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Lin AJ, Sihorwala AZ, Belardi B. Engineering Tissue-Scale Properties with Synthetic Cells: Forging One from Many. ACS Synth Biol 2023; 12:1889-1907. [PMID: 37417657 PMCID: PMC11017731 DOI: 10.1021/acssynbio.3c00061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/08/2023]
Abstract
In metazoans, living cells achieve capabilities beyond individual cell functionality by assembling into multicellular tissue structures. These higher-order structures represent dynamic, heterogeneous, and responsive systems that have evolved to regenerate and coordinate their actions over large distances. Recent advances in constructing micrometer-sized vesicles, or synthetic cells, now point to a future where construction of synthetic tissue can be pursued, a boon to pressing material needs in biomedical implants, drug delivery systems, adhesives, filters, and storage devices, among others. To fully realize the potential of synthetic tissue, inspiration has been and will continue to be drawn from new molecular findings on its natural counterpart. In this review, we describe advances in introducing tissue-scale features into synthetic cell assemblies. Beyond mere complexation, synthetic cells have been fashioned with a variety of natural and engineered molecular components that serve as initial steps toward morphological control and patterning, intercellular communication, replication, and responsiveness in synthetic tissue. Particular attention has been paid to the dynamics, spatial constraints, and mechanical strengths of interactions that drive the synthesis of this next-generation material, describing how multiple synthetic cells can act as one.
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Affiliation(s)
- Alexander J Lin
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Ahmed Z Sihorwala
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
| | - Brian Belardi
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
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2
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Izumi K, Saito C, Kawano R. Liposome Deformation Induced by Membrane-Binding Peptides. MICROMACHINES 2023; 14:373. [PMID: 36838073 PMCID: PMC9967443 DOI: 10.3390/mi14020373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 01/25/2023] [Accepted: 01/31/2023] [Indexed: 06/18/2023]
Abstract
This paper presents an investigation of liposome deformation and shape distortion using four membrane-binding peptides: TAT and C105Y as cell-penetrating peptides (CPPs), and melittin and ovispirin as antimicrobial peptides (AMPs). Liposome deformation was monitored utilizing fluorescent microscopy, while the binding of peptides to the DOPC membrane was estimated through capacitance measurements. The degree of liposome deformation and shape distortion was found to be higher for the CPPs compared to the AMPs. Additionally, it was observed that C105Y did not induce liposome rupture, unlike the other three peptides. We propose that these variations in liposome distortion may be attributed to differences in secondary structure, specifically the presence of an α-helix or random coil. Our studies offer insight into the use of peptides to elicit control of liposome architecture and may offer a promising approach for regulating the bodies of liposomal molecular robots.
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3
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Kattan J, Doerr A, Dogterom M, Danelon C. Shaping Liposomes by Cell-Free Expressed Bacterial Microtubules. ACS Synth Biol 2021; 10:2447-2455. [PMID: 34585918 PMCID: PMC8524656 DOI: 10.1021/acssynbio.1c00278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
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Genetic control over
a cytoskeletal network inside lipid vesicles
offers a potential route to controlled shape changes and DNA segregation
in synthetic cell biology. Bacterial microtubules (bMTs) are protein
filaments found in bacteria of the genus Prosthecobacter. They are formed by the tubulins BtubA and BtubB, which polymerize
in the presence of GTP. Here, we show that the tubulins BtubA/B can
be functionally expressed from DNA templates in a reconstituted transcription-translation
system, thus providing a cytosol-like environment to study their biochemical
and biophysical properties. We found that bMTs spontaneously interact
with lipid membranes and display treadmilling. When compartmentalized
inside liposomes, de novo synthesized BtubA/B tubulins
self-organize into cytoskeletal structures of different morphologies.
Moreover, bMTs can exert a pushing force on the membrane and deform
liposomes, a phenomenon that can be reversed by a light-activated
disassembly of the filaments. Our work establishes bMTs as a new building
block in synthetic biology. In the context of creating a synthetic
cell, bMTs could help shape the lipid compartment, establish polarity
or directional transport, and assist the division machinery.
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Affiliation(s)
- Johannes Kattan
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Anne Doerr
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Marileen Dogterom
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Christophe Danelon
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands
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4
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Ghilardi SJ, Aronson MS, Sgro AE. Ventral stress fibers induce plasma membrane deformation in human fibroblasts. Mol Biol Cell 2021; 32:1707-1723. [PMID: 34191528 PMCID: PMC8684729 DOI: 10.1091/mbc.e21-03-0096] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Interactions between the actin cytoskeleton and the plasma membrane are important in many eukaryotic cellular processes. During these processes, actin structures deform the cell membrane outward by applying forces parallel to the fiber’s major axis (as in migration) or they deform the membrane inward by applying forces perpendicular to the fiber’s major axis (as in the contractile ring during cytokinesis). Here we describe a novel actin–membrane interaction in human dermal myofibroblasts. When labeled with a cytosolic fluorophore, the myofibroblasts displayed prominent fluorescent structures on the ventral side of the cell. These structures are present in the cell membrane and colocalize with ventral actin stress fibers, suggesting that the stress fibers bend the membrane to form a “cytosolic pocket” that the fluorophores diffuse into, creating the observed structures. The existence of this pocket was confirmed by transmission electron microscopy. While dissolving the stress fibers, inhibiting fiber protein binding, or inhibiting myosin II binding of actin removed the observed pockets, modulating cellular contractility did not remove them. Taken together, our results illustrate a novel actin–membrane bending topology where the membrane is deformed outward rather than being pinched inward, resembling the topological inverse of the contractile ring found in cytokinesis.
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Affiliation(s)
- Samuel J Ghilardi
- Department of Biomedical Engineering and the Biological Design Center, Boston University, Boston, MA 02215
| | - Mark S Aronson
- Department of Biomedical Engineering and the Biological Design Center, Boston University, Boston, MA 02215
| | - Allyson E Sgro
- Department of Biomedical Engineering and the Biological Design Center, Boston University, Boston, MA 02215
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5
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Abstract
Giant unilamellar vesicles (GUVs) have gained great popularity as mimicries for cellular membranes. As their sizes are comfortably above the optical resolution limit, and their lipid composition is easily controlled, they are ideal for quantitative light microscopic investigation of dynamic processes in and on membranes. However, reconstitution of functional proteins into the lumen or the GUV membrane itself has proven technically challenging. In recent years, a selection of techniques has been introduced that tremendously improve GUV-assay development and enable the precise investigation of protein-membrane interactions under well-controlled conditions. Moreover, due to these methodological advances, GUVs are considered important candidates as protocells in bottom-up synthetic biology. In this review, we discuss the state of the art of the most important vesicle production and protein encapsulation methods and highlight some key protein systems whose functional reconstitution has advanced the field.
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Affiliation(s)
- Thomas Litschel
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried 82152, Germany; ,
| | - Petra Schwille
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried 82152, Germany; ,
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6
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Gharooni M, Alikhani A, Moghtaderi H, Abiri H, Mashaghi A, Abbasvandi F, Khayamian MA, Miripour ZS, Zandi A, Abdolahad M. Bioelectronics of The Cellular Cytoskeleton: Monitoring Cytoskeletal Conductance Variation for Sensing Drug Resistance. ACS Sens 2019; 4:353-362. [PMID: 30572702 DOI: 10.1021/acssensors.8b01142] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Actin and microtubules form cellular cytoskeletal network, which mediates cell shape, motility and proliferation and are key targets for cancer therapy. Changes in cytoskeletal organization dramatically affect mechanical properties of the cells and correlate with proliferative capacity and invasiveness of cancer cells. Changes in the cytoskeletal network expectedly lead to altered nonmechanical material properties including electrical conductivity as well. Here we applied, for the first time, microtubule and actin based electrical measurement to monitor changes in the electrical properties of breast cancer cells upon administration of anti-tubulin and anti-actin drugs, respectively. Semiconductive behavior of microtubules and conductive behavior of actins presented different bioelectrical responses (in similar frequencies) of the cells treated by anti-tubulin with respect to anti-actin drugs. Doped silicon nanowires were applied as the electrodes due to their enhanced interactive surface and compatibility with electronic fabrication process. We found that treatment with Mebendazole (MBZ), a microtubule destabilizing agent, decreases electrical resistance while treatment with Paclitaxel (PTX), a microtubule stabilizing agent, leads to an increase in electrical resistance. In contrast, actin destabilizing agents, Cytochalasin D (CytD), and actin stabilizing agent, Phalloidin, lead to an increased and decreased electrical resistance, respectively. Our study thus provides proof-of-principle of the usage of determining the electrical function of cytoskeletal compartments in grading of cancer as well as drug resistance assays.
