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Sidisky JM, Winters A, Caratenuto R, Babcock DT. Synaptic defects in a drosophila model of muscular dystrophy. Front Cell Neurosci 2024; 18:1381112. [PMID: 38812789 PMCID: PMC11133739 DOI: 10.3389/fncel.2024.1381112] [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: 02/02/2024] [Accepted: 04/08/2024] [Indexed: 05/31/2024] Open
Abstract
Muscular dystrophies are a devastating class of diseases that result in a progressive loss of muscle integrity. Duchenne Muscular Dystrophy, the most prevalent form of Muscular Dystrophy, is due to the loss of functional Dystrophin. While much is known regarding destruction of muscle tissue in these diseases, much less is known regarding the synaptic defects that also occur in these diseases. Synaptic defects are also among the earliest hallmarks of neurodegenerative diseases, including the neuromuscular disease Amyotrophic Lateral Sclerosis (ALS). Our current study investigates synaptic defects within adult muscle tissues as well as presynaptic motor neurons in Drosophila dystrophin mutants. Here we demonstrate that the progressive, age-dependent loss of flight ability in dystrophin mutants is accompanied by disorganization of Neuromuscular Junctions (NMJs), including impaired localization of both presynaptic and postsynaptic markers. We show that these synaptic defects, including presynaptic defects within motor neurons, are due to the loss of Dystrophin specifically within muscles. These results should help to better understand the early synaptic defects preceding cell loss in neuromuscular disorders.
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Affiliation(s)
- Jessica M. Sidisky
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, United States
- Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Cambridge, MA, United States
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Alex Winters
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, United States
| | - Russell Caratenuto
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, United States
| | - Daniel T. Babcock
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, United States
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Ermanoska B, Rodal AA. Non-muscle myosin II regulates presynaptic actin assemblies and neuronal mechanobiology. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.10.566609. [PMID: 38014140 PMCID: PMC10680633 DOI: 10.1101/2023.11.10.566609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Neuromuscular junctions (NMJs) are evolutionarily ancient, specialized contacts between neurons and muscles. Axons and NMJs must endure mechanical strain through a lifetime of muscle contraction, making them vulnerable to aging and neurodegenerative conditions. However, cellular strategies for mitigating this mechanical stress remain unknown. In this study, we used Drosophila larval NMJs to investigate the role of actin and myosin (actomyosin)-mediated contractility in generating and responding to cellular forces at the neuron-muscle interface. We identified a new long-lived, low-turnover presynaptic actin core traversing the NMJ, which partly co-localizes with non-muscle myosin II (NMII). Neuronal RNAi of NMII induced disorganization of this core, suggesting that this structure might have contractile properties. Interestingly, neuronal RNAi of NMII also decreased NMII levels in the postsynaptic muscle proximal to neurons, suggesting that neuronal actomyosin rearrangements propagate their effects trans-synaptically. We also observed reduced Integrin levels upon NMII knockdown, indicating that neuronal actomyosin disruption triggers rearrangements of Integrin-mediated connections between neurons and surrounding muscle tissue. In summary, our study identifies a previously uncharacterized presynaptic actomyosin subpopulation that upholds the neuronal mechanical continuum, transmits signals to adjacent muscle tissue, and collaborates with Integrin receptors to govern the mechanobiology of the neuromuscular junction.
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Li L, Liu H, Qian KY, Nurrish S, Zeng XT, Zeng WX, Wang J, Kaplan JM, Tong XJ, Hu Z. CASK and FARP localize two classes of post-synaptic ACh receptors thereby promoting cholinergic transmission. PLoS Genet 2022; 18:e1010211. [PMID: 36279278 PMCID: PMC9632837 DOI: 10.1371/journal.pgen.1010211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 11/03/2022] [Accepted: 10/10/2022] [Indexed: 11/06/2022] Open
Abstract
Changes in neurotransmitter receptor abundance at post-synaptic elements play a pivotal role in regulating synaptic strength. For this reason, there is significant interest in identifying and characterizing the scaffolds required for receptor localization at different synapses. Here we analyze the role of two C. elegans post-synaptic scaffolding proteins (LIN-2/CASK and FRM-3/FARP) at cholinergic neuromuscular junctions. Constitutive knockouts or muscle specific inactivation of lin-2 and frm-3 dramatically reduced spontaneous and evoked post-synaptic currents. These synaptic defects resulted from the decreased abundance of two classes of post-synaptic ionotropic acetylcholine receptors (ACR-16/CHRNA7 and levamisole-activated AChRs). LIN-2's AChR scaffolding function is mediated by its SH3 and PDZ domains, which interact with AChRs and FRM-3/FARP, respectively. Thus, our findings show that post-synaptic LIN-2/FRM-3 complexes promote cholinergic synaptic transmission by recruiting AChRs to post-synaptic elements.
