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Bender J, Kundlacz T, Rudden LSP, Frick M, Bieber J, Degiacomi MT, Schmidt C. Ca 2+-dependent lipid preferences shape synaptotagmin-1 C2A and C2B dynamics: Insights from experiments and simulations. Structure 2024:S0969-2126(24)00280-6. [PMID: 39173623 DOI: 10.1016/j.str.2024.07.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 07/04/2024] [Accepted: 07/28/2024] [Indexed: 08/24/2024]
Abstract
Signal transmission between neurons requires exocytosis of neurotransmitters from the lumen of synaptic vesicles into the synaptic cleft. Following an influx of Ca2+, this process is facilitated by the Ca2+ sensor synaptotagmin-1. The underlying mechanisms involve electrostatic and hydrophobic interactions tuning the lipid preferences of the two C2 domains of synaptotagmin-1; however, the details are still controversially discussed. We, therefore, follow a multidisciplinary approach and characterize lipid and membrane binding of the isolated C2A and C2B domains. We first target interactions with individual lipid species, and then study interactions with model membranes of liposomes. Finally, we perform molecular dynamics simulations to unravel differences in membrane binding. We found that both C2 domains, as a response to Ca2+, insert into the lipid membrane; however, C2A adopts a more perpendicular orientation while C2B remains parallel. These findings allow us to propose a mechanism for synaptotagmin-1 during membrane fusion.
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Affiliation(s)
- Julian Bender
- Interdisciplinary Research Center HALOmem, Institute of Biochemistry and Biotechnology, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120 Halle, Germany
| | - Til Kundlacz
- Interdisciplinary Research Center HALOmem, Institute of Biochemistry and Biotechnology, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120 Halle, Germany; Institute of Chemistry, Martin Luther University Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle, Germany
| | - Lucas S P Rudden
- Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
| | - Melissa Frick
- Interdisciplinary Research Center HALOmem, Institute of Biochemistry and Biotechnology, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120 Halle, Germany
| | - Julia Bieber
- Department of Chemistry - Biochemistry, Johannes Gutenberg University Mainz, Hanns-Dieter-Hüsch-Weg 17, 55128 Mainz, Germany
| | - Matteo T Degiacomi
- Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
| | - Carla Schmidt
- Interdisciplinary Research Center HALOmem, Institute of Biochemistry and Biotechnology, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120 Halle, Germany; Department of Chemistry - Biochemistry, Johannes Gutenberg University Mainz, Hanns-Dieter-Hüsch-Weg 17, 55128 Mainz, Germany.
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2
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Jaczynska K, Esser V, Xu J, Sari L, Lin MM, Rosenmund C, Rizo J. A lever hypothesis for Synaptotagmin-1 action in neurotransmitter release. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.17.599417. [PMID: 38948826 PMCID: PMC11212951 DOI: 10.1101/2024.06.17.599417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Neurotransmitter release is triggered in microseconds by Ca2+-binding to the Synaptotagmin-1 C2 domains and by SNARE complexes that form four-helix bundles between synaptic vesicles and plasma membranes, but the coupling mechanism between Ca2+-sensing and membrane fusion is unknown. Release requires extension of SNARE helices into juxtamembrane linkers that precede transmembrane regions (linker zippering) and binding of the Synaptotagmin-1 C2B domain to SNARE complexes through a 'primary interface' comprising two regions (I and II). The Synaptotagmin-1 Ca2+-binding loops were believed to accelerate membrane fusion by inducing membrane curvature, perturbing lipid bilayers or helping bridge the membranes, but SNARE complex binding orients the Ca2+-binding loops away from the fusion site, hindering these putative activities. Molecular dynamics simulations now suggest that Synaptotagmin-1 C2 domains near the site of fusion hinder SNARE action, providing an explanation for this paradox and arguing against previous models of Sytnaptotagmin-1 action. NMR experiments reveal that binding of C2B domain arginines to SNARE acidic residues at region II remains after disruption of region I. These results and fluorescence resonance energy transfer assays, together with previous data, suggest that Ca2+ causes reorientation of the C2B domain on the membrane and dissociation from the SNAREs at region I but not region II. Based on these results and molecular modeling, we propose that Synaptotagmin-1 acts as a lever that pulls the SNARE complex when Ca2+ causes reorientation of the C2B domain, facilitating linker zippering and fast membrane fusion. This hypothesis is supported by the electrophysiological data described in the accompanying paper.
