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Zhao Z, Liu X, Zong Y, Shi X, Sun Y. Cellular Processes Induced by HSV-1 Infections in Vestibular Neuritis. Viruses 2023; 16:12. [PMID: 38275947 PMCID: PMC10819745 DOI: 10.3390/v16010012] [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: 11/29/2023] [Revised: 12/18/2023] [Accepted: 12/19/2023] [Indexed: 01/27/2024] Open
Abstract
Herpesvirus is a prevalent pathogen that primarily infects human epithelial cells and has the ability to reside in neurons. In the field of otolaryngology, herpesvirus infection primarily leads to hearing loss and vestibular neuritis and is considered the primary hypothesis regarding the pathogenesis of vestibular neuritis. In this review, we provide a summary of the effects of the herpes virus on cellular processes in both host cells and immune cells, with a focus on HSV-1 as illustrative examples.
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Affiliation(s)
- Zhengdong Zhao
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China; (Z.Z.); (X.L.); (Y.Z.); (X.S.)
| | - Xiaozhou Liu
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China; (Z.Z.); (X.L.); (Y.Z.); (X.S.)
| | - Yanjun Zong
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China; (Z.Z.); (X.L.); (Y.Z.); (X.S.)
| | - Xinyu Shi
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China; (Z.Z.); (X.L.); (Y.Z.); (X.S.)
| | - Yu Sun
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China; (Z.Z.); (X.L.); (Y.Z.); (X.S.)
- Hubei Province Key Laboratory of Oral and Maxillofacial Development and Regeneration, Wuhan 430022, China
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2
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Zhou M, Vollmer B, Machala E, Chen M, Grünewald K, Arvin AM, Chiu W, Oliver SL. Targeted mutagenesis of the herpesvirus fusogen central helix captures transition states. Nat Commun 2023; 14:7958. [PMID: 38042814 PMCID: PMC10693595 DOI: 10.1038/s41467-023-43011-w] [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: 12/12/2022] [Accepted: 10/27/2023] [Indexed: 12/04/2023] Open
Abstract
Herpesviruses remain a burden for animal and human health, including the medically important varicella-zoster virus (VZV). Membrane fusion mediated by conserved core glycoproteins, the fusogen gB and the heterodimer gH-gL, enables herpesvirus cell entry. The ectodomain of gB orthologs has five domains and is proposed to transition from a prefusion to postfusion conformation but the functional relevance of the domains for this transition remains poorly defined. Here we describe structure-function studies of the VZV gB DIII central helix targeting residues 526EHV528. Critically, a H527P mutation captures gB in a prefusion conformation as determined by cryo-EM, a loss of membrane fusion in a virus free assay, and failure of recombinant VZV to spread in cell monolayers. Importantly, two predominant cryo-EM structures of gB[H527P] are identified by 3D classification and focused refinement, suggesting they represented gB conformations in transition. These studies reveal gB DIII as a critical element for herpesvirus gB fusion function.
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Affiliation(s)
- Momei Zhou
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA.
| | - Benjamin Vollmer
- Centre for Structural Systems Biology (CSSB), Hamburg, Germany
- Department of Chemistry, University of Hamburg, Hamburg, Germany
- Leibniz Institute of Virology (LIV), Hamburg, Germany
| | - Emily Machala
- Centre for Structural Systems Biology (CSSB), Hamburg, Germany
- Department of Chemistry, University of Hamburg, Hamburg, Germany
- Leibniz Institute of Virology (LIV), Hamburg, Germany
| | - Muyuan Chen
- Division of Cryo-EM and Bioimaging SSRL, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Kay Grünewald
- Centre for Structural Systems Biology (CSSB), Hamburg, Germany
- Department of Chemistry, University of Hamburg, Hamburg, Germany
- Leibniz Institute of Virology (LIV), Hamburg, Germany
| | - Ann M Arvin
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA
- Department of Microbiology & Immunology, Stanford University School of Medicine, Stanford, CA, USA
- Vir Biotechnology Inc, San Francisco, CA, USA
| | - Wah Chiu
- Division of Cryo-EM and Bioimaging SSRL, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
- Department of Microbiology & Immunology, Stanford University School of Medicine, Stanford, CA, USA
- Bioengineering, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Stefan L Oliver
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA
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3
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Kuraoka M, Aschner CB, Windsor IW, Mahant AM, Garforth SJ, Kong SL, Achkar JM, Almo SC, Kelsoe G, Herold BC. A non-neutralizing glycoprotein B monoclonal antibody protects against herpes simplex virus disease in mice. J Clin Invest 2023; 133:161968. [PMID: 36454639 PMCID: PMC9888390 DOI: 10.1172/jci161968] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 11/29/2022] [Indexed: 12/03/2022] Open
Abstract
There is an unmet need for monoclonal antibodies (mAbs) for prevention or as adjunctive treatment of herpes simplex virus (HSV) disease. Most vaccine and mAb efforts focus on neutralizing antibodies, but for HSV this strategy has proven ineffective. Preclinical studies with a candidate HSV vaccine strain, ΔgD-2, demonstrated that non-neutralizing antibodies that activate Fcγ receptors (FcγRs) to mediate antibody-dependent cellular cytotoxicity (ADCC) provide active and passive protection against HSV-1 and HSV-2. We hypothesized that this vaccine provides a tool to identify and characterize protective mAbs. We isolated HSV-specific mAbs from germinal center and memory B cells and bone marrow plasmacytes of ΔgD-2-vaccinated mice and evaluated these mAbs for binding, neutralizing, and FcγR-activating activity and for protective efficacy in mice. The most potent protective mAb, BMPC-23, was not neutralizing but activated murine FcγRIV, a biomarker of ADCC. The cryo-electron microscopic structure of the Fab-glycoprotein B (gB) assembly identified domain IV of gB as the epitope. A single dose of BMPC-23 administered 24 hours before or after viral challenge provided significant protection when configured as mouse IgG2c and protected mice expressing human FcγRIII when engineered as a human IgG1. These results highlight the importance of FcR-activating antibodies in protecting against HSV.
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Affiliation(s)
- Masayuki Kuraoka
- Department of Immunology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Clare Burn Aschner
- Department of Microbiology-Immunology, Albert Einstein College of Medicine, New York, New York, USA
| | - Ian W. Windsor
- Department of Laboratory of Molecular Medicine, Boston Children’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Aakash Mahant Mahant
- Department of Microbiology-Immunology, Albert Einstein College of Medicine, New York, New York, USA
| | | | - Susan Luozheng Kong
- Department of Laboratory of Molecular Medicine, Boston Children’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Jacqueline M. Achkar
- Department of Microbiology-Immunology, Albert Einstein College of Medicine, New York, New York, USA.,Department of Medicine, Albert Einstein College of Medicine, New York, New York, USA
| | | | - Garnett Kelsoe
- Department of Immunology, Duke University School of Medicine, Durham, North Carolina, USA.,Department of Surgery and,Duke Human Vaccine Institute, Duke University School of Medicine, Durham, North Carolina, USA
| | - Betsy C. Herold
- Department of Microbiology-Immunology, Albert Einstein College of Medicine, New York, New York, USA.,Department of Pediatrics Albert Einstein College of Medicine, New York, New York, USA
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4
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A Variant Allele in Varicella-Zoster Virus Glycoprotein B Selected during Production of the Varicella Vaccine Contributes to Its Attenuation. mBio 2022; 13:e0186422. [PMID: 35916400 PMCID: PMC9426484 DOI: 10.1128/mbio.01864-22] [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] [Indexed: 11/20/2022] Open
Abstract
Attenuation of the live varicella Oka vaccine (vOka) has been attributed to mutations in the genome acquired during cell culture passage of pOka (parent strain); however, the precise mechanisms of attenuation remain unknown. Comparative sequence analyses of several vaccine batches showed that over 100 single-nucleotide polymorphisms (SNPs) are conserved across all vaccine batches; 6 SNPs are nearly fixed, suggesting that these SNPs are responsible for attenuation. By contrast, prior analysis of chimeric vOka and pOka recombinants indicates that loci other than these six SNPs contribute to attenuation. Here, we report that pOka consists of a heterogenous population of virus sequences with two nearly equally represented bases, guanine (G) or adenine (A), at nucleotide 2096 of the ORF31 coding sequence, which encodes glycoprotein B (gB) resulting in arginine (R) or glutamine (Q), respectively, at amino acid 699 of gB. By contrast, 2096A/699Q is dominant in vOka (>99.98%). gB699Q/gH/gL showed significantly less fusion activity than gB699R/gH/gL in a cell-based fusion assay. Recombinant pOka with gB669Q (rpOka_gB699Q) had a similar growth phenotype as vOka during lytic infection in cell culture including human primary skin cells; however, rpOka_gB699R showed a growth phenotype similar to pOka. rpOka_gB699R entered neurons from axonal terminals more efficiently than rpOka_gB699Q in the presence of cell membrane-derived vesicles containing gB. Strikingly, when a mixture of pOka with both alleles equally represented was used to infect human neurons from axon terminals, pOka with gB699R was dominant for virus entry. These results identify a variant allele in gB that contributes to attenuation of vOka. IMPORTANCE The live-attenuated varicella vaccine has reduced the burden of chickenpox. Despite its development in 1974, the molecular basis for its attenuation is still not well understood. Since the live-attenuated varicella vaccine is the only licensed human herpesvirus vaccine that prevents primary disease, it is important to understand the mechanism for its attenuation. Here we identify that a variant allele in glycoprotein B (gB) selected during generation of the varicella vaccine contributes to its attenuation. This variant is impaired for fusion, virus entry into neurons from nerve terminals, and replication in human skin cells. Identification of a variant allele in gB, one of the essential herpesvirus core genes, that contributes to its attenuation may provide insights that assist in the development of other herpesvirus vaccines.
