1
|
Blasco S, Sukeník L, Vácha R. Nanoparticle induced fusion of lipid membranes. NANOSCALE 2024; 16:10221-10229. [PMID: 38679949 PMCID: PMC11138393 DOI: 10.1039/d4nr00591k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Accepted: 04/23/2024] [Indexed: 05/01/2024]
Abstract
Membrane fusion is crucial for infection of enveloped viruses, cellular transport, and drug delivery via liposomes. Nanoparticles can serve as fusogenic agents facilitating such membrane fusion for direct transmembrane transport. However, the underlying mechanisms of nanoparticle-induced fusion and the ideal properties of such nanoparticles remain largely unknown. Here, we used molecular dynamics simulations to investigate the efficacy of spheroidal nanoparticles with different size, prolateness, and ligand interaction strengths to enhance fusion between vesicles. By systematically varying nanoparticle properties, we identified how each parameter affects the fusion process and determined the optimal parameter range that promotes fusion. These findings provide valuable insights for the design and optimization of fusogenic nanoparticles with potential biotechnological and biomedical applications.
Collapse
Affiliation(s)
- Sofía Blasco
- CEITEC - Central European Institute of Technology, Kamenice 5, 625 00 Brno, Czech Republic.
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
| | - Lukáš Sukeník
- CEITEC - Central European Institute of Technology, Kamenice 5, 625 00 Brno, Czech Republic.
- Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
| | - Robert Vácha
- CEITEC - Central European Institute of Technology, Kamenice 5, 625 00 Brno, Czech Republic.
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
- Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
| |
Collapse
|
2
|
Liu W, Gao T, Li N, Shao S, Liu B. Vesicle fusion and release in neurons under dynamic mechanical equilibrium. iScience 2024; 27:109793. [PMID: 38736547 PMCID: PMC11088343 DOI: 10.1016/j.isci.2024.109793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2024] Open
Abstract
Vesicular fusion plays a pivotal role in cellular processes, involving stages like vesicle trafficking, fusion pore formation, content release, and membrane integration or separation. This dynamic process is regulated by a complex interplay of protein assemblies, osmotic forces, and membrane tension, which together maintain a mechanical equilibrium within the cell. Changes in cellular mechanics or external pressures prompt adjustments in this equilibrium, highlighting the system's adaptability. This review delves into the synergy between intracellular proteins, structural components, and external forces in facilitating vesicular fusion and release. It also explores how cells respond to mechanical stress, maintaining equilibrium and offering insights into vesicle fusion mechanisms and the development of neurological disorders.
Collapse
Affiliation(s)
- Wenhao Liu
- Cancer Hospital of Dalian University of Technology, Shenyang 110042, China
| | - Tianyu Gao
- Cancer Hospital of Dalian University of Technology, Shenyang 110042, China
| | - Na Li
- Cancer Hospital of Dalian University of Technology, Shenyang 110042, China
- Faculty of Medicine, Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Dalian University of Technology, Dalian 116024, China
| | - Shuai Shao
- Cancer Hospital of Dalian University of Technology, Shenyang 110042, China
- Faculty of Medicine, Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Dalian University of Technology, Dalian 116024, China
| | - Bo Liu
- Cancer Hospital of Dalian University of Technology, Shenyang 110042, China
- Faculty of Medicine, Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Dalian University of Technology, Dalian 116024, China
| |
Collapse
|
3
|
Di Bartolo AL, Caparotta M, Polo LM, Masone D. Myomerger Induces Membrane Hemifusion and Regulates Fusion Pore Expansion. Biochemistry 2024; 63:815-826. [PMID: 38349279 DOI: 10.1021/acs.biochem.3c00682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
Membrane fusion is a crucial mechanism in a wide variety of important events in cell biology from viral infection to exocytosis. However, despite many efforts and much progress, cell-cell fusion has remained elusive to our understanding. Along the life of the fusion pore, large conformational changes take place from the initial lipid bilayer bending, passing through the hemifusion intermediates, and ending with the formation of the first nascent fusion pore. In this sense, computer simulations are an ideal technique for describing such complex lipid remodeling at the molecular level. In this work, we studied the role played by the muscle-specific membrane protein Myomerger during the formation of the fusion pore. We have conducted μs length atomistic and coarse-grained molecular dynamics, together with free-energy calculations using ad hoc collective variables. Our results show that Myomerger favors the hemifusion diaphragm-stalk transition, reduces the nucleation-expansion energy difference, and promotes the formation of nonenlarging fusion pores.
Collapse
Affiliation(s)
- Ary Lautaro Di Bartolo
- Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
| | - Marcelo Caparotta
- Quantum Theory Project, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
| | - Luis Mariano Polo
- Instituto de Histología y Embriología de Mendoza (IHEM)─Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo, 5500 Mendoza, Argentina
| | - Diego Masone
- Instituto de Histología y Embriología de Mendoza (IHEM)─Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo, 5500 Mendoza, Argentina
- Facultad de Ingeniería, Universidad Nacional de Cuyo, 5500 Mendoza, Argentina
| |
Collapse
|
4
|
Jahn R, Cafiso DC, Tamm LK. Mechanisms of SNARE proteins in membrane fusion. Nat Rev Mol Cell Biol 2024; 25:101-118. [PMID: 37848589 DOI: 10.1038/s41580-023-00668-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/06/2023] [Indexed: 10/19/2023]
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are a family of small conserved eukaryotic proteins that mediate membrane fusion between organelles and with the plasma membrane. SNAREs are directly or indirectly anchored to membranes. Prior to fusion, complementary SNAREs assemble between membranes with the aid of accessory proteins that provide a scaffold to initiate SNARE zippering, pulling the membranes together and mediating fusion. Recent advances have enabled the construction of detailed models describing bilayer transitions and energy barriers along the fusion pathway and have elucidated the structures of SNAREs complexed in various states with regulatory proteins. In this Review, we discuss how these advances are yielding an increasingly detailed picture of the SNARE-mediated fusion pathway, leading from first contact between the membranes via metastable non-bilayer intermediates towards the opening and expansion of a fusion pore. We describe how SNARE proteins assemble into complexes, how this assembly is regulated by accessory proteins and how SNARE complexes overcome the free energy barriers that prevent spontaneous membrane fusion.
Collapse
Affiliation(s)
- Reinhard Jahn
- Laboratory of Neurobiology, Max-Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.
| | - David C Cafiso
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
| | - Lukas K Tamm
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
| |
Collapse
|
5
|
Brosio G, Rossi G, Bochicchio D. Nanoparticle-induced biomembrane fusion: unraveling the effect of core size on stalk formation. NANOSCALE ADVANCES 2023; 5:4675-4680. [PMID: 37705778 PMCID: PMC10496904 DOI: 10.1039/d3na00430a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 08/01/2023] [Indexed: 09/15/2023]
Abstract
Membrane fusion in vitro is a strategy to load model or cell-derived vesicles with proteins, drugs, and genetic materials for theranostic applications. It is thus crucial to develop strategies to control the fusion process, also through synthetic fusogenic agents. Ligand-protected, membrane-penetrating gold nanoparticles (Au NPs) can facilitate membrane fusion, but the molecular mechanisms remain unresolved. Here, we tackle NP-induced stalk formation using a coarse-grained molecular dynamics approach and enhanced sampling techniques. We show that smaller (2 nm in diameter) NPs lead to a lower free energy barrier and higher stalk stability than larger NPs (4 nm). We demonstrate that this difference is due to a different ligand conformational freedom, which in turn depends on the Au core curvature. Our study provides precious insights into the mechanisms underlying NP-mediated membrane fusion, while our computational approach is general and applicable to studying stalk formation caused by other fusogenic agents.
Collapse
Affiliation(s)
- Giorgia Brosio
- Department of Physics, University of Genoa Via Dodecaneso 33 16146 Genoa Italy
| | - Giulia Rossi
- Department of Physics, University of Genoa Via Dodecaneso 33 16146 Genoa Italy
| | - Davide Bochicchio
- Department of Physics, University of Genoa Via Dodecaneso 33 16146 Genoa Italy
| |
Collapse
|
6
|
Beaven AH, Sapp K, Sodt AJ. Simulated dynamic cholesterol redistribution favors membrane fusion pore constriction. Biophys J 2023; 122:2162-2175. [PMID: 36588341 PMCID: PMC10257089 DOI: 10.1016/j.bpj.2022.12.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 06/17/2022] [Accepted: 12/16/2022] [Indexed: 01/01/2023] Open
Abstract
Endo- and exocytosis proceed through a highly strained membrane fusion pore topology regardless of the aiding protein machinery. The membrane's lipid components bias fusion pores toward expansion or closure, modifying the necessary work done by proteins. Cholesterol, a key component of plasma membranes, promotes both inverted lipid phases with concave leaflets (i.e., negative total curvature, which thins the leaflet) and flat bilayer phases with thick, ordered hydrophobic interiors. We demonstrate by theory and simulation that both leaflets of nascent catenoidal fusion pores have negative total curvature. Furthermore, the hydrophobic core of bilayers with strong negative Gaussian curvature is thinned. Therefore, it is an open question whether cholesterol will be enriched in these regions because of the negative total curvature or depleted because of the membrane thinning. Here, we compare all-atom molecular dynamics simulations (built using a procedure to create specific fusion pore geometries) and theory to understand the underlying reasons for lipid redistribution on fusion pores. Our all-atom molecular dynamics simulations resolve this question by showing that cholesterol is strongly excluded from the thinned neck of fusion and fission pores, revealing that thickness (and/or lipid order) influences cholesterol distributions more than curvature. The results imply that cholesterol exclusion can drive fusion pore closure by creating a small, cholesterol-depleted zone in the neck. This model agrees with literature evidence that membrane reshaping is connected to cholesterol-dependent lateral phase separation.
