1
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Liu L, Duan C, Wang R. Kinetic pathway and micromechanics of fusion/fission for polyelectrolyte vesicles. J Chem Phys 2024; 160:024908. [PMID: 38214388 DOI: 10.1063/5.0185934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 12/26/2023] [Indexed: 01/13/2024] Open
Abstract
Despite the wide existence of vesicles in living cells as well as their important applications like drug delivery, the underlying mechanism of vesicle fusion/fission remains under debate. Classical models cannot fully explain recent observations in experiments and simulations. Here, we develop a constrained self-consistent field theory that allows tracking the shape evolution and free energy as a function of center-of-mass separation distance. Fusion and fission are described in a unified framework. Both the kinetic pathway and the mechanical response can be simultaneously captured. By taking vesicles formed by polyelectrolytes as a model system, we predict discontinuous transitions between the three morphologies: parent vesicle with a single cavity, hemifission/hemifusion, and two separated child vesicles, as a result of breaking topological isomorphism. With the increase in inter-vesicle repulsion, we observe a great reduction in the cleavage energy, indicating that vesicle fission can be achieved without hemifission, in good agreement with simulation results. The force-extension relationship elucidates typical plasticity for separating two vesicles. The super extensibility in the mechanical response of vesicle is in stark contrast to soft particles with other morphologies, such as cylinder and sphere. Our work elucidates the fundamental physical chemistry based on intrinsic topological features of vesicle fusion/fission, which provides insights into various phenomena observed in experiments and simulations.
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Affiliation(s)
- Luofu Liu
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA
| | - Chao Duan
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA
| | - Rui Wang
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
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2
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Niort K, Dancourt J, Boedec E, Al Amir Dache Z, Lavieu G, Tareste D. Cholesterol and Ceramide Facilitate Membrane Fusion Mediated by the Fusion Peptide of the SARS-CoV-2 Spike Protein. ACS OMEGA 2023; 8:32729-32739. [PMID: 37720777 PMCID: PMC10500581 DOI: 10.1021/acsomega.3c03610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 07/17/2023] [Indexed: 09/19/2023]
Abstract
SARS-CoV-2 entry into host cells is mediated by the Spike (S) protein of the viral envelope. The S protein is composed of two subunits: S1 that induces binding to the host cell via its interaction with the ACE2 receptor of the cell surface and S2 that triggers fusion between viral and cellular membranes. Fusion by S2 depends on its heptad repeat domains that bring membranes close together and its fusion peptide (FP) that interacts with and perturbs the membrane structure to trigger fusion. Recent studies have suggested that cholesterol and ceramide lipids from the cell surface may facilitate SARS-CoV-2 entry into host cells, but their exact mode of action remains unknown. We have used a combination of in vitro liposome-liposome and in situ cell-cell fusion assays to study the lipid determinants of S-mediated membrane fusion. Our findings reveal that both cholesterol and ceramide lipids facilitate fusion, suggesting that targeting these lipids could be effective against SARS-CoV-2. As a proof of concept, we examined the effect of chlorpromazine (CPZ), an antipsychotic drug known to perturb membrane structure. Our results show that CPZ effectively inhibits S-mediated membrane fusion, thereby potentially impeding SARS-CoV-2 entry into the host cell.
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Affiliation(s)
- Kristina Niort
- Université
Paris Cité, Inserm UMR-S 1266, Institute of Psychiatry and
Neuroscience of Paris (IPNP), Paris 75014, France
| | - Julia Dancourt
- Université
Paris Cité, Inserm U 1316, CNRS UMR 7057, Laboratoire Matières
et Systèmes Complexes (MSC), Paris 75006, France
| | - Erwan Boedec
- Université
Paris Cité, Inserm UMR-S 1266, Institute of Psychiatry and
Neuroscience of Paris (IPNP), Paris 75014, France
| | - Zahra Al Amir Dache
- Université
Paris Cité, Inserm U 1316, CNRS UMR 7057, Laboratoire Matières
et Systèmes Complexes (MSC), Paris 75006, France
| | - Grégory Lavieu
- Université
Paris Cité, Inserm U 1316, CNRS UMR 7057, Laboratoire Matières
et Systèmes Complexes (MSC), Paris 75006, France
| | - David Tareste
- Université
Paris Cité, Inserm UMR-S 1266, Institute of Psychiatry and
Neuroscience of Paris (IPNP), Paris 75014, France
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3
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Vlieghe A, Niort K, Fumat H, Guigner JM, Cohen MM, Tareste D. Role of Lipids and Divalent Cations in Membrane Fusion Mediated by the Heptad Repeat Domain 1 of Mitofusin. Biomolecules 2023; 13:1341. [PMID: 37759741 PMCID: PMC10527301 DOI: 10.3390/biom13091341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 08/21/2023] [Accepted: 08/30/2023] [Indexed: 09/29/2023] Open
Abstract
Mitochondria are highly dynamic organelles that constantly undergo fusion and fission events to maintain their shape, distribution and cellular function. Mitofusin 1 and 2 proteins are two dynamin-like GTPases involved in the fusion of outer mitochondrial membranes (OMM). Mitofusins are anchored to the OMM through their transmembrane domain and possess two heptad repeat domains (HR1 and HR2) in addition to their N-terminal GTPase domain. The HR1 domain was found to induce fusion via its amphipathic helix, which interacts with the lipid bilayer structure. The lipid composition of mitochondrial membranes can also impact fusion. However, the precise mode of action of lipids in mitochondrial fusion is not fully understood. In this study, we examined the role of the mitochondrial lipids phosphatidylethanolamine (PE), cardiolipin (CL) and phosphatidic acid (PA) in membrane fusion induced by the HR1 domain, both in the presence and absence of divalent cations (Ca2+ or Mg2+). Our results showed that PE, as well as PA in the presence of Ca2+, effectively stimulated HR1-mediated fusion, while CL had a slight inhibitory effect. By considering the biophysical properties of these lipids in the absence or presence of divalent cations, we inferred that the interplay between divalent cations and specific cone-shaped lipids creates regions with packing defects in the membrane, which provides a favorable environment for the amphipathic helix of HR1 to bind to the membrane and initiate fusion.
