1
|
Goodchild J, Walsh DL, Laurent H, Connell SD. PDMS as a Substrate for Lipid Bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:10843-10854. [PMID: 37494418 PMCID: PMC10413950 DOI: 10.1021/acs.langmuir.3c00944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2023] [Revised: 06/13/2023] [Indexed: 07/28/2023]
Abstract
PDMS (polydimethylsiloxane) is a cheap, optically clear polymer that is elastic and can be easily and quickly fabricated into a wide array of microscale and nanoscale architectures, making it a versatile substrate for biophysical experiments on cell membranes. It is easy to imagine many new experiments will be devised that require a bilayer to be placed upon a substrate that is flexible or easily cast into a desired geometry, such as in lab-on-a-chip, organ-on-chip, and microfluidic applications, or for building accurate membrane models that replicate the surface structure and elasticity of the cytoskeleton. However, PDMS has its limitations, and the extent to which the behavior of membranes is affected on PDMS has not been fully explored. We use AFM and fluorescence optical microscopy to investigate the use of PDMS as a substrate for the formation and study of supported lipid bilayers (SLBs). Lipid bilayers form on plasma-treated PDMS and show free diffusion and normal phase transitions, confirming its suitability as a model bilayer substrate. However, lipid-phase separation on PDMS is severely restricted due to the pinning of domains to surface roughness, resulting in the cessation of lateral hydrodynamic flow. We show the high-resolution porous structure of PDMS and the extreme smoothing effect of oxygen plasma treatment used to hydrophilize the surface, but this is not flat enough to allow domain formation. We also observe bilayer degradation over hour timescales, which correlates with the known hydrophobic recovery of PDMS, and establish a critical water contact angle of 30°, above which bilayers degrade or not form at all. Care must be taken as incomplete surface oxidation and hydrophobic recovery result in optically invisible membrane disruption, which will also be transparent to fluorescence microscopy and lipid diffusion measurements in the early stages.
Collapse
Affiliation(s)
- James
A. Goodchild
- Molecular
and Nanoscale Physics Group, School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Danielle L. Walsh
- Molecular
and Nanoscale Physics Group, School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Harrison Laurent
- Molecular
and Nanoscale Physics Group, School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Simon D. Connell
- Molecular
and Nanoscale Physics Group, School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom
- Bragg
Centre for Materials Research, William Henry Bragg Building, University of Leeds, Leeds LS2 9JT, United Kingdom
| |
Collapse
|
2
|
Wang HY, Chan SH, Dey S, Castello-Serrano I, Rosen MK, Ditlev JA, Levental KR, Levental I. Coupling of protein condensates to ordered lipid domains determines functional membrane organization. SCIENCE ADVANCES 2023; 9:eadf6205. [PMID: 37126554 PMCID: PMC10132753 DOI: 10.1126/sciadv.adf6205] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
During T cell activation, the transmembrane adaptor protein LAT (linker for activation of T cells) forms biomolecular condensates with Grb2 and Sos1, facilitating signaling. LAT has also been associated with cholesterol-rich condensed lipid domains; However, the potential coupling between protein condensation and lipid phase separation and its role in organizing T cell signaling were unknown. Here, we report that LAT/Grb2/Sos1 condensates reconstituted on model membranes can induce and template lipid domains, indicating strong coupling between lipid- and protein-based phase separation. Correspondingly, activation of T cells induces cytoplasmic protein condensates that associate with and stabilize raft-like membrane domains. Inversely, lipid domains nucleate and stabilize LAT protein condensates in both reconstituted and living systems. This coupling of lipid and protein assembly is functionally important, as uncoupling of lipid domains from cytoplasmic protein condensates abrogates T cell activation. Thus, thermodynamic coupling between protein condensates and ordered lipid domains regulates the functional organization of living membranes.
