1
|
TMEΜ45B Interacts with Sindbis Virus Nsp1 and Nsp4 and Inhibits Viral Replication. J Virol 2022; 96:e0091922. [PMID: 35938871 PMCID: PMC9472651 DOI: 10.1128/jvi.00919-22] [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
Alphavirus infection induces the expression of type I interferons, which inhibit the viral replication by upregulating the expression of interferon-stimulated genes (ISGs). Identification and mechanistic studies of the antiviral ISGs help to better understand how the host controls viral infection and help to better understand the viral replication process. Here, we report that the ISG product TMEM45B inhibits the replication of Sindbis virus (SINV). TMEM45B is a transmembrane protein that was detected mainly in the trans-Golgi network, endosomes, and lysosomes but not obviously at the plasma membrane or endoplasmic reticulum. TMEM45B interacted with the viral nonstructural proteins Nsp1 and Nsp4 and inhibited the translation and promoted the degradation of SINV RNA. TMEM45B overexpression rendered the intracellular membrane-associated viral RNA sensitive to RNase treatment. In line with these results, the formation of cytopathic vacuoles (CPVs) was dramatically diminished in TMEM45B-expressing cells. TMEM45B also interacted with Nsp1 and Nsp4 of chikungunya virus (CHIKV), suggesting that it may also inhibit the replication of other alphaviruses. These findings identified TMEM45B as an antiviral factor against alphaviruses and help to better understand the process of the viral genome replication. IMPORTANCE Alphaviruses are positive-stranded RNA viruses with more than 30 members. Infection with Old World alphaviruses, which comprise some important human pathogens such as chikungunya virus and Ross River virus, rarely results in fatal diseases but can lead to high morbidity in humans. Infection with New World alphaviruses usually causes serious encephalitis but low morbidity in humans. Alphavirus infection induces the expression of type I interferons, which subsequently upregulate hundreds of interferon-stimulated genes. Identification and characterization of host antiviral factors help to better understand how the viruses can establish effective infection. Here, we identified TMEM45B as a novel interferon-stimulated antiviral factor against Sindbis virus, a prototype alphavirus. TMEM45B interacted with viral proteins Nsp1 and Nsp4, interfered with the interaction between Nsp1 and Nsp4, and inhibited the viral replication. These findings provide insights into the detailed process of the viral replication and help to better understand the virus-host interactions.
Collapse
|
2
|
Pinello JF, Clark TG. HAP2-Mediated Gamete Fusion: Lessons From the World of Unicellular Eukaryotes. Front Cell Dev Biol 2022; 9:807313. [PMID: 35071241 PMCID: PMC8777248 DOI: 10.3389/fcell.2021.807313] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 11/15/2021] [Indexed: 01/29/2023] Open
Abstract
Most, if not all the cellular requirements for fertilization and sexual reproduction arose early in evolution and are retained in extant lineages of single-celled organisms including a number of important model organism species. In recent years, work in two such species, the green alga, Chlamydomonas reinhardtii, and the free-living ciliate, Tetrahymena thermophila, have lent important new insights into the role of HAP2/GCS1 as a catalyst for gamete fusion in organisms ranging from protists to flowering plants and insects. Here we summarize the current state of knowledge around how mating types from these algal and ciliate systems recognize, adhere and fuse to one another, current gaps in our understanding of HAP2-mediated gamete fusion, and opportunities for applying what we know in practical terms, especially for the control of protozoan parasites.
