1
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Wang S, Ma C. A practical guide for fast implementation of SNARE-mediated liposome fusion. BIOPHYSICS REPORTS 2024; 10:31-40. [PMID: 38737475 PMCID: PMC11079601 DOI: 10.52601/bpr.2023.230017] [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] [Received: 10/08/2023] [Accepted: 12/28/2023] [Indexed: 05/14/2024] Open
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNAER) family proteins are the engines of most intra-cellular and exocytotic membrane fusion pathways (Jahn and Scheller 2006). Over the past two decades, in-vitro liposome fusion has been proven to be a powerful tool to reconstruct physiological SNARE-mediated membrane fusion processes (Liu et al. 2017). The reconstitution of the membrane fusion process not only provides direct evidence of the capability of the cognate SNARE complex in driving membrane fusion but also allows researchers to study the functional mechanisms of regulatory proteins in related pathways (Wickner and Rizo 2017). Heretofore, a variety of delicate methods for in-vitro SNARE-mediated liposome fusion have been established (Bao et al. 2018; Diao et al. 2012; Duzgunes 2003; Gong et al. 2015; Heo et al. 2021; Kiessling et al. 2015; Kreye et al. 2008; Kyoung et al. 2013; Liu et al. 2017; Scott et al. 2003). Although technological advances have made reconstitution more physiologically relevant, increasingly elaborate experimental procedures, instruments, and data processing algorithms nevertheless hinder the non-experts from setting up basic SNARE-mediated liposome fusion assays. Here, we describe a low-cost, timesaving, and easy-to-handle protocol to set up a foundational in-vitro SNARE-mediated liposome fusion assay based on our previous publications (Liu et al. 2023; Wang and Ma 2022). The protocol can be readily adapted to assess various types of SNARE-mediated membrane fusion and the actions of fusion regulators by using appropriate alternative additives (e.g., proteins, macromolecules, chemicals, etc.). The total time required for one round of the assay is typically two days and could be extremely compressed into one day.
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Affiliation(s)
- Shen Wang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Cong Ma
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
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2
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Herianto S, Chien PJ, Ho JAA, Tu HL. Liposome-based artificial cells: From gene expression to reconstitution of cellular functions and phenotypes. BIOMATERIALS ADVANCES 2022; 142:213156. [PMID: 36302330 DOI: 10.1016/j.bioadv.2022.213156] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Accepted: 10/12/2022] [Indexed: 06/16/2023]
Abstract
Bottom-up approaches in creating artificial cells that can mimic natural cells have significant implications for both basic research and translational application. Among various artificial cell models, liposome is one of the most sophisticated systems. By encapsulating proteins and associated biomolecules, they can functionally reconstitute foundational features of biological cells, such as the ability to divide, communicate, and undergo shape deformation. Yet constructing liposome artificial cells from the genetic level, which is central to generate self-sustained systems remains highly challenging. Indeed, many studies have successfully established the expression of gene-coded proteins inside liposomes. Further, recent endeavors to build a direct integration of gene-expressed proteins for reconstituting molecular functions and phenotypes in liposomes have also significantly increased. Thus, this review presents the development of liposome-based artificial cells to demonstrate the process of gene-expressed proteins and their reconstitution to perform desired molecular and cell-like functions. The molecular and cellular phenotypes discussed here include the self-production of membrane phospholipids, division, shape deformation, self-DNA/RNA replication, fusion, and intercellular communication. Together, this review gives a comprehensive overview of gene-expressing liposomes that can stimulate further research of this technology and achieve artificial cells with superior properties in the future.
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Affiliation(s)
- Samuel Herianto
- Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan; Chemical Biology and Molecular Biophysics, Taiwan International Graduate Program, Academia Sinica, Taipei 11529, Taiwan; Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | - Po-Jen Chien
- Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan
| | - Ja-An Annie Ho
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan; BioAnalytical Chemistry and Nanobiomedicine Laboratory, Department of Biochemical Science and Technology, National Taiwan University, Taipei 10617, Taiwan
| | - Hsiung-Lin Tu
- Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan; Chemical Biology and Molecular Biophysics, Taiwan International Graduate Program, Academia Sinica, Taipei 11529, Taiwan.