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Affiliation(s)
- Anaïs Vlieghe
- Université Paris Cité, Institute of Psychiatry and Neuroscience of Paris (IPNP), Inserm UMR-S 1266, Team Membrane Traffic in Healthy & Diseased Brain, 75014 Paris, France
| | - Kristina Niort
- Université Paris Cité, Institute of Psychiatry and Neuroscience of Paris (IPNP), Inserm UMR-S 1266, Team Membrane Traffic in Healthy & Diseased Brain, 75014 Paris, France
| | - Hugo Fumat
- Université Paris Cité, Institute of Psychiatry and Neuroscience of Paris (IPNP), Inserm UMR-S 1266, Team Membrane Traffic in Healthy & Diseased Brain, 75014 Paris, France
| | - Jean-Michel Guigner
- Sorbonne Université, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), CNRS UMR 7590, MNHN, IRD UR 206, 75005 Paris, France
| | - Mickaël M. Cohen
- Sorbonne Université, Institut de Biologie Physico-Chimique (IBPC), CNRS UMR 8226, Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, 75005 Paris, France
| | - David Tareste
- Université Paris Cité, Institute of Psychiatry and Neuroscience of Paris (IPNP), Inserm UMR-S 1266, Team Membrane Traffic in Healthy & Diseased Brain, 75014 Paris, France
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4
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Golani G, Schwarz US. High curvature promotes fusion of lipid membranes: Predictions from continuum elastic theory. Biophys J 2023; 122:1868-1882. [PMID: 37077047 PMCID: PMC10209146 DOI: 10.1016/j.bpj.2023.04.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 03/19/2023] [Accepted: 04/14/2023] [Indexed: 04/21/2023] Open
Abstract
The fusion of lipid membranes progresses through a series of hemifusion intermediates with two significant energy barriers related to the formation of stalk and fusion pore, respectively. These energy barriers determine the speed and success rate of many critical biological processes, including the fusion of highly curved membranes, for example synaptic vesicles and enveloped viruses. Here we use continuum elastic theory of lipid monolayers to determine the relationship between membrane shape and energy barriers to fusion. We find that the stalk formation energy decreases with curvature by up to 31 kBT in a 20-nm-radius vesicle compared with planar membranes and by up to 8 kBT in the fusion of highly curved, long, tubular membranes. In contrast, the fusion pore formation energy barrier shows a more complicated behavior. Immediately after stalk expansion to the hemifusion diaphragm, the fusion pore formation energy barrier is low (15-25 kBT) due to lipid stretching in the distal monolayers and increased tension in highly curved vesicles. Therefore, the opening of the fusion pore is faster. However, these stresses relax over time due to lipid flip-flop from the proximal monolayer, resulting in a larger hemifusion diaphragm and a higher fusion pore formation energy barrier, up to 35 kBT. Therefore, if the fusion pore fails to open before significant lipid flip-flop takes place, the reaction proceeds to an extended hemifusion diaphragm state, which is a dead-end configuration in the fusion process and can be used to prevent viral infections. In contrast, in the fusion of long tubular compartments, the surface tension does not accumulate due to the formation of the diaphragm, and the energy barrier for pore expansion increases with curvature by up to 11 kBT. This suggests that inhibition of polymorphic virus infection could particularly target this feature of the second barrier.
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Affiliation(s)
- Gonen Golani
- Institute for Theoretical Physics and BioQuant Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
| | - Ulrich S Schwarz
- Institute for Theoretical Physics and BioQuant Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany.
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5
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Zhu Y, Sharma A, Spangler EJ, Carrillo JMY, Kumar PBS, Laradji M. Lipid vesicles induced ordered nanoassemblies of Janus nanoparticles. SOFT MATTER 2023; 19:2204-2213. [PMID: 36880601 DOI: 10.1039/d2sm01693a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Since many advanced applications require specific assemblies of nanoparticles (NPs), considerable efforts have been made to fabricate nanoassemblies with specific geometries. Although nanoassemblies can be fabricated through top-down approaches, recent advances show that intricate nanoassemblies can also be obtained through self-assembly, mediated for example by DNA strands. Here, we show, through extensive molecular dynamics simulations, that highly ordered self-assemblies of NPs can be mediated by their adhesion to lipid vesicles (LVs). Specifically, Janus NPs are considered so that the amount by which they are wrapped by the LV is controlled. The specific geometry of the nanoassembly is the result of effective curvature-mediated repulsion between the NPs and the number of NPs adhering to the LV. The NPs are arranged on the LV into polyhedra which satisfy the upper limit of Euler's polyhedral formula, including several deltahedra and three Platonic solids, corresponding to the tetrahedron, octahedron, and icosahedron.
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Affiliation(s)
- Yu Zhu
- Department of Physics and Materials Science, The University of Memphis, Memphis, TN 38152, USA.
| | - Abash Sharma
- Department of Physics and Materials Science, The University of Memphis, Memphis, TN 38152, USA.
| | - Eric J Spangler
- Department of Physics and Materials Science, The University of Memphis, Memphis, TN 38152, USA.
| | - Jan-Michael Y Carrillo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - P B Sunil Kumar
- Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
| | - Mohamed Laradji
- Department of Physics and Materials Science, The University of Memphis, Memphis, TN 38152, USA.
