1
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Sakamoto R, Murrell MP. Composite branched and linear F-actin maximize myosin-induced membrane shape changes in a biomimetic cell model. Commun Biol 2024; 7:840. [PMID: 38987288 PMCID: PMC11236970 DOI: 10.1038/s42003-024-06528-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Accepted: 07/01/2024] [Indexed: 07/12/2024] Open
Abstract
The architecture of the actin cortex determines the generation and transmission of stresses, during key events from cell division to migration. However, its impact on myosin-induced cell shape changes remains unclear. Here, we reconstitute a minimal model of the actomyosin cortex with branched or linear F-actin architecture within giant unilamellar vesicles (GUVs, liposomes). Upon light activation of myosin, neither the branched nor linear F-actin architecture alone induces significant liposome shape changes. The branched F-actin network forms an integrated, membrane-bound "no-slip boundary" -like cortex that attenuates actomyosin contractility. By contrast, the linear F-actin network forms an unintegrated "slip boundary" -like cortex, where actin asters form without inducing membrane deformations. Notably, liposomes undergo significant deformations at an optimized balance of branched and linear F-actin networks. Our findings highlight the pivotal roles of branched F-actin in force transmission and linear F-actin in force generation to yield membrane shape changes.
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Affiliation(s)
- Ryota Sakamoto
- Department of Biomedical Engineering, Yale University, 10 Hillhouse Avenue, New Haven, CT, USA
- Systems Biology Institute, 850 West Campus Drive, West Haven, CT, USA
| | - Michael P Murrell
- Department of Biomedical Engineering, Yale University, 10 Hillhouse Avenue, New Haven, CT, USA.
- Systems Biology Institute, 850 West Campus Drive, West Haven, CT, USA.
- Department of Physics, Yale University, 217 Prospect Street, New Haven, CT, USA.
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2
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Fink A, Fazliev S, Abele T, Spatz JP, Göpfrich K, Cavalcanti-Adam EA. Membrane localization of actin filaments stabilizes giant unilamellar vesicles against external deforming forces. Eur J Cell Biol 2024; 103:151428. [PMID: 38850712 DOI: 10.1016/j.ejcb.2024.151428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 05/25/2024] [Accepted: 06/03/2024] [Indexed: 06/10/2024] Open
Abstract
Actin organization is crucial for establishing cell polarity, which influences processes such as directed cell motility and division. Despite its critical role in living organisms, achieving similar polarity in synthetic cells remains challenging. In this study, we employ a bottom-up approach to investigate how molecular crowders facilitate the formation of cortex-like actin networks and how these networks localize and organize based on membrane shape. Using giant unilamellar vesicles (GUVs) as models for cell membranes, we show that actin filaments can arrange along the membrane to form cortex-like structures. Notably, this organization is achieved using only actin and crowders as a minimal set of components. We utilize surface micropatterning to examine actin filament organization in deformed GUVs adhered to various pattern shapes. Our findings indicate that at the periphery of spherical GUVs, actin bundles align along the membrane. However, in highly curved regions of adhered GUVs, actin bundles avoid crossing the highly curved edges perpendicular to the adhesion site and instead remain in the lower curved regions by aligning parallel to the micropatterned surface. Furthermore, the actin bundles increase the stiffness of the GUVs, effectively counteracting strong deformations when GUVs adhere to micropatterns. This finding is corroborated by real-time deformability cytometry on GUVs with synthetic actin cortices. By precisely manipulating the shape of GUVs, our study provides a minimal system to investigate the interplay between actin structures and the membrane. Our findings provide insights into the spatial organization of actin structures within crowded environments, specifically inside GUVs that resemble the size and shape of cells. This study advances our understanding of actin network organization and functionality within cell-sized compartments.
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Affiliation(s)
- Andreas Fink
- Department of Cellular Biophysics, Max Planck Institute for Medical Research, Jahnstraße 29, Heidelberg 69120, Germany
| | - Sunnatullo Fazliev
- Department of Cellular Biophysics, Max Planck Institute for Medical Research, Jahnstraße 29, Heidelberg 69120, Germany
| | - Tobias Abele
- Biophysical Engineering Group, Center for Molecular Biology of Heidelberg University (ZMBH) Heidelberg University, Im Neuenheimer Feld 329, Heidelberg 69120, Germany
| | - Joachim P Spatz
- Department of Cellular Biophysics, Max Planck Institute for Medical Research, Jahnstraße 29, Heidelberg 69120, Germany
| | - Kerstin Göpfrich
- Biophysical Engineering Group, Max Planck Institute for Medical Research, Jahnstraße 29, Heidelberg 69120, Germany; Biophysical Engineering Group, Center for Molecular Biology of Heidelberg University (ZMBH) Heidelberg University, Im Neuenheimer Feld 329, Heidelberg 69120, Germany
| | - Elisabetta Ada Cavalcanti-Adam
- Department of Cellular Biophysics, Max Planck Institute for Medical Research, Jahnstraße 29, Heidelberg 69120, Germany; Cellular Biomechanics, University of Bayreuth, Universitätsstraße 30, Bayreuth 95447, Germany.