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3
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Abou Karam P, Rosenhek‐Goldian I, Ziv T, Ben Ami Pilo H, Azuri I, Rivkin A, Kiper E, Rotkopf R, Cohen SR, Torrecilhas AC, Avinoam O, Rojas A, Morandi MI, Regev‐Rudzki N. Malaria parasites release vesicle subpopulations with signatures of different destinations. EMBO Rep 2022; 23:e54755. [PMID: 35642585 PMCID: PMC9253735 DOI: 10.15252/embr.202254755] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 05/02/2022] [Accepted: 05/11/2022] [Indexed: 11/09/2022] Open
Abstract
Malaria is the most serious mosquito-borne parasitic disease, caused mainly by the intracellular parasite Plasmodium falciparum. The parasite invades human red blood cells and releases extracellular vesicles (EVs) to alter its host responses. It becomes clear that EVs are generally composed of sub-populations. Seeking to identify EV subpopulations, we subject malaria-derived EVs to size-separation analysis, using asymmetric flow field-flow fractionation. Multi-technique analysis reveals surprising characteristics: we identify two distinct EV subpopulations differing in size and protein content. Small EVs are enriched in complement-system proteins and large EVs in proteasome subunits. We then measure the membrane fusion abilities of each subpopulation with three types of host cellular membranes: plasma, late and early endosome. Remarkably, small EVs fuse to early endosome liposomes at significantly greater levels than large EVs. Atomic force microscope imaging combined with machine-learning methods further emphasizes the difference in biophysical properties between the two subpopulations. These results shed light on the sophisticated mechanism by which malaria parasites utilize EV subpopulations as a communication tool to target different cellular destinations or host systems.
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Affiliation(s)
- Paula Abou Karam
- Department of Biomolecular SciencesWeizmann Institute of ScienceRehovotIsrael
| | | | - Tamar Ziv
- Smoler Proteomics CenterDepartment of BiologyTechnion – Israel Institute of TechnologyHaifaIsrael
| | - Hila Ben Ami Pilo
- Department of Biomolecular SciencesWeizmann Institute of ScienceRehovotIsrael
| | - Ido Azuri
- Bioinformatics UnitLife Sciences Core FacilitiesWeizmann Institute of ScienceRehovotIsrael
| | - Anna Rivkin
- Department of Biomolecular SciencesWeizmann Institute of ScienceRehovotIsrael
| | - Edo Kiper
- Department of Biomolecular SciencesWeizmann Institute of ScienceRehovotIsrael
| | - Ron Rotkopf
- Bioinformatics UnitLife Sciences Core FacilitiesWeizmann Institute of ScienceRehovotIsrael
| | - Sidney R Cohen
- Department of Chemical Research SupportWeizmann Institute of ScienceRehovotIsrael
| | | | - Ori Avinoam
- Department of Biomolecular SciencesWeizmann Institute of ScienceRehovotIsrael
| | - Alicia Rojas
- Laboratory of HelminthologyFaculty of MicrobiologyUniversity of Costa RicaSan JoséCosta Rica
| | - Mattia I Morandi
- Department of Biomolecular SciencesWeizmann Institute of ScienceRehovotIsrael
| | - Neta Regev‐Rudzki
- Department of Biomolecular SciencesWeizmann Institute of ScienceRehovotIsrael
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4
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Syntaxin Clustering and Optogenetic Control for Synaptic Membrane Fusion. J Mol Biol 2020; 432:4773-4782. [PMID: 32682743 DOI: 10.1016/j.jmb.2020.07.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 07/05/2020] [Accepted: 07/12/2020] [Indexed: 01/01/2023]
Abstract
Membrane fusion during synaptic transmission mediates the trafficking of chemical signals and neuronal communication. The fast kinetics of membrane fusion on the order of millisecond is precisely regulated by the assembly of SNAREs and accessory proteins. It is believed that the formation of the SNARE complex is a key step during membrane fusion. Little is known, however, about the molecular machinery that mediates the formation of a large pre-fusion complex, including multiple SNAREs and accessory proteins. Syntaxin, a transmembrane protein on the plasma membrane, has been observed to undergo oligomerization to form clusters. Whether this clustering plays a critical role in membrane fusion is poorly understood in live cells. Optogenetics is an emerging biotechnology armed with the capacity to precisely modulate protein-protein interaction in time and space. Here, we propose an experimental scheme that combines optogenetics with single-vesicle membrane fusion, aiming to gain a better understanding of the molecular mechanism by which the syntaxin cluster regulates membrane fusion. We envision that newly developed optogenetic tools could facilitate the mechanistic understanding of synaptic transmission in live cells and animals.
