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Rimbert S, Moreira JB, Xapelli S, Lévi S. Role of purines in brain development, from neuronal proliferation to synaptic refinement. Neuropharmacology 2023:109640. [PMID: 37348675 DOI: 10.1016/j.neuropharm.2023.109640] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 06/15/2023] [Accepted: 06/19/2023] [Indexed: 06/24/2023]
Abstract
The purinergic system includes P1 and P2 receptors, which are activated by ATP and its metabolites. They are expressed in adult neuronal and glial cells and are crucial in brain function, including neuromodulation and neuronal signaling. As P1 and P2 receptors are expressed throughout embryogenesis and development, purinergic signaling also has an important role in the development of the peripheral and central nervous system. In this review, we present the expression pattern and activity of purinergic receptors and of their signaling pathways during embryonic and postnatal development of the nervous system. In particular, we review the involvement of the purinergic signaling in all the crucial steps of brain development i.e. in neural stem cell proliferation, neuronal differentiation and migration as well as in astrogliogenesis and oligodendrogenesis. Then, we review data showing a crucial role of the ATP and adenosine signaling pathways in the formation of the peripheral neuromuscular junction and of central GABAergic and glutamatergic synapses. Finally, we examine the consequences of deregulation of the purinergic system during development and discuss the therapeutic potential of targeting it at adult stage in diseases with reactivation of the ATP and adenosine pathway.
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Affiliation(s)
- Solen Rimbert
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, 75005, Paris, France
| | - João B Moreira
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, 75005, Paris, France; Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal; Instituto de Medicina Molecular - João Lobo Antunes (iMM - JLA), Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Sara Xapelli
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal; Instituto de Medicina Molecular - João Lobo Antunes (iMM - JLA), Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Sabine Lévi
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, 75005, Paris, France.
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2
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Xiao Y, Zhang J, Shu X, Bai L, Xu W, Wang A, Chen A, Tu WY, Wang J, Zhang K, Luo B, Shen C. Loss of mitochondrial protein CHCHD10 in skeletal muscle causes neuromuscular junction impairment. Hum Mol Genet 2019; 29:1784-1796. [PMID: 31261376 DOI: 10.1093/hmg/ddz154] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 06/11/2019] [Accepted: 06/21/2019] [Indexed: 12/12/2022] Open
Abstract
Abstract
The neuromuscular junction (NMJ) is a synapse between motoneurons and skeletal muscles to control motor behavior. Acetylcholine receptors (AChRs) are restricted at the synaptic region for proper neurotransmission. Mutations in the mitochondrial CHCHD10 protein have been identified in multiple neuromuscular disorders; however, the physiological roles of CHCHD10 at NMJs remain elusive. Here, we report that CHCHD10 is highly expressed at the postsynapse of NMJs in skeletal muscles. Muscle conditional knockout CHCHD10 mice showed motor defects, abnormal neuromuscular transmission and NMJ structure. Mechanistically, we found that mitochondrial CHCHD10 is required for ATP production, which facilitates AChR expression and promotes agrin-induced AChR clustering. Importantly, ATP could effectively rescue the reduction of AChR clusters in the CHCHD10-ablated muscles. Our study elucidates a novel physiological role of CHCHD10 at the peripheral synapse. It suggests that mitochondria dysfunction contributes to neuromuscular pathogenesis.
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Affiliation(s)
- Yatao Xiao
- The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China 310003
- Department of Neurobiology, Key laboratory of Medical Neurobiology of Zhejiang Province, School of Medicine, Zhejiang University, Zhejiang, China 310058
| | - Jianmin Zhang
- The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China 310003
| | - Xiaoqiu Shu
- The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China 310003
| | - Lei Bai
- The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China 310003
| | - Wentao Xu
- The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China 310003
| | - Ailian Wang
- The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China 310003
| | - Aizhong Chen
- The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China 310003
| | - Wen-Yo Tu
- The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China 310003
| | - Jianwen Wang
- The First Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang, China 310003
| | - Kejing Zhang
- The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China 310003
- Department of Neurobiology, Key laboratory of Medical Neurobiology of Zhejiang Province, School of Medicine, Zhejiang University, Zhejiang, China 310058
| | - Benyan Luo
- The First Affiliated Hospital, School of Medicine, Zhejiang University, Zhejiang, China 310003
| | - Chengyong Shen
- The First Affiliated Hospital, Institute of Translational Medicine, School of Medicine, Zhejiang University, Zhejiang, China 310003
- Department of Neurobiology, Key laboratory of Medical Neurobiology of Zhejiang Province, School of Medicine, Zhejiang University, Zhejiang, China 310058
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3
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Liu Y, Sugiura Y, Chen F, Lee KF, Ye Q, Lin W. Blocking skeletal muscle DHPRs/Ryr1 prevents neuromuscular synapse loss in mutant mice deficient in type III Neuregulin 1 (CRD-Nrg1). PLoS Genet 2019; 15:e1007857. [PMID: 30870432 PMCID: PMC6417856 DOI: 10.1371/journal.pgen.1007857] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 11/28/2018] [Indexed: 11/22/2022] Open
Abstract
Schwann cells are integral components of vertebrate neuromuscular synapses; in their absence, pre-synaptic nerve terminals withdraw from post-synaptic muscles, leading to muscle denervation and synapse loss at the developing neuromuscular junction (NMJ). Here, we report a rescue of muscle denervation and neuromuscular synapses loss in type III Neuregulin 1 mutant mice (CRD-Nrg1-/-), which lack Schwann cells. We found that muscle denervation and neuromuscular synapse loss were prevented in CRD-Nrg1-/-mice when presynaptic activity was blocked by ablating a specific gene, such as Snap25 (synaptosomal-associated 25 kDa protein) or Chat (choline acetyltransferase). Further, these effects were mediated by a pathway that requires postsynaptic acetylcholine receptors (AChRs), because ablating Chrna1 (acetylcholine receptor α1 subunit), which encodes muscle-specific AChRs in CRD-Nrg1-/-mice also rescued muscle denervation. Moreover, genetically ablating muscle dihydropyridine receptor (DHPR) β1 subunit (Cacnb1) or ryanodine receptor 1 (Ryr1) also rescued muscle denervation and neuromuscular synapse loss in CRD-Nrg1-/-mice. Thus, these genetic manipulations follow a pathway-from presynaptic to postsynaptic, and, ultimately to muscle activity mediated by DHPRs and Ryr1. Importantly, electrophysiological analyses reveal robust synaptic activity in the rescued, Schwann-cell deficient NMJs in CRD-Nrg1-/-Cacnb1-/-or CRD-Nrg1-/-Ryr1-/-mutant mice. Thus, a blockade of synaptic activity, although sufficient, is not necessary to preserve NMJs that lack Schwann cells. Instead, a blockade of muscle activity mediated by DHRPs and Ryr1 is both necessary and sufficient for preserving NMJs that lack Schwann cells. These findings suggest that muscle activity mediated by DHPRs/Ryr1 may destabilize developing NMJs and that Schwann cells play crucial roles in counteracting such a destabilizing activity to preserve neuromuscular synapses during development.