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Herpes Simplex Virus Glycoprotein B Mutations Define Structural Sites in Domain I, the Membrane Proximal Region, and the Cytodomain That Regulate Entry. J Virol 2021; 95:e0105021. [PMID: 34431697 DOI: 10.1128/jvi.01050-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The viral fusion protein glycoprotein B (gB) is conserved in all herpesviruses and is essential for virus entry. During entry, gB fuses viral and host cell membranes by refolding from a prefusion to a postfusion form. We previously introduced three structure-based mutations (gB-I671A/H681A/F683A) into the domain V arm of the gB ectodomain that resulted in reduced cell-cell fusion. A virus carrying these three mutations (called gB3A) displayed a small-plaque phenotype and remarkably delayed entry into cells. To identify mutations that could counteract this phenotype, we serially passaged the gB3A virus and selected for revertant viruses with increased plaque sizes. Genomic sequencing revealed that the revertant viruses had second-site mutations in gB, including E187A, M742T, and S383F/G645R/V705I/V880G. Using expression constructs encoding these mutations, only gB-V880G was shown to enhance cell-cell fusion. In contrast, all of the revertant viruses showed enhanced entry kinetics, underscoring the fact that cell-cell fusion and virus-cell fusion are different. The results indicate that mutations in three different regions of gB (domain I, the membrane proximal region, and the cytoplasmic tail domain) can counteract the slow-entry phenotype of gB3A virus. Mapping these compensatory mutations to prefusion and postfusion structural models suggests sites of intramolecular functional interactions with the gB domain V arm that may contribute to the gB fusion function. IMPORTANCE The nine human herpesviruses are ubiquitous and cause a range of diseases in humans. Glycoprotein B (gB) is an essential viral fusion protein that is conserved in all herpesviruses. During host cell entry, gB mediates virus-cell membrane fusion by undergoing a conformational change. Structural models for the prefusion and postfusion forms of gB exist, but the details of how the protein converts from one to the other are unclear. We previously introduced structure-based mutations into gB that inhibited virus entry and fusion. By passaging this entry-deficient virus over time, we selected second-site mutations that partially restore virus entry. The locations of these mutations suggest regulatory sites that contribute to fusion and gB refolding during entry. gB is a target of neutralizing antibodies, and defining how gB refolds during entry could provide a basis for the development of fusion inhibitors for future research or clinical use.
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6
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Stanfield BA, Kousoulas KG, Fernandez A, Gershburg E. Rational Design of Live-Attenuated Vaccines against Herpes Simplex Viruses. Viruses 2021; 13:1637. [PMID: 34452501 PMCID: PMC8402837 DOI: 10.3390/v13081637] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2021] [Revised: 08/09/2021] [Accepted: 08/13/2021] [Indexed: 12/19/2022] Open
Abstract
Diseases caused by human herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) affect millions of people worldwide and range from fatal encephalitis in neonates and herpes keratitis to orofacial and genital herpes, among other manifestations. The viruses can be shed efficiently by asymptomatic carriers, causing increased rates of infection. Viral transmission occurs through direct contact of mucosal surfaces followed by initial replication of the incoming virus in skin tissues. Subsequently, the viruses infect sensory neurons in the trigeminal and lumbosacral dorsal root ganglia, where they are primarily maintained in a transcriptionally repressed state termed "latency", which persists for the lifetime of the host. HSV DNA has also been detected in other sympathetic ganglia. Periodically, latent viruses can reactivate, causing ulcerative and often painful lesions primarily at the site of primary infection and proximal sites. In the United States, recurrent genital herpes alone accounts for more than a billion dollars in direct medical costs per year, while there are much higher costs associated with the socio-economic aspects of diseased patients, such as loss of productivity due to mental anguish. Currently, there are no effective FDA-approved vaccines for either prophylactic or therapeutic treatment of human herpes simplex infections, while several recent clinical trials have failed to achieve their endpoint goals. Historically, live-attenuated vaccines have successfully combated viral diseases, including polio, influenza, measles, and smallpox. Vaccines aimed to protect against the devastation of smallpox led to the most significant achievement in medical history: the eradication of human disease by vaccination. Recently, novel approaches toward developing safe and effective live-attenuated vaccines have demonstrated high efficacy in various preclinical models of herpetic disease. This next generation of live-attenuated vaccines has been tailored to minimize vaccine-associated side effects and promote effective and long-lasting immune responses. The ultimate goal is to prevent or reduce primary infections (prophylactic vaccines) or reduce the frequency and severity of disease associated with reactivation events (therapeutic vaccines). These vaccines' "rational" design is based on our current understanding of the immunopathogenesis of herpesviral infections that guide the development of vaccines that generate robust and protective immune responses. This review covers recent advances in the development of herpes simplex vaccines and the current state of ongoing clinical trials in pursuit of an effective vaccine against herpes simplex virus infections and associated diseases.
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Affiliation(s)
- Brent A. Stanfield
- Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA;
| | - Konstantin G. Kousoulas
- Division of Biotechnology and Molecular Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
- Rational Vaccines Inc., Woburn, MA 01801, USA;
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7
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Blanco-Rodriguez G, Di Nunzio F. The Viral Capsid: A Master Key to Access the Host Nucleus. Viruses 2021; 13:v13061178. [PMID: 34203080 PMCID: PMC8234750 DOI: 10.3390/v13061178] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Revised: 06/02/2021] [Accepted: 06/16/2021] [Indexed: 12/15/2022] Open
Abstract
Viruses are pathogens that have evolved to hijack the cellular machinery to replicate themselves and spread to new cells. During the course of evolution, viruses developed different strategies to overcome the cellular defenses and create new progeny. Among them, some RNA and many DNA viruses require access to the nucleus to replicate their genome. In non-dividing cells, viruses can only access the nucleus through the nuclear pore complex (NPC). Therefore, viruses have developed strategies to usurp the nuclear transport machinery and gain access to the nucleus. The majority of these viruses use the capsid to manipulate the nuclear import machinery. However, the particular tactics employed by each virus to reach the host chromatin compartment are very different. Nevertheless, they all require some degree of capsid remodeling. Recent notions on the interplay between the viral capsid and cellular factors shine new light on the quest for the nuclear entry step and for the fate of these viruses. In this review, we describe the main components and function of nuclear transport machinery. Next, we discuss selected examples of RNA and DNA viruses (HBV, HSV, adenovirus, and HIV) that remodel their capsid as part of their strategies to access the nucleus and to replicate.