Collapse
Affiliation(s)
- Andrew H Beaven
- Unit on Membrane Chemical Physics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland; Postdoctoral Research Associate Program, National Institute of General Medical Sciences, National Institutes of Health, Bethesda, Maryland
| | - Kayla Sapp
- Unit on Membrane Chemical Physics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
| | - Alexander J Sodt
- Unit on Membrane Chemical Physics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland.
| |
Collapse
|
7
|
Canepa E, Bochicchio D, Brosio G, Silva PHJ, Stellacci F, Dante S, Rossi G, Relini A. Cholesterol-Containing Liposomes Decorated With Au Nanoparticles as Minimal Tunable Fusion Machinery. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2207125. [PMID: 36899445 DOI: 10.1002/smll.202207125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 01/30/2023] [Indexed: 06/08/2023]
Abstract
Membrane fusion is essential for the basal functionality of eukaryotic cells. In physiological conditions, fusion events are regulated by a wide range of specialized proteins, operating with finely tuned local lipid composition and ionic environment. Fusogenic proteins, assisted by membrane cholesterol and calcium ions, provide the mechanical energy necessary to achieve vesicle fusion in neuromediator release. Similar cooperative effects must be explored when considering synthetic approaches for controlled membrane fusion. We show that liposomes decorated with amphiphilic Au nanoparticles (AuLips) can act as minimal tunable fusion machinery. AuLips fusion is triggered by divalent ions, while the number of fusion events dramatically changes with, and can be finely tuned by, the liposome cholesterol content. We combine quartz-crystal-microbalance with dissipation monitoring (QCM-D), fluorescence assays, and small-angle X-ray scattering (SAXS) with molecular dynamics (MD) at coarse-grained (CG) resolution, revealing new mechanistic details on the fusogenic activity of amphiphilic Au nanoparticles (AuNPs) and demonstrating the ability of these synthetic nanomaterials to induce fusion regardless of the divalent ion used (Ca2+ or Mg2+ ). The results provide a novel contribution to developing new artificial fusogenic agents for next-generation biomedical applications that require tight control of the rate of fusion events (e.g., targeted drug delivery).
Collapse
Affiliation(s)
- Ester Canepa
- Department of Physics, University of Genoa, Genoa, 16146, Italy
- Institute of Materials Science & Engineering, EPFL, Lausanne, 1015, Switzerland
| | | | - Giorgia Brosio
- Department of Physics, University of Genoa, Genoa, 16146, Italy
| | | | - Francesco Stellacci
- Materials Characterization Facility, Istituto Italiano di Tecnologia, Genoa, 16163, Italy
| | - Silvia Dante
- Institute of Materials Science & Engineering, EPFL, Lausanne, 1015, Switzerland
| | - Giulia Rossi
- Department of Physics, University of Genoa, Genoa, 16146, Italy
| | - Annalisa Relini
- Department of Physics, University of Genoa, Genoa, 16146, Italy
| |
Collapse
|
8
|
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.
Collapse
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.
| |
Collapse
|
9
|
Ali Moussa HY, Shin KC, Ponraj J, Kim SJ, Ryu JK, Mansour S, Park Y. Requirement of Cholesterol for Calcium-Dependent Vesicle Fusion by Strengthening Synaptotagmin-1-Induced Membrane Bending. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2206823. [PMID: 37058136 DOI: 10.1002/advs.202206823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 02/09/2023] [Indexed: 05/27/2023]
Abstract
Cholesterol is essential for neuronal activity and function. Cholesterol depletion in the plasma membrane impairs synaptic transmission. However, the molecular mechanisms by which cholesterol deficiency leads to defects in vesicle fusion remain poorly understood. Here, it is shown that cholesterol is required for Ca2+ -dependent native vesicle fusion using the in vitro reconstitution of fusion and amperometry to monitor exocytosis in chromaffin cells. Purified native vesicles are crucial for the reconstitution of physiological Ca2+ -dependent fusion, because vesicle-mimicking liposomes fail to reproduce the cholesterol effect. Intriguingly, cholesterol has no effect on the membrane binding of synaptotagmin-1, a Ca2+ sensor for ultrafast fusion. Cholesterol strengthens local membrane deformation and bending induced by synaptotagmin-1, thereby lowering the energy barrier for Ca2+ -dependent fusion to occur. The data provide evidence that cholesterol depletion abolishes Ca2+ -dependent vesicle fusion by disrupting synaptotagmin-1-induced membrane bending, and suggests that cholesterol is an essential lipid regulator for Ca2+ -dependent fusion.
Collapse
Affiliation(s)
- Houda Yasmine Ali Moussa
- Neurological Disorders Research Center, Qatar Biomedical Research Institute (QBRI), Hamad Bin Khalifa University (HBKU), Qatar Foundation, Doha, Qatar
| | - Kyung Chul Shin
- Neurological Disorders Research Center, Qatar Biomedical Research Institute (QBRI), Hamad Bin Khalifa University (HBKU), Qatar Foundation, Doha, Qatar
| | | | - Soo Jin Kim
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea
| | - Je-Kyung Ryu
- Department of Physics & Astronomy, Seoul National University. 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea
| | - Said Mansour
- HBKU Core Labs, Hamad Bin Khalifa University (HBKU), Doha, Qatar
| | - Yongsoo Park
- Neurological Disorders Research Center, Qatar Biomedical Research Institute (QBRI), Hamad Bin Khalifa University (HBKU), Qatar Foundation, Doha, Qatar
- College of Health & Life Sciences (CHLS), Hamad Bin Khalifa University (HBKU), Qatar Foundation, Doha, Qatar
| |
Collapse
|
10
|
Kav B, Weikl TR, Schneck E. Measuring pico-Newton Forces with Lipid Anchors as Force Sensors in Molecular Dynamics Simulations. J Phys Chem B 2023; 127:4081-4089. [PMID: 37127845 PMCID: PMC10184124 DOI: 10.1021/acs.jpcb.3c00063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Binding forces between biomolecules are ubiquitous in nature but sometimes as weak as a few pico-Newtons (pN). In many cases, the binding partners are attached to biomembranes with the help of a lipid anchor. One important example are glycolipids that promote membrane adhesion through weak carbohydrate-carbohydrate binding between adjacent membranes. Here, we use molecular dynamics (MD) simulations to quantify the forces generated by bonds involving membrane-anchored molecules. We introduce a method in which the protrusion of the lipid anchors from the membrane acts as the force sensor. Our results with two different glycolipids reveal binding forces of up to 20 pN and corroborate the recent notion that carbohydrate-carbohydrate interactions are generic rather than specific.
Collapse
Affiliation(s)
- Batuhan Kav
- Max Planck Institute of Colloids and Interfaces, 14467, Potsdam, Germany
- Institute of Biological Information Processing: Structural Biochemistry (IBI-7), Forschungszentrum Jülich, 52428 Jülich, Germany
| | - Thomas R Weikl
- Max Planck Institute of Colloids and Interfaces, 14467, Potsdam, Germany
| | - Emanuel Schneck
- Max Planck Institute of Colloids and Interfaces, 14467, Potsdam, Germany
- Institute for Condensed Matter Physics, Technische Universität Darmstadt, 64289 Darmstadt, Germany
| |
Collapse
|
11
|
Beck K, Nandy J, Hoernke M. Membrane permeabilization can be crucially biased by a fusogenic lipid composition - leaky fusion caused by antimicrobial peptides in model membranes. SOFT MATTER 2023; 19:2919-2931. [PMID: 37010846 DOI: 10.1039/d2sm01691e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Induced membrane permeabilization or leakage is often taken as an indication for activity of membrane-active molecules, such as antimicrobial peptides (AMPs). The exact leakage mechanism is often unknown, but important, because certain mechanisms might actually contribute to microbial killing, while others are unselective, or potentially irrelevant in an in vivo situation. Using an antimicrobial example peptide (cR3W3), we illustrate one of the potentially misleading leakage mechanisms: leaky fusion, where leakage is coupled to membrane fusion. Like many others, we examine peptide-induced leakage in model vesicles consisting of binary mixtures of anionic and zwitterionic phospholipids. In fact, phosphatidylglycerol and phosphatidylethanolamine (PG/PE) are supposed to reflect bacterial membranes, but exhibit a high propensity for vesicle aggregation and fusion. We describe the implications of this vesicle fusion and aggregation for the reliability of model studies. The ambiguous role of the relatively fusogenic PE-lipids becomes clear as leakage decreases significantly when aggregation and fusion are prevented by sterical shielding. Furthermore, the mechanism of leakage changes if PE is exchanged for phosphatidylcholine (PC). We thus point out that the lipid composition of model membranes can be biased towards leaky fusion. This can lead to discrepancies between model studies and activity in true microbes, because leaky fusion is likely prevented by bacterial peptidoglycan layers. In conclusion, choosing the model membrane might implicate the type of effect (here leakage mechanism) that is observed. In the worst case, as with leaky fusion of PG/PE vesicles, this is not directly relevant for the intended antimicrobial application.
Collapse
Affiliation(s)
- Katharina Beck
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, Freiburg i. Br., Germany.
| | - Janina Nandy
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, Freiburg i. Br., Germany.
| | - Maria Hoernke
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, Freiburg i. Br., Germany.
| |
Collapse
|
12
|
Shekunov EV, Zlodeeva PD, Efimova SS, Muryleva AA, Zarubaev VV, Slita AV, Ostroumova OS. Cyclic lipopeptides as membrane fusion inhibitors against SARS-CoV-2: New tricks for old dogs. Antiviral Res 2023; 212:105575. [PMID: 36868316 PMCID: PMC9977712 DOI: 10.1016/j.antiviral.2023.105575] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 02/25/2023] [Accepted: 02/28/2023] [Indexed: 03/05/2023]
Abstract
With the resurgence of the coronavirus pandemic, the repositioning of FDA-approved drugs against coronovirus and finding alternative strategies for antiviral therapy are both important. We previously identified the viral lipid envelope as a potential target for the prevention and treatment of SARS-CoV-2 infection with plant alkaloids (Shekunov et al., 2021). Here, we investigated the effects of eleven cyclic lipopeptides (CLPs), including well-known antifungal and antibacterial compounds, on the liposome fusion triggered by calcium, polyethylene glycol 8000, and a fragment of SARS-CoV-2 fusion peptide (816-827) by calcein release assays. Differential scanning microcalorimetry of the gel-to-liquid-crystalline and lamellar-to-inverted hexagonal phase transitions and confocal fluorescence microscopy demonstrated the relation of the fusion inhibitory effects of CLPs to alterations in lipid packing, membrane curvature stress and domain organization. The antiviral effects of CLPs were evaluated in an in vitro Vero-based cell model, and aculeacin A, anidulafugin, iturin A, and mycosubtilin attenuated the cytopathogenicity of SARS-CoV-2 without specific toxicity.