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Yamase K, Tanigawa Y, Yamamoto Y, Tanaka H, Komiya T. Mouse TMCO5 is localized to the manchette microtubules involved in vesicle transfer in the elongating spermatids. PLoS One 2019; 14:e0220917. [PMID: 31393949 PMCID: PMC6687282 DOI: 10.1371/journal.pone.0220917] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 07/25/2019] [Indexed: 12/31/2022] Open
Abstract
As a result of a high-throughput in situ hybridization screening for adult mouse testes, we found that the mRNA for Tmco5 is expressed in round and elongating spermatids. Tmco5 belongs to the Tmco (Transmembrane and coiled-coil domains) gene family and has a coiled-coil domain in the N-terminal and a transmembrane domain in the C-terminal region. A monoclonal antibody raised against recombinant TMCO5 revealed that the protein is expressed exclusively in the elongating spermatids of step 9 to 12 and is localized to the manchette, a transiently emerging construction, which predominantly consists of cytoskeleton microtubules and actin filaments. This structure serves in the transport of Golgi-derived non-acrosomal vesicles. Moreover, induced expression of TMCO5 in CHO cells resulted in the co-localization of TMCO5 with β-tubulin besides the reorganization of the Golgi apparatus. Judging from the results and considering the domain structure of TMCO5, we assume that Tmco5 may have a role in vesicle transport along the manchette.
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Affiliation(s)
- Kenya Yamase
- Department of Biological Function, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi, Osaka, Japan
| | - Yoko Tanigawa
- Department of Biological Function, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi, Osaka, Japan
| | - Yasufumi Yamamoto
- Department of Biological Function, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi, Osaka, Japan
| | - Hiromitsu Tanaka
- Faculty of Pharmaceutical Sciences, Nagasaki International University, Sasebo, Nagasaki, Japan
| | - Tohru Komiya
- Department of Biological Function, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi, Osaka, Japan
- * E-mail:
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6
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Biochemical studies of membrane fusion at the single-particle level. Prog Lipid Res 2019; 73:92-100. [PMID: 30611882 DOI: 10.1016/j.plipres.2019.01.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 01/01/2019] [Accepted: 01/02/2019] [Indexed: 01/21/2023]
Abstract
To study membrane fusion mediated by synaptic proteins, proteoliposomes have been widely used for in vitro ensemble measurements with limited insights into the fusion mechanism. Single-particle techniques have proven to be powerful in overcoming the limitations of traditional ensemble methods. Here, we summarize current single-particle methods in biophysical and biochemical studies of fusion mediated by soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and other synaptic proteins, together with their advantages and limitations.
