1
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Litschel T, Kelley CF, Cheng X, Babl L, Mizuno N, Case LB, Schwille P. Membrane-induced 2D phase separation of the focal adhesion protein talin. Nat Commun 2024; 15:4986. [PMID: 38862544 PMCID: PMC11166923 DOI: 10.1038/s41467-024-49222-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 05/22/2024] [Indexed: 06/13/2024] Open
Abstract
Focal adhesions form liquid-like assemblies around activated integrin receptors at the plasma membrane. How they achieve their flexible properties is not well understood. Here, we use recombinant focal adhesion proteins to reconstitute the core structural machinery in vitro. We observe liquid-liquid phase separation of the core focal adhesion proteins talin and vinculin for a spectrum of conditions and interaction partners. Intriguingly, we show that binding to PI(4,5)P2-containing membranes triggers phase separation of these proteins on the membrane surface, which in turn induces the enrichment of integrin in the clusters. We suggest a mechanism by which 2-dimensional biomolecular condensates assemble on membranes from soluble proteins in the cytoplasm: lipid-binding triggers protein activation and thus, liquid-liquid phase separation of these membrane-bound proteins. This could explain how early focal adhesions maintain a structured and force-resistant organization into the cytoplasm, while still being highly dynamic and able to quickly assemble and disassemble.
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Affiliation(s)
- Thomas Litschel
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany.
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.
| | - Charlotte F Kelley
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Xiaohang Cheng
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Leon Babl
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Naoko Mizuno
- Department of Structural Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
- Laboratory of Structural Cell Biology, National Institutes of Health, Bethesda, MD, USA
| | - Lindsay B Case
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Petra Schwille
- Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, Martinsried, Germany.
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2
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Manori B, Vaknin A, Vaňková P, Nitzan A, Zaidel-Bar R, Man P, Giladi M, Haitin Y. Chloride intracellular channel (CLIC) proteins function as fusogens. Nat Commun 2024; 15:2085. [PMID: 38453905 PMCID: PMC10920813 DOI: 10.1038/s41467-024-46301-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Accepted: 02/19/2024] [Indexed: 03/09/2024] Open
Abstract
Chloride Intracellular Channel (CLIC) family members uniquely transition between soluble and membrane-associated conformations. Despite decades of extensive functional and structural studies, CLICs' function as ion channels remains debated, rendering our understanding of their physiological role incomplete. Here, we expose the function of CLIC5 as a fusogen. We demonstrate that purified CLIC5 directly interacts with the membrane and induces fusion, as reflected by increased liposomal diameter and lipid and content mixing between liposomes. Moreover, we show that this activity is facilitated by acidic pH, a known trigger for CLICs' transition to a membrane-associated conformation, and that increased exposure of the hydrophobic inter-domain interface is crucial for this process. Finally, mutation of a conserved hydrophobic interfacial residue diminishes the fusogenic activity of CLIC5 in vitro and impairs excretory canal extension in C. elegans in vivo. Together, our results unravel the long-sought physiological role of these enigmatic proteins.
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Grants
- 1721/16 Israel Science Foundation (ISF)
- 1653/21 Israel Science Foundation (ISF)
- 3308/20 Israel Science Foundation (ISF)
- 01214 Israel Cancer Research Fund (Israel Cancer Research Fund, Inc.)
- 19202 Israel Cancer Research Fund (Israel Cancer Research Fund, Inc.)
- 20230029 Israel Cancer Association (ICA)
- CZ.1.05/1.1.00/02.0109 Ministerstvo školstva, vedy, výskumu a športu Slovenskej republiky (Ministry of Education, Science, Research and Sport of the Slovak Republic)
- 731077 EC | Horizon 2020 Framework Programme (EU Framework Programme for Research and Innovation H2020)
- The Claire and Amedee Maratier Institute for the Study of Blindness and Visual Disorders, Faculty of Medicine, Tel-Aviv University.
- The Czech Infrastructure for Integrative Structural Biology (CIISB) grant (LM2023042).
- The Kahn Foundation's Orion project, Tel Aviv Sourasky Medical Center, Israel. The Claire and Amedee Maratier Institute for the Study of Blindness and Visual Disorders, Faculty of Medicine, Tel-Aviv University.
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Affiliation(s)
- Bar Manori
- Department of Physiology and Pharmacology, Faculty of Medicine, Tel-Aviv University, Tel-Aviv, 6997801, Israel
| | - Alisa Vaknin
- School of Chemistry, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Pavla Vaňková
- Institute of Biotechnology of the Czech Academy of Sciences, Division BioCeV, Prumyslova 595, 252 50, Vestec, Czech Republic
| | - Anat Nitzan
- Department of Cell and Developmental Biology, Faculty of Medicine, Tel-Aviv University, Tel-Aviv, 6997801, Israel
| | - Ronen Zaidel-Bar
- Department of Cell and Developmental Biology, Faculty of Medicine, Tel-Aviv University, Tel-Aviv, 6997801, Israel
| | - Petr Man
- Institute of Microbiology of the Czech Academy of Sciences, Division BioCeV, Prumyslova 595, 252 50, Vestec, Czech Republic
| | - Moshe Giladi
- Department of Physiology and Pharmacology, Faculty of Medicine, Tel-Aviv University, Tel-Aviv, 6997801, Israel.
- Tel Aviv Sourasky Medical Center, Tel Aviv, 6423906, Israel.
| | - Yoni Haitin
- Department of Physiology and Pharmacology, Faculty of Medicine, Tel-Aviv University, Tel-Aviv, 6997801, Israel.
- Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 6997801, Israel.
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3
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Malinowska AM, van Mameren J, Peterman EJG, Wuite GJL, Heller I. Introduction to Optical Tweezers: Background, System Designs, and Applications. Methods Mol Biol 2024; 2694:3-28. [PMID: 37823997 DOI: 10.1007/978-1-0716-3377-9_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
Optical tweezers are a means to manipulate objects with light. With the technique, microscopically small objects can be held and steered, allowing for accurate measurement of the forces applied to these objects. Optical tweezers can typically obtain a nanometer spatial resolution, a picoNewton force resolution, and a millisecond time resolution, which makes the technique well suited for the study of biological processes from the single-cell down to the single-molecule level. In this chapter, we aim to provide an introduction to the use of optical tweezers for single-molecule analyses. We start from the basic principles and methodology involved in optical trapping, force calibration, and force measurements. Next, we describe the components of an optical tweezers setup and their experimental relevance. Finally, we will provide an overview of the broad applications in context of biological research, with the emphasis on the measurement modes, experimental assays, and possible combinations with fluorescence microscopy techniques.
