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Skidmore AM, Bradfute SB. The life cycle of the alphaviruses: From an antiviral perspective. Antiviral Res 2023; 209:105476. [PMID: 36436722 PMCID: PMC9840710 DOI: 10.1016/j.antiviral.2022.105476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 11/18/2022] [Accepted: 11/21/2022] [Indexed: 11/27/2022]
Abstract
The alphaviruses are a widely distributed group of positive-sense, single stranded, RNA viruses. These viruses are largely arthropod-borne and can be found on all populated continents. These viruses cause significant human disease, and recently have begun to spread into new populations, such as the expansion of Chikungunya virus into southern Europe and the Caribbean, where it has established itself as endemic. The study of alphaviruses is an active and expanding field, due to their impacts on human health, their effects on agriculture, and the threat that some pose as potential agents of biological warfare and terrorism. In this systematic review we will summarize both historic knowledge in the field as well as recently published data that has potential to shift current theories in how alphaviruses are able to function. This review is comprehensive, covering all parts of the alphaviral life cycle as well as a brief overview of their pathology and the current state of research in regards to vaccines and therapeutics for alphaviral disease.
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Affiliation(s)
- Andrew M Skidmore
- Center for Global Health, Department of Internal Medicine, University of New Mexico Health Sciences Center, 915 Camino de Salud, IDTC Room 3245, Albuquerque, NM, 87131, USA.
| | - Steven B Bradfute
- Center for Global Health, Department of Internal Medicine, University of New Mexico Health Sciences Center, 915 Camino de Salud, IDTC Room 3330A, Albuquerque, NM, 87131, USA.
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2
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Wang H, Wang Z, Liu Z, Wang K, Xu W. Membrane disruption of Fusarium oxysporum f. sp. niveum induced by myriocin from Bacillus amyloliquefaciens LZN01. Microb Biotechnol 2021; 14:517-534. [PMID: 32954686 PMCID: PMC7936314 DOI: 10.1111/1751-7915.13659] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Revised: 08/10/2020] [Accepted: 08/14/2020] [Indexed: 12/28/2022] Open
Abstract
Myriocin, which is produced by Bacillus amyloliquefaciens LZN01, can inhibit the growth of Fusarium oxysporum f. sp. niveum (Fon). In the present study, the antifungal mechanism of myriocin against Fon was investigated with a focus on the effects of myriocin on the cell membrane. Myriocin decreased the membrane fluidity and destroyed the membrane integrity of Fon. Significant microscopic morphological changes, including conidial shrinkage, the appearance of larger vacuoles and inhomogeneity of electron density, were observed in myriocin-treated cells. A membrane-targeted mechanism of action was also supported by transcriptomic and proteomic analyses; a total of 560 common differentially expressed genes (DEGs) and 285 common differentially expressed proteins (DEPs) were identified. The DEGs were further verified by using RT-qPCR. The combined analysis between the transcriptome and proteome revealed that the expression of some membrane-related genes and proteins, mainly those related to sphingolipid metabolism, glycerophospholipid metabolism, steroid biosynthesis, ABC transporters and protein processing in the endoplasmic reticulum, was disordered. Myriocin affected the serine palmitoyl transferase (SPT) activity as evidenced through molecular docking. Our results indicate that myriocin has significant antifungal activity owing to its ability to induce membrane damage in Fon.
