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Alimohamadi H, Luo EWC, Gupta S, de Anda J, Yang R, Mandal T, Wong GCL. Comparing Multifunctional Viral and Eukaryotic Proteins for Generating Scission Necks in Membranes. ACS NANO 2024; 18:15545-15556. [PMID: 38838261 DOI: 10.1021/acsnano.4c00277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
Deterministic formation of membrane scission necks by protein machinery with multiplexed functions is critical in biology. A microbial example is M2 viroporin, a proton pump from the influenza A virus that is multiplexed with membrane remodeling activity to induce budding and scission in the host membrane during viral maturation. In comparison, the dynamin family constitutes a class of eukaryotic proteins implicated in mitochondrial fission, as well as various budding and endocytosis pathways. In the case of Dnm1, the mitochondrial fission protein in yeast, the membrane remodeling activity is multiplexed with mechanoenzyme activity to create fission necks. It is not clear why these functions are combined in these scission processes, which occur in drastically different compositions and solution conditions. In general, direct experimental access to changing neck sizes induced by individual proteins or peptide fragments is challenging due to the nanoscale dimensions and influence of thermal fluctuations. Here, we use a mechanical model to estimate the size of scission necks by leveraging small-angle X-ray scattering structural data of protein-lipid systems under different conditions. The influence of interfacial tension, lipid composition, and membrane budding morphology on the size of the induced scission necks is systematically investigated using our data and molecular dynamic simulations. We find that the M2 budding protein from the influenza A virus has robust pH-dependent membrane activity that induces nanoscopic necks within the range of spontaneous hemifission for a broad range of lipid compositions. In contrast, the sizes of scission necks generated by mitochondrial fission proteins strongly depend on lipid composition, which suggests a role for mechanical constriction.
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Affiliation(s)
- Haleh Alimohamadi
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, California 90025, United States
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095, United States
- California NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Elizabeth Wei-Chia Luo
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, California 90025, United States
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095, United States
- California NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Shivam Gupta
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Jaime de Anda
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, California 90025, United States
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095, United States
- California NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Rena Yang
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, California 90025, United States
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095, United States
- California NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Taraknath Mandal
- Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Gerard C L Wong
- Department of Bioengineering, University of California, Los Angeles, Los Angeles, California 90025, United States
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, United States
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095, United States
- California NanoSystems Institute, University of California, Los Angeles, California 90095, United States
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2
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Pandia S, Mahapatra A, Chakraborty H. A Coronin 1-Derived Peptide Inhibits Membrane Fusion by Modulating Membrane Organization and Dynamics. J Phys Chem B 2024; 128:4986-4995. [PMID: 38739415 DOI: 10.1021/acs.jpcb.4c00295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
Membrane fusion is considered the first step in the entry of enveloped viruses into the host cell. Several targeted strategies have been implemented to block viral entry by limiting the fusion protein to form a six-helix bundle, which is a prerequisite for fusion. Nonetheless, the development of broad-spectrum fusion inhibitors is essential to combat emerging and re-emerging viral infections. TG-23, a coronin 1, a tryptophan-aspartate-rich phagosomal protein-derived peptide, demonstrated inhibition of fusion between small unilamellar vesicles (SUVs) by modulating the membrane's physical properties. However, its inhibitory efficacy reduces with an increasing concentration of membrane cholesterol. The present work aims to develop a fusion inhibitor whose efficacy would be unaltered in the presence of membrane cholesterol. A stretch of the tryptophan-aspartic acid-containing peptide with a similar secondary structure and hydrophobicity profile of TG-23 from coronin 1 was synthesized, and its ability to inhibit SUV-SUV fusion with varying concentrations of membrane cholesterol was evaluated. Our results demonstrate that the GG-21 peptide inhibits fusion irrespective of the cholesterol content of the membrane. We have further evaluated the peptide-induced change in the membrane organization and dynamics utilizing arrays of steady-state and time-resolved fluorescence measurements and correlated these results with their effect on fusion. Interestingly, GG-21 displays inhibitory efficacy in a wide variety of lipid compositions despite having a secondary structure and physical properties similar to those of TG-23. Overall, our results advocate that the secondary structure and physical properties of the peptide may not be sufficient to predict its inhibitory efficacy.
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Affiliation(s)
- Swaratmika Pandia
- School of Chemistry, Sambalpur University, Jyoti Vihar, Burla 768 019, Odisha, India
| | - Amita Mahapatra
- School of Chemical Sciences, National Institute of Science Education and Research (NISER), Jatni, Khurda, Bhubaneswar 752050, Odisha, India
- Homi Bhabha National Institute (HBNI), Mumbai 400094, India
| | - Hirak Chakraborty
- School of Chemistry, Sambalpur University, Jyoti Vihar, Burla 768 019, Odisha, India
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3
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Beaven AH, Bikkumalla V, Chon NL, Matthews AE, Lin H, Knight JD, Sodt AJ. Synaptotagmin 7 C2 domains induce membrane curvature stress via electrostatic interactions and the wedge mechanism. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.10.575084. [PMID: 38313280 PMCID: PMC10837831 DOI: 10.1101/2024.01.10.575084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/06/2024]
Abstract
Synaptotagmin 7 (Syt-7) is part of the synaptotagmin protein family that regulates exocytotic lipid membrane fusion. Among the family, Syt-7 stands out by its membrane binding strength and stabilization of long-lived membrane fusion pores. Given that Syt-7 vesicles form long-lived fusion pores, we hypothesize that its interactions with the membrane stabilize the specific curvatures, thicknesses, and lipid compositions that support a metastable fusion pore. Using all-atom molecular dynamics simulations and FRET-based assays of Syt-7's membrane-binding C2 domains (C2A and C2B), we found that Syt-7 C2 domains sequester anionic lipids, are sensitive to cholesterol, thin membranes, and generate lipid membrane curvature by two competing, but related mechanisms. First, Syt-7 forms strong electrostatic contacts with the membrane, generating negative curvature stress. Second, Syt-7's calcium binding loops embed in the membrane surface, acting as a wedge to thin the membrane and induce positive curvature stress. These curvature mechanisms are linked by the protein insertion depth as well as the resulting protein tilt. Simplified quantitative models of the curvature-generating mechanisms link simulation observables to their membrane-reshaping effectiveness.
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Affiliation(s)
- Andrew H. Beaven
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
- Postdoctoral Research Associate Program, National Institute of General Medical Sciences, National Institutes of Health, Bethesda, MD
| | | | - Nara L. Chon
- Department of Chemistry, University of Colorado Denver, Denver, CO
| | | | - Hai Lin
- Department of Chemistry, University of Colorado Denver, Denver, CO
| | | | - Alexander J. Sodt
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
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4
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Bottacchiari M, Gallo M, Bussoletti M, Casciola CM. The local variation of the Gaussian modulus enables different pathways for fluid lipid vesicle fusion. Sci Rep 2024; 14:23. [PMID: 38168475 PMCID: PMC10762093 DOI: 10.1038/s41598-023-50922-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 12/28/2023] [Indexed: 01/05/2024] Open
Abstract
Viral infections, fertilization, neurotransmission, and many other fundamental biological processes rely on membrane fusion. Straightforward calculations based on the celebrated Canham-Helfrich elastic model predict a large topological energy barrier that prevents the fusion process from being thermally activated. While such high energy is in accordance with the physical barrier function of lipid membranes, it is difficult to reconcile with the biological mechanisms involved in fusion processes. In this work, we use a Ginzburg-Landau type of free energy that recovers the Canham-Helfrich model in the limit of small width-to-vesicle-extension ratio, with the additional ability to handle topological transitions. We show that a local modification of the Gaussian modulus in the merging region both dramatically lowers the elastic energy barrier and substantially changes the minimal energy pathway for fusion, in accordance with experimental evidence. Therefore, we discuss biological examples in which such a modification might play a crucial role.
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Affiliation(s)
- Matteo Bottacchiari
- Department of Mechanical and Aerospace Engineering, Sapienza Università di Roma, Rome, Italy
| | - Mirko Gallo
- Department of Mechanical and Aerospace Engineering, Sapienza Università di Roma, Rome, Italy
| | - Marco Bussoletti
- Department of Mechanical and Aerospace Engineering, Sapienza Università di Roma, Rome, Italy
| | - Carlo Massimo Casciola
- Department of Mechanical and Aerospace Engineering, Sapienza Università di Roma, Rome, Italy.
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Zheng L, Bandara SR, Tan Z, Leal C. Lipid nanoparticle topology regulates endosomal escape and delivery of RNA to the cytoplasm. Proc Natl Acad Sci U S A 2023; 120:e2301067120. [PMID: 37364130 PMCID: PMC10318962 DOI: 10.1073/pnas.2301067120] [Citation(s) in RCA: 40] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 05/04/2023] [Indexed: 06/28/2023] Open
Abstract
RNA therapeutics have the potential to resolve a myriad of genetic diseases. Lipid nanoparticles (LNPs) are among the most successful RNA delivery systems. Expanding their use for the treatment of more genetic diseases hinges on our ability to continuously evolve the design of LNPs with high potency, cellular-specific targeting, and low side effects. Overcoming the difficulty of releasing cargo from endocytosed LNPs remains a significant hurdle. Here, we investigate the fundamental properties of nonviral RNA nanoparticles pertaining to the activation of topological transformations of endosomal membranes and RNA translocation into the cytosol. We show that, beyond composition, LNP fusogenicity can be prescribed by designing LNP nanostructures that lower the energetic cost of fusion and fusion-pore formation with a target membrane. The inclusion of structurally active lipids leads to enhanced LNP endosomal fusion, fast evasion of endosomal entrapment, and efficacious RNA delivery. For example, conserving the lipid make-up, RNA-LNPs having cuboplex nanostructures are significantly more efficacious at endosomal escape than traditional lipoplex constructs.