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6
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Smirnova YG, Müller M. How does curvature affect the free-energy barrier of stalk formation? Small vesicles vs apposing, planar membranes. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2021; 50:253-264. [PMID: 33547940 PMCID: PMC8071802 DOI: 10.1007/s00249-020-01494-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 12/08/2020] [Accepted: 12/31/2020] [Indexed: 11/26/2022]
Abstract
Using molecular simulations of POPC lipids in conjunction with the calculation of the Minimum Free-Energy Path (MFEP), we study the effect of strong membrane curvature on the formation of the first fusion intermediate—the stalk between a vesicle and its periodic image. We find that the thermodynamic stability of this hourglass-shaped, hydrophobic connection between two vesicles is largely increased by the strong curvature of small vesicles, whereas the intrinsic barrier to form a stalk, i.e., associated with dimple formation and lipid tails protrusions, is similar to the case of two, apposing, planar membranes. A significant reduction of the barrier of stalk formation, however, stems from the lower dehydration free energy that is required to bring highly curved vesicle into a distance, at which stalk formation may occur, compared to the case of apposing, planar membranes.
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Affiliation(s)
- Y G Smirnova
- Institute for Theoretical Physics, Georg-August University, 37077, Göttingen, Germany.
| | - M Müller
- Institute for Theoretical Physics, Georg-August University, 37077, Göttingen, Germany
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7
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Gnopo YMD, Misra A, Hsu HL, DeLisa MP, Daniel S, Putnam D. Induced fusion and aggregation of bacterial outer membrane vesicles: Experimental and theoretical analysis. J Colloid Interface Sci 2020; 578:522-532. [PMID: 32540551 PMCID: PMC7487024 DOI: 10.1016/j.jcis.2020.04.068] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 04/16/2020] [Accepted: 04/17/2020] [Indexed: 11/15/2022]
Abstract
Recombinantly engineered bacterial outer membrane vesicles (OMVs) are promising vaccine delivery vehicles. The diversity of exogenous antigens delivered by OMVs can be enhanced by induced fusion of OMV populations. To date there are no reports of induced fusion of bacterial OMVs. Here we measure the pH and salt-induced aggregation and fusion of OMVs and analyze the processes against the Derjaguin-Landau-Verwey-Overbeek (DLVO) colloidal stability model. Vesicle aggregation and fusion kinetics were investigated for OMVs isolated from native E. coli (Nissle 1917) and lipopolysaccharide (LPS) modified E. coli (ClearColi) strains to evaluate the effect of lipid type on vesicle aggregation and fusion. Electrolytes and low pHs induced OMV aggregation for both native and modified LPS constructs, approaching a calculated fusion efficiency of ~25% (i.e. ~1/4 of collision events lead to fusion). However, high fusion efficiency was achieved for Nissle OMVs solely with decreased pH as opposed to a combination of low pH and increased divalent counterion concentration for ClearColi OMVs. The lipid composition of the OMVs from Nissle negatively impacted fusion in the presence of electrolytes, causing higher deviations from DLVO-predicted critical coagulation concentrations with monovalent counterions. The outcome of the work is a defined set of conditions under which investigators can induce OMVs to fuse and make various combinations of vesicle compositions.
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Affiliation(s)
- Yehou M D Gnopo
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Aditya Misra
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Hung-Lun Hsu
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Matthew P DeLisa
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Susan Daniel
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA
| | - David Putnam
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853, USA; Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853, USA.
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8
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Russell AE, Sneider A, Witwer KW, Bergese P, Bhattacharyya SN, Cocks A, Cocucci E, Erdbrügger U, Falcon-Perez JM, Freeman DW, Gallagher TM, Hu S, Huang Y, Jay SM, Kano SI, Lavieu G, Leszczynska A, Llorente AM, Lu Q, Mahairaki V, Muth DC, Noren Hooten N, Ostrowski M, Prada I, Sahoo S, Schøyen TH, Sheng L, Tesch D, Van Niel G, Vandenbroucke RE, Verweij FJ, Villar AV, Wauben M, Wehman AM, Yin H, Carter DRF, Vader P. Biological membranes in EV biogenesis, stability, uptake, and cargo transfer: an ISEV position paper arising from the ISEV membranes and EVs workshop. J Extracell Vesicles 2019; 8:1684862. [PMID: 31762963 PMCID: PMC6853251 DOI: 10.1080/20013078.2019.1684862] [Citation(s) in RCA: 155] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 08/23/2019] [Accepted: 10/04/2019] [Indexed: 02/07/2023] Open
Abstract
Paracrine and endocrine roles have increasingly been ascribed to extracellular vesicles (EVs) generated by multicellular organisms. Central to the biogenesis, content, and function of EVs are their delimiting lipid bilayer membranes. To evaluate research progress on membranes and EVs, the International Society for Extracellular Vesicles (ISEV) conducted a workshop in March 2018 in Baltimore, Maryland, USA, bringing together key opinion leaders and hands-on researchers who were selected on the basis of submitted applications. The workshop was accompanied by two scientific surveys and covered four broad topics: EV biogenesis and release; EV uptake and fusion; technologies and strategies used to study EV membranes; and EV transfer and functional assays. In this ISEV position paper, we synthesize the results of the workshop and the related surveys to outline important outstanding questions about EV membranes and describe areas of consensus. The workshop discussions and survey responses reveal that while much progress has been made in the field, there are still several concepts that divide opinion. Good consensus exists in some areas, including particular aspects of EV biogenesis, uptake and downstream signalling. Areas with little to no consensus include EV storage and stability, as well as whether and how EVs fuse with target cells. Further research is needed in these key areas, as a better understanding of membrane biology will contribute substantially towards advancing the field of extracellular vesicles.