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Affiliation(s)
| | | | | | | | - Alireza Mashaghi
- Leiden Academic Centre for Drug Research, Faculty of Mathematics and Natural Sciences, Leiden University, 2311 EZ, Leiden, The Netherlands
| | - Fereshteh Abbasvandi
- ATMP Department, Breast Cancer Research Center, Motamed Cancer Institute, ACECR, P.O. BOX 15179/64311, Tehran, Iran
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Erickson JL, Schattat MH. Shaping plastid stromules-principles of in vitro membrane tubulation applied in planta. CURRENT OPINION IN PLANT BIOLOGY 2018; 46:48-54. [PMID: 30041102 DOI: 10.1016/j.pbi.2018.07.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 07/01/2018] [Accepted: 07/06/2018] [Indexed: 05/10/2023]
Abstract
Plastids undergo drastic shape changes under stress, including the formation of stroma-filled tubules, or `stromules'. Stromules are dynamic, and may extend, branch and retract within minutes. There are two prerequisites for stromule extension: excess plastid membrane and a force(s) that shapes the membrane into a tubule. In vitro studies provide insight into the basic molecular machinery for tubulation, and are often cited when discussing stromule formation. In this review, we evaluate in vitro modes of tubulation in the context of stromule dynamics, and find that most mechanisms fail to explain stromule morphology and behavior observed in planta. Current data support a model of stromule formation relying on pulling motors (myosins and kinesins) and cytoskeleton (actin and microtubules).
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Affiliation(s)
- Jessica Lee Erickson
- Department of Plant Physiology, Institute for Biology, Martin Luther University Halle-Wittenberg, D-06099 Halle, Germany
| | - Martin Hartmut Schattat
- Department of Plant Physiology, Institute for Biology, Martin Luther University Halle-Wittenberg, D-06099 Halle, Germany.
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8
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Schön M, Mey I, Steinem C. Influence of cross-linkers on ezrin-bound minimal actin cortices. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2018; 144:91-101. [PMID: 30093083 DOI: 10.1016/j.pbiomolbio.2018.07.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 07/13/2018] [Accepted: 07/31/2018] [Indexed: 12/21/2022]
Abstract
The actin cortex is a thin network coupled to the plasma membrane of cells, responsible for e.g., cell shape, motility, growth and division. Several model systems for minimal actin cortices (MACs) have been discussed in literature trying to mimic the complex interplay of membrane and actin. We recapitulate on different types of MACs using either three dimensional droplet interfaces or lipid bilayers to which F-actin networks are attached to or planar lipid bilayers with bound actin networks. Binding of the network to the membrane interface significantly influences its properties as well as its dynamics. This in turn also influences, how cross-linkers as well as myosin motors act on the network. Here, we describe the coupling of a filamentous actin network to a model membrane via the protein ezrin, a member of the ezrin-radixin-moesin family, which forms a direct linkage between the plasma membrane and the cortical web. Ezrin binding to the membrane is achieved by the lipid PtdIns(4,5)P2, while attachment to F-actin is mediated via the C-terminal domain of the protein leading to a two dimensional arrangement of actin filaments on the membrane. Addition of cross-linkers such as fascin and α-actinin influences the architecture of the actin network, which we have investigated by means of fluorescence microscopy. The results are discussed in terms of the dynamics of the filaments on the membrane surface.
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Affiliation(s)
- Markus Schön
- Georg-August Universität Göttingen, Institut für Organische und Biomolekulare Chemie, Tammannstr. 2, 37077, Göttingen, Germany
| | - Ingo Mey
- Georg-August Universität Göttingen, Institut für Organische und Biomolekulare Chemie, Tammannstr. 2, 37077, Göttingen, Germany.
| | - Claudia Steinem
- Georg-August Universität Göttingen, Institut für Organische und Biomolekulare Chemie, Tammannstr. 2, 37077, Göttingen, Germany.
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9
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Abraham T, Mao M, Tan C. Engineering approaches of smart, bio-inspired vesicles for biomedical applications. Phys Biol 2018; 15:061001. [DOI: 10.1088/1478-3975/aac7a2] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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10
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Chabanon M, Stachowiak JC, Rangamani P. Systems biology of cellular membranes: a convergence with biophysics. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2017; 9:10.1002/wsbm.1386. [PMID: 28475297 PMCID: PMC5561455 DOI: 10.1002/wsbm.1386] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 02/02/2017] [Accepted: 02/21/2017] [Indexed: 12/12/2022]
Abstract
Systems biology and systems medicine have played an important role in the last two decades in shaping our understanding of biological processes. While systems biology is synonymous with network maps and '-omics' approaches, it is not often associated with mechanical processes. Here, we make the case for considering the mechanical and geometrical aspects of biological membranes as a key step in pushing the frontiers of systems biology of cellular membranes forward. We begin by introducing the basic components of cellular membranes, and highlight their dynamical aspects. We then survey the functions of the plasma membrane and the endomembrane system in signaling, and discuss the role and origin of membrane curvature in these diverse cellular processes. We further give an overview of the experimental and modeling approaches to study membrane phenomena. We close with a perspective on the converging futures of systems biology and membrane biophysics, invoking the need to include physical variables such as location and geometry in the study of cellular membranes. WIREs Syst Biol Med 2017, 9:e1386. doi: 10.1002/wsbm.1386 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Morgan Chabanon
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, USA
| | - Jeanne C. Stachowiak
- Department of Biomedical Engineering, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX, USA
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA, USA
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11
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12
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Siton-Mendelson O, Bernheim-Groswasser A. Toward the reconstitution of synthetic cell motility. Cell Adh Migr 2016; 10:461-474. [PMID: 27019160 DOI: 10.1080/19336918.2016.1170260] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Cellular motility is a fundamental process essential for embryonic development, wound healing, immune responses, and tissues development. Cells are mostly moving by crawling on external, or inside, substrates which can differ in their surface composition, geometry, and dimensionality. Cells can adopt different migration phenotypes, e.g., bleb-based and protrusion-based, depending on myosin contractility, surface adhesion, and cell confinement. In the few past decades, research on cell motility has focused on uncovering the major molecular players and their order of events. Despite major progresses, our ability to infer on the collective behavior from the molecular properties remains a major challenge, especially because cell migration integrates numerous chemical and mechanical processes that are coupled via feedbacks that span over large range of time and length scales. For this reason, reconstituted model systems were developed. These systems allow for full control of the molecular constituents and various system parameters, thereby providing insight into their individual roles and functions. In this review we describe the various reconstituted model systems that were developed in the past decades. Because of the multiple steps involved in cell motility and the complexity of the overall process, most of the model systems focus on very specific aspects of the individual steps of cell motility. Here we describe the main advancement in cell motility reconstitution and discuss the main challenges toward the realization of a synthetic motile cell.