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Affiliation(s)
- Lei Li
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, Australia
| | - Haowen Liu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, Australia
| | - Kang-Ying Qian
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Stephen Nurrish
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Xian-Ting Zeng
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Wan-Xin Zeng
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Jiafan Wang
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, Australia
| | - Joshua M. Kaplan
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, United States of America
- Program in Neuroscience, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Xia-Jing Tong
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Zhitao Hu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research (CJCADR), The University of Queensland, Brisbane, Australia
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4
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Guangming G, Junhua G, Chenchen Z, Yang M, Wei X. Neurexin and Neuroligins Maintain the Balance of Ghost and Satellite Boutons at the Drosophila Neuromuscular Junction. Front Neuroanat 2020; 14:19. [PMID: 32581727 PMCID: PMC7296126 DOI: 10.3389/fnana.2020.00019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 03/26/2020] [Indexed: 11/22/2022] Open
Abstract
Neurexins and neuroligins are common synaptic adhesion molecules that are associated with autism and interact with each other in the synaptic cleft. The Drosophila neuromuscular junction (NMJ) bouton is a well-known model system in neuroscience, and ghost and satellite boutons, respectively, indicate the poor development and overgrowth of the NMJ boutons. However, the Drosophila neurexin (DNrx) and Drosophila neuroligins (DNlgs) are mainly observed in type Ib boutons, indicating the ultrastructural and developmental phenotypes of the Drosophila NMJ. Here, we identified the ultrastructural and developmental features of ghost and satellite boutons by utilizing dneurexin (dnrx) and dneuroligins (dnlgs) fly mutants and other associated fly strains. Ghost boutons contain synaptic vesicles with multiple diameters but very rarely contain T-bar structures and swollen or thin subsynaptic reticulum (SSR) membranes. The muscle cell membrane is invaginated at different sites, stretches to the ghost bouton from different directions, forms several layers that enwrap the ghost bouton, and then branches into the complex SSR. Satellite boutons share a common SSR membrane and present either a typical profile in which a main bouton is encircled by small boutons or two atypical profiles in which the small boutons are grouped together or distributed in beads without a main bouton. Electron and confocal microscopy data showed that dnrx, dnlg1, dnlg2, dnlg3, and dnlg4 mutations led to ghost boutons; the overexpression of dnrx, dnlg1, dnlg2, dnlg3, and dnlg4 led to satellite boutons; and the dnlg2;dnlg3 double mutation also led to satellite boutons. These results suggested that DNrx and DNlgs jointly maintain the development and function of NMJ boutons by regulating the balance of ghost and satellite boutons in Drosophila.
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Affiliation(s)
- Gan Guangming
- School of Medicine, Southeast University, Nanjing, China.,The Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing, China
| | - Geng Junhua
- The Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing, China
| | - Zhang Chenchen
- School of Medicine, Southeast University, Nanjing, China.,The Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing, China
| | - Mou Yang
- School of Medicine, Southeast University, Nanjing, China
| | - Xie Wei
- The Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing, China.,Institute of Life Sciences, The Collaborative Innovation Center for Brain Science, Southeast University, Nanjing, China
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5
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Abstract
In this issue of Neuron, Newman et al. (2017) image calcium events at single synapses of unanesthetized Drosophila larvae. Synaptic plasticity and homeostatic regulation of synapses is established to be input specific. Furthermore, plasticity forms involve selective recruitment of previously active or silent synapses.
