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Liu Y, Pan H, Wang H, Yuan Y, Cao F, Song W, Wang Z. Mutations in the NDV fusion protein HR4 region decreased fusogenic activity due to failed protein expression. Microb Pathog 2024; 192:106713. [PMID: 38810765 DOI: 10.1016/j.micpath.2024.106713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 04/28/2024] [Accepted: 05/24/2024] [Indexed: 05/31/2024]
Abstract
Newcastle disease virus (NDV) is the pathogen of a zoonosis that is primarily transmitted by poultry and has severe infectivity and a high fatality rate. Many studies have focused on the role of the NDV fusion (F) protein in the cell-cell membrane fusion process. However, little attention has been given to the heptad repeat region, HR4, which is located in the NDV F2 subunit. Here, site-directed mutants were constructed to study the function of the NDV F protein HR4 region and identify the key amino acids in this region. Nine conserved amino acids were substituted with alanine or the corresponding amino acid of other aligned paramyxoviruses. The desired mutants were examined for changes in fusogenic activity through three kinds of membrane fusion assays and expression and proteolysis through IFA, FACS and WB. The results showed that when conserved amino acids (L81, Y84, L88, L91, L92, P94, L95 and I99) were replaced with alanine, the fusogenic activity of the F protein was abolished, possibly because of failed protein expression not only on the cell surface but also inside cells. These data indicated that the conserved amino acids above in NDV F HR4 are critical for normal protein synthesis and expression, possibly for the stability of the F protein monomer, formation of trimer and conformational changes.
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Affiliation(s)
- Yaqing Liu
- Department of Clinical Laboratory, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China; Department of Virology, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, 250014, China
| | - Huazheng Pan
- Department of Clinical Laboratory, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China
| | - Hongwei Wang
- Department of Clinical Laboratory, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China
| | - Yuan Yuan
- Department of Clinical Laboratory, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China
| | - Fangfang Cao
- Department of Clinical Laboratory, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China
| | - Wei Song
- Department of Clinical Laboratory, The Affiliated Hospital of Qingdao University, Qingdao, 266000, China
| | - Zhiyu Wang
- Department of Virology, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, 250014, China.
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Guo Y, Wu S, Li W, Yang H, Shi T, Ju B, Zhang Z, Yan R. The cryo-EM structure of homotetrameric attachment glycoprotein from langya henipavirus. Nat Commun 2024; 15:812. [PMID: 38280880 PMCID: PMC10821904 DOI: 10.1038/s41467-024-45202-5] [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: 07/07/2023] [Accepted: 01/18/2024] [Indexed: 01/29/2024] Open
Abstract
Langya Henipavirus (LayV) infection is an emerging zoonotic disease that has been causing respiratory symptoms in China since 2019. For virus entry, LayV's genome encodes the fusion protein F and the attachment glycoprotein G. However, the structural and functional information regarding LayV-G remains unclear. In this study, we revealed that LayV-G cannot bind to the receptors found in other HNVs, such as ephrin B2/B3, and it shows different antigenicity from HeV-G and NiV-G. Furthermore, we determined the near full-length structure of LayV-G, which displays a distinct mushroom-shaped configuration, distinguishing it from other attachment glycoproteins of HNV. The stalk and transmembrane regions resemble the stem and root of mushroom and four downward-tilted head domains as mushroom cap potentially interact with the F protein and influence membrane fusion process. Our findings enhance the understanding of emerging HNVs that cause human diseases through zoonotic transmission and provide implication for LayV related vaccine development.
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Affiliation(s)
- Yingying Guo
- Department of Biochemistry, School of Medicine, Key University Laboratory of Metabolism and Health of Guangdong, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, 518055, Guangdong, China.
| | - Songyue Wu
- Institute for Hepatology, National Clinical Research Center for Infectious Disease, Shenzhen Third People's Hospital, Shenzhen, China
- The Second Affiliated Hospital, School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Wenting Li
- Institute for Hepatology, National Clinical Research Center for Infectious Disease, Shenzhen Third People's Hospital, Shenzhen, China
- The Second Affiliated Hospital, School of Medicine, Southern University of Science and Technology, Shenzhen, China
| | - Haonan Yang
- Department of Biochemistry, School of Medicine, Key University Laboratory of Metabolism and Health of Guangdong, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, 518055, Guangdong, China
| | - Tianhao Shi
- Department of Biochemistry, School of Medicine, Key University Laboratory of Metabolism and Health of Guangdong, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, 518055, Guangdong, China
| | - Bin Ju
- Institute for Hepatology, National Clinical Research Center for Infectious Disease, Shenzhen Third People's Hospital, Shenzhen, China.
- The Second Affiliated Hospital, School of Medicine, Southern University of Science and Technology, Shenzhen, China.
| | - Zheng Zhang
- Institute for Hepatology, National Clinical Research Center for Infectious Disease, Shenzhen Third People's Hospital, Shenzhen, China.
- The Second Affiliated Hospital, School of Medicine, Southern University of Science and Technology, Shenzhen, China.
| | - Renhong Yan
- Department of Biochemistry, School of Medicine, Key University Laboratory of Metabolism and Health of Guangdong, Institute for Biological Electron Microscopy, Southern University of Science and Technology, Shenzhen, 518055, Guangdong, China.
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May AJ, Acharya P. Structural Studies of Henipavirus Glycoproteins. Viruses 2024; 16:195. [PMID: 38399971 PMCID: PMC10892422 DOI: 10.3390/v16020195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2023] [Revised: 01/19/2024] [Accepted: 01/24/2024] [Indexed: 02/25/2024] Open
Abstract
Henipaviruses are a genus of emerging pathogens that includes the highly virulent Nipah and Hendra viruses that cause reoccurring outbreaks of disease. Henipaviruses rely on two surface glycoproteins, known as the attachment and fusion proteins, to facilitate entry into host cells. As new and divergent members of the genus have been discovered and structurally characterized, key differences and similarities have been noted. This review surveys the available structural information on Henipavirus glycoproteins, complementing this with information from related biophysical and structural studies of the broader Paramyxoviridae family of which Henipaviruses are members. The process of viral entry is a primary focus for vaccine and drug development, and this review aims to identify critical knowledge gaps in our understanding of the mechanisms that drive Henipavirus fusion.
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Affiliation(s)
- Aaron J. May
- Duke Human Vaccine Institute, Duke University, Durham, NC 27710, USA
- Department of Biochemistry, Duke University, Durham, NC 27710, USA
| | - Priyamvada Acharya
- Duke Human Vaccine Institute, Duke University, Durham, NC 27710, USA
- Department of Biochemistry, Duke University, Durham, NC 27710, USA
- Department of Surgery, Duke University, Durham, NC 27710, USA
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Stelfox AJ, Oguntuyo KY, Rissanen I, Harlos K, Rambo R, Lee B, Bowden TA. Crystal structure and solution state of the C-terminal head region of the narmovirus receptor binding protein. mBio 2023; 14:e0139123. [PMID: 37737607 PMCID: PMC10653815 DOI: 10.1128/mbio.01391-23] [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: 06/09/2023] [Accepted: 07/05/2023] [Indexed: 09/23/2023] Open
Abstract
IMPORTANCE Genetically diverse paramyxoviruses are united in their presentation of a receptor-binding protein (RBP), which works in concert with the fusion protein to facilitate host-cell entry. The C-terminal head region of the paramyxoviral RBP, a primary determinant of host-cell tropism and inter-species transmission potential, forms structurally distinct classes dependent upon protein and glycan receptor specificity. Here, we reveal the architecture of the C-terminal head region of the RBPs from Nariva virus (NarV) and Mossman virus (MosV), two archetypal rodent-borne paramyxoviruses within the recently established genus Narmovirus, family Paramyxoviridae. Our analysis reveals that while narmoviruses retain the general architectural features associated with paramyxoviral RBPs, namely, a six-bladed β-propeller fold, they lack the structural motifs associated with known receptor-mediated host-cell entry pathways. This investigation indicates that the RBPs of narmoviruses exhibit pathobiological features that are distinct from those of other paramyxoviruses.
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Affiliation(s)
- Alice J. Stelfox
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
- European Molecular Biology Laboratory, Grenoble, France
| | | | - Ilona Rissanen
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
- Institute of Biotechnology, Helsinki Institute of Life Science HiLIFE, University of Helsinki, Helsinki, Finland
| | - Karl Harlos
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Robert Rambo
- Diamond Light Source Ltd, Harwell Science & Innovation Campus, Oxford, United Kingdom
| | - Benhur Lee
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Thomas A. Bowden
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
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Takemoto R, Hirai Y, Watanabe S, Harada H, Suzuki T, Hashiguchi T, Yanagi Y, Shirogane Y. Interaction of the Hemagglutinin Stalk Region with Cell Adhesion Molecule (CADM) 1 and CADM2 Mediates the Spread between Neurons and Neuropathogenicity of Measles Virus with a Hyperfusogenic Fusion Protein. J Virol 2023; 97:e0034023. [PMID: 37166307 PMCID: PMC10231178 DOI: 10.1128/jvi.00340-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 04/19/2023] [Indexed: 05/12/2023] Open
Abstract
Measles virus (MeV), the causative agent of measles, is an enveloped RNA virus of the family Paramyxoviridae, which remains an important cause of childhood morbidity and mortality. MeV has two envelope glycoproteins, the hemagglutinin (H) and fusion (F) proteins. During viral entry or virus-mediated fusion between infected cells and neighboring susceptible cells, the head domain of the H protein initially binds to its receptors, signaling lymphocytic activation molecule family member 1 (SLAM) and nectin-4, and then the stalk region of the H protein transmits the fusion-triggering signal to the F protein. MeV may persist in the human brain and cause a fatal neurodegenerative disease, subacute sclerosing panencephalitis (SSPE). Recently, we showed, using in vitro cell culture, that cell adhesion molecule (CADM) 1 and CADM2 are host factors that trigger hyperfusogenic mutant F proteins, causing cell-to-cell fusion and the transfer of the MeV genome between neurons. Unlike conventional receptors, CADM1 and CADM2 interact in cis (on the same membrane) with the H protein and then trigger membrane fusion. Here, we show that alanine substitutions in part of the stalk region (positions 171-175) abolish the ability of the H protein to mediate membrane fusion triggered by CADM1 and CADM2, but not by SLAM. The recombinant hyperfusogenic MeV carrying this mutant H protein loses its ability to spread in primary mouse neurons as well as its neurovirulence in experimentally infected suckling hamsters. These results indicate that CADM1 and CADM2 are key molecules for MeV propagation in the brain and its neurovirulence in vivo. IMPORTANCE Measles is an acute febrile illness with skin rash. Despite the availability of highly effective vaccines, measles is still an important cause of childhood morbidity and mortality in many countries. The World Health Organization estimates that more than 120,000 people died from measles worldwide in 2021. Measles virus (MeV), the causative agent of measles, can also cause a fatal progressive neurological disorder, subacute sclerosing panencephalitis (SSPE), several years after acute infection. There is currently no effective treatment for this disease. In this study, using recombinant MeVs with altered receptor usage patterns, we show that cell adhesion molecule (CADM) 1 and CADM2 are host factors critical for MeV spread in neurons and its neurovirulence. These findings further our understanding of the molecular mechanism of MeV neuropathogenicity.
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Affiliation(s)
- Ryuichi Takemoto
- Department of Virology, Faculty of Medicine, Kyushu University, Fukuoka, Japan
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yuichi Hirai
- Department of Virology, Faculty of Medicine, Kyushu University, Fukuoka, Japan
| | - Shumpei Watanabe
- Department of Microbiology, Faculty of Veterinary Medicine, Okayama University of Science, Ehime, Japan
| | - Hidetaka Harada
- Department of Virology, Faculty of Medicine, Kyushu University, Fukuoka, Japan
| | - Tateki Suzuki
- Laboratory of Medical Virology, Institute for Life and Medical Sciences, Kyoto University
| | - Takao Hashiguchi
- Laboratory of Medical Virology, Institute for Life and Medical Sciences, Kyoto University
| | - Yusuke Yanagi
- National Research Center for the Control and Prevention of Infectious Diseases, Nagasaki University, Nagasaki, Japan
| | - Yuta Shirogane
- Department of Virology, Faculty of Medicine, Kyushu University, Fukuoka, Japan
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Marcink TC, Zipursky G, Cheng W, Stearns K, Stenglein S, Golub K, Cohen F, Bovier F, Pfalmer D, Greninger AL, Porotto M, des Georges A, Moscona A. Subnanometer structure of an enveloped virus fusion complex on viral surface reveals new entry mechanisms. SCIENCE ADVANCES 2023; 9:eade2727. [PMID: 36763666 PMCID: PMC9917000 DOI: 10.1126/sciadv.ade2727] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 01/06/2023] [Indexed: 06/18/2023]
Abstract
Paramyxoviruses-including important pathogens like parainfluenza, measles, and Nipah viruses-use a receptor binding protein [hemagglutinin-neuraminidase (HN) for parainfluenza] and a fusion protein (F), acting in a complex, to enter cells. We use cryo-electron tomography to visualize the fusion complex of human parainfluenza virus 3 (HN/F) on the surface of authentic clinical viruses at a subnanometer resolution sufficient to answer mechanistic questions. An HN loop inserts in a pocket on F, showing how the fusion complex remains in a ready but quiescent state until activation. The globular HN heads are rotated with respect to each other: one downward to contact F, and the other upward to grapple cellular receptors, demonstrating how HN/F performs distinct steps before F activation. This depiction of viral fusion illuminates potentially druggable targets for paramyxoviruses and sheds light on fusion processes that underpin wide-ranging biological processes but have not been visualized in situ or at the present resolution.