Collapse
Affiliation(s)
- Egor V Shekunov
- Institute of Cytology of Russian Academy of Sciences, Tikhoretsky 4, 194064, Saint Petersburg, Russia
| | - Polina D Zlodeeva
- Institute of Cytology of Russian Academy of Sciences, Tikhoretsky 4, 194064, Saint Petersburg, Russia
| | - Svetlana S Efimova
- Institute of Cytology of Russian Academy of Sciences, Tikhoretsky 4, 194064, Saint Petersburg, Russia
| | - Anna A Muryleva
- Institute of Cytology of Russian Academy of Sciences, Tikhoretsky 4, 194064, Saint Petersburg, Russia; Saint-Petersburg Pasteur Institute of Epidemiology and Microbiology, Mira 14, 197101, Saint Petersburg, Russia
| | - Vladimir V Zarubaev
- Saint-Petersburg Pasteur Institute of Epidemiology and Microbiology, Mira 14, 197101, Saint Petersburg, Russia
| | - Alexander V Slita
- Saint-Petersburg Pasteur Institute of Epidemiology and Microbiology, Mira 14, 197101, Saint Petersburg, Russia
| | - Olga S Ostroumova
- Institute of Cytology of Russian Academy of Sciences, Tikhoretsky 4, 194064, Saint Petersburg, Russia.
| |
Collapse
|
13
|
van Tilburg M, Hilbers PAJ, Markvoort AJ. On the role of membrane embedding, protein rigidity and transmembrane length in lipid membrane fusion. SOFT MATTER 2023; 19:1791-1802. [PMID: 36786821 DOI: 10.1039/d2sm01582j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The fusion of biological membranes is ubiquitous in natural processes like exo- and endocytosis, intracellular trafficking and viral entry. Membrane fusion is also utilized in artificial biomimetic fusion systems, e.g. for drug delivery. Both the natural and the biomimetic fusion systems rely on a wide range of (artificial) proteins mediating the fusion process. Although the exact mechanisms of these proteins differ, clear analogies in their general behavior can be observed in bringing the membranes in close proximity and mediating the fusion reaction. In our study, we use molecular dynamics simulations with coarse grained models, mimicking the general behavior of fusion proteins (spikes), to systematically examine the effects of specific characteristics of these proteins on the fusion process. The protein characteristics considered are (i) the type of membrane embedding, i.e., either transmembrane or not, (ii) the rigidity, and (iii) the transmembrane domain (TMD) length. The results show essential differences in fusion pathway between monotopic and transmembrane spikes, in which transmembrane spikes seem to inhibit the formation of hemifusion diaphragms, leading to a faster fusion development. Furthermore, we observed that an increased rigidity and a decreased TMD length both proved to contribute to a faster fusion development. Finally, we show that a single spike may suffice to successfully induce a fusion reaction, provided that the spike is sufficiently rigid and attractive. Not only does this shed light on biological fusion of membranes, it also provides clear design rules for artificial membrane fusion systems.
Collapse
Affiliation(s)
- Marco van Tilburg
- Department of Biomedical Engineering, Computational Biology Group, Eindhoven University of Technology, The Netherlands.
| | - Peter A J Hilbers
- Department of Biomedical Engineering, Computational Biology Group, Eindhoven University of Technology, The Netherlands.
- Institute of Complex Molecular Systems, Eindhoven University of Technology, The Netherlands
| | - Albert J Markvoort
- Department of Biomedical Engineering, Computational Biology Group, Eindhoven University of Technology, The Netherlands.
- Institute of Complex Molecular Systems, Eindhoven University of Technology, The Netherlands
| |
Collapse
|
14
|
Warner JM, An D, Stratton BS, O'Shaughnessy B. A hemifused complex is the hub in a network of pathways to membrane fusion. Biophys J 2023; 122:374-385. [PMID: 36463406 PMCID: PMC9892611 DOI: 10.1016/j.bpj.2022.12.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 06/25/2022] [Accepted: 11/30/2022] [Indexed: 12/12/2022] Open
Abstract
Membrane fusion is a critical step for many essential processes, from neurotransmission to fertilization. For over 40 years, protein-free fusion driven by calcium or other cationic species has provided a simplified model of biological fusion, but the mechanisms remain poorly understood. Cation-mediated membrane fusion and permeation are essential in their own right to drug delivery strategies based on cell-penetrating peptides or cation-bearing lipid nanoparticles. Experimental studies suggest calcium drives anionic membranes to a hemifused intermediate that constitutes a hub in a network of pathways, but the pathway selection mechanism is unknown. Here we develop a mathematical model that identifies the network hub as a highly dynamic hemifusion complex. Multivalent cations drive expansion of this high-tension hemifusion interface between interacting vesicles during a brief transient. The fate of this interface determines the outcome, either fusion, dead-end hemifusion, or vesicle lysis. The model reproduces the unexplained finding that calcium-driven fusion of vesicles with planar membranes typically stalls at hemifusion, and we show the equilibrated hemifused state is a novel lens-shaped complex. Thus, membrane fusion kinetics follow a stochastic trajectory within a network of pathways, with outcome weightings set by a hemifused complex intermediate.
Collapse
Affiliation(s)
- Jason M Warner
- Department of Chemical Engineering, Columbia University, New York, New York
| | - Dong An
- Department of Chemical Engineering, Columbia University, New York, New York
| | | | - Ben O'Shaughnessy
- Department of Chemical Engineering, Columbia University, New York, New York.
| |
Collapse
|
15
|
Jeong KJ, Jeong S, Lee S, Son CY. Predictive Molecular Models for Charged Materials Systems: From Energy Materials to Biomacromolecules. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2204272. [PMID: 36373701 DOI: 10.1002/adma.202204272] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 07/05/2022] [Indexed: 06/16/2023]
Abstract
Electrostatic interactions play a dominant role in charged materials systems. Understanding the complex correlation between macroscopic properties with microscopic structures is of critical importance to develop rational design strategies for advanced materials. But the complexity of this challenging task is augmented by interfaces present in the charged materials systems, such as electrode-electrolyte interfaces or biological membranes. Over the last decades, predictive molecular simulations that are founded in fundamental physics and optimized for charged interfacial systems have proven their value in providing molecular understanding of physicochemical properties and functional mechanisms for diverse materials. Novel design strategies utilizing predictive models have been suggested as promising route for the rational design of materials with tailored properties. Here, an overview of recent advances in the understanding of charged interfacial systems aided by predictive molecular simulations is presented. Focusing on three types of charged interfaces found in energy materials and biomacromolecules, how the molecular models characterize ion structure, charge transport, morphology relation to the environment, and the thermodynamics/kinetics of molecular binding at the interfaces is discussed. The critical analysis brings two prominent field of energy materials and biological science under common perspective, to stimulate crossover in both research field that have been largely separated.
Collapse
Affiliation(s)
- Kyeong-Jun Jeong
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, South Korea
| | - Seungwon Jeong
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, South Korea
| | - Sangmin Lee
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, South Korea
| | - Chang Yun Son
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, South Korea
| |
Collapse
|
16
|
Palfreyman MT, West SE, Jorgensen EM. SNARE Proteins in Synaptic Vesicle Fusion. ADVANCES IN NEUROBIOLOGY 2023; 33:63-118. [PMID: 37615864 DOI: 10.1007/978-3-031-34229-5_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Neurotransmitters are stored in small membrane-bound vesicles at synapses; a subset of synaptic vesicles is docked at release sites. Fusion of docked vesicles with the plasma membrane releases neurotransmitters. Membrane fusion at synapses, as well as all trafficking steps of the secretory pathway, is mediated by SNARE proteins. The SNAREs are the minimal fusion machinery. They zipper from N-termini to membrane-anchored C-termini to form a 4-helix bundle that forces the apposed membranes to fuse. At synapses, the SNAREs comprise a single helix from syntaxin and synaptobrevin; SNAP-25 contributes the other two helices to complete the bundle. Unc13 mediates synaptic vesicle docking and converts syntaxin into the permissive "open" configuration. The SM protein, Unc18, is required to initiate and proofread SNARE assembly. The SNAREs are then held in a half-zippered state by synaptotagmin and complexin. Calcium removes the synaptotagmin and complexin block, and the SNAREs drive vesicle fusion. After fusion, NSF and alpha-SNAP unwind the SNAREs and thereby recharge the system for further rounds of fusion. In this chapter, we will describe the discovery of the SNAREs, their relevant structural features, models for their function, and the central role of Unc18. In addition, we will touch upon the regulation of SNARE complex formation by Unc13, complexin, and synaptotagmin.
Collapse
Affiliation(s)
- Mark T Palfreyman
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Sam E West
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Erik M Jorgensen
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA.
| |
Collapse
|
17
|
Shi S, Fan H, Hoernke M. Leaky membrane fusion: an ambivalent effect induced by antimicrobial polycations. NANOSCALE ADVANCES 2022; 4:5109-5122. [PMID: 36504745 PMCID: PMC9680940 DOI: 10.1039/d2na00464j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 10/24/2022] [Indexed: 05/28/2023]
Abstract
Both antimicrobial peptides and their synthetic mimics are potential alternatives to classical antibiotics. They can induce several membrane perturbations including permeabilization. Especially in model studies, aggregation of vesicles by such polycations is often reported. Here, we show that unintended vesicle aggregation or indeed fusion can cause apparent leakage in model studies that is not possible in most microbes, thus potentially leading to misinterpretations. The interactions of a highly charged and highly selective membrane-active polycation with negatively charged phosphatidylethanolamine/phosphatidylglycerol (PE/PG) vesicles are studied by a combination of biophysical methods. At low polycation concentrations, apparent vesicle aggregation was found to involve exchange of lipids. Upon neutralization of the negatively charged vesicles by the polycation, full fusion and leakage occurred and leaky fusion is suspected. To elucidate the interplay of leakage and fusion, we prevented membrane contacts by decorating the vesicles with PEG-chains. This inhibited fusion and also leakage activity. Leaky fusion is further corroborated by increased leakage with increasing likeliness of vesicle-vesicle contacts. Because of its similar appearance to other leakage mechanisms, leaky fusion is difficult to identify and might be overlooked and more common amongst polycationic membrane-active compounds. Regarding biological activity, leaky fusion needs to be carefully distinguished from other membrane permeabilization mechanisms, as it may be less relevant to bacteria, but potentially relevant for fungi. Furthermore, leaky fusion is an interesting effect that could help in endosomal escape for drug delivery. A comprehensive step-by-step protocol for membrane permeabilization/vesicle leakage using calcein fluorescence lifetime is provided in the ESI.
