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Castaneda N, Feuillie C, Molinari M, Kang EH. Actin Bundle Nanomechanics and Organization Are Modulated by Macromolecular Crowding and Electrostatic Interactions. Front Mol Biosci 2021; 8:760950. [PMID: 34901154 PMCID: PMC8662701 DOI: 10.3389/fmolb.2021.760950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 11/02/2021] [Indexed: 11/21/2022] Open
Abstract
The structural and mechanical properties of actin bundles are essential to eukaryotic cells, aiding in cell motility and mechanical support of the plasma membrane. Bundle formation occurs in crowded intracellular environments composed of various ions and macromolecules. Although the roles of cations and macromolecular crowding in the mechanics and organization of actin bundles have been independently established, how changing both intracellular environmental conditions influence bundle mechanics at the nanoscale has yet to be established. Here we investigate how electrostatics and depletion interactions modulate the relative Young’s modulus and height of actin bundles using atomic force microscopy. Our results demonstrate that cation- and depletion-induced bundles display an overall reduction of relative Young’s modulus depending on either cation or crowding concentrations. Furthermore, we directly measure changes to cation- and depletion-induced bundle height, indicating that bundles experience alterations to filament packing supporting the reduction to relative Young’s modulus. Taken together, our work suggests that electrostatic and depletion interactions may act counteractively, impacting actin bundle nanomechanics and organization.
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Affiliation(s)
- Nicholas Castaneda
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States.,Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, United States
| | - Cecile Feuillie
- Institute of Chemistry and Biology of Membranes and Nano-objects, CBMN CNRS UMR 5248, IPB, Université de Bordeaux, Pessac, France
| | - Michael Molinari
- Institute of Chemistry and Biology of Membranes and Nano-objects, CBMN CNRS UMR 5248, IPB, Université de Bordeaux, Pessac, France
| | - Ellen Hyeran Kang
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States.,Department of Physics, University of Central Florida, Orlando, FL, United States.,Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, United States
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2
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Sonam S, Vigouroux C, Jégou A, Romet-Lemonne G, Clainche CL, Ladoux B, Mège RM. Direct measurement of near-nanoNewton forces developed by self-organizing actomyosin fibres bound α-catenin. Biol Cell 2021; 113:441-449. [PMID: 34287982 DOI: 10.1111/boc.202100014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 06/22/2021] [Accepted: 06/28/2021] [Indexed: 12/01/2022]
Abstract
Actin cytoskeleton contractility plays a critical role in morphogenetic processes by generating forces that are then transmitted to cell-cell and cell-ECM adhesion complexes. In turn, mechanical properties of the environment are sensed and transmitted to the cytoskeleton at cell adhesion sites, influencing cellular processes such as cell migration, differentiation and survival. Anchoring of the actomyosin cytoskeleton to adhesion sites is mediated by adaptor proteins such as talin or α-catenin that link F-actin to transmembrane cell adhesion receptors, thereby allowing mechanical coupling between the intracellular and extracellular compartments. Thus, a key issue is to be able to measure the forces generated by actomyosin and transmitted to the adhesion complexes. Approaches developed in cells and those probing single molecule mechanical properties of α-catenin molecules allowed to identify α-catenin, an F-actin binding protein which binds to the cadherin complexes as a major player in cadherin-based mechanotransduction. However, it is still very difficult to bridge intercellular forces measured at cellular levels and those measured at the single-molecule level. Here, we applied an intermediate approach allowing reconstruction of the actomyosin-α-catenin complex in acellular conditions to probe directly the transmitted forces. For this, we combined micropatterning of purified α-catenin and spontaneous actomyosin network assembly in the presence of G-actin and Myosin II with microforce sensor arrays used so far to measure cell-generated forces. Using this method, we show that self-organizing actomyosin bundles bound to micrometric α-catenin patches can apply near-nanoNewton forces, paving the way for future studies on molecular/cellular mechanotarnsduction and mechanosensing. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Surabhi Sonam