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Affiliation(s)
- Tara C. Marcink
- Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Center for Host-Pathogen Interaction, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Gillian Zipursky
- Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Center for Host-Pathogen Interaction, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Wenjing Cheng
- Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Center for Host-Pathogen Interaction, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Kyle Stearns
- Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Center for Host-Pathogen Interaction, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Shari Stenglein
- Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Center for Host-Pathogen Interaction, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Kate Golub
- Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Center for Host-Pathogen Interaction, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Frances Cohen
- Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Center for Host-Pathogen Interaction, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Francesca Bovier
- Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Center for Host-Pathogen Interaction, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
| | - Daniel Pfalmer
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
| | - Alexander L. Greninger
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Matteo Porotto
- Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Center for Host-Pathogen Interaction, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Experimental Medicine, University of Campania “Luigi Vanvitelli,” 81100 Caserta, Italy
| | - Amedee des Georges
- Structural Biology Initiative, CUNY Advanced Science Research Center, City University of New York, New York, NY, USA
- Department of Chemistry and Biochemistry, The City College of New York, New York, NY, USA
- PhD Programs in Chemistry and Biochemistry, The Graduate Center, City University of New York, New York, NY, USA
| | - Anne Moscona
- Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Center for Host-Pathogen Interaction, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Microbiology and Immunology, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
- Department of Physiology and Cellular Biophysics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY, USA
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Structure and supramolecular organization of the canine distemper virus attachment glycoprotein. Proc Natl Acad Sci U S A 2023; 120:e2208866120. [PMID: 36716368 PMCID: PMC9963377 DOI: 10.1073/pnas.2208866120] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Canine distemper virus (CDV) is an enveloped RNA morbillivirus that triggers respiratory, enteric, and high incidence of severe neurological disorders. CDV induces devastating outbreaks in wild and endangered animals as well as in domestic dogs in countries associated with suboptimal vaccination programs. The receptor-binding tetrameric attachment (H)-protein is part of the morbilliviral cell entry machinery. Here, we present the cryo-electron microscopy (cryo-EM) structure and supramolecular organization of the tetrameric CDV H-protein ectodomain. The structure reveals that the morbilliviral H-protein is composed of three main domains: stalk, neck, and heads. The most unexpected feature was the inherent asymmetric architecture of the CDV H-tetramer being shaped by the neck, which folds into an almost 90° bent conformation with respect to the stalk. Consequently, two non-contacting receptor-binding H-head dimers, which are also tilted toward each other, are located on one side of an intertwined four helical bundle stalk domain. Positioning of the four protomer polypeptide chains within the neck domain is guided by a glycine residue (G158), which forms a hinge point exclusively in two protomer polypeptide chains. Molecular dynamics simulations validated the stability of the asymmetric structure under near physiological conditions and molecular docking showed that two receptor-binding sites are fully accessible. Thus, this spatial organization of the CDV H-tetramer would allow for concomitant protein interactions with the stalk and head domains without steric clashes. In summary, the structure of the CDV H-protein ectodomain provides new insights into the morbilliviral cell entry system and offers a blueprint for next-generation structure-based antiviral drug discovery.
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Novel Roles of the Nipah Virus Attachment Glycoprotein and Its Mobility in Early and Late Membrane Fusion Steps. mBio 2022; 13:e0322221. [PMID: 35506666 PMCID: PMC9239137 DOI: 10.1128/mbio.03222-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Paramyxoviridae family comprises important pathogens that include measles (MeV), mumps, parainfluenza, and the emerging deadly zoonotic Nipah virus (NiV) and Hendra virus (HeV). Paramyxoviral entry into cells requires viral-cell membrane fusion, and formation of paramyxoviral pathognomonic syncytia requires cell-cell membrane fusion. Both events are coordinated by intricate interactions between the tetrameric attachment (G/H/HN) and trimeric fusion (F) glycoproteins. We report that receptor binding induces conformational changes in NiV G that expose its stalk domain, which triggers F through a cascade from prefusion to prehairpin intermediate (PHI) to postfusion conformations, executing membrane fusion. To decipher how the NiV G stalk may trigger F, we introduced cysteines along the G stalk to increase tetrameric strength and restrict stalk mobility. While most point mutants displayed near-wild-type levels of cell surface expression and receptor binding, most yielded increased NiV G oligomeric strength, and showed remarkably strong defects in syncytium formation. Furthermore, most of these mutants displayed stronger F/G interactions and significant defects in their ability to trigger F, indicating that NiV G stalk mobility is key to proper F triggering via moderate G/F interactions. Also remarkably, a mutant capable of triggering F and of fusion pore formation yielded little syncytium formation, implicating G or G/F interactions in a late step occurring post fusion pore formation, such as the extensive fusion pore expansion required for syncytium formation. This study uncovers novel mechanisms by which the G stalk and its oligomerization/mobility affect G/F interactions, the triggering of F, and a late fusion pore expansion step-exciting novel findings for paramyxoviral attachment glycoproteins. IMPORTANCE The important Paramyxoviridae family includes measles, mumps, human parainfluenza, and the emerging deadly zoonotic Nipah virus (NiV) and Hendra virus (HeV). The deadly emerging NiV can cause neurologic and respiratory symptoms in humans with a >60% mortality rate. NiV has two surface proteins, the receptor binding protein (G) and fusion (F) glycoproteins. They mediate the required membrane fusion during viral entry into host cells and during syncytium formation, a hallmark of paramyxoviral and NiV infections. We previously discovered that the G stalk domain is important for triggering F (via largely unknown mechanisms) to induce membrane fusion. Here, we uncovered new roles and mechanisms by which the G stalk and its mobility modulate the triggering of F and also unexpectedly affect a very late step in membrane fusion, namely fusion pore expansion. Importantly, these novel findings may extend to other paramyxoviruses, offering new potential targets for therapeutic interventions.
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Dong J, Chen Y, Shi L, Shen B, Sun X, Ruan K, Xia X, Feng H, Feng N. Nanoparticles of conformation-stabilized canine distemper virus hemagglutinin are highly immunogenic and induce robust immunity. Virol J 2021; 18:229. [PMID: 34809642 PMCID: PMC8607554 DOI: 10.1186/s12985-021-01702-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 11/04/2021] [Indexed: 11/13/2022] Open
Abstract
Background Canine distemper virus (CDV) infection of ferrets, dogs, and giant pandas causes an acute systemic disease involving multiple organ systems, including the respiratory tract, lymphoid system, and central nervous system. In this study, we tested a new candidate CDV vaccine-CDV nanoparticles-based on hemagglutinin protein. Methods The nanoparticles were generated from conformation-stabilized CDV hemagglutinin tetramers. Immune responses against CDV were evaluated in mice. Immunization was initiated 6 weeks after birth and boosted two times with 4-week intervals. The blood and mucosal samples were collected 2 weeks after each immunization. Results Vaccination with CDV nanoparticles elicited high levels of IgG antibody titers in mice (approximately sevenfold to eightfold higher than that obtained with soluble CDV H protein) and mucosal immune responses and developed increased CDV-specific neutralizing antibody. The mice that received nanoparticles showed significantly higher IFN-γ- and IL-4-secreting cell population in the spleen and lymph node compared with mice immunized with soluble H protein. The co-stimulatory molecular expression of CD80 and CD86 on the surface of DCs was also upregulated. Conclusion The results demonstrate that self-assembly into nanoparticles can increase the immunogenicity of vaccine antigens, and nanoparticles assembled from conformation-stabilized CDV H protein can serve as a new CDV vaccine.
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Affiliation(s)
- Jingjian Dong
- Medical School of Jiaxing University, Jiahang Road 118#, Nanhu District, Jiaxing City, Zhejiang Province, 314001, People's Republic of China
| | - Yan Chen
- Medical School of Jiaxing University, Jiahang Road 118#, Nanhu District, Jiaxing City, Zhejiang Province, 314001, People's Republic of China
| | - Lili Shi
- Medical School of Jiaxing University, Jiahang Road 118#, Nanhu District, Jiaxing City, Zhejiang Province, 314001, People's Republic of China
| | - Bing Shen
- Medical School of Jiaxing University, Jiahang Road 118#, Nanhu District, Jiaxing City, Zhejiang Province, 314001, People's Republic of China
| | - Xianliang Sun
- Medical School of Jiaxing University, Jiahang Road 118#, Nanhu District, Jiaxing City, Zhejiang Province, 314001, People's Republic of China
| | - Kaiyi Ruan
- Medical School of Jiaxing University, Jiahang Road 118#, Nanhu District, Jiaxing City, Zhejiang Province, 314001, People's Republic of China
| | - Xianzhu Xia
- Military Veterinary Research Institute of Academy of Military Medical Sciences, Changchun, 130122, People's Republic of China
| | - Hao Feng
- Medical School of Jiaxing University, Jiahang Road 118#, Nanhu District, Jiaxing City, Zhejiang Province, 314001, People's Republic of China.
| | - Na Feng
- Military Veterinary Research Institute of Academy of Military Medical Sciences, Changchun, 130122, People's Republic of China.
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Short-stalk isoforms of CADM1 and CADM2 trigger neuropathogenic measles virus-mediated membrane fusion by interacting with the viral hemagglutinin. J Virol 2021; 96:e0194921. [PMID: 34788082 DOI: 10.1128/jvi.01949-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Measles virus (MeV), an enveloped RNA virus in the family Paramyxoviridae, usually causes acute febrile illness with skin rash, but in rare cases persists in the brain, causing a progressive neurological disorder, subacute sclerosing panencephalitis (SSPE). MeV bears two envelope glycoproteins, the hemagglutinin (H) and fusion (F) proteins. The H protein possesses a head domain that initially mediates receptor binding and a stalk domain that subsequently transmits the fusion-triggering signal to the F protein. We have recently shown that cell adhesion molecule 1 (CADM1, also known as IGSF4A, Necl-2, SynCAM1) and CADM2 (also known as IGSF4D, Necl-3, SynCAM2) are host factors enabling cell-cell membrane fusion mediated by hyperfusogenic F proteins of neuropathogenic MeVs as well as MeV spread between neurons lacking the known receptors. CADM1 and CADM2 interact in cis with the H protein on the same cell membrane, triggering hyperfusogenic F protein-mediated membrane fusion. Multiple isoforms of CADM1 and CADM2 containing various lengths of their stalk regions are generated by alternative splicing. Here we show that only short-stalk isoforms of CADM1 and CADM2 predominantly expressed in the brain induce hyperfusogenic F protein-mediated membrane fusion. While the known receptors interact in trans with the H protein through its head domain, these isoforms can interact in cis even with the H protein lacking the head domain and trigger membrane fusion, presumably through its stalk domain. Thus, our results unveil a new mechanism of viral fusion triggering by host factors. Importance Measles, an acute febrile illness with skin rash, is still an important cause of childhood morbidity and mortality worldwide. Measles virus (MeV), the causative agent of measles, may also cause a progressive neurological disorder, subacute sclerosing panencephalitis (SSPE), several years after acute infection. The disease is fatal, and no effective therapy is available. Recently, we have reported that cell adhesion molecule 1 (CADM1) and CADM2 are host factors enabling MeV cell-to-cell spread in neurons. These molecules interact in cis with the MeV attachment protein on the same cell membrane, triggering the fusion protein and causing membrane fusion. CADM1 and CADM2 are known to exist in multiple splice isoforms. In this study, we report that their short-stalk isoforms can induce membrane fusion by interacting in cis with the viral attachment protein independently of its receptor-binding head domain. This finding may have important implications for cis-acting fusion triggering by host factors.
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Yeo YY, Buchholz DW, Gamble A, Jager M, Aguilar HC. Headless Henipaviral Receptor Binding Glycoproteins Reveal Fusion Modulation by the Head/Stalk Interface and Post-receptor Binding Contributions of the Head Domain. J Virol 2021; 95:e0066621. [PMID: 34288734 PMCID: PMC8475510 DOI: 10.1128/jvi.00666-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 07/13/2021] [Indexed: 11/20/2022] Open
Abstract
Cedar virus (CedV) is a nonpathogenic member of the Henipavirus (HNV) genus of emerging viruses, which includes the deadly Nipah (NiV) and Hendra (HeV) viruses. CedV forms syncytia, a hallmark of henipaviral and paramyxoviral infections and pathogenicity. However, the intrinsic fusogenic capacity of CedV relative to NiV or HeV remains unquantified. HNV entry is mediated by concerted interactions between the attachment (G) and fusion (F) glycoproteins. Upon receptor binding by the HNV G head domain, a fusion-activating G stalk region is exposed and triggers F to undergo a conformational cascade that leads to viral entry or cell-cell fusion. Here, we demonstrate quantitatively that CedV is inherently significantly less fusogenic than NiV at equivalent G and F cell surface expression levels. We then generated and tested six headless CedV G mutants of distinct C-terminal stalk lengths, surprisingly revealing highly hyperfusogenic cell-cell fusion phenotypes 3- to 4-fold greater than wild-type CedV levels. Additionally, similarly to NiV, a headless HeV G mutant yielded a less pronounced hyperfusogenic phenotype compared to wild-type HeV. Further, coimmunoprecipitation and cell-cell fusion assays revealed heterotypic NiV/CedV functional G/F bidentate interactions, as well as evidence of HNV G head domain involvement beyond receptor binding or G stalk exposure. All evidence points to the G head/stalk junction being key to modulating HNV fusogenicity, supporting the notion that head domains play several distinct and central roles in modulating stalk domain fusion promotion. Further, this study exemplifies how CedV may help elucidate important mechanistic underpinnings of HNV entry and pathogenicity. IMPORTANCE The Henipavirus genus in the Paramyxoviridae family includes the zoonotic Nipah (NiV) and Hendra (HeV) viruses. NiV and HeV infections often cause fatal encephalitis and pneumonia, but no vaccines or therapeutics are currently approved for human use. Upon viral entry, Henipavirus infections yield the formation of multinucleated cells (syncytia). Viral entry and cell-cell fusion are mediated by the attachment (G) and fusion (F) glycoproteins. Cedar virus (CedV), a nonpathogenic henipavirus, may be a useful tool to gain knowledge on henipaviral pathogenicity. Here, using homotypic and heterotypic full-length and headless CedV, NiV, and HeV G/F combinations, we discovered that CedV G/F are significantly less fusogenic than NiV or HeV G/F, and that the G head/stalk junction is key to modulating cell-cell fusion, refining the mechanism of henipaviral membrane fusion events. Our study exemplifies how CedV may be a useful tool to elucidate broader mechanistic understanding for the important henipaviruses.