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Affiliation(s)
- Lining Zheng
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL61801
| | - Sarith R. Bandara
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL61801
| | - Zhengzhong Tan
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL61801
| | - Cecilia Leal
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, IL61801
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Beaven AH, Sapp K, Sodt AJ. Simulated dynamic cholesterol redistribution favors membrane fusion pore constriction. Biophys J 2023; 122:2162-2175. [PMID: 36588341 PMCID: PMC10257089 DOI: 10.1016/j.bpj.2022.12.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 06/17/2022] [Accepted: 12/16/2022] [Indexed: 01/01/2023] Open
Abstract
Endo- and exocytosis proceed through a highly strained membrane fusion pore topology regardless of the aiding protein machinery. The membrane's lipid components bias fusion pores toward expansion or closure, modifying the necessary work done by proteins. Cholesterol, a key component of plasma membranes, promotes both inverted lipid phases with concave leaflets (i.e., negative total curvature, which thins the leaflet) and flat bilayer phases with thick, ordered hydrophobic interiors. We demonstrate by theory and simulation that both leaflets of nascent catenoidal fusion pores have negative total curvature. Furthermore, the hydrophobic core of bilayers with strong negative Gaussian curvature is thinned. Therefore, it is an open question whether cholesterol will be enriched in these regions because of the negative total curvature or depleted because of the membrane thinning. Here, we compare all-atom molecular dynamics simulations (built using a procedure to create specific fusion pore geometries) and theory to understand the underlying reasons for lipid redistribution on fusion pores. Our all-atom molecular dynamics simulations resolve this question by showing that cholesterol is strongly excluded from the thinned neck of fusion and fission pores, revealing that thickness (and/or lipid order) influences cholesterol distributions more than curvature. The results imply that cholesterol exclusion can drive fusion pore closure by creating a small, cholesterol-depleted zone in the neck. This model agrees with literature evidence that membrane reshaping is connected to cholesterol-dependent lateral phase separation.
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Affiliation(s)
- Andrew H Beaven
- Unit on Membrane Chemical Physics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Postdoctoral Research Associate Program, National Institute of General Medical Sciences, National Institutes of Health, Bethesda, Maryland
| | - Kayla Sapp
- Unit on Membrane Chemical Physics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Alexander J Sodt
- Unit on Membrane Chemical Physics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland.
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7
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Gallen AF, Romero-Arias JR, Barrio RA, Hernandez-Machado A. Vesicle formation induced by thermal fluctuations. SOFT MATTER 2023; 19:2908-2918. [PMID: 37006200 DOI: 10.1039/d2sm01167k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The process of fission and vesicle formation depends on the geometry of the membrane that will split. For instance, a flat surface finds it difficult to form vesicles because of the lack of curved regions where to start the process. Here we show that vesicle formation can be promoted by temperature, by using a membrane phase field model with Gaussian curvature. We find a phase transition between fluctuating and vesiculation phases that depends on temperature, spontaneous curvature, and the ratio between bending and Gaussian moduli. We analysed the energy dynamical behaviour of these processes and found that the main driving ingredient is the Gaussian energy term, although the curvature energy term usually helps with the process as well. We also found that the chemical potential can be used to investigate the temperature of the system. Finally we address how temperature changes the condition for spontaneous vesiculation for all geometries, making it happen in a wider range of values of the Gaussian modulus.
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Affiliation(s)
- Andreu F Gallen
- Departament Fisica de la Materia Condensada, Universitat de Barcelona, E-08028 Barcelona, Spain.
| | - J Roberto Romero-Arias
- Instituto de Investigaciones en Matematicas Aplicadas y en Sistemas, Universidad Nacional Autonoma de Mexico, 01000 Ciudad de Mexico, Mexico
| | - Rafael A Barrio
- Instituto de Fisica, U.N.A.M., 01000, Ap. Postal 101000, Mexico D.F, Mexico
| | - Aurora Hernandez-Machado
- Departament Fisica de la Materia Condensada, Universitat de Barcelona, E-08028 Barcelona, Spain.
- Institute of Nanoscience and Nanotechnology (IN2UB), 08028 Barcelona, Spain
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8
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Ward AE, Sokovikova D, Waxham MN, Heberle FA, Levental I, Levental KR, Kiessling V, White JM, Tamm LK. Serinc5 Restricts HIV Membrane Fusion by Altering Lipid Order and Heterogeneity in the Viral Membrane. ACS Infect Dis 2023; 9:773-784. [PMID: 36946615 PMCID: PMC10366416 DOI: 10.1021/acsinfecdis.2c00478] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
The host restriction factor, Serinc5, incorporates into budding HIV particles and inhibits their infection by an incompletely understood mechanism. We have previously reported that Serinc5 but not its paralogue, Serinc2, blocks HIV cell entry by membrane fusion, specifically by inhibiting fusion pore formation and dilation. A body of work suggests that Serinc5 may alter the conformation and clustering of the HIV fusion protein, Env. To contribute an additional perspective to the developing model of Serinc5 restriction, we assessed Serinc2 and Serinc5's effects on HIV pseudoviral membranes. By measuring pseudoviral membrane thickness via cryo-electron microscopy and order via the fluorescent dye, FLIPPER-TR, Serinc5 was found to increase membrane heterogeneity, skewing the distribution toward a larger fraction of the viral membrane in an ordered phase. We also directly observed for the first time the coexistence of membrane domains within individual viral membrane envelopes. Using a total internal reflection fluorescence-based single particle fusion assay, we found that treatment of HIV pseudoviral particles with phosphatidylethanolamine (PE) rescued HIV pseudovirus fusion from restriction by Serinc5, which was accompanied by decreased membrane heterogeneity and order. This effect was specific for PE and did not depend on acyl chain length or saturation. Together, these data suggest that Serinc5 alters multiple interrelated properties of the viral membrane─lipid chain order, rigidity, line tension, and lateral pressure─which decrease the accessibility of fusion intermediates and disfavor completion of fusion. These biophysical insights into Serinc5 restriction of HIV infectivity could contribute to the development of novel antivirals that exploit the same weaknesses.
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Affiliation(s)
- Amanda E. Ward
- Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, VA 22908
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908
| | - Daria Sokovikova
- Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, VA 22908
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908
| | - Melvin Neal Waxham
- Department of Neurobiology and Anatomy, The University of Texas Health Science Center at Houston McGovern Medical School, Houston, TX 77030
| | | | - Ilya Levental
- Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, VA 22908
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908
| | - Kandice R. Levental
- Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, VA 22908
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908
| | - Volker Kiessling
- Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, VA 22908
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908
| | - Judith M. White
- Department of Cell Biology, University of Virginia Health System, Charlottesville, VA 22908
| | - Lukas K. Tamm
- Department of Molecular Physiology and Biological Physics, University of Virginia Health System, Charlottesville, VA 22908
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908
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9
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Jedrych A, Pawlak M, Gorecka E, Lewandowski W, Wojcik MM. Light-Responsive Supramolecular Nanotubes-Based Chiral Plasmonic Assemblies. ACS NANO 2023; 17:5548-5560. [PMID: 36897199 PMCID: PMC10062029 DOI: 10.1021/acsnano.2c10955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 02/27/2023] [Indexed: 06/18/2023]
Abstract
We describe the fabrication of dual-responsive (thermo/light) chiral plasmonic films. The idea is based on using photoswitchable achiral liquid crystal (LCs) forming chiral nanotubes for templating helical assemblies of Au NPs. Circular dichroism spectroscopy (CD) confirms chiroptical properties coming from the arrangement of organic and inorganic components, with up to 0.2 dissymmetry factor (g-factor). Upon exposure to UV light, organic molecules isomerize, resulting in controlled melting of organic nanotubes and/or inorganic nanohelices. The process can be reversed using visible light and further modified by varying the temperature, offering a control of chiroptical response of the composite material. These properties can play a key role in the future development of chiral plasmonics, metamaterials, and optoelectronic devices.
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10
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Tazawa K, Yamazaki M. Effect of monolayer spontaneous curvature on constant tension-induced pore formation in lipid bilayers. J Chem Phys 2023; 158:081101. [PMID: 36859073 DOI: 10.1063/5.0135561] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The methodology of constant tension-induced rupture of giant unilamellar vesicles (GUVs) has provided information on tension-induced pore formation. This method was used to investigate the effect of spontaneous curvature (H0) for a lipid monolayer on the rate constant (kr) for constant tension (σ)-induced rupture, which originates from pore formation in lipid bilayers. Lipids were incorporated with different H0 values into GUV membranes to change the overall H0 value for the GUV monolayer. The dioleoylphosphatidylglycerol (DOPG)/dioleoylphosphatidylethanolamine (DOPE) (4/6, molar ratio, here and elsewhere) monolayer has a negative H0, whereas the DOPG/dioleoylphosphatidylcholine (DOPC) (4/6) monolayer has an essentially zero H0. A higher tension was required to induce the rupture of DOPG/DOPE (4/6)-GUVs compared with DOPG/DOPC (4/6)-GUVs. The line tension (Γ) for a pre-pore in DOPG/DOPE (4/6)-GUVs, determined by the analysis of the tension dependence of kr, was 1.5 times larger than that in DOPG/DOPC (4/6)-GUVs. The kr values for GUVs comprising DOPG/DOPC/18:1 lysophosphatidylcholine (LPC) (40/55/10), which has a positive H0, were larger than those for DOPG/DOPC (4/6)-GUVs under the same tension. The Γ value for DOPG/DOPC/LPC (40/55/10)-GUVs was almost half that for DOPG/DOPC (4/6)-GUVs. These results indicate that Γ decreases with increasing H0, which results in an increase in kr. Based on these results, the effect of H0 on kr and Γ is discussed.
