1
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Pribbenow C, Owald D. Skewing information flow through pre- and postsynaptic plasticity in the mushroom bodies of Drosophila. Learn Mem 2024; 31:a053919. [PMID: 38876487 PMCID: PMC11199954 DOI: 10.1101/lm.053919.124] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Accepted: 04/26/2024] [Indexed: 06/16/2024]
Abstract
Animal brains need to store information to construct a representation of their environment. Knowledge of what happened in the past allows both vertebrates and invertebrates to predict future outcomes by recalling previous experience. Although invertebrate and vertebrate brains share common principles at the molecular, cellular, and circuit-architectural levels, there are also obvious differences as exemplified by the use of acetylcholine versus glutamate as the considered main excitatory neurotransmitters in the respective central nervous systems. Nonetheless, across central nervous systems, synaptic plasticity is thought to be a main substrate for memory storage. Therefore, how brain circuits and synaptic contacts change following learning is of fundamental interest for understanding brain computations tied to behavior in any animal. Recent progress has been made in understanding such plastic changes following olfactory associative learning in the mushroom bodies (MBs) of Drosophila A current framework of memory-guided behavioral selection is based on the MB skew model, in which antagonistic synaptic pathways are selectively changed in strength. Here, we review insights into plasticity at dedicated Drosophila MB output pathways and update what is known about the plasticity of both pre- and postsynaptic compartments of Drosophila MB neurons.
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Affiliation(s)
- Carlotta Pribbenow
- Institute of Neurophysiology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, 10117 Berlin, Germany
| | - David Owald
- Institute of Neurophysiology, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, 10117 Berlin, Germany
- Einstein Center for Neurosciences Berlin, 10117 Berlin, Germany
- NeuroCure, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, 10117 Berlin, Germany
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2
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Wu M, Jiang H, Li Q, Liu Y, Zhang H, Li X, Shao Z. OGT-1 regulates synaptic assembly through the insulin signaling pathway. J Cell Biochem 2023; 124:1919-1930. [PMID: 37991448 DOI: 10.1002/jcb.30497] [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: 07/27/2023] [Revised: 10/21/2023] [Accepted: 11/01/2023] [Indexed: 11/23/2023]
Abstract
The formation and maintenance of synapses are precisely regulated, and the misregulation often leads to neurodevelopmental or neurodegenerative disorders. Besides intrinsic genetically encoded signaling pathways, synaptic structure and function are also regulated by extrinsic factors, such as nutrients. O-GlcNAc transferase (OGT), a nutrient sensor, is abundant in the nervous system and required for synaptic plasticity, learning, and memory. However, whether OGT is involved in synaptic development and the mechanism underlying the process are largely unknown. In this study, we found that OGT-1, the OGT homolog in C. elegans, regulates the presynaptic assembly in AIY interneurons. The insulin receptor DAF-2 acts upstream of OGT-1 to promote the presynaptic assembly by positively regulating the expression of ogt-1. This insulin-OGT-1 axis functions most likely by regulating neuronal activity. In this study, we elucidated a novel mechanism for synaptic development, and provided a potential link between synaptic development and insulin-related neurological disorders.
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Affiliation(s)
- Mengting Wu
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Huihui Jiang
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Qian Li
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Yunhe Liu
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Hongjun Zhang
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Xuekun Li
- School of Medicine, The Children's Hospital, Zhejiang University, Hangzhou, China
- School of Medicine, The Institute of Translational Medicine, Zhejiang University, Hangzhou, China
- National Clinical Research Center for Child Health, Hangzhou, China
- Zhejiang University Cancer Center, Zhejiang University, Hangzhou, China
| | - Zhiyong Shao
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, China
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3
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Guss EJ, Akbergenova Y, Cunningham KL, Littleton JT. Loss of the extracellular matrix protein Perlecan disrupts axonal and synaptic stability during Drosophila development. eLife 2023; 12:RP88273. [PMID: 37368474 PMCID: PMC10328508 DOI: 10.7554/elife.88273] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2023] Open
Abstract
Heparan sulfate proteoglycans (HSPGs) form essential components of the extracellular matrix (ECM) and basement membrane (BM) and have both structural and signaling roles. Perlecan is a secreted ECM-localized HSPG that contributes to tissue integrity and cell-cell communication. Although a core component of the ECM, the role of Perlecan in neuronal structure and function is less understood. Here, we identify a role for Drosophila Perlecan in the maintenance of larval motoneuron axonal and synaptic stability. Loss of Perlecan causes alterations in the axonal cytoskeleton, followed by axonal breakage and synaptic retraction of neuromuscular junctions. These phenotypes are not prevented by blocking Wallerian degeneration and are independent of Perlecan's role in Wingless signaling. Expression of Perlecan solely in motoneurons cannot rescue synaptic retraction phenotypes. Similarly, removing Perlecan specifically from neurons, glia, or muscle does not cause synaptic retraction, indicating the protein is secreted from multiple cell types and functions non-cell autonomously. Within the peripheral nervous system, Perlecan predominantly localizes to the neural lamella, a specialized ECM surrounding nerve bundles. Indeed, the neural lamella is disrupted in the absence of Perlecan, with axons occasionally exiting their usual boundary in the nerve bundle. In addition, entire nerve bundles degenerate in a temporally coordinated manner across individual hemi-segments throughout larval development. These observations indicate disruption of neural lamella ECM function triggers axonal destabilization and synaptic retraction of motoneurons, revealing a role for Perlecan in axonal and synaptic integrity during nervous system development.
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Affiliation(s)
- Ellen J Guss
- The Picower Institute for Learning and Memory, Department of Biology, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Yulia Akbergenova
- The Picower Institute for Learning and Memory, Department of Biology, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Karen L Cunningham
- The Picower Institute for Learning and Memory, Department of Biology, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Biology, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
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4
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Falkovich R, Danielson EW, Perez de Arce K, Wamhoff EC, Strother J, Lapteva AP, Sheng M, Cottrell JR, Bathe M. A synaptic molecular dependency network in knockdown of autism- and schizophrenia-associated genes revealed by multiplexed imaging. Cell Rep 2023; 42:112430. [PMID: 37099425 DOI: 10.1016/j.celrep.2023.112430] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 01/29/2023] [Accepted: 04/08/2023] [Indexed: 04/27/2023] Open
Abstract
The complex functions of neuronal synapses depend on their tightly interconnected protein network, and their dysregulation is implicated in the pathogenesis of autism spectrum disorders and schizophrenia. However, it remains unclear how synaptic molecular networks are altered biochemically in these disorders. Here, we apply multiplexed imaging to probe the effects of RNAi knockdown of 16 autism- and schizophrenia-associated genes on the simultaneous joint distribution of 10 synaptic proteins, observing several protein composition phenotypes associated with these risk genes. We apply Bayesian network analysis to infer hierarchical dependencies among eight excitatory synaptic proteins, yielding predictive relationships that can only be accessed with single-synapse, multiprotein measurements performed simultaneously in situ. Finally, we find that central features of the network are affected similarly across several distinct gene knockdowns. These results offer insight into the convergent molecular etiology of these widespread disorders and provide a general framework to probe subcellular molecular networks.
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Affiliation(s)
- Reuven Falkovich
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Eric W Danielson
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Karen Perez de Arce
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Eike-C Wamhoff
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Juliana Strother
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Anna P Lapteva
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Morgan Sheng
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA; Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jeffrey R Cottrell
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Mark Bathe
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA; Broad Institute of MIT and Harvard, Cambridge, MA, USA; Harvard Medical School Initiative for RNA Medicine, Harvard University, Cambridge, MA, USA.
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5
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Chien C, Dickman D. One domain to rule them all: "In synapse" reconstitution of core active zone functions. Neuron 2022; 110:1435-1438. [PMID: 35512634 DOI: 10.1016/j.neuron.2022.04.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Active zones are colossal and complex molecular machines that transform electrical signals into rapid neurotransmitter secretion. In this issue of Neuron, Tan et al. (2022) elegantly distill central functions of this synaptic apparatus by tethering a small domain of the scaffold RIM near Ca2+ channels.
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Affiliation(s)
- Chun Chien
- Department of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA
| | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA.
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6
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Knodel MM, Dutta Roy R, Wittum G. Influence of T-Bar on Calcium Concentration Impacting Release Probability. Front Comput Neurosci 2022; 16:855746. [PMID: 35586479 PMCID: PMC9108211 DOI: 10.3389/fncom.2022.855746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 03/09/2022] [Indexed: 11/25/2022] Open
Abstract
The relation of form and function, namely the impact of the synaptic anatomy on calcium dynamics in the presynaptic bouton, is a major challenge of present (computational) neuroscience at a cellular level. The Drosophila larval neuromuscular junction (NMJ) is a simple model system, which allows studying basic effects in a rather simple way. This synapse harbors several special structures. In particular, in opposite to standard vertebrate synapses, the presynaptic boutons are rather large, and they have several presynaptic zones. In these zones, different types of anatomical structures are present. Some of the zones bear a so-called T-bar, a particular anatomical structure. The geometric form of the T-bar resembles the shape of the letter “T” or a table with one leg. When an action potential arises, calcium influx is triggered. The probability of vesicle docking and neurotransmitter release is superlinearly proportional to the concentration of calcium close to the vesicular release site. It is tempting to assume that the T-bar causes some sort of calcium accumulation and hence triggers a higher release probability and thus enhances neurotransmitter exocytosis. In order to study this influence in a quantitative manner, we constructed a typical T-bar geometry and compared the calcium concentration close to the active zones (AZs). We compared the case of synapses with and without T-bars. Indeed, we found a substantial influence of the T-bar structure on the presynaptic calcium concentrations close to the AZs, indicating that this anatomical structure increases vesicle release probability. Therefore, our study reveals how the T-bar zone implies a strong relation between form and function. Our study answers the question of experimental studies (namely “Wichmann and Sigrist, Journal of neurogenetics 2010”) concerning the sense of the anatomical structure of the T-bar.
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Affiliation(s)
- Markus M. Knodel
- Goethe Center for Scientific Computing (GCSC), Goethe Universität Frankfurt, Frankfurt, Germany
- *Correspondence: Markus M. Knodel ; orcid.org/0000-0001-8739-0803
| | | | - Gabriel Wittum
- Goethe Center for Scientific Computing (GCSC), Goethe Universität Frankfurt, Frankfurt, Germany
- Applied Mathematics and Computational Science, Computer, Electrical and Mathematical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
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7
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Pribbenow C, Chen YC, Heim MM, Laber D, Reubold S, Reynolds E, Balles I, Fernández-d V Alquicira T, Suárez-Grimalt R, Scheunemann L, Rauch C, Matkovic T, Rösner J, Lichtner G, Jagannathan SR, Owald D. Postsynaptic plasticity of cholinergic synapses underlies the induction and expression of appetitive and familiarity memories in Drosophila. eLife 2022; 11:80445. [PMID: 36250621 PMCID: PMC9733945 DOI: 10.7554/elife.80445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 10/17/2022] [Indexed: 12/14/2022] Open
Abstract
In vertebrates, several forms of memory-relevant synaptic plasticity involve postsynaptic rearrangements of glutamate receptors. In contrast, previous work indicates that Drosophila and other invertebrates store memories using presynaptic plasticity of cholinergic synapses. Here, we provide evidence for postsynaptic plasticity at cholinergic output synapses from the Drosophila mushroom bodies (MBs). We find that the nicotinic acetylcholine receptor (nAChR) subunit α5 is required within specific MB output neurons for appetitive memory induction but is dispensable for aversive memories. In addition, nAChR α2 subunits mediate memory expression and likely function downstream of α5 and the postsynaptic scaffold protein discs large (Dlg). We show that postsynaptic plasticity traces can be induced independently of the presynapse, and that in vivo dynamics of α2 nAChR subunits are changed both in the context of associative and non-associative (familiarity) memory formation, underlying different plasticity rules. Therefore, regardless of neurotransmitter identity, key principles of postsynaptic plasticity support memory storage across phyla.