Collapse
Affiliation(s)
- Jennifer F. Pinello
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, United States
| | - Theodore G. Clark
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY, United States
| |
Collapse
|
3
|
Glycan-dependent chikungunya viral infection divulged by antiviral activity of NAG specific chi-like lectin. Virology 2019; 526:91-98. [DOI: 10.1016/j.virol.2018.10.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Revised: 09/25/2018] [Accepted: 10/10/2018] [Indexed: 11/17/2022]
|
4
|
Tuekprakhon A, Puiprom O, Sasaki T, Michiels J, Bartholomeeusen K, Nakayama EE, Meno MK, Phadungsombat J, Huits R, Ariën KK, Luplertlop N, Shioda T, Leaungwutiwong P. Broad-spectrum monoclonal antibodies against chikungunya virus structural proteins: Promising candidates for antibody-based rapid diagnostic test development. PLoS One 2018; 13:e0208851. [PMID: 30557365 PMCID: PMC6296674 DOI: 10.1371/journal.pone.0208851] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Accepted: 11/23/2018] [Indexed: 11/19/2022] Open
Abstract
In response to the aggressive global spread of the mosquito-borne chikungunya virus (CHIKV), an accurate and accessible diagnostic tool is of high importance. CHIKV, an arthritogenic alphavirus, comprises three genotypes: East/Central/South African (ECSA), West African (WA), and Asian. A previous rapid immunochromatographic (IC) test detecting CHIKV E1 protein showed promising performance for detection of the ECSA genotype. Unfortunately, this kit exhibited lower capacity for detection of the Asian genotype, currently in circulation in the Americas, reflecting the low avidity of one of the monoclonal antibodies (mAbs) in this IC kit for the E1 protein of the Asian-genotype because of a variant amino acid sequence. To address this shortcoming, we set out to generate a new panel of broad-spectrum mouse anti-CHIKV mAbs using hybridoma technology. We report here the successful generation of mouse anti-CHIKV mAbs targeting CHIKV E1 and capsid proteins. These mAbs possessed broad reactivity to all three CHIKV genotypes, while most of the mAbs lacked cross-reactivity towards Sindbis, dengue, and Zika viruses. Two of the mAbs also lacked cross-reactivity towards other alphaviruses, including O'nyong-nyong, Ross River, Mayaro, Western Equine Encephalitis, Eastern Equine Encephalitis, and Venezuelan Equine Encephalitis viruses. In addition, another two mAbs cross-reacted weakly only with most closely related O'nyong-nyong virus. Effective diagnosis is one of the keys to disease control but to date, no antibody-based rapid IC platform for CHIKV is commercially available. Thus, the application of the mAbs characterized here in the rapid diagnostic IC kit for CHIKV detection is expected to be of great value for clinical diagnosis and surveillance purposes.
Collapse
Affiliation(s)
- Aekkachai Tuekprakhon
- Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Mahidol-Osaka Center for Infectious Diseases (MOCID), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Orapim Puiprom
- Mahidol-Osaka Center for Infectious Diseases (MOCID), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Tadahiro Sasaki
- Mahidol-Osaka Center for Infectious Diseases (MOCID), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Johan Michiels
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Koen Bartholomeeusen
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Emi E. Nakayama
- Mahidol-Osaka Center for Infectious Diseases (MOCID), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Research Institute for Microbial Diseases (RIMD), Osaka University, Osaka, Japan
| | - Michael K. Meno
- Mahidol-Osaka Center for Infectious Diseases (MOCID), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Juthamas Phadungsombat
- Mahidol-Osaka Center for Infectious Diseases (MOCID), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Ralph Huits
- Department of Clinical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Kevin K. Ariën
- Research Institute for Microbial Diseases (RIMD), Osaka University, Osaka, Japan
- Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
| | - Natthanej Luplertlop
- Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Tatsuo Shioda
- Mahidol-Osaka Center for Infectious Diseases (MOCID), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Research Institute for Microbial Diseases (RIMD), Osaka University, Osaka, Japan
- * E-mail: (TS); (PL)
| | - Pornsawan Leaungwutiwong
- Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- * E-mail: (TS); (PL)
| |
Collapse
|
5
|
Structure and interaction with lipid membrane models of Semliki Forest virus fusion peptide. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:2671-2680. [PMID: 27425030 PMCID: PMC7172313 DOI: 10.1016/j.bbamem.2016.07.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 06/21/2016] [Accepted: 07/12/2016] [Indexed: 11/24/2022]
Abstract
Semliki Forest virus (SFV) is a well-characterized alphavirus that infects cells via endocytosis and an acid-triggered fusion step using class II fusion proteins. Membrane fusion is mediated by the viral spike protein, a heterotrimer of two transmembrane subunits, E1 and E2, and a peripheral protein, E3. Sequence analysis of the E1 ectodomain of a number of alphaviruses demonstrated the presence of a highly conserved hydrophobic domain on the E1 ectodomain. This sequence was proposed to be the fusion peptide of SFV and is believed to be the domain of E1 that interacts with the target membrane and triggers fusion. Here, we investigate the structure and the interaction with lipid membrane models of 76YQCKVYTGVYPFMWGGAYCFC96 sequence from SFV, named SFV21, using optical method (ellipsometry) and vibrational spectroscopiy approaches (Polarization Modulation infra-Red Reflection Absorption Spectroscopy, PMIRRAS, and polarized ATR-FTIR). We demonstrate a structural flexibility of SFV21 sequence whether the lateral pressure and the lipid environment. In a lipid environment that mimics eukaryotic cell membranes, a conformational transition from an α-helix to a β-sheet is induced in the presence of lipid by increasing the peptide to lipid ratio, which leads to important perturbations in the membrane organisation. SFV21 fusion peptide displays structural flexibility between α-helix and β-sheets. A conformational transition from an α-helix to a β-sheet is induced by the increase of the peptide to lipid ratio. SFV21 fusion peptide leads to important perturbations in the membrane organisation.