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Affiliation(s)
- James Ashley
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Vivian Budnik
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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Lee G, Schwarz TL. Filamin, a synaptic organizer in Drosophila, determines glutamate receptor composition and membrane growth. eLife 2016; 5. [PMID: 27914199 PMCID: PMC5173320 DOI: 10.7554/elife.19991] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 11/23/2016] [Indexed: 11/27/2022] Open
Abstract
Filamin is a scaffolding protein that functions in many cells as an actin-crosslinker. FLN90, an isoform of the Drosophila ortholog Filamin/cheerio that lacks the actin-binding domain, is here shown to govern the growth of postsynaptic membrane folds and the composition of glutamate receptor clusters at the larval neuromuscular junction. Genetic and biochemical analyses revealed that FLN90 is present surrounding synaptic boutons. FLN90 is required in the muscle for localization of the kinase dPak and, downstream of dPak, for localization of the GTPase Ral and the exocyst complex to this region. Consequently, Filamin is needed for growth of the subsynaptic reticulum. In addition, in the absence of filamin, type-A glutamate receptor subunits are lacking at the postsynapse, while type-B subunits cluster correctly. Receptor composition is dependent on dPak, but independent of the Ral pathway. Thus two major aspects of synapse formation, morphological plasticity and subtype-specific receptor clustering, require postsynaptic Filamin. DOI:http://dx.doi.org/10.7554/eLife.19991.001
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Affiliation(s)
- GaYoung Lee
- The F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Thomas L Schwarz
- The F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, United States.,Department of Neurobiology, Harvard Medical School, Boston, United States
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7
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Lee SH, Kim YJ, Choi SY. BMP signaling modulates the probability of neurotransmitter release and readily releasable pools in Drosophila neuromuscular junction synapses. Biochem Biophys Res Commun 2016; 479:440-446. [DOI: 10.1016/j.bbrc.2016.09.072] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 09/15/2016] [Indexed: 11/16/2022]
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8
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The influence of postsynaptic structure on missing quanta at the Drosophila neuromuscular junction. BMC Neurosci 2016; 17:53. [PMID: 27459966 PMCID: PMC4962461 DOI: 10.1186/s12868-016-0290-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 07/20/2016] [Indexed: 11/10/2022] Open
Abstract
Background Synaptic transmission requires both pre- and post-synaptic elements for neural communication. The postsynaptic structure contributes to the ability of synaptic currents to induce voltage changes in postsynaptic cells. At the Drosophila neuromuscular junction (NMJ), the postsynaptic structure, known as the subsynaptic reticulum (SSR), consists of elaborate membrane folds that link the synaptic contacts to the muscle, but its role in synaptic physiology is poorly understood. Results In this study, we investigate the role of the SSR with simultaneous intra- and extra-cellular recordings that allow us to identify the origin of spontaneously occurring synaptic events. We compare data from Type 1b and 1s synaptic boutons, which have naturally occurring variations of the SSR, as well as from genetic mutants that up or down-regulate SSR complexity. We observed that some synaptic currents do not result in postsynaptic voltage changes, events we called ‘missing quanta’. The frequency of missing quanta is positively correlated with SSR complexity in both natural and genetically-induced variants. Rise-time and amplitude data suggest that passive membrane properties contribute to the observed differences in synaptic effectiveness. Conclusion We conclude that electrotonic decay within the postsynaptic structure contributes to the phenomenon of missing quanta. Further studies directed at understanding the role of the SSR in synaptic transmission and the potential for regulating ‘missing quanta’ will yield important information about synaptic transmission at the Drosophila NMJ.
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Wang S, Yoo S, Kim HY, Wang M, Zheng C, Parkhouse W, Krieger C, Harden N. Detection of in situ protein-protein complexes at the Drosophila larval neuromuscular junction using proximity ligation assay. J Vis Exp 2015:52139. [PMID: 25650626 DOI: 10.3791/52139] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Discs large (Dlg) is a conserved member of the membrane-associated guanylate kinase family, and serves as a major scaffolding protein at the larval neuromuscular junction (NMJ) in Drosophila. Previous studies have shown that the postsynaptic distribution of Dlg at the larval NMJ overlaps with that of Hu-li tai shao (Hts), a homologue to the mammalian adducins. In addition, Dlg and Hts are observed to form a complex with each other based on co-immunoprecipitation experiments involving whole adult fly lysates. Due to the nature of these experiments, however, it was unknown whether this complex exists specifically at the NMJ during larval development. Proximity Ligation Assay (PLA) is a recently developed technique used mostly in cell and tissue culture that can detect protein-protein interactions in situ. In this assay, samples are incubated with primary antibodies against the two proteins of interest using standard immunohistochemical procedures. The primary antibodies are then detected with a specially designed pair of oligonucleotide-conjugated secondary antibodies, termed PLA probes, which can be used to generate a signal only when the two probes have bound in close proximity to each other. Thus, proteins that are in a complex can be visualized. Here, it is demonstrated how PLA can be used to detect in situ protein-protein interactions at the Drosophila larval NMJ. The technique is performed on larval body wall muscle preparations to show that a complex between Dlg and Hts does indeed exist at the postsynaptic region of NMJs.
