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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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Waltmann C, Shrestha A, Olvera de la Cruz M. Patterning of multicomponent elastic shells by gaussian curvature. Phys Rev E 2024; 109:054409. [PMID: 38907410 DOI: 10.1103/physreve.109.054409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 04/19/2024] [Indexed: 06/24/2024]
Abstract
Recent findings suggest that shell protein distribution and the morphology of bacterial microcompartments regulate the chemical fluxes facilitating reactions which dictate their biological function. We explore how the morphology and component patterning are coupled through the competition of mean and gaussian bending energies in multicomponent elastic shells that form three-component irregular polyhedra. We observe two softer components with lower bending rigidities allocated on the edges and vertices while the harder component occupies the faces. When subjected to a nonzero interfacial line tension, the two softer components further separate and pattern into subdomains that are mediated by the gaussian curvature. We find that this degree of fractionation is maximized when there is a weaker line tension and when the ratio of bending rigidities between the two softer domains ≈2. Our results reveal a patterning mechanism in multicomponent shells that can capture the observed morphologies of bacterial microcompartments, and moreover, can be realized in synthetic vesicles.
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Affiliation(s)
| | | | - Monica Olvera de la Cruz
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
- Center for Computation and Theory of Soft Materials, Northwestern University, Evanston, Illinois 60208, USA
- Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
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3
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Chmielewski D, Su GC, Kaelber JT, Pintilie GD, Chen M, Jin J, Auguste AJ, Chiu W. Cryogenic electron microscopy and tomography reveal imperfect icosahedral symmetry in alphaviruses. PNAS NEXUS 2024; 3:pgae102. [PMID: 38525304 PMCID: PMC10959069 DOI: 10.1093/pnasnexus/pgae102] [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: 08/22/2023] [Accepted: 02/15/2024] [Indexed: 03/26/2024]
Abstract
Alphaviruses are spherical, enveloped RNA viruses with two-layered icosahedral architecture. The structures of many alphaviruses have been studied using cryogenic electron microscopy (cryo-EM) reconstructions, which impose icosahedral symmetry on the viral particles. Using cryogenic electron tomography (cryo-ET), we revealed a polarized symmetry defect in the icosahedral lattice of Chikungunya virus (CHIKV) in situ, similar to the late budding particles, suggesting the inherent imperfect symmetry originates from the final pinch-off of assembled virions. We further demonstrated this imperfect symmetry is also present in in vitro purified CHIKV and Mayaro virus, another arthritogenic alphavirus. We employed a subparticle-based single-particle analysis protocol to circumvent the icosahedral imperfection and boosted the resolution of the structure of the CHIKV to ∼3 Å resolution, which revealed detailed molecular interactions between glycoprotein E1-E2 heterodimers in the transmembrane region and multiple lipid-like pocket factors located in a highly conserved hydrophobic pocket. This complementary use of in situ cryo-ET and single-particle cryo-EM approaches provides a more precise structural description of near-icosahedral viruses and valuable insights to guide the development of structure-based antiviral therapies against alphaviruses.
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Affiliation(s)
- David Chmielewski
- Biophysics Graduate Program, Stanford University, Stanford, CA 94305, USA
| | - Guan-Chin Su
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Jason T Kaelber
- Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA
| | - Grigore D Pintilie
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Muyuan Chen
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
| | - Jing Jin
- Vitalant Research Institute, San Francisco, CA 94118, USA
- Department of Laboratory Medicine, University of California, San Francisco, CA 94143, USA
| | - Albert J Auguste
- Department of Entomology, College of Agriculture and Life Sciences, Fralin Life Science Institute, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
- Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Wah Chiu
- Biophysics Graduate Program, Stanford University, Stanford, CA 94305, USA
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA
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4
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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. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.05.574447. [PMID: 38260291 PMCID: PMC10802413 DOI: 10.1101/2024.01.05.574447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Deterministic formation of membrane scission necks by protein machinery with multiplexed functions is critical in biology. A microbial example is the M2 viroporin, a proton pump from the influenza A virus which 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 (SAXS) 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 hemi-fission 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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Ledesma-Durán A, Juárez-Valencia LH. Diffusion coefficients and MSD measurements on curved membranes and porous media. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2023; 46:70. [PMID: 37578670 DOI: 10.1140/epje/s10189-023-00329-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 07/28/2023] [Indexed: 08/15/2023]
Abstract
We study some geometric aspects that influence the transport properties of particles that diffuse on curved surfaces. We compare different approaches to surface diffusion based on the Laplace-Beltrami operator adapted to predict concentration along entire membranes, confined subdomains along surfaces, or within porous media. Our goal is to summarize, firstly, how diffusion in these systems results in different types of diffusion coefficients and mean square displacement measurements, and secondly, how these two factors are affected by the concavity of the surface, the shape of the possible barriers or obstacles that form the available domains, the sinuosity, tortuosity, and constrictions of the trajectories and even how the observation plane affects the measurements of the diffusion. In addition to presenting a critical and organized comparison between different notions of MSD, in this review, we test the correspondence between theoretical predictions and numerical simulations by performing finite element simulations and illustrate some situations where diffusion theory can be applied. We briefly reviewed computational schemes for understanding surface diffusion and finally, discussed how this work contributes to understanding the role of surface diffusion transport properties in porous media and their relationship to other transport processes.