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Affiliation(s)
- Yun Liu
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, United States of America
| | - Yoshie Sugiura
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, United States of America
| | - Fujun Chen
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, United States of America
| | - Kuo-Fen Lee
- The Salk Institute, La Jolla, United States of America
| | - Qiaohong Ye
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, United States of America
| | - Weichun Lin
- Department of Neuroscience, UT Southwestern Medical Center, Dallas, United States of America
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4
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Wang JY, Chen F, Fu XQ, Ding CS, Zhou L, Zhang XH, Luo ZG. Caspase-3 cleavage of dishevelled induces elimination of postsynaptic structures. Dev Cell 2014; 28:670-84. [PMID: 24631402 DOI: 10.1016/j.devcel.2014.02.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Revised: 12/17/2013] [Accepted: 02/13/2014] [Indexed: 11/19/2022]
Abstract
During the development of vertebrate neuromuscular junction (NMJ), agrin stabilizes, whereas acetylcholine (ACh) destabilizes AChR clusters, leading to the refinement of synaptic connections. The intracellular mechanism underlying this counteractive interaction remains elusive. Here, we show that caspase-3, the effector protease involved in apoptosis, mediates elimination of AChR clusters. We found that caspase-3 was activated by cholinergic stimulation of cultured muscle cells without inducing cell apoptosis and that this activation was prevented by agrin. Interestingly, inhibition of caspase-3 attenuated ACh agonist-induced dispersion of AChR clusters. Furthermore, we identified Dishevelled1 (Dvl1), a Wnt signaling protein involved in AChR clustering, as the substrate of caspase-3. Blocking Dvl1 cleavage prevented induced dispersion of AChR clusters. Finally, inhibition or genetic ablation of caspase-3 or expression of a caspase-3-resistant form of Dvl1 caused stabilization of aneural AChR clusters. Thus, caspase-3 plays an important role in the elimination of postsynaptic structures during the development of NMJs.
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MESH Headings
- Acetylcholine/metabolism
- Adaptor Proteins, Signal Transducing/antagonists & inhibitors
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Agrin/physiology
- Animals
- Caspase 3/metabolism
- Cells, Cultured
- Dishevelled Proteins
- Electrophysiology
- Embryo, Mammalian/cytology
- Embryo, Mammalian/metabolism
- Image Processing, Computer-Assisted
- Immunoenzyme Techniques
- Mice
- Mice, Knockout
- Motor Neurons/cytology
- Motor Neurons/metabolism
- Muscle, Skeletal/cytology
- Muscle, Skeletal/metabolism
- Neuromuscular Junction/physiology
- Phosphoproteins/antagonists & inhibitors
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- RNA, Small Interfering/genetics
- Rats
- Rats, Sprague-Dawley
- Receptors, Cholinergic/metabolism
- Signal Transduction
- Synaptic Potentials/physiology
- Synaptic Transmission
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Affiliation(s)
- Jin-Yuan Wang
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China; Graduate School, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Fei Chen
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Xiu-Qing Fu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China; Graduate School, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Chuang-Shi Ding
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China; School of Life Science and Technology, ShanghaiTech University, 319 Yueyang Road, Shanghai 200031, China
| | - Li Zhou
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China; Graduate School, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Xiao-Hui Zhang
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Zhen-Ge Luo
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China; Graduate School, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China; School of Life Science and Technology, ShanghaiTech University, 319 Yueyang Road, Shanghai 200031, China.
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5
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Naumenko NV, Uzinskaya KV, Shakirzyanova AV, Urazaev AK, Zefirov AL. Adenosine triphosphoric acid as a factor of nervous regulation of Na+/K+/2Cl- cotransport in rat skeletal muscle fibers. Bull Exp Biol Med 2010; 147:583-6. [PMID: 19907744 DOI: 10.1007/s10517-009-0575-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Exogenous adenosine triphosphoric acid produces a biphasic effect on the resting membrane potential of muscle fibers in rat diaphragm. Depolarization of the sarcolemma observed 10 min after application of adenosine triphosphoric acid results from activation of Na(+)/K(+)/2Cl(-) cotransport. The increase in chloride cotransport is related to activation of postsynaptic P2Y receptors and protein kinase C. Repolarization of the membrane develops 40 min after treatment with adenosine triphosphoric acid and after 50 min the resting membrane potential almost returns the control level. This increase in the resting membrane potential of the sarcolemma is probably associated with activation of the Na(+)/K(+) pump and increase in membrane permeability for chlorine ions in response to long-term activity of Cl(-) cotransport. Thus, adenosine triphosphoric acid co-secreted with acetylcholine in the neuromuscular synapse probably plays a role in the regulation resting membrane potential and cell volume of muscle fibers.
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Affiliation(s)
- N V Naumenko
- Kazan State Medical University, Tatarstan, Russia.
