1
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Zens B, Fäßler F, Hansen JM, Hauschild R, Datler J, Hodirnau VV, Zheden V, Alanko J, Sixt M, Schur FK. Lift-out cryo-FIBSEM and cryo-ET reveal the ultrastructural landscape of extracellular matrix. J Cell Biol 2024; 223:e202309125. [PMID: 38506714 PMCID: PMC10955043 DOI: 10.1083/jcb.202309125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 02/19/2024] [Accepted: 03/01/2024] [Indexed: 03/21/2024] Open
Abstract
The extracellular matrix (ECM) serves as a scaffold for cells and plays an essential role in regulating numerous cellular processes, including cell migration and proliferation. Due to limitations in specimen preparation for conventional room-temperature electron microscopy, we lack structural knowledge on how ECM components are secreted, remodeled, and interact with surrounding cells. We have developed a 3D-ECM platform compatible with sample thinning by cryo-focused ion beam milling, the lift-out extraction procedure, and cryo-electron tomography. Our workflow implements cell-derived matrices (CDMs) grown on EM grids, resulting in a versatile tool closely mimicking ECM environments. This allows us to visualize ECM for the first time in its hydrated, native context. Our data reveal an intricate network of extracellular fibers, their positioning relative to matrix-secreting cells, and previously unresolved structural entities. Our workflow and results add to the structural atlas of the ECM, providing novel insights into its secretion and assembly.
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Affiliation(s)
- Bettina Zens
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Florian Fäßler
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Jesse M. Hansen
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Robert Hauschild
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Julia Datler
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | | | - Vanessa Zheden
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Jonna Alanko
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Michael Sixt
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Florian K.M. Schur
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
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2
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Wozny MR, Di Luca A, Morado DR, Picco A, Khaddaj R, Campomanes P, Ivanović L, Hoffmann PC, Miller EA, Vanni S, Kukulski W. In situ architecture of the ER-mitochondria encounter structure. Nature 2023:10.1038/s41586-023-06050-3. [PMID: 37165187 DOI: 10.1038/s41586-023-06050-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 04/04/2023] [Indexed: 05/12/2023]
Abstract
The endoplasmic reticulum and mitochondria are main hubs of eukaryotic membrane biogenesis that rely on lipid exchange via membrane contact sites1-3, but the underpinning mechanisms remain poorly understood. In yeast, tethering and lipid transfer between the two organelles is mediated by the endoplasmic reticulum-mitochondria encounter structure (ERMES), a four-subunit complex of unresolved stoichiometry and architecture4-6. Here we determined the molecular organization of ERMES within Saccharomyces cerevisiae cells using integrative structural biology by combining quantitative live imaging, cryo-correlative microscopy, subtomogram averaging and molecular modelling. We found that ERMES assembles into approximately 25 discrete bridge-like complexes distributed irregularly across a contact site. Each bridge consists of three synaptotagmin-like mitochondrial lipid binding protein domains oriented in a zig-zag arrangement. Our molecular model of ERMES reveals a pathway for lipids. These findings resolve the in situ supramolecular architecture of a major inter-organelle lipid transfer machinery and provide a basis for the mechanistic understanding of lipid fluxes in eukaryotic cells.
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Affiliation(s)
- Michael R Wozny
- MRC Laboratory of Molecular Biology, Cambridge, UK
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
| | - Andrea Di Luca
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Dustin R Morado
- MRC Laboratory of Molecular Biology, Cambridge, UK
- SciLifeLab, Solna, Sweden
- Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Andrea Picco
- Department of Biochemistry, University of Geneva, Geneva, Switzerland
| | - Rasha Khaddaj
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Pablo Campomanes
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Lazar Ivanović
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Patrick C Hoffmann
- MRC Laboratory of Molecular Biology, Cambridge, UK
- Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | | | - Stefano Vanni
- Department of Biology, University of Fribourg, Fribourg, Switzerland.
| | - Wanda Kukulski
- MRC Laboratory of Molecular Biology, Cambridge, UK.
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
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3
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Chua EYD, Mendez JH, Rapp M, Ilca SL, Tan YZ, Maruthi K, Kuang H, Zimanyi CM, Cheng A, Eng ET, Noble AJ, Potter CS, Carragher B. Better, Faster, Cheaper: Recent Advances in Cryo-Electron Microscopy. Annu Rev Biochem 2022; 91:1-32. [PMID: 35320683 PMCID: PMC10393189 DOI: 10.1146/annurev-biochem-032620-110705] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cryo-electron microscopy (cryo-EM) continues its remarkable growth as a method for visualizing biological objects, which has been driven by advances across the entire pipeline. Developments in both single-particle analysis and in situ tomography have enabled more structures to be imaged and determined to better resolutions, at faster speeds, and with more scientists having improved access. This review highlights recent advances at each stageof the cryo-EM pipeline and provides examples of how these techniques have been used to investigate real-world problems, including antibody development against the SARS-CoV-2 spike during the recent COVID-19 pandemic.
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Affiliation(s)
- Eugene Y D Chua
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
- National Center for CryoEM Access and Training, New York, NY, USA
| | - Joshua H Mendez
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
- National Center for CryoEM Access and Training, New York, NY, USA
| | - Micah Rapp
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
| | - Serban L Ilca
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
| | - Yong Zi Tan
- Department of Biological Sciences, National University of Singapore, Singapore;
- Disease Intervention Technology Laboratory, Agency for Science, Technology and Research (A*STAR), Singapore
| | - Kashyap Maruthi
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
- National Resource for Automated Molecular Microscopy, New York, NY, USA
| | - Huihui Kuang
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
- National Resource for Automated Molecular Microscopy, New York, NY, USA
| | - Christina M Zimanyi
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
- National Center for CryoEM Access and Training, New York, NY, USA
| | - Anchi Cheng
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
- National Resource for Automated Molecular Microscopy, New York, NY, USA
| | - Edward T Eng
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
- National Center for CryoEM Access and Training, New York, NY, USA
| | - Alex J Noble
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
- National Resource for Automated Molecular Microscopy, New York, NY, USA
- National Center for In-Situ Tomographic Ultramicroscopy, New York, NY, USA
- Simons Machine Learning Center, New York, NY, USA
| | - Clinton S Potter
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
- National Center for CryoEM Access and Training, New York, NY, USA
- National Resource for Automated Molecular Microscopy, New York, NY, USA
- National Center for In-Situ Tomographic Ultramicroscopy, New York, NY, USA
- Simons Machine Learning Center, New York, NY, USA
| | - Bridget Carragher
- New York Structural Biology Center, New York, NY, USA; , , , , , , , , , , ,
- Simons Electron Microscopy Center, New York, NY, USA
- National Center for CryoEM Access and Training, New York, NY, USA
- National Resource for Automated Molecular Microscopy, New York, NY, USA
- National Center for In-Situ Tomographic Ultramicroscopy, New York, NY, USA
- Simons Machine Learning Center, New York, NY, USA
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4
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Liu HF, Zhou Y, Bartesaghi A. High-resolution structure determination using high-throughput electron cryo-tomography. Acta Crystallogr D Struct Biol 2022; 78:817-824. [PMID: 35775981 PMCID: PMC9248845 DOI: 10.1107/s2059798322005010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 05/10/2022] [Indexed: 11/12/2022] Open
Abstract
In this article, it is shown that high-throughput strategies for tomographic data acquisition combined with unsupervised techniques for image analysis provide the foundation for closing the resolution gap between the high-resolution strategies used to study molecular assemblies reconstituted in vitro and techniques for in situ structure determination. Tomographic reconstruction of frozen-hydrated specimens followed by extraction and averaging of sub-tomograms has successfully been used to determine the structure of macromolecules in their native environment at resolutions that are high enough to reveal molecular level interactions. The low throughput characteristic of tomographic data acquisition combined with the complex data-analysis pipeline that is required to obtain high-resolution maps, however, has limited the applicability of this technique to favorable samples or to resolutions that are too low to provide useful mechanistic information. Recently, beam image-shift electron cryo-tomography (BISECT), a strategy to significantly accelerate the acquisition of tilt series without sacrificing image quality, was introduced. The ability to produce thousands of high-quality tilt series during a single microscope session, however, introduces significant bottlenecks in the downstream data analysis, which has so far relied on specialized pipelines. Here, recent advances in accurate estimation of the contrast transfer function and self-tuning exposure-weighting routines that contribute to improving the resolution and streamlining the structure-determination process using sub-volume averaging are reviewed. Ultimately, the combination of automated data-driven techniques for image analysis together with high-throughput strategies for tilt-series acquisition will pave the way for tomography to become the technique of choice for in situ structure determination.