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Affiliation(s)
- Hengxu Wang
- College of Life Science and AgroforestryQiqihar UniversityQiqihar161006China
- Key Laboratory of Urban AgricultureMinistry of Agriculture and Rural AffairsShanghai200240China
- Heilongjiang Provincial Technology Innovation Center of Agromicrobial Preparation IndustrializationQiqihar161006China
| | - Zhigang Wang
- College of Life Science and AgroforestryQiqihar UniversityQiqihar161006China
- Key Laboratory of Urban AgricultureMinistry of Agriculture and Rural AffairsShanghai200240China
- Heilongjiang Provincial Technology Innovation Center of Agromicrobial Preparation IndustrializationQiqihar161006China
| | - Zeping Liu
- College of Life Science and AgroforestryQiqihar UniversityQiqihar161006China
- Heilongjiang Provincial Technology Innovation Center of Agromicrobial Preparation IndustrializationQiqihar161006China
| | - Kexin Wang
- College of Life Science and AgroforestryQiqihar UniversityQiqihar161006China
- Heilongjiang Provincial Technology Innovation Center of Agromicrobial Preparation IndustrializationQiqihar161006China
| | - Weihui Xu
- College of Life Science and AgroforestryQiqihar UniversityQiqihar161006China
- Key Laboratory of Urban AgricultureMinistry of Agriculture and Rural AffairsShanghai200240China
- Heilongjiang Provincial Technology Innovation Center of Agromicrobial Preparation IndustrializationQiqihar161006China
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3
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Yan H, Lu Y, Li X, Yi Y, Wang X, Shan Y, Liu B, Zhou Y, Lü X. Action mode of bacteriocin BM1829 against Escherichia coli and Staphylococcus aureus. FOOD BIOSCI 2021. [DOI: 10.1016/j.fbio.2020.100794] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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4
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Characterization of antibacterial activity and mechanisms of two linear derivatives of bactenecin. Lebensm Wiss Technol 2019. [DOI: 10.1016/j.lwt.2019.02.073] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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5
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Vdovikova S, Luhr M, Szalai P, Nygård Skalman L, Francis MK, Lundmark R, Engedal N, Johansson J, Wai SN. A Novel Role of Listeria monocytogenes Membrane Vesicles in Inhibition of Autophagy and Cell Death. Front Cell Infect Microbiol 2017; 7:154. [PMID: 28516064 PMCID: PMC5413512 DOI: 10.3389/fcimb.2017.00154] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 04/12/2017] [Indexed: 11/13/2022] Open
Abstract
Bacterial membrane vesicle (MV) production has been mainly studied in Gram-negative species. In this study, we show that Listeria monocytogenes, a Gram-positive pathogen that causes the food-borne illness listeriosis, produces MVs both in vitro and in vivo. We found that a major virulence factor, the pore-forming hemolysin listeriolysin O (LLO), is tightly associated with the MVs, where it resides in an oxidized, inactive state. Previous studies have shown that LLO may induce cell death and autophagy. To monitor possible effects of LLO and MVs on autophagy, we performed assays for LC3 lipidation and LDH sequestration as well as analysis by confocal microscopy of HEK293 cells expressing GFP-LC3. The results revealed that MVs alone did not affect autophagy whereas they effectively abrogated autophagy induced by pure LLO or by another pore-forming toxin from Vibrio cholerae, VCC. Moreover, Listeria monocytogenes MVs significantly decreased Torin1-stimulated macroautophagy. In addition, MVs protected against necrosis of HEK293 cells caused by the lytic action of LLO. We explored the mechanisms of LLO-induced autophagy and cell death and demonstrated that the protective effect of MVs involves an inhibition of LLO-induced pore formation resulting in inhibition of autophagy and the lytic action on eukaryotic cells. Further, we determined that these MVs help bacteria to survive inside eukaryotic cells (mouse embryonic fibroblasts). Taken together, these findings suggest that intracellular release of MVs from L. monocytogenes may represent a bacterial strategy to survive inside host cells, by its control of LLO activity and by avoidance of destruction from the autophagy system during infection.
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Affiliation(s)
- Svitlana Vdovikova
- Department of Molecular Biology, Umeå UniversityUmeå, Sweden.,Laboratory for Molecular Infection Medicine Sweden, Umeå UniversityUmeå, Sweden.,Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
| | - Morten Luhr
- Centre for Molecular Medicine Norway, Nordic EMBL Partnership, University of OsloOslo, Norway
| | - Paula Szalai
- Centre for Molecular Medicine Norway, Nordic EMBL Partnership, University of OsloOslo, Norway
| | - Lars Nygård Skalman
- Laboratory for Molecular Infection Medicine Sweden, Umeå UniversityUmeå, Sweden.,Department of Medical Biochemistry and Biophysics, Umeå UniversityUmeå, Sweden
| | - Monika K Francis
- Laboratory for Molecular Infection Medicine Sweden, Umeå UniversityUmeå, Sweden.,Department of Medical Biochemistry and Biophysics, Umeå UniversityUmeå, Sweden
| | - Richard Lundmark
- Laboratory for Molecular Infection Medicine Sweden, Umeå UniversityUmeå, Sweden.,Department of Medical Biochemistry and Biophysics, Umeå UniversityUmeå, Sweden.,Department of Integrative Medical Biology, Umeå UniversityUmeå, Sweden
| | - Nikolai Engedal
- Centre for Molecular Medicine Norway, Nordic EMBL Partnership, University of OsloOslo, Norway
| | - Jörgen Johansson
- Department of Molecular Biology, Umeå UniversityUmeå, Sweden.,Laboratory for Molecular Infection Medicine Sweden, Umeå UniversityUmeå, Sweden.,Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