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Affiliation(s)
- Kanta Tazawa
- Physics Course, Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, Shizuoka 422-8529, Japan
| | - Masahito Yamazaki
- Physics Course, Department of Science, Graduate School of Integrated Science and Technology, Shizuoka University, Shizuoka 422-8529, Japan
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11
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Kalutskii MA, Galimzyanov TR, Pinigin KV. Determination of elastic parameters of lipid membranes from simulation under varied external pressure. Phys Rev E 2023; 107:024414. [PMID: 36932616 DOI: 10.1103/physreve.107.024414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 01/27/2023] [Indexed: 06/18/2023]
Abstract
Many cellular processes such as endocytosis, exocytosis, and vesicle trafficking involve membrane deformations, which can be analyzed in the framework of the elastic theories of lipid membranes. These models operate with phenomenological elastic parameters. A connection between these parameters and the internal structure of lipid membranes can be provided by three-dimensional (3D) elastic theories. Considering a membrane as a 3D layer, Campelo et al. [F. Campelo et al., Adv. Colloid Interface Sci. 208, 25 (2014)10.1016/j.cis.2014.01.018] developed a theoretical basis for the calculation of elastic parameters. In this work we generalize and improve this approach by considering a more general condition of global incompressibility instead of local incompressibility. Crucially, we find an important correction to the theory of Campelo et al., which if not taken into account leads to a significant miscalculation of elastic parameters. With the total volume conservation taken into account, we derive an expression for the local Poisson's ratio, which determines how the local volume changes upon stretching and permits a more precise determination of elastic parameters. Also, we substantially simplify the procedure by calculating the derivatives of the moments of the local tension with respect to stretching instead of calculating the local stretching modulus. We obtain a relation between the Gaussian curvature modulus as a function of stretching and the bending modulus, showing that these two elastic parameters are not independent, as was previously assumed. The proposed algorithm is applied to membranes composed of pure dipalmitoylphosphatidylcholine (DPPC), dioleoylphosphatidylcholine (DOPC), and their mixture. The following elastic parameters of these systems are obtained: the monolayer bending and stretching moduli, spontaneous curvature, neutral surface position, and local Poisson's ratio. It is shown that the bending modulus of the DPPC/DOPC mixture follows a more complex trend than predicted by the classical Reuss averaging, which is often employed in theoretical frameworks.
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Affiliation(s)
- Maksim A Kalutskii
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31/4 Leninskiy Prospekt, Moscow 119071, Russia
- Department of Theoretical Physics and Quantum Technologies, National University of Science and Technology "MISiS," 4 Leninskiy Prospekt, 119049 Moscow, Russia
| | - Timur R Galimzyanov
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31/4 Leninskiy Prospekt, Moscow 119071, Russia
- Department of Theoretical Physics and Quantum Technologies, National University of Science and Technology "MISiS," 4 Leninskiy Prospekt, 119049 Moscow, Russia
| | - Konstantin V Pinigin
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31/4 Leninskiy Prospekt, Moscow 119071, Russia
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12
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Jiménez-Munguía I, Beaven AH, Blank PS, Sodt AJ, Zimmerberg J. Interferon-induced transmembrane protein 3 (IFITM3) and its antiviral activity. Curr Opin Struct Biol 2022; 77:102467. [PMID: 36306674 DOI: 10.1016/j.sbi.2022.102467] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 08/05/2022] [Accepted: 08/15/2022] [Indexed: 01/30/2023]
Abstract
Infections caused by enveloped viruses require fusion with cellular membranes for viral genome entry. Viral entry occurs following an interaction of viral and cellular membranes allowing the formation of fusion pores, by which the virus accesses the cytoplasm. Here, we focus on interferon-induced transmembrane protein 3 (IFITM3) and its antiviral activity. IFITM3 is predicted to block or stall viral fusion at an intermediate state, causing viral propagation to fail. After introducing IFITM3, we describe the generalized lipid membrane fusion pathway and how it can be stalled, particularly with respect to IFITM3, and current questions regarding IFITM3's topology, with specific emphasis on IFITM3's amphipathic α-helix (AAH) 59V-68M, which is necessary for the antiviral activity. We report new hydrophobicity and hydrophobic moment calculations for this peptide and a variety of active site peptides from known membrane-remodeling proteins. Finally, we discuss the effects of posttranslational modifications and localization, how IFITM3's AAH may block viral fusion, and possible ramifications of membrane composition.
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Affiliation(s)
- I Jiménez-Munguía
- Section on Integrative Biophysics Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), MD, USA
| | - A H Beaven
- Unit on Membrane Chemical Physics Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH) MD, USA; Postdoctoral Research Associate Program, National Institute of General Medical Sciences National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - P S Blank
- Section on Integrative Biophysics Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), MD, USA
| | - A J Sodt
- Unit on Membrane Chemical Physics Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH) MD, USA.
| | - J Zimmerberg
- Section on Integrative Biophysics Division of Basic and Translational Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), MD, USA.
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13
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Pinigin KV. Determination of Elastic Parameters of Lipid Membranes with Molecular Dynamics: A Review of Approaches and Theoretical Aspects. MEMBRANES 2022; 12:membranes12111149. [PMID: 36422141 PMCID: PMC9692374 DOI: 10.3390/membranes12111149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 11/07/2022] [Accepted: 11/10/2022] [Indexed: 05/12/2023]
Abstract
Lipid membranes are abundant in living organisms, where they constitute a surrounding shell for cells and their organelles. There are many circumstances in which the deformations of lipid membranes are involved in living cells: fusion and fission, membrane-mediated interaction between membrane inclusions, lipid-protein interaction, formation of pores, etc. In all of these cases, elastic parameters of lipid membranes are important for the description of membrane deformations, as these parameters determine energy barriers and characteristic times of membrane-involved phenomena. Since the development of molecular dynamics (MD), a variety of in silico methods have been proposed for the determination of elastic parameters of simulated lipid membranes. These MD methods allow for the consideration of details unattainable in experimental techniques and represent a distinct scientific field, which is rapidly developing. This work provides a review of these MD approaches with a focus on theoretical aspects. Two main challenges are identified: (i) the ambiguity in the transition from the continuum description of elastic theories to the discrete representation of MD simulations, and (ii) the determination of intrinsic elastic parameters of lipid mixtures, which is complicated due to the composition-curvature coupling effect.
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Affiliation(s)
- Konstantin V Pinigin
- A. N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31/4 Leninskiy Prospekt, 119071 Moscow, Russia
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14
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Surmeier G, Dogan-Surmeier S, Paulus M, Albers C, Latarius J, Sternemann C, Schneider E, Tolan M, Nase J. The interaction of viral fusion peptides with lipid membranes. Biophys J 2022; 121:3811-3825. [PMID: 36110043 PMCID: PMC9674987 DOI: 10.1016/j.bpj.2022.09.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 05/13/2022] [Accepted: 09/12/2022] [Indexed: 11/02/2022] Open
Abstract
In this paper, we studied fusogenic peptides of class I-III fusion proteins, which are relevant to membrane fusion for certain enveloped viruses, in contact with model lipid membranes. We resolved the vertical structure and examined the adsorption or penetration behavior of the fusogenic peptides at phospholipid Langmuir monolayers with different initial surface pressures with x-ray reflectometry. We show that the fusion loops of tick-borne encephalitis virus (TBEV) glycoprotein E and vesicular stomatitis virus (VSV) G-protein are not able to insert deeply into model lipid membranes, as they adsorbed mainly underneath the headgroups with only limited penetration depths into the lipid films. In contrast, we observed that the hemagglutinin 2 fusion peptide (HA2-FP) and the VSV-transmembrane domain (VSV-TMD) can penetrate deeply into the membranes. However, in the case of VSV-TMD, the penetration was suppressed already at low surface pressures, whereas HA2-FP was able to insert even into highly compressed films. Membrane fusion is accompanied by drastic changes of the membrane curvature. To investigate how the peptides affect the curvature of model lipid membranes, we examined the effect of the fusogenic peptides on the equilibration of cubic monoolein structures after a phase transition from a lamellar state induced by an abrupt hydrostatic pressure reduction. We monitored this process in presence and absence of the peptides with small-angle x-ray scattering and found that HA2-FP and VSV-TMD drastically accelerate the equilibration, while the fusion loops of TBEV and VSV stabilize the swollen state of the lipid structures. In this work, we show that the class I fusion peptide of HA2 penetrates deeply into the hydrophobic region of membranes and is able to promote and accelerate the formation of negative curvature. In contrast, we found that the class II and III fusion loops of TBEV and VSV tend to counteract negative membrane curvature.
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Affiliation(s)
- Göran Surmeier
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, Germany
| | | | - Michael Paulus
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, Germany
| | - Christian Albers
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, Germany
| | - Jan Latarius
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, Germany
| | | | - Eric Schneider
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, Germany
| | - Metin Tolan
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, Germany
| | - Julia Nase
- Fakultät Physik/DELTA, Technische Universität Dortmund, Dortmund, Germany
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15
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Mittal A, Chauhan A. Aspects of Biological Replication and Evolution Independent of the Central Dogma: Insights from Protein-Free Vesicular Transformations and Protein-Mediated Membrane Remodeling. J Membr Biol 2022; 255:185-209. [PMID: 35333977 PMCID: PMC8951669 DOI: 10.1007/s00232-022-00230-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 03/06/2022] [Indexed: 11/21/2022]
Abstract
Biological membrane remodeling is central to living systems. In spite of serving as “containers” of whole-living systems and functioning as dynamic compartments within living systems, biological membranes still find a “blue collar” treatment compared to the “white collar” nucleic acids and proteins in biology. This may be attributable to the fact that scientific literature on biological membrane remodeling is only 50 years old compared to ~ 150 years of literature on proteins and a little less than 100 years on nucleic acids. However, recently, evidence for symbiotic origins of eukaryotic cells from data only on biological membranes was reported. This, coupled with appreciation of reproducible amphiphilic self-assemblies in aqueous environments (mimicking replication), has already initiated discussions on origins of life beyond nucleic acids and proteins. This work presents a comprehensive compilation and meta-analyses of data on self-assembly and vesicular transformations in biological membranes—starting from model membranes to establishment of Influenza Hemagglutinin-mediated membrane fusion as a prototypical remodeling system to a thorough comparison between enveloped mammalian viruses and cellular vesicles. We show that viral membrane fusion proteins, in addition to obeying “stoichiometry-driven protein folding”, have tighter compositional constraints on their amino acid occurrences than general-structured proteins, regardless of type/class. From the perspective of vesicular assemblies and biological membrane remodeling (with and without proteins) we find that cellular vesicles are quite different from viruses. Finally, we propose that in addition to pre-existing thermodynamic frameworks, kinetic considerations in de novo formation of metastable membrane structures with available “third-party” constituents (including proteins) were not only crucial for origins of life but also continue to offer morphological replication and/or functional mechanisms in modern life forms, independent of the central dogma.