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5
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Baatsen P, Gabarre S, Vints K, Wouters R, Vandael D, Goodchild R, Munck S, Gounko NV. Preservation of Fluorescence Signal and Imaging Optimization for Integrated Light and Electron Microscopy. Front Cell Dev Biol 2022; 9:737621. [PMID: 34977003 PMCID: PMC8715528 DOI: 10.3389/fcell.2021.737621] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Accepted: 11/25/2021] [Indexed: 11/13/2022] Open
Abstract
Life science research often needs to define where molecules are located within the complex environment of a cell or tissue. Genetically encoded fluorescent proteins and or fluorescence affinity-labeling are the go-to methods. Although recent fluorescent microscopy methods can provide localization of fluorescent molecules with relatively high resolution, an ultrastructural context is missing. This is solved by imaging a region of interest with correlative light and electron microscopy (CLEM). We have adopted a protocol that preserves both genetically-encoded and antibody-derived fluorescent signals in resin-embedded cell and tissue samples and provides high-resolution electron microscopy imaging of the same thin section. This method is particularly suitable for dedicated CLEM instruments that combine fluorescence and electron microscopy optics. In addition, we optimized scanning EM imaging parameters for samples of varying thicknesses. These protocols will enable rapid acquisition of CLEM information from samples and can be adapted for three-dimensional EM.
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Affiliation(s)
- Pieter Baatsen
- VIB-KU Leuven Center for Brain and Disease Research, Electron Microscopy Platform and VIB-Bioimaging Core, Leuven, Belgium.,KU Leuven Department of Neurosciences, Leuven Brain Institute, Leuven, Belgium
| | - Sergio Gabarre
- VIB-KU Leuven Center for Brain and Disease Research, Electron Microscopy Platform and VIB-Bioimaging Core, Leuven, Belgium.,KU Leuven Department of Neurosciences, Leuven Brain Institute, Leuven, Belgium.,VIB-KU Leuven Center for Brain and Disease Research, Light Microscopy Expertise Unit and VIB Bioimaging Core, Leuven, Belgium
| | - Katlijn Vints
- VIB-KU Leuven Center for Brain and Disease Research, Electron Microscopy Platform and VIB-Bioimaging Core, Leuven, Belgium.,KU Leuven Department of Neurosciences, Leuven Brain Institute, Leuven, Belgium
| | - Rosanne Wouters
- KU Leuven Department of Neurosciences, Leuven Brain Institute, Leuven, Belgium.,VIB-KU Leuven Center for Brain and Disease Research, Laboratory for Membrane Trafficking, Leuven, Belgium
| | - Dorien Vandael
- VIB-KU Leuven Center for Brain and Disease Research, Electron Microscopy Platform and VIB-Bioimaging Core, Leuven, Belgium.,KU Leuven Department of Neurosciences, Leuven Brain Institute, Leuven, Belgium
| | - Rose Goodchild
- KU Leuven Department of Neurosciences, Leuven Brain Institute, Leuven, Belgium.,VIB-KU Leuven Center for Brain and Disease Research, Laboratory for Dystonia Research, Leuven, Belgium
| | - Sebastian Munck
- KU Leuven Department of Neurosciences, Leuven Brain Institute, Leuven, Belgium.,VIB-KU Leuven Center for Brain and Disease Research, Light Microscopy Expertise Unit and VIB Bioimaging Core, Leuven, Belgium
| | - Natalia V Gounko
- VIB-KU Leuven Center for Brain and Disease Research, Electron Microscopy Platform and VIB-Bioimaging Core, Leuven, Belgium.,KU Leuven Department of Neurosciences, Leuven Brain Institute, Leuven, Belgium
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6
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Scher N, Rechav K, Paul-Gilloteaux P, Avinoam O. In situ fiducial markers for 3D correlative cryo-fluorescence and FIB-SEM imaging. iScience 2021; 24:102714. [PMID: 34258551 PMCID: PMC8253967 DOI: 10.1016/j.isci.2021.102714] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/12/2021] [Accepted: 06/08/2021] [Indexed: 11/26/2022] Open
Abstract
Imaging of cells and tissues has improved significantly over the last decade. Dual-beam instruments with a focused ion beam mounted on a scanning electron microscope (FIB-SEM), offering high-resolution 3D imaging of large volumes and fields-of-view are becoming widely used in the life sciences. FIB-SEM has most recently been implemented on fully hydrated, cryo-immobilized, biological samples. Correlative light and electron microscopy workflows combining fluorescence microscopy (FM) with FIB-SEM imaging exist, whereas workflows combining cryo-FM and cryo-FIB-SEM imaging are not yet commonly available. Here, we demonstrate that fluorescently labeled lipid droplets can serve as in situ fiducial markers for correlating cryo-FM and FIB-SEM datasets and that this approach can be used to target the acquisition of large FIB-SEM stacks spanning tens of microns under cryogenic conditions. We also show that cryo-FIB-SEM imaging is particularly informative for questions related to organelle structure and inter-organellar contacts, nuclear organization, and mineral deposits in cells.
