1
|
Bao Z, Cui C, Liu C, Long Y, Wong RMY, Chai S, Qin L, Rubin C, Yip BHK, Xu Z, Jiang Q, Chow SK, Cheung W. Prevention of age-related neuromuscular junction degeneration in sarcopenia by low-magnitude high-frequency vibration. Aging Cell 2024; 23:e14156. [PMID: 38532712 PMCID: PMC11258441 DOI: 10.1111/acel.14156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Revised: 03/11/2024] [Accepted: 03/12/2024] [Indexed: 03/28/2024] Open
Abstract
Neuromuscular junction (NMJ) degeneration is one of pathological factors of sarcopenia. Low-magnitude high-frequency vibration (LMHFV) was reported effective in alleviating the sarcopenia progress. However, no previous study has investigated treatment effects of LMHFV targeting NMJ degeneration in sarcopenia. We first compared morphological differences of NMJ between sarcopenic and non-sarcopenic subjects, as well as young and old C57BL/6 mice. We then systematically characterized the age-related degeneration of NMJ in SAMP8 against its control strain, SAMR1 mice, from 3 to 12 months old. We also investigated effects of LMHFV in SAMP8 on the maintenance of NMJ during the onset of sarcopenia with respect to the Agrin-LRP4-MuSK-Dok7 pathway and investigated the mechanism related to ERK1/2 signaling. We observed sarcopenic/old NMJ presented increased acetylcholine receptors (AChRs) cluster fragmentation and discontinuity than non-sarcopenic/young NMJ. In SAMP8, NMJ degeneration (morphologically at 6 months and functionally at 8 months) was observed associated with the sarcopenia onset (10 months). SAMR1 showed improved NMJ morphology and function compared with SAMP8 at 10 months. Skeletal muscle performance was improved at Month 4 post-LMHFV treatment. Vibration group presented improved NMJ function at Months 2 and 6 posttreatment, accompanied with alleviated morphological degeneration at Month 4 posttreatment. LMHFV increased Dok7 expression at Month 4 posttreatment. In vitro, LMHFV could promote AChRs clustering in myotubes by increasing Dok7 expression through suppressing ERK1/2 phosphorylation. In conclusion, NMJ degeneration was observed associated with the sarcopenia onset in SAMP8. LMHFV may attenuate NMJ degeneration and sarcopenia progression by increasing Dok7 expression through suppressing ERK1/2 phosphorylation.
Collapse
Affiliation(s)
- Zhengyuan Bao
- Musculoskleletal Research Laboratory, Department of Orthopaedics and Traumatology, Prince of Wales HospitalThe Chinese University of Hong KongHong Kong SARChina
- Division of Sports Medicine and Adult Reconstructive Surgery, Department of Orthopedic Surgery, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical SchoolNanjing UniversityNanjingJiangsuChina
| | - Can Cui
- Musculoskleletal Research Laboratory, Department of Orthopaedics and Traumatology, Prince of Wales HospitalThe Chinese University of Hong KongHong Kong SARChina
| | - Chaoran Liu
- Musculoskleletal Research Laboratory, Department of Orthopaedics and Traumatology, Prince of Wales HospitalThe Chinese University of Hong KongHong Kong SARChina
| | - Yufeng Long
- Musculoskleletal Research Laboratory, Department of Orthopaedics and Traumatology, Prince of Wales HospitalThe Chinese University of Hong KongHong Kong SARChina
| | - Ronald Man Yeung Wong
- Musculoskleletal Research Laboratory, Department of Orthopaedics and Traumatology, Prince of Wales HospitalThe Chinese University of Hong KongHong Kong SARChina
| | - Senlin Chai
- Musculoskleletal Research Laboratory, Department of Orthopaedics and Traumatology, Prince of Wales HospitalThe Chinese University of Hong KongHong Kong SARChina
- Division of Sports Medicine and Adult Reconstructive Surgery, Department of Orthopedic Surgery, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical SchoolNanjing UniversityNanjingJiangsuChina
| | - Ling Qin
- Musculoskleletal Research Laboratory, Department of Orthopaedics and Traumatology, Prince of Wales HospitalThe Chinese University of Hong KongHong Kong SARChina
| | - Clinton Rubin
- Department of Biomedical EngineeringStony Brook UniversityStony BrookNew YorkUSA
| | - Benjamin Hon Kei Yip
- School of Public Health and Primary Care, Faculty of MedicineThe Chinese University of Hong KongHong Kong SARChina
| | - Zhihong Xu
- Division of Sports Medicine and Adult Reconstructive Surgery, Department of Orthopedic Surgery, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical SchoolNanjing UniversityNanjingJiangsuChina
| | - Qing Jiang
- Division of Sports Medicine and Adult Reconstructive Surgery, Department of Orthopedic Surgery, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical SchoolNanjing UniversityNanjingJiangsuChina
| | - Simon Kwoon‐Ho Chow
- Musculoskleletal Research Laboratory, Department of Orthopaedics and Traumatology, Prince of Wales HospitalThe Chinese University of Hong KongHong Kong SARChina
- Department of Orthopaedic SurgeryStanford UniversityStanfordCaliforniaUSA
| | - Wing‐Hoi Cheung
- Musculoskleletal Research Laboratory, Department of Orthopaedics and Traumatology, Prince of Wales HospitalThe Chinese University of Hong KongHong Kong SARChina
- Li Ka Shing Institute of Health SciencesThe Chinese University of Hong KongHong Kong SARChina
| |
Collapse
|
2
|
Rudolf R, Kettelhut IC, Navegantes LCC. Sympathetic innervation in skeletal muscle and its role at the neuromuscular junction. J Muscle Res Cell Motil 2024; 45:79-86. [PMID: 38367152 PMCID: PMC11096211 DOI: 10.1007/s10974-024-09665-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Accepted: 01/30/2024] [Indexed: 02/19/2024]
Abstract
Neuromuscular junctions are the synapses between motor neurons and skeletal muscle fibers, which mediate voluntary muscle movement. Since neuromuscular junctions are also tightly associated with the capping function of terminal Schwann cells, these synapses have been classically regarded as tripartite chemical synapses. Although evidences from sympathetic innervation of neuromuscular junctions was described approximately a century ago, the essential presence and functional relevance of sympathetic contribution to the maintenance and modulation of neuromuscular junctions was demonstrated only recently. These findings shed light on the pathophysiology of different clinical conditions and can optimize surgical and clinical treatment modalities for skeletal muscle disorders.
Collapse
Affiliation(s)
- Rüdiger Rudolf
- Center for Mass Spectrometry and Optical Spectroscopy, Mannheim University of Applied Sciences, 68163, Mannheim, Germany.
- Interdisciplinary Center for Neurosciences, Heidelberg University, 69117, Heidelberg, Germany.
- Mannheim Center for Translational Neuroscience, Medical Faculty Mannheim Heidelberg University, 69167, Mannheim, Germany.
| | - Isis C Kettelhut
- Department of Biochemistry & Immunology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto-SP, 14049900, Brazil
| | - Luiz Carlos C Navegantes
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto-SP, 14049900, Brazil
| |
Collapse
|
3
|
Sun Y, Wang Y, Liu C, Huang Y, Long Q, Ju C, Zhang C, Chen Y. Targeted degradation of oncogenic BCR-ABL by silencing the gene of NEDD8 E3 ligase RAPSYN. J Nanobiotechnology 2024; 22:247. [PMID: 38741123 PMCID: PMC11089668 DOI: 10.1186/s12951-024-02505-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Accepted: 04/29/2024] [Indexed: 05/16/2024] Open
Abstract
Tyrosine kinase inhibitors have been the standard treatment for patients with Philadelphia chromosome-positive (Ph+) leukemia. However, a series of issues, including drug resistance, relapse and intolerance, are still an unmet medical need. Here, we report the targeted siRNA-based lipid nanoparticles in Ph+ leukemic cell lines for gene therapy of Ph+ leukemia, which specifically targets a recently identified NEDD8 E3 ligase RAPSYN in Ph+ leukemic cells to disrupt the neddylation of oncogenic BCR-ABL. To achieve the specificity for Ph+ leukemia therapy, a single-chain fragment variable region (scFv) of anti-CD79B monoclonal antibody was covalently conjugated on the surface of OA2-siRAPSYN lipid nanoparticles to generate the targeted lipid nanoparticles (scFv-OA2-siRAPSYN). Through effectively silencing RAPSYN gene in leukemic cell lines by the nanoparticles, BCR-ABL was remarkably degraded accompanied by the inhibition of proliferation and the promotion of apoptosis. The specific targeting, therapeutic effects and systemic safety were further evaluated and demonstrated in cell line-derived mouse models. The present study has not only addressed the clinical need of Ph+ leukemia, but also enabled gene therapy against a less druggable target.
