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Heidari M, Gaichies T, Leibler L, Labousse M. Polymer time crystal: Mechanical activation of reversible bonds by low-amplitude high frequency excitations. SCIENCE ADVANCES 2024; 10:eadn6107. [PMID: 38781335 PMCID: PMC11114238 DOI: 10.1126/sciadv.adn6107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 04/17/2024] [Indexed: 05/25/2024]
Abstract
Reversible supramolecular bonds play an important role in materials science and in biological systems. The equilibrium between open and closed bonds and the association rate can be controlled thermally, chemically, by mechanical pulling, by ultrasound, or by catalysts. In practice, these intrinsic equilibrium methods either suffer from a limited range of tunability or may damage the material. Here, we present a nonequilibrium strategy that exploits the dissipative properties of the system to control and change the dynamic properties of sacrificial and reversible networks. We show theoretically and numerically how high-frequency mechanical oscillations of very low amplitude can open or close bonds. This mechanism indicates how reversible bonds could alleviate mechanical fatigue of materials especially at low temperatures where they are fragile. In another area, it suggests that the system can be actively modified by the application of ultrasound to induce gel-fluid transitions and to activate or deactivate adhesion properties.
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Affiliation(s)
- Maziar Heidari
- Gulliver, CNRS, ESPCI Paris, Université PSL, 75005 Paris, France
| | - Théophile Gaichies
- Gulliver, CNRS, ESPCI Paris, Université PSL, 75005 Paris, France
- Département de chimie, École normale supérieure, Université PSL, 75005 Paris, France
| | - Ludwik Leibler
- Gulliver, CNRS, ESPCI Paris, Université PSL, 75005 Paris, France
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2
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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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3
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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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4
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Janeš JA, Stumpf H, Schmidt D, Seifert U, Smith AS. Statistical Mechanics of an Elastically Pinned Membrane: Static Profile and Correlations. Biophys J 2018; 116:283-295. [PMID: 30598285 DOI: 10.1016/j.bpj.2018.12.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 11/22/2018] [Accepted: 12/03/2018] [Indexed: 12/13/2022] Open
Abstract
The relation between thermal fluctuations and the mechanical response of a free membrane has been explored in great detail, both theoretically and experimentally. However, understanding this relationship for membranes locally pinned by proteins is significantly more challenging. Given that the coupling of the membrane to the cell cytoskeleton, to the extracellular matrix, and to other internal structures is crucial for the regulation of a number of cellular processes, understanding the role of the pinning is of great interest. In this manuscript, we consider a single protein (elastic spring of a finite rest length) pinning a membrane modeled in the Monge gauge. First, we determine the Green's function for the system and complement this approach by the calculation of the mode-coupling coefficients for the plane wave expansion and the orthonormal fluctuation modes, in turn building a set of tools for numerical and analytic studies of a pinned membrane. Furthermore, we explore static correlations of the free and the pinned membrane, as well as the membrane shape, showing that all three are mutually interdependent and have an identical long-range behavior characterized by the correlation length. Interestingly, the latter displays a nonmonotonic behavior as a function of membrane tension. Importantly, exploiting these relations allows for the experimental determination of the elastic parameters of the pinning. Last but not least, we calculate the interaction potential between two pinning sites and show that even in the absence of the membrane deformation, the pinnings will be subject to an attractive force because of changes in membrane fluctuations.
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Affiliation(s)
- Josip Augustin Janeš
- PULS Group, Institut für Theoretische Physik and Cluster of Excellence, Engineering of Advanced Materials, Friedrich Alexander Universität Erlangen-Nürnberg, Erlangen, Germany; Institut Ruđer Bošković, Zagreb, Croatia
| | - Henning Stumpf
- PULS Group, Institut für Theoretische Physik and Cluster of Excellence, Engineering of Advanced Materials, Friedrich Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Daniel Schmidt
- PULS Group, Institut für Theoretische Physik and Cluster of Excellence, Engineering of Advanced Materials, Friedrich Alexander Universität Erlangen-Nürnberg, Erlangen, Germany; II. Institut für Theoretische Physik, Universität Stuttgart, Stuttgart, Germany
| | - Udo Seifert
- II. Institut für Theoretische Physik, Universität Stuttgart, Stuttgart, Germany
| | - Ana-Sunčana Smith
- PULS Group, Institut für Theoretische Physik and Cluster of Excellence, Engineering of Advanced Materials, Friedrich Alexander Universität Erlangen-Nürnberg, Erlangen, Germany; Institut Ruđer Bošković, Zagreb, Croatia.
