish TA, McGarvey MJ, Pranjol MZI. SARS-CoV-2-host cell surface interactions and potential antiviral therapies. Interface Focus 2022; 12:20200081. [PMID: 34956606 PMCID: PMC8662392 DOI: 10.1098/rsfs.2020.0081] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 10/13/2021] [Indexed: 12/13/2022] Open
Abstract
In this review, we reveal the latest developments at the interface between SARS-CoV-2 and the host cell surface. In particular, we evaluate the current and potential mechanisms of binding, fusion and the conformational changes of the spike (S) protein to host cell surface receptors, especially the human angiotensin-converting enzyme 2 (ACE2) receptor. For instance, upon the initial attachment, the receptor binding domain of the S protein forms primarily hydrogen bonds with the protease domain of ACE2 resulting in conformational changes within the secondary structure. These surface interactions are of paramount importance and have been therapeutically exploited for antiviral design, such as monoclonal antibodies. Additionally, we provide an insight into novel therapies that target viral non-structural proteins, such as viral RNA polymerase. An example of which is remdesivir which has now been approved for use in COVID-19 patients by the US Food and Drug Administration. Establishing further understanding of the molecular details at the cell surface will undoubtably aid the development of more efficacious and selectively targeted therapies to reduce the burden of COVID-19.
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Affiliation(s)
| | - Alex Look
- School of Life Sciences, University of Sussex, Falmer, UK
| | - Marta Grillo
- School of Life Sciences, University of Sussex, Falmer, UK
| | - Tanveer A. Tabish
- Faculty of Engineering, Department of Materials, Royal School of Mines, Imperial College London, London, UK
| | - Michael J. McGarvey
- Department of Infectious Disease, Faculty of Medicine, Imperial College London, London, UK
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2
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Mechanistic insights of host cell fusion of SARS-CoV-1 and SARS-CoV-2 from atomic resolution structure and membrane dynamics. Biophys Chem 2020; 265:106438. [PMID: 32721790 PMCID: PMC7375304 DOI: 10.1016/j.bpc.2020.106438] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/16/2020] [Accepted: 07/17/2020] [Indexed: 01/04/2023]
Abstract
The emerging and re-emerging viral diseases are continuous threats to the wellbeing of human life. Previous outbreaks of Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS had evidenced potential threats of coronaviruses in human health. The recent pandemic due to SARS-CoV-2 is overwhelming and has been going beyond control. Vaccines and antiviral drugs are ungently required to mitigate the pandemic. Therefore, it is important to comprehend the mechanistic details of viral infection process. The fusion between host cell and virus being the first step of infection, understanding the fusion mechanism could provide crucial information to intervene the infection process. Interestingly, all enveloped viruses contain fusion protein on their envelope that acts as fusion machine. For coronaviruses, the spike or S glycoprotein mediates successful infection through receptor binding and cell fusion. The cell fusion process requires merging of virus and host cell membranes, and that is essentially performed by the S2 domain of the S glycoprotein. In this review, we have discussed cell fusion mechanism of SARS-CoV-1 from available atomic resolution structures and membrane binding of fusion peptides. We have further discussed about the cell fusion of SARS-CoV-2 in the context of present pandemic situation.
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3
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Zhang Y, Guan X, Chen Z, Cao D, Kang Z, Shen Q, Lei Q, Li F, Li H, Leghari MF, Wang Y, Qi X, Wang X, Gao Y. The high conserved cellular receptors of avian leukosis virus subgroup J in Chinese local chickens contributes to its wide host range. Poult Sci 2019; 97:4187-4192. [PMID: 30107614 DOI: 10.3382/ps/pey331] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 08/06/2018] [Indexed: 02/05/2023] Open
Abstract
Avian leukosis virus (ALV) is a tumor-inducing virus that spreads among most chicken species, causing serious financial losses for the poultry industry. Subgroup J avian leukosis virus (ALV-J) is a recombinant exogenous ALV, which shows more extensive host range in comparison with other subgroups, especially in Chinese local chickens. To identify the relationship between ALV-J host range and the polymorphism of its cellular receptors, we performed a wide range epidemiological investigation of current ALV-J infection in Chinese local chickens, and discovered that all the 18 local chicken breeds being investigated from main local chicken breeding provinces were ALV-J positive. Furthermore, we cloned ALV-J cellular receptor genes of chNHE1 and chANXA2 of these 18 chicken breeds. Sequence alignment demonstrated that despite several regular mutations at the nucleotide level, there were no corresponding amino acid mutations for either chNHE1 gene or chANXA2 gene. Additionally, virus entry assay indicated that the level of viral enter into cells is stable among different chicken breeds. Results of this study indicated that the wide host range of ALV-J in Chinese local chickens was partially due to the high conservatism of its cellular receptors, and also provide target sites for drug design of resistance to ALV-J infection.