- Université de Paris, CNRS, Institut Jacques Monod, Paris, France
| | - Clémence Vigouroux
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, 91198, France
| | - Antoine Jégou
- Université de Paris, CNRS, Institut Jacques Monod, Paris, France
| | | | - Christophe Le Clainche
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, 91198, France
| | - Benoit Ladoux
- Université de Paris, CNRS, Institut Jacques Monod, Paris, France
| | - René Marc Mège
- Université de Paris, CNRS, Institut Jacques Monod, Paris, France
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3
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Castaneda N, Park J, Kang EH. Regulation of Actin Bundle Mechanics and Structure by Intracellular Environmental Factors. FRONTIERS IN PHYSICS 2021; 9:675885. [PMID: 34422787 PMCID: PMC8376200 DOI: 10.3389/fphy.2021.675885] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The mechanical and structural properties of actin cytoskeleton drive various cellular processes, including structural support of the plasma membrane and cellular motility. Actin monomers assemble into double-stranded helical filaments as well as higher-ordered structures such as bundles and networks. Cells incorporate macromolecular crowding, cation interactions, and actin-crosslinking proteins to regulate the organization of actin bundles. Although the roles of each of these factors in actin bundling have been well-known individually, how combined factors contribute to actin bundle assembly, organization, and mechanics is not fully understood. Here, we describe recent studies that have investigated the mechanisms of how intracellular environmental factors influence actin bundling. This review highlights the effects of macromolecular crowding, cation interactions, and actin-crosslinking proteins on actin bundle organization, structure, and mechanics. Understanding these mechanisms is important in determining in vivo actin biophysics and providing insights into cell physiology.
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Affiliation(s)
- Nicholas Castaneda
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, United States
| | - Jinho Park
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States
- Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, United States
| | - Ellen Hyeran Kang
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States
- Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, United States
- Department of Physics, University of Central Florida, Orlando, FL, United States
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4
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Schroer CFE, Baldauf L, van Buren L, Wassenaar TA, Melo MN, Koenderink GH, Marrink SJ. Charge-dependent interactions of monomeric and filamentous actin with lipid bilayers. Proc Natl Acad Sci U S A 2020; 117:5861-5872. [PMID: 32123101 PMCID: PMC7084070 DOI: 10.1073/pnas.1914884117] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The cytoskeletal protein actin polymerizes into filaments that are essential for the mechanical stability of mammalian cells. In vitro experiments showed that direct interactions between actin filaments and lipid bilayers are possible and that the net charge of the bilayer as well as the presence of divalent ions in the buffer play an important role. In vivo, colocalization of actin filaments and divalent ions are suppressed, and cells rely on linker proteins to connect the plasma membrane to the actin network. Little is known, however, about why this is the case and what microscopic interactions are important. A deeper understanding is highly beneficial, first, to obtain understanding in the biological design of cells and, second, as a possible basis for the building of artificial cortices for the stabilization of synthetic cells. Here, we report the results of coarse-grained molecular dynamics simulations of monomeric and filamentous actin in the vicinity of differently charged lipid bilayers. We observe that charges on the lipid head groups strongly determine the ability of actin to adsorb to the bilayer. The inclusion of divalent ions leads to a reversal of the binding affinity. Our in silico results are validated experimentally by reconstitution assays with actin on lipid bilayer membranes and provide a molecular-level understanding of the actin-membrane interaction.