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5
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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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6
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Nabavi SS, Hartmann MA. Weak reversible cross links may decrease the strength of aligned fiber bundles. SOFT MATTER 2016; 12:2047-2055. [PMID: 26750612 DOI: 10.1039/c5sm02614h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Reversible cross-linking is an effective strategy to specifically tailor the mechanical properties of polymeric materials that can be found in a variety of biological as well as man-made materials. Using a simple model in this paper the influence of weak, reversible cross-links on the mechanical properties of aligned fiber bundles is investigated. Special emphasis in this analysis is put on the strength of the investigated structures. Using Monte Carlo methods two topologies of cross-links exceeding the strength of the covalent backbone are studied. Most surprisingly only two cross-links are sufficient to break the backbone of a multi chain system, resulting in a reduced strength of the material. The found effect crucially depends on the ratio of inter- to intra-chain cross-links and, thus, on the grafting density that determines this ratio.
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Affiliation(s)
- S Soran Nabavi
- Institute of Physics, Montanuniversitaet Leoben, Franz-Josef Strasse 18, 8700 Leoben, Austria.
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7
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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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van der Meulen SAJ, Helms G, Dogterom M. Solid colloids with surface-mobile linkers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:233101. [PMID: 25993272 DOI: 10.1088/0953-8984/27/23/233101] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In this report we review the possibilities of using colloids with surface mobile linkers for the study of colloidal self-assembly processes. A promising route to create systems with mobile linkers is the use of lipid (bi-)layers. These lipid layers can be either used in the form of vesicles or as coatings for hard colloids and emulsion droplets. Inside the lipid bilayers molecules can be inserted via membrane anchors. Due to the fluidity of the lipid bilayer, the anchored molecules remain mobile. The use of different lipid mixtures even allows creating Janus-like particles that exhibit directional bonding if linkers are used which have a preference for a certain lipid phase. In nature mobile linkers can be found e.g. as receptors in cells. Therefore, towards the end of the review, we also briefly address the possibility of using colloids with surface mobile linkers as model systems to mimic cell-cell interactions and cell adhesion processes.
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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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10
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Bihr T, Fenz S, Sackmann E, Merkel R, Seifert U, Sengupta K, Smith AS. Association rates of membrane-coupled cell adhesion molecules. Biophys J 2014; 107:L33-6. [PMID: 25468354 PMCID: PMC4255260 DOI: 10.1016/j.bpj.2014.10.033] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 10/13/2014] [Accepted: 10/24/2014] [Indexed: 11/20/2022] Open
Abstract
Thus far, understanding how the confined cellular environment affects the lifetime of bonds, as well as the extraction of complexation rates, has been a major challenge in studies of cell adhesion. Based on a theoretical description of the growth curves of adhesion domains, we present a new (to our knowledge) method to measure the association rate k(on) of ligand-receptor pairs incorporated into lipid membranes. As a proof of principle, we apply this method to several systems. We find that the k(on) for the interaction of biotin with neutravidin is larger than that for integrin binding to RGD or sialyl Lewis(x) to E-selectin. Furthermore, we find k(on) to be enhanced by membrane fluctuations that increase the probability for encounters between the binders. The opposite effect on k(on) could be attributed to the presence of repulsive polymers that mimic the glycocalyx, which points to two potential mechanisms for controlling the speed of protein complexation during the cell recognition process.