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Affiliation(s)
- Aditya Mittal
- Kusuma School of Biological Sciences, Indian Institute of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi, 110016, India. .,Supercomputing Facility for Bioinformatics and Computational Biology (SCFBio), IIT Delhi, Hauz Khas, New Delhi, 110016, India.
| | - Akanksha Chauhan
- Kusuma School of Biological Sciences, Indian Institute of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi, 110016, India
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16
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Siegel DP. Bicontinuous inverted cubic phase stabilization as an index of antimicrobial and membrane fusion peptide activity. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183815. [PMID: 34748744 DOI: 10.1016/j.bbamem.2021.183815] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 10/06/2021] [Accepted: 10/29/2021] [Indexed: 02/07/2023]
Abstract
Some antimicrobial peptides (AMPs) and membrane fusion-catalyzing peptides (FPs) stabilize bicontinuous inverted cubic (QII) phases. Previous authors proposed a topological rationale: since AMP-induced pores, fusion intermediates, and QII phases all have negative Gaussian curvature (NGC), peptides which produce NGC in one structure also do it in another. This assumes that peptides change the curvature energy of the lipid membranes. Here I test this with a Helfrich curvature energy model. First, experimentally, I show that lipid systems often used to study peptide NGC have NGC without peptides at higher temperatures. To determine the net effect of an AMP on NGC, the equilibrium phase behavior of the host lipids must be determined. Second, the model shows that AMPs must make large changes in the curvature energy to stabilize AMP-induced pores. Peptide-induced changes in elastic constants affect pores and QII phase differently. Changes in spontaneous curvature affect them in opposite ways. The observed correlation between QII phase stabilization and AMP activity doesn't show that AMPs act by lowering pore curvature energy. A different rationale is proposed. In theory, AMPs could simultaneously stabilize QII phase and pores by drastically changing two particular elastic constants. This could be tested by measuring AMP effects on the individual constants. I propose experiments to do that. Unlike AMPs, FPs must make only small changes in the curvature energy to catalyze fusion. It they act in this way, their fusion activity should correlate with their ability to stabilize QII phases.
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Affiliation(s)
- D P Siegel
- Givaudan Inc., 1199 Edison Drive, Cincinnati, OH 45216, United States of America.
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17
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de Lange N, Kleijn JM, Leermakers FAM. Self-consistent field modeling of mesomorphic phase changes of monoolein and phospholipids in response to additives. Phys Chem Chem Phys 2021; 23:14093-14108. [PMID: 34159985 DOI: 10.1039/d1cp00697e] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Mapping the topological phase behaviour of lipids in aqueous solution is time consuming and finding the ideal lipid system for a desired application is often a matter of trial and error. Modelling techniques that can accurately predict the mesomorphic phase behaviour of lipid systems are therefore of paramount importance. Here, the self-consistent field theory of Scheutjens and Fleer (SF-SCF) in which a lattice refinement has been implemented, is used to scrutinize how various additives modify the self-assembled phase behaviour of monoolein (MO) and 1,2-dioleoyl-phosphatidylcholine (DOPC) lipids in water. The mesomorphic behaviour is inferred from trends in the mechanical properties of equilibrium lipid bilayers with increasing additive content. More specifically, we focus on the Helfrich parameters, that is, the mean and Gaussian bending rigidities (κ and [small kappa, Greek, macron], respectively) supplemented with the spontaneous curvature of the monolayer (Jm0). We use previously established interaction parameters that position the unperturbed DOPC system in the lamellar Lα phase ([small kappa, Greek, macron] < 0, κ > 0 and Jm0 ≈ 0). Similar interaction parameters position the MO system firmly in a bicontinuous cubic phase ([small kappa, Greek, macron] > 0). In line with experimental data, a mixture of MO and DOPC tends to be in one of these two phases, depending on the mixing ratio. Moreover we find good correlations between predicted trends and experimental data concerning the phase changes of MO in response to a wide range of additives. These correlations give credibility to the use of SF-SCF modelling as a valuable tool to quickly explore the mesomorphic phase space of (phospho)lipid bilayer systems including additives.
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Affiliation(s)
- N de Lange
- Physical Chemistry & Soft Matter, Wageningen University and Research, Stippeneng 4, 6708 WE, Wageningen, The Netherlands.
| | - J M Kleijn
- Physical Chemistry & Soft Matter, Wageningen University and Research, Stippeneng 4, 6708 WE, Wageningen, The Netherlands.
| | - F A M Leermakers
- Physical Chemistry & Soft Matter, Wageningen University and Research, Stippeneng 4, 6708 WE, Wageningen, The Netherlands.
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18
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Marx L, Semeraro EF, Mandl J, Kremser J, Frewein MP, Malanovic N, Lohner K, Pabst G. Bridging the Antimicrobial Activity of Two Lactoferricin Derivatives in E. coli and Lipid-Only Membranes. FRONTIERS IN MEDICAL TECHNOLOGY 2021; 3:625975. [PMID: 35047906 PMCID: PMC8757871 DOI: 10.3389/fmedt.2021.625975] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 01/19/2021] [Indexed: 11/13/2022] Open
Abstract
We coupled the antimicrobial activity of two well-studied lactoferricin derivatives, LF11-215 and LF11-324, in Escherichia coli and different lipid-only mimics of its cytoplasmic membrane using a common thermodynamic framework for peptide partitioning. In particular, we combined an improved analysis of microdilution assays with ζ-potential measurements, which allowed us to discriminate between the maximum number of surface-adsorbed peptides and peptides fully partitioned into the bacteria. At the same time, we measured the partitioning of the peptides into vesicles composed of phosphatidylethanolamine (PE), phosphatidylgylcerol (PG), and cardiolipin (CL) mixtures using tryptophan fluorescence and determined their membrane activity using a dye leakage assay and small-angle X-ray scattering. We found that the vast majority of LF11-215 and LF11-324 readily enter inner bacterial compartments, whereas only 1-5% remain surface bound. We observed comparable membrane binding of both peptides in membrane mimics containing PE and different molar ratios of PG and CL. The peptides' activity caused a concentration-dependent dye leakage in all studied membrane mimics; however, it also led to the formation of large aggregates, part of which contained collapsed multibilayers with sandwiched peptides in the interstitial space between membranes. This effect was least pronounced in pure PG vesicles, requiring also the highest peptide concentration to induce membrane permeabilization. In PE-containing systems, we additionally observed an effective shielding of the fluorescent dyes from leakage even at highest peptide concentrations, suggesting a coupling of the peptide activity to vesicle fusion, being mediated by the intrinsic lipid curvatures of PE and CL. Our results thus show that LF11-215 and LF11-324 effectively target inner bacterial components, while the stored elastic stress makes membranes more vulnerable to peptide translocation.
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Affiliation(s)
- Lisa Marx
- Department of Biophysics, Institute of Molecular Biosciences, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
- Field of Excellence BioHealth—University of Graz, Graz, Austria
| | - Enrico F. Semeraro
- Department of Biophysics, Institute of Molecular Biosciences, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
- Field of Excellence BioHealth—University of Graz, Graz, Austria
| | - Johannes Mandl
- Department of Biophysics, Institute of Molecular Biosciences, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
- Field of Excellence BioHealth—University of Graz, Graz, Austria
| | - Johannes Kremser
- Department of Biophysics, Institute of Molecular Biosciences, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
- Field of Excellence BioHealth—University of Graz, Graz, Austria
| | - Moritz P. Frewein
- Department of Biophysics, Institute of Molecular Biosciences, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
- Field of Excellence BioHealth—University of Graz, Graz, Austria
- Soft Matter Science and Support Group, Institut Laue-Langevin, Grenoble, France
| | - Nermina Malanovic
- Department of Biophysics, Institute of Molecular Biosciences, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
- Field of Excellence BioHealth—University of Graz, Graz, Austria
| | - Karl Lohner
- Department of Biophysics, Institute of Molecular Biosciences, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
- Field of Excellence BioHealth—University of Graz, Graz, Austria
| | - Georg Pabst
- Department of Biophysics, Institute of Molecular Biosciences, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
- Field of Excellence BioHealth—University of Graz, Graz, Austria
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19
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Lee J, Kreutzberger AJB, Odongo L, Nelson EA, Nyenhuis DA, Kiessling V, Liang B, Cafiso DS, White JM, Tamm LK. Ebola virus glycoprotein interacts with cholesterol to enhance membrane fusion and cell entry. Nat Struct Mol Biol 2021; 28:181-189. [PMID: 33462517 PMCID: PMC7992113 DOI: 10.1038/s41594-020-00548-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 12/07/2020] [Indexed: 12/14/2022]
Abstract
Cholesterol serves critical roles in enveloped virus fusion by modulating membrane properties. The glycoprotein (GP) of Ebola virus (EBOV) promotes fusion in the endosome, a process that requires the endosomal cholesterol transporter NPC1. However, the role of cholesterol in EBOV fusion is unclear. Here we show that cholesterol in GP-containing membranes enhances fusion and the membrane-proximal external region and transmembrane (MPER/TM) domain of GP interacts with cholesterol via several glycine residues in the GP2 TM domain, notably G660. Compared to wild-type (WT) counterparts, a G660L mutation caused a more open angle between MPER and TM domains in an MPER/TM construct, higher probability of stalling at hemifusion for GP2 proteoliposomes and lower cell entry of virus-like particles (VLPs). VLPs with depleted cholesterol show reduced cell entry, and VLPs produced under cholesterol-lowering statin conditions show less frequent entry than respective controls. We propose that cholesterol-TM interactions affect structural features of GP2, thereby facilitating fusion and cell entry.
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Affiliation(s)
- Jinwoo Lee
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA
| | - Alex J B Kreutzberger
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
| | - Laura Odongo
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
| | - Elizabeth A Nelson
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Cell Biology, University of Virginia, Charlottesville, VA, USA
| | - David A Nyenhuis
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
| | - Volker Kiessling
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
| | - Binyong Liang
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
| | - David S Cafiso
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
| | - Judith M White
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA
- Department of Cell Biology, University of Virginia, Charlottesville, VA, USA
| | - Lukas K Tamm
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA, USA.
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA.