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Affiliation(s)
- Aldo Ledesma-Durán
- Departmento de Matemáticas, Universidad Autónoma Metropolitana, CDMX, Mexico
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6
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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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7
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Farag H, Peters B. Free energy barriers for anti-freeze protein engulfment in ice: Effects of supercooling, footprint size, and spatial separation. J Chem Phys 2023; 158:094501. [PMID: 36889941 DOI: 10.1063/5.0131983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Anti-freeze proteins (AFPs) protect organisms at freezing conditions by attaching to the ice surface and arresting its growth. Each adsorbed AFP locally pins the ice surface, resulting in a metastable dimple for which the interfacial forces counteract the driving force for growth. As supercooling increases, these metastable dimples become deeper, until metastability is lost in an engulfment event where the ice irreversibly swallows the AFP. Engulfment resembles nucleation in some respects, and this paper develops a model for the "critical profile" and free energy barrier for the engulfment process. Specifically, we variationally optimize the ice-water interface and estimate the free energy barrier as a function of the supercooling, the AFP footprint size, and the distance to neighboring AFPs on the ice surface. Finally, we use symbolic regression to derive a simple closed-form expression for the free energy barrier as a function of two physically interpretable, dimensionless parameters.
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Affiliation(s)
- Hossam Farag
- Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Baron Peters
- Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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8
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Remodeling of the Plasma Membrane by Surface-Bound Protein Monomers and Oligomers: The Critical Role of Intrinsically Disordered Regions. J Membr Biol 2022; 255:651-663. [PMID: 35930019 PMCID: PMC9718270 DOI: 10.1007/s00232-022-00256-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 07/07/2022] [Indexed: 12/24/2022]
Abstract
The plasma membrane (PM) of cells is a dynamic structure whose morphology and composition is in constant flux. PM morphologic changes are particularly relevant for the assembly and disassembly of signaling platforms involving surface-bound signaling proteins, as well as for many other mechanochemical processes that occur at the PM surface. Surface-bound membrane proteins (SBMP) require efficient association with the PM for their function, which is often achieved by the coordinated interactions of intrinsically disordered regions (IDRs) and globular domains with membrane lipids. This review focuses on the role of IDR-containing SBMPs in remodeling the composition and curvature of the PM. The ability of IDR-bearing SBMPs to remodel the Gaussian and mean curvature energies of the PM is intimately linked to their ability to sort subsets of phospholipids into nanoclusters. We therefore discuss how IDRs of many SBMPs encode lipid-binding specificity or facilitate cluster formation, both of which increase their membrane remodeling capacity, and how SBMP oligomers alter membrane shape by monolayer surface area expansion and molecular crowding.
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9
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Jiang X, Harker-Kirschneck L, Vanhille-Campos C, Pfitzner AK, Lominadze E, Roux A, Baum B, Šarić A. Modelling membrane reshaping by staged polymerization of ESCRT-III filaments. PLoS Comput Biol 2022; 18:e1010586. [PMID: 36251703 PMCID: PMC9612822 DOI: 10.1371/journal.pcbi.1010586] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 10/27/2022] [Accepted: 09/19/2022] [Indexed: 12/24/2022] Open
Abstract
ESCRT-III filaments are composite cytoskeletal polymers that can constrict and cut cell membranes from the inside of the membrane neck. Membrane-bound ESCRT-III filaments undergo a series of dramatic composition and geometry changes in the presence of an ATP-consuming Vps4 enzyme, which causes stepwise changes in the membrane morphology. We set out to understand the physical mechanisms involved in translating the changes in ESCRT-III polymer composition into membrane deformation. We have built a coarse-grained model in which ESCRT-III polymers of different geometries and mechanical properties are allowed to copolymerise and bind to a deformable membrane. By modelling ATP-driven stepwise depolymerisation of specific polymers, we identify mechanical regimes in which changes in filament composition trigger the associated membrane transition from a flat to a buckled state, and then to a tubule state that eventually undergoes scission to release a small cargo-loaded vesicle. We then characterise how the location and kinetics of polymer loss affects the extent of membrane deformation and the efficiency of membrane neck scission. Our results identify the near-minimal mechanical conditions for the operation of shape-shifting composite polymers that sever membrane necks.
