1
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Dinet C, Torres-Sánchez A, Lanfranco R, Di Michele L, Arroyo M, Staykova M. Patterning and dynamics of membrane adhesion under hydraulic stress. Nat Commun 2023; 14:7445. [PMID: 37978292 PMCID: PMC10656516 DOI: 10.1038/s41467-023-43246-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2023] [Accepted: 11/02/2023] [Indexed: 11/19/2023] Open
Abstract
Hydraulic fracturing plays a major role in cavity formation during embryonic development, when pressurized fluid opens microlumens at cell-cell contacts, which evolve to form a single large lumen. However, the fundamental physical mechanisms behind these processes remain masked by the complexity and specificity of biological systems. Here, we show that adhered lipid vesicles subjected to osmotic stress form hydraulic microlumens similar to those in cells. Combining vesicle experiments with theoretical modelling and numerical simulations, we provide a physical framework for the hydraulic reconfiguration of cell-cell adhesions. We map the conditions for microlumen formation from a pristine adhesion, the emerging dynamical patterns and their subsequent maturation. We demonstrate control of the fracturing process depending on the applied pressure gradients and the type and density of membrane bonds. Our experiments further reveal an unexpected, passive transition of microlumens to closed buds that suggests a physical route to adhesion remodeling by endocytosis.
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Affiliation(s)
- Céline Dinet
- Department of Physics, Durham University, Durham, UK
- Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, CNRS-Aix-Marseille University, 31 Chemin Joseph Aiguier, 13009, Marseille, France
| | - Alejandro Torres-Sánchez
- Universitat Politècnica de Catalunya-BarcelonaTech, 08034, Barcelona, Spain
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, 08028, Barcelona, Spain
- European Molecular Biology Laboratory (EMBL-Barcelona), 08003, Barcelona, Spain
| | - Roberta Lanfranco
- Department of Physics, Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Lorenzo Di Michele
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK
- Department of Chemistry, Imperial College of London, London, UK
| | - Marino Arroyo
- Universitat Politècnica de Catalunya-BarcelonaTech, 08034, Barcelona, Spain.
- Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology, 08028, Barcelona, Spain.
- Centre Internacional de Mètodes Numèrics en Enginyeria (CIMNE), 08034, Barcelona, Spain.
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2
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Lin AJ, Sihorwala AZ, Belardi B. Engineering Tissue-Scale Properties with Synthetic Cells: Forging One from Many. ACS Synth Biol 2023; 12:1889-1907. [PMID: 37417657 PMCID: PMC11017731 DOI: 10.1021/acssynbio.3c00061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/08/2023]
Abstract
In metazoans, living cells achieve capabilities beyond individual cell functionality by assembling into multicellular tissue structures. These higher-order structures represent dynamic, heterogeneous, and responsive systems that have evolved to regenerate and coordinate their actions over large distances. Recent advances in constructing micrometer-sized vesicles, or synthetic cells, now point to a future where construction of synthetic tissue can be pursued, a boon to pressing material needs in biomedical implants, drug delivery systems, adhesives, filters, and storage devices, among others. To fully realize the potential of synthetic tissue, inspiration has been and will continue to be drawn from new molecular findings on its natural counterpart. In this review, we describe advances in introducing tissue-scale features into synthetic cell assemblies. Beyond mere complexation, synthetic cells have been fashioned with a variety of natural and engineered molecular components that serve as initial steps toward morphological control and patterning, intercellular communication, replication, and responsiveness in synthetic tissue. Particular attention has been paid to the dynamics, spatial constraints, and mechanical strengths of interactions that drive the synthesis of this next-generation material, describing how multiple synthetic cells can act as one.
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Affiliation(s)
- Alexander J Lin
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Ahmed Z Sihorwala
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
| | - Brian Belardi
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
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3
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Abdelrahman A, Smith AS, Sengupta K. Observing Membrane and Cell Adhesion via Reflection Interference Contrast Microscopy. Methods Mol Biol 2023; 2654:123-135. [PMID: 37106179 DOI: 10.1007/978-1-0716-3135-5_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
Reflection interference contrast microscopy (RICM) is an optical microscopy technique ideally suited for imaging adhesion. While RICM (and the closely related interference reflection microscopy (IRM)) has been extensively used qualitatively or semiquantitatively to image cells, including immune cells, it can also be used quantitatively to measure membrane to surface distance, especially for model membranes. Here, we present a protocol for RICM and IRM imaging and the details of semiquantitative and quantitative analysis.
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Affiliation(s)
- Ahmed Abdelrahman
- Aix Marseille University, CNRS, CINAM, Turing Centre for Living Systems, Marseille, France
| | - Ana-Sunčana Smith
- PULS Group, Department of Physics, Centre for Computational Materials and Processes, Friedrich Alexander University Erlangen-Nürnberg, IZNF, Erlangen, Germany.
- Group for Computational Life Sciences, Division of Physical Chemistry, Ruđer Bošković Institute, Zagreb, Croatia.
| | - Kheya Sengupta
- Aix Marseille University, CNRS, CINAM, Turing Centre for Living Systems, Marseille, France
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4
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Le Verge-Serandour M, Turlier H. A hydro-osmotic coarsening theory of biological cavity formation. PLoS Comput Biol 2021; 17:e1009333. [PMID: 34478457 PMCID: PMC8445475 DOI: 10.1371/journal.pcbi.1009333] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 09/16/2021] [Accepted: 08/09/2021] [Indexed: 02/06/2023] Open
Abstract
Fluid-filled biological cavities are ubiquitous, but their collective dynamics has remained largely unexplored from a physical perspective. Based on experimental observations in early embryos, we propose a model where a cavity forms through the coarsening of myriad of pressurized micrometric lumens, that interact by ion and fluid exchanges through the intercellular space. Performing extensive numerical simulations, we find that hydraulic fluxes lead to a self-similar coarsening of lumens in time, characterized by a robust dynamic scaling exponent. The collective dynamics is primarily controlled by hydraulic fluxes, which stem from lumen pressures differences and are dampened by water permeation through the membrane. Passive osmotic heterogeneities play, on the contrary, a minor role on cavity formation but active ion pumping can largely modify the coarsening dynamics: it prevents the lumen network from a collective collapse and gives rise to a novel coalescence-dominated regime exhibiting a distinct scaling law. Interestingly, we prove numerically that spatially biasing ion pumping may be sufficient to position the cavity, suggesting a novel mode of symmetry breaking to control tissue patterning. Providing generic testable predictions, our model forms a comprehensive theoretical basis for hydro-osmotic interaction between biological cavities, that shall find wide applications in embryo and tissue morphogenesis.
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Affiliation(s)
- Mathieu Le Verge-Serandour
- Center for Interdisciplinary Research in Biology, Collège de France, PSL Research University, CNRS UMR7241, INSERM U1050, Paris, France
| | - Hervé Turlier
- Center for Interdisciplinary Research in Biology, Collège de France, PSL Research University, CNRS UMR7241, INSERM U1050, Paris, France
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5
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Souissi M, Pernier J, Rossier O, Giannone G, Le Clainche C, Helfer E, Sengupta K. Integrin-Functionalised Giant Unilamellar Vesicles via Gel-Assisted Formation: Good Practices and Pitfalls. Int J Mol Sci 2021; 22:6335. [PMID: 34199292 PMCID: PMC8231826 DOI: 10.3390/ijms22126335] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 05/26/2021] [Accepted: 06/08/2021] [Indexed: 01/16/2023] Open
Abstract
Giant unilamellar vesicles (GUV) are powerful tools to explore physics and biochemistry of the cell membrane in controlled conditions. For example, GUVs were extensively used to probe cell adhesion, but often using non-physiological linkers, due to the difficulty of incorporating transmembrane adhesion proteins into model membranes. Here we describe a new protocol for making GUVs incorporating the transmembrane protein integrin using gel-assisted swelling. We report an optimised protocol, enumerating the pitfalls encountered and precautions to be taken to maintain the robustness of the protocol. We characterise intermediate steps of small proteoliposome formation and the final formed GUVs. We show that the integrin molecules are successfully incorporated and are functional.