Collapse
MESH Headings
- Animals
- Humans
- Mice
- Apoptosis/drug effects
- Cell Line, Tumor
- Cell Proliferation/drug effects
- Fusion Proteins, bcr-abl/genetics
- Fusion Proteins, bcr-abl/metabolism
- Gene Silencing
- Genetic Therapy/methods
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/drug therapy
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/therapy
- Mice, Inbred BALB C
- Nanoparticles/chemistry
- NEDD8 Protein/metabolism
- NEDD8 Protein/genetics
- RNA, Small Interfering
- Ubiquitin-Protein Ligases/metabolism
- Ubiquitin-Protein Ligases/genetics
- Muscle Proteins/metabolism
Collapse
Affiliation(s)
- Yanzi Sun
- State Key Laboratory of Natural Medicines and Laboratory of Chemical Biology, China Pharmaceutical University, 639 Longmian Ave, Nanjing, 211198, Jiangsu, China
| | - Yishu Wang
- State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, Center of Advanced Pharmaceuticals and Biomaterials, China Pharmaceutical University, Nanjing, 210009, People's Republic of China
| | - Chunyan Liu
- State Key Laboratory of Natural Medicines and Laboratory of Chemical Biology, China Pharmaceutical University, 639 Longmian Ave, Nanjing, 211198, Jiangsu, China
| | - Yingshuang Huang
- State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, Center of Advanced Pharmaceuticals and Biomaterials, China Pharmaceutical University, Nanjing, 210009, People's Republic of China
| | - Qiulin Long
- State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, Center of Advanced Pharmaceuticals and Biomaterials, China Pharmaceutical University, Nanjing, 210009, People's Republic of China
| | - Caoyun Ju
- State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, Center of Advanced Pharmaceuticals and Biomaterials, China Pharmaceutical University, Nanjing, 210009, People's Republic of China.
| | - Can Zhang
- State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, Center of Advanced Pharmaceuticals and Biomaterials, China Pharmaceutical University, Nanjing, 210009, People's Republic of China.
| | - Yijun Chen
- State Key Laboratory of Natural Medicines and Laboratory of Chemical Biology, China Pharmaceutical University, 639 Longmian Ave, Nanjing, 211198, Jiangsu, China.
| |
Collapse
|
4
|
Eguchi T, Tezuka T, Watanabe Y, Inoue-Yamauchi A, Sagara H, Ozawa M, Yamanashi Y. Calcium-binding protein 7 expressed in muscle negatively regulates age-related degeneration of neuromuscular junctions in mice. iScience 2024; 27:108997. [PMID: 38327785 PMCID: PMC10847746 DOI: 10.1016/j.isci.2024.108997] [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: 08/30/2023] [Revised: 12/05/2023] [Accepted: 01/19/2024] [Indexed: 02/09/2024] Open
Abstract
The neuromuscular junction (NMJ) forms centrally in myotubes and, as the only synapse between motor neuron and myotube, are indispensable for motor activity. The midmuscle formation of NMJs, including midmuscle-restricted expression of NMJ-related genes, is governed by the muscle-specific kinase (MuSK). However, mechanisms underlying MuSK-mediated signaling are unclear. Here, we find that the Calcium-binding protein 7 (Cabp7) gene shows midmuscle-restricted expression, and muscle-specific depletion of Cabp7 in mice accelerated age-related NMJ degeneration, muscle weakness/atrophy, and motor dysfunction. Surprisingly, forced expression in muscle of CIP, an inhibitory peptide of the negative regulator of NMJ formation cyclin-dependent kinase 5 (Cdk5), restored NMJ integrity and muscle strength, and healed muscle atrophy in muscle-specific Cabp7-deficient mice, which showed increased muscle expression of the Cdk5 activator p25. These findings together demonstrate that MuSK-mediated signaling induces muscle expression of Cabp7, which suppresses age-related NMJ degeneration likely by attenuating p25 expression, providing insights into prophylactic/therapeutic intervention against age-related motor dysfunction.
Collapse
Affiliation(s)
- Takahiro Eguchi
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Tohru Tezuka
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Yuji Watanabe
- Medical Proteomics Laboratory, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Akane Inoue-Yamauchi
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Hiroshi Sagara
- Medical Proteomics Laboratory, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Manabu Ozawa
- Laboratory of Reproductive Systems Biology, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
- Core Laboratory for Developing Advanced Animal Models, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Yuji Yamanashi
- Division of Genetics, The Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| |
Collapse
|
5
|
Qaisar R. Targeting neuromuscular junction to treat neuromuscular disorders. Life Sci 2023; 333:122186. [PMID: 37858716 DOI: 10.1016/j.lfs.2023.122186] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Revised: 10/07/2023] [Accepted: 10/16/2023] [Indexed: 10/21/2023]
Abstract
The integrity and preservation of the neuromuscular junction (NMJ), the interface between the motor neuron and skeletal muscle, is critical for maintaining a healthy skeletal muscle. The structural and/or functional defects in the three cellular components of NMJ, namely the pre-synaptic terminal, synaptic cleft, and post-synaptic region, negatively affect skeletal muscle mass and/or strength. Therefore, NMJ repair appears to be an appropriate therapy for muscle disorders. Mouse models provide a detailed molecular characterization of various cellular components of NMJ with relevance to human diseases. This review discusses different molecular targets on the three cellular components of NMJ for treating muscle diseases. The potential effects of these therapies on NMJ morphology and motor performance, their therapeutic efficacy, and clinical relevance are discussed. Collectively, the available data supports targeting NMJ alone or as an adjunct therapy in treating muscle disorders. However, the potential impact of such interventions on human patients with muscle disorders requires further investigation.
Collapse
Affiliation(s)
- Rizwan Qaisar
- Basic Medical Sciences, College of Medicine, University of Sharjah, Sharjah, United Arab Emirates; Space Medicine Research Group, Sharjah Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates; Cardiovascular Research Group, Sharjah Institute for Medical and Health Sciences, University of Sharjah, Sharjah 27272, United Arab Emirates.
| |
Collapse
|
6
|
Navarro-Martínez A, Vicente-García C, Carvajal JJ. NMJ-related diseases beyond the congenital myasthenic syndromes. Front Cell Dev Biol 2023; 11:1216726. [PMID: 37601107 PMCID: PMC10436495 DOI: 10.3389/fcell.2023.1216726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 07/21/2023] [Indexed: 08/22/2023] Open
Abstract
Neuromuscular junctions (NMJs) are a special type of chemical synapse that transmits electrical stimuli from motor neurons (MNs) to their innervating skeletal muscle to induce a motor response. They are an ideal model for the study of synapses, given their manageable size and easy accessibility. Alterations in their morphology or function lead to neuromuscular disorders, such as the congenital myasthenic syndromes, which are caused by mutations in proteins located in the NMJ. In this review, we highlight novel potential candidate genes that may cause or modify NMJs-related pathologies in humans by exploring the phenotypes of hundreds of mouse models available in the literature. We also underscore the fact that NMJs may differ between species, muscles or even sexes. Hence the importance of choosing a good model organism for the study of NMJ-related diseases: only taking into account the specific features of the mammalian NMJ, experimental results would be efficiently translated to the clinic.