Collapse
Affiliation(s)
- Hong-Yin Wang
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22903, USA
| | - Sze Ham Chan
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22903, USA
| | - Simli Dey
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22903, USA
| | - Ivan Castello-Serrano
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22903, USA
| | - Michael K Rosen
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jonathon A Ditlev
- Department of Biophysics and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Program in Molecular Medicine, Program in Cell Biology, Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Kandice R Levental
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22903, USA
| | - Ilya Levental
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22903, USA
| |
Collapse
|
3
|
Pro-inflammatory protein S100A9 alters membrane organization by dispersing ordered domains. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184113. [PMID: 36567033 DOI: 10.1016/j.bbamem.2022.184113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 12/06/2022] [Accepted: 12/16/2022] [Indexed: 12/24/2022]
Abstract
Pro-inflammatory, calcium-binding protein S100A9 is localized in the cytoplasm of many cells and regulates several intracellular and extracellular processes. S100A9 is involved in neuroinflammation associated with the pathogenesis of Alzheimer's disease (AD). The number of studies on the impact of S100A9 in co-aggregation processes with amyloid-like proteins is increasing. However, there is still a lack of data on how this protein interacts with lipid membranes. We employed atomic force microscopy (AFM), dynamic light scattering (DLS), and fluorescence measurements (Laurdan and Thioflavin-T) to study the interaction between protein and the membrane surface. We used lipid vesicles in bulk and planar tethered lipid bilayers as biomimetic membrane models. We demonstrated that the protein accumulates on negatively charged lipid bilayers but with no further loss of the bilayer's integrity. The most important result is that the initial adsorption and accumulation of apo-form of S100A9 on the lipid membrane surface is lipid phase-sensitive. The breaking down of raft-like and disappearance of gel-like domains indicate that protein incorporates into the hydrophobic part of the lipid bilayer. We observed the most noticeable loss of integrity in lipid bilayers constructed from a lipid mixture (brain total lipid extract). Understanding the function and interactions of these proteins in cellular environments might expand the development of new diagnostic and therapeutic approaches for AD or other related diseases.
Collapse
|
4
|
Khmelinskaia A, Schwille P, Franquelim HG. Binding and Characterization of DNA Origami Nanostructures on Lipid Membranes. Methods Mol Biol 2023; 2639:231-255. [PMID: 37166721 DOI: 10.1007/978-1-0716-3028-0_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
DNA origami is an extremely versatile nanoengineering tool with widespread applicability in various fields of research, including membrane physiology and biophysics. The possibility to easily modify DNA strands with lipophilic moieties enabled the recent development of a variety of membrane-active DNA origami devices. Biological membranes, as the core barriers of the cells, display vital structural and functional roles. Therefore, lipid bilayers are widely popular targets of DNA origami nanotechnology for synthetic biology and biomedical applications. In this chapter, we summarize the typical experimental methods used to investigate the interaction of DNA origami with synthetic membrane models. Herein, we present detailed protocols for the production of lipid model membranes and characterization of membrane-targeted DNA origami nanostructures using different microscopy approaches.
Collapse
Affiliation(s)
- Alena Khmelinskaia
- Max Planck Institute of Biochemistry, Munich, Germany
- Institute of Protein Design, University of Washington, Seattle, WA, USA
- Life & Medical Sciences Institute (LIMES), University of Bonn, Bonn, Germany
| | | | - Henri G Franquelim
- Max Planck Institute of Biochemistry, Munich, Germany.
- Interfaculty Centre for Bioactive Matter (b-ACTmatter), Leipzig University, Leipzig, Germany.
| |
Collapse
|
5
|
Nast-Kolb T, Bleicher P, Payr M, Bausch AR. VASP localization to lipid bilayers induces polymerization driven actin bundle formation. Mol Biol Cell 2022; 33:ar91. [PMID: 35830600 PMCID: PMC9582628 DOI: 10.1091/mbc.e21-11-0577] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Actin bundles constitute important cytoskeleton structures and enable a scaffold for force transmission inside cells. Actin bundles are formed by proteins, with multiple F-actin binding domains cross-linking actin filaments to each other. Vasodilator-stimulated phosphoprotein (VASP) has mostly been reported as an actin elongator, but it has been shown to be a bundling protein as well and is found in bundled actin structures at filopodia and adhesion sites. Based on in vitro experiments, it remains unclear when and how VASP can act as an actin bundler or elongator. Here we demonstrate that VASP bound to membranes facilitates the formation of large actin bundles during polymerization. The alignment by polymerization requires the fluidity of the lipid bilayers. The mobility within the bilayer enables VASP to bind to filaments and capture and track growing barbed ends. VASP itself phase separates into a protein-enriched phase on the bilayer. This VASP-rich phase nucleates and accumulates at bundles during polymerization, which in turn leads to a reorganization of the underlying lipid bilayer. Our findings demonstrate that the nature of VASP localization is decisive for its function. The up-concentration based on VASP’s affinity to actin during polymerization enables it to simultaneously fulfill the function of an elongator and a bundler.
