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Heiligenstein X, Lucas MS. One for All, All for One: A Close Look at In-Resin Fluorescence Protocols for CLEM. Front Cell Dev Biol 2022; 10:866472. [PMID: 35846358 PMCID: PMC9280628 DOI: 10.3389/fcell.2022.866472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 06/13/2022] [Indexed: 11/13/2022] Open
Abstract
Sample preparation is the novel bottleneck for high throughput correlative light and electron microscopy (CLEM). Protocols suitable for both imaging methods must therefore balance the requirements of each technique. For fluorescence light microscopy, a structure of interest can be targeted using: 1) staining, which is often structure or tissue specific rather than protein specific, 2) dye-coupled proteins or antibodies, or 3) genetically encoded fluorescent proteins. Each of these three methods has its own advantages. For ultrastructural investigation by electron microscopy (EM) resin embedding remains a significant sample preparation approach, as it stabilizes the sample such that it withstands the vacuum conditions of the EM, and enables long-term storage. Traditionally, samples are treated with heavy metal salts prior to resin embedding, in order to increase imaging contrast for EM. This is particularly important for volume EM (vEM) techniques. Yet, commonly used contrasting agents (e.g., osmium tetroxide, uranyl acetate) tend to impair fluorescence. The discovery that fluorescence can be preserved in resin-embedded specimens after mild heavy metal staining was a game changer for CLEM. These so-called in-resin fluorescence protocols present a significant leap forward for CLEM approaches towards high precision localization of a fluorescent signal in (volume) EM data. Integrated microscopy approaches, combining LM and EM detection into a single instrument certainly require such an “all in one” sample preparation. Preserving, or adding, dedicated fluorescence prior to resin embedding requires a compromise, which often comes at the expense of EM imaging contrast and membrane visibility. Especially vEM can be strongly hampered by a lack of heavy metal contrasting. This review critically reflects upon the fundamental aspects of resin embedding with regard to 1) specimen fixation and the physics and chemistry underlying the preservation of protein structure with respect to fluorescence and antigenicity, 2) optimization of EM contrast for transmission or scanning EM, and 3) the choice of embedding resin. On this basis, various existing workflows employing in-resin fluorescence are described, highlighting their common features, discussing advantages and disadvantages of the respective approach, and finally concluding with promising future developments for in-resin CLEM.
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Affiliation(s)
| | - Miriam S. Lucas
- Scientific Center for Light and Electron Microscopy (ScopeM), ETH Zurich, Zurich, Switzerland
- *Correspondence: Miriam S. Lucas,
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2
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Barcytė D, Eikrem W, Engesmo A, Seoane S, Wohlmann J, Horák A, Yurchenko T, Eliáš M. Olisthodiscus represents a new class of Ochrophyta. JOURNAL OF PHYCOLOGY 2021; 57:1094-1118. [PMID: 33655496 DOI: 10.1111/jpy.13155] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 12/08/2020] [Accepted: 01/04/2021] [Indexed: 06/12/2023]
Abstract
The phylogenetic diversity of Ochrophyta, a diverse and ecologically important radiation of algae, is still incompletely understood even at the level of the principal lineages. One taxon that has eluded simple classification is the marine flagellate genus Olisthodiscus. We investigated Olisthodiscus luteus K-0444 and documented its morphological and genetic differences from the NIES-15 strain, which we described as Olisthodiscus tomasii sp. nov. Phylogenetic analyses of combined 18S and 28S rRNA sequences confirmed that Olisthodiscus constitutes a separate, deep, ochrophyte lineage, but its position could not be resolved. To overcome this problem, we sequenced the plastid genome of O. luteus K-0444 and used the new data in multigene phylogenetic analyses, which suggested that Olisthodiscus is a sister lineage of the class Pinguiophyceae within a broader clade additionally including Chrysophyceae, Synchromophyceae, and Eustigmatophyceae. Surprisingly, the Olisthodiscus plastid genome contained three genes, ycf80, cysT, and cysW, inherited from the rhodophyte ancestor of the ochrophyte plastid yet lost from all other ochrophyte groups studied so far. Combined with nuclear genes for CysA and Sbp proteins, Olisthodiscus is the only known ochrophyte possessing a plastidial sulfate transporter SulT. In addition, the finding of a cemA gene in the Olisthodiscus plastid genome and an updated phylogenetic analysis ruled out the previously proposed hypothesis invoking horizontal cemA transfer from a green algal plastid into Synurales. Altogether, Olisthodiscus clearly represents a novel phylogenetically distinct ochrophyte lineage, which we have proposed as a new class, Olisthodiscophyceae.
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Affiliation(s)
- Dovilė Barcytė
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, 710 00, Ostrava, Czech Republic
| | - Wenche Eikrem
- Norwegian Institute for Water Research, Gaustadallèen 21, 0349, Oslo, Norway
- Natural history Museum, University of Oslo, P.O. Box 1172 Blindern, 0318, Oslo, Norway
- Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0316, Oslo, Norway
| | - Anette Engesmo
- Norwegian Institute for Water Research, Gaustadallèen 21, 0349, Oslo, Norway
- Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0316, Oslo, Norway
| | - Sergio Seoane
- Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU), 48940, Leioa, Spain
| | - Jens Wohlmann
- Department of Biosciences, University of Oslo, P.O. Box 1066 Blindern, 0316, Oslo, Norway
| | - Aleš Horák
- Biology Centre, Czech Academy of Sciences, Institute of Parasitology, Branišovská 31, 37005, České Budějovice, Czech Republic
- Department of Molecular Biology, Faculty of Science, University of South Bohemia, Branišovská 31, 37005, České Budějovice, Czech Republic
| | - Tatiana Yurchenko
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, 710 00, Ostrava, Czech Republic
| | - Marek Eliáš
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, 710 00, Ostrava, Czech Republic
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3
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Wild P, Leisinger S, de Oliveira AP, Doehner J, Schraner EM, Fraevel C, Ackermann M, Kaech A. Nuclear envelope impairment is facilitated by the herpes simplex virus 1 Us3 kinase. F1000Res 2019; 8:198. [PMID: 31249678 PMCID: PMC6584977 DOI: 10.12688/f1000research.17802.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/11/2019] [Indexed: 12/22/2022] Open
Abstract
Background: Capsids of herpes simplex virus 1 (HSV-1) are assembled in the nucleus, translocated either to the perinuclear space by budding at the inner nuclear membrane acquiring tegument and envelope, or released to the cytosol in a "naked" state via impaired nuclear pores that finally results in impairment of the nuclear envelope. The Us3 gene encodes a protein acting as a kinase, which is responsible for phosphorylation of numerous viral and cellular substrates. The Us3 kinase plays a crucial role in nucleus to cytoplasm capsid translocation. We thus investigate the nuclear surface in order to evaluate the significance of Us3 in maintenance of the nuclear envelope during HSV-1 infection. Methods: To address alterations of the nuclear envelope and capsid nucleus to cytoplasm translocation related to the function of the Us3 kinase we investigated cells infected with wild type HSV-1 or the Us3 deletion mutant R7041(∆Us3) by transmission electron microscopy, focused ion-beam electron scanning microscopy, cryo-field emission scanning electron microscopy, confocal super resolution light microscopy, and polyacrylamide gel electrophoresis. Results: Confocal super resolution microscopy and cryo-field emission scanning electron microscopy revealed decrement in pore numbers in infected cells. Number and degree of pore impairment was significantly reduced after infection with R7041(∆Us3) compared to infection with wild type HSV-1. The nuclear surface was significantly enlarged in cells infected with any of the viruses. Morphometric analysis revealed that additional nuclear membranes were produced forming multiple folds and caveolae, in which virions accumulated as documented by three-dimensional reconstruction after ion-beam scanning electron microscopy. Finally, significantly more R7041(∆Us3) capsids were retained in the nucleus than wild-type capsids whereas the number of R7041(∆Us3) capsids in the cytosol was significantly lower. Conclusions: The data indicate that Us3 kinase is involved in facilitation of nuclear pore impairment and, concomitantly, in capsid release through impaired nuclear envelope.
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Affiliation(s)
- Peter Wild
- Department of Veterinary Anatomy, University of Zuerich, Zürich, CH-8057, Switzerland
| | - Sabine Leisinger
- Department of Veterinary Anatomy, University of Zuerich, Zürich, CH-8057, Switzerland
| | | | - Jana Doehner
- Center for Microcopy and Image Analysis, Universit of Zürich, Zürich, CH-8057, Switzerland
| | - Elisabeth M. Schraner
- Department of Veterinary Anatomy, University of Zuerich, Zürich, CH-8057, Switzerland
- Instute of Virology, University of Zürich, Zürich, ZH-8057, Switzerland
| | - Cornel Fraevel
- Instute of Virology, University of Zürich, Zürich, ZH-8057, Switzerland
| | - Mathias Ackermann
- Instute of Virology, University of Zürich, Zürich, ZH-8057, Switzerland
| | - Andres Kaech
- Center for Microcopy and Image Analysis, Universit of Zürich, Zürich, CH-8057, Switzerland
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4
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Reipert S, Goldammer H, Richardson C, Goldberg MW, Hawkins TJ, Hollergschwandtner E, Kaufmann WA, Antreich S, Stierhof YD. Agitation Modules: Flexible Means to Accelerate Automated Freeze Substitution. J Histochem Cytochem 2018; 66:903-921. [PMID: 29969056 DOI: 10.1369/0022155418786698] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
For ultrafast fixation of biological samples to avoid artifacts, high-pressure freezing (HPF) followed by freeze substitution (FS) is preferred over chemical fixation at room temperature. After HPF, samples are maintained at low temperature during dehydration and fixation, while avoiding damaging recrystallization. This is a notoriously slow process. McDonald and Webb demonstrated, in 2011, that sample agitation during FS dramatically reduces the necessary time. Then, in 2015, we (H.G. and S.R.) introduced an agitation module into the cryochamber of an automated FS unit and demonstrated that the preparation of algae could be shortened from days to a couple of hours. We argued that variability in the processing, reproducibility, and safety issues are better addressed using automated FS units. For dissemination, we started low-cost manufacturing of agitation modules for two of the most widely used FS units, the Automatic Freeze Substitution Systems, AFS(1) and AFS2, from Leica Microsystems, using three dimensional (3D)-printing of the major components. To test them, several labs independently used the modules on a wide variety of specimens that had previously been processed by manual agitation, or without agitation. We demonstrate that automated processing with sample agitation saves time, increases flexibility with respect to sample requirements and protocols, and produces data of at least as good quality as other approaches.