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Affiliation(s)
- Simon Wang
- Department of Molecular Biology and Biochemistry, Simon Fraser University
| | - SooHyun Yoo
- Department of Molecular Biology and Biochemistry, Simon Fraser University
| | - Hae-Yoon Kim
- Department of Molecular Biology and Biochemistry, Simon Fraser University
| | - Mannan Wang
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University
| | - Clare Zheng
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University
| | - Wade Parkhouse
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University
| | - Charles Krieger
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University
| | - Nicholas Harden
- Department of Molecular Biology and Biochemistry, Simon Fraser University;
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10
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Wang SJH, Tsai A, Wang M, Yoo S, Kim HY, Yoo B, Chui V, Kisiel M, Stewart B, Parkhouse W, Harden N, Krieger C. Phospho-regulated Drosophila adducin is a determinant of synaptic plasticity in a complex with Dlg and PIP2 at the larval neuromuscular junction. Biol Open 2014; 3:1196-206. [PMID: 25416060 PMCID: PMC4265757 DOI: 10.1242/bio.20148342] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Accepted: 10/15/2014] [Indexed: 12/12/2022] Open
Abstract
Adducin is a ubiquitously expressed actin- and spectrin-binding protein involved in cytoskeleton organization, and is regulated through phosphorylation of the myristoylated alanine-rich C-terminal kinase (MARCKS)-homology domain by protein kinase C (PKC). We have previously shown that the Drosophila adducin, Hu-li tai shao (Hts), plays a role in larval neuromuscular junction (NMJ) growth. Here, we find that the predominant isoforms of Hts at the NMJ contain the MARCKS-homology domain, which is important for interactions with Discs large (Dlg) and phosphatidylinositol 4,5-bisphosphate (PIP2). Through the use of Proximity Ligation Assay (PLA), we show that the adducin-like Hts isoforms are in complexes with Dlg and PIP2 at the NMJ. We provide evidence that Hts promotes the phosphorylation and delocalization of Dlg at the NMJ through regulation of the transcript distribution of the PAR-1 and CaMKII kinases in the muscle. We also show that Hts interactions with Dlg and PIP2 are impeded through phosphorylation of the MARCKS-homology domain. These results are further evidence that Hts is a signaling-responsive regulator of synaptic plasticity in Drosophila.
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Affiliation(s)
- Simon Ji Hau Wang
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Amy Tsai
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Mannan Wang
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - SooHyun Yoo
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Hae-Yoon Kim
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Byoungjoo Yoo
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Vincent Chui
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Marta Kisiel
- Department of Biology, University of Toronto at Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada
| | - Bryan Stewart
- Department of Biology, University of Toronto at Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada
| | - Wade Parkhouse
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Nicholas Harden
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Charles Krieger
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
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Teodoro RO, Pekkurnaz G, Nasser A, Higashi-Kovtun ME, Balakireva M, McLachlan IG, Camonis J, Schwarz TL. Ral mediates activity-dependent growth of postsynaptic membranes via recruitment of the exocyst. EMBO J 2013; 32:2039-55. [PMID: 23812009 DOI: 10.1038/emboj.2013.147] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 05/28/2013] [Indexed: 11/09/2022] Open
Abstract
Remodelling neuronal connections by synaptic activity requires membrane trafficking. We present evidence for a signalling pathway by which synaptic activity and its consequent Ca(2+) influx activate the small GTPase Ral and thereby recruit exocyst proteins to postsynaptic zones. In accord with the ability of the exocyst to direct delivery of post-Golgi vesicles, constitutively active Ral expressed in Drosophila muscle causes the exocyst to be concentrated in the region surrounding synaptic boutons and consequently enlarges the membrane folds of the postsynaptic plasma membrane (the subsynaptic reticulum, SSR). SSR growth requires Ral and the exocyst component Sec5 and Ral-induced enlargement of these membrane folds does not occur in sec5(-/-) muscles. Chronic changes in synaptic activity influence the plastic growth of this membrane in a manner consistent with activity-dependent activation of Ral. Thus, Ral regulation of the exocyst represents a control point for postsynaptic plasticity. This pathway may also function in mammals as expression of activated RalA in hippocampal neurons increases dendritic spine density in an exocyst-dependent manner and increases Sec5 in spines.