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Affiliation(s)
- Carsten F E Schroer
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Lucia Baldauf
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
- Living Matter Department, AMOLF, 1098 XG Amsterdam, The Netherlands
| | - Lennard van Buren
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands
- Living Matter Department, AMOLF, 1098 XG Amsterdam, The Netherlands
| | - Tsjerk A Wassenaar
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Manuel N Melo
- Instituto de Tecnologia Química e Biológica, New University of Lisbon, 2780-157, Oeiras, Portugal
| | - Gijsje H Koenderink
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2629 HZ Delft, The Netherlands;
- Living Matter Department, AMOLF, 1098 XG Amsterdam, The Netherlands
| | - Siewert J Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands;
- Zernike Institute for Advanced Materials, University of Groningen, 9747 AG, Groningen, The Netherlands
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5
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Yu M, Le S, Efremov AK, Zeng X, Bershadsky A, Yan J. Effects of Mechanical Stimuli on Profilin- and Formin-Mediated Actin Polymerization. NANO LETTERS 2018; 18:5239-5247. [PMID: 29976069 DOI: 10.1021/acs.nanolett.8b02211] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Self-assembling actin filaments not only form the basis of the cytoskeleton network in cells but also are utilized as nanosized building blocks to make novel active matter in which the dynamic polymerization and depolymerization of actin filaments play a key role. Formins belong to a main family of actin nucleation factors that bind to the barbed end of actin filaments and regulate actin polymerization through an interaction with profilin. Due to actomyosin contractility and relative rotation between formin and actin filaments, formin-dependent actin polymerization is subject to force and rotation constraints. However, it remains unclear how force and rotation constraints affect formin-dependent actin polymerization in the presence of profilin. Here, we show that for rotation-unconstrained actin filaments, elongation is accelerated by both force and profilin. The combined effect leads to surprisingly fast actin elongation that can approach the diffusion-limited rate at forces of a few piconewtons. The elongation of rotation-constrained filaments is also accelerated by profilin but is insensitive to applied force. We show that FH2, the main actin binding domain, plays the primary mechanosensing role. Together, the findings not only significantly advance our understanding of the mechanochemical regulation of formin-mediated actin polymerization in cells but also can potentially be utilized to make novel actin-based active matter.
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Affiliation(s)
- Miao Yu
- Mechanobiology Institute, National University of Singapore , Singapore 117411
- Department of Physics , National University of Singapore , Singapore 117542
| | - Shimin Le
- Mechanobiology Institute, National University of Singapore , Singapore 117411
- Department of Physics , National University of Singapore , Singapore 117542
| | - Artem K Efremov
- Mechanobiology Institute, National University of Singapore , Singapore 117411
- Centre for Bioimaging Sciences , National University of Singapore , Singapore 117546
| | - Xiangjun Zeng
- Department of Physics , National University of Singapore , Singapore 117542
| | - Alexander Bershadsky
- Mechanobiology Institute, National University of Singapore , Singapore 117411
- Department of Molecular Cell Biology , Weizmann Institute of Science , Rehovot 76100 , Israel
| | - Jie Yan
- Mechanobiology Institute, National University of Singapore , Singapore 117411
- Department of Physics , National University of Singapore , Singapore 117542
- Centre for Bioimaging Sciences , National University of Singapore , Singapore 117546
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6
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Rückerl F, Lenz M, Betz T, Manzi J, Martiel JL, Safouane M, Paterski-Boujemaa R, Blanchoin L, Sykes C. Adaptive Response of Actin Bundles under Mechanical Stress. Biophys J 2017; 113:1072-1079. [PMID: 28877490 PMCID: PMC5611681 DOI: 10.1016/j.bpj.2017.07.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 07/24/2017] [Accepted: 07/31/2017] [Indexed: 11/17/2022] Open
Abstract
Actin is one of the main components of the architecture of cells. Actin filaments form different polymer networks with versatile mechanical properties that depend on their spatial organization and the presence of cross-linkers. Here, we investigate the mechanical properties of actin bundles in the absence of cross-linkers. Bundles are polymerized from the surface of mDia1-coated latex beads, and deformed by manipulating both ends through attached beads held by optical tweezers, allowing us to record the applied force. Bundle properties are strikingly different from the ones of a homogeneous isotropic beam. Successive compression and extension leads to a decrease in the buckling force that we attribute to the bundle remaining slightly curved after the first deformation. Furthermore, we find that the bundle is solid, and stiff to bending, along the long axis, whereas it has a liquid and viscous behavior in the transverse direction. Interpretation of the force curves using a Maxwell visco-elastic model allows us to extract the bundle mechanical parameters and confirms that the bundle is composed of weakly coupled filaments. At short times, the bundle behaves as an elastic material, whereas at long times, filaments flow in the longitudinal direction, leading to bundle restructuring. Deviations from the model reveal a complex adaptive rheological behavior of bundles. Indeed, when allowed to anneal between phases of compression and extension, the bundle reinforces. Moreover, we find that the characteristic visco-elastic time is inversely proportional to the compression speed. Actin bundles are therefore not simple force transmitters, but instead, complex mechano-transducers that adjust their mechanics to external stimulation. In cells, where actin bundles are mechanical sensors, this property could contribute to their adaptability.