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Affiliation(s)
- Mariem Souissi
- Aix Marseille Univ, CNRS, Centre Interdisciplinaire de Nanoscience de Marseille (CINAM), Turing Centre for Living Systems, 13009 Marseille, France;
| | - Julien Pernier
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France; (J.P.); (C.L.C.)
| | - Olivier Rossier
- Univ. Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, 33000 Bordeaux, France; (O.R.); (G.G.)
| | - Gregory Giannone
- Univ. Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, IINS, UMR 5297, 33000 Bordeaux, France; (O.R.); (G.G.)
| | - Christophe Le Clainche
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France; (J.P.); (C.L.C.)
| | - Emmanuèle Helfer
- Aix Marseille Univ, CNRS, Centre Interdisciplinaire de Nanoscience de Marseille (CINAM), Turing Centre for Living Systems, 13009 Marseille, France;
| | - Kheya Sengupta
- Aix Marseille Univ, CNRS, Centre Interdisciplinaire de Nanoscience de Marseille (CINAM), Turing Centre for Living Systems, 13009 Marseille, France;
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6
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Casas-Ferrer L, Brisson A, Massiera G, Casanellas L. Design of vesicle prototissues as a model for cellular tissues. SOFT MATTER 2021; 17:5061-5072. [PMID: 33929482 DOI: 10.1039/d1sm00336d] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Synthesizing biomimetic prototissues with predictable physical properties is a promising tool for the study of cellular tissues, as they would enable to test systematically the role of individual physical mechanisms on complex biological processes. The aim of this study is to design a biomimetic cohesive tissue with tunable mechanical properties by the controlled assembly of giant unillamelar vesicles (GUV). GUV-GUV specific adhesion is mediated by the inclusion of the streptavidin-biotin pair, or DNA complementary strands. Using a simple assembly protocol, we are capable of synthesizing vesicle prototissues of spheroidal or sheet-like morphologies, with predictable cell-cell adhesion strengths, typical sizes, and degree of compaction.
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Affiliation(s)
- Laura Casas-Ferrer
- Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier. Place Eugène Bataillon, 34095 Montpellier, France.
| | - Amaury Brisson
- Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier. Place Eugène Bataillon, 34095 Montpellier, France.
| | - Gladys Massiera
- Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier. Place Eugène Bataillon, 34095 Montpellier, France.
| | - Laura Casanellas
- Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier. Place Eugène Bataillon, 34095 Montpellier, France.
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7
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Koch S, Seinen AB, Kamel M, Kuckla D, Monzel C, Kedrov A, Driessen AJM. Single-molecule analysis of dynamics and interactions of the SecYEG translocon. FEBS J 2020; 288:2203-2221. [PMID: 33058437 DOI: 10.1111/febs.15596] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 09/11/2020] [Accepted: 10/12/2020] [Indexed: 12/19/2022]
Abstract
Protein translocation and insertion into the bacterial cytoplasmic membrane are the essential processes mediated by the Sec machinery. The core machinery is composed of the membrane-embedded translocon SecYEG that interacts with the secretion-dedicated ATPase SecA and translating ribosomes. Despite the simplicity and the available structural insights on the system, diverse molecular mechanisms and functional dynamics have been proposed. Here, we employ total internal reflection fluorescence microscopy to study the oligomeric state and diffusion of SecYEG translocons in supported lipid bilayers at the single-molecule level. Silane-based coating ensured the mobility of lipids and reconstituted translocons within the bilayer. Brightness analysis suggested that approx. 70% of the translocons were monomeric. The translocons remained in a monomeric form upon ribosome binding, but partial oligomerization occurred in the presence of nucleotide-free SecA. Individual trajectories of SecYEG in the lipid bilayer revealed dynamic heterogeneity of diffusion, as translocons commonly switched between slow and fast mobility modes with corresponding diffusion coefficients of 0.03 and 0.7 µm2 ·s-1 . Interactions with SecA ATPase had a minor effect on the lateral mobility, while bound ribosome:nascent chain complexes substantially hindered the diffusion of single translocons. Notably, the mobility of the translocon:ribosome complexes was not affected by the solvent viscosity or macromolecular crowding modulated by Ficoll PM 70, so it was largely determined by interactions within the lipid bilayer and at the interface. We suggest that the complex mobility of SecYEG arises from the conformational dynamics of the translocon and protein:lipid interactions.
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Affiliation(s)
- Sabrina Koch
- Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, Zernike Institute for Advanced Materials, University of Groningen, The Netherlands
| | - Anne-Bart Seinen
- Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, Zernike Institute for Advanced Materials, University of Groningen, The Netherlands.,Biophysics, AMOLF, Amsterdam, The Netherlands
| | - Michael Kamel
- Synthetic Membrane Systems, Institute of Biochemistry, Heinrich Heine University Düsseldorf, Germany
| | - Daniel Kuckla
- Experimental Medical Physics, Department of Physics, Heinrich Heine University Düsseldorf, Germany
| | - Cornelia Monzel
- Experimental Medical Physics, Department of Physics, Heinrich Heine University Düsseldorf, Germany
| | - Alexej Kedrov
- Synthetic Membrane Systems, Institute of Biochemistry, Heinrich Heine University Düsseldorf, Germany
| | - Arnold J M Driessen
- Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, Zernike Institute for Advanced Materials, University of Groningen, The Netherlands
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8
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Belardi B, Son S, Felce JH, Dustin ML, Fletcher DA. Cell-cell interfaces as specialized compartments directing cell function. Nat Rev Mol Cell Biol 2020; 21:750-764. [PMID: 33093672 DOI: 10.1038/s41580-020-00298-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/09/2020] [Indexed: 12/14/2022]
Abstract
Cell-cell interfaces are found throughout multicellular organisms, from transient interactions between motile immune cells to long-lived cell-cell contacts in epithelia. Studies of immune cell interactions, epithelial cell barriers, neuronal contacts and sites of cell-cell fusion have identified a core set of features shared by cell-cell interfaces that critically control their function. Data from diverse cell types also show that cells actively and passively regulate the localization, strength, duration and cytoskeletal coupling of receptor interactions governing cell-cell signalling and physical connections between cells, indicating that cell-cell interfaces have a unique membrane organization that emerges from local molecular and cellular mechanics. In this Review, we discuss recent findings that support the emerging view of cell-cell interfaces as specialized compartments that biophysically constrain the arrangement and activity of their protein, lipid and glycan components. We also review how these biophysical features of cell-cell interfaces allow cells to respond with high selectivity and sensitivity to multiple inputs, serving as the basis for wide-ranging cellular functions. Finally, we consider how the unique properties of cell-cell interfaces present opportunities for therapeutic intervention.
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Affiliation(s)
- Brian Belardi
- Department of Bioengineering & Biophysics Program, UC Berkeley, Berkeley, CA, USA
| | - Sungmin Son
- Department of Bioengineering & Biophysics Program, UC Berkeley, Berkeley, CA, USA
| | | | | | - Daniel A Fletcher
- Department of Bioengineering & Biophysics Program, UC Berkeley, Berkeley, CA, USA. .,Division of Biological Systems & Engineering, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. .,Chan Zuckerberg Biohub, San Francisco, CA, USA.
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9
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Abstract
Many critical biological events, including biochemical signaling, membrane traffic, and cell motility, originate at membrane surfaces. Each such event requires that members of a specific group of proteins and lipids rapidly assemble together at a specific site on the membrane surface. Understanding the biophysical mechanisms that stabilize these assemblies is critical to decoding and controlling cellular functions. In this article, we review progress toward a quantitative biophysical understanding of the mechanisms that drive membrane heterogeneity and organization. We begin from a physical perspective, reviewing the fundamental principles and key experimental evidence behind each proposed mechanism. We then shift to a biological perspective, presenting key examples of the role of heterogeneity in biology and asking which physical mechanisms may be responsible. We close with an applied perspective, noting that membrane heterogeneity provides a novel therapeutic target that is being exploited by a growing number of studies at the interface of biology, physics, and engineering.