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Affiliation(s)
- Xiuyun Jiang
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London, United Kingdom
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Lena Harker-Kirschneck
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London, United Kingdom
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
| | - Christian Vanhille-Campos
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London, United Kingdom
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | | | - Elene Lominadze
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London, United Kingdom
| | - Aurélien Roux
- Department of Biochemistry, University of Geneva, Geneva, Switzerland
| | - Buzz Baum
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Anđela Šarić
- Department of Physics and Astronomy, Institute for the Physics of Living Systems, University College London, London, United Kingdom
- Medical Research Council Laboratory for Molecular Cell Biology, University College London, London, United Kingdom
- Institute of Science and Technology Austria, Klosterneuburg, Austria
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10
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Dharmavaram S, Wan X, Perotti LE. A Lagrangian Thin-Shell Finite Element Method for Interacting Particles on Fluid Membranes. MEMBRANES 2022; 12:960. [PMID: 36295719 PMCID: PMC9608239 DOI: 10.3390/membranes12100960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 09/21/2022] [Accepted: 09/26/2022] [Indexed: 06/16/2023]
Abstract
A recurring motif in soft matter and biophysics is modeling the mechanics of interacting particles on fluid membranes. One of the main outstanding challenges in these applications is the need to model the strong coupling between the substrate deformation and the particles' positions as the latter freely move on the former. This work presents a thin-shell finite element formulation based on subdivision surfaces to compute equilibrium configurations of a thin fluid shell with embedded particles. We use a variational Lagrangian framework to couple the mechanics of the particles and the substrate without having to resort to ad hoc constraints to anchor the particles to the surface. Unlike established methods for such systems, the particles are allowed to move between elements of the finite element mesh. This is achieved by parametrizing the particle locations on the reference configuration. Using the Helfrich-Canham energy as a model for fluid shells, we present the finite element method's implementation and an efficient search algorithm required to locate particles on the reference mesh. Several analyses with varying numbers of particles are finally presented reproducing symmetries observed in the classic Thomson problem and showcasing the coupling between interacting particles and deformable membranes.
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Affiliation(s)
- Sanjay Dharmavaram
- Department of Mathematics, Bucknell University, 1 Dent Drive, Lewisburg, PA 17837, USA
| | - Xinran Wan
- Language Technologies Institute, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA
| | - Luigi E. Perotti
- Mechanical and Aerospace Engineering Department, University of Central Florida, 12760 Pegasus Drive, Orlando, FL 32816, USA
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11
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Guo SK, Sodt AJ, Johnson ME. Large self-assembled clathrin lattices spontaneously disassemble without sufficient adaptor proteins. PLoS Comput Biol 2022; 18:e1009969. [PMID: 35312692 PMCID: PMC8979592 DOI: 10.1371/journal.pcbi.1009969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 03/31/2022] [Accepted: 02/24/2022] [Indexed: 11/18/2022] Open
Abstract
Clathrin-coated structures must assemble on cell membranes to internalize receptors, with the clathrin protein only linked to the membrane via adaptor proteins. These structures can grow surprisingly large, containing over 20 clathrin, yet they often fail to form productive vesicles, instead aborting and disassembling. We show that clathrin structures of this size can both form and disassemble spontaneously when adaptor protein availability is low, despite high abundance of clathrin. Here, we combine recent in vitro kinetic measurements with microscopic reaction-diffusion simulations and theory to differentiate mechanisms of stable vs unstable clathrin assembly on membranes. While in vitro conditions drive assembly of robust, stable lattices, we show that concentrations, geometry, and dimensional reduction in physiologic-like conditions do not support nucleation if only the key adaptor AP-2 is included, due to its insufficient abundance. Nucleation requires a stoichiometry of adaptor to clathrin that exceeds 1:1, meaning additional adaptor types are necessary to form lattices successfully and efficiently. We show that the critical nucleus contains ~25 clathrin, remarkably similar to sizes of the transient and abortive structures observed in vivo. Lastly, we quantify the cost of bending the membrane under our curved clathrin lattices using a continuum membrane model. We find that the cost of bending the membrane could be largely offset by the energetic benefit of forming curved rather than flat structures, with numbers comparable to experiments. Our model predicts how adaptor density can tune clathrin-coated structures from the transient to the stable, showing that active energy consumption is therefore not required for lattice disassembly or remodeling during growth, which is a critical advance towards predicting productive vesicle formation.