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Affiliation(s)
- Florian Rückerl
- CNRS, Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Paris, France; Sorbonne Universités, UPMC University Paris 06, Paris, France
| | - Martin Lenz
- CNRS, LPTMS, University Paris-Sud, Orsay, France
| | - Timo Betz
- CNRS, Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Paris, France; Sorbonne Universités, UPMC University Paris 06, Paris, France
| | - John Manzi
- CNRS, Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Paris, France; Sorbonne Universités, UPMC University Paris 06, Paris, France
| | - Jean-Louis Martiel
- CNRS/CEA/INRA/UJF, Laboratoire de Physiologie Cellulaire Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, Grenoble, France
| | - Mahassine Safouane
- CNRS, Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Paris, France; Sorbonne Universités, UPMC University Paris 06, Paris, France
| | - Rajaa Paterski-Boujemaa
- CNRS/CEA/INRA/UJF, Laboratoire de Physiologie Cellulaire Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, Grenoble, France
| | - Laurent Blanchoin
- CNRS/CEA/INRA/UJF, Laboratoire de Physiologie Cellulaire Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, Grenoble, France.
| | - Cécile Sykes
- CNRS, Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Paris, France; Sorbonne Universités, UPMC University Paris 06, Paris, France.
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7
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Abstract
Thirty years after their invention by Arthur Ashkin and colleagues at Bell Labs in 1986 [1], optical tweezers (or traps) have become a versatile tool to address numerous biological problems. Put simply, an optical trap is a highly focused laser beam that is capable of holding and applying forces to micron-sized dielectric objects. However, their development over the last few decades has converted these tools from boutique instruments into highly versatile instruments of molecular biophysics. This introductory chapter intends to give a brief overview of the field, highlight some important scientific achievements, and demonstrate why optical traps have become a powerful tool in the biological sciences. We introduce a typical optical setup, describe the basic theoretical concepts of how trapping forces arise, and present the quantitative position and force measurement techniques that are most widely used today.
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8
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The dynamics of filament assembly define cytoskeletal network morphology. Nat Commun 2016; 7:13827. [PMID: 28000681 PMCID: PMC5187503 DOI: 10.1038/ncomms13827] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 11/04/2016] [Indexed: 11/22/2022] Open
Abstract
The actin cytoskeleton is a key component in the machinery of eukaryotic cells, and it self-assembles out of equilibrium into a wide variety of biologically crucial structures. Although the molecular mechanisms involved are well characterized, the physical principles governing the spatial arrangement of actin filaments are not understood. Here we propose that the dynamics of actin network assembly from growing filaments results from a competition between diffusion, bundling and steric hindrance, and is responsible for the range of observed morphologies. Our model and simulations thus predict an abrupt dynamical transition between homogeneous and strongly bundled networks as a function of the actin polymerization rate. This suggests that cells may effect dramatic changes to their internal architecture through minute modifications of their nonequilibrium dynamics. Our results are consistent with available experimental data.
The dynamics of actin cytoskeleton is essential to the function of living cells. Here, Foffano et al. describe a nonequilibrium filament model to mimic the formation of cytoskeleton and pinpoint the key role played by the actin entanglement during the transition from homogeneous to bundled networks.
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9
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Geiger B, Spatz J. Application of synthetic biology approaches for understanding encounters between cells and their microenvironment. Cell Adh Migr 2016; 10:447-450. [PMID: 27442709 DOI: 10.1080/19336918.2016.1215184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Affiliation(s)
- Benjamin Geiger
- a Department of Molecular Cell Biology Weizmann Institute of Science , Rehovot , Israel
| | - Joachim Spatz
- b Department of Biointerphase Science & Technology Max Planck Institute for Medical Research Jahnstraße, Heidelberg, Germany Laboratory of Biophysical Chemistry Institute of Physical Chemistry, University of Heidelberg Im Neuenheimer Feld, Heidelberg , Germany
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10
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Schnauß J, Golde T, Schuldt C, Schmidt BUS, Glaser M, Strehle D, Händler T, Heussinger C, Käs JA. Transition from a Linear to a Harmonic Potential in Collective Dynamics of a Multifilament Actin Bundle. PHYSICAL REVIEW LETTERS 2016; 116:108102. [PMID: 27015510 DOI: 10.1103/physrevlett.116.108102] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Indexed: 05/22/2023]
Abstract
Attractive depletion forces between rodlike particles in highly crowded environments have been shown through recent modeling and experimental approaches to induce different structural and dynamic signatures depending on relative orientation between rods. For example, it has been demonstrated that the axial attraction between two parallel rods yields a linear energy potential corresponding to a constant contractile force of 0.1 pN. Here, we extend pairwise, depletion-induced interactions to a multifilament level with actin bundles, and find contractile forces up to 3 pN. Forces generated due to bundle relaxation were not constant, but displayed a harmonic potential and decayed exponentially with a mean decay time of 3.4 s. Through an analytical model, we explain these different fundamental dynamics as an emergent, collective phenomenon stemming from the additive, pairwise interactions of filaments within a bundle.