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3
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Okada S, Shoji K. Microrail-assisted liposome trapping and aligning in microfluidic channels. RSC Adv 2024; 14:18003-18010. [PMID: 38841399 PMCID: PMC11152143 DOI: 10.1039/d4ra02094d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 05/28/2024] [Indexed: 06/07/2024] Open
Abstract
Liposome assemblies with a specific shape are potential cell tissue models for studying intercellular communication. Microfluidic channels that can trap liposomes have been constructed to achieve efficient and high-throughput manipulation and observation of liposomes. However, the trapping and alignment of multiple liposomes in a specific space are still challenging because the liposomes are soft and easily ruptured. In this study, we focused on a microrail-assisted technique for manipulating water-in-oil (w/o) emulsions. In this technique, w/o emulsions are trapped under the microrails through a surface energy gradient. First, we investigated whether the microrail channel can be applied for liposome trapping and alignment and found that the numerical simulations showed that drag forces in the direction of the microrail acted on the liposomes, thereby moving the liposomes from the main channel to the microrail. Next, we designed a microrail device based on the simulation results and trapped liposomes using the device. Resultantly, 24.7 ± 8.5 liposomes were aligned under the microrail within an hour, and the microrail was filled with liposomes for 3 hours. Finally, we prepared the microrail devices with y-shaped and ring-shaped microrails and demonstrated the construction of liposome assemblies with specific shapes, not only the straight shape. Our results indicate that the microrail-assisted technique is a valuable method for manipulating liposomes because it has the potential to provide various-shaped liposome assemblies. We believe the microrail channel will be a powerful tool for constructing liposome-based cell-cell interaction models.
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Affiliation(s)
- Shun Okada
- Department of Mechanical Engineering, Nagaoka University of Technology 1603-1 Kamitomioka Nagaoka Niigata 940-2188 Japan
| | - Kan Shoji
- Department of Mechanical Engineering, Nagaoka University of Technology 1603-1 Kamitomioka Nagaoka Niigata 940-2188 Japan
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4
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Chandrasekaran A, Graham K, Stachowiak JC, Rangamani P. Kinetic trapping organizes actin filaments within liquid-like protein droplets. Nat Commun 2024; 15:3139. [PMID: 38605007 PMCID: PMC11009352 DOI: 10.1038/s41467-024-46726-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 03/07/2024] [Indexed: 04/13/2024] Open
Abstract
Several actin-binding proteins (ABPs) phase separate to form condensates capable of curating the actin network shapes. Here, we use computational modeling to understand the principles of actin network organization within VASP condensate droplets. Our simulations reveal that the different actin shapes, namely shells, rings, and mixture states are highly dependent on the kinetics of VASP-actin interactions, suggesting that they arise from kinetic trapping. Specifically, we show that reducing the residence time of VASP on actin filaments reduces degree of bundling, thereby promoting assembly of shells rather than rings. We validate the model predictions experimentally using a VASP-mutant with decreased bundling capability. Finally, we investigate the ring opening within deformed droplets and found that the sphere-to-ellipsoid transition is favored under a wide range of filament lengths while the ellipsoid-to-rod transition is only permitted when filaments have a specific range of lengths. Our findings highlight key mechanisms of actin organization within phase-separated ABPs.
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Affiliation(s)
- Aravind Chandrasekaran
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, 92093-0411, USA
| | - Kristin Graham
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, 78712, USA
| | - Jeanne C Stachowiak
- Department of Biomedical Engineering, University of Texas at Austin, Austin, TX, 78712, USA.
- Department of Chemical Engineering, University of Texas at Austin, Austin, TX, 78712, USA.
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, 92093-0411, USA.
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5
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Waechtler BE, Jayasankar R, Morin EP, Robinson DN. Benefits and challenges of reconstituting the actin cortex. Cytoskeleton (Hoboken) 2024. [PMID: 38520148 DOI: 10.1002/cm.21855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 02/21/2024] [Accepted: 03/05/2024] [Indexed: 03/25/2024]
Abstract
The cell's ability to change shape is a central feature in many cellular processes, including cytokinesis, motility, migration, and tissue formation. The cell constructs a network of contractile proteins underneath the cell membrane to form the cortex, and the reorganization of these components directly contributes to cellular shape changes. The desire to mimic these cell shape changes to aid in the creation of a synthetic cell has been increasing. Therefore, membrane-based reconstitution experiments have flourished, furthering our understanding of the minimal components the cell uses throughout these processes. Although biochemical approaches increased our understanding of actin, myosin II, and actin-associated proteins, using membrane-based reconstituted systems has further expanded our understanding of actin structures and functions because membrane-cortex interactions can be analyzed. In this review, we highlight the recent developments in membrane-based reconstitution techniques. We examine the current findings on the minimal components needed to recapitulate distinct actin structures and functions and how they relate to the cortex's impact on cellular mechanical properties. We also explore how co-processing of computational models with wet-lab experiments enhances our understanding of these properties. Finally, we emphasize the benefits and challenges inherent to membrane-based, reconstitution assays, ranging from the advantage of precise control over the system to the difficulty of integrating these findings into the complex cellular environment.
