1
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Lira RB, Hammond JCF, Cavalcanti RRM, Rous M, Riske KA, Roos WH. The underlying mechanical properties of membranes tune their ability to fuse. J Biol Chem 2023; 299:105430. [PMID: 37926280 PMCID: PMC10716014 DOI: 10.1016/j.jbc.2023.105430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 10/16/2023] [Accepted: 10/23/2023] [Indexed: 11/07/2023] Open
Abstract
Membrane fusion is a ubiquitous process associated with a multitude of biological events. Although it has long been appreciated that membrane mechanics plays an important role in membrane fusion, the molecular interplay between mechanics and fusion has remained elusive. For example, although different lipids modulate membrane mechanics differently, depending on their composition, molar ratio, and complex interactions, differing lipid compositions may lead to similar mechanical properties. This raises the question of whether (i) the specific lipid composition or (ii) the average mesoscale mechanics of membranes acts as the determining factor for cellular function. Furthermore, little is known about the potential consequences of fusion on membrane disruption. Here, we use a combination of confocal microscopy, time-resolved imaging, and electroporation to shed light onto the underlying mechanical properties of membranes that regulate membrane fusion. Fusion efficiency follows a nearly universal behavior that depends on membrane fluidity parameters, such as membrane viscosity and bending rigidity, rather than on specific lipid composition. This helps explaining why the charged and fluid membranes of the inner leaflet of the plasma membrane are more fusogenic than their outer counterparts. Importantly, we show that physiological levels of cholesterol, a key component of biological membranes, has a mild effect on fusion but significantly enhances membrane mechanical stability against pore formation, suggesting that its high cellular levels buffer the membrane against disruption. The ability of membranes to efficiently fuse while preserving their integrity may have given evolutionary advantages to cells by enabling their function while preserving membrane stability.
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Affiliation(s)
- Rafael B Lira
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Groningen, Netherlands.
| | - Jayna C F Hammond
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Groningen, Netherlands
| | | | - Madelief Rous
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Groningen, Netherlands
| | - Karin A Riske
- Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Wouter H Roos
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Groningen, Netherlands.
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2
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Sokolova A, Galic M. Modulation of self-organizing circuits at deforming membranes by intracellular and extracellular factors. Biol Chem 2023; 404:417-425. [PMID: 36626681 DOI: 10.1515/hsz-2022-0290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 12/16/2022] [Indexed: 01/12/2023]
Abstract
Mechanical forces exerted to the plasma membrane induce cell shape changes. These transient shape changes trigger, among others, enrichment of curvature-sensitive molecules at deforming membrane sites. Strikingly, some curvature-sensing molecules not only detect membrane deformation but can also alter the amplitude of forces that caused to shape changes in the first place. This dual ability of sensing and inducing membrane deformation leads to the formation of curvature-dependent self-organizing signaling circuits. How these cell-autonomous circuits are affected by auxiliary parameters from inside and outside of the cell has remained largely elusive. Here, we explore how such factors modulate self-organization at the micro-scale and its emerging properties at the macroscale.
