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Slepukhin VM, Levine AJ. Braiding Dynamics in Semiflexible Filament Bundles under Oscillatory Forcing. Polymers (Basel) 2021; 13:2195. [PMID: 34279339 PMCID: PMC8271738 DOI: 10.3390/polym13132195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 06/25/2021] [Accepted: 06/25/2021] [Indexed: 11/16/2022] Open
Abstract
We examine the nonequilibrium production of topological defects-braids-in semiflexible filament bundles under cycles of compression and tension. During these cycles, the period of compression facilitates the thermally activated pair production of braid/anti-braid pairs, which then may separate when the bundle is under tension. As a result, appropriately tuned alternating periods of compression and extension should lead to the proliferation of braid defects in a bundle so that the linear density of these pairs far exceeds that expected in the thermal equilibrium. Secondly, we examine the slow extension of braided bundles under tension, showing that their end-to-end length creeps nonmonotonically under a fixed force due to braid deformation and the motion of the braid pair along the bundle. We conclude with a few speculations regarding experiments on semiflexible filament bundles and their networks.
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Affiliation(s)
- Valentin M Slepukhin
- Department of Physics & Astronomy, University of California, Los Angeles, CA 90095, USA
| | - Alex J Levine
- Department of Physics & Astronomy, University of California, Los Angeles, CA 90095, USA
- Department of Chemistry & Biochemistry, University of California, Los Angeles, CA 90095, USA
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2
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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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3
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Elbalasy I, Mollenkopf P, Tutmarc C, Herrmann H, Schnauß J. Keratins determine network stress responsiveness in reconstituted actin-keratin filament systems. SOFT MATTER 2021; 17:3954-3962. [PMID: 33724291 DOI: 10.1039/d0sm02261f] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The cytoskeleton is a major determinant of cell mechanics, and alterations in the central mechanical aspects of cells are observed during many pathological situations. Therefore, it is essential to investigate the interplay between the main filament systems of the cytoskeleton in the form of composite networks. Here, we investigate the role of keratin intermediate filaments (IFs) in network strength by studying in vitro reconstituted actin and keratin 8/18 composite filament networks via bulk shear rheology. We co-polymerized these structural proteins in varying ratios and recorded how their relative content affects the overall mechanical response of the various composites. For relatively small deformations, we found that all composites exhibited an intermediate linear viscoelastic behaviour compared to that of the pure networks. In stark contrast, when larger deformations were imposed the composites displayed increasing strain stiffening behaviour with increasing keratin content. The extent of strain stiffening is much more pronounced than in corresponding experiments performed with vimentin IF as a composite network partner for actin. Our results provide new insights into the mechanical interplay between actin and keratin filaments in which keratin provides reinforcement to actin. This interplay may contribute to the overall integrity of cells. Hence, the high keratin 8/18 content of mechanically stressed simple epithelial cell layers, as found in the lung and the intestine, provides an explanation for their exceptional stability.
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Affiliation(s)
- Iman Elbalasy
- Peter-Debye Institute for Soft Matter Physics, Leipzig University, 04103 Leipzig, Germany
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Jaswandkar SV, Faisal HMN, Katti KS, Katti DR. Dissociation Mechanisms of G-actin Subunits Govern Deformation Response of Actin Filament. Biomacromolecules 2021; 22:907-917. [PMID: 33481563 DOI: 10.1021/acs.biomac.0c01602] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Actin molecules are essential structural components of the cellular cytoskeleton. Here, we report a comprehensive analysis of F-actin's deformation behavior and highlight underlying mechanisms using steered molecular dynamics simulations (SMD). The investigation of F-actin was done under tension, compression, bending, and torsion. We report that the dissociation pattern of conformational locks at intrastrand and interstrand G-actin interfaces regulates the deformation response of F-actin. The conformational locks at the G-actin interfaces are portrayed by a spheroidal joint, interlocking serrated plates' analogy. Further, the SMD simulation approach was utilized to evaluate Young's modulus, flexural rigidity, persistent length, and torsional rigidity of F-actin, and the values obtained were found to be consistent with available experimental data. The evaluation of the mechanical properties of actin and the insight into the fundamental mechanisms contributing to its resilience described here are necessary for developing accurate models of eukaryotic cells and for assessing cellular viability and mobility.
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Affiliation(s)
- Sharad V Jaswandkar
- Department of Civil and Environmental Engineering, North Dakota State University, Fargo, North Dakota 58105, United States
| | - H M Nasrullah Faisal
- Department of Civil and Environmental Engineering, North Dakota State University, Fargo, North Dakota 58105, United States
| | - Kalpana S Katti
- Department of Civil and Environmental Engineering, North Dakota State University, Fargo, North Dakota 58105, United States
| | - Dinesh R Katti
- Department of Civil and Environmental Engineering, North Dakota State University, Fargo, North Dakota 58105, United States
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5
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Caillol S. Special Issue "Natural Polymers and Biopolymers II". Molecules 2020; 26:molecules26010112. [PMID: 33383720 PMCID: PMC7796038 DOI: 10.3390/molecules26010112] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Accepted: 12/25/2020] [Indexed: 02/07/2023] Open
Affiliation(s)
- Sylvain Caillol
- ICGM, Univ Montpellier, CNRS, ENSCM, 34296 Montpellier, France
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6
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Lehmann K, Shayegan M, Blab GA, Forde NR. Optical Tweezers Approaches for Probing Multiscale Protein Mechanics and Assembly. Front Mol Biosci 2020; 7:577314. [PMID: 33134316 PMCID: PMC7573139 DOI: 10.3389/fmolb.2020.577314] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 08/27/2020] [Indexed: 01/09/2023] Open
Abstract
Multi-step assembly of individual protein building blocks is key to the formation of essential higher-order structures inside and outside of cells. Optical tweezers is a technique well suited to investigate the mechanics and dynamics of these structures at a variety of size scales. In this mini-review, we highlight experiments that have used optical tweezers to investigate protein assembly and mechanics, with a focus on the extracellular matrix protein collagen. These examples demonstrate how optical tweezers can be used to study mechanics across length scales, ranging from the single-molecule level to fibrils to protein networks. We discuss challenges in experimental design and interpretation, opportunities for integration with other experimental modalities, and applications of optical tweezers to current questions in protein mechanics and assembly.
