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Zhao Y, Fang Q, Sharma S, Jakhanwal S, Jahn R, Lindau M. All SNAP25 molecules in the vesicle-plasma membrane contact zone change conformation during vesicle priming. Proc Natl Acad Sci U S A 2024; 121:e2309161121. [PMID: 38170748 PMCID: PMC10786266 DOI: 10.1073/pnas.2309161121] [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: 06/06/2023] [Accepted: 11/27/2023] [Indexed: 01/05/2024] Open
Abstract
In neuronal cell types, vesicular exocytosis is governed by the SNARE (soluble NSF attachment receptor) complex consisting of synaptobrevin2, SNAP25, and syntaxin1. These proteins are required for vesicle priming and fusion. We generated an improved SNAP25-based SNARE COmplex Reporter (SCORE2) incorporating mCeruelan3 and Venus and overexpressed it in SNAP25 knockout embryonic mouse chromaffin cells. This construct rescues vesicle fusion with properties indistinguishable from fusion in wild-type cells. Combining electrochemical imaging of individual release events using electrochemical detector arrays with total internal reflection fluorescence resonance energy transfer (TIR-FRET) imaging reveals a rapid FRET increase preceding individual fusion events by 65 ms. The experiments are performed under conditions of a steady-state cycle of docking, priming, and fusion, and the delay suggests that the FRET change reflects tight docking and priming of the vesicle, followed by fusion after ~65 ms. Given the absence of wt SNAP25, SCORE2 allows determination of the number of molecules at fusion sites and the number that changes conformation. The number of SNAP25 molecules changing conformation in the priming step increases with vesicle size and SNAP25 density in the plasma membrane and equals the number of copies present in the vesicle-plasma membrane contact zone. We estimate that in wt cells, 6 to 7 copies of SNAP25 change conformation during the priming step.
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Affiliation(s)
- Ying Zhao
- Nanoscale Cell Biology, Max-Planck-Institute for Biophysical Chemistry, GöttingenD-37077, Germany
| | - Qinghua Fang
- Nanoscale Cell Biology, Max-Planck-Institute for Biophysical Chemistry, GöttingenD-37077, Germany
| | - Satyan Sharma
- Nanoscale Cell Biology, Max-Planck-Institute for Biophysical Chemistry, GöttingenD-37077, Germany
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala75124, Sweden
| | - Shrutee Jakhanwal
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, GöttingenD-37077, Germany
| | - Reinhard Jahn
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, GöttingenD-37077, Germany
| | - Manfred Lindau
- Nanoscale Cell Biology, Max-Planck-Institute for Biophysical Chemistry, GöttingenD-37077, Germany
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, FL33136
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2
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Aldahabi M, Balint F, Holderith N, Lorincz A, Reva M, Nusser Z. Different priming states of synaptic vesicles underlie distinct release probabilities at hippocampal excitatory synapses. Neuron 2022; 110:4144-4161.e7. [PMID: 36261033 PMCID: PMC9796815 DOI: 10.1016/j.neuron.2022.09.035] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 07/28/2022] [Accepted: 09/27/2022] [Indexed: 12/12/2022]
Abstract
A stunning example of synaptic diversity is the postsynaptic target cell-type-dependent difference in synaptic efficacy in cortical networks. Here, we show that CA1 pyramidal cell (PC) to fast spiking interneuron (FSIN) connections have 10-fold larger release probability (Pv) than those on oriens lacunosum-moleculare (O-LM) interneurons. Freeze-fracture immunolabeling revealed that different nano-topologies and coupling distances between Ca2+ channels and release sites (RSs) are not responsible for the distinct Pv. Although [Ca2+] transients are 40% larger in FSINs innervating boutons, when [Ca2+] entry is matched in the two bouton populations, EPSCs in O-LM cells are still 7-fold smaller. However, application of a phorbol ester analog resulted in a ∼2.5-fold larger augmentation at PC - O-LM compared to PC - FSIN synapses, suggesting incomplete docking or priming of vesicles. Similar densities of docked vesicles rule out distinct RS occupancies and demonstrate that incompletely primed, but docked, vesicles limit the output of PC - O-LM synapses.
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Affiliation(s)
- Mohammad Aldahabi
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest 1083, Hungary,János Szentágothai School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Flora Balint
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest 1083, Hungary
| | - Noemi Holderith
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest 1083, Hungary
| | - Andrea Lorincz
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest 1083, Hungary
| | - Maria Reva
- Unit of Synapse and Circuit Dynamics, CNRS UMR 3571, Institute Pasteur, Paris, France
| | - Zoltan Nusser
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine, Budapest 1083, Hungary,Corresponding author
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3
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Tan C, de Nola G, Qiao C, Imig C, Born RT, Brose N, Kaeser PS. Munc13 supports fusogenicity of non-docked vesicles at synapses with disrupted active zones. eLife 2022; 11:79077. [PMID: 36398873 PMCID: PMC9822248 DOI: 10.7554/elife.79077] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 11/17/2022] [Indexed: 11/19/2022] Open
Abstract
Active zones consist of protein scaffolds that are tightly attached to the presynaptic plasma membrane. They dock and prime synaptic vesicles, couple them to voltage-gated Ca2+ channels, and direct neurotransmitter release toward postsynaptic receptor domains. Simultaneous RIM + ELKS ablation disrupts these scaffolds, abolishes vesicle docking, and removes active zone-targeted Munc13, but some vesicles remain releasable. To assess whether this enduring vesicular fusogenicity is mediated by non-active zone-anchored Munc13 or is Munc13-independent, we ablated Munc13-1 and Munc13-2 in addition to RIM + ELKS in mouse hippocampal neurons. The hextuple knockout synapses lacked docked vesicles, but other ultrastructural features were near-normal despite the strong genetic manipulation. Removing Munc13 in addition to RIM + ELKS impaired action potential-evoked vesicle fusion more strongly than RIM + ELKS knockout by further decreasing the releasable vesicle pool. Hence, Munc13 can support some fusogenicity without RIM and ELKS, and presynaptic recruitment of Munc13, even without active zone anchoring, suffices to generate some fusion-competent vesicles.
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Affiliation(s)
- Chao Tan
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Giovanni de Nola
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Claire Qiao
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Cordelia Imig
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark.,Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Goettingen, Germany
| | - Richard T Born
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Goettingen, Germany
| | - Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, United States
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4
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Mizuno K, Izumi T. Munc13b stimulus-dependently accumulates on granuphilin-mediated, docked granules prior to fusion. Cell Struct Funct 2022; 47:31-41. [PMID: 35387942 PMCID: PMC10511056 DOI: 10.1247/csf.22005] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 03/30/2022] [Indexed: 11/11/2022] Open
Abstract
The Rab27 effector granuphilin plays an indispensable role in stable docking of secretory granules to the plasma membrane by interacting with the complex of Munc18-1 and the fusion-incompetent, closed form of syntaxins-1~3. Although this process prevents spontaneous granule exocytosis, those docked granules actively fuse in parallel with other undocked granules after stimulation. Therefore, it is postulated that the closed form of syntaxins must be converted into the fusion-competent open form in a stimulus-dependent manner. Although Munc13 family proteins are generally thought to prime docked vesicles by facilitating conformational change in syntaxins, it is unknown which isoform acts in granuphilin-mediated, docked granule exocytosis. In the present study, we show that, although both Munc13a and Munc13b are expressed in mouse pancreatic islets and their beta-cell line MIN6, the silencing of Munc13b, but not that of Munc13a, severely affects glucose-induced insulin secretion. Furthermore, Munc13b accumulates on a subset of granules beneath the plasma membrane just prior to fusion during stimulation, whereas Munc13a is translocated to the plasma membrane where granules do not exist. When fluorescently labeled granuphilin was introduced to discriminate between molecularly docked granules and other undocked granules in living cells, Munc13b downregulation was observed to preferentially decrease the fusion of granuphilin-positive granules immobilized to the plasma membrane. These findings suggest that Munc13b promotes insulin exocytosis by clustering on molecularly docked granules in a stimulus-dependent manner.Key words: docking, insulin, live cell imaging, priming, TIRF microscopy.
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Affiliation(s)
- Kouichi Mizuno
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan
| | - Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan
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5
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Wang S, Ma C. Neuronal SNARE complex assembly guided by Munc18-1 and Munc13-1. FEBS Open Bio 2022; 12:1939-1957. [PMID: 35278279 PMCID: PMC9623535 DOI: 10.1002/2211-5463.13394] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 02/28/2022] [Accepted: 03/10/2022] [Indexed: 01/25/2023] Open
Abstract
Neurotransmitter release by Ca2+ -triggered synaptic vesicle exocytosis is essential for information transmission in the nervous system. The soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs) syntaxin-1, SNAP-25, and synaptobrevin-2 form the SNARE complex to bring synaptic vesicles and the plasma membranes together and to catalyze membrane fusion. Munc18-1 and Munc13-1 regulate synaptic vesicle priming via orchestrating neuronal SNARE complex assembly. In this review, we summarize recent advances toward the functions and molecular mechanisms of Munc18-1 and Munc13-1 in guiding neuronal SNARE complex assembly, and discuss the functional similarities and differences between Munc18-1 and Munc13-1 in neurons and their homologs in other intracellular membrane trafficking systems.