Collapse
|
6
|
Abstract
Chikungunya virus (CHIKV) is a rapidly emerging mosquito-borne alphavirus causing millions of infections in the tropical and subtropical regions of the world. CHIKV infection often leads to an acute self-limited febrile illness with debilitating myalgia and arthralgia. A potential long-term complication of CHIKV infection is severe joint pain, which can last for months to years. There are no vaccines or specific therapeutics available to prevent or treat infection. This review describes the critical steps in CHIKV cell entry. We summarize the latest studies on the virus-cell tropism, virus-receptor binding, internalization, membrane fusion and review the molecules and compounds that have been described to interfere with virus cell entry. The aim of the review is to give the reader a state-of-the-art overview on CHIKV cell entry and to provide an outlook on potential new avenues in CHIKV research.
Collapse
|
7
|
Residue-level resolution of alphavirus envelope protein interactions in pH-dependent fusion. Proc Natl Acad Sci U S A 2015; 112:2034-9. [PMID: 25646410 DOI: 10.1073/pnas.1414190112] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Alphavirus envelope proteins, organized as trimers of E2-E1 heterodimers on the surface of the pathogenic alphavirus, mediate the low pH-triggered fusion of viral and endosomal membranes in human cells. The lack of specific treatment for alphaviral infections motivates our exploration of potential antiviral approaches by inhibiting one or more fusion steps in the common endocytic viral entry pathway. In this work, we performed constant pH molecular dynamics based on an atomic model of the alphavirus envelope with icosahedral symmetry. We have identified pH-sensitive residues that cause the largest shifts in thermodynamic driving forces under neutral and acidic pH conditions for various fusion steps. A series of conserved interdomain His residues is identified to be responsible for the pH-dependent conformational changes in the fusion process, and ligand binding sites in their vicinity are anticipated to be potential drug targets aimed at inhibiting viral infections.
Collapse
|
8
|
Exposure of epitope residues on the outer face of the chikungunya virus envelope trimer determines antibody neutralizing efficacy. J Virol 2014; 88:14364-79. [PMID: 25275138 DOI: 10.1128/jvi.01943-14] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
UNLABELLED Chikungunya virus (CHIKV) is a reemerging alphavirus that causes a debilitating arthritic disease and infects millions of people and for which no specific treatment is available. Like many alphaviruses, the structural targets on CHIKV that elicit a protective humoral immune response in humans are poorly defined. Here we used phage display against virus-like particles (VLPs) to isolate seven human monoclonal antibodies (MAbs) against the CHIKV envelope glycoproteins E2 and E1. One MAb, IM-CKV063, was highly neutralizing (50% inhibitory concentration, 7.4 ng/ml), demonstrated high-affinity binding (320 pM), and was capable of therapeutic and prophylactic protection in multiple animal models up to 24 h postexposure. Epitope mapping using a comprehensive shotgun mutagenesis library of 910 mutants with E2/E1 alanine mutations demonstrated that IM-CKV063 binds to an intersubunit conformational epitope on domain A, a functionally important region of E2. MAbs against the highly conserved fusion loop have not previously been reported but were also isolated in our studies. Fusion loop MAbs were broadly cross-reactive against diverse alphaviruses but were nonneutralizing. Fusion loop MAb reactivity was affected by temperature and reactivity conditions, suggesting that the fusion loop is hidden in infectious virions. Visualization of the binding sites of 15 different MAbs on the structure of E2/E1 revealed that all epitopes are located at the membrane-distal region of the E2/E1 spike. Interestingly, epitopes on the exposed topmost and outer surfaces of the E2/E1 trimer structure were neutralizing, whereas epitopes facing the interior of the trimer were not, providing a rationale for vaccine design and therapeutic MAb development using the intact CHIKV E2/E1 trimer. IMPORTANCE CHIKV is the most important alphavirus affecting humans, resulting in a chronic arthritic condition that can persist for months or years. In recent years, millions of people have been infected globally, and the spread of CHIKV to the Americas is now beginning, with over 100,000 cases occurring in the Caribbean within 6 months of its arrival. Our study reports on seven human MAbs against the CHIKV envelope, including a highly protective MAb and rarely isolated fusion loop MAbs. Epitope mapping of these MAbs demonstrates how some E2/E1 epitopes are exposed or hidden from the human immune system and suggests a structural mechanism by which these MAbs protect (or fail to protect) against CHIKV infection. Our results suggest that the membrane-distal end of CHIKV E2/E1 is the primary target for the humoral immune response to CHIKV, and antibodies targeting the exposed topmost and outer surfaces of the E2/E1 trimer determine the neutralizing efficacy of this response.
