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Pfaff-Kilgore JM, Davidson E, Kadash-Edmondson K, Hernandez M, Rosenberg E, Chambers R, Castelli M, Clementi N, Mancini N, Bailey JR, Crowe JE, Law M, Doranz BJ. Sites of vulnerability in HCV E1E2 identified by comprehensive functional screening. Cell Rep 2022; 39:110859. [PMID: 35613596 PMCID: PMC9281441 DOI: 10.1016/j.celrep.2022.110859] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 12/08/2021] [Accepted: 05/01/2022] [Indexed: 12/15/2022] Open
Abstract
The E1 and E2 envelope proteins of hepatitis C virus (HCV) form a heterodimer that drives virus-host membrane fusion. Here, we analyze the role of each amino acid in E1E2 function, expressing 545 individual alanine mutants of E1E2 in human cells, incorporating them into infectious viral pseudoparticles, and testing them against 37 different monoclonal antibodies (MAbs) to ascertain full-length translation, folding, heterodimer assembly, CD81 binding, viral pseudoparticle incorporation, and infectivity. We propose a model describing the role of each critical residue in E1E2 functionality and use it to examine how MAbs neutralize infection by exploiting functionally critical sites of vulnerability on E1E2. Our results suggest that E1E2 is a surprisingly fragile protein complex where even a single alanine mutation at 92% of positions disrupts its function. The amino-acid-level targets identified are highly conserved and functionally critical and can be exploited for improved therapies and vaccines.
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Affiliation(s)
| | - Edgar Davidson
- Integral Molecular, Inc., 3711 Market St, Philadelphia, PA 19104, USA
| | | | - Mayda Hernandez
- Integral Molecular, Inc., 3711 Market St, Philadelphia, PA 19104, USA
| | - Erin Rosenberg
- Integral Molecular, Inc., 3711 Market St, Philadelphia, PA 19104, USA
| | - Ross Chambers
- Integral Molecular, Inc., 3711 Market St, Philadelphia, PA 19104, USA
| | - Matteo Castelli
- Laboratory of Medical Microbiology and Virology, University Vita-Salute San Raffaele, Milan, Italy
| | - Nicola Clementi
- Laboratory of Medical Microbiology and Virology, University Vita-Salute San Raffaele, Milan, Italy; IRCSS San Raffaele Hospital, Milan, Italy
| | - Nicasio Mancini
- Laboratory of Medical Microbiology and Virology, University Vita-Salute San Raffaele, Milan, Italy; IRCSS San Raffaele Hospital, Milan, Italy
| | - Justin R Bailey
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - James E Crowe
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Vaccine Center, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Mansun Law
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Benjamin J Doranz
- Integral Molecular, Inc., 3711 Market St, Philadelphia, PA 19104, USA.
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Ströh LJ, Krey T. HCV Glycoprotein Structure and Implications for B-Cell Vaccine Development. Int J Mol Sci 2020; 21:ijms21186781. [PMID: 32947858 PMCID: PMC7555785 DOI: 10.3390/ijms21186781] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Revised: 09/12/2020] [Accepted: 09/14/2020] [Indexed: 02/06/2023] Open
Abstract
Despite the approval of highly efficient direct-acting antivirals in the last decade Hepatitis C virus (HCV) remains a global health burden and the development of a vaccine would constitute an important step towards the control of HCV. The high genetic variability of the viral glycoproteins E1 and E2, which carry the main neutralizing determinants, together with their intrinsic structural flexibility, the high level of glycosylation that shields conserved neutralization epitopes and immune evasion using decoy epitopes renders the design of an efficient vaccine challenging. Recent structural and functional analyses have highlighted the role of the CD81 receptor binding site on E2, which overlaps with those neutralization epitopes within E2 that have been structurally characterized to date. This CD81 binding site consists of three distinct segments including “epitope I”, “epitope II” and the “CD81 binding loop”. In this review we summarize the structural features of the HCV glycoproteins that have been derived from X-ray structures of neutralizing and non-neutralizing antibody fragments complexed with either recombinant E2 or epitope-derived linear peptides. We focus on the current understanding how neutralizing antibodies interact with their cognate antigen, the structural features of the respective neutralization epitopes targeted by nAbs and discuss the implications for informed vaccine design.