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Affiliation(s)
- Timo Bihr
- Institut für Theoretische Physik and Cluster of Excellence Engineering of Advanced Materials, Friedrich-Alexander-Universität, Erlangen, Germany; II. Institut für Theoretische Physik, Universität Stuttgart, Stuttgart, Germany
| | - Susanne Fenz
- Institute of Complex Systems 7: Biomechanics Forschungszentrum Jülich, Jülich, Germany; Department of Cell and Developmental Biology, Theodor-Boveri-Institute, Universität Würzburg, Würzburg, Germany
| | - Erich Sackmann
- Physics Department, Biophysics E22, Technische Universität München, München, Germany
| | - Rudolf Merkel
- Institute of Complex Systems 7: Biomechanics Forschungszentrum Jülich, Jülich, Germany
| | - Udo Seifert
- II. Institut für Theoretische Physik, Universität Stuttgart, Stuttgart, Germany
| | - Kheya Sengupta
- Aix-Marseille Université, CNRS, CINaM UMR 7325, Marseille, France
| | - Ana-Sunčana Smith
- Institut für Theoretische Physik and Cluster of Excellence Engineering of Advanced Materials, Friedrich-Alexander-Universität, Erlangen, Germany; Institute Ruđer Bošković, Division of Physical Chemistry, Zagreb, Croatia.
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11
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Sackmann E, Smith AS. Physics of cell adhesion: some lessons from cell-mimetic systems. SOFT MATTER 2014; 10:1644-59. [PMID: 24651316 PMCID: PMC4028615 DOI: 10.1039/c3sm51910d] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Cell adhesion is a paradigm of the ubiquitous interplay of cell signalling, modulation of material properties and biological functions of cells. It is controlled by competition of short range attractive forces, medium range repellant forces and the elastic stresses associated with local and global deformation of the composite cell envelopes. We review the basic physical rules governing the physics of cell adhesion learned by studying cell-mimetic systems and demonstrate the importance of these rules in the context of cellular systems. We review how adhesion induced micro-domains couple to the intracellular actin and microtubule networks allowing cells to generate strong forces with a minimum of attractive cell adhesion molecules (CAMs) and to manipulate other cells through filopodia over micrometer distances. The adhesion strength can be adapted to external force fluctuations within seconds by varying the density of attractive and repellant CAMs through exocytosis and endocytosis or protease-mediated dismantling of the CAM-cytoskeleton link. Adhesion domains form local end global biochemical reaction centres enabling the control of enzymes. Actin-microtubule crosstalk at adhesion foci facilitates the mechanical stabilization of polarized cell shapes. Axon growth in tissue is guided by attractive and repulsive clues controlled by antagonistic signalling pathways.
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Affiliation(s)
- Erich Sackmann
- Physics Department Technical University Munich, Germany
- Department of Physics, Ludwig-Maximillian University, Munich, Germany
| | - Ana-Sunčana Smith
- Institute for Theoretical Physics, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany
- Institute Rud̷er Bošković, Zagreb, Croatia.
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12
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Kunze A, Bally M, Höök F, Larson G. Equilibrium-fluctuation-analysis of single liposome binding events reveals how cholesterol and Ca2+ modulate glycosphingolipid trans-interactions. Sci Rep 2013; 3:1452. [PMID: 23486243 PMCID: PMC3596795 DOI: 10.1038/srep01452] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Accepted: 03/01/2013] [Indexed: 12/18/2022] Open
Abstract
Carbohydrate-carbohydrate interactions (CCIs) are of central importance for several biological processes. However, the ultra-weak nature of CCIs generates difficulties in studying this interaction, thus only little is known about CCIs. Here we present a highly sensitive equilibrium-fluctuation-analysis of single liposome binding events to supported lipid bilayers (SLBs) based on total internal reflection fluorescence (TIRF) microscopy that allows us to determine apparent kinetic rate constants of CCIs. The liposomes and SLBs both contained natural Le(x) glycosphingolipids (Galβ4(Fucα3)GlcNAcβ3Galβ4Glcβ1Cer), which were employed to mimic cell-cell contacts. The kinetic parameters of the self-interaction between Le(x)-containing liposomes and SLBs were measured and found to be modulated by bivalent cations. Even more interestingly, upon addition of cholesterol, the strength of the CCIs increases, suggesting that this interaction is strongly influenced by a cholesterol-dependent presentation and/or spatial organization of glycosphingolipids in cell membranes.
