1
|
Schmidt L, Tüting C, Kyrilis FL, Hamdi F, Semchonok DA, Hause G, Meister A, Ihling C, Stubbs MT, Sinz A, Kastritis PL. Delineating organizational principles of the endogenous L-A virus by cryo-EM and computational analysis of native cell extracts. Commun Biol 2024; 7:557. [PMID: 38730276 PMCID: PMC11087493 DOI: 10.1038/s42003-024-06204-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 04/17/2024] [Indexed: 05/12/2024] Open
Abstract
The high abundance of most viruses in infected host cells benefits their structural characterization. However, endogenous viruses are present in low copy numbers and are therefore challenging to investigate. Here, we retrieve cell extracts enriched with an endogenous virus, the yeast L-A virus. The determined cryo-EM structure discloses capsid-stabilizing cation-π stacking, widespread across viruses and within the Totiviridae, and an interplay of non-covalent interactions from ten distinct capsomere interfaces. The capsid-embedded mRNA decapping active site trench is supported by a constricting movement of two flexible opposite-facing loops. tRNA-loaded polysomes and other biomacromolecules, presumably mRNA, are found in virus proximity within the cell extract. Mature viruses participate in larger viral communities resembling their rare in-cell equivalents in terms of size, composition, and inter-virus distances. Our results collectively describe a 3D-architecture of a viral milieu, opening the door to cell-extract-based high-resolution structural virology.
Collapse
Affiliation(s)
- Lisa Schmidt
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, Halle/Saale, Germany
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, Halle/Saale, Germany
- Technical Biogeochemistry, Helmholtz Centre for Environmental Research, Permoserstraße 15, Leipzig, Germany
| | - Christian Tüting
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, Halle/Saale, Germany.
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, Halle/Saale, Germany.
| | - Fotis L Kyrilis
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, Halle/Saale, Germany
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, Halle/Saale, Germany
- Institute of Chemical Biology, National Hellenic Research Foundation, Athens, Greece
| | - Farzad Hamdi
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, Halle/Saale, Germany
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, Halle/Saale, Germany
| | - Dmitry A Semchonok
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, Halle/Saale, Germany
| | - Gerd Hause
- Biozentrum, Martin Luther University Halle-Wittenberg, Weinbergweg 22, Halle/Saale, Germany
| | - Annette Meister
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, Halle/Saale, Germany
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, Halle/Saale, Germany
| | - Christian Ihling
- Institute of Pharmacy, Center for Structural Mass Spectrometry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3, Halle (Saale), Germany
| | - Milton T Stubbs
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, Halle/Saale, Germany
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, Halle/Saale, Germany
| | - Andrea Sinz
- Institute of Pharmacy, Center for Structural Mass Spectrometry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3, Halle (Saale), Germany
| | - Panagiotis L Kastritis
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, Halle/Saale, Germany.
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, Halle/Saale, Germany.
- Institute of Chemical Biology, National Hellenic Research Foundation, Athens, Greece.
- Biozentrum, Martin Luther University Halle-Wittenberg, Weinbergweg 22, Halle/Saale, Germany.
| |
Collapse
|
2
|
Azimi FC, Dean TT, Minari K, Basso LGM, Vance TDR, Serrão VHB. A Frame-by-Frame Glance at Membrane Fusion Mechanisms: From Viral Infections to Fertilization. Biomolecules 2023; 13:1130. [PMID: 37509166 PMCID: PMC10377500 DOI: 10.3390/biom13071130] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 07/09/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023] Open
Abstract
Viral entry and fertilization are distinct biological processes that share a common mechanism: membrane fusion. In viral entry, enveloped viruses attach to the host cell membrane, triggering a series of conformational changes in the viral fusion proteins. This results in the exposure of a hydrophobic fusion peptide, which inserts into the host membrane and brings the viral and host membranes into close proximity. Subsequent structural rearrangements in opposing membranes lead to their fusion. Similarly, membrane fusion occurs when gametes merge during the fertilization process, though the exact mechanism remains unclear. Structural biology has played a pivotal role in elucidating the molecular mechanisms underlying membrane fusion. High-resolution structures of the viral and fertilization fusion-related proteins have provided valuable insights into the conformational changes that occur during this process. Understanding these mechanisms at a molecular level is essential for the development of antiviral therapeutics and tools to influence fertility. In this review, we will highlight the biological importance of membrane fusion and how protein structures have helped visualize both common elements and subtle divergences in the mechanisms behind fusion; in addition, we will examine the new tools that recent advances in structural biology provide researchers interested in a frame-by-frame understanding of membrane fusion.
