1
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Han Y, Yu L. Calcium ions promote migrasome formation via Synaptotagmin-1. J Cell Biol 2024; 223:e202402060. [PMID: 38647453 PMCID: PMC11035859 DOI: 10.1083/jcb.202402060] [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: 02/08/2024] [Revised: 03/27/2024] [Accepted: 04/09/2024] [Indexed: 04/25/2024] Open
Abstract
Migrasomes, organelles crucial for cell communication, undergo distinct stages of nucleation, maturation, and expansion. The regulatory mechanisms of migrasome formation, particularly through biological cues, remain largely unexplored. This study reveals that calcium is essential for migrasome formation. Furthermore, we identify that Synaptotagmin-1 (Syt1), a well-known calcium sensor, is not only enriched in migrasomes but also indispensable for their formation. The calcium-binding ability of Syt1 is key to initiating migrasome formation. The recruitment of Syt1 to migrasome formation sites (MFS) triggers the swelling of MFS into unstable precursors, which are subsequently stabilized through the sequential recruitment of tetraspanins. Our findings reveal how calcium regulates migrasome formation and propose a sequential interaction model involving Syt1 and Tetraspanins in the formation and stabilization of migrasomes.
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Affiliation(s)
- Yiyang Han
- State Key Laboratory of Membrane Biology, Tsinghua University–Peking University Joint Center for Life Sciences, Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, China
| | - Li Yu
- State Key Laboratory of Membrane Biology, Tsinghua University–Peking University Joint Center for Life Sciences, Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, China
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2
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Otrin N, Otrin L, Bednarz C, Träger TK, Hamdi F, Kastritis PL, Ivanov I, Sundmacher K. Protein-Rich Rafts in Hybrid Polymer/Lipid Giant Unilamellar Vesicles. Biomacromolecules 2024; 25:778-791. [PMID: 38190609 PMCID: PMC10865357 DOI: 10.1021/acs.biomac.3c00972] [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: 09/13/2023] [Revised: 12/20/2023] [Accepted: 12/20/2023] [Indexed: 01/10/2024]
Abstract
Considerable attention has been dedicated to lipid rafts due to their importance in numerous cell functions such as membrane trafficking, polarization, and signaling. Next to studies in living cells, artificial micrometer-sized vesicles with a minimal set of components are established as a major tool to understand the phase separation dynamics and their intimate interplay with membrane proteins. In parallel, mixtures of phospholipids and certain amphiphilic polymers simultaneously offer an interface for proteins and mimic this segregation behavior, presenting a tangible synthetic alternative for fundamental studies and bottom-up design of cellular mimics. However, the simultaneous insertion of complex and sensitive membrane proteins is experimentally challenging and thus far has been largely limited to natural lipids. Here, we present the co-reconstitution of the proton pump bo3 oxidase and the proton consumer ATP synthase in hybrid polymer/lipid giant unilamellar vesicles (GUVs) via fusion/electroformation. Variations of the current method allow for tailored reconstitution protocols and control of the vesicle size. In particular, mixing of protein-free and protein-functionalized nanosized vesicles in the electroformation film results in larger GUVs, while separate reconstitution of the respiratory enzymes enables higher ATP synthesis rates. Furthermore, protein labeling provides a synthetic mechanism for phase separation and protein sequestration, mimicking lipid- and protein-mediated domain formation in nature. The latter means opens further possibilities for re-enacting phenomena like supercomplex assembly or symmetry breaking and enriches the toolbox of bottom-up synthetic biology.
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Affiliation(s)
- Nika Otrin
- Process
Systems Engineering, Max Planck Institute
for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany
| | - Lado Otrin
- Process
Systems Engineering, Max Planck Institute
for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany
| | - Claudia Bednarz
- Process
Systems Engineering, Max Planck Institute
for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany
| | - Toni K. Träger
- Interdisciplinary
Research Center HALOmem and Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Biozentrum, 06120 Halle/Saale, Germany
| | - Farzad Hamdi
- Interdisciplinary
Research Center HALOmem and Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Biozentrum, 06120 Halle/Saale, Germany
| | - Panagiotis L. Kastritis
- Interdisciplinary
Research Center HALOmem and Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Biozentrum, 06120 Halle/Saale, Germany
- Institute
of Chemical Biology, National Hellenic Research
Foundation, 11635 Athens, Greece
| | - Ivan Ivanov
- Process
Systems Engineering, Max Planck Institute
for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany
- Grup
de Biotecnologia Molecular i Industrial, Department of Chemical Engineering, Universitat Politècnica de Catalunya, Rambla Sant Nebridi 22, 08222 Terrassa, Spain
| | - Kai Sundmacher
- Process
Systems Engineering, Max Planck Institute
for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany
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3
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Grusky DS, Bhattacharya A, Boxer SG. Secondary Ion Mass Spectrometry of Single Giant Unilamellar Vesicles Reveals Compositional Variability. J Am Chem Soc 2023; 145:27521-27530. [PMID: 38056605 PMCID: PMC10904076 DOI: 10.1021/jacs.3c09039] [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] [Indexed: 12/08/2023]
Abstract
Giant unilamellar vesicles (GUVs) are a widely used model system to interrogate lipid phase behavior, study biomembrane mechanics, reconstitute membrane proteins, and provide a chassis for synthetic cells. It is generally assumed that the composition of individual GUVs is the same as the nominal stock composition; however, there may be significant compositional variability between individual GUVs. Although this compositional heterogeneity likely impacts phase behavior, the function and incorporation of membrane proteins, and the encapsulation of biochemical reactions, it has yet to be directly quantified. To assess heterogeneity, we use secondary ion mass spectrometry (SIMS) to probe the composition of individual GUVs using non-perturbing isotopic labels. Both 13C- and 2H-labeled lipids are incorporated into a ternary mixture, which is then used to produce GUVs via gentle hydration or electroformation. Simultaneous detection of seven different ion species via SIMS allows for the concentration of 13C- and 2H-labeled lipids in single GUVs to be quantified using calibration curves, which correlate ion intensity to composition. Additionally, the relative concentration of 13C- and 2H-labeled lipids is assessed for each GUV via the ion ratio 2H-/13C-, which is highly sensitive to compositional differences between individual GUVs and circumvents the need for calibration by using standards. Both quantification methods suggest that gentle hydration produces GUVs with greater compositional variability than those formed by electroformation. However, both gentle hydration and electroformation display standard deviations in composition (n = 30 GUVs) on the order of 1-4 mol %, consistent with variability seen in previous indirect measurements.