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Affiliation(s)
- Brooke E Waechtler
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Rajan Jayasankar
- Department of Chemical and Biomolecular Engineering, Whiting School of Engineering, Baltimore, Maryland, USA
| | - Emma P Morin
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Douglas N Robinson
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Chemical and Biomolecular Engineering, Whiting School of Engineering, Baltimore, Maryland, USA
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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6
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Maffeis V, Heuberger L, Nikoletić A, Schoenenberger C, Palivan CG. Synthetic Cells Revisited: Artificial Cells Construction Using Polymeric Building Blocks. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2305837. [PMID: 37984885 PMCID: PMC10885666 DOI: 10.1002/advs.202305837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 10/06/2023] [Indexed: 11/22/2023]
Abstract
The exponential growth of research on artificial cells and organelles underscores their potential as tools to advance the understanding of fundamental biological processes. The bottom-up construction from a variety of building blocks at the micro- and nanoscale, in combination with biomolecules is key to developing artificial cells. In this review, artificial cells are focused upon based on compartments where polymers are the main constituent of the assembly. Polymers are of particular interest due to their incredible chemical variety and the advantage of tuning the properties and functionality of their assemblies. First, the architectures of micro- and nanoscale polymer assemblies are introduced and then their usage as building blocks is elaborated upon. Different membrane-bound and membrane-less compartments and supramolecular structures and how they combine into advanced synthetic cells are presented. Then, the functional aspects are explored, addressing how artificial organelles in giant compartments mimic cellular processes. Finally, how artificial cells communicate with their surrounding and each other such as to adapt to an ever-changing environment and achieve collective behavior as a steppingstone toward artificial tissues, is taken a look at. Engineering artificial cells with highly controllable and programmable features open new avenues for the development of sophisticated multifunctional systems.
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Affiliation(s)
- Viviana Maffeis
- Department of ChemistryUniversity of BaselMattenstrasse 22BaselCH‐4002Switzerland
- NCCR‐Molecular Systems EngineeringBPR 1095, Mattenstrasse 24aBaselCH‐4058Switzerland
| | - Lukas Heuberger
- Department of ChemistryUniversity of BaselMattenstrasse 22BaselCH‐4002Switzerland
| | - Anamarija Nikoletić
- Department of ChemistryUniversity of BaselMattenstrasse 22BaselCH‐4002Switzerland
- Swiss Nanoscience InstituteUniversity of BaselKlingelbergstrasse 82BaselCH‐4056Switzerland
| | | | - Cornelia G. Palivan
- Department of ChemistryUniversity of BaselMattenstrasse 22BaselCH‐4002Switzerland
- NCCR‐Molecular Systems EngineeringBPR 1095, Mattenstrasse 24aBaselCH‐4058Switzerland
- Swiss Nanoscience InstituteUniversity of BaselKlingelbergstrasse 82BaselCH‐4056Switzerland
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7
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Kandiyoth FB, Michelot A. Reconstitution of actin-based cellular processes: Why encapsulation changes the rules. Eur J Cell Biol 2023; 102:151368. [PMID: 37922812 DOI: 10.1016/j.ejcb.2023.151368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 10/02/2023] [Accepted: 10/20/2023] [Indexed: 11/07/2023] Open
Abstract
While in vitro reconstitution of cellular processes is progressing rapidly, the encapsulation of biomimetic systems to reproduce the cellular environment is a major challenge. Here we review the difficulties, using reconstitution of processes dependent on actin polymerization as an example. Some of the problems are purely technical, due to the need for engineering strategies to encapsulate concentrated solutions in micrometer-sized compartments. However, other significant issues arise from the reduction of experimental volumes, which alters the chemical evolution of these non-equilibrium systems. Important parameters to consider for successful reconstitutions are the amount of each component, their consumption and renewal rates to guarantee their continuous availability.
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Affiliation(s)
| | - Alphée Michelot
- Aix Marseille Univ, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France.
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8
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Van de Cauter L, van Buren L, Koenderink GH, Ganzinger KA. Exploring Giant Unilamellar Vesicle Production for Artificial Cells - Current Challenges and Future Directions. SMALL METHODS 2023; 7:e2300416. [PMID: 37464561 DOI: 10.1002/smtd.202300416] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 05/30/2023] [Indexed: 07/20/2023]
Abstract
Creating an artificial cell from the bottom up is a long-standing challenge and, while significant progress has been made, the full realization of this goal remains elusive. Arguably, one of the biggest hurdles that researchers are facing now is the assembly of different modules of cell function inside a single container. Giant unilamellar vesicles (GUVs) have emerged as a suitable container with many methods available for their production. Well-studied swelling-based methods offer a wide range of lipid compositions but at the expense of limited encapsulation efficiency. Emulsion-based methods, on the other hand, excel at encapsulation but are only effective with a limited set of membrane compositions and may entrap residual additives in the lipid bilayer. Since the ultimate artificial cell will need to comply with both specific membrane and encapsulation requirements, there is still no one-method-fits-all solution for GUV formation available today. This review discusses the state of the art in different GUV production methods and their compatibility with GUV requirements and operational requirements such as reproducibility and ease of use. It concludes by identifying the most pressing issues and proposes potential avenues for future research to bring us one step closer to turning artificial cells into a reality.