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Affiliation(s)
- Agata M Malinowska
- LaserLaB Amsterdam and Department of Physics and Astronomy, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Joost van Mameren
- Institute of Physics, University of Amsterdam, Amsterdam, The Netherlands
| | - Erwin J G Peterman
- LaserLaB Amsterdam and Department of Physics and Astronomy, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Gijs J L Wuite
- LaserLaB Amsterdam and Department of Physics and Astronomy, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Iddo Heller
- LaserLaB Amsterdam and Department of Physics and Astronomy, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
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4
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Shendrik P, Golani G, Dharan R, Schwarz US, Sorkin R. Membrane Tension Inhibits Lipid Mixing by Increasing the Hemifusion Stalk Energy. ACS NANO 2023; 17:18942-18951. [PMID: 37669531 PMCID: PMC7615193 DOI: 10.1021/acsnano.3c04293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Accepted: 08/23/2023] [Indexed: 09/07/2023]
Abstract
Fusion of biological membranes is fundamental in various physiological events. The fusion process involves several intermediate stages with energy barriers that are tightly dependent on the mechanical and physical properties of the system, one of which is membrane tension. As previously established, the late stages of fusion, including hemifusion diaphragm and pore expansions, are favored by membrane tension. However, a current understanding of how the energy barrier of earlier fusion stages is affected by membrane tension is lacking. Here, we apply a newly developed experimental approach combining micropipette-aspirated giant unilamellar vesicles and optically trapped membrane-coated beads, revealing that membrane tension inhibits lipid mixing. We show that lipid mixing is 6 times slower under a tension of 0.12 mN/m compared with tension-free membranes. Furthermore, using continuum elastic theory, we calculate the dependence of the hemifusion stalk formation energy on membrane tension and intermembrane distance and find the increase in the corresponding energy barrier to be 1.6 kBT in our setting, which can explain the increase in lipid mixing time delay. Finally, we show that tension can be a significant factor in the stalk energy if the pre-fusion intermembrane distance is on the order of several nanometers, while for membranes that are tightly docked, tension has a negligible effect.
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Affiliation(s)
- Petr Shendrik
- School
of Chemistry, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
- Center
of Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Gonen Golani
- Institute
for Theoretical Physics and BioQuant Center for Quantitative Biology, Heidelberg University, 69120, Heidelberg, Germany
| | - Raviv Dharan
- School
of Chemistry, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
- Center
of Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, 6997801, Israel
| | - Ulrich S. Schwarz
- Institute
for Theoretical Physics and BioQuant Center for Quantitative Biology, Heidelberg University, 69120, Heidelberg, Germany
| | - Raya Sorkin
- School
of Chemistry, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, 6997801, Israel
- Center
of Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, 6997801, Israel
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5
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Studying membrane fusion using supported lipid bilayers on superparamagnetic beads. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184070. [PMID: 36220376 DOI: 10.1016/j.bbamem.2022.184070] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 09/29/2022] [Accepted: 10/03/2022] [Indexed: 11/13/2022]
Abstract
The fusion between two lipid membranes is a ubiquitous mechanism in cell traffic and pathogens invasion. Yet it is not well understood how two distinct bilayers overcome the energy barriers towards fusion and reorganize themselves to form a unique continuous bilayer. The magnitudes and numbers of these energy barriers are themselves an open question. To tackle these issues, we developed a new tool that allows to control the forces applied between two supported lipid bilayers (SLBs) deposited on superparamagnetic beads. By applying a magnetic field, the beads self-organize along field lines in chains of beads and compress the two membranes on the contact zone. Using the diffusion of fluorescently labelled lipids from one bilayer to the other allows us to identify fusion of the bilayers in contact. We applied increasing forces on SLBs and increased the occurrence of fusion. This experimental system allows the simultaneous study of tens of facing bilayers in a single experiment and mitigates the stochasticity of the fusion process. It is thus a powerful tool to test the various parameters involved in the membrane fusion process.
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6
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Optical Tweezers to Force Information out of Biological and Synthetic Systems One Molecule at a Time. BIOPHYSICA 2022. [DOI: 10.3390/biophysica2040047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Over the last few decades, in vitro single-molecule manipulation techniques have enabled the use of force and displacement as controlled variables in biochemistry. Measuring the effect of mechanical force on the real-time kinetics of a biological process gives us access to the rates, equilibrium constants and free-energy landscapes of the mechanical steps of the reaction; this information is not accessible by ensemble assays. Optical tweezers are the current method of choice in single-molecule manipulation due to their versatility, high force and spatial and temporal resolutions. The aim of this review is to describe the contributions of our lab in the single-molecule manipulation field. We present here several optical tweezers assays refined in our laboratory to probe the dynamics and mechano-chemical properties of biological molecular motors and synthetic molecular devices at the single-molecule level.
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7
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Cheppali SK, Dharan R, Sorkin R. Forces of Change: Optical Tweezers in Membrane Remodeling Studies. J Membr Biol 2022; 255:677-690. [PMID: 35616705 DOI: 10.1007/s00232-022-00241-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 04/22/2022] [Indexed: 12/24/2022]
Abstract
Optical tweezers allow precise measurement of forces and distances with piconewton and nanometer precision, and have thus been instrumental in elucidating the mechanistic details of various biological processes. Some examples include the characterization of motor protein activity, studies of protein-DNA interactions, and characterizing protein folding trajectories. The use of optical tweezers (OT) to study membranes is, however, much less abundant. Here, we review biophysical studies of membranes that utilize optical tweezers, with emphasis on various assays that have been developed and their benefits and limitations. First, we discuss assays that employ membrane-coated beads, and overview protein-membrane interactions studies based on manipulation of such beads. We further overview a body of studies that make use of a very powerful experimental tool, the combination of OT, micropipette aspiration, and fluorescence microscopy, that allow detailed studies of membrane curvature generation and sensitivity. Finally, we describe studies focused on membrane fusion and fission. We then summarize the overall progress in the field and outline future directions.
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Affiliation(s)
- Sudheer K Cheppali
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv, Israel.,Center for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, Israel.,Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv, Israel.,Center for Light-Matter Interaction, Tel Aviv University, Tel Aviv, Israel
| | - Raviv Dharan
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv, Israel.,Center for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, Israel.,Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv, Israel.,Center for Light-Matter Interaction, Tel Aviv University, Tel Aviv, Israel
| | - Raya Sorkin
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv, Israel. .,Center for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, Israel. .,Center for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv, Israel. .,Center for Light-Matter Interaction, Tel Aviv University, Tel Aviv, Israel.