Collapse
Affiliation(s)
| | - Cristina Vicente-García
- Centro Andaluz de Biología del Desarrollo, CSIC-UPO-JA, Universidad Pablo de Olavide, Sevilla, Spain
| | | |
Collapse
|
7
|
Functional Nutrients to Ameliorate Neurogenic Muscle Atrophy. Metabolites 2022; 12:metabo12111149. [DOI: 10.3390/metabo12111149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/15/2022] [Accepted: 11/17/2022] [Indexed: 11/22/2022] Open
Abstract
Neurogenic muscle atrophy is a debilitating condition that occurs from nerve trauma in association with diseases or during aging, leading to reduced interaction between motoneurons and skeletal fibers. Current therapeutic approaches aiming at preserving muscle mass in a scenario of decreased nervous input include physical activity and employment of drugs that slow down the progression of the condition yet provide no concrete resolution. Nutritional support appears as a precious tool, adding to the success of personalized medicine, and could thus play a relevant part in mitigating neurogenic muscle atrophy. We herein summarize the molecular pathways triggered by denervation of the skeletal muscle that could be affected by functional nutrients. In this narrative review, we examine and discuss studies pertaining to the use of functional ingredients to counteract neurogenic muscle atrophy, focusing on their preventive or curative means of action within the skeletal muscle. We reviewed experimental models of denervation in rodents and in amyotrophic lateral sclerosis, as well as that caused by aging, considering the knowledge generated with use of animal experimental models and, also, from human studies.
Collapse
|
8
|
Liao Z, Xiao M, Chen J, Yang Y, Lyu Q, Zhou J, Sun Y, Zhao Y, Fan Z, Yu J, Wu Y, Chen Q, Wu J, Xiao Q. CHRNA1 induced sarcopenia through neuromuscular synaptic elimination. Exp Gerontol 2022; 166:111891. [PMID: 35809807 DOI: 10.1016/j.exger.2022.111891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/25/2022] [Accepted: 07/04/2022] [Indexed: 11/04/2022]
Abstract
Sarcopenia seriously affects the quality of life of the elderly, but its molecular mechanism is still unclear. Degeneration in muscle innervation is related to age-related movement disorders and muscle atrophy. The expression of CHRNA1 is increased in the skeletal muscle of the elderly, and in aging rodents. Therefore, we investigated whether CHRNA1 induces the occurrence and development of sarcopenia. Compared with the control group, local injection of AAV9-CHRNA1 into the hindlimb muscles decreased the percentage of muscle innervation. At the same time, the skeletal muscle mass decreased, as manifested by a decrease in the gastrocnemius mass index and the cross-sectional area of the muscle fibers. The function of skeletal muscle also decreased, which was manifested by decreases of compound muscle action potential and muscle contractility. Therefore, we concluded that upregulation of CHRNA1 can induce and aggravate sarcopenia.
Collapse
Affiliation(s)
- Zhiyin Liao
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China
| | - Minghan Xiao
- Department of Cardiology, University of Chinese Academy of Sciences, No. 118, Xingguang Avenue, Liangjiang New Area, 401147 Chongqing, China
| | - Jinliang Chen
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China
| | - Yunfei Yang
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China
| | - Qiong Lyu
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China
| | - Jing Zhou
- Department of Clinic, Chongqing Medical And Pharmaceutical College, No. 82, University Town Middle Road, Shapingba District, 401331 Chongqing, China
| | - Yue Sun
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China
| | - Yuxing Zhao
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China
| | - Zhen Fan
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China
| | - Jing Yu
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China
| | - Yongxin Wu
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China
| | - Qiunan Chen
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China
| | - Jianghao Wu
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China
| | - Qian Xiao
- Department of Geriatrics, the First Affiliated Hospital of Chongqing Medical University, Friendship Road 1, Yuan Jiagang, 400016 Chongqing, China.
| |
Collapse
|
9
|
Kaplan MM, Flucher BE. Counteractive and cooperative actions of muscle β-catenin and CaV1.1 during early neuromuscular synapse formation. iScience 2022; 25:104025. [PMID: 35340430 PMCID: PMC8941212 DOI: 10.1016/j.isci.2022.104025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 01/07/2022] [Accepted: 03/01/2022] [Indexed: 11/29/2022] Open
Abstract
Activity-dependent calcium signals in developing muscle play a crucial role in neuromuscular junction (NMJ) formation. However, its downstream effectors and interactions with other regulators of pre- and postsynaptic differentiation are poorly understood. Here, we demonstrate that the skeletal muscle calcium channel CaV1.1 and β-catenin interact in various ways to control NMJ development. They differentially regulate nerve branching and presynaptic innervation patterns during the initial phase of NMJ formation. Conversely, they cooperate in regulating postsynaptic AChR clustering, synapse formation, and the proper organization of muscle fibers in mouse diaphragm. CaV1.1 does not directly regulate β-catenin expression but differentially controls the activity of its transcriptional co-regulators TCF/Lef and YAP. These findings suggest a crosstalk between CaV1.1 and β-catenin in the activity-dependent transcriptional regulation of genes involved in specific pre- and postsynaptic aspects of NMJ formation. Neuromuscular junction formation requires either muscle calcium or β-catenin signaling Complementary actions of CaV1.1 and β-catenin control presynaptic innervation patterns Parallel actions of CaV1.1 and β-catenin are crucial for postsynaptic AChR clustering Loss of CaV1.1 differentially regulates activity of β-catenin targets TCF/Lef and YAP
Collapse
Affiliation(s)
- Mehmet Mahsum Kaplan
- Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
- Corresponding author
| | - Bernhard E. Flucher
- Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
| |
Collapse
|
10
|
Xing G, Jing H, Yu Z, Chen P, Wang H, Xiong WC, Mei L. Membraneless condensates by Rapsn phase separation as a platform for neuromuscular junction formation. Neuron 2021; 109:1963-1978.e5. [PMID: 34033754 DOI: 10.1016/j.neuron.2021.04.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 03/27/2021] [Accepted: 04/22/2021] [Indexed: 12/29/2022]
Abstract
Our daily life depends on muscle contraction, a process that is controlled by the neuromuscular junction (NMJ). However, the mechanisms of NMJ assembly remain unclear. Here we show that Rapsn, a protein critical for NMJ formation, undergoes liquid-liquid phase separation (LLPS) and condensates into liquid-like assemblies. Such assemblies can recruit acetylcholine receptors (AChRs), cytoskeletal proteins, and signaling proteins for postsynaptic differentiation. Rapsn LLPS requires multivalent binding of tetratricopeptide repeats (TPRs) and is increased by Musk signaling. The capacity of Rapsn to condensate and co-condensate with interaction proteins is compromised by mutations of congenital myasthenic syndromes (CMSs). NMJ formation is impaired in mutant mice carrying a CMS-associated, LLPS-deficient mutation. These results reveal a critical role of Rapsn LLPS in forming a synaptic semi-membraneless compartment for NMJ formation.
Collapse
Affiliation(s)
- Guanglin Xing
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Hongyang Jing
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Zheng Yu
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Peng Chen
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Hongsheng Wang
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA
| | - Wen-Cheng Xiong
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH 44106, USA.
| | - Lin Mei
- Department of Neurosciences, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA; Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH 44106, USA.
| |
Collapse
|
11
|
Rodríguez Cruz PM, Cossins J, Beeson D, Vincent A. The Neuromuscular Junction in Health and Disease: Molecular Mechanisms Governing Synaptic Formation and Homeostasis. Front Mol Neurosci 2020; 13:610964. [PMID: 33343299 PMCID: PMC7744297 DOI: 10.3389/fnmol.2020.610964] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 10/30/2020] [Indexed: 12/28/2022] Open
Abstract
The neuromuscular junction (NMJ) is a highly specialized synapse between a motor neuron nerve terminal and its muscle fiber that are responsible for converting electrical impulses generated by the motor neuron into electrical activity in the muscle fibers. On arrival of the motor nerve action potential, calcium enters the presynaptic terminal, which leads to the release of the neurotransmitter acetylcholine (ACh). ACh crosses the synaptic gap and binds to ACh receptors (AChRs) tightly clustered on the surface of the muscle fiber; this leads to the endplate potential which initiates the muscle action potential that results in muscle contraction. This is a simplified version of the events in neuromuscular transmission that take place within milliseconds, and are dependent on a tiny but highly structured NMJ. Much of this review is devoted to describing in more detail the development, maturation, maintenance and regeneration of the NMJ, but first we describe briefly the most important molecules involved and the conditions that affect their numbers and function. Most important clinically worldwide, are myasthenia gravis (MG), the Lambert-Eaton myasthenic syndrome (LEMS) and congenital myasthenic syndromes (CMS), each of which causes specific molecular defects. In addition, we mention the neurotoxins from bacteria, snakes and many other species that interfere with neuromuscular transmission and cause potentially fatal diseases, but have also provided useful probes for investigating neuromuscular transmission. There are also changes in NMJ structure and function in motor neuron disease, spinal muscle atrophy and sarcopenia that are likely to be secondary but might provide treatment targets. The NMJ is one of the best studied and most disease-prone synapses in the nervous system and it is amenable to in vivo and ex vivo investigation and to systemic therapies that can help restore normal function.