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Affiliation(s)
- Rita O Teodoro
- The F.M. Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital, Boston, MA, USA.
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12
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Menon KP, Carrillo RA, Zinn K. Development and plasticity of the Drosophila larval neuromuscular junction. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2013; 2:647-70. [PMID: 24014452 DOI: 10.1002/wdev.108] [Citation(s) in RCA: 157] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The Drosophila larval neuromuscular system is relatively simple, containing only 32 motor neurons in each abdominal hemisegment, and its neuromuscular junctions (NMJs) have been studied extensively. NMJ synapses exhibit developmental and functional plasticity while displaying stereotyped connectivity. Drosophila Type I NMJ synapses are glutamatergic, while the vertebrate NMJ uses acetylcholine as its primary neurotransmitter. The larval NMJ synapses use ionotropic glutamate receptors (GluRs) that are homologous to AMPA-type GluRs in the mammalian brain, and they have postsynaptic scaffolds that resemble those found in mammalian postsynaptic densities. These features make the Drosophila neuromuscular system an excellent genetic model for the study of excitatory synapses in the mammalian central nervous system. The first section of the review presents an overview of NMJ development. The second section describes genes that regulate NMJ development, including: (1) genes that positively and negatively regulate growth of the NMJ, (2) genes required for maintenance of NMJ bouton structure, (3) genes that modulate neuronal activity and alter NMJ growth, (4) genes involved in transsynaptic signaling at the NMJ. The third section describes genes that regulate acute plasticity, focusing on translational regulatory mechanisms. As this review is intended for a developmental biology audience, it does not cover NMJ electrophysiology in detail, and does not review genes for which mutations produce only electrophysiological but no structural phenotypes.
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Affiliation(s)
- Kaushiki P Menon
- Broad Center, Division of Biology, California Institute of Technology, Pasadena, CA, USA
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13
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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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14
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Glutamate receptors in synaptic assembly and plasticity: case studies on fly NMJs. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 970:3-28. [PMID: 22351049 DOI: 10.1007/978-3-7091-0932-8_1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The molecular and cellular mechanisms that control the composition and functionality of ionotropic glutamate receptors may be considered as most important "set screws" for adjusting excitatory transmission in the course of developmental and experience-dependent changes within neural networks. The Drosophila larval neuromuscular junction has emerged as one important invertebrate model system to study the formation, maintenance, and plasticity-related remodeling of glutamatergic synapses in vivo. By exploiting the unique genetic accessibility of this organism combined with diverse tools for manipulation and analysis including electrophysiology and state of the art imaging, considerable progress has been made to characterize the role of glutamate receptors during the orchestration of junctional development, synaptic activity, and synaptogenesis. Following an introduction to basic features of this model system, we will mainly focus on conceptually important findings such as the selective impact of glutamate receptor subtypes on the formation of new synapses, the coordination of presynaptic maturation and receptor subtype composition, the role of nonvesicularly released glutamate on the synaptic localization of receptors, or the homeostatic feedback of receptor functionality on presynaptic transmitter release.