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Affiliation(s)
- Guillermo Blanco-Rodriguez
- Advanced Molecular Virology and Retroviral Dynamics Group, Department of Virology, Pasteur Institute, 75015 Paris, France;
- Immunity and Cancer Department, Curie Institute, PSL Research University, INSERM U932, 75005 Paris, France
| | - Francesca Di Nunzio
- Advanced Molecular Virology and Retroviral Dynamics Group, Department of Virology, Pasteur Institute, 75015 Paris, France;
- Correspondence:
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8
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Madavaraju K, Koganti R, Volety I, Yadavalli T, Shukla D. Herpes Simplex Virus Cell Entry Mechanisms: An Update. Front Cell Infect Microbiol 2021; 10:617578. [PMID: 33537244 PMCID: PMC7848091 DOI: 10.3389/fcimb.2020.617578] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 12/02/2020] [Indexed: 12/17/2022] Open
Abstract
Herpes simplex virus (HSV) can infect a broad host range and cause mild to life threating infections in humans. The surface glycoproteins of HSV are evolutionarily conserved and show an extraordinary ability to bind more than one receptor on the host cell surface. Following attachment, the virus fuses its lipid envelope with the host cell membrane and releases its nucleocapsid along with tegument proteins into the cytosol. With the help of tegument proteins and host cell factors, the nucleocapsid is then docked into the nuclear pore. The viral double stranded DNA is then released into the host cell’s nucleus. Released viral DNA either replicates rapidly (more commonly in non-neuronal cells) or stays latent inside the nucleus (in sensory neurons). The fusion of the viral envelope with host cell membrane is a key step. Blocking this step can prevent entry of HSV into the host cell and the subsequent interactions that ultimately lead to production of viral progeny and cell death or latency. In this review, we have discussed viral entry mechanisms including the pH-independent as well as pH-dependent endocytic entry, cell to cell spread of HSV and use of viral glycoproteins as an antiviral target.
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Affiliation(s)
- Krishnaraju Madavaraju
- Shukla Lab, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States
| | - Raghuram Koganti
- Shukla Lab, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States
| | - Ipsita Volety
- Shukla Lab, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States
| | - Tejabhiram Yadavalli
- Shukla Lab, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States
| | - Deepak Shukla
- Shukla Lab, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States.,Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, United States
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Vallbracht M, Klupp BG, Mettenleiter TC. Influence of N-glycosylation on Expression and Function of Pseudorabies Virus Glycoprotein gB. Pathogens 2021; 10:61. [PMID: 33445487 PMCID: PMC7827564 DOI: 10.3390/pathogens10010061] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 01/07/2021] [Accepted: 01/07/2021] [Indexed: 01/13/2023] Open
Abstract
Envelope glycoprotein (g)B is conserved throughout the Herpesviridae and mediates fusion of the viral envelope with cellular membranes for infectious entry and spread. Like all viral envelope fusion proteins, gB is modified by asparagine (N)-linked glycosylation. Glycans can contribute to protein function, intracellular transport, trafficking, structure and immune evasion. gB of the alphaherpesvirus pseudorabies virus (PrV) contains six consensus sites for N-linked glycosylation, but their functional relevance is unknown. Here, we investigated the occupancy and functional relevance of N-glycosylation sites in PrV gB. To this end, all predicted N-glycosylation sites were inactivated either singly or in combination by the introduction of conservative mutations (N➔Q). The resulting proteins were tested for expression, fusion activity in cell-cell fusion assays and complementation of a gB-deficient PrV mutant. Our results indicate that all six sites are indeed modified. However, while glycosylation at most sites was dispensable for gB expression and fusogenicity, inactivation of N154 and N700 affected gB processing by furin cleavage and surface localization. Although all single mutants were functional in cell-cell fusion and viral entry, simultaneous inactivation of all six N-glycosylation sites severely impaired fusion activity and viral entry, suggesting a critical role of N-glycans for maintaining gB structure and function.
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Affiliation(s)
| | | | - Thomas C. Mettenleiter
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany; (M.V.); (B.G.K.)
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10
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Oliver SL, Xing Y, Chen DH, Roh SH, Pintilie GD, Bushnell DA, Sommer MH, Yang E, Carfi A, Chiu W, Arvin AM. The N-terminus of varicella-zoster virus glycoprotein B has a functional role in fusion. PLoS Pathog 2021; 17:e1008961. [PMID: 33411789 PMCID: PMC7817050 DOI: 10.1371/journal.ppat.1008961] [Citation(s) in RCA: 7] [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: 09/09/2020] [Revised: 01/20/2021] [Accepted: 12/01/2020] [Indexed: 12/13/2022] Open
Abstract
Varicella-zoster virus (VZV) is a medically important alphaherpesvirus that induces fusion of the virion envelope and the cell membrane during entry, and between cells to form polykaryocytes within infected tissues during pathogenesis. All members of the Herpesviridae, including VZV, have a conserved core fusion complex composed of glycoproteins, gB, gH and gL. The ectodomain of the primary fusogen, gB, has five domains, DI-V, of which DI contains the fusion loops needed for fusion function. We recently demonstrated that DIV is critical for fusion initiation, which was revealed by a 2.8Å structure of a VZV neutralizing mAb, 93k, bound to gB and mutagenesis of the gB-93k interface. To further assess the mechanism of mAb 93k neutralization, the binding site of a non-neutralizing mAb to gB, SG2, was compared to mAb 93k using single particle cryogenic electron microscopy (cryo-EM). The gB-SG2 interface partially overlapped with that of gB-93k but, unlike mAb 93k, mAb SG2 did not interact with the gB N-terminus, suggesting a potential role for the gB N-terminus in membrane fusion. The gB ectodomain structure in the absence of antibody was defined at near atomic resolution by single particle cryo-EM (3.9Å) of native, full-length gB purified from infected cells and by X-ray crystallography (2.4Å) of the transiently expressed ectodomain. Both structures revealed that the VZV gB N-terminus (aa72-114) was flexible based on the absence of visible structures in the cryo-EM or X-ray crystallography data but the presence of gB N-terminal peptides were confirmed by mass spectrometry. Notably, N-terminal residues 109KSQD112 were predicted to form a small α-helix and alanine substitution of these residues abolished cell-cell fusion in a virus-free assay. Importantly, transferring the 109AAAA112 mutation into the VZV genome significantly impaired viral propagation. These data establish a functional role for the gB N-terminus in membrane fusion broadly relevant to the Herpesviridae.
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Affiliation(s)
- Stefan L. Oliver
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail:
| | - Yi Xing
- GSK Vaccines, Cambridge, Massachusetts, United States of America
| | - Dong-Hua Chen
- Structural Biology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Soung Hun Roh
- Department of Biological Sciences, Institute of Molecular Biology & Genetics, Seoul National University, Seoul, Korea
| | - Grigore D. Pintilie
- Bioengineering, Stanford University School of Medicine, Stanford, California, United States of America
| | - David A. Bushnell
- Structural Biology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Marvin H. Sommer
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Edward Yang
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Andrea Carfi
- GSK Vaccines, Cambridge, Massachusetts, United States of America
| | - Wah Chiu
- Bioengineering, Stanford University School of Medicine, Stanford, California, United States of America
- Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
- Division of Cryo-EM and Bioimaging SSRL, SLAC National Accelerator Laboratory, Menlo Park, California, United States of America
| | - Ann M. Arvin
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America
- Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, United States of America
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11
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Abstract
Herpesviruses are ubiquitous, double-stranded DNA, enveloped viruses that establish lifelong infections and cause a range of diseases. Entry into host cells requires binding of the virus to specific receptors, followed by the coordinated action of multiple viral entry glycoproteins to trigger membrane fusion. Although the core fusion machinery is conserved for all herpesviruses, each species uses distinct receptors and receptor-binding glycoproteins. Structural studies of the prototypical herpesviruses herpes simplex virus 1 (HSV-1), HSV-2, human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) entry glycoproteins have defined the interaction sites for glycoprotein complexes and receptors, and have revealed conformational changes that occur on receptor binding. Recent crystallography and electron microscopy studies have refined our model of herpesvirus entry into cells, clarifying both the conserved features and the unique features. In this Review, we discuss recent insights into herpesvirus entry by analysing the structures of entry glycoproteins, including the diverse receptor-binding glycoproteins (HSV-1 glycoprotein D (gD), EBV glycoprotein 42 (gp42) and HCMV gH-gL-gO trimer and gH-gL-UL128-UL130-UL131A pentamer), as well gH-gL and the fusion protein gB, which are conserved in all herpesviruses.