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6
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Jia M, Li MX, Fields RD, Nelson PG. Extracellular ATP in activity-dependent remodeling of the neuromuscular junction. Dev Neurobiol 2007; 67:924-32. [PMID: 17506503 DOI: 10.1002/dneu.20402] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Electrical activity during early development affects the development and maintenance of synapses (Spitzer [2006]: Nature 4447:707-712), but the intercellular signals regulating maintenance of synapses are not well identified. At the neuromuscular junction, adenosine 5-triphosphate (ATP) is coreleased with acetylcholine at activated nerve terminals to modulate synaptic function. Here we use cocultured mouse motor neurons and muscle cells in a three-compartment cell culture chamber to test whether endogenously released ATP plays a role in activity-dependent maintenance of neuromuscular synapses. The results suggest that ATP release at the synapse counters the negative effect of electrical activity, thus stabilizing activated synapses. Confirming our previous work (Li et al. [2001]: Nat Neurosci 4:871-872), we found that in doubly innervated muscles, electrical stimulation induced heterosynaptic downregulation of the nonstimulated convergent input to the muscle fiber with no or little change of the stimulated inputs. However, in preparations that were stimulated in the presence of apyrase, an enzyme that degrades extracellular ATP, synapse downregulation of stimulated inputs was substantial and significant, and end plate potentials were reduced. Apyrase treatment for 20 h in the absence of stimulation did result in moderate diminution, but this was prevented by blocking spontaneous neural activity with tetrodotoxin. The P2 receptor blocker, suramin, also induced activity-dependent synapse diminution. The decrease in synaptic efficacy produced by prolonged stimulation in the presence of apyrase persisted for greater than 20 h, consistent with a developmental time-course and distinct from the rapid neuromodulatory actions of ATP that have been demonstrated by others. We conclude that extracellular ATP promotes stabilization of the neuromuscular junction and may play a role in activity-dependent synaptic modification during development.
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Affiliation(s)
- Min Jia
- National Institute of Child Health and Human Development, The National Institutes of Health, Bethesda, Maryland 20892, USA.
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7
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Ryten M, Koshi R, Knight GE, Turmaine M, Dunn P, Cockayne DA, Ford APW, Burnstock G. Abnormalities in neuromuscular junction structure and skeletal muscle function in mice lacking the P2X2 nucleotide receptor. Neuroscience 2007; 148:700-11. [PMID: 17706883 DOI: 10.1016/j.neuroscience.2007.06.050] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Revised: 06/25/2007] [Accepted: 07/05/2007] [Indexed: 11/30/2022]
Abstract
ATP is co-released in significant quantities with acetylcholine from motor neurons at skeletal neuromuscular junctions (NMJ). However, the role of this neurotransmitter in muscle function remains unclear. The P2X2 ion channel receptor subunit is expressed during development of the skeletal NMJ, but not in adult muscle fibers, although it is re-expressed during muscle fiber regeneration. Using mice deficient for the P2X2 receptor subunit for ATP (P2X2(-/-)), we demonstrate a role for purinergic signaling in NMJ development. Whereas control NMJs were characterized by precise apposition of pre-synaptic motor nerve terminals and post-synaptic junctional folds rich in acetylcholine receptors (AChRs), NMJs in P2X2(-/-) mice were disorganized: misapposition of nerve terminals and post-synaptic AChR expression localization was common; the density of post-synaptic junctional folds was reduced; and there was increased end-plate fragmentation. These changes in NMJ structure were associated with muscle fiber atrophy. In addition there was an increase in the proportion of fast type muscle fibers. These findings demonstrate a role for P2X2 receptor-mediated signaling in NMJ formation and suggest that purinergic signaling may play an as yet largely unrecognized part in synapse formation.
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Affiliation(s)
- M Ryten
- Autonomic Neuroscience Centre, Royal Free and University College Medical School, Rowland Hill Street, London NW3 2PF, UK
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8
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Lin W, Dominguez B, Yang J, Aryal P, Brandon EP, Gage FH, Lee KF. Neurotransmitter acetylcholine negatively regulates neuromuscular synapse formation by a Cdk5-dependent mechanism. Neuron 2005; 46:569-79. [PMID: 15944126 DOI: 10.1016/j.neuron.2005.04.002] [Citation(s) in RCA: 176] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2004] [Revised: 12/23/2004] [Accepted: 04/03/2005] [Indexed: 10/25/2022]
Abstract
Synapse formation requires interactions between pre- and postsynaptic cells to establish the connection of a presynaptic nerve terminal with the neurotransmitter receptor-rich postsynaptic apparatus. At developing vertebrate neuromuscular junctions, acetylcholine receptor (AChR) clusters of nascent postsynaptic apparatus are not apposed by presynaptic nerve terminals. Two opposing activities subsequently promote the formation of synapses: positive signals stabilize the innervated AChR clusters, whereas negative signals disperse those that are not innervated. Although the nerve-derived protein agrin has been suggested to be a positive signal, the negative signals remain elusive. Here, we show that cyclin-dependent kinase 5 (Cdk5) is activated by ACh agonists and is required for the ACh agonist-induced dispersion of the AChR clusters that have not been stabilized by agrin. Genetic elimination of Cdk5 or blocking ACh production prevents the dispersion of AChR clusters in agrin mutants. Therefore, we propose that ACh negatively regulates neuromuscular synapse formation through a Cdk5-dependent mechanism.
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Affiliation(s)
- Weichun Lin
- The Salk Institute, La Jolla, California 92037, USA
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9
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Martinez-Pena y Valenzuela I, Hume RI, Krejci E, Akaaboune M. In vivo regulation of acetylcholinesterase insertion at the neuromuscular junction. J Biol Chem 2005; 280:31801-8. [PMID: 15998641 DOI: 10.1074/jbc.m502874200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The efficiency of synaptic transmission between nerve and muscle depends on the number and density of acetylcholinesterase molecules (AChE) at the neuromuscular junction. However, little is known about the way this density is maintained and regulated in vivo. By using time lapse and quantitative fluorescence imaging assays in living mice, we demonstrated that insertion of new AChEs occurs within hours of saturating pre-existing AChEs with fasciculin2, a snake toxin that selectively labels AChE. In the absence of muscle postsynaptic activity or evoked nerve presynaptic neurotransmitter release, AChE insertion was decreased significantly, whereas direct stimulation of the muscle completely restored AChE insertion to control levels. This activity-dependent AChE insertion is mediated by intracellular calcium. In muscle stimulated in the presence of a Ca2+ channel blocker or calcium-permeable Ca2+ chelator, AChE insertion into synapses was significantly decreased, whereas ryanodine or ionophore A12387 treatment of blocked and unstimulated synapses significantly increased AChE insertion. These results demonstrated that synaptic activity is critical for AChE insertion and indicated that a rise in intracellular calcium either through voltage-gated calcium channels or from intracellular stores is critical for proper AChE insertion into the adult synapse.