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Affiliation(s)
- Luisa J. Ströh
- Institute of Virology, Hannover Medical School, 30625 Hannover, Germany;
| | - Thomas Krey
- Institute of Virology, Hannover Medical School, 30625 Hannover, Germany;
- Center of Structural and Cell Biology in Medicine, Institute of Biochemistry, University of Luebeck, 23562 Luebeck, Germany
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 30625 Hannover, Germany
- German Center for Infection Research (DZIF), Partner Site Hamburg-Luebeck-Borstel-Riems, 23562 Luebeck, Germany
- Excellence Cluster 2155 RESIST, Hannover Medical School, 30625 Hannover, Germany
- Centre for Structural Systems Biology (CSSB), 22607 Hamburg, Germany
- Correspondence: ; Tel.: +49-(0)451–3101-3101
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Guest JD, Pierce BG. Computational Modeling of Hepatitis C Virus Envelope Glycoprotein Structure and Recognition. Front Immunol 2018; 9:1117. [PMID: 29892287 PMCID: PMC5985375 DOI: 10.3389/fimmu.2018.01117] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 05/03/2018] [Indexed: 12/16/2022] Open
Abstract
Hepatitis C virus (HCV) is a major global health concern, and though therapeutic options have improved, no vaccine is available despite decades of research. As HCV can rapidly mutate to evade the immune response, an effective HCV vaccine must rely on identification and characterization of sites critical for broad immune protection and viral neutralization. This knowledge depends on structural and mechanistic insights of the E1 and E2 envelope glycoproteins, which assemble as a heterodimer on the surface of the virion, engage coreceptors during host cell entry, and are the primary targets of antibodies. Due to the challenges in determining experimental structures, structural information on E1 and E2 and their interaction is relatively limited, providing opportunities to model the structures, interactions, and dynamics of these proteins. This review highlights efforts to model the E2 glycoprotein structure, the assembly of the functional E1E2 heterodimer, the structure and binding of human coreceptors, and recognition by key neutralizing antibodies. We also discuss a comparison of recently described models of full E1E2 heterodimer structures, a simulation of the dynamics of key epitope sites, and modeling glycosylation. These modeling efforts provide useful mechanistic hypotheses for further experimental studies of HCV envelope assembly, recognition, and viral fitness, and underscore the benefit of combining experimental and computational modeling approaches to reveal new insights. Additionally, computational design approaches have produced promising candidates for epitope-based vaccine immunogens that specifically target key epitopes, providing a possible avenue to optimize HCV vaccines versus using native glycoproteins. Advancing knowledge of HCV envelope structure and immune recognition is highly applicable toward the development of an effective vaccine for HCV and can provide lessons and insights relevant to modeling and characterizing other viruses.