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Affiliation(s)
- Dashiel S Grusky
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
| | - Ahanjit Bhattacharya
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
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4
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Lipowsky R, Pramanik S, Benk AS, Tarnawski M, Spatz JP, Dimova R. Elucidating the Morphology of the Endoplasmic Reticulum: Puzzles and Perspectives. ACS NANO 2023. [PMID: 37377213 DOI: 10.1021/acsnano.3c01338] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/29/2023]
Abstract
Artificial or synthetic organelles are a key challenge for bottom-up synthetic biology. So far, synthetic organelles have typically been based on spherical membrane compartments, used to spatially confine selected chemical reactions. In vivo, these compartments are often far from being spherical and can exhibit rather complex architectures. A particularly fascinating example is provided by the endoplasmic reticulum (ER), which extends throughout the whole cell by forming a continuous network of membrane nanotubes connected by three-way junctions. The nanotubes have a typical diameter of between 50 and 100 nm. In spite of much experimental progress, several fundamental aspects of the ER morphology remain elusive. A long-standing puzzle is the straight appearance of the tubules in the light microscope, which form irregular polygons with contact angles close to 120°. Another puzzling aspect is the nanoscopic shapes of the tubules and junctions, for which very different images have been obtained by electron microcopy and structured illumination microscopy. Furthermore, both the formation and maintenance of the reticular networks require GTP and GTP-hydrolyzing membrane proteins. In fact, the networks are destroyed by the fragmentation of nanotubes when the supply of GTP is interrupted. Here, it is argued that all of these puzzling observations are intimately related to each other and to the dimerization of two membrane proteins anchored to the same membrane. So far, the functional significance of this dimerization process remained elusive and, thus, seemed to waste a lot of GTP. However, this process can generate an effective membrane tension that stabilizes the irregular polygonal geometry of the reticular networks and prevents the fragmentation of their tubules, thereby maintaining the integrity of the ER. By incorporating the GTP-hydrolyzing membrane proteins into giant unilamellar vesicles, the effective membrane tension will become accessible to systematic experimental studies.
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Affiliation(s)
- Reinhard Lipowsky
- Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany
| | - Shreya Pramanik
- Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany
| | - Amelie S Benk
- Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | | | - Joachim P Spatz
- Max Planck Institute for Medical Research, 69120 Heidelberg, Germany
| | - Rumiana Dimova
- Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany
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5
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Moreno-Pescador G, Arastoo MR, Ruhoff VT, Chiantia S, Daniels R, Bendix PM. Thermoplasmonic Vesicle Fusion Reveals Membrane Phase Segregation of Influenza Spike Proteins. NANO LETTERS 2023; 23:3377-3384. [PMID: 37040311 PMCID: PMC10141563 DOI: 10.1021/acs.nanolett.3c00371] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Many cellular processes involve the lateral organization of integral and peripheral membrane proteins into nanoscale domains. Despite the biological significance, the mechanisms that facilitate membrane protein clustering into nanoscale lipid domains remain enigmatic. In cells, the analysis of membrane protein phase affinity is complicated by the size and temporal nature of ordered and disordered lipid domains. To overcome these limitations, we developed a method for delivering membrane proteins from transfected cells into phase-separated model membranes that combines optical trapping with thermoplasmonic-mediated membrane fusion and confocal imaging. Using this approach, we observed clear phase partitioning into the liquid disordered phase following the transfer of GFP-tagged influenza hemagglutinin and neuraminidase from transfected cell membranes to giant unilamellar vesicles. The generic platform presented here allows investigation of the phase affinity of any plasma membrane protein which can be labeled or tagged with a fluorescent marker.
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Affiliation(s)
| | - Mohammad Reza Arastoo
- Niels
Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 København Ø, Denmark
| | | | - Salvatore Chiantia
- Institute
of Biochemistry and Biology, University
of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
| | - Robert Daniels
- Division
of Viral Products, Center for Biologics
Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland 20993, United States
| | - Poul Martin Bendix
- Niels
Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 København Ø, Denmark
- Email
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6
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Bailoni E, Partipilo M, Coenradij J, Grundel DAJ, Slotboom DJ, Poolman B. Minimal Out-of-Equilibrium Metabolism for Synthetic Cells: A Membrane Perspective. ACS Synth Biol 2023; 12:922-946. [PMID: 37027340 PMCID: PMC10127287 DOI: 10.1021/acssynbio.3c00062] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Indexed: 04/08/2023]
Abstract
Life-like systems need to maintain a basal metabolism, which includes importing a variety of building blocks required for macromolecule synthesis, exporting dead-end products, and recycling cofactors and metabolic intermediates, while maintaining steady internal physical and chemical conditions (physicochemical homeostasis). A compartment, such as a unilamellar vesicle, functionalized with membrane-embedded transport proteins and metabolic enzymes encapsulated in the lumen meets these requirements. Here, we identify four modules designed for a minimal metabolism in a synthetic cell with a lipid bilayer boundary: energy provision and conversion, physicochemical homeostasis, metabolite transport, and membrane expansion. We review design strategies that can be used to fulfill these functions with a focus on the lipid and membrane protein composition of a cell. We compare our bottom-up design with the equivalent essential modules of JCVI-syn3a, a top-down genome-minimized living cell with a size comparable to that of large unilamellar vesicles. Finally, we discuss the bottlenecks related to the insertion of a complex mixture of membrane proteins into lipid bilayers and provide a semiquantitative estimate of the relative surface area and lipid-to-protein mass ratios (i.e., the minimal number of membrane proteins) that are required for the construction of a synthetic cell.