| | - Sun N Wai
- Department of Molecular Biology, Umeå UniversityUmeå, Sweden.,Laboratory for Molecular Infection Medicine Sweden, Umeå UniversityUmeå, Sweden.,Umeå Centre for Microbial Research, Umeå UniversityUmeå, Sweden
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Lee W, Lee DG. Fungicidal mechanisms of the antimicrobial peptide Bac8c. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:673-9. [PMID: 25434926 DOI: 10.1016/j.bbamem.2014.11.024] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Revised: 11/10/2014] [Accepted: 11/20/2014] [Indexed: 10/24/2022]
Abstract
Bac8c (RIWVIWRR-NH2) is an analogue peptide derived through complete substitution analysis of the linear bovine host defense peptide variant Bac2A. In the present study, the antifungal mechanism of Bac8c against pathogenic fungi was investigated, with a particular focus on the effects of Bac8c on the cytoplasmic membrane. We used bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC4(3)] staining and 3,3'-dipropylthiacarbocyanine iodide [DiSC3(5)] assays to show that Bac8c induced disturbances in the membrane potential of Candida albicans. An increase in membrane permeability and suppression of cell wall regeneration were also observed in Bac8c-treated C. albicans. We studied the effects of Bac8c treatment on model membranes to elucidate its antifungal mechanism. Using calcein and FITC-labeled dextran leakage assays from Bac8c-treated large unilamellar vesicles (LUVs) and giant unilamellar vesicles (GUVs), we found that Bac8c has a pore-forming action on fungal membranes, with an estimated pore radius of between 2.3 and 3.3 nm. A membrane-targeted mechanism of action was also supported by the observation of potassium release from the cytosol of Bac8c-treated C. albicans. These results indicate that Bac8c is considered as a potential candidate to develop a novel antimicrobial agent because of its low-cost production characteristics and high antimicrobial activity via its ability to induce membrane perturbations in fungi.
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Affiliation(s)
- Wonyoung Lee
- School of Life Sciences, BK 21 Plus KNU Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daehak-ro 80, Buk-gu, Daegu 702-701, Republic of Korea
| | - Dong Gun Lee
- School of Life Sciences, BK 21 Plus KNU Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Daehak-ro 80, Buk-gu, Daegu 702-701, Republic of Korea.
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Lee H, Choi H, Ko HJ, Woo ER, Lee DG. Antifungal effect and mode of action of glochidioboside against Candida albicans membranes. Biochem Biophys Res Commun 2014; 444:30-5. [DOI: 10.1016/j.bbrc.2014.01.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 01/06/2014] [Indexed: 01/05/2023]
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8
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Choi H, Hwang JS, Lee DG. Antifungal effect and pore-forming action of lactoferricin B like peptide derived from centipede Scolopendra subspinipes mutilans. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2745-50. [DOI: 10.1016/j.bbamem.2013.07.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 06/28/2013] [Accepted: 07/12/2013] [Indexed: 11/13/2022]
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9
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Barbour A, Philip K, Muniandy S. Enhanced production, purification, characterization and mechanism of action of salivaricin 9 lantibiotic produced by Streptococcus salivarius NU10. PLoS One 2013; 8:e77751. [PMID: 24147072 PMCID: PMC3797685 DOI: 10.1371/journal.pone.0077751] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 09/06/2013] [Indexed: 01/28/2023] Open
Abstract
Background Lantibiotics are small lanthionine-containing bacteriocins produced by lactic acid bacteria. Salivaricin 9 is a newly discovered lantibiotic produced by Streptococcus salivarius. In this study we present the mechanism of action of salivaricin 9 and some of its properties. Also we developed new methods to produce and purify the lantibiotic from strain NU10. Methodology / Principal Findings Salivaricin 9 was found to be auto-regulated when an induction assay was applied and this finding was used to develop a successful salivaricin 9 production system in liquid medium. A combination of XAD-16 and cation exchange chromatography was used to purify the secondary metabolite which was shown to have a molecular weight of approximately 3000 Da by SDS-PAGE. MALDI-TOF MS analysis indicated the presence of salivaricin 9, a 2560 Da lantibiotic. Salivaricin 9 is a bactericidal molecule targeting the cytoplasmic membrane of sensitive cells. The membrane permeabilization assay showed that salivaricin 9 penetrated the cytoplasmic membrane and induced pore formation which resulted in cell death. The morphological changes of test bacterial strains incubated with salivaricin 9 were visualized using Scanning Electron Microscopy which confirmed a pore forming mechanism of inhibition. Salivaricin 9 retained biological stability when exposed to high temperature (90-100°C) and stayed bioactive at pH ranging 2 to 10. When treated with proteinase K or peptidase, salivaricin 9 lost all antimicrobial activity, while it remained active when treated with lyticase, catalase and certain detergents. Conclusion The mechanism of antimicrobial action of a newly discovered lantibiotic salivaricin 9 was elucidated in this study. Salivaricin 9 penetrated the cytoplasmic membrane of its targeted cells and induced pore formation. This project has given new insights on lantibiotic peptides produced by S. salivarius isolated from the oral cavities of Malaysian subjects.