Collapse
|
9
|
Costin JM, Zaitseva E, Kahle KM, Nicholson CO, Rowe DK, Graham AS, Bazzone LE, Hogancamp G, Figueroa Sierra M, Fong RH, Yang ST, Lin L, Robinson JE, Doranz BJ, Chernomordik LV, Michael SF, Schieffelin JS, Isern S. Mechanistic study of broadly neutralizing human monoclonal antibodies against dengue virus that target the fusion loop. J Virol 2013; 87:52-66. [PMID: 23077306 PMCID: PMC3536401 DOI: 10.1128/jvi.02273-12] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Accepted: 10/10/2012] [Indexed: 11/20/2022] Open
Abstract
There are no available vaccines for dengue, the most important mosquito-transmitted viral disease. Mechanistic studies with anti-dengue virus (DENV) human monoclonal antibodies (hMAbs) provide a rational approach to identify and characterize neutralizing epitopes on DENV structural proteins that can serve to inform vaccine strategies. Here, we report a class of hMAbs that is likely to be an important determinant in the human humoral response to DENV infection. In this study, we identified and characterized three broadly neutralizing anti-DENV hMAbs: 4.8A, D11C, and 1.6D. These antibodies were isolated from three different convalescent patients with distinct histories of DENV infection yet demonstrated remarkable similarities. All three hMAbs recognized the E glycoprotein with high affinity, neutralized all four serotypes of DENV, and mediated antibody-dependent enhancement of infection in Fc receptor-bearing cells at subneutralizing concentrations. The neutralization activities of these hMAbs correlated with a strong inhibition of virus-liposome and intracellular fusion, not virus-cell binding. We mapped epitopes of these antibodies to the highly conserved fusion loop region of E domain II. Mutations at fusion loop residues W101, L107, and/or G109 significantly reduced the binding of the hMAbs to E protein. The results show that hMAbs directed against the highly conserved E protein fusion loop block viral entry downstream of virus-cell binding by inhibiting E protein-mediated fusion. Characterization of hMAbs targeting this region may provide new insights into DENV vaccine and therapeutic strategies.
Collapse
Affiliation(s)
- Joshua M. Costin
- Department of Biological Sciences, Florida Gulf Coast University, Fort Myers, Florida, USA
| | - Elena Zaitseva
- Section on Membrane Biology, Laboratory of Cellular and Molecular Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | | | - Cindo O. Nicholson
- Department of Biological Sciences, Florida Gulf Coast University, Fort Myers, Florida, USA
| | - Dawne K. Rowe
- Department of Biological Sciences, Florida Gulf Coast University, Fort Myers, Florida, USA
| | - Amanda S. Graham
- Department of Biological Sciences, Florida Gulf Coast University, Fort Myers, Florida, USA
| | - Lindsey E. Bazzone
- Section of Pediatric Infectious Disease, Department of Pediatrics, Tulane University School of Medicine, New Orleans, Louisiana, USA
| | - Greg Hogancamp
- Department of Biological Sciences, Florida Gulf Coast University, Fort Myers, Florida, USA
| | | | - Rachel H. Fong
- Integral Molecular, Inc., Philadelphia, Pennsylvania, USA
| | - Sung-Tae Yang
- Section on Membrane Biology, Laboratory of Cellular and Molecular Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Li Lin
- Communicable Disease Center, Tan Tock Seng Hospital, Singapore
| | - James E. Robinson
- Section of Pediatric Infectious Disease, Department of Pediatrics, Tulane University School of Medicine, New Orleans, Louisiana, USA
| | | | - Leonid V. Chernomordik
- Section on Membrane Biology, Laboratory of Cellular and Molecular Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Scott F. Michael
- Department of Biological Sciences, Florida Gulf Coast University, Fort Myers, Florida, USA
| | - John S. Schieffelin
- Section of Pediatric Infectious Disease, Department of Pediatrics, Tulane University School of Medicine, New Orleans, Louisiana, USA
| | - Sharon Isern
- Department of Biological Sciences, Florida Gulf Coast University, Fort Myers, Florida, USA
| |
Collapse
|
10
|
Abstract
The study of enveloped animal viruses has greatly advanced our understanding of the general properties of membrane fusion and of the specific pathways that viruses use to infect the host cell. The membrane fusion proteins of the alphaviruses and flaviviruses have many similarities in structure and function. As reviewed here, alphaviruses use receptor-mediated endocytic uptake and low pH-triggered membrane fusion to deliver their RNA genomes into the cytoplasm. Recent advances in understanding the biochemistry and structure of the alphavirus membrane fusion protein provide a clearer picture of this fusion reaction, including the protein’s conformational changes during fusion and the identification of key domains. These insights into the alphavirus fusion mechanism suggest new areas for experimental investigation and potential inhibitor strategies for anti-viral therapy.