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Affiliation(s)
- Orit Siton-Mendelson
- a Department of Chemical Engineering and the Ilse Kats Institute for Nanoscale Science and Technology , Ben-Gurion University of the Negev , Beer-Sheva , Israel
| | - Anne Bernheim-Groswasser
- a Department of Chemical Engineering and the Ilse Kats Institute for Nanoscale Science and Technology , Ben-Gurion University of the Negev , Beer-Sheva , Israel
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13
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Tsai FC, Koenderink GH. Shape control of lipid bilayer membranes by confined actin bundles. SOFT MATTER 2015; 11:8834-8847. [PMID: 26395896 DOI: 10.1039/c5sm01583a] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In living cells, lipid membranes and biopolymers determine each other's conformation in a delicate force balance. Cellular polymers such as actin filaments are strongly confined by the plasma membrane in cell protrusions such as lamellipodia and filopodia. Conversely, protrusion formation is facilitated by actin-driven membrane deformation and these protrusions are maintained by dense actin networks or bundles of actin filaments. Here we investigate the mechanical interplay between actin bundles and lipid bilayer membranes by reconstituting a minimal model system based on cell-sized liposomes with encapsulated actin filaments bundled by fascin. To address the competition between the deformability of the membrane and the enclosed actin bundles, we tune the bundle stiffness (through the fascin-to-actin molar ratio) and the membrane rigidity (through protein decoration). Using confocal microscopy and quantitative image analysis, we show that actin bundles deform the liposomes into a rich set of morphologies. For liposomes having a small membrane bending rigidity, the actin bundles tend to generate finger-like membrane protrusions that resemble cellular filopodia. Stiffer bundles formed at high crosslink density stay straight in the liposome body, whereas softer bundles formed at low crosslink density are bent and kinked. When the membrane has a large bending rigidity, membrane protrusions are suppressed. In this case, membrane enclosure forces the actin bundles to organize into cortical rings, to minimize the energy cost associated with filament bending. Our results highlight the importance of taking into account mechanical interactions between the actin cytoskeleton and the membrane to understand cell shape control.
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Affiliation(s)
- Feng-Ching Tsai
- FOM Institute AMOLF, Systems Biophysics Department, Science Park 104, 1098 XG Amsterdam, The Netherlands.
| | - Gijsje Hendrika Koenderink
- FOM Institute AMOLF, Systems Biophysics Department, Science Park 104, 1098 XG Amsterdam, The Netherlands.
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Reconstituting the actin cytoskeleton at or near surfaces in vitro. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:3006-14. [PMID: 26235437 DOI: 10.1016/j.bbamcr.2015.07.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 07/15/2015] [Accepted: 07/16/2015] [Indexed: 01/08/2023]
Abstract
Actin filament dynamics have been studied for decades in pure protein solutions or in cell extracts, but a breakthrough in the field occurred at the turn of the century when it became possible to reconstitute networks of actin filaments, growing in a controlled but physiological manner on surfaces, mimicking the actin assembly that occurs at the plasma membrane during cell protrusion and cell shape changes. The story begins with the bacteria Listeria monocytogenes, the study of which led to the reconstitution of cellular actin polymerization on a variety of supports including plastic beads. These studies made possible the development of liposome-type substrates for filament assembly and micropatterning of actin polymerization nucleation. Based on the accumulated expertise of the last 15 years, many exciting approaches are being developed, including the addition of myosin to biomimetic actin networks to study the interplay between actin structure and contractility. The field is now poised to make artificial cells with a physiological and dynamic actin cytoskeleton, and subsequently to put these cells together to make in vitro tissues. This article is part of a Special Issue entitled: Mechanobiology.
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15
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Choi HJ, Song JM, Bondy BJ, Compans RW, Kang SM, Prausnitz MR. Effect of Osmotic Pressure on the Stability of Whole Inactivated Influenza Vaccine for Coating on Microneedles. PLoS One 2015; 10:e0134431. [PMID: 26230936 PMCID: PMC4521748 DOI: 10.1371/journal.pone.0134431] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2015] [Accepted: 07/10/2015] [Indexed: 11/18/2022] Open
Abstract
Enveloped virus vaccines can be damaged by high osmotic strength solutions, such as those used to protect the vaccine antigen during drying, which contain high concentrations of sugars. We therefore studied shrinkage and activity loss of whole inactivated influenza virus in hyperosmotic solutions and used those findings to improve vaccine coating of microneedle patches for influenza vaccination. Using stopped-flow light scattering analysis, we found that the virus underwent an initial shrinkage on the order of 10% by volume within 5 s upon exposure to a hyperosmotic stress difference of 217 milliosmolarity. During this shrinkage, the virus envelope had very low osmotic water permeability (1 - 6×10-4 cm s-1) and high Arrhenius activation energy (Ea = 15.0 kcal mol-1), indicating that the water molecules diffused through the viral lipid membranes. After a quasi-stable state of approximately 20 s to 2 min, depending on the species and hypertonic osmotic strength difference of disaccharides, there was a second phase of viral shrinkage. At the highest osmotic strengths, this led to an undulating light scattering profile that appeared to be related to perturbation of the viral envelope resulting in loss of virus activity, as determined by in vitro hemagglutination measurements and in vivo immunogenicity studies in mice. Addition of carboxymethyl cellulose effectively prevented vaccine activity loss in vitro and in vivo, believed to be due to increasing the viscosity of concentrated sugar solution and thereby reducing osmotic stress during coating of microneedles. These results suggest that hyperosmotic solutions can cause biphasic shrinkage of whole inactivated influenza virus which can damage vaccine activity at high osmotic strength and that addition of a viscosity enhancer to the vaccine coating solution can prevent osmotically driven damage and thereby enable preparation of stable microneedle coating formulations for vaccination.
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Affiliation(s)
- Hyo-Jick Choi
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States of America
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada
| | - Jae-Min Song
- Department of Global Medical Science, Sungshin Women's University, Seoul, Korea
| | - Brian J. Bondy
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States of America
| | - Richard W. Compans
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Sang-Moo Kang
- Center for Inflammation, Immunity, & Infection and Department of Biology, Georgia State University, Atlanta, Georgia, United States of America
| | - Mark R. Prausnitz
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States of America
- * E-mail:
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16
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Integration of actin dynamics and cell adhesion by a three-dimensional, mechanosensitive molecular clutch. Nat Cell Biol 2015; 17:955-63. [PMID: 26121555 DOI: 10.1038/ncb3191] [Citation(s) in RCA: 330] [Impact Index Per Article: 36.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 05/15/2015] [Indexed: 12/12/2022]
Abstract
During cell migration, the forces generated in the actin cytoskeleton are transmitted across transmembrane receptors to the extracellular matrix or other cells through a series of mechanosensitive, regulable protein-protein interactions termed the molecular clutch. In integrin-based focal adhesions, the proteins forming this linkage are organized into a conserved three-dimensional nano-architecture. Here we discuss how the physical interactions between the actin cytoskeleton and focal-adhesion-associated molecules mediate force transmission from the molecular clutch to the extracellular matrix.
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17
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Brüggemann D, Frohnmayer JP, Spatz JP. Model systems for studying cell adhesion and biomimetic actin networks. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2014; 5:1193-202. [PMID: 25161853 PMCID: PMC4142981 DOI: 10.3762/bjnano.5.131] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 06/25/2014] [Indexed: 05/28/2023]
Abstract
Many cellular processes, such as migration, proliferation, wound healing and tumor progression are based on cell adhesion. Amongst different cell adhesion molecules, the integrin receptors play a very significant role. Over the past decades the function and signalling of various such integrins have been studied by incorporating the proteins into lipid membranes. These proteolipid structures lay the foundation for the development of artificial cells, which are able to adhere to substrates. To build biomimetic models for studying cell shape and spreading, actin networks can be incorporated into lipid vesicles, too. We here review the mechanisms of integrin-mediated cell adhesion and recent advances in the field of minimal cells towards synthetic adhesion. We focus on reconstituting integrins into lipid structures for mimicking cell adhesion and on the incorporation of actin networks and talin into model cells.