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Affiliation(s)
- Wade F Zeno
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA;
| | - Kasey J Day
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA;
| | - Vernita D Gordon
- Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
- Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Jeanne C Stachowiak
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA;
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA
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10
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Bartelt SM, Chervyachkova E, Ricken J, Wegner SV. Mimicking Adhesion in Minimal Synthetic Cells. ACTA ACUST UNITED AC 2019; 3:e1800333. [DOI: 10.1002/adbi.201800333] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 02/12/2019] [Indexed: 01/10/2023]
Affiliation(s)
- Solveig M. Bartelt
- Max Planck Institute of Polymer Research Ackermannweg 10 55128 Mainz Germany
| | | | - Julia Ricken
- Max Planck Institute for Medical Research Jahnstraße 29 69120 Heidelberg Germany
| | - Seraphine V. Wegner
- Max Planck Institute of Polymer Research Ackermannweg 10 55128 Mainz Germany
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11
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Omidvar R, Römer W. Glycan-decorated protocells: novel features for rebuilding cellular processes. Interface Focus 2019; 9:20180084. [PMID: 30842879 DOI: 10.1098/rsfs.2018.0084] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/14/2019] [Indexed: 02/06/2023] Open
Abstract
In synthetic biology approaches, lipid vesicles are widely used as protocell models. While many compounds have been encapsulated in vesicles (e.g. DNA, cytoskeleton and enzymes), the incorporation of glycocalyx components in the lipid bilayer has attracted much less attention so far. In recent years, glycoconjugates have been integrated in the membrane of giant unilamellar vesicles (GUVs). These minimal membrane systems have largely contributed to shed light on the molecular mechanisms of cellular processes. In this review, we first introduce several preparation and biophysical characterization methods of GUVs. Then, we highlight specific applications of protocells investigating glycolipid-mediated endocytosis of toxins, viruses and bacteria. In addition, we delineate how prototissues have been assembled from glycan-decorated protocells by using lectin-mediated cross-linking of opposed glycoreceptors (e.g. glycolipids and glycopeptides). In future applications, glycan-decorated protocells might be useful for investigating cell-cell interactions (e.g. adhesion and communication). We also speculate about the implication of lectin-glycoreceptor interactions in membrane fusion processes.
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Affiliation(s)
- Ramin Omidvar
- Faculty of Biology, Albert-Ludwigs-University Freiburg, Schänzlestraße 1, 79104 Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, Albert-Ludwigs-University Freiburg, Schänzlestraße 18, 79104 Freiburg, Germany.,Freiburg Center for Interactive Materials and Bioinspired Technology (FIT), Albert-Ludwigs-University Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany
| | - Winfried Römer
- Faculty of Biology, Albert-Ludwigs-University Freiburg, Schänzlestraße 1, 79104 Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, Albert-Ludwigs-University Freiburg, Schänzlestraße 18, 79104 Freiburg, Germany.,Freiburg Center for Interactive Materials and Bioinspired Technology (FIT), Albert-Ludwigs-University Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany
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12
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Guha S, Ghimire J, Wu E, Wimley WC. Mechanistic Landscape of Membrane-Permeabilizing Peptides. Chem Rev 2019; 119:6040-6085. [PMID: 30624911 DOI: 10.1021/acs.chemrev.8b00520] [Citation(s) in RCA: 150] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Membrane permeabilizing peptides (MPPs) are as ubiquitous as the lipid bilayer membranes they act upon. Produced by all forms of life, most membrane permeabilizing peptides are used offensively or defensively against the membranes of other organisms. Just as nature has found many uses for them, translational scientists have worked for decades to design or optimize membrane permeabilizing peptides for applications in the laboratory and in the clinic ranging from antibacterial and antiviral therapy and prophylaxis to anticancer therapeutics and drug delivery. Here, we review the field of membrane permeabilizing peptides. We discuss the diversity of their sources and structures, the systems and methods used to measure their activities, and the behaviors that are observed. We discuss the fact that "mechanism" is not a discrete or a static entity for an MPP but rather the result of a heterogeneous and dynamic ensemble of structural states that vary in response to many different experimental conditions. This has led to an almost complete lack of discrete three-dimensional active structures among the thousands of known MPPs and a lack of useful or predictive sequence-structure-function relationship rules. Ultimately, we discuss how it may be more useful to think of membrane permeabilizing peptides mechanisms as broad regions of a mechanistic landscape rather than discrete molecular processes.
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Affiliation(s)
- Shantanu Guha
- Department of Biochemistry and Molecular Biology Tulane University School of Medicine , New Orleans , Louisiana 70112 , United States
| | - Jenisha Ghimire
- Department of Biochemistry and Molecular Biology Tulane University School of Medicine , New Orleans , Louisiana 70112 , United States
| | - Eric Wu
- Department of Biochemistry and Molecular Biology Tulane University School of Medicine , New Orleans , Louisiana 70112 , United States
| | - William C Wimley
- Department of Biochemistry and Molecular Biology Tulane University School of Medicine , New Orleans , Louisiana 70112 , United States
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13
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Bartelt SM, Steinkühler J, Dimova R, Wegner SV. Light-Guided Motility of a Minimal Synthetic Cell. NANO LETTERS 2018; 18:7268-7274. [PMID: 30350637 DOI: 10.1021/acs.nanolett.8b03469] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Cell motility is an important but complex process; as cells move, new adhesions form at the front and adhesions disassemble at the back. To replicate this dynamic and spatiotemporally controlled asymmetry of adhesions and achieve motility in a minimal synthetic cell, we controlled the adhesion of a model giant unilamellar vesicle (GUV) to the substrate with light. For this purpose, we immobilized the proteins iLID and Micro, which interact under blue light and dissociate from each other in the dark, on a substrate and a GUV, respectively. Under blue light, the protein interaction leads to adhesion of the vesicle to the substrate, which is reversible in the dark. The high spatiotemporal control provided by light, allowed partly illuminating the GUV and generating an asymmetry in adhesions. Consequently, the GUV moves into the illuminated area, a process that can be repeated over multiple cycles. Thus, our system reproduces the dynamic spatiotemporal distribution of adhesions and establishes mimetic motility of a synthetic cell.
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Affiliation(s)
- Solveig M Bartelt
- Max Planck Institute for Polymer Research , Ackermannweg 10 , 55128 Mainz , Germany
| | - Jan Steinkühler
- Theory and Bio-Systems , Max Planck Institute of Colloids and Interfaces , Science Park Golm, 14424 Potsdam , Germany
| | - Rumiana Dimova
- Theory and Bio-Systems , Max Planck Institute of Colloids and Interfaces , Science Park Golm, 14424 Potsdam , Germany
| | - Seraphine V Wegner
- Max Planck Institute for Polymer Research , Ackermannweg 10 , 55128 Mainz , Germany
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14
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Junghans V, Santos AM, Lui Y, Davis SJ, Jönsson P. Dimensions and Interactions of Large T-Cell Surface Proteins. Front Immunol 2018; 9:2215. [PMID: 30319654 PMCID: PMC6170634 DOI: 10.3389/fimmu.2018.02215] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Accepted: 09/06/2018] [Indexed: 11/23/2022] Open
Abstract
The first step of the adaptive immune response involves the interaction of T cells that express T-cell receptors (TCRs) with peptide-loaded major histocompatibility complexes expressed by antigen-presenting cells (APCs). Exactly how this leads to activation of the TCR and to downstream signaling is uncertain, however. Recent findings suggest that one of the key events is the exclusion of the large receptor-type tyrosine phosphatase CD45, from close contacts formed at sites of T-cell/APC interaction. If this is true, a full understanding of how close contact formation leads to signaling would require insights into the structures of, and interactions between, large membrane proteins like CD45 and other proteins forming the glycocalyx, such as CD43. Structural insights into the overall dimensions of these proteins using crystallographic methods are hard to obtain, and their conformations on the cell surface are also unknown. Several imaging-based optical microscopy techniques have however been developed for analyzing protein dimensions and orientation on model cell surfaces with nanometer precision. Here we review some of these methods with a focus on the use of hydrodynamic trapping, which relies on liquid flow from a micropipette to move and trap membrane-associated fluorescently labeled molecules. Important insights that have been obtained include (i) how protein flexibility and coverage might affect the effective heights of these molecules, (ii) the height of proteins on the membrane as a key parameter determining how they will distribute in cell-cell contacts, and (iii) how repulsive interactions between the extracellular parts of the proteins influences protein aggregation and distribution.