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Affiliation(s)
- Carlotta Pribbenow
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Yi-chun Chen
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - M-Marcel Heim
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Desiree Laber
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Silas Reubold
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Eric Reynolds
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Isabella Balles
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Tania Fernández-d V Alquicira
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Raquel Suárez-Grimalt
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany,Einstein Center for Neurosciences BerlinBerlinGermany
| | - Lisa Scheunemann
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany,NeuroCure, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany,Institut für Biologie, Freie Universität BerlinBerlinGermany
| | - Carolin Rauch
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - Tanja Matkovic
- Institut für Biologie, Freie Universität BerlinBerlinGermany
| | - Jörg Rösner
- NWFZ, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthGreifswaldGermany
| | - Gregor Lichtner
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany,Universitätsmedizin Greifswald, Department of Anesthesia, Critical Care, Emergency and Pain MedicineGreifswaldGermany
| | - Sridhar R Jagannathan
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
| | - David Owald
- Institute of Neurophysiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany,Einstein Center for Neurosciences BerlinBerlinGermany,NeuroCure, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Berlin Institute of HealthBerlinGermany
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8
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Ramesh N, Escher MJF, Mampell MM, Böhme MA, Götz TWB, Goel P, Matkovic T, Petzoldt AG, Dickman D, Sigrist SJ. Antagonistic interactions between two Neuroligins coordinate pre- and postsynaptic assembly. Curr Biol 2021; 31:1711-1725.e5. [PMID: 33651992 DOI: 10.1016/j.cub.2021.01.093] [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: 05/11/2020] [Revised: 11/18/2020] [Accepted: 01/26/2021] [Indexed: 12/17/2022]
Abstract
As a result of developmental synapse formation, the presynaptic neurotransmitter release machinery becomes accurately matched with postsynaptic neurotransmitter receptors. Trans-synaptic signaling is executed through cell adhesion proteins such as Neurexin::Neuroligin pairs but also through diffusible and cytoplasmic signals. How exactly pre-post coordination is ensured in vivo remains largely enigmatic. Here, we identified a "molecular choreography" coordinating pre- with postsynaptic assembly during the developmental formation of Drosophila neuromuscular synapses. Two presynaptic Neurexin-binding scaffold proteins, Syd-1 and Spinophilin (Spn), spatio-temporally coordinated pre-post assembly in conjunction with two postsynaptically operating, antagonistic Neuroligin species: Nlg1 and Nlg2. The Spn/Nlg2 module promoted active zone (AZ) maturation by driving the accumulation of AZ scaffold proteins critical for synaptic vesicle release. Simultaneously, these regulators restricted postsynaptic glutamate receptor incorporation. Both functions of the Spn/Nlg2 module were directly antagonized by Syd-1/Nlg1. Nlg1 and Nlg2 also had divergent effects on Nrx-1 in vivo motility. Concerning diffusible signals, Spn and Syd-1 antagonistically controlled the levels of Munc13-family protein Unc13B at nascent AZs, whose release function facilitated glutamate receptor incorporation at assembling postsynaptic specializations. As a result, we here provide direct in vivo evidence illustrating how a highly regulative and interleaved communication between cell adhesion protein signaling complexes and diffusible signals allows for a precise coordination of pre- with postsynaptic assembly. It will be interesting to analyze whether this logic also transfers to plasticity processes.
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Affiliation(s)
- Niraja Ramesh
- Institute for Biology and Genetics, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany
| | - Marc J F Escher
- Institute for Biology and Genetics, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany
| | - Malou M Mampell
- Institute for Biology and Genetics, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany
| | - Mathias A Böhme
- Institute for Biology and Genetics, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany; Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany
| | - Torsten W B Götz
- Institute for Biology and Genetics, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany
| | - Pragya Goel
- Department of Neurobiology, University of Southern California, Los Angeles, CA, USA
| | - Tanja Matkovic
- Institute for Biology and Genetics, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany
| | - Astrid G Petzoldt
- Institute for Biology and Genetics, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany
| | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA, USA
| | - Stephan J Sigrist
- Institute for Biology and Genetics, Freie Universität Berlin, Takustraße 6, 14195 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin, Charitéplatz 1, 10117 Berlin, Germany.
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9
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Jäpel M, Gerth F, Sakaba T, Bacetic J, Yao L, Koo SJ, Maritzen T, Freund C, Haucke V. Intersectin-Mediated Clearance of SNARE Complexes Is Required for Fast Neurotransmission. Cell Rep 2021; 30:409-420.e6. [PMID: 31940485 DOI: 10.1016/j.celrep.2019.12.035] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 11/11/2019] [Accepted: 12/12/2019] [Indexed: 12/12/2022] Open
Abstract
The rapid replenishment of release-ready synaptic vesicles (SVs) at a limiting number of presynaptic release sites is required to sustain high-frequency neurotransmission in CNS neurons. Failure to clear release sites from previously exocytosed material has been shown to impair vesicle replenishment and, therefore, fast neurotransmission. The identity of this material and the machinery that removes it from release sites have remained enigmatic. Here we show that the endocytic scaffold protein intersectin 1 clears release sites by direct SH3 domain-mediated association with a non-canonical proline-rich segment of synaptobrevin assembled into the SNARE complex for neuroexocytosis. Acute structure-based or sustained genetic interference with SNARE complex recognition by intersectin 1 causes a rapid stimulation frequency-dependent depression of neurotransmission due to impaired replenishment of release-ready SVs. These findings identify a key molecular mechanism that underlies exo-endocytic coupling during fast neurotransmitter release at central synapses.
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Affiliation(s)
- Maria Jäpel
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Molecular Pharmacology & Cell Biology, 13125 Berlin, Germany
| | - Fabian Gerth
- Freie Universität Berlin, Faculty of Biology, Chemistry, Pharmacy, 14195 Berlin, Germany
| | - Takeshi Sakaba
- Doshisha University, Graduate School of Brain Science, Kyoto 610-0394, Japan
| | - Jelena Bacetic
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Molecular Pharmacology & Cell Biology, 13125 Berlin, Germany; Freie Universität Berlin, Faculty of Biology, Chemistry, Pharmacy, 14195 Berlin, Germany
| | - Lijun Yao
- Max-Planck-Institute for Biophysical Chemistry, Department of Membrane Biophysics, 37077 Göttingen, Germany
| | - Seong-Joo Koo
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Molecular Pharmacology & Cell Biology, 13125 Berlin, Germany
| | - Tanja Maritzen
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Molecular Pharmacology & Cell Biology, 13125 Berlin, Germany
| | - Christian Freund
- Freie Universität Berlin, Faculty of Biology, Chemistry, Pharmacy, 14195 Berlin, Germany
| | - Volker Haucke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Department of Molecular Pharmacology & Cell Biology, 13125 Berlin, Germany; Freie Universität Berlin, Faculty of Biology, Chemistry, Pharmacy, 14195 Berlin, Germany; NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, 10117 Berlin, Germany.
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10
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Özel MN, Kulkarni A, Hasan A, Brummer J, Moldenhauer M, Daumann IM, Wolfenberg H, Dercksen VJ, Kiral FR, Weiser M, Prohaska S, von Kleist M, Hiesinger PR. Serial Synapse Formation through Filopodial Competition for Synaptic Seeding Factors. Dev Cell 2019; 50:447-461.e8. [PMID: 31353313 DOI: 10.1016/j.devcel.2019.06.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 05/15/2019] [Accepted: 06/21/2019] [Indexed: 11/15/2022]
Abstract
Following axon pathfinding, growth cones transition from stochastic filopodial exploration to the formation of a limited number of synapses. How the interplay of filopodia and synapse assembly ensures robust connectivity in the brain has remained a challenging problem. Here, we developed a new 4D analysis method for filopodial dynamics and a data-driven computational model of synapse formation for R7 photoreceptor axons in developing Drosophila brains. Our live data support a "serial synapse formation" model, where at any time point only 1-2 "synaptogenic" filopodia suppress the synaptic competence of other filopodia through competition for synaptic seeding factors. Loss of the synaptic seeding factors Syd-1 and Liprin-α leads to a loss of this suppression, filopodial destabilization, and reduced synapse formation. The failure to form synapses can cause the destabilization and secondary retraction of axon terminals. Our model provides a filopodial "winner-takes-all" mechanism that ensures the formation of an appropriate number of synapses.
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Affiliation(s)
- M Neset Özel
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany; Neuroscience Graduate Program, UT Southwestern Medical Center Dallas, Dallas, TX 75390, USA
| | - Abhishek Kulkarni
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Amr Hasan
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Josephine Brummer
- Department of Visual Data Analysis, Zuse Institute Berlin, 14195 Berlin, Germany
| | - Marian Moldenhauer
- Computational Medicine and Numerical Mathematics, Zuse Institute Berlin, 14195 Berlin, Germany; Department of Mathematics and Informatics, Freie Universität Berlin, 14195 Berlin, Germany
| | - Ilsa-Maria Daumann
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Heike Wolfenberg
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Vincent J Dercksen
- Department of Visual Data Analysis, Zuse Institute Berlin, 14195 Berlin, Germany
| | - F Ridvan Kiral
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Martin Weiser
- Computational Medicine and Numerical Mathematics, Zuse Institute Berlin, 14195 Berlin, Germany
| | - Steffen Prohaska
- Department of Visual Data Analysis, Zuse Institute Berlin, 14195 Berlin, Germany
| | - Max von Kleist
- Department of Mathematics and Informatics, Freie Universität Berlin, 14195 Berlin, Germany.
| | - P Robin Hiesinger
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany.
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11
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Liu K, Jones S, Minis A, Rodriguez J, Molina H, Steller H. PI31 Is an Adaptor Protein for Proteasome Transport in Axons and Required for Synaptic Development. Dev Cell 2019; 50:509-524.e10. [PMID: 31327739 DOI: 10.1016/j.devcel.2019.06.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 04/18/2019] [Accepted: 06/14/2019] [Indexed: 12/13/2022]
Abstract
Protein degradation by the ubiquitin-proteasome system is critical for neuronal function. Neurons utilize microtubule-dependent molecular motors to allocate proteasomes to synapses, but how proteasomes are coupled to motors and how this is regulated to meet changing demand for protein breakdown remain largely unknown. We show that the conserved proteasome-binding protein PI31 serves as an adaptor to couple proteasomes with dynein light chain proteins (DYNLL1/2). The inactivation of PI31 inhibited proteasome motility in axons and disrupted synaptic proteostasis, structure, and function. Moreover, phosphorylation of PI31 by p38 MAPK enhanced binding to DYNLL1/2 and promoted the directional movement of proteasomes in axons, suggesting a mechanism to regulate loading of proteasomes onto motors. Inactivation of PI31 in mouse neurons attenuated proteasome movement in axons, indicating this process is conserved. Because mutations affecting PI31 activity are associated with human neurodegenerative diseases, impairment of PI31-mediated axonal transport of proteasomes may contribute to these disorders.
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Affiliation(s)
- Kai Liu
- Strang Laboratory of Apoptosis and Cancer Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Sandra Jones
- Strang Laboratory of Apoptosis and Cancer Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Adi Minis
- Strang Laboratory of Apoptosis and Cancer Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Jose Rodriguez
- Strang Laboratory of Apoptosis and Cancer Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Henrik Molina
- Proteomics Resource Center, The Rockefeller University, New York, NY 10065, USA
| | - Hermann Steller
- Strang Laboratory of Apoptosis and Cancer Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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12
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Dorgans K, Demais V, Bailly Y, Poulain B, Isope P, Doussau F. Short-term plasticity at cerebellar granule cell to molecular layer interneuron synapses expands information processing. eLife 2019; 8:41586. [PMID: 31081751 PMCID: PMC6533085 DOI: 10.7554/elife.41586] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 05/11/2019] [Indexed: 12/14/2022] Open
Abstract
Information processing by cerebellar molecular layer interneurons (MLIs) plays a crucial role in motor behavior. MLI recruitment is tightly controlled by the profile of short-term plasticity (STP) at granule cell (GC)-MLI synapses. While GCs are the most numerous neurons in the brain, STP diversity at GC-MLI synapses is poorly documented. Here, we studied how single MLIs are recruited by their distinct GC inputs during burst firing. Using slice recordings at individual GC-MLI synapses of mice, we revealed four classes of connections segregated by their STP profile. Each class differentially drives MLI recruitment. We show that GC synaptic diversity is underlain by heterogeneous expression of synapsin II, a key actor of STP and that GC terminals devoid of synapsin II are associated with slow MLI recruitment. Our study reveals that molecular, structural and functional diversity across GC terminals provides a mechanism to expand the coding range of MLIs.