Collapse
Affiliation(s)
- Shuai Shi
- Chemistry and Pharmacy, Albert-Ludwigs-Universität 79104 Freiburg i.Br. Germany
| | - Helen Fan
- Leslie Dan Faculty of Pharmacy, University of Toronto Toronto Canada
| | - Maria Hoernke
- Chemistry and Pharmacy, Albert-Ludwigs-Universität 79104 Freiburg i.Br. Germany
| |
Collapse
|
18
|
Di Bartolo AL, Tomes CN, Mayorga LS, Masone D. Enhanced Expansion and Reduced Kiss-and-Run Events in Fusion Pores Steered by Synaptotagmin-1 C2B Domains. J Chem Theory Comput 2022; 18:4544-4554. [PMID: 35759758 DOI: 10.1021/acs.jctc.2c00424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fusion pore controls the release of exocytotic vesicle contents through a precise orchestration of lipids from the fusing membranes and proteins. There is a major lipid reorganization during the different stages in life of the fusion pore (membrane fusion, nucleation, and expansion) that can be scrutinized thermodynamically. In this work, using umbrella sampling simulations we describe the expansion of the fusion pore. We have calculated free energy profiles to drive a nascent, just nucleated, fusion pore to its expanded configuration. We have quantified the effects on the free energy of one and two Synaptotagmin-1 C2B domains in the cytosolic space. We show that C2B domains cumulatively reduce the cost for expansion, favoring the system to evolve toward full fusion. Finally, by conducting thousands of unbiased molecular dynamics simulations, we show that C2B domains significantly decrease the probability of kiss-and-run events.
Collapse
Affiliation(s)
- Ary Lautaro Di Bartolo
- Instituto de Histología y Embriología de Mendoza (IHEM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina.,Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
| | - Claudia N Tomes
- Instituto de Histología y Embriología de Mendoza (IHEM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina.,Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
| | - Luis S Mayorga
- Instituto de Histología y Embriología de Mendoza (IHEM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina.,Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
| | - Diego Masone
- Instituto de Histología y Embriología de Mendoza (IHEM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina.,Facultad de Ingeniería, Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
| |
Collapse
|
19
|
Marrink SJ, Monticelli L, Melo MN, Alessandri R, Tieleman DP, Souza PCT. Two decades of Martini: Better beads, broader scope. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2022. [DOI: 10.1002/wcms.1620] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Siewert J. Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials University of Groningen Groningen The Netherlands
| | - Luca Monticelli
- Molecular Microbiology and Structural Biochemistry (MMSB ‐ UMR 5086) CNRS & University of Lyon Lyon France
| | - Manuel N. Melo
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa Oeiras Portugal
| | - Riccardo Alessandri
- Pritzker School of Molecular Engineering University of Chicago Chicago Illinois USA
| | - D. Peter Tieleman
- Centre for Molecular Simulation and Department of Biological Sciences University of Calgary Alberta Canada
| | - Paulo C. T. Souza
- Molecular Microbiology and Structural Biochemistry (MMSB ‐ UMR 5086) CNRS & University of Lyon Lyon France
| |
Collapse
|
20
|
Joardar A, Pattnaik GP, Chakraborty H. Mechanism of Membrane Fusion: Interplay of Lipid and Peptide. J Membr Biol 2022; 255:211-224. [PMID: 35435451 PMCID: PMC9014786 DOI: 10.1007/s00232-022-00233-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 03/25/2022] [Indexed: 11/26/2022]
Abstract
Membrane fusion is an essential process for the survival of eukaryotes and the entry of enveloped viruses into host cells. A proper understanding of the mechanism of membrane fusion would provide us a handle to manipulate several biological pathways, and design efficient vaccines against emerging and re-emerging viral infections. Although fusion proteins take the central stage in catalyzing the process, role of lipid composition is also of paramount importance. Lipid composition modulates membrane organization and dynamics and impacts the lipid–protein (peptide) interaction. Moreover, the intrinsic curvature of lipids has strong impact on the formation of stalk and hemifusion diaphragm. Detection of transiently stable intermediates remains the bottleneck in the understanding of fusion mechanism. In order to circumvent this challenge, analytical methods can be employed to determine the kinetic parameters from ensemble average measurements of observables, such as lipid mixing, content mixing, and content leakage. The current review aims to present an analytical method that would aid our understanding of the fusion mechanism, provides a better insight into the role of lipid shape, and discusses the interplay of lipid and peptide in membrane fusion.
Collapse
Affiliation(s)
- Ankita Joardar
- School of Chemistry, Sambalpur University, Jyoti Vihar, Burla, Odisha, 768019, India
| | | | - Hirak Chakraborty
- School of Chemistry, Sambalpur University, Jyoti Vihar, Burla, Odisha, 768019, India.
| |
Collapse
|
21
|
Tuerkova A, Kasson PM. Computational methods to study enveloped viral entry. Biochem Soc Trans 2021; 49:2527-2537. [PMID: 34783344 PMCID: PMC10184508 DOI: 10.1042/bst20210190] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 10/25/2021] [Accepted: 10/27/2021] [Indexed: 12/15/2022]
Abstract
The protein-membrane interactions that mediate viral infection occur via loosely ordered, transient assemblies, creating challenges for high-resolution structure determination. Computational methods and in particular molecular dynamics simulation have thus become important adjuncts for integrating experimental data, developing mechanistic models, and suggesting testable hypotheses regarding viral function. However, the large molecular scales of virus-host interaction also create challenges for detailed molecular simulation. For this reason, continuum membrane models have played a large historical role, although they have become less favored for high-resolution models of protein assemblies and lipid organization. Here, we review recent progress in the field, with an emphasis on the insight that has been gained using a mixture of coarse-grained and atomic-resolution molecular dynamics simulations. Based on successes and challenges to date, we suggest a multiresolution strategy that should yield the best mixture of computational efficiency and physical fidelity. This strategy may facilitate further simulations of viral entry by a broader range of viruses, helping illuminate the diversity of viral entry strategies and the essential common elements that can be targeted for antiviral therapies.
Collapse
Affiliation(s)
- Alzbeta Tuerkova
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
| | - Peter M Kasson
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
- Departments of Molecular Physiology and Biomedical Engineering, University of Virginia, Charlottesville, VA 22908, U.S.A
| |
Collapse
|
22
|
Joardar A, Pattnaik GP, Chakraborty H. Effect of Phosphatidylethanolamine and Oleic Acid on Membrane Fusion: Phosphatidylethanolamine Circumvents the Classical Stalk Model. J Phys Chem B 2021; 125:13192-13202. [PMID: 34839659 DOI: 10.1021/acs.jpcb.1c08044] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Membrane fusion is one of the most important processes for the survival of eukaryotic cells and entry of enveloped viruses to the host cells. Lipid composition plays a crucial role in the process by modulating the organization and dynamics of the membrane, as well as the structure and conformation of membrane proteins. Phosphatidylethanolamine (PE), a lipid molecule with intrinsic negative curvature, promotes membrane fusion by stabilizing the non-lamellar intermediate structures in the fusion process. Conversely, oleic acid (OA), with intrinsic positive curvature, inhibits membrane fusion. The current study aimed to investigate polyethylene glycol-mediated lipid mixing, content mixing, content leakage, and depth-dependent membrane organization and dynamics, using arrays of steady-state and time-resolved fluorescence techniques, to determine the causative role of PE and OA in membrane fusion. The results demonstrated that the presence of 30 mol % PE in the membrane promotes membrane fusion through a mechanism that circumvents the classical stalk model. On the contrary, membranes containing OA showed reduced rate and extent of fusion, despite following the same mechanism. Collectively, our findings in terms of membrane organization and dynamics indicated a plausible role of PE and OA in membrane fusion.
Collapse
Affiliation(s)
- Ankita Joardar
- School of Chemistry, Sambalpur University, Jyoti Vihar, Burla, Odisha 768 019, India
| | | | - Hirak Chakraborty
- School of Chemistry, Sambalpur University, Jyoti Vihar, Burla, Odisha 768 019, India
| |
Collapse
|
23
|
Arribas Perez M, Beales PA. Biomimetic Curvature and Tension-Driven Membrane Fusion Induced by Silica Nanoparticles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:13917-13931. [PMID: 34788054 DOI: 10.1021/acs.langmuir.1c02492] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Fusion events in living cells are intricate phenomena that require the coordinate action of multicomponent protein complexes. However, simpler synthetic tools to control membrane fusion in artificial cells are highly desirable. Native membrane fusion machinery mediates fusion, driving a delicate balance of membrane curvature and tension between two closely apposed membranes. Here, we show that silica nanoparticles (SiO2 NPs) at a size close to the cross-over between tension-driven and curvature-driven interaction regimes initiate efficient fusion of biomimetic model membranes. Fusion efficiency and mechanisms are studied by Förster resonance energy transfer and confocal fluorescence microscopy. SiO2 NPs induce a slight increase in lipid packing likely to increase the lateral tension of the membrane. We observe a connection between membrane tension and fusion efficiency. Finally, real-time confocal fluorescence microscopy reveals three distinct mechanistic pathways for membrane fusion. SiO2 NPs show significant potential for inclusion in the synthetic biology toolkit for membrane remodeling and fusion in artificial cells.