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15
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Wang S, Yang J, Tsai A, Kuca T, Sanny J, Lee J, Dong K, Harden N, Krieger C. Drosophila adducin regulates Dlg phosphorylation and targeting of Dlg to the synapse and epithelial membrane. Dev Biol 2011; 357:392-403. [PMID: 21791202 DOI: 10.1016/j.ydbio.2011.07.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 07/06/2011] [Accepted: 07/07/2011] [Indexed: 12/20/2022]
Abstract
Adducin is a cytoskeletal protein having regulatory roles that involve actin filaments, functions that are inhibited by phosphorylation of adducin by protein kinase C. Adducin is hyperphosphorylated in nervous system tissue in patients with the neurodegenerative disease amyotrophic lateral sclerosis, and mice lacking β-adducin have impaired synaptic plasticity and learning. We have found that Drosophila adducin, encoded by hu-li tai shao (hts), is localized to the post-synaptic larval neuromuscular junction (NMJ) in a complex with the scaffolding protein Discs large (Dlg), a regulator of synaptic plasticity during growth of the NMJ. hts mutant NMJs are underdeveloped, whereas over-expression of Hts promotes Dlg phosphorylation, delocalizes Dlg away from the NMJ, and causes NMJ overgrowth. Dlg is a component of septate junctions at the lateral membrane of epithelial cells, and we show that Hts regulates Dlg localization in the amnioserosa, an embryonic epithelium, and that embryos doubly mutant for hts and dlg exhibit defects in epithelial morphogenesis. The phosphorylation of Dlg by the kinases PAR-1 and CaMKII has been shown to disrupt Dlg targeting to the NMJ and we present evidence that Hts regulates Dlg targeting to the NMJ in muscle and the lateral membrane of epithelial cells by controlling the protein levels of PAR-1 and CaMKII, and consequently the extent of Dlg phosphorylation.
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Affiliation(s)
- Simon Wang
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6
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Zheng CY, Seabold GK, Horak M, Petralia RS. MAGUKs, synaptic development, and synaptic plasticity. Neuroscientist 2011; 17:493-512. [PMID: 21498811 DOI: 10.1177/1073858410386384] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
MAGUKs are proteins that act as key scaffolds in surface complexes containing receptors, adhesion proteins, and various signaling molecules. These complexes evolved prior to the appearance of multicellular animals and play key roles in cell-cell intercommunication. A major example of this is the neuronal synapse, which contains several presynaptic and postsynaptic MAGUKs including PSD-95, SAP102, SAP97, PSD-93, CASK, and MAGIs. Here, they play roles in both synaptic development and in later synaptic plasticity events. During development, MAGUKs help to organize the postsynaptic density via associations with other scaffolding proteins, such as Shank, and the actin cytoskeleton. They affect the clustering of glutamate receptors and other receptors, and these associations change with development. MAGUKs are involved in long-term potentiation and depression (e.g., via their phosphorylation by kinases and phosphorylation of other proteins associated with MAGUKs). Importantly, synapse development and function are dependent on the kind of MAGUK present. For example, SAP102 shows high mobility and is present in early synaptic development. Later, much of SAP102 is replaced by PSD-95, a more stable synaptic MAGUK; this is associated with changes in glutamate receptor types that are characteristic of synaptic maturation.
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Affiliation(s)
- Chan-Ying Zheng
- National Institute on Deafness and Other Communication Disorders/National Institutes of Health, Bethesda, MD 20892-8027, USA
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Thomas U, Kobler O, Gundelfinger ED. TheDrosophilaLarval Neuromuscular Junction as a Model for Scaffold Complexes at Glutamatergic Synapses: Benefits and Limitations. J Neurogenet 2010; 24:109-19. [DOI: 10.3109/01677063.2010.493589] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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A perisynaptic ménage à trois between Dlg, DLin-7, and Metro controls proper organization of Drosophila synaptic junctions. J Neurosci 2010; 30:5811-24. [PMID: 20427642 DOI: 10.1523/jneurosci.0778-10.2010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Structural plasticity of synaptic junctions is a prerequisite to achieve and modulate connectivity within nervous systems, e.g., during learning and memory formation. It demands adequate backup systems that allow remodeling while retaining sufficient stability to prevent unwanted synaptic disintegration. The strength of submembranous scaffold complexes, which are fundamental to the architecture of synaptic junctions, likely constitutes a crucial determinant of synaptic stability. Postsynaptic density protein-95 (PSD-95)/ Discs-large (Dlg)-like membrane-associated guanylate kinases (DLG-MAGUKs) are principal scaffold proteins at both vertebrate and invertebrate synapses. At Drosophila larval glutamatergic neuromuscular junctions (NMJs) DlgA and DlgS97 exert pleiotropic functions, probably reflecting a few known and a number of yet-unknown binding partners. In this study we have identified Metro, a novel p55/MPP-like Drosophila MAGUK as a major binding partner of perisynaptic DlgS97 at larval NMJs. Based on homotypic LIN-2,-7 (L27) domain interactions, Metro stabilizes junctional DlgS97 in a complex with the highly conserved adaptor protein DLin-7. In a remarkably interdependent manner, Metro and DLin-7 act downstream of DlgS97 to control NMJ expansion and proper establishment of synaptic boutons. Using quantitative 3D-imaging we further demonstrate that the complex controls the size of postsynaptic glutamate receptor fields. Our findings accentuate the importance of perisynaptic scaffold complexes for synaptic stabilization and organization.