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Affiliation(s)
- Yao Zhang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, Heilongjiang Province, PR China
| | - Xiaolu Guan
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, Heilongjiang Province, PR China
| | - Zhiwu Chen
- Guangxi Jinling Husbandry Group CO., LTD, Lu Ping Country, Nanning 530000, Guangxi Zhuang Autonomous Region, PR China
| | - Dingguo Cao
- Institute of Poultry Science, Shandong Academy of Agricultural Science, Jinan, Shandong 250100, China
| | - Zhaofeng Kang
- Institute of Animal Husbandry and Veterinary, Jiangxi Academy of Agricultural Science, Nanchang 330200, China
| | - Qiancheng Shen
- Guangxi Jinling Husbandry Group CO., LTD, Lu Ping Country, Nanning 530000, Guangxi Zhuang Autonomous Region, PR China
| | - Qiuxia Lei
- Institute of Poultry Science, Shandong Academy of Agricultural Science, Jinan, Shandong 250100, China
| | - Fuwei Li
- Institute of Poultry Science, Shandong Academy of Agricultural Science, Jinan, Shandong 250100, China
| | - Haiqin Li
- Institute of Animal Husbandry and Veterinary, Jiangxi Academy of Agricultural Science, Nanchang 330200, China
| | - Muhammad Farooque Leghari
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, Heilongjiang Province, PR China
| | - Yongqiang Wang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, Heilongjiang Province, PR China
| | - Xiaole Qi
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, Heilongjiang Province, PR China
| | - Xiaomei Wang
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, Heilongjiang Province, PR China
| | - Yulong Gao
- Division of Avian Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, Heilongjiang Province, PR China
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4
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White JM, Whittaker GR. Fusion of Enveloped Viruses in Endosomes. Traffic 2016; 17:593-614. [PMID: 26935856 PMCID: PMC4866878 DOI: 10.1111/tra.12389] [Citation(s) in RCA: 281] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Revised: 02/25/2016] [Accepted: 02/25/2016] [Indexed: 12/12/2022]
Abstract
Ari Helenius launched the field of enveloped virus fusion in endosomes with a seminal paper in the Journal of Cell Biology in 1980. In the intervening years, a great deal has been learned about the structures and mechanisms of viral membrane fusion proteins as well as about the endosomes in which different enveloped viruses fuse and the endosomal cues that trigger fusion. We now recognize three classes of viral membrane fusion proteins based on structural criteria and four mechanisms of fusion triggering. After reviewing general features of viral membrane fusion proteins and viral fusion in endosomes, we delve into three characterized mechanisms for viral fusion triggering in endosomes: by low pH, by receptor binding plus low pH and by receptor binding plus the action of a protease. We end with a discussion of viruses that may employ novel endosomal fusion‐triggering mechanisms. A key take‐home message is that enveloped viruses that enter cells by fusing in endosomes traverse the endocytic pathway until they reach an endosome that has all of the environmental conditions (pH, proteases, ions, intracellular receptors and lipid composition) to (if needed) prime and (in all cases) trigger the fusion protein and to support membrane fusion.