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Affiliation(s)
- Siegfried Reipert
- Core Facility Cell Imaging and Ultrastructure Research, University of Vienna, Vienna, Austria
| | - Helmuth Goldammer
- Core Facility Cell Imaging and Ultrastructure Research, University of Vienna, Vienna, Austria
| | | | - Martin W Goldberg
- Department of Biosciences, Durham University, Durham, United Kingdom
| | - Timothy J Hawkins
- Department of Biosciences, Durham University, Durham, United Kingdom
| | | | - Walter A Kaufmann
- Electron Microscopy Facility, Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Sebastian Antreich
- Core Facility Cell Imaging and Ultrastructure Research, University of Vienna, Vienna, Austria
| | - York-Dieter Stierhof
- Center for Plant Molecular Biology (ZMBP), Microscopy, University of Tübingen, Tübingen, Germany
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5
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Lemercier N, Middel V, Hentsch D, Taubert S, Takamiya M, Beil T, Vonesch JL, Baumbach T, Schultz P, Antony C, Strähle U. Microtome-integrated microscope system for high sensitivity tracking of in-resin fluorescence in blocks and ultrathin sections for correlative microscopy. Sci Rep 2017; 7:13583. [PMID: 29051533 PMCID: PMC5648784 DOI: 10.1038/s41598-017-13348-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 09/22/2017] [Indexed: 12/02/2022] Open
Abstract
Many areas of biological research demand the combined use of different imaging modalities to cover a wide range of magnifications and measurements or to place fluorescent patterns into an ultrastructural context. A technically difficult problem is the efficient specimen transfer between different imaging modalities without losing the coordinates of the regions-of-interest (ROI). Here, we report a new and highly sensitive integrated system that combines a custom designed microscope with an ultramicrotome for in-resin-fluorescence detection in blocks, ribbons and sections on EM-grids. Although operating with long-distance lenses, this system achieves a very high light sensitivity. Our instrumental set-up and operating workflow are designed to investigate rare events in large tissue volumes. Applications range from studies of individual immune, stem and cancer cells to the investigation of non-uniform subcellular processes. As a use case, we present the ultrastructure of a single membrane repair patch on a muscle fiber in intact muscle in a whole animal context.
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Affiliation(s)
- Nicolas Lemercier
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 1, rue Laurent Fries, 67404, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, 1, rue Laurent Fries, 67404, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, 1, rue Laurent Fries, 67404, Illkirch, France.,Université de Strasbourg, 1, rue Laurent Fries, 67404, Illkirch, France
| | - Volker Middel
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Didier Hentsch
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 1, rue Laurent Fries, 67404, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, 1, rue Laurent Fries, 67404, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, 1, rue Laurent Fries, 67404, Illkirch, France.,Université de Strasbourg, 1, rue Laurent Fries, 67404, Illkirch, France
| | - Serge Taubert
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 1, rue Laurent Fries, 67404, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, 1, rue Laurent Fries, 67404, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, 1, rue Laurent Fries, 67404, Illkirch, France.,Université de Strasbourg, 1, rue Laurent Fries, 67404, Illkirch, France
| | - Masanari Takamiya
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Tanja Beil
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Jean-Luc Vonesch
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 1, rue Laurent Fries, 67404, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, 1, rue Laurent Fries, 67404, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, 1, rue Laurent Fries, 67404, Illkirch, France.,Université de Strasbourg, 1, rue Laurent Fries, 67404, Illkirch, France
| | - Tilo Baumbach
- Laboratory for Applications of Synchrotron Radiation, Karlsruhe Institute of Technology, Kaiserstr. 12, 76131, Karlsruhe, Germany
| | - Patrick Schultz
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 1, rue Laurent Fries, 67404, Illkirch, France. .,Centre National de la Recherche Scientifique, UMR7104, 1, rue Laurent Fries, 67404, Illkirch, France. .,Institut National de la Santé et de la Recherche Médicale, U964, 1, rue Laurent Fries, 67404, Illkirch, France. .,Université de Strasbourg, 1, rue Laurent Fries, 67404, Illkirch, France.
| | - Claude Antony
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 1, rue Laurent Fries, 67404, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, 1, rue Laurent Fries, 67404, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, 1, rue Laurent Fries, 67404, Illkirch, France.,Université de Strasbourg, 1, rue Laurent Fries, 67404, Illkirch, France.,Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - Uwe Strähle
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
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6
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Wild P, Kaech A, Schraner EM, Walser L, Ackermann M. Endoplasmic reticulum-to-Golgi transitions upon herpes virus infection. F1000Res 2017; 6:1804. [PMID: 30135710 PMCID: PMC6080407 DOI: 10.12688/f1000research.12252.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/29/2017] [Indexed: 09/29/2023] Open
Abstract
Background: Herpesvirus capsids are assembled in the nucleus before they are translocated to the perinuclear space by budding, acquiring tegument and envelope, or releasing to the cytoplasm in a "naked" state via impaired nuclear envelope. One model proposes that envelopment, "de-envelopment" and "re-envelopment" are essential steps for production of infectious virus. Glycoproteins gB/gH were reported to be essential for de-envelopment, by fusion of the "primary" envelope with the outer nuclear membrane. Yet, a high proportion of enveloped virions generated from genomes with deleted gB/gH were found in the cytoplasm and extracellular space, suggesting the existence of an alternative exit route. Methods: We investigated the relatedness between the nuclear envelope and membranes of the endoplasmic reticulum and Golgi complex, in cells infected with either herpes simplex virus 1 (HSV-1) or a Us3 deletion mutant thereof, or with bovine herpesvirus 1 (BoHV-1) by transmission and scanning electron microscopy, employing freezing technique protocols that lead to improved spatial and temporal resolution. Results: Scanning electron microscopy showed the Golgi complex as a compact entity in a juxtanuclear position covered by a membrane on the cis face. Transmission electron microscopy revealed that Golgi membranes merge with membranes of the endoplasmic reticulum forming an entity with the perinuclear space. All compartments contained enveloped virions. After treatment with brefeldin A, HSV-1 virions aggregated in the perinuclear space and endoplasmic reticulum, while infectious progeny virus was still produced. Conclusions: The data strongly suggest that virions are intraluminally transported from the perinuclear space via Golgi complex-endoplasmic reticulum transitions into Golgi cisternae for packaging into transport vacuoles. Furthermore, virions derived by budding at nuclear membranes are infective as has been shown for HSV-1 Us3 deletion mutants, which almost entirely accumulate in the perinuclear space. Therefore, de-envelopment followed by re-envelopment is not essential for production of infective progeny virus.
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Affiliation(s)
- Peter Wild
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Andres Kaech
- Center for Microscopy and Image Analysis, Zürich, Switzerland
| | - Elisabeth M. Schraner
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Ladina Walser
- Institute of Veterinary Anatomy, Zürich, Switzerland
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7
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Wild P, Kaech A, Schraner EM, Walser L, Ackermann M. Endoplasmic reticulum-to-Golgi transitions upon herpes virus infection. F1000Res 2017; 6:1804. [PMID: 30135710 PMCID: PMC6080407 DOI: 10.12688/f1000research.12252.2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/19/2018] [Indexed: 11/23/2022] Open
Abstract
Background: Herpesvirus capsids are assembled in the nucleus, translocated to the perinuclear space by budding, acquiring tegument and envelope, or released to the cytoplasm via impaired nuclear envelope. One model proposes that envelopment, "de-envelopment" and "re-envelopment" is essential for production of infectious virus. Glycoproteins gB/gH were reported to be essential for de-envelopment, by fusion of the "primary" envelope with the outer nuclear membrane. Yet, a high proportion of enveloped virions generated from genomes with deleted gB/gH were found in the cytoplasm and extracellular space, suggesting the existence of alternative exit routes. Methods: We investigated the relatedness between the nuclear envelope and membranes of the endoplasmic reticulum and Golgi complex, in cells infected with either herpes simplex virus 1 (HSV-1) or a Us3 deletion mutant thereof, or with bovine herpesvirus 1 (BoHV-1) by transmission and scanning electron microscopy, employing freezing technique protocols. Results: The Golgi complex is a compact entity in a juxtanuclear position covered by a membrane on the cis face. Golgi membranes merge with membranes of the endoplasmic reticulum forming an entity with the perinuclear space. All compartments contained enveloped virions. After treatment with brefeldin A, HSV-1 virions aggregated in the perinuclear space and endoplasmic reticulum, while infectious progeny virus was still produced. Conclusions: The data suggest that virions derived by budding at nuclear membranes are intraluminally transported from the perinuclear space via Golgi -endoplasmic reticulum transitions into Golgi cisternae for packaging. Virions derived by budding at nuclear membranes are infective like Us3 deletion mutants, which accumulate in the perinuclear space. Therefore, i) de-envelopment followed by re-envelopment is not essential for production of infective progeny virus, ii) the process taking place at the outer nuclear membrane is budding not fusion, and iii) naked capsids gain access to the cytoplasmic matrix via impaired nuclear envelope as reported earlier.