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Affiliation(s)
- Shen Wang
- Key Laboratory of Molecular Biophysics of the Ministry of EducationCollege of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
| | - Cong Ma
- Key Laboratory of Molecular Biophysics of the Ministry of EducationCollege of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
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6
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Holderith N, Aldahabi M, Nusser Z. Selective Enrichment of Munc13-2 in Presynaptic Active Zones of Hippocampal Pyramidal Cells That Innervate mGluR1α Expressing Interneurons. Front Synaptic Neurosci 2022; 13:773209. [PMID: 35221979 PMCID: PMC8866005 DOI: 10.3389/fnsyn.2021.773209] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 12/27/2021] [Indexed: 11/13/2022] Open
Abstract
Selective distribution of proteins in presynaptic active zones (AZs) is a prerequisite for generating postsynaptic target cell type-specific differences in presynaptic vesicle release probability (Pv) and short-term plasticity, a characteristic feature of cortical pyramidal cells (PCs). In the hippocampus of rodents, somatostatin and mGluR1α expressing interneurons (mGluR1α+ INs) receive small, facilitating excitatory postsynaptic currents (EPSCs) from PCs and express Elfn1 that trans-synaptically recruits mGluR7 into the presynaptic AZ of PC axons. Here we show that Elfn1 also has a role in the selective recruitment of Munc13-2, a synaptic vesicle priming and docking protein, to PC AZs that innervate mGluR1α+ INs. In Elfn1 knock-out mice, unitary EPSCs (uEPSCs) in mGluR1α+ INs have threefold larger amplitudes with less pronounced short-term facilitation, which might be the consequence of the loss of either mGluR7 or Munc13-2 or both. Conditional genetic deletion of Munc13-2 from CA1 PCs results in the loss of Munc13-2, but not mGluR7 from the AZs, and has no effect on the amplitude of uEPSCs and leaves the characteristic short-term facilitation intact at PC to mGluR1α+ IN connection. Our results demonstrate that Munc13-1 alone is capable of imposing low Pv at PC to mGluR1α+ IN synapses and Munc13-2 has yet an unknown role in this synapse.
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Affiliation(s)
- Noemi Holderith
- Institute of Experimental Medicine, Eotvos Lorand Research Network, Budapest, Hungary
| | - Mohammad Aldahabi
- Institute of Experimental Medicine, Eotvos Lorand Research Network, Budapest, Hungary
- János Szentágothai School of Neurosciences, Semmelweis University, Budapest, Hungary
| | - Zoltan Nusser
- Institute of Experimental Medicine, Eotvos Lorand Research Network, Budapest, Hungary
- *Correspondence: Zoltan Nusser,
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7
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Banerjee A, Imig C, Balakrishnan K, Kershberg L, Lipstein N, Uronen RL, Wang J, Cai X, Benseler F, Rhee JS, Cooper BH, Liu C, Wojcik SM, Brose N, Kaeser PS. Molecular and functional architecture of striatal dopamine release sites. Neuron 2022; 110:248-265.e9. [PMID: 34767769 PMCID: PMC8859508 DOI: 10.1016/j.neuron.2021.10.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 09/22/2021] [Accepted: 10/19/2021] [Indexed: 01/21/2023]
Abstract
Despite the importance of dopamine for striatal circuit function, mechanistic understanding of dopamine transmission remains incomplete. We recently showed that dopamine secretion relies on the presynaptic scaffolding protein RIM, indicating that it occurs at active zone-like sites similar to classical synaptic vesicle exocytosis. Here, we establish using a systematic gene knockout approach that Munc13 and Liprin-α, active zone proteins for vesicle priming and release site organization, are important for dopamine secretion. Furthermore, RIM zinc finger and C2B domains, which bind to Munc13 and Liprin-α, respectively, are needed to restore dopamine release after RIM ablation. In contrast, and different from typical synapses, the active zone scaffolds RIM-BP and ELKS, and RIM domains that bind to them, are expendable. Hence, dopamine release necessitates priming and release site scaffolding by RIM, Munc13, and Liprin-α, but other active zone proteins are dispensable. Our work establishes that efficient release site architecture mediates fast dopamine exocytosis.
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Affiliation(s)
- Aditi Banerjee
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | | | - Lauren Kershberg
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Noa Lipstein
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Riikka-Liisa Uronen
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Jiexin Wang
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Xintong Cai
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Fritz Benseler
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Jeong Seop Rhee
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Changliang Liu
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
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8
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Hassan Z, Kumar ND, Reggiori F, Khan G. How Viruses Hijack and Modify the Secretory Transport Pathway. Cells 2021; 10:2535. [PMID: 34685515 PMCID: PMC8534161 DOI: 10.3390/cells10102535] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/28/2021] [Accepted: 09/06/2021] [Indexed: 12/23/2022] Open
Abstract
Eukaryotic cells contain dynamic membrane-bound organelles that are constantly remodeled in response to physiological and environmental cues. Key organelles are the endoplasmic reticulum, the Golgi apparatus and the plasma membrane, which are interconnected by vesicular traffic through the secretory transport route. Numerous viruses, especially enveloped viruses, use and modify compartments of the secretory pathway to promote their replication, assembly and cell egression by hijacking the host cell machinery. In some cases, the subversion mechanism has been uncovered. In this review, we summarize our current understanding of how the secretory pathway is subverted and exploited by viruses belonging to Picornaviridae, Coronaviridae, Flaviviridae,Poxviridae, Parvoviridae and Herpesviridae families.
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Affiliation(s)
- Zubaida Hassan
- Department of Medical Microbiology and Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain P.O. Box 17666, United Arab Emirates;
- Department of Microbiology, School of Life Sciences, Modibbo Adama University, Yola PMB 2076, Nigeria
| | - Nilima Dinesh Kumar
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, 9713 AV Groningen, The Netherlands; (N.D.K.); (F.R.)
- Department of Medical Microbiology and Infection Prevention, University of Groningen, University Medical Center Groningen, 9713 AV Groningen, The Netherlands
| | - Fulvio Reggiori
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, 9713 AV Groningen, The Netherlands; (N.D.K.); (F.R.)
| | - Gulfaraz Khan
- Department of Medical Microbiology and Immunology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain P.O. Box 17666, United Arab Emirates;
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9
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The Phosphoprotein Synapsin Ia Regulates the Kinetics of Dense-Core Vesicle Release. J Neurosci 2021; 41:2828-2841. [PMID: 33632727 DOI: 10.1523/jneurosci.2593-19.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 02/02/2021] [Accepted: 02/04/2021] [Indexed: 12/19/2022] Open
Abstract
Common fusion machinery mediates the Ca2+-dependent exocytosis of synaptic vesicles (SVs) and dense-core vesicles (DCVs). Previously, Synapsin Ia (Syn Ia) was found to localize to SVs, essential for mobilizing SVs to the plasma membrane through phosphorylation. However, whether (or how) the phosphoprotein Syn Ia plays a role in regulating DCV exocytosis remains unknown. To answer these questions, we measured the dynamics of DCV exocytosis by using single-vesicle amperometry in PC12 cells (derived from the pheochromocytoma of rats of unknown sex) overexpressing wild-type or phosphodeficient Syn Ia. We found that overexpression of phosphodeficient Syn Ia decreased the DCV secretion rate, specifically via residues previously shown to undergo calmodulin-dependent kinase (CaMK)-mediated phosphorylation (S9, S566, and S603). Moreover, the fusion pore kinetics during DCV exocytosis were found to be differentially regulated by Syn Ia and two phosphodeficient Syn Ia mutants (Syn Ia-S62A and Syn Ia-S9,566,603A). Kinetic analysis suggested that Syn Ia may regulate the closure and dilation of DCV fusion pores via these sites, implying the potential interactions of Syn Ia with certain DCV proteins involved in the regulation of fusion pore dynamics. Furthermore, we predicted the interaction of Syn Ia with several DCV proteins, including Synaptophysin (Syp) and soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins. By immunoprecipitation, we found that Syn Ia interacted with Syp via phosphorylation. Moreover, a proximity ligation assay (PLA) confirmed their phosphorylation-dependent, in situ interaction on DCVs. Together, these findings reveal a phosphorylation-mediated regulation of DCV exocytosis by Syn Ia.SIGNIFICANCE STATEMENT Although they exhibit distinct exocytosis dynamics upon stimulation, synaptic vesicles (SVs) and dense-core vesicles (DCVs) may undergo co-release in neurons and neuroendocrine cells through an undefined molecular mechanism. Synapsin Ia (Syn Ia) is known to recruit SVs to the plasma membrane via phosphorylation. Here, we examined whether Syn Ia also affects the dynamics of DCV exocytosis. We showed that Syn Ia regulates the DCV secretion rate and fusion pore kinetics during DCV exocytosis. Moreover, Syn Ia-mediated regulation of DCV exocytosis depends on phosphorylation. We further found that Syn Ia interacts with Synaptophysin (Syp) on DCVs in a phosphorylation-dependent manner. Thus, these results suggest that Syn Ia may regulate the release of DCVs via phosphorylation.