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Affiliation(s)
- Judith M White
- Department of Cell Biology, University of Virginia, Charlottesville, VA, USA
| | - Gary R Whittaker
- Department of Microbiology & Immunology, Cornell University, Ithaca, NY, USA
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5
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Aydin H, Smrke BM, Lee JE. Structural characterization of a fusion glycoprotein from a retrovirus that undergoes a hybrid 2-step entry mechanism. FASEB J 2013; 27:5059-71. [PMID: 24036886 PMCID: PMC7164122 DOI: 10.1096/fj.13-232371] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Entry of enveloped viruses into host cells is mediated by their surface envelope glycoproteins (Env). On the surface of the virus, Env is in a metastable, prefusion state, primed to catalyze the fusion of the viral and host membranes. An external trigger is needed to promote the drastic conformational changes necessary for the fusion subunit to fold into the low‐energy, 6‐helix bundle. These triggers typically facilitate pH‐independent entry at the plasma membrane or pH‐dependent entry in a low‐pH endosomal compartment. The α‐retrovirus avian sarcoma leukosis virus (ASLV) has a rare, 2‐step entry mechanism with both pH‐dependent and pH‐independent features. Here, we present the 2.0‐Å‐resolution crystal structure of the ASLV transmembrane (TM) fusion protein. Our structural and biophysical studies indicated that unlike other pH‐dependent or pH‐independent viral TMs, the ASLV fusion subunit is stable irrespective of pH. Two histidine residues (His490 and His492) in the chain reversal region confer stability at low pH. A structural comparison of class I viral fusion proteins suggests that the presence of a positive charge, either a histidine or arginine amino acid, stabilizes a helical dipole moment and is a signature of fusion proteins active at low pH. The structure now reveals key residues and features that explain its 2‐step mechanism, and we discuss the implications of the ASLV TM structure in the context of general mechanisms required for membrane fusion.—Aydin, H., Smrke, B.M., Lee, J. E. Structural characterization of a fusion glycoprotein from a retrovirus that undergoes a hybrid 2‐step entry mechanism. FASEB J. 27, 5059–5071 (2013). http://www.fasebj.org
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Affiliation(s)
- Halil Aydin
- 11 King's College Cir., Rm. 6316, Toronto, ON, Canada M5S 1A8.
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Visualization of the two-step fusion process of the retrovirus avian sarcoma/leukosis virus by cryo-electron tomography. J Virol 2012; 86:12129-37. [PMID: 22933285 DOI: 10.1128/jvi.01880-12] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Retrovirus infection starts with the binding of envelope glycoproteins to host cell receptors. Subsequently, conformational changes in the glycoproteins trigger fusion of the viral and cellular membranes. Some retroviruses, such as avian sarcoma/leukosis virus (ASLV), employ a two-step mechanism in which receptor binding precedes low-pH activation and fusion. We used cryo-electron tomography to study virion/receptor/liposome complexes that simulate the interactions of ASLV virions with cells. Binding the soluble receptor at neutral pH resulted in virions capable of binding liposomes tightly enough to alter their curvature. At virion-liposome interfaces, the glycoproteins are ∼3-fold more concentrated than elsewhere in the viral envelope, indicating specific recruitment to these sites. Subtomogram averaging showed that the oblate globular domain in the prehairpin intermediate (presumably the receptor-binding domain) is connected to both the target and the viral membrane by 2.5-nm-long stalks and is partially disordered, compared with its native conformation. Upon lowering the pH, fusion took place. Fusion is a stochastic process that, once initiated, must be rapid, as only final (postfusion) products were observed. These fusion products showed glycoprotein spikes on their surface, with their interiors occupied by patches of dense material but without capsids, implying their disassembly. In addition, some of the products presented a density layer underlying and resolved from the viral membrane, which may represent detachment of the matrix protein to facilitate the fusion process.
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Spring-loaded model revisited: paramyxovirus fusion requires engagement of a receptor binding protein beyond initial triggering of the fusion protein. J Virol 2011; 85:12867-80. [PMID: 21976650 DOI: 10.1128/jvi.05873-11] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During paramyxovirus entry into a host cell, receptor engagement by a specialized binding protein triggers conformational changes in the adjacent fusion protein (F), leading to fusion between the viral and cell membranes. According to the existing paradigm of paramyxovirus membrane fusion, the initial activation of F by the receptor binding protein sets off a spring-loaded mechanism whereby the F protein progresses independently through the subsequent steps in the fusion process, ending in membrane merger. For human parainfluenza virus type 3 (HPIV3), the receptor binding protein (hemagglutinin-neuraminidase [HN]) has three functions: receptor binding, receptor cleaving, and activating F. We report that continuous receptor engagement by HN activates F to advance through the series of structural rearrangements required for fusion. In contrast to the prevailing model, the role of HN-receptor engagement in the fusion process is required beyond an initiating step, i.e., it is still required even after the insertion of the fusion peptide into the target cell membrane, enabling F to mediate membrane merger. We also report that for Nipah virus, whose receptor binding protein has no receptor-cleaving activity, the continuous stimulation of the F protein by a receptor-engaged binding protein is key for fusion. We suggest a general model for paramyxovirus fusion activation in which receptor engagement plays an active role in F activation, and the continued engagement of the receptor binding protein is essential to F protein function until the onset of membrane merger. This model has broad implications for the mechanism of paramyxovirus fusion and for strategies to prevent viral entry.