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Affiliation(s)
- Anastasiia Sokolova
- Institute of Medical Physics and Biophysics, University of Münster, Robert-Koch-Straße 31, 48149 Münster, Germany.,CiM-IMRPS Graduate Program, Schlossplatz 5, 48149 Münster, Germany
| | - Milos Galic
- Institute of Medical Physics and Biophysics, University of Münster, Robert-Koch-Straße 31, 48149 Münster, Germany.,'Cells in Motion' Interfaculty Centre, University of Münster, Röntgenstraße 16, 48149 Münster, Germany
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3
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Haselwandter CA, Guo YR, Fu Z, MacKinnon R. Elastic properties and shape of the Piezo dome underlying its mechanosensory function. Proc Natl Acad Sci U S A 2022; 119:e2208034119. [PMID: 36166476 DOI: 10.1073/pnas.2208034119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Over the past two decades, structural biology has provided much insight into the shape of membrane proteins. Beyond shape, however, membrane protein function can also depend on the protein’s elastic properties. It has been difficult to characterize protein elastic properties in freestanding, unperturbed lipid bilayer membranes, which is the scenario most relevant for cell membranes. Here we show that, through a physical understanding of how proteins deform lipid bilayer membranes, it is possible to deduce elastic properties of membrane proteins solely from observations of membrane shape. On this basis, we provide the biophysical principles and mechanisms underlying the tension-dependent activation of the mechanosensitive ion channel Piezo, which mediates the sensation of touch and many other important biological processes. We show in the companion paper that the free membrane shape of lipid bilayer vesicles containing the mechanosensitive ion channel Piezo can be predicted, with no free parameters, from membrane elasticity theory together with measurements of the protein geometry and vesicle size [C. A. Haselwandter, Y. R. Guo, Z. Fu, R. MacKinnon, Proc. Natl. Acad. Sci. U.S.A., 10.1073/pnas.2208027119 (2022)]. Here we use these results to determine the force that the Piezo dome exerts on the free membrane and hence, that the free membrane exerts on the Piezo dome, for a range of vesicle sizes. From vesicle shape measurements alone, we thus obtain a force–distortion relationship for the Piezo dome, from which we deduce the Piezo dome’s intrinsic radius of curvature, 42±12 nm, and bending stiffness, 18±2.1 kBT, in freestanding lipid bilayer membranes mimicking cell membranes. Applying these estimates to a spherical cap model of Piezo embedded in a lipid bilayer, we suggest that Piezo’s intrinsic curvature, surrounding membrane footprint, small stiffness, and large area are the key properties of Piezo that give rise to low-threshold, high-sensitivity mechanical gating.
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4
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Abstract
The transport of macromolecules and nanoscopic particles to a target cellular site is a crucial aspect in many physiological processes. This directional motion is generally controlled via active mechanical and chemical processes. Here we show, by means of molecular dynamics simulations and an analytical theory, that completely passive nanoparticles can exhibit directional motion when embedded in nonuniform mechanical environments. Specifically, we study the motion of a passive nanoparticle adhering to a mechanically nonuniform elastic membrane. We observe a nonmonotonic affinity of the particle to the membrane as a function of the membrane's rigidity, which results in the particle transport. This transport can be both up or down the rigidity gradient, depending on the absolute values of the rigidities that the gradient spans across. We conclude that rigidity gradients can be used to direct average motion of passive macromolecules and nanoparticles on deformable membranes, resulting in the preferential accumulation of the macromolecules in regions of certain mechanical properties.
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Affiliation(s)
- Ivan Palaia
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London WC1E 6BT, United Kingdom
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom
| | - Alexandru Paraschiv
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London WC1E 6BT, United Kingdom
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom
| | - Vincent E Debets
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
- Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Cornelis Storm
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
- Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Anđela Šarić
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London WC1E 6BT, United Kingdom
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom
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5
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Abstract
The transport of macromolecules and nanoscopic particles to a target cellular site is a crucial aspect in many physiological processes. This directional motion is generally controlled via active mechanical and chemical processes. Here we show, by means of molecular dynamics simulations and an analytical theory, that completely passive nanoparticles can exhibit directional motion when embedded in nonuniform mechanical environments. Specifically, we study the motion of a passive nanoparticle adhering to a mechanically nonuniform elastic membrane. We observe a nonmonotonic affinity of the particle to the membrane as a function of the membrane's rigidity, which results in the particle transport. This transport can be both up or down the rigidity gradient, depending on the absolute values of the rigidities that the gradient spans across. We conclude that rigidity gradients can be used to direct average motion of passive macromolecules and nanoparticles on deformable membranes, resulting in the preferential accumulation of the macromolecules in regions of certain mechanical properties.