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Affiliation(s)
- Lori Van de Cauter
- Autonomous Matter Department, AMOLF, Amsterdam, 1098 XG, The Netherlands
| | - Lennard van Buren
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, 2629 HZ, The Netherlands
| | - Gijsje H Koenderink
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, 2629 HZ, The Netherlands
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9
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Colin A, Kotila T, Guérin C, Orhant-Prioux M, Vianay B, Mogilner A, Lappalainen P, Théry M, Blanchoin L. Recycling of the actin monomer pool limits the lifetime of network turnover. EMBO J 2023; 42:e112717. [PMID: 36912152 PMCID: PMC10152149 DOI: 10.15252/embj.2022112717] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 02/10/2023] [Accepted: 02/21/2023] [Indexed: 03/14/2023] Open
Abstract
Intracellular organization is largely mediated by actin turnover. Cellular actin networks continuously assemble and disassemble, while maintaining their overall appearance. This behavior, called "dynamic steady state," allows cells to sense and adapt to their environment. However, how structural stability can be maintained during the constant turnover of a limited actin monomer pool is poorly understood. To answer this question, we developed an experimental system where polystyrene beads are propelled by an actin comet in a microwell containing a limited amount of components. We used the speed and the size of the actin comet tails to evaluate the system's monomer consumption and its lifetime. We established the relative contribution of actin assembly, disassembly, and recycling for a bead movement over tens of hours. Recycling mediated by cyclase-associated protein (CAP) is the key step in allowing the reuse of monomers for multiple assembly cycles. ATP supply and protein aging are also factors that limit the lifetime of actin turnover. This work reveals the balancing mechanism for long-term network assembly with a limited amount of building blocks.
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Affiliation(s)
- Alexandra Colin
- CytoMorpho Lab, Laboratoire de Physiologie Cellulaire & Végétale, Interdisciplinary Research Institute of Grenoble, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Tommi Kotila
- Institute of Biotechnology and Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Christophe Guérin
- CytoMorpho Lab, Laboratoire de Physiologie Cellulaire & Végétale, Interdisciplinary Research Institute of Grenoble, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Magali Orhant-Prioux
- CytoMorpho Lab, Laboratoire de Physiologie Cellulaire & Végétale, Interdisciplinary Research Institute of Grenoble, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France
| | - Benoit Vianay
- CytoMorpho Lab, Institut de Recherche Saint Louis, U976 Human Immunology Pathophysiology Immunotherapy (HIPI), University of Paris, INSERM, CEA, Paris, France
| | - Alex Mogilner
- Courant Institute of Mathematical Sciences, New York University, New York, NY, USA.,Department of Biology, New York University, New York, NY, USA
| | - Pekka Lappalainen
- Institute of Biotechnology and Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Manuel Théry
- CytoMorpho Lab, Laboratoire de Physiologie Cellulaire & Végétale, Interdisciplinary Research Institute of Grenoble, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France.,CytoMorpho Lab, Institut de Recherche Saint Louis, U976 Human Immunology Pathophysiology Immunotherapy (HIPI), University of Paris, INSERM, CEA, Paris, France
| | - Laurent Blanchoin
- CytoMorpho Lab, Laboratoire de Physiologie Cellulaire & Végétale, Interdisciplinary Research Institute of Grenoble, University of Grenoble-Alpes, CEA, CNRS, INRA, Grenoble, France.,CytoMorpho Lab, Institut de Recherche Saint Louis, U976 Human Immunology Pathophysiology Immunotherapy (HIPI), University of Paris, INSERM, CEA, Paris, France
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10
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Baldauf L, Frey F, Arribas Perez M, Idema T, Koenderink GH. Branched actin cortices reconstituted in vesicles sense membrane curvature. Biophys J 2023:S0006-3495(23)00124-8. [PMID: 36806830 DOI: 10.1016/j.bpj.2023.02.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 11/16/2022] [Accepted: 02/14/2023] [Indexed: 02/19/2023] Open
Abstract
The actin cortex is a complex cytoskeletal machinery that drives and responds to changes in cell shape. It must generate or adapt to plasma membrane curvature to facilitate diverse functions such as cell division, migration, and phagocytosis. Due to the complex molecular makeup of the actin cortex, it remains unclear whether actin networks are inherently able to sense and generate membrane curvature, or whether they rely on their diverse binding partners to accomplish this. Here, we show that curvature sensing is an inherent capability of branched actin networks nucleated by Arp2/3 and VCA. We develop a robust method to encapsulate actin inside giant unilamellar vesicles (GUVs) and assemble an actin cortex at the inner surface of the GUV membrane. We show that actin forms a uniform and thin cortical layer when present at high concentration and distinct patches associated with negative membrane curvature at low concentration. Serendipitously, we find that the GUV production method also produces dumbbell-shaped GUVs, which we explain using mathematical modeling in terms of membrane hemifusion of nested GUVs. We find that branched actin networks preferentially assemble at the neck of the dumbbells, which possess a micrometer-range convex curvature comparable with the curvature of the actin patches found in spherical GUVs. Minimal branched actin networks can thus sense membrane curvature, which may help mammalian cells to robustly recruit actin to curved membranes to facilitate diverse cellular functions such as cytokinesis and migration.