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Affiliation(s)
- Nadav Scher
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Katya Rechav
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel
| | - Perrine Paul-Gilloteaux
- Structure Fédérative de Recherche François Bonamy, INSERM, CNRS, Université de Nantes, Nantes, France
| | - Ori Avinoam
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
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7
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Bouvette J, Liu HF, Du X, Zhou Y, Sikkema AP, da Fonseca Rezende E Mello J, Klemm BP, Huang R, Schaaper RM, Borgnia MJ, Bartesaghi A. Beam image-shift accelerated data acquisition for near-atomic resolution single-particle cryo-electron tomography. Nat Commun 2021; 12:1957. [PMID: 33785757 PMCID: PMC8009872 DOI: 10.1038/s41467-021-22251-8] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 03/08/2021] [Indexed: 11/19/2022] Open
Abstract
Tomographic reconstruction of cryopreserved specimens imaged in an electron microscope followed by extraction and averaging of sub-volumes has been successfully used to derive atomic models of macromolecules in their biological environment. Eliminating biochemical isolation steps required by other techniques, this method opens up the cell to in-situ structural studies. However, the need to compensate for errors in targeting introduced during mechanical navigation of the specimen significantly slows down tomographic data collection thus limiting its practical value. Here, we introduce protocols for tilt-series acquisition and processing that accelerate data collection speed by up to an order of magnitude and improve map resolution compared to existing approaches. We achieve this by using beam-image shift to multiply the number of areas imaged at each stage position, by integrating geometrical constraints during imaging to achieve high precision targeting, and by performing per-tilt astigmatic CTF estimation and data-driven exposure weighting to improve final map resolution. We validated our beam image-shift electron cryo-tomography (BISECT) approach by determining the structure of a low molecular weight target (~300 kDa) at 3.6 Å resolution where density for individual side chains is clearly resolved. Tomographic reconstructions of cryopreserved specimens enable in-situ structural studies. Here, the authors present the beam image-shift electron cryo-tomography (BISECT) approach that accelerates data collection speed and improves the map resolution compared to earlier approaches and present the in vitro structure of a 300 kDa protein complex that was solved at 3.6 Å resolution as a test case.
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Affiliation(s)
- Jonathan Bouvette
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Hsuan-Fu Liu
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, USA
| | - Xiaochen Du
- Department of Computer Science, Duke University, Durham, NC, USA.,Department of Chemistry, Duke University, Durham, NC, USA
| | - Ye Zhou
- Department of Computer Science, Duke University, Durham, NC, USA
| | - Andrew P Sikkema
- Epigenetics & Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Juliana da Fonseca Rezende E Mello
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Bradley P Klemm
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Rick Huang
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, MD, USA
| | - Roel M Schaaper
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA
| | - Mario J Borgnia
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, USA.
| | - Alberto Bartesaghi
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, USA. .,Department of Computer Science, Duke University, Durham, NC, USA. .,Department of Electrical and Computer Engineering, Duke University, Durham, NC, USA.
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8
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Yang JE, Larson MR, Sibert BS, Shrum S, Wright ER. CorRelator: Interactive software for real-time high precision cryo-correlative light and electron microscopy. J Struct Biol 2021; 213:107709. [PMID: 33610654 PMCID: PMC8601405 DOI: 10.1016/j.jsb.2021.107709] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 01/06/2021] [Accepted: 02/11/2021] [Indexed: 12/31/2022]
Abstract
Cryo-correlative light and electron microscopy (CLEM) is a technique that uses the spatiotemporal cues from fluorescence light microscopy (FLM) to investigate the high-resolution ultrastructure of biological samples by cryo-electron microscopy (cryo-EM). Cryo-CLEM provides advantages for identifying and distinguishing fluorescently labeled proteins, macromolecular complexes, and organelles from the cellular environment. Challenges remain on how correlation workflows and software tools are implemented on different microscope platforms to support automated cryo-EM data acquisition. Here, we present CorRelator: an open-source desktop application that bridges between cryo-FLM and real-time cryo-EM/ET automated data collection. CorRelator implements a pixel-coordinate-to-stage-position transformation for flexible, high accuracy on-the-fly and post-acquisition correlation. CorRelator can be integrated into cryo-CLEM workflows and easily adapted to standard fluorescence and transmission electron microscope (TEM) system configurations. CorRelator was benchmarked under live-cell and cryogenic conditions using several FLM and TEM instruments, demonstrating that CorRelator reliably supports real-time, automated correlative cryo-EM/ET acquisition, through a combination of software-aided and interactive alignment. CorRelator is a cross-platform software package featuring an intuitive Graphical User Interface (GUI) that guides the user through the correlation process. CorRelator source code is available at: https://github.com/wright-cemrc-projects/corr.
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Affiliation(s)
- Jie E Yang
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States
| | - Matthew R Larson
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States
| | - Bryan S Sibert
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States
| | - Samantha Shrum
- Biophysics Graduate Program, University of Wisconsin, Madison, WI 53706, United States
| | - Elizabeth R Wright
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Cryo-Electron Microscopy Research Center, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States; Biophysics Graduate Program, University of Wisconsin, Madison, WI 53706, United States; Morgridge Institute for Research, Madison, WI, 53715, United States; Midwest Center for Cryo-Electron Tomography, Department of Biochemistry, University of Wisconsin, Madison, WI 53706, United States.
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9
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Berger C, Ravelli RBG, López-Iglesias C, Peters PJ. Endocytosed nanogold fiducials for improved in-situ cryo-electron tomography tilt-series alignment. J Struct Biol 2021; 213:107698. [PMID: 33545353 DOI: 10.1016/j.jsb.2021.107698] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 12/24/2020] [Accepted: 01/13/2021] [Indexed: 11/17/2022]
Abstract
Cryo-electron tomography (CET) on cryo-focused ion beam (FIB)-milled lamellae is becoming a powerful technique for determining the structure of macromolecular complexes in their native cellular environment. Prior to tomogram reconstruction, CET tilt-series recorded on FIB lamellae need to be aligned. Traditionally, CET tilt-series alignment is performed with 5-20 nm gold fiducials, but it has thus far proven difficult to apply this to FIB lamellae of eukaryotic cells. In here, we describe a simple method to allow uptake of bovine serum albumin (BSA)-gold fiducials into mammalian cells via endocytosis, which can subsequently be used as fiducials for tilt-series alignment of cryo-FIB lamellae. We compare the alignment of tilt-series with BSA-gold fiducials to fiducial-less patch-tracking, and find better alignment results with BSA-gold. This technique can contribute to understand cells at a structural and ultrastructural level with both cryo- and room-temperature electron tomography. Furthermore, fluorescently labeled BSA-gold has the potential to be used as fiducials for correlative light and electron microscopy studies.
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Affiliation(s)
- Casper Berger
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, the Netherlands
| | - Raimond B G Ravelli
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, the Netherlands
| | - Carmen López-Iglesias
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, the Netherlands
| | - Peter J Peters
- Division of Nanoscopy, Maastricht Multimodal Molecular Imaging Institute, Maastricht University, the Netherlands.
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10
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Quemin ERJ, Machala EA, Vollmer B, Pražák V, Vasishtan D, Rosch R, Grange M, Franken LE, Baker LA, Grünewald K. Cellular Electron Cryo-Tomography to Study Virus-Host Interactions. Annu Rev Virol 2020; 7:239-262. [PMID: 32631159 DOI: 10.1146/annurev-virology-021920-115935] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Viruses are obligatory intracellular parasites that reprogram host cells upon infection to produce viral progeny. Here, we review recent structural insights into virus-host interactions in bacteria, archaea, and eukaryotes unveiled by cellular electron cryo-tomography (cryoET). This advanced three-dimensional imaging technique of vitreous samples in near-native state has matured over the past two decades and proven powerful in revealing molecular mechanisms underlying viral replication. Initial studies were restricted to cell peripheries and typically focused on early infection steps, analyzing surface proteins and viral entry. Recent developments including cryo-thinning techniques, phase-plate imaging, and correlative approaches have been instrumental in also targeting rare events inside infected cells. When combined with advances in dedicated image analyses and processing methods, details of virus assembly and egress at (sub)nanometer resolution were uncovered. Altogether, we provide a historical and technical perspective and discuss future directions and impacts of cryoET for integrative structural cell biology analyses of viruses.