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Affiliation(s)
- Peter Wild
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Andres Kaech
- Center for Microscopy and Image Analysis, Zürich, Switzerland
| | - Elisabeth M. Schraner
- Institute of Veterinary Anatomy, Zürich, Switzerland
- Institute of Virology, Zürich, Switzerland
| | - Ladina Walser
- Institute of Veterinary Anatomy, Zürich, Switzerland
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8
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Vogt CM, Schraner EM, Aguilar C, Eichwald C. Heterologous expression of antigenic peptides in Bacillus subtilis biofilms. Microb Cell Fact 2016; 15:137. [PMID: 27514610 PMCID: PMC4982213 DOI: 10.1186/s12934-016-0532-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 07/27/2016] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Numerous strategies have been developed for the display of heterologous proteins in the surface of live bacterial carriers, which can be used as vaccines, immune-modulators, cancer therapy or bioremediation. Bacterial biofilms have emerged as an interesting approach for the expression of proteins of interest. Bacillus subtilis is a well-described, endospore-forming organism that is able to form biofilms and also used as a probiotic, thus making it a suitable candidate for the display of heterologous proteins within the biofilm. Here, we describe the use of TasA, an important structural component of the biofilms formed by B. subtilis, as a genetic tool for the display of heterologous proteins. RESULTS We first engineered the fusion protein TasA-mCherry and showed that was widely deployed within the B. subtilis biofilms. A significant enhancement of the expression of TasA-mCherry within the biofilm was obtained when depleting both tasA and sinR genes. We subsequently engineered fusion proteins of TasA to antigenic peptides of the E. granulosus parasite, paramyosin and tropomyosin. Our results show that the antigens were well expressed within the biofilm as denoted by macrostructure complementation and by the detection of the fusion protein in both immunoblot and immunohistochemistry. In addition, we show that the recombinant endospores of B. subtilis preserve their biophysical and morphological properties. CONCLUSIONS In this work we provide strong evidence pointing that TasA is a suitable candidate for the display of heterologous peptides, such as antigens, cytokines, enzymes or antibodies, in the B. subtilis biofilms. Finally, our data portray that the recombinant endospores preserve their morphological and biophysical properties and could be an excellent tool to facilitate the transport and the administration.
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Affiliation(s)
- Cédric M. Vogt
- Institute of Virology, University of Zurich, Winterthurerstrasse 266a, 8057 Zurich, Switzerland
| | - Elisabeth M. Schraner
- Institute of Virology, University of Zurich, Winterthurerstrasse 266a, 8057 Zurich, Switzerland
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Claudio Aguilar
- rqmicro Ltd, ETH, Otto-Stern-Weg 7, 8093 Zurich, Switzerland
| | - Catherine Eichwald
- Institute of Virology, University of Zurich, Winterthurerstrasse 266a, 8057 Zurich, Switzerland
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9
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Johnson E, Seiradake E, Jones EY, Davis I, Grünewald K, Kaufmann R. Correlative in-resin super-resolution and electron microscopy using standard fluorescent proteins. Sci Rep 2015; 5:9583. [PMID: 25823571 PMCID: PMC4379466 DOI: 10.1038/srep09583] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 03/05/2015] [Indexed: 11/15/2022] Open
Abstract
We introduce a method for correlative in-resin super-resolution fluorescence and electron microscopy (EM) of biological structures in mammalian culture cells. Cryo-fixed resin embedded samples offer superior structural preservation, performing in-resin super-resolution, however, remains a challenge. We identified key aspects of the sample preparation procedure of high pressure freezing, freeze substitution and resin embedding that are critical for preserving fluorescence and photo-switching of standard fluorescent proteins, such as mGFP, mVenus and mRuby2. This enabled us to combine single molecule localization microscopy with transmission electron microscopy imaging of standard fluorescent proteins in cryo-fixed resin embedded cells. We achieved a structural resolution of 40-50 nm (~17 nm average single molecule localization accuracy) in the fluorescence images without the use of chemical fixation or special fluorophores. Using this approach enabled the correlation of fluorescently labeled structures to the ultrastructure in the same cell at the nanometer level and superior structural preservation.
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Affiliation(s)
- Errin Johnson
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK
| | - Elena Seiradake
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, UK
| | - E. Yvonne Jones
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, UK
| | - Ilan Davis
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Kay Grünewald
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, UK
| | - Rainer Kaufmann
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3 7BN, UK
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
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10
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Wild P, Leisinger S, de Oliveira AP, Schraner EM, Kaech A, Ackermann M, Tobler K. Herpes simplex virus 1 Us3 deletion mutant is infective despite impaired capsid translocation to the cytoplasm. Viruses 2015; 7:52-71. [PMID: 25588052 PMCID: PMC4306828 DOI: 10.3390/v7010052] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 12/30/2014] [Indexed: 11/29/2022] Open
Abstract
Herpes simplex virus 1 (HSV-1) capsids are assembled in the nucleus bud at the inner nuclear membrane into the perinuclear space, acquiring envelope and tegument. In theory, these virions are de-enveloped by fusion of the envelope with the outer nuclear membrane and re-enveloped by Golgi membranes to become infective. Us3 enables the nucleus to cytoplasm capsid translocation. Nevertheless, Us3 is not essential for the production of infective progeny viruses. Determination of phenotype distribution by quantitative electron microscopy, and calculation per mean nuclear or cell volume revealed the following: (i) The number of R7041(∆US3) capsids budding at the inner nuclear membrane was significantly higher than that of wild type HSV-1; (ii) The mean number of R7041(∆US3) virions per mean cell volume was 2726, that of HSV-1 virions 1460 by 24 h post inoculation; (iii) 98% of R7041(∆US3) virions were in the perinuclear space; (iv) The number of R7041(∆US3) capsids in the cytoplasm, including those budding at Golgi membranes, was significantly reduced. Cell associated R7041(∆US3) yields were 2.37×10(8) and HSV-1 yields 1.57×10(8) PFU/mL by 24 h post inoculation. We thus conclude that R7041(∆US3) virions, which acquire envelope and tegument by budding at the inner nuclear membrane into the perinuclear space, are infective.
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Affiliation(s)
- Peter Wild
- Institute of Veterinar Anatomy, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland.
| | - Sabine Leisinger
- Institute of Veterinar Anatomy, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland.
| | | | - Elisabeth M Schraner
- Institute of Veterinar Anatomy, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland.
| | - Andres Kaech
- Center for Microscopy and Image Analysis, Winterthurerstrasse 190,CH-8057 Zürich, Switzerland.
| | - Mathias Ackermann
- Institute of Virology, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland.
| | - Kurt Tobler
- Institute of Virology, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland.
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11
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Faso C, Konrad C, Schraner EM, Hehl AB. Export of cyst wall material and Golgi organelle neogenesis in Giardia lamblia depend on endoplasmic reticulum exit sites. Cell Microbiol 2012; 15:537-53. [PMID: 23094658 DOI: 10.1111/cmi.12054] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 10/05/2012] [Accepted: 10/11/2012] [Indexed: 12/01/2022]
Abstract
Giardia lamblia parasitism accounts for the majority of cases of parasitic diarrheal disease, making this flagellated eukaryote the most successful intestinal parasite worldwide. This organism has undergone secondary reduction/elimination of entire organelle systems such as mitochondria and Golgi. However, trophozoite to cyst differentiation (encystation) requires neogenesis of Golgi-like secretory organelles named encystation-specific vesicles (ESVs), which traffic, modify and partition cyst wall proteins produced exclusively during encystation. In this work we ask whether neogenesis of Golgi-related ESVs during G. lamblia differentiation, similarly to Golgi biogenesis in more complex eukaryotes, requires the maintenance of distinct COPII-associated endoplasmic reticulum (ER) subdomains in the form of ER exit sites (ERES) and whether ERES are also present in non-differentiating trophozoites. To address this question, we identified conserved COPII components in G. lamblia cells and determined their localization, quantity and dynamics at distinct ERES domains in vegetative and differentiating trophozoites. Analogous to ERES and Golgi biogenesis, these domains were closely associated to early stages of newly generated ESV. Ectopic expression of non-functional Sar1 GTPase variants caused ERES collapse and, consequently, ESV ablation, leading to impaired parasite differentiation. Thus, our data show how ERES domains remain conserved in G. lamblia despite elimination of steady-state Golgi. Furthermore, the fundamental eukaryotic principle of ERES to Golgi/Golgi-like compartment correspondence holds true in differentiating Giardia presenting streamlined machinery for secretory organelle biogenesis and protein trafficking. However, in the Golgi-less trophozoites ERES exist as stable ER subdomains, likely as the sole sorting centres for secretory traffic.