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Affiliation(s)
- Eleonora Bailoni
- Department
of Biochemistry and Molecular Systems Biology, Groningen Biomolecular
Sciences and Biotechnology Institute, University
of Groningen, Nijenborgh
4, 9747 AG Groningen, The Netherlands
| | - Michele Partipilo
- Department
of Biochemistry and Molecular Systems Biology, Groningen Biomolecular
Sciences and Biotechnology Institute, University
of Groningen, Nijenborgh
4, 9747 AG Groningen, The Netherlands
| | - Jelmer Coenradij
- Department
of Biochemistry and Molecular Systems Biology, Groningen Biomolecular
Sciences and Biotechnology Institute, University
of Groningen, Nijenborgh
4, 9747 AG Groningen, The Netherlands
| | - Douwe A. J. Grundel
- Department
of Biochemistry and Molecular Systems Biology, Groningen Biomolecular
Sciences and Biotechnology Institute, University
of Groningen, Nijenborgh
4, 9747 AG Groningen, The Netherlands
| | - Dirk J. Slotboom
- Department
of Biochemistry and Molecular Systems Biology, Groningen Biomolecular
Sciences and Biotechnology Institute, University
of Groningen, Nijenborgh
4, 9747 AG Groningen, The Netherlands
| | - Bert Poolman
- Department
of Biochemistry and Molecular Systems Biology, Groningen Biomolecular
Sciences and Biotechnology Institute, University
of Groningen, Nijenborgh
4, 9747 AG Groningen, The Netherlands
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7
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Dolder N, Müller P, von Ballmoos C. Experimental platform for the functional investigation of membrane proteins in giant unilamellar vesicles. SOFT MATTER 2022; 18:5877-5893. [PMID: 35916307 PMCID: PMC9364335 DOI: 10.1039/d2sm00551d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Giant unilamellar vesicles (GUVs) are micrometer-sized model membrane systems that can be viewed directly under the microscope. They serve as scaffolds for the bottom-up creation of synthetic cells, targeted drug delivery and have been widely used to study membrane related phenomena in vitro. GUVs are also of interest for the functional investigation of membrane proteins that carry out many key cellular functions. A major hurdle to a wider application of GUVs in this field is the diversity of existing protocols that are optimized for individual proteins. Here, we compare PVA assisted and electroformation techniques for GUV formation under physiologically relevant conditions, and analyze the effect of immobilization on vesicle structure and membrane tightness towards small substrates and protons. There, differences in terms of yield, size, and leakage of GUVs produced by PVA assisted swelling and electroformation were found, dependent on salt and buffer composition. Using fusion of oppositely charged membranes to reconstitute a model membrane protein, we find that empty vesicles and proteoliposomes show similar fusion behavior, which allows for a rapid estimation of protein incorporation using fluorescent lipids.
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Affiliation(s)
- Nicolas Dolder
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Philipp Müller
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
| | - Christoph von Ballmoos
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
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8
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Himbert S, Gastaldo IP, Ahmed R, Pomier KM, Cowbrough B, Jahagirdar D, Ros S, Juhasz J, Stöver HDH, Ortega J, Melacini G, Bowdish DME, Rheinstädter MC. Erythro-VLPs: Anchoring SARS-CoV-2 spike proteins in erythrocyte liposomes. PLoS One 2022; 17:e0263671. [PMID: 35275926 PMCID: PMC8916654 DOI: 10.1371/journal.pone.0263671] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 01/24/2022] [Indexed: 12/12/2022] Open
Abstract
Novel therapeutic strategies are needed to control the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) pandemic. Here, we present a protocol to anchor the SARS-CoV-2 spike (S-)protein in the cytoplasmic membranes of erythrocyte liposomes. A surfactant was used to stabilize the S-protein’s structure in the aqueous environment before insertion and to facilitate reconstitution of the S-proteins in the erythrocyte membranes. The insertion process was studied using coarse grained Molecular Dynamics (MD) simulations. Liposome formation and S-protein anchoring was studied by dynamic light scattering (DLS), ELV-protein co-sedimentation assays, fluorescent microcopy and cryo-TEM. The Erythro-VLPs (erythrocyte based virus like particles) have a well defined size of ∼200 nm and an average protein density on the outer membrane of up to ∼300 proteins/μm2. The correct insertion and functional conformation of the S-proteins was verified by dose-dependent binding to ACE-2 (angiotensin converting enzyme 2) in biolayer interferometry (BLI) assays. Seroconversion was observed in a pilot mouse trial after 14 days when administered intravenously, based on enzyme-linked immunosorbent assays (ELISA). This red blood cell based platform can open novel possibilities for therapeutics for the coronavirus disease (COVID-19) including variants, and other viruses in the future.