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Affiliation(s)
- Ashley E. Russell
- Department of Molecular and Comparative Pathobiology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Alexandra Sneider
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, USA
| | - Kenneth W. Witwer
- Department of Molecular and Comparative Pathobiology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Paolo Bergese
- Department of Molecular and Translational Medicine, Università degli Studi di Brescia, CSGI and INSTM, Brescia, Italy
| | | | | | - Emanuele Cocucci
- Division of Pharmaceutics and Pharmacology, College of Pharmacy, Columbus, OH, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, USA
| | | | - Juan M. Falcon-Perez
- Exosomes laboratory and Metabolomics Platform, CIC bioGUNE, CIBERehd, Bizkaia, Spain
- IKERBASQUE, Basque Foundation for Science, Bizkaia, Spain
| | - David W. Freeman
- Laboratory of Epidemiology and Population Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Thomas M. Gallagher
- Department of Microbiology and Immunology, Loyola University Chicago, Chicago, IL, USA
| | - Shuaishuai Hu
- School of Biological and Healthy Sciences, Technological University Dublin, Dublin, Ireland
| | - Yiyao Huang
- Department of Molecular and Comparative Pathobiology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Department of Clinical Laboratory Medicine, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Steven M. Jay
- Fischell Department of Bioengineering, University of Maryland, College Park, MD, USA
| | - Shin-ichi Kano
- Department of Psychiatry and Behavioral Neurobiology, The University of Alabama at Birmingham School of Medicine, Birmingham, AL, USA
| | - Gregory Lavieu
- INSERM U932, Institut Curie, PSL Research University, France
| | | | - Alicia M. Llorente
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Quan Lu
- Program in Molecular and Integrative Physiological Sciences Departments of Environmental Health, Genetics & Complex Diseases Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Vasiliki Mahairaki
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Dillon C. Muth
- Department of Molecular and Comparative Pathobiology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Nicole Noren Hooten
- Laboratory of Epidemiology and Population Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Matias Ostrowski
- INBIRS Institute, UBA-CONICET School of Medicine University of Buenos Aires, Buenos Aires, Argentina
| | | | - Susmita Sahoo
- Cardiovascular Research Center, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Tine Hiorth Schøyen
- Department of Molecular and Comparative Pathobiology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
- K. G. Jebsen - Thrombosis Research and Expertise Center (TREC), Department of Clinical Medicine, UiT - The Arctic University of Norway, Tromsø, Norway
| | - Lifu Sheng
- Department of Pathology, University of Washington School of Medicine, Seattle, WA, USA
| | - Deanna Tesch
- Department of Chemistry, Shaw University, Raleigh, NC, USA
| | - Guillaume Van Niel
- Institute for Psychiatry and Neuroscience of Paris, INSERM U1266, Hopital Saint-Anne, Université Descartes, Paris, France
| | - Roosmarijn E. Vandenbroucke
- VIB Center for Inflammation Research, Ghent, Belgium
- Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium
| | - Frederik J. Verweij
- Institute for Psychiatry and Neuroscience of Paris, INSERM U1266, Hopital Saint-Anne, Université Descartes, Paris, France
| | - Ana V. Villar
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC) CSIC-Universidad de Cantabria and Departamento de Fisiología y Farmacología, Universidad de Cantabria, Santander, Spain
| | - Marca Wauben
- Department of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Ann M. Wehman
- Rudolf Virchow Center, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Hang Yin
- School of Pharmaceutical Sciences, Tsinghua University-Peking University Joint Center for Life Sciences, Tsinghua University, Beijing, China
| | | | - Pieter Vader
- Laboratory of Clinical Chemistry and Haematology & Department of Experimental Cardiology, University Medical Center Utrecht, Utrecht, The Netherlands
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9
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Nguyen TT, Cramb DT. Elucidation of the mechanism and energy barrier for anesthetic triggered membrane fusion in model membranes. CAN J CHEM 2019. [DOI: 10.1139/cjc-2018-0405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Membrane fusion is vital for cellular function and is generally mediated via fusogenic proteins and peptides. The mechanistic details and subsequently the transition state dynamics of membrane fusion will be dependent on the type of the fusogenic agent. We have previously established the potential of general anesthetics as a new class of fusion triggering agents in model membranes. We employed two-photon excitation fluorescence cross-correlation spectroscopy (TPE-FCCS) to report on vesicle association kinetics and steady-state fluorescence dequenching assays to monitor lipid mixing kinetics. Using halothane to trigger fusion in 110 nm diameter dioleoylphosphatidylcholine (DOPC) liposomes, we found that lipid rearrangement towards the formation of the fusion stalk was rate limiting. The activation barrier for halothane induced membrane fusion in 110 nm vesicles was found to be ∼40 kJ mol−1. We calculated the enthalpy and entropy of the transition state to be ∼40 kJ mol−1and ∼180 J mol−1K−1, respectively. We have found that the addition of halothane effectively lowers the energy barrier for membrane fusion in less curved vesicles largely due to entropic advantages.
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Affiliation(s)
- Trinh T. Nguyen
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
| | - David T. Cramb
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada
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10
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Manca F, Pincet F, Truskinovsky L, Rothman JE, Foret L, Caruel M. SNARE machinery is optimized for ultrafast fusion. Proc Natl Acad Sci U S A 2019; 116:2435-2442. [PMID: 30700546 PMCID: PMC6377469 DOI: 10.1073/pnas.1820394116] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
SNARE proteins zipper to form complexes (SNAREpins) that power vesicle fusion with target membranes in a variety of biological processes. A single SNAREpin takes about 1 s to fuse two bilayers, yet a handful can ensure release of neurotransmitters from synaptic vesicles much faster: in a 10th of a millisecond. We propose that, similar to the case of muscle myosins, the ultrafast fusion results from cooperative action of many SNAREpins. The coupling originates from mechanical interactions induced by confining scaffolds. Each SNAREpin is known to have enough energy to overcome the fusion barrier of 25-[Formula: see text]; however, the fusion barrier only becomes relevant when the SNAREpins are nearly completely zippered, and from this state, each SNAREpin can deliver only a small fraction of this energy as mechanical work. Therefore, they have to act cooperatively, and we show that at least three of them are needed to ensure fusion in less than a millisecond. However, to reach the prefusion state collectively, starting from the experimentally observed half-zippered metastable state, the SNAREpins have to mechanically synchronize, which takes more time as the number of SNAREpins increases. Incorporating this somewhat counterintuitive idea in a simple coarse-grained model results in the prediction that there should be an optimum number of SNAREpins for submillisecond fusion: three to six over a wide range of parameters. Interestingly, in situ cryoelectron microscope tomography has very recently shown that exactly six SNAREpins participate in the fusion of each synaptic vesicle. This number is in the range predicted by our theory.