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Affiliation(s)
- Kevin Dorgans
- Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212, Université de Strasbourg, Strasbourg, France
| | - Valérie Demais
- Plateforme Imagerie in vitro, CNRS UPS 3156, Strasbourg, France
| | - Yannick Bailly
- Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212, Université de Strasbourg, Strasbourg, France.,Plateforme Imagerie in vitro, CNRS UPS 3156, Strasbourg, France
| | - Bernard Poulain
- Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212, Université de Strasbourg, Strasbourg, France
| | - Philippe Isope
- Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212, Université de Strasbourg, Strasbourg, France
| | - Frédéric Doussau
- Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212, Université de Strasbourg, Strasbourg, France
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13
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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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14
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Presynaptic Biogenesis Requires Axonal Transport of Lysosome-Related Vesicles. Neuron 2018; 99:1216-1232.e7. [DOI: 10.1016/j.neuron.2018.08.004] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 05/18/2018] [Accepted: 08/02/2018] [Indexed: 01/05/2023]
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15
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Sugie A, Marchetti G, Tavosanis G. Structural aspects of plasticity in the nervous system of Drosophila. Neural Dev 2018; 13:14. [PMID: 29960596 PMCID: PMC6026517 DOI: 10.1186/s13064-018-0111-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 06/12/2018] [Indexed: 12/15/2022] Open
Abstract
Neurons extend and retract dynamically their neurites during development to form complex morphologies and to reach out to their appropriate synaptic partners. Their capacity to undergo structural rearrangements is in part maintained during adult life when it supports the animal's ability to adapt to a changing environment or to form lasting memories. Nonetheless, the signals triggering structural plasticity and the mechanisms that support it are not yet fully understood at the molecular level. Here, we focus on the nervous system of the fruit fly to ask to which extent activity modulates neuronal morphology and connectivity during development. Further, we summarize the evidence indicating that the adult nervous system of flies retains some capacity for structural plasticity at the synaptic or circuit level. For simplicity, we selected examples mostly derived from studies on the visual system and on the mushroom body, two regions of the fly brain with extensively studied neuroanatomy.
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Affiliation(s)
- Atsushi Sugie
- Center for Transdisciplinary Research, Niigata University, Niigata, 951-8585 Japan
- Brain Research Institute, Niigata University, Niigata, 951-8585 Japan
| | | | - Gaia Tavosanis
- Center for Neurodegenerative Diseases (DZNE), 53127 Bonn, Germany
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16
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Rai D, Dey S, Ray K. A method for estimating relative changes in the synaptic density in Drosophila central nervous system. BMC Neurosci 2018; 19:30. [PMID: 29769037 PMCID: PMC5956817 DOI: 10.1186/s12868-018-0430-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 05/02/2018] [Indexed: 12/16/2022] Open
Abstract
Background Synapse density is an essential indicator of development and functioning of the central nervous system. It is estimated indirectly through the accumulation of pre and postsynaptic proteins in tissue sections. 3D reconstruction of the electron microscopic images in serial sections is one of the most definitive means of estimating the formation of active synapses in the brain. It is tedious and highly skill-dependent. Confocal imaging of whole mounts or thick sections of the brain provides a natural alternative for rapid gross estimation of the synapse density in large areas. The optical resolution and other deep-tissue imaging aberrations limit the quantitative scope of this technique. Results Here we demonstrate a simple sample preparation method that could enhance the clarity of the confocal images of the neuropil regions of the ventral nerve cord of Drosophila larvae, providing a clear view of synapse distributions. We estimated the gross volume occupied by the synaptic junctions using 3D object counter plug-in of Fiji/ImageJ®. It gave us a proportional estimate of the number of synaptic junctions in the neuropil region. The method is corroborated by correlated super-resolution imaging analysis and through genetic perturbation of synaptogenesis in the larval brain. Conclusions The method provides a significant improvement in the relative estimate of region-specific synapse density in the central nervous system. Also, it reduced artifacts in the super-resolution images obtained using the stimulated emission depletion microscopy technique. Electronic supplementary material The online version of this article (10.1186/s12868-018-0430-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Dipti Rai
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, 400005, India
| | - Swagata Dey
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, 400005, India
| | - Krishanu Ray
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, 400005, India.
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17
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Complexin Mutants Reveal Partial Segregation between Recycling Pathways That Drive Evoked and Spontaneous Neurotransmission. J Neurosci 2017; 37:383-396. [PMID: 28077717 DOI: 10.1523/jneurosci.1854-16.2016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Revised: 11/10/2016] [Accepted: 11/15/2016] [Indexed: 11/21/2022] Open
Abstract
Synaptic vesicles fuse at morphological specializations in the presynaptic terminal termed active zones (AZs). Vesicle fusion can occur spontaneously or in response to an action potential. Following fusion, vesicles are retrieved and recycled within nerve terminals. It is still unclear whether vesicles that fuse spontaneously or following evoked release share similar recycling mechanisms. Genetic deletion of the SNARE-binding protein complexin dramatically increases spontaneous fusion, with the protein serving as the synaptic vesicle fusion clamp at Drosophila synapses. We examined synaptic vesicle recycling pathways at complexin null neuromuscular junctions, where spontaneous release is dramatically enhanced. We combined loading of the lipophilic dye FM1-43 with photoconversion, electron microscopy, and electrophysiology to monitor evoked and spontaneous recycling vesicle pools. We found that the total number of recycling vesicles was equal to those retrieved through spontaneous and evoked pools, suggesting that retrieval following fusion is partially segregated for spontaneous and evoked release. In addition, the kinetics of FM1-43 destaining and synaptic depression measured in the presence of the vesicle-refilling blocker bafilomycin indicated that spontaneous and evoked recycling pools partially intermix during the release process. Finally, FM1-43 photoconversion combined with electron microscopy analysis indicated that spontaneous recycling preferentially involves synaptic vesicles in the vicinity of AZs, whereas vesicles recycled following evoked release involve a larger intraterminal pool. Together, these results suggest that spontaneous and evoked vesicles use separable recycling pathways and then partially intermix during subsequent rounds of fusion. SIGNIFICANCE STATEMENT Neurotransmitter release involves fusion of synaptic vesicles with the plasma membrane in response to an action potential, or spontaneously in the absence of stimulation. Upon fusion, vesicles are retrieved and recycled, and it is unclear whether recycling pathways for evoked and spontaneous vesicles are segregated after fusion. We addressed this question by taking advantage of preparations lacking the synaptic protein complexin, which have elevated spontaneous release that enables reliable tracking of the spontaneous recycling pool. Our results suggest that spontaneous and evoked recycling pathways are segregated during the retrieval process but can partially intermix during stimulation.
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18
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Roy-Carson S, Natukunda K, Chou HC, Pal N, Farris C, Schneider SQ, Kuhlman JA. Defining the transcriptomic landscape of the developing enteric nervous system and its cellular environment. BMC Genomics 2017; 18:290. [PMID: 28403821 PMCID: PMC5389105 DOI: 10.1186/s12864-017-3653-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 03/22/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Motility and the coordination of moving food through the gastrointestinal tract rely on a complex network of neurons known as the enteric nervous system (ENS). Despite its critical function, many of the molecular mechanisms that direct the development of the ENS and the elaboration of neural network connections remain unknown. The goal of this study was to transcriptionally identify molecular pathways and candidate genes that drive specification, differentiation and the neural circuitry of specific neural progenitors, the phox2b expressing ENS cell lineage, during normal enteric nervous system development. Because ENS development is tightly linked to its environment, the transcriptional landscape of the cellular environment of the intestine was also analyzed. RESULTS Thousands of zebrafish intestines were manually dissected from a transgenic line expressing green fluorescent protein under the phox2b regulatory elements [Tg(phox2b:EGFP) w37 ]. Fluorescence-activated cell sorting was used to separate GFP-positive phox2b expressing ENS progenitor and derivatives from GFP-negative intestinal cells. RNA-seq was performed to obtain accurate, reproducible transcriptional profiles and the unbiased detection of low level transcripts. Analysis revealed genes and pathways that may function in ENS cell determination, genes that may be identifiers of different ENS subtypes, and genes that define the non-neural cellular microenvironment of the ENS. Differential expression analysis between the two cell populations revealed the expected neuronal nature of the phox2b expressing lineage including the enrichment for genes required for neurogenesis and synaptogenesis, and identified many novel genes not previously associated with ENS development. Pathway analysis pointed to a high level of G-protein coupled pathway activation, and identified novel roles for candidate pathways such as the Nogo/Reticulon axon guidance pathway in ENS development. CONCLUSION We report the comprehensive gene expression profiles of a lineage-specific population of enteric progenitors, their derivatives, and their microenvironment during normal enteric nervous system development. Our results confirm previously implicated genes and pathways required for ENS development, and also identify scores of novel candidate genes and pathways. Thus, our dataset suggests various potential mechanisms that drive ENS development facilitating characterization and discovery of novel therapeutic strategies to improve gastrointestinal disorders.
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Affiliation(s)
- Sweta Roy-Carson
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA
| | - Kevin Natukunda
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA
| | - Hsien-Chao Chou
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA.,Present Address: National Cancer Institute, US National Institutes of Health, Bethesda, Maryland, USA
| | - Narinder Pal
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA.,Present address: North Central Regional Plant Introduction Station, 1305 State Ave, Ames, IA, 50014, USA
| | - Caitlin Farris
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA.,Present address: Pioneer Hi-Bred International, Johnson, IA, 50131, USA
| | - Stephan Q Schneider
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA
| | - Julie A Kuhlman
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA. .,642 Science II, Iowa State University, Ames, IA, 50011, USA.
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19
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Sugie A, Möhl C, Hakeda-Suzuki S, Matsui H, Suzuki T, Tavosanis G. Analyzing Synaptic Modulation of Drosophila melanogaster Photoreceptors after Exposure to Prolonged Light. J Vis Exp 2017. [PMID: 28287587 DOI: 10.3791/55176] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The nervous system has the remarkable ability to adapt and respond to various stimuli. This neural adjustment is largely achieved through plasticity at the synaptic level. The Active Zone (AZ) is the region at the presynaptic membrane that mediates neurotransmitter release and is composed of a dense collection of scaffold proteins. AZs of Drosophila melanogaster (Drosophila) photoreceptors undergo molecular remodeling after prolonged exposure to natural ambient light. Thus the level of neuronal activity can rearrange the molecular composition of the AZ and contribute to the regulation of the functional output. Starting from the light exposure set-up preparation to the immunohistochemistry, this protocol details how to quantify the number, the spatial distribution, and the delocalization level of synaptic molecules at AZs in Drosophila photoreceptors. Using image analysis software, clusters of the GFP-fused AZ component Bruchpilot were identified for each R8 photoreceptor (R8) axon terminal. Detected Bruchpilot spots were automatically assigned to individual R8 axons. To calculate the distribution of spot frequency along the axon, we implemented a customized software plugin. Each axon's start-point and end-point were manually defined and the position of each Bruchpilot spot was projected onto the connecting line between start and end-point. Besides the number of Bruchpilot clusters, we also quantified the delocalization level of Bruchpilot-GFP within the clusters. These measurements reflect in detail the spatially resolved synaptic dynamics in a single neuron under different environmental conditions to stimuli.