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Affiliation(s)
- Sebastian Himbert
- Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada
- Origins Institute, McMaster University, Hamilton, ON, Canada
| | - Isabella Passos Gastaldo
- Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada
- Origins Institute, McMaster University, Hamilton, ON, Canada
| | - Rashik Ahmed
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton ON, Canada
| | - Karla Martinez Pomier
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton ON, Canada
| | - Braeden Cowbrough
- Department of Medicine, McMaster University, Hamilton, ON, Canada
- McMaster Immunology Research Centre, McMaster University, Hamilton, ON, Canada
| | - Dushyant Jahagirdar
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC, Canada
| | - Samantha Ros
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada
| | - Janos Juhasz
- Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada
- Juravinski Cancer Centre, Department of Medical Physics, Hamilton, ON, Canada
| | - Harald D. H. Stöver
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada
| | - Joaquin Ortega
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC, Canada
| | - Giuseppe Melacini
- Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON, Canada
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton ON, Canada
| | - Dawn M. E. Bowdish
- Department of Medicine, McMaster University, Hamilton, ON, Canada
- McMaster Immunology Research Centre, McMaster University, Hamilton, ON, Canada
- Firestone Institute for Respiratory Health, St. Joseph’s Healthcare, Hamilton, ON, Canada
| | - Maikel C. Rheinstädter
- Department of Physics and Astronomy, McMaster University, Hamilton, ON, Canada
- Origins Institute, McMaster University, Hamilton, ON, Canada
- * E-mail:
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9
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Mathiassen PPM, Pomorski TG. A Fluorescence-based Assay for Measuring Phospholipid Scramblase Activity in Giant Unilamellar Vesicles. Bio Protoc 2022; 12:e4366. [PMID: 35434199 PMCID: PMC8983165 DOI: 10.21769/bioprotoc.4366] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Revised: 11/09/2021] [Accepted: 03/01/2022] [Indexed: 07/28/2023] Open
Abstract
Transbilayer movement of phospholipids in biological membranes is mediated by a diverse set of lipid transporters. Among them are scramblases that facilitate rapid bi-directional movement of lipids without metabolic energy input. In this protocol, we describe the incorporation of phospholipid scramblases into giant unilamellar vesicles (GUVs) formed from scramblase-containing large unilamellar vesicles by electroformation. We also describe how to analyze their activity using membrane-impermeant sodium dithionite, to bleach symmetrically incorporated fluorescent ATTO488-conjugated phospholipids. The fluorescence-based readout allows single vesicle tracking for a large number of settled/immobilized GUVs, and provides a well-defined experimental setup to directly characterize these lipid transporters at the molecular level. Graphic abstract: Giant unilamellar vesicles (GUVs) are formed by electroformation from large unilamellar vesicles (LUVs) containing phospholipid scramblases (purple) and trace amounts of a fluorescent lipid reporter (green). The scramblase activity is analyzed by a fluorescence-based assay of single GUVs, using the membrane-impermeant quencher dithionite. Sizes not to scale. Modified from Mathiassen et al. (2021).
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Affiliation(s)
- Patricia P. M. Mathiassen
- Department of Molecular Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780, Bochum, Germany
| | - Thomas Günther Pomorski
- Department of Molecular Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780, Bochum, Germany
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg C, Denmark
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10
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Olivi L, Berger M, Creyghton RNP, De Franceschi N, Dekker C, Mulder BM, Claassens NJ, Ten Wolde PR, van der Oost J. Towards a synthetic cell cycle. Nat Commun 2021; 12:4531. [PMID: 34312383 PMCID: PMC8313558 DOI: 10.1038/s41467-021-24772-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 06/29/2021] [Indexed: 02/08/2023] Open
Abstract
Recent developments in synthetic biology may bring the bottom-up generation of a synthetic cell within reach. A key feature of a living synthetic cell is a functional cell cycle, in which DNA replication and segregation as well as cell growth and division are well integrated. Here, we describe different approaches to recreate these processes in a synthetic cell, based on natural systems and/or synthetic alternatives. Although some individual machineries have recently been established, their integration and control in a synthetic cell cycle remain to be addressed. In this Perspective, we discuss potential paths towards an integrated synthetic cell cycle.
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Affiliation(s)
- Lorenzo Olivi
- Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands
| | | | | | - Nicola De Franceschi
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Cees Dekker
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | | | - Nico J Claassens
- Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands
| | | | - John van der Oost
- Laboratory of Microbiology, Wageningen University, Wageningen, The Netherlands.
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11
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Endoplasmic reticulum phospholipid scramblase activity revealed after protein reconstitution into giant unilamellar vesicles containing a photostable lipid reporter. Sci Rep 2021; 11:14364. [PMID: 34257324 PMCID: PMC8277826 DOI: 10.1038/s41598-021-93664-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 06/28/2021] [Indexed: 02/04/2023] Open
Abstract
Transbilayer movement of phospholipids in biological membranes is mediated by a diverse set of lipid transporters. Among them are scramblases that facilitate a rapid bi-directional movement of lipids without metabolic energy input. Here, we established a new fluorescence microscopy-based assay for detecting phospholipid scramblase activity of membrane proteins upon their reconstitution into giant unilamellar vesicles formed from proteoliposomes by electroformation. The assay is based on chemical bleaching of fluorescence of a photostable ATTO-dye labeled phospholipid with the membrane-impermeant reductant sodium dithionite. We demonstrate that this new methodology is suitable for the study of the scramblase activity of the yeast endoplasmic reticulum at single vesicle level.