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Affiliation(s)
- Yao Yu Yeo
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - David W. Buchholz
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Amandine Gamble
- Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, USA
| | - Mason Jager
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Hector C. Aguilar
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
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12
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Unique Tropism and Entry Mechanism of Mumps Virus. Viruses 2021; 13:v13091746. [PMID: 34578327 PMCID: PMC8471308 DOI: 10.3390/v13091746] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 08/28/2021] [Accepted: 08/30/2021] [Indexed: 12/19/2022] Open
Abstract
Mumps virus (MuV) is an important human pathogen that causes parotitis, orchitis, oophoritis, meningitis, encephalitis, and sensorineural hearing loss. Although mumps is a vaccine-preventable disease, sporadic outbreaks have occurred worldwide, even in highly vaccinated populations. MuV not only causes systemic infection but also has a unique tropism to glandular tissues and the central nervous system. In general, tropism can be defined by multiple factors in the viral life cycle, including its entry, interaction with host factors, and host-cell immune responses. Although the underlying mechanisms of MuV tropism remain to be fully understood, recent studies on virus-host interactions have provided insights into viral pathogenesis. This review was aimed at summarizing the entry process of MuV by focusing on the glycan receptors, particularly the recently identified receptors with a trisaccharide core motif, and their interactions with the viral attachment proteins. Here, we describe the receptor structures, their distribution in the human body, and the recently identified host factors for MuV and analyze their relationship with MuV tropism.
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13
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Novel Roles of the N1 Loop and N4 Alpha-Helical Region of the Nipah Virus Fusion Glycoprotein in Modulating Early and Late Steps of the Membrane Fusion Cascade. J Virol 2021; 95:JVI.01707-20. [PMID: 33568505 DOI: 10.1128/jvi.01707-20] [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] [Received: 08/29/2020] [Accepted: 01/27/2021] [Indexed: 11/20/2022] Open
Abstract
Nipah virus (NiV) is a zoonotic bat henipavirus in the family Paramyxoviridae NiV is deadly to humans, infecting host cells by direct fusion of the viral and host cell plasma membranes. This membrane fusion process is coordinated by the receptor-binding attachment (G) and fusion (F) glycoproteins. Upon G-receptor binding, F fuses membranes via a cascade that sequentially involves F-triggering, fusion pore formation, and viral or genome entry into cells. Using NiV as an important paramyxoviral model, we identified two novel regions in F that modulate the membrane fusion cascade. For paramyxoviruses and other viral families with class I fusion proteins, the heptad repeat 1 (HR1) and HR2 regions in the fusion protein prefusion conformation bind to form a six-helix bundle in the postfusion conformation. Here, structural comparisons between the F prefusion and postfusion conformations revealed that a short loop region (N1) undergoes dramatic spatial reorganization and a short alpha helix (N4) undergoes secondary structural changes. The roles of the N1 and N4 regions during the membrane fusion cascade, however, remain unknown for henipaviruses and paramyxoviruses. By performing alanine scanning mutagenesis and various functional analyses, we report that specific residues within these regions alter various steps in the membrane fusion cascade. While the N1 region affects early F-triggering, the N4 region affects F-triggering, F thermostability, and extensive fusion pore expansion during syncytium formation, also uncovering a link between F-G interactions and F-triggering. These novel mechanistic roles expand our understanding of henipaviral and paramyxoviral F-triggering, viral entry, and cell-cell fusion (syncytia), a pathognomonic feature of paramyxoviral infections.IMPORTANCE Henipaviruses infect bats, agriculturally important animals, and humans, with high mortality rates approaching ∼75% in humans. Known human outbreaks have been concentrated in Southeast Asia and Australia. Furthermore, about 20 new henipaviral species have been recently discovered in bats, with geographical spans in Asia, Africa, and South America. The development of antiviral therapeutics requires a thorough understanding of the mechanism of viral entry into host cells. In this study, we discovered novel roles of two regions within the fusion protein of the deadly henipavirus NiV. Such roles were in allowing viral entry into host cells and cell-cell fusion, a pathological hallmark of this and other paramyxoviruses. These novel roles were in the previously undescribed N1 and N4 regions within the fusion protein, modulating early and late steps of these important processes of viral infection and henipaviral disease. Notably, this knowledge may apply to other henipaviruses and more broadly to other paramyxoviruses.
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14
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Wong JJ, Chen Z, Chung JK, Groves JT, Jardetzky TS. EphrinB2 clustering by Nipah virus G is required to activate and trap F intermediates at supported lipid bilayer-cell interfaces. SCIENCE ADVANCES 2021; 7:eabe1235. [PMID: 33571127 PMCID: PMC7840137 DOI: 10.1126/sciadv.abe1235] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 12/07/2020] [Indexed: 06/12/2023]
Abstract
Paramyxovirus membrane fusion requires an attachment protein that binds to a host cell receptor and a fusion protein that merges the viral and host membranes. For Nipah virus (NiV), the G attachment protein binds ephrinB2/B3 receptors and activates F-mediated fusion. To visualize dynamic events of these proteins at the membrane interface, we reconstituted NiV fusion activation by overlaying F- and G-expressing cells onto ephrinB2-functionalized supported lipid bilayers and used TIRF microscopy to follow F, G, and ephrinB2. We found that G and ephrinB2 form clusters and that oligomerization of ephrinB2 is necessary for F activation. Single-molecule tracking of F particles revealed accumulation of an immobilized intermediate upon activation. We found no evidence for stable F-G protein complexes before or after activation. These observations lead to a revised model for NiV fusion activation and provide a foundation for investigating other multicomponent viral fusion systems.
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Affiliation(s)
- Joyce J Wong
- Department of Structural Biology, Stanford University, Stanford, CA, USA
| | - Zhongwen Chen
- Multiscale Research Institute of Complex Systems, Fudan University, Shanghai, China
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA
| | - Jean K Chung
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA
| | - Jay T Groves
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA.
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15
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Third Helical Domain of the Nipah Virus Fusion Glycoprotein Modulates both Early and Late Steps in the Membrane Fusion Cascade. J Virol 2020; 94:JVI.00644-20. [PMID: 32669342 DOI: 10.1128/jvi.00644-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 07/08/2020] [Indexed: 01/21/2023] Open
Abstract
Medically important paramyxoviruses, such as measles, mumps, parainfluenza, Nipah, and Hendra viruses, infect host cells by directing fusion of the viral and cellular plasma membranes. Upon infection, paramyxoviruses cause a second type of membrane fusion, cell-cell fusion (syncytium formation), which is linked to pathogenicity. Host cell receptor binding causes conformational changes in the attachment glycoprotein (HN, H, or G) that trigger a conformational cascade in the fusion (F) glycoprotein that mediates membrane fusion. F, a class I fusion protein, contains the archetypal heptad repeat regions 1 (HR1) and 2 (HR2). It is well established that binding of HR1 and HR2 is key to fusing viral and cellular membranes. In this study, we uncovered a novel fusion-modulatory role of a third structurally conserved helical region (HR3) in F. Based on its location within the F structure, and structural differences between its prefusion and postfusion conformations, we hypothesized that the HR3 modulates triggering of the F conformational cascade (still requiring G). We used the deadly Nipah virus (NiV) as an important paramyxoviral model to perform alanine scan mutagenesis and a series of multidisciplinary structural/functional analyses that dissect the various states of the membrane fusion cascade. Remarkably, we found that specific residues within the HR3 modulate not only early F-triggering but also late extensive fusion pore expansion steps in the membrane fusion cascade. Our results characterize these novel fusion-modulatory roles of the F HR3, improving our understanding of the membrane fusion process for NiV and likely for the related Henipavirus genus and possibly Paramyxoviridae family members.IMPORTANCE The Paramyxoviridae family includes important human and animal pathogens, such as measles, mumps, and parainfluenza viruses and the deadly henipaviruses Nipah (NiV) and Hendra (HeV) viruses. Paramyxoviruses infect the respiratory tract and the central nervous system (CNS) and can be highly infectious. Most paramyxoviruses have a limited host range. However, the biosafety level 4 NiV and HeV are highly pathogenic and have a wide mammalian host range. Nipah viral infections result in acute respiratory syndrome and severe encephalitis in humans, leading to 40 to 100% mortality rates. The lack of licensed vaccines or therapeutic approaches against NiV and other important paramyxoviruses underscores the need to understand viral entry mechanisms. In this study, we uncovered a novel role of a third helical region (HR3) of the NiV fusion glycoprotein in the membrane fusion process that leads to viral entry. This discovery sets HR3 as a new candidate target for antiviral strategies for NiV and likely for related viruses.
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16
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Chi M, Liu Y, Wen H, Zhao L, Song Y, Liu N, Chi L, Wang Z. Role of the head-stalk linker region (aa115-122) of Newcastle disease virus haemagglutinin-neuraminidase in regulating fusion triggering. J Gen Virol 2020; 101:5-20. [PMID: 31702540 DOI: 10.1099/jgv.0.001349] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
To gain insights into the role of the head-stalk linker region in the fusion triggering, we constructed mutants by deleting or substituting the linker region (115-NGAANNSG-122) of Newcastle disease virus (NDV) haemagglutinin-neuraminidase (HN) with the corresponding sequences of other paramyxoviruses. The results showed that these HN mutants exhibited different levels of fusion-triggering activity, but most of them maintained comparable levels with wide-type HN in both receptor recognition and neuraminidase activity. We tried to figure out reasons for fusion alteration through assessing the expression and the oligomeric state of HN mutants. Moreover, four mutants with significant fusion changes were introduced into the headless HN stem (HN1-123) to intensively investigate the role of the linker region in fusion triggering. Consequently, the stability of HN oligomers and the structural integrity of the 4 helical-bundle of stalk have complicated influences on the alteration of fusion-triggering activities for different mutants. These data suggested that the head-stalk linker could regulate the fusion triggering at both full-length and headless HN levels.
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Affiliation(s)
- Miaomiao Chi
- Department of Virology, School of Public Health, Shandong University, Jinan 250012, PR China
| | - Ying Liu
- Department of Virology, School of Public Health, Shandong University, Jinan 250012, PR China
| | - Hongling Wen
- Department of Virology, School of Public Health, Shandong University, Jinan 250012, PR China
| | - Li Zhao
- Department of Virology, School of Public Health, Shandong University, Jinan 250012, PR China
| | - Yanyan Song
- Department of Virology, School of Public Health, Shandong University, Jinan 250012, PR China
| | - Na Liu
- Department of Virology, School of Public Health, Shandong University, Jinan 250012, PR China
| | - Lianli Chi
- State Key Laboratory of Microbial Technology, National Glycoengineering Research Center, Shandong University, Jinan 250100, PR China
| | - Zhiyu Wang
- The Key Laboratory for Experimental Teratology of the Ministry of Education, Shandong University, Jinan 250012, PR China.,Department of Virology, School of Public Health, Shandong University, Jinan 250012, PR China
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17
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Aggarwal M, Plemper RK. Structural Insight into Paramyxovirus and Pneumovirus Entry Inhibition. Viruses 2020; 12:E342. [PMID: 32245118 PMCID: PMC7150754 DOI: 10.3390/v12030342] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2020] [Revised: 03/17/2020] [Accepted: 03/18/2020] [Indexed: 01/04/2023] Open
Abstract
Paramyxoviruses and pneumoviruses infect cells through fusion (F) protein-mediated merger of the viral envelope with target membranes. Members of these families include a range of major human and animal pathogens, such as respiratory syncytial virus (RSV), measles virus (MeV), human parainfluenza viruses (HPIVs), and highly pathogenic Nipah virus (NiV). High-resolution F protein structures in both the metastable pre- and the postfusion conformation have been solved for several members of the families and a number of F-targeting entry inhibitors have progressed to advanced development or clinical testing. However, small-molecule RSV entry inhibitors have overall disappointed in clinical trials and viral resistance developed rapidly in experimental settings and patients, raising the question of whether the available structural information may provide a path to counteract viral escape through proactive inhibitor engineering. This article will summarize current mechanistic insight into F-mediated membrane fusion and examine the contribution of structural information to the development of small-molecule F inhibitors. Implications are outlined for future drug target selection and rational drug engineering strategies.
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Affiliation(s)
| | - Richard K Plemper
- Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, USA;
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18
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Azarm KD, Lee B. Differential Features of Fusion Activation within the Paramyxoviridae. Viruses 2020; 12:v12020161. [PMID: 32019182 PMCID: PMC7077268 DOI: 10.3390/v12020161] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 01/25/2020] [Accepted: 01/29/2020] [Indexed: 12/13/2022] Open
Abstract
Paramyxovirus (PMV) entry requires the coordinated action of two envelope glycoproteins, the receptor binding protein (RBP) and fusion protein (F). The sequence of events that occurs during the PMV entry process is tightly regulated. This regulation ensures entry will only initiate when the virion is in the vicinity of a target cell membrane. Here, we review recent structural and mechanistic studies to delineate the entry features that are shared and distinct amongst the Paramyxoviridae. In general, we observe overarching distinctions between the protein-using RBPs and the sialic acid- (SA-) using RBPs, including how their stalk domains differentially trigger F. Moreover, through sequence comparisons, we identify greater structural and functional conservation amongst the PMV fusion proteins, as compared to the RBPs. When examining the relative contributions to sequence conservation of the globular head versus stalk domains of the RBP, we observe that, for the protein-using PMVs, the stalk domains exhibit higher conservation and find the opposite trend is true for SA-using PMVs. A better understanding of conserved and distinct features that govern the entry of protein-using versus SA-using PMVs will inform the rational design of broader spectrum therapeutics that impede this process.