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10
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Tawfik B, Martins JS, Houy S, Imig C, Pinheiro PS, Wojcik SM, Brose N, Cooper BH, Sørensen JB. Synaptotagmin-7 places dense-core vesicles at the cell membrane to promote Munc13-2- and Ca 2+-dependent priming. eLife 2021; 10:64527. [PMID: 33749593 PMCID: PMC8012061 DOI: 10.7554/elife.64527] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 03/19/2021] [Indexed: 12/17/2022] Open
Abstract
Synaptotagmins confer calcium-dependence to the exocytosis of secretory vesicles, but how coexpressed synaptotagmins interact remains unclear. We find that synaptotagmin-1 and synaptotagmin-7 when present alone act as standalone fast and slow Ca2+-sensors for vesicle fusion in mouse chromaffin cells. When present together, synaptotagmin-1 and synaptotagmin-7 are found in largely non-overlapping clusters on dense-core vesicles. Synaptotagmin-7 stimulates Ca2+-dependent vesicle priming and inhibits depriming, and it promotes ubMunc13-2- and phorbolester-dependent priming, especially at low resting calcium concentrations. The priming effect of synaptotagmin-7 increases the number of vesicles fusing via synaptotagmin-1, while negatively affecting their fusion speed, indicating both synergistic and competitive interactions between synaptotagmins. Synaptotagmin-7 places vesicles in close membrane apposition (<6 nm); without it, vesicles accumulate out of reach of the fusion complex (20-40 nm). We suggest that a synaptotagmin-7-dependent movement toward the membrane is involved in Munc13-2/phorbolester/Ca2+-dependent priming as a prelude to fast and slow exocytosis triggering.
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Affiliation(s)
- Bassam Tawfik
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Joana S Martins
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Sébastien Houy
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Paulo S Pinheiro
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark.,Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
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11
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Liu C, Zhao Y, Xi H, Jiang J, Yu Y, Dong W. The Membrane Interaction of Alpha-Synuclein. Front Cell Neurosci 2021; 15:633727. [PMID: 33746714 PMCID: PMC7969880 DOI: 10.3389/fncel.2021.633727] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 01/28/2021] [Indexed: 12/12/2022] Open
Abstract
A presynaptic protein closely related to Parkinson's disease (PD), α-synuclein (α-Syn), has been studied extensively regarding its pathogenic mechanisms. As a physiological protein in presynapses, however, α-Syn's physiological function remains unclear. Its location in nerve terminals and effects on membrane fusion also imply its functional role in synaptic transmission, including its possible interaction with high-curvature membranes via its N-terminus and amorphous C-terminus. PD-related mutants that disrupt the membrane interaction (e.g., A30P and G51D) additionally suggest a relationship between α-Syn's pathogenic mechanisms and physiological roles through the membrane binding. Here, we summarize recent research on how α-Syn and its variants interact with membranes and influence synaptic transmission. We list several membrane-related connections between the protein's physiological function and the pathological mechanisms that stand to expand current understandings of α-Syn.
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Affiliation(s)
- Cencen Liu
- Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Yunfei Zhao
- Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Huan Xi
- Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Jie Jiang
- Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Yang Yu
- Department of Histology and Embryology, School of Basic Medical Sciences, Southwest Medical University, Luzhou, China
| | - Wei Dong
- Key Laboratory of Medical Electrophysiology of Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China.,Department of Neurosurgery, Affiliated Hospital of Southwest Medical University, Luzhou, China.,Neurosurgical Clinical Research Center of Sichuan Province, Luzhou, China
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12
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Walker DM, Zhou X, Cunningham AM, Lipschultz AP, Ramakrishnan A, Cates HM, Bagot RC, Shen L, Zhang B, Nestler EJ. Sex-Specific Transcriptional Changes in Response to Adolescent Social Stress in the Brain's Reward Circuitry. Biol Psychiatry 2021; 91:118-128. [PMID: 33892914 PMCID: PMC8382786 DOI: 10.1016/j.biopsych.2021.02.964] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 02/04/2021] [Accepted: 02/18/2021] [Indexed: 02/01/2023]
Abstract
BACKGROUND Sex differences in addiction have been described in humans and animal models. A key factor that influences addiction in both males and females is adolescent experience. Adolescence is associated with higher vulnerability to substance use disorders, and male rodents subjected to adolescent social isolation (SI) stress form stronger preferences for drugs of abuse in adulthood. However, little is known about how females respond to SI, and few studies have investigated the transcriptional changes induced by SI in the brain's reward circuitry. METHODS We tested the hypothesis that SI alters the transcriptome in a persistent and sex-specific manner in prefrontal cortex, nucleus accumbens, and ventral tegmental area. Mice were isolated or group housed from postnatal day P22 to P42, then group housed until ∼P90. Transcriptome-wide changes were investigated by RNA sequencing after acute or chronic cocaine or saline administration. RESULTS We found that SI disrupts sex-specific transcriptional responses to cocaine and reduces sex differences in gene expression across all three brain regions. Furthermore, SI induces gene expression profiles in males that more closely resemble group-housed females, suggesting that SI "feminizes" the male transcriptome. Coexpression analysis reveals that such disruption of sex differences in gene expression alters sex-specific gene networks and identifies potential sex-specific key drivers of these transcriptional changes. CONCLUSIONS Together, these data show that SI has region-specific effects on sex-specific transcriptional responses to cocaine and provide a better understanding of reward-associated transcription that differs in males and females.
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Affiliation(s)
- Deena M. Walker
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029,Persons to whom all correspondence should be addressed and lead contacts: Eric J. Nestler, M.D., Ph.D. () and Deena M. Walker ()
| | - Xianxiao Zhou
- Department of Genetics and Genomic Sciences and Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, New York, NY, 10029,Mount Sinai Center for Transformative Disease Modeling, Icahn School of Medicine at Mount Sinai, New York, NY, 10029
| | - Ashley M. Cunningham
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029
| | - Andrew P. Lipschultz
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029
| | - Aarthi Ramakrishnan
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029
| | - Hannah M. Cates
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029
| | - Rosemary C. Bagot
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029
| | - Li Shen
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029
| | - Bin Zhang
- Department of Genetics and Genomic Sciences and Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, New York, NY, 10029,Mount Sinai Center for Transformative Disease Modeling, Icahn School of Medicine at Mount Sinai, New York, NY, 10029
| | - Eric J. Nestler
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029,Persons to whom all correspondence should be addressed and lead contacts: Eric J. Nestler, M.D., Ph.D. () and Deena M. Walker ()
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13
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Huang WQ, Lin Q, Chen S, Sun L, Chen Q, Yi K, Li Z, Ma Q, Tzeng CM. Integrated analysis of microRNA and mRNA expression profiling identifies BAIAP3 as a novel target of dysregulated hsa-miR-1972 in age-related white matter lesions. Aging (Albany NY) 2021; 13:4674-4695. [PMID: 33561007 PMCID: PMC7906144 DOI: 10.18632/aging.202562] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 11/18/2020] [Indexed: 11/25/2022]
Abstract
White matter lesions known as leukoaraiosis (LA) are cerebral white matter hyperintensities observed in elderly individuals. Currently, no reliable molecular biomarkers are available for monitoring their progression over time. To identify biomarkers for the onset and progression of LA, we analyzed whole blood-based, microRNA expression profiles of leukoaraiosis, validated those exhibiting significant microRNA changes in clinical subjects by means of quantitative real-time polymerase chain reactions and determined the function of miRNA in cell lines by means of microRNA mimic transfection assays. A total of seven microRNAs were found to be significantly down-regulated in leukoaraiosis. Among the microRNAs, hsa-miR-1972 was downregulated during the early onset phase of leukoaraiosis, as confirmed in independent patients, and it was found to target leukoaraiosis-dependent BAIAP3, decreasing its expression in 293T cell lines. Functional enrichment analysis revealed that significantly dysregulated miRNAs-mRNAs changes associated with the onset of leukoaraiosis were involved in neurogenesis, neuronal development, and differentiation. Taken together, the study identified a set of candidate microRNA biomarkers that may usefully monitor the onset and progression of leukoaraiosis. Given the enrichment of leukoaraiosis-associated microRNAs and mRNAs in neuron part and membrane system, BAIAP3 could potentially represent a novel target of hsa-miR-1972 in leukoaraiosis through which microRNAs are involved in the pathogenesis of white matter lesions.