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7
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Kreutzberger AJB, Kiessling V, Liang B, Yang ST, Castle JD, Tamm LK. Asymmetric Phosphatidylethanolamine Distribution Controls Fusion Pore Lifetime and Probability. Biophys J 2017; 113:1912-1915. [PMID: 29037600 DOI: 10.1016/j.bpj.2017.09.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 09/11/2017] [Accepted: 09/13/2017] [Indexed: 01/18/2023] Open
Abstract
Little attention has been given to how the asymmetric lipid distribution of the plasma membrane might facilitate fusion pore formation during exocytosis. Phosphatidylethanolamine (PE), a cone-shaped phospholipid, is predominantly located in the inner leaflet of the plasma membrane and has been proposed to promote membrane deformation and stabilize fusion pores during exocytotic events. To explore this possibility, we modeled exocytosis using plasma membrane SNARE-containing planar-supported bilayers and purified neuroendocrine dense core vesicles (DCVs) as fusion partners, and we examined how different PE distributions between the two leaflets of the supported bilayers affected SNARE-mediated fusion. Using total internal reflection fluorescence microscopy, the fusion of single DCVs with the planar-supported bilayer was monitored by observing DCV-associated neuropeptide Y tagged with a fluorescent protein. The time-dependent line shape of the fluorescent signal enables detection of DCV docking, fusion-pore opening, and vesicle collapse into the planar membrane. Four different distributions of PE in the planar bilayer mimicking the plasma membrane were examined: exclusively in the leaflet facing the DCVs; exclusively in the opposite leaflet; equally distributed in both leaflets; and absent from both leaflets. With PE in the leaflet facing the DCVs, overall fusion was most efficient and the extended fusion pore lifetime (0.7 s) enabled notable detection of content release preceding vesicle collapse. All other PE distributions decreased fusion efficiency, altered pore lifetime, and reduced content release. With PE exclusively in the opposite leaflet, resolution of pore opening and content release was lost.
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Affiliation(s)
- Alex J B Kreutzberger
- Department of Molecular Physiology and Biological Physics, Center for Cell and Membrane Physiology at the University of Virginia, Charlottesville, Virginia
| | - Volker Kiessling
- Department of Molecular Physiology and Biological Physics, Center for Cell and Membrane Physiology at the University of Virginia, Charlottesville, Virginia
| | - Binyong Liang
- Department of Molecular Physiology and Biological Physics, Center for Cell and Membrane Physiology at the University of Virginia, Charlottesville, Virginia
| | - Sung-Tae Yang
- Department of Molecular Physiology and Biological Physics, Center for Cell and Membrane Physiology at the University of Virginia, Charlottesville, Virginia
| | - J David Castle
- Department of Cell Biology, Center for Cell and Membrane Physiology at the University of Virginia, Charlottesville, Virginia
| | - Lukas K Tamm
- Department of Molecular Physiology and Biological Physics, Center for Cell and Membrane Physiology at the University of Virginia, Charlottesville, Virginia.
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8
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Wang T, Li L, Hong W. SNARE proteins in membrane trafficking. Traffic 2017; 18:767-775. [PMID: 28857378 DOI: 10.1111/tra.12524] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 08/25/2017] [Accepted: 08/25/2017] [Indexed: 12/25/2022]
Abstract
SNAREs are the core machinery mediating membrane fusion. In this review, we provide an update on the recent progress on SNAREs regulating membrane fusion events, especially the more detailed fusion processes dissected by well-developed biophysical methods and in vitro single molecule analysis approaches. We also briefly summarize the relevant research from Chinese laboratories and highlight the significant contributions on our understanding of SNARE-mediated membrane trafficking from scientists in China.