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Affiliation(s)
- Emmanuelle R J Quemin
- Centre for Structural Systems Biology, Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, University of Hamburg, D-22607 Hamburg, Germany;
| | - Emily A Machala
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Benjamin Vollmer
- Centre for Structural Systems Biology, Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, University of Hamburg, D-22607 Hamburg, Germany;
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Vojtěch Pražák
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Daven Vasishtan
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Rene Rosch
- Centre for Structural Systems Biology, Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, University of Hamburg, D-22607 Hamburg, Germany;
| | - Michael Grange
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Linda E Franken
- Centre for Structural Systems Biology, Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, University of Hamburg, D-22607 Hamburg, Germany;
| | - Lindsay A Baker
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | - Kay Grünewald
- Centre for Structural Systems Biology, Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, University of Hamburg, D-22607 Hamburg, Germany;
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
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11
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Yang Q, Kempken F. The Composition and the Structure of MCC/Eisosomes in Neurospora crassa. Front Microbiol 2020; 11:2115. [PMID: 33071997 PMCID: PMC7533531 DOI: 10.3389/fmicb.2020.02115] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 08/11/2020] [Indexed: 12/15/2022] Open
Abstract
MCC/eisosomes are protein-organized domains in the plasma membrane of fungi and algae. However, the composition and function(s) of MCC/eisosomes in the filamentous fungus Neurospora crassa were previously unknown. To identify proteins that localize to MCC/eisosomes in N. crassa, we isolated proteins that co-purified with the core MCC/eisosome protein LSP-1, which was tagged with GFP. Proteins that co-fractionated with LSP-1:GFP were then identified by mass spectrometry. Eighteen proteins were GFP-tagged and used to identify six proteins that highly colocalized with the MCC/eisosome marker LSP-1:RFP, while five other proteins showed partial overlap with MCC/eisosomes. Seven of these proteins showed amino acid sequence homology with proteins known to localize to MCC/eisosomes in the yeast Saccharomyces cerevisiae. However, homologs of three proteins known to localize to MCC/eisosomes in S. cerevisiae (Can1, Pkh1/2, and Fhn1) were not found to colocalize with MCC/eisosome proteins in N. crassa by fluorescence microscopy. Interestingly, one new eisosome protein (glutamine-fructose-6-phosphate aminotransferase, gene ID: NCU07366) was detected in our studies. These findings demonstrate that there are interspecies differences of the protein composition of MCC/eisosomes. To gain further insight, molecular modeling and bioinformatics analysis of the identified proteins were used to propose the organization of MCC/eisosomes in N. crassa. A model will be discussed for how the broad range of functions predicted for the proteins localized to MCC/eisosomes, including cell wall synthesis, response and signaling, transmembrane transport, and actin organization, suggests that MCC/eisosomes act as organizing centers in the plasma membrane.
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Affiliation(s)
- Qin Yang
- Department of Genetics and Molecular Biology, Botanical Institute and Botanic Garden, Kiel University, Kiel, Germany
| | - Frank Kempken
- Department of Genetics and Molecular Biology, Botanical Institute and Botanic Garden, Kiel University, Kiel, Germany
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12
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Plasma Membrane MCC/Eisosome Domains Promote Stress Resistance in Fungi. Microbiol Mol Biol Rev 2020; 84:84/4/e00063-19. [PMID: 32938742 DOI: 10.1128/mmbr.00063-19] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
There is growing appreciation that the plasma membrane orchestrates a diverse array of functions by segregating different activities into specialized domains that vary in size, stability, and composition. Studies with the budding yeast Saccharomyces cerevisiae have identified a novel type of plasma membrane domain known as the MCC (membrane compartment of Can1)/eisosomes that correspond to stable furrows in the plasma membrane. MCC/eisosomes maintain proteins at the cell surface, such as nutrient transporters like the Can1 arginine symporter, by protecting them from endocytosis and degradation. Recent studies from several fungal species are now revealing new functional roles for MCC/eisosomes that enable cells to respond to a wide range of stressors, including changes in membrane tension, nutrition, cell wall integrity, oxidation, and copper toxicity. The different MCC/eisosome functions are often intertwined through the roles of these domains in lipid homeostasis, which is important for proper plasma membrane architecture and cell signaling. Therefore, this review will emphasize the emerging models that explain how MCC/eisosomes act as hubs to coordinate cellular responses to stress. The importance of MCC/eisosomes is underscored by their roles in virulence for fungal pathogens of plants, animals, and humans, which also highlights the potential of these domains to act as novel therapeutic targets.
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13
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Dey G, Culley S, Curran S, Schmidt U, Henriques R, Kukulski W, Baum B. Closed mitosis requires local disassembly of the nuclear envelope. Nature 2020; 585:119-123. [PMID: 32848252 PMCID: PMC7610560 DOI: 10.1038/s41586-020-2648-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 05/21/2020] [Indexed: 01/15/2023]
Abstract
At the end of mitosis, eukaryotic cells must segregate the two copies of their replicated genome into two new nuclear compartments1. They do this either by first dismantling and later reassembling the nuclear envelope in an 'open mitosis' or by reshaping an intact nucleus and then dividing it into two in a 'closed mitosis'2,3. Mitosis has been studied in a wide variety of eukaryotes for more than a century4, but how the double membrane of the nuclear envelope is split into two at the end of a closed mitosis without compromising the impermeability of the nuclear compartment remains unknown5. Here, using the fission yeast Schizosaccharomyces pombe (a classical model for closed mitosis5), genetics, live-cell imaging and electron tomography, we show that nuclear fission is achieved via local disassembly of nuclear pores within the narrow bridge that links segregating daughter nuclei. In doing so, we identify the protein Les1, which is localized to the inner nuclear envelope and restricts the process of local nuclear envelope breakdown to the bridge midzone to prevent the leakage of material from daughter nuclei. The mechanism of local nuclear envelope breakdown in a closed mitosis therefore closely mirrors nuclear envelope breakdown in open mitosis3, revealing an unexpectedly high conservation of nuclear remodelling mechanisms across diverse eukaryotes.
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Affiliation(s)
- Gautam Dey
- MRC Laboratory for Molecular Cell Biology, London, UK.
| | - Siân Culley
- MRC Laboratory for Molecular Cell Biology, London, UK
| | | | - Uwe Schmidt
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
- Center for Systems Biology Dresden, Dresden, Germany
| | | | | | - Buzz Baum
- MRC Laboratory for Molecular Cell Biology, London, UK.
- Institute for the Physics of Living Systems, University College London, London, UK.