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Affiliation(s)
- Lucia Baldauf
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Felix Frey
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Marcos Arribas Perez
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands
| | - Timon Idema
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands.
| | - Gijsje H Koenderink
- Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands.
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11
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Akenuwa OH, Abel SM. Organization and dynamics of cross-linked actin filaments in confined environments. Biophys J 2023; 122:30-42. [PMID: 36461638 PMCID: PMC9822838 DOI: 10.1016/j.bpj.2022.11.2944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 11/02/2022] [Accepted: 11/28/2022] [Indexed: 12/03/2022] Open
Abstract
The organization of the actin cytoskeleton is impacted by the interplay between physical confinement, features of cross-linking proteins, and deformations of semiflexible actin filaments. Some cross-linking proteins preferentially bind filaments in parallel, although others bind more indiscriminately. However, a quantitative understanding of how the mode of binding influences the assembly of actin networks in confined environments is lacking. Here we employ coarse-grained computer simulations to study the dynamics and organization of semiflexible actin filaments in confined regions upon the addition of cross-linkers. We characterize how the emergent behavior is influenced by the system shape, the number and type of cross-linking proteins, and the length of filaments. Structures include isolated clusters of filaments, highly connected filament bundles, and networks of interconnected bundles and loops. Elongation of one dimension of the system promotes the formation of long bundles that align with the elongated axis. Dynamics are governed by rapid cross-linking into aggregates, followed by a slower change in their shape and connectivity. Cross-linking decreases the average bending energy of short or sparsely connected filaments by suppressing shape fluctuations. However, it increases the average bending energy in highly connected networks because filament bundles become deformed, and small numbers of filaments exhibit long-lived, highly unfavorable configurations. Indiscriminate cross-linking promotes the formation of high-energy configurations due to the increased likelihood of unfavorable, difficult-to-relax configurations at early times. Taken together, this work demonstrates physical mechanisms by which cross-linker binding and physical confinement impact the emergent behavior of actin networks, which is relevant both in cells and in synthetic environments.
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Affiliation(s)
- Oghosa H Akenuwa
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee
| | - Steven M Abel
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee.
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12
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Lopes dos Santos R, Campillo C. Studying actin-induced cell shape changes using Giant Unilamellar Vesicles and reconstituted actin networks. Biochem Soc Trans 2022; 50:1527-1539. [PMID: 36111807 PMCID: PMC9704537 DOI: 10.1042/bst20220900] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 08/12/2022] [Accepted: 08/22/2022] [Indexed: 10/05/2023]
Abstract
Cell shape changes that are fuelled by the dynamics of the actomyosin cytoskeleton control cellular processes such as motility and division. However, the mechanisms of interplay between cell membranes and actomyosin are complicated to decipher in the complex environment of the cytoplasm. Using biomimetic systems offers an alternative approach to studying cell shape changes in assays with controlled biochemical composition. Biomimetic systems allow quantitative experiments that can help to build physical models describing the processes of cell shape changes. This article reviews works in which actin networks are reconstructed inside or outside cell-sized Giant Unilamellar Vesicles (GUVs), which are models of cell membranes. We show how various actin networks affect the shape and mechanics of GUVs and how some cell shape changes can be reproduced in vitro using these minimal systems.
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Affiliation(s)
- Rogério Lopes dos Santos
- LAMBE, Université d'Evry Val d'Essonne, CNRS, CEA, Université Paris-Saclay, 91025 Evry-Courcouronnes, France
| | - Clément Campillo
- LAMBE, Université d'Evry Val d'Essonne, CNRS, CEA, Université Paris-Saclay, 91025 Evry-Courcouronnes, France
- Institut Universitaire de France (IUF), Paris, France
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13
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Yanagisawa M. Cell-size space effects on phase separation of binary polymer blends. Biophys Rev 2022; 14:1093-1103. [PMID: 36345284 PMCID: PMC9636348 DOI: 10.1007/s12551-022-01001-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/26/2022] [Indexed: 12/22/2022] Open
Abstract
Within living cells, a diverse array of biomolecules is present at high concentrations. To better understand how molecular behavior differs under such conditions (collectively described as macromolecular crowding), the crowding environment has been reproduced inside artificial cells. We have previously shown that the combination of macromolecular crowding and microscale geometries imposed by the artificial cells can alter the molecular behaviors induced by macromolecular crowding in bulk solutions. We have named the effect that makes such a difference the cell-size space effect (CSE). Here, we review the underlying biophysics of CSE for phase separation of binary polymer blends. We discuss how the cell-size space can initiate phase separation, unlike nano-sized spaces, which are known to hinder nucleation and phase separation. Additionally, we discuss how the dimensions of the artificial cell and its membrane characteristics can significantly impact phase separation dynamics and equilibrium composition. Although these findings are, of themselves, very interesting, their real significance may lie in helping to clarify the functions of the cell membrane and space size in the regulation of intracellular phase separation.