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Affiliation(s)
- Tuanlao Wang
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, China
| | - Liangcheng Li
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, China
| | - Wanjin Hong
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, China.,Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
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9
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Kreutzberger AJB, Kiessling V, Liang B, Seelheim P, Jakhanwal S, Jahn R, Castle JD, Tamm LK. Reconstitution of calcium-mediated exocytosis of dense-core vesicles. SCIENCE ADVANCES 2017; 3:e1603208. [PMID: 28776026 PMCID: PMC5517108 DOI: 10.1126/sciadv.1603208] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 06/15/2017] [Indexed: 05/11/2023]
Abstract
Regulated exocytosis is a process by which neurotransmitters, hormones, and secretory proteins are released from the cell in response to elevated levels of calcium. In cells, secretory vesicles are targeted to the plasma membrane, where they dock, undergo priming, and then fuse with the plasma membrane in response to calcium. The specific roles of essential proteins and how calcium regulates progression through these sequential steps are currently incompletely resolved. We have used purified neuroendocrine dense-core vesicles and artificial membranes to reconstruct in vitro the serial events that mimic SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-dependent membrane docking and fusion during exocytosis. Calcium recruits these vesicles to the target membrane aided by the protein CAPS (calcium-dependent activator protein for secretion), whereas synaptotagmin catalyzes calcium-dependent fusion; both processes are dependent on phosphatidylinositol 4,5-bisphosphate. The soluble proteins Munc18 and complexin-1 are necessary to arrest vesicles in a docked state in the absence of calcium, whereas CAPS and/or Munc13 are involved in priming the system for an efficient fusion reaction.
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Affiliation(s)
- Alex J. B. Kreutzberger
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Volker Kiessling
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Binyong Liang
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Patrick Seelheim
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Shrutee Jakhanwal
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Reinhard Jahn
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - J. David Castle
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
| | - Lukas K. Tamm
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
- Corresponding author.
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10
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Yang ST, Kreutzberger AJB, Kiessling V, Ganser-Pornillos BK, White JM, Tamm LK. HIV virions sense plasma membrane heterogeneity for cell entry. SCIENCE ADVANCES 2017; 3:e1700338. [PMID: 28782011 PMCID: PMC5489272 DOI: 10.1126/sciadv.1700338] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 05/12/2017] [Indexed: 05/20/2023]
Abstract
It has been proposed that cholesterol in host cell membranes plays a pivotal role for cell entry of HIV. However, it remains largely unknown why virions prefer cholesterol-rich heterogeneous membranes to uniformly fluid membranes for membrane fusion. Using giant plasma membrane vesicles containing cholesterol-rich ordered and cholesterol-poor fluid lipid domains, we demonstrate that the HIV receptor CD4 is substantially sequestered into ordered domains, whereas the co-receptor CCR5 localizes preferentially at ordered/disordered domain boundaries. We also show that HIV does not fuse from within ordered regions of the plasma membrane but rather at their boundaries. Ordered/disordered lipid domain coexistence is not required for HIV attachment but is a prerequisite for successful fusion. We propose that HIV virions sense and exploit membrane discontinuities to gain entry into cells. This study provides surprising answers to the long-standing question about the roles of cholesterol and ordered lipid domains in cell entry of HIV and perhaps other enveloped viruses.
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Affiliation(s)
- Sung-Tae Yang
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Alex J. B. Kreutzberger
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Volker Kiessling
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Barbie K. Ganser-Pornillos
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Judith M. White
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
| | - Lukas K. Tamm
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22908, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
- Corresponding author.
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11
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Zdanowicz R, Kreutzberger A, Liang B, Kiessling V, Tamm LK, Cafiso DS. Complexin Binding to Membranes and Acceptor t-SNAREs Explains Its Clamping Effect on Fusion. Biophys J 2017; 113:1235-1250. [PMID: 28456331 DOI: 10.1016/j.bpj.2017.04.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 03/31/2017] [Accepted: 04/04/2017] [Indexed: 02/07/2023] Open
Abstract
Complexin-1 is a SNARE effector protein that decreases spontaneous neurotransmitter release and enhances evoked release. Complexin binds to the fully assembled four-helical neuronal SNARE core complex as revealed in competing molecular models derived from x-ray crystallography. Presently, it is unclear how complexin binding to the postfusion complex accounts for its effects upon spontaneous and evoked release in vivo. Using a combination of spectroscopic and imaging methods, we characterize in molecular detail how complexin binds to the 1:1 plasma membrane t-SNARE complex of syntaxin-1a and SNAP-25 while simultaneously binding the lipid bilayer at both its N- and C-terminal ends. These interactions are cooperative, and binding to the prefusion acceptor t-SNARE complex is stronger than to the postfusion core complex. This complexin interaction reduces the affinity of synaptobrevin-2 for the 1:1 complex, thereby retarding SNARE assembly and vesicle docking in vitro. The results provide the basis for molecular models that account for the observed clamping effect of complexin beginning with the acceptor t-SNARE complex and the subsequent activation of the clamped complex by Ca2+ and synaptotagmin.