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Affiliation(s)
- Ivan Palaia
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London WC1E 6BT, United Kingdom
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom
| | - Alexandru Paraschiv
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London WC1E 6BT, United Kingdom
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom
| | - Vincent E Debets
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
- Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Cornelis Storm
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
- Institute for Complex Molecular Systems, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
| | - Anđela Šarić
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London WC1E 6BT, United Kingdom
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom
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6
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Przybyło M, Drabik D, Doskocz J, Iglič A, Langner M. The Effect of the Osmotically Active Compound Concentration Difference on the Passive Water and Proton Fluxes across a Lipid Bilayer. Int J Mol Sci 2021; 22:11099. [PMID: 34681757 DOI: 10.3390/ijms222011099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 10/08/2021] [Accepted: 10/11/2021] [Indexed: 11/16/2022] Open
Abstract
The molecular details of the passive water flux across the hydrophobic membrane interior are still a matter of debate. One of the postulated mechanisms is the spontaneous, water-filled pore opening, which facilitates the hydrophilic connection between aqueous phases separated by the membrane. In the paper, we provide experimental evidence showing that the spontaneous lipid pore formation correlates with the membrane mechanics; hence, it depends on the composition of the lipid bilayer and the concentration of the osmotically active compound. Using liposomes as an experimental membrane model, osmotically induced water efflux was measured with the stopped-flow technique. Shapes of kinetic curves obtained at low osmotic pressure differences are interpreted in terms of two events: the lipid pore opening and water flow across the aqueous channel. The biological significance of the dependence of the lipid pore formation on the concentration difference of an osmotically active compound was illustrated by the demonstration that osmotically driven water flow can be accompanied by the dissipation of the pH gradient. The application of the Helfrich model to describe the probability of lipid pore opening was validated by demonstrating that the probability of pore opening correlates with the membrane bending rigidity. The correlation was determined by experimentally derived bending rigidity coefficients and probabilities of lipid pores opening.
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7
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Doskocz J, Dałek P, Przybyło M, Trzebicka B, Foryś A, Kobyliukh A, Iglič A, Langner M. The Elucidation of the Molecular Mechanism of the Extrusion Process. Materials (Basel) 2021; 14:4278. [PMID: 34361472 DOI: 10.3390/ma14154278] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 07/27/2021] [Accepted: 07/27/2021] [Indexed: 02/02/2023]
Abstract
Extrusion is a popular method for producing homogenous population of unilamellar liposomes. The technique relies on forcing a lipid suspension through cylindrical pores in a polycarbonate membrane. The quantification of the extrusion and/or recalibration processes make possible the acquisition of experimental data, which can be correlated with the mechanical properties of the lipid bilayer. In this work, the force needed for the extrusion process was correlated with the mechanical properties of a lipid bilayer derived from other experiments. Measurements were performed using a home-made dedicated device capable of maintaining a stable volumetric flux of a liposome suspension through well-defined pores and to continuously measure the extrusion force. Based on the obtained results, the correlation between the lipid bilayer bending rigidity and extrusion force was derived. Specifically, it was found that the bending rigidity of liposomes formed from well-defined lipid mixtures agrees with data obtained by others using flicker-noise spectroscopy or micromanipulation. The other issue addressed in the presented studies was the identification of molecular mechanisms leading to the formation of unilamellar vesicles in the extrusion process. Finally, it was demonstrated that during the extrusion, lipids are not exchanged between vesicles, i.e., vesicles can divide but no membrane fusion or lipid exchange between bilayers was detected.