Collapse
Affiliation(s)
- Pedro M. Rodríguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Judith Cossins
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| |
Collapse
|
12
|
Cao M, Koneczny I, Vincent A. Myasthenia Gravis With Antibodies Against Muscle Specific Kinase: An Update on Clinical Features, Pathophysiology and Treatment. Front Mol Neurosci 2020; 13:159. [PMID: 32982689 PMCID: PMC7492727 DOI: 10.3389/fnmol.2020.00159] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 08/03/2020] [Indexed: 12/24/2022] Open
Abstract
Muscle Specific Kinase myasthenia gravis (MuSK-MG) is an autoimmune disease that impairs neuromuscular transmission leading to generalized muscle weakness. Compared to the more common myasthenia gravis with antibodies against the acetylcholine receptor (AChR), MuSK-MG affects mainly the bulbar and respiratory muscles, with more frequent and severe myasthenic crises. Treatments are usually less effective with the need for prolonged, high doses of steroids and other immunosuppressants to control symptoms. Under physiological condition, MuSK regulates a phosphorylation cascade which is fundamental for the development and maintenance of postsynaptic AChR clusters at the neuromuscular junction (NMJ). Agrin, secreted by the motor nerve terminal into the synaptic cleft, binds to low density lipoprotein receptor-related protein 4 (LRP4) which activates MuSK. In MuSK-MG, monovalent MuSK-IgG4 autoantibodies block MuSK-LRP4 interaction preventing MuSK activation and leading to the dispersal of AChR clusters. Lower levels of divalent MuSK IgG1, 2, and 3 antibody subclasses are also present but their contribution to the pathogenesis of the disease remains controversial. This review aims to provide a detailed update on the epidemiological and clinical features of MuSK-MG, focusing on the pathophysiological mechanisms and the latest indications regarding the efficacy and safety of different treatment options.
Collapse
Affiliation(s)
- Michelangelo Cao
- Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| | - Inga Koneczny
- Division of Neuropathology and Neurochemistry, Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom
| |
Collapse
|
13
|
Xing G, Xiong WC, Mei L. Rapsyn as a signaling and scaffolding molecule in neuromuscular junction formation and maintenance. Neurosci Lett 2020; 731:135013. [DOI: 10.1016/j.neulet.2020.135013] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 04/23/2020] [Indexed: 12/20/2022]
|
14
|
Takamori M. Myasthenia Gravis: From the Viewpoint of Pathogenicity Focusing on Acetylcholine Receptor Clustering, Trans-Synaptic Homeostasis and Synaptic Stability. Front Mol Neurosci 2020; 13:86. [PMID: 32547365 PMCID: PMC7272578 DOI: 10.3389/fnmol.2020.00086] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/28/2020] [Indexed: 12/18/2022] Open
Abstract
Myasthenia gravis (MG) is a disease of the postsynaptic neuromuscular junction (NMJ) where nicotinic acetylcholine (ACh) receptors (AChRs) are targeted by autoantibodies. Search for other pathogenic antigens has detected the antibodies against muscle-specific tyrosine kinase (MuSK) and low-density lipoprotein-related protein 4 (Lrp4), both causing pre- and post-synaptic impairments. Agrin is also suspected as a fourth pathogen. In a complex NMJ organization centering on MuSK: (1) the Wnt non-canonical pathway through the Wnt-Lrp4-MuSK cysteine-rich domain (CRD)-Dishevelled (Dvl, scaffold protein) signaling acts to form AChR prepatterning with axonal guidance; (2) the neural agrin-Lrp4-MuSK (Ig1/2 domains) signaling acts to form rapsyn-anchored AChR clusters at the innervated stage of muscle; (3) adaptor protein Dok-7 acts on MuSK activation for AChR clustering from “inside” and also on cytoskeleton to stabilize AChR clusters by the downstream effector Sorbs1/2; (4) the trans-synaptic retrograde signaling contributes to the presynaptic organization via: (i) Wnt-MuSK CRD-Dvl-β catenin-Slit 2 pathway; (ii) Lrp4; and (iii) laminins. The presynaptic Ca2+ homeostasis conditioning ACh release is modified by autoreceptors such as M1-type muscarinic AChR and A2A adenosine receptors. The post-synaptic structure is stabilized by: (i) laminin-network including the muscle-derived agrin; (ii) the extracellular matrix proteins (including collagen Q/perlecan and biglycan which link to MuSK Ig1 domain and CRD); and (iii) the dystrophin-associated glycoprotein complex. The study on MuSK ectodomains (Ig1/2 domains and CRD) recognized by antibodies suggested that the MuSK antibodies were pathologically heterogeneous due to their binding to multiple functional domains. Focussing one of the matrix proteins, biglycan which functions in the manner similar to collagen Q, our antibody assay showed the negative result in MG patients. However, the synaptic stability may be impaired by antibodies against MuSK ectodomains because of the linkage of biglycan with MuSK Ig1 domain and CRD. The pathogenic diversity of MG is discussed based on NMJ signaling molecules.
Collapse
|
15
|
Arakawa M, Wagatsuma A. 1α, 25(OH) 2D 3 regulates agrin-induced acetylcholine receptor clustering through upregulation of rapsyn expression in C2C12 myotubes. Biochem Biophys Res Commun 2020; 525:S0006-291X(20)30293-X. [PMID: 32081417 DOI: 10.1016/j.bbrc.2020.02.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 02/04/2020] [Indexed: 12/26/2022]
Abstract
The active form of vitamin D (1α, 25-dihydroxyvitamin D3 [1α, 25(OH)2D3], referred to as 1,25D) has been suggested to play a pivotal role in skeletal muscle function and metabolism. However, the mechanisms through which 1,25D functions in this tissue remain to be elucidated. Recent studies have shown that vitamin D signaling regulates neuromuscular maintenance and improves locomotion in mice. In the present study, we examined the effects of 1,25D on neuromuscular synaptogenesis by measuring clustering of acetylcholine receptors (AChRs) in C2C12 myotubes. 1,25D treatment enhanced the agrin-induced AChR clustering in myotubes compared to treatment with agrin alone. Furthermore, siRNA-mediated knockdown of the vitamin D receptor (VDR) decreased the agrin-induced AChR clustering. 1,25D increased the expression of rapsyn, which is necessary for AChR clustering, while demonstrating no effect on other neuromuscular junction-related genes. In addition, rapsyn expression was dependent on 1,25D-VDR signaling. These results suggest that 1,25D-VDR signaling may regulate rapsin expression, resulting in the up-regulation of agrin-induced AChR clustering.
Collapse
Affiliation(s)
- Masayuki Arakawa
- Laboratory of Virology, Institute of Microbial Chemistry, 5-14-23 Kamiosaki, Shinagawa-ku, Tokyo, 141-0021, Japan
| | - Akira Wagatsuma
- Laboratory of Muscle Biology, Tokyo Woman's Christian University, 2-6-1 Zempukuji, Suginami-ku, Tokyo, 167-8585, Japan.
| |
Collapse
|
16
|
Swenarchuk LE. Nerve, Muscle, and Synaptogenesis. Cells 2019; 8:cells8111448. [PMID: 31744142 PMCID: PMC6912269 DOI: 10.3390/cells8111448] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 11/06/2019] [Accepted: 11/06/2019] [Indexed: 12/21/2022] Open
Abstract
The vertebrate skeletal neuromuscular junction (NMJ) has long served as a model system for studying synapse structure, function, and development. Over the last several decades, a neuron-specific isoform of agrin, a heparan sulfate proteoglycan, has been identified as playing a central role in synapse formation at all vertebrate skeletal neuromuscular synapses. While agrin was initially postulated to be the inductive molecule that initiates synaptogenesis, this model has been modified in response to work showing that postsynaptic differentiation can develop in the absence of innervation, and that synapses can form in transgenic mice in which the agrin gene is ablated. In place of a unitary mechanism for neuromuscular synapse formation, studies in both mice and zebrafish have led to the proposal that two mechanisms mediate synaptogenesis, with some synapses being induced by nerve contact while others involve the incorporation of prepatterned postsynaptic structures. Moreover, the current model also proposes that agrin can serve two functions, to induce synaptogenesis and to stabilize new synapses, once these are formed. This review examines the evidence for these propositions, and concludes that it remains possible that a single molecular mechanism mediates synaptogenesis at all NMJs, and that agrin acts as a stabilizer, while its role as inducer is open to question. Moreover, if agrin does not act to initiate synaptogenesis, it follows that as yet uncharacterized molecular interactions are required to play this essential inductive role. Several alternatives to agrin for this function are suggested, including focal pericellular proteolysis and integrin signaling, but all require experimental validation.