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12
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Staneva G, Watanabe C, Puff N, Yordanova V, Seigneuret M, Angelova MI. Amyloid-β Interactions with Lipid Rafts in Biomimetic Systems: A Review of Laboratory Methods. Methods Mol Biol 2021; 2187:47-86. [PMID: 32770501 DOI: 10.1007/978-1-0716-0814-2_4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Biomimetic lipid bilayer systems are a useful tool for modeling specific properties of cellular membranes in order to answer key questions about their structure and functions. This approach has prompted scientists from all over the world to create more and more sophisticated model systems in order to decipher the complex lateral and transverse organization of cellular plasma membranes. Among a variety of existing biomembrane domains, lipid rafts are defined as small, dynamic, and ordered assemblies of lipids and proteins, enriched in cholesterol and sphingolipids. Lipid rafts appear to be involved in the development of Alzheimer's disease (AD) by affecting the aggregation of the amyloid-β (Aβ) peptide at neuronal membranes thereby forming toxic oligomeric species. In this review, we summarize the laboratory methods which allow to study the interaction of Aβ with lipid rafts. We describe step by step protocols to form giant (GUVs) and large unilamellar vesicles (LUVs) containing raft-mimicking domains surrounded by membrane nonraft regions. Using fluorescence microscopy GUV imaging protocols, one can design experiments to visualize micron-scale raft-like domains, to determine the micron-scale demixing temperature of a given lipid mixture, construct phase diagram, and photogenerate domains in order to assess the dynamics of raft formation and raft size distribution. LUV fluorescence spectroscopy protocols with proper data analysis can be used to measure molecular packing of raft/nonraft regions of the membrane, to report on nanoscale raft formation and determine nanoscale demixing temperature. Because handling of the Aβ requires dedicated laboratory experience, we present illustrated protocols for Aβ-stock aliquoting, Aβ aqueous solubilization, oligomer preparation, determination of the Aβ concentration before and after filtration. Thioflavin binding, dynamic light scattering, and transmission electron microscopy protocols are described as complementary methods to detect Aβ aggregation kinetics, aggregate sizes, and morphologies of observed aggregates.
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Affiliation(s)
- Galya Staneva
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria.
| | - Chiho Watanabe
- Komaba Institute for Science, The University of Tokyo, Tokyo, Japan
| | - Nicolas Puff
- Faculty of Science and Engineering, UFR 925 Physics, Sorbonne Université, Paris, France
- Laboratoire Matière et Systèmes Complexes (MSC) UMR 7057 CNRS, Université Paris Diderot - Paris 7, Université de Paris, Paris, France
| | - Vesela Yordanova
- Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria
| | - Michel Seigneuret
- Laboratoire Matière et Systèmes Complexes (MSC) UMR 7057 CNRS, Université Paris Diderot - Paris 7, Université de Paris, Paris, France
| | - Miglena I Angelova
- Faculty of Science and Engineering, UFR 925 Physics, Sorbonne Université, Paris, France
- Laboratoire Matière et Systèmes Complexes (MSC) UMR 7057 CNRS, Université Paris Diderot - Paris 7, Université de Paris, Paris, France
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13
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Fusion Pore Formation Observed during SNARE-Mediated Vesicle Fusion with Pore-Spanning Membranes. Biophys J 2020; 119:151-161. [PMID: 32533941 DOI: 10.1016/j.bpj.2020.05.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 05/22/2020] [Accepted: 05/26/2020] [Indexed: 12/27/2022] Open
Abstract
Planar pore-spanning membranes (PSMs) have been shown to be a versatile tool to resolve elementary steps of the neuronal fusion process. However, in previous studies, we monitored only lipid mixing between fusing large unilamellar vesicles and PSMs and did not gather information about the formation of fusion pores. To address this important step of the fusion process, we entrapped sulforhodamine B at self-quenching concentrations into large unilamellar vesicles containing the v-SNARE synaptobrevin 2, which were docked and fused with lipid-labeled PSMs containing the t-SNARE acceptor complex ΔN49 prepared on gold-coated porous silicon substrates. By dual-color spinning disk fluorescence microscopy with a time resolution of ∼20 ms, we could unambiguously distinguish between bursting vesicles, which was only rarely observed (<0.01%), and fusion pore formation. From the time-resolved dual-color fluorescence time traces, we were able to identify different fusion pathways, including remaining three-dimensional postfusion structures with released content and transient openings and closings of the fusion pores. Our results on fusion pore formation and lipid diffusion from the PSM into the fusing vesicle let us conclude that the content release, i.e., fusion pore formation after the merger of the two lipid membranes occurs almost simultaneously.
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14
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Physicochemical considerations for bottom-up synthetic biology. Emerg Top Life Sci 2019; 3:445-458. [PMID: 33523159 PMCID: PMC7289010 DOI: 10.1042/etls20190017] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 08/05/2019] [Accepted: 08/07/2019] [Indexed: 12/18/2022]
Abstract
The bottom-up construction of synthetic cells from molecular components is arguably one of the most challenging areas of research in the life sciences. We review the impact of confining biological systems in synthetic vesicles. Complex cell-like systems require control of the internal pH, ionic strength, (macro)molecular crowding, redox state and metabolic energy conservation. These physicochemical parameters influence protein activity and need to be maintained within limits to ensure the system remains in steady-state. We present the physicochemical considerations for building synthetic cells with dimensions ranging from the smallest prokaryotes to eukaryotic cells.
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15
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Velasco-Olmo A, Ormaetxea Gisasola J, Martinez Galvez JM, Vera Lillo J, Shnyrova AV. Combining patch-clamping and fluorescence microscopy for quantitative reconstitution of cellular membrane processes with Giant Suspended Bilayers. Sci Rep 2019; 9:7255. [PMID: 31076583 PMCID: PMC6510758 DOI: 10.1038/s41598-019-43561-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 04/26/2019] [Indexed: 01/24/2023] Open
Abstract
In vitro reconstitution and microscopic visualization of membrane processes is an indispensable source of information about a cellular function. Here we describe a conceptionally novel free-standing membrane template that facilitates such quantitative reconstitution of membrane remodelling at different scales. The Giant Suspended Bilayers (GSBs) spontaneously swell from lipid lamella reservoir deposited on microspheres. GSBs attached to the reservoir can be prepared from virtually any lipid composition following a fast procedure. Giant unilamellar vesicles can be further obtained by GSB detachment from the microspheres. The reservoir stabilizes GSB during deformations, mechanical micromanipulations, and fluorescence microscopy observations, while GSB-reservoir boundary enables the exchange of small solutes with GSB interior. These unique properties allow studying macro- and nano-scale membrane deformations, adding membrane-active compounds to both sides of GSB membrane and applying patch-clamp based approaches, thus making GSB a versatile tool for reconstitution and quantification of cellular membrane trafficking events.