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10
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Ling KKY, Siow NL, Choi RCY, Tsim KWK. ATP potentiates the formation of AChR aggregate in the co-culture of NG108-15 cells with C2C12 myotubes. FEBS Lett 2005; 579:2469-74. [PMID: 15848190 DOI: 10.1016/j.febslet.2005.03.054] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Revised: 02/17/2005] [Accepted: 03/22/2005] [Indexed: 11/30/2022]
Abstract
The role of adenosine 5'-triphosphate (ATP) and P2Y(1) nucleotide receptor in potentiating agrin-induced acetylcholine receptor (AChR) aggregation is being demonstrated in a co-culture system of NG108-15 cell, a mouse neuroblastoma X rat glioma hybrid cell line that resembles spinal motor neuron, with C2C12 myotube. In the co-cultures, antagonized P2Y(1) receptors showed a reduction in NG108-15 cell-induced AChR aggregation. Parallel to this observation, cultured NG108-15 cell secreted ATP into the conditioned medium in a time-dependent manner. Enhancement of ATP release from the cultured NG108-15 cells by overexpression of active mutants of small GTPases increased the aggregation of AChRs in co-culturing with C2C12 myotubes. In addition, ecto-nucleotidase was revealed in the co-culture, which rapidly degraded the applied ATP. These results support the notion that ATP has a role in directing the formation of post-synaptic apparatus in vertebrate neuromuscular junctions.
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Affiliation(s)
- Karen K Y Ling
- Department of Biology and Molecular Neuroscience Center, The Hong Kong University of Science and Technology, China
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11
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Ling KKY, Siow NL, Choi RCY, Ting AKL, Kong LW, Tsim KWK. ATP potentiates agrin-induced AChR aggregation in cultured myotubes: activation of RhoA in P2Y1 nucleotide receptor signaling at vertebrate neuromuscular junctions. J Biol Chem 2004; 279:31081-8. [PMID: 15145960 DOI: 10.1074/jbc.m403316200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
At vertebrate neuromuscular junctions, ATP is known to stabilize acetylcholine in the synaptic vesicles and to be co-released with it. We have shown previously that a nucleotide receptor, P2Y(1) receptor, is localized at the nmjs, and we propose that this mediates a trophic role for synaptic ATP there. In cultured myotubes, the activation of P2Y(1) receptors modulated agrin-induced acetylcholine receptor (AChR) aggregation in a potentiation manner. This potentiation effect in agrin-induced AChR aggregation was reduced by antagonizing the P2Y(1) receptors. The guanosine triphosphatase RhoA was shown to be responsible for this P2Y(1)-potentiated effect. The localization of RhoA in rat and chicken skeletal muscles was restricted at the neuromuscular junctions. Application of P2Y(1) agonists in cultured myotubes induced RhoA activation, which showed an additive effect with agrin-induced RhoA activation. Over-expression of dominant-negative mutant of RhoA in cultured myotubes diminished the agrin-induced AChR aggregation, as well as the potentiation effect of P2Y(1)-specific agonist. Application of UTP in the cultures also triggered similar responses as did 2-methylthioadenosine 5'-diphosphate, suggesting the involvement of other subtypes of P2Y receptors. These results demonstrate that RhoA could serve as a downstream mediator of signaling mediated by P2Y(1) receptor and agrin, which therefore synergizes the effects of the two neuron-derived trophic factors in modulating the formation and/or maintenance of post-synaptic apparatus at the neuromuscular junctions.
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Affiliation(s)
- Karen K Y Ling
- Department of Biology and Molecular Neuroscience Center, Hong Kong University of Science and Technology, Hong Kong, China
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12
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Szabo M, Salpeter EE, Randall W, Salpeter MM. Transients in acetylcholine receptor site density and degradation during reinnervation of mouse sternomastoid muscle. J Neurochem 2003; 84:180-8. [PMID: 12485414 DOI: 10.1046/j.1471-4159.2003.01542.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The degradation rates of acetylcholine receptors (AchRs) were evaluated at the neuromuscular junction during and just after reinnervation of denervated muscles. When mouse sternomastoid muscles are denervated by multiple nerve crush, reinnervation begins 2-4 days later and is complete by day 7-9 after the last crush. In fully innervated muscles, the AChR degradation rate is stable and slow (t1/2 approximately 10 days), whereas after denervation the newly inserted receptors degrade rapidly (t1/2 approximately 1.2 days). The composite profile of degradation, which a mixture of the stable and the rapid receptors would give, is not observed during reinnervation. Instead, the receptors inserted between 2.5 and 7.5 days after the last crush all have an intermediate degradation rate of t1/2 approximately 3.7 days with standard error +/- 0.3 days. The total receptor site density at the endplate was evaluated during denervation and during reinnervation. As predicted theoretically, the site density increased substantially, but temporarily, after denervation. An analogous deleterious substantial decrease in density would be expected during reinnervation, without the intermediate receptor. This decrease is not observed, however, because of a large insertion rate at intermediate times (3000 +/- 700 receptor complexes per micro m2 per day). The endplate density of receptors thus remains relatively constant.