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Affiliation(s)
| | - Ana Mafalda Santos
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Yuan Lui
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Simon J. Davis
- Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Peter Jönsson
- Department of Chemistry, Lund University, Lund, Sweden
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15
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Benard E, Nunès JA, Limozin L, Sengupta K. T Cells on Engineered Substrates: The Impact of TCR Clustering Is Enhanced by LFA-1 Engagement. Front Immunol 2018; 9:2085. [PMID: 30279692 PMCID: PMC6154019 DOI: 10.3389/fimmu.2018.02085] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 08/23/2018] [Indexed: 12/15/2022] Open
Abstract
We created APC-mimetic synthetic substrates to study the impact of ligand clustering on T cell activation and spreading. The substrates exhibit antibodies directed against the TCR-complex in the form of a patterned array of sub micrometric dots surrounded by a fluid supported lipid bilayer (SLB) which may itself be functionalized with another bio-molecule. We show that for T cell adhesion mediated by T cell receptor (TCR) alone, in the patterned, but not in the corresponding homogeneous controls, the TCR, ZAP-70 and actin are present in the form of clusters or patches that co-localize with the ligand-dots. However, global cell scale parameters like cell area and actin distribution are only weakly impacted by ligand clustering. In presence of ICAM-1 - the ligand of the T cell integrin LFA-1 - on the SLB, the TCR is still clustered due to the patterning of its ligands, but now global parameters are also impacted. The actin organization changes to a peripheral ring, resembling the classical actin distribution seen on homogeneous substrates, the patterned membrane topography disappears and the membrane is flat, whereas the cell area increases significantly. These observations taken together point to a possible pivotal role for LFA-1 in amplifying the effect of TCR-clustering. No such effect is evident for co-engagement of CD28, affected via its ligand B7.2. Unlike on ICAM-1, on B7.2 cell spreading and actin organization are similar for homogeneous and patterned substrates. However, TCR and ZAP-70 clusters are still formed in the patterned case. These results indicate complementary role for LFA-1 and CD28 in the regulation and putative coupling of TCR micro-clusters to actin. The engineered substrates presented here clearly have the potential to act as platform for fundamental research in immune cell biology, as well as translational analyses in immunotherapy, for example to screen molecules for their role in T cell adhesion/activation.
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Affiliation(s)
| | - Jacques A Nunès
- CNRS, UMR7258, Centre de Recherche en Cancerologie de Marseille, Immunity and Cancer Team, Institut Paoli-Calmettes, Inserm, U1068, Aix-Marseille Université UM 105, Marseille, France
| | - Laurent Limozin
- LAI, CNRS UMR 7333, INSERM UMR 1067, Aix-Marseille Université, Marseille, France
| | - Kheya Sengupta
- CNRS, CINaM UMR 7325, Aix-Marseille Université, Marseille, France
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16
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Abstract
How do the cells in our body reconfigure their shape to achieve complex tasks like migration and mitosis, yet maintain their shape in response to forces exerted by, for instance, blood flow and muscle action? Cell shape control is defined by a delicate mechanical balance between active force generation and passive material properties of the plasma membrane and the cytoskeleton. The cytoskeleton forms a space-spanning fibrous network comprising three subsystems: actin, microtubules and intermediate filaments. Bottom-up reconstitution of minimal synthetic cells where these cytoskeletal subsystems are encapsulated inside a lipid vesicle provides a powerful avenue to dissect the force balance that governs cell shape control. Although encapsulation is technically demanding, a steady stream of advances in this technique has made the reconstitution of shape-changing minimal cells increasingly feasible. In this topical review we provide a route-map of the recent advances in cytoskeletal encapsulation techniques and outline recent reports that demonstrate shape change phenomena in simple biomimetic vesicle systems. We end with an outlook toward the next steps required to achieve more complex shape changes with the ultimate aim of building a fully functional synthetic cell with the capability to autonomously grow, divide and move.
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Affiliation(s)
- Yuval Mulla
- These authors contributed equally to this work
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17
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Shindell O, Mica N, Cheng KH, Wang E, Gordon VD. Dynamic Fingering in Adhered Lipid Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:4673-4680. [PMID: 29363972 DOI: 10.1021/acs.langmuir.7b03708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Artificial lipid membranes incorporating proteins have frequently been used as models for the dynamic organization of biological structures in living cells as well as in the development of biology-inspired technologies. We report here on the experimental demonstration and characterization of a pattern-forming process that occurs in a lipid bilayer membrane adhered via biotin-avidin binding to a second lipid membrane that is supported by a solid substrate. Adhesion regions are roughly circular with a diameter of about 25 μm. Using confocal fluorescence microscopy, we record time series of dynamic fingering patterns that grow in the upper lipid membrane and intermembrane biotin-avidin bonds. The fingers are micrometer-scale elongated pores that grow from the edge of an already-stabilized hole. Finger growth is saltatory on the scale of tens of seconds. We find that as the fingers grow and the density of adhesion proteins increases, the rate of finger growth decreases exponentially and the width of newly formed fingers decreases linearly. We show that these findings are consistent with a thermodynamic description of dynamic pore formation and stabilization.
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Affiliation(s)
- Orrin Shindell
- Center for Nonlinear Dynamics and Department of Physics , University of Texas at Austin , Austin 78712 , United States
- Department of Physics and Astronomy , Trinity University , San Antonio , Texas 78212 , United States
| | - Natalie Mica
- Center for Nonlinear Dynamics and Department of Physics , University of Texas at Austin , Austin 78712 , United States
- School of Physics and Astronomy , University of St. Andrews , Saint Andrews , Scotland KY16 9AJ , U.K
| | - Kwan H Cheng
- Department of Physics and Astronomy , Trinity University , San Antonio , Texas 78212 , United States
| | - Exing Wang
- Department of Cell Systems & Anatomy , University of Texas Health Science Center San Antonio , San Antonio , Texas 78229 , United States
| | - Vernita D Gordon
- Center for Nonlinear Dynamics and Department of Physics , University of Texas at Austin , Austin 78712 , United States
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18
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Glazier R, Salaita K. Supported lipid bilayer platforms to probe cell mechanobiology. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2017; 1859:1465-1482. [PMID: 28502789 PMCID: PMC5531615 DOI: 10.1016/j.bbamem.2017.05.005] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Revised: 05/09/2017] [Accepted: 05/09/2017] [Indexed: 12/15/2022]
Abstract
Mammalian and bacterial cells sense and exert mechanical forces through the process of mechanotransduction, which interconverts biochemical and physical signals. This is especially important in contact-dependent signaling, where ligand-receptor binding occurs at cell-cell or cell-ECM junctions. By virtue of occurring within these specialized junctions, receptors engaged in contact-dependent signaling undergo oligomerization and coupling with the cytoskeleton as part of their signaling mechanisms. While our ability to measure and map biochemical signaling within cell junctions has advanced over the past decades, physical cues remain difficult to map in space and time. Recently, supported lipid bilayer (SLB) technologies have emerged as a flexible platform to mimic and perturb cell-cell and cell-ECM junctions, allowing one to study membrane receptor mechanotransduction. Changing the lipid composition and underlying substrate tunes bilayer fluidity, and lipid and ligand micro- and nano-patterning spatially control positioning and clustering of receptors. Patterning metal gridlines within SLBs confines lipid mobility and introduces mechanical resistance. Here we review fundamental SLB mechanics and how SLBs can be engineered as tunable cell substrates for mechanotransduction studies. Finally, we highlight the impact of this work in understanding the biophysical mechanisms of cell adhesion. This article is part of a Special Issue entitled: Interactions between membrane receptors in cellular membranes edited by Kalina Hristova.
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Affiliation(s)
- Roxanne Glazier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, and Emory University, Atlanta, GA 30322, United States
| | - Khalid Salaita
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, and Emory University, Atlanta, GA 30322, United States; Department of Chemistry, Emory University, Atlanta, GA 30322, United States..
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19
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Sustained α-catenin Activation at E-cadherin Junctions in the Absence of Mechanical Force. Biophys J 2017; 111:1044-52. [PMID: 27602732 DOI: 10.1016/j.bpj.2016.06.027] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 05/08/2016] [Accepted: 06/24/2016] [Indexed: 11/22/2022] Open
Abstract
Mechanotransduction at E-cadherin junctions has been postulated to be mediated in part by a force-dependent conformational activation of α-catenin. Activation of α-catenin allows it to interact with vinculin in addition to F-actin, resulting in a strengthening of junctions. Here, using E-cadherin adhesions reconstituted on synthetic, nanopatterned membranes, we show that activation of α-catenin is dependent on E-cadherin clustering, and is sustained in the absence of mechanical force or association with F-actin or vinculin. Adhesions were formed by filopodia-mediated nucleation and micron-scale assembly of E-cadherin clusters, which could be distinguished as either peripheral or central assemblies depending on their relative location at the cell-bilayer adhesion. Whereas F-actin, vinculin, and phosphorylated myosin light chain associated only with the peripheral assemblies, activated α-catenin was present in both peripheral and central assemblies, and persisted in the central assemblies in the absence of actomyosin tension. Impeding filopodia-mediated nucleation and micron-scale assembly of E-cadherin adhesion complexes by confining the movement of bilayer-bound E-cadherin on nanopatterned substrates reduced the levels of activated α-catenin. Taken together, these results indicate that although the initial activation of α-catenin requires micron-scale clustering that may allow the development of mechanical forces, sustained force is not required for maintaining α-catenin in the active state.