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Affiliation(s)
- Wen-Qing Huang
- Shanghai Institute of Precision Medicine (SHIPM), Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Translational Medicine Research Center (TMRC), School of Pharmaceutical Sciences, Xiamen University, Xiamen, Fujian, China
| | - Qing Lin
- Department of Neurology, The First Affiliated Hospital of Xiamen University, Xiamen, Fujian, China.,Xiamen Key Laboratory of Brain Center, The First Affiliated Hospital of Xiamen University, Xiamen, Fujian, China.,School of Medicine, Xiamen University, Xiamen, Fujian, China.,The First Clinical College of Fujian Medical University, Fuzhou, Fujian, China
| | - Shuai Chen
- Department of Otolaryngology-Head and Neck Surgery, Xiamen Key Laboratory of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of Xiamen University, Xiamen, Fujian, China.,Chen Zhi-nan Academician Workstation, Institute of Basic and Translational Medicine, Xi'an Medical University, Xi'an, Shanxi, China
| | - Lixiang Sun
- Translational Medicine Research Center (TMRC), School of Pharmaceutical Sciences, Xiamen University, Xiamen, Fujian, China
| | - Qingjie Chen
- Department of Nuclear Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China
| | - Kehui Yi
- Department of Neurology, The First Affiliated Hospital of Xiamen University, Xiamen, Fujian, China.,Department of Neurology, Zhongshan Xiamen Hospital, Fudan University, Xiamen, Fujian, China
| | - Zhi Li
- Translational Medicine Research Center (TMRC), School of Pharmaceutical Sciences, Xiamen University, Xiamen, Fujian, China
| | - Qilin Ma
- Department of Neurology, The First Affiliated Hospital of Xiamen University, Xiamen, Fujian, China.,Xiamen Key Laboratory of Brain Center, The First Affiliated Hospital of Xiamen University, Xiamen, Fujian, China.,School of Medicine, Xiamen University, Xiamen, Fujian, China.,The First Clinical College of Fujian Medical University, Fuzhou, Fujian, China
| | - Chi-Meng Tzeng
- Translational Medicine Research Center (TMRC), School of Pharmaceutical Sciences, Xiamen University, Xiamen, Fujian, China.,College of Pharmaceutical Sciences, Nanjing Tech University, Nanjing, Jiangsu, China
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14
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Houy S, Martins JS, Mohrmann R, Sørensen JB. Measurements of Exocytosis by Capacitance Recordings and Calcium Uncaging in Mouse Adrenal Chromaffin Cells. Methods Mol Biol 2021; 2233:233-251. [PMID: 33222139 DOI: 10.1007/978-1-0716-1044-2_16] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Fusion of vesicles with the plasma membrane and liberation of their contents is a multistep process involving several proteins. Correctly assigning the role of specific proteins and reactions in this cascade requires a measurement method with high temporal resolution. Patch-clamp recordings of cell membrane capacitance in combination with calcium measurements, calcium uncaging, and carbon-fiber amperometry allow for the accurate determination of vesicle pool sizes, their fusion kinetics, and their secreted oxidizable content. Here, we will describe this method in a model system for neurosecretion, the adrenal chromaffin cells, which secrete adrenaline.
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Affiliation(s)
- Sébastien Houy
- Department of Neuroscience, University of Copenhagen, Copenhagen N, Denmark
| | - Joana S Martins
- Department of Neuroscience, University of Copenhagen, Copenhagen N, Denmark
| | - Ralf Mohrmann
- Institute for Physiology, Otto-von-Guericke University, Magdeburg, Germany
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15
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Galgano D, Soheili T, Voss M, Torralba-Raga L, Tesi B, Cichocki F, Andre I, Rettig J, Cavazzana M, Bryceson Y. Alternative UNC13D Promoter Encodes a Functional Munc13-4 Isoform Predominantly Expressed in Lymphocytes and Platelets. Front Immunol 2020; 11:1154. [PMID: 32582217 PMCID: PMC7296141 DOI: 10.3389/fimmu.2020.01154] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 05/11/2020] [Indexed: 12/17/2022] Open
Abstract
Autosomal recessive mutations in genes required for cytotoxicity are causative of a life-threatening, early-onset hyperinflammatory syndrome termed familial hemophagocytic lymphohistiocytosis (FHL). Mutations in UNC13D cause FHL type 3. UNC13D encodes Munc13-4, a member of the Unc13 protein family which control SNARE complex formation and vesicle fusion. We have previously identified FHL3-associated mutations in the first intron of UNC13D which control transcription from an alternative transcriptional start site. Using isoform specific antibodies, we demonstrate that this alternative Munc13-4 isoform with a unique N-terminus is preferentially expressed in human lymphocytes and platelets, as compared to the conventional isoform that was mostly expressed in monocytes and neutrophils. The distinct N-terminal of the two isoforms did not impact on Munc13-4 localization or trafficking to the immunological synapse of cytotoxic T cells. Moreover, ectopic expression of both isoforms efficiently restored exocytosis by FHL3 patient-derived Munc13-4 deficient T cells. Thus, we demonstrate that the conventional and alternative Munc13-4 isoforms have different expression pattern in hematopoietic cell subsets, but display similar localization and contribution to T cell exocytosis. The use of an alternative transcriptional starting site (TSS) in lymphocytes and platelets could be selected for increasing the overall levels of Munc13-4 expression for efficient secretory granule release.
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Affiliation(s)
- Donatella Galgano
- Department of Medicine, Center for Hematology and Regenerative Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Tayebeh Soheili
- Human Lymphohematopoiesis Laboratory, INSERM UMR 1163, IMAGINE Institute, Paris, France
| | - Matthias Voss
- Department of Medicine, Center for Hematology and Regenerative Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Lamberto Torralba-Raga
- Department of Medicine, Center for Hematology and Regenerative Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Bianca Tesi
- Department of Clinical Genetics, Karolinska University Hospital, Stockholm, Sweden.,Department of Molecular Medicine and Surgery, Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Frank Cichocki
- Division of Hematology, Oncology and Transplantation, University of Minnesota, Minneapolis, MN, United States
| | - Isabelle Andre
- Human Lymphohematopoiesis Laboratory, INSERM UMR 1163, IMAGINE Institute, Paris, France.,Paris Descartes-Sorbonne Paris Cité University, Imagine Institute, Paris, France
| | - Jens Rettig
- Cellular Neurophysiology Laboratory, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Marina Cavazzana
- Human Lymphohematopoiesis Laboratory, INSERM UMR 1163, IMAGINE Institute, Paris, France.,Paris Descartes-Sorbonne Paris Cité University, Imagine Institute, Paris, France.,Biotherapy Department, Hôpital Necker-Enfants malades, Assistance Publique-Hôpitaux de Paris, Paris, France.,Biotherapy Clinical Investigation Center, Groupe Hospitalier Universitaire Ouest, Assistance Publique-Hôpitaux de Paris, INSERM, Paris, France
| | - Yenan Bryceson
- Department of Medicine, Center for Hematology and Regenerative Medicine, Karolinska Institutet, Stockholm, Sweden.,Broegelmann Research Laboratory, Department of Clinical Sciences, University of Bergen, Bergen, Norway
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16
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Gowrisankaran S, Houy S, Del Castillo JGP, Steubler V, Gelker M, Kroll J, Pinheiro PS, Schwitters D, Halbsgut N, Pechstein A, van Weering JRT, Maritzen T, Haucke V, Raimundo N, Sørensen JB, Milosevic I. Endophilin-A coordinates priming and fusion of neurosecretory vesicles via intersectin. Nat Commun 2020; 11:1266. [PMID: 32152276 PMCID: PMC7062783 DOI: 10.1038/s41467-020-14993-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 02/12/2020] [Indexed: 12/17/2022] Open
Abstract
Endophilins-A are conserved endocytic adaptors with membrane curvature-sensing and -inducing properties. We show here that, independently of their role in endocytosis, endophilin-A1 and endophilin-A2 regulate exocytosis of neurosecretory vesicles. The number and distribution of neurosecretory vesicles were not changed in chromaffin cells lacking endophilin-A, yet fast capacitance and amperometry measurements revealed reduced exocytosis, smaller vesicle pools and altered fusion kinetics. The levels and distributions of the main exocytic and endocytic factors were unchanged, and slow compensatory endocytosis was not robustly affected. Endophilin-A’s role in exocytosis is mediated through its SH3-domain, specifically via a direct interaction with intersectin-1, a coordinator of exocytic and endocytic traffic. Endophilin-A not able to bind intersectin-1, and intersectin-1 not able to bind endophilin-A, resulted in similar exocytic defects in chromaffin cells. Altogether, we report that two endocytic proteins, endophilin-A and intersectin-1, are enriched on neurosecretory vesicles and regulate exocytosis by coordinating neurosecretory vesicle priming and fusion. Endophilins-A are conserved membrane-associated proteins required for endocytosis. Here, the authors report that endophilins-A also promote exocytosis of neurosecretory vesicles by coordinating priming and fusion through intersectin-1, independently of their roles in different types of endocytosis.
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Affiliation(s)
- Sindhuja Gowrisankaran
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Sébastien Houy
- University of Copenhagen, Department for Neuroscience, Faculty of Health and Medical Sciences, Copenhagen, Denmark
| | - Johanna G Peña Del Castillo
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Vicky Steubler
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Monika Gelker
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Jana Kroll
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Paulo S Pinheiro
- University of Copenhagen, Department for Neuroscience, Faculty of Health and Medical Sciences, Copenhagen, Denmark.,Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Dirk Schwitters
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Nils Halbsgut
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany
| | - Arndt Pechstein
- Leibniz Research Institute for Molecular Pharmacology, Molecular Physiology and Cell Biology Section, Berlin, Germany
| | - Jan R T van Weering
- Department of Clinical Genetics, Center for Neurogenomics and Cognitive Research, Amsterdam UMC, Amsterdam, The Netherlands
| | - Tanja Maritzen
- Leibniz Research Institute for Molecular Pharmacology, Molecular Physiology and Cell Biology Section, Berlin, Germany
| | - Volker Haucke
- Leibniz Research Institute for Molecular Pharmacology, Molecular Physiology and Cell Biology Section, Berlin, Germany
| | - Nuno Raimundo
- Institute for Cellular Biochemistry, University Medical Center Göttingen (UMG), Göttingen, Germany
| | - Jakob B Sørensen
- University of Copenhagen, Department for Neuroscience, Faculty of Health and Medical Sciences, Copenhagen, Denmark.
| | - Ira Milosevic
- European Neuroscience Institute-A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society Göttingen, Göttingen, Germany.