Collapse
Affiliation(s)
- Margaret Kielian
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-718-430-3638; Fax: +1-718-430-8574
| | | | | |
Collapse
|
11
|
Abstract
In this report the basis for the structural architecture of the envelope of hantaviruses, family Bunyaviridae, is systematically studied by the interactions of two glycoproteins N and C (Gn and Gc, respectively) and their respective disulfide bridge-mediated homo- and heteromeric oligomerizations. In virion extracts Gn and Gc associated in both homo- and hetero-oligomers which were, at least partially, thiol bridge mediated. Due to strong homo-oligomerization, the hetero-oligomers of Gn and Gc are likely to be mediated by homo-oligomeric subunits. A reversible pH-induced disappearance of a neutralizing epitope in Gc and dissociation of the Gn-Gc complex at pH values below 6.2 provide proteochemical evidence for the fusogenicity of Gc. Incomplete inactivation of virions at acidic pH indicates that additional factors are required for hantavirus fusion, as in the case of pestiviruses of the Flaviviridae. Based on similarities to class II fusion proteins, a structure model was created of hantavirus Gc using the Semliki Forest virus E1 protein as a template. In total, 10 binding regions for Gn were found by peptide scanning, of which five represent homotypic (Gn(I) to Gn(V)) and five represent heterotypic (Gc(I) to Gc(V)) interaction sites that we assign as intra- and interspike connections, respectively. In conclusion, the glycoprotein associations were compiled to a model wherein the surface of hantaviruses is formed of homotetrameric Gn complexes interconnected with Gc homodimers. This organization would create the grid-like surface pattern described earlier for hantaviruses in negatively stained electron microscopy specimens.
Collapse
|
12
|
Jose J, Snyder JE, Kuhn RJ. A structural and functional perspective of alphavirus replication and assembly. Future Microbiol 2009; 4:837-56. [PMID: 19722838 DOI: 10.2217/fmb.09.59] [Citation(s) in RCA: 234] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Alphaviruses are small, spherical, enveloped, positive-sense ssRNA viruses responsible for a considerable number of human and animal diseases. Alphavirus members include Chikungunya virus, Sindbis virus, Semliki Forest virus, the western, eastern and Venezuelan equine encephalitis viruses, and the Ross River virus. Alphaviruses can cause arthritic diseases and encephalitis in humans and animals and continue to be a worldwide threat. The viruses are transmitted by blood-sucking arthropods, and replicate in both arthropod and vertebrate hosts. Alphaviruses form spherical particles (65-70 nm in diameter) with icosahedral symmetry and a triangulation number of four. The icosahedral structures of alphaviruses have been defined to very high resolutions by cryo-electron microscopy and crystallographic studies. In this review, we summarize the major events in alphavirus infection: entry, replication, assembly and budding. We focus on data acquired from structural and functional studies of the alphaviruses. These structural and functional data provide a broader perspective of the virus lifecycle and structure, and allow additional insight into these important viruses.
Collapse
Affiliation(s)
- Joyce Jose
- Department of Biological Sciences, Bindley Bioscience Center, Lilly Hall of Life Sciences, 915 West State St., Purdue University, West Lafayette, IN 47907, USA.
| | | | | |
Collapse
|
13
|
E1 mutants identify a critical region in the trimer interface of the Semliki forest virus fusion protein. J Virol 2009; 83:11298-306. [PMID: 19692469 DOI: 10.1128/jvi.01147-09] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The alphavirus Semliki Forest virus (SFV) uses a membrane fusion reaction to infect host cells. Fusion of the virus and cell membranes is triggered by low pH in the endosome and is mediated by the viral membrane protein E1. During fusion, E1 inserts into the target membrane, trimerizes, and refolds into a hairpin conformation. Formation of the E1 homotrimer is critical to membrane fusion, but the mechanism of trimerization is not understood. The crystal structure of the postfusion E1 trimer shows that an aspartate residue, D188, is positioned in the central core trimer interface. D188 is conserved in all reported alphavirus E1 sequences. We tested the contribution of this amino acid to trimerization and fusion by replacing D188 with alanine (D188A) or lysine (D188K) in an SFV infectious clone. These mutations were predicted to disrupt specific interactions at this position and/or change their pH dependence. Our results indicated that the D188K mutation blocked SFV fusion and infection. At low pH, D188K E1 inserted into target membranes but was trapped as a target membrane-inserted monomer that did not efficiently form the stable core trimer. In contrast, the D188A mutant was infectious, although trimerization and fusion required a lower pH. While there are extensive contacts between E1 subunits in the homotrimer, the D188K mutant identifies an important "hot spot" for protein-protein interactions within the core trimer.