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Affiliation(s)
- Abdelahhad Barbour
- Institute of Biological Sciences, Microbiology Division, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia
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Lee RCH, Hapuarachchi HC, Chen KC, Hussain KM, Chen H, Low SL, Ng LC, Lin R, Ng MML, Chu JJH. Mosquito cellular factors and functions in mediating the infectious entry of chikungunya virus. PLoS Negl Trop Dis 2013; 7:e2050. [PMID: 23409203 PMCID: PMC3567007 DOI: 10.1371/journal.pntd.0002050] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Accepted: 12/19/2012] [Indexed: 12/01/2022] Open
Abstract
Chikungunya virus (CHIKV) is an arthropod-borne virus responsible for recent epidemics in the Asia Pacific regions. A customized gene expression microarray of 18,760 transcripts known to target Aedes mosquito genome was used to identify host genes that are differentially regulated during the infectious entry process of CHIKV infection on C6/36 mosquito cells. Several genes such as epsin I (EPN1), epidermal growth factor receptor pathway substrate 15 (EPS15) and Huntingtin interacting protein I (HIP1) were identified to be differentially expressed during CHIKV infection and known to be involved in clathrin-mediated endocytosis (CME). Transmission electron microscopy analyses further revealed the presence of CHIKV particles within invaginations of the plasma membrane, resembling clathrin-coated pits. Characterization of vesicles involved in the endocytic trafficking processes of CHIKV revealed the translocation of the virus particles to the early endosomes and subsequently to the late endosomes and lysosomes. Treatment with receptor-mediated endocytosis inhibitor, monodansylcadaverine and clathrin-associated drug inhibitors, chlorpromazine and dynasore inhibited CHIKV entry, whereas no inhibition was observed with caveolin-related drug inhibitors. Inhibition of CHIKV entry upon treatment with low-endosomal pH inhibitors indicated that low pH is essential for viral entry processes. CHIKV entry by clathrin-mediated endocytosis was validated via overexpression of a dominant-negative mutant of Eps15, in which infectious entry was reduced, while siRNA-based knockdown of genes associated with CME, low endosomal pH and RAB trafficking proteins exhibited significant levels of CHIKV inhibition. This study revealed, for the first time, that the infectious entry of CHIKV into mosquito cells is mediated by the clathrin-dependent endocytic pathway. Deciphering the much neglected aspects of cellular factors in contributing to the infectious entry of CHIKV into mosquito cells may enhance our understanding of the conservation or diversity of these host factors amongst mammalian and arthropod for successful CHIKV replication. The study revealed that the infectious entry of chikungunya virus (CHIKV) into mosquito cells is mediated by the clathrin-dependent endocytic pathway. A customized gene expression microarray known to target the Aedes mosquito genome was used to identify host genes that are differentially regulated upon CHIKV infection. A combination of bio-imaging studies and pharmacological inhibitors confirmed the involvement of clathrin-mediated endocytosis as well as the importance of low endosomal pH during CHIKV infectious entry. Furthermore, the clathrin heavy chain, Eps15, RAB5, RAB7 and vacuolar ATPase B are shown to be essential for the infectious entry process of CHIKV. This study aims to underline the importance of cellular factors, particularly those associated with clathrin-dependent endocytosis, in mediating the infectious entry of CHIKV into mosquito cells.