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17
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Kobbersmed JR, Grasskamp AT, Jusyte M, Böhme MA, Ditlevsen S, Sørensen JB, Walter AM. Rapid regulation of vesicle priming explains synaptic facilitation despite heterogeneous vesicle:Ca 2+ channel distances. eLife 2020; 9:51032. [PMID: 32077852 PMCID: PMC7145420 DOI: 10.7554/elife.51032] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 02/14/2020] [Indexed: 12/27/2022] Open
Abstract
Chemical synaptic transmission relies on the Ca2+-induced fusion of transmitter-laden vesicles whose coupling distance to Ca2+ channels determines synaptic release probability and short-term plasticity, the facilitation or depression of repetitive responses. Here, using electron- and super-resolution microscopy at the Drosophila neuromuscular junction we quantitatively map vesicle:Ca2+ channel coupling distances. These are very heterogeneous, resulting in a broad spectrum of vesicular release probabilities within synapses. Stochastic simulations of transmitter release from vesicles placed according to this distribution revealed strong constraints on short-term plasticity; particularly facilitation was difficult to achieve. We show that postulated facilitation mechanisms operating via activity-dependent changes of vesicular release probability (e.g. by a facilitation fusion sensor) generate too little facilitation and too much variance. In contrast, Ca2+-dependent mechanisms rapidly increasing the number of releasable vesicles reliably reproduce short-term plasticity and variance of synaptic responses. We propose activity-dependent inhibition of vesicle un-priming or release site activation as novel facilitation mechanisms. Cells in the nervous system of all animals communicate by releasing and sensing chemicals at contact points named synapses. The ‘talking’ (or pre-synaptic) cell stores the chemicals close to the synapse, in small spheres called vesicles. When the cell is activated, calcium ions flow in and interact with the release-ready vesicles, which then spill the chemicals into the synapse. In turn, the ‘listening’ (or post-synaptic) cell can detect the chemicals and react accordingly. When the pre-synaptic cell is activated many times in a short period, it can release a greater quantity of chemicals, allowing a bigger reaction in the post-synaptic cell. This phenomenon is known as facilitation, but it is still unclear how exactly it can take place. This is especially the case when many of the vesicles are not ready to respond, for example when they are too far from where calcium flows into the cell. Computer simulations have been created to model facilitation but they have assumed that all vesicles are placed at the same distance to the calcium entry point: Kobbersmed et al. now provide evidence that this assumption is incorrect. Two high-resolution imaging techniques were used to measure the actual distances between the vesicles and the calcium source in the pre-synaptic cells of fruit flies: this showed that these distances are quite variable – some vesicles sit much closer to the source than others. This information was then used to create a new computer model to simulate facilitation. The results from this computing work led Kobbersmed et al. to suggest that facilitation may take place because a calcium-based mechanism in the cell increases the number of vesicles ready to release their chemicals. This new model may help researchers to better understand how the cells in the nervous system work. Ultimately, this can guide experiments to investigate what happens when information processing at synapses breaks down, for example in diseases such as epilepsy.
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Affiliation(s)
- Janus Rl Kobbersmed
- Department of Mathematical Sciences, University of Copenhagen, København, Denmark.,Department of Neuroscience, University of Copenhagen, København, Denmark
| | - Andreas T Grasskamp
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany
| | - Meida Jusyte
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany.,Einstein Center for Neuroscience, Berlin, Germany
| | - Mathias A Böhme
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany
| | - Susanne Ditlevsen
- Department of Mathematical Sciences, University of Copenhagen, København, Denmark
| | | | - Alexander M Walter
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany.,Einstein Center for Neuroscience, Berlin, Germany
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18
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Carbone E, Borges R, Eiden LE, García AG, Hernández‐Cruz A. Chromaffin Cells of the Adrenal Medulla: Physiology, Pharmacology, and Disease. Compr Physiol 2019; 9:1443-1502. [DOI: 10.1002/cphy.c190003] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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19
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Neher E, Brose N. Dynamically Primed Synaptic Vesicle States: Key to Understand Synaptic Short-Term Plasticity. Neuron 2018; 100:1283-1291. [DOI: 10.1016/j.neuron.2018.11.024] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 10/26/2018] [Accepted: 11/13/2018] [Indexed: 01/09/2023]
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20
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Huang CC, Chiu TY, Lee TY, Hsieh HJ, Lin CC, Kao LS. Soluble α-synuclein facilitates priming and fusion by releasing Ca 2+ from the thapsigargin-sensitive Ca 2+ pool in PC12 cells. J Cell Sci 2018; 131:jcs.213017. [PMID: 30404828 DOI: 10.1242/jcs.213017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 10/12/2018] [Indexed: 02/01/2023] Open
Abstract
α-Synuclein is associated with Parkinson's disease, and is mainly localized in presynaptic terminals and regulates exocytosis, but its physiological roles remain controversial. Here, we studied the effects of soluble and aggregated α-synuclein on exocytosis, and explored the molecular mechanism by which α-synuclein interacts with regulatory proteins, including Rab3A, Munc13-1 (also known as Unc13a) and Munc18-1 (also known as STXBP1), in order to regulate exocytosis. Through fluorescence recovery after photobleaching experiments, overexpressed α-synuclein in PC12 cells was found to be in a monomeric form, which promotes exocytosis. In contrast, aggregated α-synuclein induced by lactacystin treatment inhibits exocytosis. Our results show that α-synuclein is involved in vesicle priming and fusion. α-Synuclein and phorbol 12-myristate 13-acetate (PMA), which is known to enhance vesicle priming mediated by Rab3A, Munc13-1 and Munc18-1, act on the same population of vesicles, but regulate priming independently. Furthermore, the results show a novel effects of α-synuclein on mobilizing Ca2+ release from thapsigargin-sensitive Ca2+ pools to enhance the ATP-induced [Ca2+]i increase, which enhances vesicle fusion. Our results provide a detailed understanding of the action of α-synuclein during the final steps of exocytosis.
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Affiliation(s)
- Chien-Chang Huang
- Brain Research Center, National Yang-Ming University, Taipei 112, Taiwan, Republic of China.,Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan, Republic of China
| | - Tai-Yu Chiu
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan, Republic of China
| | - Tzu-Ying Lee
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan, Republic of China
| | - Hsin-Jui Hsieh
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan, Republic of China
| | - Chung-Chih Lin
- Brain Research Center, National Yang-Ming University, Taipei 112, Taiwan, Republic of China .,Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan, Republic of China.,Biophotonics Interdisciplinary Research Center, National Yang-Ming University, Taipei 112, Taiwan, Republic of China
| | - Lung-Sen Kao
- Brain Research Center, National Yang-Ming University, Taipei 112, Taiwan, Republic of China .,Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan, Republic of China
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21
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Ghelani T, Sigrist SJ. Coupling the Structural and Functional Assembly of Synaptic Release Sites. Front Neuroanat 2018; 12:81. [PMID: 30386217 PMCID: PMC6198076 DOI: 10.3389/fnana.2018.00081] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 09/18/2018] [Indexed: 01/04/2023] Open
Abstract
Information processing in our brains depends on the exact timing of calcium (Ca2+)-activated exocytosis of synaptic vesicles (SVs) from unique release sites embedded within the presynaptic active zones (AZs). While AZ scaffolding proteins obviously provide an efficient environment for release site function, the molecular design creating such release sites had remained unknown for a long time. Recent advances in visualizing the ultrastructure and topology of presynaptic protein architectures have started to elucidate how scaffold proteins establish “nanodomains” that connect voltage-gated Ca2+ channels (VGCCs) physically and functionally with release-ready SVs. Scaffold proteins here seem to operate as “molecular rulers or spacers,” regulating SV-VGCC physical distances within tens of nanometers and, thus, influence the probability and plasticity of SV release. A number of recent studies at Drosophila and mammalian synapses show that the stable positioning of discrete clusters of obligate release factor (M)Unc13 defines the position of SV release sites, and the differential expression of (M)Unc13 isoforms at synapses can regulate SV-VGCC coupling. We here review the organization of matured AZ scaffolds concerning their intrinsic organization and role for release site formation. Moreover, we also discuss insights into the developmental sequence of AZ assembly, which often entails a tightening between VGCCs and SV release sites. The findings discussed here are retrieved from vertebrate and invertebrate preparations and include a spectrum of methods ranging from cell biology, super-resolution light and electron microscopy to biophysical and electrophysiological analysis. Our understanding of how the structural and functional organization of presynaptic AZs are coupled has matured, as these processes are crucial for the understanding of synapse maturation and plasticity, and, thus, accurate information transfer and storage at chemical synapses.
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Affiliation(s)
- Tina Ghelani
- Faculty of Biology, Chemistry, Pharmacy, Freie Universität Berlin, Berlin, Germany
| | - Stephan J Sigrist
- Faculty of Biology, Chemistry, Pharmacy, Freie Universität Berlin, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Berlin, Germany
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22
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Abstract
Phosphoinositides (PtdIns) play important roles in exocytosis and are thought to regulate secretory granule docking by co-clustering with the SNARE protein syntaxin to form a docking receptor in the plasma membrane. Here we tested this idea by high-resolution total internal reflection imaging of EGFP-labeled PtdIns markers or syntaxin-1 at secretory granule release sites in live insulin-secreting cells. In intact cells, PtdIns markers distributed evenly across the plasma membrane with no preference for granule docking sites. In contrast, syntaxin-1 was found clustered in the plasma membrane, mostly beneath docked granules. We also observed rapid accumulation of syntaxin-1 at sites where granules arrived to dock. Acute depletion of plasma membrane phosphatidylinositol (4,5) bisphosphate (PtdIns(4,5)P2 ) by recruitment of a 5'-phosphatase strongly inhibited Ca2+ -dependent exocytosis, but had no effect on docked granules or the distribution and clustering of syntaxin-1. Cell permeabilization by α-toxin or formaldehyde-fixation caused PtdIns marker to slowly cluster, in part near docked granules. In summary, our data indicate that PtdIns(4,5)P2 accelerates granule priming, but challenge a role of PtdIns in secretory granule docking or clustering of syntaxin-1 at the release site.