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12
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Localization of the Interaction Site of Herpes Simplex Virus Glycoprotein D (gD) on the Membrane Fusion Regulator, gH/gL. J Virol 2020; 94:JVI.00983-20. [PMID: 32759318 DOI: 10.1128/jvi.00983-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 07/27/2020] [Indexed: 12/12/2022] Open
Abstract
A cascade of protein-protein interactions between four herpes simplex virus (HSV) glycoproteins (gD, gH/gL, and gB) drive fusion between the HSV envelope and host membrane, thereby allowing for virus entry and infection. Specifically, binding of gD to one of its receptors induces a conformational change that allows gD to bind to the regulatory complex gH/gL, which then activates the fusogen gB, resulting in membrane fusion. Using surface plasmon resonance and a panel of anti-gD monoclonal antibodies (MAbs) that sterically blocked the interaction, we previously showed that gH/gL binds directly to gD at sites distinct from the gD receptor binding site. Here, using an analogous strategy, we first evaluated the ability of a panel of uncharacterized anti-gH/gL MAbs to block binding to gD and/or inhibit fusion. We found that the epitopes of four gD-gH/gL-blocking MAbs were located within flexible regions of the gH N terminus and the gL C terminus, while the fifth was placed around gL residue 77. Taken together, our data localized the gD binding region on gH/gL to a group of gH and gL residues at the membrane distal region of the heterodimer. Surprisingly, a second set of MAbs did not block gD-gH/gL binding but instead stabilized the complex by altering the kinetic binding. However, despite this prolonged gD-gH/gL interaction, "stabilizing" MAbs also inhibited cell-cell fusion, suggesting a unique mechanism by which the fusion process is halted. Our findings support targeting the gD-gH/gL interaction to prevent fusion in both therapeutic and vaccine strategies against HSV.IMPORTANCE Key to developing a human HSV vaccine is an understanding of the virion glycoproteins involved in entry. HSV employs multiple glycoproteins for attachment, receptor interaction, and membrane fusion. Determining how these proteins function was resolved, in part, by structural biology coupled with immunological and biologic evidence. After binding, virion gD interacts with a receptor to activate the regulator gH/gL complex, triggering gB to drive fusion. Multiple questions remain, one being the physical location of each glycoprotein interaction site. Using protective antibodies with known epitopes, we documented the long-sought interaction between gD and gH/gL, detailing the region on gD important to create the gD-gH/gL triplex. Now, we have identified the corresponding gD contact sites on gH/gL. Concurrently we discovered a novel mechanism whereby gH/gL antibodies stabilize the complex and inhibit fusion progression. Our model for the gD-gH/gL triplex provides a new framework for studying fusion, which identifies targets for vaccine development.
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Quemin ERJ, Machala EA, Vollmer B, Pražák V, Vasishtan D, Rosch R, Grange M, Franken LE, Baker LA, Grünewald K. Cellular Electron Cryo-Tomography to Study Virus-Host Interactions. Annu Rev Virol 2020; 7:239-262. [PMID: 32631159 DOI: 10.1146/annurev-virology-021920-115935] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Viruses are obligatory intracellular parasites that reprogram host cells upon infection to produce viral progeny. Here, we review recent structural insights into virus-host interactions in bacteria, archaea, and eukaryotes unveiled by cellular electron cryo-tomography (cryoET). This advanced three-dimensional imaging technique of vitreous samples in near-native state has matured over the past two decades and proven powerful in revealing molecular mechanisms underlying viral replication. Initial studies were restricted to cell peripheries and typically focused on early infection steps, analyzing surface proteins and viral entry. Recent developments including cryo-thinning techniques, phase-plate imaging, and correlative approaches have been instrumental in also targeting rare events inside infected cells. When combined with advances in dedicated image analyses and processing methods, details of virus assembly and egress at (sub)nanometer resolution were uncovered. Altogether, we provide a historical and technical perspective and discuss future directions and impacts of cryoET for integrative structural cell biology analyses of viruses.
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Affiliation(s)
- Emmanuelle R J Quemin
- Centre for Structural Systems Biology, Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, University of Hamburg, D-22607 Hamburg, Germany;
| | - Emily A Machala
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Benjamin Vollmer
- Centre for Structural Systems Biology, Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, University of Hamburg, D-22607 Hamburg, Germany;
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Vojtěch Pražák
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Daven Vasishtan
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Rene Rosch
- Centre for Structural Systems Biology, Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, University of Hamburg, D-22607 Hamburg, Germany;
| | - Michael Grange
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Linda E Franken
- Centre for Structural Systems Biology, Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, University of Hamburg, D-22607 Hamburg, Germany;
| | - Lindsay A Baker
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Kay Grünewald
- Centre for Structural Systems Biology, Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, University of Hamburg, D-22607 Hamburg, Germany;
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
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14
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Vollmer B, Pražák V, Vasishtan D, Jefferys EE, Hernandez-Duran A, Vallbracht M, Klupp BG, Mettenleiter TC, Backovic M, Rey FA, Topf M, Grünewald K. The prefusion structure of herpes simplex virus glycoprotein B. SCIENCE ADVANCES 2020; 6:eabc1726. [PMID: 32978151 PMCID: PMC7518877 DOI: 10.1126/sciadv.abc1726] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 08/12/2020] [Indexed: 05/03/2023]
Abstract
Cell entry of enveloped viruses requires specialized viral proteins that mediate fusion with the host membrane by substantial structural rearrangements from a metastable pre- to a stable postfusion conformation. This metastability renders the herpes simplex virus 1 (HSV-1) fusion glycoprotein B (gB) highly unstable such that it readily converts into the postfusion form, thereby precluding structural elucidation of the pharmacologically relevant prefusion conformation. By identification of conserved sequence signatures and molecular dynamics simulations, we devised a mutation that stabilized this form. Functionally locking gB allowed the structural determination of its membrane-embedded prefusion conformation at sub-nanometer resolution and enabled the unambiguous fit of all ectodomains. The resulting pseudo-atomic model reveals a notable conservation of conformational domain rearrangements during fusion between HSV-1 gB and the vesicular stomatitis virus glycoprotein G, despite their very distant phylogeny. In combination with our comparative sequence-structure analysis, these findings suggest common fusogenic domain rearrangements in all class III viral fusion proteins.
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Affiliation(s)
- B Vollmer
- Oxford Particle Imaging Centre, Department of Structural Biology, Wellcome Centre Human Genetics, University of Oxford, Oxford, UK
- Centre for Structural Systems Biology, Heinrich-Pette-Institut, Leibniz-Institut für Experimentelle Virologie, Hamburg, Germany
| | - V Pražák
- Oxford Particle Imaging Centre, Department of Structural Biology, Wellcome Centre Human Genetics, University of Oxford, Oxford, UK
| | - D Vasishtan
- Oxford Particle Imaging Centre, Department of Structural Biology, Wellcome Centre Human Genetics, University of Oxford, Oxford, UK
| | - E E Jefferys
- Department of Biochemistry, University of Oxford, Oxford, UK
| | | | - M Vallbracht
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Insel Riems, Germany
| | - B G Klupp
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Insel Riems, Germany
| | - T C Mettenleiter
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Insel Riems, Germany
| | - M Backovic
- Institut Pasteur, Structural Virology Unit, Department of Virology, Paris, France
| | - F A Rey
- Institut Pasteur, Structural Virology Unit, Department of Virology, Paris, France
| | - M Topf
- Institute of Structural and Molecular Biology, Birkbeck, London, UK
| | - K Grünewald
- Oxford Particle Imaging Centre, Department of Structural Biology, Wellcome Centre Human Genetics, University of Oxford, Oxford, UK.