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Affiliation(s)
- Ariana Velasco-Olmo
- Biofisika Institute (UPV/EHU, CSIC) and Department of Biochemistry and Molecular Biology, University of the Basque Country, Bilbao, Spain
| | - Julene Ormaetxea Gisasola
- Biofisika Institute (UPV/EHU, CSIC) and Department of Biochemistry and Molecular Biology, University of the Basque Country, Bilbao, Spain
| | - Juan Manuel Martinez Galvez
- Biofisika Institute (UPV/EHU, CSIC) and Department of Biochemistry and Molecular Biology, University of the Basque Country, Bilbao, Spain
| | - Javier Vera Lillo
- Biofisika Institute (UPV/EHU, CSIC) and Department of Biochemistry and Molecular Biology, University of the Basque Country, Bilbao, Spain
| | - Anna V Shnyrova
- Biofisika Institute (UPV/EHU, CSIC) and Department of Biochemistry and Molecular Biology, University of the Basque Country, Bilbao, Spain.
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16
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Pick H, Alves AC, Vogel H. Single-Vesicle Assays Using Liposomes and Cell-Derived Vesicles: From Modeling Complex Membrane Processes to Synthetic Biology and Biomedical Applications. Chem Rev 2018; 118:8598-8654. [PMID: 30153012 DOI: 10.1021/acs.chemrev.7b00777] [Citation(s) in RCA: 99] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The plasma membrane is of central importance for defining the closed volume of cells in contradistinction to the extracellular environment. The plasma membrane not only serves as a boundary, but it also mediates the exchange of physical and chemical information between the cell and its environment in order to maintain intra- and intercellular functions. Artificial lipid- and cell-derived membrane vesicles have been used as closed-volume containers, representing the simplest cell model systems to study transmembrane processes and intracellular biochemistry. Classical examples are studies of membrane translocation processes in plasma membrane vesicles and proteoliposomes mediated by transport proteins and ion channels. Liposomes and native membrane vesicles are widely used as model membranes for investigating the binding and bilayer insertion of proteins, the structure and function of membrane proteins, the intramembrane composition and distribution of lipids and proteins, and the intermembrane interactions during exo- and endocytosis. In addition, natural cell-released microvesicles have gained importance for early detection of diseases and for their use as nanoreactors and minimal protocells. Yet, in most studies, ensembles of vesicles have been employed. More recently, new micro- and nanotechnological tools as well as novel developments in both optical and electron microscopy have allowed the isolation and investigation of individual (sub)micrometer-sized vesicles. Such single-vesicle experiments have revealed large heterogeneities in the structure and function of membrane components of single vesicles, which were hidden in ensemble studies. These results have opened enormous possibilities for bioanalysis and biotechnological applications involving unprecedented miniaturization at the nanometer and attoliter range. This review will cover important developments toward single-vesicle analysis and the central discoveries made in this exciting field of research.
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Affiliation(s)
- Horst Pick
- Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Ana Catarina Alves
- Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
| | - Horst Vogel
- Institute of Chemical Sciences and Engineering , Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne , Switzerland
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17
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Ali Doosti B, Cans AS, Jeffries GDM, Lobovkina T. Membrane Remodeling of Giant Vesicles in Response to Localized Calcium Ion Gradients. J Vis Exp 2018. [PMID: 30059020 PMCID: PMC6126466 DOI: 10.3791/57789] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
In a wide variety of fundamental cell processes, such as membrane trafficking and apoptosis, cell membrane shape transitions occur concurrently with local variations in calcium ion concentration. The main molecular components involved in these processes have been identified; however, the specific interplay between calcium ion gradients and the lipids within the cell membrane is far less known, mainly due to the complex nature of biological cells and the difficultly of observation schemes. To bridge this gap, a synthetic approach is successfully implemented to reveal the localized effect of calcium ions on cell membrane mimics. Establishing a mimic to resemble the conditions within a cell is a severalfold problem. First, an adequate biomimetic model with appropriate dimensions and membrane composition is required to capture the physical properties of cells. Second, a micromanipulation setup is needed to deliver a small amount of calcium ions to a particular membrane location. Finally, an observation scheme is required to detect and record the response of the lipid membrane to the external stimulation. This article offers a detailed biomimetic approach for studying the calcium ion-membrane interaction, where a lipid vesicle system, consisting of a giant unilamellar vesicle (GUV) connected to a multilamellar vesicle (MLV), is exposed to a localized calcium gradient formed using a microinjection system. The dynamics of the ionic influence on the membrane were observed using fluorescence microscopy and recorded at video frame rates. As a result of the membrane stimulation, highly curved membrane tubular protrusions (MTPs) formed inside the GUV, oriented away from the membrane. The described approach induces the remodeling of the lipid membrane and MTP production in an entirely contactless and controlled manner. This approach introduces a means to address the details of calcium ion-membrane interactions, providing new avenues to study the mechanisms of cell membrane reshaping.