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Affiliation(s)
| | - Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
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23
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Dominguez N, van Weering JRT, Borges R, Toonen RFG, Verhage M. Dense-core vesicle biogenesis and exocytosis in neurons lacking chromogranins A and B. J Neurochem 2018; 144:241-254. [PMID: 29178418 PMCID: PMC5814729 DOI: 10.1111/jnc.14263] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 11/16/2017] [Accepted: 11/20/2017] [Indexed: 11/26/2022]
Abstract
Chromogranin A and B (Cgs) are considered to be master regulators of cargo sorting for the regulated secretory pathway (RSP) and dense-core vesicle (DCV) biogenesis. To test this, we analyzed the release of neuropeptide Y (NPY)-pHluorin, a live RSP reporter, and the distribution, number, and appearance of DCVs, in mouse hippocampal neurons lacking expression of CHGA and CHGB genes. qRT-PCR analysis showed that expression of other granin family members was not significantly altered in CgA/B-/- neurons. As synaptic maturation of developing neurons depends on secretion of trophic factors in the RSP, we first analyzed neuronal development in standardized neuronal cultures. Surprisingly, dendritic and axonal length, arborization, synapse density, and synaptic vesicle accumulation in synapses were all normal in CgA/B-/- neurons. Moreover, the number of DCVs outside the soma, stained with endogenous marker Secretogranin II, the number of NPY-pHluorin puncta, and the total amount of reporter in secretory compartments, as indicated by pH-sensitive NPY-pHluorin fluorescence, were all normal in CgA/B-/- neurons. Electron microscopy revealed that synapses contained a normal number of DCVs, with a normal diameter, in CgA/B-/- neurons. In contrast, CgA/B-/- chromaffin cells contained fewer and smaller secretory vesicles with a smaller core size, as previously reported. Finally, live-cell imaging at single vesicle resolution revealed a normal number of fusion events upon bursts of action potentials in CgA/B-/- neurons. These events had normal kinetics and onset relative to the start of stimulation. Taken together, these data indicate that the two chromogranins are dispensable for cargo sorting in the RSP and DCV biogenesis in mouse hippocampal neurons.
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Affiliation(s)
- Natalia Dominguez
- Department of Clinical GeneticsCenter for Neurogenomics and Cognitive Research (CNCR)VU University Amsterdam and VU University Medical Center (VUmc)AmsterdamThe Netherlands
| | - Jan R. T. van Weering
- Department of Clinical GeneticsCenter for Neurogenomics and Cognitive Research (CNCR)VU University Amsterdam and VU University Medical Center (VUmc)AmsterdamThe Netherlands
| | - Ricardo Borges
- Unidad de FarmacologíaFacultad de MedicinaUniversidad de la LagunaTenerifeSpain
| | - Ruud F. G. Toonen
- Functional GenomicsCenter for Neurogenomics and Cognitive Research (CNCR)VU University Amsterdam and VU University Medical Center (VUmc)AmsterdamThe Netherlands
| | - Matthijs Verhage
- Department of Clinical GeneticsCenter for Neurogenomics and Cognitive Research (CNCR)VU University Amsterdam and VU University Medical Center (VUmc)AmsterdamThe Netherlands
- Functional GenomicsCenter for Neurogenomics and Cognitive Research (CNCR)VU University Amsterdam and VU University Medical Center (VUmc)AmsterdamThe Netherlands
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24
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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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25
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Walter AM, Böhme MA, Sigrist SJ. Vesicle release site organization at synaptic active zones. Neurosci Res 2017; 127:3-13. [PMID: 29275162 DOI: 10.1016/j.neures.2017.12.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 12/04/2017] [Accepted: 12/06/2017] [Indexed: 11/30/2022]
Abstract
Information transfer between nerve cells (neurons) forms the basis of behavior, emotion, and survival. Signal transduction from one neuron to another occurs at synapses, and relies on both electrical and chemical signal propagation. At chemical synapses, incoming electrical action potentials trigger the release of chemical neurotransmitters that are sensed by the connected cell and here reconverted to an electrical signal. The presynaptic conversion of an electrical to a chemical signal is an energy demanding, highly regulated process that relies on a complex, evolutionarily conserved molecular machinery. Here, we review the biophysical characteristics of this process, the current knowledge of the molecules operating in this reaction and genetic specializations that may have evolved to shape inter-neuronal signaling.
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Affiliation(s)
- Alexander M Walter
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, Berlin 13125, Germany.
| | - Mathias A Böhme
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Robert-Roessle-Straße 10, Berlin 13125, Germany
| | - Stephan J Sigrist
- Freie Universität Berlin, Institute for Biology/Genetics, Takustraße 6, 14195 Berlin, Germany; NeuroCure, Cluster of Excellence, Charité Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany.
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26
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Higashio H, Satoh YI, Saino T. Inhibitory role of Munc13-1 in antigen-induced mast cell degranulation. Biomed Res 2017; 38:321-329. [PMID: 29225210 DOI: 10.2220/biomedres.38.321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Secretory granules (SGs) of mast cells are lysosome-related organelles that contain various inflammatory molecules such as histamine, which are stored in the cytoplasm. Mast cell degranulation is the regulated exocytosis of SGs in response to external stimuli, such as the antigen-mediated cross-linking of the high-affinity IgE receptor, FcεRI. Upon stimulation, SGs undergo priming to become fusion-competent prior to fusing with the plasma membrane, which is mediated by Munc13-4, one of the five members of the vesicle-priming Munc13 protein family. Although Munc13-4 is shown to be crucial for mast cell degranulation, the functional involvement of other Munc13 isoform(s) remains unknown. Herein, this was investigated using the RBL-2H3 mast cell line. We found that Munc13-1 and Munc13-4 are the only Munc13 isoforms that are expressed in the RBL-2H3 cells, and Munc13-1 is distributed in the cytoplasm, but highly concentrated on the late endosome and/or lysosome. Unexpectedly, antigen-induced degranulation was considerably increased by Munc13-1 knockdown, but decreased by its overexpression. Further, we found that the hypersecretion phenotype of the Munc13-1-knockdown cells was attenuated by simultaneous Munc13-4 knockdown. These results suggested that Munc13-1 has an inhibitory role in antigen-induced mast cell degranulation, which is performed in a Munc13-4-dependent manner.
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Affiliation(s)
- Hironori Higashio
- Department of Chemistry, Center for Liberal Arts and Sciences, Iwate Medical University
| | - Yoh-Ichi Satoh
- Department of Anatomy (Cell Biology), Iwate Medical University.,Department of Medical Education, Iwate Medical University
| | - Tomoyuki Saino
- Department of Anatomy (Cell Biology), Iwate Medical University
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27
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Walter AM, Müller R, Tawfik B, Wierda KD, Pinheiro PS, Nadler A, McCarthy AW, Ziomkiewicz I, Kruse M, Reither G, Rettig J, Lehmann M, Haucke V, Hille B, Schultz C, Sørensen JB. Phosphatidylinositol 4,5-bisphosphate optical uncaging potentiates exocytosis. eLife 2017; 6:30203. [PMID: 29068313 PMCID: PMC5711374 DOI: 10.7554/elife.30203] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 10/24/2017] [Indexed: 12/14/2022] Open
Abstract
Phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2] is essential for exocytosis. Classical ways of manipulating PI(4,5)P2 levels are slower than its metabolism, making it difficult to distinguish effects of PI(4,5)P2 from those of its metabolites. We developed a membrane-permeant, photoactivatable PI(4,5)P2, which is loaded into cells in an inactive form and activated by light, allowing sub-second increases in PI(4,5)P2 levels. By combining this compound with electrophysiological measurements in mouse adrenal chromaffin cells, we show that PI(4,5)P2 uncaging potentiates exocytosis and identify synaptotagmin-1 (the Ca2+ sensor for exocytosis) and Munc13-2 (a vesicle priming protein) as the relevant effector proteins. PI(4,5)P2 activation of exocytosis did not depend on the PI(4,5)P2-binding CAPS-proteins, suggesting that PI(4,5)P2 uncaging may bypass CAPS-function. Finally, PI(4,5)P2 uncaging triggered the rapid fusion of a subset of readily-releasable vesicles, revealing a rapid role of PI(4,5)P2 in fusion triggering. Thus, optical uncaging of signaling lipids can uncover their rapid effects on cellular processes and identify lipid effectors. Cells in our body communicate by releasing compounds called transmitters that carry signals from one cell to the next. Packages called vesicles store transmitters within the signaling cell. When the cell needs to send a signal, the vesicles fuse with the cell's membrane and release their cargo. For many signaling processes, such as those used by neurons, this fusion is regulated, fast, and coupled to the signal that the cell receives to activate release. Specialized molecular machines made up of proteins and fatty acid molecules called signaling lipids enable this to happen. One signaling lipid called PI(4,5)P2 (short for phosphatidylinositol 4,5-bisphosphate) is essential for vesicle fusion as well as for other processes in cells. It interacts with several proteins that help it control fusion and the release of transmitter. While it is possible to study the role of these proteins using genetic tools to inactivate them, the signaling lipids are more difficult to manipulate. Existing methods result in slow changes in PI(4,5)P2 levels, making it hard to directly attribute later changes to PI(4,5)P2. Walter, Müller, Tawfik et al. developed a new method to measure how PI(4,5)P2 affects transmitter release in living mammalian cells, which causes a rapid increase in PI(4,5)P2 levels. The method uses a chemical compound called “caged PI(4,5)P2” that can be loaded into cells but remains undetected until ultraviolet light is shone on it. The ultraviolet light uncages the compound, generating active PI(4,5)P2 in less than one second. Walter et al. found that when they uncaged PI(4,5)P2 in this way, the amount of transmitter released by cells increased. Combining this with genetic tools, it was possible to investigate which proteins of the release machinery were required for this effect. The results suggest that two different types of proteins that interact with PI(4,5)P2 are needed: one must bind PI(4,5)P2 to carry out its role and the other helps PI(4,5)P2 accumulate at the site of vesicle fusion. The new method also allowed Walter et al. to show that a fast increase in PI(4,5)P2 triggers a subset of vesicles to fuse very rapidly. This shows that PI(4,5)P2 rapidly regulates the release of transmitter. Caged PI(4,5)P2 will be useful to study other processes in cells that need PI(4,5)P2, helping scientists understand more about how signaling lipids control many different events at cellular membranes.