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20
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Caparotta M, Tomes CN, Mayorga LS, Masone D. The Synaptotagmin-1 C2B Domain Is a Key Regulator in the Stabilization of the Fusion Pore. J Chem Theory Comput 2020; 16:7840-7851. [DOI: 10.1021/acs.jctc.0c00734] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Marcelo Caparotta
- Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), Mendoza 5500, Argentina
| | - Claudia N. Tomes
- Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), Mendoza 5500, Argentina
- Instituto de Histología y Embriología de Mendoza (IHEM) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), Mendoza 5500, Argentina
| | - Luis S. Mayorga
- Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), Mendoza 5500, Argentina
- Instituto de Histología y Embriología de Mendoza (IHEM) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), Mendoza 5500, Argentina
| | - Diego Masone
- Instituto de Histología y Embriología de Mendoza (IHEM) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), Mendoza 5500, Argentina
- Facultad de Ingeniería, Universidad Nacional de Cuyo (UNCuyo), Mendoza 5500, Argentina
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21
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Mechanistic insights of host cell fusion of SARS-CoV-1 and SARS-CoV-2 from atomic resolution structure and membrane dynamics. Biophys Chem 2020; 265:106438. [PMID: 32721790 PMCID: PMC7375304 DOI: 10.1016/j.bpc.2020.106438] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/16/2020] [Accepted: 07/17/2020] [Indexed: 01/04/2023]
Abstract
The emerging and re-emerging viral diseases are continuous threats to the wellbeing of human life. Previous outbreaks of Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS had evidenced potential threats of coronaviruses in human health. The recent pandemic due to SARS-CoV-2 is overwhelming and has been going beyond control. Vaccines and antiviral drugs are ungently required to mitigate the pandemic. Therefore, it is important to comprehend the mechanistic details of viral infection process. The fusion between host cell and virus being the first step of infection, understanding the fusion mechanism could provide crucial information to intervene the infection process. Interestingly, all enveloped viruses contain fusion protein on their envelope that acts as fusion machine. For coronaviruses, the spike or S glycoprotein mediates successful infection through receptor binding and cell fusion. The cell fusion process requires merging of virus and host cell membranes, and that is essentially performed by the S2 domain of the S glycoprotein. In this review, we have discussed cell fusion mechanism of SARS-CoV-1 from available atomic resolution structures and membrane binding of fusion peptides. We have further discussed about the cell fusion of SARS-CoV-2 in the context of present pandemic situation.
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22
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Wang Z, Servio P, Rey AD. Rate of Entropy Production in Evolving Interfaces and Membranes under Astigmatic Kinematics: Shape Evolution in Geometric-Dissipation Landscapes. ENTROPY (BASEL, SWITZERLAND) 2020; 22:E909. [PMID: 33286678 PMCID: PMC7597146 DOI: 10.3390/e22090909] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 08/10/2020] [Accepted: 08/15/2020] [Indexed: 11/28/2022]
Abstract
This paper presents theory and simulation of viscous dissipation in evolving interfaces and membranes under kinematic conditions, known as astigmatic flow, ubiquitous during growth processes in nature. The essential aim is to characterize and explain the underlying connections between curvedness and shape evolution and the rate of entropy production due to viscous bending and torsion rates. The membrane dissipation model used here is known as the Boussinesq-Scriven fluid model. Since the standard approaches in morphological evolution are based on the average, Gaussian and deviatoric curvatures, which comingle shape with curvedness, this paper introduces a novel decoupled approach whereby shape is independent of curvedness. In this curvedness-shape landscape, the entropy production surface under constant homogeneous normal velocity decays with growth but oscillates with shape changes. Saddles and spheres are minima while cylindrical patches are maxima. The astigmatic flow trajectories on the entropy production surface, show that only cylinders and spheres grow under the constant shape. Small deviations from cylindrical shapes evolve towards spheres or saddles depending on the initial condition, where dissipation rates decrease. Taken together the results and analysis provide novel and significant relations between shape evolution and viscous dissipation in deforming viscous membrane and surfaces.
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Affiliation(s)
| | | | - Alejandro D. Rey
- Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, QC H3A 2B2, Canada; (Z.W.); (P.S.)
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23
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Abstract
Vesicle structures primarily embody spherical capsules composed of a single or multiple bilayers, entrapping a pool of aqueous solution in their interior. The bilayers can be synthesised by phospholipids or other amphiphiles (surfactants, block copolymers, etc.). Vesicles with broad-spectrum applications in numerous scientific disciplines, including biochemistry, biophysics, biology, and various pharmaceutical industries, have attracted widespread attention. Consequently, a multitude of protocols have been devised and proposed for their fabrication. In this review, with a motivation to derive the basic conditions for the formation of vesicles, the associated thermodynamic and kinetic aspects are comprehensively appraised. Contextually, an all-purpose overview of the underlying thermodynamics of bilayer/membrane generation and deformation, including the chemical potential of aggregates, geometric packing and the concept of elastic properties, is presented. Additionally, the current review highlights the probable, inherent mechanisms of vesicle formation under distinct modes of manufacturing. We lay focus on vesicle formation from pre-existing bilayers, as well as from bilayers, which form when lipids from an organic solvent are transferred into an aqueous medium. Furthermore, we outline the kinetic effects on vesicle formation from the lamellar phase, with and without the presence of shearing force. Wherever required, the experimental and/or theoretical outcomes, the driving forces for vesicle size selection, and various scaling laws are also reviewed, all of which facilitate an overall improved understanding of the vesicle formation mechanisms.
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Affiliation(s)
- Chandra Has
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Sharadwata Pan
- School of Life Sciences Weihenstephan, Technical University of Munich, Freising, Germany
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24
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Cholesterol alters the inhibitory efficiency of peptide-based membrane fusion inhibitor. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:183056. [DOI: 10.1016/j.bbamem.2019.183056] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 07/31/2019] [Accepted: 08/23/2019] [Indexed: 11/21/2022]
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25
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Terzi MM, Deserno M, Nagle JF. Mechanical properties of lipid bilayers: a note on the Poisson ratio. SOFT MATTER 2019; 15:9085-9092. [PMID: 31657434 DOI: 10.1039/c9sm01290g] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We investigate the Poisson ratio ν of fluid lipid bilayers, i.e., the question how area strains compare to the changes in membrane thickness (or, equivalently, volume) that accompany them. We first examine existing experimental results on the area- and volume compressibility of lipid membranes. Analyzing them within the framework of linear elasticity theory for homogeneous thin fluid sheets leads us to conclude that lipid membrane deformations are to a very good approximation volume-preserving, with a Poisson ratio that is likely about 3% smaller than the common soft matter limit . These results are fully consistent with atomistic simulations of a DOPC membrane at varying amount of applied lateral stress, for which we instead deduce ν by directly comparing area- and volume strains. To assess the problematic assumption of transverse homogeneity, we also define a depth-resolved Poisson ratio ν(z) and determine it through a refined analysis of the same set of simulations. We find that throughout the membrane's thickness, ν(z) is close to the value derived assuming homogeneity, with only minor variations of borderline statistical significance.
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Affiliation(s)
- M Mert Terzi
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - Markus Deserno
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
| | - John F Nagle
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
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26
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Zhou X. Boundary behaviour of open vesicles in axisymmetric case. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:315101. [PMID: 30986769 DOI: 10.1088/1361-648x/ab1980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A continuous transformation from a closed vesicle to an open vesicle requires that the area of open hole enlarges from zero. Since the shape equation and boundary conditions of lipid open vesicles with free edges have been obtained, we want to know whether this process can be achieved with valid parameters. By studying the boundary conditions in the axisymmetric case, the analytic expression of the boundary edges is obtained generally. It reveals that the radius and line tension of boundary edges are confined strongly by bending moduli. In some cases, there is the minimal nonzero boundary radius and the line tension needs to surmount the maxim following the increase of boundary radius. Without the spontaneous curvature, the line tension will trend to infinite when the boundary radius shrinks to zero. The continuous opening up process requires that the spontaneous curvature is nonzero and the ratio between the bending moduli of Gauss curvature and mean curvature satisfies [Formula: see text], which is smaller than the value [Formula: see text] from experiments and simulations. This result indicates that the opening up process is discontinuous.
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Affiliation(s)
- Xiaohua Zhou
- Shaanxi Engineering Research Center of Controllable Neutron Source, Xijing University, Xi'an 710123, People's Republic of China
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27
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Yao C, Kang Z, Yu B, Chen Q, Liu Y, Wang Q. All-Factor Analysis and Correlations on the Transmembrane Process for Arginine-Rich Cell-Penetrating Peptides. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:9286-9296. [PMID: 31265309 DOI: 10.1021/acs.langmuir.9b01169] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Currently, arginine-rich cell-penetrating peptides (CPPs), due to their little cytotoxicity and high transmembrane efficiency, are considered as one of the important intracellular carriers. Although the mechanism of the transmembrane process for arginine-rich CPPs was proposed, the quantitative correlations and the key factors involved in this process still deserve further investigation. In this study, all-atom molecular dynamics and the umbrella sampling technique were employed to study the arginine-rich CPPs transmembrane process. In the adsorption process of CPPs from solution to the surface of the lipid bilayer, the adsorption free energy (ΔGA) is found to be linearly related to the interaction energy change (ΔEA): ΔGA = 0.0426ΔEA + 36.7, R2 = 0.92. In the CPPs transmembrane process, the transmembrane free energy barrier (ΔGB) is roughly correlated with the corresponding interaction energy change (ΔEB): ΔGB = 0.108ΔEB +135, R2 = 0.73. The multiple salt bridges of guanidinium-PO4 account for 65% of the overall interaction energy, so the increased negative charges of the lipid bilayer or more salt bridges would facilitate CPPs adsorption and transmembrane processes. Also, the increased negative charges of the lipid bilayer would reduce the amount of water to be carried into the pore and further reduce the ΔGB. The peptide backbone would not have a direct impact on transmembrane efficiency. The ΔGB is also found to be related to the length of the pore (L): ΔGB = 46.2L - 31.3, R2 = 0.92, which makes the transmembrane efficiency estimable. This work is expected to deliver an in-depth understanding and help the optimization of CPPs.