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Affiliation(s)
- Klaudia Jaczynska
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Victoria Esser
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Junjie Xu
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Levent Sari
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Milo M. Lin
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Christian Rosenmund
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Neurophysiology, Berlin, Germany
- NeuroCure Cluster of Excellence, Berlin, Germany
| | - Josep Rizo
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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3
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Bykhovskaia M. Dynamic Formation of the Protein-Lipid Pre-fusion Complex. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.17.589983. [PMID: 38659925 PMCID: PMC11042276 DOI: 10.1101/2024.04.17.589983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Synaptic vesicles (SVs) fuse with the presynaptic membrane (PM) to release neuronal transmitters. The SV protein Synaptotagmin 1 (Syt1) serves as a Ca2+ sensor for evoked fusion. Syt1 is thought to trigger fusion by penetrating into PM upon Ca2+ binding, however the mechanistic detail of this process is still debated. Syt1 interacts with the SNARE complex, a coiled-coil four-helical bundle that enables the SV-PM attachment. The SNARE-associated protein Complexin (Cpx) promotes the Ca2+-dependent fusion, possibly interacting with Syt1. We employed all-atom molecular dynamics (MD) to investigate the formation of the Syt1-SNARE-Cpx complex interacting with the lipid bilayers of PM and SV. Our simulations demonstrated that the PM-Syt1-SNARE-Cpx complex can transition to a "dead-end" state, wherein Syt1 attaches tightly to PM but does not immerse into it, as opposed to a pre-fusion state, which has the tips of the Ca2+-bound C2 domains of Syt1 inserted into PM. Our simulations unraveled the sequence of Syt1 conformational transitions, including the simultaneous Syt1 docking to the SNARE-Cpx bundle and PM, followed by the Ca2+ chelation and the penetration of the tips of Syt1 domains into PM, leading to the pre-fusion state of the protein-lipid complex. Importantly, we found that the direct Syt1-Cpx interactions are required to promote these transitions. Thus, we developed the all-atom dynamic model of the conformational transitions that lead to the formation of the pre-fusion PM-Syt1-SNARE-Cpx complex. Our simulations also revealed an alternative "dead-end" state of the protein-lipid complex that can be formed if this pathway is disrupted.
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4
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Queiroz Zetune Villa Real K, Mougios N, Rehm R, Sograte-Idrissi S, Albert L, Rahimi AM, Maidorn M, Hentze J, Martínez-Carranza M, Hosseini H, Saal KA, Oleksiievets N, Prigge M, Tsukanov R, Stenmark P, Fornasiero EF, Opazo F. A Versatile Synaptotagmin-1 Nanobody Provides Perturbation-Free Live Synaptic Imaging And Low Linkage-Error in Super-Resolution Microscopy. SMALL METHODS 2023; 7:e2300218. [PMID: 37421204 DOI: 10.1002/smtd.202300218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 06/09/2023] [Indexed: 07/10/2023]
Abstract
Imaging of living synapses has relied for over two decades on the overexpression of synaptic proteins fused to fluorescent reporters. This strategy alters the stoichiometry of synaptic components and ultimately affects synapse physiology. To overcome these limitations, here a nanobody is presented that binds the calcium sensor synaptotagmin-1 (NbSyt1). This nanobody functions as an intrabody (iNbSyt1) in living neurons and is minimally invasive, leaving synaptic transmission almost unaffected, as suggested by the crystal structure of the NbSyt1 bound to Synaptotagmin-1 and by the physiological data. Its single-domain nature enables the generation of protein-based fluorescent reporters, as showcased here by measuring spatially localized presynaptic Ca2+ with a NbSyt1- jGCaMP8 chimera. Moreover, the small size of NbSyt1 makes it ideal for various super-resolution imaging methods. Overall, NbSyt1 is a versatile binder that will enable imaging in cellular and molecular neuroscience with unprecedented precision across multiple spatiotemporal scales.