Collapse
|
17
|
Machado J, Silveira WA, Gonçalves DA, Schavinski AZ, Khan MM, Zanon NM, Diaz MB, Rudolf R, Kettelhut IC, Navegantes LC. α-Calcitonin gene-related peptide inhibits autophagy and calpain systems and maintains the stability of neuromuscular junction in denervated muscles. Mol Metab 2019; 28:91-106. [PMID: 31331823 PMCID: PMC6822259 DOI: 10.1016/j.molmet.2019.06.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 06/23/2019] [Accepted: 06/28/2019] [Indexed: 11/25/2022] Open
Abstract
OBJECTIVE Although it is well established that a-calcitonin gene-related peptide (CGRP) stabilizes muscle-type cholinergic receptors nicotinic subunits (AChR), the underlying mechanism by which this neuropeptide regulates muscle protein metabolism and neuromuscular junction (NMJ) morphology is unclear. METHODS To elucidate the mechanisms how CGRP controls NMJ stability in denervated mice skeletal muscles, we carried out physiological, pharmacological, and molecular analyses of atrophic muscles induced by sciatic nerve transection. RESULTS Here, we report that CGRP treatment in vivo abrogated the deleterious effects on NMJ upon denervation (DEN), an effect that was associated with suppression of skeletal muscle proteolysis, but not stimulation of protein synthesis. CGRP also blocked the DEN-induced increase in endocytic AChR vesicles and the elevation of autophagosomes per NMJ area. The treatment of denervated animals with rapamycin blocked the stimulatory effects of CGRP on mTORC1 and its inhibitory actions on autophagic flux and NMJ degeneration. Furthermore, CGRP inhibited the DEN-induced hyperactivation of Ca2+-dependent proteolysis, a degradative system that has been shown to destabilize NMJ. Consistently, calpain was found to be activated by cholinergic stimulation in myotubes leading to the dispersal of AChR clusters, an effect that was abolished by CGRP. CONCLUSION Taken together, these data suggest that the inhibitory effect of CGRP on autophagy and calpain may represent an important mechanism for the preservation of synapse morphology when degradative machinery is exacerbated upon denervation conditions.
Collapse
Affiliation(s)
- Juliano Machado
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil; Department of Biochemistry/Immunology, Ribeirão Preto Medical School/University of São Paulo, Ribeirão Preto, São Paulo, Brazil; Institute for Diabetes and Cancer (IDC), Helmholtz Center Munich, 85764, Neuherberg, Germany; Joint Heidelberg-IDC Translational Diabetes Program, Inner Medicine I, Heidelberg University Hospital, 69120, Heidelberg, Germany.
| | - Wilian A Silveira
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
| | - Dawit A Gonçalves
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil; Department of Biochemistry/Immunology, Ribeirão Preto Medical School/University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
| | - Aline Zanatta Schavinski
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
| | - Muzamil M Khan
- Institute of Molecular and Cell Biology, University of Applied Sciences Mannheim, Mannheim, Germany; Institute of Medical Technology, University of Heidelberg and University of Applied Sciences Mannheim, Mannheim, Germany.
| | - Neusa M Zanon
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
| | - Mauricio Berriel Diaz
- Institute for Diabetes and Cancer (IDC), Helmholtz Center Munich, 85764, Neuherberg, Germany; Joint Heidelberg-IDC Translational Diabetes Program, Inner Medicine I, Heidelberg University Hospital, 69120, Heidelberg, Germany.
| | - Rüdiger Rudolf
- Institute of Molecular and Cell Biology, University of Applied Sciences Mannheim, Mannheim, Germany; Institute of Medical Technology, University of Heidelberg and University of Applied Sciences Mannheim, Mannheim, Germany.
| | - Isis C Kettelhut
- Department of Biochemistry/Immunology, Ribeirão Preto Medical School/University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
| | - Luiz C Navegantes
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
| |
Collapse
|
18
|
Rudolf R, Straka T. Nicotinic acetylcholine receptor at vertebrate motor endplates: Endocytosis, recycling, and degradation. Neurosci Lett 2019; 711:134434. [PMID: 31421156 DOI: 10.1016/j.neulet.2019.134434] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 08/08/2019] [Accepted: 08/14/2019] [Indexed: 12/31/2022]
Abstract
At vertebrate motor endplates, the conversion of nerve impulses into muscle contraction is initiated by binding of acetylcholine to its nicotinic receptor (nAChR) at the postsynapse. Efficiency and safety of this process are dependent on proper localization, density, and molecular composition of the receptors. To warrant this, intricate machineries regulating the turnover of nAChR are in place. They control and execute the processes of i) expression, ii) delivery to the postsynaptic membrane, iii) clustering at the plasma membrane, iv) endocytic retrieval, v) activity-dependent recycling, and vi) degradation of nAChR. Concentrating on aspects iv-vi, this review addresses the current status of techniques, concepts, and open questions on endocytosis, recycling, and degradation of nAChR. A picture is emerging, that shows connections between executing machineries and their regulators. The first group includes the actin cytoskeleton, myosin motor proteins, Rab G-proteins, and the autophagic cascade. The second group features protein kinases A and C, Cdk5, and CaMKII as well as other components like the E3-ligase MuRF1 and the membrane shaping regulator, SH3GLB1. Recent studies have started to shed light onto nerve inputs that appear to master the tuning of the postsynaptic protein trafficking apparatus and the expression of critical components for nAChR turnover.
Collapse
Affiliation(s)
- Rüdiger Rudolf
- Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, Mannheim, Germany; Interdisciplinary Center for Neurosciences, Heidelberg University, Heidelberg, Germany; Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany.
| | - Tatjana Straka
- Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, Mannheim, Germany; Interdisciplinary Center for Neurosciences, Heidelberg University, Heidelberg, Germany; Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
| |
Collapse
|
19
|
Koppel N, Friese MB, Cardasis HL, Neubert TA, Burden SJ. Vezatin is required for the maturation of the neuromuscular synapse. Mol Biol Cell 2019; 30:2571-2583. [PMID: 31411944 PMCID: PMC6740198 DOI: 10.1091/mbc.e19-06-0313] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Key genes, such as Agrin, Lrp4, and MuSK, are required for the initial formation, subsequent maturation, and long-term stabilization of mammalian neuromuscular synapses. Additional molecules are thought to function selectively during the evolution and stabilization of these synapses, but these molecular players are largely unknown. Here, we used mass spectrometry to identify vezatin, a two-pass transmembrane protein, as an acetylcholine receptor (AChR)–associated protein, and we provide evidence that vezatin binds directly to AChRs. We show that vezatin is dispensable for the formation of synapses but plays a later role in the emergence of a topologically complex and branched shape of the synapse, as well as the stabilization of AChRs. In addition, neuromuscular synapses in vezatin mutant mice display premature signs of deterioration, normally found only during aging. Thus, vezatin has a selective role in the structural elaboration and postnatal maturation of murine neuromuscular synapses.