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Affiliation(s)
- Jörg Schnauß
- Institute of Experimental Physics I, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
| | - Tom Golde
- Institute of Experimental Physics I, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
| | - Carsten Schuldt
- Institute of Experimental Physics I, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
| | - B U Sebastian Schmidt
- Institute of Experimental Physics I, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
| | - Martin Glaser
- Institute of Experimental Physics I, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
| | - Dan Strehle
- Institute of Experimental Physics I, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
| | - Tina Händler
- Institute of Experimental Physics I, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
| | - Claus Heussinger
- Institute for Theoretical Physics, Georg-August University of Göttingen, Friedrich-Hund Platz 1, 37077 Göttingen, Germany
| | - Josef A Käs
- Institute of Experimental Physics I, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
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11
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Quadt KA, Streichfuss M, Moreau CA, Spatz JP, Frischknecht F. Coupling of Retrograde Flow to Force Production During Malaria Parasite Migration. ACS NANO 2016; 10:2091-2102. [PMID: 26792112 DOI: 10.1021/acsnano.5b06417] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Migration of malaria parasites is powered by a myosin motor that moves actin filaments, which in turn link to adhesive proteins spanning the plasma membrane. The retrograde flow of these adhesins appears to be coupled to forward locomotion. However, the contact dynamics between the parasite and the substrate as well as the generation of forces are complex and their relation to retrograde flow is unclear. Using optical tweezers we found retrograde flow rates up to 15 μm/s contrasting with parasite average speeds of 1-2 μm/s. We found that a surface protein, TLP, functions in reducing retrograde flow for the buildup of adhesive force and that actin dynamics appear optimized for the generation of force but not for maximizing the speed of retrograde flow. These data uncover that TLP acts by modulating actin dynamics or actin filament organization and couples retrograde flow to force production in malaria parasites.
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Affiliation(s)
- Katharina A Quadt
- Integrative Parasitology, Center for Infectious Diseases, University of Heidelberg Medical School , Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Martin Streichfuss
- Integrative Parasitology, Center for Infectious Diseases, University of Heidelberg Medical School , Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
- University of Heidelberg , Department of Biophysical Chemistry and Max Planck Institute for Intelligent Systems, Department of New Materials and Biosystems, Heisenbergstr. 3, 70569 Stuttgart, Germany
| | - Catherine A Moreau
- Integrative Parasitology, Center for Infectious Diseases, University of Heidelberg Medical School , Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Joachim P Spatz
- University of Heidelberg , Department of Biophysical Chemistry and Max Planck Institute for Intelligent Systems, Department of New Materials and Biosystems, Heisenbergstr. 3, 70569 Stuttgart, Germany
| | - Friedrich Frischknecht
- Integrative Parasitology, Center for Infectious Diseases, University of Heidelberg Medical School , Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
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12
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Raoufi M, Aslankoohi N, Mollenhauer C, Boehm H, Spatz JP, Brüggemann D. Template-assisted extrusion of biopolymer nanofibers under physiological conditions. Integr Biol (Camb) 2016; 8:1059-1066. [DOI: 10.1039/c6ib00045b] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Biomedical applications ranging from tissue engineering to drug delivery systems require versatile biomaterials based on the scalable and tunable production of biopolymer nanofibers under physiological conditions.