- Centre for Structural Systems Biology, Heinrich-Pette-Institut, Leibniz-Institut für Experimentelle Virologie, Hamburg, Germany
- Department of Chemistry, MIN Faculty, Universität Hamburg, Hamburg, Germany
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15
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A glycoprotein B-neutralizing antibody structure at 2.8 Å uncovers a critical domain for herpesvirus fusion initiation. Nat Commun 2020; 11:4141. [PMID: 32811830 PMCID: PMC7435202 DOI: 10.1038/s41467-020-17911-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 07/21/2020] [Indexed: 11/24/2022] Open
Abstract
Members of the Herpesviridae, including the medically important alphaherpesvirus varicella-zoster virus (VZV), induce fusion of the virion envelope with cell membranes during entry, and between cells to form polykaryocytes in infected tissues. The conserved glycoproteins, gB, gH and gL, are the core functional proteins of the herpesvirus fusion complex. gB serves as the primary fusogen via its fusion loops, but functions for the remaining gB domains remain unexplained. As a pathway for biological discovery of domain function, our approach used structure-based analysis of the viral fusogen together with a neutralizing antibody. We report here a 2.8 Å cryogenic-electron microscopy structure of native gB recovered from VZV-infected cells, in complex with a human monoclonal antibody, 93k. This high-resolution structure guided targeted mutagenesis at the gB-93k interface, providing compelling evidence that a domain spatially distant from the gB fusion loops is critical for herpesvirus fusion, revealing a potential new target for antiviral therapies. Herpesvirus virions have an outer lipid membrane dotted with glycoproteins that enable fusion with cell membranes to initiate entry and establish infection. Here the authors elucidate the structural mechanism of a neutralizing antibody derived from a patient infected by the herpesvirus varicella-zoster virus and targeted to its fusogen, glycoprotein-B.
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16
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Komala Sari T, Gianopulos KA, Weed DJ, Schneider SM, Pritchard SM, Nicola AV. Herpes Simplex Virus Glycoprotein C Regulates Low-pH Entry. mSphere 2020; 5:e00826-19. [PMID: 32024702 PMCID: PMC7002311 DOI: 10.1128/msphere.00826-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 01/15/2020] [Indexed: 12/18/2022] Open
Abstract
Herpes simplex viruses (HSVs) cause significant morbidity and mortality in humans worldwide. Herpesviruses mediate entry by a multicomponent virus-encoded machinery. Herpesviruses enter cells by endosomal low-pH and pH-neutral mechanisms in a cell-specific manner. HSV mediates cell entry via the envelope glycoproteins gB and gD and the heterodimer gH/gL regardless of pH or endocytosis requirements. Specifics concerning HSV envelope proteins that function selectively in a given entry pathway have been elusive. Here, we demonstrate that gC regulates cell entry and infection by a low-pH pathway. Conformational changes in the core herpesviral fusogen gB are critical for membrane fusion. The presence of gC conferred a higher pH threshold for acid-induced antigenic changes in gB. Thus, gC may selectively facilitate low-pH entry by regulating conformational changes in the fusion protein gB. We propose that gC modulates the HSV fusion machinery during entry into pathophysiologically relevant cells, such as human epidermal keratinocytes.IMPORTANCE Herpesviruses are ubiquitous pathogens that cause lifelong latent infections and that are characterized by multiple entry pathways. We propose that herpes simplex virus (HSV) gC plays a selective role in modulating HSV entry, such as entry into epithelial cells, by a low-pH pathway. gC facilitates a conformational change of the main fusogen gB, a class III fusion protein. We propose a model whereby gC functions with gB, gD, and gH/gL to allow low-pH entry. In the absence of gC, HSV entry occurs at a lower pH, coincident with trafficking to a lower pH compartment where gB changes occur at more acidic pHs. This report identifies a new function for gC and provides novel insight into the complex mechanism of HSV entry and fusion.
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Affiliation(s)
- Tri Komala Sari
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
- Protein Biotechnology Graduate Training Program, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Katrina A Gianopulos
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
- Protein Biotechnology Graduate Training Program, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Darin J Weed
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
- Protein Biotechnology Graduate Training Program, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Seth M Schneider
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Suzanne M Pritchard
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
| | - Anthony V Nicola
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA
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17
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Tuzmen C, Cairns TM, Atanasiu D, Lou H, Saw WT, Hall BL, Cohen JB, Cohen GH, Glorioso JC. Point Mutations in Retargeted gD Eliminate the Sensitivity of EGFR/EGFRvIII-Targeted HSV to Key Neutralizing Antibodies. MOLECULAR THERAPY-METHODS & CLINICAL DEVELOPMENT 2020; 16:145-154. [PMID: 32042851 PMCID: PMC7000558 DOI: 10.1016/j.omtm.2019.12.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 12/26/2019] [Indexed: 11/29/2022]
Abstract
Effective oncolytic virotherapy may require systemic delivery, tumor targeting, and resistance to virus-neutralizing (VN) antibodies. Since herpes simplex virus (HSV) glycoprotein D (gD) is the viral attachment/entry protein and predominant VN target, we examined the impact of gD retargeting alone and in combination with alterations in dominant VN epitopes on virus susceptibility to VN antibodies. We compared the binding of a panel of anti-gD monoclonal antibodies (mAbs) that mimic antibody specificities in human HSV-immune sera to the purified ectodomains of wild-type and retargeted gD, revealing the retention of two prominent epitopes. Substitution of a key residue in each epitope, separately and together, revealed that both substitutions (1) blocked retargeted gD recognition by mAbs to the respective epitopes, and, in combination, caused a global reduction in mAb binding; (2) protected against fusion inhibition by VN mAbs reactive with each epitope in virus-free cell-cell fusion assays; and (3) increased the resistance of retargeted HSV-1 to these VN mAbs. Although the combined modifications of retargeted gD allowed bona fide retargeting, incorporation into virions was partially compromised. Our results indicate that stacking of epitope mutations can additively block retargeted gD recognition by VN antibodies but also that improvements in gD incorporation into virus particles may be required.
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Affiliation(s)
- Ceren Tuzmen
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Tina M Cairns
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Doina Atanasiu
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Huan Lou
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Wan Ting Saw
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Bonnie L Hall
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Justus B Cohen
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA 15219, USA
| | - Gary H Cohen
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Joseph C Glorioso
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA 15219, USA
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18
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White EM, Stampfer SD, Heldwein EE. Expression, Purification, and Crystallization of HSV-1 Glycoproteins for Structure Determination. Methods Mol Biol 2020; 2060:377-393. [PMID: 31617192 PMCID: PMC9903252 DOI: 10.1007/978-1-4939-9814-2_23] [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: 02/09/2023]
Abstract
Herpes simplex viruses utilize glycoproteins displayed on the viral envelope to perform a variety of functions in the viral infectious cycle. Structural and functional studies of these viral glycoproteins can benefit from biochemical, biophysical, and structural analysis of purified proteins. Here, we describe a general protocol for expression and purification of viral glycoproteins from insect cells based on those developed for the HSV-1 gB and HSV-2 gH/gL ectodomains as well as the protocol for crystallization of these glycoproteins. This protocol can be used for generating milligram amounts of wild-type (WT) or mutant gB and gH/gL ectodomains or can be adapted to produce purified ectodomains of glycoproteins from HSV or other herpesviruses for biochemical and structural studies.