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Affiliation(s)
- Dorothea Brüggemann
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- Department of Biophysical Chemistry, University of Heidelberg, INF 253, D-69120 Heidelberg, Germany
| | - Johannes P Frohnmayer
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- Department of Biophysical Chemistry, University of Heidelberg, INF 253, D-69120 Heidelberg, Germany
| | - Joachim P Spatz
- Department of New Materials and Biosystems, Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
- Department of Biophysical Chemistry, University of Heidelberg, INF 253, D-69120 Heidelberg, Germany
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18
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Urakami N, Takaki A, Imai M, Yamamoto T. Molecular dynamics simulation for shape change of water-in-oil droplets. MOLECULAR SIMULATION 2014. [DOI: 10.1080/08927022.2014.931582] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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19
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Wu KCW, Yang CY, Cheng CM. Using cell structures to develop functional nanomaterials and nanostructures – case studies of actin filaments and microtubules. Chem Commun (Camb) 2014; 50:4148-57. [DOI: 10.1039/c4cc00005f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Actin filaments and microtubules are utilized as building blocks to create functional nanomaterials and nanostructures for nature-inspired small-scale devices and systems.
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Affiliation(s)
- Kevin Chia-Wen Wu
- Department of Chemical Engineering
- National Taiwan University
- Taipei 10617, Taiwan
| | - Chung-Yao Yang
- Institute of Nanoengineering and Microsystems
- National Tsing Hua University
- Hsinchu 30013, Taiwan
| | - Chao-Min Cheng
- Institute of Nanoengineering and Microsystems
- National Tsing Hua University
- Hsinchu 30013, Taiwan
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20
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Kapus A, Janmey P. Plasma membrane--cortical cytoskeleton interactions: a cell biology approach with biophysical considerations. Compr Physiol 2013; 3:1231-81. [PMID: 23897686 DOI: 10.1002/cphy.c120015] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
From a biophysical standpoint, the interface between the cell membrane and the cytoskeleton is an intriguing site where a "two-dimensional fluid" interacts with an exceedingly complex three-dimensional protein meshwork. The membrane is a key regulator of the cytoskeleton, which not only provides docking sites for cytoskeletal elements through transmembrane proteins, lipid binding-based, and electrostatic interactions, but also serves as the source of the signaling events and molecules that control cytoskeletal organization and remolding. Conversely, the cytoskeleton is a key determinant of the biophysical and biochemical properties of the membrane, including its shape, tension, movement, composition, as well as the mobility, partitioning, and recycling of its constituents. From a cell biological standpoint, the membrane-cytoskeleton interplay underlies--as a central executor and/or regulator--a multitude of complex processes including chemical and mechanical signal transduction, motility/migration, endo-/exo-/phagocytosis, and other forms of membrane traffic, cell-cell, and cell-matrix adhesion. The aim of this article is to provide an overview of the tight structural and functional coupling between the membrane and the cytoskeleton. As biophysical approaches, both theoretical and experimental, proved to be instrumental for our understanding of the membrane/cytoskeleton interplay, this review will "oscillate" between the cell biological phenomena and the corresponding biophysical principles and considerations. After describing the types of connections between the membrane and the cytoskeleton, we will focus on a few key physical parameters and processes (force generation, curvature, tension, and surface charge) and will discuss how these contribute to a variety of fundamental cell biological functions.
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Affiliation(s)
- András Kapus
- Keenan Research Center, Li Ka Shing Knowledge Institute, St. Michael's Hospital and Department of Surgery, University of Toronto, Ontario, Canada.
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21
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Joshi SD, Davidson LA. Epithelial machines of morphogenesis and their potential application in organ assembly and tissue engineering. Biomech Model Mechanobiol 2012; 11:1109-21. [PMID: 22854913 PMCID: PMC3664917 DOI: 10.1007/s10237-012-0423-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 07/17/2012] [Indexed: 01/16/2023]
Abstract
Sheets of embryonic epithelial cells coordinate their efforts to create diverse tissue structures such as pits, grooves, tubes, and capsules that lead to organ formation. Such cells can use a number of cell behaviors including contractility, proliferation, and directed movement to create these structures. By contrast, tissue engineers and researchers in regenerative medicine seeking to produce organs for repair or replacement therapy can combine cells with synthetic polymeric scaffolds. Tissue engineers try to achieve these goals by shaping scaffold geometry in such a way that cells embedded within these scaffold self-assemble to form a tissue, for instance aligning to synthetic fibers, and assembling native extracellular matrix to form the desired tissue-like structure. Although self-assembly is a dominant process that guides tissue assembly both within the embryo and within artificial tissue constructs, we know little about these critical processes. Here, we compare and contrast strategies of tissue assembly used by embryos to those used by engineers during epithelial morphogenesis and highlight opportunities for future applications of developmental biology in the field of tissue engineering.
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Affiliation(s)
- Sagar D. Joshi
- Department of Bioengineering, University of Pittsburgh, 3501 Fifth Avenue, Pittsburgh PA 15213
| | - Lance A. Davidson
- Departments of Bioengineering and Developmental Biology, University of Pittsburgh, 3501 Fifth Avenue, Pittsburgh PA 15213
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22
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Hammer DA, Kamat NP. Towards an artificial cell. FEBS Lett 2012; 586:2882-90. [PMID: 22841716 DOI: 10.1016/j.febslet.2012.07.044] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 07/17/2012] [Accepted: 07/17/2012] [Indexed: 12/31/2022]
Abstract
We are on the verge of producing "synthetic cells," or protocells, in which some, many or all of the tasks of a real biological cell are harnessed into a synthetic platform. Such advances are made possible through genetic engineering, microfabrication technologies, and the development of cellular membranes from new surfactants that extend beyond phospholipids in stability and chemical control, and can be used to introduce designer functionality into membranes and cells. We review some of the recent advances in the development of synthetic cells and suggest future exciting directions.
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Affiliation(s)
- Daniel A Hammer
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
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23
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Vogel SK, Schwille P. Minimal systems to study membrane-cytoskeleton interactions. Curr Opin Biotechnol 2012; 23:758-65. [PMID: 22503237 DOI: 10.1016/j.copbio.2012.03.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 03/21/2012] [Accepted: 03/22/2012] [Indexed: 11/16/2022]
Abstract
In the context of minimal systems design, there are two areas in which the reductionist approach has been particularly successful: studies of molecular motors on cytoskeletal filaments, and of protein-lipid interactions in model membranes. However, a minimal cortex, that is, the interface between membrane and cytoskeleton, has just begun to be functionally reconstituted. A key property of living cells is their ability to change their shape in response to extracellular and intracellular stimuli. Although studied in live cells since decades, the mutual dependence between cytoskeleton and membrane dynamics in these large-scale transformations is still poorly understood. Here we report on inspiring recent in vitro work in this direction, and the promises it holds for a better understanding of key cellular processes.
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Affiliation(s)
- Sven K Vogel
- Max Planck Institute of Biochemistry, Department of Cellular and Molecular Biophysics, Am Klopferspitz 18, D-82152 Martinsried, Germany
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24
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COLE CHRISTINELIND, QIAN HONG. THE BROWNIAN RATCHET REVISITED: DIFFUSION FORMALISM, POLYMER-BARRIER ATTRACTIONS, AND MULTIPLE FILAMENTOUS BUNDLE GROWTH. ACTA ACUST UNITED AC 2011. [DOI: 10.1142/s1793048011001269] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Actin polymerization driven stochastic movement of the bacteria Listeria monocytogenes is often measured using single-particle tracking (SPT) methodology and analyzed in terms of statistics. Experimental results suggested a dynamic association between the growing actin filaments and the propelled bacteria. Based on an alternative mathematical formalism for a Brownian ratchet (BR), we introduce such an attractive interaction into the one-dimensional BR model and show that its effect is equivalent to an external resistant force on the bacterium. Such a force significantly reduces the Brownian motion of a driven bacterium, and accentuates the stepping due to polymerization. We then consider the growth, with and without a barrier, of a filamentous bundle consisting of N identical filaments. It is shown that the bundle grows with a similar rate as a single filament in the absence of a load, but can oppose N times the external force under the stalling condition. A set of relationships describing the velocity of the bacterium movement (Vz) and its apparent diffusivity (Dz) as functions of the resistant force (F) and the number of filaments in a bundle (N) are obtained. The theoretical study suggests methods for data analysis in future experiments with applied external resistant force.