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Affiliation(s)
- Angelika Kunze
- Department of Clinical Chemistry and Transfusion Medicine, Sahlgrenska Academy, University of Gothenburg, SE-413 45 Göteborg, Sweden
| | - Marta Bally
- Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
| | - Fredrik Höök
- Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
| | - Göran Larson
- Department of Clinical Chemistry and Transfusion Medicine, Sahlgrenska Academy, University of Gothenburg, SE-413 45 Göteborg, Sweden
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13
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Investigating cell-ECM contact changes in response to hypoosmotic stimulation of hepatocytes in vivo with DW-RICM. PLoS One 2012; 7:e48100. [PMID: 23110181 PMCID: PMC3482193 DOI: 10.1371/journal.pone.0048100] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 09/20/2012] [Indexed: 11/19/2022] Open
Abstract
Hepatocyte volume regulation has been shown to play an important role in cellular metabolism, proliferation, viability and especially in hepatic functions such as bile formation and proteolysis. Recent studies on liver explants led to the assumption that cell volume changes present a trigger for outside-in signaling via integrins, a protein family involved in mediating cellular response to binding to the extracellular matrix (ECM). However, it remains elusive how these volume change related signaling events are transducted on a single cell level and how these events are influenced and controlled by ECM interactions. One could speculate that an increase in cell volume leads to an increase in integrin/ECM contacts which causes activation of integrins, which act as mechano-sensors. In order to test this idea, it was an important issue to quantify the cell volume-dependence of the contact areas between the cell and the surrounding ECM. In this study we used two wavelength reflection interference contrast microscopy (DW-RICM) to directly observe the dynamics of cell-substrate contacts, mimicking cell-ECM interactions, in response to a controlled and well-defined volume change induced by hypoosmotic stimulation. This is the first time a non-invasive, label-free method is used to uncover a volume change related response of in vitro hepatocytes in real time. The cell cluster analysis we present here agrees well with previous studies on ex vivo whole liver explants. Moreover, we show that the increase in contact area after cell swelling is a reversible process, while the reorganisation of contacts depends on the type of ECM molecules presented to the cells. As our method complements common whole liver studies providing additional insight on a cell cluster level, we expect this technique to be particular suitable for further detailed studies of osmotic stimulation not only in hepatocytes, but also other cell types.
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14
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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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15
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Lorenz B, de Cienfuegos LÁ, Oelkers M, Kriemen E, Brand C, Stephan M, Sunnick E, Yüksel D, Kalsani V, Kumar K, Werz DB, Janshoff A. Model system for cell adhesion mediated by weak carbohydrate-carbohydrate interactions. J Am Chem Soc 2012; 134:3326-9. [PMID: 22296574 PMCID: PMC3288207 DOI: 10.1021/ja210304j] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The multivalent carbohydrate-carbohydrate interaction between membrane-anchored epitopes derived from the marine sponge Microciona prolifera has been explored by colloidal probe microscopy. An in situ coupling of sulfated and non-sulfated disaccharides to membrane-coated surfaces was employed to mimic native cell-cell contacts.The dynamic strength of the homomeric self-association was measured as a function of calcium ions and loading rate. A deterministic model was used to estimate the basic energy landscape and number of participating bonds in the contact zone.
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Affiliation(s)
- Bärbel Lorenz
- Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
| | | | - Marieelen Oelkers
- Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
| | - Ella Kriemen
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany
| | - Christian Brand
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany
| | - Milena Stephan
- Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
| | - Eva Sunnick
- Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
| | - Deniz Yüksel
- Department of Chemistry, Pearson Chemistry Laboratory, 62 Talbot Avenue, Tufts University, 62 Talbot Avenue, Medford, MA 02155
| | - Venkateshwarlu Kalsani
- Department of Chemistry, Pearson Chemistry Laboratory, 62 Talbot Avenue, Tufts University, 62 Talbot Avenue, Medford, MA 02155
| | - Krishna Kumar
- Department of Chemistry, Pearson Chemistry Laboratory, 62 Talbot Avenue, Tufts University, 62 Talbot Avenue, Medford, MA 02155
| | - Daniel B Werz
- Institute of Organic and Biomolecular Chemistry, University of Göttingen, Tammannstr. 2, 37077 Göttingen, Germany
| | - Andreas Janshoff
- Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
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