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8
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Drabik D, Chodaczek G, Kraszewski S. Effect of Amyloid-β Monomers on Lipid Membrane Mechanical Parameters-Potential Implications for Mechanically Driven Neurodegeneration in Alzheimer's Disease. Int J Mol Sci 2020; 22:E18. [PMID: 33375009 DOI: 10.3390/ijms22010018] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 12/17/2020] [Accepted: 12/17/2020] [Indexed: 01/21/2023] Open
Abstract
Alzheimer’s disease (AD) is a neurodegenerative disease that results in memory loss and the impairment of cognitive skills. Several mechanisms of AD’s pathogenesis were proposed, such as the progressive accumulation of amyloid-β (Aβ) and τ pathology. Nevertheless, the exact neurodegenerative mechanism of the Aβ remains complex and not fully understood. This paper proposes an alternative hypothesis of the mechanism based on maintaining the neuron membrane’s mechanical balance. The incorporation of Aβ decreases the lipid membrane’s elastic properties, which eventually leads to the impairment of membrane clustering, disruption of mechanical wave propagation, and change in gamma oscillations. The first two disrupt the neuron’s ability to function correctly while the last one decreases sensory encoding and perception enabling. To begin discussing this mechanical-balance hypothesis, we measured the effect of two selected peptides, Aβ-40 and Aβ-42, as well as their fluorescently labeled modification, on membrane mechanical properties. The decrease of bending rigidity, consistent for all investigated peptides, was observed using molecular dynamic studies and experimental flicker-noise techniques. Additionally, wave propagation was investigated with molecular dynamic studies in membranes with and without incorporated neurodegenerative peptides. A change in membrane behavior was observed in the membrane system with incorporated Aβ.
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9
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Seneviratne R, Jeuken LJC, Rappolt M, Beales PA. Hybrid Vesicle Stability under Sterilisation and Preservation Processes Used in the Manufacture of Medicinal Formulations. Polymers (Basel) 2020; 12:polym12040914. [PMID: 32326448 PMCID: PMC7240416 DOI: 10.3390/polym12040914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 03/30/2020] [Accepted: 04/09/2020] [Indexed: 11/16/2022] Open
Abstract
Sterilisation and preservation of vesicle formulations are important considerations for their viable manufacture for industry applications, particular those intended for medicinal use. Here, we undertake an initial investigation of the stability of hybrid lipid-block copolymer vesicles to common sterilisation and preservation processes, with particular interest in how the block copolymer component might tune vesicle stability. We investigate two sizes of polybutadiene-block-poly(ethylene oxide) polymers (PBd12-PEO11 and PBd22-PEO14) mixed with the phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) considering the encapsulation stability of a fluorescent cargo and the colloidal stability of vesicle size distributions. We find that autoclaving and lyophilisation cause complete loss of encapsulation stability under the conditions studied here. Filtering through 200 nm pores appears to be viable for sterilisation for all vesicle compositions with comparatively low release of encapsulated cargo, even for vesicle size distributions which extend beyond the 200 nm filter pore size. Freeze-thaw of vesicles also shows promise for the preservation of hybrid vesicles with high block copolymer content. We discuss the process stability of hybrid vesicles in terms of the complex mechanical interplay between bending resistance, stretching elasticity and lysis strain of these membranes and propose strategies for future work to further enhance the process stability of these vesicle formulations.