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14
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Reliable estimation of membrane curvature for cryo-electron tomography. PLoS Comput Biol 2020; 16:e1007962. [PMID: 32776920 PMCID: PMC7444595 DOI: 10.1371/journal.pcbi.1007962] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 08/20/2020] [Accepted: 05/18/2020] [Indexed: 01/01/2023] Open
Abstract
Curvature is a fundamental morphological descriptor of cellular membranes. Cryo-electron tomography (cryo-ET) is particularly well-suited to visualize and analyze membrane morphology in a close-to-native state and molecular resolution. However, current curvature estimation methods cannot be applied directly to membrane segmentations in cryo-ET, as these methods cannot cope with some of the artifacts introduced during image acquisition and membrane segmentation, such as quantization noise and open borders. Here, we developed and implemented a Python package for membrane curvature estimation from tomogram segmentations, which we named PyCurv. From a membrane segmentation, a signed surface (triangle mesh) is first extracted. The triangle mesh is then represented by a graph, which facilitates finding neighboring triangles and the calculation of geodesic distances necessary for local curvature estimation. PyCurv estimates curvature based on tensor voting. Beside curvatures, this algorithm also provides robust estimations of surface normals and principal directions. We tested PyCurv and three well-established methods on benchmark surfaces and biological data. This revealed the superior performance of PyCurv not only for cryo-ET, but also for data generated by other techniques such as light microscopy and magnetic resonance imaging. Altogether, PyCurv is a versatile open-source software to reliably estimate curvature of membranes and other surfaces in a wide variety of applications. Membrane curvature plays a central role in many cellular processes like cell division, organelle shaping and membrane contact sites. While cryo-electron tomography (cryo-ET) allows the visualization of cellular membranes in 3D at molecular resolution and close-to-native conditions, there is a lack of computational methods to quantify membrane curvature from cryo-ET data. Therefore, we developed a computational procedure for membrane curvature estimation from tomogram segmentations and implemented it in a software package called PyCurv. PyCurv converts a membrane segmentation, i.e. a set of voxels, into a surface, i.e. a mesh of triangles. PyCurv uses the local geometrical information to reliably estimate the local surface orientation, the principal (maximum and minimum) curvatures and their directions. PyCurv outperforms well-established curvature estimation methods, and it can also be applied to data generated by other imaging techniques.
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15
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Athanasopoulos A, André B, Sophianopoulou V, Gournas C. Fungal plasma membrane domains. FEMS Microbiol Rev 2020; 43:642-673. [PMID: 31504467 DOI: 10.1093/femsre/fuz022] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 08/25/2019] [Indexed: 12/11/2022] Open
Abstract
The plasma membrane (PM) performs a plethora of physiological processes, the coordination of which requires spatial and temporal organization into specialized domains of different sizes, stability, protein/lipid composition and overall architecture. Compartmentalization of the PM has been particularly well studied in the yeast Saccharomyces cerevisiae, where five non-overlapping domains have been described: The Membrane Compartments containing the arginine permease Can1 (MCC), the H+-ATPase Pma1 (MCP), the TORC2 kinase (MCT), the sterol transporters Ltc3/4 (MCL), and the cell wall stress mechanosensor Wsc1 (MCW). Additional cortical foci at the fungal PM are the sites where clathrin-dependent endocytosis occurs, the sites where the external pH sensing complex PAL/Rim localizes, and sterol-rich domains found in apically grown regions of fungal membranes. In this review, we summarize knowledge from several fungal species regarding the organization of the lateral PM segregation. We discuss the mechanisms of formation of these domains, and the mechanisms of partitioning of proteins there. Finally, we discuss the physiological roles of the best-known membrane compartments, including the regulation of membrane and cell wall homeostasis, apical growth of fungal cells and the newly emerging role of MCCs as starvation-protective membrane domains.
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Affiliation(s)
- Alexandros Athanasopoulos
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
| | - Bruno André
- Molecular Physiology of the Cell laboratory, Université Libre de Bruxelles (ULB), Institut de Biologie et de Médecine Moléculaires, rue des Pr Jeener et Brachet 12, 6041, Gosselies, Belgium
| | - Vicky Sophianopoulou
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
| | - Christos Gournas
- Microbial Molecular Genetics Laboratory, Institute of Biosciences and Applications, National Centre for Scientific Research 'Demokritos,' Patr. Grigoriou E & 27 Neapoleos St. 15341, Agia Paraskevi, Greece
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16
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Ganeva I, Kukulski W. Membrane Architecture in the Spotlight of Correlative Microscopy. Trends Cell Biol 2020; 30:577-587. [DOI: 10.1016/j.tcb.2020.04.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 03/27/2020] [Accepted: 04/01/2020] [Indexed: 12/19/2022]
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17
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Böhning J, Bharat TAM. Towards high-throughput in situ structural biology using electron cryotomography. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 160:97-103. [PMID: 32579969 DOI: 10.1016/j.pbiomolbio.2020.05.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 05/21/2020] [Accepted: 05/27/2020] [Indexed: 01/11/2023]
Abstract
Electron cryotomography is a rapidly evolving method for imaging macromolecules directly within the native environment of cells and tissues. Combined with sub-tomogram averaging, it allows structural and cell biologists to obtain sub-nanometre resolution structures in situ. However, low throughput in cryo-ET sample preparation and data acquisition, as well as difficulties in target localisation and sub-tomogram averaging image processing, limit its widespread usability. In this review, we discuss new advances in the field that address these throughput and technical problems. We focus on recent efforts made to resolve issues in sample thinning, improvement in data collection speed at the microscope, strategies for localisation of macromolecules using correlated light and electron microscopy and advancements made to improve resolution in sub-tomogram averaging. These advances will considerably decrease the amount of time and effort required for cryo-ET and sub-tomogram averaging, ushering in a new era of structural biology where in situ macromolecular structure determination will be routine.
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Affiliation(s)
- Jan Böhning
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom; Central Oxford Structural Microscopy and Imaging Centre, South Parks Road, Oxford OX1 3RE, United Kingdom
| | - Tanmay A M Bharat
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom; Central Oxford Structural Microscopy and Imaging Centre, South Parks Road, Oxford OX1 3RE, United Kingdom.
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18
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Babst M. Regulation of nutrient transporters by metabolic and environmental stresses. Curr Opin Cell Biol 2020; 65:35-41. [PMID: 32200208 DOI: 10.1016/j.ceb.2020.02.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 02/15/2020] [Indexed: 12/17/2022]
Abstract
The yeast plasma membrane is a selective barrier between an erratic environment and the cell's metabolism. Nutrient transporters are the gatekeepers that control the import of molecules feeding into the metabolic pathways. Nutrient import adjusts rapidly to changes in metabolism and the environment, which is accomplished by regulating the surface expression of transporters. Recent studies indicate that the lipid environment in which transporters function regulates ubiquitination efficiency and endocytosis of these proteins. Changes in the lipid environment are caused by lateral movements of the transporters between different membrane domains and by the influence of the extracellular environment on the fluidity of the plasma membrane.
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Affiliation(s)
- Markus Babst
- Henry Eyring Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112, USA.
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19
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Nepal B, Sepehri A, Lazaridis T. Mechanisms of negative membrane curvature sensing and generation by ESCRT III subunit Snf7. Protein Sci 2020; 29:1473-1485. [PMID: 32142182 DOI: 10.1002/pro.3851] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 03/03/2020] [Accepted: 03/04/2020] [Indexed: 12/13/2022]
Abstract
Certain proteins have the propensity to bind to negatively curved membranes and generate negative membrane curvature. The mechanism of action of these proteins is much less studied and understood than those that sense and generate positive curvature. In this work, we use implicit membrane modeling to explore the mechanism of an important negative curvature sensing and generating protein: the main ESCRT III subunit Snf7. We find that Snf7 monomers alone can sense negative curvature and that curvature sensitivity increases for dimers and trimers. We have observed spontaneous bending of Snf7 oligomers into circular structures with preferred radius of ~20 nm. The preferred curvature of Snf7 filaments is further confirmed by the simulations of preformed spirals on a cylindrical membrane surface. Snf7 filaments cannot bind with the same interface to flat and curved membranes. We find that even when a filament has the preferred radius, it is always less stable on the flat membrane surface than on the interior cylindrical membrane surface. This provides an additional energy for membrane bending which has not been considered in the spiral spring model. Furthermore, the rings on the cylindrical spirals are bridged together by helix 4 and hence are extra stabilized compared to the spirals on the flat membrane surface.