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Affiliation(s)
- Karine Queiroz Zetune Villa Real
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration (BIN), University Medical Center Göttingen, 37075, Göttingen, Germany
| | - Nikolaos Mougios
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration (BIN), University Medical Center Göttingen, 37075, Göttingen, Germany
| | - Ronja Rehm
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany
| | - Shama Sograte-Idrissi
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration (BIN), University Medical Center Göttingen, 37075, Göttingen, Germany
| | - László Albert
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration (BIN), University Medical Center Göttingen, 37075, Göttingen, Germany
| | - Amir Mohammad Rahimi
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration (BIN), University Medical Center Göttingen, 37075, Göttingen, Germany
| | - Manuel Maidorn
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration (BIN), University Medical Center Göttingen, 37075, Göttingen, Germany
| | - Jannik Hentze
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration (BIN), University Medical Center Göttingen, 37075, Göttingen, Germany
| | - Markel Martínez-Carranza
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Stockholm, SE-10691, Sweden
| | - Hassan Hosseini
- Research Group Neuromodulatory Networks, Leibniz Institute for Neurobiology, 39118, Magdeburg, Germany
| | - Kim-Ann Saal
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany
| | - Nazar Oleksiievets
- III. Institute of Physics - Biophysics, Georg August University, 37077, Göttingen, Germany
| | - Matthias Prigge
- Research Group Neuromodulatory Networks, Leibniz Institute for Neurobiology, 39118, Magdeburg, Germany
- Center for Behavioral Brain Sciences, 39118, Magdeburg, Germany
| | - Roman Tsukanov
- III. Institute of Physics - Biophysics, Georg August University, 37077, Göttingen, Germany
| | - Pål Stenmark
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Stockholm, SE-10691, Sweden
| | - Eugenio F Fornasiero
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany
| | - Felipe Opazo
- Institute of Neuro- and Sensory Physiology, University Medical Center Göttingen, 37073, Göttingen, Germany
- Center for Biostructural Imaging of Neurodegeneration (BIN), University Medical Center Göttingen, 37075, Göttingen, Germany
- NanoTag Biotechnologies GmbH, 37079, Göttingen, Germany
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5
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Bykhovskaia M. Molecular Dynamics Simulations of the Proteins Regulating Synaptic Vesicle Fusion. MEMBRANES 2023; 13:307. [PMID: 36984694 PMCID: PMC10058449 DOI: 10.3390/membranes13030307] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 02/11/2023] [Accepted: 03/01/2023] [Indexed: 06/18/2023]
Abstract
Neuronal transmitters are packaged in synaptic vesicles (SVs) and released by the fusion of SVs with the presynaptic membrane (PM). An inflow of Ca2+ into the nerve terminal triggers fusion, and the SV-associated protein Synaptotagmin 1 (Syt1) serves as a Ca2+ sensor. In preparation for fusion, SVs become attached to the PM by the SNARE protein complex, a coiled-coil bundle that exerts the force overcoming SV-PM repulsion. A cytosolic protein Complexin (Cpx) attaches to the SNARE complex and differentially regulates the evoked and spontaneous release components. It is still debated how the dynamic interactions of Syt1, SNARE proteins and Cpx lead to fusion. This problem is confounded by heterogeneity in the conformational states of the prefusion protein-lipid complex and by the lack of tools to experimentally monitor the rapid conformational transitions of the complex, which occur at a sub-millisecond scale. However, these complications can be overcome employing molecular dynamics (MDs), a computational approach that enables simulating interactions and conformational transitions of proteins and lipids. This review discusses the use of molecular dynamics for the investigation of the pre-fusion protein-lipid complex. We discuss the dynamics of the SNARE complex between lipid bilayers, as well as the interactions of Syt1 with lipids and SNARE proteins, and Cpx regulating the assembly of the SNARE complex.
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Affiliation(s)
- Maria Bykhovskaia
- Neurology Department, Wayne State University, Detroit, MI 48202, USA
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6
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Xue M, Cao Y, Shen C, Guo W. Computational Advances of Protein/Neurotransmitter-membrane Interactions Involved in Vesicle Fusion and Neurotransmitter Release. J Mol Biol 2023; 435:167818. [PMID: 36089056 DOI: 10.1016/j.jmb.2022.167818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 08/22/2022] [Accepted: 09/04/2022] [Indexed: 02/04/2023]
Abstract
Vesicle fusion is of crucial importance to neuronal communication at neuron terminals. The exquisite but complex fusion machinery for neurotransmitter release is tightly controlled and regulated by protein/neurotransmitter-membrane interactions. Computational 'microscopies', in particular molecular dynamics simulations and related techniques, have provided notable insight into the physiological process over the past decades, and have made enormous contributions to fields such as neurology, pharmacology and pathophysiology. Here we review the computational advances of protein/neurotransmitter-membrane interactions related to presynaptic vesicle-membrane fusion and neurotransmitter release, and outline the in silico challenges ahead for understanding this important physiological process.
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Affiliation(s)
- Minmin Xue
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
| | - Yuwei Cao
- State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing, China
| | - Chun Shen
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
| | - Wanlin Guo
- Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education, State Key Laboratory of Mechanics and Control of Mechanical Structures, and Institute for Frontier Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing, China.