Collapse
Affiliation(s)
- Farshad C Azimi
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Trevor T Dean
- Pharmaceutical Sciences, University of Illinois Chicago, Chicago, IL 60612, USA
| | - Karine Minari
- Biomolecular Cryo-Electron Microscopy Facility, University of California-Santa Cruz, Santa Cruz, CA 95064, USA
| | - Luis G M Basso
- Laboratório de Ciências Físicas, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Rio de Janeiro 28013-602, Brazil
| | - Tyler D R Vance
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Vitor Hugo B Serrão
- Biomolecular Cryo-Electron Microscopy Facility, University of California-Santa Cruz, Santa Cruz, CA 95064, USA
- Department of Chemistry and Biochemistry, University of California-Santa Cruz, Santa Cruz, CA 95064, USA
| |
Collapse
|
3
|
Zimmermann L, Chlanda P. Cryo-electron tomography of viral infection - from applications to biosafety. Curr Opin Virol 2023; 61:101338. [PMID: 37348443 DOI: 10.1016/j.coviro.2023.101338] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 04/25/2023] [Accepted: 05/28/2023] [Indexed: 06/24/2023]
Abstract
Cellular cryo-electron tomography (cryo-ET) offers 3D snapshots at molecular resolution capturing pivotal steps during viral infection. However, tomogram quality depends on the vitrification level of the sample and its thickness. In addition, mandatory inactivation protocols to assure biosafety when handling highly pathogenic viruses during cryo-ET can compromise sample preservation. Here, we focus on different strategies applied in cryo-ET and discuss their advantages and limitations with reference to severe acute respiratory syndrome coronavirus 2 studies. We highlight the importance of virus-like particle (VLP) and replicon systems to study virus assembly and replication in a cellular context without inactivation protocols. We discuss the application of chemical fixation and different irradiation methods in cryo-ET sample preparation and acquisition workflows.
Collapse
Affiliation(s)
- Liv Zimmermann
- Schaller Research Groups, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Petr Chlanda
- Schaller Research Groups, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany.
| |
Collapse
|
4
|
Sarca AD, Sardo L, Fukuda H, Matsui H, Shirakawa K, Horikawa K, Takaori-Kondo A, Izumi T. FRET-Based Detection and Quantification of HIV-1 Virion Maturation. Front Microbiol 2021; 12:647452. [PMID: 33767685 PMCID: PMC7985248 DOI: 10.3389/fmicb.2021.647452] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 01/18/2021] [Indexed: 01/27/2023] Open
Abstract
HIV-1 infectivity is achieved through virion maturation. Virus particles undergo structural changes via cleavage of the Gag polyprotein mediated by the viral protease, causing the transition from an uninfectious to an infectious status. The majority of proviruses in people living with HIV-1 treated with combination antiretroviral therapy are defective with large internal deletions. Defective proviral DNA frequently preserves intact sequences capable of expressing viral structural proteins to form virus-like particles whose maturation status is an important factor for chronic antigen-mediated immune stimulation and inflammation. Thus, novel methods to study the maturation capability of defective virus particles are needed to characterize their immunogenicity. To build a quantitative tool to study virion maturation in vitro, we developed a novel single virion visualization technique based on fluorescence resonance energy transfer (FRET). We inserted an optimized intramolecular CFP-YPF FRET donor-acceptor pair bridged with an HIV-1 protease cleavage sequence between the Gag MA-CA domains. This system allowed us to microscopically distinguish mature and immature virions via their FRET signal when the FRET donor and acceptor proteins were separated by the viral protease during maturation. We found that approximately 80% of the FRET labeled virus particles were mature with equivalent infectivity to wild type. The proportion of immature virions was increased by treatment of virus producer cells with a protease inhibitor in a dose-dependent manner, which corresponded to a relative decrease in infectivity. Potential areas of application for this tool are assessing maturation efficiency in different cell type settings of intact or deficient proviral DNA integrated cells. We believe that this FRET-based single-virion imaging platform will facilitate estimating the impact on the immune system of both extracellular intact and defective viruses by quantifying the Gag maturation status.