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Affiliation(s)
- Baharan Ali Doosti
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology
| | - Ann-Sofie Cans
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology
| | - Gavin D M Jeffries
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology
| | - Tatsiana Lobovkina
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology;
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18
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A convenient protocol for generating giant unilamellar vesicles containing SNARE proteins using electroformation. Sci Rep 2018; 8:9422. [PMID: 29930377 PMCID: PMC6013450 DOI: 10.1038/s41598-018-27456-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 05/29/2018] [Indexed: 01/05/2023] Open
Abstract
Reconstitution of membrane proteins in artificial membranes is an essential prerequisite for functional studies that depend on the context of an intact membrane. While straight-forward protocols for reconstituting proteins in small unilamellar vesicles were developed many years ago, it is much more difficult to prepare large membranes containing membrane proteins at biologically relevant concentrations. Giant unilamellar vesicles (GUVs) represent a model system that is characterised by low curvature, controllable tension, and large surface that can be easily visualised with microscopy, but protein insertion is notoriously difficult. Here we describe a convenient method for efficient generation of GUVs containing functionally active SNARE proteins that govern exocytosis of synaptic vesicles. Preparation of proteo-GUVs requires a simple, in-house-built device, standard and inexpensive electronic equipment, and employs a straight-forward protocol that largely avoids damage of the proteins. The procedure allows upscaling and multiplexing, thus providing a platform for establishing and optimizing preparation of GUVs containing membrane proteins for a diverse array of applications.
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19
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Abstract
Patch-clamp electrophysiology is the standard technique used for the high-resolution functional measurements on ion channels. While studies using patch clamp are commonly carried out following ion channel expression in a heterologous system such as Xenopus oocytes or tissue culture cells, these studies can also be carried out using ion channels reconstituted into lipid vesicles. In this chapter, we describe the methodology for reconstituting ion channels into liposomes and the procedure for the generation of unilamellar blisters from these liposomes that are suitable for patch clamp. Here, we focus on the bacterial K+ channel KcsA, although the methodologies described in this chapter should be applicable for the functional analysis of other ion channels.
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Affiliation(s)
- Kimberly Matulef
- Program in Chemical Biology, Department of Physiology and Pharmacology, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Mail Code L334, Portland, OR, 97239, USA
| | - Francis I Valiyaveetil
- Department of Physiology and Pharmacology, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Mail Code L334, Portland, OR, 97239, USA.
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20
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Prévost C, Tsai FC, Bassereau P, Simunovic M. Pulling Membrane Nanotubes from Giant Unilamellar Vesicles. J Vis Exp 2017. [PMID: 29286431 DOI: 10.3791/56086] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The reshaping of the cell membrane is an integral part of many cellular phenomena, such as endocytosis, trafficking, the formation of filopodia, etc. Many different proteins associate with curved membranes because of their ability to sense or induce membrane curvature. Typically, these processes involve a multitude of proteins making them too complex to study quantitatively in the cell. We describe a protocol to reconstitute a curved membrane in vitro, mimicking a curved cellular structure, such as the endocytic neck. A giant unilamellar vesicle (GUV) is used as a model of a cell membrane, whose internal pressure and surface tension are controlled with micropipette aspiration. Applying a point pulling force on the GUV using optical tweezers creates a nanotube of high curvature connected to a flat membrane. This method has traditionally been used to measure the fundamental mechanical properties of lipid membranes, such as bending rigidity. In recent years, it has been expanded to study how proteins interact with membrane curvature and the way they affect the shape and the mechanics of membranes. A system combining micromanipulation, microinjection, optical tweezers, and confocal microscopy allows measurement of membrane curvature, membrane tension, and the surface density of proteins, concurrently. From these measurements, many important mechanical and morphological properties of the protein-membrane system can be inferred. In addition, we lay out a protocol of creating GUVs in the presence of physiological salt concentration, and a method of quantifying the surface density of proteins on the membrane from fluorescence intensities of labeled proteins and lipids.
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Affiliation(s)
- Coline Prévost
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168; Department of Genetics and Complex Diseases, T. H. Chan School of Public Health, Harvard Medical School; Department of Cell Biology, Harvard Medical School
| | - Feng-Ching Tsai
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168; Sorbonne Universités, UPMC University Paris 06
| | - Patricia Bassereau
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168; Sorbonne Universités, UPMC University Paris 06;
| | - Mijo Simunovic
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168; Center for Studies in Physics and Biology, The Rockefeller University
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21
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Stein H, Spindler S, Bonakdar N, Wang C, Sandoghdar V. Production of Isolated Giant Unilamellar Vesicles under High Salt Concentrations. Front Physiol 2017; 8:63. [PMID: 28243205 PMCID: PMC5303729 DOI: 10.3389/fphys.2017.00063] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/23/2017] [Indexed: 12/22/2022] Open
Abstract
The cell membrane forms a dynamic and complex barrier between the living cell and its environment. However, its in vivo studies are difficult because it consists of a high variety of lipids and proteins and is continuously reorganized by the cell. Therefore, membrane model systems with precisely controlled composition are used to investigate fundamental interactions of membrane components under well-defined conditions. Giant unilamellar vesicles (GUVs) offer a powerful model system for the cell membrane, but many previous studies have been performed in unphysiologically low ionic strength solutions which might lead to altered membrane properties, protein stability and lipid-protein interaction. In the present work, we give an overview of the existing methods for GUV production and present our efforts on forming single, free floating vesicles up to several tens of μm in diameter and at high yield in various buffer solutions with physiological ionic strength and pH.