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Affiliation(s)
- Rafal Zdanowicz
- Department of Chemistry, University of Virginia, Charlottesville, Virginia; Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia
| | - Alex Kreutzberger
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia; Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia
| | - Binyong Liang
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia; Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia
| | - Volker Kiessling
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia; Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia
| | - Lukas K Tamm
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia; Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia.
| | - David S Cafiso
- Department of Chemistry, University of Virginia, Charlottesville, Virginia; Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia.
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12
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Kiessling V, Liang B, Kreutzberger AJB, Tamm LK. Planar Supported Membranes with Mobile SNARE Proteins and Quantitative Fluorescence Microscopy Assays to Study Synaptic Vesicle Fusion. Front Mol Neurosci 2017; 10:72. [PMID: 28360838 PMCID: PMC5352703 DOI: 10.3389/fnmol.2017.00072] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 03/03/2017] [Indexed: 12/31/2022] Open
Abstract
Synaptic vesicle membrane fusion, the process by which neurotransmitter gets released at the presynaptic membrane is mediated by a complex interplay between proteins and lipids. The realization that the lipid bilayer is not just a passive environment where other molecular players like SNARE proteins act, but is itself actively involved in the process, makes the development of biochemical and biophysical assays particularly challenging. We summarize in vitro assays that use planar supported membranes and fluorescence microscopy to address some of the open questions regarding the molecular mechanisms of SNARE-mediated membrane fusion. Most of the assays discussed in this mini-review were developed in our lab over the last 15 years. We emphasize the sample requirements that we found are important for the successful application of these methods.
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Affiliation(s)
- Volker Kiessling
- Center for Membrane and Cell Physiology, University of VirginiaCharlottesville, VA, USA; Department of Molecular Physiology and Biological Physics, University of VirginiaCharlottesville, VA, USA
| | - Binyong Liang
- Center for Membrane and Cell Physiology, University of VirginiaCharlottesville, VA, USA; Department of Molecular Physiology and Biological Physics, University of VirginiaCharlottesville, VA, USA
| | - Alex J B Kreutzberger
- Center for Membrane and Cell Physiology, University of VirginiaCharlottesville, VA, USA; Department of Molecular Physiology and Biological Physics, University of VirginiaCharlottesville, VA, USA
| | - Lukas K Tamm
- Center for Membrane and Cell Physiology, University of VirginiaCharlottesville, VA, USA; Department of Molecular Physiology and Biological Physics, University of VirginiaCharlottesville, VA, USA
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13
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Kreutzberger AJB, Liang B, Kiessling V, Tamm LK. Assembly and Comparison of Plasma Membrane SNARE Acceptor Complexes. Biophys J 2016; 110:2147-50. [PMID: 27178662 DOI: 10.1016/j.bpj.2016.04.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 03/11/2016] [Accepted: 04/08/2016] [Indexed: 12/16/2022] Open
Abstract