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19
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Chéneau C, Coulon F, Porkolab V, Fieschi F, Laurant S, Razanajaona-Doll D, Pin JJ, Borst EM, Messerle M, Bressollette-Bodin C, Halary F. Fine Mapping the Interaction Between Dendritic Cell-Specific Intercellular Adhesion Molecule (ICAM)-3-Grabbing Nonintegrin and the Cytomegalovirus Envelope Glycoprotein B. J Infect Dis 2019; 218:490-503. [PMID: 29648611 PMCID: PMC6049025 DOI: 10.1093/infdis/jiy194] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 04/03/2018] [Indexed: 12/22/2022] Open
Abstract
Background Human cytomegalovirus (HCMV) is a leading cause of virally induced congenital disorders and morbidities in immunocompromised individuals, ie, transplant, cancer, or acquired immune deficiency syndrome patients. Human cytomegalovirus infects virtually all cell types through the envelope glycoprotein complex gH/gL/gO with or without a contribution of the pentameric gH/gL/pUL128L. Together with gH/gL, the HCMV envelope glycoprotein B (gB) contributes to the viral fusion machinery. Methods We previously showed that gB is a ligand for the C-type lectin dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) contributing to HCMV attachment to and infection of DC-SIGN-expressing cells. However, the features of the DC-SIGN/gB interaction remain unclear. To address this point, the role of glycans on gB and the consequences of mutagenesis and antibody-mediated blockades on both partners were examined in this study. Results We identified DC-SIGN amino acid residues involved in this interaction through an extensive mutagenesis study. We also showed the importance of high-mannose N-glycans decorating the asparagine residue at position 208, demonstrating that the antigenic domain 5 on gB is involved in the interaction with DC-SIGN. Finally, antibody-mediated blockades allowed us to identify DC-SIGN as a major HCMV attachment receptor on monocyte-derived dendritic cells. Conclusions Taken together, these results have permitted us to fine-map the interaction between DC-SIGN and HCMV gB.
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Affiliation(s)
- Coraline Chéneau
- Centre de Recherche en Transplantation et Immunologie UMR1064, INSERM, Université de Nantes, France.,Institut de Transplantation Urologie Néphrologie, Centre Hospitalier Universitaire (CHU) Nantes, France
| | - Flora Coulon
- Centre de Recherche en Transplantation et Immunologie UMR1064, INSERM, Université de Nantes, France.,Institut de Transplantation Urologie Néphrologie, Centre Hospitalier Universitaire (CHU) Nantes, France
| | - Vanessa Porkolab
- Université Grenoble Alpes, Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique, Institute de Biologie Structurale, Grenoble, France
| | - Franck Fieschi
- Université Grenoble Alpes, Commissariat à l'Energie Atomique, Centre National de la Recherche Scientifique, Institute de Biologie Structurale, Grenoble, France
| | | | | | | | - Eva Maria Borst
- Institute of Virology, Hannover Medical School, Hannover, Germany
| | - Martin Messerle
- Institute of Virology, Hannover Medical School, Hannover, Germany
| | - Céline Bressollette-Bodin
- Centre de Recherche en Transplantation et Immunologie UMR1064, INSERM, Université de Nantes, France.,Institut de Transplantation Urologie Néphrologie, Centre Hospitalier Universitaire (CHU) Nantes, France.,Service de Virologie Clinique, CHU Hotel Dieu, Nantes, France
| | - Franck Halary
- Centre de Recherche en Transplantation et Immunologie UMR1064, INSERM, Université de Nantes, France.,Institut de Transplantation Urologie Néphrologie, Centre Hospitalier Universitaire (CHU) Nantes, France
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Vallbracht M, Backovic M, Klupp BG, Rey FA, Mettenleiter TC. Common characteristics and unique features: A comparison of the fusion machinery of the alphaherpesviruses Pseudorabies virus and Herpes simplex virus. Adv Virus Res 2019; 104:225-281. [PMID: 31439150 DOI: 10.1016/bs.aivir.2019.05.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Membrane fusion is a fundamental biological process that allows different cellular compartments delimited by a lipid membrane to release or exchange their respective contents. Similarly, enveloped viruses such as alphaherpesviruses exploit membrane fusion to enter and infect their host cells. For infectious entry the prototypic human Herpes simplex viruses 1 and 2 (HSV-1 and -2, collectively termed HSVs) and the porcine Pseudorabies virus (PrV) utilize four different essential envelope glycoproteins (g): the bona fide fusion protein gB and the regulatory heterodimeric gH/gL complex that constitute the "core fusion machinery" conserved in all members of the Herpesviridae; and the subfamily specific receptor binding protein gD. These four components mediate attachment and fusion of the virion envelope with the host cell plasma membrane through a tightly regulated sequential activation process. Although PrV and the HSVs are closely related and employ the same set of glycoproteins for entry, they show remarkable differences in the requirements for fusion. Whereas the HSVs strictly require all four components for membrane fusion, PrV can mediate cell-cell fusion without gD. Moreover, in contrast to the HSVs, PrV provides a unique opportunity for reversion analyses of gL-negative mutants by serial cell culture passaging, due to a limited cell-cell spread capacity of gL-negative PrV not observed in the HSVs. This allows a more direct analysis of the function of gH/gL during membrane fusion. Unraveling the molecular mechanism of herpesvirus fusion has been a goal of fundamental research for years, and yet important mechanistic details remain to be uncovered. Nevertheless, the elucidation of the crystal structures of all key players involved in PrV and HSV membrane fusion, coupled with a wealth of functional data, has shed some light on this complex puzzle. In this review, we summarize and discuss the contemporary knowledge on the molecular mechanism of entry and membrane fusion utilized by the alphaherpesvirus PrV, and highlight similarities but also remarkable differences in the requirements for fusion between PrV and the HSVs.
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Affiliation(s)
- Melina Vallbracht
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany.
| | - Marija Backovic
- Institut Pasteur, Unité de Virologie Structurale, UMR3569 (CNRS), Paris, France
| | - Barbara G Klupp
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany
| | - Felix A Rey
- Institut Pasteur, Unité de Virologie Structurale, UMR3569 (CNRS), Paris, France
| | - Thomas C Mettenleiter
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany
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Abstract
In this chapter, we present an overview on betaherpesvirus entry, with a focus on human cytomegalovirus, human herpesvirus 6A and human herpesvirus 6B. Human cytomegalovirus (HCMV) is a complex human pathogen with a genome of 235kb encoding more than 200 genes. It infects a broad range of cell types by switching its viral ligand on the virion, using the trimer gH/gL/gO for infection of fibroblasts and the pentamer gH/gL/UL128/UL130/UL131 for infection of other cells such as epithelial and endothelial cells, leading to membrane fusion mediated by the fusion protein gB. Adding to this scenario, however, accumulating data reveal the actual complexity in the viral entry process of HCMV with an intricate interplay among viral and host factors. Key novel findings include the identification of entry receptors platelet-derived growth factor-α receptor (PDGFRα) and Netropilin-2 (Nrp2) for trimer and pentamer, respectively, the determination of atomic structures of the fusion protein gB and the pentamer, and the in situ visualization of the state and arrangement of functional glycoproteins on virion. This is covered in the first part of this review. The second part focusses on HHV-6 which is a T lymphotropic virus categorized as two distinct virus species, HHV-6A and HHV-6B based on differences in epidemiological, biological, and immunological aspects, although homology of their entire genome sequences is nearly 90%. HHV-6B is a causative agent of exanthema subitum (ES), but the role of HHV-6A is unknown. HHV-6B reactivation occasionally causes encephalitis in patients with hematopoietic stem cell transplant. The HHV-6 specific envelope glycoprotein complex, gH/gL/gQ1/gQ2 is a viral ligand for the entry receptor. Recently, each virus has been found to recognize a different cellular receptor, CD46 for HHV 6A amd CD134 for HHV 6B. These findings show that distinct receptor recognition differing between both viruses could explain their different pathogenesis.