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Affiliation(s)
- Cai Yao
- Department of Chemistry and Soft Matter Research Center , Zhejiang University , Hangzhou 310027 , China
| | - Zhengzhong Kang
- Department of Chemistry and Soft Matter Research Center , Zhejiang University , Hangzhou 310027 , China
| | - Bin Yu
- Department of Chemistry and Soft Matter Research Center , Zhejiang University , Hangzhou 310027 , China
| | - Qu Chen
- School of Biological and Chemical Engineering , Zhejiang University of Science and Technology , Hangzhou 310023 , China
| | - Yingchun Liu
- Department of Chemistry and Soft Matter Research Center , Zhejiang University , Hangzhou 310027 , China
| | - Qi Wang
- Department of Chemistry and Soft Matter Research Center , Zhejiang University , Hangzhou 310027 , China
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28
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Smith DJ, Klauda JB, Sodt AJ. Simulation Best Practices for Lipid Membranes [Article v1.0]. LIVING JOURNAL OF COMPUTATIONAL MOLECULAR SCIENCE 2019; 1:5966. [PMID: 36204133 PMCID: PMC9534443 DOI: 10.33011/livecoms.1.1.5966] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/06/2023]
Abstract
We establish a reliable and robust standardization of settings for practical molecular dynamics (MD) simulations of pure and mixed (single- and multi-component) lipid bilayer membranes. In lipid membranes research, particle-based molecular simulations are a powerful tool alongside continuum theory, lipidomics, and model, in vitro, and in vivo experiments. Molecular simulations can provide precise and reproducible spatiotemporal (atomic- and femtosecond-level) information about membrane structure, mechanics, thermodynamics, kinetics, and dynamics. Yet the simulation of lipid membranes can be a daunting task, given the uniqueness of lipid membranes relative to conventional liquid-liquid and solid-liquid interfaces, the immense and complex thermodynamic and statistical mechanical theory, the diversity of multiscale lipid models, limitations of modern computing power, the difficulty and ambiguity of simulation controls, finite size effects, competitive continuum simulation alternatives, and the desired application, including vesicle experiments and biological membranes. These issues can complicate an essential understanding of the field of lipid membranes, and create major bottlenecks to simulation advancement. In this article, we clarify these issues and present a consistent, thorough, and user-friendly framework for the design of state-of-the-art lipid membrane MD simulations. We hope to allow early-career researchers to quickly overcome common obstacles in the field of lipid membranes and reach maximal impact in their simulations.
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Affiliation(s)
- David J. Smith
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA, USA
| | - Jeffery B. Klauda
- Department of Chemical and Biomolecular Engineering and Biophysics Program, University of Maryland, College Park, MD, USA
| | - Alexander J. Sodt
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
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29
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Urakami N, Jimbo T, Sakuma Y, Imai M. Molecular mechanism of vesicle division induced by coupling between lipid geometry and membrane curvatures. SOFT MATTER 2018. [PMID: 29517793 DOI: 10.1039/c7sm02188g] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We investigated the effects of lipid geometry on vesicle division using coarse grained molecular dynamics simulations. When the vesicle is composed of zero and negative spontaneous curvature lipids (ZSLs and NSLs), the difference in their molecular spontaneous curvatures destabilizes the neck of the limiting shape vesicle. In the vesicle division pathway, the neck developed into the stalk intermediates. The stalk was broken when the NSLs were expelled from the stalk. Free energy analysis shows that the coupling between the lipid geometry and the Gaussian rigidity is responsible for the observed vesicle division.
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Affiliation(s)
- Naohito Urakami
- Department of Physics and Informatics, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, 753-8512, Japan.
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30
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Elías-Wolff F, Lindén M, Lyubartsev AP, Brandt EG. Computing Curvature Sensitivity of Biomolecules in Membranes by Simulated Buckling. J Chem Theory Comput 2018; 14:1643-1655. [PMID: 29350922 DOI: 10.1021/acs.jctc.7b00878] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Membrane curvature sensing, where the binding free energies of membrane-associated molecules depend on the local membrane curvature, is a key factor to modulate and maintain the shape and organization of cell membranes. However, the microscopic mechanisms are not well understood, partly due to absence of efficient simulation methods. Here, we describe a method to compute the curvature dependence of the binding free energy of a membrane-associated probe molecule that interacts with a buckled membrane, which has been created by lateral compression of a flat bilayer patch. This buckling approach samples a wide range of curvatures in a single simulation, and anisotropic effects can be extracted from the orientation statistics. We develop an efficient and robust algorithm to extract the motion of the probe along the buckled membrane surface, and evaluate its numerical properties by extensive sampling of three coarse-grained model systems: local lipid density in a curved environment for single-component bilayers, curvature preferences of individual lipids in two-component membranes, and curvature sensing by a homotrimeric transmembrane protein. The method can be used to complement experimental data from curvature partition assays and provides additional insight into mesoscopic theories and molecular mechanisms for curvature sensing.
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Affiliation(s)
- Federico Elías-Wolff
- Department of Biochemistry and Biophysics , Stockholm University , SE-106 91 Stockholm , Sweden.,Department of Materials and Environmental Chemistry , Stockholm University , SE-106 91 Stockholm , Sweden
| | - Martin Lindén
- Department of Cell and Molecular Biology , Uppsala University , SE-751 05 Uppsala , Sweden
| | - Alexander P Lyubartsev
- Department of Materials and Environmental Chemistry , Stockholm University , SE-106 91 Stockholm , Sweden
| | - Erik G Brandt
- Department of Materials and Environmental Chemistry , Stockholm University , SE-106 91 Stockholm , Sweden
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31
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Liu X, Tian F, Yue T, Zhang X, Zhong C. Pulling force and surface tension drive membrane fusion. J Chem Phys 2017; 147:194703. [PMID: 29166098 DOI: 10.1063/1.4997393] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Despite catalyzed by fusion proteins of quite different molecular architectures, intracellular, viral, and cell-to-cell fusions are found to have the essential common features and the nearly same nature of transition states. The similarity inspires us to find a more general catalysis mechanism for membrane fusion that minimally depends on the specific structures of fusion proteins. In this work, we built a minimal model for membrane fusion, and by using dissipative particle dynamics simulations, we propose a mechanism that the pulling force generated by fusion proteins initiates the fusion process and the membrane tension regulates the subsequent fusion stages. The model shows different features compared to previous computer simulation studies: the pulling force catalyzes membrane fusion through lipid head overcrowding in the contacting region, leading to an increase in the head-head repulsion and/or the unfavorable head-tail contacts from opposing membranes, both of which destabilize the contacting leaflets and thus promote membrane fusion or vesicle rupture. Our simulations produce a variety of shapes and intermediates, closely resembling cases seen experimentally. Our work strongly supports the view that the tight pulling mechanism is a conserved feature of fusion protein-mediated fusion and that the membrane tension plays an essential role in fusion.
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Affiliation(s)
- Xuejuan Liu
- State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Falin Tian
- State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Tongtao Yue
- State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580, People's Republic of China
| | - Xianren Zhang
- State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Chongli Zhong
- State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
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32
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Levin A, Jeworrek C, Winter R, Weise K, Czeslik C. Lipid Phase Control and Secondary Structure of Viral Fusion Peptides Anchored in Monoolein Membranes. J Phys Chem B 2017; 121:8492-8502. [PMID: 28829131 DOI: 10.1021/acs.jpcb.7b06400] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fusion of lipid membranes involves major changes of the membrane curvatures and is mediated by fusion proteins that bind to the lipid membranes. For a better understanding of the way fusion proteins steer this process, we have studied the interaction of two different viral fusion peptides, HA2-FP and TBEV-FP, with monoolein mesophases as a function of temperature and pressure at limited hydration. The fusion peptides are derived from the influenza virus hemagglutinin fusion protein (HA2-FP) and from the tick-borne encephalitis virus envelope glycoprotein E (TBEV-FP). By using synchrotron X-ray diffraction, the changes of the monoolein phase behavior upon binding the peptides have been determined and the concomitant secondary structures of the peptides have been analyzed by FTIR spectroscopy. As main results we have found that the fusion peptides interact differently with monoolein and change the pressure and temperature dependent lipid phase behavior to different extents. However, they both destabilize the fluid lamellar phase and favor phases with negative curvature, i.e. inverse bicontinuous cubic and inverse hexagonal phases. These peptide-induced phase changes can partially be reversed by the application of high pressure, demonstrating that the promotion of negative curvature is achieved by a less dense packing of the monoolein membranes by the fusion peptides. Pressure jumps across the cubic-lamellar phase transition reveal that HA2-FP has a negligible effect on the rates of the cubic and the lamellar phase formation. Interestingly, the secondary structures of the fusion peptides appear unaffected by monoolein fluid-fluid phase transitions, suggesting that the fusion peptides are the structure dominant species in the fusion process of lipid membranes.
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Affiliation(s)
- Artem Levin
- Department of Chemistry and Chemical Biology, TU Dortmund University , D-44221 Dortmund, Germany
| | - Christoph Jeworrek
- Department of Chemistry and Chemical Biology, TU Dortmund University , D-44221 Dortmund, Germany
| | - Roland Winter
- Department of Chemistry and Chemical Biology, TU Dortmund University , D-44221 Dortmund, Germany
| | - Katrin Weise
- Department of Chemistry and Chemical Biology, TU Dortmund University , D-44221 Dortmund, Germany
| | - Claus Czeslik
- Department of Chemistry and Chemical Biology, TU Dortmund University , D-44221 Dortmund, Germany
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33
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Zelisko M, Ahmadpoor F, Gao H, Sharma P. Determining the Gaussian Modulus and Edge Properties of 2D Materials: From Graphene to Lipid Bilayers. PHYSICAL REVIEW LETTERS 2017; 119:068002. [PMID: 28949621 DOI: 10.1103/physrevlett.119.068002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Indexed: 06/07/2023]
Abstract
The dominant deformation behavior of two-dimensional materials (bending) is primarily governed by just two parameters: bending rigidity and the Gaussian modulus. These properties also set the energy scale for various important physical and biological processes such as pore formation, cell fission and generally, any event accompanied by a topological change. Unlike the bending rigidity, the Gaussian modulus is, however, notoriously difficult to evaluate via either experiments or atomistic simulations. In this Letter, recognizing that the Gaussian modulus and edge tension play a nontrivial role in the fluctuations of a 2D material edge, we derive closed-form expressions for edge fluctuations. Combined with atomistic simulations, we use the developed approach to extract the Gaussian modulus and edge tension at finite temperatures for both graphene and various types of lipid bilayers. Our results possibly provide the first reliable estimate of this elusive property at finite temperatures and appear to suggest that earlier estimates must be revised. In particular, we show that, if previously estimated properties are employed, the graphene-free edge will exhibit unstable behavior at room temperature. Remarkably, in the case of graphene, we show that the Gaussian modulus and edge tension even change sign at finite temperatures.