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Affiliation(s)
- Fabio Manca
- Laboratoire de Physique de l'Ecole Normale Supérieure (LPENS), CNRS, Ecole Normale Supérieure, 75005 Paris, France
- LPENS, Sorbonne Université, 75005 Paris, France
- LPENS, Université Paris-Diderot, 75005 Paris, France
- LPENS, Université PSL, 75005 Paris, France
| | - Frederic Pincet
- Laboratoire de Physique de l'Ecole Normale Supérieure (LPENS), CNRS, Ecole Normale Supérieure, 75005 Paris, France
- LPENS, Sorbonne Université, 75005 Paris, France
- LPENS, Université Paris-Diderot, 75005 Paris, France
- LPENS, Université PSL, 75005 Paris, France
| | - Lev Truskinovsky
- Physique et Mécanique des Milieux Hétérogènes, CNRS, Ecole Supérieure de Physique et de Chimie Industrielles, Université PSL, 75231 Paris Cedex 05, France
| | - James E Rothman
- Department of Cell Biology, Yale University, New Haven, CT 06520;
- Department of Experimental Epilepsy, Institute of Neurology, University College London, London WC1E 6BT, United Kingdom
| | - Lionel Foret
- Laboratoire de Physique de l'Ecole Normale Supérieure (LPENS), CNRS, Ecole Normale Supérieure, 75005 Paris, France
- LPENS, Sorbonne Université, 75005 Paris, France
- LPENS, Université Paris-Diderot, 75005 Paris, France
- LPENS, Université PSL, 75005 Paris, France
| | - Matthieu Caruel
- Modélisation et Simulation Multi-Echelle, CNRS, Université Paris-Est Créteil, 94010 Créteil Cedex, France
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11
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Mattila JP, Shnyrova AV, Sundborger AC, Hortelano ER, Fuhrmans M, Neumann S, Müller M, Hinshaw JE, Schmid SL, Frolov VA. A hemi-fission intermediate links two mechanistically distinct stages of membrane fission. Nature 2015; 524:109-113. [PMID: 26123023 PMCID: PMC4529379 DOI: 10.1038/nature14509] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Accepted: 05/05/2015] [Indexed: 12/22/2022]
Abstract
Fusion and fission drive all vesicular transport. Although topologically opposite, these reactions pass through the same hemi-fusion/fission intermediate1,2, characterized by a ‘stalk’ in which only the inner monolayers of the two compartments have merged to form a localized non-bilayer connection1-3. Formation of the hemi-fission intermediate requires energy input from proteins catalyzing membrane remodeling; however the relationship between protein conformational rearrangements and hemi-fusion/fission remains obscure. Here we analyzed how the GTPase cycle of dynamin, the prototypical membrane fission catalyst4-6, is directly coupled to membrane remodeling. We used intra-molecular chemical cross-linking to stabilize dynamin in its GDP•AlF4--bound transition-state. In the absence of GTP this conformer produced stable hemi-fission, but failed to progress to complete fission, even in the presence of GTP. Further analysis revealed that the pleckstrin homology domain (PHD) locked in its membrane-inserted state facilitated hemi-fission. A second mode of dynamin activity, fueled by GTP hydrolysis, couples dynamin disassembly with cooperative diminishing of the PHD wedging, thus destabilizing the hemi-fission intermediate to complete fission. Molecular simulations corroborate the bimodal character of dynamin action and indicate radial and axial forces as dominant, although not independent drivers of hemi-fission and fission transformations, respectively. Mirrored in the fusion reaction7-8, the force bimodality might constitute a general paradigm for leakage-free membrane remodeling.
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Affiliation(s)
- Juha-Pekka Mattila
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75201
| | - Anna V Shnyrova
- Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of The Basque Country, Leioa, Spain
| | - Anna C Sundborger
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892
| | - Eva Rodriguez Hortelano
- Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of The Basque Country, Leioa, Spain
| | - Marc Fuhrmans
- Institute for Theoretical Physics, Georg-August University, 37077 Göttingen, Germany
| | - Sylvia Neumann
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037
| | - Marcus Müller
- Institute for Theoretical Physics, Georg-August University, 37077 Göttingen, Germany
| | - Jenny E Hinshaw
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892
| | - Sandra L Schmid
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75201
| | - Vadim A Frolov
- Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of The Basque Country, Leioa, Spain.,IKERBASQUE, Basque Foundation of Science, Bilbao, Spain
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12
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pH Alters PEG-mediated fusion of phosphatidylethanolamine-containing vesicles. Biophys J 2015; 107:1327-38. [PMID: 25229141 DOI: 10.1016/j.bpj.2014.07.048] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 07/18/2014] [Accepted: 07/25/2014] [Indexed: 11/22/2022] Open
Abstract
Here, we examine the different mechanisms of poly(ethylene glycol)-mediated fusion of small unilamellar vesicles composed of dioleoylphosphatidylcholine/dioleoylphosphatidylethanolamine (DOPE)/sphingomyelin/cholesterol in a molar ratio of 35:30:15:20 at pH 7.4 versus pH 5. In doing so, we test the hypothesis that fusion of this lipid mixture should be influenced by differences in hydration of DOPE at these two pH values. An examination of the literature reveals that DOPE should be less hydrated at pH 5 (where influenza virus particles fuse with endosome membranes) than at pH 7.4 (where synaptic vesicles or HIV virus particles fuse with plasma membrane). Ensemble kinetic experiments revealed substantial differences in fusion of this plasma membrane mimetic system at these two pH values. The most dramatic difference was the observation of two intermediates at pH 5 but loss of one of these fusion intermediates at pH 7.4. Analysis of data collected at several temperatures also revealed that formation of the initial fusion intermediate (stalk) was favored at pH 7.4 due to increased activation entropy. Our observations support the hypothesis that the different negative intrinsic curvature of DOPE can account for different fusion paths and activation thermodynamics in steps of the fusion process at these two pH values. Finally, the effects of 2 mol % hexadecane on fusion at both pH values seemed to have similar origins for step 1 (promotion of acyl chain or hydrocarbon excursion into interbilayer space) and step 3 (reduction of interstice energy leading to expansion to a critical stalk radius). Different hexadecane effects on activation thermodynamics at these two pH values can also be related to altered DOPE hydration. The results support our kinetic model for fusion and offer insight into the critical role of phosphatidylethanolamine in fusion.