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Affiliation(s)
- Miho Yanagisawa
- Graduate School of Arts and Sciences, Komaba Institute for Science, The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo, 153-8902 Japan
- Department of Physics, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo, 113-0033 Japan
- Center for Complex Systems Biology, Universal Biology Institute, The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo, 153-8902 Japan
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14
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Abstract
One of the major challenges of bottom-up synthetic biology is rebuilding a minimal cell division machinery. From a reconstitution perspective, the animal cell division apparatus is mechanically the simplest and therefore attractive to rebuild. An actin-based ring produces contractile force to constrict the membrane. By contrast, microbes and plant cells have a cell wall, so division requires concerted membrane constriction and cell wall synthesis. Furthermore, reconstitution of the actin division machinery helps in understanding the physical and molecular mechanisms of cytokinesis in animal cells and thus our own cells. In this review, we describe the state-of-the-art research on reconstitution of minimal actin-mediated cytokinetic machineries. Based on the conceptual requirements that we obtained from the physics of the shape changes involved in cell division, we propose two major routes for building a minimal actin apparatus capable of division. Importantly, we acknowledge both the passive and active roles that the confining lipid membrane can play in synthetic cytokinesis. We conclude this review by identifying the most pressing challenges for future reconstitution work, thereby laying out a roadmap for building a synthetic cell equipped with a minimal actin division machinery.
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15
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Mondal A, Morrison G. Compression-induced buckling of a semiflexible filament in two and three dimensions. J Chem Phys 2022; 157:104903. [DOI: 10.1063/5.0104910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The ability of biomolecules to exert forces on their surroundings or resist compression from the environment is essential in a variety of biologically relevant contexts. For filaments in the low-temperature limit and under a constant compressive force, Euler buckling theory predicts a sudden transition from a compressed to a bent state in these slender rods. In this paper, we use a mean-field theory to show that if a semiflexible chain is compressed at a finite temperature with a fixed end-to-end distance (permitting fluctuations in the compressive forces), it exhibits a continuous phase transition to a buckled state at a critical level of compression. We determine a quantitatively accurate prediction of the transverse position distribution function of the midpoint of the chain that indicates this transition. We find the mean compressive forces are non-monotonic as the extension of the filament varies, consistent with the observation that strongly buckled filaments are less able to bear an external load. We also find that for the fixed extension (isometric) ensemble, the buckling transition does not coincide with the local minimum of the mean force (in contrast to Euler buckling). We also show the theory is highly sensitive to fluctuations in length in two dimensions, and that the buckling transition can still be accurately recovered by accounting for those fluctuations. These predictions may be useful in understanding the behavior of filamentous biomolecules compressed by fluctuating forces, relevant in a variety of biological contexts.
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Affiliation(s)
- Ananya Mondal
- Physics, University of Houston, United States of America
| | - Greg Morrison
- Physics, University of Houston, United States of America
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16
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Jahnke K, Huth V, Mersdorf U, Liu N, Göpfrich K. Bottom-Up Assembly of Synthetic Cells with a DNA Cytoskeleton. ACS NANO 2022; 16:7233-7241. [PMID: 35377150 PMCID: PMC9134502 DOI: 10.1021/acsnano.1c10703] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Cytoskeletal elements, like actin and myosin, have been reconstituted inside lipid vesicles toward the vision to reconstruct cells from the bottom up. Here, we realize the de novo assembly of entirely artificial DNA-based cytoskeletons with programmed multifunctionality inside synthetic cells. Giant unilamellar lipid vesicles (GUVs) serve as cell-like compartments, in which the DNA cytoskeletons are repeatedly and reversibly assembled and disassembled with light using the cis-trans isomerization of an azobenzene moiety positioned in the DNA tiles. Importantly, we induced ordered bundling of hundreds of DNA filaments into more rigid structures with molecular crowders. We quantify and tune the persistence length of the bundled filaments to achieve the formation of ring-like cortical structures inside GUVs, resembling actin rings that form during cell division. Additionally, we show that DNA filaments can be programmably linked to the compartment periphery using cholesterol-tagged DNA as a linker. The linker concentration determines the degree of the cortex-like network formation, and we demonstrate that the DNA cortex-like network can deform GUVs from within. All in all, this showcases the potential of DNA nanotechnology to mimic the diverse functions of a cytoskeleton in synthetic cells.