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Nieratschker V, Schubert A, Jauch M, Bock N, Bucher D, Dippacher S, Krohne G, Asan E, Buchner S, Buchner E. Bruchpilot in ribbon-like axonal agglomerates, behavioral defects, and early death in SRPK79D kinase mutants of Drosophila. PLoS Genet 2009; 5:e1000700. [PMID: 19851455 PMCID: PMC2759580 DOI: 10.1371/journal.pgen.1000700] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Accepted: 09/23/2009] [Indexed: 12/18/2022] Open
Abstract
Defining the molecular structure and function of synapses is a central theme in brain research. In Drosophila the Bruchpilot (BRP) protein is associated with T-shaped ribbons ("T-bars") at presynaptic active zones (AZs). BRP is required for intact AZ structure and normal evoked neurotransmitter release. By screening for mutations that affect the tissue distribution of Bruchpilot, we have identified a P-transposon insertion in gene CG11489 (location 79D) which shows high homology to mammalian genes for SR protein kinases (SRPKs). SRPKs phosphorylate serine-arginine rich splicing factors (SR proteins). Since proteins expressed from CG11489 cDNAs phosphorylate a peptide from a human SR protein in vitro, we name CG11489 the Drosophila Srpk79D gene. We have characterized Srpk79D transcripts and generated a null mutant. Mutation of the Srpk79D gene causes conspicuous accumulations of BRP in larval and adult nerves. At the ultrastructural level, these correspond to extensive axonal agglomerates of electron-dense ribbons surrounded by clear vesicles. Basic synaptic structure and function at larval neuromuscular junctions appears normal, whereas life expectancy and locomotor behavior of adult mutants are significantly impaired. All phenotypes of the mutant can be largely or completely rescued by panneural expression of SRPK79D isoforms. Isoform-specific antibodies recognize panneurally overexpressed GFP-tagged SRPK79D-PC isoform co-localized with BRP at presynaptic active zones while the tagged -PB isoform is found in spots within neuronal perikarya. SRPK79D concentrations in wild type apparently are too low to be revealed by these antisera. We propose that the Drosophila Srpk79D gene characterized here may be expressed at low levels throughout the nervous system to prevent the assembly of BRP containing agglomerates in axons and maintain intact brain function. The discovery of an SR protein kinase required for normal BRP distribution calls for the identification of its substrate and the detailed analysis of SRPK function for the maintenance of nervous system integrity.