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13
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Expansion of the fusion stalk and its implication for biological membrane fusion. Proc Natl Acad Sci U S A 2014; 111:11043-8. [PMID: 25024174 DOI: 10.1073/pnas.1323221111] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Over the past 20 years, it has been widely accepted that membrane fusion proceeds via a hemifusion step before opening of the productive fusion pore. An initial hourglass-shaped lipid structure, the fusion stalk, is formed between the adjacent membrane leaflets (cis leaflets). It remains controversial if and how fusion proteins drive the subsequent transition (expansion) of the stalk into a fusion pore. Here, we propose a comprehensive and consistent thermodynamic understanding in terms of the underlying free-energy landscape of stalk expansion. We illustrate how the underlying free energy landscape of stalk expansion and the concomitant pathway is altered by subtle differences in membrane environment, such as leaflet composition, asymmetry, and flexibility. Nonleaky stalk expansion (stalk widening) requires the formation of a critical trans-leaflet contact. The fusion machinery can mechanically enforce trans-leaflet contact formation either by directly enforcing the trans-leaflets in close proximity, or by (electrostatically) condensing the area of the cis leaflets. The rate of these fast fusion reactions may not be primarily limited by the energetics but by the forces that the fusion proteins are able to exert.
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14
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Nishizawa M, Nishizawa K. Molecular dynamics simulation analysis of membrane defects and pore propensity of hemifusion diaphragms. Biophys J 2013; 104:1038-48. [PMID: 23473486 PMCID: PMC3870803 DOI: 10.1016/j.bpj.2013.01.022] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 01/17/2013] [Accepted: 01/18/2013] [Indexed: 12/25/2022] Open
Abstract
Membrane fusion often exhibits slow dynamics in electrophysiological experiments, involving prespike foot and fusion pore-flickering, but the structural basis of such phenomena remains unclear. Hemifusion intermediates have been implicated in the early phase of membrane fusion. To elucidate the dynamics of formation of membrane defects and pores within the hemifusion diaphragm (HD), atomistic and coarse-grained models of hemifusion intermediates were constructed using dipalmitoylphosphatidylcholine or dioleoylphosphatidylcholine membranes. The work necessary to displace a lipid molecule to the hydrophobic core of the bilayer was measured. For a lipid within the HD with radius of 4 nm, the work was ∼80 kJ/mol, similar to that in a planar bilayer. The work was much less (∼40 kJ/mol) when the HD was surrounded by a steep stalk, i.e., stalk wings forming a large angle at the junction of three bilayers. In the latter case, the lipid displacement engendered formation of a pore contacting the HD rim. The work was similarly small (40 kJ/mol) for a small HD of 1.5 nm radius, where a pore formed and grew rapidly, quickly generating a toroidal structure (<40 ns). Combining the steep stalk and the small HD decreased the work further, although quantitative analysis was difficult because the latter system was not in a stable equilibrium state. Results suggest that fine tuning of fusion dynamics requires strict control of the HD size and the angle between the expanded stalk and HD. In additional free simulations, the steep stalk facilitated widening of a preformed pore contacting the HD rim.
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15
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Risselada HJ, Marelli G, Fuhrmans M, Smirnova YG, Grubmüller H, Marrink SJ, Müller M. Line-tension controlled mechanism for influenza fusion. PLoS One 2012; 7:e38302. [PMID: 22761674 PMCID: PMC3386277 DOI: 10.1371/journal.pone.0038302] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 05/03/2012] [Indexed: 11/19/2022] Open
Abstract
Our molecular simulations reveal that wild-type influenza fusion peptides are able to stabilize a highly fusogenic pre-fusion structure, i.e. a peptide bundle formed by four or more trans-membrane arranged fusion peptides. We rationalize that the lipid rim around such bundle has a non-vanishing rim energy (line-tension), which is essential to (i) stabilize the initial contact point between the fusing bilayers, i.e. the stalk, and (ii) drive its subsequent evolution. Such line-tension controlled fusion event does not proceed along the hypothesized standard stalk-hemifusion pathway. In modeled influenza fusion, single point mutations in the influenza fusion peptide either completely inhibit fusion (mutants G1V and W14A) or, intriguingly, specifically arrest fusion at a hemifusion state (mutant G1S). Our simulations demonstrate that, within a line-tension controlled fusion mechanism, these known point mutations either completely inhibit fusion by impairing the peptide's ability to stabilize the required peptide bundle (G1V and W14A) or stabilize a persistent bundle that leads to a kinetically trapped hemifusion state (G1S). In addition, our results further suggest that the recently discovered leaky fusion mutant G13A, which is known to facilitate a pronounced leakage of the target membrane prior to lipid mixing, reduces the membrane integrity by forming a 'super' bundle. Our simulations offer a new interpretation for a number of experimentally observed features of the fusion reaction mediated by the prototypical fusion protein, influenza hemagglutinin, and might bring new insights into mechanisms of other viral fusion reactions.