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Affiliation(s)
- Si-Kao Guo
- TC Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Alexander J. Sodt
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Margaret E. Johnson
- TC Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
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12
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Jones PE, Pérez-Segura C, Bryer AJ, Perilla JR, Hadden-Perilla JA. Molecular dynamics of the viral life cycle: progress and prospects. Curr Opin Virol 2021; 50:128-138. [PMID: 34464843 PMCID: PMC8651149 DOI: 10.1016/j.coviro.2021.08.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 08/09/2021] [Accepted: 08/09/2021] [Indexed: 01/29/2023]
Abstract
Molecular dynamics (MD) simulations across spatiotemporal resolutions are widely applied to study viruses and represent the central technique uniting the field of computational virology. We discuss the progress of MD in elucidating the dynamics of the viral life cycle, including the status of modeling intact extracellular virions and leveraging advanced simulations to mimic active life cycle processes. We further remark on the prospects of MD for continued contributions to the basic science characterization of viruses, especially given the increasing availability of high-quality experimental data and supercomputing power. Overall, integrative computational methods that are closely guided by experiments are unmatched in the level of detail they provide, enabling-now and in the future-new discoveries relevant to thwarting viral infection.
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Affiliation(s)
- Peter Eugene Jones
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
| | - Carolina Pérez-Segura
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
| | - Alexander J Bryer
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
| | - Juan R Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States
| | - Jodi A Hadden-Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, United States.
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13
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Machado MR, Pantano S. Fighting viruses with computers, right now. Curr Opin Virol 2021; 48:91-99. [PMID: 33975154 DOI: 10.1016/j.coviro.2021.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/20/2021] [Accepted: 04/06/2021] [Indexed: 10/21/2022]
Abstract
The synergistic conjunction of various technological revolutions with the accumulated knowledge and workflows is rapidly transforming several scientific fields. Particularly, Virology can now feed from accurate physical models, polished computational tools, and massive computational power to readily integrate high-resolution structures into biological representations of unprecedented detail. That preparedness allows for the first time to get crucial information for vaccine and drug design from in-silico experiments against emerging pathogens of worldwide concern at relevant action windows. The present work reviews some of the main milestones leading to these breakthroughs in Computational Virology, providing an outlook for future developments in capacity building and accessibility to computational resources.
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Affiliation(s)
- Matías R Machado
- Biomolecular Simulations Group, Institut Pasteur de Montevideo, Mataojo 2020, Montevideo, 11400, Uruguay.
| | - Sergio Pantano
- Biomolecular Simulations Group, Institut Pasteur de Montevideo, Mataojo 2020, Montevideo, 11400, Uruguay.
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14
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Abstract
We propose a three-dimensional mathematical model to describe dynamical processes of membrane fission. The model is based on a phase field equation that includes the Gaussian curvature contribution to the bending energy. With the addition of the Gaussian curvature energy term numerical simulations agree with the predictions that tubular shapes can break down into multiple vesicles. A dispersion relation obtained with linear analysis predicts the wavelength of the instability and the number of formed vesicles. Finally, a membrane shape diagram is obtained for the different Gaussian and bending modulus, showing different shape regimes.