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Affiliation(s)
- Atsushi Sugie
- Department of Neuroscience of Disease, Center for Transdisciplinary Research, Niigata University; Brain Research Institute, Niigata University; Dendrite Differentiation, German Center for Neurodegenerative Diseases (DZNE);
| | - Christoph Möhl
- Image and Data Analysis Facility, German Center for Neurodegenerative Diseases (DZNE);
| | - Satoko Hakeda-Suzuki
- Graduate School of Life Science and Technology, Tokyo Institute of Technology (Titech)
| | - Hideaki Matsui
- Department of Neuroscience of Disease, Center for Transdisciplinary Research, Niigata University; Brain Research Institute, Niigata University
| | - Takashi Suzuki
- Graduate School of Life Science and Technology, Tokyo Institute of Technology (Titech)
| | - Gaia Tavosanis
- Dendrite Differentiation, German Center for Neurodegenerative Diseases (DZNE)
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20
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Dzyubenko E, Rozenberg A, Hermann DM, Faissner A. Colocalization of synapse marker proteins evaluated by STED-microscopy reveals patterns of neuronal synapse distribution in vitro. J Neurosci Methods 2016; 273:149-159. [PMID: 27615741 DOI: 10.1016/j.jneumeth.2016.09.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 08/30/2016] [Accepted: 09/07/2016] [Indexed: 01/08/2023]
Abstract
BACKGROUND Quantification of synapses and their morphological analysis are extensively used in network development and connectivity studies, drug screening and other areas of neuroscience. Thus, a number of quantitative approaches were introduced so far. However, most of the available methods are highly tailored to specific applications and have limitations for widespread use. NEW METHOD We present a new plugin for the open-source software ImageJ to provide a modifiable, high-throughput and easy to use method for synaptic puncta analysis. Our approach is based on colocalization of pre- and postsynaptic protein markers. Structurally completed glutamatergic and GABAergic synapses were identified by VGLUT1-PSD95 and VGAT-gephyrin colocalization, respectively. By combining conventional confocal microscopy with stimulated emission depletion (STED) imaging, we propose a method to quantify the number of scaffolding protein clusters, recruited to a single postsynaptic density. RESULTS In a proof-of-concept study, we reveal the differential distribution of glutamatergic and GABAergic synapse density with reference to perineuronal net (PNN) expression. Using super-resolution STED imaging, we demonstrate that postsynaptic puncta of completed synapses are composed of significantly more protein clusters, compared to uncompleted synapses. COMPARISON WITH EXISTING METHODS Our Synapse Counter plugin for ImageJ offers a rapid and unbiased research tool for a broad spectrum of neuroscientists. The proposed method of synaptic protein clusters quantification exploits super-resolution imaging to provide a comprehensive approach to the analysis of postsynaptic density composition. CONCLUSIONS Our results strongly substantiate the benefits of colocalization-based synapse detection.
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Affiliation(s)
- Egor Dzyubenko
- Department of Cell Morphology and Molecular Neurobiology, Ruhr-University Bochum, Germany; International School of Neuroscience (IGSN), Ruhr-University Bochum, Germany
| | - Andrey Rozenberg
- Department of Animal Ecology, Evolution and Biodiversity, Ruhr-University Bochum, Germany
| | - Dirk M Hermann
- Department of Neurology, University Hospital Essen, Germany
| | - Andreas Faissner
- Department of Cell Morphology and Molecular Neurobiology, Ruhr-University Bochum, Germany.
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21
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Zhang YV, Hannan SB, Stapper ZA, Kern JV, Jahn TR, Rasse TM. The Drosophila KIF1A Homolog unc-104 Is Important for Site-Specific Synapse Maturation. Front Cell Neurosci 2016; 10:207. [PMID: 27656128 PMCID: PMC5011141 DOI: 10.3389/fncel.2016.00207] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 08/19/2016] [Indexed: 11/13/2022] Open
Abstract
Mutations in the kinesin-3 family member KIF1A have been associated with hereditary spastic paraplegia (HSP), hereditary and sensory autonomic neuropathy type 2 (HSAN2) and non-syndromic intellectual disability (ID). Both autosomal recessive and autosomal dominant forms of inheritance have been reported. Loss of KIF1A or its homolog unc-104 causes early postnatal or embryonic lethality in mice and Drosophila, respectively. In this study, we use a previously described hypomorphic allele of unc-104, unc-104(bris) , to investigate the impact of partial loss-of-function of kinesin-3 on synapse maturation at the Drosophila neuromuscular junction (NMJ). Unc-104(bris) mutants exhibit structural defects where a subset of synapses at the NMJ lack all investigated active zone (AZ) proteins, suggesting a complete failure in the formation of the cytomatrix at the active zone (CAZ) at these sites. Modulating synaptic Bruchpilot (Brp) levels by ectopic overexpression or RNAi-mediated knockdown suggests that the loss of AZ components such as Ca(2+) channels and Liprin-α is caused by impaired kinesin-3 based transport rather than due to the absence of the key AZ organizer protein, Brp. In addition to defects in CAZ assembly, unc-104(bris) mutants display further defects such as depletion of dense core and synaptic vesicle (SV) markers from the NMJ. Notably, the level of Rab3, which is important for the allocation of AZ proteins to individual release sites, was severely reduced at unc-104(bris) mutant NMJs. Overexpression of Rab3 partially ameliorates synaptic phenotypes of unc-104(bris) larvae, suggesting that lack of presynaptic Rab3 contributes to defects in synapse maturation.
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Affiliation(s)
- Yao V Zhang
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of TübingenTübingen, Germany; Graudate School of Cellular and Molecular Neuroscience, University of TübingenTübingen, Germany; The Picower Institute for Learning and Memory, Department of Biology and Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridge, MA, USA
| | - Shabab B Hannan
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of TübingenTübingen, Germany; Graudate School of Cellular and Molecular Neuroscience, University of TübingenTübingen, Germany; Schaller Research Group at the University of Heidelberg and DKFZ, Proteostasis in Neurodegenerative Disease (B180), German Cancer Research CenterHeidelberg, Germany
| | - Zeenna A Stapper
- Schaller Research Group at the University of Heidelberg and DKFZ, Proteostasis in Neurodegenerative Disease (B180), German Cancer Research Center Heidelberg, Germany
| | - Jeannine V Kern
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen Tübingen, Germany
| | - Thomas R Jahn
- Schaller Research Group at the University of Heidelberg and DKFZ, Proteostasis in Neurodegenerative Disease (B180), German Cancer Research Center Heidelberg, Germany
| | - Tobias M Rasse
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of TübingenTübingen, Germany; Schaller Research Group at the University of Heidelberg and DKFZ, Proteostasis in Neurodegenerative Disease (B180), German Cancer Research CenterHeidelberg, Germany
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22
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Jiang X, Nardelli J. Cellular and molecular introduction to brain development. Neurobiol Dis 2016; 92:3-17. [PMID: 26184894 PMCID: PMC4720585 DOI: 10.1016/j.nbd.2015.07.007] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Revised: 07/07/2015] [Accepted: 07/09/2015] [Indexed: 12/13/2022] Open
Abstract
Advances in the study of brain development over the last decades, especially recent findings regarding the evolutionary expansion of the human neocortex, and large-scale analyses of the proteome/transcriptome in the human brain, have offered novel insights into the molecular mechanisms guiding neural maturation, and the pathophysiology of multiple forms of neurological disorders. As a preamble to reviews of this issue, we provide an overview of the cellular, molecular and genetic bases of brain development with an emphasis on the major mechanisms associated with landmarks of normal neural development in the embryonic stage and early postnatal life, including neural stem/progenitor cell proliferation, cortical neuronal migration, evolution and folding of the cerebral cortex, synaptogenesis and neural circuit development, gliogenesis and myelination. We will only briefly depict developmental disorders that result from perturbations of these cellular or molecular mechanisms, and the most common perinatal brain injuries that could disturb normal brain development.
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Affiliation(s)
- Xiangning Jiang
- Department of Pediatrics, University of California, San Francisco, CA 94158, USA
| | - Jeannette Nardelli
- Inserm, U1141, Paris 75019, France; Université Paris Diderot, Sorbonne Paris Cité, UMRS 1141, Paris 75019, France.
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23
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Muhammad K, Reddy-Alla S, Driller JH, Schreiner D, Rey U, Böhme MA, Hollmann C, Ramesh N, Depner H, Lützkendorf J, Matkovic T, Götz T, Bergeron DD, Schmoranzer J, Goettfert F, Holt M, Wahl MC, Hell SW, Scheiffele P, Walter AM, Loll B, Sigrist SJ. Presynaptic spinophilin tunes neurexin signalling to control active zone architecture and function. Nat Commun 2015; 6:8362. [PMID: 26471740 PMCID: PMC4633989 DOI: 10.1038/ncomms9362] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 08/13/2015] [Indexed: 11/17/2022] Open
Abstract
Assembly and maturation of synapses at the Drosophila neuromuscular junction
(NMJ) depend on trans-synaptic neurexin/neuroligin signalling, which is promoted by
the scaffolding protein Syd-1 binding to neurexin. Here we report that the scaffold
protein spinophilin binds to the C-terminal portion of neurexin and is needed to
limit neurexin/neuroligin signalling by acting antagonistic to Syd-1. Loss of
presynaptic spinophilin results in the formation of excess, but atypically small
active zones. Neuroligin-1/neurexin-1/Syd-1 levels are increased at
spinophilin mutant NMJs, and removal of single copies of the
neurexin-1, Syd-1 or neuroligin-1 genes suppresses the
spinophilin-active zone phenotype. Evoked transmission is strongly reduced at
spinophilin terminals, owing to a severely reduced release probability at
individual active zones. We conclude that presynaptic spinophilin fine-tunes
neurexin/neuroligin signalling to control active zone number and functionality,
thereby optimizing them for action potential-induced exocytosis. Synaptic assembly depends on trans-synaptic Neurexin/Neuroligin
signalling. Here, Muhammad et al. show that Spinophilin, a pre-synaptic
scaffolding protein, interacts with Neurexin, in competition with Syd-1, to regulate the
formation and function of synaptic active zones at Drosophila neuromuscular
junctions.