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Affiliation(s)
- Johnathan D Guest
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, MD, United States.,Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, United States
| | - Brian G Pierce
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, MD, United States.,Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, United States
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Hepatitis C Virus Envelope Glycoprotein E1 Forms Trimers at the Surface of the Virion. J Virol 2015; 89:10333-46. [PMID: 26246575 DOI: 10.1128/jvi.00991-15] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 07/13/2015] [Indexed: 01/08/2023] Open
Abstract
UNLABELLED In hepatitis C virus (HCV)-infected cells, the envelope glycoproteins E1 and E2 assemble as a heterodimer. To investigate potential changes in the oligomerization of virion-associated envelope proteins, we performed SDS-PAGE under reducing conditions but without thermal denaturation. This revealed the presence of SDS-resistant trimers of E1 in the context of cell-cultured HCV (HCVcc) as well as in the context of HCV pseudoparticles (HCVpp). The formation of E1 trimers was found to depend on the coexpression of E2. To further understand the origin of E1 trimer formation, we coexpressed in bacteria the transmembrane (TM) domains of E1 (TME1) and E2 (TME2) fused to reporter proteins and analyzed the fusion proteins by SDS-PAGE and Western blotting. As expected for strongly interacting TM domains, TME1-TME2 heterodimers resistant to SDS were observed. These analyses also revealed homodimers and homotrimers of TME1, indicating that such complexes are stable species. The N-terminal segment of TME1 exhibits a highly conserved GxxxG sequence, a motif that is well documented to be involved in intramembrane protein-protein interactions. Single or double mutations of the glycine residues (Gly354 and Gly358) in this motif markedly decreased or abrogated the formation of TME1 homotrimers in bacteria, as well as homotrimers of E1 in both HCVpp and HCVcc systems. A concomitant loss of infectivity was observed, indicating that the trimeric form of E1 is essential for virus infectivity. Taken together, these results indicate that E1E2 heterodimers form trimers on HCV particles, and they support the hypothesis that E1 could be a fusion protein. IMPORTANCE HCV glycoproteins E1 and E2 play an essential role in virus entry into liver cells as well as in virion morphogenesis. In infected cells, these two proteins form a complex in which E2 interacts with cellular receptors, whereas the function of E1 remains poorly understood. However, recent structural data suggest that E1 could be the protein responsible for the process of fusion between viral and cellular membranes. Here we investigated the oligomeric state of HCV envelope glycoproteins. We demonstrate that E1 forms functional trimers after virion assembly and that in addition to the requirement for E2, a determinant for this oligomerization is present in a conserved GxxxG motif located within the E1 transmembrane domain. Taken together, these results indicate that a rearrangement of E1E2 heterodimer complexes likely occurs during the assembly of HCV particles to yield a trimeric form of the E1E2 heterodimer. Gaining structural information on this trimer will be helpful for the design of an anti-HCV vaccine.
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Akbar R, Jusoh SA. Stability, orientation and position preference of the stem region (residues 689-703) in Hepatitis C Virus (HCV) envelope glycoprotein E2: a molecular dynamics study. F1000Res 2014; 2:64. [PMID: 24555044 PMCID: PMC3886794 DOI: 10.12688/f1000research.2-64.v2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/15/2013] [Indexed: 12/11/2022] Open
Abstract
Envelope glycoproteins of Hepatitis C Virus (HCV) play an important role in the virus assembly and initial entry into host cells. Conserved charged residues of the E2 transmembrane (TM) domain were shown to be responsible for the heterodimerization with envelope glycoprotein E1. Despite intensive research on both envelope glycoproteins, the structural information is still not fully understood. Recent findings have revealed that the stem (ST) region of E2 also functions in the initial stage of the viral life cycle. We have previously shown the effect of the conserved charged residues on the TM helix monomer of E2. Here, we extended the model of the TM domain by adding the adjacent ST segment. Explicit molecular dynamics simulations were performed for the E2 amphiphilic segment of the ST region connected to the putative TM domain (residues 683-746). Structural conformation and behavior are studied and compared with the nuclear magnetic resonance (NMR)-derived segment of E2 (
2KQZ.pdb). We observed that the central helix of the ST region (residues 689 - 703) remained stable as a helix in-plane to the lipid bilayer. Furthermore, the TM domain appeared to provide minimal contribution to the structural stability of the amphipathic region. This study also provides insight into the orientation and positional preferences of the ST segment with respect to the membrane lipid-water interface.