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19
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Navaratnarajah CK, Generous AR, Yousaf I, Cattaneo R. Receptor-mediated cell entry of paramyxoviruses: Mechanisms, and consequences for tropism and pathogenesis. J Biol Chem 2020; 295:2771-2786. [PMID: 31949044 DOI: 10.1074/jbc.rev119.009961] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Research in the last decade has uncovered many new paramyxoviruses, airborne agents that cause epidemic diseases in animals including humans. Most paramyxoviruses enter epithelial cells of the airway using sialic acid as a receptor and cause only mild disease. However, others cross the epithelial barrier and cause more severe disease. For some of these viruses, the host receptors have been identified, and the mechanisms of cell entry have been elucidated. The tetrameric attachment proteins of paramyxoviruses have vastly different binding affinities for their cognate receptors, which they contact through different binding surfaces. Nevertheless, all input signals are converted to the same output: conformational changes that trigger refolding of trimeric fusion proteins and membrane fusion. Experiments with selectively receptor-blinded viruses inoculated into their natural hosts have provided insights into tropism, identifying the cells and tissues that support growth and revealing the mechanisms of pathogenesis. These analyses also shed light on diabolically elegant mechanisms used by morbilliviruses, including the measles virus, to promote massive amplification within the host, followed by efficient aerosolization and rapid spread through host populations. In another paradigm of receptor-facilitated severe disease, henipaviruses, including Nipah and Hendra viruses, use different members of one protein family to cause zoonoses. Specific properties of different paramyxoviruses, like neurotoxicity and immunosuppression, are now understood in the light of receptor specificity. We propose that research on the specific receptors for several newly identified members of the Paramyxoviridae family that may not bind sialic acid is needed to anticipate their zoonotic potential and to generate effective vaccines and antiviral compounds.
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Affiliation(s)
| | - Alex R Generous
- Mayo Clinic Graduate School of Biomedical Sciences, Virology and Gene Therapy Track, Mayo Clinic, Rochester, Minnesota 55905
| | - Iris Yousaf
- Mayo Clinic Graduate School of Biomedical Sciences, Virology and Gene Therapy Track, Mayo Clinic, Rochester, Minnesota 55905
| | - Roberto Cattaneo
- Department of Molecular Medicine, Mayo Clinic, Rochester, Minnesota 55905.
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20
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Abstract
Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract disease in young children and elderly people. Although the virus was isolated in 1955, an effective RSV vaccine has not been developed, and the only licensed intervention is passive immunoprophylaxis of high-risk infants with a humanized monoclonal antibody. During the past 5 years, however, there has been substantial progress in our understanding of the structure and function of the RSV glycoproteins and their interactions with host cell factors that mediate entry. This period has coincided with renewed interest in developing effective interventions, including the isolation of potent monoclonal antibodies and small molecules and the design of novel vaccine candidates. In this Review, we summarize the recent findings that have begun to elucidate RSV entry mechanisms, describe progress on the development of new interventions and conclude with a perspective on gaps in our knowledge that require further investigation. Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract disease in young children and elderly people. In this Review, Battles and McLellan summarize our current understanding of RSV entry, describe progress on the development of new interventions and conclude with a perspective on gaps in our knowledge that require further investigation.
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Affiliation(s)
- Michael B Battles
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
| | - Jason S McLellan
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX, USA.
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21
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Disruption of the Dimer-Dimer Interaction of the Mumps Virus Attachment Protein Head Domain, Aided by an Anion Located at the Interface, Compromises Membrane Fusion Triggering. J Virol 2020; 94:JVI.01732-19. [PMID: 31619562 DOI: 10.1128/jvi.01732-19] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 10/10/2019] [Indexed: 12/26/2022] Open
Abstract
Mumps virus (MuV), an enveloped negative-strand RNA virus belonging to the family Paramyxoviridae, enters the host cell through membrane fusion mediated by two viral envelope proteins, an attachment protein hemagglutinin-neuraminidase (MuV-HN) and a fusion (F) protein. However, how the binding of MuV-HN to glycan receptors triggers membrane fusion is not well understood. The crystal structure of the MuV-HN head domain forms a tetramer (dimer of dimers) like other paramyxovirus attachment proteins. In the structure, a sulfate ion (SO4 2-) was found at the interface between two dimers, which may be replaced by a hydrogen phosphate ion (HPO4 2-) under physiological conditions. The anion is captured by the side chain of a positively charged arginine residue at position 139 of one monomer each from both dimers. Substitution of alanine or lysine for arginine at this position compromised the fusion support activity of MuV-HN without affecting its cell surface expression, glycan-receptor binding, and interaction with the F protein. Furthermore, the substitution appeared to affect the tetramer formation of the head domain as revealed by blue native-PAGE analysis. These results, together with our previous similar findings with the measles virus attachment protein head domain, suggest that the dimer-dimer interaction within the tetramer may play an important role in triggering membrane fusion during paramyxovirus entry.IMPORTANCE Despite the use of effective live vaccines, mumps outbreaks still occur worldwide. Mumps virus (MuV) infection typically causes flu-like symptoms and parotid gland swelling but sometimes leads to orchitis, oophoritis, and neurological complications, such as meningitis, encephalitis, and deafness. MuV enters the host cell through membrane fusion mediated by two viral proteins, a receptor-binding attachment protein, and a fusion protein, but its detailed mechanism is not fully understood. In this study, we show that the tetramer (dimer of dimers) formation of the MuV attachment protein head domain is supported by an anion located at the interface between two dimers and that the dimer-dimer interaction plays an important role in triggering the activation of the fusion protein and causing membrane fusion. These results not only further our understanding of MuV entry but provide useful information about a possible target for antiviral drugs.
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22
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Du Pont V, Jiang Y, Plemper RK. Bipartite interface of the measles virus phosphoprotein X domain with the large polymerase protein regulates viral polymerase dynamics. PLoS Pathog 2019; 15:e1007995. [PMID: 31381607 PMCID: PMC6695210 DOI: 10.1371/journal.ppat.1007995] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 08/15/2019] [Accepted: 07/22/2019] [Indexed: 11/18/2022] Open
Abstract
Measles virus (MeV) is a highly contagious, re-emerging, major human pathogen. Replication requires a viral RNA-dependent RNA polymerase (RdRP) consisting of the large (L) polymerase protein complexed with the homo-tetrameric phosphoprotein (P). In addition, P mediates interaction with the nucleoprotein (N)-encapsidated viral RNA genome. The nature of the P:L interface and RdRP negotiation of the ribonucleoprotein template are poorly understood. Based on biochemical interface mapping, swapping of the central P tetramerization domain (OD) for yeast GCN4, and functional assays, we demonstrate that the MeV P-to-L interface is bipartite, comprising a coiled-coil microdomain proximal to the OD and an unoccupied face of the triangular prism-shaped C-terminal P X-domain (P-XD), which is distinct from the known P-XD face that binds N-tail. Mixed null-mutant P tetramers regained L-binding competence in a ratio-dependent manner and fully reclaimed bioactivity in minireplicon assays and recombinant MeV, demonstrating that the individual L-binding interface elements are physically and mechanistically distinct. P-XD binding competence to L and N was likewise trans-complementable, which, combined with mathematical modeling, enabled the mechanistic characterization of P through two- and stoichiometrically-controlled three-way complementations. Only one each of the four XDs per P tetramer must be L or N binding-competent for bioactivity, but interaction of the same P-XD with L and N was mutually exclusive, and L binding superseded engaging N. Mixed P tetramers with a single, designated L binding-competent P-XD caused significant RdRP hyperactivity, outlining a model of iterative resolution and reformation of the P-XD:L interface regulating polymerase mobility. MeV belongs to the order of non-segmented negative polarity RNA viruses, which includes devastating human pathogens. While all feature encapsidated RNA genomes and P-L type polymerase complexes, insight into the intermolecular interactions within the polymerase hetero-oligomer and between the polymerase complex and the RNA-encapsidating N protein is rudimentary. Our mapping of the MeV P-to-L interaction revealed a bipartite interface with physically and mechanistically distinct contact zones, which provided a unique experimental platform to dissect the stoichiometry and dynamics of P interactions with L and N through functional trans-complementation assays in minireplicon settings and, ensuring physiological significance, recombinant virions. The identification and functional characterization of a novel L-binding face on the P-XD triangular prism, distinct from the side contacting N-tail, places P-XD at the center of a regulatory mechanism that controls the dynamics of polymerase advancement along the encapsidated genome through iterative separation and restoration of P-XD interaction with L. These observations and the high structural homology of polymerase components within the Paramyxoviridae recommend the P-XD:L protein-protein interface as premier target for directed drug discovery against emerging and re-emerging paramyxoviruses.
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Affiliation(s)
- Venice Du Pont
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia, United States of America
| | - Yi Jiang
- Department of Mathematics and Statistics, Georgia State University, Atlanta, Georgia, United States of America
| | - Richard K. Plemper
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia, United States of America
- * E-mail:
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23
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Nipah and Hendra Virus Glycoproteins Induce Comparable Homologous but Distinct Heterologous Fusion Phenotypes. J Virol 2019; 93:JVI.00577-19. [PMID: 30971473 DOI: 10.1128/jvi.00577-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 04/07/2019] [Indexed: 02/02/2023] Open
Abstract
Nipah and Hendra viruses (NiV and HeV) exhibit high lethality in humans and are biosafety level 4 (BSL-4) paramyxoviruses in the growing genus Henipavirus The attachment (G) and fusion (F) envelope glycoproteins are both required for viral entry into cells and for cell-cell fusion, which is pathognomonic of henipaviral infections. Here, we compared the fusogenic capacities between homologous and heterologous pairs of NiV and HeV glycoproteins. Importantly, to accurately measure their fusogenic capacities, as these depend on glycoprotein cell surface expression (CSE) levels, we inserted identical extracellular tags to both fusion (FLAG tags) or both attachment (hemagglutinin [HA] tags) glycoproteins. Importantly, these tags were placed in extracellular sites where they did not affect glycoprotein expression or function. NiV and HeV glycoproteins induced comparable levels of homologous HEK293T cell-cell fusion. Surprisingly, however, while the heterologous NiV F/HeV G (NF/HG) combination yielded a hypofusogenic phenotype, the heterologous HeV F/NiV G (HF/NG) combination yielded a hyperfusogenic phenotype. Pseudotyped viral entry levels primarily corroborated the fusogenic phenotypes of the glycoprotein pairs analyzed. Furthermore, we constructed G and F chimeras that allowed us to map the overall regions in G and F that contributed to these hyperfusogenic or hypofusogenic phenotypes. Importantly, the fusogenic phenotypes of the glycoprotein combinations negatively correlated with the avidities of F-G interactions, supporting the F/G dissociation model of henipavirus-induced membrane fusion, even in the context of heterologous glycoprotein pairs.IMPORTANCE The NiV and HeV henipaviruses are BSL-4 pathogens transmitted from bats. NiV and HeV often lead to human death and animal diseases. The formation of multinucleated cells (syncytia) is a hallmark of henipaviral infections and is caused by fusion of cells coordinated by interactions of the viral attachment (G) and fusion (F) glycoproteins. We found via various assays that viral entry and syncytium formation depend on the viral origin of the glycoproteins, with HeV F and NiV G promoting higher membrane fusion levels than their counterparts. This is important knowledge, since both viruses use the same bat vector species and potential coinfections of these or subsequent hosts may alter the outcome of disease.
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Regulatory Role of the Morbillivirus Attachment Protein Head-to-Stalk Linker Module in Membrane Fusion Triggering. J Virol 2018; 92:JVI.00679-18. [PMID: 29997204 DOI: 10.1128/jvi.00679-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 07/05/2018] [Indexed: 12/12/2022] Open
Abstract
Morbillivirus (e.g., measles virus [MeV] and canine distemper virus [CDV]) host cell entry is coordinated by two interacting envelope glycoproteins, namely, an attachment (H) protein and a fusion (F) protein. The ectodomain of H proteins consists of stalk, connector, and head domains that assemble into functional noncovalent dimer-of-dimers. The role of the C-terminal module of the H-stalk domain (termed linker) and the connector, although putatively able to assume flexible structures and allow receptor-induced structural rearrangements, remains largely unexplored. Here, we carried out a nonconservative mutagenesis scan analysis of the MeV and CDV H-linker/connector domains. Our data demonstrated that replacing isoleucine 146 in H-linker (H-I146) with any charged amino acids prevented virus-mediated membrane fusion activity, despite proper trafficking of the mutants to the cell surface and preserved binding efficiency to the SLAM/CD150 receptor. Nondenaturing electrophoresis revealed that these charged amino acid changes led to the formation of irregular covalent H tetramers rather than functional dimer-of-dimers formed when isoleucine or other hydrophobic amino acids were present at residue position 146. Remarkably, we next demonstrated that covalent H tetramerization per se was not the only mechanism preventing F activation. Indeed, the neutral glycine mutant (H-I146G), which exhibited strong covalent tetramerization propensity, maintained limited fusion promotion activity. Conversely, charged H-I146 mutants, which additionally carried alanine substitution of natural cysteines (H-C139A and H-C154A) and thus were unable to form covalently linked tetramers, were fusion activation defective. Our data suggest a dual regulatory role of the hydrophobic residue at position 146 of the morbillivirus head-to-stalk H-linker module: securing the assembly of productive dimer-of-dimers and contributing to receptor-induced F-triggering activity.IMPORTANCE MeV and CDV remain important human and animal pathogens. Development of antivirals may significantly support current global vaccination campaigns. Cell entry is orchestrated by two interacting glycoproteins (H and F). The current hypothesis postulates that tetrameric H ectodomains (composed of stalk, connector, and head domains) undergo receptor-induced rearrangements to productively trigger F; these conformational changes may be regulated by the H-stalk C-terminal module (linker) and the following connector domain. Mutagenesis scan analysis of both microdomains revealed that replacing amino acid 146 in the H-linker region with nonhydrophobic residues produced covalent H tetramers which were compromised in triggering membrane fusion activity. However, these mutant proteins retained their ability to traffic to the cell surface and to bind to the virus receptor. These data suggest that the morbillivirus linker module contributes to the folding of functional pre-F-triggering H tetramers. Furthermore, such structures might be critical to convert receptor engagement into F activation.