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Affiliation(s)
- Karzan Muhammad
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | - Suneel Reddy-Alla
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | - Jan H Driller
- Freie Universität Berlin, Institut für Chemie und Biochemie /Strukturbiochmie, Takustrasse 6, Berlin D-14195, Germany
| | - Dietmar Schreiner
- Biozentrum, University of Basel, Klingelbergstrasse 50-70, Basel 4056, Switzerland
| | - Ulises Rey
- NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | | | | | - Niraja Ramesh
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany
| | - Harald Depner
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | | | - Tanja Matkovic
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | - Torsten Götz
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
| | | | - Jan Schmoranzer
- Freie Universität Berlin, Institut für Chemie und Biochemie /Strukturbiochmie, Takustrasse 6, Berlin D-14195, Germany.,Leibniz Institut für Molekulare Pharmakologie, Robert-Roessle-Strasse 10, Berlin 13125, Germany
| | - Fabian Goettfert
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
| | - Mathew Holt
- VIB Center for the Biology of Disease, Herestraat 49, Leuven 3000, Belgium
| | - Markus C Wahl
- Freie Universität Berlin, Institut für Chemie und Biochemie /Strukturbiochmie, Takustrasse 6, Berlin D-14195, Germany
| | - Stefan W Hell
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
| | - Peter Scheiffele
- Biozentrum, University of Basel, Klingelbergstrasse 50-70, Basel 4056, Switzerland
| | - Alexander M Walter
- NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany.,Leibniz Institut für Molekulare Pharmakologie, Robert-Roessle-Strasse 10, Berlin 13125, Germany
| | - Bernhard Loll
- Freie Universität Berlin, Institut für Chemie und Biochemie /Strukturbiochmie, Takustrasse 6, Berlin D-14195, Germany
| | - Stephan J Sigrist
- Freie Universität Berlin, Institute for Biology/Genetics, Takustrasse 6, Berlin 14195, Germany.,NeuroCure, Charité, Charitéplatz 1, Berlin 10117, Germany
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24
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Zhou J, Liu Z, Yu J, Han X, Fan S, Shao W, Chen J, Qiao R, Xie P. Quantitative Proteomic Analysis Reveals Molecular Adaptations in the Hippocampal Synaptic Active Zone of Chronic Mild Stress-Unsusceptible Rats. Int J Neuropsychopharmacol 2015; 19:pyv100. [PMID: 26364272 PMCID: PMC4772275 DOI: 10.1093/ijnp/pyv100] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 08/31/2015] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND While stressful events are recognized as an important cause of major depressive disorder, some individuals exposed to life stressors maintain normal psychological functioning. The molecular mechanism(s) underlying this phenomenon remain unclear. Abnormal transmission and plasticity of hippocampal synapses have been implied to play a key role in the pathoetiology of major depressive disorder. METHODS A chronic mild stress protocol was applied to separate susceptible and unsusceptible rat subpopulations. Proteomic analysis using an isobaric tag for relative and absolute quantitation coupled with tandem mass spectrometry was performed to identify differential proteins in enriched hippocampal synaptic junction preparations. RESULTS A total of 4318 proteins were quantified, and 89 membrane proteins were present in differential amounts. Of these, SynaptomeDB identified 81 (91%) having a synapse-specific localization. The unbiased profiles identified several candidate proteins within the synaptic junction that may be associated with stress vulnerability or insusceptibility. Subsequent functional categorization revealed that protein systems particularly involved in membrane trafficking at the synaptic active zone exhibited a positive strain as potential molecular adaptations in the unsusceptible rats. Moreover, through STRING and immunoblotting analysis, membrane-associated GTP-bound Rab3a and Munc18-1 appear to coregulate syntaxin-1/SNAP25/VAMP2 assembly at the hippocampal presynaptic active zone of unsusceptible rats, facilitating SNARE-mediated membrane fusion and neurotransmitter release, and may be part of a stress-protection mechanism in actively maintaining an emotional homeostasis. CONCLUSIONS The present results support the concept that there is a range of potential protein adaptations in the hippocampal synaptic active zone of unsusceptible rats, revealing new investigative targets that may contribute to a better understanding of stress insusceptibility.
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Affiliation(s)
- Jian Zhou
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Chongqing Key Laboratory of Neurobiology, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China (Drs Liu, Han, Fan, Shao, and Xie)
| | - Zhao Liu
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Chongqing Key Laboratory of Neurobiology, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China (Drs Liu, Han, Fan, Shao, and Xie)
| | - Jia Yu
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Chongqing Key Laboratory of Neurobiology, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China (Drs Liu, Han, Fan, Shao, and Xie)
| | - Xin Han
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Chongqing Key Laboratory of Neurobiology, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China (Drs Liu, Han, Fan, Shao, and Xie)
| | - Songhua Fan
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Chongqing Key Laboratory of Neurobiology, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China (Drs Liu, Han, Fan, Shao, and Xie)
| | - Weihua Shao
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Chongqing Key Laboratory of Neurobiology, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China (Drs Liu, Han, Fan, Shao, and Xie)
| | - Jianjun Chen
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Chongqing Key Laboratory of Neurobiology, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China (Drs Liu, Han, Fan, Shao, and Xie)
| | - Rui Qiao
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Chongqing Key Laboratory of Neurobiology, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China (Drs Liu, Han, Fan, Shao, and Xie)
| | - Peng Xie
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Chongqing Key Laboratory of Neurobiology, Chongqing, China (Drs Zhou, Liu, Yu, Han, Fan, Shao, Chen, Qiao, and Xie); Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China (Drs Liu, Han, Fan, Shao, and Xie).
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25
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Ackermann F, Waites CL, Garner CC. Presynaptic active zones in invertebrates and vertebrates. EMBO Rep 2015; 16:923-38. [PMID: 26160654 DOI: 10.15252/embr.201540434] [Citation(s) in RCA: 92] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 06/19/2015] [Indexed: 11/09/2022] Open
Abstract
The regulated release of neurotransmitter occurs via the fusion of synaptic vesicles (SVs) at specialized regions of the presynaptic membrane called active zones (AZs). These regions are defined by a cytoskeletal matrix assembled at AZs (CAZ), which functions to direct SVs toward docking and fusion sites and supports their maturation into the readily releasable pool. In addition, CAZ proteins localize voltage-gated Ca(2+) channels at SV release sites, bringing the fusion machinery in close proximity to the calcium source. Proteins of the CAZ therefore ensure that vesicle fusion is temporally and spatially organized, allowing for the precise and reliable release of neurotransmitter. Importantly, AZs are highly dynamic structures, supporting presynaptic remodeling, changes in neurotransmitter release efficacy, and thus presynaptic forms of plasticity. In this review, we discuss recent advances in the study of active zones, highlighting how the CAZ molecularly defines sites of neurotransmitter release, endocytic zones, and the integrity of synapses.
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Affiliation(s)
- Frauke Ackermann
- German Center for Neurodegenerative Disease, Charité Medical University, Berlin, Germany
| | - Clarissa L Waites
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Craig C Garner
- German Center for Neurodegenerative Disease, Charité Medical University, Berlin, Germany
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26
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Sugie A, Hakeda-Suzuki S, Suzuki E, Silies M, Shimozono M, Möhl C, Suzuki T, Tavosanis G. Molecular Remodeling of the Presynaptic Active Zone of Drosophila Photoreceptors via Activity-Dependent Feedback. Neuron 2015; 86:711-25. [PMID: 25892303 DOI: 10.1016/j.neuron.2015.03.046] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 02/10/2015] [Accepted: 03/18/2015] [Indexed: 11/27/2022]
Abstract
Neural activity contributes to the regulation of the properties of synapses in sensory systems, allowing for adjustment to a changing environment. Little is known about how synaptic molecular components are regulated to achieve activity-dependent plasticity at central synapses. Here, we found that after prolonged exposure to natural ambient light the presynaptic active zone in Drosophila photoreceptors undergoes reversible remodeling, including loss of Bruchpilot, DLiprin-α, and DRBP, but not of DSyd-1 or Cacophony. The level of depolarization of the postsynaptic neurons is critical for the light-induced changes in active zone composition in the photoreceptors, indicating the existence of a feedback signal. In search of this signal, we have identified a crucial role of microtubule meshwork organization downstream of the divergent canonical Wnt pathway, potentially via Kinesin-3 Imac. These data reveal that active zone composition can be regulated in vivo and identify the underlying molecular machinery.
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Affiliation(s)
- Atsushi Sugie
- Dendrite Differentiation, German Center for Neurodegenerative Diseases (DZNE), Bonn 53175, Germany
| | - Satoko Hakeda-Suzuki
- Core Division of Advanced Research, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology (Titech), Yokohama 226-8501, Japan
| | - Emiko Suzuki
- Gene Network Laboratory, National Institute of Genetics and Department of Genetics, SOKENDAI, Mishima 411-8540, Japan
| | - Marion Silies
- European Neuroscience Institute (ENI), 37077 Göttingen, Germany
| | - Mai Shimozono
- Core Division of Advanced Research, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology (Titech), Yokohama 226-8501, Japan
| | - Christoph Möhl
- Image and Data Analysis Facility, German Center for Neurodegenerative Diseases (DZNE), Bonn 53175, Germany
| | - Takashi Suzuki
- Core Division of Advanced Research, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology (Titech), Yokohama 226-8501, Japan.
| | - Gaia Tavosanis
- Dendrite Differentiation, German Center for Neurodegenerative Diseases (DZNE), Bonn 53175, Germany.
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27
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Cherra SJ, Jin Y. Advances in synapse formation: forging connections in the worm. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2015; 4:85-97. [PMID: 25472860 PMCID: PMC4339659 DOI: 10.1002/wdev.165] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Revised: 10/09/2014] [Accepted: 10/24/2014] [Indexed: 12/27/2022]
Abstract
UNLABELLED Synapse formation is the quintessential process by which neurons form specific connections with their targets to enable the development of functional circuits. Over the past few decades, intense research efforts have identified thousands of proteins that localize to the pre- and postsynaptic compartments. Genetic dissection has provided important insights into the nexus of the molecular and cellular network, and has greatly advanced our knowledge about how synapses form and function physiologically. Moreover, recent studies have highlighted the complex regulation of synapse formation with the identification of novel mechanisms involving cell interactions from non-neuronal sources. In this review, we cover the conserved pathways required for synaptogenesis and place specific focus on new themes of synapse modulation arising from studies in Caenorhabditis elegans. For further resources related to this article, please visit the WIREs website. CONFLICT OF INTEREST The authors have declared no conflicts of interest for this article.
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Affiliation(s)
- Salvatore J. Cherra
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego
| | - Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego
- Howard Hughes Medical Institute
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28
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Ehmann N, Sauer M, Kittel RJ. Super-resolution microscopy of the synaptic active zone. Front Cell Neurosci 2015; 9:7. [PMID: 25688186 PMCID: PMC4311638 DOI: 10.3389/fncel.2015.00007] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 01/07/2015] [Indexed: 12/31/2022] Open
Abstract
Brain function relies on accurate information transfer at chemical synapses. At the presynaptic active zone (AZ) a variety of specialized proteins are assembled to complex architectures, which set the basis for speed, precision and plasticity of synaptic transmission. Calcium channels are pivotal for the initiation of excitation-secretion coupling and, correspondingly, capture a central position at the AZ. Combining quantitative functional studies with modeling approaches has provided predictions of channel properties, numbers and even positions on the nanometer scale. However, elucidating the nanoscopic organization of the surrounding protein network requires direct ultrastructural access. Without this information, knowledge of molecular synaptic structure-function relationships remains incomplete. Recently, super-resolution microscopy (SRM) techniques have begun to enter the neurosciences. These approaches combine high spatial resolution with the molecular specificity of fluorescence microscopy. Here, we discuss how SRM can be used to obtain information on the organization of AZ proteins.
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Affiliation(s)
- Nadine Ehmann
- Department of Neurophysiology, Institute of Physiology, University of Würzburg Würzburg, Germany
| | - Markus Sauer
- Department of Biotechnology and Biophysics, University of Würzburg Würzburg, Germany
| | - Robert J Kittel
- Department of Neurophysiology, Institute of Physiology, University of Würzburg Würzburg, Germany
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29
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Urwyler O, Izadifar A, Dascenco D, Petrovic M, He H, Ayaz D, Kremer A, Lippens S, Baatsen P, Guérin CJ, Schmucker D. Investigating CNS synaptogenesis at single-synapse resolution by combining reverse genetics with correlative light and electron microscopy. Development 2014; 142:394-405. [PMID: 25503410 DOI: 10.1242/dev.115071] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Determining direct synaptic connections of specific neurons in the central nervous system (CNS) is a major technical challenge in neuroscience. As a corollary, molecular pathways controlling developmental synaptogenesis in vivo remain difficult to address. Here, we present genetic tools for efficient and versatile labeling of organelles, cytoskeletal components and proteins at single-neuron and single-synapse resolution in Drosophila mechanosensory (ms) neurons. We extended the imaging analysis to the ultrastructural level by developing a protocol for correlative light and 3D electron microscopy (3D CLEM). We show that in ms neurons, synaptic puncta revealed by genetically encoded markers serve as a reliable indicator of individual active zones. Block-face scanning electron microscopy analysis of ms axons revealed T-bar-shaped dense bodies and other characteristic ultrastructural features of CNS synapses. For a mechanistic analysis, we directly combined the single-neuron labeling approach with cell-specific gene disruption techniques. In proof-of-principle experiments we found evidence for a highly similar requirement for the scaffolding molecule Liprin-α and its interactors Lar and DSyd-1 (RhoGAP100F) in synaptic vesicle recruitment. This suggests that these important synapse regulators might serve a shared role at presynaptic sites within the CNS. In principle, our CLEM approach is broadly applicable to the developmental and ultrastructural analysis of any cell type that can be targeted with genetically encoded markers.