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15
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Hagan MF, Grason GM. Equilibrium mechanisms of self-limiting assembly. REVIEWS OF MODERN PHYSICS 2021; 93:025008. [PMID: 35221384 PMCID: PMC8880259 DOI: 10.1103/revmodphys.93.025008] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Self-assembly is a ubiquitous process in synthetic and biological systems, broadly defined as the spontaneous organization of multiple subunits (e.g. macromolecules, particles) into ordered multi-unit structures. The vast majority of equilibrium assembly processes give rise to two states: one consisting of dispersed disassociated subunits, and the other, a bulk-condensed state of unlimited size. This review focuses on the more specialized class of self-limiting assembly, which describes equilibrium assembly processes resulting in finite-size structures. These systems pose a generic and basic question, how do thermodynamic processes involving non-covalent interactions between identical subunits "measure" and select the size of assembled structures? In this review, we begin with an introduction to the basic statistical mechanical framework for assembly thermodynamics, and use this to highlight the key physical ingredients that ensure equilibrium assembly will terminate at finite dimensions. Then, we introduce examples of self-limiting assembly systems, and classify them within this framework based on two broad categories: self-closing assemblies and open-boundary assemblies. These include well-known cases in biology and synthetic soft matter - micellization of amphiphiles and shell/tubule formation of tapered subunits - as well as less widely known classes of assemblies, such as short-range attractive/long-range repulsive systems and geometrically-frustrated assemblies. For each of these self-limiting mechanisms, we describe the physical mechanisms that select equilibrium assembly size, as well as potential limitations of finite-size selection. Finally, we discuss alternative mechanisms for finite-size assemblies, and draw contrasts with the size-control that these can achieve relative to self-limitation in equilibrium, single-species assemblies.
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Affiliation(s)
- Michael F Hagan
- Martin Fisher School of Physics, Brandeis University, Waltham, MA 02454, USA
| | - Gregory M Grason
- Department of Polymer Science and Engineering, University of Massachusetts, Amherst, MA 01003, USA
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Bruinsma RF, Wuite GJL, Roos WH. Physics of viral dynamics. NATURE REVIEWS. PHYSICS 2021; 3:76-91. [PMID: 33728406 PMCID: PMC7802615 DOI: 10.1038/s42254-020-00267-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 11/20/2020] [Indexed: 05/12/2023]
Abstract
Viral capsids are often regarded as inert structural units, but in actuality they display fascinating dynamics during different stages of their life cycle. With the advent of single-particle approaches and high-resolution techniques, it is now possible to scrutinize viral dynamics during and after their assembly and during the subsequent development pathway into infectious viruses. In this Review, the focus is on the dynamical properties of viruses, the different physical virology techniques that are being used to study them, and the physical concepts that have been developed to describe viral dynamics.
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Affiliation(s)
- Robijn F. Bruinsma
- Department of Physics and Astronomy, University of California, Los Angeles, California, USA
| | - Gijs J. L. Wuite
- Fysica van levende systemen, Vrije Universiteit, Amsterdam, the Netherlands
| | - Wouter H. Roos
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Groningen, the Netherlands
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Pazzi J, Subramaniam AB. Nanoscale Curvature Promotes High Yield Spontaneous Formation of Cell-Mimetic Giant Vesicles on Nanocellulose Paper. ACS APPLIED MATERIALS & INTERFACES 2020; 12:56549-56561. [PMID: 33284582 DOI: 10.1021/acsami.0c14485] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
To date, techniques for the assembly of phospholipid films into cell-like giant unilamellar vesicles (GUVs) use planar surfaces and require the application of electric fields or dissolved molecules to obtain adequate yields. Here, we present the use of nanocellulose paper, which are surfaces composed of entangled cylindrical nanofibers, to promote the facile and high yield assembly of GUVs. Use of nanocellulose paper results in up to a 100 000-fold reduction in costs while increasing yields compared to extant surface-assisted assembly techniques. Quantitative measurements of yields and the distributions of sizes using large data set confocal microscopy illuminates the mechanism of assembly. We present a thermodynamic "budding and merging", BNM, model that offers a unified explanation for the differences in the yields and sizes of GUVs obtained from surfaces of varying geometry and chemistry. The BNM model considers the change in free energy due to budding by balancing the elastic, adhesion, and edge energies of a section of a surface-attached membrane that transitions into a surface-attached spherical bud. The model reveals that the formation of GUVs is spontaneous on hydrophilic surfaces consisting of entangled cylindrical nanofibers with dimensions similar to nanocellulose fibers. This work advances understanding of the effects of surface properties on the assembly of GUVs. It also addresses practical barriers that currently impede the promising use of GUVs as vehicles for the delivery of drugs, for the manufacturing of synthetic cells, and for the assembly of artificial tissues at scale.
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Affiliation(s)
- Joseph Pazzi
- Department of Bioengineering, University of California, Merced, Merced, California 95343, United States
| | - Anand Bala Subramaniam
- Department of Bioengineering, University of California, Merced, Merced, California 95343, United States
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