51
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Transbilayer Movement of Sphingomyelin Precedes Catastrophic Breakage of Enterobacteria-Containing Vacuoles. Curr Biol 2020; 30:2974-2983.e6. [PMID: 32649908 PMCID: PMC7416114 DOI: 10.1016/j.cub.2020.05.083] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 04/11/2020] [Accepted: 05/27/2020] [Indexed: 01/01/2023]
Abstract
Pathogenic bacteria enter the cytosol of host cells through uptake into bacteria-containing vacuoles (BCVs) and subsequent rupture of the vacuolar membrane [1]. Bacterial invaders are sensed either directly, through cytosolic pattern-recognition receptors specific for bacterial ligands, or indirectly, through danger receptors that bind host molecules displayed in an abnormal context, for example, glycans on damaged BCVs [2, 3, 4]. In contrast to damage caused by Listeria monocytogenes, a Gram-positive bacterium, BCV rupture by Gram-negative pathogens such as Shigella flexneri or Salmonella Typhimurium remains incompletely understood [5, 6]. The latter may cause membrane damage directly, when inserting their Type Three Secretion needles into host membranes, or indirectly through translocated bacterial effector proteins [7, 8, 9]. Here, we report that sphingomyelin, an abundant lipid of the luminal leaflet of BCV membranes, and normally absent from the cytosol, becomes exposed to the cytosol as an early predictive marker of BCV rupture by Gram-negative bacteria. To monitor subcellular sphingomyelin distribution, we generated a live sphingomyelin reporter from Lysenin, a sphingomyelin-specific toxin from the earthworm Eisenia fetida [10, 11]. Using super resolution live imaging and correlative light and electron microscopy (CLEM), we discovered that BCV rupture proceeds through two distinct successive stages: first, sphingomyelin is gradually translocated into the cytosolic leaflet of the BCV, invariably followed by cytosolic exposure of glycans, which recruit galectin-8, indicating bacterial entry into the cytosol. Exposure of sphingomyelin on BCVs may therefore act as an early danger signal alerting the cell to imminent bacterial invasion. Lysenin serves as a reporter of sphingomyelin exposure in the mammalian cytosol Chemical-, toxin-, or pathogen-induced membrane damage exposes sphingomyelin Sphingomyelin exposure precedes catastrophic breakage of bacteria-containing vacuoles Cytosolic sphingomyelin is indicative of membrane stress and imminent pathogen entry
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52
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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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53
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Jiang Y, He R, Shi Y, Liang J, Zhao L. Plasma exosomes protect against cerebral ischemia/reperfusion injury via exosomal HSP70 mediated suppression of ROS. Life Sci 2020; 256:117987. [PMID: 32569778 DOI: 10.1016/j.lfs.2020.117987] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 06/16/2020] [Accepted: 06/16/2020] [Indexed: 12/12/2022]
Abstract
AIMS Ischemic stroke is the leading cause of severe disability and death worldwide. As the pathogenesis of stroke has not been clearly elucidated and the ability of current therapeutic drugs on crossing the blood-brain barrier (BBB) is extremely low, there is no effective strategy to treat stroke. We aim at investigating the specific advantages of using plasma exosomes (Pla-Exo) for targeting ischemic brain and exploring its underlying mechanism in neuroprotection. MAIN METHODS Pla-Exo was obtained by a gradient ultracentrifugation of fresh plasma. The quantification of penetrated Pla-Exo through BBB was investigated in vitro BBB model, furthermore, the effects of Pla-Exo and exosomal HSP70 on cerebral ischemia/reperfusion injury were evaluated. KEY FINDINGS Pla-Exo enhanced BBB crossing by specific interaction between Pla-Exo inherited heat shock protein 70 (HSP70) and endothelial Toll-like receptor 4 (TLR4). As expected, Pla-Exo increased HSP70 expression in the ischemic region through the transfer of HSP70, and led to HSP70 mediated suppression of ROS, thus alleviating cerebral ischemia/reperfusion (I/R) injury by attenuating the deterioration of BBB and preventing mitochondria damage. SIGNIFICANCE These findings indicated that Pla-Exo can provide protection against ischemia-reperfusion injury via the regulation of HSP70 and it should be further studied as a potential candidate for protection against ischemic injury.