Collapse
Affiliation(s)
- Marcos Arribas Perez
- Astbury Centre for Structural Molecular Biology and School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K
| | - Paul A Beales
- Astbury Centre for Structural Molecular Biology and School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K
- Bragg Centre for Materials Research, University of Leeds, Leeds LS2 9JT, U.K
| |
Collapse
|
24
|
Poojari CS, Scherer KC, Hub JS. Free energies of membrane stalk formation from a lipidomics perspective. Nat Commun 2021; 12:6594. [PMID: 34782611 PMCID: PMC8593120 DOI: 10.1038/s41467-021-26924-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 10/18/2021] [Indexed: 11/21/2022] Open
Abstract
Many biological membranes are asymmetric and exhibit complex lipid composition, comprising hundreds of distinct chemical species. Identifying the biological function and advantage of this complexity is a central goal of membrane biology. Here, we study how membrane complexity controls the energetics of the first steps of membrane fusions, that is, the formation of a stalk. We first present a computationally efficient method for simulating thermodynamically reversible pathways of stalk formation at coarse-grained resolution. The method reveals that the inner leaflet of a typical plasma membrane is far more fusogenic than the outer leaflet, which is likely an adaptation to evolutionary pressure. To rationalize these findings by the distinct lipid compositions, we computed ~200 free energies of stalk formation in membranes with different lipid head groups, tail lengths, tail unsaturations, and sterol content. In summary, the simulations reveal a drastic influence of the lipid composition on stalk formation and a comprehensive fusogenicity map of many biologically relevant lipid classes. Fusion of cellular membranes begins with the formation of a stalk. Here, the authors develop a computationally efficient method for coarse-grained simulations of stalk formation and apply this approach to comprehensively analyse how stalk formation is influenced by the membrane lipid composition.
Collapse
Affiliation(s)
- Chetan S Poojari
- Saarland University, Theoretical Physics and Center for Biophysics, Saarland University, Saarbrücken, Germany
| | - Katharina C Scherer
- Saarland University, Theoretical Physics and Center for Biophysics, Saarland University, Saarbrücken, Germany
| | - Jochen S Hub
- Saarland University, Theoretical Physics and Center for Biophysics, Saarland University, Saarbrücken, Germany.
| |
Collapse
|
25
|
Chappa V, Smirnova Y, Komorowski K, Müller M, Salditt T. The effect of polydispersity, shape fluctuations and curvature on small unilamellar vesicle small-angle X-ray scattering curves. J Appl Crystallogr 2021; 54:557-568. [PMID: 33953656 PMCID: PMC8056763 DOI: 10.1107/s1600576721001461] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 02/08/2021] [Indexed: 11/27/2022] Open
Abstract
It is a challenge to distinguish the effect of shape fluctuations and size polydispersity on experimental small-angle X-ray scattering curves of small unilamellar vesicles. Here it is shown that both effects have distinguishable spectral patterns, and an efficient simulation tool is presented for simulating and analysing experimental data. The importance of curvature-induced electron-density profile asymmetry for estimating the vesicle size from SAXS scattering curves is also demonstrated. Small unilamellar vesicles (20–100 nm diameter) are model systems for strongly curved lipid membranes, in particular for cell organelles. Routinely, small-angle X-ray scattering (SAXS) is employed to study their size and electron-density profile (EDP). Current SAXS analysis of small unilamellar vesicles (SUVs) often employs a factorization into the structure factor (vesicle shape) and the form factor (lipid bilayer electron-density profile) and invokes additional idealizations: (i) an effective polydispersity distribution of vesicle radii, (ii) a spherical vesicle shape and (iii) an approximate account of membrane asymmetry, a feature particularly relevant for strongly curved membranes. These idealizations do not account for thermal shape fluctuations and also break down for strong salt- or protein-induced deformations, as well as vesicle adhesion and fusion, which complicate the analysis of the lipid bilayer structure. Presented here are simulations of SAXS curves of SUVs with experimentally relevant size, shape and EDPs of the curved bilayer, inferred from coarse-grained simulations and elasticity considerations, to quantify the effects of size polydispersity, thermal fluctuations of the SUV shape and membrane asymmetry. It is observed that the factorization approximation of the scattering intensity holds even for small vesicle radii (∼30 nm). However, the simulations show that, for very small vesicles, a curvature-induced asymmetry arises in the EDP, with sizeable effects on the SAXS curve. It is also demonstrated that thermal fluctuations in shape and the size polydispersity have distinguishable signatures in the SAXS intensity. Polydispersity gives rise to low-q features, whereas thermal fluctuations predominantly affect the scattering at larger q, related to membrane bending rigidity. Finally, it is shown that simulation of fluctuating vesicle ensembles can be used for analysis of experimental SAXS curves.
Collapse
Affiliation(s)
- Veronica Chappa
- Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen 37077, Germany
| | - Yuliya Smirnova
- Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen 37077, Germany
| | - Karlo Komorowski
- Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen 37077, Germany
| | - Marcus Müller
- Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen 37077, Germany
| | - Tim Salditt
- Faculty of Physics, University of Göttingen, Friedrich-Hund-Platz 1, Göttingen 37077, Germany
| |
Collapse
|
26
|
Witt H, Savić F, Verbeek S, Dietz J, Tarantola G, Oelkers M, Geil B, Janshoff A. Membrane fusion studied by colloidal probes. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2021; 50:223-237. [PMID: 33599795 PMCID: PMC8071799 DOI: 10.1007/s00249-020-01490-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 12/19/2020] [Indexed: 12/12/2022]
Abstract
Membrane-coated colloidal probes combine the benefits of solid-supported membranes with a more complex three-dimensional geometry. This combination makes them a powerful model system that enables the visualization of dynamic biological processes with high throughput and minimal reliance on fluorescent labels. Here, we want to review recent applications of colloidal probes for the study of membrane fusion. After discussing the advantages and disadvantages of some classical vesicle-based fusion assays, we introduce an assay using optical detection of fusion between membrane-coated glass microspheres in a quasi two-dimensional assembly. Then, we discuss free energy considerations of membrane fusion between supported bilayers, and show how colloidal probes can be combined with atomic force microscopy or optical tweezers to access the fusion process with even greater detail.
Collapse
Affiliation(s)
- Hannes Witt
- Institute for Physical Chemistry, University of Göttingen, 37075, Göttingen, Germany.,Physics of Living Systems, Vrije Universiteit Amsterdam, 1081 HV, Amsterdam, The Netherlands
| | - Filip Savić
- Institute for Physical Chemistry, University of Göttingen, 37075, Göttingen, Germany
| | - Sarah Verbeek
- Institute for Physical Chemistry, University of Göttingen, 37075, Göttingen, Germany
| | - Jörn Dietz
- Institute for Physical Chemistry, University of Göttingen, 37075, Göttingen, Germany
| | - Gesa Tarantola
- Institute for Physical Chemistry, University of Göttingen, 37075, Göttingen, Germany
| | - Marieelen Oelkers
- Institute for Physical Chemistry, University of Göttingen, 37075, Göttingen, Germany
| | - Burkhard Geil
- Institute for Physical Chemistry, University of Göttingen, 37075, Göttingen, Germany
| | - Andreas Janshoff
- Institute for Physical Chemistry, University of Göttingen, 37075, Göttingen, Germany.
| |
Collapse
|
27
|
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.
Collapse
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
| |
Collapse
|
28
|
Risselada HJ, Grubmüller H. How proteins open fusion pores: insights from molecular simulations. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2020; 50:279-293. [PMID: 33340336 PMCID: PMC8071795 DOI: 10.1007/s00249-020-01484-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 11/16/2020] [Accepted: 11/24/2020] [Indexed: 02/06/2023]
Abstract
Fusion proteins can play a versatile and involved role during all stages of the fusion reaction. Their roles go far beyond forcing the opposing membranes into close proximity to drive stalk formation and fusion. Molecular simulations have played a central role in providing a molecular understanding of how fusion proteins actively overcome the free energy barriers of the fusion reaction up to the expansion of the fusion pore. Unexpectedly, molecular simulations have revealed a preference of the biological fusion reaction to proceed through asymmetric pathways resulting in the formation of, e.g., a stalk-hole complex, rim-pore, or vertex pore. Force-field based molecular simulations are now able to directly resolve the minimum free-energy path in protein-mediated fusion as well as quantifying the free energies of formed reaction intermediates. Ongoing developments in Graphics Processing Units (GPUs), free energy calculations, and coarse-grained force-fields will soon gain additional insights into the diverse roles of fusion proteins.
Collapse
Affiliation(s)
- H Jelger Risselada
- Department of Theoretical Physics, Georg-August University of Göttingen, Göttingen, Germany. .,Leiden University, Leiden Institute of Chemistry (LIC), Leiden, The Netherlands.
| | - Helmut Grubmüller
- Max Planck Institute for Biophysical Chemistry, Theoretical and Computational Biophysics Department, Göttingen, Germany
| |
Collapse
|
29
|
Bubnis G, Grubmüller H. Sequential Water and Headgroup Merger: Membrane Poration Paths and Energetics from MD Simulations. Biophys J 2020; 119:2418-2430. [PMID: 33189685 PMCID: PMC7822740 DOI: 10.1016/j.bpj.2020.10.037] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 10/07/2020] [Accepted: 10/23/2020] [Indexed: 01/06/2023] Open
Abstract
Membrane topology changes such as poration, stalk formation, and hemifusion rupture are essential to cellular function, but their molecular details, energetics, and kinetics are still not fully understood. Here, we present a unified energetic and mechanistic picture of metastable pore defects in tensionless lipid membranes. We used an exhaustive committor analysis to test and select optimal reaction coordinates and also to determine the nucleation mechanism. These reaction coordinates were used to calculate free-energy landscapes that capture the full process and end states. The identified barriers agree with the committor analysis. To enable sufficient sampling of the complete transition path for our molecular dynamics simulations, we developed a “gizmo” potential biasing scheme. The simulations suggest that the essential step in the nucleation is the initial merger of lipid headgroups at the nascent pore center. To facilitate this event, an indentation pathway is energetically preferred to a hydrophobic defect. Continuous water columns that span the indentation were determined to be on-path transients that precede the nucleation barrier. This study gives a quantitative description of the nucleation mechanism and energetics of small metastable pores and illustrates a systematic approach to uncover the mechanisms of diverse cellular membrane remodeling processes.