Collapse
Affiliation(s)
- T Nast-Kolb
- Lehrstuhl für Biophysik E27, Physik-Department, Technische Universität München, Garching, Germany and
| | - P Bleicher
- Lehrstuhl für Biophysik E27, Physik-Department, Technische Universität München, Garching, Germany and.,Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892
| | - M Payr
- Lehrstuhl für Biophysik E27, Physik-Department, Technische Universität München, Garching, Germany and.,Structural and Computational Biology Unit, EMBL Heidelberg, Meyerhoferstr. 1, 69117 Heidelberg, Germany
| | - A R Bausch
- Center for Protein Assemblies (CPA), Ernst-Otto-Fischer Str. 8, 85747 Garching, Germany
| |
Collapse
|
6
|
Sych T, Gurdap CO, Wedemann L, Sezgin E. How Does Liquid-Liquid Phase Separation in Model Membranes Reflect Cell Membrane Heterogeneity? MEMBRANES 2021; 11:323. [PMID: 33925240 PMCID: PMC8146956 DOI: 10.3390/membranes11050323] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 04/22/2021] [Accepted: 04/26/2021] [Indexed: 11/22/2022]
Abstract
Although liquid-liquid phase separation of cytoplasmic or nuclear components in cells has been a major focus in cell biology, it is only recently that the principle of phase separation has been a long-standing concept and extensively studied in biomembranes. Membrane phase separation has been reconstituted in simplified model systems, and its detailed physicochemical principles, including essential phase diagrams, have been extensively explored. These model membrane systems have proven very useful to study the heterogeneity in cellular membranes, however, concerns have been raised about how reliably they can represent native membranes. In this review, we will discuss how phase-separated membrane systems can mimic cellular membranes and where they fail to reflect the native cell membrane heterogeneity. We also include a few humble suggestions on which phase-separated systems should be used for certain applications, and which interpretations should be avoided to prevent unreliable conclusions.
Collapse
Affiliation(s)
| | | | | | - Erdinc Sezgin
- Science for Life Laboratory, Department of Women’s and Children’s Health, Karolinska Institutet, 17165 Solna, Sweden; (T.S.); (C.O.G.); (L.W.)
| |
Collapse
|
7
|
Kataoka-Hamai C, Kawakami K. Domain Sorting in Giant Unilamellar Vesicles Adsorbed on Glass. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:1082-1088. [PMID: 33440115 DOI: 10.1021/acs.langmuir.0c02843] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Giant unilamellar vesicles (GUVs) adsorb to a solid surface and rupture to form a planar bilayer patch. These bilayer patches are used to investigate the properties and functions of biological membranes. Therefore, it is crucial to understand the mechanisms of GUV adsorption. In this study, we investigate the adsorption of phase-separated GUVs on glass using fluorescence microscopy. GUVs containing liquid-ordered (Lo) and liquid-disordered (Ld) phases underwent domain sorting after adsorption. The Ld domain in the unbound region migrated to the highly curved region near the edge of the adsorbed region. Additionally, the Lo phase grew linearly along the edge of the adsorbed region, creating a thin ring-like domain. After the domain sorting event, the GUV ruptured to form a planar bilayer patch with circular-patterned domains in the initially adsorbed area. We found that domain sorting was promoted by increasing the extent of GUV deformation. These results suggest that both the Ld and Lo domains are reorganized for stabilizing the curved bilayer region in adsorbed GUVs.