Collapse
Affiliation(s)
- Anamaria D Sarca
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Luca Sardo
- Department of Biological Sciences, University of the Sciences, Philadelphia, PA, United States
| | - Hirofumi Fukuda
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Hiroyuki Matsui
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kotaro Shirakawa
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kazuki Horikawa
- Department of Optical Imaging, Advanced Research Promotion Center, Tokushima University, Tokushima, Japan
| | - Akifumi Takaori-Kondo
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Taisuke Izumi
- Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| |
Collapse
|
5
|
Genetic, Morphological and Antigenic Relationships between Mesonivirus Isolates from Australian Mosquitoes and Evidence for Their Horizontal Transmission. Viruses 2020; 12:v12101159. [PMID: 33066222 PMCID: PMC7602028 DOI: 10.3390/v12101159] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 10/08/2020] [Accepted: 10/08/2020] [Indexed: 12/26/2022] Open
Abstract
The Mesoniviridae are a newly assigned family of viruses in the order Nidovirales. Unlike other nidoviruses, which include the Coronaviridae, mesoniviruses are restricted to mosquito hosts and do not infect vertebrate cells. To date there is little information on the morphological and antigenic characteristics of this new group of viruses and a dearth of mesonivirus-specific research tools. In this study we determined the genetic relationships of recent Australian isolates of Alphamesonivirus 4 (Casuarina virus—CASV) and Alphamesonivirus 1 (Nam Dinh virus—NDiV), obtained from multiple mosquito species. Australian isolates of NDiV showed high-level similarity to the prototype NDiV isolate from Vietnam (99% nucleotide (nt) and amino acid (aa) identity). Isolates of CASV from Central Queensland were genetically very similar to the prototype virus from Darwin (95–96% nt and 91–92% aa identity). Electron microscopy studies demonstrated that virion diameter (≈80 nm) and spike length (≈10 nm) were similar for both viruses. Monoclonal antibodies specific to CASV and NDiV revealed a close antigenic relationship between the two viruses with 13/34 mAbs recognising both viruses. We also detected NDiV RNA on honey-soaked nucleic acid preservation cards fed on by wild mosquitoes supporting a possible mechanism of horizontal transmission between insects in nature.
Collapse
|
6
|
Koehler M, Delguste M, Sieben C, Gillet L, Alsteens D. Initial Step of Virus Entry: Virion Binding to Cell-Surface Glycans. Annu Rev Virol 2020; 7:143-165. [PMID: 32396772 DOI: 10.1146/annurev-virology-122019-070025] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Virus infection is an intricate process that requires the concerted action of both viral and host cell components. Entry of viruses into cells is initiated by interactions between viral proteins and cell-surface receptors. Various cell-surface glycans function as initial, usually low-affinity attachment factors, providing a first anchor of the virus to the cell surface, and further facilitate high-affinity binding to virus-specific cell-surface receptors, while other glycans function as specific entry receptors themselves. It is now possible to rapidly identify specific glycan receptors using different techniques, define atomic-level structures of virus-glycan complexes, and study these interactions at the single-virion level. This review provides a detailed overview of the role of glycans in viral infection and highlights experimental approaches to study virus-glycan binding along with specific examples. In particular, we highlight the development of the atomic force microscope to investigate interactions with glycans at the single-virion level directly on living mammalian cells, which offers new perspectives to better understand virus-glycan interactions in physiologically relevant conditions.
Collapse
Affiliation(s)
- Melanie Koehler
- Louvain Institute of Biomolecular Science and Technology, Université Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium;
| | - Martin Delguste
- Louvain Institute of Biomolecular Science and Technology, Université Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium;
| | - Christian Sieben
- Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Laurent Gillet
- Immunology-Vaccinology Laboratory, Department of Infectious and Parasitic Diseases, Fundamental and Applied Research for Animals and Health center (FARAH), University of Liège, 4000 Liège, Belgium
| | - David Alsteens
- Louvain Institute of Biomolecular Science and Technology, Université Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium; .,Walloon Excellence in Life sciences and Biotechnology (WELBIO), 1300 Wavre, Belgium
| |
Collapse
|
7
|
Ueda G, Antanasijevic A, Fallas JA, Sheffler W, Copps J, Ellis D, Hutchinson GB, Moyer A, Yasmeen A, Tsybovsky Y, Park YJ, Bick MJ, Sankaran B, Gillespie RA, Brouwer PJM, Zwart PH, Veesler D, Kanekiyo M, Graham BS, Sanders RW, Moore JP, Klasse PJ, Ward AB, King NP, Baker D. Tailored design of protein nanoparticle scaffolds for multivalent presentation of viral glycoprotein antigens. eLife 2020; 9:57659. [PMID: 32748788 PMCID: PMC7402677 DOI: 10.7554/elife.57659] [Citation(s) in RCA: 103] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 07/02/2020] [Indexed: 02/06/2023] Open
Abstract
Multivalent presentation of viral glycoproteins can substantially increase the elicitation of antigen-specific antibodies. To enable a new generation of anti-viral vaccines, we designed self-assembling protein nanoparticles with geometries tailored to present the ectodomains of influenza, HIV, and RSV viral glycoprotein trimers. We first de novo designed trimers tailored for antigen fusion, featuring N-terminal helices positioned to match the C termini of the viral glycoproteins. Trimers that experimentally adopted their designed configurations were incorporated as components of tetrahedral, octahedral, and icosahedral nanoparticles, which were characterized by cryo-electron microscopy and assessed for their ability to present viral glycoproteins. Electron microscopy and antibody binding experiments demonstrated that the designed nanoparticles presented antigenically intact prefusion HIV-1 Env, influenza hemagglutinin, and RSV F trimers in the predicted geometries. This work demonstrates that antigen-displaying protein nanoparticles can be designed from scratch, and provides a systematic way to investigate the influence of antigen presentation geometry on the immune response to vaccination.