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7
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Akefe IO, Osborne SL, Matthews B, Wallis TP, Meunier FA. Lipids and Secretory Vesicle Exocytosis. ADVANCES IN NEUROBIOLOGY 2023; 33:357-397. [PMID: 37615874 DOI: 10.1007/978-3-031-34229-5_14] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
In recent years, the number of studies implicating lipids in the regulation of synaptic vesicle exocytosis has risen considerably. It has become increasingly clear that lipids such as phosphoinositides, lysophospholipids, cholesterol, arachidonic acid and myristic acid play critical regulatory roles in the processes leading up to exocytosis. Lipids may affect membrane fusion reactions by altering the physical properties of the membrane, recruiting key regulatory proteins, concentrating proteins into exocytic "hotspots" or by modulating protein functions allosterically. Discrete changes in phosphoinositides concentration are involved in multiple trafficking events including exocytosis and endocytosis. Lipid-modifying enzymes such as the DDHD2 isoform of phospholipase A1 were recently shown to contribute to memory acquisition via dynamic modifications of the brain lipid landscape. Considering the increasing reports on neurodegenerative disorders associated with aberrant intracellular trafficking, an improved understanding of the control of lipid pathways is physiologically and clinically significant and will afford unique insights into mechanisms and therapeutic methods for neurodegenerative diseases. Consequently, this chapter will discuss the different classes of lipids, phospholipase enzymes, the evidence linking them to synaptic neurotransmitter release and how they act to regulate key steps in the multi-step process leading to neuronal communication and memory acquisition.
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Affiliation(s)
- Isaac O Akefe
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, St Lucia, QLD, Australia
| | - Shona L Osborne
- ARC Training Centre for Innovation in Biomedical Imaging Technology (CIBIT), The University of Queensland, St Lucia, QLD, Australia
| | - Benjamin Matthews
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, St Lucia, QLD, Australia
| | - Tristan P Wallis
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, St Lucia, QLD, Australia
| | - Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain Institute, The University of Queensland, St Lucia, QLD, Australia.
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, Australia.
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8
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Rizo J, Sari L, Qi Y, Im W, Lin MM. All-atom molecular dynamics simulations of Synaptotagmin-SNARE-complexin complexes bridging a vesicle and a flat lipid bilayer. eLife 2022; 11:76356. [PMID: 35708237 PMCID: PMC9239685 DOI: 10.7554/elife.76356] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 06/15/2022] [Indexed: 12/14/2022] Open
Abstract
Synaptic vesicles are primed into a state that is ready for fast neurotransmitter release upon Ca2+-binding to Synaptotagmin-1. This state likely includes trans-SNARE complexes between the vesicle and plasma membranes that are bound to Synaptotagmin-1 and complexins. However, the nature of this state and the steps leading to membrane fusion are unclear, in part because of the difficulty of studying this dynamic process experimentally. To shed light into these questions, we performed all-atom molecular dynamics simulations of systems containing trans-SNARE complexes between two flat bilayers or a vesicle and a flat bilayer with or without fragments of Synaptotagmin-1 and/or complexin-1. Our results need to be interpreted with caution because of the limited simulation times and the absence of key components, but suggest mechanistic features that may control release and help visualize potential states of the primed Synaptotagmin-1-SNARE-complexin-1 complex. The simulations suggest that SNAREs alone induce formation of extended membrane-membrane contact interfaces that may fuse slowly, and that the primed state contains macromolecular assemblies of trans-SNARE complexes bound to the Synaptotagmin-1 C2B domain and complexin-1 in a spring-loaded configuration that prevents premature membrane merger and formation of extended interfaces, but keeps the system ready for fast fusion upon Ca2+ influx.
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Affiliation(s)
- Josep Rizo
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Levent Sari
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, United States.,Green Center for Systems Biology, The University of Texas Southwestern Medical Center, Dallas, United States
| | - Yife Qi
- Department of Medicinal Chemistry, School of Pharmacy, Fudan University, Shanghai, China
| | - Wonpil Im
- Department of Biological Sciences, Lehigh University, Bethlehem, United States.,Department of Chemistry, Lehigh University, Bethlehem, United States.,Department of Bioengineering, Lehigh University, Bethlehem, United States.,Department of Computer Science and Engineering, Lehigh University, Bethlehem, United States
| | - Milo M Lin
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, United States.,Green Center for Systems Biology, The University of Texas Southwestern Medical Center, Dallas, United States
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9
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Wu Z, Dharan N, McDargh ZA, Thiyagarajan S, O'Shaughnessy B, Karatekin E. The neuronal calcium sensor Synaptotagmin-1 and SNARE proteins cooperate to dilate fusion pores. eLife 2021; 10:68215. [PMID: 34190041 PMCID: PMC8294851 DOI: 10.7554/elife.68215] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 06/29/2021] [Indexed: 02/07/2023] Open
Abstract
All membrane fusion reactions proceed through an initial fusion pore, including calcium-triggered release of neurotransmitters and hormones. Expansion of this small pore to release cargo is energetically costly and regulated by cells, but the mechanisms are poorly understood. Here, we show that the neuronal/exocytic calcium sensor Synaptotagmin-1 (Syt1) promotes expansion of fusion pores induced by SNARE proteins. Pore dilation relied on calcium-induced insertion of the tandem C2 domain hydrophobic loops of Syt1 into the membrane, previously shown to reorient the C2 domain. Mathematical modelling suggests that C2B reorientation rotates a bound SNARE complex so that it exerts force on the membranes in a mechanical lever action that increases the height of the fusion pore, provoking pore dilation to offset the bending energy penalty. We conclude that Syt1 exerts novel non-local calcium-dependent mechanical forces on fusion pores that dilate pores and assist neurotransmitter and hormone release.