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Affiliation(s)
- CHRISTINE LIND COLE
- Department of Applied Mathematics, University of Washington, Box 352420 Seattle, WA 98195-2420, USA
| | - HONG QIAN
- Department of Applied Mathematics, University of Washington, Box 352420 Seattle, WA 98195-2420, USA
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25
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Dempwolff F, Reimold C, Reth M, Graumann PL. Bacillus subtilis MreB orthologs self-organize into filamentous structures underneath the cell membrane in a heterologous cell system. PLoS One 2011; 6:e27035. [PMID: 22069484 PMCID: PMC3206058 DOI: 10.1371/journal.pone.0027035] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 10/09/2011] [Indexed: 11/25/2022] Open
Abstract
Actin-like bacterial cytoskeletal element MreB has been shown to be essential for the maintenance of rod cell shape in many bacteria. MreB forms rapidly remodelling helical filaments underneath the cell membrane in Bacillus subtilis and in other bacterial cells, and co-localizes with its two paralogs, Mbl and MreBH. We show that MreB localizes as dynamic bundles of filaments underneath the cell membrane in Drosophila S2 Schneider cells, which become highly stable when the ATPase motif in MreB is modified. In agreement with ATP-dependent filament formation, the depletion of ATP in the cells lead to rapid dissociation of MreB filaments. Extended induction of MreB resulted in the formation of membrane protrusions, showing that like actin, MreB can exert force against the cell membrane. Mbl also formed membrane associated filaments, while MreBH formed filaments within the cytosol. When co-expressed, MreB, Mbl and MreBH built up mixed filaments underneath the cell membrane. Membrane protein RodZ localized to endosomes in S2 cells, but localized to the cell membrane when co-expressed with Mbl, showing that bacterial MreB/Mbl structures can recruit a protein to the cell membrane. Thus, MreB paralogs form a self-organizing and dynamic filamentous scaffold underneath the membrane that is able to recruit other proteins to the cell surface.
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Affiliation(s)
- Felix Dempwolff
- Mikrobiologie, Fakultät für Biologie, Universität Freiburg, Freiburg, Germany
| | - Christian Reimold
- Mikrobiologie, Fakultät für Biologie, Universität Freiburg, Freiburg, Germany
| | - Michael Reth
- Immunbiologie, Fakultät für Biologie, Universität Freiburg, Freiburg, Germany
- Bioss, Universität Freiburg, Freiburg, Germany
| | - Peter L. Graumann
- Mikrobiologie, Fakultät für Biologie, Universität Freiburg, Freiburg, Germany
- Bioss, Universität Freiburg, Freiburg, Germany
- * E-mail:
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Takiguchi K, Negishi M, Tanaka-Takiguchi Y, Homma M, Yoshikawa K. Transformation of actoHMM assembly confined in cell-sized liposome. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:11528-35. [PMID: 21819144 PMCID: PMC3171996 DOI: 10.1021/la2016287] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
To construct a simple model of a cellular system equipped with motor proteins, cell-sized giant liposomes encapsulating various amounts of actoHMM, the complexes of actin filaments (F-actin) and heavy meromyosin (HMM, an actin-related molecular motor), with a depletion reagent to mimic the crowding effect of inside of living cell, were prepared. We adapted the methodology of the spontaneous transfer of water-in-oil (W/O) droplets through a phospholipid monolayer into the bulk aqueous phase and successfully prepared stable giant liposomes encapsulating the solution with a physiological salt concentration containing the desired concentrations of actoHMM, which had been almost impossible to obtain using currently adapted methodologies such as natural swelling and electro-formation on an electrode. We then examined the effect of ATP on the cytoskeleton components confined in those cell-sized liposomes, because ATP is known to drive the sliding motion for actoHMM. We added α-hemolysin, a bacterial membrane pore-forming toxin, to the bathing solution and obtained liposomes with the protein pores embedded on the bilayer membrane to allow the transfer of ATP inside the liposomes. We show that, by the ATP supply, the actoHMM bundles inside the liposomes exhibit specific changes in spatial distribution, caused by the active sliding between F-actin and HMM. Interestingly, all F-actins localized around the inner periphery of liposomes smaller than a critical size, whereas in the bulk solution and also in larger liposomes, the actin bundles formed aster-like structures under the same conditions.
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Affiliation(s)
- Kingo Takiguchi
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
- Phone: +81-52-789-2993 (K.T.); +81-75-753-3812 (K.Y.). Fax: +81-52-789-3001 (K.T.); +81-75-753-3779 (K.Y.). E-mail: (K.T.); (K.Y.)
| | - Makiko Negishi
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yohko Tanaka-Takiguchi
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Michio Homma
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Kenichi Yoshikawa
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
- Phone: +81-52-789-2993 (K.T.); +81-75-753-3812 (K.Y.). Fax: +81-52-789-3001 (K.T.); +81-75-753-3779 (K.Y.). E-mail: (K.T.); (K.Y.)
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27
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Degradation of HIF-1alpha under hypoxia combined with induction of Hsp90 polyubiquitination in cancer cells by hypericin: a unique cancer therapy. PLoS One 2011; 6:e22849. [PMID: 21949677 PMCID: PMC3176203 DOI: 10.1371/journal.pone.0022849] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 06/30/2011] [Indexed: 01/01/2023] Open
Abstract
The perihydroxylated perylene quinone hypericin has been reported to possess potent anti-metastatic and antiangiogenic activities, generated by targeting diverse crossroads of cancer-promoting processes via unique mechanisms. Hypericin is the only known exogenous reagent that can induce forced poly-ubiquitination and accelerated degradation of heat shock protein 90 (Hsp90) in cancer cells. Hsp90 client proteins are thereby destabilized and rapidly degraded. Hsp70 client proteins may potentially be also affected via preventing formation of hsp90-hsp70 intermediate complexes. We show here that hypericin also induces enhanced degradation of hypoxia-inducible factor 1α (HIF-1α) in two human tumor cell lines, U87-MG glioblastoma and RCC-C2VHL−/− renal cell carcinoma and in the non-malignant ARPE19 retinal pigment epithelial cell line. The hypericin-accelerated turnover of HIF-1α, the regulatory precursor of the HIF-1 transcription factor which promotes hypoxic stress and angiogenic responses, overcomes the physiologic HIF-1α protein stabilization which occurs in hypoxic cells. The hypericin effect also eliminates the high HIF-1α levels expressed constitutively in the von-Hippel Lindau protein (pVHL)-deficient RCC-C2VHL−/− renal cell carcinoma cell line. Unlike the normal ubiquitin-proteasome pathway-dependent turnover of HIF-α proteins which occurs in normoxia, the hypericin-induced HIF-1α catabolism can occur independently of cellular oxygen levels or pVHL-promoted ubiquitin ligation of HIF-1α. It is mediated by lysosomal cathepsin-B enzymes with cathepsin-B activity being optimized in the cells through hypericin-mediated reduction in intracellular pH. Our findings suggest that hypericin may potentially be useful in preventing growth of tumors in which HIF-1α plays pivotal roles, and in pVHL ablated tumor cells such as renal cell carcinoma through elimination of elevated HIF-1α contents in these cells, scaling down the excessive angiogenesis which characterizes these tumors.