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Affiliation(s)
- Herre Jelger Risselada
- Theoretical Molecular Biophysics Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
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16
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Zhu T, Jiang Z, Ma Y. Lipid exchange between membranes: effects of membrane surface charge, composition, and curvature. Colloids Surf B Biointerfaces 2012; 97:155-61. [PMID: 22609597 DOI: 10.1016/j.colsurfb.2012.04.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Revised: 03/15/2012] [Accepted: 04/18/2012] [Indexed: 11/20/2022]
Abstract
Intermembrane lipid exchange is critical to membrane functions and pharmaceutical applications. The exchange process is not fully understood and it is explored by quartz crystal microbalance with dissipation monitor method in this research. It is found that intermembrane lipid exchange is accelerated with the decrease of vesicle size and the increase of charge and liquid crystalline lipid composition ratio. Vesicle adsorption rate, membrane lateral pressure gradient, and lipid lateral diffusion coefficient are inferred to be critical in deciding the lipid exchange kinetics between membranes. Besides that, the membrane contact situation during lipid exchange is also studied. The maximum total membrane contact area is found to increase with the decrease of vesicle size, charged and liquid crystalline lipid composition ratio. A competition mechanism between the vesicle adsorption rate and the intermembrane lipid exchange rate was proposed to control the maximum total membrane contact area.
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Affiliation(s)
- Tao Zhu
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
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17
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Risselada HJ, Grubmüller H. How SNARE molecules mediate membrane fusion: recent insights from molecular simulations. Curr Opin Struct Biol 2012; 22:187-96. [PMID: 22365575 DOI: 10.1016/j.sbi.2012.01.007] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 01/11/2012] [Accepted: 01/13/2012] [Indexed: 10/28/2022]
Abstract
SNARE molecules are the core constituents of the protein machinery that facilitate fusion of synaptic vesicles with the presynaptic plasma membrane, resulting in the release of neurotransmitter. On a molecular level, SNARE complexes seem to play a quite versatile and involved role during all stages of fusion. In addition to merely triggering fusion by forcing the opposing membranes into close proximity, SNARE complexes are now seen to also overcome subsequent fusion barriers and to actively guide the fusion reaction up to the expansion of the fusion pore. Here, we review recent advances in the understanding of SNARE-mediated membrane fusion by molecular simulations.
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Affiliation(s)
- Herre Jelger Risselada
- Theoretical Molecular Biophysics Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
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18
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Abstract
Dynamin, best studied for its role in clathrin-mediated endocytosis, is the prototypical member of a family of multidomain GTPases involved in fission and remodeling of multiple organelles. Recent studies have shown that dynamin alone can catalyze fission of membrane tubules and vesicle formation from planar lipid templates. Thus, dynamin appears to be a self-sufficient fission machine. Here we review the biochemical activities and structural features of dynamin required for fission activity. As all changes in membrane topology require energetically unfavorable rearrangements of the lipid bilayer, we discuss the interplay between dynamin and its lipid substrates that are critical to defining a nonleaky pathway to membrane fission. We propose a two-stage model for dynamin-catalyzed fission. In stage one, dynamin's mechanochemical activities induce localized curvature stress and position its lipid-interacting pleckstrin homology domains to create a catalytic center that, in stage two, guides lipid remodeling through hemifission intermediates to drive membrane fission.
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Affiliation(s)
- Sandra L Schmid
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
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19
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Müller M, Schick M. An Alternate Path for Fusion and its Exploration by Field-Theoretic Means. CURRENT TOPICS IN MEMBRANES 2011; 68:295-323. [DOI: 10.1016/b978-0-12-385891-7.00012-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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20
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Nikolaus J, Warner JM, O'Shaughnessy B, Herrmann A. The pathway to membrane fusion through hemifusion. CURRENT TOPICS IN MEMBRANES 2011; 68:1-32. [PMID: 21771493 DOI: 10.1016/b978-0-12-385891-7.00001-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Jörg Nikolaus
- Department of Biology, Faculty of Mathematics and Natural Sciences I, Humboldt-University Berlin, Berlin, Germany
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21
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Baoukina S, Tieleman DP. Direct simulation of protein-mediated vesicle fusion: lung surfactant protein B. Biophys J 2010; 99:2134-42. [PMID: 20923647 PMCID: PMC3042587 DOI: 10.1016/j.bpj.2010.07.049] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Revised: 07/22/2010] [Accepted: 07/23/2010] [Indexed: 10/19/2022] Open
Abstract
We simulated spontaneous fusion of small unilamellar vesicles mediated by lung surfactant protein B (SP-B) using the MARTINI force field. An SP-B monomer triggers fusion events by anchoring two vesicles and facilitating the formation of a lipid bridge between the proximal leaflets. Once a lipid bridge is formed, fusion proceeds via a previously described stalk - hemifusion diaphragm - pore-opening pathway. In the absence of protein, fusion of vesicles was not observed in either unbiased simulations or upon application of a restraining potential to maintain the vesicles in close proximity. The shape of SP-B appears to enable it to bind to two vesicles at once, forcing their proximity, and to facilitate the initial transfer of lipids to form a high-energy hemifusion intermediate. Our results may provide insight into more general mechanisms of protein-mediated membrane fusion, and a possible role of SP-B in the secretory pathway and transfer of lung surfactant to the gas exchange interface.