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8
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Cheppali SK, Dharan R, Katzenelson R, Sorkin R. Supported Natural Membranes on Microspheres for Protein-Protein Interaction Studies. ACS APPLIED MATERIALS & INTERFACES 2022; 14:49532-49541. [PMID: 36306148 DOI: 10.1021/acsami.2c13095] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Multiple biological and pathological processes, such as signaling, cell-cell communication, and infection by various viruses, occur at the plasma membrane. The eukaryotic plasma membrane is made up of thousands of different lipids, membrane proteins, and glycolipids, and its composition is dynamic and constantly changing. Due to the central importance of membranes on the one hand and their complexity on the other, membrane model systems are instrumental for interrogating membrane-related biological processes. Here, we develop a new tool for protein-membrane interaction studies. Our method is based on natural membranes obtained from extracellular vesicles. We form membrane bilayers supported on polystyrene microspheres that can be trapped and manipulated using optical tweezers. This method allows working with membrane proteins of interest within a background of native membrane components where their correct orientation is preserved. We demonstrate our method's applicability by successfully measuring the interaction forces between the Spike protein of SARS-CoV-2 and its human receptor, ACE2. We further show that these interactions are blocked by the addition of an antibody against the receptor binding domain of the Spike protein. Our approach is versatile and broadly applicable for various membrane biology and biophysics questions.
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Affiliation(s)
- Sudheer K Cheppali
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv, Israel6997801
- Center for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, Israel6997801
- Center for Light-Matter Interaction, Tel Aviv University, Tel Aviv, Israel6997801
| | - Raviv Dharan
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv, Israel6997801
- Center for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, Israel6997801
- Center for Light-Matter Interaction, Tel Aviv University, Tel Aviv, Israel6997801
| | - Roni Katzenelson
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv, Israel6997801
- Center for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, Israel6997801
- Center for Light-Matter Interaction, Tel Aviv University, Tel Aviv, Israel6997801
| | - Raya Sorkin
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv, Israel6997801
- Center for Physics and Chemistry of Living Systems, Tel Aviv University, Tel Aviv, Israel6997801
- Center for Light-Matter Interaction, Tel Aviv University, Tel Aviv, Israel6997801
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9
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Bisio H, Krishnan A, Marq JB, Soldati-Favre D. Toxoplasma gondii phosphatidylserine flippase complex ATP2B-CDC50.4 critically participates in microneme exocytosis. PLoS Pathog 2022; 18:e1010438. [PMID: 35325010 PMCID: PMC8982854 DOI: 10.1371/journal.ppat.1010438] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Revised: 04/05/2022] [Accepted: 03/11/2022] [Indexed: 12/22/2022] Open
Abstract
Regulated microneme secretion governs motility, host cell invasion and egress in the obligate intracellular apicomplexans. Intracellular calcium oscillations and phospholipid dynamics critically regulate microneme exocytosis. Despite its importance for the lytic cycle of these parasites, molecular mechanistic details about exocytosis are still missing. Some members of the P4-ATPases act as flippases, changing the phospholipid distribution by translocation from the outer to the inner leaflet of the membrane. Here, the localization and function of the repertoire of P4-ATPases was investigated across the lytic cycle of Toxoplasma gondii. Of relevance, ATP2B and the non-catalytic subunit cell division control protein 50.4 (CDC50.4) form a stable heterocomplex at the parasite plasma membrane, essential for microneme exocytosis. This complex is responsible for flipping phosphatidylserine, which presumably acts as a lipid mediator for organelle fusion with the plasma membrane. Overall, this study points toward the importance of phosphatidylserine asymmetric distribution at the plasma membrane for microneme exocytosis. Biological membranes display diverse functions, including membrane fusion, which are conferred by a defined composition and organization of proteins and lipids. Apicomplexan parasites possess specialized secretory organelles (micronemes), implicated in motility, invasion and egress from host cells. Microneme exocytosis is already known to depend on phosphatidic acid for its fusion with the plasma membrane. Here we identify a type P4-ATPase and its CDC50 chaperone (ATP2B-CDC50.4) that act as a flippase and contribute to the enrichment of phosphatidylserine (PS) in the inner leaflet of the parasite plasma membrane. The disruption of PS asymmetric distribution at the plasma membrane impacts microneme exocytosis. Overall, our results shed light on the importance of membrane homeostasis and lipid composition in controlling microneme secretion.
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Affiliation(s)
- Hugo Bisio
- Department of Microbiology and Molecular Medicine, CMU, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Aarti Krishnan
- Department of Microbiology and Molecular Medicine, CMU, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Jean-Baptiste Marq
- Department of Microbiology and Molecular Medicine, CMU, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Dominique Soldati-Favre
- Department of Microbiology and Molecular Medicine, CMU, Faculty of Medicine, University of Geneva, Geneva, Switzerland
- * E-mail:
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10
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Bourgeois-Jaarsma Q, Miaja Hernandez P, Groffen AJ. Ca 2+ sensor proteins in spontaneous release and synaptic plasticity: Limited contribution of Doc2c, rabphilin-3a and synaptotagmin 7 in hippocampal glutamatergic neurons. Mol Cell Neurosci 2021; 112:103613. [PMID: 33753311 DOI: 10.1016/j.mcn.2021.103613] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 03/09/2021] [Accepted: 03/13/2021] [Indexed: 11/28/2022] Open
Abstract
Presynaptic neurotransmitter release is strictly regulated by SNARE proteins, Ca2+ and a number of Ca2+ sensors including synaptotagmins (Syts) and Double C2 domain proteins (Doc2s). More than seventy years after the original description of spontaneous release, the mechanism that regulates this process is still poorly understood. Syt-1, Syt7 and Doc2 proteins contribute predominantly, but not exclusively, to synchronous, asynchronous and spontaneous phases of release. The proteins share a conserved tandem C2 domain architecture, but are functionally diverse in their subcellular location, Ca2+-binding properties and protein interactions. In absence of Syt-1, Doc2a and -b, neurons still exhibit spontaneous vesicle fusion which remains Ca2+-sensitive, suggesting the existence of additional sensors. Here, we selected Doc2c, rabphilin-3a and Syt-7 as three potential Ca2+ sensors for their sequence homology with Syt-1 and Doc2b. We genetically ablated each candidate gene in absence of Doc2a and -b and investigated spontaneous and evoked release in glutamatergic hippocampal neurons, cultured either in networks or on microglial islands (autapses). The removal of Doc2c had no effect on spontaneous or evoked release. Syt-7 removal also did not affect spontaneous release, although it altered short-term plasticity by accentuating short-term depression. The removal of rabphilin caused an increased spontaneous release frequency in network cultures, an effect that was not observed in autapses. Taken together, we conclude that Doc2c and Syt-7 do not affect spontaneous release of glutamate in hippocampal neurons, while our results suggest a possible regulatory role of rabphilin-3a in neuronal networks. These findings importantly narrow down the repertoire of synaptic Ca2+ sensors that may be implicated in the spontaneous release of glutamate.