Collapse
Affiliation(s)
- Natasha Koppel
- Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| | - Matthew B Friese
- Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| | - Helene L Cardasis
- Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| | - Thomas A Neubert
- Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| | - Steven J Burden
- Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| |
Collapse
|
20
|
Paz ML, Barrantes FJ. Autoimmune Attack of the Neuromuscular Junction in Myasthenia Gravis: Nicotinic Acetylcholine Receptors and Other Targets. ACS Chem Neurosci 2019; 10:2186-2194. [PMID: 30916550 DOI: 10.1021/acschemneuro.9b00041] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The nicotinic acetylcholine receptor (nAChR) family, the archetype member of the pentameric ligand-gated ion channels, is ubiquitously distributed in the central and peripheral nervous systems, and its members are the targets for both genetic and acquired forms of neurological disorders. In the central nervous system, nAChRs contribute to the pathological mechanisms of neurodegenerative disorders, such as Alzheimer and Parkinson diseases. In the peripheral nerve-muscle synapse, the vertebrate neuromuscular junction, "classical" myasthenia gravis (MG) and other forms of neuromuscular transmission disorders are antibody-mediated autoimmune diseases. In MG, antibodies to the nAChR bind to the postsynaptic receptors and activate the classical complement pathway culminating in the formation of the membrane attack complex, with the subsequent destruction of the postsynaptic apparatus. Divalent nAChR-antibodies also cause internalization and loss of the nAChRs. Loss of receptors by either mechanism results in the muscle weakness and fatigability that typify the clinical manifestations of the disease. Other targets for antibodies, in a minority of patients, include muscle specific kinase (MuSK) and low-density lipoprotein related protein 4 (LRP4). This brief Review analyzes the current status of muscle-type nAChR in relation to the pathogenesis of autoimmune diseases affecting the peripheral cholinergic synapse.
Collapse
Affiliation(s)
- Mariela L. Paz
- Immunology Department, Faculty of Pharmacy and Biochemistry, IDEHU-CONICET, University of Buenos Aires, Junin 956, C1113AAD Buenos Aires, Argentina
| | - Francisco J. Barrantes
- Laboratory of Molecular Neurobiology, Biomedical Research Institute (BIOMED), UCA-CONICET, Av. Alicia Moreau de Justo 1600, C1107AFF Buenos Aires, Argentina
| |
Collapse
|
21
|
Grassi F, Fucile S. Calcium influx through muscle nAChR-channels: One route, multiple roles. Neuroscience 2019; 439:117-124. [PMID: 30999028 DOI: 10.1016/j.neuroscience.2019.04.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 04/01/2019] [Accepted: 04/04/2019] [Indexed: 01/31/2023]
Abstract
Although Ca2+ influx through muscle nAChR-channels has been described over the past 40 years, its functions remain still poorly understood. In this review we suggest possible roles of Ca2+ entry at all stages of muscle development, summarizing the evidence present in literature. nAChRs are expressed in myoblasts prior to fusion, and can be activated in the absence of an ACh-releasing nerve terminal, with Ca2+ influx likely contributing to regulate cell fusion. Upon establishment of nerve-muscle contact, Ca2+ influx contributes to orchestrate the signaling required for the correct formation of the neuromuscular junction. Finally, in the mature synapse, Ca2+ entry through postsynaptic nAChR-channels - highly Ca2+ permeable, in particular in humans - acts on K+ and Na+ channels to shape endplate excitability. However, when genetic defects cause excessive channel activation, Ca2+ influx becomes toxic and causes endplate myopathy. Throughout the review, we highlight how Ricardo Miledi has contributed to construct this whole body of knowledge, from the initial description of Ca2+ permeability of endplate nAChR channels, to the rationale for the treatment of endplate excitotoxic damage under pathological conditions. This article is part of a Special Issue entitled: SI: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.
Collapse
Affiliation(s)
- Francesca Grassi
- Department of Physiology and Pharmacology, Sapienza University, piazzale Aldo Moro 5, 00185, Rome, Italy.
| | - Sergio Fucile
- Department of Physiology and Pharmacology, Sapienza University, piazzale Aldo Moro 5, 00185, Rome, Italy; IRCCS Neuromed, Viale dell'Elettronica, 86077, Pozzilli, Italy
| |
Collapse
|
22
|
Gould TW, Dominguez B, de Winter F, Yeo GW, Liu P, Sundararaman B, Stark T, Vu A, Degen JL, Lin W, Lee KF. Glial cells maintain synapses by inhibiting an activity-dependent retrograde protease signal. PLoS Genet 2019; 15:e1007948. [PMID: 30870413 PMCID: PMC6417855 DOI: 10.1371/journal.pgen.1007948] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 01/08/2019] [Indexed: 12/28/2022] Open
Abstract
Glial cells regulate multiple aspects of synaptogenesis. In the absence of Schwann cells, a peripheral glial cell, motor neurons initially innervate muscle but then degenerate. Here, using a genetic approach, we show that neural activity-regulated negative factors produced by muscle drive neurodegeneration in Schwann cell-deficient mice. We find that thrombin, the hepatic serine protease central to the hemostatic coagulation cascade, is one such negative factor. Trancriptomic analysis shows that expression of the antithrombins serpin C1 and D1 is significantly reduced in Schwann cell-deficient mice. In the absence of peripheral neuromuscular activity, neurodegeneration is completely blocked, and expression of prothrombin in muscle is markedly reduced. In the absence of muscle-derived prothrombin, neurodegeneration is also markedly reduced. Together, these results suggest that Schwann cells regulate NMJs by opposing the effects of activity-regulated, muscle-derived negative factors and provide the first genetic evidence that thrombin plays a central role outside of the coagulation system.
Collapse
Affiliation(s)
- Thomas W. Gould
- Peptide Biology Laboratories, Salk Institute, La Jolla, CA, United States of America
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States of America
| | - Bertha Dominguez
- Peptide Biology Laboratories, Salk Institute, La Jolla, CA, United States of America
| | - Fred de Winter
- Peptide Biology Laboratories, Salk Institute, La Jolla, CA, United States of America
- Department of Neuroregeneration, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
| | - Gene W. Yeo
- Department of Cellular and Molecular Medicine, Sanford Consortium for Regenerative Medicine, Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, CA, United States of America
| | - Patrick Liu
- Department of Cellular and Molecular Medicine, Sanford Consortium for Regenerative Medicine, Stem Cell Program and Institute for Genomic Medicine, University of California at San Diego, La Jolla, CA, United States of America
| | - Balaji Sundararaman
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States of America
| | - Thomas Stark
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States of America
| | - Anthony Vu
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States of America
| | - Jay L. Degen
- Division of Experimental Hematology, Cancer and Blood Diseases Institute, Cincinnati Children’s Hospital Research Foundation, Cincinnati, OH, United States of America
| | - Weichun Lin
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX, United States of America
| | - Kuo-Fen Lee
- Peptide Biology Laboratories, Salk Institute, La Jolla, CA, United States of America
- * E-mail:
| |
Collapse
|
23
|
Oury J, Liu Y, Töpf A, Todorovic S, Hoedt E, Preethish-Kumar V, Neubert TA, Lin W, Lochmüller H, Burden SJ. MACF1 links Rapsyn to microtubule- and actin-binding proteins to maintain neuromuscular synapses. J Cell Biol 2019; 218:1686-1705. [PMID: 30842214 PMCID: PMC6504910 DOI: 10.1083/jcb.201810023] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 01/07/2019] [Accepted: 02/07/2019] [Indexed: 12/20/2022] Open
Abstract
Oury et al. show that the scaffolding protein MACF1 links Rapsyn, which binds acetylcholine receptors, to the microtubule- and actin-network at neuromuscular synapses. MACF1 thereby plays a role in synaptic maturation in mice, and mutations of MACF1 are associated with congenital myasthenia in humans. Complex mechanisms are required to form neuromuscular synapses, direct their subsequent maturation, and maintain the synapse throughout life. Transcriptional and post-translational pathways play important roles in synaptic differentiation and direct the accumulation of the neurotransmitter receptors, acetylcholine receptors (AChRs), to the postsynaptic membrane, ensuring for reliable synaptic transmission. Rapsyn, an intracellular peripheral membrane protein that binds AChRs, is essential for synaptic differentiation, but how Rapsyn acts is poorly understood. We screened for proteins that coisolate with AChRs in a Rapsyn-dependent manner and show that microtubule actin cross linking factor 1 (MACF1), a scaffolding protein with binding sites for microtubules (MT) and actin, is concentrated at neuromuscular synapses, where it binds Rapsyn and serves as a synaptic organizer for MT-associated proteins, EB1 and MAP1b, and the actin-associated protein, Vinculin. MACF1 plays an important role in maintaining synaptic differentiation and efficient synaptic transmission in mice, and variants in MACF1 are associated with congenital myasthenia in humans.