Collapse
Affiliation(s)
- Chiho Kataoka-Hamai
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| | - Kohsaku Kawakami
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
| |
Collapse
|
8
|
Patel P, Santo KP, Burgess S, Vishnyakov A, Neimark AV. Stability of Lipid Coatings on Nanoparticle-Decorated Surfaces. ACS NANO 2020; 14:17273-17284. [PMID: 33226210 DOI: 10.1021/acsnano.0c07298] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Lipid membranes supported on solid surfaces and nanoparticles find multiple applications in industrial and biomedical technologies. Here, we explore in silico the mechanisms of the interactions of lipid membranes with nanostructured surfaces with deposited nanoparticles and explain the characteristic particle size dependence of the uniformity and stability of lipid coatings observed in vitro. Simulations are performed to demonstrate the specifics of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid membrane adhesion to hydrophilic and hydrophobic nanoparticles ranging in size from 1.5 to 40 nm using an original coarse-grained molecular dynamics model with implicit solvent and large simulation boxes (scales up to 280 × 154 × 69 nm3). We find that one of the major factors that affects the uniformity and stability of lipid coatings is the disjoining pressure in the water hydration layer formed between the lipid membrane and hydrophilic solid surface. This effect is accounted for by introducing a special long-range lipid-solid interaction potential that mimics the effects of the disjoining pressure in thin water layers. Our simulations reveal the physical mechanisms of interactions of lipid bilayers with solid surfaces that are responsible for the experimentally observed nonmonotonic particle size dependence of the uniformity and stability of lipid coatings: particles smaller than the hydration layer thickness (<2-3 nm) or larger than ∼20 nm are partially or fully enfolded by a lipid bilayer, whereas particles of the intermediate size (5-20 nm) cause membrane perforation and pore formation. In contrast, hydrophobic nanoparticles, which repel the hydration layer, tend to be encapsulated within the hydrophobic interior of the membrane and coated by the lipid monolayer. The proposed model can be further extended and applied to a wide class of systems comprising nanoparticles and nanostructured substrates interacting with lipid and surfactant bilayers and monolayers.
Collapse
Affiliation(s)
- Parva Patel
- Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Kolattukudy P Santo
- Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Sean Burgess
- Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Aleksey Vishnyakov
- Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
- Skolkovo Institute of Technology, Moscow 143005, Russia
| | - Alexander V Neimark
- Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| |
Collapse
|
9
|
Abstract
Transmembrane proteins involved in metabolic redox reactions and photosynthesis catalyse a plethora of key energy-conversion processes and are thus of great interest for bioelectrocatalysis-based applications. The development of membrane protein modified electrodes has made it possible to efficiently exchange electrons between proteins and electrodes, allowing mechanistic studies and potentially applications in biofuels generation and energy conversion. Here, we summarise the most common electrode modification and their characterisation techniques for membrane proteins involved in biofuels conversion and semi-artificial photosynthesis. We discuss the challenges of applications of membrane protein modified electrodes for bioelectrocatalysis and comment on emerging methods and future directions, including recent advances in membrane protein reconstitution strategies and the development of microbial electrosynthesis and whole-cell semi-artificial photosynthesis.
Collapse
|
10
|
Duman AN. Grain analysis of atomic force microscopy images via persistent homology. Ultramicroscopy 2020; 220:113176. [PMID: 33249346 DOI: 10.1016/j.ultramic.2020.113176] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 10/26/2020] [Accepted: 11/13/2020] [Indexed: 11/27/2022]
Abstract
Atomic force microscopy (AFM) is an established technique in nanoscale grain analysis due to its accuracy in producing 3-dimensional images. Even though height threshold and watershed algorithms are commonly used to determine the grain size and number of grains, they mostly require image processing that result in the change of topographical features of the surface that generates misleading conclusions. In this study, we use persistent homology, a method of representing topological features, to obtain more accurate information about the granular surfaces from unprocessed AFM images than the conventional methods. The method is also useful as a robust alternative to common parameters describing the topography of the AFM images. Most of these parameters such as arithmetic roughness and root-mean-squared roughness are represented by a single number which results in uncertainty in characterization of different surfaces. Persistent homology provides more precise summary about surface properties than a single parameter.
Collapse
Affiliation(s)
- Ali Nabi Duman
- Department of Mathematics and Statistics, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia.