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Affiliation(s)
- Carmen Faso
- Laboratory of Molecular Parasitology, Institute of Parasitology, University of Zurich, Winterthurerstrasse 266a, 8057, Zurich, Switzerland
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12
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Eichwald C, Arnoldi F, Laimbacher AS, Schraner EM, Fraefel C, Wild P, Burrone OR, Ackermann M. Rotavirus viroplasm fusion and perinuclear localization are dynamic processes requiring stabilized microtubules. PLoS One 2012; 7:e47947. [PMID: 23110139 PMCID: PMC3479128 DOI: 10.1371/journal.pone.0047947] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 09/17/2012] [Indexed: 12/21/2022] Open
Abstract
Rotavirus viroplasms are cytosolic, electron-dense inclusions corresponding to the viral machinery of replication responsible for viral template transcription, dsRNA genome segments replication and assembly of new viral cores. We have previously observed that, over time, those viroplasms increase in size and decrease in number. Therefore, we hypothesized that this process was dependent on the cellular microtubular network and its associated dynamic components. Here, we present evidence demonstrating that viroplasms are dynamic structures, which, in the course of an ongoing infection, move towards the perinuclear region of the cell, where they fuse among each other, thereby gaining considerably in size and, simultaneouly, explaining the decrease in numbers. On the viral side, this process seems to depend on VP2 for movement and on NSP2 for fusion. On the cellular side, both the temporal transition and the maintenance of the viroplasms are dependent on the microtubular network, its stabilization by acetylation, and, surprisingly, on a kinesin motor of the kinesin-5 family, Eg5. Thus, we provide for the first time deeper insights into the dynamics of rotavirus replication, which can explain the behavior of viroplasms in the infected cell.
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13
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Wild P, de Oliveira AP, Sonda S, Schraner EM, Ackermann M, Tobler K. The herpes simplex virus 1 U(S)3 regulates phospholipid synthesis. Virology 2012; 432:353-60. [PMID: 22789738 DOI: 10.1016/j.virol.2012.06.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 05/07/2012] [Accepted: 06/12/2012] [Indexed: 10/28/2022]
Abstract
Herpes simplex virus type 1 capsids bud at nuclear and Golgi membranes for envelopment by phospholipid bilayers. In the absence of U(S)3, nuclear membranes form multiple folds harboring virions that suggests disturbance in membrane turnover. Therefore, we investigated phospholipid metabolism in cells infected with the U(S)3 deletion mutant R7041(ΔU(S)3), and quantified membranes involved in viral envelopment. We report that (i) [(3)H]-choline incorporation into nuclear membranes and cytoplasmic membranes was enhanced peaking at 12 or 20 h post inoculation with wild type HSV-1 and R7041(ΔU(S)3), respectively, (ii) the surface area of nuclear membranes increased until 24 h of R7041(ΔU(S)3) infection forming folds that equaled ~45% of the nuclear surface, (iii) the surface area of viral envelopes between nuclear membranes equaled ~2400 R7041(ΔU(S)3) virions per cell, and (iv) during R7041(ΔU(S)3) infection, the Golgi complex expanded dramatically. The data indicate that U(S)3 plays a significant role in regulation of membrane biosynthesis.
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Affiliation(s)
- Peter Wild
- Institute of Veterinary Anatomy, University of Zürich, Switzerland.
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14
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Sutter E, de Oliveira AP, Tobler K, Schraner EM, Sonda S, Kaech A, Lucas MS, Ackermann M, Wild P. Herpes simplex virus 1 induces de novo phospholipid synthesis. Virology 2012; 429:124-35. [PMID: 22560864 DOI: 10.1016/j.virol.2012.04.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 03/02/2012] [Accepted: 04/10/2012] [Indexed: 11/25/2022]
Abstract
Herpes simplex virus type 1 capsids bud at nuclear membranes and Golgi membranes acquiring an envelope composed of phospholipids. Hence, we measured incorporation of phospholipid precursors into these membranes, and quantified changes in size of cellular compartments by morphometric analysis. Incorporation of [³H]-choline into both nuclear and cytoplasmic membranes was significantly enhanced upon infection. [³H]-choline was also part of isolated virions even grown in the presence of brefeldin A. Nuclei expanded early in infection. The Golgi complex and vacuoles increased substantially whereas the endoplasmic reticulum enlarged only temporarily. The data suggest that HSV-1 stimulates phospholipid synthesis, and that de novo synthesized phospholipids are inserted into nuclear and cytoplasmic membranes to i) maintain membrane integrity in the course of nuclear and cellular expansion, ii) to supply membrane constituents for envelopment of capsids by budding at nuclear membranes and Golgi membranes, and iii) to provide membranes for formation of transport vacuoles.
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Affiliation(s)
- Esther Sutter
- Electron Microscopy, Institute of Veterinary Anatomy, University of Zürich, Switzerland
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15
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Hübner S, Efthymiadis A. Recent progress in histochemistry and cell biology. Histochem Cell Biol 2012; 137:403-57. [PMID: 22366957 DOI: 10.1007/s00418-012-0933-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/06/2012] [Indexed: 01/06/2023]
Abstract
Studies published in Histochemistry and Cell Biology in the year 2011 represent once more a manifest of established and newly sophisticated techniques being exploited to put tissue- and cell type-specific molecules into a functional context. The review is therefore the Histochemistry and Cell Biology's yearly intention to provide interested readers appropriate summaries of investigations touching the areas of tissue biology, developmental biology, the biology of the immune system, stem cell research, the biology of subcellular compartments, in order to put the message of such studies into natural scientific-/human- and also pathological-relevant correlations.
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Affiliation(s)
- Stefan Hübner
- Institute of Anatomy and Cell Biology, University of Würzburg, Würzburg, Germany.
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16
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Sobol M, Nebesářová J, Hozák P. A method for preserving ultrastructural properties of mitotic cells for subsequent immunogold labeling using low-temperature embedding in LR White resin. Histochem Cell Biol 2010; 135:103-10. [DOI: 10.1007/s00418-010-0771-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/01/2010] [Indexed: 10/18/2022]
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17
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Comparison of methods of high-pressure freezing and automated freeze-substitution of suspension cells combined with LR White embedding. Histochem Cell Biol 2010; 134:631-41. [DOI: 10.1007/s00418-010-0757-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/20/2010] [Indexed: 10/18/2022]
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18
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Bottova I, Hehl AB, Stefanić S, Fabriàs G, Casas J, Schraner E, Pieters J, Sonda S. Host cell P-glycoprotein is essential for cholesterol uptake and replication of Toxoplasma gondii. J Biol Chem 2009; 284:17438-48. [PMID: 19389707 DOI: 10.1074/jbc.m809420200] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
P-glycoprotein (P-gp) is a membrane-bound efflux pump that actively exports a wide range of compounds from the cell and is associated with the phenomenon of multidrug resistance. However, the role of P-gp in normal physiological processes remains elusive. Using P-gp-deficient fibroblasts, we showed that P-gp was critical for the replication of the intracellular parasite Toxoplasma gondii but was not involved in invasion of host cells by the parasite. Importantly, we found that the protein participated in the transport of host-derived cholesterol to the intracellular parasite. T. gondii replication in P-gp-deficient host cells not only resulted in reduced cholesterol content in the parasite but also altered its sphingolipid metabolism. In addition, we found that different levels of P-gp expression modified the cholesterol metabolism in uninfected fibroblasts. Collectively our findings reveal a key and previously undocumented role of P-gp in host-parasite interaction and suggest a physiological role for P-gp in cholesterol trafficking in mammalian cells.
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Affiliation(s)
- Iveta Bottova
- Institute of Parasitology, University of Zurich, Zurich, Switzerland
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19
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Wild P, Senn C, Manera CL, Sutter E, Schraner EM, Tobler K, Ackermann M, Ziegler U, Lucas MS, Kaech A. Exploring the nuclear envelope of herpes simplex virus 1-infected cells by high-resolution microscopy. J Virol 2009; 83:408-19. [PMID: 18922868 PMCID: PMC2612326 DOI: 10.1128/jvi.01568-08] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Accepted: 10/06/2008] [Indexed: 01/11/2023] Open
Abstract
Herpesviruses are composed of capsid, tegument, and envelope. Capsids assemble in the nucleus and exit the nucleus by budding at the inner nuclear membrane, acquiring tegument and the envelope. This study focuses on the changes of the nuclear envelope during herpes simplex virus 1 (HSV-1) infection in HeLa and Vero cells by employing preparation techniques at ambient and low temperatures for high-resolution scanning and transmission electron microscopy and confocal laser scanning microscopy. Cryo-field emission scanning electron microscopy of freeze-fractured cells showed for the first time budding of capsids at the nuclear envelope at the third dimension with high activity at 10 h and low activity at 15 h of incubation. The mean number of pores was significantly lower, and the mean interpore distance and the mean interpore area were significantly larger than those for mock-infected cells 15 h after inoculation. Forty-five percent of nuclear pores in HSV-1-infected cells were dilated to more than 140 nm. Nuclear material containing capsids protrude through them into the cytoplasm. Examination of in situ preparations after dry fracturing revealed significant enlargements of the nuclear pore diameter and of the nuclear pore central channel in HSV-1-infected cells compared to mock-infected cells. The demonstration of nucleoporins by confocal microscopy also revealed fewer pores but focal enhancement of fluorescence signals in HSV-1-infected cells, whereas Western blots showed no loss of nucleoporins from cells. The data suggest that infection with HSV-1 alters the number, size, and architecture of nuclear pores without a loss of nucleoporins from altered nuclear pore complexes.