Collapse
Affiliation(s)
- Julien Oury
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, NY
| | - Yun Liu
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX
| | - Ana Töpf
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - Slobodanka Todorovic
- Clinic for Neurology and Psychiatry for Children and Youth, Belgrade, Serbia and Faculty of Medicine, University of Belgrade, Belgrade, Serbia
| | - Esthelle Hoedt
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, NY
| | | | - Thomas A Neubert
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, NY
| | - Weichun Lin
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX
| | - Hanns Lochmüller
- Department of Neuropediatrics and Muscle Disorders, Medical Center, University of Freiburg, Faculty of Medicine, Freiburg, Germany.,Centro Nacional de Análisis Genómico, Center for Genomic Regulation, Barcelona Institute of Science and Technology, Barcelona, Spain.,Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Canada.,Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, Canada
| | - Steven J Burden
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, NY
| |
Collapse
|
24
|
Translating genetic, biochemical and structural information to the calpain view of development. Mech Dev 2018; 154:240-250. [DOI: 10.1016/j.mod.2018.07.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 07/31/2018] [Accepted: 07/31/2018] [Indexed: 01/30/2023]
|
25
|
Neurotrophins and cholinergic enzyme regulated by calpain-2: New insights into neuronal apoptosis induced by polybrominated diphenyl ether-153. Toxicol Lett 2018; 291:29-38. [DOI: 10.1016/j.toxlet.2018.03.033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 02/28/2018] [Accepted: 03/31/2018] [Indexed: 02/06/2023]
|
26
|
Rodríguez Cruz PM, Palace J, Beeson D. The Neuromuscular Junction and Wide Heterogeneity of Congenital Myasthenic Syndromes. Int J Mol Sci 2018; 19:ijms19061677. [PMID: 29874875 PMCID: PMC6032286 DOI: 10.3390/ijms19061677] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 05/17/2018] [Accepted: 05/21/2018] [Indexed: 01/16/2023] Open
Abstract
Congenital myasthenic syndromes (CMS) are genetic disorders characterised by impaired neuromuscular transmission. This review provides an overview on CMS and highlights recent advances in the field, including novel CMS causative genes and improved therapeutic strategies. CMS due to mutations in SLC5A7 and SLC18A3, impairing the synthesis and recycling of acetylcholine, have recently been described. In addition, a novel group of CMS due to mutations in SNAP25B, SYT2, VAMP1, and UNC13A1 encoding molecules implicated in synaptic vesicles exocytosis has been characterised. The increasing number of presynaptic CMS exhibiting CNS manifestations along with neuromuscular weakness demonstrate that the myasthenia can be only a small part of a much more extensive disease phenotype. Moreover, the spectrum of glycosylation abnormalities has been increased with the report that GMPPB mutations can cause CMS, thus bridging myasthenic disorders with dystroglycanopathies. Finally, the discovery of COL13A1 mutations and laminin α5 deficiency has helped to draw attention to the role of extracellular matrix proteins for the formation and maintenance of muscle endplates. The benefit of β2-adrenergic agonists alone or combined with pyridostigmine or 3,4-Dyaminopiridine is increasingly being reported for different subtypes of CMS including AChR-deficiency and glycosylation abnormalities, thus expanding the therapeutic repertoire available.
Collapse
Affiliation(s)
- Pedro M Rodríguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK.
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford OX3 9DS, UK.
| | - Jacqueline Palace
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK.
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford OX3 9DU, UK.
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford OX3 9DS, UK.
| |
Collapse
|
27
|
Animal Models of the Neuromuscular Junction, Vitally Informative for Understanding Function and the Molecular Mechanisms of Congenital Myasthenic Syndromes. Int J Mol Sci 2018; 19:ijms19051326. [PMID: 29710836 PMCID: PMC5983836 DOI: 10.3390/ijms19051326] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 04/24/2018] [Accepted: 04/25/2018] [Indexed: 01/16/2023] Open
Abstract
The neuromuscular junction is the point of contact between motor nerve and skeletal muscle, its vital role in muscle function is reliant on the precise location and function of many proteins. Congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders of neuromuscular transmission with 30 or more implicated proteins. The use of animal models has been instrumental in determining the specific role of many CMS-related proteins. The mouse neuromuscular junction (NMJ) has been extensively studied in animal models of CMS due to its amenability for detailed electrophysiological and histological investigations and relative similarity to human NMJ. As well as their use to determine the precise molecular mechanisms of CMS variants, where an animal model accurately reflects the human phenotype they become useful tools for study of therapeutic interventions. Many of the animal models that have been important in deconvolving the complexities of neuromuscular transmission and revealing the molecular mechanisms of disease are highlighted.
Collapse
|
28
|
Shanmukha S, Narayanappa G, Nalini A, Alladi PA, Raju TR. Sporadic amyotrophic lateral sclerosis (SALS) - skeletal muscle response to cerebrospinal fluid from SALS patients in a rat model. Dis Model Mech 2018; 11:11/4/dmm031997. [PMID: 29666144 PMCID: PMC5963857 DOI: 10.1242/dmm.031997] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 03/05/2018] [Indexed: 01/17/2023] Open
Abstract
Skeletal muscle atrophy is the most prominent feature of amyotrophic lateral sclerosis (ALS), an adult-onset neurodegenerative disease of motor neurons. However, the contribution of skeletal muscle to disease progression remains elusive. Our previous studies have shown that intrathecal injection of cerebrospinal fluid from sporadic ALS patients (ALS-CSF) induces several degenerative changes in motor neurons and glia of neonatal rats. Here, we describe various pathologic events in the rat extensor digitorum longus muscle following intrathecal injection of ALS-CSF. Adenosine triphosphatase staining and electron microscopic (EM) analysis revealed significant atrophy and grouping of type 2 fibres in ALS-CSF-injected rats. Profound neuromuscular junction (NMJ) damage, such as fragmentation accompanied by denervation, were revealed by α-bungarotoxin immunostaining. Altered expression of key NMJ proteins, rapsyn and calpain, was also observed by immunoblotting. In addition, EM analysis showed sarcolemmal folding, Z-line streaming, structural alterations of mitochondria and dilated sarcoplasmic reticulum. The expression of trophic factors was affected, with significant downregulation of vascular endothelial growth factor (VEGF), marginal reduction in insulin-like growth factor-1 (IGF-1), and upregulation of brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF). However, motor neurons might be unable to harness the enhanced levels of BDNF and GDNF, owing to impaired NMJs. We propose that ALS-CSF triggers motor neuronal degeneration, resulting in pathological changes in the skeletal muscle. Muscle damage further aggravates the motor neuronal pathology, because of the interdependency between them. This sets in a vicious cycle, leading to rapid and progressive loss of motor neurons, which could explain the relentless course of ALS.This article has an associated First Person interview with the first author of the paper.