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20
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Benard E, Pi F, Ozerov I, Charrier A, Sengupta K. Ligand Nano-cluster Arrays in a Supported Lipid Bilayer. J Vis Exp 2017:55060. [PMID: 28518120 PMCID: PMC5565094 DOI: 10.3791/55060] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Currently there is considerable interest in creating ordered arrays of adhesive protein islands in a sea of passivated surface for cell biological studies. In the past years, it has become increasingly clear that living cells respond, not only to the biochemical nature of the molecules presented to them but also to the way these molecules are presented. Creating protein micro-patterns is therefore now standard in many biology laboratories; nano-patterns are also more accessible. However, in the context of cell-cell interactions, there is a need to pattern not only proteins but also lipid bilayers. Such dual proteo-lipidic patterning has so far not been easily accessible. We offer a facile technique to create protein nano-dots supported on glass and propose a method to backfill the inter-dot space with a supported lipid bilayer (SLB). From photo-bleaching of tracer fluorescent lipids included in the SLB, we demonstrate that the bilayer exhibits considerable in-plane fluidity. Functionalizing the protein dots with fluorescent groups allows us to image them and to show that they are ordered in a regular hexagonal lattice. The typical dot size is about 800 nm and the spacing demonstrated here is 2 microns. These substrates are expected to serve as useful platforms for cell adhesion, migration and mechano-sensing studies.
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Affiliation(s)
| | - Fuwei Pi
- Aix-Marseille Université, CNRS, UMR 7325, CINaM; State Key Laboratory of Food Science and Technology, School of Food Science of Jiangnan University
| | - Igor Ozerov
- Aix-Marseille Université, CNRS, UMR 7325, CINaM
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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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Amjad OA, Mognetti BM, Cicuta P, Di Michele L. Membrane Adhesion through Bridging by Multimeric Ligands. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:1139-1146. [PMID: 28068766 DOI: 10.1021/acs.langmuir.6b03692] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Ligand/receptor multivalent interactions have been exploited to drive self-assembly of nanoparticles, hard colloids, and, more recently, compliant units including emulsion droplets and lipid vesicles. In deformable liposomes, formation of links between two membranes produces morphological changes depending on the amount of ligands in the environment. Here, we study a proof-of-concept biosensing system in which single lipid vesicles adhere to a flat supported lipid bilayer, both decorated with membrane-anchored biotinylated receptors. Adhesion is driven by multivalent streptavidin (SA) ligands forming bridges between the vesicles and the supported bilayer. Upon changing the concentration of ligands, we characterize the morphological and mechanical changes of the vesicles, including the formation of a stable adhesion patch, membrane tension, and the kinetics of bridge rupture/formation. We observe vesicle binding only within a specific range of ligand concentrations: adhesion does not occur if the amount of SA is either too low or too high. A theoretical model is presented, elucidating the mechanism underlying this observation, particularly, the role of SA multivalency in determining the onset of adhesion. We elaborate on how the behavior of membranes studied here could be exploited in next-generation (bio)molecular analytical devices.
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Affiliation(s)
- Omar A Amjad
- Biological and Soft Systems, Cavendish Laboratory, University of Cambridge , JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Bortolo M Mognetti
- Université libre de Bruxelles (ULB) , Interdisciplinary Center for Nonlinear Phenomena and Complex Systems, Campus Plaine, CP 231, Blvd. du Triomphe, B-1050 Brussels, Belgium
| | - Pietro Cicuta
- Biological and Soft Systems, Cavendish Laboratory, University of Cambridge , JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Lorenzo Di Michele
- Biological and Soft Systems, Cavendish Laboratory, University of Cambridge , JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
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24
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Pontani LL, Jorjadze I, Brujic J. Cis and Trans Cooperativity of E-Cadherin Mediates Adhesion in Biomimetic Lipid Droplets. Biophys J 2016; 110:391-399. [PMID: 26789762 DOI: 10.1016/j.bpj.2015.11.3514] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 10/30/2015] [Accepted: 11/25/2015] [Indexed: 11/29/2022] Open
Abstract
The regulation of cell-cell adhesion is important in cell motility, tissue growth, and for the mechanical integrity of tissues. Although the role of active cytoskeleton dynamics in regulating cadherin interactions is crucial in vivo, here we present a biomimetic emulsion system to characterize the passive E-cadherin-mediated adhesion between droplets. The visualization of a three-dimensional assembly of lipid droplets, functionalized with extracellular E-cadherin domains, reveals a hierarchy of homophilic interactions. First, the high interfacial tension of droplets facilitates trans cadherin-cadherin adhesion, which is strong enough to stabilize looser than random close packing configurations. Second, fluorescence enhancement shows that adding clustering agents, such as calcium or chelating ligands, favor the lateral cis adhesion of the already bound cadherin pairs over the clustering of monomer cadherin on the surface. Finally, above a threshold cadherin and calcium concentration, the cis and trans protein interactions become strong enough to trigger and promote droplet fusion. While E-cadherin is not known to participate in cellular fusion, this mechanism is general because replacing calcium with cholesterol to cluster the cadherin-carrying lipids also promotes fusion. These results suggest that passive clustering, via calcium-induced dimerization or membrane ordering, may contribute to the reinforcement of cell-cell contacts. Alternatively, a molecular switch for fusion offers a route to mixing droplet contents and controlling their size in situ.
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Affiliation(s)
- Lea-Laetitia Pontani
- Department of Physics and Center for Soft Matter Research, New York University, New York, New York; Institut des NanoSciences de Paris, UMR 7588, Centre National de la Recherche Scientifique-University Pierre et Marie Curie, University of Paris 6, Paris, France.
| | - Ivane Jorjadze
- Department of Physics and Center for Soft Matter Research, New York University, New York, New York
| | - Jasna Brujic
- Department of Physics and Center for Soft Matter Research, New York University, New York, New York.
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25
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Ge Y, Lin YH, Lautscham LA, Goldmann WH, Fabry B, Naumann CA. N-cadherin-functionalized polymer-tethered multi-bilayer: a cell surface-mimicking substrate to probe cellular mechanosensitivity. SOFT MATTER 2016; 12:8274-8284. [PMID: 27731476 DOI: 10.1039/c6sm01673a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Fate and function of anchorage-dependent cells depend on a variety of environmental cues, including those of mechanical nature. Previous progress in the understanding of cellular mechanosensitivity has been closely linked to the availability of artificial cell substrates of adjustable viscoelasticity, allowing for a direct correlation between substrate stiffness and cell response. Exemplary, polymeric gel substrates with polymer-conjugated cell-substrate linkers provided valuable insight into the role of mechanical signals during cell migration in an extracellular matrix environment. In contrast, less is known about the role of external mechanical signals across cell-cell interfaces, in part, due to the limitations of traditional polymeric substrates to mimic the remarkable dynamics of cell-cell linkages. To overcome this shortcoming, we introduce a cell surface-mimicking cell substrate of adjustable stiffness, which is comprised of a polymer-tethered lipid multi-bilayer stack with N-cadherin linkers. Unlike traditional polymeric cell substrates with polymer-conjugated linkers, this novel artificial cell substrate is able to replicate the dynamic assembly/disassembly of cadherin linkers into linker clusters and the long-range movements of cadherin-based cell-substrate linkages observed at cell-cell interfaces. Moreover, substrate stiffness can be changed by adjusting the number of bilayers in the multi-bilayer stack, thus enabling the analysis of cellular mechanosensitivity in the presence of artificial cell-cell linkages. The presented biomembrane-mimicking cell substrate provides a valuable tool to explore the functional role of mechanical cues from neighboring cells.