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Affiliation(s)
- Yibing Jiang
- School of Pharmacy, Jinzhou Medical University, Jinzhou 121000, PR China
| | - Ruyi He
- School of Pharmacy, Jinzhou Medical University, Jinzhou 121000, PR China
| | - Yijie Shi
- School of Pharmacy, Jinzhou Medical University, Jinzhou 121000, PR China
| | - Jia Liang
- Life Science Institution, Jinzhou Medical University, Jinzhou 121000, PR China
| | - Liang Zhao
- School of Pharmacy, Jinzhou Medical University, Jinzhou 121000, PR China.
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54
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Wagner FR, Watanabe R, Schampers R, Singh D, Persoon H, Schaffer M, Fruhstorfer P, Plitzko J, Villa E. Preparing samples from whole cells using focused-ion-beam milling for cryo-electron tomography. Nat Protoc 2020; 15:2041-2070. [PMID: 32405053 PMCID: PMC8053421 DOI: 10.1038/s41596-020-0320-x] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 03/06/2020] [Indexed: 12/31/2022]
Abstract
Recent advances have made cryogenic (cryo) electron microscopy a key technique to achieve near-atomic-resolution structures of biochemically isolated macromolecular complexes. Cryo-electron tomography (cryo-ET) can give unprecedented insight into these complexes in the context of their natural environment. However, the application of cryo-ET is limited to samples that are thinner than most cells, thereby considerably reducing its applicability. Cryo-focused-ion-beam (cryo-FIB) milling has been used to carve (micromachining) out 100-250-nm-thin regions (called lamella) in the intact frozen cells. This procedure opens a window into the cells for high-resolution cryo-ET and structure determination of biomolecules in their native environment. Further combination with fluorescence microscopy allows users to determine cells or regions of interest for the targeted fabrication of lamellae and cryo-ET imaging. Here, we describe how to prepare lamellae using a microscope equipped with both FIB and scanning electron microscopy modalities. Such microscopes (Aquilos Cryo-FIB/Scios/Helios or CrossBeam) are routinely referred to as dual-beam microscopes, and they are equipped with a cryo-stage for all operations in cryogenic conditions. The basic principle of the described methodologies is also applicable for other types of dual-beam microscopes equipped with a cryo-stage. We also briefly describe how to integrate fluorescence microscopy data for targeted milling and critical considerations for cryo-ET data acquisition of the lamellae. Users familiar with cryo-electron microscopy who get basic training in dual-beam microscopy can complete the protocol within 2-3 d, allowing for several pause points during the procedure.
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Affiliation(s)
- Felix R Wagner
- Section of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA
- Department of Molecular Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | - Reika Watanabe
- Section of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | | | - Digvijay Singh
- Section of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | - Hans Persoon
- Thermo Fisher Scientific, Eindhoven, the Netherlands
| | - Miroslava Schaffer
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Peter Fruhstorfer
- Thermo Fisher Scientific, Eindhoven, the Netherlands
- Eppendorf AG, Hamburg, Germany
| | - Jürgen Plitzko
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Elizabeth Villa
- Section of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA.
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55
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Abstract
Mitochondria are essential for eukaryotic life. These double-membrane organelles often form highly dynamic tubular networks interacting with many cellular structures. Their highly convoluted contiguous inner membrane compartmentalizes the organelle, which is crucial for mitochondrial function. Since the diameter of the mitochondrial tubules is generally close to the diffraction limit of light microscopy, it is often challenging, if not impossible, to visualize submitochondrial structures or protein distributions using conventional light microscopy. This renders super-resolution microscopy particularly valuable, and attractive, for studying mitochondria. Super-resolution microscopy encompasses a diverse set of approaches that extend resolution, as well as nanoscopy techniques that can even overcome the diffraction limit. In this review, we provide an overview of recent studies using super-resolution microscopy to investigate mitochondria, discuss the strengths and opportunities of the various methods in addressing specific questions in mitochondrial biology, and highlight potential future developments.