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Ke Z, Strauss JD, Hampton CM, Brindley MA, Dillard RS, Leon F, Lamb KM, Plemper RK, Wright ER. Promotion of virus assembly and organization by the measles virus matrix protein. Nat Commun 2018; 9:1736. [PMID: 29712906 PMCID: PMC5928126 DOI: 10.1038/s41467-018-04058-2] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 03/29/2018] [Indexed: 12/05/2022] Open
Abstract
Measles virus (MeV) remains a major human pathogen, but there are presently no licensed antivirals to treat MeV or other paramyxoviruses. Here, we use cryo-electron tomography (cryo-ET) to elucidate the principles governing paramyxovirus assembly in MeV-infected human cells. The three-dimensional (3D) arrangement of the MeV structural proteins including the surface glycoproteins (F and H), matrix protein (M), and the ribonucleoprotein complex (RNP) are characterized at stages of virus assembly and budding, and in released virus particles. The M protein is observed as an organized two-dimensional (2D) paracrystalline array associated with the membrane. A two-layered F–M lattice is revealed suggesting that interactions between F and M may coordinate processes essential for MeV assembly. The RNP complex remains associated with and in close proximity to the M lattice. In this model, the M lattice facilitates the well-ordered incorporation and concentration of the surface glycoproteins and the RNP at sites of virus assembly. Virus assembly is technically challenging to study. Here the authors use cryo-electron tomography of measles virus-infected human cells to determine native-state virus structure and they locate well-ordered M lattices that organize viral glycoproteins, RNP, and drive assembly.
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Affiliation(s)
- Zunlong Ke
- Division of Infectious Diseases, Department of Pediatrics, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, GA, 30322, USA.,School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Joshua D Strauss
- Division of Infectious Diseases, Department of Pediatrics, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, GA, 30322, USA
| | - Cheri M Hampton
- Division of Infectious Diseases, Department of Pediatrics, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, GA, 30322, USA
| | - Melinda A Brindley
- Department of Infectious Diseases, Department of Population Health and Center for Vaccines and Immunology, University of Georgia, Athens, GA, 30602, USA.,Institute for Biomedical Sciences, Georgia State University, Atlanta, GA, 30303, USA
| | - Rebecca S Dillard
- Division of Infectious Diseases, Department of Pediatrics, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, GA, 30322, USA
| | - Fredrick Leon
- Division of Infectious Diseases, Department of Pediatrics, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, GA, 30322, USA
| | - Kristen M Lamb
- Division of Infectious Diseases, Department of Pediatrics, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, GA, 30322, USA
| | - Richard K Plemper
- Institute for Biomedical Sciences, Georgia State University, Atlanta, GA, 30303, USA.
| | - Elizabeth R Wright
- Division of Infectious Diseases, Department of Pediatrics, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, GA, 30322, USA. .,Robert P. Apkarian Integrated Electron Microscopy Core, Emory University, Atlanta, GA, 30322, USA.
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Functional analysis of amino acids at stalk/head interface of human parainfluenza virus type 3 hemagglutinin-neuraminidase protein in the membrane fusion process. Virus Genes 2018. [PMID: 29516315 DOI: 10.1007/s11262-018-1546-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Human parainfluenza virus type 3 (hPIV3) is an important respiratory pathogen that causes the majority of viral pneumonia of infants and young children. hPIV3 can infect host cells through the synergistic action of hemagglutinin-neuraminidase (HN) protein and the homotypic fusion (F) protein on the viral surface. HN protein plays a variety of roles during the virus invasion process, such as promoting viral particles to bind to receptors, cleaving sialic acid, and activating the F protein. Crystal structure research shows that HN tetramer adopted a "heads-down" conformation, at least two heads dimmer on flank of the four-helix bundle stalk, which forms a symmetrical interaction interface. The stalk region determines interactions and activation of F protein in specificity, and the heads in down position statically shield these residues. In order to make further research on the function of these amino acids at the hPIV3 HN stalk/head interface, fifteen mutations (8 sites from stalk and 7 sites from head) were engineered into this interface by site-directed mutagenesis in this study. Alanine substitution in this region of hPIV3 HN had various effects on cell fusion promotion, receptor binding, and neuraminidase activity. Besides, L151A also affected surface protein expression efficiency. Moreover, I112A, D120A, and R122A mutations of the stalk region that were masked by global head in down position had influence on the interaction between F and HN proteins.
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27
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Ha MN, Delpeut S, Noyce RS, Sisson G, Black KM, Lin LT, Bilimoria D, Plemper RK, Privé GG, Richardson CD. Mutations in the Fusion Protein of Measles Virus That Confer Resistance to the Membrane Fusion Inhibitors Carbobenzoxy-d-Phe-l-Phe-Gly and 4-Nitro-2-Phenylacetyl Amino-Benzamide. J Virol 2017; 91:e01026-17. [PMID: 28904193 PMCID: PMC5686717 DOI: 10.1128/jvi.01026-17] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Accepted: 08/27/2017] [Indexed: 11/20/2022] Open
Abstract
The inhibitors carbobenzoxy (Z)-d-Phe-l-Phe-Gly (fusion inhibitor peptide [FIP]) and 4-nitro-2-phenylacetyl amino-benzamide (AS-48) have similar efficacies in blocking membrane fusion and syncytium formation mediated by measles virus (MeV). Other homologues, such as Z-d-Phe, are less effective but may act through the same mechanism. In an attempt to map the site of action of these inhibitors, we generated mutant viruses that were resistant to the inhibitory effects of Z-d-Phe-l-Phe-Gly. These 10 mutations were localized to the heptad repeat B (HRB) region of the fusion protein, and no changes were observed in the viral hemagglutinin, which is the receptor attachment protein. Mutations were validated in a luciferase-based membrane fusion assay, using transfected fusion and hemagglutinin expression plasmids or with syncytium-based assays in Vero, Vero-SLAM, and Vero-Nectin 4 cell lines. The changes I452T, D458N, D458G/V459A, N462K, N462H, G464E, and I483R conferred resistance to both FIP and AS-48 without compromising membrane fusion. The inhibitors did not block hemagglutinin protein-mediated binding to the target cell. Edmonston vaccine/laboratory and IC323 wild-type strains were equally affected by the inhibitors. Escape mutations were mapped upon a three-dimensional (3D) structure modeled from the published crystal structure of parainfluenzavirus 5 fusion protein. The most effective mutations were situated in a region located near the base of the globular head and its junction with the alpha-helical stalk of the prefusion protein. We hypothesize that the fusion inhibitors could interfere with the structural changes that occur between the prefusion and postfusion conformations of the fusion protein.IMPORTANCE Due to lapses in vaccination worldwide that have caused localized outbreaks, measles virus (MeV) has regained importance as a pathogen. Antiviral agents against measles virus are not commercially available but could be useful in conjunction with MeV eradication vaccine programs and as a safeguard in oncolytic viral therapy. Three decades ago, the small hydrophobic peptide Z-d-Phe-l-Phe-Gly (FIP) was shown to block MeV infections and syncytium formation in monkey kidney cell lines. The exact mechanism of its action has yet to be determined, but it does appear to have properties similar to those of another chemical inhibitor, AS-48, which appears to interfere with the conformational change in the viral F protein that is required to elicit membrane fusion. Escape mutations were used to map the site of action for FIP. Knowledge gained from these studies could help in the design of new inhibitors against morbilliviruses and provide additional knowledge concerning the mechanism of virus-mediated membrane fusion.
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Affiliation(s)
- Michael N Ha
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Department of Pediatrics, IWK Health Centre, Canadian Center for Vaccinology, Goldbloom Pavilion, Halifax, Nova Scotia, Canada
| | - Sébastien Delpeut
- Department of Pediatrics, IWK Health Centre, Canadian Center for Vaccinology, Goldbloom Pavilion, Halifax, Nova Scotia, Canada
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Ryan S Noyce
- Department of Pediatrics, IWK Health Centre, Canadian Center for Vaccinology, Goldbloom Pavilion, Halifax, Nova Scotia, Canada
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
- Department of Microbiology and Immunology, University of Alberta, Edmonton, Canada
| | - Gary Sisson
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Karen M Black
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Liang-Tzung Lin
- Department of Microbiology and Immunology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Darius Bilimoria
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Vertex Pharmaceuticals (Canada) Incorporated, Laval, Quebec, Canada
| | - Richard K Plemper
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia, USA
| | - Gilbert G Privé
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Christopher D Richardson
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Department of Pediatrics, IWK Health Centre, Canadian Center for Vaccinology, Goldbloom Pavilion, Halifax, Nova Scotia, Canada
- Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada
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Wong JJW, Young TA, Zhang J, Liu S, Leser GP, Komives EA, Lamb RA, Zhou ZH, Salafsky J, Jardetzky TS. Monomeric ephrinB2 binding induces allosteric changes in Nipah virus G that precede its full activation. Nat Commun 2017; 8:781. [PMID: 28974687 PMCID: PMC5626764 DOI: 10.1038/s41467-017-00863-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 08/01/2017] [Indexed: 11/09/2022] Open
Abstract
Nipah virus is an emergent paramyxovirus that causes deadly encephalitis and respiratory infections in humans. Two glycoproteins coordinate the infection of host cells, an attachment protein (G), which binds to cell surface receptors, and a fusion (F) protein, which carries out the process of virus-cell membrane fusion. The G protein binds to ephrin B2/3 receptors, inducing G conformational changes that trigger F protein refolding. Using an optical approach based on second harmonic generation, we show that monomeric and dimeric receptors activate distinct conformational changes in G. The monomeric receptor-induced changes are not detected by conformation-sensitive monoclonal antibodies or through electron microscopy analysis of G:ephrinB2 complexes. However, hydrogen/deuterium exchange experiments confirm the second harmonic generation observations and reveal allosteric changes in the G receptor binding and F-activating stalk domains, providing insights into the pathway of receptor-activated virus entry.Nipah virus causes encephalitis in humans. Here the authors use a multidisciplinary approach to study the binding of the viral attachment protein G to its host receptor ephrinB2 and show that monomeric and dimeric receptors activate distinct conformational changes in G and discuss implications for receptor-activated virus entry.
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Affiliation(s)
- Joyce J W Wong
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | | | - Jiayan Zhang
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA.,Department of Microbiology, Immunology & Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA.,California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Shiheng Liu
- Department of Microbiology, Immunology & Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA.,California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - George P Leser
- Howard Hughes Medical Institute, Northwestern University, Evanston, IL, 60208-3500, USA.,Department of Molecular Biosciences, Northwestern University, Evanston, IL, 60208-3500, USA
| | - Elizabeth A Komives
- Department of Chemistry and Biochemistry, University of California San Diego, San Diego, CA, 92093, USA
| | - Robert A Lamb
- Howard Hughes Medical Institute, Northwestern University, Evanston, IL, 60208-3500, USA.,Department of Molecular Biosciences, Northwestern University, Evanston, IL, 60208-3500, USA
| | - Z Hong Zhou
- Department of Microbiology, Immunology & Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA.,California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | | | - Theodore S Jardetzky
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, 94305, USA.
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29
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Cox RM, Plemper RK. Structure and organization of paramyxovirus particles. Curr Opin Virol 2017; 24:105-114. [PMID: 28601688 DOI: 10.1016/j.coviro.2017.05.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 05/08/2017] [Accepted: 05/24/2017] [Indexed: 11/25/2022]
Abstract
The paramyxovirus family comprises major human and animal pathogens such as measles virus (MeV), mumps virus (MuV), the parainfluenzaviruses, Newcastle disease virus (NDV), and the highly pathogenic zoonotic hendra (HeV) and nipah (NiV) viruses. Paramyxovirus particles are pleomorphic, with a lipid envelope, nonsegmented RNA genomes of negative polarity, and densely packed glycoproteins on the virion surface. A number of crystal structures of different paramyxovirus proteins and protein fragments were solved, but the available information concerning overall virion organization remains limited. However, recent studies have reported cryo-electron tomography-based reconstructions of Sendai virus (SeV), MeV, NDV, and human parainfluenza virus type 3 (HPIV3) particles and a surface assessment of NiV-derived virus-like particles (VLPs), which have yielded innovative hypotheses concerning paramyxovirus particle assembly, budding, and organization. Following a summary of the current insight into paramyxovirus virion morphology, this review will focus on discussing the implications of these particle reconstructions on the present models of paramyxovirus assembly and infection.
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Affiliation(s)
- Robert M Cox
- Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, United States
| | - Richard K Plemper
- Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, United States.
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30
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Tahara M, Takeda M. [Measles Virus]. Uirusu 2017; 67:3-16. [PMID: 29593149 DOI: 10.2222/jsv.67.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Measles virus (MeV) is exceptionally contagious and still a major cause of death in child.However, recently significant progress towards the elimination of measles has been made through increased vaccination coverage of measles-containing vaccines. The hemagglutinin (H) protein of MeV interacts with a cellular receptor, and this interaction is the first step of infection. MeV uses two different receptors, signaling lymphocyte activation molecule (SLAM) and nectin-4 expressed on immune cells and epithelial cells, respectively. The interactions of MeV with these receptors nicely explain the immune suppressive and high contagious properties of MeV. Binding of the H protein to a receptor triggers conformational changes in the fusion (F) protein, inducing fusion between viral and host plasma membranes for entry. The stalk region of the H protein plays a key role in the F protein-triggering. Recent studies of the H protein epitopes have revealed that the receptor binding site of the H protein constitutes a major neutralizing epitope. The interaction with two proteinaceous receptors probably imposes strong functional constraints on this epitope for amino acid changes. This would be a reason why measles vaccines, which are derived from MV strains isolated more than 60 years ago, are still highly effective against all MV strains currently circulating.