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Affiliation(s)
- Maria Szabo
- Department of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853, USA
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13
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Expression of the P2Y1 nucleotide receptor in chick muscle: its functional role in the regulation of acetylcholinesterase and acetylcholine receptor. J Neurosci 2002. [PMID: 11717356 DOI: 10.1523/jneurosci.21-23-09224.2001] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In vertebrate neuromuscular junctions, ATP is stored at the motor nerve terminals and is co-released with acetylcholine during neural stimulation. Here, we provide several lines of evidence that the synaptic ATP can act as a synapse-organizing factor to induce the expression of acetylcholinesterase (AChE) and acetylcholine receptor (AChR) in muscles, mediated by a metabotropic ATP receptor subtype, the P2Y(1) receptor. The activation of the P2Y(1) receptor by adenine nucleotides stimulated the accumulation of inositol phosphates and intracellular Ca(2+) mobilization in cultured chick myotubes. P2Y(1) receptor mRNA in chicken muscle is very abundant before hatching and again increases in the adult. The P2Y(1) receptor protein is shown to be restricted to the neuromuscular junctions and colocalized with AChRs in adult muscle (chicken, Xenopus, and rat) but not in the chick embryo. In chicks after hatching, this P2Y(1) localization develops over approximately 3 weeks. Denervation or crush of the motor nerve (in chicken or rat) caused up to 90% decrease in the muscle P2Y(1) transcript, which was restored on regeneration, whereas the AChR mRNA greatly increased. Last, mRNAs encoding the AChE catalytic subunit and the AChR alpha-subunit were induced when the P2Y(1) receptors were activated by specific agonists or by overexpression of P2Y(1) receptors in cultured myotubes; those agonists likewise induced the activity in the myotubes of promoter-reporter gene constructs for those subunits, actions that were blocked by a P2Y(1)-specific antagonist. These results provide evidence for a novel function of ATP in regulating the gene expression of those two postsynaptic effectors.
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Choi RC, Man ML, Ling KK, Ip NY, Simon J, Barnard EA, Tsim KW. Expression of the P2Y1 nucleotide receptor in chick muscle: its functional role in the regulation of acetylcholinesterase and acetylcholine receptor. J Neurosci 2001; 21:9224-34. [PMID: 11717356 PMCID: PMC6763911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2001] [Revised: 09/06/2001] [Accepted: 09/12/2001] [Indexed: 02/22/2023] Open
Abstract
In vertebrate neuromuscular junctions, ATP is stored at the motor nerve terminals and is co-released with acetylcholine during neural stimulation. Here, we provide several lines of evidence that the synaptic ATP can act as a synapse-organizing factor to induce the expression of acetylcholinesterase (AChE) and acetylcholine receptor (AChR) in muscles, mediated by a metabotropic ATP receptor subtype, the P2Y(1) receptor. The activation of the P2Y(1) receptor by adenine nucleotides stimulated the accumulation of inositol phosphates and intracellular Ca(2+) mobilization in cultured chick myotubes. P2Y(1) receptor mRNA in chicken muscle is very abundant before hatching and again increases in the adult. The P2Y(1) receptor protein is shown to be restricted to the neuromuscular junctions and colocalized with AChRs in adult muscle (chicken, Xenopus, and rat) but not in the chick embryo. In chicks after hatching, this P2Y(1) localization develops over approximately 3 weeks. Denervation or crush of the motor nerve (in chicken or rat) caused up to 90% decrease in the muscle P2Y(1) transcript, which was restored on regeneration, whereas the AChR mRNA greatly increased. Last, mRNAs encoding the AChE catalytic subunit and the AChR alpha-subunit were induced when the P2Y(1) receptors were activated by specific agonists or by overexpression of P2Y(1) receptors in cultured myotubes; those agonists likewise induced the activity in the myotubes of promoter-reporter gene constructs for those subunits, actions that were blocked by a P2Y(1)-specific antagonist. These results provide evidence for a novel function of ATP in regulating the gene expression of those two postsynaptic effectors.
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MESH Headings
- Acetylcholinesterase/metabolism
- Adenine Nucleotides/pharmacology
- Adenosine Triphosphate/metabolism
- Aging/metabolism
- Animals
- COS Cells
- Calcium/metabolism
- Cells, Cultured
- Chick Embryo
- Chickens
- Inositol Phosphates/metabolism
- Motor Neurons/physiology
- Muscle, Skeletal/cytology
- Muscle, Skeletal/metabolism
- Nerve Crush
- Nerve Regeneration/physiology
- Neuromuscular Junction/metabolism
- RNA, Messenger/metabolism
- Rats
- Receptors, Cholinergic/genetics
- Receptors, Cholinergic/metabolism
- Receptors, Purinergic P2/biosynthesis
- Receptors, Purinergic P2/drug effects
- Receptors, Purinergic P2/genetics
- Receptors, Purinergic P2Y1
- Spinal Cord/metabolism
- Transfection
- Xenopus
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Affiliation(s)
- R C Choi
- Department of Biology, Molecular Neuroscience Center and Biotechnology Research Institute, Hong Kong University of Science and Technology, Hong Kong, China
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15
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Sava A, Barisone I, Di Mauro D, Fumagalli G, Sala C. Modulation of nicotinic acetylcholine receptor turnover by tyrosine phosphorylation in rat myotubes. Neurosci Lett 2001; 313:37-40. [PMID: 11684334 DOI: 10.1016/s0304-3940(01)02244-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The muscle nicotinic acetylcholine receptor (AChR) turns over at different rates depending on stage of synaptogenesis and innervation. Tyrosine phosphorylation modulates desensitization, interaction with cytoskeleton and lateral mobility in the membrane of AChR. To determine whether tyrosine phosphorylation also modulates the turnover of AChR, myotubes in vitro were exposed to the tyrosine phosphatase inhibitor pervanadate. Our data indicate that a transient increase of phosphotyrosine levels stabilized a fraction of AChRs. The effects were limited to the non-epsilon subunit-containing AChRs already present in the membrane. Tyrosine phosphorylation of the receptor occurred on the beta subunit, was transient and stable molecules were not selectively tyrosine phosphorylated. The data indicate that modulation of phosphotyrosine levels in muscle cells provides signals to control AChR metabolic stability.