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Affiliation(s)
- Binod Nepal
- Department of Chemistry, City College of New York, New York, New York, USA
| | - Aliasghar Sepehri
- Department of Chemistry, City College of New York, New York, New York, USA
| | - Themis Lazaridis
- Department of Chemistry, City College of New York, New York, New York, USA.,Graduate Programs in Chemistry, Biochemistry, and Physics, The Graduate Center, City University of New York, New York, New York, USA
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20
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Ng CT, Gan L. Investigating eukaryotic cells with cryo-ET. Mol Biol Cell 2020; 31:87-100. [PMID: 31935172 PMCID: PMC6960407 DOI: 10.1091/mbc.e18-05-0329] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 11/25/2019] [Accepted: 11/29/2019] [Indexed: 01/06/2023] Open
Abstract
The interior of eukaryotic cells is mysterious. How do the large communities of macromolecular machines interact with each other? How do the structures and positions of these nanoscopic entities respond to new stimuli? Questions like these can now be answered with the help of a method called electron cryotomography (cryo-ET). Cryo-ET will ultimately reveal the inner workings of a cell at the protein, secondary structure, and perhaps even side-chain levels. Combined with genetic or pharmacological perturbation, cryo-ET will allow us to answer previously unimaginable questions, such as how structure, biochemistry, and forces are related in situ. Because it bridges structural biology and cell biology, cryo-ET is indispensable for structural cell biology-the study of the 3-D macromolecular structure of cells. Here we discuss some of the key ideas, strategies, auxiliary techniques, and innovations that an aspiring structural cell biologist will consider when planning to ask bold questions.
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Affiliation(s)
- Cai Tong Ng
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore 117543
| | - Lu Gan
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore 117543
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21
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Appadurai D, Gay L, Moharir A, Lang MJ, Duncan MC, Schmidt O, Teis D, Vu TN, Silva M, Jorgensen EM, Babst M. Plasma membrane tension regulates eisosome structure and function. Mol Biol Cell 2019; 31:287-303. [PMID: 31851579 PMCID: PMC7183764 DOI: 10.1091/mbc.e19-04-0218] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Eisosomes are membrane furrows at the cell surface of yeast that have been shown to function in two seemingly distinct pathways, membrane stress response and regulation of nutrient transporters. We found that many stress conditions affect both of these pathways by changing plasma membrane tension and thus the morphology and composition of eisosomes. For example, alkaline stress causes swelling of the cell and an endocytic response, which together increase membrane tension, thereby flattening the eisosomes. The flattened eisosomes affect membrane stress pathways and release nutrient transporters, which aids in their down-regulation. In contrast, glucose starvation or hyperosmotic shock causes cell shrinking, which results in membrane slack and the deepening of eisosomes. Deepened eisosomes are able to trap nutrient transporters and protect them from rapid endocytosis. Therefore, eisosomes seem to coordinate the regulation of both membrane tension and nutrient transporter stability.
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Affiliation(s)
- Daniel Appadurai
- Henry Eyring Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112
| | - Lincoln Gay
- Henry Eyring Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112
| | - Akshay Moharir
- Henry Eyring Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112
| | - Michael J Lang
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Mara C Duncan
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109
| | - Oliver Schmidt
- Division of Cell Biology, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - David Teis
- Division of Cell Biology, Medical University of Innsbruck, Innsbruck 6020, Austria
| | - Thien N Vu
- School of Biological Sciences, Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT 84112
| | - Malan Silva
- School of Biological Sciences, Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT 84112
| | - Erik M Jorgensen
- School of Biological Sciences, Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT 84112
| | - Markus Babst
- Henry Eyring Center for Cell and Genome Science, University of Utah, Salt Lake City, UT 84112
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22
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Hoffmann PC, Bharat TAM, Wozny MR, Boulanger J, Miller EA, Kukulski W. Tricalbins Contribute to Cellular Lipid Flux and Form Curved ER-PM Contacts that Are Bridged by Rod-Shaped Structures. Dev Cell 2019; 51:488-502.e8. [PMID: 31743663 PMCID: PMC6863393 DOI: 10.1016/j.devcel.2019.09.019] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 08/06/2019] [Accepted: 09/25/2019] [Indexed: 11/25/2022]
Abstract
Lipid flow between cellular organelles occurs via membrane contact sites. Extended-synaptotagmins, known as tricalbins in yeast, mediate lipid transfer between the endoplasmic reticulum (ER) and plasma membrane (PM). How these proteins regulate membrane architecture to transport lipids across the aqueous space between bilayers remains unknown. Using correlative microscopy, electron cryo-tomography, and high-throughput genetics, we address the interplay of architecture and function in budding yeast. We find that ER-PM contacts differ in protein composition and membrane morphology, not in intermembrane distance. In situ electron cryo-tomography reveals the molecular organization of tricalbin-mediated contacts, suggesting a structural framework for putative lipid transfer. Genetic analysis uncovers functional overlap with cellular lipid routes, such as maintenance of PM asymmetry. Further redundancies are suggested for individual tricalbin protein domains. We propose a modularity of molecular and structural functions of tricalbins and of their roles within the cellular network of lipid distribution pathways.
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Affiliation(s)
- Patrick C Hoffmann
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Tanmay A M Bharat
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK; Central Oxford Structural Microscopy and Imaging Centre, South Parks Road, Oxford OX1 3RE, UK
| | - Michael R Wozny
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Jerome Boulanger
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Elizabeth A Miller
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Wanda Kukulski
- Cell Biology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
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23
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Sulkowski NI, Hardy GG, Brun YV, Bharat TAM. A Multiprotein Complex Anchors Adhesive Holdfast at the Outer Membrane of Caulobacter crescentus. J Bacteriol 2019; 201:e00112-19. [PMID: 31061167 PMCID: PMC6707917 DOI: 10.1128/jb.00112-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 04/26/2019] [Indexed: 01/11/2023] Open
Abstract
Adhesion allows microbes to colonize surfaces and is the first stage in biofilm formation. Stable attachment of the freshwater alphaproteobacterium Caulobacter crescentus to surfaces requires an adhesive polysaccharide called holdfast, which is synthesized at a specific cell pole and ultimately found at the tip of cylindrical extensions of the cell envelope called stalks. Secretion and anchoring of holdfast to the cell surface are governed by proteins HfsDAB and HfaABD, respectively. The arrangement and organization of these proteins with respect to each other and the cell envelope, and the mechanism by which the holdfast is anchored on cells, are unknown. In this study, we have imaged a series of C. crescentus mutants using electron cryotomography, revealing the architecture and arrangement of the molecular machinery involved in holdfast anchoring in cells. We found that the holdfast is anchored to cells by a defined complex made up of the HfaABD proteins and that the HfsDAB secretion proteins are essential for proper assembly and localization of the HfaABD anchor. Subtomogram averaging of cell stalk tips showed that the HfaABD complex spans the outer membrane. The anchor protein HfaB is the major component of the anchor complex located on the periplasmic side of the outer membrane, while HfaA and HfaD are located on the cell surface. HfaB is the critical component of the complex, without which no HfaABD complex was observed in cells. These results allow us to propose a working model of holdfast anchoring, laying the groundwork for further structural and cell biological investigations.IMPORTANCE Adhesion and biofilm formation are fundamental processes that accompany bacterial colonization of surfaces, which are of critical importance in many infections. Caulobacter crescentus biofilm formation proceeds via irreversible adhesion mediated by a polar polysaccharide called holdfast. Mechanistic and structural details of how the holdfast is secreted and anchored on cells are still lacking. Here, we have assigned the location and described the arrangement of the holdfast anchor complex. This work increases our knowledge of the relatively underexplored field of polysaccharide-mediated adhesion by identifying structural elements that anchor polysaccharides to the cell envelope, which is important in a variety of bacterial species.