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Affiliation(s)
- Rahmad Akbar
- Bioinformatics Unit, Universiti Teknologi MARA (UiTM), Bandar Puncak Alam, 42300, Malaysia
| | - Siti Azma Jusoh
- Bioinformatics Unit, Universiti Teknologi MARA (UiTM), Bandar Puncak Alam, 42300, Malaysia
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Ranjbar MM, Ghorban K, Alavian SM, Keyvani H, Dadmanesh M, Roayaei Ardakany A, Motedayen MH, Sazmand A. GB Virus C/Hepatitis G Virus Envelope Glycoprotein E2: Computational Molecular Features and Immunoinformatics Study. HEPATITIS MONTHLY 2013; 13:e15342. [PMID: 24403917 PMCID: PMC3877655 DOI: 10.5812/hepatmon.15342] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 12/01/2013] [Accepted: 12/01/2013] [Indexed: 12/11/2022]
Abstract
INTRODUCTION GB virus C (GBV-C) or hepatitis G virus (HGV) is an enveloped, RNA positive-stranded flavivirus-like particle. E2 envelope protein of GBV-C plays an important role in virus entry into the cytosol, genotyping and as a marker for diagnosing GBV-C infections. Also, there is discussion on relations between E2 protein and gp41 protein of HIV. The purposes of our study are to multi aspect molecular evaluation of GB virus C E2 protein from its characteristics, mutations, structures and antigenicity which would help to new directions for future researches. EVIDENCE ACQUISITION Briefly, steps followed here were; retrieving reference sequences of E2 protein, entropy plot evaluation for finding the mutational /conservative regions, analyzing potential Glycosylation, Phosphorylation and Palmitoylation sites, prediction of primary, secondary and tertiary structures, then amino acid distributions and transmembrane topology, prediction of T and B cell epitopes, and finally visualization of epitopes and variations regions in 3D structure. RESULTS Based on the entropy plot, 3 hypervariable regions (HVR) observed along E2 protein located in residues 133-135, 256-260 and 279-281. Analyzing primary structure of protein sequence revealed basic nature, instability, and low hydrophilicity of this protein. Transmembrane topology prediction showed that residues 257-270 presented outside, while residues 234- 256 and 271-293 were transmembrane regions. Just one N-glycosylation site, 5 potential phosphorylated peptides and two palmitoylation were found. Secondary structure revealed that this protein has 6 α-helix, 12 β-strand 17 Coil structures. Prediction of T-cell epitopes based on HLA-A*02:01 showed that epitope NH3-LLLDFVFVL-COOH is the best antigen icepitope. Comparative analysis for consensus B-cell epitopes regarding transmembrane topology, based on physico-chemical and machine learning approaches revealed that residue 231- 296 (NH2- EARLVPLILLLLWWWVNQLAVLGLPAVEAAVAGEVFAGPALSWCLGLPVVSMILGLANLVLYFRWL-COOH) is most effective and probable B cell epitope for E2 protein. CONCLUSIONS The comprehensive analysis of a protein with important roles has never been easy, and in case of E2 envelope glycoprotein of HGV, there is no much data on its molecular and immunological features, clinical significance and its pathogenic potential in hepatitis or any other GBV-C related diseases. So, results of the present study may explain some structural, physiological and immunological functions of this protein in GBV-C, as well as designing new diagnostic kits and besides, help to better understandingE2 protein characteristic and other members of Flavivirus family, especially HCV.