Collapse
|
14
|
Wu SR, Haag L, Sjöberg M, Garoff H, Hammar L. The dynamic envelope of a fusion class II virus. E3 domain of glycoprotein E2 precursor in Semliki Forest virus provides a unique contact with the fusion protein E1. J Biol Chem 2008; 283:26452-60. [PMID: 18596032 DOI: 10.1074/jbc.m801470200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In alphaviruses, here represented by Semliki Forest virus, infection requires an acid-responsive spike configuration to facilitate membrane fusion. The creation of this relies on the chaperone function of glycoprotein E2 precursor (p62) and its maturation cleavage into the small external E3 and the membrane-anchored E2 glycoproteins. To reveal how the E3 domain of p62 exerts its control of spike functions, we determine the structure of a p62 cleavage-impaired mutant virus particle (SQL) by electron cryomicroscopy. A comparison with the earlier solved wild type virus structure reveals that the E3 domain of p62(SQL) forms a bulky side protrusion in the spike head region. This establishes a gripper over part of domain II of the fusion protein, with a cotter-like connection downward to a hydrophobic cluster in its central beta-sheet. This finding reevaluates the role of the precursor from being only a provider of a shield over the fusion loop to a structural playmate in formation of the fusogenic architecture.
Collapse
Affiliation(s)
- Shang-Rung Wu
- Department of Biosciences and Nutrition, Karolinska Institutet, SE-14157 Huddinge, Sweden.
| | | | | | | | | |
Collapse
|
15
|
Wu SR, Haag L, Hammar L, Wu B, Garoff H, Xing L, Murata K, Cheng RH. The dynamic envelope of a fusion class II virus. Prefusion stages of semliki forest virus revealed by electron cryomicroscopy. J Biol Chem 2006; 282:6752-62. [PMID: 17192272 DOI: 10.1074/jbc.m609125200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Semliki Forest virus is among the prototypes for Class II virus fusion and targets the endosomal membrane. Fusion protein E1 and its envelope companion E2 are both anchored in the viral membrane and form an external shell with protruding spikes. In acid environments, mimicking the early endosomal milieu, surface epitopes in the virus rearrange along with exposure of the fusion loop. To visualize this transformation into a fusogenic stage, we determined the structure of the virus at gradually lower pH values. The results show that while the fusion loop is available for external interaction and the shell and stalk domains of the spike begin to deteriorate, the E1 and E2 remain in close contact in the spike head. This unexpected observation points to E1 and E2 cooperation beyond the fusion loop exposure stage and implies a more prominent role for E2 in guiding membrane close encounter than has been earlier anticipated.
Collapse
Affiliation(s)
- Shang-Rung Wu
- Department of Biosciences and Nutrition, Karolinska Institutet, S-141 57 Huddinge, Sweden.
| | | | | | | | | | | | | | | |
Collapse
|
16
|
Moser R, Snyers L, Wruss J, Angulo J, Peters H, Peters T, Blaas D. Neutralization of a common cold virus by concatemers of the third ligand binding module of the VLDL-receptor strongly depends on the number of modules. Virology 2005; 338:259-69. [PMID: 15950998 DOI: 10.1016/j.virol.2005.05.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Revised: 04/22/2005] [Accepted: 05/13/2005] [Indexed: 10/25/2022]
Abstract
Concatemers of various numbers of the third ligand binding repeat of human very-low density lipoprotein receptor arranged in tandem were fused to maltose-binding protein and expressed as soluble polypeptides. These artificial receptors protected HeLa cells against infection with human rhinovirus serotype 2 (HRV2) to a degree that strongly increased with the number of repeats present; maximal protection was seen for the pentameric concatemer (MBP-V33333). This V3 pentamer neutralized HRV2 more efficiently than a recombinant protein with the entire ligand binding domain of the native receptor encompassing all 8 non-identical repeats. A concatemer of seven V3 modules (MBP-V3333333) was also less neutralizing. Neutralization was correlated with the degree of inhibition of virus binding to the cell surface. The results were in agreement with kinetic measurements using Biacore instrumentation demonstrating an increase in avidity with the number of modules present. At low concentrations of the receptor fragments, a 1:1 Langmuir kinetics was observed which became of complex type in the higher concentration range. This is most likely a consequence of receptor molecules simultaneously binding via several modules. Since there is no viral aggregation, neutralization of viral infectivity results from blockage of the receptor binding sites and possibly from inhibition of viral uncoating by crosslinking the viral capsid subunits via multi-module binding. Finally, the low affinity of the single V3 module allowed demonstrating the possibility of mapping the binding epitope of the V3 receptor fragment by saturation transfer difference nuclear magnetic resonance methodology.