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Affiliation(s)
- Stefan Jakobs
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany;
- Clinic of Neurology, University Medical Center Göttingen, 37075 Göttingen, Germany
| | - Till Stephan
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany;
- Clinic of Neurology, University Medical Center Göttingen, 37075 Göttingen, Germany
| | - Peter Ilgen
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany;
- Clinic of Neurology, University Medical Center Göttingen, 37075 Göttingen, Germany
| | - Christian Brüser
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany;
- Clinic of Neurology, University Medical Center Göttingen, 37075 Göttingen, Germany
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56
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Moldoveanu T, Czabotar PE. BAX, BAK, and BOK: A Coming of Age for the BCL-2 Family Effector Proteins. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a036319. [PMID: 31570337 DOI: 10.1101/cshperspect.a036319] [Citation(s) in RCA: 97] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The BCL-2 family of proteins control a key checkpoint in apoptosis, that of mitochondrial outer membrane permeabilization or, simply, mitochondrial poration. The family consists of three subgroups: BH3-only initiators that respond to apoptotic stimuli; antiapoptotic guardians that protect against cell death; and the membrane permeabilizing effectors BAX, BAK, and BOK. On activation, effector proteins are converted from inert monomers into membrane permeabilizing oligomers. For many years, this process has been poorly understood at the molecular level, but a number of recent advances have provided important insights. We review the regulation of these effectors, their activation, subsequent conformational changes, and the ensuing oligomerization events that enable mitochondrial poration, which initiates apoptosis through release of key signaling factors such as cytochrome c We highlight the mysteries that remain in understanding these important proteins in an endeavor to provide a comprehensive picture of where the field currently sits and where it is moving toward.
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Affiliation(s)
- Tudor Moldoveanu
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.,Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis Tennessee 38105, USA
| | - Peter E Czabotar
- Walter and Eliza Hall Institute of Medical Research, University of Melbourne, Parkville, Victoria 3052, Australia.,Department of Medical Biology, University of Melbourne, Parkville, Victoria 3010, Australia
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57
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Riley JS, Tait SW. Mitochondrial DNA in inflammation and immunity. EMBO Rep 2020; 21:e49799. [PMID: 32202065 PMCID: PMC7132203 DOI: 10.15252/embr.201949799] [Citation(s) in RCA: 420] [Impact Index Per Article: 105.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 01/31/2020] [Accepted: 03/03/2020] [Indexed: 12/14/2022] Open
Abstract
Mitochondria are cellular organelles that orchestrate a vast range of biological processes, from energy production and metabolism to cell death and inflammation. Despite this seemingly symbiotic relationship, mitochondria harbour within them a potent agonist of innate immunity: their own genome. Release of mitochondrial DNA into the cytoplasm and out into the extracellular milieu activates a plethora of different pattern recognition receptors and innate immune responses, including cGAS‐STING, TLR9 and inflammasome formation leading to, among others, robust type I interferon responses. In this Review, we discuss how mtDNA can be released from the mitochondria, the various inflammatory pathways triggered by mtDNA release and its myriad biological consequences for health and disease.
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Affiliation(s)
- Joel S Riley
- Cancer Research UK Beatson Institute, Glasgow, UK.,Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Stephen Wg Tait
- Cancer Research UK Beatson Institute, Glasgow, UK.,Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
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58
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Zachs T, Schertel A, Medeiros J, Weiss GL, Hugener J, Matos J, Pilhofer M. Fully automated, sequential focused ion beam milling for cryo-electron tomography. eLife 2020; 9:e52286. [PMID: 32149604 PMCID: PMC7082125 DOI: 10.7554/elife.52286] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Accepted: 03/07/2020] [Indexed: 11/13/2022] Open
Abstract
Cryo-electron tomography (cryoET) has become a powerful technique at the interface of structural biology and cell biology, due to its unique ability for imaging cells in their native state and determining structures of macromolecular complexes in their cellular context. A limitation of cryoET is its restriction to relatively thin samples. Sample thinning by cryo-focused ion beam (cryoFIB) milling has significantly expanded the range of samples that can be analyzed by cryoET. Unfortunately, cryoFIB milling is low-throughput, time-consuming and manual. Here, we report a method for fully automated sequential cryoFIB preparation of high-quality lamellae, including rough milling and polishing. We reproducibly applied this method to eukaryotic and bacterial model organisms, and show that the resulting lamellae are suitable for cryoET imaging and subtomogram averaging. Since our method reduces the time required for lamella preparation and minimizes the need for user input, we envision the technique will render previously inaccessible projects feasible.