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Affiliation(s)
- Olivier Urwyler
- Neuronal Wiring Laboratory, Vesalius Research Center, VIB, Herestraat 49 box 912, Leuven 3000, Belgium Neuronal Wiring Laboratory, Vesalius Research Center, Department of Oncology, KU Leuven, Herestraat 49 box 912, Leuven 3000, Belgium
| | - Azadeh Izadifar
- Neuronal Wiring Laboratory, Vesalius Research Center, VIB, Herestraat 49 box 912, Leuven 3000, Belgium Neuronal Wiring Laboratory, Vesalius Research Center, Department of Oncology, KU Leuven, Herestraat 49 box 912, Leuven 3000, Belgium
| | - Dan Dascenco
- Neuronal Wiring Laboratory, Vesalius Research Center, VIB, Herestraat 49 box 912, Leuven 3000, Belgium Neuronal Wiring Laboratory, Vesalius Research Center, Department of Oncology, KU Leuven, Herestraat 49 box 912, Leuven 3000, Belgium
| | - Milan Petrovic
- Neuronal Wiring Laboratory, Vesalius Research Center, VIB, Herestraat 49 box 912, Leuven 3000, Belgium Neuronal Wiring Laboratory, Vesalius Research Center, Department of Oncology, KU Leuven, Herestraat 49 box 912, Leuven 3000, Belgium
| | - Haihuai He
- Neuronal Wiring Laboratory, Vesalius Research Center, VIB, Herestraat 49 box 912, Leuven 3000, Belgium Neuronal Wiring Laboratory, Vesalius Research Center, Department of Oncology, KU Leuven, Herestraat 49 box 912, Leuven 3000, Belgium
| | - Derya Ayaz
- Neuronal Wiring Laboratory, Vesalius Research Center, VIB, Herestraat 49 box 912, Leuven 3000, Belgium Neuronal Wiring Laboratory, Vesalius Research Center, Department of Oncology, KU Leuven, Herestraat 49 box 912, Leuven 3000, Belgium
| | - Anna Kremer
- VIB, Bio Imaging Core Gent, Technologiepark 927, Zwijnaarde 9052, Belgium Department of Biomedical Molecular Biology, University of Gent, Technologiepark 927, Zwijnaarde 9052, Belgium
| | - Saskia Lippens
- VIB, Bio Imaging Core Gent, Technologiepark 927, Zwijnaarde 9052, Belgium Department of Biomedical Molecular Biology, University of Gent, Technologiepark 927, Zwijnaarde 9052, Belgium
| | - Pieter Baatsen
- VIB, Center for the Biology of Disease, Herestraat 49 box 602, Leuven 3000, Belgium
| | - Christopher J Guérin
- VIB, Bio Imaging Core Gent, Technologiepark 927, Zwijnaarde 9052, Belgium Department of Biomedical Molecular Biology, University of Gent, Technologiepark 927, Zwijnaarde 9052, Belgium VIB, Inflammation Research Center Microscopy and Cytometry Core, Technologiepark 927, Zwijnaarde 9052, Belgium
| | - Dietmar Schmucker
- Neuronal Wiring Laboratory, Vesalius Research Center, VIB, Herestraat 49 box 912, Leuven 3000, Belgium Neuronal Wiring Laboratory, Vesalius Research Center, Department of Oncology, KU Leuven, Herestraat 49 box 912, Leuven 3000, Belgium
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30
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Bell ME, Bourne JN, Chirillo MA, Mendenhall JM, Kuwajima M, Harris KM. Dynamics of nascent and active zone ultrastructure as synapses enlarge during long-term potentiation in mature hippocampus. J Comp Neurol 2014; 522:3861-84. [PMID: 25043676 PMCID: PMC4167938 DOI: 10.1002/cne.23646] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Revised: 06/23/2014] [Accepted: 06/30/2014] [Indexed: 11/08/2022]
Abstract
Nascent zones and active zones are adjacent synaptic regions that share a postsynaptic density, but nascent zones lack the presynaptic vesicles found at active zones. Here dendritic spine synapses were reconstructed through serial section electron microscopy (3DEM) and EM tomography to investigate nascent zone dynamics during long-term potentiation (LTP) in mature rat hippocampus. LTP was induced with theta-burst stimulation, and comparisons were made with control stimulation in the same hippocampal slices at 5 minutes, 30 minutes, and 2 hours post-induction and to perfusion-fixed hippocampus in vivo. Nascent zones were present at the edges of ∼35% of synapses in perfusion-fixed hippocampus and as many as ∼50% of synapses in some hippocampal slice conditions. By 5 minutes, small dense-core vesicles known to transport active zone proteins moved into more presynaptic boutons. By 30 minutes, nascent zone area decreased, without significant change in synapse area, suggesting that presynaptic vesicles were recruited to preexisting nascent zones. By 2 hours, both nascent and active zones were enlarged. Immunogold labeling revealed glutamate receptors in nascent zones; however, average distances from nascent zones to docked presynaptic vesicles ranged from 170 ± 5 nm in perfusion-fixed hippocampus to 251 ± 4 nm at enlarged synapses by 2 hours during LTP. Prior stochastic modeling suggests that decrease in glutamate concentration reduces the probability of glutamate receptor activation from 0.4 at the center of release to 0.1 just 200 nm away. Thus, conversion of nascent zones to functional active zones likely requires the recruitment of presynaptic vesicles during LTP.
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Affiliation(s)
- Maria Elizabeth Bell
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
| | - Jennifer N. Bourne
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
| | - Michael A. Chirillo
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
- The University of Texas Medical School, Houston, TX 77030
| | - John M. Mendenhall
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
| | - Masaaki Kuwajima
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
| | - Kristen M. Harris
- Center for Learning and Memory, Department of Neuroscience, Institute for Neuroscience, University of Texas, Austin, TX 78712
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31
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Drosophila Syd-1, liprin-α, and protein phosphatase 2A B' subunit Wrd function in a linear pathway to prevent ectopic accumulation of synaptic materials in distal axons. J Neurosci 2014; 34:8474-87. [PMID: 24948803 DOI: 10.1523/jneurosci.0409-14.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
During synaptic development, presynaptic differentiation occurs as an intrinsic property of axons to form specialized areas of plasma membrane [active zones (AZs)] that regulate exocytosis and endocytosis of synaptic vesicles. Genetic and biochemical studies in vertebrate and invertebrate model systems have identified a number of proteins involved in AZ assembly. However, elucidating the molecular events of AZ assembly in a spatiotemporal manner remains a challenge. Syd-1 (synapse defective-1) and Liprin-α have been identified as two master organizers of AZ assembly. Genetic and imaging analyses in invertebrates show that Syd-1 works upstream of Liprin-α in synaptic assembly through undefined mechanisms. To understand molecular pathways downstream of Liprin-α, we performed a proteomic screen of Liprin-α-interacting proteins in Drosophila brains. We identify Drosophila protein phosphatase 2A (PP2A) regulatory subunit B' [Wrd (Well Rounded)] as a Liprin-α-interacting protein, and we demonstrate that it mediates the interaction of Liprin-α with PP2A holoenzyme and the Liprin-α-dependent synaptic localization of PP2A. Interestingly, loss of function in syd-1, liprin-α, or wrd shares a common defect in which a portion of synaptic vesicles, dense-core vesicles, and presynaptic cytomatrix proteins ectopically accumulate at the distal, but not proximal, region of motoneuron axons. Strong genetic data show that a linear syd-1/liprin-α/wrd pathway in the motoneuron antagonizes glycogen synthase kinase-3β kinase activity to prevent the ectopic accumulation of synaptic materials. Furthermore, we provide data suggesting that the syd-1/liprin-α/wrd pathway stabilizes AZ specification at the nerve terminal and that such a novel function is independent of the roles of syd-1/liprin-α in regulating the morphology of the T-bar structural protein BRP (Bruchpilot).
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32
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Meriney SD, Umbach JA, Gundersen CB. Fast, Ca2+-dependent exocytosis at nerve terminals: shortcomings of SNARE-based models. Prog Neurobiol 2014; 121:55-90. [PMID: 25042638 DOI: 10.1016/j.pneurobio.2014.07.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 04/14/2014] [Accepted: 07/03/2014] [Indexed: 11/30/2022]
Abstract
Investigations over the last two decades have made major inroads in clarifying the cellular and molecular events that underlie the fast, synchronous release of neurotransmitter at nerve endings. Thus, appreciable progress has been made in establishing the structural features and biophysical properties of the calcium (Ca2+) channels that mediate the entry into nerve endings of the Ca2+ ions that trigger neurotransmitter release. It is now clear that presynaptic Ca2+ channels are regulated at many levels and the interplay of these regulatory mechanisms is just beginning to be understood. At the same time, many lines of research have converged on the conclusion that members of the synaptotagmin family serve as the primary Ca2+ sensors for the action potential-dependent release of neurotransmitter. This identification of synaptotagmins as the proteins which bind Ca2+ and initiate the exocytotic fusion of synaptic vesicles with the plasma membrane has spurred widespread efforts to reveal molecular details of synaptotagmin's action. Currently, most models propose that synaptotagmin interfaces directly or indirectly with SNARE (soluble, N-ethylmaleimide sensitive factor attachment receptors) proteins to trigger membrane fusion. However, in spite of intensive efforts, the field has not achieved consensus on the mechanism by which synaptotagmins act. Concurrently, the precise sequence of steps underlying SNARE-dependent membrane fusion remains controversial. This review considers the pros and cons of the different models of SNARE-mediated membrane fusion and concludes by discussing a novel proposal in which synaptotagmins might directly elicit membrane fusion without the intervention of SNARE proteins in this final fusion step.
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Affiliation(s)
- Stephen D Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Joy A Umbach
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095, USA
| | - Cameron B Gundersen
- Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, CA 90095, USA.
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Ahmed WW, Saif TA. Active transport of vesicles in neurons is modulated by mechanical tension. Sci Rep 2014; 4:4481. [PMID: 24670781 PMCID: PMC3967286 DOI: 10.1038/srep04481] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 02/24/2014] [Indexed: 11/19/2022] Open
Abstract
Effective intracellular transport of proteins and organelles is critical in cells, and is especially important for ensuring proper neuron functionality. In neurons, most proteins are synthesized in the cell body and must be transported through thin structures over long distances where normal diffusion is insufficient. Neurons transport subcellular cargo along axons and neurites through a stochastic interplay of active and passive transport. Mechanical tension is critical in maintaining proper function in neurons, but its role in transport is not well understood. To this end, we investigate the active and passive transport of vesicles in Aplysia neurons while changing neurite tension via applied strain, and quantify the resulting dynamics. We found that tension in neurons modulates active transport of vesicles by increasing the probability of active motion, effective diffusivity, and induces a retrograde bias. We show that mechanical tension modulates active transport processes in neurons and that external forces can couple to internal (subcellular) forces and change the overall transport dynamics.
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Affiliation(s)
- Wylie W Ahmed
- 1] Department of Mechanical Science and Engineering, University of Illinois, Urbana, IL 61801 [2]
| | - Taher A Saif
- Department of Mechanical Science and Engineering, University of Illinois, Urbana, IL 61801
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Chen Y, Akin O, Nern A, Tsui CYK, Pecot MY, Zipursky SL. Cell-type-specific labeling of synapses in vivo through synaptic tagging with recombination. Neuron 2014; 81:280-93. [PMID: 24462095 PMCID: PMC4025979 DOI: 10.1016/j.neuron.2013.12.021] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/27/2013] [Indexed: 11/19/2022]
Abstract
The study of synaptic specificity and plasticity in the CNS is limited by the inability to efficiently visualize synapses in identified neurons using light microscopy. Here, we describe synaptic tagging with recombination (STaR), a method for labeling endogenous presynaptic and postsynaptic proteins in a cell-type-specific fashion. We modified genomic loci encoding synaptic proteins within bacterial artificial chromosomes such that these proteins, expressed at endogenous levels and with normal spatiotemporal patterns, were labeled in an inducible fashion in specific neurons through targeted expression of site-specific recombinases. Within the Drosophila visual system, the number and distribution of synapses correlate with electron microscopy studies. Using two different recombination systems, presynaptic and postsynaptic specializations of synaptic pairs can be colabeled. STaR also allows synapses within the CNS to be studied in live animals noninvasively. In principle, STaR can be adapted to the mammalian nervous system.