Collapse
Affiliation(s)
- Greg Bubnis
- Department of Theoretical and Computational Biophysics, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; Weill Institute for Neurosciences and Department of Neurology, University of California San Francisco, San Francisco, California.
| | - Helmut Grubmüller
- Department of Theoretical and Computational Biophysics, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
| |
Collapse
|
30
|
Endter LJ, Smirnova Y, Risselada HJ. Density Field Thermodynamic Integration (DFTI): A "Soft" Approach to Calculate the Free Energy of Surfactant Self-Assemblies. J Phys Chem B 2020; 124:6775-6785. [PMID: 32631061 DOI: 10.1021/acs.jpcb.0c03982] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thermodynamic integration is one of the most established methods to quantify excess free energies between different metastable states. Excess intermolecular interactions in surfactant assemblies are on the scale of the energy of thermal fluctuations. Therefore, these materials can be deformed and topologically altered via relatively small mechanical stresses. It is thus intuitive to design reaction paths and associated order parameters that exploit the "soft" nature of these materials to mechanically rather than alchemically morph surfactant assemblies from state to state. Here, we propose a novel method coined "density field thermodynamic integration" (DFTI) that adopts the universality and transferability of alchemical methods while simultaneously exploiting the soft excess interactions between surfactant molecules. DFTI was designed for a rapid quantification of the free energy differences between different metastable structures in soft fluid materials. The DFTI method uses an external field coupled to the local density to mechanically morph the system between metastable states of interest. Here, we explored the capability of the DFTI method to swiftly and accurately calculate free energy differences between states. To this aim, we studied two different coarse-grained lipidic surfactant systems: (i) a fusion stalk and (ii) a worm-like micelle. Our results illustrate that DFTI can provide an efficient, versatile, and rather reliable method to calculate the free energy differences between surfactant assemblies.
Collapse
Affiliation(s)
- Laura Josefine Endter
- Institute for Theoretical Physics, Georg-August University, 37077 Göttingen, Germany
| | - Yuliya Smirnova
- Institute for Theoretical Physics, Georg-August University, 37077 Göttingen, Germany
| | - Herre Jelger Risselada
- Institute for Theoretical Physics, Georg-August University, 37077 Göttingen, Germany.,Leiden Institute of Chemistry (LIC), University of Leiden, 2311 Leiden,The Netherlands.,Chemical Deptartment, Leibniz Institute of Surface Modifications, 04318 Leipzig, Germany
| |
Collapse
|
31
|
Calcium-triggered fusion of lipid membranes is enabled by amphiphilic nanoparticles. Proc Natl Acad Sci U S A 2020; 117:18470-18476. [PMID: 32690682 DOI: 10.1073/pnas.1902597117] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Lipid membrane fusion is an essential process for a number of critical biological functions. The overall process is thermodynamically favorable but faces multiple kinetic barriers along the way. Inspired by nature's engineered proteins such as SNAP receptor [soluble N-ethylmale-imide-sensitive factor-attachment protein receptor (SNARE)] complexes or viral fusogenic proteins that actively promote the development of membrane proximity, nucleation of a stalk, and triggered expansion of the fusion pore, here we introduce a synthetic fusogen that can modulate membrane fusion and equivalently prime lipid membranes for calcium-triggered fusion. Our fusogen consists of a gold nanoparticle functionalized with an amphiphilic monolayer of alkanethiol ligands that had previously been shown to fuse with lipid bilayers. While previous efforts to develop synthetic fusogens have only replicated the initial steps of the fusion cascade, we use molecular simulations and complementary experimental techniques to demonstrate that these nanoparticles can induce the formation of a lipid stalk and also drive its expansion into a fusion pore upon the addition of excess calcium. These results have important implications in general understanding of stimuli-triggered fusion and the development of synthetic fusogens for biomedical applications.
Collapse
|
32
|
SNAREs, tethers and SM proteins: how to overcome the final barriers to membrane fusion? Biochem J 2020; 477:243-258. [PMID: 31951000 DOI: 10.1042/bcj20190050] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 12/04/2019] [Accepted: 12/16/2019] [Indexed: 12/18/2022]
Abstract
Physiological membrane vesicles are built to separate reaction spaces in a stable manner, even when they accidentally collide or are kept in apposition by spatial constraints in the cell. This requires a natural resistance to fusion and mixing of their content, which originates from substantial energetic barriers to membrane fusion [1]. To facilitate intracellular membrane fusion reactions in a controlled manner, proteinaceous fusion machineries have evolved. An important open question is whether protein fusion machineries actively pull the fusion reaction over the present free energy barriers, or whether they rather catalyze fusion by lowering those barriers. At first sight, fusion proteins such as SNARE complexes and viral fusion proteins appear to act as nano-machines, which mechanically transduce force to the membranes and thereby overcome the free energy barriers [2,3]. Whether fusion proteins additionally alter the free energy landscape of the fusion reaction via catalytic roles is less obvious. This is a question that we shall discuss in this review, with particular focus on the influence of the eukaryotic SNARE-dependent fusion machinery on the final step of the reaction, the formation and expansion of the fusion pore.
Collapse
|
33
|
Akimov SA, Molotkovsky RJ, Kuzmin PI, Galimzyanov TR, Batishchev OV. Continuum Models of Membrane Fusion: Evolution of the Theory. Int J Mol Sci 2020; 21:E3875. [PMID: 32485905 PMCID: PMC7312925 DOI: 10.3390/ijms21113875] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 05/24/2020] [Accepted: 05/27/2020] [Indexed: 12/18/2022] Open
Abstract
Starting from fertilization, through tissue growth, hormone secretion, synaptic transmission, and sometimes morbid events of carcinogenesis and viral infections, membrane fusion regulates the whole life of high organisms. Despite that, a lot of fusion processes still lack well-established models and even a list of main actors. A merger of membranes requires their topological rearrangements controlled by elastic properties of a lipid bilayer. That is why continuum models based on theories of membrane elasticity are actively applied for the construction of physical models of membrane fusion. Started from the view on the membrane as a structureless film with postulated geometry of fusion intermediates, they developed along with experimental and computational techniques to a powerful tool for prediction of the whole process with molecular accuracy. In the present review, focusing on fusion processes occurring in eukaryotic cells, we scrutinize the history of these models, their evolution and complication, as well as open questions and remaining theoretical problems. We show that modern approaches in this field allow continuum models of membrane fusion to stand shoulder to shoulder with molecular dynamics simulations, and provide the deepest understanding of this process in multiple biological systems.
Collapse
Affiliation(s)
- Sergey A. Akimov
- Laboratory of Bioelectrochemistry, A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31/4 Leninskiy Prospekt, 119071 Moscow, Russia; (R.J.M.); (P.I.K.); (T.R.G.); (O.V.B.)
| | | | | | | | | |
Collapse
|
34
|
Benhaim MA, Lee KK. New Biophysical Approaches Reveal the Dynamics and Mechanics of Type I Viral Fusion Machinery and Their Interplay with Membranes. Viruses 2020; 12:E413. [PMID: 32276357 PMCID: PMC7232462 DOI: 10.3390/v12040413] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 04/04/2020] [Accepted: 04/04/2020] [Indexed: 12/27/2022] Open
Abstract
Protein-mediated membrane fusion is a highly regulated biological process essential for cellular and organismal functions and infection by enveloped viruses. During viral entry the membrane fusion reaction is catalyzed by specialized protein machinery on the viral surface. These viral fusion proteins undergo a series of dramatic structural changes during membrane fusion where they engage, remodel, and ultimately fuse with the host membrane. The structural and dynamic nature of these conformational changes and their impact on the membranes have long-eluded characterization. Recent advances in structural and biophysical methodologies have enabled researchers to directly observe viral fusion proteins as they carry out their functions during membrane fusion. Here we review the structure and function of type I viral fusion proteins and mechanisms of protein-mediated membrane fusion. We highlight how recent technological advances and new biophysical approaches are providing unprecedented new insight into the membrane fusion reaction.
Collapse
Affiliation(s)
- Mark A. Benhaim
- Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195-7610, USA;
| | - Kelly K. Lee
- Department of Medicinal Chemistry, University of Washington, Seattle, WA 98195-7610, USA;
- Biological Physics Structure and Design Program, University of Washington, Seattle, WA 98195-7610, USA
| |
Collapse
|
35
|
Influenza hemagglutinin drives viral entry via two sequential intramembrane mechanisms. Proc Natl Acad Sci U S A 2020; 117:7200-7207. [PMID: 32188780 DOI: 10.1073/pnas.1914188117] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Enveloped viruses enter cells via a process of membrane fusion between the viral envelope and a cellular membrane. For influenza virus, mutational data have shown that the membrane-inserted portions of the hemagglutinin protein play a critical role in achieving fusion. In contrast to the relatively well-understood ectodomain, a predictive mechanistic understanding of the intramembrane mechanisms by which influenza hemagglutinin drives fusion has been elusive. We used molecular dynamics simulations of fusion between a full-length hemagglutinin proteoliposome and a lipid bilayer to analyze these mechanisms. In our simulations, hemagglutinin first acts within the membrane to increase lipid tail protrusion and promote stalk formation and then acts to engage the distal leaflets of each membrane and promote stalk widening, curvature, and eventual fusion. These two sequential mechanisms, one occurring before stalk formation and one after, are consistent with our experimental measurements of single-virus fusion kinetics to liposomes of different sizes. The resulting model also helps explain and integrate previous mutational and biophysical data, particularly the mutational sensitivity of the fusion peptide N terminus and the length sensitivity of the transmembrane domain. We hypothesize that entry by other enveloped viruses may also use sequential processes of acyl tail exposure, followed by membrane curvature and distal leaflet engagement.