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Affiliation(s)
- Rashmi Seneviratne
- School of Chemistry, Astbury Centre for Structural Molecular Biology and Bragg Centre for Materials Research, University of Leeds, Leeds LS2 9JT, UK;
| | - Lars J. C. Jeuken
- School of Biomedical Sciences, Astbury Centre for Structural Molecular Biology and Bragg Centre for Materials Research, University of Leeds, Leeds LS2 9JT, UK;
| | - Michael Rappolt
- School of Food Science and Nutrition and Bragg Centre for Materials Research, University of Leeds, Leeds LS2 9JT, UK;
| | - Paul A. Beales
- School of Chemistry, Astbury Centre for Structural Molecular Biology and Bragg Centre for Materials Research, University of Leeds, Leeds LS2 9JT, UK;
- Correspondence:
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10
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Dai Z, Yu M, Yi X, Wu Z, Tian F, Miao Y, Song W, He S, Ahmad E, Guo S, Zhu C, Zhang X, Li Y, Shi X, Wang R, Gan Y. Chain-Length- and Saturation-Tuned Mechanics of Fluid Nanovesicles Direct Tumor Delivery. ACS Nano 2019; 13:7676-7689. [PMID: 31187973 DOI: 10.1021/acsnano.9b01181] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Small unilamellar vesicles (SUVs), ubiquitous in organisms, play key and active roles in various biological processes. Although the physical properties of the constituent lipid molecules (i.e., the acyl chain length and saturation) are known to affect the mechanical properties of SUVs and consequently regulate their biological behaviors and functions, the underlying mechanism remains elusive. Here, we combined theoretical modeling and experimental investigation to probe the mechanical behaviors of SUVs with different lipid compositions. The membrane bending rigidity of SUVs increased with increasing chain length and saturation, resulting in differences in the vesicle rigidity and deformable capacity. Furthermore, we tested the tumor delivery capacity of liposomes with low, intermediate, and high rigidity as typical models for SUVs. Interestingly, liposomes with intermediate rigidity exhibited better tumor extracellular matrix diffusion and multicellular spheroid (MCS) penetration and retention than that of their stiffer or softer counterparts, contributing to improved tumor suppression. Stiff SUVs had superior cellular internalization capacity but intermediate tumor delivery efficacy. Stimulated emission depletion microscopy directly showed that the optimal formulation was able to transform to a rod-like shape in MCSs, which stimulated fast transport in tumor tissues. In contrast, stiff liposomes hardly deformed, whereas soft liposomes changed their shape irregularly, which slowed their MCS penetration. Our findings introduce special perspectives from which to map the detailed mechanical properties of SUVs with different compositions, provide clues for understanding the biological functions of SUVs, and suggest that liposome mechanics may be a design parameter for enhancing drug delivery.
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Affiliation(s)
- Zhuo Dai
- School of Pharmacy , Shanghai University of Traditional Chinese Medicine , Shanghai 201203 , China
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Miaorong Yu
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Xin Yi
- Beijing Innovation Center for Engineering Science and Advanced Technology, and Department of Mechanics and Engineering Science, College of Engineering , Peking University , Beijing 100871 , China
| | - Zeming Wu
- Beijing Innovation Center for Engineering Science and Advanced Technology, and Department of Mechanics and Engineering Science, College of Engineering , Peking University , Beijing 100871 , China
| | - Falin Tian
- CAS Key Laboratory for Nanosystem and Hierarchy Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology , Chinese Academy of Sciences , Beijing 100190 , China
| | - Yunqiu Miao
- School of Pharmacy , Shanghai University of Traditional Chinese Medicine , Shanghai 201203 , China
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Wenyi Song
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Shufang He
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Ejaj Ahmad
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Shiyan Guo
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Chunliu Zhu
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Xinxin Zhang
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
| | - Yiming Li
- School of Pharmacy , Shanghai University of Traditional Chinese Medicine , Shanghai 201203 , China
| | - Xinghua Shi
- University of Chinese Academy of Sciences , Beijing 100049 , China
- CAS Key Laboratory for Nanosystem and Hierarchy Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology , Chinese Academy of Sciences , Beijing 100190 , China
| | - Rui Wang
- School of Pharmacy , Shanghai University of Traditional Chinese Medicine , Shanghai 201203 , China
| | - Yong Gan
- Shanghai Institute of Materia Medica , Chinese Academy of Sciences , Shanghai 201203 , China
- University of Chinese Academy of Sciences , Beijing 100049 , China
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11
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Abstract
Piezo1 is an ion channel that gates open when mechanical force is applied to a cell membrane, thus allowing cells to detect and respond to mechanical stimulation. Molecular structures of Piezo1 reveal a large ion channel with an unusually curved shape. This study analyzes how such a curved ion channel interacts energetically with the cell membrane. Through membrane mechanical calculations, we show that Piezo1 deforms the membrane shape outside the perimeter of the channel into a curved 'membrane footprint'. This membrane footprint amplifies the sensitivity of Piezo1 to changes in membrane tension, rendering it exquisitely responsive. We assert that the shape of the Piezo channel is an elegant example of molecular form evolved to optimize a specific function, in this case tension sensitivity. Furthermore, the predicted influence of the membrane footprint on Piezo gating is consistent with the demonstrated importance of membrane-cytoskeletal attachments to Piezo gating.