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Affiliation(s)
- Regina Ching Hua Lee
- Laboratory of Molecular RNA Virology and Antiviral Strategies, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, Singapore
| | | | - Karen Caiyun Chen
- Laboratory of Molecular RNA Virology and Antiviral Strategies, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, Singapore
| | - Khairunnisa' Mohamed Hussain
- Laboratory of Molecular RNA Virology and Antiviral Strategies, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, Singapore
| | - Huixin Chen
- Laboratory of Molecular RNA Virology and Antiviral Strategies, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, Singapore
| | - Swee Ling Low
- Enviromental Health Institute, National Environmental Agency, Singapore, Singapore
| | - Lee Ching Ng
- Enviromental Health Institute, National Environmental Agency, Singapore, Singapore
| | - Raymond Lin
- National Public Health Laboratory, Ministry of Health, Singapore, Singapore
| | - Mary Mah-Lee Ng
- Flavivirology Laboratory, Department of Microbiology, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, Singapore
| | - Justin Jang Hann Chu
- Laboratory of Molecular RNA Virology and Antiviral Strategies, Yong Loo Lin School of Medicine, National University Health System, National University of Singapore, Singapore, Singapore
- * E-mail:
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Replication of alphaviruses: a review on the entry process of alphaviruses into cells. Adv Virol 2011; 2011:249640. [PMID: 22312336 PMCID: PMC3265296 DOI: 10.1155/2011/249640] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 05/03/2011] [Indexed: 02/04/2023] Open
Abstract
Alphaviruses are small, enveloped viruses, ~70 nm in diameter, containing a single-stranded, positive-sense, RNA genome. Viruses belonging to this genus are predominantly arthropod-borne viruses, known to cause disease in humans. Their potential threat to human health was most recently exemplified by the 2005 Chikungunya virus outbreak in La Reunion, highlighting the necessity to understand events in the life-cycle of these medically important human pathogens. The replication and propagation of viruses is dependent on entry into permissive cells. Viral entry is initiated by attachment of virions to cells, leading to internalization, and uncoating to release genetic material for replication and propagation. Studies on alphaviruses have revealed entry via a receptor-mediated, endocytic pathway. In this paper, the different stages of alphavirus entry are examined, with examples from Semliki Forest virus, Sindbis virus, Chikungunya virus, and Venezuelan equine encephalitis virus described.
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Lee J, Hwang JS, Hwang B, Kim JK, Kim SR, Kim Y, Lee DG. Influence of the papiliocin peptide derived from Papilio xuthus on the perturbation of fungal cell membranes. FEMS Microbiol Lett 2010; 311:70-5. [DOI: 10.1111/j.1574-6968.2010.02073.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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13
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The regulation of disassembly of alphavirus cores. Arch Virol 2009; 154:381-90. [PMID: 19225713 DOI: 10.1007/s00705-009-0333-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 01/22/2009] [Indexed: 10/21/2022]
Abstract
Alphaviruses are used as model viruses for structure determination and for analysis of virus entry. They are used also as vectors for protein expression and gene therapy. Virus particles are assembled by budding, using preformed cores and a modified cellular membrane. During entry, alphaviruses release the viral core into the cytoplasm. Cores are disassembled during virus entry and accumulate in the cytoplasm during virus multiplication. The regulation of core disassembly is the subject of this review. A working model compatible with all experimental data is formulated. This model comprises the following steps: (1) The incoming core is present in the cytoplasm in a metastable state, primed for disassembly. A core structure containing the so-called linker region of the core protein in an exposed position susceptible to proteolytic cleavage on the core surface might represent the primed state. (2) The primed core allows access of cellular proteins to the viral genome RNA, e.g. initiation factors of protein synthesis. (3) In a following step, ribosomal 60S subunits bind to the complex and lead to core disassembly with a concomitant transfer of core protein or of core protein fragments to the 28S rRNA. The linker region may be involved in this transfer. (4) During the later stages of virus multiplication, cellular components involved in step (2) and/or in step (3) are inactivated. This inactivation might involve the binding of newly synthesised core protein to 28S rRNA. (5) Unprimed cores, e.g. core particles containing the linker region in an unexposed position, are assembled during virus multiplication. Priming of cores and inactivation of host-cell factors each represent a complete mechanism of regulation of core disassembly. Future experiments will show whether or not both processes are actually used. Since alphaviruses, e.g. Chikungunya virus, Ross River virus, Semliki Forest virus, and Sindbis virus, are human pathogens, these experiments are of practical relevance, since they might identify targets for antiviral chemotherapy.
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Abstract
Enveloped viruses penetrate the host cells by fusion of the viral envelope with a cellular target membrane. One of the best studied viruses with respect to its penetration and uncoating is the alphavirus Semliki Forest virus that is taken up by endocytosis. The alphavirus membrane glycoprotein E1 harbors a so-called fusion peptide, which is responsible for interaction with the endosomal membrane, leading to fusion. Besides this fusion process, cell infection by alphaviruses is accompanied by membrane permeability changes, thus implying some form of pore across the membrane. However, the ability of E1 protein to form ion pores has not been widely accepted. This review provides an overview of studies that confirm earlier results predicting the formation of a proteinaceous pore by the alphavirus spike proteins. Furthermore, different models to explain this pore formation during virus entry are discussed.