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Affiliation(s)
- Kevin Jahnke
- Biophysical
Engineering Group, Max Planck Institute
for Medical Research, Jahnstraße 29, D-69120 Heidelberg, Germany
- Department
of Physics and Astronomy, Heidelberg University, D-69120 Heidelberg, Germany
| | - Vanessa Huth
- Biophysical
Engineering Group, Max Planck Institute
for Medical Research, Jahnstraße 29, D-69120 Heidelberg, Germany
- Department
of Physics and Astronomy, Heidelberg University, D-69120 Heidelberg, Germany
| | - Ulrike Mersdorf
- Department
of Biomolecular Mechanisms, Max Planck Institute
for Medical Research, Jahnstraße 29, D-69120 Heidelberg, Germany
| | - Na Liu
- 2nd
Physics Institute, University of Stuttgart, Im Pfaffenwaldring 57, D-70569 Stuttgart, Germany
- Max
Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
| | - Kerstin Göpfrich
- Biophysical
Engineering Group, Max Planck Institute
for Medical Research, Jahnstraße 29, D-69120 Heidelberg, Germany
- Department
of Physics and Astronomy, Heidelberg University, D-69120 Heidelberg, Germany
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17
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Bashirzadeh Y, Moghimianavval H, Liu AP. Encapsulated actomyosin patterns drive cell-like membrane shape changes. iScience 2022; 25:104236. [PMID: 35521522 PMCID: PMC9061794 DOI: 10.1016/j.isci.2022.104236] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 01/26/2022] [Accepted: 04/07/2022] [Indexed: 11/21/2022] Open
Abstract
Cell shape changes from locomotion to cytokinesis are, to a large extent, driven by myosin-driven remodeling of cortical actin patterns. Passive crosslinkers such as α-actinin and fascin as well as actin nucleator Arp2/3 complex largely determine actin network architecture and, consequently, membrane shape changes. Here we reconstitute actomyosin networks inside cell-sized lipid bilayer vesicles and show that depending on vesicle size and concentrations of α-actinin and fascin actomyosin networks assemble into ring and aster-like patterns. Anchoring actin to the membrane does not change actin network architecture yet exerts forces and deforms the membrane when assembled in the form of a contractile ring. In the presence of α-actinin and fascin, an Arp2/3 complex-mediated actomyosin cortex is shown to assemble a ring-like pattern at the equatorial cortex followed by myosin-driven clustering and consequently blebbing. An active gel theory unifies a model for the observed membrane shape changes induced by the contractile cortex. Myosin, α-actinin, and fascin drive the formation of diverse actin patterns in GUVs A self-assembling membrane-bound contractile ring pattern slightly deforms GUVs Dendritic actomyosin requires actin crosslinkers for clustering and GUV blebbing A physical model describes membrane deformation at the site of actomyosin cluster
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18
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Moghimianavval H, Hsu YY, Groaz A, Liu AP. In Vitro Reconstitution Platforms of Mammalian Cell-Free Expressed Membrane Proteins. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2022; 2433:105-120. [PMID: 34985740 DOI: 10.1007/978-1-0716-1998-8_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Membrane proteins are essential components in cell membranes and enable cells to communicate with their outside environment and to carry out intracellular signaling. Functional reconstitution of complex membrane proteins using cell-free expression (CFE) systems has been proved to be challenging mainly due to the lack of necessary machinery for proper folding and translocation of nascent membrane proteins and their delivery to the supplied synthetic bilayers. Here, we provide protocols for detergent-free, cell-free reconstitution of functional membrane proteins using HeLa-based CFE system and outline assays for studying their membrane insertion, topology, and their orientation upon incorporation into the supported lipid bilayers or bilayers of giant unilamellar vesicles as well as methods to isolate functional translocated cell-free produced membrane proteins.
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Affiliation(s)
| | - Yen-Yu Hsu
- University of Michigan, Ann Arbor, MI, USA
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19
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Zhovmer AS, Manning A, Smith C, Hayes JB, Burnette DT, Wang J, Cartagena-Rivera AX, Dokholyan NV, Singh RK, Tabdanov ED. Mechanical Counterbalance of Kinesin and Dynein Motors in a Microtubular Network Regulates Cell Mechanics, 3D Architecture, and Mechanosensing. ACS NANO 2021; 15:17528-17548. [PMID: 34677937 PMCID: PMC9291236 DOI: 10.1021/acsnano.1c04435] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Microtubules (MTs) and MT motor proteins form active 3D networks made of unstretchable cables with rod-like bending mechanics that provide cells with a dynamically changing structural scaffold. In this study, we report an antagonistic mechanical balance within the dynein-kinesin microtubular motor system. Dynein activity drives the microtubular network inward compaction, while isolated activity of kinesins bundles and expands MTs into giant circular bands that deform the cell cortex into discoids. Furthermore, we show that dyneins recruit MTs to sites of cell adhesion, increasing the topographic contact guidance of cells, while kinesins antagonize it via retraction of MTs from sites of cell adhesion. Actin-to-microtubule translocation of septin-9 enhances kinesin-MT interactions, outbalances the activity of kinesins over that of dyneins, and induces the discoid architecture of cells. These orthogonal mechanisms of MT network reorganization highlight the existence of an intricate mechanical balance between motor activities of kinesins and dyneins that controls cell 3D architecture, mechanics, and cell-microenvironment interactions.