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Affiliation(s)
- Yi Chen
- Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Orkun Akin
- Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Aljoscha Nern
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147-2408, USA
| | - C Y Kimberly Tsui
- Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Matthew Y Pecot
- Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - S Lawrence Zipursky
- Department of Biological Chemistry, Howard Hughes Medical Institute, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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Lohmann C, Kessels HW. The developmental stages of synaptic plasticity. J Physiol 2014; 592:13-31. [PMID: 24144877 PMCID: PMC3903349 DOI: 10.1113/jphysiol.2012.235119] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 10/16/2013] [Indexed: 01/17/2023] Open
Abstract
The brain is programmed to drive behaviour by precisely wiring the appropriate neuronal circuits. Wiring and rewiring of neuronal circuits largely depends on the orchestrated changes in the strengths of synaptic contacts. Here, we review how the rules of synaptic plasticity change during development of the brain, from birth to independence. We focus on the changes that occur at the postsynaptic side of excitatory glutamatergic synapses in the rodent hippocampus and neocortex. First we summarize the current data on the structure of synapses and the developmental expression patterns of the key molecular players of synaptic plasticity, N-methyl-d-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, as well as pivotal kinases (Ca(2+)/calmodulin-dependent protein kinase II, protein kinase A, protein kinase C) and phosphatases (PP1, PP2A, PP2B). In the second part we relate these findings to important characteristics of the emerging network. We argue that the concerted and gradual shifts in the usage of plasticity molecules comply with the changing need for (re)wiring neuronal circuits.
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Affiliation(s)
- Christian Lohmann
- C. Lohmann and H. W. Kessels: The Netherlands Institute for Neuroscience, the Royal Academy of Arts and Sciences, Meibergdreef 47, 1105 BA, Amsterdam, the Netherlands. Emails: ,
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Frias CP, Wierenga CJ. Activity-dependent adaptations in inhibitory axons. Front Cell Neurosci 2013; 7:219. [PMID: 24312009 PMCID: PMC3836028 DOI: 10.3389/fncel.2013.00219] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 10/30/2013] [Indexed: 11/13/2022] Open
Abstract
Synaptic connections in our brains change continuously and throughout our lifetime. Despite ongoing synaptic changes, a healthy balance between excitation and inhibition is maintained by various forms of homeostatic and activity-dependent adaptations, ensuring stable functioning of neuronal networks. In this review we summarize experimental evidence for activity-dependent changes occurring in inhibitory axons, in cultures as well as in vivo. Axons form many presynaptic terminals, which are dynamic structures sharing presynaptic material along the axonal shaft. We discuss how internal (e.g., vesicle sharing) and external factors (e.g., binding of cell adhesion molecules or secreted factors) may affect the formation and plasticity of inhibitory synapses.
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Affiliation(s)
| | - Corette J. Wierenga
- Division of Cell Biology, Faculty of Science, Utrecht UniversityUtrecht, Netherlands
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Juranek JK, Mukherjee K, Siddiqui TJ, Kaplan BJ, Li JY, Ahnert-Hilger G, Jahn R, Calka J. Active zone protein expression changes at the key stages of cerebellar cortex neurogenesis in the rat. Acta Histochem 2013; 115:616-25. [PMID: 23434052 DOI: 10.1016/j.acthis.2013.01.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 01/15/2013] [Accepted: 01/16/2013] [Indexed: 12/11/2022]
Abstract
Signal transduction and neurotransmitter release in the vertebrate central nervous system are confined to the structurally complex presynaptic electron dense projections called "active zones." Although the nature of these projections remains a mystery, genetic and biochemical work has provided evidence for the active zone (AZ) associated proteins i.e. Piccolo/Aczonin, Bassoon, RIM1/Unc10, Munc13/Unc13, Liprin-α/SYD2/Dliprin and ELKS/CAST/BRP and their specific molecular functions. It still remains unclear, however, what their precise contribution is to the AZ assembly. In our project, we studied in Wistar rats the temporal and spatial distribution of AZ proteins and their colocalization with Synaptophysin in the developing cerebellar cortex at key stages of cerebellum neurogenesis. Our study demonstrated that AZ proteins were already present at the very early stages of cerebellar neurogenesis and exhibited distinct spatial and temporal variations in immunoexpression throughout the course of the study. Colocalization analysis revealed that the colocalization pattern was time-dependent and different for each studied protein. The highest collective mean percentage of colocalization (>85%) was observed at postnatal day (PD) 5, followed by PD10 (>83%) and PD15 (>80%). The findings of our study shed light on AZ protein immunoexpression changes during cerebellar cortex neurogenesis and help frame a hypothetical model of AZ assembly.
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Synaptic changes in the dentate gyrus of APP/PS1 transgenic mice revealed by electron microscopy. J Neuropathol Exp Neurol 2013; 72:386-95. [PMID: 23584198 PMCID: PMC3678882 DOI: 10.1097/nen.0b013e31828d41ec] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Supplemental digital content is available in the text. Numerous studies have reported widespread synaptic dysfunction or loss in early stages of both Alzheimer disease (AD) patients and animal models; it is widely accepted that synapse loss is the major structural correlate of cognitive dysfunction. Elucidation of the changes that may affect synapses is crucial for understanding the pathogenic mechanisms underlying AD, but ultrastructural preservation of human postmortem brain tissue is often poor, and classical methods for quantification of synapses have significant technical limitations. We previously observed changes in dendritic spines in plaque-free regions of the neuropil of the dentate gyrus of double-transgenic APP/PS1 (amyloid precursor protein/presenilin 1) model mice by light microscopy. Here, we used electron microscopy to examine possible synaptic alterations in this region. We used standard stereologic techniques to determine numbers of synapses per volume. We were able to reconstruct and analyze thousands of synapses and their 3-dimensional characteristics using a focused ion beam/scanning electron microscope and 3-dimensional reconstruction software (EspINA), which performs semiautomated segmentation of synapses. Our results show that both numbers of synapses per volume and synaptic morphology are affected in plaque-free regions of APP/PS1 mice. Therefore, changes in the number and morphology of synapses seem to be widespread alterations in this animal model.
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Wu YE, Huo L, Maeder CI, Feng W, Shen K. The balance between capture and dissociation of presynaptic proteins controls the spatial distribution of synapses. Neuron 2013; 78:994-1011. [PMID: 23727120 DOI: 10.1016/j.neuron.2013.04.035] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/23/2013] [Indexed: 11/19/2022]
Abstract
The location, size, and number of synapses critically influence the specificity and strength of neural connections. In axons, synaptic vesicle (SV) and active zone (AZ) proteins are transported by molecular motors and accumulate at discrete presynaptic loci. Little is known about the mechanisms coordinating presynaptic protein transport and deposition to achieve proper distribution of synaptic material. Here we show that SV and AZ proteins exhibit extensive cotransport and undergo frequent pauses. At the axonal and synaptic pause sites, the balance between the capture and dissociation of mobile transport packets determines the extent of presynaptic assembly. The small G protein ARL-8 inhibits assembly by promoting dissociation, while a JNK kinase pathway and AZ assembly proteins inhibit dissociation. Furthermore, ARL-8 directly binds to the UNC-104/KIF1A motor to limit the capture efficiency. Together, molecular regulation of the dichotomy between axonal trafficking and local assembly controls vital aspects of synapse formation and maintenance.
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Affiliation(s)
- Ye E Wu
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
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40
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Long JB, Van Vactor D. Embryonic and larval neural connectivity: progressive changes in synapse form and function at the neuromuscular junction mediated by cytoskeletal regulation. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2013; 2:747-65. [PMID: 24123935 DOI: 10.1002/wdev.114] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
During development, precise formation of millions of synaptic connections is critical for the formation of a functional nervous system. Synaptogenesis is a complex multistep process in which axons follow gradients of secreted and cell surface guidance cues to reach their target area, at which point they must accurately distinguish their specific target. Upon target recognition, the axonal growth cone undergoes rapid growth and morphological changes, ultimately forming a functional synapse that continues to remodel during activity-dependent plasticity. Significant evidence suggests that the underlying actin and microtubule (MT) cytoskeletons are key effectors throughout synaptogenesis downstream of numerous receptors and signaling pathways. An increasing number of cytoskeletal-associated proteins have been shown to influence actin and MT stability and dynamics and many of these regulators have been implicated during synaptic morphogenesis using both mammalian and invertebrate model systems. In this review, we present an overview of the role cytoskeletal regulators play during the formation of the Drosophila neuromuscular junction.
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Affiliation(s)
- Jennifer B Long
- Department of Cell Biology and Program in Neuroscience, Harvard Medical School, Boston, MA, USA
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41
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Fife, a Drosophila Piccolo-RIM homolog, promotes active zone organization and neurotransmitter release. J Neurosci 2013. [PMID: 23197698 DOI: 10.1523/jneurosci.3267-12.2012] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neuronal communication depends on the precisely orchestrated release of neurotransmitter at specialized sites called active zones (AZs). A small number of scaffolding and cytoskeletal proteins comprising the cytomatrix of the active zone (CAZ) are thought to organize the architecture and functional properties of AZs. The majority of CAZ proteins are evolutionarily conserved, underscoring the fundamental similarities in neurotransmission at all synapses. However, core CAZ proteins Piccolo and Bassoon have long been believed exclusive to vertebrates, raising intriguing questions about the conservation of the molecular mechanisms that regulate presynaptic properties. Here, we present the identification of a piccolo-rim-related gene in invertebrates, together with molecular phylogenetic analyses that indicate the encoded proteins may represent Piccolo orthologs. In accordance, we find that the Drosophila homolog, Fife, is neuronal and localizes to presynaptic AZs. To investigate the in vivo function of Fife, we generated a deletion of the fife locus. We find that evoked neurotransmitter release is substantially decreased in fife mutants and loss of fife results in motor deficits. Through morphological analysis of fife synapses, we identify underlying AZ abnormalities including pervasive presynaptic membrane detachments and reduced synaptic vesicle clustering. Our data demonstrate the conservation of a Piccolo-related protein in invertebrates and identify critical roles for Fife in regulating AZ structure and function. These findings suggest the CAZ is more conserved than previously thought, and open the door to a more complete understanding of how CAZ proteins regulate presynaptic structure and function through genetic studies in simpler model systems.
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42
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Kasai H, Takahashi N, Tokumaru H. Distinct Initial SNARE Configurations Underlying the Diversity of Exocytosis. Physiol Rev 2012; 92:1915-64. [DOI: 10.1152/physrev.00007.2012] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The dynamics of exocytosis are diverse and have been optimized for the functions of synapses and a wide variety of cell types. For example, the kinetics of exocytosis varies by more than five orders of magnitude between ultrafast exocytosis in synaptic vesicles and slow exocytosis in large dense-core vesicles. However, in all cases, exocytosis is mediated by the same fundamental mechanism, i.e., the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. It is often assumed that vesicles need to be docked at the plasma membrane and SNARE proteins must be preassembled before exocytosis is triggered. However, this model cannot account for the dynamics of exocytosis recently reported in synapses and other cells. For example, vesicles undergo exocytosis without prestimulus docking during tonic exocytosis of synaptic vesicles in the active zone. In addition, epithelial and hematopoietic cells utilize cAMP and kinases to trigger slow exocytosis of nondocked vesicles. In this review, we summarize the manner in which the diversity of exocytosis reflects the initial configurations of SNARE assembly, including trans-SNARE, binary-SNARE, unitary-SNARE, and cis-SNARE configurations. The initial SNARE configurations depend on the particular SNARE subtype (syntaxin, SNAP25, or VAMP), priming proteins (Munc18, Munc13, CAPS, complexin, or snapin), triggering proteins (synaptotagmins, Doc2, and various protein kinases), and the submembraneous cytomatrix, and they are the key to determining the kinetics of subsequent exocytosis. These distinct initial configurations will help us clarify the common SNARE assembly processes underlying exocytosis and membrane trafficking in eukaryotic cells.