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Affiliation(s)
- Fabian Käsermann
- University of Bern, Department of Chemistry & Biochemistry, Bern, Switzerland and, ZLB Behring AG, Switzerland
| | - Christoph Kempf
- University of Bern, Department of Chemistry & Biochemistry, Bern, Switzerland and, ZLB Behring AG, Switzerland
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Koschinski A, Wengler G, Wengler G, Repp H. Rare earth ions block the ion pores generated by the class II fusion proteins of alphaviruses and allow analysis of the biological functions of these pores. J Gen Virol 2005; 86:3311-3320. [PMID: 16298976 DOI: 10.1099/vir.0.81096-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recently, class II fusion proteins have been identified on the surface of alpha- and flaviviruses. These proteins have two functions besides membrane fusion: they generate an isometric lattice on the viral surface and they form ion-permeable pores at low pH. An attempt was made to identify inhibitors for the ion pores generated by the fusion proteins of the alphaviruses Semliki Forest virus and Sindbis virus. These pores can be detected and analysed in three situations: (i) in the target membrane during virus entry, by performing patch-clamp measurements of membrane currents; (ii) in the virus particle, by studying the entry of propidium iodide; and (iii) in the plasma membrane of infected cells, by Fura-2 fluorescence imaging of Ca2+ entry into infected cells. It is shown here that, at a concentration of 0·1 mM, rare earth ions block the ion permeability of alphavirus ion pores in all three situations. Even at a concentration of 0·5 mM, these ions do not block formation of the viral fusion pore, as they do not inhibit entry or multiplication of alphaviruses. The data indicate that ions flow through the ion pores into the virus particle in the endosome and from the endosome into the cytoplasm after fusion of the viral envelope with the endosomal membrane. These ion flows, however, are not necessary for productive infection. The possibility that the ability of class II fusion proteins to form ion-permeable pores reflects their origin from protein toxins that form ion-permeable pores, and that entry via class II fusion proteins may resemble the entry of non-enveloped viruses, is discussed.
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Affiliation(s)
- Andreas Koschinski
- Rudolf-Buchheim-Institut für Pharmakologie, Justus-Liebig-Universität, D-35392 Giessen, Germany
| | - Gerd Wengler
- Institut für Virologie, Fachbereich Veterinärmedizin, Justus-Liebig-Universität, D-35392 Giessen, Germany
| | - Gisela Wengler
- Institut für Virologie, Fachbereich Veterinärmedizin, Justus-Liebig-Universität, D-35392 Giessen, Germany
| | - Holger Repp
- Rudolf-Buchheim-Institut für Pharmakologie, Justus-Liebig-Universität, D-35392 Giessen, Germany
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Nieva JL, Sanz MA, Carrasco L. Membrane-permeabilizing motif in Semliki forest virus E1 glycoprotein. FEBS Lett 2004; 576:417-22. [PMID: 15498572 DOI: 10.1016/j.febslet.2004.09.061] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2004] [Revised: 09/15/2004] [Accepted: 09/23/2004] [Indexed: 11/26/2022]
Abstract
Cell infection by alphaviruses is accompanied by membrane permeability changes. New predictive approaches, including the computation of interfacial affinity and corresponding hydrophobic moments, suggest a segmented amphipathic-at-interface domain in the stem region of Semliki Forest virus fusion protein E1. Expression of E1 sequences in Escherichia coli cells confirmed that the membrane proximal plus transmembrane (TM) domain unit permeabilizes cells as efficiently as the 6K viroporin. Both our predictive and experimental data support the involvement of the E1 stem-TM region in membrane insertion and permeabilization. We propose to combine Wimley-White hydrophobicity analysis with expression-coupled permeability assays in order to identify viral products implied in breaching cell membrane barriers during infection.
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Affiliation(s)
- José L Nieva
- Unidad de Biofísica (CSIC-UPV/EHU), Departamento de Bioquímica, Universidad del País Vasco, Apdo., 644, 48080 Bilbao, Spain.
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Wengler G, Koschinski A, Wengler G, Repp H. During entry of alphaviruses, the E1 glycoprotein molecules probably form two separate populations that generate either a fusion pore or ion-permeable pores. J Gen Virol 2004; 85:1695-1701. [PMID: 15166454 DOI: 10.1099/vir.0.79845-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Studies using the alphavirus Semliki Forest virus have indicated that the viral E1 fusion protein forms two types of pore: fusion pores and ion-permeable pores. The formation of ion-permeable pores has not been generally accepted, partly because it was not evident how the protein might form these different pores. Here it is proposed that the choice of the target membrane determines whether a fusion pore or ion-permeable pores are formed. The fusion protein is activated in the endosome and for steric reasons only a fraction of the activated molecules can interact with the endosomal membrane. This target membrane reaction forms the fusion pore. It is proposed that the rest of the activated molecules interact with the membrane in which the protein is anchored and that this self-membrane reaction leads to formation of ion-permeable pores, which can be detected in the target membrane after fusion of the viral membrane into the target membrane.