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Affiliation(s)
- Hannah Stein
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Susann Spindler
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Navid Bonakdar
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Chun Wang
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Vahid Sandoghdar
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
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22
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Stein H, Spindler S, Bonakdar N, Wang C, Sandoghdar V. Production of Isolated Giant Unilamellar Vesicles under High Salt Concentrations. Front Physiol 2017; 8:63. [PMID: 28243205 DOI: 10.3389/fphys.2017.00063/full] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/23/2017] [Indexed: 05/27/2023] Open
Abstract
The cell membrane forms a dynamic and complex barrier between the living cell and its environment. However, its in vivo studies are difficult because it consists of a high variety of lipids and proteins and is continuously reorganized by the cell. Therefore, membrane model systems with precisely controlled composition are used to investigate fundamental interactions of membrane components under well-defined conditions. Giant unilamellar vesicles (GUVs) offer a powerful model system for the cell membrane, but many previous studies have been performed in unphysiologically low ionic strength solutions which might lead to altered membrane properties, protein stability and lipid-protein interaction. In the present work, we give an overview of the existing methods for GUV production and present our efforts on forming single, free floating vesicles up to several tens of μm in diameter and at high yield in various buffer solutions with physiological ionic strength and pH.
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Affiliation(s)
- Hannah Stein
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Susann Spindler
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
| | - Navid Bonakdar
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Chun Wang
- Max Planck Institute for the Science of Light Erlangen, Germany
| | - Vahid Sandoghdar
- Friedrich-Alexander University Erlangen-NurembergErlangen, Germany; Max Planck Institute for the Science of LightErlangen, Germany
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23
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Abstract
Studying how the membrane modulates ion channel and transporter activity is challenging because cells actively regulate membrane properties, whereas existing in vitro systems have limitations, such as residual solvent and unphysiologically high membrane tension. Cell-sized giant unilamellar vesicles (GUVs) would be ideal for in vitro electrophysiology, but efforts to measure the membrane current of intact GUVs have been unsuccessful. In this work, two challenges for obtaining the "whole-GUV" patch-clamp configuration were identified and resolved. First, unless the patch pipette and GUV pressures are precisely matched in the GUV-attached configuration, breaking the patch membrane also ruptures the GUV. Second, GUVs shrink irreversibly because the membrane/glass adhesion creating the high-resistance seal (>1 GΩ) continuously pulls membrane into the pipette. In contrast, for cell-derived giant plasma membrane vesicles (GPMVs), breaking the patch membrane allows the GPMV contents to passivate the pipette surface, thereby dynamically blocking membrane spreading in the whole-GMPV mode. To mimic this dynamic passivation mechanism, beta-casein was encapsulated into GUVs, yielding a stable, high-resistance, whole-GUV configuration for a range of membrane compositions. Specific membrane capacitance measurements confirmed that the membranes were truly solvent-free and that membrane tension could be controlled over a physiological range. Finally, the potential for ion transport studies was tested using the model ion channel, gramicidin, and voltage-clamp fluorometry measurements were performed with a voltage-dependent fluorophore/quencher pair. Whole-GUV patch-clamping allows ion transport and other voltage-dependent processes to be studied while controlling membrane composition, tension, and shape.
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24
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Berthaud A, Quemeneur F, Deforet M, Bassereau P, Brochard-Wyart F, Mangenot S. Spreading of porous vesicles subjected to osmotic shocks: the role of aquaporins. SOFT MATTER 2016; 12:1601-1609. [PMID: 26662491 DOI: 10.1039/c5sm01654a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Aquaporin 0 (AQP0) is a transmembrane protein specific to the eye lens, involved as a water carrier across the lipid membranes. During eye lens maturation, AQP0s are truncated by proteolytic cleavage. We investigate in this work the capability of truncated AQP0 to conduct water across membranes. We developed a method to accurately determine water permeability across lipid membranes and across proteins from the deflation under osmotic pressure of giant unilamellar vesicles (GUVs) deposited on an adhesive substrate. Using reflection interference contrast microscopy (RICM), we measure the spreading area of GUVs during deswelling. We interpret these results using a model based on hydrodynamic, binder diffusion towards the contact zone, and Helfrich's law for the membrane tension, which allows us to relate the spread area to the vesicle internal volume. We first study the specific adhesion of vesicles coated with biotin spreading on a streptavidin substrate. We then determine the permeability of a single functional AQP0 and demonstrate that truncated AQP0 is no more a water channel.
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Affiliation(s)
- Alice Berthaud
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, 75005, Paris, France.
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25
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Lagny TJ, Bassereau P. Bioinspired membrane-based systems for a physical approach of cell organization and dynamics: usefulness and limitations. Interface Focus 2015; 5:20150038. [PMID: 26464792 PMCID: PMC4590427 DOI: 10.1098/rsfs.2015.0038] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Being at the periphery of each cell compartment and enclosing the entire cell while interacting with a large part of cell components, cell membranes participate in most of the cell's vital functions. Biologists have worked for a long time on deciphering how membranes are organized, how they contribute to trafficking, motility, cytokinesis, cell-cell communication, information transport, etc., using top-down approaches and always more advanced techniques. In contrast, physicists have developed bottom-up approaches and minimal model membrane systems of growing complexity in order to build up general models that explain how cell membranes work and how they interact with proteins, e.g. the cytoskeleton. We review the different model membrane systems that are currently available, and how they can help deciphering cell functioning, but also list their limitations. Model membrane systems are also used in synthetic biology and can have potential applications beyond basic research. We discuss the possible synergy between the development of complex in vitro membrane systems in a biological context and for technological applications. Questions that could also be discussed are: what can we still do with synthetic systems, where do we stop building up and which are the alternative solutions?
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Affiliation(s)
- Thibaut J Lagny
- Institut Curie, PSL Research University , Laboratory PhysicoChimie Curie , 75248 Paris, Cedex 05 , France ; CNRS , UMR168, 75248 Paris, Cedex 05 , France ; Université Pierre et Marie Curie , 75252 Paris, Cedex 05 , France
| | - Patricia Bassereau
- Institut Curie, PSL Research University , Laboratory PhysicoChimie Curie , 75248 Paris, Cedex 05 , France ; CNRS , UMR168, 75248 Paris, Cedex 05 , France ; Université Pierre et Marie Curie , 75252 Paris, Cedex 05 , France
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