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Affiliation(s)
- Quentin Bourgeois-Jaarsma
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
| | - Pablo Miaja Hernandez
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
| | - Alexander J Groffen
- Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VU University, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands; Department of Clinical Genetics, VU Medical Center, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands.
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11
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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] [MESH Headings] [Grants] [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.
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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.
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12
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Sudhakar S, Abdosamadi MK, Jachowski TJ, Bugiel M, Jannasch A, Schäffer E. Germanium nanospheres for ultraresolution picotensiometry of kinesin motors. Science 2021; 371:371/6530/eabd9944. [PMID: 33574186 DOI: 10.1126/science.abd9944] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 12/02/2020] [Indexed: 02/06/2023]
Abstract
Kinesin motors are essential for the transport of cellular cargo along microtubules. How the motors step, detach, and cooperate with each other is still unclear. To dissect the molecular motion of kinesin-1, we developed germanium nanospheres as ultraresolution optical trapping probes. We found that single motors took 4-nanometer center-of-mass steps. Furthermore, kinesin-1 never detached from microtubules under hindering load conditions. Instead, it slipped on microtubules in microsecond-long, 8-nanometer steps and remained in this slip state before detaching or reengaging in directed motion. Unexpectedly, reengagement and thus rescue of directed motion was more frequent. Our observations broaden our knowledge on the mechanochemical cycle and slip state of kinesin. This state and rescue need to be accounted for to understand long-range transport by teams of motors.
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Affiliation(s)
- Swathi Sudhakar
- Eberhard Karls Universität Tübingen, Cellular Nanoscience (ZMBP), Auf der Morgenstelle 32, 72076 Tübingen, Germany
| | - Mohammad Kazem Abdosamadi
- Eberhard Karls Universität Tübingen, Cellular Nanoscience (ZMBP), Auf der Morgenstelle 32, 72076 Tübingen, Germany
| | - Tobias Jörg Jachowski
- Eberhard Karls Universität Tübingen, Cellular Nanoscience (ZMBP), Auf der Morgenstelle 32, 72076 Tübingen, Germany
| | - Michael Bugiel
- Eberhard Karls Universität Tübingen, Cellular Nanoscience (ZMBP), Auf der Morgenstelle 32, 72076 Tübingen, Germany
| | - Anita Jannasch
- Eberhard Karls Universität Tübingen, Cellular Nanoscience (ZMBP), Auf der Morgenstelle 32, 72076 Tübingen, Germany
| | - Erik Schäffer
- Eberhard Karls Universität Tübingen, Cellular Nanoscience (ZMBP), Auf der Morgenstelle 32, 72076 Tübingen, Germany.
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13
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Doc2 Proteins Are Not Required for the Increased Spontaneous Release Rate in Synaptotagmin-1-Deficient Neurons. J Neurosci 2020; 40:2606-2617. [PMID: 32098902 DOI: 10.1523/jneurosci.0309-19.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 01/10/2020] [Accepted: 01/23/2020] [Indexed: 11/21/2022] Open
Abstract
Regulated secretion is controlled by Ca2+ sensors with different affinities and subcellular distributions. Inactivation of Syt1 (synaptotagmin-1), the main Ca2+ sensor for synchronous neurotransmission in many neurons, enhances asynchronous and spontaneous release rates, suggesting that Syt1 inhibits other sensors with higher Ca2+ affinities and/or lower cooperativities. Such sensors could include Doc2a and Doc2b, which have been implicated in spontaneous and asynchronous neurotransmitter release and compete with Syt1 for binding SNARE complexes. Here, we tested this hypothesis using triple-knock-out mice. Inactivation of Doc2a and Doc2b in Syt1-deficient neurons did not reduce the high spontaneous release rate. Overexpression of Doc2b variants in triple-knock-out neurons reduced spontaneous release but did not rescue synchronous release. A chimeric construct in which the C2AB domain of Syt1 was substituted by that of Doc2b did not support synchronous release either. Conversely, the soluble C2AB domain of Syt1 did not affect spontaneous release. We conclude that the high spontaneous release rate in synaptotagmin-deficient neurons does not involve the binding of Doc2 proteins to Syt1 binding sites in the SNARE complex. Instead, our results suggest that the C2AB domains of Syt1 and Doc2b specifically support synchronous and spontaneous release by separate mechanisms. (Both male and female neurons were studied without sex determination.)SIGNIFICANCE STATEMENT Neurotransmission in the brain is regulated by presynaptic Ca2+ concentrations. Multiple Ca2+ sensor proteins contribute to synchronous (Syt1, Syt2), asynchronous (Syt7), and spontaneous (Doc2a/Doc2b) phases of neurotransmitter release. Genetic ablation of synchronous release was previously shown to affect other release phases, suggesting that multiple sensors may compete for similar release sites, together encoding stimulus-secretion coupling over a large range of synaptic Ca2+ concentrations. Here, we investigated the extent of functional overlap between Syt1, Doc2a, and Doc2b by reintroducing wild-type and mutant proteins in triple-knock-out neurons, and conclude that the sensors are highly specialized for different phases of release.
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14
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Synaptotagmin-1 and Doc2b Exhibit Distinct Membrane-Remodeling Mechanisms. Biophys J 2019; 118:643-656. [PMID: 31952804 DOI: 10.1016/j.bpj.2019.12.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 12/13/2019] [Accepted: 12/16/2019] [Indexed: 11/24/2022] Open
Abstract
Synaptotagmin-1 (Syt1) is a calcium sensor protein that is critical for neurotransmission and is therefore extensively studied. Here, we use pairs of optically trapped beads coated with SNARE-free synthetic membranes to investigate Syt1-induced membrane remodeling. This activity is compared with that of Doc2b, which contains a conserved C2AB domain and induces membrane tethering and hemifusion in this cell-free model. We find that the soluble C2AB domain of Syt1 strongly affects the probability and strength of membrane-membrane interactions in a strictly Ca2+- and protein-dependent manner. Single-membrane loading of Syt1 yielded the highest probability and force of membrane interactions, whereas in contrast, Doc2b was more effective after loading both membranes. A lipid-mixing assay with confocal imaging reveals that both Syt1 and Doc2b are able to induce hemifusion; however, significantly higher Syt1 concentrations are required. Consistently, both C2AB fragments cause a reduction in the membrane-bending modulus, as measured by a method based on atomic force microscopy. This lowering of the energy required for membrane deformation may contribute to Ca2+-induced fusion.