Neuronal exocytotic membrane fusion occurs on a fast timescale and is dependent on interactions between the vesicle SNARE synaptobrevin-2 and the plasma membrane SNAREs syntaxin-1a and SNAP-25 with a 1:1:1 stoichiometry. Reproducing fast fusion rates as observed in cells by reconstitution in vitro has been hindered by the spontaneous assembly of a 2:1 syntaxin-1a:SNAP-25 complex on target membranes that kinetically alters the binding of synaptobrevin-2. Previously, an artificial SNARE acceptor complex consisting of 1:1:1 syntaxin-1a(residues 183-288):SNAP-25:syb(residues 49-96) was found to greatly accelerate the rates of lipid mixing of reconstituted target and vesicle SNARE proteoliposomes. Here we present two (to our knowledge) new procedures to assemble membrane-bound 1:1 SNARE acceptor complexes that produce fast and efficient fusion without the need of the syb(49-96) peptide. In the first procedure, syntaxin-1a is purified in a strictly monomeric form and subsequently assembled with SNAP-25 in detergent with the correct 1:1 stoichiometry. In the second procedure, monomeric syntaxin-1a and dodecylated (d-)SNAP-25 are separately reconstituted into proteoliposomes and subsequently assembled in the plane of merged target lipid bilayers. Examining single particle fusion between synaptobrevin-2 proteoliposomes and planar-supported bilayers containing the two different SNARE acceptor complexes revealed similar fast rates of fusion. Changing the stoichiometry of syntaxin-1a and d-SNAP-25 in the target bilayer had significant effects on docking, but little effect on the rates of synaptobrevin-2 proteoliposome fusion.
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Affiliation(s)
- Alex J B Kreutzberger
- Center for Membrane and Cell Physiology and Department of Molecular Physiology & Biological Physics, University of Virginia, Charlottesville, Virginia
| | - Binyong Liang
- Center for Membrane and Cell Physiology and Department of Molecular Physiology & Biological Physics, University of Virginia, Charlottesville, Virginia
| | - Volker Kiessling
- Center for Membrane and Cell Physiology and Department of Molecular Physiology & Biological Physics, University of Virginia, Charlottesville, Virginia
| | - Lukas K Tamm
- Center for Membrane and Cell Physiology and Department of Molecular Physiology & Biological Physics, University of Virginia, Charlottesville, Virginia.
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High cholesterol obviates a prolonged hemifusion intermediate in fast SNARE-mediated membrane fusion. Biophys J 2016. [PMID: 26200867 DOI: 10.1016/j.bpj.2015.06.022] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Cholesterol is essential for exocytosis in secretory cells, but the exact molecular mechanism by which it facilitates exocytosis is largely unknown. Distinguishing contributions from the lateral organization and dynamics of membrane proteins to vesicle docking and fusion and the promotion of fusion pores by negative intrinsic spontaneous curvature and other mechanical effects of cholesterol have been elusive. To shed more light on this process, we examined the effect of cholesterol on SNARE-mediated membrane fusion in a single-vesicle assay that is capable of resolving docking and elementary steps of fusion with millisecond time resolution. The effect of cholesterol on fusion pore formation between synaptobrevin-2 (VAMP-2)-containing proteoliposomes and acceptor t-SNARE complex-containing planar supported bilayers was examined using both membrane and content fluorescent markers. This approach revealed that increasing cholesterol in either the t-SNARE or the v-SNARE membrane favors a mechanism of direct fusion pore opening, whereas low cholesterol favors a mechanism leading to a long-lived (>5 s) hemifusion state. The amount of cholesterol in the target membrane had no significant effect on docking of synaptobrevin vesicles. Comparative studies with α-tocopherol (vitamin E) show that the negative intrinsic spontaneous curvature of cholesterol and its presumed promotion of a very short-lived (<50 ms) lipid stalk intermediate is the main factor that favors rapid fusion pore opening at high cholesterol. This study also shows that this single-vesicle fusion assay can distinguish between hemifusion and full fusion with only a single lipid dye, thereby freeing up a fluorescence channel for the simultaneous measurement of another parameter in fast time-resolved fusion assays.
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