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Affiliation(s)
- Matthew Zelisko
- Department of Mechanical Engineering, University of Houston, Houston, Texas 77204, USA
| | - Fatemeh Ahmadpoor
- Department of Mechanical Engineering, University of Houston, Houston, Texas 77204, USA
- School of Engineering, Brown University, Providence, Rhode Island 02912, USA
| | - Huajian Gao
- School of Engineering, Brown University, Providence, Rhode Island 02912, USA
| | - Pradeep Sharma
- Department of Mechanical Engineering, University of Houston, Houston, Texas 77204, USA
- Department of Physics, University of Houston, Houston, Texas 77204, USA
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34
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Sodt AJ, Beaven AH, Andersen OS, Im W, Pastor RW. Gramicidin A Channel Formation Induces Local Lipid Redistribution II: A 3D Continuum Elastic Model. Biophys J 2017; 112:1198-1213. [PMID: 28355547 DOI: 10.1016/j.bpj.2017.01.035] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 01/11/2017] [Accepted: 01/30/2017] [Indexed: 12/20/2022] Open
Abstract
To change conformation, a protein must deform the surrounding bilayer. In this work, a three-dimensional continuum elastic model for gramicidin A in a lipid bilayer is shown to describe the sensitivity to thickness, curvature stress, and the mechanical properties of the lipid bilayer. A method is demonstrated to extract the gramicidin-lipid boundary condition from all-atom simulations that can be used in the three-dimensional continuum model. The boundary condition affects the deformation dramatically, potentially much more than typical variations in the material stiffness do as lipid composition is changed. Moreover, it directly controls the sensitivity to curvature stress. The curvature stress and hydrophobic surfaces of the all-atom and continuum models are found to be in excellent agreement. The continuum model is applied to estimate the enrichment of hydrophobically matched lipids near the channel in a mixture, and the results agree with single-channel experiments and extended molecular dynamics simulations from the companion article by Beaven et al. in this issue of Biophysical Journal.
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Affiliation(s)
- Alexander J Sodt
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland.
| | - Andrew H Beaven
- Department of Chemistry, The University of Kansas, Lawrence, Kansas
| | - Olaf S Andersen
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York
| | - Wonpil Im
- Department of Biological Sciences and Bioengineering Program, Lehigh University, Bethlehem, Pennsylvania
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
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35
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Meher G, Chakraborty H. Organization and dynamics of Trp14 of hemagglutinin fusion peptide in membrane mimetic environment. Chem Phys Lipids 2017; 205:48-54. [DOI: 10.1016/j.chemphyslip.2017.04.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 04/14/2017] [Accepted: 04/26/2017] [Indexed: 01/01/2023]
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36
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Achiral symmetry breaking and positive Gaussian modulus lead to scalloped colloidal membranes. Proc Natl Acad Sci U S A 2017; 114:E3376-E3384. [PMID: 28411214 DOI: 10.1073/pnas.1617043114] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
In the presence of a nonadsorbing polymer, monodisperse rod-like particles assemble into colloidal membranes, which are one-rod-length-thick liquid-like monolayers of aligned rods. Unlike 3D edgeless bilayer vesicles, colloidal monolayer membranes form open structures with an exposed edge, thus presenting an opportunity to study elasticity of fluid sheets. Membranes assembled from single-component chiral rods form flat disks with uniform edge twist. In comparison, membranes composed of a mixture of rods with opposite chiralities can have the edge twist of either handedness. In this limit, disk-shaped membranes become unstable, instead forming structures with scalloped edges, where two adjacent lobes with opposite handedness are separated by a cusp-shaped point defect. Such membranes adopt a 3D configuration, with cusp defects alternatively located above and below the membrane plane. In the achiral regime, the cusp defects have repulsive interactions, but away from this limit we measure effective long-ranged attractive binding. A phenomenological model shows that the increase in the edge energy of scalloped membranes is compensated by concomitant decrease in the deformation energy due to Gaussian curvature associated with scalloped edges, demonstrating that colloidal membranes have positive Gaussian modulus. A simple excluded volume argument predicts the sign and magnitude of the Gaussian curvature modulus that is in agreement with experimental measurements. Our results provide insight into how the interplay between membrane elasticity, geometrical frustration, and achiral symmetry breaking can be used to fold colloidal membranes into 3D shapes.
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37
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Chakraborty H, Lentz BR, Kombrabail M, Krishnamoorthy G, Chattopadhyay A. Depth-Dependent Membrane Ordering by Hemagglutinin Fusion Peptide Promotes Fusion. J Phys Chem B 2017; 121:1640-1648. [DOI: 10.1021/acs.jpcb.7b00684] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hirak Chakraborty
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
- School
of Chemistry, Sambalpur University, Jyoti Vihar, Burla, Odisha 768 019, India
| | - Barry R. Lentz
- Department
of Biochemistry and Biophysics and Program in Molecular and Cellular
Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States
| | - Mamata Kombrabail
- Department
of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhaba Road, Mumbai, India
| | - G. Krishnamoorthy
- Department
of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhaba Road, Mumbai, India
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38
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Chang CW, Chiang CW, Jackson MB. Fusion pores and their control of neurotransmitter and hormone release. J Gen Physiol 2017; 149:301-322. [PMID: 28167663 PMCID: PMC5339513 DOI: 10.1085/jgp.201611724] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Revised: 01/06/2017] [Accepted: 01/19/2017] [Indexed: 11/20/2022] Open
Abstract
Chang et al. review fusion pore structure and dynamics and discuss the implications for hormone and neurotransmitter release Ca2+-triggered exocytosis functions broadly in the secretion of chemical signals, enabling neurons to release neurotransmitters and endocrine cells to release hormones. The biological demands on this process can vary enormously. Although synapses often release neurotransmitter in a small fraction of a millisecond, hormone release can be orders of magnitude slower. Vesicles usually contain multiple signaling molecules that can be released selectively and conditionally. Cells are able to control the speed, concentration profile, and content selectivity of release by tuning and tailoring exocytosis to meet different biological demands. Much of this regulation depends on the fusion pore—the aqueous pathway by which molecules leave a vesicle and move out into the surrounding extracellular space. Studies of fusion pores have illuminated how cells regulate secretion. Furthermore, the formation and growth of fusion pores serve as a readout for the progress of exocytosis, thus revealing key kinetic stages that provide clues about the underlying mechanisms. Herein, we review the structure, composition, and dynamics of fusion pores and discuss the implications for molecular mechanisms as well as for the cellular regulation of neurotransmitter and hormone release.
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Affiliation(s)
- Che-Wei Chang
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705
| | - Chung-Wei Chiang
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705
| | - Meyer B Jackson
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705
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39
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X-ray structural investigations of fusion intermediates: Lipid model systems and beyond. Semin Cell Dev Biol 2016; 60:65-77. [DOI: 10.1016/j.semcdb.2016.06.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 06/15/2016] [Accepted: 06/20/2016] [Indexed: 11/20/2022]
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40
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Kawamoto S, Klein ML, Shinoda W. Coarse-grained molecular dynamics study of membrane fusion: Curvature effects on free energy barriers along the stalk mechanism. J Chem Phys 2016; 143:243112. [PMID: 26723597 DOI: 10.1063/1.4933087] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effects of membrane curvature on the free energy barrier for membrane fusion have been investigated using coarse-grained molecular dynamics (CG-MD) simulations, assuming that fusion takes place through a stalk intermediate. Free energy barriers were estimated for stalk formation as well as for fusion pore formation using the guiding potential method. Specifically, the three different geometries of two apposed membranes were considered: vesicle-vesicle, vesicle-planar, and planar-planar membranes. The free energy barriers for the resulting fusion were found to depend importantly on the fusing membrane geometries; the lowest barrier was obtained for vesicular membranes. Further, lipid sorting was observed in fusion of the mixed membranes of dimyristoyl phosphatidylcholine and dioleoyl phosphatidylethanolamine (DOPE). Specifically, DOPE molecules were found to assemble around the stalk to support the highly negative curved membrane surface. A consistent result for lipid sorting was observed when a simple continuum model (CM) was used, where the Helfrich energy and mixing entropy of the lipids were taken into account. However, the CM predicts a much higher free energy barrier than found using CG-MD. This discrepancy originates from the conformational changes of lipids, which were not considered in the CM. The results of the CG-MD simulations reveal that a large conformational change in the lipid takes place around the stalk region, which results in a reduction of free energy barriers along the stalk mechanism of membrane fusion.
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Affiliation(s)
- Shuhei Kawamoto
- Department of Applied Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
| | - Michael L Klein
- Institute for Computational Molecular Science, Temple University, SERC Building 1925 North 12th Street, Philadelphia, Pennsylvania 19122, USA
| | - Wataru Shinoda
- Department of Applied Chemistry, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
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41
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Fan ZA, Tsang KY, Chen SH, Chen YF. Revisit the Correlation between the Elastic Mechanics and Fusion of Lipid Membranes. Sci Rep 2016; 6:31470. [PMID: 27534263 PMCID: PMC4989284 DOI: 10.1038/srep31470] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 07/18/2016] [Indexed: 01/10/2023] Open
Abstract
Membrane fusion is a vital process in key cellular events. The fusion capability of a membrane depends on its elastic properties and varies with its lipid composition. It is believed that as the composition varies, the consequent change in C0 (monolayer spontaneous curvature) is the major factor dictating fusion, owing to the associated variation in GEs (elastic energies) of the fusion intermediates (e.g. stalk). By exploring the correlations among fusion, C0 and Kcp (monolayer bending modulus), we revisit this long-held belief and re-examine the fusogenic contributions of some relevant factors. We observe that not only C0 but also Kcp variations affect fusion, with depression in Kcp leading to suppression in fusion. Variations in GEs and inter-membrane interactions cannot account for the Kcp-fusion correlation; fusion is suppressed even as the GEs decrease with Kcp, indicating the presence of factor(s) with fusogenic importance overtaking that of GE. Furthermore, analyses find that the C0 influence on fusion is effected via modulating GE of the pre-fusion planar membrane, rather than stalk. The results support a recent proposition calling for a paradigm shift from the conventional view of fusion and may reshape our understanding to the roles of fusogenic proteins in regulating cellular fusion machineries.