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Affiliation(s)
- Mohammad Raoufi
- Department of Biointerphase Science & Technology
- Max Planck Institute for Medical Research
- 69120 Heidelberg
- Germany
- Department of Biophysical Chemistry
| | - Neda Aslankoohi
- Department of Biointerphase Science & Technology
- Max Planck Institute for Medical Research
- 69120 Heidelberg
- Germany
- Department of Biophysical Chemistry
| | - Christine Mollenhauer
- Department of Biointerphase Science & Technology
- Max Planck Institute for Medical Research
- 69120 Heidelberg
- Germany
- Department of Biophysical Chemistry
| | - Heike Boehm
- Department of Biointerphase Science & Technology
- Max Planck Institute for Medical Research
- 69120 Heidelberg
- Germany
- Department of Biophysical Chemistry
| | - Joachim P. Spatz
- Department of Biointerphase Science & Technology
- Max Planck Institute for Medical Research
- 69120 Heidelberg
- Germany
- Department of Biophysical Chemistry
| | - Dorothea Brüggemann
- Department of Biointerphase Science & Technology
- Max Planck Institute for Medical Research
- 69120 Heidelberg
- Germany
- Department of Biophysical Chemistry
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13
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Cell sensing of physical properties at the nanoscale: Mechanisms and control of cell adhesion and phenotype. Acta Biomater 2016; 30:26-48. [PMID: 26596568 DOI: 10.1016/j.actbio.2015.11.027] [Citation(s) in RCA: 111] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Revised: 11/10/2015] [Accepted: 11/16/2015] [Indexed: 12/24/2022]
Abstract
The chemistry, geometry, topography and mechanical properties of biomaterials modulate biochemical signals (in particular ligand-receptor binding events) that control cells-matrix interactions. In turn, the regulation of cell adhesion by the biochemical and physical properties of the matrix controls cell phenotypes such as proliferation, motility and differentiation. In particular, nanoscale geometrical, topographical and mechanical properties of biomaterials are essential to achieve control of the cell-biomaterials interface. The design of such nanoscale architectures and platforms requires understanding the molecular mechanisms underlying adhesion formation and the assembly of the actin cytoskeleton. This review presents some of the important molecular mechanisms underlying cell adhesion to biomaterials mediated by integrins and discusses the nanoscale engineered platforms used to control these processes. Such nanoscale understanding of the cell-biomaterials interface offers exciting opportunities for the design of biomaterials and their application to the field of tissue engineering. STATEMENT OF SIGNIFICANCE Biomaterials design is important in the fields of regenerative medicine and tissue engineering, in particular to allow the long term expansion of stem cells and the engineering of scaffolds for tissue regeneration. Cell adhesion to biomaterials often plays a central role in regulating cell phenotype. It is emerging that physical properties of biomaterials, and more generally the microenvironment, regulate such behaviour. In particular, cells respond to nanoscale physical properties of their matrix. Understanding how such nanoscale physical properties control cell adhesion is therefore essential for biomaterials design. To this aim, a deeper understanding of molecular processes controlling cell adhesion, but also a greater control of matrix engineering is required. Such multidisciplinary approaches shed light on some of the fundamental mechanisms via which cell adhesions sense their nanoscale physical environment.
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14
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Maier T, Haraszti T. Reversibility and Viscoelastic Properties of Micropillar Supported and Oriented Magnesium Bundled F-Actin. PLoS One 2015; 10:e0136432. [PMID: 26322783 PMCID: PMC4556452 DOI: 10.1371/journal.pone.0136432] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 08/04/2015] [Indexed: 11/19/2022] Open
Abstract
Filamentous actin is one of the most important cytoskeletal elements. Not only is it responsible for the elastic properties of many cell types, but it also plays a vital role in cellular adhesion and motility. Understanding the bundling kinetics of actin filaments is important in the formation of various cytoskeletal structures, such as filopodia and stress fibers. Utilizing a unique pillar-structured microfluidic device, we investigated the time dependence of bundling kinetics of pillar supported free-standing actin filaments. Microparticles attached to the filaments allowed the measurement of thermal motion, and we found that bundling takes place at lower concentrations than previously found in 3-dimensional actin gels, i.e. actin filaments formed bundles in the presence of 5-12 mM of magnesium chloride in a time-dependent manner. The filaments also displayed long term stability for up to hours after removing the magnesium ions from the buffer, which suggests that there is an extensive hysteresis between cation induced crosslinking and decrosslinking.