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Affiliation(s)
- A Sava
- Department of Medicine & Public Health, Section of Pharmacology, School of Medicine, University of Verona, Policlinico Borgo Roma, 37134 Verona, Italy
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16
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Bezakova G, Rabben I, Sefland I, Fumagalli G, Lømo T. Neural agrin controls acetylcholine receptor stability in skeletal muscle fibers. Proc Natl Acad Sci U S A 2001; 98:9924-9. [PMID: 11493710 PMCID: PMC55554 DOI: 10.1073/pnas.171539698] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2000] [Indexed: 11/18/2022] Open
Abstract
At mammalian neuromuscular junctions (NMJs), innervation induces and maintains the metabolic stability of acetylcholine receptors (AChRs). To explore whether neural agrin may cause similar receptor stabilization, we injected neural agrin cDNA of increasing transfection efficiencies into denervated adult rat soleus (SOL) muscles. As the efficiency increased, the amount of recombinant neural agrin expressed in the muscles also increased. This agrin aggregated AChRs on muscle fibers, whose half-life increased in a dose-dependent way from 1 to 10 days. Electrical muscle stimulation enhanced the stability of AChRs with short half-lives. Therefore, neural agrin can stabilize aggregated AChRs in a concentration- and activity-dependent way. However, there was no effect of stimulation on AChRs with a long half-life (10 days). Thus, at sufficiently high concentrations, neural agrin alone can stabilize AChRs to levels characteristic of innervated NMJs.
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Affiliation(s)
- G Bezakova
- Department of Physiology, University of Oslo, Norway
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17
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Long-term nicotine adaptation in Caenorhabditis elegans involves PKC-dependent changes in nicotinic receptor abundance. J Neurosci 2001. [PMID: 11102488 DOI: 10.1523/jneurosci.20-23-08802.2000] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Chronic exposure to nicotine leads to long-term changes in both the abundance and activity of nicotinic acetylcholine receptors, processes thought to contribute to nicotine addiction. We have found that in Caenorhabditis elegans, prolonged nicotine treatment results in a long-lasting decrease in the abundance of nicotinic receptors that control egg-laying. In naive animals, acute exposure to cholinergic agonists led to the efficient stimulation of egg-laying, a response mediated by a nicotinic receptor functionally expressed in the vulval muscle cells. Overnight exposure to nicotine led to a specific and long-lasting change in egg-laying behavior, which rendered the nicotine-adapted animals insensitive to simulation of egg-laying by the nicotinic agonist and was accompanied by a promoter-independent reduction in receptor protein levels. Mutants defective in the gene tpa-1, which encodes a homolog of protein kinase C (PKC), failed to undergo adaptation to nicotine; after chronic nicotine exposure they remained sensitive to cholinergic agonists and retained high levels of receptor protein in the vulval muscles. These results suggest that PKC-dependent signaling pathways may promote nicotine adaptation via regulation of nicotinic receptor synthesis or degradation.
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18
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Waggoner LE, Dickinson KA, Poole DS, Tabuse Y, Miwa J, Schafer WR. Long-term nicotine adaptation in Caenorhabditis elegans involves PKC-dependent changes in nicotinic receptor abundance. J Neurosci 2000; 20:8802-11. [PMID: 11102488 PMCID: PMC6773091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023] Open
Abstract
Chronic exposure to nicotine leads to long-term changes in both the abundance and activity of nicotinic acetylcholine receptors, processes thought to contribute to nicotine addiction. We have found that in Caenorhabditis elegans, prolonged nicotine treatment results in a long-lasting decrease in the abundance of nicotinic receptors that control egg-laying. In naive animals, acute exposure to cholinergic agonists led to the efficient stimulation of egg-laying, a response mediated by a nicotinic receptor functionally expressed in the vulval muscle cells. Overnight exposure to nicotine led to a specific and long-lasting change in egg-laying behavior, which rendered the nicotine-adapted animals insensitive to simulation of egg-laying by the nicotinic agonist and was accompanied by a promoter-independent reduction in receptor protein levels. Mutants defective in the gene tpa-1, which encodes a homolog of protein kinase C (PKC), failed to undergo adaptation to nicotine; after chronic nicotine exposure they remained sensitive to cholinergic agonists and retained high levels of receptor protein in the vulval muscles. These results suggest that PKC-dependent signaling pathways may promote nicotine adaptation via regulation of nicotinic receptor synthesis or degradation.
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Affiliation(s)
- L E Waggoner
- Department of Biology, University of California, San Diego, La Jolla, California 92093-0349, USA
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19
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Lanuza MA, Li MX, Jia M, Kim S, Davenport R, Dunlap V, Nelson PG. Protein kinase C-mediated changes in synaptic efficacy at the neuromuscular junction in vitro: the role of postsynaptic acetylcholine receptors. J Neurosci Res 2000; 61:616-25. [PMID: 10972958 DOI: 10.1002/1097-4547(20000915)61:6<616::aid-jnr5>3.0.co;2-n] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Activation of a mouse in vitro neuromuscular synapse produces a reduction in synaptic efficacy which is greater for nonactivated than for activated inputs to the myotubes. This has been shown to require thrombin and thrombin receptor activation and to involve a protein kinase C (PKC)-mediated step. We show in the present work that phorbol ester activation of PKC produces physiological loss of synapses in a time- and dose-related manner. We observe, using quantitative imaging methods, a parallel loss of acetylcholine receptors (AChR) from synaptically functional neurite-associated receptor aggregates in nerve-muscle cocultures. Biochemical measurements of total AChR show that PKC activation reduces both AChR stability (increases receptor loss) and receptor insertion into the surface membrane. Taken together, the data suggest that PKC activation decreases the stability of AChR aggregates in the muscle surface membrane. We conclude that PKC plays a crucial role in activity-dependent synapse reduction and does so, at least in part, by altering AChR stability.