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Affiliation(s)
- Alexander S. Zhovmer
- Center
for Biologics Evaluation and Research, U.S.
Food and Drug Administration, Silver Spring, Maryland 20903, United States
- . Tel: 1-301-402-1606
| | - Alexis Manning
- Center
for Biologics Evaluation and Research, U.S.
Food and Drug Administration, Silver Spring, Maryland 20903, United States
| | - Chynna Smith
- Section
on Mechanobiology, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - James B. Hayes
- Department
of Cell and Developmental Biology, Vanderbilt Medical Center, University of Vanderbilt, Nashville, Tennessee 37232, United States
| | - Dylan T. Burnette
- Department
of Cell and Developmental Biology, Vanderbilt Medical Center, University of Vanderbilt, Nashville, Tennessee 37232, United States
| | - Jian Wang
- Department
of Pharmacology, Penn State College of Medicine, Pennsylvania State University, Hummelstown, Pennsylvania 17036, United States
| | - Alexander X. Cartagena-Rivera
- Section
on Mechanobiology, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, United States
- . Tel: 1-301-503-4033
| | - Nikolay V. Dokholyan
- Department
of Pharmacology, Penn State College of Medicine, Pennsylvania State University, Hummelstown, Pennsylvania 17036, United States
- Department
of Biochemistry & Molecular Biology, Penn State College of Medicine, Pennsylvania State University, Hershey, Pennsylvania 17033, United States
- . Tel: 1-717-531-5177
| | - Rakesh K. Singh
- Department
of Obstetrics and Gynecology, University
of Rochester Medical Center, Rochester, New York 14620, United States
- . Tel: 1-585-276-6281
| | - Erdem D. Tabdanov
- Department
of Pharmacology, Penn State College of Medicine, Pennsylvania State University, Hummelstown, Pennsylvania 17036, United States
- . Tel: 1-717-531-0003 Ext: 4430
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20
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Sharma B, Moghimianavval H, Hwang SW, Liu AP. Synthetic Cell as a Platform for Understanding Membrane-Membrane Interactions. MEMBRANES 2021; 11:912. [PMID: 34940413 PMCID: PMC8706075 DOI: 10.3390/membranes11120912] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/10/2021] [Accepted: 11/16/2021] [Indexed: 01/27/2023]
Abstract
In the pursuit of understanding life, model membranes made of phospholipids were envisaged decades ago as a platform for the bottom-up study of biological processes. Micron-sized lipid vesicles have gained great acceptance as their bilayer membrane resembles the natural cell membrane. Important biological events involving membranes, such as membrane protein insertion, membrane fusion, and intercellular communication, will be highlighted in this review with recent research updates. We will first review different lipid bilayer platforms used for incorporation of integral membrane proteins and challenges associated with their functional reconstitution. We next discuss different methods for reconstitution of membrane fusion and compare their fusion efficiency. Lastly, we will highlight the importance and challenges of intercellular communication between synthetic cells and synthetic cells-to-natural cells. We will summarize the review by highlighting the challenges and opportunities associated with studying membrane-membrane interactions and possible future research directions.
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Affiliation(s)
- Bineet Sharma
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; (B.S.); (H.M.)
| | - Hossein Moghimianavval
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; (B.S.); (H.M.)
| | - Sung-Won Hwang
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA;
| | - Allen P. Liu
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA; (B.S.); (H.M.)
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI 48105, USA
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48105, USA
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21
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A strong nonequilibrium bound for sorting of cross-linkers on growing biopolymers. Proc Natl Acad Sci U S A 2021; 118:2102881118. [PMID: 34518221 DOI: 10.1073/pnas.2102881118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2021] [Indexed: 12/18/2022] Open
Abstract
Understanding the role of nonequilibrium driving in self-organization is crucial for developing a predictive description of biological systems, yet it is impeded by their complexity. The actin cytoskeleton serves as a paradigm for how equilibrium and nonequilibrium forces combine to give rise to self-organization. Motivated by recent experiments that show that actin filament growth rates can tune the morphology of a growing actin bundle cross-linked by two competing types of actin-binding proteins [S. L. Freedman et al., Proc. Natl. Acad. Sci. U.S.A. 116, 16192-16197 (2019)], we construct a minimal model for such a system and show that the dynamics of a growing actin bundle are subject to a set of thermodynamic constraints that relate its nonequilibrium driving, morphology, and molecular fluxes. The thermodynamic constraints reveal the importance of correlations between these molecular fluxes and offer a route to estimating microscopic driving forces from microscopy experiments.
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