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Affiliation(s)
- Zhenyong Wu
- Department of Cellular and Molecular Physiology, Yale University, New Haven, United States.,Nanobiology Institute, Yale University, West Haven, United States
| | - Nadiv Dharan
- Department of Chemical Engineering, Columbia University, New York, United States
| | - Zachary A McDargh
- Department of Chemical Engineering, Columbia University, New York, United States
| | - Sathish Thiyagarajan
- Department of Chemical Engineering, Columbia University, New York, United States
| | - Ben O'Shaughnessy
- Department of Chemical Engineering, Columbia University, New York, United States
| | - Erdem Karatekin
- Department of Cellular and Molecular Physiology, Yale University, New Haven, United States.,Nanobiology Institute, Yale University, West Haven, United States.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States.,Saints-Pères Paris Institute for the Neurosciences (SPPIN), Université de Paris, Centre National de la Recherche Scientifique (CNRS) UMR 8003, Paris, France
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10
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Tagoe DNA, Drozda AA, Falco JA, Bechtel TJ, Weerapana E, Gubbels MJ. Ferlins and TgDOC2 in Toxoplasma Microneme, Rhoptry and Dense Granule Secretion. Life (Basel) 2021; 11:217. [PMID: 33803212 PMCID: PMC7999867 DOI: 10.3390/life11030217] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Revised: 03/02/2021] [Accepted: 03/05/2021] [Indexed: 12/25/2022] Open
Abstract
The host cell invasion process of apicomplexan parasites like Toxoplasma gondii is facilitated by sequential exocytosis of the microneme, rhoptry and dense granule organelles. Exocytosis is facilitated by a double C2 domain (DOC2) protein family. This class of C2 domains is derived from an ancestral calcium (Ca2+) binding archetype, although this feature is optional in extant C2 domains. DOC2 domains provide combinatorial power to the C2 domain, which is further enhanced in ferlins that harbor 5-7 C2 domains. Ca2+ conditionally engages the C2 domain with lipids, membranes, and/or proteins to facilitating vesicular trafficking and membrane fusion. The widely conserved T. gondii ferlins 1 (FER1) and 2 (FER2) are responsible for microneme and rhoptry exocytosis, respectively, whereas an unconventional TgDOC2 is essential for microneme exocytosis. The general role of ferlins in endolysosmal pathways is consistent with the repurposed apicomplexan endosomal pathways in lineage specific secretory organelles. Ferlins can facilitate membrane fusion without SNAREs, again pertinent to the Apicomplexa. How temporal raises in Ca2+ combined with spatiotemporally available membrane lipids and post-translational modifications mesh to facilitate sequential exocytosis events is discussed. In addition, new data on cross-talk between secretion events together with the identification of a new microneme protein, MIC21, is presented.
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Affiliation(s)
- Daniel N. A. Tagoe
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA; (D.N.A.T.); (A.A.D.)
| | - Allison A. Drozda
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA; (D.N.A.T.); (A.A.D.)
| | - Julia A. Falco
- Department of Chemistry, Boston College, Chestnut Hill, MA 02467, USA; (J.A.F.); (T.J.B.); (E.W.)
| | - Tyler J. Bechtel
- Department of Chemistry, Boston College, Chestnut Hill, MA 02467, USA; (J.A.F.); (T.J.B.); (E.W.)
| | - Eranthie Weerapana
- Department of Chemistry, Boston College, Chestnut Hill, MA 02467, USA; (J.A.F.); (T.J.B.); (E.W.)
| | - Marc-Jan Gubbels
- Department of Biology, Boston College, Chestnut Hill, MA 02467, USA; (D.N.A.T.); (A.A.D.)
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