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Affiliation(s)
- M A Lanuza
- Unitat díHistologia i Neurobiologia, Facultat Medicina i Ciencies de la Salut, Universitat Rovira i Virgili, Reus, Spain
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20
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Choi RC, Siow NL, Zhu SQ, Tsim KW. The cAMP-dependent protein kinase mediates the expression of AChE in chick myotubes. Neuroreport 2000; 11:801-6. [PMID: 10757523 DOI: 10.1097/00001756-200003200-00029] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Calcitonin gene-related peptide (CGRP), a neuropeptide synthesized by motor neurons, stimulates the expression of AChR and AChE at the vertebrate neuromuscular junctions. The signaling mechanism of CGRP-induced AChE expression in muscle was determined both in vitro and in vivo. In cultured chick myotubes, the intracellular cAMP-dependent protein kinase (PKA) activity increased to approximately 2-fold after the application of CGRP or PKA activators; the induction was blocked by PKA inhibitors. in vivo transfection analysis on chick gastrocnemius muscles showed that the transfection of cDNA encoding constitutively active mutant Galphas increased the expression of AChE mRNA and protein to approximately 2-fold, while the constitutively active mutant Galphai cDNA transfection showed an opposite effect. The induced catalytic subunit of AChE at approximately 105 kDa was determined by specific antibody. These findings indicate that the CGRP-induced AChE expression in chick muscle is mediated by a PKA-dependent pathway.
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Affiliation(s)
- R C Choi
- Department of Biology and Biotechnology Research Institute, The Hong Kong University of Science and Technology, Kowloon, China
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21
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Gonzalez M, Ruggiero FP, Chang Q, Shi YJ, Rich MM, Kraner S, Balice-Gordon RJ. Disruption of Trkb-mediated signaling induces disassembly of postsynaptic receptor clusters at neuromuscular junctions. Neuron 1999; 24:567-83. [PMID: 10595510 DOI: 10.1016/s0896-6273(00)81113-7] [Citation(s) in RCA: 177] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Neurotrophins and tyrosine receptor kinase (Trk) receptors are expressed in skeletal muscle, but it is unclear what functional role Trk-mediated signaling plays during postnatal life. Full-length TrkB (trkB.FL) as well as truncated TrkB (trkB.t1) were found to be localized primarily to the postsynaptic acetylcholine receptor- (AChR-) rich membrane at neuromuscular junctions. In vivo, dominant-negative manipulation of TrkB signaling using adenovirus to overexpress trkB.t1 in mouse sternomastoid muscle fibers resulted in the disassembly of postsynaptic AChR clusters at neuromuscular junctions, similar to that observed in mutant trkB+/- mice. When TrkB-mediated signaling was disrupted in cultured myotubes in the absence of motor nerve terminals and Schwann cells, agrin-induced AChR clusters were also disassembled. These results demonstrate a novel role for neurotrophin signaling through TrkB receptors on muscle fibers in the ongoing maintenance of postsynaptic AChR regions.
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Affiliation(s)
- M Gonzalez
- Department of Neuroscience University of Pennsylvania School of Medicine, Philadelphia 19104, USA
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22
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Abstract
We describe the formation, maturation, elimination, maintenance, and regeneration of vertebrate neuromuscular junctions (NMJs), the best studied of all synapses. The NMJ forms in a series of steps that involve the exchange of signals among its three cellular components--nerve terminal, muscle fiber, and Schwann cell. Although essentially any motor axon can form NMJs with any muscle fiber, an additional set of cues biases synapse formation in favor of appropriate partners. The NMJ is functional at birth but undergoes numerous alterations postnatally. One step in maturation is the elimination of excess inputs, a competitive process in which the muscle is an intermediary. Once elimination is complete, the NMJ is maintained stably in a dynamic equilibrium that can be perturbed to initiate remodeling. NMJs regenerate following damage to nerve or muscle, but this process differs in fundamental ways from embryonic synaptogenesis. Finally, we consider the extent to which the NMJ is a suitable model for development of neuron-neuron synapses.
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Affiliation(s)
- J R Sanes
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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23
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Sala C, Francolini M, Di Mauro D, Fumagalli G. Role of subunit composition in determining acetylcholine receptor degradation rates in rat myotubes. Neurosci Lett 1998; 256:1-4. [PMID: 9832202 DOI: 10.1016/s0304-3940(98)00752-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
During neuromuscular junction maturation, the rapidly degrading receptors (Rr; t1/2 approximately equal to 1 day) are replaced by metabolically stable molecules (Rs; t1/2 approximately equal to 10 days). Rr and Rs do not interconvert, are differently regulated after denervation in adult muscle and are endowed of unique responses to stabilizing agents. In cultured rat myotubes all the epsilon subunit-containing acetylcholine receptors (epsilon-AchRs) are of the Rs type. In the present study we show that Rs exist also in absence of epsilon-AChR and that nonepsilon-(presumably gamma-)AChRs can be included in the Rs pool when epsilon-AChR expression is low. The data indicate that Rs metabolic properties are independent of AChR subunit composition and that epsilon subunit is a signal to efficiently sort AChR molecules to the Rs pool.
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Affiliation(s)
- C Sala
- CNR Center of Cellular and Molecular Pharmacology, Department of Medical Pharmacology, University of Milano, Milan, Italy
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24
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Rossi S, Katz S, Rotundo R. Control of acetylcholinesterase gene expression in tissue-cultured skeletal muscle: Opposite regulation by protein kinases A and C. ACTA ACUST UNITED AC 1998. [DOI: 10.1016/s0928-4257(99)80102-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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25
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Szewczyk A, Pikuła S. Adenosine 5'-triphosphate: an intracellular metabolic messenger. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1365:333-53. [PMID: 9711292 DOI: 10.1016/s0005-2728(98)00094-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- A Szewczyk
- Department of Molecular and Cellular Neurobiology, Nencki Institute of Experimental Biology, Warsaw, Poland.