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Affiliation(s)
| | - Khodayar Ghorban
- Department of Immunology, School of Medicine, AJA University of Medical Sciences, Tehran, IR Iran
| | - Seyed Moayed Alavian
- Middle East Liver Diseases Center (MELD), Tehran, IR Iran
- Baqiyatallah Research Center for Gastroenterology and Liver Diseases, Baqiyatallh University of Medical Sciences, Tehran, IR Iran
- Corresponding Author: Seyed Moayed Alavian, Baqiyatallah Research Center for Gastroenterology and Liver Diseases, Baqiyatallh University of Medical Sciences, Tehran, IR Iran. Tel/Fax: +98-2188945186, E-mail:
| | - Hossein Keyvani
- Department of Virology, Tehran University of Medical Sciences, Tehran, IR Iran
| | - Maryam Dadmanesh
- Department of Infectious Diseases, School of Medicine, AJA University of Medical Sciences, Tehran, IR Iran
| | | | | | - Alireza Sazmand
- Department of Agriculture, Payame Noor University, Yazd, IR Iran
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Jusoh SA, Helms V. Helical integrity and microsolvation of transmembrane domains from Flaviviridae envelope glycoproteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:1040-9. [PMID: 21223949 DOI: 10.1016/j.bbamem.2011.01.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2010] [Revised: 11/23/2010] [Accepted: 01/04/2011] [Indexed: 01/24/2023]
Abstract
Charged and polar amino acids in the transmembrane domains of integral membrane proteins can be crucial for protein function and also promote helix-helix association or protein oligomerization. Yet, our current understanding is still limited on how these hydrophilic amino acids are efficiently translocated from the Sec61/SecY translocon into the cell membrane during the biogenesis of membrane proteins. In hepatitis C virus, the putative transmembrane segments of envelope glycoproteins E1 and E2 were suggested to heterodimerize via a Lys-Asp ion-pair in the host endoplasmic reticulum. Therefore in this work, we carried out molecular dynamic simulations in explicit lipid bilayer and solvent environment to explore the stability of all possible bridging ion-pairs using the model of H-segment helix dimers. We observed that, frequently, several water molecules penetrated from the interface into the membrane core to stabilize the charged and polar pairs. The hydration time and amount of water molecules in the membrane core depended on the position of the charged residues as well as on the type of ion-pairs. Similar microsolvation events were observed in simulations of the putative E1-E2 transmembrane helix dimers. Simulations of helix monomers from other members of the Flaviviridae family suggest that these systems show similar behaviors. Thus this study illustrates the important contribution of water microsolvation to overcome the unfavorable energetic cost of burying charged and polar amino acids in membrane lipid bilayers. Also, it emphasizes the novel role of bridging charged or polar interactions stabilized by water molecules in the hydrophobic lipid bilayer core that has an important biological function for helix dimerization in several envelope glycoproteins from the family of Flaviviridae viruses.
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Zimmermann R, Eyrisch S, Ahmad M, Helms V. Protein translocation across the ER membrane. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:912-24. [PMID: 20599535 DOI: 10.1016/j.bbamem.2010.06.015] [Citation(s) in RCA: 176] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 06/11/2010] [Accepted: 06/14/2010] [Indexed: 01/02/2023]
Abstract
Protein translocation into the endoplasmic reticulum (ER) is the first and decisive step in the biogenesis of most extracellular and many soluble organelle proteins in eukaryotic cells. It is mechanistically related to protein export from eubacteria and archaea and to the integration of newly synthesized membrane proteins into the ER membrane and the plasma membranes of eubacteria and archaea (with the exception of tail anchored membrane proteins). Typically, protein translocation into the ER involves cleavable amino terminal signal peptides in precursor proteins and sophisticated transport machinery components in the cytosol, the ER membrane, and the ER lumen. Depending on the hydrophobicity and/or overall amino acid content of the precursor protein, transport can occur co- or posttranslationally. The respective mechanism determines the requirements for certain cytosolic transport components. The two mechanisms merge at the level of the ER membrane, specifically, at the heterotrimeric Sec61 complex present in the membrane. The Sec61 complex provides a signal peptide recognition site and forms a polypeptide conducting channel. Apparently, the Sec61 complex is gated by various ligands, such as signal peptides of the transport substrates, ribosomes (in cotranslational transport), and the ER lumenal molecular chaperone, BiP. Binding of BiP to the incoming polypeptide contributes to efficiency and unidirectionality of transport. Recent insights into the structure of the Sec61 complex and the comparison of the transport mechanisms and machineries in the yeast Saccharomyces cerevisiae, the human parasite Trypanosoma brucei, and mammals have various important mechanistic as well as potential medical implications. This article is part of a Special Issue entitled Protein translocation across or insertion into membranes.
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Affiliation(s)
- Richard Zimmermann
- Medical Biochemistry & Molecular Biology, Saarland University, D-66041 Homburg, Germany.
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