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Affiliation(s)
- Christoph A Haselwandter
- Department of Physics & Astronomy, University of Southern California, Los Angeles, United States.,Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, Howard Hughes Medical Institute, The Rockefeller University, New York, United States
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12
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McDargh ZA, Deserno M. Dynamin's helical geometry does not destabilize membranes during fission. Traffic 2018; 19:328-335. [PMID: 29437294 DOI: 10.1111/tra.12555] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 02/02/2018] [Accepted: 02/04/2018] [Indexed: 11/29/2022]
Abstract
It is now widely accepted that dynamin-mediated fission is a fundamentally mechanical process: dynamin undergoes a GTP-dependent conformational change, constricting the neck between two compartments, somehow inducing their fission. However, the exact connection between dynamin's conformational change and the scission of the neck is still unclear. In this paper, we re-evaluate the suggestion that a change in the pitch or radius of dynamin's helical geometry drives the lipid bilayer through a mechanical instability, similar to a well-known phenomenon occurring in soap films. We find that, contrary to previous claims, there is no such instability. This lends credence to an alternative model, in which dynamin drives the membrane up an energy barrier, allowing thermal fluctuations to take it into the hemifission state.
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Affiliation(s)
- Zachary A McDargh
- Chemical Engineering Department, Columbia University, New York, New York
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania
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13
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Vorselen D, MacKintosh FC, Roos WH, Wuite GJ. Competition between Bending and Internal Pressure Governs the Mechanics of Fluid Nanovesicles. ACS Nano 2017; 11:2628-2636. [PMID: 28273422 PMCID: PMC5371924 DOI: 10.1021/acsnano.6b07302] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Accepted: 03/08/2017] [Indexed: 05/24/2023]
Abstract
Nanovesicles (∼100 nm) are ubiquitous in cell biology and an important vector for drug delivery. Mechanical properties of vesicles are known to influence cellular uptake, but the mechanism by which deformation dynamics affect internalization is poorly understood. This is partly due to the fact that experimental studies of the mechanics of such vesicles remain challenging, particularly at the nanometer scale where appropriate theoretical models have also been lacking. Here, we probe the mechanical properties of nanoscale liposomes using atomic force microscopy (AFM) indentation. The mechanical response of the nanovesicles shows initial linear behavior and subsequent flattening corresponding to inward tether formation. We derive a quantitative model, including the competing effects of internal pressure and membrane bending, that corresponds well to these experimental observations. Our results are consistent with a bending modulus of the lipid bilayer of ∼14kbT. Surprisingly, we find that vesicle stiffness is pressure dominated for adherent vesicles under physiological conditions. Our experimental method and quantitative theory represents a robust approach to study the mechanics of nanoscale vesicles, which are abundant in biology, as well as being of interest for the rational design of liposomal vectors for drug delivery.