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Affiliation(s)
- Tobias Zachs
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule ZürichZürichSwitzerland
| | - Andreas Schertel
- Carl Zeiss Microscopy GmbH, Zeiss Customer Center EuropeOberkochenGermany
| | - João Medeiros
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule ZürichZürichSwitzerland
| | - Gregor L Weiss
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule ZürichZürichSwitzerland
| | - Jannik Hugener
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule ZürichZürichSwitzerland
- Institute of Biochemistry, Eidgenössische Technische Hochschule ZürichZürichSwitzerland
| | - Joao Matos
- Institute of Biochemistry, Eidgenössische Technische Hochschule ZürichZürichSwitzerland
| | - Martin Pilhofer
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule ZürichZürichSwitzerland
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59
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Bock FJ, Tait SWG. Mitochondria as multifaceted regulators of cell death. Nat Rev Mol Cell Biol 2020; 21:85-100. [PMID: 31636403 DOI: 10.1038/s41580-019-0173-8] [Citation(s) in RCA: 1179] [Impact Index Per Article: 294.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/30/2019] [Indexed: 12/12/2022]
Abstract
Through their many and varied metabolic functions, mitochondria power life. Paradoxically, mitochondria also have a central role in apoptotic cell death. Upon induction of mitochondrial apoptosis, mitochondrial outer membrane permeabilization (MOMP) usually commits a cell to die. Apoptotic signalling downstream of MOMP involves cytochrome c release from mitochondria and subsequent caspase activation. As such, targeting MOMP in order to manipulate cell death holds tremendous therapeutic potential across different diseases, including neurodegenerative diseases, autoimmune disorders and cancer. In this Review, we discuss new insights into how mitochondria regulate apoptotic cell death. Surprisingly, recent data demonstrate that besides eliciting caspase activation, MOMP engages various pro-inflammatory signalling functions. As we highlight, together with new findings demonstrating cell survival following MOMP, this pro-inflammatory role suggests that mitochondria-derived signalling downstream of pro-apoptotic cues may also have non-lethal functions. Finally, we discuss the importance and roles of mitochondria in other forms of regulated cell death, including necroptosis, ferroptosis and pyroptosis. Collectively, these new findings offer exciting, unexplored opportunities to target mitochondrial regulation of cell death for clinical benefit.
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Affiliation(s)
- Florian J Bock
- Cancer Research UK Beatson Institute, Institute of Cancer Sciences, University of Glasgow, Glasgow, UK
| | - Stephen W G Tait
- Cancer Research UK Beatson Institute, Institute of Cancer Sciences, University of Glasgow, Glasgow, UK.
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60
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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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61
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Toro-Nahuelpan M, Zagoriy I, Senger F, Blanchoin L, Théry M, Mahamid J. Tailoring cryo-electron microscopy grids by photo-micropatterning for in-cell structural studies. Nat Methods 2020; 17:50-54. [PMID: 31740821 DOI: 10.21203/rs.2.12377/v1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 10/07/2019] [Indexed: 05/22/2023]
Abstract
Spatially controlled cell adhesion on electron microscopy supports remains a bottleneck in specimen preparation for cellular cryo-electron tomography. Here, we describe contactless and mask-free photo-micropatterning of electron microscopy grids for site-specific deposition of extracellular matrix-related proteins. We attained refined cell positioning for micromachining by cryo-focused ion beam milling. Complex micropatterns generated predictable intracellular organization, allowing direct correlation between cell architecture and in-cell three-dimensional structural characterization of the underlying molecular machinery.