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Affiliation(s)
- Y Ge
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University, Indianapolis, 46202 USA.
| | - Y H Lin
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University, Indianapolis, 46202 USA.
| | - L A Lautscham
- Department of Biophysics, University of Erlangen-Nuremberg, Erlangen, 91052, Germany
| | - W H Goldmann
- Department of Biophysics, University of Erlangen-Nuremberg, Erlangen, 91052, Germany
| | - B Fabry
- Department of Biophysics, University of Erlangen-Nuremberg, Erlangen, 91052, Germany
| | - C A Naumann
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University, Indianapolis, 46202 USA.
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26
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Hartel AJW, Glogger M, Jones NG, Abuillan W, Batram C, Hermann A, Fenz SF, Tanaka M, Engstler M. N-glycosylation enables high lateral mobility of GPI-anchored proteins at a molecular crowding threshold. Nat Commun 2016; 7:12870. [PMID: 27641538 PMCID: PMC5031801 DOI: 10.1038/ncomms12870] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 08/09/2016] [Indexed: 01/17/2023] Open
Abstract
The protein density in biological membranes can be extraordinarily high, but the impact of molecular crowding on the diffusion of membrane proteins has not been studied systematically in a natural system. The diversity of the membrane proteome of most cells may preclude systematic studies. African trypanosomes, however, feature a uniform surface coat that is dominated by a single type of variant surface glycoprotein (VSG). Here we study the density-dependence of the diffusion of different glycosylphosphatidylinositol-anchored VSG-types on living cells and in artificial membranes. Our results suggest that a specific molecular crowding threshold (MCT) limits diffusion and hence affects protein function. Obstacles in the form of heterologous proteins compromise the diffusion coefficient and the MCT. The trypanosome VSG-coat operates very close to its MCT. Importantly, our experiments show that N-linked glycans act as molecular insulators that reduce retarding intermolecular interactions allowing membrane proteins to function correctly even when densely packed.
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Affiliation(s)
- Andreas J. W. Hartel
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Marius Glogger
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Nicola G. Jones
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Wasim Abuillan
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, Heidelberg 69120, Germany
| | - Christopher Batram
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Anne Hermann
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Susanne F. Fenz
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
| | - Motomu Tanaka
- Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, Heidelberg 69120, Germany
- Institute for Integrated Cell-Material Science (WPI iCeMS), Kyoto University, Kyoto 606-8501, Japan
| | - Markus Engstler
- Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, Würzburg 97074, Germany
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27
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Biswas KH, Groves JT. A Microbead Supported Membrane-Based Fluorescence Imaging Assay Reveals Intermembrane Receptor-Ligand Complex Dimension with Nanometer Precision. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:6775-6780. [PMID: 27264296 DOI: 10.1021/acs.langmuir.6b01377] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Receptor-ligand complexes spanning a cell-cell interface inevitably establish a preferred intermembrane spacing based on the molecular dimensions and orientation of the complexes. This couples molecular binding events to membrane mechanics and large-scale spatial organization of receptors on the cell surface. Here, we describe a straightforward, epi-fluorescence-based method to precisely determine intermembrane receptor-ligand dimension at adhesions established by receptor-ligand binding between apposed membranes in vitro. Adhesions were reconstituted between planar and silica microbead supported membranes via specific interaction between cognate receptor/ligand pairs (EphA2/EphrinA1 and E-cadherin/anti-E-cadherin antibody). Epi-fluorescence imaging of the ligand enrichment zone in the supported membrane beneath the adhering microbead, combined with a simple geometrical interpretation, proves sufficient to estimate intermembrane receptor-ligand dimension with better than 1 nm precision. An advantage of this assay is that no specialized equipment or imaging methods are required.
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Affiliation(s)
- Kabir H Biswas
- Mechanobiology Institute, National University of Singapore , Singapore 117411, Singapore
| | - Jay T Groves
- Mechanobiology Institute, National University of Singapore , Singapore 117411, Singapore
- Department of Chemistry, University of California , Berkeley, California 94720, United States
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28
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Monzel C, Schmidt D, Seifert U, Smith AS, Merkel R, Sengupta K. Nanometric thermal fluctuations of weakly confined biomembranes measured with microsecond time-resolution. SOFT MATTER 2016; 12:4755-4768. [PMID: 27142463 DOI: 10.1039/c6sm00412a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We probe the bending fluctuations of bio-membranes using highly deflated giant unilamellar vesicles (GUVs) bound to a substrate by a weak potential arising from generic interactions. The substrate is either homogeneous, with GUVs bound only by the weak potential, or is chemically functionalized with a micro-pattern of very strong specific binders. In both cases, the weakly adhered membrane is seen to be confined at a well-defined distance above the surface while it continues to fluctuate strongly. We quantify the fluctuations of the weakly confined membrane at the substrate proximal surface as well as of the free membrane at the distal surface of the same GUV. This strategy enables us to probe in detail the damping of fluctuations in the presence of the substrate, and to independently measure the membrane tension and the strength of the generic interaction potential. Measurements were done using two complementary techniques - dynamic optical displacement spectroscopy (DODS, resolution: 20 nm, 10 μs), and dual wavelength reflection interference contrast microscopy (DW-RICM, resolution: 4 nm, 50 ms). After accounting for the spatio-temporal resolution of the techniques, an excellent agreement between the two measurements was obtained. For both weakly confined systems we explore in detail the link between fluctuations on the one hand and membrane tension and the interaction potential on the other hand.
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Affiliation(s)
- Cornelia Monzel
- Aix-Marseille Université, CNRS UMR 7325 (Centre Interdisciplinaire de Nanosciences de Marseille - CINaM), Marseille Cedex 9, France. and Institute of Complex Systems 7 (ICS-7), Forschungszentrum Jülich, Jülich, Germany
| | - Daniel Schmidt
- II. Institut für Theoretische Physik, Universität Stuttgart, Germany and Institut für Theoretische Physik, Friedrich Alexander Universität Erlangen-Nürnberg, Germany
| | - Udo Seifert
- II. Institut für Theoretische Physik, Universität Stuttgart, Germany
| | - Ana-Sunčana Smith
- Institut für Theoretische Physik, Friedrich Alexander Universität Erlangen-Nürnberg, Germany and Division of Physical Chemistry, Ruđer Bošković Institute, 10000 Zagreb, Croatia
| | - Rudolf Merkel
- Institute of Complex Systems 7 (ICS-7), Forschungszentrum Jülich, Jülich, Germany
| | - Kheya Sengupta
- Aix-Marseille Université, CNRS UMR 7325 (Centre Interdisciplinaire de Nanosciences de Marseille - CINaM), Marseille Cedex 9, France.
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E-cadherin junction formation involves an active kinetic nucleation process. Proc Natl Acad Sci U S A 2015; 112:10932-7. [PMID: 26290581 DOI: 10.1073/pnas.1513775112] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Epithelial (E)-cadherin-mediated cell-cell junctions play important roles in the development and maintenance of tissue structure in multicellular organisms. E-cadherin adhesion is thus a key element of the cellular microenvironment that provides both mechanical and biochemical signaling inputs. Here, we report in vitro reconstitution of junction-like structures between native E-cadherin in living cells and the extracellular domain of E-cadherin (E-cad-ECD) in a supported membrane. Junction formation in this hybrid live cell-supported membrane configuration requires both active processes within the living cell and a supported membrane with low E-cad-ECD mobility. The hybrid junctions recruit α-catenin and exhibit remodeled cortical actin. Observations suggest that the initial stages of junction formation in this hybrid system depend on the trans but not the cis interactions between E-cadherin molecules, and proceed via a nucleation process in which protrusion and retraction of filopodia play a key role.
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Gordon VD, O'Halloran TJ, Shindell O. Membrane adhesion and the formation of heterogeneities: biology, biophysics, and biotechnology. Phys Chem Chem Phys 2015; 17:15522-33. [PMID: 25866854 PMCID: PMC4465551 DOI: 10.1039/c4cp05876c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Membrane adhesion is essential to many vital biological processes. Sites of membrane adhesion are often associated with heterogeneities in the lipid and protein composition of the membrane. These heterogeneities are thought to play functional roles by facilitating interactions between proteins. However, the causal links between membrane adhesion and membrane heterogeneities are not known. Here we survey the state of the field and indicate what we think are understudied areas ripe for development.
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Affiliation(s)
- V D Gordon
- The University of Texas at Austin, Department of Physics and Center for Nonlinear Dynamics, 2515 Speedway, Stop C1610, Austin, Texas 78712-1199, USA.