Collapse
|
36
|
Kabelka I, Pachler M, Prévost S, Letofsky-Papst I, Lohner K, Pabst G, Vácha R. Magainin 2 and PGLa in Bacterial Membrane Mimics II: Membrane Fusion and Sponge Phase Formation. Biophys J 2019; 118:612-623. [PMID: 31952806 DOI: 10.1016/j.bpj.2019.12.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 12/06/2019] [Accepted: 12/16/2019] [Indexed: 12/23/2022] Open
Abstract
We studied the synergistic mechanism of equimolar mixtures of magainin 2 (MG2a) and PGLa in phosphatidylethanolamine/phosphatidylglycerol mimics of Gram-negative cytoplasmic membranes. In a preceding article of this series, we reported on the early onset of parallel heterodimer formation of the two antimicrobial peptides already at low concentrations and the resulting defect formation in the membranes. Here, we focus on the structures of the peptide-lipid aggregates occurring in the synergistic regime at elevated peptide concentrations. Using a combination of calorimetric, scattering, electron microscopic, and in silico techniques, we demonstrate that the two peptides, even if applied individually, transform originally large unilamellar vesicles into multilamellar vesicles with a collapsed interbilayer spacing resulting from peptide-induced adhesion. Interestingly, the adhesion does not lead to a peptide-induced lipid separation of charged and charge-neutral species. In addition to this behavior, equimolar mixtures of MG2a and PGLa formed surface-aligned fibril-like structures, which induced adhesion zones between the membranes and the formation of transient fusion stalks in molecular dynamics simulations and a coexisting sponge phase observed by small-angle x-ray scattering. The previously reported increased leakage of lipid vesicles of identical composition in the presence of MG2a/PGLa mixtures is therefore related to a peptide-induced cross-linking of bilayers.
Collapse
Affiliation(s)
- Ivo Kabelka
- CEITEC-Central European Institute of Technology, Brno, Czech Republic; National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Michael Pachler
- Biophysics Division, Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria; BioTechMed Graz, Graz, Austria
| | | | - Ilse Letofsky-Papst
- Institute for Electron Microscopy and Nanoanalysis and Center for Electron Microscopy, Graz University of Technology, Graz, Austria
| | - Karl Lohner
- Biophysics Division, Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria; BioTechMed Graz, Graz, Austria
| | - Georg Pabst
- Biophysics Division, Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria; BioTechMed Graz, Graz, Austria
| | - Robert Vácha
- CEITEC-Central European Institute of Technology, Brno, Czech Republic; National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czech Republic; Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Brno, Czech Republic.
| |
Collapse
|
37
|
Peruzzi JA, Jacobs ML, Vu TQ, Wang KS, Kamat NP. Barcoding Biological Reactions with DNA-Functionalized Vesicles. Angew Chem Int Ed Engl 2019; 58:18683-18690. [PMID: 31596992 PMCID: PMC6901749 DOI: 10.1002/anie.201911544] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Indexed: 11/08/2022]
Abstract
Targeted vesicle fusion is a promising approach to selectively control interactions between vesicle compartments and would enable the initiation of biological reactions in complex aqueous environments. Here, we explore how two features of vesicle membranes, DNA tethers and phase-segregated membranes, promote fusion between specific vesicle populations. Membrane phase-segregation provides an energetic driver for membrane fusion that increases the efficiency of DNA-mediated fusion events. The orthogonality provided by DNA tethers allows us to direct fusion and delivery of DNA cargo to specific vesicle populations. Vesicle fusion between DNA-tethered vesicles can be used to initiate in vitro protein expression to produce model soluble and membrane proteins. Engineering orthogonal fusion events between DNA-tethered vesicles provides a new strategy to control the spatiotemporal dynamics of cell-free reactions, expanding opportunities to engineer artificial cellular systems.
Collapse
Affiliation(s)
- Justin A Peruzzi
- Department of Chemical and Biological Engineering, Northwestern University, USA
| | - Miranda L Jacobs
- Department of Biomedical Engineering, Northwestern University, McCormick School of Engineering, Technological Institute, 2145 Sheridan Road, Evanston, Il, 60208, USA
| | - Timothy Q Vu
- Department of Biomedical Engineering, Northwestern University, McCormick School of Engineering, Technological Institute, 2145 Sheridan Road, Evanston, Il, 60208, USA
| | - Kenneth S Wang
- Department of Biomedical Engineering, Northwestern University, McCormick School of Engineering, Technological Institute, 2145 Sheridan Road, Evanston, Il, 60208, USA
| | - Neha P Kamat
- Department of Biomedical Engineering, Northwestern University, McCormick School of Engineering, Technological Institute, 2145 Sheridan Road, Evanston, Il, 60208, USA
- Center for Synthetic Biology, Northwestern University, USA
- Chemistry of Life Processes Institute, Northwestern University, USA
| |
Collapse
|
38
|
Peruzzi JA, Jacobs ML, Vu TQ, Wang KS, Kamat NP. Barcoding Biological Reactions with DNA‐Functionalized Vesicles. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201911544] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Justin A. Peruzzi
- Department of Chemical and Biological Engineering Northwestern University USA
| | - Miranda L. Jacobs
- Department of Biomedical Engineering Northwestern University McCormick School of Engineering Technological Institute 2145 Sheridan Road Evanston Il 60208 USA
| | - Timothy Q. Vu
- Department of Biomedical Engineering Northwestern University McCormick School of Engineering Technological Institute 2145 Sheridan Road Evanston Il 60208 USA
| | - Kenneth S. Wang
- Department of Biomedical Engineering Northwestern University McCormick School of Engineering Technological Institute 2145 Sheridan Road Evanston Il 60208 USA
| | - Neha P. Kamat
- Department of Biomedical Engineering Northwestern University McCormick School of Engineering Technological Institute 2145 Sheridan Road Evanston Il 60208 USA
- Center for Synthetic Biology Northwestern University USA
- Chemistry of Life Processes Institute Northwestern University USA
| |
Collapse
|
39
|
Reid LM, Verma CS, Essex JW. The role of molecular simulations in understanding the mechanisms of cell-penetrating peptides. Drug Discov Today 2019; 24:1821-1835. [DOI: 10.1016/j.drudis.2019.06.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 05/12/2019] [Accepted: 06/17/2019] [Indexed: 01/06/2023]
|
40
|
Abstract
Many bacterial species contain dynamin-like proteins (DLPs). However, so far the functional mechanisms of bacterial DLPs are poorly understood. DynA in Bacillus subtilis is a 2-headed DLP, mediating nucleotide-independent membrane tethering in vitro and contributing to the innate immunity of bacteria against membrane stress and phage infection. Here, we employed content mixing and lipid mixing assays in reconstituted systems to study if DynA induces membrane full fusion, characterize its subunits in membrane fusion, and further test the possibility that GTP hydrolysis of DynA may act on the fusion-through-hemifusion pathway. Our results based on fluorescence resonance energy transfer indicated that DynA could induce aqueous content mixing even in the absence of GTP. Moreover, DynA-induced membrane fusion in vitro is a thermo-promoted slow process, and it has phospholipid and membrane curvature preferences. The D1 part of DynA is crucial for membrane binding and fusion, whereas D2 subunit plays a role in facilitating membrane fusion. Surprisingly, digestion of DynA mediated an instant rise of content exchange, supporting the assumption that disassembly of DynA is a driving force for fusion-through-hemifusion. DynA is a rare example of a membrane fusion catalyst that lacks a transmembrane domain and hence sets this system apart from well-characterized fusion systems such as the soluble N-ethyl maleimide sensitive factor attachment protein receptor complexes.-Guo, L., Bramkamp, M. Bacterial dynamin-like protein DynA mediates lipid and content mixing.
Collapse
Affiliation(s)
- Lijun Guo
- Ludwig-Maximilians-Universität München, Fakultät Biologie, Planegg-Martinsried, Germany
| | - Marc Bramkamp
- Ludwig-Maximilians-Universität München, Fakultät Biologie, Planegg-Martinsried, Germany
| |
Collapse
|
41
|
Risselada HJ. Cholesterol: The Plasma Membrane's Constituent that Chooses Sides. Biophys J 2019; 116:2235-2236. [PMID: 31103232 DOI: 10.1016/j.bpj.2019.05.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 04/26/2019] [Accepted: 05/01/2019] [Indexed: 11/18/2022] Open
Affiliation(s)
- Herre Jelger Risselada
- Georg-August University, Institute for Theoretical Physics, Göttingen, Germany; Leiden University, Leiden Institute of Chemistry, Leiden, The Netherlands; Leibniz Institute for Surface Modifications, Leipzig, Germany.
| |
Collapse
|
42
|
Lu T, Guo H. How the Membranes Fuse: From Spontaneous to Induced. ADVANCED THEORY AND SIMULATIONS 2019. [DOI: 10.1002/adts.201900032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Teng Lu
- Beijing National Laboratory for Molecular SciencesJoint Laboratory of Polymer Sciences and MaterialsState Key Laboratory of Polymer Physics and ChemistryInstitute of Chemistry, Chinese Academy of Sciences Beijing 100190 China
| | - Hongxia Guo
- Beijing National Laboratory for Molecular SciencesJoint Laboratory of Polymer Sciences and MaterialsState Key Laboratory of Polymer Physics and ChemistryInstitute of Chemistry, Chinese Academy of Sciences Beijing 100190 China
- Division of Polymer Science and MaterialsSchool of Chemical SciencesUniversity of Chinese Academy of Sciences Beijing 100049 China
| |
Collapse
|
43
|
Marrink SJ, Corradi V, Souza PC, Ingólfsson HI, Tieleman DP, Sansom MS. Computational Modeling of Realistic Cell Membranes. Chem Rev 2019; 119:6184-6226. [PMID: 30623647 PMCID: PMC6509646 DOI: 10.1021/acs.chemrev.8b00460] [Citation(s) in RCA: 408] [Impact Index Per Article: 81.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Indexed: 12/15/2022]
Abstract
Cell membranes contain a large variety of lipid types and are crowded with proteins, endowing them with the plasticity needed to fulfill their key roles in cell functioning. The compositional complexity of cellular membranes gives rise to a heterogeneous lateral organization, which is still poorly understood. Computational models, in particular molecular dynamics simulations and related techniques, have provided important insight into the organizational principles of cell membranes over the past decades. Now, we are witnessing a transition from simulations of simpler membrane models to multicomponent systems, culminating in realistic models of an increasing variety of cell types and organelles. Here, we review the state of the art in the field of realistic membrane simulations and discuss the current limitations and challenges ahead.