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8
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Anterograde or retrograde transsynaptic labeling of CNS neurons with vesicular stomatitis virus vectors. Proc Natl Acad Sci U S A 2011; 108:15414-9. [PMID: 21825165 DOI: 10.1073/pnas.1110854108] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To understand how the nervous system processes information, a map of the connections among neurons would be of great benefit. Here we describe the use of vesicular stomatitis virus (VSV) for tracing neuronal connections in vivo. We made VSV vectors that used glycoprotein (G) genes from several other viruses. The G protein from lymphocytic choriomeningitis virus endowed VSV with the ability to spread transsynaptically, specifically in an anterograde direction, whereas the rabies virus glycoprotein gave a specifically retrograde transsynaptic pattern. The use of an avian G protein fusion allowed specific targeting of cells expressing an avian receptor, which allowed a demonstration of monosynaptic anterograde tracing from defined cells. Synaptic connectivity of pairs of virally labeled cells was demonstrated by using slice cultures and electrophysiology. In vivo infections of several areas in the mouse brain led to the predicted patterns of spread for anterograde or retrograde tracers.
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9
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Li Q, Ali MA, Wang K, Sayre D, Hamel FG, Fischer ER, Bennett RG, Cohen JI. Insulin degrading enzyme induces a conformational change in varicella-zoster virus gE, and enhances virus infectivity and stability. PLoS One 2010; 5:e11327. [PMID: 20593027 PMCID: PMC2892511 DOI: 10.1371/journal.pone.0011327] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Accepted: 04/25/2010] [Indexed: 11/19/2022] Open
Abstract
Varicella-zoster virus (VZV) glycoprotein E (gE) is essential for virus infectivity and binds to a cellular receptor, insulin-degrading enzyme (IDE), through its unique amino terminal extracellular domain. Previous work has shown IDE plays an important role in VZV infection and virus cell-to-cell spread, which is the sole route for VZV spread in vitro. Here we report that a recombinant soluble IDE (rIDE) enhances VZV infectivity at an early step of infection associated with an increase in virus internalization, and increases cell-to-cell spread. VZV mutants lacking the IDE binding domain of gE were impaired for syncytia formation and membrane fusion. Pre-treatment of cell-free VZV with rIDE markedly enhanced the stability of the virus over a range of conditions. rIDE interacted with gE to elicit a conformational change in gE and rendered it more susceptible to proteolysis. Co-incubation of rIDE with gE modified the size of gE. We propose that the conformational change in gE elicited by IDE enhances infectivity and stability of the virus and leads to increased fusogenicity during VZV infection. The ability of rIDE to enhance infectivity of cell-free VZV over a wide range of incubation times and temperatures suggests that rIDE may be useful for increasing the stability of varicella or zoster vaccines.