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15
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Ma G, Hu C, Li S, Gao X, Li H, Hu X. Simultaneous, hybrid single-molecule method by optical tweezers and fluorescence. NANOTECHNOLOGY AND PRECISION ENGINEERING 2019. [DOI: 10.1016/j.npe.2019.11.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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16
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Piontek MC, Lira RB, Roos WH. Active probing of the mechanical properties of biological and synthetic vesicles. Biochim Biophys Acta Gen Subj 2019; 1865:129486. [PMID: 31734458 DOI: 10.1016/j.bbagen.2019.129486] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Revised: 11/05/2019] [Accepted: 11/09/2019] [Indexed: 02/07/2023]
Abstract
BACKGROUND The interest in mechanics of synthetic and biological vesicles has been continuously growing during the last decades. Liposomes serve as model systems for investigating fundamental membrane processes and properties. More recently, extracellular vesicles (EVs) have been investigated mechanically as well. EVs are widely studied in fundamental and applied sciences, but their material properties remained elusive until recently. Elucidating the mechanical properties of vesicles is essential to unveil the mechanisms behind a variety of biological processes, e.g. budding, vesiculation and cellular uptake mechanisms. SCOPE OF REVIEW The importance of mechanobiology for studies of vesicles and membranes is discussed, as well as the different available techniques to probe their mechanical properties. In particular, the mechanics of vesicles and membranes as obtained by nanoindentation, micropipette aspiration, optical tweezers, electrodeformation and electroporation experiments is addressed. MAJOR CONCLUSIONS EVs and liposomes possess an astonishing rich, diverse behavior. To better understand their properties, and for optimization of their applications in nanotechnology, an improved understanding of their mechanical properties is needed. Depending on the size of the vesicles and the specific scientific question, different techniques can be chosen for their mechanical characterization. GENERAL SIGNIFICANCE Understanding the mechanical properties of vesicles is necessary to gain deeper insight in the fundamental biological mechanisms involved in vesicle generation and cellular uptake. This furthermore facilitates technological applications such as using vesicles as targeted drug delivery vehicles. Liposome studies provide insight into fundamental membrane processes and properties, whereas the role and functioning of EVs in biology and medicine are increasingly elucidated.
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Affiliation(s)
- Melissa C Piontek
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands.
| | - Rafael B Lira
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands.
| | - Wouter H Roos
- Moleculaire Biofysica, Zernike Instituut, Rijksuniversiteit Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands.
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17
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Varga K, Jiang ZJ, Gong LW. Phosphatidylserine is critical for vesicle fission during clathrin-mediated endocytosis. J Neurochem 2019; 152:48-60. [PMID: 31587282 DOI: 10.1111/jnc.14886] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 09/25/2019] [Accepted: 10/01/2019] [Indexed: 12/11/2022]
Abstract
Phosphatidylserine (PS), a negatively charged phospholipid present predominantly at the inner leaflet of the plasma membrane, has been widely implicated in many cellular processes including membrane trafficking. Along this line, PS has been demonstrated to be important for endocytosis, however, the involved mechanisms remain uncertain. By monitoring clathrin-mediated endocytosis (CME) of single vesicles in mouse chromaffin cells using cell-attached capacitance measurements that offer millisecond time resolution, we demonstrate in the present study that the fission-pore duration is reduced by PS addition, indicating a stimulatory role of PS in regulating the dynamics of vesicle fission during CME. Furthermore, our results show that the PS-mediated effect on the fission-pore duration is Ca2+ -dependent and abolished in the absence of synaptotagmin 1 (Syt1), implying that Syt1 is necessary for the stimulatory role of PS in vesicle fission during CME. Consistently, a Syt1 mutant with a defective PS-Syt1 interaction increases the fission-pore duration. Taken together, our study suggests that PS-Syt1 interaction may be critical in regulating fission dynamics during CME.
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Affiliation(s)
- Kelly Varga
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, USA.,Department of Biological Sciences, University of North Texas at Dallas, Dallas, Texas, USA
| | - Zhong-Jiao Jiang
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Liang-Wei Gong
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
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18
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Doc2b Ca 2+ binding site mutants enhance synaptic release at rest at the expense of sustained synaptic strength. Sci Rep 2019; 9:14408. [PMID: 31594980 PMCID: PMC6783474 DOI: 10.1038/s41598-019-50684-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Accepted: 09/11/2019] [Indexed: 12/01/2022] Open
Abstract
Communication between neurons involves presynaptic neurotransmitter release which can be evoked by action potentials or occur spontaneously as a result of stochastic vesicle fusion. The Ca2+-binding double C2 proteins Doc2a and –b were implicated in spontaneous and asynchronous evoked release, but the mechanism remains unclear. Here, we compared wildtype Doc2b with two Ca2+ binding site mutants named DN and 6A, previously classified as gain- and loss-of-function mutants. They carry the substitutions D218,220N or D163,218,220,303,357,359A respectively. We found that both mutants bound phospholipids at low Ca2+ concentrations and were membrane-associated in resting neurons, thus mimicking a Ca2+-activated state. Their overexpression in hippocampal primary cultured neurons had similar effects on spontaneous and evoked release, inducing high mEPSC frequencies and increased short-term depression. Together, these data suggest that the DN and 6A mutants both act as gain-of-function mutants at resting conditions.
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19
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Dols-Perez A, Marin V, Amador GJ, Kieffer R, Tam D, Aubin-Tam ME. Artificial Cell Membranes Interfaced with Optical Tweezers: A Versatile Microfluidics Platform for Nanomanipulation and Mechanical Characterization. ACS APPLIED MATERIALS & INTERFACES 2019; 11:33620-33627. [PMID: 31448892 PMCID: PMC6753654 DOI: 10.1021/acsami.9b09983] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Cell lipid membranes are the site of vital biological processes, such as motility, trafficking, and sensing, many of which involve mechanical forces. Elucidating the interplay between such bioprocesses and mechanical forces requires the use of tools that apply and measure piconewton-level forces, e.g., optical tweezers. Here, we introduce the combination of optical tweezers with free-standing lipid bilayers, which are fully accessible on both sides of the membrane. In the vicinity of the lipid bilayer, optical trapping would normally be impossible due to optical distortions caused by pockets of the solvent trapped within the membrane. We solve this by drastically reducing the size of these pockets via tuning of the solvent and flow cell material. In the resulting flow cells, lipid nanotubes are straightforwardly pushed or pulled and reach lengths above half a millimeter. Moreover, the controlled pushing of a lipid nanotube with an optically trapped bead provides an accurate and direct measurement of important mechanical properties. In particular, we measure the membrane tension of a free-standing membrane composed of a mixture of dioleoylphosphatidylcholine (DOPC) and dipalmitoylphosphatidylcholine (DPPC) to be 4.6 × 10-6 N/m. We demonstrate the potential of the platform for biophysical studies by inserting the cell-penetrating trans-activator of transcription (TAT) peptide in the lipid membrane. The interactions between the TAT peptide and the membrane are found to decrease the value of the membrane tension to 2.1 × 10-6 N/m. This method is also fully compatible with electrophysiological measurements and presents new possibilities for the study of membrane mechanics and the creation of artificial lipid tube networks of great importance in intra- and intercellular communication.