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Affiliation(s)
- Maino Tahara
- Department of Virology III, National Institute of Infectious Diseases
| | - Makoto Takeda
- Department of Virology III, National Institute of Infectious Diseases
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31
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Site-specific glycosylation of the Newcastle disease virus haemagglutinin-neuraminidase. Glycoconj J 2016; 34:181-197. [DOI: 10.1007/s10719-016-9750-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 11/10/2016] [Accepted: 11/14/2016] [Indexed: 12/14/2022]
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32
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Multiple Strategies Reveal a Bidentate Interaction between the Nipah Virus Attachment and Fusion Glycoproteins. J Virol 2016; 90:10762-10773. [PMID: 27654290 DOI: 10.1128/jvi.01469-16] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 09/14/2016] [Indexed: 11/20/2022] Open
Abstract
The paramyxoviral family contains many medically important viruses, including measles virus, mumps virus, parainfluenza viruses, respiratory syncytial virus, human metapneumovirus, and the deadly zoonotic henipaviruses Hendra and Nipah virus (NiV). To both enter host cells and spread from cell to cell within infected hosts, the vast majority of paramyxoviruses utilize two viral envelope glycoproteins: the attachment glycoprotein (G, H, or hemagglutinin-neuraminidase [HN]) and the fusion glycoprotein (F). Binding of G/H/HN to a host cell receptor triggers structural changes in G/H/HN that in turn trigger F to undergo a series of conformational changes that result in virus-cell (viral entry) or cell-cell (syncytium formation) membrane fusion. The actual regions of G/H/HN and F that interact during the membrane fusion process remain relatively unknown though it is generally thought that the paramyxoviral G/H/HN stalk region interacts with the F head region. Studies to determine such interactive regions have relied heavily on coimmunoprecipitation approaches, whose limitations include the use of detergents and the micelle-mediated association of proteins. Here, we developed a flow-cytometric strategy capable of detecting membrane protein-protein interactions by interchangeably using the full-length form of G and a soluble form of F, or vice versa. Using both coimmunoprecipitation and flow-cytometric strategies, we found a bidentate interaction between NiV G and F, where both the stalk and head regions of NiV G interact with F. This is a new structural-biological finding for the paramyxoviruses. Additionally, our studies disclosed regions of the NiV G and F glycoproteins dispensable for the G and F interactions. IMPORTANCE Nipah virus (NiV) is a zoonotic paramyxovirus that causes high mortality rates in humans, with no approved treatment or vaccine available for human use. Viral entry into host cells relies on two viral envelope glycoproteins: the attachment (G) and fusion (F) glycoproteins. Binding of G to the ephrinB2 or ephrinB3 cell receptors triggers conformational changes in G that in turn cause F to undergo conformational changes that result in virus-host cell membrane fusion and viral entry. It is currently unknown, however, which specific regions of G and F interact during membrane fusion. Past efforts to determine the interacting regions have relied mainly on coimmunoprecipitation, a technique with some pitfalls. We developed a flow-cytometric assay to study membrane protein-protein interactions, and using this assay we report a bidentate interaction whereby both the head and stalk regions of NiV G interact with NiV F, a new finding for the paramyxovirus family.
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Adu-Gyamfi E, Kim LS, Jardetzky TS, Lamb RA. Flexibility of the Head-Stalk Linker Domain of Paramyxovirus HN Glycoprotein Is Essential for Triggering Virus Fusion. J Virol 2016; 90:9172-81. [PMID: 27489276 PMCID: PMC5044854 DOI: 10.1128/jvi.01187-16] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Accepted: 07/25/2016] [Indexed: 12/17/2022] Open
Abstract
UNLABELLED The Paramyxoviridae comprise a large family of enveloped, negative-sense, single-stranded RNA viruses with significant economic and public health implications. For nearly all paramyxoviruses, infection is initiated by fusion of the viral and host cell plasma membranes in a pH-independent fashion. Fusion is orchestrated by the receptor binding protein hemagglutinin-neuraminidase (HN; also called H or G depending on the virus type) protein and a fusion (F) protein, the latter undergoing a major refolding process to merge the two membranes. Mechanistic details regarding the coupling of receptor binding to F activation are not fully understood. Here, we have identified the flexible loop region connecting the bulky enzymatically active head and the four-helix bundle stalk to be essential for fusion promotion. Proline substitution in this region of HN of parainfluenza virus 5 (PIV5) and Newcastle disease virus HN abolishes cell-cell fusion, whereas HN retains receptor binding and neuraminidase activity. By using reverse genetics, we engineered recombinant PIV5-EGFP viruses with mutations in the head-stalk linker region of HN. Mutations in this region abolished virus recovery and infectivity. In sum, our data suggest that the loop region acts as a "hinge" around which the bulky head of HN swings to-and-fro to facilitate timely HN-mediate F-triggering, a notion consistent with the stalk-mediated activation model of paramyxovirus fusion. IMPORTANCE Paramyxovirus fusion with the host cell plasma membrane is essential for virus infection. Membrane fusion is orchestrated via interaction of the receptor binding protein (HN, H, or G) with the viral fusion glycoprotein (F). Two distinct models have been suggested to describe the mechanism of fusion: these include "the clamp" and the "provocateur" model of activation. By using biochemical and reverse genetics tools, we have obtained strong evidence in favor of the HN stalk-mediated activation of paramyxovirus fusion. Specifically, our data strongly support the notion that the short linker between the head and stalk plays a role in "conformational switching" of the head group to facilitate F-HN interaction and triggering.
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Affiliation(s)
- Emmanuel Adu-Gyamfi
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois, USA
| | - Lori S Kim
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois, USA
| | - Theodore S Jardetzky
- Howard Hughes Medical Institute, Northwestern University, Evanston, Illinois, USA
| | - Robert A Lamb
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois, USA Department of Structural Biology, Stanford University, Stanford, California, USA
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Lin LT, Richardson CD. The Host Cell Receptors for Measles Virus and Their Interaction with the Viral Hemagglutinin (H) Protein. Viruses 2016; 8:v8090250. [PMID: 27657109 PMCID: PMC5035964 DOI: 10.3390/v8090250] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 08/29/2016] [Accepted: 09/02/2016] [Indexed: 12/14/2022] Open
Abstract
The hemagglutinin (H) protein of measles virus (MeV) interacts with a cellular receptor which constitutes the initial stage of infection. Binding of H to this host cell receptor subsequently triggers the F protein to activate fusion between virus and host plasma membranes. The search for MeV receptors began with vaccine/laboratory virus strains and evolved to more relevant receptors used by wild-type MeV. Vaccine or laboratory strains of measles virus have been adapted to grow in common cell lines such as Vero and HeLa cells, and were found to use membrane cofactor protein (CD46) as a receptor. CD46 is a regulator that normally prevents cells from complement-mediated self-destruction, and is found on the surface of all human cells, with the exception of erythrocytes. Mutations in the H protein, which occur during adaptation and allow the virus to use CD46 as a receptor, have been identified. Wild-type isolates of measles virus cannot use the CD46 receptor. However, both vaccine/laboratory and wild-type strains can use an immune cell receptor called signaling lymphocyte activation molecule family member 1 (SLAMF1; also called CD150) and a recently discovered epithelial receptor known as Nectin-4. SLAMF1 is found on activated B, T, dendritic, and monocyte cells, and is the initial target for infections by measles virus. Nectin-4 is an adherens junction protein found at the basal surfaces of many polarized epithelial cells, including those of the airways. It is also over-expressed on the apical and basal surfaces of many adenocarcinomas, and is a cancer marker for metastasis and tumor survival. Nectin-4 is a secondary exit receptor which allows measles virus to replicate and amplify in the airways, where the virus is expelled from the body in aerosol droplets. The amino acid residues of H protein that are involved in binding to each of the receptors have been identified through X-ray crystallography and site-specific mutagenesis. Recombinant measles “blind” to each of these receptors have been constructed, allowing the virus to selectively infect receptor specific cell lines. Finally, the observations that SLAMF1 is found on lymphomas and that Nectin-4 is expressed on the cell surfaces of many adenocarcinomas highlight the potential of measles virus for oncolytic therapy. Although CD46 is also upregulated on many tumors, it is less useful as a target for cancer therapy, since normal human cells express this protein on their surfaces.
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Affiliation(s)
- Liang-Tzung Lin
- Department of Microbiology and Immunology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 11031, Taiwan.
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 11031, Taiwan.
| | - Christopher D Richardson
- Department of Microbiology and Immunology, Dalhousie University, 5850 College St., Halifax, NS B3H 4R2, Canada.
- Department of Pediatrics and Canadian Center for Vaccinology, Izaak Walton Killam Health Centre, Halifax, NS B3K 6R8, Canada.
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Mutagenesis of Paramyxovirus Hemagglutinin-Neuraminidase Membrane-Proximal Stalk Region Influences Stability, Receptor Binding, and Neuraminidase Activity. J Virol 2016; 90:7778-88. [PMID: 27334593 DOI: 10.1128/jvi.00896-16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 06/13/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Paramyxoviridae consist of a large family of enveloped, negative-sense, nonsegmented single-stranded RNA viruses that account for a significant number of human and animal diseases. The fusion process for nearly all paramyxoviruses involves the mixing of the host cell plasma membrane and the virus envelope in a pH-independent fashion. Fusion is orchestrated via the concerted action of two surface glycoproteins: an attachment protein called hemagglutinin-neuraminidase (HN [also called H or G depending on virus type and substrate]), which acts as a receptor binding protein, and a fusion (F) protein, which undergoes a major irreversible refolding process to merge the two membranes. Recent biochemical evidence suggests that receptor binding by HN is dispensable for cell-cell fusion. However, factors that influence the stability and/or conformation of the HN 4-helix bundle (4HB) stalk have not been studied. Here, we used oxidative cross-linking as well as functional assays to investigate the role of the structurally unresolved membrane-proximal stalk region (MPSR) (residues 37 to 58) of HN in the context of headless and full-length HN membrane fusion promotion. Our data suggest that the receptor binding head serves to stabilize the stalk to regulate fusion. Moreover, we found that the MPSR of HN modulates receptor binding and neuraminidase activity without a corresponding regulation of F triggering. IMPORTANCE Paramyxoviruses require two viral membrane glycoproteins, the attachment protein variously called HN, H, or G and the fusion protein (F), to couple host receptor recognition to virus-cell fusion. The HN protein has a globular head that is attached to a membrane-anchored flexible stalk of ∼80 residues and has three activities: receptor binding, neuraminidase, and fusion activation. In this report, we have identified the functional significance of the membrane-proximal stalk region (MPSR) (HN, residues 37 to 56) of the paramyxovirus parainfluenza virus (PIV5), a region of the HN stalk that has not had its structure determined by X-ray crystallography. Our data suggest that the MPSR influences receptor binding and neuraminidase activity via an indirect mechanism. Moreover, the receptor binding head group stabilizes the 4HB stalk as part of the general mechanism to fine-tune F-activation.
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Abstract
The family Paramyxoviridae includes many viruses that significantly affect human and animal health. An essential step in the paramyxovirus life cycle is viral entry into host cells, mediated by virus-cell membrane fusion. Upon viral entry, infection results in expression of the paramyxoviral glycoproteins on the infected cell surface. This can lead to cell-cell fusion (syncytia formation), often linked to pathogenesis. Thus membrane fusion is essential for both viral entry and cell-cell fusion and an attractive target for therapeutic development. While there are important differences between viral-cell and cell-cell membrane fusion, many aspects are conserved. The paramyxoviruses generally utilize two envelope glycoproteins to orchestrate membrane fusion. Here, we discuss the roles of these glycoproteins in distinct steps of the membrane fusion process. These findings can offer insights into evolutionary relationships among Paramyxoviridae genera and offer future targets for prophylactic and therapeutic development.
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Measles Virus Fusion Protein: Structure, Function and Inhibition. Viruses 2016; 8:112. [PMID: 27110811 PMCID: PMC4848605 DOI: 10.3390/v8040112] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 03/26/2016] [Accepted: 04/14/2016] [Indexed: 01/02/2023] Open
Abstract
Measles virus (MeV), a highly contagious member of the Paramyxoviridae family, causes measles in humans. The Paramyxoviridae family of negative single-stranded enveloped viruses includes several important human and animal pathogens, with MeV causing approximately 120,000 deaths annually. MeV and canine distemper virus (CDV)-mediated diseases can be prevented by vaccination. However, sub-optimal vaccine delivery continues to foster MeV outbreaks. Post-exposure prophylaxis with antivirals has been proposed as a novel strategy to complement vaccination programs by filling herd immunity gaps. Recent research has shown that membrane fusion induced by the morbillivirus glycoproteins is the first critical step for viral entry and infection, and determines cell pathology and disease outcome. Our molecular understanding of morbillivirus-associated membrane fusion has greatly progressed towards the feasibility to control this process by treating the fusion glycoprotein with inhibitory molecules. Current approaches to develop anti-membrane fusion drugs and our knowledge on drug resistance mechanisms strongly suggest that combined therapies will be a prerequisite. Thus, discovery of additional anti-fusion and/or anti-attachment protein small-molecule compounds may eventually translate into realistic therapeutic options.