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Affiliation(s)
- Alexander M Walter
- Neurosecretion group, Center for Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Rainer Müller
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Bassam Tawfik
- Neurosecretion group, Center for Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Keimpe Db Wierda
- Neurosecretion group, Center for Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Paulo S Pinheiro
- Neurosecretion group, Center for Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - André Nadler
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany.,Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Anthony W McCarthy
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Iwona Ziomkiewicz
- Neurosecretion group, Center for Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Discovery Sciences, AstraZeneca, Cambridge, United Kingdom
| | - Martin Kruse
- Department of Physiology and Biophysics, School of Medicine, University of Washington, Seattle, United States
| | - Gregor Reither
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Jens Rettig
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Martin Lehmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Volker Haucke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | - Bertil Hille
- Department of Physiology and Biophysics, School of Medicine, University of Washington, Seattle, United States
| | - Carsten Schultz
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany
| | - Jakob Balslev Sørensen
- Neurosecretion group, Center for Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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28
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van Keimpema L, Kooistra R, Toonen RF, Verhage M. CAPS-1 requires its C2, PH, MHD1 and DCV domains for dense core vesicle exocytosis in mammalian CNS neurons. Sci Rep 2017; 7:10817. [PMID: 28883501 PMCID: PMC5589909 DOI: 10.1038/s41598-017-10936-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 08/16/2017] [Indexed: 01/11/2023] Open
Abstract
CAPS (calcium-dependent activator protein for secretion) are multi-domain proteins involved in regulated exocytosis of synaptic vesicles (SVs) and dense core vesicles (DCVs). Here, we assessed the contribution of different CAPS-1 domains to its subcellular localization and DCV exocytosis by expressing CAPS-1 mutations in four functional domains in CAPS-1/-2 null mutant (CAPS DKO) mouse hippocampal neurons, which are severely impaired in DCV exocytosis. CAPS DKO neurons showed normal development and no defects in DCV biogenesis and their subcellular distribution. Truncation of the CAPS-1 C-terminus (CAPS Δ654-1355) impaired CAPS-1 synaptic enrichment. Mutations in the C2 (K428E or G476E) or pleckstrin homology (PH; R558D/K560E/K561E) domain did not. However, all mutants rescued DCV exocytosis in CAPS DKO neurons to only 20% of wild type CAPS-1 exocytosis capacity. To assess the relative importance of CAPS for both secretory pathways, we compared effect sizes of CAPS-1/-2 deficiency on SV and DCV exocytosis. Using the same (intense) stimulation, DCV exocytosis was impaired relatively strong (96% inhibition) compared to SV exocytosis (39%). Together, these data show that the CAPS-1 C-terminus regulates synaptic enrichment of CAPS-1. All CAPS-1 functional domains are required, and the C2 and PH domain together are not sufficient, for DCV exocytosis in mammalian CNS neurons.
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Affiliation(s)
- Linda van Keimpema
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University, 1081 HV, Amsterdam, The Netherlands
- Sylics (Synaptologics BV), PO box 71033, 1008 BA, Amsterdam, The Netherlands
| | - Robbelien Kooistra
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University, 1081 HV, Amsterdam, The Netherlands
| | - Ruud F Toonen
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University, 1081 HV, Amsterdam, The Netherlands.
| | - Matthijs Verhage
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University, 1081 HV, Amsterdam, The Netherlands.
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29
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How does the stimulus define exocytosis in adrenal chromaffin cells? Pflugers Arch 2017; 470:155-167. [DOI: 10.1007/s00424-017-2052-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 07/28/2017] [Accepted: 08/01/2017] [Indexed: 12/28/2022]
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30
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Neurosecretion: what can we learn from chromaffin cells. Pflugers Arch 2017; 470:7-11. [PMID: 28801866 PMCID: PMC5748399 DOI: 10.1007/s00424-017-2051-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 07/31/2017] [Accepted: 08/01/2017] [Indexed: 12/16/2022]
Abstract
Many of the molecular players in the stimulus-secretion chain are similarly active in neurosecretion and catecholamine release. Therefore, studying chromaffin cells uncovered many details of the processes of docking, priming, and exocytosis of vesicles. However, morphological specializations at synapses, called active zones (AZs), confer extra speed of response and another layer of control to the fast release of vesicles by action potentials. Work at the Calyx of Held, a glutamatergic nerve terminal, has shown that in addition to such rapidly released vesicles, there is a pool of “Slow Vesicles,” which are held to be perfectly release-competent, but lack a final step of tight interaction with the AZ. It is argued here that such “Slow Vesicles” have many properties in common with chromaffin granules. The added complexity in the AZ-dependent regulation of “Fast Vesicles” can lead to misinterpretation of data on neurosecretion. Therefore, the study of Slow Vesicles and of chromaffin granules may provide a clearer picture of the early steps in the highly regulated process of neurosecretion.
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31
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Extension of Helix 12 in Munc18-1 Induces Vesicle Priming. J Neurosci 2017; 36:6881-91. [PMID: 27358447 DOI: 10.1523/jneurosci.0007-16.2016] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2016] [Accepted: 05/14/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Munc18-1 is essential for vesicle fusion and participates in the docking of large dense-core vesicles to the plasma membrane. Recent structural data suggest that conformational changes in the 12th helix of the Munc18-1 domain 3a within the Munc18-1:syntaxin complex result in an additional interaction with synaptobrevin-2/VAMP2 (vesicle-associated membrane protein 2), leading to SNARE complex formation. To test this hypothesis in living cells, we examined secretion from Munc18-1-null mouse adrenal chromaffin cells expressing Munc18-1 mutants designed to either perturb the extension of helix 12 (Δ324-339), block its interaction with synaptobrevin-2 (L348R), or extend the helix to promote coil-coil interactions with other proteins (P335A). The mutants rescued vesicle docking and syntaxin-1 targeting to the plasma membrane, with the exception of P335A that only supported partial syntaxin-1 targeting. Disruptive mutations (L348R or Δ324-339) lowered the secretory amplitude by decreasing vesicle priming, whereas P335A markedly increased priming and secretory amplitude. The mutants displayed unchanged kinetics and Ca(2+) dependence of fusion, indicating that the mutations specifically affect the vesicle priming step. Mutation of a nearby tyrosine (Y337A), which interacts with closed syntaxin-1, mildly increased secretory amplitude. This correlated with results from an in vitro fusion assay probing the functions of Munc18-1, indicating an easier transition to the extended state in the mutant. Our findings support the notion that a conformational transition within the Munc18-1 domain 3a helix 12 leads to opening of a closed Munc18-1:syntaxin complex, followed by productive SNARE complex assembly and vesicle priming. SIGNIFICANCE STATEMENT The essential postdocking role of Munc18-1 in vesicular exocytosis has remained elusive, but recent data led to the hypothesis that the extension of helix 12 in Munc18 within domain 3a leads to synaptobrevin-2/VAMP2 interaction and SNARE complex formation. Using both lack-of-function and gain-of-function mutants, we here report that the conformation of helix 12 predicts vesicle priming and secretory amplitude in living chromaffin cells. The effects of mutants on secretion could not be explained by differences in syntaxin-1 chaperoning/localization or vesicle docking, and the fusion kinetics and calcium dependence were unchanged, indicating that the effect of helix 12 extension is specific for the vesicle-priming step. We conclude that a conformational change within helix 12 is responsible for the essential postdocking role of Munc18-1 in neurosecretion.