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Affiliation(s)
- Mauricio Toro-Nahuelpan
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Ievgeniia Zagoriy
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Fabrice Senger
- CytomorphoLab, Interdisciplinary Research Institute of Grenoble, Laboratoire de Physiologie Cellulaire et Végétale, Université Grenoble-Alpes/CEA/CNRS/INRA, Grenoble, France
| | - Laurent Blanchoin
- CytomorphoLab, Interdisciplinary Research Institute of Grenoble, Laboratoire de Physiologie Cellulaire et Végétale, Université Grenoble-Alpes/CEA/CNRS/INRA, Grenoble, France
- CytomorphoLab, Hôpital Saint Louis, Institut Universitaire d'Hématologie, Université Paris Diderot, Paris, France
| | - Manuel Théry
- CytomorphoLab, Interdisciplinary Research Institute of Grenoble, Laboratoire de Physiologie Cellulaire et Végétale, Université Grenoble-Alpes/CEA/CNRS/INRA, Grenoble, France
- CytomorphoLab, Hôpital Saint Louis, Institut Universitaire d'Hématologie, Université Paris Diderot, Paris, France
| | - Julia Mahamid
- Structural and Computational Biology Unit, European Molecular Biology Laboratory, Heidelberg, Germany.
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62
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Tailoring cryo-electron microscopy grids by photo-micropatterning for in-cell structural studies. Nat Methods 2019; 17:50-54. [PMID: 31740821 PMCID: PMC6949126 DOI: 10.1038/s41592-019-0630-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 10/07/2019] [Indexed: 01/01/2023]
Abstract
Spatially-controlled cell adhesion on electron microscopy (EM) supports remains a
bottleneck in specimen preparation for cellular cryo-electron tomography. Here,
we describe contactless and mask-free photo-micropatterning of EM grids for
site-specific deposition of extracellular matrix (ECM)-related proteins. We
attained refined cell positioning for micromachining by cryo-focused ion beam
milling. Complex micropatterns generated predictable intracellular organization,
allowing direct correlation between cell architecture and
in-cell 3D-structural characterization of the underlying
molecular machinery.
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63
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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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64
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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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65
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Vringer E, Tait SWG. Mitochondria and Inflammation: Cell Death Heats Up. Front Cell Dev Biol 2019; 7:100. [PMID: 31316979 PMCID: PMC6610339 DOI: 10.3389/fcell.2019.00100] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Accepted: 05/23/2019] [Indexed: 01/12/2023] Open
Abstract
Mitochondrial outer membrane permeabilization (MOMP) is essential to initiate mitochondrial apoptosis. Due to the disruption of mitochondrial outer membrane integrity, intermembrane space proteins, notably cytochrome c, are released into the cytosol whereupon they activate caspase proteases and apoptosis. Beyond its well-established apoptotic role, MOMP has recently been shown to display potent pro-inflammatory effects. These include mitochondrial DNA dependent activation of cGAS-STING signaling leading to a type I interferon response. Secondly, via an IAP-regulated mechanism, MOMP can engage pro-inflammatory NF-κB signaling. During cell death, apoptotic caspase activity inhibits mitochondrial dependent inflammation. Importantly, by engaging an immunogenic form of cell death, inhibiting caspase function can effectively inhibit tumorigenesis. Unexpectedly, these studies reveal mitochondria as inflammatory signaling hubs during cell death and demonstrate its potential for therapeutic exploitation.
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Affiliation(s)
- Esmee Vringer
- Cancer Research UK, Beatson Institute, Glasgow, United Kingdom.,Institute of Cancer Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Stephen W G Tait
- Cancer Research UK, Beatson Institute, Glasgow, United Kingdom.,Institute of Cancer Sciences, University of Glasgow, Glasgow, United Kingdom
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66
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Abstract
Of all the macromolecular assemblies of life, the least understood is the biomembrane. This is especially true in regard to its atomic structure. Ideas on biomembranes, developed in the last 200 years, culminated in the fluid mosaic model of the membrane. In this essay, I provide a historical outline of how we arrived at our current understanding of biomembranes and the models we use to describe them. A selection of direct experimental findings on the nano-scale structure of biomembranes is taken up to discuss their physical nature, and special emphasis is put on the surprising insights that arise from atomic scale descriptions.
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