| |
Collapse
|
11
|
Miller EJ, Ratajczak AM, Anthony AA, Mottau M, Rivera Gonzalez XI, Honerkamp-Smith AR. Divide and conquer: How phase separation contributes to lateral transport and organization of membrane proteins and lipids. Chem Phys Lipids 2020; 233:104985. [DOI: 10.1016/j.chemphyslip.2020.104985] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 09/18/2020] [Accepted: 09/28/2020] [Indexed: 01/06/2023]
|
12
|
Woodward X, Kelly CV. Single-lipid dynamics in phase-separated supported lipid bilayers. Chem Phys Lipids 2020; 233:104991. [PMID: 33121937 DOI: 10.1016/j.chemphyslip.2020.104991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 10/02/2020] [Accepted: 10/06/2020] [Indexed: 11/26/2022]
Abstract
Phase separation is a fundamental organizing mechanism on cellular membranes. Lipid phases have complex dependencies on the membrane composition, curvature, tension, and temperature. Lipid diffusion rates vary by up to ten-fold between liquid-disordered (Ld) and liquid-ordered (Lo) phases depending on the membrane composition, measurement technique, and the surrounding environment. This manuscript reports the lipid diffusion on phase-separated supported lipid bilayers (SLBs) with varying temperature, composition, and lipid phase. Lipid diffusion is measured by single-particle tracking (SPT) and fluorescence correlation spectroscopy (FCS) via custom data acquisition and analysis protocols that apply to diverse membranes systems. Traditionally, SPT is sensitive to diffuser aggregation, whereas the diffusion rates reported by FCS are unaffected by the presence of immobile aggregates. Within this manuscript, we report (1) improved single-particle tracking analysis of lipid diffusion, (2) comparison and consistency between diffusion measurement methods for non-Brownian diffusers, and (3) the application of these methods to measure the phase, temperature, and composition dependencies in lipid diffusion. We demonstrate improved SPT analysis methods that yield consistent FCS and SPT diffusion results even when most fluorescent lipids are frequently confined within aggregates within the membrane. With varying membrane composition and temperature, we demonstrate differences in diffusion between the Ld and Lo phases of SLBs.
Collapse
Affiliation(s)
- Xinxin Woodward
- Department of Physics and Astronomy, Wayne State University, Detroit, MI, United States
| | - Christopher V Kelly
- Department of Physics and Astronomy, Wayne State University, Detroit, MI, United States.
| |
Collapse
|
13
|
Benedetti F, Fu L, Thalmann F, Charitat T, Rubin A, Loison C. Coarse-Grain Simulations of Solid Supported Lipid Bilayers with Varying Hydration Levels. J Phys Chem B 2020; 124:8287-8298. [DOI: 10.1021/acs.jpcb.0c03913] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Florian Benedetti
- Institut Lumière Matière, University of Lyon, Université Claude Bernard Lyon 1, CNRS, F-69622, Villeurbanne, France
| | - Li Fu
- Institut Charles Sadron, Université de Strasbourg, CNRS, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France
| | - Fabrice Thalmann
- Institut Charles Sadron, Université de Strasbourg, CNRS, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France
| | - Thierry Charitat
- Institut Charles Sadron, Université de Strasbourg, CNRS, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France
| | - Anne Rubin
- Institut Charles Sadron, Université de Strasbourg, CNRS, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France
| | - Claire Loison
- Institut Lumière Matière, University of Lyon, Université Claude Bernard Lyon 1, CNRS, F-69622, Villeurbanne, France
| |
Collapse
|
14
|
Direct label-free imaging of nanodomains in biomimetic and biological membranes by cryogenic electron microscopy. Proc Natl Acad Sci U S A 2020; 117:19943-19952. [PMID: 32759206 DOI: 10.1073/pnas.2002200117] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The nanoscale organization of biological membranes into structurally and compositionally distinct lateral domains is believed to be central to membrane function. The nature of this organization has remained elusive due to a lack of methods to directly probe nanoscopic membrane features. We show here that cryogenic electron microscopy (cryo-EM) can be used to directly image coexisting nanoscopic domains in synthetic and bioderived membranes without extrinsic probes. Analyzing a series of single-component liposomes composed of synthetic lipids of varying chain lengths, we demonstrate that cryo-EM can distinguish bilayer thickness differences as small as 0.5 Å, comparable to the resolution of small-angle scattering methods. Simulated images from computational models reveal that features in cryo-EM images result from a complex interplay between the atomic distribution normal to the plane of the bilayer and imaging parameters. Simulations of phase-separated bilayers were used to predict two sources of contrast between coexisting ordered and disordered phases within a single liposome, namely differences in membrane thickness and molecular density. We observe both sources of contrast in biomimetic membranes composed of saturated lipids, unsaturated lipids, and cholesterol. When extended to isolated mammalian plasma membranes, cryo-EM reveals similar nanoscale lateral heterogeneities. The methods reported here for direct, probe-free imaging of nanodomains in unperturbed membranes open new avenues for investigation of nanoscopic membrane organization.