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Affiliation(s)
- Peter Wild
- Electron Microscopy, Institute of Virology, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland.
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20
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Abstract
The default pathway of cell-surface T-cell receptor (TCR) complex formation, and the subsequent transport to the membrane, is thought to entail endoplasmic reticulum (ER) localization followed by proteasome degradation of the unassembled chains. We show herein an alternative pathway: short, incomplete peptide versions of TCRbeta naturally occur in the thymus. Such peptides, which have minimally lost the leader sequence or have been massively truncated, leaving only the very C terminus intact, are sorted preferentially to the mitochondrion. As a consequence of the mitochondrial localization, apoptotic cell death is induced. Structure function analysis showed that both the specific localization and induction of apoptosis depend on the transmembrane domain (TMD) and associated residues at the COOH-terminus of TCR. Truncated forms of TCR, such as the short peptides that we detected in the thymus, may be products of protein degradation within thymocytes. Alternatively, they may occur through the translation of truncated mRNAs resulting from unfruitful rearrangement or from germline transcription. It is proposed that mitochondria serve as a subcellular sequestration site for incomplete TCR molecules.
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21
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Strádalová V, Gaplovská-Kyselá K, Hozák P. Ultrastructural and nuclear antigen preservation after high-pressure freezing/freeze-substitution and low-temperature LR White embedding of HeLa cells. Histochem Cell Biol 2008; 130:1047-52. [PMID: 18797913 DOI: 10.1007/s00418-008-0504-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/31/2008] [Indexed: 12/01/2022]
Abstract
A protocol for high-pressure freezing and LR White embedding of mammalian cells suitable for fine ultrastructural studies in combination with immunogold labelling is presented. HeLa S3 cells enclosed in low-temperature gelling agarose were high-pressure frozen, freeze-substituted in acetone, and embedded in LR White at 0 degrees C. The morphology of such cells and the preservation of nuclear antigens were excellent in comparison with chemically fixed cells embedded in the same resin. The immunolabelling signal for different nuclear antigens was 4-to-13 times higher in high-pressure frozen than in chemically fixed cells. We conclude that one can successfully use high-pressure freezing/freeze-substitution and LR White embedding as an alternative of Lowicryl resins.
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Affiliation(s)
- Vendula Strádalová
- Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, v.v.i., Vídenská 1083, 142 20, Prague, Czech Republic
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22
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Abstract
Electron microscopy is a powerful tool to visualize viruses in diagnostic as well as in research settings for investigating viral structure and virus-cell interactions. Here, a simple but efficient method is described for demonstrating viruses by negative staining, and its limit is discussed. A prerequisite to obtain reliable information on virus-cell interactions is excellent preservation of cellular and viral ultrastructure. The crux is that during fixation and embedding, by applying conventional protocols about 50% of the lipids are lost, which results in loss of integrity of cell membranes. To achieve good preservation of cellular architectures, good contrast, and both high spatial and temporal resolution, methods for freezing, freeze-substitution, and freeze-etching are described and their applicability discussed mostly taking complicated built herpes viruses as examples.
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Affiliation(s)
- Peter Wild
- Electron Microscopy, Institutes of Veterinary Anatomy and of Virology, University of Zürich, CH-8057 Zürich, Switzerland
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23
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Verkade P. Moving EM: the Rapid Transfer System as a new tool for correlative light and electron microscopy and high throughput for high-pressure freezing. J Microsc 2008; 230:317-28. [PMID: 18445162 DOI: 10.1111/j.1365-2818.2008.01989.x] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
In this paper, the Rapid Transfer System (RTS), an attachment to the Leica EMPACT2 high-pressure freezer, is described as a new tool for special applications within the cryofixation field. The RTS is an automated system that allows for fast processing of samples (<5 s) that make it possible for the first time to use high-pressure freezing in combination with high time resolution correlative light and electron microscopy. In addition, with a working cycle of 30 s this rapid turn over time allows one to acquire more samples of biopsy material before it deteriorates than with other HPF machines with longer cycle times. With the use of the RTS it was possible to obtain three samples each of four different tissues in 6 min. Together with the finding that 90% of samples of cells grown on sapphire discs were well frozen, the RTS was both fast and reliable. Most important, together with other newly developed accessories, the RTS made it possible to capture specific events occurring live in the cell as observed by light microscopy, to cryofix that sample/event within 4 s, and then to analyze that event at high resolution in the electron microscope with excellent preservation of ultra-structure. These developments should give us the tools to unravel intracellular processes that can be observed by live cell imaging but are too rare or fast to be picked up by routine EM methods or where the history of a structure is necessary to be able to discern its nature.
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Affiliation(s)
- P Verkade
- School of Medical Sciences, University Walk, Bristol, BS8 1TD, United Kingdom.
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24
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Buser C, Walther P. Freeze-substitution: the addition of water to polar solvents enhances the retention of structure and acts at temperatures around -60 degrees C. J Microsc 2008; 230:268-77. [PMID: 18445157 DOI: 10.1111/j.1365-2818.2008.01984.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
High-pressure freezing followed by freeze substitution and plastic embedding is becoming a more widely used method for TEM sample preparation. Here, we have investigated the influence of solvents, fixative concentrations and water content in the substitution medium on the sample quality of high-pressure frozen, freeze-substituted and plastic embedded mammalian cell culture monolayers. We found that the visibility of structural details was optimal with acetone and that extraction increased with both increasing and decreasing solvent polarity. Interestingly, the addition of water to polar solvents increased the sample quality, while being destructive when added to apolar solvents. The positive effect of water addition is saturable in acetone and ethanol at 5%(v/v), but even addition of up to 20% water has no negative effect on the sample structure. Therefore, a medium based on acetone containing fixatives and 5% water is most optimal for the substitution of mammalian cell cultures. In addition, our results suggest that the presence of water is critical for the retention of structure at temperatures around -60 degrees C.
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Affiliation(s)
- C Buser
- Zentrale Einrichtung Elektronenmikroskopie, Universitaet Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany
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25
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de Oliveira AP, Glauser DL, Laimbacher AS, Strasser R, Schraner EM, Wild P, Ziegler U, Breakefield XO, Ackermann M, Fraefel C. Live visualization of herpes simplex virus type 1 compartment dynamics. J Virol 2008; 82:4974-90. [PMID: 18337577 PMCID: PMC2346754 DOI: 10.1128/jvi.02431-07] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2007] [Accepted: 02/29/2008] [Indexed: 11/20/2022] Open
Abstract
We have constructed a recombinant herpes simplex virus type 1 (HSV-1) that simultaneously encodes selected structural proteins from all three virion compartments-capsid, tegument, and envelope-fused with autofluorescent proteins. This triple-fluorescent recombinant, rHSV-RYC, was replication competent, albeit with delayed kinetics, incorporated the fusion proteins into all three virion compartments, and was comparable to wild-type HSV-1 at the ultrastructural level. The VP26 capsid fusion protein (monomeric red fluorescent protein [mRFP]-VP26) was first observed throughout the nucleus and later accumulated in viral replication compartments. In the course of infection, mRFP-VP26 formed small foci in the periphery of the replication compartments that expanded and coalesced over time into much larger foci. The envelope glycoprotein H (gH) fusion protein (enhanced yellow fluorescent protein [EYFP]-gH) was first observed accumulating in a vesicular pattern in the cytoplasm and was then incorporated primarily into the nuclear membrane. The VP16 tegument fusion protein (VP16-enhanced cyan fluorescent protein [ECFP]) was first observed in a diffuse nuclear pattern and then accumulated in viral replication compartments. In addition, it also formed small foci in the periphery of the replication compartments which, however, did not colocalize with the small mRFP-VP26 foci. Later, VP16-ECFP was redistributed out of the nucleus into the cytoplasm, where it accumulated in vesicular foci and in perinuclear clusters reminiscent of the Golgi apparatus. Late in infection, mRFP-VP26, EYFP-gH, and VP16-ECFP were found colocalizing in dots at the plasma membrane, possibly representing mature progeny virus. In summary, this study provides new insights into the dynamics of compartmentalization and interaction among capsid, tegument, and envelope proteins. Similar strategies can also be applied to assess other dynamic events in the virus life cycle, such as entry and trafficking.