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Affiliation(s)
- Daan Vorselen
- Department
of Physics and Astronomy and LaserLab, Vrije
Universiteit Amsterdam, Amsterdam, 1081 HV, The Netherlands
- Department
of Oral Function and Restorative Dentistry, Academic Centre for Dentistry
Amsterdam (ACTA), Research Institute MOVE, University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, 1081 LA, The Netherlands
| | - Fred C. MacKintosh
- Department
of Physics and Astronomy and LaserLab, Vrije
Universiteit Amsterdam, Amsterdam, 1081 HV, The Netherlands
- Departments
of Chemical & Biomolecular Engineering, Chemistry, and Physics
& Astronomy, Rice University, Houston, Texas 77005, United States
- Center
for Theoretical Biophysics, Rice University, Houston, Texas 77030, United States
| | - Wouter H. Roos
- Department
of Physics and Astronomy and LaserLab, Vrije
Universiteit Amsterdam, Amsterdam, 1081 HV, The Netherlands
- Moleculaire
Biofysica, Zernike Instituut, Rijksuniversiteit
Groningen, Nijenborgh
4, Groningen, 9747 AG, The Netherlands
| | - Gijs J.L. Wuite
- Department
of Physics and Astronomy and LaserLab, Vrije
Universiteit Amsterdam, Amsterdam, 1081 HV, The Netherlands
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14
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Gordon SD, Jackson JC, Rogers SM, Windmill JFC. Listening to the environment: hearing differences from an epigenetic effect in solitarious and gregarious locusts. Proc Biol Sci 2015; 281:rspb.2014.1693. [PMID: 25274362 PMCID: PMC4213621 DOI: 10.1098/rspb.2014.1693] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Locusts display a striking form of phenotypic plasticity, developing into either a lone-living solitarious phase or a swarming gregarious phase depending on population density. The two phases differ extensively in appearance, behaviour and physiology. We found that solitarious and gregarious locusts have clear differences in their hearing, both in their tympanal and neuronal responses. We identified significant differences in the shape of the tympana that may be responsible for the variations in hearing between locust phases. We measured the nanometre mechanical responses of the ear's tympanal membrane to sound, finding that solitarious animals exhibit greater displacement. Finally, neural experiments signified that solitarious locusts have a relatively stronger response to high frequencies. The enhanced response to high-frequency sounds in the nocturnally flying solitarious locusts suggests greater investment in detecting the ultrasonic echolocation calls of bats, to which they are more vulnerable than diurnally active gregarious locusts. This study highlights the importance of epigenetic effects set forth during development and begins to identify how animals are equipped to match their immediate environmental needs.
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Affiliation(s)
- Shira D Gordon
- Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, UK
| | - Joseph C Jackson
- Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, UK
| | | | - James F C Windmill
- Department of Electronic and Electrical Engineering, University of Strathclyde, Glasgow, UK
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15
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Abstract
Studies on the deformation behaviours of cellular entities, such as coated microbubbles and liposomes subject to a cavitation flow, become increasingly important for the advancement of ultrasonic imaging and drug delivery. Numerical simulations for bubble dynamics of ultrasound contrast agents based on the boundary integral method are presented in this work. The effects of the encapsulating shell are estimated by adapting Hoff's model used for thin-shell contrast agents. The viscosity effects are estimated by including the normal viscous stress in the boundary condition. In parallel, mechanical models of cell membranes and liposomes as well as state-of-the-art techniques for quantitative measurement of viscoelasticity for a single cell or coated microbubbles are reviewed. The future developments regarding modelling and measurement of the material properties of the cellular entities for cutting-edge biomedical applications are also discussed.
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Affiliation(s)
- Qianxi Wang
- School of Mathematics , University of Birmingham , Birmingham B15 2TY , UK
| | - Kawa Manmi
- School of Mathematics , University of Birmingham , Birmingham B15 2TY , UK ; Department of Mathematics, College of Science , Salahaddin University-Erbil , Kurdistan Region , Iraq
| | - Kuo-Kang Liu
- School of Engineering , University of Warwick , Coventry CV4 7AL , UK
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16
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Jadidi T, Seyyed-Allaei H, Tabar MRR, Mashaghi A. Poisson's Ratio and Young's Modulus of Lipid Bilayers in Different Phases. Front Bioeng Biotechnol 2014; 2:8. [PMID: 25152882 PMCID: PMC4126470 DOI: 10.3389/fbioe.2014.00008] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 04/04/2014] [Indexed: 11/18/2022] Open
Abstract
A general computational method is introduced to estimate the Poisson's ratio for membranes with small thickness. In this method, the Poisson's ratio is calculated by utilizing a rescaling of inter-particle distances in one lateral direction under periodic boundary conditions. As an example for the coarse grained lipid model introduced by Lenz and Schmid, we calculate the Poisson's ratio in the gel, fluid, and interdigitated phases. Having the Poisson's ratio, enable us to obtain the Young's modulus for the membranes in different phases. The approach may be applied to other membranes such as graphene and tethered membranes in order to predict the temperature dependence of its Poisson's ratio and Young's modulus.