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26
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Epsilon subunit-containing acetylcholine receptors in myotubes belong to the slowly degrading population. J Neurosci 1997. [PMID: 9364041 DOI: 10.1523/jneurosci.17-23-08937.1997] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Two types of muscle acetylcholine receptors (AChRs) can be distinguished on the basis of their degradation rates and sensitivities to innervation, muscle activity, and agents elevating intracellular cAMP. The first type (Rs), is present in a stable form (degradation t1/2 = approximately 10 d) at the adult innervated neuromuscular junctions (NMJs). Rs can also exist in a less stable form (called accelerated Rs; t1/2 = approximately 3-5 d) at denervated NMJs and in aneurally cultured myotubes; agents that increase intracellular cAMP reversibly modulate Rs stability. The second type of AChR is a rapidly degrading receptor (Rr) expressed only in embryonic and noninnervated muscles. Rr can be stabilized by ATP and not by cAMP. This study tested the hypothesis that the degradation properties unique to the Rs are attributable to the presence of the epsilon subunit. Immunoprecipitation and Western blot analysis of AChRs extracted from rat muscle cells in tissue culture showed that AChRs recognized by antibodies against the epsilon subunit degraded as a single population with a half-life similar to that of the slow component, Rs, in these cells. In addition, as for Rs receptors in denervated NMJs and cultured muscle cell, the degradation rate of these epsilon-containing AChRs was stabilized by dibutyryl-cAMP. The data indicate that the epsilon-containing AChRs behave like Rs. Thus, the presence of the epsilon subunit is sufficient for selecting an AChR molecule to the Rs pool.
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27
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Sala C, O'Malley J, Xu R, Fumagalli G, Salpeter MM. Epsilon subunit-containing acetylcholine receptors in myotubes belong to the slowly degrading population. J Neurosci 1997; 17:8937-44. [PMID: 9364041 PMCID: PMC6573614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/1997] [Accepted: 09/12/1997] [Indexed: 02/05/2023] Open
Abstract
Two types of muscle acetylcholine receptors (AChRs) can be distinguished on the basis of their degradation rates and sensitivities to innervation, muscle activity, and agents elevating intracellular cAMP. The first type (Rs), is present in a stable form (degradation t1/2 = approximately 10 d) at the adult innervated neuromuscular junctions (NMJs). Rs can also exist in a less stable form (called accelerated Rs; t1/2 = approximately 3-5 d) at denervated NMJs and in aneurally cultured myotubes; agents that increase intracellular cAMP reversibly modulate Rs stability. The second type of AChR is a rapidly degrading receptor (Rr) expressed only in embryonic and noninnervated muscles. Rr can be stabilized by ATP and not by cAMP. This study tested the hypothesis that the degradation properties unique to the Rs are attributable to the presence of the epsilon subunit. Immunoprecipitation and Western blot analysis of AChRs extracted from rat muscle cells in tissue culture showed that AChRs recognized by antibodies against the epsilon subunit degraded as a single population with a half-life similar to that of the slow component, Rs, in these cells. In addition, as for Rs receptors in denervated NMJs and cultured muscle cell, the degradation rate of these epsilon-containing AChRs was stabilized by dibutyryl-cAMP. The data indicate that the epsilon-containing AChRs behave like Rs. Thus, the presence of the epsilon subunit is sufficient for selecting an AChR molecule to the Rs pool.
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Affiliation(s)
- C Sala
- Consiglio Nazionale delle Ricerche, Center of Cellular and Molecular Pharmacology, Department of Medical Pharmacology, University of Milan, 20129 Milan, Italy
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Abstract
Acetylcholine receptors (AChRs) are present at the top of the postsynaptic membrane of the neuromuscular junction (NMJ) at very high density, possibly anchored to cytoskeletal elements. The present study investigated whether AChR degradation is affected in animals lacking dystrophin, a protein that is an integral part of the cytoskeletal complex and is missing in Duchenne muscular dystrophy. The animal model for Duchenne muscular dystrophy, the mutant mdx mouse, was used to determine whether disruption of the cytoskeleton, caused by the absence of dystrophin, affects AChR degradation. Of the two populations of junctional AChRs, Rs (expressed in innervated adult muscles) and Rr (expressed in embryonic or denervated muscles), only Rs are affected in mdx animals. In innervated mdx soleus, diaphragm, and sternomastoid muscles, the AChRs have an accelerated degradation rate (t1/2 of approximately 3-5 d), similar to that acquired by Rs in control muscles after denervation. The Rs in mdx NMJs do not accelerate further when the muscles are denervated. The absence of dystrophin does not affect the degradation rate of the Rr AChRs (t1/2 of 1 d), which are expressed after denervation in mdx as in control muscles. These results suggest that dystrophin or an intact cytoskeletal complex may be required for neuronal stabilization of Rs receptors at the adult neuromuscular junctions.
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Xu R, Salpeter MM. Acetylcholine receptors in innervated muscles of dystrophic mdx mice degrade as after denervation. J Neurosci 1997; 17:8194-200. [PMID: 9334395 PMCID: PMC6573762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Acetylcholine receptors (AChRs) are present at the top of the postsynaptic membrane of the neuromuscular junction (NMJ) at very high density, possibly anchored to cytoskeletal elements. The present study investigated whether AChR degradation is affected in animals lacking dystrophin, a protein that is an integral part of the cytoskeletal complex and is missing in Duchenne muscular dystrophy. The animal model for Duchenne muscular dystrophy, the mutant mdx mouse, was used to determine whether disruption of the cytoskeleton, caused by the absence of dystrophin, affects AChR degradation. Of the two populations of junctional AChRs, Rs (expressed in innervated adult muscles) and Rr (expressed in embryonic or denervated muscles), only Rs are affected in mdx animals. In innervated mdx soleus, diaphragm, and sternomastoid muscles, the AChRs have an accelerated degradation rate (t1/2 of approximately 3-5 d), similar to that acquired by Rs in control muscles after denervation. The Rs in mdx NMJs do not accelerate further when the muscles are denervated. The absence of dystrophin does not affect the degradation rate of the Rr AChRs (t1/2 of 1 d), which are expressed after denervation in mdx as in control muscles. These results suggest that dystrophin or an intact cytoskeletal complex may be required for neuronal stabilization of Rs receptors at the adult neuromuscular junctions.
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Affiliation(s)
- R Xu
- Section of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853, USA
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