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Affiliation(s)
- Anna Paula de Oliveira
- Institute of Virology, University of Zurich, Winterthurerstrasse 266a, CH-8057 Zurich, Switzerland
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26
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HAGEN C, GRÜNEWALD K. Microcarriers for high-pressure freezing and cryosectioning of adherent cells. J Microsc 2008; 230:288-96. [DOI: 10.1111/j.1365-2818.2008.01987.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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27
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Reipert S, Wiche G. Chapter 10 High-Pressure Freezing and Low-Temperature Fixation of Cell Monolayers Grown on Sapphire Coverslips. Methods Cell Biol 2008; 88:165-80. [DOI: 10.1016/s0091-679x(08)00410-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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28
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Gaechter V, Schraner E, Wild P, Hehl AB. The single dynamin family protein in the primitive protozoan Giardia lamblia is essential for stage conversion and endocytic transport. Traffic 2007; 9:57-71. [PMID: 17892527 DOI: 10.1111/j.1600-0854.2007.00657.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dynamins are universally conserved large guanosine triphosphatases, which function as mechanoenzymes in membrane scission. The primitive protozoan Giardia lamblia has a single dynamin-related protein (GlDRP) with an unusual domain structure. Giardia lacks a Golgi apparatus but generates transient Golgi-like delay compartments dubbed encystation-specific vesicles (ESVs), which serve to accumulate and mature cyst wall proteins during differentiation to infectious cyst forms. Here, we analyze the function of GlDRP during growth and encystation and demonstrate that it relocalizes from peripheral endosomal-lysosomal compartments to nascent ESVs. We show that GlDRP is necessary for secretion of the cyst wall material and ESV homeostasis. Expression of a dominant-negative GlDRP variant does not interfere with ESV formation but blocks cyst formation completely prior to regulated exocytosis. GlDRP colocalizes with clathrin at the cell periphery and is necessary for endocytosis of surface proteins to endosomal-lysosomal organelles in trophozoites. Electron microscopy and live cell imaging reveal gross morphological changes as well as functional impairment of the endocytic system in cells expressing the dominant-negative GlDRP. Thus, giardial DRP plays a key role in two distinct trafficking pathways and in organelle homeostasis, both essential functions for the proliferation of the parasite in the gut and its transmission to a new host.
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Affiliation(s)
- Verena Gaechter
- Institute of Parasitology, University of Zürich, Winterthurerstrasse 266a, 8057 Zürich, Switzerland
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29
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Yakushevska AE, Lebbink MN, Geerts WJC, Spek L, van Donselaar EG, Jansen KA, Humbel BM, Post JA, Verkleij AJ, Koster AJ. STEM tomography in cell biology. J Struct Biol 2007; 159:381-91. [PMID: 17600727 DOI: 10.1016/j.jsb.2007.04.006] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 04/12/2007] [Accepted: 04/14/2007] [Indexed: 11/27/2022]
Abstract
Transmission electron tomography has been used in biological sciences for quite some time and proven to be a valuable tool. However, to date, the different Scanning Transmission modes are almost not used for electron tomography on resin-embedded biological material. We explored different STEM modes on epon-embedded, osmium-uranyl-lead-stained biological material. Bright Field-TEM and High Angle Annular Dark Field-STEM tomograms from the same areas were recorded and compared. Contrast and signal-to-noise ratios were calculated. Template matching was used to validate results obtained in Bright Field-TEM and High Angle Annular Dark Field-STEM tomograms. It is concluded that High Angle Annular Dark Field-STEM gives a five times better contrast and signal-to-noise ratio than Bright Field-TEM. Template matching showed that 1.3 times more information could be extracted from High Angle Annular Dark Field-STEM tomograms than from Bright Field-TEM tomograms.
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Affiliation(s)
- A E Yakushevska
- Cellular Architecture and Dynamics, Institute of Biomembranes, Faculty of Science, Padualaan 8, 3584 CH Utrecht, The Netherlands
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Matsko NB. Atomic force microscopy applied to study macromolecular content of embedded biological material. Ultramicroscopy 2007; 107:95-105. [PMID: 16875783 DOI: 10.1016/j.ultramic.2006.05.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Revised: 05/18/2006] [Accepted: 05/31/2006] [Indexed: 11/29/2022]
Abstract
We demonstrate that atomic force microscopy represents a powerful tool for the estimation of structural preservation of biological samples embedded in epoxy resin, in terms of their macromolecular distribution and architecture. The comparison of atomic force microscopy (AFM) and transmission electron microscopy (TEM) images of a biosample (Caenorhabditis elegans) prepared following to different types of freeze-substitution protocols (conventional OsO4 fixation, epoxy fixation) led to the conclusion that high TEM stainability of the sample results from a low macromolecular density of the cellular matrix. We propose a novel procedure aimed to obtain AFM and TEM images of the same particular organelle, which strongly facilitates AFM image interpretation and reveals new ultrastructural aspects (mainly protein arrangement) of a biosample in addition to TEM data.
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Affiliation(s)
- Nadejda B Matsko
- Electron Microscopy Centre, Institute of Applied Physics, HPM C 15.1, ETH-Hoenggerberg, CH-8093, Zuerich, Switzerland.
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Zechmann B, Müller M, Zellnig G. Membrane associated qualitative differences in cell ultrastructure of chemically and high pressure cryofixed plant cells. J Struct Biol 2006; 158:370-7. [PMID: 17270463 DOI: 10.1016/j.jsb.2006.12.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Revised: 12/15/2006] [Accepted: 12/19/2006] [Indexed: 10/23/2022]
Abstract
Membrane contrast can sometimes be poor in biological samples after high pressure freezing (HPF) and freeze substitution (FS). The addition of water to the FS-medium has been shown to improve membrane contrast in animal tissue and yeast. In the present study we tested the effects of 1% and 5% water added to the FS-medium (2% osmium with 0.2% uranyl acetate in anhydrous acetone) on the quality and visibility of membranes in high pressure frozen leaf samples of Cucurbita pepo L. plants and compared them to chemically fixed cells (3% glutaraldehyde post-fixed with 1% osmium tetroxide). The addition of water to the FS-medium drastically decreased the amounts of well preserved cells and did not significantly improve the quality nor visibility of membranes. In samples that were freeze substituted in FS-media containing 1% and 5% water the width of thylakoid membranes was found to be significantly increased of about 20% and the perinuclear space was up to 76% wider in comparison to what was found in samples which were freeze substituted without water. No differences were found in the thickness of membranes between chemically and cryofixed cells that were freeze substituted in the FS-medium without water. Nevertheless, in chemically fixed cells the intrathylakoidal space was about 120% wider than in cryofixed cells that were freeze substituted with or without water. The present results demonstrate that the addition of water to the FS-medium does not improve membrane contrast but changes the width of thylakoid membranes and the perinuclear space in the present plant material. The addition of water to the FS-medium is therefore not as essential for improved membrane contrast in the investigated plant samples as it was observed in cells of animal tissues and yeast cells.
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Affiliation(s)
- Bernd Zechmann
- University of Graz, Institute of Plant Sciences, 8010 Graz, Austria.
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Jiménez N, Humbel BM, van Donselaar E, Verkleij AJ, Burger KNJ. Aclar discs: a versatile substrate for routine high-pressure freezing of mammalian cell monolayers. J Microsc 2006; 221:216-23. [PMID: 16551282 DOI: 10.1111/j.1365-2818.2006.01558.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
High-pressure freezing avoids the artefacts induced by conventional chemical fixation, and, in combination with freeze-substitution and plastic embedding, is a reliable method for the ultrastructural analysis of mammalian cell monolayers. In order to high-pressure freeze mammalian cell monolayers, cells have to be seeded on a suitable substrate. Unfortunately, electron microscopy analysis is often hampered by poor cell growth, changes in cell morphology induced by the cell substrate or cell loss during processing. We report a method to culture, high-pressure freeze, freeze-substitute and plastic embed mammalian cell monolayers. The method is based on the use of Aclar, a copolymer film with properties very similar to those of tissue culture plastic. We show that Aclar discs support the normal growth and morphology of a wide variety of mammalian cell types, and form an ideal starting point for high-pressure freezing, freeze-substitution and plastic embedding. We present a complete protocol, which, because of its simplicity and reproducibility, provides a method suitable for the routine analysis of mammalian cell monolayers by electron microscopy and tomography.
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Affiliation(s)
- N Jiménez
- Department of Molecular Cell Biology, Institute of Biomembranes, Utrecht University, Utrecht, The Netherlands.
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33
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Leuzinger H, Ziegler U, Schraner EM, Fraefel C, Glauser DL, Heid I, Ackermann M, Mueller M, Wild P. Herpes simplex virus 1 envelopment follows two diverse pathways. J Virol 2005; 79:13047-59. [PMID: 16189007 PMCID: PMC1235821 DOI: 10.1128/jvi.79.20.13047-13059.2005] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Herpesvirus envelopment is assumed to follow an uneconomical pathway including primary envelopment at the inner nuclear membrane, de-envelopment at the outer nuclear membrane, and reenvelopment at the trans-Golgi network. In contrast to the hypothesis of de-envelopment by fusion of the primary envelope with the outer nuclear membrane, virions were demonstrated to be transported from the perinuclear space to rough endoplasmic reticulum (RER) cisternae. Here we show by high-resolution microscopy that herpes simplex virus 1 envelopment follows two diverse pathways. First, nuclear envelopment includes budding of capsids at the inner nuclear membrane into the perinuclear space whereby tegument and a thick electron dense envelope are acquired. The substance responsible for the dense envelope is speculated to enable intraluminal transportation of virions via RER into Golgi cisternae. Within Golgi cisternae, virions are packaged into transport vacuoles containing one or several virions. Second, for cytoplasmic envelopment, capsids gain direct access from the nucleus to the cytoplasm via impaired nuclear pores. Cytoplasmic capsids could bud at the outer nuclear membrane, at membranes of RER, Golgi cisternae, and large vacuoles, and at banana-shaped membranous entities that were found to continue into Golgi membranes. Envelopes originating by budding at the outer nuclear membrane and RER membrane also acquire a dense substance. Budding at Golgi stacks, designated wrapping, results in single virions within small vacuoles that contain electron-dense substances between envelope and vacuolar membranes.