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Meyer EJ, Ikmi A, Gibson MC. Interkinetic nuclear migration is a broadly conserved feature of cell division in pseudostratified epithelia. Curr Biol 2011; 21:485-91. [PMID: 21376598 DOI: 10.1016/j.cub.2011.02.002] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 12/07/2010] [Accepted: 02/01/2011] [Indexed: 12/19/2022]
Abstract
Animal development requires tight integration between the processes of proliferative growth and epithelial morphogenesis, both of which play out at the level of individual cells. In this respect, not only must polarized epithelial cells assume complex morphologies, these distinct forms must be radically and repeatedly transformed to permit mitosis. A dramatic illustration of this integration between epithelial morphogenesis and cell proliferation is interkinetic nuclear migration (IKNM), wherein the nuclei of pseudostratified epithelial cells translocate to the apical epithelial surface to execute cell division. IKNM is widely considered a hallmark of pseudostratified vertebrate neuroepithelia, and prior investigations have proposed both actomyosin- and microtubule-dependent mechanisms for apical localization of the mitotic nucleus. Here, using comparative functional analysis in arthropod and cnidarian systems (Drosophila melanogaster and Nematostella vectensis), we show that actomyosin-dependent IKNM is likely to be a general feature of mitosis in pseudostratified epithelia throughout Eumetazoa. Furthermore, our studies suggest a mechanistic link between IKNM and the fundamental process of mitotic cell rounding.
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Affiliation(s)
- Emily J Meyer
- Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA
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29
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Vigfúsdóttir ÁT, Pasrija C, Thakore PI, Schmidt RB, Hsieh AH. Role of Pericellular Matrix in Mesenchymal Stem Cell Deformation during Chondrogenic Differentiation. Cell Mol Bioeng 2010. [DOI: 10.1007/s12195-010-0135-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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30
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Walde P, Cosentino K, Engel H, Stano P. Giant Vesicles: Preparations and Applications. Chembiochem 2010; 11:848-65. [DOI: 10.1002/cbic.201000010] [Citation(s) in RCA: 556] [Impact Index Per Article: 39.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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31
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Affiliation(s)
- C.B. SHUSTER
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - I.M. HERMAN
- Department of Physiology, Tufts University School of Medicine, Boston, MA, USA
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32
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Biology under construction: in vitro reconstitution of cellular function. Nat Rev Mol Cell Biol 2009; 10:644-50. [PMID: 19672276 DOI: 10.1038/nrm2746] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We are much better at taking cells apart than putting them together. Reconstitution of biological processes from component molecules has been a powerful but difficult approach to studying functional organization in biology. Recently, the convergence of biochemical and cell biological advances with new experimental and computational tools is providing the opportunity to reconstitute increasingly complex processes. We predict that this bottom-up strategy will uncover basic processes that guide cellular assembly, advancing both basic and applied sciences.
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Takiguchi K, Yamada A, Negishi M, Honda M, Tanaka-Takiguchi Y, Yoshikawa K. Chapter 3 - Construction of cell-sized liposomes encapsulating actin and actin-cross-linking proteins. Methods Enzymol 2009; 464:31-53. [PMID: 19903549 DOI: 10.1016/s0076-6879(09)64003-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2023]
Abstract
To shed light on the mechanism underlying the active morphogenesis of living cells in relation to the organization of internal cytoskeletal networks, the development of new methodologies to construct artificial cell models is crucial. Here, we describe the successful construction of cell-sized liposomes entrapping cytoskeletal proteins. We discuss experimental protocols to prepare giant liposomes encapsulating desired amounts of actin and cross-linking proteins including molecular motor proteins, such as fascin, alpha-actinin, filamin, myosin-I isolated from brush border (BBMI), and heavy meromyosin (HMM). Subfragment 1 (S-1) is also studied in comparison to HMM, where S-1 and HMM are single-headed and double-headed derivatives of conventional myosin (myosin-II), respectively. In the absence of cross-linking proteins, actin filaments (F-actin) are distributed homogeneously without any order within the liposomes. In contrast, when actin is encapsulated together with an actin-cross-linking protein, mesh structures emerge that are similar to those in living motile cells. Optical microscopic observations on the active morphological changes of the liposomes are reported.
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Affiliation(s)
- Kingo Takiguchi
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan
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34
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Doherty GJ, McMahon HT. Mediation, modulation, and consequences of membrane-cytoskeleton interactions. Annu Rev Biophys 2008; 37:65-95. [PMID: 18573073 DOI: 10.1146/annurev.biophys.37.032807.125912] [Citation(s) in RCA: 238] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Elements of the cytoskeleton interact intimately and communicate bidirectionally with cellular membranes. Such interactions are critical for a host of cellular processes. Here we focus on the many types of interactions that exist between the cytoskeleton and the plasma membrane to illustrate why these cellular components can never truly be studied in isolation in vivo. We discuss how membrane-cytoskeleton interactions are mediated and modulated, and how many proteins involved in these interactions are disrupted in human disease. We then highlight key molecular and physical variables that must be considered in order to mechanistically dissect events associated with changes in plasma membrane morphology. These considerations are integrated into the context of cell migration, filopodia formation, and clathrin-mediated endocytosis to show how a holistic view of the plasma membrane-cytoskeleton interface can allow for the appropriate interpretation of experimental findings and provide novel mechanistic insight into these important cellular events.
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Affiliation(s)
- Gary J Doherty
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, United Kingdom.
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35
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Membrane-substrate interface: Phospholipid bilayers at chemically and topographically structured surfaces. Biointerphases 2008; 3:FA22. [DOI: 10.1116/1.2889055] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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36
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Lee HK, Soukasene S, Jiang H, Zhang S, Feng W, Stupp SI. Light-induced self-assembly of nanofibers inside liposomes. SOFT MATTER 2008; 4:962-964. [PMID: 19412333 PMCID: PMC2662686 DOI: 10.1039/b719486b] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Spatially confined self-assembly of peptide amphiphile nanofibers inside liposomes is triggered by light.
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Affiliation(s)
- Hyung-Kun Lee
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA. E-mail: ; Fax: (+1) 847-491-3010
| | - Stephen Soukasene
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA. E-mail: ; Fax: (+1) 847-491-3010
| | - Hongzhou Jiang
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA. E-mail: ; Fax: (+1) 847-491-3010
| | - Shuming Zhang
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA. E-mail: ; Fax: (+1) 847-491-3010
| | - Wenchun Feng
- Department of Chemistry, Northwestern University, Evanston, IL, USA
| | - Samuel I. Stupp
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA. E-mail: ; Fax: (+1) 847-491-3010
- Department of Chemistry, Northwestern University, Evanston, IL, USA
- Feinberg School of Medicine, Chicago, IL, USA
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Théry M, Bornens M. Get round and stiff for mitosis. HFSP JOURNAL 2008; 2:65-71. [PMID: 19404473 DOI: 10.2976/1.2895661] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Indexed: 01/06/2023]
Abstract
Cell rounding is a common feature of cell division. The spherical shape that cells adopt during mitosis is apparently neither a simple detachment nor a global softening or stiffening that allows cells to adopt what seems to be a mechanical equilibrium. It is a highly complex mechanical transformation by which membrane folding and peripheral signals focusing can match spindle size in order to ensure a proper cell division. Recent new insight into the mechanism involved will prompt the scientific community to focus on the regulation of the physical links that exist between the lipid bilayer membrane and the underlying actin cytoskeleton since it now appears that these will strongly influence some crucial cellular events such as the spatial organization of cell division.