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Affiliation(s)
- Timo Maier
- Max Planck Institute for Intelligent Systems, Department of New Materials and Biosystems, Heisenberg str. 3, D-70569 Stuttgart, Germany
- University of Heidelberg, Institute of Physical Chemistry, Department of Biophysical Chemistry, Im Neuenheimer Feld 253, D-69120 Heidelberg, Germany
| | - Tamás Haraszti
- Max Planck Institute for Intelligent Systems, Department of New Materials and Biosystems, Heisenberg str. 3, D-70569 Stuttgart, Germany
- University of Heidelberg, Institute of Physical Chemistry, Department of Biophysical Chemistry, Im Neuenheimer Feld 253, D-69120 Heidelberg, Germany
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15
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Cajamarca L, Grason GM. Geometry of flexible filament cohesion: better contact through twist? J Chem Phys 2015; 141:174904. [PMID: 25381544 DOI: 10.1063/1.4900983] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Cohesive interactions between filamentous molecules have broad implications for a range of biological and synthetic materials. While long-standing theoretical approaches have addressed the problem of inter-filament forces from the limit of infinitely rigid rods, the ability of flexible filaments to deform intra-filament shape in response to changes in inter-filament geometry has a profound affect on the nature of cohesive interactions. In this paper, we study two theoretical models of inter-filament cohesion in the opposite limit, in which filaments are sufficiently flexible to maintain cohesive contact along their contours, and address, in particular, the role played by helical-interfilament geometry in defining interactions. Specifically, we study models of featureless, tubular filaments interacting via: (1) pair-wise Lennard-Jones (LJ) interactions between surface elements and (2) depletion-induced filament binding stabilized by electrostatic surface repulsion. Analysis of these models reveals a universal preference for cohesive filament interactions for non-zero helical skew, and further, that in the asymptotic limit of vanishing interaction range relative to filament diameter, the skew-dependence of cohesion approaches a geometrically defined limit described purely by the close-packing geometry of twisted tubular filaments. We further analyze non-universal features of the skew-dependence of cohesion at small-twist for both potentials, and argue that in the LJ model the pair-wise surface attraction generically destabilizes parallel filaments, while in the second model, pair-wise electrostatic repulsion in combination with non-pairwise additivity of depletion leads to a meta-stable parallel state.
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Affiliation(s)
- Luis Cajamarca
- Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003, USA
| | - Gregory M Grason
- Department of Polymer Science, University of Massachusetts, Amherst, Massachusetts 01003, USA
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16
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Hilitski F, Ward AR, Cajamarca L, Hagan MF, Grason GM, Dogic Z. Measuring cohesion between macromolecular filaments one pair at a time: depletion-induced microtubule bundling. PHYSICAL REVIEW LETTERS 2015; 114:138102. [PMID: 25884139 DOI: 10.1103/physrevlett.114.138102] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Indexed: 05/26/2023]
Abstract
In the presence of nonadsorbing polymers, colloidal particles experience ubiquitous attractive interactions induced by depletion forces. Here, we measure the depletion interaction between a pair of microtubule filaments using a method that combines single filament imaging with optical trapping. By quantifying the dependence of filament cohesion on both polymer concentration and solution ionic strength, we demonstrate that the minimal model of depletion, based on the Asakura-Oosawa theory, fails to quantitatively describe the experimental data. By measuring the cohesion strength in two- and three- filament bundles, we verify pairwise additivity of depletion interactions for the specific experimental conditions. The described experimental technique can be used to measure pairwise interactions between various biological or synthetic filaments and complements information extracted from bulk osmotic stress experiments.