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Affiliation(s)
- Helene Leuzinger
- Electron Microscopy, Institutes of Veterinary Anatomy and of Virology, Zürich, Switzerland
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34
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Matsko N, Mueller M. Epoxy resin as fixative during freeze-substitution. J Struct Biol 2005; 152:92-103. [PMID: 16214372 DOI: 10.1016/j.jsb.2005.07.005] [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: 03/23/2005] [Revised: 07/15/2005] [Accepted: 07/19/2005] [Indexed: 10/25/2022]
Abstract
An alternative protocol for freeze-substitution is described. Araldite/Epon embedding medium (20% in acetone) is first used as a stabilizer (as e.g., OsO(4)) and then as embedding medium. The major components of the Araldite/Epon resin formulation react with proteins and lipids and provide for an excellent preservation and reasonable visualisation of the ultrastructure. The ultrastructural appearance can be deliberately influenced with the standard freeze-substitution procedure [Van Harreveld, A., Crowell, J., 1964. Electron microscopy after rapid freezing on a metal surface and substitution fixation. Anat. Rec. 149, 381-386.] using OsO(4) as stabilizing agent by protocols which degrade cytoplasmic and membrane proteins. Epoxy stabilized and embedded samples may become an important tool to get information about the effects of different reagents and protocols used in freeze-substitution. We believe that an in-depth understanding of the procedures is required to correctly interpret images and to complement studies of dynamic processes by light microscopy with reliable, highly detailed ultrastructural information. The block face of epoxy stabilized samples after ultrathin sectioning is highly suited for the analysis of the ultrastructure by AFM.
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Affiliation(s)
- Nadezda Matsko
- Electron Microscopy Center, Institute of Applied Physics, ETH-Hoenggerberg, CH-8093 , Zuerich, Switzerland
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35
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Zechmann B, Müller M, Zellnig G. Effects of different fixation and freeze substitution methods on the ultrastructural preservation of ZYMV-infected Cucurbita pepo (L.) leaves. Microscopy (Oxf) 2005; 54:393-402. [PMID: 16123060 DOI: 10.1093/jmicro/dfi054] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2023] Open
Abstract
Different fixation protocols [chemical fixation, plunge and high pressure freezing (HPF)] were used to study the effects of Zucchini yellow mosaic virus (ZYMV) disease on the ultrastructure of adult leaves of Styrian oil pumpkin plants (Cucurbita pepo L. subsp. pepo var. styriaca Greb.) with the transmission electron microscope. Additionally, different media were tested for freeze substitution (FS) to evaluate differences in the ultrastructural preservation of cryofixed plant leaf cells. FS was either performed in (i) 2% osmium tetroxide in anhydrous acetone containing 0.2% uranyl acetate, (ii) 0.01% safranin in anhydrous acetone, (iii) 0.5% glutaraldehyde in anhydrous acetone or (iv) anhydrous acetone. No ultrastructural differences were found in well-preserved cells of plunge and high pressure frozen samples. Cryofixed cells showed a finer granulated cytosol and smoother membranes, than what was found in chemically fixed samples. HPF led in comparison to plunge frozen plant material to an excellent preservation of vascular bundle cells. The use of FS-media such as anhydrous acetone, 0.01% safranin and 0.5% glutaraldehyde led to low membrane contrast and did not preserve the inner fine structures of mitochondria. Additionally, the use of 0.5% glutaraldehyde caused the cytosol to be fuzzy and partly loosened. ZYMV-induced ultrastructural alterations like cylindrical inclusions and dilated ER-cisternae did not differ between chemically fixed and cryofixed cells and were found within the cytosol of infected leaf cells and within sieve tube elements. The results demonstrate specific structural differences depending on the FS-medium used, which has to be considered for investigations of selected cell structures.
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Affiliation(s)
- Bernd Zechmann
- University of Graz, Institute of Plant Sciences, Schubertstrasse 51, 8010 Graz, Austria.
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36
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Murk JLAN, Lebbink MN, Humbel BM, Geerts WJC, Griffith JM, Langenberg DML, Verreck FAW, Verkleij AJ, Koster AJ, Geuze HJ, Kleijmeer MJ. 3-D Structure of multilaminar lysosomes in antigen presenting cells reveals trapping of MHC II on the internal membranes. Traffic 2005; 5:936-45. [PMID: 15522096 DOI: 10.1111/j.1600-0854.2004.00235.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In late endosomes and lysosomes of antigen presenting cells major histocompatibility complex class II (MHC II) molecules bind peptides from degraded internalized pathogens. These compartments are called MHC class II compartments (MIICs), and from here peptide-loaded MHC II is transported to the cell surface for presentation to helper T-lymphocytes to generate an immune response. Recent studies from our group in mouse dendritic cells indicate that the MHC class II on internal vesicles of multivesicular late endosomes or multivesicular bodies is the main source of MHC II at the plasma membrane. We showed that dendritic cell activation triggers a back fusion mechanism whereby MHC II from the inner membranes is delivered to the multivesicular bodies' outer membrane. Another type of MIIC in B-lymphocytes and dendritic cells is more related to lysosomes and often appears as a multilaminar organelle with abundant MHC II-enriched internal membrane sheets. These multilaminar lysosomes have a functioning peptide-loading machinery, but to date it is not clear whether peptide-loaded MHC II molecules from the internal membranes can make their way to the cell surface and contribute to T cell activation. To obtain detailed information on the membrane organization of multilaminar lysosomes and investigate possible escape routes from the lumen of this organelle, we performed electron tomography on cryo-immobilized B-lymphocytes and dendritic cells. Our high-resolution 3-D reconstructions of multilaminar lysosomes indicate that their membranes are organized in such a way that MHC class II may be trapped on the inner membranes, without the possibility to escape to the cell surface.
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Affiliation(s)
- Jean-Luc A N Murk
- Department of Cell Biology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, the Netherlands
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37
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Wild P, Engels M, Senn C, Tobler K, Ziegler U, Schraner EM, Loepfe E, Ackermann M, Mueller M, Walther P. Impairment of nuclear pores in bovine herpesvirus 1-infected MDBK cells. J Virol 2005; 79:1071-83. [PMID: 15613336 PMCID: PMC538577 DOI: 10.1128/jvi.79.2.1071-1083.2005] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Herpesvirus capsids originating in the nucleus overcome the nucleocytoplasmic barrier by budding at the inner nuclear membrane. The fate of the resulting virions is still under debate. The fact that capsids approach Golgi membranes from the cytoplasmic side led to the theory of fusion between the viral envelope and the outer nuclear membrane, resulting in the release of capsids into the cytoplasm. We recently discovered a continuum from the perinuclear space to the Golgi complex implying (i) intracisternal viral transportation from the perinuclear space directly into Golgi cisternae and (ii) the existence of an alternative pathway of capsids from the nucleus to the cytoplasm. Here, we analyzed the nuclear surface by high-resolution microscopy. Confocal microscopy of MDBK cells infected with recombinant bovine herpesvirus 1 expressing green fluorescent protein fused to VP26 (a minor capsid protein) revealed distortions of the nuclear surface in the course of viral multiplication. High-resolution scanning and transmission electron microscopy proved the distortions to be related to enlargement of nuclear pores through which nuclear content including capsids protrudes into the cytoplasm, suggesting that capsids use impaired nuclear pores as gateways to gain access to the cytoplasmic matrix. Close examination of Golgi membranes, rough endoplasmic reticulum, and outer nuclear membrane yielded capsid-membrane interaction of high identity to the budding process at the inner nuclear membrane. These observations signify the ability of capsids to induce budding at any cell membrane, provided the fusion machinery is present and/or budding is not suppressed by viral proteins.
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Affiliation(s)
- Peter Wild
- Electron Microscopy Institute of Veterinary Anatomy, Winterthurerstrasse 266a, CH-8057 Zürich, Switzerland.
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38
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Mathis A, Wild P, Deplazes P, Boettger EC. The mitochondrial ribosome of the protozoan Acanthamoeba castellanii is the target for macrolide antibiotics. Mol Biochem Parasitol 2004; 135:225-9. [PMID: 15110464 DOI: 10.1016/j.molbiopara.2004.02.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2003] [Revised: 02/06/2004] [Accepted: 02/24/2004] [Indexed: 11/20/2022]
Affiliation(s)
- Alexander Mathis
- Institute of Parasitology, University of Zürich, Winterthurerstrasse 266A, 8057 Zürich, Switzerland.
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39
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Murk JLAN, Humbel BM, Ziese U, Griffith JM, Posthuma G, Slot JW, Koster AJ, Verkleij AJ, Geuze HJ, Kleijmeer MJ. Endosomal compartmentalization in three dimensions: implications for membrane fusion. Proc Natl Acad Sci U S A 2003; 100:13332-7. [PMID: 14597718 PMCID: PMC263806 DOI: 10.1073/pnas.2232379100] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Endosomes are major sorting stations in the endocytic route that send proteins and lipids to multiple destinations in the cell, including the cell surface, Golgi complex, and lysosomes. They have an intricate architecture of internal membrane structures enclosed by an outer membrane. Recycling proteins remain on the outer membrane, whereas proteins that are destined for degradation in the lysosome are sorted to the interior. Recently, a retrograde pathway was discovered whereby molecules, like MHC class II of the immune system, return from the internal structures to the outer membrane, allowing their further transport to the cell surface for T cell activation. Whether this return involves back fusion of free vesicles with the outer membrane, or occurs via the continuity of the two membrane domains, is an unanswered question. By electron tomography of cryo-immobilized cells we now demonstrate that, in multivesicular endosomes of B-lymphocytes and dendritic cells, the inner membranes are free vesicles. Hence, protein transport from inner to outer membranes cannot occur laterally in the plane of the membrane, but requires fusion between the two membrane domains. This implies the existence of an intracellular machinery that mediates fusion between the exoplasmic leaflets of the membranes involved, which is opposite to regular intracellular fusion between cytoplasmic leaflets. In addition, our 3D reconstructions reveal the presence of clathrin-coated areas at the cytoplasmic face of the outer membrane, known to participate in protein sorting to the endosomal interior. Interestingly, profiles reminiscent of inward budding vesicles were often in close proximity to the coats.