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Affiliation(s)
- Qingxue Li
- Laboratory of Clinical Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Mir A. Ali
- Laboratory of Clinical Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Kening Wang
- Laboratory of Clinical Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Dean Sayre
- Laboratory of Clinical Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Frederick G. Hamel
- Research Service, Omaha VA Medical Center and the Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Elizabeth R. Fischer
- Research Technology Branch, Rocky Mountain Laboratories, National Institutes of Health, Hamilton, Montana, United States of America
| | - Robert G. Bennett
- Research Service, Omaha VA Medical Center and the Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - Jeffrey I. Cohen
- Laboratory of Clinical Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
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Zhang XY, Kutner RH, Bialkowska A, Marino MP, Klimstra WB, Reiser J. Cell-specific targeting of lentiviral vectors mediated by fusion proteins derived from Sindbis virus, vesicular stomatitis virus, or avian sarcoma/leukosis virus. Retrovirology 2010; 7:3. [PMID: 20100344 PMCID: PMC2823649 DOI: 10.1186/1742-4690-7-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Accepted: 01/25/2010] [Indexed: 01/02/2023] Open
Abstract
Background The ability to efficiently and selectively target gene delivery vectors to specific cell types in vitro and in vivo remains one of the formidable challenges in gene therapy. We pursued two different strategies to target lentiviral vector delivery to specific cell types. In one of the strategies, vector particles bearing a membrane-bound stem cell factor sequence plus a separate fusion protein based either on Sindbis virus strain TR339 glycoproteins or the vesicular stomatitis virus G glycoprotein were used to selectively transduce cells expressing the corresponding stem cell factor receptor (c-kit). An alternative approach involved soluble avian sarcoma/leukosis virus receptors fused to cell-specific ligands including stem cell factor and erythropoietin for targeting lentiviral vectors pseudotyped with avian sarcoma/leukosis virus envelope proteins to cells that express the corresponding receptors. Results The titers of unconcentrated vector particles bearing Sindbis virus strain TR339 or vesicular stomatitis virus G fusion proteins plus stem cell factor in the context of c-kit expressing cells were up to 3.2 × 105 transducing units per ml while vector particles lacking the stem cell factor ligand displayed titers that were approximately 80 fold lower. On cells that lacked the c-kit receptor, the titers of stem cell factor-containing vectors were approximately 40 times lower compared to c-kit-expressing cells. Lentiviral vectors pseudotyped with avian sarcoma/leukosis virus subgroup A or B envelope proteins and bearing bi-functional bridge proteins encoding erythropoietin or stem cell factor fused to the soluble extracellular domains of the avian sarcoma/leukosis virus subgroup A or B receptors resulted in efficient transduction of erythropoietin receptor or c-kit-expressing cells. Transduction of erythropoietin receptor-expressing cells mediated by bi-functional bridge proteins was found to be dependent on the dose, the correct subgroup-specific virus receptor and the correct envelope protein. Furthermore, transduction was completely abolished in the presence of anti-erythropoietin antibody. Conclusions Our results indicate that the avian sarcoma/leukosis virus bridge strategy provides a reliable approach for cell-specific lentiviral vector targeting. The background levels were lower compared to alternative strategies involving Sindbis virus strain TR339 or vesicular stomatitis virus fusion proteins.
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Affiliation(s)
- Xian-Yang Zhang
- Gene Therapy Program, Department of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA
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11
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Wang E, Obeng-Adjei N, Ying Q, Meertens L, Dragic T, Davey RA, Ross SR. Mouse mammary tumor virus uses mouse but not human transferrin receptor 1 to reach a low pH compartment and infect cells. Virology 2008; 381:230-40. [PMID: 18829060 PMCID: PMC2641025 DOI: 10.1016/j.virol.2008.08.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Revised: 07/31/2008] [Accepted: 08/01/2008] [Indexed: 11/24/2022]
Abstract
Mouse mammary tumor virus (MMTV) is a pH-dependent virus that uses mouse transferrin receptor 1 (TfR1) for entry into cells. Previous studies demonstrated that MMTV could induce pH 5-dependent fusion-from-with of mouse cells. Here we show that the MMTV envelope-mediated cell–cell fusion requires both the entry receptor and low pH (pH 5). Although expression of the MMTV envelope and TfR1 was sufficient to mediate low pH-dependent syncytia formation, virus infection required trafficking to a low pH compartment; infection was independent of cathepsin-mediated proteolysis. Human TfR1 did not support virus infection, although envelope-mediated syncytia formation occurred with human cells after pH 5 treatment and this fusion depended on TfR1 expression. However, although the MMTV envelope bound human TfR1, virus was only internalized and trafficked to a low pH compartment in cells expressing mouse TfR1. Thus, while human TfR1 supported cell–cell fusion, because it was not internalized when bound to MMTV, it did not function as an entry receptor. Our data suggest that MMTV uses TfR1 for all steps of entry: cell attachment, induction of the conformational changes in Env required for membrane fusion and internalization to an appropriate acidic compartment.