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Affiliation(s)
- Aurora Dols-Perez
- Department
of Bionanoscience, Kavli Institute of Nanoscience,
Delft University of Technology, Van der Maasweg 9, Delft 2629 HZ, The Netherlands
| | - Victor Marin
- Department
of Bionanoscience, Kavli Institute of Nanoscience,
Delft University of Technology, Van der Maasweg 9, Delft 2629 HZ, The Netherlands
| | - Guillermo J. Amador
- Department
of Bionanoscience, Kavli Institute of Nanoscience,
Delft University of Technology, Van der Maasweg 9, Delft 2629 HZ, The Netherlands
- Laboratory
for Aero and Hydrodynamics, Delft University
of Technology, Delft 2628 CD, The Netherlands
| | - Roland Kieffer
- Department
of Bionanoscience, Kavli Institute of Nanoscience,
Delft University of Technology, Van der Maasweg 9, Delft 2629 HZ, The Netherlands
| | - Daniel Tam
- Laboratory
for Aero and Hydrodynamics, Delft University
of Technology, Delft 2628 CD, The Netherlands
| | - Marie-Eve Aubin-Tam
- Department
of Bionanoscience, Kavli Institute of Nanoscience,
Delft University of Technology, Van der Maasweg 9, Delft 2629 HZ, The Netherlands
- E-mail: (M.A.)
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20
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Rinaldin M, Verweij RW, Chakraborty I, Kraft DJ. Colloid supported lipid bilayers for self-assembly. SOFT MATTER 2019; 15:1345-1360. [PMID: 30565635 PMCID: PMC6371764 DOI: 10.1039/c8sm01661e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 10/23/2018] [Indexed: 05/10/2023]
Abstract
The use of colloid supported lipid bilayers (CSLBs) has recently been extended to create colloidal joints, that enable the assembly of structures with internal degrees of flexibility, and to study lipid membranes on curved and closed geometries. These novel applications of CSLBs rely on previously unappreciated properties: the simultaneous fluidity of the bilayer, lateral mobility of inserted (linker) molecules and colloidal stability. Here we characterize every step in the manufacturing of CSLBs in view of these requirements using confocal microscopy and fluorescence recovery after photobleaching (FRAP). Specifically, we have studied the influence of different particle properties (roughness, surface charge, chemical composition, polymer coating) on the quality and mobility of the supported bilayer. We find that the insertion of lipopolymers in the bilayer can affect its homogeneity and fluidity. We improve the colloidal stability by inserting lipopolymers or double-stranded inert DNA into the bilayer. We include surface-mobile DNA linkers and use FRAP to characterize their lateral mobility both in their freely diffusive and bonded state. Finally, we demonstrate the self-assembly of flexibly linked structures from the CSLBs modified with surface-mobile DNA linkers. Our work offers a collection of experimental tools for working with CSLBs in applications ranging from controlled bottom-up self-assembly to model membrane studies.
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Affiliation(s)
- Melissa Rinaldin
- Huygens-Kamerlingh Onnes Lab, Universiteit Leiden
,
P.O. Box 9504
, 2300 RA Leiden
, The Netherlands
.
- Instituut-Lorentz, Universiteit Leiden
,
P.O. Box 9506
, 2300 RA Leiden
, The Netherlands
| | - Ruben W. Verweij
- Huygens-Kamerlingh Onnes Lab, Universiteit Leiden
,
P.O. Box 9504
, 2300 RA Leiden
, The Netherlands
.
| | - Indrani Chakraborty
- School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University
,
Tel Aviv 69978
, Israel
| | - Daniela J. Kraft
- Huygens-Kamerlingh Onnes Lab, Universiteit Leiden
,
P.O. Box 9504
, 2300 RA Leiden
, The Netherlands
.
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21
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Marré ML, Piganelli JD, James EA. Protecting functional β cells with a therapeutic peptide. ANNALS OF TRANSLATIONAL MEDICINE 2018; 6:372. [PMID: 30370299 DOI: 10.21037/atm.2018.07.26] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Meghan L Marré
- Division of Pediatric Surgery, Department of Surgery, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Jon D Piganelli
- Division of Pediatric Surgery, Department of Surgery, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Eddie A James
- Benaroya Research Institute at Virginia Mason, Seattle, WA, USA
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22
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Aslamy A, Oh E, Olson EM, Zhang J, Ahn M, Moin ASM, Tunduguru R, Salunkhe VA, Veluthakal R, Thurmond DC. Doc2b Protects β-Cells Against Inflammatory Damage and Enhances Function. Diabetes 2018; 67:1332-1344. [PMID: 29661782 PMCID: PMC6014558 DOI: 10.2337/db17-1352] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 04/09/2018] [Indexed: 12/12/2022]
Abstract
Loss of functional β-cell mass is an early feature of type 1 diabetes. To release insulin, β-cells require soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes, as well as SNARE complex regulatory proteins like double C2 domain-containing protein β (Doc2b). We hypothesized that Doc2b deficiency or overabundance may confer susceptibility or protection, respectively, to the functional β-cell mass. Indeed, Doc2b+/- knockout mice show an unusually severe response to multiple-low-dose streptozotocin (MLD-STZ), resulting in more apoptotic β-cells and a smaller β-cell mass. In addition, inducible β-cell-specific Doc2b-overexpressing transgenic (βDoc2b-dTg) mice show improved glucose tolerance and resist MLD-STZ-induced disruption of glucose tolerance, fasting hyperglycemia, β-cell apoptosis, and loss of β-cell mass. Mechanistically, Doc2b enrichment enhances glucose-stimulated insulin secretion (GSIS) and SNARE activation and prevents the appearance of apoptotic markers in response to cytokine stress and thapsigargin. Furthermore, expression of a peptide containing the Doc2b tandem C2A and C2B domains is sufficient to confer the beneficial effects of Doc2b enrichment on GSIS, SNARE activation, and apoptosis. These studies demonstrate that Doc2b enrichment in the β-cell protects against diabetogenic and proapoptotic stress. Furthermore, they identify a Doc2b peptide that confers the beneficial effects of Doc2b and may be a therapeutic candidate for protecting functional β-cell mass.