Collapse
Affiliation(s)
- George Ueda
- Department of Biochemistry, University of WashingtonSeattleUnited States,Institute for Protein Design, University of WashingtonSeattleUnited States
| | - Aleksandar Antanasijevic
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States,International AIDS Vaccine Initiative Neutralizing Antibody Center, the Collaboration for AIDS Vaccine Discovery (CAVD) and Scripps Consortium for HIV/AIDS Vaccine Development (CHAVD), The Scripps Research InstituteLa JollaUnited States
| | - Jorge A Fallas
- Department of Biochemistry, University of WashingtonSeattleUnited States,Institute for Protein Design, University of WashingtonSeattleUnited States
| | - William Sheffler
- Department of Biochemistry, University of WashingtonSeattleUnited States,Institute for Protein Design, University of WashingtonSeattleUnited States
| | - Jeffrey Copps
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States,International AIDS Vaccine Initiative Neutralizing Antibody Center, the Collaboration for AIDS Vaccine Discovery (CAVD) and Scripps Consortium for HIV/AIDS Vaccine Development (CHAVD), The Scripps Research InstituteLa JollaUnited States
| | - Daniel Ellis
- Department of Biochemistry, University of WashingtonSeattleUnited States,Institute for Protein Design, University of WashingtonSeattleUnited States
| | - Geoffrey B Hutchinson
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of HealthBethesdaUnited States
| | - Adam Moyer
- Department of Biochemistry, University of WashingtonSeattleUnited States,Institute for Protein Design, University of WashingtonSeattleUnited States
| | - Anila Yasmeen
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell UniversityNew YorkUnited States
| | - Yaroslav Tsybovsky
- Electron Microscopy Laboratory, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research sponsored by the National Cancer InstituteFrederickUnited States
| | - Young-Jun Park
- Department of Biochemistry, University of WashingtonSeattleUnited States
| | - Matthew J Bick
- Department of Biochemistry, University of WashingtonSeattleUnited States,Institute for Protein Design, University of WashingtonSeattleUnited States
| | - Banumathi Sankaran
- Berkeley Center for Structural Biology, Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley LaboratoryBerkeleyUnited States
| | - Rebecca A Gillespie
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of HealthBethesdaUnited States
| | - Philip JM Brouwer
- Amsterdam UMC, Department of Medical Microbiology, Amsterdam Infection & Immunity Institute, University of AmsterdamAmsterdamNetherlands
| | - Peter H Zwart
- Berkeley Center for Structural Biology, Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley LaboratoryBerkeleyUnited States,Center for Advanced Mathematics in Energy Research Applications, Computational Research Division, Lawrence Berkeley LaboratoryBerkeleyUnited States
| | - David Veesler
- Department of Biochemistry, University of WashingtonSeattleUnited States
| | - Masaru Kanekiyo
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of HealthBethesdaUnited States
| | - Barney S Graham
- Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of HealthBethesdaUnited States
| | - Rogier W Sanders
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell UniversityNew YorkUnited States,Amsterdam UMC, Department of Medical Microbiology, Amsterdam Infection & Immunity Institute, University of AmsterdamAmsterdamNetherlands
| | - John P Moore
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell UniversityNew YorkUnited States
| | - Per Johan Klasse
- Department of Microbiology and Immunology, Weill Cornell Medicine, Cornell UniversityNew YorkUnited States
| | - Andrew B Ward
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States,International AIDS Vaccine Initiative Neutralizing Antibody Center, the Collaboration for AIDS Vaccine Discovery (CAVD) and Scripps Consortium for HIV/AIDS Vaccine Development (CHAVD), The Scripps Research InstituteLa JollaUnited States
| | - Neil P King
- Department of Biochemistry, University of WashingtonSeattleUnited States,Institute for Protein Design, University of WashingtonSeattleUnited States