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Affiliation(s)
- Feodor Hilitski
- Department of Physics, Brandeis University, Waltham, Massachusetts 02454, USA
| | - Andrew R Ward
- Department of Physics, Brandeis University, Waltham, Massachusetts 02454, USA
| | - Luis Cajamarca
- Department of Physics, University of Massachusetts at Amherst, Amherst, Massachusetts 01003, USA
| | - Michael F Hagan
- Department of Physics, Brandeis University, Waltham, Massachusetts 02454, USA
| | - Gregory M Grason
- Department of Polymer Science and Engineering, University of Massachusetts at Amherst, Amherst, Massachusetts 01003, USA
| | - Zvonimir Dogic
- Department of Physics, Brandeis University, Waltham, Massachusetts 02454, USA
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17
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Deshpande S, Pfohl T. Real-time dynamics of emerging actin networks in cell-mimicking compartments. PLoS One 2015; 10:e0116521. [PMID: 25785606 PMCID: PMC4364982 DOI: 10.1371/journal.pone.0116521] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 12/10/2014] [Indexed: 01/07/2023] Open
Abstract
Understanding the cytoskeletal functionality and its relation to other cellular components and properties is a prominent question in biophysics. The dynamics of actin cytoskeleton and its polymorphic nature are indispensable for the proper functioning of living cells. Actin bundles are involved in cell motility, environmental exploration, intracellular transport and mechanical stability. Though the viscoelastic properties of actin-based structures have been extensively probed, the underlying microstructure dynamics, especially their disassembly, is not fully understood. In this article, we explore the rich dynamics and emergent properties exhibited by actin bundles within flow-free confinements using a microfluidic set-up and epifluorescence microscopy. After forming entangled actin filaments within cell-sized quasi two-dimensional confinements, we induce their bundling using three different fundamental mechanisms: counterion condensation, depletion interactions and specific protein-protein interactions. Intriguingly, long actin filaments form emerging networks of actin bundles via percolation leading to remarkable properties such as stress generation and spindle-like intermediate structures. Simultaneous sharing of filaments in different links of the network is an important parameter, as short filaments do not form networks but segregated clusters of bundles instead. We encounter a hierarchical process of bundling and its subsequent disassembly. Additionally, our study suggests that such percolated networks are likely to exist within living cells in a dynamic fashion. These observations render a perspective about differential cytoskeletal responses towards numerous stimuli.
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Affiliation(s)
- Siddharth Deshpande
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
| | - Thomas Pfohl
- Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
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18
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Blanchoin L, Boujemaa-Paterski R, Sykes C, Plastino J. Actin dynamics, architecture, and mechanics in cell motility. Physiol Rev 2014; 94:235-63. [PMID: 24382887 DOI: 10.1152/physrev.00018.2013] [Citation(s) in RCA: 857] [Impact Index Per Article: 85.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Tight coupling between biochemical and mechanical properties of the actin cytoskeleton drives a large range of cellular processes including polarity establishment, morphogenesis, and motility. This is possible because actin filaments are semi-flexible polymers that, in conjunction with the molecular motor myosin, can act as biological active springs or "dashpots" (in laymen's terms, shock absorbers or fluidizers) able to exert or resist against force in a cellular environment. To modulate their mechanical properties, actin filaments can organize into a variety of architectures generating a diversity of cellular organizations including branched or crosslinked networks in the lamellipodium, parallel bundles in filopodia, and antiparallel structures in contractile fibers. In this review we describe the feedback loop between biochemical and mechanical properties of actin organization at the molecular level in vitro, then we integrate this knowledge into our current understanding of cellular actin organization and its physiological roles.
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19
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How actin network dynamics control the onset of actin-based motility. Proc Natl Acad Sci U S A 2012; 109:14440-5. [PMID: 22908255 DOI: 10.1073/pnas.1117096109] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cells use their dynamic actin network to control their mechanics and motility. These networks are made of branched actin filaments generated by the Arp2/3 complex. Here we study under which conditions the microscopic organization of branched actin networks builds up a sufficient stress to trigger sustained motility. In our experimental setup, dynamic actin networks or "gels" are grown on a hard bead in a controlled minimal protein system containing actin monomers, profilin, the Arp2/3 complex and capping protein. We vary protein concentrations and follow experimentally and through simulations the shape and mechanical properties of the actin gel growing around beads. Actin gel morphology is controlled by elementary steps including "primer" contact, growth of the network, entanglement, mechanical interaction and force production. We show that varying the biochemical orchestration of these steps can lead to the loss of network cohesion and the lack of effective force production. We propose a predictive phase diagram of actin gel fate as a function of protein concentrations. This work unveils how, in growing actin networks, a tight biochemical and physical coupling smoothens initial primer-caused heterogeneities and governs force buildup and cell motility.
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