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32
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Zhang X, Jiang S, Mitok KA, Li L, Attie AD, Martin TFJ. BAIAP3, a C2 domain-containing Munc13 protein, controls the fate of dense-core vesicles in neuroendocrine cells. J Cell Biol 2017. [PMID: 28626000 PMCID: PMC5496627 DOI: 10.1083/jcb.201702099] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Zhang et al. conducted a siRNA screen of C2 domain proteins involved in regulated peptide secretion. One of the hits, a Munc13 family member BAIAP3, was characterized as endosome localized involved in post-exocytic dense-core vesicle protein recycling to the TGN. BAIAP3 knockdown inhibited dense-core vesicle maturation/stability in neuroendocrine/endocrine cells. Dense-core vesicle (DCV) exocytosis is a SNARE (soluble N-ethylmaleimide–sensitive fusion attachment protein receptor)-dependent anterograde trafficking pathway that requires multiple proteins for regulation. Several C2 domain–containing proteins are known to regulate Ca2+-dependent DCV exocytosis in neuroendocrine cells. In this study, we identified others by screening all (∼139) human C2 domain–containing proteins by RNA interference in neuroendocrine cells. 40 genes were identified, including several encoding proteins with known roles (CAPS [calcium-dependent activator protein for secretion 1], Munc13-2, RIM1, and SYT10) and many with unknown roles. One of the latter, BAIAP3, is a secretory cell–specific Munc13-4 paralog of unknown function. BAIAP3 knockdown caused accumulation of fusion-incompetent DCVs in BON neuroendocrine cells and lysosomal degradation (crinophagy) of insulin-containing DCVs in INS-1 β cells. BAIAP3 localized to endosomes was required for Golgi trans-Golgi network 46 (TGN46) recycling, exhibited Ca2+-stimulated interactions with TGN SNAREs, and underwent Ca2+-stimulated TGN recruitment. Thus, unlike other Munc13 proteins, BAIAP3 functions indirectly in DCV exocytosis by affecting DCV maturation through its role in DCV protein recycling. Ca2+ rises that stimulate DCV exocytosis may stimulate BAIAP3-dependent retrograde trafficking to maintain DCV protein homeostasis and DCV function.
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Affiliation(s)
- Xingmin Zhang
- Department of Biochemistry, University of Wisconsin, Madison, WI.,Program in Cellular and Molecular Biology, University of Wisconsin, Madison, WI
| | - Shan Jiang
- School of Pharmacy, University of Wisconsin, Madison, WI
| | - Kelly A Mitok
- Department of Biochemistry, University of Wisconsin, Madison, WI
| | - Lingjun Li
- School of Pharmacy, University of Wisconsin, Madison, WI
| | - Alan D Attie
- Department of Biochemistry, University of Wisconsin, Madison, WI
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33
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Abstract
The functions of four of the five proteins in the mammalian uncoordinated-13 (Munc13) family have been identified as priming factors in SNARE-dependent exocytosis. In this issue, Zhang et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201702099) show that the fifth member, BAIAP3 (brain-specific angiogenesis inhibitor I-associated protein 3), acts in retrograde trafficking by returning secretory vesicle material to the trans-Golgi network. In its absence, secretory vesicle formation is impaired, leading to accumulation of immature vesicles, or lysosomal vesicle degradation.
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Affiliation(s)
- Jakob B Sørensen
- Center for Neuroscience, University of Copenhagen, Copenhagen, Denmark
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34
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Van Vactor D, Sigrist SJ. Presynaptic morphogenesis, active zone organization and structural plasticity in Drosophila. Curr Opin Neurobiol 2017; 43:119-129. [PMID: 28388491 DOI: 10.1016/j.conb.2017.03.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 03/06/2017] [Accepted: 03/08/2017] [Indexed: 12/31/2022]
Abstract
Effective adaptation of neural circuit function to a changing environment requires many forms of plasticity. Among these, structural plasticity is one of the most durable, and is also an intrinsic part of the developmental logic for the formation and refinement of synaptic connectivity. Structural plasticity of presynaptic sites can involve the addition, remodeling, or removal of pre- and post-synaptic elements. However, this requires coordination of morphogenesis and assembly of the subcellular machinery for neurotransmitter release within the presynaptic neuron, as well as coordination of these events with the postsynaptic cell. While much progress has been made in revealing the cell biological mechanisms of postsynaptic structural plasticity, our understanding of presynaptic mechanisms is less complete.
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Affiliation(s)
- David Van Vactor
- Department of Cell Biology and Program in Neuroscience, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA; Okinawa Institute of Science and Technology, Graduate University, Tancha 1919-1, Onna-son, Okinawa, Japan.
| | - Stephan J Sigrist
- Institut für Biologie/Genetik and NeuroCure, Freie Universität Berlin, Takustrasse 6, D-14195 Berlin, Germany.
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35
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Woo SS, James DJ, Martin TFJ. Munc13-4 functions as a Ca 2+ sensor for homotypic secretory granule fusion to generate endosomal exocytic vacuoles. Mol Biol Cell 2017; 28:792-808. [PMID: 28100639 PMCID: PMC5349786 DOI: 10.1091/mbc.e16-08-0617] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 01/06/2017] [Accepted: 01/11/2017] [Indexed: 12/22/2022] Open
Abstract
Munc13-4 is a Ca2+-dependent SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)- and phospholipid-binding protein that localizes to and primes secretory granules (SGs) for Ca2+-evoked secretion in various secretory cells. Studies in mast cell-like RBL-2H3 cells provide direct evidence that Munc13-4 with its two Ca2+-binding C2 domains functions as a Ca2+ sensor for SG exocytosis. Unexpectedly, Ca2+ stimulation also generated large (>2.4 μm in diameter) Munc13-4+/Rab7+/Rab11+ endosomal vacuoles. Vacuole generation involved the homotypic fusion of Munc13-4+/Rab7+ SGs, followed by a merge with Rab11+ endosomes, and depended on Ca2+ binding to Munc13-4. Munc13-4 promoted the Ca2+-stimulated fusion of VAMP8-containing liposomes with liposomes containing exocytic or endosomal Q-SNAREs and directly interacted with late endosomal SNARE complexes. Thus Munc13-4 is a tethering/priming factor and Ca2+ sensor for both heterotypic SG-plasma membrane and homotypic SG-SG fusion. Total internal reflection fluorescence microscopy imaging revealed that vacuoles were exocytic and mediated secretion of β-hexosaminidase and cytokines accompanied by Munc13-4 diffusion onto the plasma membrane. The results provide new molecular insights into the mechanism of multigranular compound exocytosis commonly observed in various secretory cells.
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Affiliation(s)
- Sang Su Woo
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Declan J James
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Thomas F J Martin
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
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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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Toft-Bertelsen TL, Ziomkiewicz I, Houy S, Pinheiro PS, Sørensen JB. Regulation of Ca2+ channels by SNAP-25 via recruitment of syntaxin-1 from plasma membrane clusters. Mol Biol Cell 2016; 27:3329-3341. [PMID: 27605709 PMCID: PMC5170865 DOI: 10.1091/mbc.e16-03-0184] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 09/01/2016] [Indexed: 12/20/2022] Open
Abstract
SNAP-25 regulates Ca2+ channels in an unknown manner. Endogenous and exogenous SNAP-25 inhibit Ca2+ currents indirectly by recruiting syntaxin-1 from clusters on the plasma membrane, thereby making it available for Ca2+ current inhibition. Thus the cell can regulate Ca2+ influx by expanding or contracting syntaxin-1 clusters. SNAP-25 regulates Ca2+ channels, with potentially important consequences for diseases involving an aberrant SNAP-25 expression level. How this regulation is executed mechanistically remains unknown. We investigated this question in mouse adrenal chromaffin cells and found that SNAP-25 inhibits Ca2+ currents, with the B-isoform being more potent than the A-isoform, but not when syntaxin-1 is cleaved by botulinum neurotoxin C. In contrast, syntaxin-1 inhibits Ca2+ currents independently of SNAP-25. Further experiments using immunostaining showed that endogenous or exogenous SNAP-25 expression recruits syntaxin-1 from clusters on the plasma membrane, thereby increasing the immunoavailability of syntaxin-1 and leading indirectly to Ca2+ current inhibition. Expression of Munc18-1, which recruits syntaxin-1 within the exocytotic pathway, does not modulate Ca2+ channels, whereas overexpression of the syntaxin-binding protein Doc2B or ubMunc13-2 increases syntaxin-1 immunoavailability and concomitantly down-regulates Ca2+ currents. Similar findings were obtained upon chemical cholesterol depletion, leading directly to syntaxin-1 cluster dispersal and Ca2+ current inhibition. We conclude that clustering of syntaxin-1 allows the cell to maintain a high syntaxin-1 expression level without compromising Ca2+ influx, and recruitment of syntaxin-1 from clusters by SNAP-25 expression makes it available for regulating Ca2+ channels. This mechanism potentially allows the cell to regulate Ca2+ influx by expanding or contracting syntaxin-1 clusters.
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Affiliation(s)
- Trine Lisberg Toft-Bertelsen
- Neurosecretion Group, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Iwona Ziomkiewicz
- Neurosecretion Group, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Sébastien Houy
- Neurosecretion Group, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Paulo S Pinheiro
- Neurosecretion Group, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark
| | - Jakob B Sørensen
- Neurosecretion Group, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark
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Böhme MA, Beis C, Reddy-Alla S, Reynolds E, Mampell MM, Grasskamp AT, Lützkendorf J, Bergeron DD, Driller JH, Babikir H, Göttfert F, Robinson IM, O'Kane CJ, Hell SW, Wahl MC, Stelzl U, Loll B, Walter AM, Sigrist SJ. Active zone scaffolds differentially accumulate Unc13 isoforms to tune Ca2+ channel–vesicle coupling. Nat Neurosci 2016; 19:1311-20. [DOI: 10.1038/nn.4364] [Citation(s) in RCA: 136] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 07/20/2016] [Indexed: 01/05/2023]
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