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38
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Stone JA, Nicola AV, Baum LG, Aguilar HC. Multiple Novel Functions of Henipavirus O-glycans: The First O-glycan Functions Identified in the Paramyxovirus Family. PLoS Pathog 2016; 12:e1005445. [PMID: 26867212 PMCID: PMC4750917 DOI: 10.1371/journal.ppat.1005445] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 01/19/2016] [Indexed: 01/13/2023] Open
Abstract
O-linked glycosylation is a ubiquitous protein modification in organisms belonging to several kingdoms. Both microbial and host protein glycans are used by many pathogens for host invasion and immune evasion, yet little is known about the roles of O-glycans in viral pathogenesis. Reportedly, there is no single function attributed to O-glycans for the significant paramyxovirus family. The paramyxovirus family includes many important pathogens, such as measles, mumps, parainfluenza, metapneumo- and the deadly Henipaviruses Nipah (NiV) and Hendra (HeV) viruses. Paramyxoviral cell entry requires the coordinated actions of two viral membrane glycoproteins: the attachment (HN/H/G) and fusion (F) glycoproteins. O-glycan sites in HeV G were recently identified, facilitating use of the attachment protein of this deadly paramyxovirus as a model to study O-glycan functions. We mutated the identified HeV G O-glycosylation sites and found mutants with altered cell-cell fusion, G conformation, G/F association, viral entry in a pseudotyped viral system, and, quite unexpectedly, pseudotyped viral F protein incorporation and processing phenotypes. These are all important functions of viral glycoproteins. These phenotypes were broadly conserved for equivalent NiV mutants. Thus our results identify multiple novel and pathologically important functions of paramyxoviral O-glycans, paving the way to study O-glycan functions in other paramyxoviruses and enveloped viruses. Glycosylation is a protein modification process that occurs inside cells, in which specific types of sugars (glycans) are added to certain amino acids in some proteins. Glycosylation happens for many organisms, from microbes to mammals, including many pathogens. Altered glycosylation is increasingly being associated with auto-immune diseases and cancer, highlighting the need to better understand glycosylation. There are two types of sugars added during the glycosylation process: N-glycans and O-glycans. While the roles of N-glycans have been extensively reported for many organisms, the roles of O-glycans remain largely unknown, particularly for viruses. The paramyxoviruses are a medically important family of viruses that include the highly lethal Hendra (HeV) and Nipah (NiV) viruses. Viral entry into host cells and spread from cell to cell relies on two viral proteins: G and F. Here we mutated known O-glycan locations in the HeV and NiV G proteins. Loss of O-glycans affected several viral processes crucial to viral entry and spread from cell to cell. Our results are the first reported functions for paramyxoviral O-glycans, contributing to the field of viral entry and spread, and helping pave the way for future functional studies in other pathogens.
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Affiliation(s)
- Jacquelyn A. Stone
- Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, United States of America
| | - Anthony V. Nicola
- Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, United States of America
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, United States of America
| | - Linda G. Baum
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, California, United States of America
| | - Hector C. Aguilar
- Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, United States of America
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, United States of America
- * E-mail:
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Sawatsky B, Bente DA, Czub M, von Messling V. Morbillivirus and henipavirus attachment protein cytoplasmic domains differently affect protein expression, fusion support and particle assembly. J Gen Virol 2016; 97:1066-1076. [PMID: 26813519 PMCID: PMC7482510 DOI: 10.1099/jgv.0.000415] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The amino-terminal cytoplasmic domains of paramyxovirus attachment glycoproteins
include trafficking signals that influence protein processing and cell surface
expression. To characterize the role of the cytoplasmic domain in protein expression,
fusion support and particle assembly in more detail, we constructed chimeric Nipah
virus (NiV) glycoprotein (G) and canine distemper virus (CDV) haemagglutinin (H)
proteins carrying the respective heterologous cytoplasmic domain, as well as a series
of mutants with progressive deletions in this domain. CDV H retained fusion function
and was normally expressed on the cell surface with a heterologous cytoplasmic
domain, while the expression and fusion support of NiV G was dramatically decreased
when its cytoplasmic domain was replaced with that of CDV H. The cell surface
expression and fusion support functions of CDV H were relatively insensitive to
cytoplasmic domain deletions, while short deletions in the corresponding region of
NiV G dramatically decreased both. In addition, the first 10 residues of the CDV H
cytoplasmic domain strongly influence its incorporation into virus-like particles
formed by the CDV matrix (M) protein, while the co-expression of NiV M with NiV G had
no significant effect on incorporation of G into particles. The cytoplasmic domains
of both the CDV H and NiV G proteins thus contribute differently to the virus life
cycle.
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Affiliation(s)
- Bevan Sawatsky
- Galveston National Laboratory, University of Texas Medical Branch, Galveston, Texas, USA.,INRS-Institut Armand-Frappier, University of Quebec, Laval, Quebec, Canada.,Veterinary Medicine Division, Paul-Ehrlich-Institute, Langen, Germany.,Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Dennis A Bente
- Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, Texas, USA.,Galveston National Laboratory, University of Texas Medical Branch, Galveston, Texas, USA
| | - Markus Czub
- Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Veronika von Messling
- INRS-Institut Armand-Frappier, University of Quebec, Laval, Quebec, Canada.,Veterinary Medicine Division, Paul-Ehrlich-Institute, Langen, Germany
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40
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Canine Distemper Virus Fusion Activation: Critical Role of Residue E123 of CD150/SLAM. J Virol 2015; 90:1622-37. [PMID: 26608324 DOI: 10.1128/jvi.02405-15] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 11/18/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Measles virus (MeV) and canine distemper virus (CDV) possess tetrameric attachment proteins (H) and trimeric fusion proteins, which cooperate with either SLAM or nectin 4 receptors to trigger membrane fusion for cell entry. While the MeV H-SLAM cocrystal structure revealed the binding interface, two distinct oligomeric H assemblies were also determined. In one of the conformations, two SLAM units were sandwiched between two discrete H head domains, thus spotlighting two binding interfaces ("front" and "back"). Here, we investigated the functional relevance of both interfaces in activating the CDV membrane fusion machinery. While alanine-scanning mutagenesis identified five critical regulatory residues in the front H-binding site of SLAM, the replacement of a conserved glutamate residue (E at position 123, replaced with A [E123A]) led to the most pronounced impact on fusion promotion. Intriguingly, while determination of the interaction of H with the receptor using soluble constructs revealed reduced binding for the identified SLAM mutants, no effect was recorded when physical interaction was investigated with the full-length counterparts of both molecules. Conversely, although mutagenesis of three strategically selected residues within the back H-binding site of SLAM did not substantially affect fusion triggering, nevertheless, the mutants weakened the H-SLAM interaction recorded with the membrane-anchored protein constructs. Collectively, our findings support a mode of binding between the attachment protein and the V domain of SLAM that is common to all morbilliviruses and suggest a major role of the SLAM residue E123, located at the front H-binding site, in triggering the fusion machinery. However, our data additionally support the hypothesis that other microdomain(s) of both glycoproteins (including the back H-binding site) might be required to achieve fully productive H-SLAM interactions. IMPORTANCE A complete understanding of the measles virus and canine distemper virus (CDV) cell entry molecular framework is still lacking, thus impeding the rational design of antivirals. Both viruses share many biological features that partially rely on the use of analogous Ig-like host cell receptors, namely, SLAM and nectin 4, for entering immune and epithelial cells, respectively. Here, we provide evidence that the mode of binding between the membrane-distal V domain of SLAM and the attachment protein (H) of morbilliviruses is very likely conserved. Moreover, although structural information revealed two discrete conformational states of H, one of the structures displayed two H-SLAM binding interfaces ("front" and "back"). Our data not only spotlight the front H-binding site of SLAM as the main determinant of membrane fusion promotion but suggest that the triggering efficiency of the viral entry machinery may rely on a local conformational change within the front H-SLAM interactive site rather than the binding affinity.
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The Fusion Protein Specificity of the Parainfluenza Virus Hemagglutinin-Neuraminidase Protein Is Not Solely Defined by the Primary Structure of Its Stalk Domain. J Virol 2015; 89:12374-87. [PMID: 26423949 DOI: 10.1128/jvi.01448-15] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Accepted: 09/24/2015] [Indexed: 02/06/2023] Open
Abstract
UNLABELLED Virus-specific interaction between the attachment protein (HN) and the fusion protein (F) is prerequisite for the induction of membrane fusion by parainfluenza viruses. This HN-F interaction presumably is mediated by particular amino acids in the HN stalk domain and those in the F head domain. We found in the present study, however, that a simian virus 41 (SV41) F-specific chimeric HPIV2 HN protein, SCA, whose cytoplasmic, transmembrane, and stalk domains were derived from the SV41 HN protein, could not induce cell-cell fusion of BHK-21 cells when coexpressed with an SV41 HN-specific chimeric PIV5 F protein, no. 36. Similarly, a headless form of the SV41 HN protein failed to induce fusion with chimera no. 36, whereas it was able to induce fusion with the SV41 F protein. Interestingly, replacement of 13 amino acids of the SCA head domain, which are located at or around the dimer interface of the head domain, with SV41 HN counterparts resulted in a chimeric HN protein, SCA-RII, which induced fusion with chimera no. 36 but not with the SV41 F protein. More interestingly, retroreplacement of 11 out of the 13 amino acids of SCA-RII with the SCA counterparts resulted in another chimeric HN protein, IM18, which induced fusion either with chimera no. 36 or with the SV41 F protein, similar to the SV41 HN protein. Thus, we conclude that the F protein specificity of the HN protein that is observed in the fusion event is not solely defined by the primary structure of the HN stalk domain. IMPORTANCE It is appreciated that the HN head domain initially conceals the HN stalk domain but exposes it after the head domain has bound to the receptors, which allows particular amino acids in the stalk domain to interact with the F protein and trigger it to induce fusion. However, other regulatory roles of the HN head domain in the fusion event have been ill defined. We have shown in the current study that removal of the head domain or amino acid substitutions in a particular region of the head domain drastically change the F protein specificity of the HN protein, suggesting that the ability of a given HN protein to interact with an F protein is defined not only by the primary structure of the HN stalk domain but also by its conformation. This notion seems to account for the unidirectional substitutability among rubulavirus HN proteins in triggering noncognate F proteins.
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Chung HK, Jacobs CL, Huo Y, Yang J, Krumm SA, Plemper RK, Tsien RY, Lin MZ. Tunable and reversible drug control of protein production via a self-excising degron. Nat Chem Biol 2015. [PMID: 26214256 PMCID: PMC4543534 DOI: 10.1038/nchembio.1869] [Citation(s) in RCA: 155] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
An effective method for direct chemical control over the production of specific proteins would be widely useful. We describe Small Molecule-Assisted Shutoff (SMASh), a technique in which proteins are fused to a degron that removes itself in the absence of drug, leaving untagged protein. Clinically tested HCV protease inhibitors can then block degron removal, inducing rapid degradation of subsequently synthesized protein copies. SMASh allows reversible and dose-dependent shutoff of various proteins in multiple mammalian cell types and in yeast. We also used SMASh to confer drug responsiveness onto a RNA virus for which no licensed inhibitors exist. As SMASh does not require permanent fusion of a large domain, it should be useful when control over protein production with minimal structural modification is desired. Furthermore, as SMASh only involves a single genetic modification and does not rely on modulating protein-protein interactions, it should be easy to generalize to multiple biological contexts.
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Affiliation(s)
- Hokyung K Chung
- Department of Biology, Stanford University, Stanford, California, USA
| | - Conor L Jacobs
- Department of Biology, Stanford University, Stanford, California, USA
| | - Yunwen Huo
- Department of Pediatrics, Stanford University, Stanford, California, USA
| | - Jin Yang
- Department of Pharmacology, University of California, San Diego, La Jolla, California, USA
| | - Stefanie A Krumm
- Department of Pediatrics, Emory University, Atlanta, Georgia, USA
| | - Richard K Plemper
- 1] Department of Pediatrics, Emory University, Atlanta, Georgia, USA. [2] Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia, USA
| | - Roger Y Tsien
- 1] Department of Pharmacology, University of California, San Diego, La Jolla, California, USA. [2] Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, USA. [3] Howard Hughes Medical Institute, University of California, San Diego, La Jolla, California, USA
| | - Michael Z Lin
- 1] Department of Pediatrics, Stanford University, Stanford, California, USA. [2] Department of Bioengineering, Stanford University, Stanford, California, USA
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Ader-Ebert N, Khosravi M, Herren M, Avila M, Alves L, Bringolf F, Örvell C, Langedijk JP, Zurbriggen A, Plemper RK, Plattet P. Sequential conformational changes in the morbillivirus attachment protein initiate the membrane fusion process. PLoS Pathog 2015; 11:e1004880. [PMID: 25946112 PMCID: PMC4422687 DOI: 10.1371/journal.ppat.1004880] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 04/14/2015] [Indexed: 11/18/2022] Open
Abstract
Despite large vaccination campaigns, measles virus (MeV) and canine distemper virus (CDV) cause major morbidity and mortality in humans and animals, respectively. The MeV and CDV cell entry system relies on two interacting envelope glycoproteins: the attachment protein (H), consisting of stalk and head domains, co-operates with the fusion protein (F) to mediate membrane fusion. However, how receptor-binding by the H-protein leads to F-triggering is not fully understood. Here, we report that an anti-CDV-H monoclonal antibody (mAb-1347), which targets the linear H-stalk segment 126-133, potently inhibits membrane fusion without interfering with H receptor-binding or F-interaction. Rather, mAb-1347 blocked the F-triggering function of H-proteins regardless of the presence or absence of the head domains. Remarkably, mAb-1347 binding to headless CDV H, as well as standard and engineered bioactive stalk-elongated CDV H-constructs treated with cells expressing the SLAM receptor, was enhanced. Despite proper cell surface expression, fusion promotion by most H-stalk mutants harboring alanine substitutions in the 126-138 "spacer" section was substantially impaired, consistent with deficient receptor-induced mAb-1347 binding enhancement. However, a previously reported F-triggering defective H-I98A variant still exhibited the receptor-induced "head-stalk" rearrangement. Collectively, our data spotlight a distinct mechanism for morbillivirus membrane fusion activation: prior to receptor contact, at least one of the morbillivirus H-head domains interacts with the membrane-distal "spacer" domain in the H-stalk, leaving the F-binding site located further membrane-proximal in the stalk fully accessible. This "head-to-spacer" interaction conformationally stabilizes H in an auto-repressed state, which enables intracellular H-stalk/F engagement while preventing the inherent H-stalk's bioactivity that may prematurely activate F. Receptor-contact disrupts the "head-to-spacer" interaction, which subsequently "unlocks" the stalk, allowing it to rearrange and trigger F. Overall, our study reveals essential mechanistic requirements governing the activation of the morbillivirus membrane fusion cascade and spotlights the H-stalk "spacer" microdomain as a possible drug target for antiviral therapy.