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Affiliation(s)
- Enxiu Wang
- Department of Microbiology and Abramson Family Cancer Center, University of Pennsylvania, 313BRBII/III, 421 Curie Blvd., Philadelphia, PA 19104, USA
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12
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Huerta V, Chinea G, Fleitas N, Sarría M, Sánchez J, Toledo P, Padrón G. Characterization of the interaction of domain III of the envelope protein of dengue virus with putative receptors from CHO cells. Virus Res 2008; 137:225-34. [PMID: 18723056 DOI: 10.1016/j.virusres.2008.07.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Revised: 07/04/2008] [Accepted: 07/16/2008] [Indexed: 10/21/2022]
Abstract
Domain III (DIII) of the envelope protein of dengue virus (DENV) contains structural determinants for the interaction with cellular receptors. In the present study a solid phase assay and recombinant fusion proteins containing DENV-DIII of serotypes 1 and 2 were used to study structural features of the interaction of the envelope protein with putative receptors present in the microsomal fraction of CHO cells. Recombinant fusion proteins showed specific interaction with proteins present in the microsomal fraction. Binding of the fusion proteins across the pH range of 5.5-8.0 resembled that of virus particles, peaking at pH 6.0. This suggests that the interaction of DIII with cell receptor(s) is strengthened at endosomal pH. The effect of reduction and carbamidomethylation of cysteine residues on the binding to the microsomal fraction and in their recognition by antibodies suggests that the region of DIII that is interacting with putative receptor(s) overlaps only partially with a dominant epitope of the antibody response. The analysis of the residue conservation profile indicates that the surface of DIII is composed typically of specific sub-complex residues with an increased representation of specific type/subtype residues found at the surface that closely correlates with the dominant neutralizing epitope.
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Affiliation(s)
- Vivian Huerta
- Center for Genetic Engineering and Biotechnology, P.O. Box 6162, Habana 10600, Cuba.
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13
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White JM, Delos SE, Brecher M, Schornberg K. Structures and mechanisms of viral membrane fusion proteins: multiple variations on a common theme. Crit Rev Biochem Mol Biol 2008; 43:189-219. [PMID: 18568847 DOI: 10.1080/10409230802058320] [Citation(s) in RCA: 651] [Impact Index Per Article: 40.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Recent work has identified three distinct classes of viral membrane fusion proteins based on structural criteria. In addition, there are at least four distinct mechanisms by which viral fusion proteins can be triggered to undergo fusion-inducing conformational changes. Viral fusion proteins also contain different types of fusion peptides and vary in their reliance on accessory proteins. These differing features combine to yield a rich diversity of fusion proteins. Yet despite this staggering diversity, all characterized viral fusion proteins convert from a fusion-competent state (dimers or trimers, depending on the class) to a membrane-embedded homotrimeric prehairpin, and then to a trimer-of-hairpins that brings the fusion peptide, attached to the target membrane, and the transmembrane domain, attached to the viral membrane, into close proximity thereby facilitating the union of viral and target membranes. During these conformational conversions, the fusion proteins induce membranes to progress through stages of close apposition, hemifusion, and then the formation of small, and finally large, fusion pores. Clearly, highly divergent proteins have converged on the same overall strategy to mediate fusion, an essential step in the life cycle of every enveloped virus.
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Affiliation(s)
- Judith M White
- Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908-0732, USA.
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Kolokoltsov AA, Deniger D, Fleming EH, Roberts NJ, Karpilow JM, Davey RA. Small interfering RNA profiling reveals key role of clathrin-mediated endocytosis and early endosome formation for infection by respiratory syncytial virus. J Virol 2007; 81:7786-800. [PMID: 17494077 PMCID: PMC1933373 DOI: 10.1128/jvi.02780-06] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Respiratory syncytial virus (RSV) is a common cause of respiratory tract infections in infants and the elderly. Like many other pH-independent enveloped viruses, RSV is thought to enter at the cell surface, independently of common endocytic pathways. We have used a targeted small interfering RNA (siRNA) library to identify key cellular genes involved in cytoskeletal dynamics and endosome trafficking that are important for RSV infection. Surprisingly, RSV infection was potently inhibited by siRNAs targeting genes associated with clathrin-mediated endocytosis, including clathrin light chain. The important role of clathrin-mediated endocytosis was confirmed by the expression of well-characterized dominant-negative mutants of genes in this pathway and by using the clathrin endocytosis inhibitor chlorpromazine. We conclude that, while RSV may be competent to enter at the cell surface, clathrin function and endocytosis are a necessary and important part of a productive RSV infection, even though infection is strictly independent of pH. These findings raise the possibility that other pH-independent viruses may share a similar dependence on endocytosis for infection and provide a new potential avenue for treatment of infection.