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Affiliation(s)
- Tayebeh Jadidi
- Department of Physics, University of Osnabrück, Osnabrück, Germany
| | | | - M. Reza Rahimi Tabar
- Department of Physics, Sharif University of Technology, Tehran, Iran
- Institute of Physics, Carl-von-Ossietzky University, Oldenburg, Germany
| | - Alireza Mashaghi
- Kavli Institute of Nanoscience, Delft University of Technology, Delft, Netherlands
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17
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Abstract
In the experimental approach to a synthetic minimal cell, the membrane compartment is a main component. Lipid vesicles represent the natural host for the artificial reconstruction of a cytomimetic membrane skeleton able to support mechanical function. Using the membrane component of human erythroid cells, we have reconstructed a membrane shell composed of a spectrin skeleton and fed by ATP. The structural and mechanical analysis reveals this spectrin skeleton as topological network supporting mechanical rigidity. Such an artificial shell would define a membrane compartment mechanically stable under physiological conditions.
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Affiliation(s)
- Iván López-Montero
- Mechanics of Biological Systems and Department of Physical Chemistry I, Universidad Complutense, 28040 Madrid, Spain
| | - Ruddi Rodríguez-García
- Mechanics of Biological Systems and Department of Physical Chemistry I, Universidad Complutense, 28040 Madrid, Spain
| | - Francisco Monroy
- Mechanics of Biological Systems and Department of Physical Chemistry I, Universidad Complutense, 28040 Madrid, Spain
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18
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Heinrich MC, Capraro BR, Tian A, Isas JM, Langen R, Baumgart T. Quantifying Membrane Curvature Generation of Drosophila Amphiphysin N-BAR Domains. J Phys Chem Lett 2010; 1:3401-3406. [PMID: 23772271 PMCID: PMC3679405 DOI: 10.1021/jz101403q] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Biological membrane functions are coupled to membrane curvature, the regulation of which often involves membrane-associated proteins. The membrane-binding N-terminal amphipathic helix-containing BIN/Amphiphysin/Rvs (N-BAR) domain of amphiphysin is implicated in curvature generation and maintenance. Improving the mechanistic understanding of membrane curvature regulation by N-BAR domains requires quantitative experimental characterization. We have measured tube pulling force modulation by the N-BAR domain of Drosophila amphiphysin (DA-N-BAR) bound to tubular membranes pulled from micropipette-aspirated giant vesicles. We observed that fluorescently-labeled DA-N-BAR showed significantly higher protein density on tubules compared to the connected low-curvature vesicle membrane. Furthermore, we found the equilibrium tube pulling force to be systematically dependent on the aqueous solution concentration of DA-N-BAR, thereby providing the first quantitative assessment of spontaneous curvature generation. At sufficiently high protein concentrations, pulled tubes required no external force to maintain mechanical equilibrium, in agreement with the qualitative spontaneous tubulation previously reported for amphiphysin.
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Affiliation(s)
| | | | - Aiwei Tian
- University of Pennsylvania, Department of Chemistry
- University of Pennsylvania, Department of Chemical and Biomolecular Engineering
| | - Jose M. Isas
- University of Southern California, Department of Biochemistry and Molecular Biology
| | - Ralf Langen
- University of Southern California, Department of Biochemistry and Molecular Biology
| | - Tobias Baumgart
- University of Pennsylvania, Department of Chemistry
- University of Pennsylvania, Department of Chemical and Biomolecular Engineering
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