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Affiliation(s)
- Nina I Sulkowski
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
- Central Oxford Structural and Molecular Imaging Centre, Oxford, United Kingdom
| | - Gail G Hardy
- Department of Biology, Indiana University, Bloomington, Indiana, USA
| | - Yves V Brun
- Department of Biology, Indiana University, Bloomington, Indiana, USA
- Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montréal, Québec, Canada
| | - Tanmay A M Bharat
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
- Central Oxford Structural and Molecular Imaging Centre, Oxford, United Kingdom
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24
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Ebrahimkutty MP, Galic M. Receptor‐Free Signaling at Curved Cellular Membranes. Bioessays 2019; 41:e1900068. [DOI: 10.1002/bies.201900068] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 07/09/2019] [Indexed: 11/10/2022]
Affiliation(s)
- Mirsana P. Ebrahimkutty
- DFG Cluster of Excellence “Cells in Motion”University of Muenster Muenster 48149 Germany
- Institute of Medical Physics and BiophysicsUniversity of Muenster Muenster 48149 Germany
- CIM‐IMRPS Graduate School Muenster 48149 Germany
| | - Milos Galic
- DFG Cluster of Excellence “Cells in Motion”University of Muenster Muenster 48149 Germany
- Institute of Medical Physics and BiophysicsUniversity of Muenster Muenster 48149 Germany
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25
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Otegui MS, Pennington JG. Electron tomography in plant cell biology. Microscopy (Oxf) 2019; 68:69-79. [PMID: 30452668 DOI: 10.1093/jmicro/dfy133] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 10/15/2018] [Accepted: 10/31/2018] [Indexed: 12/11/2022] Open
Abstract
Electron tomography (ET) approaches are based on the imaging of a biological specimen at different tilt angles by transmission electron microscopy (TEM). ET can be applied to both plastic-embedded and frozen samples. Technological advancements in TEM, direct electron detection, automated image collection, and imaging processing algorithms allow for 2-7-nm scale axial resolution in tomographic reconstructions of cells and organelles. In this review, we discussed the application of ET in plant cell biology and new opportunities for imaging plant cells by cryo-ET and other 3D electron microscopy approaches.
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Affiliation(s)
- Marisa S Otegui
- Department of Botany, University of Wisconsin-Madison, 430 Lincoln Drive, Madison WI, USA.,Laboratory of Molecular and Cellular Biology, University of Wisconsin-Madison, 1525 Linden Drive, Madison WI, USA.,Department of Genetics, University of Wisconsin-Madison, 425 Henry Mall, Madison WI, USA
| | - Jannice G Pennington
- Institute for Molecular Virology, University of Wisconsin-Madison, 1525 Linden Drive, Madison WI, USA.,Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, USA
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26
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Imaging of post-mortem human brain tissue using electron and X-ray microscopy. Curr Opin Struct Biol 2019; 58:138-148. [PMID: 31349127 DOI: 10.1016/j.sbi.2019.06.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 05/26/2019] [Accepted: 06/10/2019] [Indexed: 12/12/2022]
Abstract
Electron microscopy imaging of post-mortem human brain (PMHB) comes with a unique set of challenges due to numerous parameters beyond the researcher's control. Nevertheless, the wealth of information provided by the ultrastructural analysis of PMHB is proving crucial in our understanding of neurodegenerative diseases. This review highlights the importance of such studies and covers challenges, limitations and recent developments in the application of current EM imaging, including cryo-ET and correlative hybrid techniques, on PMHB.
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27
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Gan L, Ng CT, Chen C, Cai S. A collection of yeast cellular electron cryotomography data. Gigascience 2019; 8:giz077. [PMID: 31247098 PMCID: PMC6596884 DOI: 10.1093/gigascience/giz077] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Revised: 05/09/2019] [Accepted: 06/10/2019] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND Cells are powered by a large set of macromolecular complexes, which work together in a crowded environment. The in situ mechanisms of these complexes are unclear because their 3D distribution, organization, and interactions are largely unknown. Electron cryotomography (cryo-ET) can address these knowledge gaps because it produces cryotomograms-3D images that reveal biological structure at ∼4-nm resolution. Cryo-ET uses no fixation, dehydration, staining, or plastic embedment, so cellular features are visualized in a life-like, frozen-hydrated state. To study chromatin and mitotic machinery in situ, we subjected yeast cells to genetic and chemical perturbations, cryosectioned them, and then imaged the cells by cryo-ET. FINDINGS Here we share >1,000 cryo-ET raw datasets of cryosectioned budding yeast Saccharomyces cerevisiaecollected as part of previously published studies. These data will be valuable to cell biologists who are interested in the nanoscale organization of yeasts and of eukaryotic cells in general. All the unpublished tilt series and a subset of corresponding cryotomograms have been deposited in the EMPIAR resource for the community to use freely. To improve tilt series discoverability, we have uploaded metadata and preliminary notes to publicly accessible Google Sheets, EMPIAR, and GigaDB. CONCLUSIONS Cellular cryo-ET data can be mined to obtain new cell-biological, structural, and 3D statistical insights in situ. These data contain structures not visible in traditional electron-microscopy data. Template matching and subtomogram averaging of known macromolecular complexes can reveal their 3D distributions and low-resolution structures. Furthermore, these data can serve as testbeds for high-throughput image-analysis pipelines, as training sets for feature-recognition software, for feasibility analysis when planning new structural-cell-biology projects, and as practice data for students.
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Affiliation(s)
- Lu Gan
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Cai Tong Ng
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Chen Chen
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543
| | - Shujun Cai
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543
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28
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Babst M. Eisosomes at the intersection of TORC1 and TORC2 regulation. Traffic 2019; 20:543-551. [PMID: 31038844 DOI: 10.1111/tra.12651] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 04/24/2019] [Accepted: 04/26/2019] [Indexed: 12/14/2022]
Abstract
Eisosomes are furrows in the yeast plasma membrane that form a membrane domain with distinct lipid and protein composition. Recent studies highlighted the importance of this domain for the regulation of proton-nutrient symporters. The amino acids and other nutrients, which these transporters deliver to the cytoplasm not only feed into metabolic pathways but also activate the metabolic regulator TORC1. Eisosomes have also been shown to harbor the membrane stress sensors Slm1 and Slm2. Membrane tension caused by hypoosmotic shock results in the redistribution of Slm1/2 from eisosomes to TORC2 which in turn regulates lipid synthesis. Therefore, eisosomes function upstream of both TORC1 and TORC2 regulation.