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Affiliation(s)
- Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Noriko Takahashi
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Hiroshi Tokumaru
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
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43
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Cooperation of Syd-1 with Neurexin synchronizes pre- with postsynaptic assembly. Nat Neurosci 2012; 15:1219-26. [PMID: 22864612 DOI: 10.1038/nn.3183] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 07/02/2012] [Indexed: 12/19/2022]
Abstract
Synapse formation and maturation requires bidirectional communication across the synaptic cleft. The trans-synaptic Neurexin-Neuroligin complex can bridge this cleft, and severe synapse assembly deficits are found in Drosophila melanogaster neuroligin (Nlg1, dnlg1) and neurexin (Nrx-1, dnrx) mutants. We show that the presynaptic active zone protein Syd-1 interacts with Nrx-1 to control synapse formation at the Drosophila neuromuscular junction. Mutants in Syd-1 (RhoGAP100F, dsyd-1), Nrx-1 and Nlg1 shared active zone cytomatrix defects, which were nonadditive. Syd-1 and Nrx-1 formed a complex in vivo, and Syd-1 was important for synaptic clustering and immobilization of Nrx-1. Consequently, postsynaptic clustering of Nlg1 was affected in Syd-1 mutants, and in vivo glutamate receptor incorporation was changed in Syd-1, Nrx-1 and Nlg1 mutants. Stabilization of nascent Syd-1-Liprin-α (DLiprin-α) clusters, important to initialize active zone formation, was Nlg1 dependent. Thus, cooperation between Syd-1 and Nrx-1-Nlg1 seems to orchestrate early assembly processes between pre- and postsynaptic membranes, promoting avidity of newly forming synaptic scaffolds.
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44
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Structure–function relationships in human d-amino acid oxidase. Amino Acids 2012; 43:1833-50. [DOI: 10.1007/s00726-012-1345-4] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 06/16/2012] [Indexed: 01/01/2023]
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45
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Koper A, Schenck A, Prokop A. Analysis of adhesion molecules and basement membrane contributions to synaptic adhesion at the Drosophila embryonic NMJ. PLoS One 2012; 7:e36339. [PMID: 22558441 PMCID: PMC3340374 DOI: 10.1371/journal.pone.0036339] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Accepted: 03/30/2012] [Indexed: 12/12/2022] Open
Abstract
Synapse formation and maintenance crucially underlie brain function in health and disease. Both processes are believed to depend on cell adhesion molecules (CAMs). Many different classes of CAMs localise to synapses, including cadherins, protocadherins, neuroligins, neurexins, integrins, and immunoglobulin adhesion proteins, and further contributions come from the extracellular matrix and its receptors. Most of these factors have been scrutinised by loss-of-function analyses in animal models. However, which adhesion factors establish the essential physical links across synaptic clefts and allow the assembly of synaptic machineries at the contact site in vivo is still unclear. To investigate these key questions, we have used the neuromuscular junction (NMJ) of Drosophila embryos as a genetically amenable model synapse. Our ultrastructural analyses of NMJs lacking different classes of CAMs revealed that loss of all neurexins, all classical cadherins or all glutamate receptors, as well as combinations between these or with a Laminin deficiency, failed to reveal structural phenotypes. These results are compatible with a view that these CAMs might have no structural role at this model synapse. However, we consider it far more likely that they operate in a redundant or well buffered context. We propose a model based on a multi-adaptor principle to explain this phenomenon. Furthermore, we report a new CAM-independent adhesion mechanism that involves the basement membranes (BM) covering neuromuscular terminals. Thus, motorneuronal terminals show strong partial detachment of the junction when BM-to-cell surface attachment is impaired by removing Laminin A, or when BMs lose their structural integrity upon loss of type IV collagens. We conclude that BMs are essential to tie embryonic motorneuronal terminals to the muscle surface, lending CAM-independent structural support to their adhesion. Therefore, future developmental studies of these synaptic junctions in Drosophila need to consider the important contribution made by BM-dependent mechanisms, in addition to CAM-dependent adhesion.
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Affiliation(s)
- Andre Koper
- Faculty of Life Sciences, Wellcome Trust Centre for Cell-Matrix Research, Manchester, United Kingdom
| | - Annette Schenck
- Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Andreas Prokop
- Faculty of Life Sciences, Wellcome Trust Centre for Cell-Matrix Research, Manchester, United Kingdom
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46
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Jordán-Álvarez S, Fouquet W, Sigrist SJ, Acebes A. Presynaptic PI3K activity triggers the formation of glutamate receptors at neuromuscular terminals of Drosophila. J Cell Sci 2012; 125:3621-9. [PMID: 22505608 DOI: 10.1242/jcs.102806] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Synapse transmission depends on the precise structural and functional assembly between pre- and postsynaptic elements. This tightly regulated interaction has been thoroughly characterised in vivo in the Drosophila glutamatergic larval neuromuscular junction (NMJ) synapse, a suitable model to explore synapse formation, dynamics and plasticity. Previous findings have demonstrated that presynaptic upregulation of phosphoinositide 3-kinase (PI3K) increases synapse number, generating new functional contacts and eliciting changes in behaviour. Here, we show that genetically driven overexpression of PI3K in the presynaptic element also leads to a correlated increase in the levels of glutamate receptor (GluRII) subunits and the number of postsynaptic densities (PSDs), without altering GluRII formation and assembly dynamics. In addition to GluRIIs, presynaptic PI3K activity also modifies the expression of the postsynaptic protein Discs large (Dlg). Remarkably, PI3K specifically overexpressed in the final larval stages is sufficient for the formation of NMJ synapses. No differences in the number of synapses and PSDs were detected when PI3K was selectively expressed in the postsynaptic compartment. Taken together, these results demonstrate that PI3K-dependent synaptogenesis plays an instructive role in PSD formation and growth from the presynaptic side.
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Affiliation(s)
- Sheila Jordán-Álvarez
- Cajal Institute, Consejo Superior de Investigaciones Científicas, Ave Dr Arce 37, Madrid 28002, Spain
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47
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Abstract
The cytoskeleton forms the backbone of neuronal architecture, sustaining its form and size, subcellular compartments and cargo logistics. The synaptic cytoskeleton can be categorized in the microtubule-based core cytoskeleton and the cortical membrane skeleton. While central microtubules form the fundamental basis for the construction of elaborate neuronal processes, including axons and synapses, cortical actin filaments are generally considered to function as mediators of synapse dynamics and plasticity. More recently, the submembranous network of spectrin and ankyrin molecules has been involved in the regulation of synaptic stability and maintenance. Disruption of the synaptic cytoskeleton primarily affects the stability and maturation of synapses but also secondarily disturbs neuronal communication. Consequently, a variety of inherited diseases are accompanied by cytoskeletal malfunctions, including spastic paraplegias, spinocerebellar ataxias, and mental retardation. Since the primary reasons for many of these diseases are still unknown model organisms with a conserved repertoire of cytoskeletal elements help to understand the underlying biological mechanisms. The astonishing technical as well as genetic accessibility of synapses in Drosophila has shown that loss of the cytoskeletal architecture leads to axonal transport defects, synaptic maturation deficits, and retraction of synaptic boutons, before synaptic terminals finally detach from their target cells, suggesting that similar processes could be involved in human neuronal diseases.
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Affiliation(s)
- Bernd Goellner
- Heinrich-Heine-University Düsseldorf, Functional Cell Morphology Lab, Düsseldorf, Germany
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48
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Ahmed WW, Li TC, Rubakhin SS, Chiba A, Sweedler JV, Saif TA. Mechanical tension modulates local and global vesicle dynamics in neurons. Cell Mol Bioeng 2012; 5:155-164. [PMID: 23002399 DOI: 10.1007/s12195-012-0223-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Growing experimental evidence suggests that mechanical tension plays a significant role in determining the growth, guidance, and function of neurons. Mechanical tension in axons contributes to neurotransmitter clustering at the Drosophila neuromuscular junction (NMJ) and is actively regulated by neurons both in vitro and in vivo. In this work, we applied mechanical strain on in vivo Drosophila neurons and in vitro Aplysia neurons and studied their vesicle dynamics by live-imaging. Our experiments show that mechanical stretch modulates the dynamics of vesicles in two different model systems: (1) The global accumulation of synaptic vesicles (SV) at the Drosophila NMJ and (2) the local motion of individual large dense core vesicles (LDCV) in Aplysia neurites. Specifically, a sustained stretch results in enhanced SV accumulation in the Drosophila NMJ. This increased SV accumulation occurs in the absence of extracellular Ca(2+), plateaus after approximately 50 min, and persists for at least 30 min after stretch is reduced. On the other hand, mechanical compression in Aplysia neurites immediately disrupts LDCV motion, leading to decreased range and processivity. This impairment of LDCV motion persists for at least 15 min after tension is restored. These results show that mechanical stretch modulates both local and global vesicle dynamics and strengthens the notion that tension serves a role in regulating neuronal function.
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Affiliation(s)
- W W Ahmed
- Department of Mechanical Science and Engineering, University of Illinois, Urbana, IL 61801 ; Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana, IL 61801
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Andlauer TFM, Sigrist SJ. In vivo imaging of Drosophila larval neuromuscular junctions to study synapse assembly. Cold Spring Harb Protoc 2012; 2012:407-13. [PMID: 22474662 DOI: 10.1101/pdb.top068577] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In the past decade, a significant number of proteins involved in the developmental assembly and maturation of synapses have been identified. However, detailed knowledge of the molecular processes underlying developmental synapse assembly is still sparse. Here, we discuss an approach that makes extended in vivo imaging of selected proteins in live Drosophila larvae feasible at a single-synapse resolution. The intact larvae are anesthetized and neuromuscular junctions (NMJs) are noninvasively imaged with confocal microscopy. This method allows for both protein trafficking and protein turnover kinetics to be studied at various points in time during the development of an animal. These data contribute to our understanding of synaptic assembly under in vivo conditions.
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Clarke GL, Chen J, Nishimune H. Presynaptic Active Zone Density during Development and Synaptic Plasticity. Front Mol Neurosci 2012; 5:12. [PMID: 22438837 PMCID: PMC3305919 DOI: 10.3389/fnmol.2012.00012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 01/30/2012] [Indexed: 12/13/2022] Open
Abstract
Neural circuits transmit information through synapses, and the efficiency of synaptic transmission is closely related to the density of presynaptic active zones, where synaptic vesicles are released. The goal of this review is to highlight recent insights into the molecular mechanisms that control the number of active zones per presynaptic terminal (active zone density) during developmental and stimulus-dependent changes in synaptic efficacy. At the neuromuscular junctions (NMJs), the active zone density is preserved across species, remains constant during development, and is the same between synapses with different activities. However, the NMJ active zones are not always stable, as exemplified by the change in active zone density during acute experimental manipulation or as a result of aging. Therefore, a mechanism must exist to maintain its density. In the central nervous system (CNS), active zones have restricted maximal size, exist in multiple numbers in larger presynaptic terminals, and maintain a constant density during development. These findings suggest that active zone density in the CNS is also controlled. However, in contrast to the NMJ, active zone density in the CNS can also be increased, as observed in hippocampal synapses in response to synaptic plasticity. Although the numbers of known active zone proteins and protein interactions have increased, less is known about the mechanism that controls the number or spacing of active zones. The following molecules are known to control active zone density and will be discussed herein: extracellular matrix laminins and voltage-dependent calcium channels, amyloid precursor proteins, the small GTPase Rab3, an endocytosis mechanism including synaptojanin, cytoskeleton protein spectrins and β-adducin, and a presynaptic web including spectrins. The molecular mechanisms that organize the active zone density are just beginning to be elucidated.
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Affiliation(s)
- Gwenaëlle L Clarke
- Department of Anatomy and Cell Biology, University of Kansas Medical School Kansas City, KS, USA
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