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Affiliation(s)
- Mitsuhiro Nishimura
- Division of Clinical Virology, Center for Infectious Diseases, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yasuko Mori
- Division of Clinical Virology, Center for Infectious Diseases, Kobe University Graduate School of Medicine, Kobe, Japan.
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Yamamoto Y, Yamamoto T, Aoyama Y, Fujimoto W. Cell-to-cell transmission of HSV-1 in differentiated keratinocytes promotes multinucleated giant cell formation. J Dermatol Sci 2019; 93:14-23. [DOI: 10.1016/j.jdermsci.2018.09.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 08/29/2018] [Accepted: 09/12/2018] [Indexed: 11/26/2022]
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23
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Atanasiu D, Saw WT, Lazear E, Whitbeck JC, Cairns TM, Lou H, Eisenberg RJ, Cohen GH. Using Antibodies and Mutants To Localize the Presumptive gH/gL Binding Site on Herpes Simplex Virus gD. J Virol 2018; 92:e01694-18. [PMID: 30282715 PMCID: PMC6258950 DOI: 10.1128/jvi.01694-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 09/28/2018] [Indexed: 02/02/2023] Open
Abstract
HSV virus-cell and cell-cell fusion requires multiple interactions between four essential virion envelope glycoproteins, gD, gB, gH, and gL, and between gD and a cellular receptor, nectin-1 or herpesvirus entry mediator (HVEM). Current models suggest that binding of gD to receptors induces a conformational change that leads to activation of gH/gL and consequent triggering of the prefusion form of gB to promote membrane fusion. Since protein-protein interactions guide each step of fusion, identifying the sites of interaction may lead to the identification of potential therapeutic targets that block this process. We have previously identified two "faces" on gD: one for receptor binding and the other for its presumed interaction with gH/gL. We previously separated the gD monoclonal antibodies (MAbs) into five competition communities. MAbs from two communities (MC2 and MC5) neutralize virus infection and block cell-cell fusion but do not block receptor binding, suggesting that they block binding of gD to gH/gL. Using a combination of classical epitope mapping of gD mutants with fusion and entry assays, we identified two residues (R67 and P54) on the presumed gH/gL interaction face of gD that allowed for fusion and viral entry but were no longer sensitive to inhibition by MC2 or MC5, yet both were blocked by other MAbs. As neutralizing antibodies interfere with essential steps in the fusion pathway, our studies strongly suggest that these key residues block the interaction of gD with gH/gL.IMPORTANCE Virus entry and cell-cell fusion mediated by HSV require gD, gH/gL, gB, and a gD receptor. Neutralizing antibodies directed against any of these proteins bind to residues within key functional sites and interfere with an essential step in the fusion pathway. Thus, the epitopes of these MAbs identify critical, functional sites on their target proteins. Unlike many anti-gD MAbs, which block binding of gD to a cellular receptor, two, MC2 and MC5, block a separate, downstream step in the fusion pathway which is presumed to be the activation of the modulator of fusion, gH/gL. By combining epitope mapping of a panel of gD mutants with fusion and virus entry assays, we have identified residues that are critical in the binding and function of these two MAbs. This new information helps to define the site of the presumptive interaction of gD with gH/gL, of which we have limited knowledge.
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Affiliation(s)
- Doina Atanasiu
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Wan Ting Saw
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Eric Lazear
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - J Charles Whitbeck
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Tina M Cairns
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Huan Lou
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Roselyn J Eisenberg
- School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Gary H Cohen
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
- Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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24
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Si Z, Zhang J, Shivakoti S, Atanasov I, Tao CL, Hui WH, Zhou K, Yu X, Li W, Luo M, Bi GQ, Zhou ZH. Different functional states of fusion protein gB revealed on human cytomegalovirus by cryo electron tomography with Volta phase plate. PLoS Pathog 2018; 14:e1007452. [PMID: 30507948 PMCID: PMC6307773 DOI: 10.1371/journal.ppat.1007452] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 12/27/2018] [Accepted: 11/02/2018] [Indexed: 11/25/2022] Open
Abstract
Human cytomegalovirus (HCMV) enters host by glycoprotein B (gB)-mediated membrane fusion upon receptor-binding to gH/gL-related complexes, causing devastating diseases such as birth defects. Although an X-ray crystal structure of the recombinant gB ectodomain at postfusion conformation is available, the structures of prefusion gB and its complex with gH/gL on the viral envelope remain elusive. Here, we demonstrate the utility of cryo electron tomography (cryoET) with energy filtering and the cutting-edge technologies of Volta phase plate (VPP) and direct electron-counting detection to capture metastable prefusion viral fusion proteins and report the structures of glycoproteins in the native environment of HCMV virions. We established the validity of our approach by obtaining cryoET in situ structures of the vesicular stomatitis virus (VSV) glycoprotein G trimer (171 kD) in prefusion and postfusion conformations, which agree with the known crystal structures of purified G trimers in both conformations. The excellent contrast afforded by these technologies has enabled us to identify gB trimers (303kD) in two distinct conformations in HCMV tomograms and obtain their in situ structures at up to 21 Å resolution through subtomographic averaging. The predominant conformation (79%), which we designate as gB prefusion conformation, fashions a globular endodomain and a Christmas tree-shaped ectodomain, while the minority conformation (21%) has a columnar tree-shaped ectodomain that matches the crystal structure of the "postfusion" gB ectodomain. We also observed prefusion gB in complex with an "L"-shaped density attributed to the gH/gL complex. Integration of these structures of HCMV glycoproteins in multiple functional states and oligomeric forms with existing biochemical data and domain organization of other class III viral fusion proteins suggests that gH/gL receptor-binding triggers conformational changes of gB endodomain, which in turn triggers two essential steps to actuate virus-cell membrane fusion: exposure of gB fusion loops and unfurling of gB ectodomain.
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Affiliation(s)
- Zhu Si
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, P.R. China
- Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, California, United States of America
| | - Jiayan Zhang
- Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, California, United States of America
- Molecular Biology Institute, UCLA, Los Angeles, CA, United States of America
| | - Sakar Shivakoti
- Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, California, United States of America
| | - Ivo Atanasov
- California NanoSystems Institute, UCLA, Los Angeles, CA, United States of America
| | - Chang-Lu Tao
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, P.R. China
| | - Wong H. Hui
- California NanoSystems Institute, UCLA, Los Angeles, CA, United States of America
| | - Kang Zhou
- California NanoSystems Institute, UCLA, Los Angeles, CA, United States of America
| | - Xuekui Yu
- Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, California, United States of America
| | - Weike Li
- Department of Chemistry, Georgia State University, Atlanta, GA, United States of America
| | - Ming Luo
- Department of Chemistry, Georgia State University, Atlanta, GA, United States of America
| | - Guo-Qiang Bi
- School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, P.R. China
| | - Z. Hong Zhou
- Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, California, United States of America
- Molecular Biology Institute, UCLA, Los Angeles, CA, United States of America
- California NanoSystems Institute, UCLA, Los Angeles, CA, United States of America
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25
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Fan Q, Kopp SJ, Byskosh NC, Connolly SA, Longnecker R. Natural Selection of Glycoprotein B Mutations That Rescue the Small-Plaque Phenotype of a Fusion-Impaired Herpes Simplex Virus Mutant. mBio 2018; 9:e01948-18. [PMID: 30327436 PMCID: PMC6191544 DOI: 10.1128/mbio.01948-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 09/10/2018] [Indexed: 11/20/2022] Open
Abstract
Glycoprotein B (gB) is a conserved viral fusion protein that is required for herpesvirus entry. To mediate fusion with the cellular membrane, gB refolds from a prefusion to a postfusion conformation. We hypothesize that an interaction between the C-terminal arm and the central coiled coil of the herpes simplex virus 1 (HSV-1) gB ectodomain is critical for fusion. We previously reported that three mutations in the C-terminal arm (I671A/H681A/F683A, called gB3A) greatly reduced cell-cell fusion and that virus carrying these mutations had a small-plaque phenotype and delayed entry into cells. By serially passaging gB3A virus, we selected three revertant viruses with larger plaques. These revertant viruses acquired mutations in gB that restore the fusion function of gB3A, including gB-A683V, gB-S383F/G645R/V705I/A855V, and gB-T509M/N709H. V705I and N709H are novel mutations that map to the portion of domain V that enters domain I in the postfusion structure. S383F, G645R, and T509M are novel mutations that map to an intersection of three domains in a prefusion model of gB. We introduced these second-site mutations individually and in combination into wild-type gB and gB3A to examine the impact of the mutations on fusion and expression. V705I and A855V (a known hyperfusogenic mutation) restored the fusion function of gB3A, whereas S383F and G645R dampened fusion and T509M and N709H worked in concert to restore gB3A fusion. The results identify two regions in the gB ectodomain that modulate the fusion activity of gB, potentially by impacting intramolecular interactions and stability of the prefusion and/or postfusion gB trimer.IMPORTANCE Glycoprotein B (gB) is an essential viral protein that is conserved in all herpesviruses and is required for virus entry. gB is thought to undergo a conformational change that provides the energy to fuse the viral and cellular membranes; however, the details of this conformational change and the structure of the prefusion and intermediate conformations of gB are not known. Previously, we demonstrated that mutations in the gB "arm" region inhibit fusion and impart a small-plaque phenotype. Using serial passage of a virus carrying these mutations, we identified revertants with restored plaque size. The revertant viruses acquired novel mutations in gB that restored fusion function and mapped to two sites in the gB ectodomain. This work supports our hypothesis that an interaction between the gB arm and the core of gB is critical for gB refolding and provides details about the function of gB in herpesvirus-mediated fusion and subsequent virus entry.