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Affiliation(s)
- Vanessa Nieratschker
- Department of Genetics and Neurobiology, Julius-Maximilians-University, Würzburg, Germany
| | - Alice Schubert
- Department of Genetics and Neurobiology, Julius-Maximilians-University, Würzburg, Germany
| | - Mandy Jauch
- Department of Genetics and Neurobiology, Julius-Maximilians-University, Würzburg, Germany
| | - Nicole Bock
- Department of Genetics and Neurobiology, Julius-Maximilians-University, Würzburg, Germany
| | - Daniel Bucher
- Department of Genetics and Neurobiology, Julius-Maximilians-University, Würzburg, Germany
| | - Sonja Dippacher
- Department of Genetics and Neurobiology, Julius-Maximilians-University, Würzburg, Germany
- Institute of Anatomy and Cell Biology, Julius-Maximilians-University, Würzburg, Germany
| | - Georg Krohne
- Department of Electron Microscopy, Julius-Maximilians-University, Würzburg, Germany
| | - Esther Asan
- Institute of Anatomy and Cell Biology, Julius-Maximilians-University, Würzburg, Germany
| | - Sigrid Buchner
- Department of Genetics and Neurobiology, Julius-Maximilians-University, Würzburg, Germany
| | - Erich Buchner
- Department of Genetics and Neurobiology, Julius-Maximilians-University, Würzburg, Germany
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DLGS97/SAP97 is developmentally upregulated and is required for complex adult behaviors and synapse morphology and function. J Neurosci 2008; 28:304-14. [PMID: 18171947 DOI: 10.1523/jneurosci.4395-07.2008] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The synaptic membrane-associated guanylate kinase (MAGUK) scaffolding protein family is thought to play key roles in synapse assembly and synaptic plasticity. Evidence supporting these roles in vivo is scarce, as a consequence of gene redundancy in mammals. The genome of Drosophila contains only one MAGUK gene, discs large (dlg), from which two major proteins originate: DLGA [PSD95 (postsynaptic density 95)-like] and DLGS97 [SAP97 (synapse-associated protein)-like]. These differ only by the inclusion in DLGS97 of an L27 domain, important for the formation of supramolecular assemblies. Known dlg mutations affect both forms and are lethal at larval stages attributable to tumoral overgrowth of epithelia. We generated independent null mutations for each, dlgA and dlgS97. These allowed unveiling of a shift in expression during the development of the nervous system: predominant expression of DLGA in the embryo, balanced expression of both during larval stages, and almost exclusive DLGS97 expression in the adult brain. Loss of embryonic DLGS97 does not alter the development of the nervous system. At larval stages, DLGA and DLGS97 fulfill both unique and partially redundant functions in the neuromuscular junction. Contrary to dlg and dlgA mutants, dlgS97 mutants are viable to adulthood, but they exhibit marked alterations in complex behaviors such as phototaxis, circadian activity, and courtship, whereas simpler behaviors like locomotion and odor and light perception are spared. We propose that the increased repertoire of associations of a synaptic scaffold protein given by an additional domain of protein-protein interaction underlies its ability to integrate molecular networks required for complex functions in adult synapses.
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Yanay C, Morpurgo N, Linial M. Evolution of insect proteomes: insights into synapse organization and synaptic vesicle life cycle. Genome Biol 2008; 9:R27. [PMID: 18257909 PMCID: PMC2374702 DOI: 10.1186/gb-2008-9-2-r27] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Revised: 12/06/2007] [Accepted: 02/07/2008] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND The molecular components in synapses that are essential to the life cycle of synaptic vesicles are well characterized. Nonetheless, many aspects of synaptic processes, in particular how they relate to complex behaviour, remain elusive. The genomes of flies, mosquitoes, the honeybee and the beetle are now fully sequenced and span an evolutionary breadth of about 350 million years; this provides a unique opportunity to conduct a comparative genomics study of the synapse. RESULTS We compiled a list of 120 gene prototypes that comprise the core of presynaptic structures in insects. Insects lack several scaffolding proteins in the active zone, such as bassoon and piccollo, and the most abundant protein in the mammalian synaptic vesicle, namely synaptophysin. The pattern of evolution of synaptic protein complexes is analyzed. According to this analysis, the components of presynaptic complexes as well as proteins that take part in organelle biogenesis are tightly coordinated. Most synaptic proteins are involved in rich protein interaction networks. Overall, the number of interacting proteins and the degrees of sequence conservation between human and insects are closely correlated. Such a correlation holds for exocytotic but not for endocytotic proteins. CONCLUSION This comparative study of human with insects sheds light on the composition and assembly of protein complexes in the synapse. Specifically, the nature of the protein interaction graphs differentiate exocytotic from endocytotic proteins and suggest unique evolutionary constraints for each set. General principles in the design of proteins of the presynaptic site can be inferred from a comparative study of human and insect genomes.
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Affiliation(s)
- Chava Yanay
- Department of Biological Chemistry, Institute of Life Sciences, Givat Ram Campus, Hebrew University of Jerusalem, Jerusalem 91904, Israel.
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