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Affiliation(s)
- Markus Babst
- Henry Eyring Center for Cell and Genome Science, University of Utah, Salt Lake City, Utah
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29
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Ader NR, Hoffmann PC, Ganeva I, Borgeaud AC, Wang C, Youle RJ, Kukulski W. Molecular and topological reorganizations in mitochondrial architecture interplay during Bax-mediated steps of apoptosis. eLife 2019; 8:40712. [PMID: 30714902 PMCID: PMC6361589 DOI: 10.7554/elife.40712] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 01/22/2019] [Indexed: 12/25/2022] Open
Abstract
During apoptosis, Bcl-2 proteins such as Bax and Bak mediate the release of pro-apoptotic proteins from the mitochondria by clustering on the outer mitochondrial membrane and thereby permeabilizing it. However, it remains unclear how outer membrane openings form. Here, we combined different correlative microscopy and electron cryo-tomography approaches to visualize the effects of Bax activity on mitochondria in human cells. Our data show that Bax clusters localize near outer membrane ruptures of highly variable size. Bax clusters contain structural elements suggesting a higher order organization of their components. Furthermore, unfolding of inner membrane cristae is coupled to changes in the supramolecular assembly of ATP synthases, particularly pronounced at membrane segments exposed to the cytosol by ruptures. Based on our results, we propose a comprehensive model in which molecular reorganizations of the inner membrane and sequestration of outer membrane components into Bax clusters interplay in the formation of outer membrane ruptures. Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
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Affiliation(s)
- Nicholas R Ader
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.,Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Patrick C Hoffmann
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Iva Ganeva
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Alicia C Borgeaud
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Chunxin Wang
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Richard J Youle
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, United States
| | - Wanda Kukulski
- Cell Biology Division, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
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30
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Pfeffer S, Mahamid J. Unravelling molecular complexity in structural cell biology. Curr Opin Struct Biol 2018; 52:111-118. [PMID: 30339965 DOI: 10.1016/j.sbi.2018.08.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 06/18/2018] [Accepted: 08/29/2018] [Indexed: 12/14/2022]
Abstract
Structural and cell biology have traditionally been separate disciplines and employed techniques that were well defined within the realm of either one or the other. Recent technological breakthroughs propelled electron microscopy of frozen hydrated specimens (cryo-EM) followed by single-particle analysis (SPA) to become a widely applied approach for obtaining near-atomic resolution structures of purified macromolecules. In parallel, ongoing developments on sample preparation are increasingly successful in bringing molecular views into cell biology. Cryo-electron tomography (cryo-ET) has so far served as the main imaging modality employed in these efforts towards obtaining three-dimensional (3D) volumes of heterogeneous molecular assemblies. We review the state-of-the-art in cryo-ET and computational processing and describe the current opportunities and frontiers for in-cell applications.
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Affiliation(s)
- Stefan Pfeffer
- Centre for Molecular Biology of Heidelberg University (ZMBH), 69120 Heidelberg, Germany
| | - Julia Mahamid
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
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31
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Cryo-ET reveals the macromolecular reorganization of S. pombe mitotic chromosomes in vivo. Proc Natl Acad Sci U S A 2018; 115:10977-10982. [PMID: 30297429 DOI: 10.1073/pnas.1720476115] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Chromosomes condense during mitosis in most eukaryotes. This transformation involves rearrangements at the nucleosome level and has consequences for transcription. Here, we use cryo-electron tomography (cryo-ET) to determine the 3D arrangement of nuclear macromolecular complexes, including nucleosomes, in frozen-hydrated Schizosaccharomyces pombe cells. Using 3D classification analysis, we did not find evidence that nucleosomes resembling the crystal structure are abundant. This observation and those from other groups support the notion that a subset of fission yeast nucleosomes may be partially unwrapped in vivo. In both interphase and mitotic cells, there is also no evidence of monolithic structures the size of Hi-C domains. The chromatin is mingled with two features: pockets, which are positions free of macromolecular complexes; and "megacomplexes," which are multimegadalton globular complexes like preribosomes. Mitotic chromatin is more crowded than interphase chromatin in subtle ways. Nearest-neighbor distance analyses show that mitotic chromatin is more compacted at the oligonucleosome than the dinucleosome level. Like interphase, mitotic chromosomes contain megacomplexes and pockets. This uneven chromosome condensation helps explain a longstanding enigma of mitosis: a subset of genes is up-regulated.
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32
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Melia CE, Bharat TAM. Locating macromolecules and determining structures inside bacterial cells using electron cryotomography. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2018; 1866:973-981. [PMID: 29908328 PMCID: PMC6052677 DOI: 10.1016/j.bbapap.2018.06.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 05/30/2018] [Accepted: 06/11/2018] [Indexed: 01/01/2023]
Abstract
Electron cryotomography (cryo-ET) is an imaging technique uniquely suited to the study of bacterial ultrastructure and cell biology. Recent years have seen a surge in structural and cell biology research on bacteria using cryo-ET. This research has driven major technical developments in the field, with applications emerging to address a wide range of biological questions. In this review, we explore the diversity of cryo-ET approaches used for structural and cellular microbiology, with a focus on in situ localization and structure determination of macromolecules. The first section describes strategies employed to locate target macromolecules within large cellular volumes. Next, we explore methods to study thick specimens by sample thinning. Finally, we review examples of macromolecular structure determination in a cellular context using cryo-ET. The examples outlined serve as powerful demonstrations of how the cellular location, structure, and function of any bacterial macromolecule of interest can be investigated using cryo-ET.
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Affiliation(s)
- Charlotte E Melia
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
| | - Tanmay A M Bharat
- Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom; Central Oxford Structural and Molecular Imaging Centre, University of Oxford, Oxford OX1 3RE, United Kingdom.
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33
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Cai S, Böck D, Pilhofer M, Gan L. The in situ structures of mono-, di-, and trinucleosomes in human heterochromatin. Mol Biol Cell 2018; 29:2450-2457. [PMID: 30091658 PMCID: PMC6233054 DOI: 10.1091/mbc.e18-05-0331] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The in situ three-dimensional organization of chromatin at the nucleosome and oligonucleosome levels is unknown. Here we use cryo-electron tomography to determine the in situ structures of HeLa nucleosomes, which have canonical core structures and asymmetric, flexible linker DNA. Subtomogram remapping suggests that sequential nucleosomes in heterochromatin follow irregular paths at the oligonucleosome level. This basic principle of higher-order repressive chromatin folding is compatible with the conformational variability of the two linker DNAs at the single-nucleosome level.
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Affiliation(s)
- Shujun Cai
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore 117543
| | - Désirée Böck
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
| | - Martin Pilhofer
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule Zürich, CH-8093 Zürich, Switzerland
| | - Lu Gan
- Department of Biological Sciences and Centre for BioImaging Sciences, National University of Singapore, Singapore 117543
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