Collapse
Affiliation(s)
- Rosita Moser
- Max F. Perutz Laboratories, University Departments at the Vienna Biocenter, Department of Medical Biochemistry, Medical University of Vienna, Dr. Bohr Gasse 9/3, A-1030 Vienna, Austria
| | | | | | | | | | | | | |
Collapse
|
17
|
Waarts BL, Smit JM, Aneke OJC, McInerney GM, Liljeström P, Bittman R, Wilschut J. Reversible acid-induced inactivation of the membrane fusion protein of Semliki Forest virus. J Virol 2005; 79:7942-8. [PMID: 15919953 PMCID: PMC1143635 DOI: 10.1128/jvi.79.12.7942-7948.2005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously, it has been shown that the exposure of Semliki Forest virus (SFV) to a mildly acidic environment induces a rapid and complete loss of the ability of the virus to bind and fuse to target membranes added subsequently. In the present study, incubation of SFV at low pH followed by a specific reneutralization step resulted in a partial reversion of this loss of viral fusion capacity, as assessed in a liposomal model system. Also, the ability of the viral E1 fusion protein to undergo liposome-stimulated trimerization was restored. Furthermore, acid-treated and neutralized SFV largely retained infectivity. Exposure of SFV to low pH induced dissociation of the E1/E2 heterodimer, which was not reversed upon neutralization. It is concluded that the SFV E1 fusion protein, after acid-induced dissociation from E2, rapidly adopts an intermediate, nontrimeric conformation in which it is no longer able to interact with target membrane lipids. Neutralization restores the ability of E1 to interact with membranes. This interaction, however, remains strictly dependent on low pH.
Collapse
Affiliation(s)
- Barry-Lee Waarts
- Department of Medical Microbiology, Molecular Virology Section, University Medical Center Groningen, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | | | | | | | | | | | | |
Collapse
|
18
|
La Linn M, Eble JA, Lübken C, Slade RW, Heino J, Davies J, Suhrbier A. An arthritogenic alphavirus uses the α1β1 integrin collagen receptor. Virology 2005; 336:229-39. [PMID: 15892964 DOI: 10.1016/j.virol.2005.03.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2004] [Revised: 01/03/2005] [Accepted: 03/15/2005] [Indexed: 01/23/2023]
Abstract
Ross River (RR) virus is an alphavirus endemic to Australia and New Guinea and is the aetiological agent of epidemic polyarthritis or RR virus disease. Here we provide evidence that RR virus uses the collagen-binding alpha1beta1 integrin as a cellular receptor. Infection could be inhibited by collagen IV and antibodies specific for the beta1 and alpha1 integrin proteins, and fibroblasts from alpha1-integrin-/- mice were less efficiently infected than wild-type fibroblasts. Soluble alpha1beta1 integrin bound immobilized RR virus, and peptides representing the alpha1beta1 integrin binding-site on collagen IV inhibited virus binding to cells. We speculate that two highly conserved regions within the cell-receptor binding domain of E2 mimic collagen and provide access to cellular collagen-binding receptors.
Collapse
Affiliation(s)
- May La Linn
- The Australian Centre for International and Tropical Health and Nutrition, Brisbane, Queensland, Australia
| | | | | | | | | | | | | |
Collapse
|
19
|
Abstract
In the year 2003 there was a 17% increase in the number of publications citing work performed using optical biosensor technology compared with the previous year. We collated the 962 total papers for 2003, identified the geographical regions where the work was performed, highlighted the instrument types on which it was carried out, and segregated the papers by biological system. In this overview, we spotlight 13 papers that should be on everyone's 'must read' list for 2003 and provide examples of how to identify and interpret high-quality biosensor data. Although we still find that the literature is replete with poorly performed experiments, over-interpreted results and a general lack of understanding of data analysis, we are optimistic that these shortcomings will be addressed as biosensor technology continues to mature.