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Affiliation(s)
- Arianne Aslamy
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN
| | - Eunjin Oh
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Erika M Olson
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Jing Zhang
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Miwon Ahn
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Abu Saleh Md Moin
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Ragadeepthi Tunduguru
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
- Department of Diabetes Complications and Metabolism, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Vishal A Salunkhe
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Rajakrishnan Veluthakal
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
| | - Debbie C Thurmond
- Department of Molecular and Cellular Endocrinology, Diabetes and Metabolic Research Institute, Beckman Research Institute of City of Hope, Duarte, CA
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN
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23
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Melcr J, Martinez-Seara H, Nencini R, Kolafa J, Jungwirth P, Ollila OHS. Accurate Binding of Sodium and Calcium to a POPC Bilayer by Effective Inclusion of Electronic Polarization. J Phys Chem B 2018; 122:4546-4557. [DOI: 10.1021/acs.jpcb.7b12510] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Josef Melcr
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 117 20 Prague 6, Czech Republic
| | - Hector Martinez-Seara
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 117 20 Prague 6, Czech Republic
| | - Ricky Nencini
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 117 20 Prague 6, Czech Republic
| | - Jiří Kolafa
- Department of Physical Chemistry, Institute of Chemical Technology, 166 28 Prague 6, Czech Republic
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 117 20 Prague 6, Czech Republic
- Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland
| | - O. H. Samuli Ollila
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 117 20 Prague 6, Czech Republic
- Institute of Biotechnology, University of Helsinki, 00100 Helsinki, Finland
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24
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van Mameren J, Wuite GJL, Heller I. Introduction to Optical Tweezers: Background, System Designs, and Commercial Solutions. Methods Mol Biol 2018; 1665:3-23. [PMID: 28940061 DOI: 10.1007/978-1-4939-7271-5_1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Optical tweezers are a means to manipulate objects with light. With the technique, microscopically small objects can be held and steered, while forces on the trapped objects can be accurately measured and exerted. Optical tweezers can typically obtain a nanometer spatial resolution, a picoNewton force resolution, and a millisecond time resolution, which makes them excellently suited to study biological processes from the single-cell down to the single-molecule level. In this chapter, we will provide an introduction on the use of optical tweezers in single-molecule approaches. We will introduce the basic principles and methodology involved in optical trapping, force calibration, and force measurements. Next we describe the components of an optical tweezers setup and their experimental relevance in single-molecule approaches. Finally, we provide a concise overview of commercial optical tweezers systems. Commercial systems are becoming increasingly available and provide access to single-molecule optical tweezers experiments without the need for a thorough background in physics.
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Affiliation(s)
- Joost van Mameren
- Institute of Physics, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Gijs J L Wuite
- LaserLaB and Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands.
| | - Iddo Heller
- LaserLaB and Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands
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25
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Houy S, Groffen AJ, Ziomkiewicz I, Verhage M, Pinheiro PS, Sørensen JB. Doc2B acts as a calcium sensor for vesicle priming requiring synaptotagmin-1, Munc13-2 and SNAREs. eLife 2017; 6:27000. [PMID: 29274147 PMCID: PMC5758110 DOI: 10.7554/elife.27000] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 12/21/2017] [Indexed: 01/08/2023] Open
Abstract
Doc2B is a cytosolic protein with binding sites for Munc13 and Tctex-1 (dynein light chain), and two C2-domains that bind to phospholipids, Ca2+ and SNAREs. Whether Doc2B functions as a calcium sensor akin to synaptotagmins, or in other calcium-independent or calcium-dependent capacities is debated. We here show by mutation and overexpression that Doc2B plays distinct roles in two sequential priming steps in mouse adrenal chromaffin cells. Mutating Ca2+-coordinating aspartates in the C2A-domain localizes Doc2B permanently at the plasma membrane, and renders an upstream priming step Ca2+-independent, whereas a separate function in downstream priming depends on SNARE-binding, Ca2+-binding to the C2B-domain of Doc2B, interaction with ubMunc13-2 and the presence of synaptotagmin-1. Another function of Doc2B – inhibition of release during sustained calcium elevations – depends on an overlapping protein domain (the MID-domain), but is separate from its Ca2+-dependent priming function. We conclude that Doc2B acts as a vesicle priming protein.
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Affiliation(s)
- Sébastien Houy
- Neuronal Secretion Group, Department of Neuroscience, University of Copenhagen, København, Denmark
| | - Alexander J Groffen
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research, VU Medical Center, Amsterdam, Netherlands
| | - Iwona Ziomkiewicz
- Neuronal Secretion Group, Department of Neuroscience, University of Copenhagen, København, Denmark.,Discovery Sciences, Innovative Medicines and Early Development, AstraZeneca R&D, Cambridge, United Kingdom
| | - Matthijs Verhage
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research, VU Medical Center, Amsterdam, Netherlands.,Department of Functional Genomics, Faculty of Science, Center for Neurogenomics and Cognitive Research, VrijeUniversiteit, Amsterdam, Netherlands
| | - Paulo S Pinheiro
- Neuronal Secretion Group, Department of Neuroscience, University of Copenhagen, København, Denmark
| | - Jakob Balslev Sørensen
- Neuronal Secretion Group, Department of Neuroscience, University of Copenhagen, København, Denmark
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26
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Ma L, Cai Y, Li Y, Jiao J, Wu Z, O'Shaughnessy B, De Camilli P, Karatekin E, Zhang Y. Single-molecule force spectroscopy of protein-membrane interactions. eLife 2017; 6:30493. [PMID: 29083305 PMCID: PMC5690283 DOI: 10.7554/elife.30493] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 10/29/2017] [Indexed: 12/17/2022] Open
Abstract
Many biological processes rely on protein–membrane interactions in the presence of mechanical forces, yet high resolution methods to quantify such interactions are lacking. Here, we describe a single-molecule force spectroscopy approach to quantify membrane binding of C2 domains in Synaptotagmin-1 (Syt1) and Extended Synaptotagmin-2 (E-Syt2). Syts and E-Syts bind the plasma membrane via multiple C2 domains, bridging the plasma membrane with synaptic vesicles or endoplasmic reticulum to regulate membrane fusion or lipid exchange, respectively. In our approach, single proteins attached to membranes supported on silica beads are pulled by optical tweezers, allowing membrane binding and unbinding transitions to be measured with unprecedented spatiotemporal resolution. C2 domains from either protein resisted unbinding forces of 2–7 pN and had binding energies of 4–14 kBT per C2 domain. Regulation by bilayer composition or Ca2+ recapitulated known properties of both proteins. The method can be widely applied to study protein–membrane interactions.