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Schmidt D, Bihr T, Fenz S, Merkel R, Seifert U, Sengupta K, Smith AS. Crowding of receptors induces ring-like adhesions in model membranes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2984-91. [PMID: 26028591 DOI: 10.1016/j.bbamcr.2015.05.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 05/21/2015] [Accepted: 05/22/2015] [Indexed: 10/23/2022]
Abstract
The dynamics of formation of macromolecular structures in adherent membranes is a key to a number of cellular processes. However, the interplay between protein reaction kinetics, diffusion and the morphology of the growing domains, governed by membrane mediated interactions, is still poorly understood. Here we show, experimentally and in simulations, that a rich phase diagram emerges from the competition between binding, cooperativity, molecular crowding and membrane spreading. In the cellular context, the spontaneously-occurring organization of adhesion domains in ring-like morphologies is particularly interesting. These are stabilized by the crowding of bulky proteins, and the membrane-transmitted correlations between bonds. Depending on the density of the receptors, this phase may be circumvented, and instead, the adhesions may grow homogeneously in the contact zone between two membranes. If the development of adhesion occurs simultaneously with membrane spreading, much higher accumulation of binders can be achieved depending on the velocity of spreading. The mechanisms identified here, in the context of our mimetic model, may shed light on the structuring of adhesions in the contact zones between two living cells. This article is part of a Special Issue entitled: Mechanobiology.
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Affiliation(s)
- Daniel Schmidt
- Institut für Theoretische Physik and Cluster of Excellence: Engineering of Advanced Materials, Friedrich Alexander Universität Erlangen-Nürnberg, 91052 Erlangen, Germany; II. Institut für Theoretische Physik, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Timo Bihr
- Institut für Theoretische Physik and Cluster of Excellence: Engineering of Advanced Materials, Friedrich Alexander Universität Erlangen-Nürnberg, 91052 Erlangen, Germany; II. Institut für Theoretische Physik, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Susanne Fenz
- Institute of Complex Systems 7: Biomechanics, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany; Lehrstuhl für Zell- und Entwicklungsbiologie (Zoologie I), Biozentrum der Universität Würzburg, 97074 Würzburg, Germany
| | - Rudolf Merkel
- Institute of Complex Systems 7: Biomechanics, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Udo Seifert
- II. Institut für Theoretische Physik, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Kheya Sengupta
- Aix-Marseille Université, CNRS, CINaM UMR 7325, 13288 Marseille, France
| | - Ana-Sunčana Smith
- Institut für Theoretische Physik and Cluster of Excellence: Engineering of Advanced Materials, Friedrich Alexander Universität Erlangen-Nürnberg, 91052 Erlangen, Germany; Insitut Ruđer Bošković, 10000 Zagreb, Croatia.
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Shindell O, Mica N, Ritzer M, Gordon VD. Specific adhesion of membranes simultaneously supports dual heterogeneities in lipids and proteins. Phys Chem Chem Phys 2015; 17:15598-607. [DOI: 10.1039/c4cp05877a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Membrane adhesion mediated by one protein species simultaneously stabilizes both ordered-phase and disordered-phase heterogeneities, distinct from the non-adhered membrane.
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Affiliation(s)
- O. Shindell
- The University of Texas at Austin
- Department of Physics and Center for Nonlinear Dynamics
- Austin
- USA
| | - N. Mica
- The University of Texas at Austin
- Department of Physics and Center for Nonlinear Dynamics
- Austin
- USA
| | - M. Ritzer
- The University of Texas at Austin
- Department of Physics and Center for Nonlinear Dynamics
- Austin
- USA
| | - V. D. Gordon
- The University of Texas at Austin
- Department of Physics and Center for Nonlinear Dynamics
- Austin
- USA
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33
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Ligand-mediated friction determines morphodynamics of spreading T cells. Biophys J 2014; 107:2629-38. [PMID: 25468342 DOI: 10.1016/j.bpj.2014.10.044] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 10/03/2014] [Accepted: 10/28/2014] [Indexed: 11/22/2022] Open
Abstract
Spreading of T cells on antigen presenting cells is a crucial initial step in immune response. Spreading occurs through rapid morphological changes concomitant with the reorganization of surface receptors and of the cytoskeleton. Ligand mobility and frictional coupling of receptors to the cytoskeleton were separately recognized as important factors but a systematic study to explore their biophysical role in spreading was hitherto missing. To explore the impact of ligand mobility, we prepared chemically identical substrates on which molecules of anti-CD3 (capable of binding and activating the T cell receptor complex), were either immobilized or able to diffuse. We quantified the T cell spreading area and cell edge dynamics using quantitative reflection interference contrast microscopy, and imaged the actin distribution. On mobile ligands, as compared to fixed ligands, the cells spread much less, the actin is centrally, rather than peripherally distributed and the edge dynamics is largely altered. Blocking myosin-II or adding molecules of ICAM1 on the substrate largely abrogates these differences. We explain these observations by building a model based on the balance of forces between activation-dependent actin polymerization and actomyosin-generated tension on one hand, and on the frictional coupling of the ligand-receptor complexes with the actin cytoskeleton, the membrane and the substrate, on the other hand. Introducing the measured edge velocities in the model, we estimate the coefficient of frictional coupling between T Cell receptors or LFA-1 and the actin cytoskeleton. Our results provide for the first time, to our knowledge, a quantitative framework bridging T cell-specific biology with concepts developed for integrin-based mechanisms of spreading.
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Cell-sized liposomes reveal how actomyosin cortical tension drives shape change. Proc Natl Acad Sci U S A 2013; 110:16456-61. [PMID: 24065829 DOI: 10.1073/pnas.1221524110] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Animal cells actively generate contractile stress in the actin cortex, a thin actin network beneath the cell membrane, to facilitate shape changes during processes like cytokinesis and motility. On the microscopic scale, this stress is generated by myosin molecular motors, which bind to actin cytoskeletal filaments and use chemical energy to exert pulling forces. To decipher the physical basis for the regulation of cell shape changes, here, we use a cell-like system with a cortex anchored to the outside or inside of a liposome membrane. This system enables us to dissect the interplay between motor pulling forces, cortex-membrane anchoring, and network connectivity. We show that cortices on the outside of liposomes either spontaneously rupture and relax built-up mechanical stress by peeling away around the liposome or actively compress and crush the liposome. The decision between peeling and crushing depends on the cortical tension determined by the amount of motors and also on the connectivity of the cortex and its attachment to the membrane. Membrane anchoring strongly affects the morphology of cortex contraction inside liposomes: cortices contract inward when weakly attached, whereas they contract toward the membrane when strongly attached. We propose a physical model based on a balance of active tension and mechanical resistance to rupture. Our findings show how membrane attachment and network connectivity are able to regulate actin cortex remodeling and membrane-shape changes for cell polarization.
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35
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Höfling F, Franosch T. Anomalous transport in the crowded world of biological cells. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2013; 76:046602. [PMID: 23481518 DOI: 10.1088/0034-4885/76/4/046602] [Citation(s) in RCA: 580] [Impact Index Per Article: 52.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
A ubiquitous observation in cell biology is that the diffusive motion of macromolecules and organelles is anomalous, and a description simply based on the conventional diffusion equation with diffusion constants measured in dilute solution fails. This is commonly attributed to macromolecular crowding in the interior of cells and in cellular membranes, summarizing their densely packed and heterogeneous structures. The most familiar phenomenon is a sublinear, power-law increase of the mean-square displacement (MSD) as a function of the lag time, but there are other manifestations like strongly reduced and time-dependent diffusion coefficients, persistent correlations in time, non-Gaussian distributions of spatial displacements, heterogeneous diffusion and a fraction of immobile particles. After a general introduction to the statistical description of slow, anomalous transport, we summarize some widely used theoretical models: Gaussian models like fractional Brownian motion and Langevin equations for visco-elastic media, the continuous-time random walk model, and the Lorentz model describing obstructed transport in a heterogeneous environment. Particular emphasis is put on the spatio-temporal properties of the transport in terms of two-point correlation functions, dynamic scaling behaviour, and how the models are distinguished by their propagators even if the MSDs are identical. Then, we review the theory underlying commonly applied experimental techniques in the presence of anomalous transport like single-particle tracking, fluorescence correlation spectroscopy (FCS) and fluorescence recovery after photobleaching (FRAP). We report on the large body of recent experimental evidence for anomalous transport in crowded biological media: in cyto- and nucleoplasm as well as in cellular membranes, complemented by in vitro experiments where a variety of model systems mimic physiological crowding conditions. Finally, computer simulations are discussed which play an important role in testing the theoretical models and corroborating the experimental findings. The review is completed by a synthesis of the theoretical and experimental progress identifying open questions for future investigation.