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Dixit SS, Szmodis A, Parikh AN. Glass Bead Probes of Local Structural and Mechanical Properties of Fluid, Supported Membranes. Chemphyschem 2006; 7:1678-81. [PMID: 16847842 DOI: 10.1002/cphc.200600222] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Sanhita S Dixit
- Department of Applied Science and Biophysics Graduate Group, University of California, Davis, CA 95616, USA
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39
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Cortès S, Glade N, Chartier I, Tabony J. Microtubule self-organisation by reaction–diffusion processes in miniature cell-sized containers and phospholipid vesicles. Biophys Chem 2006; 120:168-77. [PMID: 16337731 DOI: 10.1016/j.bpc.2005.11.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Revised: 11/02/2005] [Accepted: 11/03/2005] [Indexed: 11/23/2022]
Abstract
Under appropriate conditions, in vitro microtubule preparations self-organise over macroscopic distances by a process of reaction and diffusion. To investigate whether such self-organisation can also occur in objects as small as a cell or an embryo we carried out experiments in miniature containers of cellular dimension. When assembled under self-organising conditions in wells of 120-500 microm, microtubules developed organised structures. Self-organisation is strongly affected by shape, being highly favoured by elongated forms. In wells of more complex shape, geometrical factors may either oppose or strengthen one another and so inhibit or reinforce self-organisation. Microtubules were also assembled within phospholipid vesicles of 2-5 microm diameter. Under self-organising conditions, we observed large shape changes from spheroids to long tubes (50-100 microm) and intertwined coils. We conclude that self-organisation of microtubules by reaction-diffusion processes can occur in containers of cellular dimensions and is capable of strongly deforming the cellular membrane.
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Affiliation(s)
- Sandra Cortès
- Commissariat à l'Energie Atomique, Département Réponse et Dynamique Cellulaires, Laboratoire d'Immunochimie, INSERM U548, D.S.V, C.E.A. Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France
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40
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Hase M, Yoshikawa K. Structural transition of actin filament in a cell-sized water droplet with a phospholipid membrane. J Chem Phys 2006; 124:104903. [PMID: 16542100 DOI: 10.1063/1.2174004] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Actin filament, F-actin, is a semiflexible polymer with a negative charge, and is one of the main constituents of cell membranes. To clarify the effect of cross talk between a phospholipid membrane and actin filaments in cells, we conducted microscopic observations on the structural changes in actin filaments in a cell-sized (several tens of micrometers in diameter) water droplet coated with a phospholipid membrane such as phosphatidylserine (PS; negatively charged head group) or phosphatidylethanolamine (PE; neutral head group) as a simple model of a living cell membrane. With PS, actin filaments are distributed uniformly in the water phase without adsorption onto the membrane surface between 2 and 6 mM Mg2+, while between 6 and 12 mM Mg2+, actin filaments are adsorbed onto the inner membrane surface. With PE, the actin filaments are uniformly adsorbed onto the inner membrane surface between 2 and 12 mM Mg2+. With both PS and PE membranes, at Mg2+ concentrations higher than 12 mM, thick bundles are formed in the bulk water droplet accompanied by the dissolution of actin filaments from the membrane surface. The attraction between actin filaments and membrane is attributable to an increase in the translational entropy of counterions accompanied by the adsorption of actin filaments onto the membrane surface. These results suggest that a microscopic water droplet coated with phospholipid can serve as an easy-to-handle model of cell membranes.
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Affiliation(s)
- M Hase
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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Terasawa K, Taguchi T, Momota R, Naito I, Murakami T, Ohtsuka A. Human erythrocytes possess a cytoplasmic endoskeleton containing .BETA.-actin and neurofilament protein. ACTA ACUST UNITED AC 2006; 69:329-40. [PMID: 17372389 DOI: 10.1679/aohc.69.329] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The biconcave disc shape of mammalian erythrocytes has been considered to be maintained only with a membrane underlain by a membranous cytoskeleton. Our improved ion-etching/scanning electron microscopy and saponin-ethanol treatment combined with immunocytochemistry in the human red blood cell revealed the three-dimensional structure of this cytoplasmic endoskeleton apart from the classical membranous cytoskeleton. The endoskeletal meshwork images obtained by the saponin-ethanol treatment corresponded to those by the repeated ion-etching method. The actin-rich endoskeleton was divided into two layers, one superficial and the other deep. The superficial filaments were perpendicularly connected to the membranous cytoskeleton, while the deep filaments formed an irregularly directed complicated meshwork. In the transitional hillside region between the convex periphery and concave center, the endoskeletal filaments containing a neurofilament protein ran parallel to the hillside slope toward the concave center. The endoskeleton of the erythrocyte associating with the membranous cytoskeleton may serve to keep its unique biconcave disc shape deformable, pliable, and restorable against external circumstances.
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Affiliation(s)
- Kazutaka Terasawa
- Department of Human Morphology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
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Ladam G, Vonna L, Sackmann E. Protrusion force transmission of amoeboid cells crawling on soft biological tissue. Acta Biomater 2005; 1:485-97. [PMID: 16701829 DOI: 10.1016/j.actbio.2005.06.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2005] [Revised: 05/19/2005] [Accepted: 06/07/2005] [Indexed: 01/15/2023]
Abstract
We applied a colloidal force microscopy technique to measure the spreading and retraction forces generated by protrusions (pseudopodia) of vegetative amoeboid cells (Dictyostelium discoideum) adhering on soft tissue analogues composed of 2-mm thick hydrogels of hyaluronic acid exhibiting Young's moduli between 10 and 200 Pa. Local shear deformations of the polymer films evoked by magnetic tweezers and by cellular protrusions were determined by analyzing the deflections of colloidal beads randomly deposited on the surface of the polymer cushions, which enabled us to measure forces generated by advancing ("pushing" forces) and retracting ("pulling" forces) protrusions in a direct way. We found that the maximum amplitudes generated by the advancing protrusions (pushes) decrease with increasing stiffness of the HA substrate while the amplitudes of the retractions do not show such a dependence. The maximum forces transmitted by the advancing and retracting protrusions increase with increasing stiffness of the HA films (from 0.02 to 1 nN for the case of pushing). The protrusions spread or retract with constant velocities which are higher for retractions (100 nm s(-1)) than for spreadings (50 nm s(-1)) and are not significantly influenced by the substrate rigidity. We provide evidence that elastic equilibrium during protrusion formation and retraction is maintained by local elastic dipole fields generated at the rim of the protrusions. A model of protrusion force transmission by coupling of growing actin gel in the cytoplasm of the protrusions to cell surface receptors through talin clutches is proposed.
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Affiliation(s)
- Guy Ladam
- Laboratoire de Biophysique et Biomatériaux, Université de Rouen, Centre Universitaire d'Evreux, 1 rue du 7ème Chasseurs, BP 281, 27002 Evreux Cedex, France.
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Li S, Nickels J, Palmer AF. Liposome-encapsulated actin–hemoglobin (LEAcHb) artificial blood substitutes. Biomaterials 2005; 26:3759-69. [PMID: 15621266 DOI: 10.1016/j.biomaterials.2004.09.015] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2004] [Accepted: 09/08/2004] [Indexed: 10/26/2022]
Abstract
A new approach to enhance the circulation persistence of liposomes has been applied to develop liposome-encapsulated actin-hemoglobin (LEAcHb) dispersions as potential blood substitutes by introducing an actin matrix into the liposome aqueous core. Asymmetric flow field-flow fractionation coupled with multi-angle static light scattering was used to study the shape, size distribution, and encapsulation efficiency of liposome-encapsulated hemoglobin (LEHb) and LEAcHb dispersions. By polymerizing monomeric actin into filamentous actin inside the liposome aqueous core, LEAcHb particles transformed into a disk-like shape. We studied the effect of an encapsulated actin matrix on the size distribution, hemoglobin (Hb) encapsulation efficiency, oxygen affinity, and methemoglobin (MetHb) level of LEAcHb dispersions, and compared them with plain LEHb dispersions (without actin). LEHb, and LEAcHb dispersions extruded through 400 nm membranes were injected into rats and it was observed that LEAcHb dispersions with 1mg/mL of actin enhanced the circulatory half-life versus LEHb dispersions. The circulatory characteristics of empty PEGylated and non-PEGylated actin-containing liposomes (without Hb) were studied as controls for the LEHb and LEAcHb dispersions in this paper, which displayed maximum circulatory half-lives greater than 72 h. Taken together the results of this study supports our hypothesis that a lipid membrane supported by an underlying actin matrix will extend the circulatory half-life of LEHb dispersions.