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Affiliation(s)
- Andrey A Kolokoltsov
- Department of Microbiology and Immunology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX, USA
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15
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Babel AR, Bruce J, Young JA. The hr1 and fusion peptide regions of the subgroup B avian sarcoma and leukosis virus envelope glycoprotein influence low pH-dependent membrane fusion. PLoS One 2007; 2:e171. [PMID: 17245447 PMCID: PMC1764858 DOI: 10.1371/journal.pone.0000171] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2006] [Accepted: 12/22/2006] [Indexed: 11/18/2022] Open
Abstract
The avian sarcoma and leukosis virus (ASLV) envelope glycoprotein (Env) is activated to trigger fusion by a two-step mechanism involving receptor-priming and low pH fusion activation. In order to identify regions of ASLV Env that can regulate this process, a genetic selection method was used to identify subgroup B (ASLV-B) virus-infected cells resistant to low pH-triggered fusion when incubated with cells expressing the cognate TVB receptor. The subgroup B viral Env (envB) genes were then isolated from these cells and characterized by DNA sequencing. This led to identification of two frequent EnvB alterations which allowed TVB receptor-binding but altered the pH-threshold of membrane fusion activation: a 13 amino acid deletion in the host range 1 (hr1) region of the surface (SU) EnvB subunit, and the A32V amino acid change within the fusion peptide of the transmembrane (TM) EnvB subunit. These data indicate that these two regions of EnvB can influence the pH threshold of fusion activation.
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Affiliation(s)
- Angeline Rose Babel
- McArdle Laboratory for Cancer Research, Department of Oncology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - James Bruce
- Institute for Molecular Virology, Bock Laboratories, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - John A.T. Young
- Infectious Disease Laboratory, The Salk Institute for Biological Studies, La Jolla, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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Contreras-Alcantara S, Godby JA, Delos SE. The Single Ligand-binding Repeat of Tva, a Low Density Lipoprotein Receptor-related Protein, Contains Two Ligand-binding Surfaces. J Biol Chem 2006; 281:22827-38. [PMID: 16769730 DOI: 10.1074/jbc.m512599200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The receptor for avian sarcoma/leukosis virus subtype A (ASLV-A), Tva, is the simplest member of the low density lipoprotein receptor family containing a single ligand-binding repeat (LBR). Most LBRs contain a central Trp (Trp33 in Tva) that is important for ligand binding and, for the low density lipoprotein receptor, is associated with familial hypercholesterolemia. The Tva ligand-binding module contains a second Trp (Trp48) that is part of a DEW motif present in a subset of LBRs. Trp48 is important for ASLV-A infectivity. A soluble Tva (sTva) ligand-binding module is sufficient for ASLV-A infectivity. Tva interacts with the viral glycoprotein, and a soluble receptor-binding domain (SUA) binds sTva with picomolar affinity. We investigated whether Tva, a retroviral receptor, could behave as a classic LBR by assessing sTva interactions with the universal receptor-associated protein (RAP) and comparing these interactions with those between sTva and its viral ligand (SUA). To address the role of the two Trp residues in Tva function, we prepared sTva harboring mutations of Trp33, Trp48, or both and determined the binding kinetics with RAP and SUA. We found that sTva behaved as a "normal" receptor toward RAP, requiring both calcium and Trp33 for binding. However, sTva binding to SUA required neither calcium nor Trp33. Furthermore, sTva could bind both RAP and SUA simultaneously. These results show that the single LBR of Tva has two ligand-binding sites, raising the possibility that other LBRs may also.
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Abstract
We identified 1113 articles (103 reviews, 1010 primary research articles) published in 2005 that describe experiments performed using commercially available optical biosensors. While this number of publications is impressive, we find that the quality of the biosensor work in these articles is often pretty poor. It is a little disappointing that there appears to be only a small set of researchers who know how to properly perform, analyze, and present biosensor data. To help focus the field, we spotlight work published by 10 research groups that exemplify the quality of data one should expect to see from a biosensor experiment. Also, in an effort to raise awareness of the common problems in the biosensor field, we provide side-by-side examples of good and bad data sets from the 2005 literature.
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Affiliation(s)
- Rebecca L Rich
- Center for Biomolecular Interaction Analysis, University of Utah, Salt Lake City, UT 84132, USA
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