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Affiliation(s)
- Zih-An Fan
- Department of Chemical and Materials Engineering, National Central University, No. 300, Zhongda Rd., Zhongli District, Taoyuan 32001, Taiwan
| | - Kuan-Yu Tsang
- Department of Chemical and Materials Engineering, National Central University, No. 300, Zhongda Rd., Zhongli District, Taoyuan 32001, Taiwan
| | - Si-Han Chen
- Department of Chemical and Materials Engineering, National Central University, No. 300, Zhongda Rd., Zhongli District, Taoyuan 32001, Taiwan
| | - Yi-Fan Chen
- Department of Chemical and Materials Engineering, National Central University, No. 300, Zhongda Rd., Zhongli District, Taoyuan 32001, Taiwan
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42
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Ryham RJ, Klotz TS, Yao L, Cohen FS. Calculating Transition Energy Barriers and Characterizing Activation States for Steps of Fusion. Biophys J 2016; 110:1110-24. [PMID: 26958888 PMCID: PMC4788739 DOI: 10.1016/j.bpj.2016.01.013] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 01/05/2016] [Accepted: 01/13/2016] [Indexed: 12/29/2022] Open
Abstract
We use continuum mechanics to calculate an entire least energy pathway of membrane fusion, from stalk formation, to pore creation, and through fusion pore enlargement. The model assumes that each structure in the pathway is axially symmetric. The static continuum stalk structure agrees quantitatively with experimental stalk architecture. Calculations show that in a stalk, the distal monolayer is stretched and the stored stretching energy is significantly less than the tilt energy of an unstretched distal monolayer. The string method is used to determine the energy of the transition barriers that separate intermediate states and the dynamics of two bilayers as they pass through them. Hemifusion requires a small amount of energy independently of lipid composition, while direct transition from a stalk to a fusion pore without a hemifusion intermediate is highly improbable. Hemifusion diaphragm expansion is spontaneous for distal monolayers containing at least two lipid components, given sufficiently negative diaphragm spontaneous curvature. Conversely, diaphragms formed from single-component distal monolayers do not expand without the continual injection of energy. We identify a diaphragm radius, below which central pore expansion is spontaneous. For larger diaphragms, prior studies have shown that pore expansion is not axisymmetric, and here our calculations supply an upper bound for the energy of the barrier against pore formation. The major energy-requiring deformations in the steps of fusion are: widening of a hydrophobic fissure in bilayers for stalk formation, splay within the expanding hemifusion diaphragm, and fissure widening initiating pore formation in a hemifusion diaphragm.
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Affiliation(s)
- Rolf J Ryham
- Department of Mathematics, Fordham University, Bronx, New York.
| | - Thomas S Klotz
- Department of Computational and Applied Mathematics, Rice University, Houston, Texas
| | - Lihan Yao
- Department of Mathematics, Fordham University, Bronx, New York
| | - Fredric S Cohen
- Department of Molecular Biophysics and Physiology, Rush University, Chicago, Illinois
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Hammel I, Meilijson I. Function Suggests Nano-Structure: Quantitative Structural Support for SNARE-Mediated Pore Formation. Neurotox Res 2015; 29:1-9. [PMID: 26407673 DOI: 10.1007/s12640-015-9559-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 08/22/2015] [Accepted: 08/24/2015] [Indexed: 10/23/2022]
Abstract
Granule secretory content is released in either basal or calcium-activated complete exocytosis mode. A vital element in these processes is the establishment of a fusion pore between the granule membrane and the plasma membrane, initiated by the formation of a circular rosette docking arrangement of SNARE protein complexes. The controversially disputed number of SNARE complexes needed for granule priming leading to the formation of the fusion pore, is granule-size dependent and varies between secretion modes. Resorting to a statistical mechanics approach that views SNARE complexes and Ca(2+) ions as interacting particles, we have developed a relationship that links secretion rate to SNARE rosette size, Ca(2+) concentration and Ca(2+) ion cooperativity. Data are presented and discussed which suggest this SNARE-dependent generalization of existing narrow-range biophysical models that correlate secretion rate with Ca(2+) concentration and maximal Ca(2+) ion cooperativity. Evidence from dozens of examples in the literature advocate for this relation, which holds through the entire biological range. The coalescence of so many areas of diverse research methodologies has greatly augmented our understanding of so many different sequences of granule life cycle. Accordingly, these new tools may become valuable in a variety of electrophysiological experiments.
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Affiliation(s)
- Ilan Hammel
- Department of Pathology, Sackler Faculty of Medicine, Tel Aviv University, 6997801, Tel Aviv, Israel.
| | - Isaac Meilijson
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Mathematical Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
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44
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Abstract
The SNARE (Soluble NSF Attachment protein REceptor) complex, which in mammalian neurosecretory cells is composed of the proteins synaptobrevin 2 (also called VAMP2), syntaxin, and SNAP-25, plays a key role in vesicle fusion. In this review, we discuss the hypothesis that, in neurosecretory cells, fusion pore formation is directly accomplished by a conformational change in the SNARE complex via movement of the transmembrane domains.
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Affiliation(s)
- Qinghua Fang
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York; and Laboratory for Nanoscale Cell Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | - Manfred Lindau
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York; and Laboratory for Nanoscale Cell Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
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45
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Frolov VA, Escalada A, Akimov SA, Shnyrova AV. Geometry of membrane fission. Chem Phys Lipids 2015; 185:129-40. [DOI: 10.1016/j.chemphyslip.2014.07.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 07/16/2014] [Accepted: 07/18/2014] [Indexed: 11/24/2022]
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46
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Deserno M. Fluid lipid membranes: From differential geometry to curvature stresses. Chem Phys Lipids 2015; 185:11-45. [DOI: 10.1016/j.chemphyslip.2014.05.001] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 04/21/2014] [Accepted: 05/06/2014] [Indexed: 10/25/2022]
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47
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Membrane curvature modulation of protein activity determined by NMR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:220-8. [DOI: 10.1016/j.bbamem.2014.05.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 04/28/2014] [Accepted: 05/04/2014] [Indexed: 02/04/2023]
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48
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Abstract
Biological membranes are composed largely of lipids and proteins. The most common arrangement of lipids in biological membranes is as a bilayer. This arrangement spontaneously forms a barrier for the passage of polar materials. The bilayer is thin but can have a large area in the dimension perpendicular to its thickness. The physical nature of the bilayer membrane will vary according to the conditions of the environment as well as the chemical structure of the lipid constituents of the bilayer. These physical properties determine the function of the membrane together with specific structural features of the lipids that allow them to have signaling properties. The lipids of the membrane are not uniformly distributed. There is an intrinsic asymmetry between the two monolayers that constitute the bilayer. In addition, some lipids tend to be enriched in particular regions of the membrane, termed domains. There is evidence that certain domains recruit specific proteins into that domain. This has been suggested to be important for allowing interaction among different proteins involved in certain signal transduction pathways. Membrane lipids have important roles in determining the physical properties of the membrane, in modulating the activity of membrane-bound proteins and in certain cases being specific secondary messengers that can interact with specific proteins. A large variety of lipids present in biological membranes result in them possessing many functions.
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Affiliation(s)
- Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, Canada, L8S 4K1,
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49
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Meriney SD, Umbach JA, Gundersen CB. Fast, Ca2+-dependent exocytosis at nerve terminals: shortcomings of SNARE-based models. Prog Neurobiol 2014; 121:55-90. [PMID: 25042638 DOI: 10.1016/j.pneurobio.2014.07.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 04/14/2014] [Accepted: 07/03/2014] [Indexed: 11/30/2022]
Abstract
Investigations over the last two decades have made major inroads in clarifying the cellular and molecular events that underlie the fast, synchronous release of neurotransmitter at nerve endings. Thus, appreciable progress has been made in establishing the structural features and biophysical properties of the calcium (Ca2+) channels that mediate the entry into nerve endings of the Ca2+ ions that trigger neurotransmitter release. It is now clear that presynaptic Ca2+ channels are regulated at many levels and the interplay of these regulatory mechanisms is just beginning to be understood. At the same time, many lines of research have converged on the conclusion that members of the synaptotagmin family serve as the primary Ca2+ sensors for the action potential-dependent release of neurotransmitter. This identification of synaptotagmins as the proteins which bind Ca2+ and initiate the exocytotic fusion of synaptic vesicles with the plasma membrane has spurred widespread efforts to reveal molecular details of synaptotagmin's action. Currently, most models propose that synaptotagmin interfaces directly or indirectly with SNARE (soluble, N-ethylmaleimide sensitive factor attachment receptors) proteins to trigger membrane fusion. However, in spite of intensive efforts, the field has not achieved consensus on the mechanism by which synaptotagmins act. Concurrently, the precise sequence of steps underlying SNARE-dependent membrane fusion remains controversial. This review considers the pros and cons of the different models of SNARE-mediated membrane fusion and concludes by discussing a novel proposal in which synaptotagmins might directly elicit membrane fusion without the intervention of SNARE proteins in this final fusion step.
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Affiliation(s)
- Stephen D Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Joy A Umbach
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095, USA
| | - Cameron B Gundersen
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095, USA.
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50
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Kawamoto S, Shinoda W. Free energy analysis along the stalk mechanism of membrane fusion. SOFT MATTER 2014; 10:3048-3054. [PMID: 24695575 DOI: 10.1039/c3sm52344f] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The free energy profile of the stalk model of membrane fusion has been calculated using coarse-grained molecular dynamics simulations. The proposed method guides the lipid configuration using a guiding wall potential to make the transition from two apposed membranes to a stalk and a fusion pore. The free energy profile is obtained with a thermodynamic integration scheme using the mean force working on the guiding wall as a response of the system. We applied the method to two apposed flat bilayers composed of dioleoyl phosphatidylethanolamine/dioleoyl phosphatidylcholine expanding over the simulation box under the periodic boundary conditions. The two transition states are identified as pre-stalk and pre-pore states. The free energy barrier for the latter is confirmed to be in good agreement with that estimated by the pulling method. The present method provides a practical way to calculate the free energy profile along the stalk mechanism.
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Affiliation(s)
- Shuhei Kawamoto
- Health Research Institute, National Institute of Advanced Industrial Science & Technology (AIST), 1-8-31, Midorigaoka, Ikeda, Osaka 563-8577, Japan.
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