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Affiliation(s)
| | - D. Peter Tieleman
- Department of Biological Sciences, University of Calgary, Calgary, Canada
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22
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Raudino A, Pannuzzo M. Nucleation theory with delayed interactions: An application to the early stages of the receptor-mediated adhesion/fusion kinetics of lipid vesicles. J Chem Phys 2010; 132:045103. [DOI: 10.1063/1.3290823] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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23
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Frolov VA, Zimmerberg J. Cooperative elastic stresses, the hydrophobic effect, and lipid tilt in membrane remodeling. FEBS Lett 2010; 584:1824-9. [PMID: 20100479 DOI: 10.1016/j.febslet.2010.01.039] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Accepted: 01/19/2010] [Indexed: 10/19/2022]
Abstract
One of the fundamental properties of biological membranes is the high lateral integrity provided by the lipid bilayer, the structural core and the foundation of their barrier function. This tensile strength is due to the intrinsic properties of amphiphilic lipid molecules, which spontaneously self-assemble into a stable bilayer structure due to the hydrophobic effect. In the highly dynamic life of cellular membranes systems, however, this integrity has to be regularly compromised. One of the emerging puzzles is the mechanism of localized rupture of lipid monolayer, the formation of tiny hydrophobic patches and flipping of lipid tails between closely apposed monolayers. The energy cost of such processes is prohibitively high, unless cooperative deformations in a small membrane patch are carefully organized. Here we review the latest experimental and theoretical data on how such deformations can be conducted, specifically describing how elastic stresses yield tilting of lipids leading to cooperative restructuring of lipid monolayers. Proteins specializing in membrane remodeling assemble into closely packed circular complexes to arrange these deformations in time and space.
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Affiliation(s)
- Vadim A Frolov
- Unidad de Biofisica (Centro Mixto CSIC-UPV/EHU), Leioa 48940, Spain
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24
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Minimum membrane bending energies of fusion pores. J Membr Biol 2009; 231:101-15. [PMID: 19865786 DOI: 10.1007/s00232-009-9209-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Accepted: 09/24/2009] [Indexed: 10/20/2022]
Abstract
Membranes fuse by forming highly curved intermediates, culminating in structures described as fusion pores. These hourglass-like figures that join two fusing membranes have high bending energies, which can be estimated using continuum elasticity models. Fusion pore bending energies depend strongly on shape, and the present study developed a method for determining the shape that minimizes bending energy. This was first applied to a fusion pore modeled as a single surface and then extended to a more realistic model treating a bilayer as two monolayers. For the two-monolayer model, fusion pores were found to have metastable states with energy minima at particular values of the pore diameter and bilayer separation. Fusion pore energies were relatively insensitive to membrane thickness but highly sensitive to spontaneous curvature and membrane asymmetry. With symmetrical bilayers and monolayer spontaneous curvatures of -0.1 nm(-1) (a typical value) separated by 6 nm (closest distance determined by repulsive hydration forces), fusion pore formation required 43-65 kT. The pore radius of approximately 2.25 nm fell within the range estimated from conductance measurements. With bilayer separation >6 nm, fusion pore formation required less energy, suggesting that protein scaffolds can promote fusion by bending membranes toward one another. With nonzero spontaneous monolayer curvature, the shape that minimized the energy change during fusion pore formation differed from the shape that minimized its energy after it formed. Thus, a nascent fusion pore will relax spontaneously to a new shape, consistent with the experimentally observed expansion of nascent fusion pores during viral fusion.
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Lin L, Yan Z, Gu J, Zhang Y, Feng Z, Yu Y. UV-Responsive Behavior of Azopyridine-Containing Diblock Copolymeric Vesicles: Photoinduced Fusion, Disintegration and Rearrangement. Macromol Rapid Commun 2009; 30:1089-93. [DOI: 10.1002/marc.200900105] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 03/24/2009] [Accepted: 03/25/2009] [Indexed: 11/06/2022]
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Daoulas KC, Müller M. Comparison of Simulations of Lipid Membranes with Membranes of Block Copolymers. ADVANCES IN POLYMER SCIENCE 2009. [DOI: 10.1007/978-3-642-10479-4_7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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27
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Smith SM, Renden R, von Gersdorff H. Synaptic vesicle endocytosis: fast and slow modes of membrane retrieval. Trends Neurosci 2008; 31:559-68. [PMID: 18817990 DOI: 10.1016/j.tins.2008.08.005] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Revised: 08/18/2008] [Accepted: 08/19/2008] [Indexed: 10/21/2022]
Abstract
Several modes of synaptic vesicle release, retrieval and recycling have been identified. In a well-established mode of exocytosis, termed 'full-collapse fusion', vesicles empty their neurotransmitter content fully into the synaptic cleft by flattening out and becoming part of the presynaptic membrane. The fused vesicle membrane is then reinternalized via a slow and clathrin-dependent mode of compensatory endocytosis that takes several seconds. A more fleeting mode of vesicle fusion, termed 'kiss-and-run' exocytosis or 'flicker-fusion', indicates that during synaptic transmission some vesicles are only briefly connected to the presynaptic membrane by a transient fusion pore. Finally, a mode that retrieves a large amount of membrane, equivalent to that of several fused vesicles, termed 'bulk endocytosis', has been found after prolonged exocytosis. We are of the opinion that both fast and slow modes of endocytosis co-exist at central nervous system nerve terminals and that one mode can predominate depending on stimulus strength, temperature and synaptic maturation.
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Affiliation(s)
- Stephen M Smith
- Division of Pulmonary and Critical Care Medicine, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, USA
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28
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Abstract
Diverse membrane fusion reactions in biology involve close contact between two lipid bilayers, followed by the local distortion of the individual bilayers and reformation into a single, merged membrane. We consider the structures and energies of the fusion intermediates identified in experimental and theoretical work on protein-free lipid bilayers. On the basis of this analysis, we then discuss the conserved fusion-through-hemifusion pathway of merger between biological membranes and propose that the entire progression, from the close juxtaposition of membrane bilayers to the expansion of a fusion pore, is controlled by protein-generated membrane stresses.
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Affiliation(s)
- Leonid V Chernomordik
- Section on Membrane Biology, Laboratory of Cellular and Molecular Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1855, USA.
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