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Affiliation(s)
- Gerd Wengler
- Institut für Virologie der Veterinärmedizin, Justus-Liebig-Universität, D-35392 Giessen, Germany
| | - Andreas Koschinski
- Rudolf-Buchheim-Institut für Pharmakologie, Justus-Liebig-Universität, D-35392 Giessen, Germany
| | - Gisela Wengler
- Institut für Virologie der Veterinärmedizin, Justus-Liebig-Universität, D-35392 Giessen, Germany
| | - Holger Repp
- Rudolf-Buchheim-Institut für Pharmakologie, Justus-Liebig-Universität, D-35392 Giessen, Germany
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Koschinski A, Wengler G, Wengler G, Repp H. The membrane proteins of flaviviruses form ion-permeable pores in the target membrane after fusion: identification of the pores and analysis of their possible role in virus infection. J Gen Virol 2003; 84:1711-1721. [PMID: 12810864 DOI: 10.1099/vir.0.19062-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recently, we presented evidence that the E1 fusion protein of the alphavirus Semliki Forest virus forms ion-permeable pores in the target membrane after fusion. We proposed that the homologous fusion proteins of flaviviruses and hepatitis C virus form similar pores. To test this hypothesis for the E fusion protein of flaviviruses, the release of [(3)H]choline from liposomes by the flavivirus West Nile (WN) virus was determined. [(3)H]Choline was released at mildly acid pH. The pH threshold depended on the lipid composition. Release from certain liposomes was activated even at neutral pH. To identify the generation of individual pores, single cells were investigated with the patch-clamp technique. The formation of individual pores during low pH-induced WN virus entry at the plasma membrane occurred within seconds. These experiments were performed in parallel with Semliki Forest virus. The results indicated that, similar to alphavirus infection, infection with flaviviruses via endosomes leads to the formation of ion-permeable pores in the endosome after fusion, which allows the flow of protons from the endosome into the cytoplasm during virus entry. However, in vitro translation experiments of viral cores showed that, in contrast to alphaviruses, which probably need this proton flow for core disassembly, the genome RNA of WN virus present in the viral core is directly accessible for translation. For entry of flaviviruses, therefore, a second pathway for productive infection may exist, in which fusion of the viral membrane is activated at neutral pH by contact with a plasma membrane of appropriate lipid composition.
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Affiliation(s)
- Andreas Koschinski
- Rudolf-Buchheim-Institut für Pharmakologie1, Justus-Liebig-Universität, D-35392 Giessen, Germany
| | - Gerd Wengler
- Institut für Virologie der Veterinärmedizin2, Justus-Liebig-Universität, D-35392 Giessen, Germany
| | - Gisela Wengler
- Institut für Virologie der Veterinärmedizin2, Justus-Liebig-Universität, D-35392 Giessen, Germany
| | - Holger Repp
- Rudolf-Buchheim-Institut für Pharmakologie1, Justus-Liebig-Universität, D-35392 Giessen, Germany
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Sanz MA, Rejas MT, Carrasco L. Individual expression of sindbis virus glycoproteins. E1 alone promotes cell fusion. Virology 2003; 305:463-72. [PMID: 12573591 DOI: 10.1006/viro.2002.1771] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The envelope of alphavirus particles contains two major glycoproteins, E1 and E2, that participate in virus entry and assembly of new virus particles. Interactions between these glycoproteins determine their correct functioning. The expression of each glycoprotein in the absence of the other counterpart was achieved by means of electroporation of modified Sindbis virus (SV) genomes. In addition, in trans coexpression of both glycoproteins was also tested in BHK cells. Synthesis of the E1 glycoprotein alone gave rise to cell fusion after incubation in low-pH medium. In addition, expression of E1 in the absence of the E2 precursor, PE2 (E3+E2), induced the formation of cytoplasmic vacuoles in the transfected cells. The normal phenotype was recovered when PE2 was coexpressed in trans with E1. Moreover, this coexpression modified the processing of the PE2 glycoprotein. PE2 synthesized in the absence of E1 gave rise to a product, E2', whose migration was slower in SDS-polyacrylamide gel than that of genuine E2 from SV-infected cells. This alteration was corrected upon in trans coexpression of E1 and PE2. These results suggest that the two glycoproteins, E1 and PE2, interact after their expression from two separate SV genomes. Notably, BHK cells cotransfected with the two modified genomes produced SV particles. Our findings suggest that SV E1 and E2 synthesized in trans can interact with each other and participate together with capsid protein in the assembly of new virus particles.