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Affiliation(s)
- Shuliang Li
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, 171 Fitzpatrick Hall, Notre Dame, IN 46556, USA
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Fujibuchi T, Abe Y, Takeuchi T, Imai Y, Kamei Y, Murase R, Ueda N, Shigemoto K, Yamamoto H, Kito K. AIP1/WDR1 supports mitotic cell rounding. Biochem Biophys Res Commun 2005; 327:268-75. [PMID: 15629458 DOI: 10.1016/j.bbrc.2004.11.156] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2004] [Indexed: 11/30/2022]
Abstract
The actin cytoskeleton plays a fundamental role in configuring cell shapes and movements. Actin interacting protein 1 (AIP1)/tryptophan-aspartate-repeat protein 1 (WDR1) induces actin severing and disassembly cooperating with ADF/cofilin. We found that mitotic cell flattening but not rounding was manifested by suppression of AIP1/WDR1 in cells. This mitotic cell flattening was not due to any changes in phosphorylation and distribution of cofilin in cells. We carried out a direct observation of actin filament severing/disassembly assay and found that phosphorylated cofilin still somewhat severs/disassembles actin filaments and that AIP1/WDR1 effaces this in vitro. We suggest that the phosphorylation of ADF/cofilin will be insufficient to completely inhibit actin turnover during mitosis, and that AIP1/WDR1 could abort the severing/disassembly activity somewhat still carried out due to phosphorylated ADF/cofilin. This mechanism could be required to induce cell morphologic changes, especially mitotic cell rounding.
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Affiliation(s)
- Taketsugu Fujibuchi
- Division of Molecular Pathology, Department of Pathology, National University Corporation, Ehime University School of Medicine, Toh-on, Ehime 791-0295, Japan
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Li S, Palmer AF. Structure of small actin-containing liposomes probed by atomic force microscopy: effect of actin concentration & liposome size. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:7917-7925. [PMID: 15350053 DOI: 10.1021/la049035t] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Actin-containing liposomes were prepared via extrusion through 400 and 600 nm pore diameter membranes at different monomeric actin concentrations in low ionic strength buffer (G-buffer). After subjecting the liposome dispersions to high ionic strength polymerization buffer (F-buffer), topological changes in liposome structure were studied using atomic force microscopy (AFM). Paired dumbbell, horseshoelike, and disklike assemblies were observed for actin-containing liposomes extruded through 400 and 600 nm pore diameter membranes. The topology of actin-containing liposomes was found to be highly dependent on both liposome size and actin concentration. At 1 mg/mL actin, the actin-containing liposomes transformed into a disklike shape, whereas, at 5 mg/mL actin, the actin-containing liposomes retained a spherical shape. On the basis of these observations, we hypothesize that actin could either polymerize on the surface of the inner leaflet of the liposome membrane or polymerize in the aqueous core of the liposome. We explain the associated shape changes induced in actin-containing liposomes on the basis of the hypothesized mechanism of actin polymerization inside the liposomes. At higher actin concentrations (5 mg/mL), we observed membrane-induced actin self-assembly in G-buffer, which implies that G-actin is able to interact directly with lipid bilayers at sufficiently high concentrations.
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Affiliation(s)
- Shuliang Li
- Department of Chemical & Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA
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Li S, Palmer AF. Effect of actin concentration on the structure of actin-containing liposomes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:4629-39. [PMID: 15969175 DOI: 10.1021/la0364690] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Liposomes encapsulating monomeric actin (G-actin) were produced via extrusion through 400 and 600 nm pore diameter polycarbonate membranes in low ionic strength buffer (G-buffer). After actin-containing liposomes were subjected to high ionic strength polymerization buffer (F-buffer), morphological changes in the structure of actin-containing liposomes were studied using asymmetric flow field-flow fractionation (AFFF) coupled with multiangle static light scattering (MASLS). The general shape of these liposomes was initially determined by fitting three form factors, which describe the angular distribution of scattered light from a spherical thin shell, thin disk, and thin rod, to the experimentally measured light scattering spectra to regress the dimensions of the liposomes corresponding to the proposed geometry. Light scattering spectra that yielded a best fit to the thin disk model were analyzed further and fit to the ellipsoidal of revolution form factor to regress both the major and minor axis dimensions. The results of this analysis showed that actin-containing liposomes extruded through 400 and 600 nm pore diameter membranes in F-buffer, at a low actin concentration (0.1 mg/mL), assumed a spherical shape, which is also the case for plain liposomes (no actin present) in G-buffer and F-buffer. When the actin concentration was increased to 1 mg/mL, the polymerizing actin filaments stretched the initially spherical liposome into a disklike shape. However, when the actin concentration was further increased to 5 mg/mL, the liposomes reverted back to a spherical shape.
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Affiliation(s)
- Shuliang Li
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA
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Miyata H. A study of lamellipodial membrane dynamics by optical trapping technique: implication of motor activity in movements. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2004; 538:335-45; discussion 345. [PMID: 15098680 DOI: 10.1007/978-1-4419-9029-7_31] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Hidetake Miyata
- Physics Department, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan
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Abstract
Mechanical work in cells is performed by specialized motor proteins that operate in a continuous mechanochemical cycle. Less complex, but still efficient, 'one-shot' motors evolved based on the assembly and disassembly of polymers. We review the mechanisms of pushing and pulling by actin and microtubule filaments and the organizational principles of actin networks. We show how these polymer force generators are used for the propulsion of intracellular pathogens, protrusion of lamellipodia and mitotic movements. We discuss several examples of cellular forces generated by the assembly and disassembly of polymer gels.
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Affiliation(s)
- Alex Mogilner
- Department of Mathematics, University of California, Davis, CA 95616, USA.
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Abstract
Actin performs structural as well as motor-like functions in eukaryotic cells. Orthologues of actin have also been identified in bacteria, where they perform an essential function during cell growth. Bacterial actins are implicated in the maintenance of rod-shaped cell morphology, and appear to form a cytoskeletal structure, localising as helical filaments underneath the cell membrane. Recently, a plasmid-borne actin orthologue has been shown to perform a mitotic-like function during segregation of a plasmid, and chromosomally encoded actin proteins were found to play an important role in chromosome segregation. Based on the findings that actin filaments are dynamic structures in two bacterial species, we propose that actins perform motor functions rather than a purely structural role in bacteria. We suggest that an intracellular motor exists in bacteria that could be derived from an ancestral actin motor that was present in cells early in evolution.
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Affiliation(s)
- Peter L Graumann
- Biochemie, Fachbereich Chemie, Philipps-Universität Marburg, Germany.
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Vasanji A, Ghosh PK, Graham LM, Eppell SJ, Fox PL. Polarization of Plasma Membrane Microviscosity during Endothelial Cell Migration. Dev Cell 2004; 6:29-41. [PMID: 14723845 DOI: 10.1016/s1534-5807(03)00397-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Cell movement is characterized by anterior-posterior polarization of multiple cell structures. We show here that the plasma membrane is polarized in moving endothelial cells (EC); in particular, plasma membrane microviscosity (PMM) is increased at the cell leading edge. Our studies indicate that cholesterol has an important role in generation of this microviscosity gradient. In vitro studies using synthetic lipid vesicles show that membrane microviscosity has a substantial and biphasic influence on actin dynamics; a small amount of cholesterol increases actin-mediated vesicle deformation, whereas a large amount completely inhibits deformation. Experiments in migrating ECs confirm the important role of PMM on actin dynamics. Angiogenic growth factor-stimulated cells exhibit substantially increased membrane microviscosity at the cell front but, unexpectedly, show decreased rates of actin polymerization. Our results suggest that increased PMM in lamellipodia may permit more productive actin filament and meshwork formation, resulting in enhanced rates of cell movement.
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Affiliation(s)
- Amit Vasanji
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA
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