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Affiliation(s)
- Nadine Ader-Ebert
- Division of Neurological Sciences, Department of Clinical Research and Veterinary Public Health (DCR-VPH), Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Mojtaba Khosravi
- Division of Neurological Sciences, Department of Clinical Research and Veterinary Public Health (DCR-VPH), Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Michael Herren
- Division of Neurological Sciences, Department of Clinical Research and Veterinary Public Health (DCR-VPH), Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Mislay Avila
- Division of Neurological Sciences, Department of Clinical Research and Veterinary Public Health (DCR-VPH), Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Lisa Alves
- Division of Neurological Sciences, Department of Clinical Research and Veterinary Public Health (DCR-VPH), Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Fanny Bringolf
- Division of Neurological Sciences, Department of Clinical Research and Veterinary Public Health (DCR-VPH), Vetsuisse Faculty, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Claes Örvell
- Division of Laboratory Medicine, Karolinska University Hospital Huddinge, Stockholm, Sweden
| | | | - Andreas Zurbriggen
- Division of Neurological Sciences, Department of Clinical Research and Veterinary Public Health (DCR-VPH), Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Richard K. Plemper
- Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia, United States of America
| | - Philippe Plattet
- Division of Neurological Sciences, Department of Clinical Research and Veterinary Public Health (DCR-VPH), Vetsuisse Faculty, University of Bern, Bern, Switzerland
- * E-mail:
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44
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Harrison SC. Viral membrane fusion. Virology 2015; 479-480:498-507. [PMID: 25866377 DOI: 10.1016/j.virol.2015.03.043] [Citation(s) in RCA: 510] [Impact Index Per Article: 56.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 02/23/2015] [Accepted: 03/10/2015] [Indexed: 11/27/2022]
Abstract
Membrane fusion is an essential step when enveloped viruses enter cells. Lipid bilayer fusion requires catalysis to overcome a high kinetic barrier; viral fusion proteins are the agents that fulfill this catalytic function. Despite a variety of molecular architectures, these proteins facilitate fusion by essentially the same generic mechanism. Stimulated by a signal associated with arrival at the cell to be infected (e.g., receptor or co-receptor binding, proton binding in an endosome), they undergo a series of conformational changes. A hydrophobic segment (a "fusion loop" or "fusion peptide") engages the target-cell membrane and collapse of the bridging intermediate thus formed draws the two membranes (virus and cell) together. We know of three structural classes for viral fusion proteins. Structures for both pre- and postfusion conformations of illustrate the beginning and end points of a process that can be probed by single-virion measurements of fusion kinetics.
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Affiliation(s)
- Stephen C Harrison
- Boston Children׳s Hospital, Harvard Medical School, and Howard Hughes Medical Institute, 3 Blackfan Circle, Boston, MA 02115, United States.
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45
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Bose S, Jardetzky TS, Lamb RA. Timing is everything: Fine-tuned molecular machines orchestrate paramyxovirus entry. Virology 2015; 479-480:518-31. [PMID: 25771804 PMCID: PMC4424121 DOI: 10.1016/j.virol.2015.02.037] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 01/21/2015] [Accepted: 02/18/2015] [Indexed: 11/30/2022]
Abstract
The Paramyxoviridae include some of the great and ubiquitous disease-causing viruses of humans and animals. In most paramyxoviruses, two viral membrane glycoproteins, fusion protein (F) and receptor binding protein (HN, H or G) mediate a concerted process of recognition of host cell surface molecules followed by fusion of viral and cellular membranes, resulting in viral nucleocapsid entry into the cytoplasm. The interactions between the F and HN, H or G viral glycoproteins and host molecules are critical in determining host range, virulence and spread of these viruses. Recently, atomic structures, together with biochemical and biophysical studies, have provided major insights into how these two viral glycoproteins successfully interact with host receptors on cellular membranes and initiate the membrane fusion process to gain entry into cells. These studies highlight the conserved core mechanisms of paramyxovirus entry that provide the fundamental basis for rational anti-viral drug design and vaccine development. New structural and functional insights into paramyxovirus entry mechanisms. Current data on paramyxovirus glycoproteins suggest a core conserved entry mechanism. Diverse mechanisms preventing premature fusion activation exist in these viruses. Precise spacio-temporal interplay between paramyxovirus glycoproteins initiate entry.
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Affiliation(s)
- Sayantan Bose
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208-3500, United States.
| | - Theodore S Jardetzky
- Department of Structural Biology and Program in Immunology, Stanford University School of Medicine, Stanford, CA 94305, United States
| | - Robert A Lamb
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208-3500, United States; Howard Hughes Medical Institute, Northwestern University, Evanston, IL 60208-3500, United States.
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Electron tomography imaging of surface glycoproteins on human parainfluenza virus 3: association of receptor binding and fusion proteins before receptor engagement. mBio 2015; 6:e02393-14. [PMID: 25691596 PMCID: PMC4337575 DOI: 10.1128/mbio.02393-14] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In order to deliver their genetic material to host cells during infection, enveloped viruses use specialized proteins on their surfaces that bind cellular receptors and induce fusion of the viral and host membranes. In paramyxoviruses, a diverse family of single-stranded RNA (ssRNA) viruses, including several important respiratory pathogens, such as parainfluenza viruses, the attachment and fusion machinery is composed of two separate proteins: a receptor binding protein (hemagglutinin-neuraminidase [HN]) and a fusion (F) protein that interact to effect membrane fusion. Here we used negative-stain and cryo-electron tomography to image the 3-dimensional ultrastructure of human parainfluenza virus 3 (HPIV3) virions in the absence of receptor engagement. We observed that HN exists in at least two organizations. The first were arrays of tetrameric HN that lacked closely associated F proteins: in these purely HN arrays, HN adopted a “heads-down” configuration. In addition, we observed regions of complex surface density that contained HN in an apparently extended “heads-up” form, colocalized with prefusion F trimers. This colocalization with prefusion F prior to receptor engagement supports a model for fusion in which HN in its heads-up state and F may interact prior to receptor engagement without activating F, and that interaction with HN in this configuration is not sufficient to activate F. Only upon receptor engagement by HN’s globular head does HN transmit its activating signal to F. Human parainfluenza virus 3 (HPIV3) is an enveloped, ssRNA virus that can cause serious respiratory illness, especially in children. HPIV3, like most other paramyxoviruses, uses two specialized proteins to mediate cell entry: the fusion protein (F) and the receptor binding protein, hemagglutinin-neuraminidase (HN). F becomes activated to mediate fusion during entry when it is triggered by a signal from HN. Here we used electron tomography to reconstruct the 3-dimensional ultrastructure of HPIV3. From these structures, we could discern the distribution and, in some cases, conformation of HN and F proteins, which provided an understanding of their interrelationship on virions. HN is found in arrays alone in one conformation and interspersed with prefusion F trimers in another. The data support a model of paramyxovirus membrane fusion in which HN associates with F before receptor engagement, and receptor engagement by the globular head of HN switches the HN-F interaction into one of fusion activation.
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Palgen JL, Jurgens EM, Moscona A, Porotto M, Palermo LM. Unity in diversity: shared mechanism of entry among paramyxoviruses. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 129:1-32. [PMID: 25595799 DOI: 10.1016/bs.pmbts.2014.10.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The Paramyxoviridae family includes many viruses that are pathogenic in humans, including parainfluenza viruses, measles virus, respiratory syncytial virus, and the emerging zoonotic Henipaviruses. No effective treatments are currently available for these viruses, and there is a need for efficient antiviral therapies. Paramyxoviruses enter the target cell by binding to a cell surface receptor and then fusing the viral envelope with the target cell membrane, allowing the release of the viral genome into the cytoplasm. Blockage of these crucial steps prevents infection and disease. Binding and fusion are driven by two virus-encoded glycoproteins, the receptor-binding protein and the fusion protein, that together form the viral "fusion machinery." The development of efficient antiviral drugs requires a deeper understanding of the mechanism of action of the Paramyxoviridae fusion machinery, which is still controversial. Here, we review recent structural and functional data on these proteins and the current understanding of the mechanism of the paramyxovirus cell entry process.
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Affiliation(s)
- Jean-Louis Palgen
- Department of Pediatrics, Weill Cornell Medical College, Cornell University, New York, USA; Department of Biology, Ecole Normale Supérieure, Lyon, France
| | - Eric M Jurgens
- Department of Pediatrics, Weill Cornell Medical College, Cornell University, New York, USA
| | - Anne Moscona
- Department of Pediatrics, Weill Cornell Medical College, Cornell University, New York, USA; Department of Microbiology and Immunology, Weill Cornell Medical College, Cornell University, New York, USA
| | - Matteo Porotto
- Department of Pediatrics, Weill Cornell Medical College, Cornell University, New York, USA.
| | - Laura M Palermo
- Department of Pediatrics, Weill Cornell Medical College, Cornell University, New York, USA; Department of Microbiology and Immunology, Weill Cornell Medical College, Cornell University, New York, USA
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Nipah virus attachment glycoprotein stalk C-terminal region links receptor binding to fusion triggering. J Virol 2014; 89:1838-50. [PMID: 25428863 DOI: 10.1128/jvi.02277-14] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Membrane fusion is essential for paramyxovirus entry into target cells and for the cell-cell fusion (syncytia) that results from many paramyxoviral infections. The concerted efforts of two membrane-integral viral proteins, the attachment (HN, H, or G) and fusion (F) glycoproteins, mediate membrane fusion. The emergent Nipah virus (NiV) is a highly pathogenic and deadly zoonotic paramyxovirus. We recently reported that upon cell receptor ephrinB2 or ephrinB3 binding, at least two conformational changes occur in the NiV-G head, followed by one in the NiV-G stalk, that subsequently result in F triggering and F execution of membrane fusion. However, the domains and residues in NiV-G that trigger F and the specific events that link receptor binding to F triggering are unknown. In the present study, we identified a NiV-G stalk C-terminal region (amino acids 159 to 163) that is important for multiple G functions, including G tetramerization, conformational integrity, G-F interactions, receptor-induced conformational changes in G, and F triggering. On the basis of these results, we propose that this NiV-G region serves as an important structural and functional linker between the NiV-G head and the rest of the stalk and is critical in propagating the F-triggering signal via specific conformational changes that open a concealed F-triggering domain(s) in the G stalk. These findings broaden our understanding of the mechanism(s) of receptor-induced paramyxovirus F triggering during viral entry and cell-cell fusion. IMPORTANCE The emergent deadly viruses Nipah virus (NiV) and Hendra virus belong to the Henipavirus genus in the Paramyxoviridae family. NiV infections target endothelial cells and neurons and, in humans, result in 40 to 75% mortality rates. The broad tropism of the henipaviruses and the unavailability of therapeutics threaten the health of humans and livestock. Viral entry into host cells is the first step of henipavirus infections, which ultimately cause syncytium formation. After attaching to the host cell receptor, henipaviruses enter the target cell via direct viral-cell membrane fusion mediated by two membrane glycoproteins: the attachment protein (G) and the fusion protein (F). In this study, we identified and characterized a region in the NiV-G stalk C-terminal domain that links receptor binding to fusion triggering via several important glycoprotein functions. These findings advance our understanding of the membrane fusion-triggering mechanism(s) of the henipaviruses and the paramyxoviruses.
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Measles virus glycoprotein complexes preassemble intracellularly and relax during transport to the cell surface in preparation for fusion. J Virol 2014; 89:1230-41. [PMID: 25392208 DOI: 10.1128/jvi.02754-14] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
UNLABELLED Measles virus (MeV), a morbillivirus within the paramyxovirus family, expresses two envelope glycoproteins. The attachment (H) protein mediates receptor binding, followed by triggering of the fusion (F) protein, which leads to merger of the viral envelope with target cell membranes. Receptor binding by members of related paramyxovirus genera rearranges the head domains of the attachment proteins, liberating an F-contact domain within the attachment protein helical stalk. However, morbillivirus glycoproteins first assemble intracellularly prior to receptor binding, raising the question of whether alternative protein-protein interfaces are involved or whether an entirely distinct triggering principle is employed. To test these possibilities, we generated headless H stem mutants of progressively shorter length. Conformationally restricted H stems remained capable of intracellular assembly with a standard F protein and a soluble MeV F mutant. Proteolytic maturation of F, but not the altered biochemical conditions at the cell surface, reduces the strength of glycoprotein interaction, readying the complexes for triggering. F mutants stabilized in the prefusion conformation interact with H intracellularly and at the cell surface, while destabilized F mutants interact only intracellularly, prior to F maturation. These results showcase an MeV entry machinery that functionally varies conserved motifs of the proposed paramyxovirus infection pathway. Intracellular and plasma membrane-resident MeV glycoprotein complexes employ the same protein-protein interface. F maturation prepares for complex separation after triggering, and the H head domains in prereceptor-bound conformation prevent premature stalk rearrangements and F activation. Intracellular preassembly affects MeV fusion profiles and may contribute to the high cell-to-cell fusion activity characteristic of the morbillivirus genus. IMPORTANCE Paramyxoviruses of the morbillivirus genus, such as measles, are highly contagious, major human and animal pathogens. MeV envelope glycoproteins preassemble intracellularly into tightly associated hetero-oligomers. To address whether preassembly reflects a unique measles virus entry strategy, we characterized the protein-protein interface of intracellular and surface-exposed fusion complexes and investigated the effect of the attachment protein head domains, glycoprotein maturation, and altered biochemical conditions at the cell surface on measles virus fusion complexes. Our results demonstrate that measles virus functionally varies conserved elements of the paramyxovirus entry pathway, providing a possible explanation for the high cell-to-cell fusion activity of morbilliviruses. Insight gained from these data affects the design of effective broad-spectrum paramyxovirus entry inhibitors.
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Canine distemper virus envelope protein interactions modulated by hydrophobic residues in the fusion protein globular head. J Virol 2014; 89:1445-51. [PMID: 25355896 DOI: 10.1128/jvi.01828-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Membrane fusion for morbillivirus cell entry relies on critical interactions between the viral fusion (F) and attachment (H) envelope glycoproteins. Through extensive mutagenesis of an F cavity recently proposed to contribute to F's interaction with the H protein, we identified two neighboring hydrophobic residues responsible for severe F-to-H binding and fusion-triggering deficiencies when they were mutated in combination. Since both residues reside on one side of the F cavity, the data suggest that H binds the F globular head domain sideways.
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