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Affiliation(s)
- Miguel Angel Sanz
- Centro de Biología Molecular (CSIC-UAM), Universidad Autónoma, Cantoblanco, 28049 Madrid, Spain.
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Smit JM, Li G, Schoen P, Corver J, Bittman R, Lin KC, Wilschut J. Fusion of alphaviruses with liposomes is a non-leaky process. FEBS Lett 2002; 521:62-6. [PMID: 12067727 DOI: 10.1016/s0014-5793(02)02823-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
It has been reported that low-pH-induced fusion of influenza virus with liposomes results in rapid and extensive release of both low- and high-molecular-weight substances from the liposomes [Günther-Ausborn et al., J. Biol. Chem. 270 (1995) 29279-29285; Shangguan et al., Biochemistry 35 (1996) 4956-4965]. Here, we demonstrate retention of encapsulated water-soluble compounds during fusion of Semliki Forest virus (SFV) or Sindbis virus with liposomes at low pH. Under conditions allowing complete fusion of the liposomes, a limited fluorescence dequenching of liposome-encapsulated calcein was observed, particularly for SFV. Also, radioactively labeled inulin or sucrose were largely retained. Freezing and thawing of the viruses in the absence of sucrose resulted in an enhanced leakiness of fusion. These results support the notion that the alphavirus fusion event per se is non-leaky and may well involve a discrete hemifusion intermediate.
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Affiliation(s)
- Jolanda M Smit
- Department of Medical Microbiology, Molecular Virology Section, University of Groningen and Academic Hospital, Ant. Deusinglaan 1, 9713 AV Groningen, The Netherlands
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Nyfeler S, Senn K, Kempf C. Expression of Semliki Forest virus E1 protein in Escherichia coli. Low pH-induced pore formation. J Biol Chem 2001; 276:15453-7. [PMID: 11278826 DOI: 10.1074/jbc.m011061200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Exposure of Semliki Forest virus 1 to mildly acidic conditions results in conformational changes of the viral spike proteins, which in turn leads to a pore formation across its membrane. The ability to form a pore has been ascribed to the ectodomain of the Semliki Forest virus (SFV) E1 spike protein. To elucidate whether the E1 protein per se is sufficient for low pH-dependent pore formation, we expressed E1 in Escherichia coli in an inducible manner using the pET11c expression system. The data obtained clearly showed that the E1 protein was expressed in the bacterial cell membrane and that exposure of E. coli expressing the SFV E1 protein to low pH (<6.2) resulted in a permeability change of the membrane. Thus, we conclude that the E1 protein of SFV per se is sufficient to promote pore formation under mildly acidic conditions.
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Affiliation(s)
- S Nyfeler
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
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Corver J, Bron R, Snippe H, Kraaijeveld C, Wilschut J. Membrane fusion activity of Semliki Forest virus in a liposomal model system: specific inhibition by Zn2+ ions. Virology 1997; 238:14-21. [PMID: 9375004 DOI: 10.1006/viro.1997.8799] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Semliki Forest virus (SFV) has been shown previously to fuse efficiently with cholesterol- and sphingolipid-containing liposomal model membranes in a low-pH-dependent manner. Several steps can be distinguished in this process, including low-pH-induced irreversible binding of the virus to the liposomes, facilitated by target membrane cholesterol, and subsequent fusion of the viral membrane with the liposomal bilayer, specifically catalyzed by target membrane sphingolipid. Binding and fusion are mediated by the heterodimeric viral envelope glycoprotein E2/E1. At low pH the heterodimer dissociates, and the E1 monomers convert to a homotrimeric structure, the presumed fusion-active conformation of the viral spike. In this paper, we demonstrate that SFV-liposome fusion is specifically inhibited by Zn2+ ions. The inhibition is at the level of the fusion reaction itself, since virus-liposome binding was found to be unaffected. Zn2+ did not inhibit E2/E1 dissociation, but severely inhibited exposure of an acid-specific epitope on E1, E1 homotrimer formation, and acquisition of trypsin-resistance. It is concluded that virus--liposome binding solely requires low-pH-induced E2/E1 heterodimer dissociation, while fusion depends on further rearrangements in the E1 spike protein. As these rearrangements occur subsequent to the binding step, their precise course, including the formation of a fusion complex, may be influenced by interaction of E1 with target membrane lipids.
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Affiliation(s)
- J Corver
- Department of Physiological Chemistry, GUIDE, University of Groningen, The Netherlands
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