Collapse
Affiliation(s)
- Siewert J. Marrink
- Groningen
Biomolecular Sciences and Biotechnology Institute & Zernike Institute
for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Valentina Corradi
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Paulo C.T. Souza
- Groningen
Biomolecular Sciences and Biotechnology Institute & Zernike Institute
for Advanced Materials, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Helgi I. Ingólfsson
- Biosciences
and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States
| | - D. Peter Tieleman
- Centre
for Molecular Simulation and Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada
| | - Mark S.P. Sansom
- Department
of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
| |
Collapse
|
44
|
Shaaban A, Dhara M, Frisch W, Harb A, Shaib AH, Becherer U, Bruns D, Mohrmann R. The SNAP-25 linker supports fusion intermediates by local lipid interactions. eLife 2019; 8:41720. [PMID: 30883328 PMCID: PMC6422494 DOI: 10.7554/elife.41720] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 03/05/2019] [Indexed: 12/22/2022] Open
Abstract
SNAP-25 is an essential component of SNARE complexes driving fast Ca2+-dependent exocytosis. Yet, the functional implications of the tandem-like structure of SNAP-25 are unclear. Here, we have investigated the mechanistic role of the acylated “linker” domain that concatenates the two SNARE motifs within SNAP-25. Refuting older concepts of an inert connector, our detailed structure-function analysis in murine chromaffin cells demonstrates that linker motifs play a crucial role in vesicle priming, triggering, and fusion pore expansion. Mechanistically, we identify two synergistic functions of the SNAP-25 linker: First, linker motifs support t-SNARE interactions and accelerate ternary complex assembly. Second, the acylated N-terminal linker segment engages in local lipid interactions that facilitate fusion triggering and pore evolution, putatively establishing a favorable membrane configuration by shielding phospholipid headgroups and affecting curvature. Hence, the linker is a functional part of the fusion complex that promotes secretion by SNARE interactions as well as concerted lipid interplay.
Collapse
Affiliation(s)
- Ahmed Shaaban
- ZHMB, Saarland University, Homburg, Germany.,Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Madhurima Dhara
- Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Walentina Frisch
- Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Ali Harb
- ZHMB, Saarland University, Homburg, Germany
| | - Ali H Shaib
- Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Ute Becherer
- Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Dieter Bruns
- Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Ralf Mohrmann
- ZHMB, Saarland University, Homburg, Germany.,Institute for Physiology, Otto-von-Guericke University, Magdeburg, Germany.,Center for Behavioral Brain Science, Otto-von-Guericke University, Magdeburg, Germany
| |
Collapse
|
45
|
Santiago R, Reigada R. Interaction modes between nanosized graphene flakes and liposomes: Adsorption, insertion and membrane fusion. Biochim Biophys Acta Gen Subj 2019; 1863:723-731. [PMID: 30716365 DOI: 10.1016/j.bbagen.2019.01.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 01/14/2019] [Accepted: 01/29/2019] [Indexed: 12/15/2022]
Abstract
BACKGROUND Understanding the effects of graphene-based nanomaterials on lipid membranes is critical to determine their environmental impact and their efficiency in the biomedical context. Graphene has been reported to favourably interact with biological and model lipid membranes. METHODS We report on a systematic coarse-grained molecular dynamics study of the interaction modes of graphene nanometric flakes with POPC/cholesterol liposome membranes. We have simulated graphene layers with a variety of sizes and oxidation degrees, and we have analyzed the trajectories, the interaction modes, and the energetics of the observed phenomena. RESULTS Three interaction modes are reported. Graphene can be transiently adsorbed onto the liposome membrane and/or inserted in its hydrophobic region. Inserted nanosheets prefer a perpendicular orientation, and tilt in order to maximize the contact with phospholipid tails while avoiding the contact with cholesterol molecules. When placed between two liposomes, graphene facilitates their fusion in a single vesicle. CONCLUSIONS Graphene can be temporary adsorbed on the liposome before insertion. Bilayer curvature has an influence on the orientation of inserted graphene particles. Cholesterol molecules are depleted from the surrounding of graphene particles. Graphene layers may catalyse membrane fusion by bypassing the energy barrier required in stalk formation. GENERAL SIGNIFICANCE Nanometric graphene layers can be adsorbed/inserted in lipid-based membranes in different manners and affect the cholesterol distribution in the membrane, implying important consequences on the structure and functionality of biological cell membranes, and on the bioaccumulation of graphene in living organisms. The graphene-mediated mechanism opens new possibilities for vesicle fusion in the experimental context.
Collapse
Affiliation(s)
- Raul Santiago
- Department de Ciència dels Materials i Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Barcelona, Spain
| | - Ramon Reigada
- Department de Ciència dels Materials i Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Barcelona, Spain.
| |
Collapse
|
46
|
Thermodynamically reversible paths of the first fusion intermediate reveal an important role for membrane anchors of fusion proteins. Proc Natl Acad Sci U S A 2019; 116:2571-2576. [PMID: 30700547 DOI: 10.1073/pnas.1818200116] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Biological membrane fusion proceeds via an essential topological transition of the two membranes involved. Known players such as certain lipid species and fusion proteins are generally believed to alter the free energy and thus the rate of the fusion reaction. Quantifying these effects by theory poses a major challenge since the essential reaction intermediates are collective, diffusive and of a molecular length scale. We conducted molecular dynamics simulations in conjunction with a state-of-the-art string method to resolve the minimum free-energy path of the first fusion intermediate state, the so-called stalk. We demonstrate that the isolated transmembrane domains (TMDs) of fusion proteins such as SNARE molecules drastically lower the free energy of both the stalk barrier and metastable stalk, which is not trivially explained by molecular shape arguments. We relate this effect to the local thinning of the membrane (negative hydrophobic mismatch) imposed by the TMDs which favors the nearby presence of the highly bent stalk structure or prestalk dimple. The distance between the membranes is the most crucial determinant of the free energy of the stalk, whereas the free-energy barrier changes only slightly. Surprisingly, fusion enhancing lipids, i.e., lipids with a negative spontaneous curvature, such as PE lipids have little effect on the free energy of the stalk barrier, likely because of its single molecular nature. In contrast, the lipid shape plays a crucial role in overcoming the hydration repulsion between two membranes and thus rather lowers the total work required to form a stalk.
Collapse
|
47
|
Jefferys EE, Sansom MSP. Computational Virology: Molecular Simulations of Virus Dynamics and Interactions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1215:201-233. [DOI: 10.1007/978-3-030-14741-9_10] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
|
48
|
Mattie S, Kazmirchuk T, Mui J, Vali H, Brett CL. Visualization of SNARE-Mediated Organelle Membrane Hemifusion by Electron Microscopy. Methods Mol Biol 2019; 1860:361-377. [PMID: 30317518 DOI: 10.1007/978-1-4939-8760-3_24] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
SNARE-mediated membrane fusion is required for membrane trafficking as well as organelle biogenesis and homeostasis. The membrane fusion reaction involves sequential formation of hemifusion intermediates, whereby lipid monolayers partially mix on route to complete bilayer merger. Studies of the Saccharomyces cerevisiae lysosomal vacuole have revealed many of the fundamental mechanisms that drive the membrane fusion process, as well as features unique to organelle fusion. However, until recently, it has not been amenable to electron microscopy methods that have been invaluable for studying hemifusion in other model systems. Herein, we describe a method to visualize hemifusion intermediates during homotypic vacuole membrane fusion in vitro by transmission electron microscopy (TEM), electron tomography, and cryogenic electron microscopy (cryoEM). This method facilitates acquisition of invaluable ultrastructural data needed to comprehensively understand how fusogenic lipids and proteins contribute to SNARE-mediated membrane fusion-by-hemifusion and the unique features of organelle versus small-vesicle fusion.
Collapse
Affiliation(s)
- Sevan Mattie
- Department of Biology, Concordia University, Montréal, QC, Canada.,Montreal Neurological Hospital and Institute, McGill University, Montréal, QC, Canada
| | - Tom Kazmirchuk
- Department of Biology, Concordia University, Montréal, QC, Canada
| | - Jeannie Mui
- Facility for Electron Microscopy Research, Department of Anatomy and Cell Biology, McGill University, Montréal, QC, Canada
| | - Hojatollah Vali
- Facility for Electron Microscopy Research, Department of Anatomy and Cell Biology, McGill University, Montréal, QC, Canada
| | | |
Collapse
|
49
|
Molecular mechanism of fusion pore formation driven by the neuronal SNARE complex. Proc Natl Acad Sci U S A 2018; 115:12751-12756. [PMID: 30482862 DOI: 10.1073/pnas.1816495115] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Release of neurotransmitters from synaptic vesicles begins with a narrow fusion pore, the structure of which remains unresolved. To obtain a structural model of the fusion pore, we performed coarse-grained molecular dynamics simulations of fusion between a nanodisc and a planar bilayer bridged by four partially unzipped SNARE complexes. The simulations revealed that zipping of SNARE complexes pulls the polar C-terminal residues of the synaptobrevin 2 and syntaxin 1A transmembrane domains to form a hydrophilic core between the two distal leaflets, inducing fusion pore formation. The estimated conductances of these fusion pores are in good agreement with experimental values. Two SNARE protein mutants inhibiting fusion experimentally produced no fusion pore formation. In simulations in which the nanodisc was replaced by a 40-nm vesicle, an extended hemifusion diaphragm formed but a fusion pore did not, indicating that restricted SNARE mobility is required for rapid fusion pore formation. Accordingly, rapid fusion pore formation also occurred in the 40-nm vesicle system when SNARE mobility was restricted by external forces. Removal of the restriction is required for fusion pore expansion.
Collapse
|
50
|
Chanaday NL, Kavalali ET. Time course and temperature dependence of synaptic vesicle endocytosis. FEBS Lett 2018; 592:3606-3614. [DOI: 10.1002/1873-3468.13268] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 10/02/2018] [Accepted: 10/06/2018] [Indexed: 11/07/2022]
Affiliation(s)
- Natali L. Chanaday
- Department of Pharmacology; Vanderbilt Brain Institute; Vanderbilt University; Nashville TN USA
| | - Ege T. Kavalali
- Department of Pharmacology; Vanderbilt Brain Institute; Vanderbilt University; Nashville TN USA
| |
Collapse
|