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Affiliation(s)
- Kathrin Lehmann
- Department of Physics, Simon Fraser University, Burnaby, BC, Canada.,Soft Condensed Matter and Biophysics, Utrecht University, Utrecht, Netherlands
| | - Marjan Shayegan
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, United States
| | - Gerhard A Blab
- Soft Condensed Matter and Biophysics, Utrecht University, Utrecht, Netherlands
| | - Nancy R Forde
- Department of Physics, Simon Fraser University, Burnaby, BC, Canada.,Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.,Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada.,Centre for Cell Biology, Development and Disease (C2D2), Simon Fraser University, Burnaby, BC, Canada
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Adamatzky A, Schnauß J, Huber F. Actin droplet machine. ROYAL SOCIETY OPEN SCIENCE 2019; 6:191135. [PMID: 31903204 PMCID: PMC6936293 DOI: 10.1098/rsos.191135] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Accepted: 11/04/2019] [Indexed: 05/06/2023]
Abstract
The actin droplet machine is a computer model of a three-dimensional network of actin bundles developed in a droplet of a physiological solution, which implements mappings of sets of binary strings. The actin bundle network is conductive to travelling excitations, i.e. impulses. The machine is interfaced with an arbitrary selected set of k electrodes through which stimuli, binary strings of length k represented by impulses generated on the electrodes, are applied and responses are recorded. The responses are recorded in a form of impulses and then converted to binary strings. The machine's state is a binary string of length k: if there is an impulse recorded on the ith electrode, there is a '1' in the ith position of the string, and '0' otherwise. We present a design of the machine and analyse its state transition graphs. We envisage that actin droplet machines could form an elementary processor of future massive parallel computers made from biopolymers.
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Affiliation(s)
- Andrew Adamatzky
- Unconventional Computing Laboratory, Department of Computer Science, University of the West of England, Bristol, UK
| | - Jörg Schnauß
- Soft Matter Physics Division, Peter Debye Institute for Soft Matter Physics, Faculty of Physics and Earth Sciences, Leipzig University, Germany & Fraunhofer Institute for Cell Therapy and Immunology (IZI), DNA Nanodevices Unit, Leipzig, Germany
| | - Florian Huber
- Netherlands eScience Center, Science Park 140, 1098 XG Amsterdam, The Netherlands
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9
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Meinhövel F, Stange R, Schnauß J, Sauer M, Käs JA, Remmerbach TW. Changing cell mechanics—a precondition for malignant transformation of oral squamous carcinoma cells. CONVERGENT SCIENCE PHYSICAL ONCOLOGY 2018. [DOI: 10.1088/2057-1739/aac72d] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Lorenz JS, Schnauß J, Glaser M, Sajfutdinow M, Schuldt C, Käs JA, Smith DM. Synthetic Transient Crosslinks Program the Mechanics of Soft, Biopolymer-Based Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1706092. [PMID: 29446165 PMCID: PMC5878933 DOI: 10.1002/adma.201706092] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 12/20/2017] [Indexed: 05/21/2023]
Abstract
Actin networks are adaptive materials enabling dynamic and static functions of living cells. A central element for tuning their underlying structural and mechanical properties is the ability to reversibly connect, i.e., transiently crosslink, filaments within the networks. Natural crosslinkers, however, vary across many parameters. Therefore, systematically studying the impact of their fundamental properties like size and binding strength is unfeasible since their structural parameters cannot be independently tuned. Herein, this problem is circumvented by employing a modular strategy to construct purely synthetic actin crosslinkers from DNA and peptides. These crosslinkers mimic both intuitive and noncanonical mechanical properties of their natural counterparts. By isolating binding affinity as the primary control parameter, effects on structural and dynamic behaviors of actin networks are characterized. A concentration-dependent triphasic behavior arises from both strong and weak crosslinkers due to emergent structural polymorphism. Beyond a certain threshold, strong binding leads to a nonmonotonic elastic pulse, which is a consequence of self-destruction of the mechanical structure of the underlying network. The modular design also facilitates an orthogonal regulatory mechanism based on enzymatic cleaving. This approach can be used to guide the rational design of further biomimetic components for programmable modulation of the properties of biomaterials and cells.
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Affiliation(s)
- Jessica S Lorenz
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
| | - Jörg Schnauß
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
- Peter Debye Institute for Soft Matter Physics, Leipzig University, 04103, Leipzig, Germany
| | - Martin Glaser
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
- Peter Debye Institute for Soft Matter Physics, Leipzig University, 04103, Leipzig, Germany
| | - Martin Sajfutdinow
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
| | - Carsten Schuldt
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
- Peter Debye Institute for Soft Matter Physics, Leipzig University, 04103, Leipzig, Germany
| | - Josef A Käs
- Peter Debye Institute for Soft Matter Physics, Leipzig University, 04103, Leipzig, Germany
| | - David M Smith
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), 04103, Leipzig, Germany
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