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Affiliation(s)
- J L A N Murk
- Department of Cell Biology, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands
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40
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Marti M, Regös A, Li Y, Schraner EM, Wild P, Müller N, Knopf LG, Hehl AB. An ancestral secretory apparatus in the protozoan parasite Giardia intestinalis. J Biol Chem 2003; 278:24837-48. [PMID: 12711599 DOI: 10.1074/jbc.m302082200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The protozoan parasite Giardia intestinalis belongs to one of the earliest diverged eukaryotic lineages. This is also reflected in a simple intracellular organization, as Giardia lacks common subcellular compartments such as mitochondria, peroxisomes, and apparently also a Golgi apparatus. During encystation, developmentally regulated formation of large secretory compartments containing cyst wall material occurs. Despite the lack of any morphological similarities, these encystation-specific vesicles (ESVs) show several biochemical characteristics of maturing Golgi cisternae. Previous studies suggested that Golgi structure and function are induced only during encystation in Giardia, giving rise to the hypothesis that ESVs, as a Giardia Golgi equivalent, are generated de novo. Alternatively, ESV compartments could be built on the template structure of a cryptic Golgi in trophozoites in response to ER export of cyst wall material during encystation. We addressed this question by defining the molecular framework of the Giardia secretory apparatus using a comparative genomic approach. Analysis of the corresponding transcriptome during growth and encystation revealed surprisingly little stage-specific regulation. A panel of antibodies was generated against selected marker proteins to investigate the developmental dynamics of the endomembrane system. We show evidence that Giardia accommodates the export of large amounts of cyst wall material through re-organization of membrane compartment(s) in trophozoites with biochemical similarities to ESVs. This suggests that ESVs are selectively stabilized Golgi-like compartments in a unique and archetypical secretory system, which arise from a structural template in trophozoites rather than being generated de novo.
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Affiliation(s)
- Matthias Marti
- Institute of Parasitology, University of Zürich, Switzerland
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41
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Baumberger N, Steiner M, Ryser U, Keller B, Ringli C. Synergistic interaction of the two paralogous Arabidopsis genes LRX1 and LRX2 in cell wall formation during root hair development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2003; 35:71-81. [PMID: 12834403 DOI: 10.1046/j.1365-313x.2003.01784.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
LRR-extensins (LRX) form a family of structural cell wall proteins containing a receptor-like domain. The functional analysis of Arabidopsis LRX1 has shown that it is involved in cell morphogenesis of root hairs. In this work, we have studied LRX2, a paralog of LRX1. LRX2 expression is mainly found in roots and is responsive to factors promoting or repressing root hair formation. The function of LRX1 and LRX2 was tested by the expression of a truncated LRX2 and different LRX1/LRX2 chimaeric proteins. Using complementation of the lrx1 phenotype as the parameter for protein function, our experiments indicate that LRX1 and LRX2 are functionally similar but show differences in their activity. Genetic analysis revealed that single lrx2 mutants do not show any defect in root hair morphogenesis, but synergistically interact with the lrx1 mutation. lrx1/lrx2 double mutants have a significantly enhanced lrx1 phenotype, resulting in frequent rupture of the root hairs soon after their initiation. Analysis of the root hair cell wall ultrastructure by transmission electron microscopy (TEM) revealed the formation of osmophilic aggregates within the wall, as well as local disintegration of the wall structure in the double mutant, but not in wild-type plants. Our results indicate that LRX1 and LRX2 have overlapping functions in root hair formation, and that they likely regulate cell morphogenesis by promoting proper development of the cell wall.
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Affiliation(s)
- N Baumberger
- Institute of Plant Biology, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland
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42
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Marti M, Li Y, Schraner EM, Wild P, Köhler P, Hehl AB. The secretory apparatus of an ancient eukaryote: protein sorting to separate export pathways occurs before formation of transient Golgi-like compartments. Mol Biol Cell 2003; 14:1433-47. [PMID: 12686599 PMCID: PMC153112 DOI: 10.1091/mbc.e02-08-0467] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Transmission of the protozoan parasite Giardia intestinalis to vertebrate hosts presupposes the encapsulation of trophozoites into an environmentally resistant and infectious cyst form. We have previously shown that cyst wall proteins were faithfully sorted to large encystation-specific vesicles (ESVs), despite the absence of a recognizable Golgi apparatus. Here, we demonstrate that sorting to a second constitutively active pathway transporting variant-specific surface proteins (VSPs) to the surface depended on the cytoplasmic VSP tail. Moreover, pulsed endoplasmic reticulum (ER) export of chimeric reporters containing functional signals for both pathways showed that protein sorting was done at or very soon after export from the ER. Correspondingly, we found that a limited number of novel transitional ER-like structures together with small transport intermediates were generated during encystation. Colocalization of transitional ER regions and early ESVs with coat protein (COP) II and of maturing ESVs with COPI and clathrin strongly suggested that ESVs form by fusion of ER-derived vesicles and subsequently undergo maturation by retrograde transport. Together, the data supported the hypothesis that in Giardia, a primordial secretory apparatus is in operation by which proteins are sorted in the early secretory pathway, and the developmentally induced ESVs carry out at least some Golgi functions.
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Affiliation(s)
- Matthias Marti
- Institute of Parasitology, University of Zürich, CH-8057 Zürich, Switzerland
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43
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Reipert S, Fischer I, Wiche G. Cryofixation of epithelial cells grown on sapphire coverslips by impact freezing. J Microsc 2003; 209:76-80. [PMID: 12588524 DOI: 10.1046/j.1365-2818.2003.01103.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Rapid cryofixation of cells cultured on coverslips without the use of chemical fixatives has proved advantageous for the immunolocalization of antigens by electron microscopy. Here, we demonstrate the application of sapphire-attached tissue culture cells (PtK2 epithelial cells and mouse myoblasts) to metal-mirror impact freezing. The potential of the Leica EM-CPC cryoworkstation for routine freezing and for safe transfer of the cryofrozen samples into a sapphire disc magazine for freeze-substitution (SD-FS unit) has been exploited. Subsequently, the SD-FS unit has been tested for its use in methanol freeze-substitution and low temperature embedding for immunoelectron microscopy. The structural preservation of Lowicryl HM20-embedded cells has been assessed as being free of damage by large ice crystals.
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Affiliation(s)
- S Reipert
- Institute of Biochemistry and Molecular Cell Biology, University of Vienna, Vienna Biocenter, 1030 Vienna, Austria.
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44
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Wild P, Schraner EM, Cantieni D, Loepfe E, Walther P, Müller M, Engels M. The significance of the Golgi complex in envelopment of bovine herpesvirus 1 (BHV-1) as revealed by cryobased electron microscopy. Micron 2002; 33:327-37. [PMID: 11814872 DOI: 10.1016/s0968-4328(01)00037-3] [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]
Abstract
Nucleocapsids of herpesviruses originate in the nucleus of host cells and bud through the inner nuclear membrane acquiring tegument and envelope. The release of the enveloped virus particle from the perinuclear space is unknown. Cryobased electron microscopic imaging revealed enveloped virus particles within cisterns associated with the perinuclear space, a pre-Golgi compartment connecting Golgi cisterns to the perinuclear space, and enveloped virus particles in Golgi cisterns where they are packaged into transport vacuoles by membrane fission. To our knowledge, our images show for the first time the connectivity from the perinuclear space to Golgi cisterns. The data strongly indicate an intracisternal transport of enveloped virus particles from the budding site to the packaging site. Budding starts by condensation at the inner membrane. Condensation involving the viral envelope and peripheral tegument was persistent in virus particles within perinuclear space and associated cisterns. Virus particles within Golgi cisterns and transport vacuoles originating by Golgi membrane fission, however, lacked condensation. Instead, spikes were clearly evident. The phenomenon of condensation is considered likely to be responsible for preventing fusion of the viral envelope with cisternal membranes and/or for driving virions from the perinuclear space to Golgi cisterns. Glycoprotein K is discussed to likely play a role in the intracisternal transportation of virions. In addition to the pathway including intracisternal transport and packaging, there were clear indications for the well-known pathway involving wrapping of cytoplasmic nucleocapsids by Golgi membranes. The origin of the cytoplasmic nucleocapsids, however, remains obscure. Lack of evidence for release of nucleocapsids at the outer nuclear membrane suggests that the process is very rapid, or that nucleocapsids pass the nucleocytoplasmic barrier via an alternative route.
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Affiliation(s)
- Peter Wild
- Electron Microscopy, Institute of Veterinary Anatomy, Zürich, Switzerland.
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