Collapse
|
15
|
Céspedes PF, Beckers D, Dustin ML, Sezgin E. Model membrane systems to reconstitute immune cell signaling. FEBS J 2020; 288:1070-1090. [DOI: 10.1111/febs.15488] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 06/26/2020] [Accepted: 07/14/2020] [Indexed: 12/26/2022]
Affiliation(s)
- Pablo F. Céspedes
- Kennedy Institute of Rheumatology Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences University of Oxford UK
| | - Daniel Beckers
- MRC Human Immunology Unit MRC Weatherall Institute of Molecular Medicine University of Oxford UK
| | - Michael L. Dustin
- Kennedy Institute of Rheumatology Nuffield Department of Orthopedics, Rheumatology and Musculoskeletal Sciences University of Oxford UK
| | - Erdinc Sezgin
- MRC Human Immunology Unit MRC Weatherall Institute of Molecular Medicine University of Oxford UK
- Science for Life Laboratory Department of Women's and Children's Health Karolinska Institutet Stockholm Sweden
| |
Collapse
|
16
|
Rinaldin M, Fonda P, Giomi L, Kraft DJ. Lipid exchange enhances geometric pinning in multicomponent membranes on patterned substrates. SOFT MATTER 2020; 16:4932-4940. [PMID: 32435786 DOI: 10.1039/c9sm02393c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Experiments on supported lipid bilayers featuring liquid ordered/disordered domains have shown that the spatial arrangement of the lipid domains and their chemical composition are strongly affected by the curvature of the substrate. Furthermore, theoretical predictions suggest that both these effects are intimately related with the closed topology of the bilayer. In this work, we test this hypothesis by fabricating supported membranes consisting of colloidal particles of various shapes lying on a flat substrate. A single lipid bilayer coats both colloids and substrate, allowing local lipid exchange between them, thus rendering the system thermodynamically open, i.e. able to exchange heat and molecules with an external reservoir in the neighborhood of the colloid. By reconstructing the Gibbs phase diagram for this system, we demonstrate that the free-energy landscape is directly influenced by the geometry of the colloid. In addition, we find that local lipid exchange enhances the pinning of the liquid disordered phase in highly curved regions. This allows us to provide estimates of the bending moduli difference of the domains. Finally, by combining experimental and numerical data, we forecast the outcome of possible experiments on catenoidal and conical necks and show that these geometries could greatly improve the precision of the current estimates of the bending moduli.
Collapse
Affiliation(s)
- Melissa Rinaldin
- Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, The Netherlands.
| | | | | | | |
Collapse
|
17
|
Beckers D, Urbancic D, Sezgin E. Impact of Nanoscale Hindrances on the Relationship between Lipid Packing and Diffusion in Model Membranes. J Phys Chem B 2020; 124:1487-1494. [PMID: 32026676 PMCID: PMC7050011 DOI: 10.1021/acs.jpcb.0c00445] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
![]()
Membrane
models have allowed for precise study of the plasma membrane’s
biophysical properties, helping to unravel both structural and dynamic
motifs within cell biology. Freestanding and supported bilayer systems
are popular models to reconstitute membrane-related processes. Although
it is well-known that each have their advantages and limitations,
comprehensive comparison of their biophysical properties is still
lacking. Here, we compare the diffusion and lipid packing in giant
unilamellar vesicles, planar and spherical supported membranes, and
cell-derived giant plasma membrane vesicles. We apply florescence
correlation spectroscopy (FCS), spectral imaging, and super-resolution
stimulated emission depletion FCS to study the diffusivity, lipid
packing, and nanoscale architecture of these membrane systems, respectively.
Our data show that lipid packing and diffusivity is tightly correlated
in freestanding bilayers. However, nanoscale interactions in the supported
bilayers cause deviation from this correlation. These data are essential
to develop accurate theoretical models of the plasma membrane and
will serve as a guideline for suitable model selection in future studies
to reconstitute biological processes.
Collapse
Affiliation(s)
- Daniel Beckers
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine , University of Oxford , Oxford OX3 9DS , U.K
| | - Dunja Urbancic
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine , University of Oxford , Oxford OX3 9DS , U.K.,Faculty of Pharmacy , University of Ljubljana , Askerceva cesta 7 , 1000 Ljubljana , Slovenia
| | - Erdinc Sezgin
- MRC Human Immunology Unit, MRC Weatherall Institute of Molecular Medicine , University of Oxford , Oxford OX3 9DS , U.K.,Science for Life Laboratory, Department of Women's and Children's Health , Karolinska Institutet , Solna , Sweden
| |
Collapse
|