Collapse
Affiliation(s)
- Rebecca L Rich
- Center for Biomolecular Interaction Analysis, University of Utah, Salt Lake City, UT 84132, USA
| | | |
Collapse
|
20
|
Chanel-Vos C, Kielian M. A conserved histidine in the ij loop of the Semliki Forest virus E1 protein plays an important role in membrane fusion. J Virol 2004; 78:13543-52. [PMID: 15564465 PMCID: PMC533937 DOI: 10.1128/jvi.78.24.13543-13552.2004] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The enveloped alphavirus Semliki Forest virus (SFV) infects cells via a low pH-triggered membrane fusion reaction mediated by the E1 protein. E1 is a class II fusion protein that contains the hydrophobic fusion peptide loop and converts to a stable homotrimer during the fusion reaction. Intriguingly, the fusion loop is closely associated with a loop connecting the i and j beta-strands. This ij loop plays a role in the cholesterol dependence of membrane fusion and is specifically susceptible to proteolysis in the protease-resistant E1 homotrimer. The SFV ij loop contains a histidine residue at position 230. Sequence comparisons revealed that an analogous histidine is completely conserved in all alphavirus and flavivirus fusion proteins. An E1 H230A mutant was constructed using the SFV infectious clone. Although cells infected with H230A RNA produced virus particles, these virions were completely noninfectious and were blocked in both cell-cell fusion and lipid mixing assays. The H230A virions efficiently bound to cell surface receptors and responded to low pH by undergoing acid-dependent conformational changes including dissociation of the E1/E2 dimer, exposure of the fusion loop, association with target liposomes, exposure of acid-conformation-specific epitopes, and formation of the stable E1 homotrimer. Studies with a soluble fragment of E1 showed that the mutant protein was defective in lipid-dependent conformational changes. Our results indicate that the E1 ij loop and the conserved H230 residue play a critical role in alphavirus-membrane fusion and suggest the presence of a previously undescribed late intermediate in the fusion reaction.
Collapse
Affiliation(s)
- Chantal Chanel-Vos
- Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
| | | |
Collapse
|
21
|
Ferracci G, Seagar M, Joël C, Miquelis R, Lévêque C. Real time analysis of intact organelles using surface plasmon resonance. Anal Biochem 2004; 334:367-75. [PMID: 15494144 DOI: 10.1016/j.ab.2004.08.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2004] [Indexed: 10/26/2022]
Abstract
Membrane proteins remain refractory to standard protein chip analysis. They are typically expressed at low densities in distinct subcellular compartments, their biological activity can depend on assembly into macromolecular complexes in a specific lipid environment. We report here a real-time, label-free method to analyze membrane proteins inserted in isolated native synaptic vesicles. Using surface plasmon resonance-based biomolecular interaction analysis (Biacore), organelle capture from minute quantities of 10,000 g brain supernatant (1-10 microg) was monitored. Immunological and morphological characterization indicated that pure intact synaptic vesicles were immobilized on sensor chips. Vesicle chips were stable for days, allowing repetitive use with multiple analytes. This method provides an efficient way in which to characterize organelle membrane components in their native context. Organelle chips allow a broad range of measurements, including interactions of exogenous ligands with the organelle surface (kinetics, Kd), and protein profiling.
Collapse
Affiliation(s)
- Géraldine Ferracci
- Unité de Méthodologie des Interactions Moléculaires, Institut Jean Roche, Faculté de Médecine secteur Nord, 13916 Marseille, France
| | | | | | | | | |
Collapse
|
22
|
Gibbons DL, Ahn A, Liao M, Hammar L, Cheng RH, Kielian M. Multistep regulation of membrane insertion of the fusion peptide of Semliki Forest virus. J Virol 2004; 78:3312-8. [PMID: 15016852 PMCID: PMC371068 DOI: 10.1128/jvi.78.7.3312-3318.2004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A prevailing model for virus membrane fusion proteins has been that the hydrophobic fusion peptide is hidden in the prefusion conformation, becomes exposed once the fusion reaction is triggered, and then either inserts into target membranes or is rapidly inactivated. This model is in general agreement with the structure and mechanism of class I fusion proteins, such as the influenza virus hemagglutinin. We here describe studies of the class II fusion protein E1 from the alphavirus Semliki Forest virus (SFV). SFV fusion is triggered by low pH, which releases E1 from its heterodimeric interaction with the E2 protein and induces the formation of a stable E1 homotrimer. The exposure and target membrane interaction of the E1 fusion peptide (residues 83 to 100) were followed using a monoclonal antibody (MAb E1f) mapping to E1 residues 85 to 95. In agreement with the known structure of SFV and other alphaviruses, the fusion peptide was shielded in native SFV particles and exposed when E1-E2 dimer dissociation was triggered by acidic pH. In contrast, the fusion peptide on purified E1 ectodomains (E1(*)) was fully accessible at neutral pH. Functional assays showed that MAb E1f binding at neutral pH prevented subsequent low-pH-triggered E1(*) interaction with target membranes and trimerization. E1(*) was not inactivated by low pH when treated either in the absence of target membranes or in the presence of fusion-inactive cholesterol-deficient liposomes. Thus, the membrane insertion of the E1 fusion peptide is regulated by additional low-pH-dependent steps after exposure, perhaps involving an E1-cholesterol interaction.
Collapse
Affiliation(s)
- Don L Gibbons
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
| | | | | | | | | | | |
Collapse
|