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Affiliation(s)
- Lu Ma
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States.,CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China.,Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Yiying Cai
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States.,Department of Neuroscience, Yale University School of Medicine, New Haven, United States.,Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, United States.,Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, United States
| | - Yanghui Li
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States.,College of Optical and Electronic Technology, China Jiliang University, Hangzhou, China
| | - Junyi Jiao
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States.,Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, United States
| | - Zhenyong Wu
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, United States.,Nanobiology Institute, Yale University, West Haven, United States
| | - Ben O'Shaughnessy
- Department of Chemical Engineering, Columbia University, New York, United States
| | - Pietro De Camilli
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States.,Department of Neuroscience, Yale University School of Medicine, New Haven, United States.,Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, United States.,Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, United States.,Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, United States
| | - Erdem Karatekin
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, United States.,Nanobiology Institute, Yale University, West Haven, United States.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States.,Laboratoire de Neurophotonique, Faculté des Sciences Fondamentales et Biomédicales, Centre National de la Recherche Scientifique (CNRS) UMR 8250, Université Paris Descartes, Paris, France
| | - Yongli Zhang
- Department of Cell Biology, Yale University School of Medicine, New Haven, United States
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27
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Mattie S, McNally EK, Karim MA, Vali H, Brett CL. How and why intralumenal membrane fragments form during vacuolar lysosome fusion. Mol Biol Cell 2017; 28:309-321. [PMID: 27881666 PMCID: PMC5231899 DOI: 10.1091/mbc.e15-11-0759] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 11/04/2016] [Accepted: 11/18/2016] [Indexed: 11/11/2022] Open
Abstract
Lysosomal membrane fusion mediates the last step of the autophagy and endocytosis pathways and supports organelle remodeling and biogenesis. Because fusogenic proteins and lipids concentrate in a ring at the vertex between apposing organelle membranes, the encircled area of membrane can be severed and internalized within the lumen as a fragment upon lipid bilayer fusion. How or why this intralumenal fragment forms during fusion, however, is not entirely clear. To better understand this process, we studied fragment formation during homotypic vacuolar lysosome membrane fusion in Saccharomyces cerevisiae Using cell-free fusion assays and light microscopy, we find that GTPase activation and trans-SNARE complex zippering have opposing effects on fragment formation and verify that this affects the morphology of the fusion product and regulates transporter protein degradation. We show that fragment formwation is limited by stalk expansion, a key intermediate of the lipid bilayer fusion reaction. Using electron microscopy, we present images of hemifusion diaphragms that form as stalks expand and propose a model describing how the fusion machinery regulates fragment formation during lysosome fusion to control morphology and protein lifetimes.
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Affiliation(s)
- Sevan Mattie
- Department of Biology, Concordia University, Montréal, QC H4B 1R6, Canada
| | - Erin K McNally
- Department of Biology, Concordia University, Montréal, QC H4B 1R6, Canada
| | - Mahmoud A Karim
- Department of Biology, Concordia University, Montréal, QC H4B 1R6, Canada
| | - Hojatollah Vali
- Department of Anatomy and Cell Biology, McGill University, Montréal, QC H3A 0C7, Canada
| | - Christopher L Brett
- Department of Biology, Concordia University, Montréal, QC H4B 1R6, Canada
- Department of Anatomy and Cell Biology, McGill University, Montréal, QC H3A 0C7, Canada
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28
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Hashemi Shabestari M, Meijering AEC, Roos WH, Wuite GJL, Peterman EJG. Recent Advances in Biological Single-Molecule Applications of Optical Tweezers and Fluorescence Microscopy. Methods Enzymol 2016; 582:85-119. [PMID: 28062046 DOI: 10.1016/bs.mie.2016.09.047] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Over the past two decades, single-molecule techniques have evolved into robust tools to study many fundamental biological processes. The combination of optical tweezers with fluorescence microscopy and microfluidics provides a powerful single-molecule manipulation and visualization technique that has found widespread application in biology. In this combined approach, the spatial (~nm) and temporal (~ms) resolution, as well as the force scale (~pN) accessible to optical tweezers is complemented with the power of fluorescence microscopy. Thereby, it provides information on the local presence, identity, spatial dynamics, and conformational dynamics of single biomolecules. Together, these techniques allow comprehensive studies of, among others, molecular motors, protein-protein and protein-DNA interactions, biomolecular conformational changes, and mechanotransduction pathways. In this chapter, recent applications of fluorescence microscopy in combination with optical trapping are discussed. After an introductory section, we provide a description of instrumentation together with the current capabilities and limitations of the approaches. Next we summarize recent studies that applied this combination of techniques in biological systems and highlight some representative biological assays to mark the exquisite opportunities that optical tweezers combined with fluorescence microscopy provide.
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Affiliation(s)
| | | | - W H Roos
- Moleculaire Biofysica, Zernike Institute, Rijksuniversiteit Groningen, Groningen, The Netherlands
| | - G J L Wuite
- Vrije Universiteit, Amsterdam, The Netherlands
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29
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Pinheiro PS, Houy S, Sørensen JB. C2-domain containing calcium sensors in neuroendocrine secretion. J Neurochem 2016; 139:943-958. [DOI: 10.1111/jnc.13865] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 09/17/2016] [Accepted: 10/05/2016] [Indexed: 12/11/2022]
Affiliation(s)
- Paulo S. Pinheiro
- Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
| | - Sébastien Houy
- Department of Neuroscience and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - Jakob B. Sørensen
- Department of Neuroscience and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
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30
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SNARE-mediated membrane fusion trajectories derived from force-clamp experiments. Proc Natl Acad Sci U S A 2016; 113:13051-13056. [PMID: 27807132 DOI: 10.1073/pnas.1615885113] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Fusion of lipid bilayers is usually prevented by large energy barriers arising from removal of the hydration shell, formation of highly curved structures, and, eventually, fusion pore widening. Here, we measured the force-dependent lifetime of fusion intermediates using membrane-coated silica spheres attached to cantilevers of an atomic-force microscope. Analysis of time traces obtained from force-clamp experiments allowed us to unequivocally assign steps in deflection of the cantilever to membrane states during the SNARE-mediated fusion with solid-supported lipid bilayers. Force-dependent lifetime distributions of the various intermediate fusion states allowed us to propose the likelihood of different fusion pathways and to assess the main free energy barrier, which was found to be related to passing of the hydration barrier and splaying of lipids to eventually enter either the fully fused state or a long-lived hemifusion intermediate. The results were compared with SNARE mutants that arrest adjacent bilayers in the docked state and membranes in the absence of SNAREs but presence of PEG or calcium. Only with the WT SNARE construct was appreciable merging of both bilayers observed.
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