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Affiliation(s)
- Felix Höfling
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, and Institut für Theoretische Physik IV, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
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36
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Abstract
Tremendous progress has been made in recent years in understanding the working of the living cell, including its micro-anatomy, signalling networks, and regulation of genes. However, an understanding of cellular phenomena using fundamental laws starting from first principles is still very far away. Part of the reason is that a cell is an active and exquisitely complex system where every part is linked to the other. Thus, it is difficult or even impossible to design experiments that selectively and exclusively probe a chosen aspect of the cell. Various kinds of idealised systems and cell models have been used to circumvent this problem. An important example is a giant unilamellar vesicle (GUV, also called giant liposome), which provides a cell-sized confined volume to study biochemical reactions as well as self-assembly processes that occur on the membrane. The GUV membrane can be designed suitably to present selected, correctly-oriented cell-membrane proteins, whose mobility is confined to two dimensions. Here, we present recent advances in GUV design and the use of GUVs as cell models that enable quantitative testing leading to insight into the working of real cells. We briefly recapitulate important classical concepts in membrane biophysics emphasising the advantages and limitations of GUVs. We then present results obtained over the last decades using GUVs, choosing the formation of membrane domains and cell adhesion as examples for in-depth treatment. Insight into cell adhesion obtained using micro-interferometry is treated in detail. We conclude by summarising the open questions and possible future directions.
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Affiliation(s)
- Susanne F Fenz
- Leiden Institute of Physics: Physics of Life Processes, Leiden University, The Netherlands
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37
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Feracci H, Gutierrez BS, Hempel W, Gil IS. Organic Nanoparticles. NANOBIOTECHNOLOGY - INORGANIC NANOPARTICLES VS ORGANIC NANOPARTICLES 2012. [DOI: 10.1016/b978-0-12-415769-9.00008-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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38
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Dumas C, El Zein R, Dallaporta H, Charrier AM. Autonomic self-healing lipid monolayer: a new class of ultrathin dielectric. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:13643-7. [PMID: 21967619 DOI: 10.1021/la202333n] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The electrical performance of stabilized lipid monolayers on H-terminated silicon is reported for the first time. We show that these 2.7 nm thick only ultrathin layers present extremely low current leakage at high electric field and high breakdown voltage that both compare favorably with the best data reported on organic thin film dielectrics. We demonstrate a very unique property of autonomic self-healing of the layer at room temperature with the total recovery of its performance after electrical breakdown. The mechanisms involved in breakdown and self-healing are described.
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Affiliation(s)
- Carine Dumas
- Centre Interdisciplinaire de Nanoscience de Marseille, CINaM, UPR CNRS 3118, Aix-Marseille Université, Campus de Luminy, Case 913, 13288 Marseille Cedex 9, France
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39
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Fenz SF, Bihr T, Merkel R, Seifert U, Sengupta K, Smith AS. Switching from ultraweak to strong adhesion. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2011; 23:2622-6. [PMID: 21495083 DOI: 10.1002/adma.201004097] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Indexed: 05/13/2023]
Affiliation(s)
- Susanne F Fenz
- Institute of Complex Systems 7: Biomechanics Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
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40
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Dieluweit S, Csiszár A, Rubner W, Fleischhauer J, Houben S, Merkel R. Mechanical properties of bare and protein-coated giant unilamellar phospholipid vesicles. A comparative study of micropipet aspiration and atomic force microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:11041-11049. [PMID: 20355933 DOI: 10.1021/la1005242] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
In this study, protein-coated giant phospholipid vesicles were used to model cell plasma membranes coated by surface protein layers that increase membrane stiffness under mechanical or osmotic stress. These changed mechanical properties like bending stiffness, membrane area compressibility modulus, and effective Young's modulus were determined by micropipet aspiration, while bending stiffness, effective Young's modulus, and effective spring constant of vesicles were analyzed by AFM. The experimental setups, the applied models, and the results using both methods were compared here. As demonstrated before, we found that bare vesicles were best probed by micropipet aspiration due to its high sensitivity. The mechanical properties of vesicles with protein surface layers were, however, better determined by AFM because it enables very local deformations of the membrane with barely any structural damage to the protein layer. Mechanical properties of different species of coating proteins, here streptavidin and avidin, could be clearly distinguished using this technique.
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Affiliation(s)
- Sabine Dieluweit
- Institute of Bio- and Nanosystems, Biomechanics (IBN-4), Research Centre Juelich, Germany
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Csiszár A, Hersch N, Dieluweit S, Biehl R, Merkel R, Hoffmann B. Novel Fusogenic Liposomes for Fluorescent Cell Labeling and Membrane Modification. Bioconjug Chem 2010; 21:537-43. [DOI: 10.1021/bc900470y] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Agnes Csiszár
- Institute of Bio- and Nanosystems, IBN-4, Biomechanics, and Institute of Solid State Research, IFF-5, Neutron Scattering, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Nils Hersch
- Institute of Bio- and Nanosystems, IBN-4, Biomechanics, and Institute of Solid State Research, IFF-5, Neutron Scattering, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Sabine Dieluweit
- Institute of Bio- and Nanosystems, IBN-4, Biomechanics, and Institute of Solid State Research, IFF-5, Neutron Scattering, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Ralf Biehl
- Institute of Bio- and Nanosystems, IBN-4, Biomechanics, and Institute of Solid State Research, IFF-5, Neutron Scattering, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Rudolf Merkel
- Institute of Bio- and Nanosystems, IBN-4, Biomechanics, and Institute of Solid State Research, IFF-5, Neutron Scattering, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Bernd Hoffmann
- Institute of Bio- and Nanosystems, IBN-4, Biomechanics, and Institute of Solid State Research, IFF-5, Neutron Scattering, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
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Monzel C, Fenz SF, Merkel R, Sengupta K. Probing biomembrane dynamics by dual-wavelength reflection interference contrast microscopy. Chemphyschem 2010; 10:2828-38. [PMID: 19821476 DOI: 10.1002/cphc.200900645] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We present an improved analysis of reflection interference contrast microscopy (RICM) images, recorded to investigate model membrane systems that mimic cell adhesion. The model systems were giant unilamellar vesicles (GUV) adhering via specific ligand-receptor interactions to supported lipid bilayers (SLB) or to patterns of receptors. Conventional RICM and dual-wavelength RICM (DW-RICM) were applied to measure absolute optical distances between the biomembranes and planar substrates. We developed algorithms for a straightforward implementation of an automated, time-resolved reconstruction of the membrane conformations from RICM/DW-RICM images, taking into account all the interfaces in the system and blurring of the data due to camera noise. Finally, we demonstrate the validity and usefulness of this new approach by analyzing the topography and fluctuations of a bound membrane in the steady state and its dynamic adaptation to osmotic pressure changes. These measurements clearly show that macroscopic membrane flow through tightly adhered area is possible in our system.
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Affiliation(s)
- Cornelia Monzel
- Institute of Bio- and Nanosystems 4 (IBN 4), Research Centre Jülich, Wilhelm-Johnen-Strasse, 52425 Jülich, Germany
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43
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Limozin L, Sengupta K. Quantitative reflection interference contrast microscopy (RICM) in soft matter and cell adhesion. Chemphyschem 2010; 10:2752-68. [PMID: 19816893 DOI: 10.1002/cphc.200900601] [Citation(s) in RCA: 146] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Adhesion can be quantified by measuring the distance between the interacting surfaces. Reflection interference contrast microscopy (RICM), with its ability to measure inter-surface distances under water with nanometric precision and milliseconds time resolution, is ideally suited to studying the dynamics of adhesion in soft systems. Recent technical developments, which include innovative image analysis and the use of multi-coloured illumination, have led to renewed interest in this technique. Unambiguous quantitative measurements have been achieved for colloidal beads and model membranes, thus revealing new insights and applications. Quantification of data from cells shows exciting prospects. Herein, we review the basic principles and recent developments of RICM applied to studies of dynamical adhesion processes in soft matter and cell biology and provide practical hints to potential users.
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Affiliation(s)
- Laurent Limozin
- Adhesion and Inflammation, CNRS UMR 6212, Inserm U600, Aix-Marseille University, Luminy, Marseille, France.
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