| | - David Baker
- Department of Biochemistry, University of WashingtonSeattleUnited States,Institute for Protein Design, University of WashingtonSeattleUnited States,Howard Hughes Medical Institute, University of WashingtonSeattleUnited States
| |
Collapse
|
8
|
Influenza Virus-Liposome Fusion Studies Using Fluorescence Dequenching and Cryo-electron Tomography. Methods Mol Biol 2019; 1836:261-279. [PMID: 30151578 DOI: 10.1007/978-1-4939-8678-1_13] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
Abstract
Influenza virus enters host cells by fusion of viral and endosomal membranes mediated by the influenza hemagglutinin (HA). The pathway of HA-catalyzed fusion has been widely investigated in influenza virus membrane fusion with liposomes. In this chapter we describe methodology for studying the virus-liposome fusion system using a combination of fluorescence dequenching assays and cryo-electron tomography (cryo-ET). In particular, the fluorescence dequenching is used to monitor the efficiency of membrane fusion between whole influenza viruses labeled with a lipophilic dye (DiD) in the membrane and liposomes labeled with a water-soluble dye (sulforhodamine B). By simultaneously monitoring the two fluorescent signals, we can determine the relative time scales of liposomal content leakage or transfer vs. lipid merging. In addition, cryo-ET offers a means of imaging three-dimensional snapshots of different stages of virus-liposome fusion such as prefusion, fusion intermediates, and postfusion.
Collapse
|
9
|
Leppänen M, Sundberg LR, Laanto E, de Freitas Almeida GM, Papponen P, Maasilta IJ. Imaging Bacterial Colonies and Phage-Bacterium Interaction at Sub-Nanometer Resolution Using Helium-Ion Microscopy. ACTA ACUST UNITED AC 2017; 1:e1700070. [PMID: 32646179 DOI: 10.1002/adbi.201700070] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 06/01/2017] [Indexed: 11/11/2022]
Abstract
Imaging of microbial interactions has so far been based on well-established electron microscopy methods. This study presents a new way to study bacterial colonies and interactions between bacteria and their viruses, bacteriophages (phages), in situ on agar plates using helium ion microscopy (HIM). In biological imaging, HIM has advantages over traditional scanning electron microscopy with its sub-nanometer resolution, increased surface sensitivity, and the possibility to image nonconductive samples. Furthermore, by controlling the He beam dose or by using heavier Ne ions, the HIM instrument provides the possibility to mill out material in the samples, allowing for subsurface imaging and in situ sectioning. Here, the first HIM-images of bacterial colonies and phage-bacterium interactions are presented at different stages of the infection as they occur on an agar culture. The feasibility of neon and helium milling is also demonstrated to reveal the subsurface structures of bacterial colonies on agar substrate, and in some cases also structure inside individual bacteria after cross-sectioning. The study concludes that HIM offers great opportunities to advance the studies of microbial imaging, in particular in the area of interaction of viruses with cells.
Collapse
Affiliation(s)
- Miika Leppänen
- Nanoscience Center, Department of Physics, University of Jyvaskyla, P. O. Box 35, FI-40014, Jyväskylä, Finland.,Nanoscience Center, Center of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyvaskyla, FI-40014, Jyväskylä, Finland
| | - Lotta-Riina Sundberg
- Nanoscience Center, Center of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyvaskyla, FI-40014, Jyväskylä, Finland
| | - Elina Laanto
- Nanoscience Center, Center of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyvaskyla, FI-40014, Jyväskylä, Finland
| | - Gabriel Magno de Freitas Almeida
- Nanoscience Center, Center of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyvaskyla, FI-40014, Jyväskylä, Finland
| | - Petri Papponen
- Nanoscience Center, Center of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyvaskyla, FI-40014, Jyväskylä, Finland
| | - Ilari J Maasilta
- Nanoscience Center, Department of Physics, University of Jyvaskyla, P. O. Box 35, FI-40014, Jyväskylä, Finland
| |
Collapse
|