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Affiliation(s)
- Qing Fan
- Department of Microbiology-Immunology, Feinberg School of Medicine of Northwestern University, Chicago, Illinois, USA
| | - Sarah J Kopp
- Department of Microbiology-Immunology, Feinberg School of Medicine of Northwestern University, Chicago, Illinois, USA
| | - Nina C Byskosh
- Department of Microbiology-Immunology, Feinberg School of Medicine of Northwestern University, Chicago, Illinois, USA
| | - Sarah A Connolly
- Department of Health Sciences, Department of Biological Sciences, DePaul University, Chicago, Illinois, USA
| | - Richard Longnecker
- Department of Microbiology-Immunology, Feinberg School of Medicine of Northwestern University, Chicago, Illinois, USA
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26
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Nelson CS, Herold BC, Permar SR. A new era in cytomegalovirus vaccinology: considerations for rational design of next-generation vaccines to prevent congenital cytomegalovirus infection. NPJ Vaccines 2018; 3:38. [PMID: 30275984 PMCID: PMC6148244 DOI: 10.1038/s41541-018-0074-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 07/07/2018] [Accepted: 07/11/2018] [Indexed: 02/07/2023] Open
Abstract
Human cytomegalovirus (HCMV), a member of the beta-herpesvirus family, is the most common cause of congenital infection worldwide as well as an important cause of morbidity in transplant recipients and immunosuppressed individuals. An estimated 1 in 150 infants are infected with HCMV at birth, which can result in lifelong, debilitating neurologic sequelae including microcephaly, sensorineural hearing loss, and cognitive impairment. Natural maternal immunity to HCMV decreases the frequency of reinfection and reduces risk of congenital transmission but does not completely protect against neonatal disease. Thus, a vaccine to reduce the incidence and severity of infant infection is a public health priority. A variety of candidate HCMV vaccine approaches have been tried previously, including live-attenuated viruses, glycoprotein subunit formulations, viral vectors, and single/bivalent DNA plasmids, but all have failed to reach target endpoints in clinical trials. Nevertheless, there is a great deal to be learned from the successes and failures of the HCMV vaccine field (both congenital and transplant-associated), as well as from vaccine development efforts for other herpesvirus pathogens including herpes simplex virus 1 and 2, varicella zoster virus, and Epstein-Barr virus. Here, we review those successes and failures, evaluating recent cutting-edge discoveries that have shaped the HCMV vaccine field and identifying topics of critical importance for future investigation. These considerations will inform rational design and evaluation of next-generation vaccines to prevent HCMV-associated congenital infection and disease.
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Affiliation(s)
- Cody S. Nelson
- Human Vaccine Institute, Duke University Medical Center, Durham, NC USA
| | - Betsy C. Herold
- Department of Pediatrics, Albert Einstein College of Medicine, Bronx, NY USA
| | - Sallie R. Permar
- Human Vaccine Institute, Duke University Medical Center, Durham, NC USA
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27
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Cooper RS, Georgieva ER, Borbat PP, Freed JH, Heldwein EE. Structural basis for membrane anchoring and fusion regulation of the herpes simplex virus fusogen gB. Nat Struct Mol Biol 2018; 25:416-424. [PMID: 29728654 PMCID: PMC5942590 DOI: 10.1038/s41594-018-0060-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 03/28/2018] [Indexed: 11/26/2022]
Abstract
Viral fusogens merge viral and cell membranes during cell penetration. Their ectodomains drive fusion by undergoing large-scale refolding, but little is known about the functionally important regions located within or near the membrane. Here, we report the crystal structure of the full-length glycoprotein B, the fusogen from Herpes Simplex Virus, complemented by electron spin resonance measurements. The membrane-proximal (MPR), transmembrane (TMD), and cytoplasmic (CTD) domains form a uniquely folded trimeric pedestal beneath the ectodomain, which balances dynamic flexibility with extensive, stabilizing membrane interactions. Hyperfusogenic mutations within the CTD destabilize it, targeting trimeric interfaces, structural motifs, and membrane-interacting elements. Thus, we propose that the CTD trimer observed in the structure stabilizes gB in its prefusion state despite being appended to the postfusion ectodomain. Our data suggest a model for how this dynamic, membrane-dependent “clamp” controls the fusogenic refolding of gB.
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Affiliation(s)
- Rebecca S Cooper
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
| | - Elka R Georgieva
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA.,National Biomedical Center for Advanced Electron Spin Resonance Technology (ACERT), Cornell University, Ithaca, NY, USA
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA.,National Biomedical Center for Advanced Electron Spin Resonance Technology (ACERT), Cornell University, Ithaca, NY, USA
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA.,National Biomedical Center for Advanced Electron Spin Resonance Technology (ACERT), Cornell University, Ithaca, NY, USA
| | - Ekaterina E Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA.
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28
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Abou-Hamdan A, Belot L, Albertini A, Gaudin Y. Monomeric Intermediates Formed by Vesiculovirus Glycoprotein during Its Low-pH-induced Structural Transition. J Mol Biol 2018; 430:1685-1695. [PMID: 29678555 PMCID: PMC7126088 DOI: 10.1016/j.jmb.2018.04.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 04/06/2018] [Accepted: 04/10/2018] [Indexed: 01/26/2023]
Abstract
Vesiculovirus G is the prototype of class III viral fusion glycoproteins. The structures of both G pre- and post-fusion conformation have been determined. The structure of monomeric intermediates reveals the pathway of the transition. A fusion-loop-exposing antiparallel dimer may initiate the fusion process. Those data challenge the current model proposed for viral membrane fusion.
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Affiliation(s)
- Abbas Abou-Hamdan
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Laura Belot
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Aurélie Albertini
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France
| | - Yves Gaudin
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette cedex, France.
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29
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Vennard LM, Atanasiu D, Saw WT, Eisenberg RJ, Cohen GH, Fontana J. Recent insights into the structural characterization of herpes simplex virus fusion protein, gB. Future Virol 2018. [DOI: 10.2217/fvl-2017-0124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Lorelai M Vennard
- Faculty of Biology & Astbury Center for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Doina Atanasiu
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Wan Ting Saw
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Roselyn J Eisenberg
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Gary H Cohen
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Juan Fontana
- Faculty of Biology & Astbury Center for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
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