Collapse
Affiliation(s)
- Shruthi Shanmukha
- Department of Neurophysiology, National Institute of Mental Health and Neurosciences, Hosur Road, Bangalore 560 029, India
| | - Gayathri Narayanappa
- Department of Neuropathology, National Institute of Mental Health and Neurosciences, Hosur Road, Bangalore 560 029, India
| | - Atchayaram Nalini
- Department of Neurology, National Institute of Mental Health and Neurosciences, Hosur Road, Bangalore 560 029, India
| | - Phalguni Anand Alladi
- Department of Neurophysiology, National Institute of Mental Health and Neurosciences, Hosur Road, Bangalore 560 029, India
| | - Trichur R Raju
- Department of Neurophysiology, National Institute of Mental Health and Neurosciences, Hosur Road, Bangalore 560 029, India
| |
Collapse
|
29
|
Morren J, Li Y. Myasthenia gravis with muscle-specific tyrosine kinase antibodies: A narrative review. Muscle Nerve 2018; 58:344-358. [DOI: 10.1002/mus.26107] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 02/09/2018] [Accepted: 02/18/2018] [Indexed: 12/14/2022]
Affiliation(s)
- John Morren
- Neuromuscular Center, Neurological Institute, Cleveland Clinic, 9500 Euclid Avenue, Desk S90; Cleveland Ohio 44195 USA
| | - Yuebing Li
- Neuromuscular Center, Neurological Institute, Cleveland Clinic, 9500 Euclid Avenue, Desk S90; Cleveland Ohio 44195 USA
| |
Collapse
|
30
|
Affiliation(s)
- Lei Li
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Wen-Cheng Xiong
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
- Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA
| | - Lin Mei
- Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
- Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA
| |
Collapse
|
31
|
Fundamental Molecules and Mechanisms for Forming and Maintaining Neuromuscular Synapses. Int J Mol Sci 2018; 19:ijms19020490. [PMID: 29415504 PMCID: PMC5855712 DOI: 10.3390/ijms19020490] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 01/24/2018] [Accepted: 01/29/2018] [Indexed: 02/08/2023] Open
Abstract
The neuromuscular synapse is a relatively large synapse with hundreds of active zones in presynaptic motor nerve terminals and more than ten million acetylcholine receptors (AChRs) in the postsynaptic membrane. The enrichment of proteins in presynaptic and postsynaptic membranes ensures a rapid, robust, and reliable synaptic transmission. Over fifty years ago, classic studies of the neuromuscular synapse led to a comprehensive understanding of how a synapse looks and works, but these landmark studies did not reveal the molecular mechanisms responsible for building and maintaining a synapse. During the past two-dozen years, the critical molecular players, responsible for assembling the specialized postsynaptic membrane and regulating nerve terminal differentiation, have begun to be identified and their mechanism of action better understood. Here, we describe and discuss five of these key molecular players, paying heed to their discovery as well as describing their currently understood mechanisms of action. In addition, we discuss the important gaps that remain to better understand how these proteins act to control synaptic differentiation and maintenance.
Collapse
|
32
|
Kung FH, Sillitti D, Shrirao AB, Shreiber DI, Firestein BL. Collagen nanofibre anisotropy induces myotube differentiation and acetylcholine receptor clustering. J Tissue Eng Regen Med 2018; 12:e2010-e2019. [DOI: 10.1002/term.2632] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Revised: 11/28/2017] [Accepted: 12/12/2017] [Indexed: 02/03/2023]
Affiliation(s)
- Frank H. Kung
- Department of Cell Biology and NeuroscienceRutgers University Piscataway NJ USA
| | - David Sillitti
- Department of Biomedical EngineeringRutgers University Piscataway NJ USA
| | - Anil B. Shrirao
- Department of Biomedical EngineeringRutgers University Piscataway NJ USA
| | - David I. Shreiber
- Department of Biomedical EngineeringRutgers University Piscataway NJ USA
- Graduate Faculty in Biomedical EngineeringRutgers University Piscataway NJ USA
| | - Bonnie L. Firestein
- Department of Cell Biology and NeuroscienceRutgers University Piscataway NJ USA
- Graduate Faculty in Biomedical EngineeringRutgers University Piscataway NJ USA
| |
Collapse
|
33
|
Ghazanfari N, Trajanovska S, Morsch M, Liang SX, Reddel SW, Phillips WD. The mouse passive-transfer model of MuSK myasthenia gravis: disrupted MuSK signaling causes synapse failure. Ann N Y Acad Sci 2017; 1412:54-61. [DOI: 10.1111/nyas.13513] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 09/05/2017] [Accepted: 09/09/2017] [Indexed: 12/21/2022]
Affiliation(s)
- Nazanin Ghazanfari
- Physiology and Bosch Institute; University of Sydney; Sydney New South Wales Australia
| | - Sofie Trajanovska
- Physiology and Bosch Institute; University of Sydney; Sydney New South Wales Australia
| | - Marco Morsch
- Physiology and Bosch Institute; University of Sydney; Sydney New South Wales Australia
- Department of Biomedical Sciences; Macquarie University; Sydney New South Wales Australia
| | - Simon X. Liang
- Department of Biochemistry and Molecular Biology, College of Basic Medical Sciences; Liaoning Medical University; Jinzhou China
| | - Stephen W. Reddel
- Department of Molecular Medicine; Concord Hospital; Sydney New South Wales Australia
| | - William D. Phillips
- Physiology and Bosch Institute; University of Sydney; Sydney New South Wales Australia
| |
Collapse
|
34
|
Ohno K, Ohkawara B, Ito M. Agrin-LRP4-MuSK signaling as a therapeutic target for myasthenia gravis and other neuromuscular disorders. Expert Opin Ther Targets 2017; 21:949-958. [PMID: 28825343 DOI: 10.1080/14728222.2017.1369960] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
INTRODUCTION Signal transduction at the neuromuscular junction (NMJ) is compromised in a diverse array of diseases including myasthenia gravis, Lambert-Eaton myasthenic syndrome, Isaacs' syndrome, congenital myasthenic syndromes, Fukuyama-type congenital muscular dystrophy, amyotrophic lateral sclerosis, and sarcopenia. Except for sarcopenia, all are orphan diseases. In addition, the NMJ signal transduction is impaired by tetanus, botulinum, curare, α-bungarotoxin, conotoxins, organophosphate, sarin, VX, and soman to name a few. Areas covered: This review covers the agrin-LRP4-MuSK signaling pathway, which drives clustering of acetylcholine receptors (AChRs) and ensures efficient signal transduction at the NMJ. We also address diseases caused by autoantibodies against the NMJ molecules and by germline mutations in genes encoding the NMJ molecules. Expert opinion: Representative small compounds to treat the defective NMJ signal transduction are cholinesterase inhibitors, which exert their effects by increasing the amount of acetylcholine at the synaptic space. Another possible therapeutic strategy to enhance the NMJ signal transduction is to increase the number of AChRs, but no currently available drug has this functionality.
Collapse
Affiliation(s)
- Kinji Ohno
- a Division of Neurogenetics , Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Bisei Ohkawara
- a Division of Neurogenetics , Nagoya University Graduate School of Medicine , Nagoya , Japan
| | - Mikako Ito
- a Division of Neurogenetics , Nagoya University Graduate School of Medicine , Nagoya , Japan
| |
Collapse
|
35
|
AChRs Are Essential for the Targeting of Rapsyn to the Postsynaptic Membrane of NMJs in Living Mice. J Neurosci 2017; 36:5680-5. [PMID: 27225759 DOI: 10.1523/jneurosci.4580-15.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 04/13/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED Rapsyn, a 43 kDa scaffold protein, is required for the clustering of acetylcholine receptors (AChRs) at synaptic sites between mammalian motor neurons and muscle cells. However, the mechanism by which rapsyn is inserted and retained at postsynaptic sites at the neuromuscular junction (NMJ) in vivo remains largely unknown. We found that neither the N-terminal myristoylation nor the cysteine-rich RING H2 domain of rapsyn is required for its stable association with the postsynaptic membrane of NMJs. When N-myristoylation-defective rapsyn-EGFP mutant (G2A) and RING-H2 domain truncated rapsyn-EGFP were electroporated into sternomastoid muscles, a strong rapsyn fluorescent signal was observed selectively at synapses, similar to WT rapsyn-EGFP. The targeting of rapsyn-EGFP (WT and mutants) is independent of synaptic activity because they were inserted at denervated NMJs. However, when the coiled-coil domain (the AChR-binding domain of rapsyn) is deleted, rapsyn fails to associate with AChRs at NMJs of living mice. In cultured myoblasts (in which AChRs are absent), myristoylated WT rapsyn mostly localizes to lysosomes and is not associated with the plasma membrane. However, in the presence of AChR subunits, rapsyn molecules were targeted to the cell surface and formed aggregates with AChRs. The targeting of AChRs to the cell membrane, in contrast, does not require rapsyn because expressed AChRs are visible on the cell membranes of rapsyn-deficient myoblasts. These results provide evidence for an active role of AChRs in the targeting of rapsyn to the NMJ in vivo SIGNIFICANCE STATEMENT Rapsyn is required for the clustering of acetylcholine receptors (AChRs) at postsynaptic sites. However, the mechanism by which rapsyn is targeted to synaptic sites at the vertebrate neuromuscular junction remains unclear. In this study, we showed that the coiled-coil domain of rapsyn is required for its targeting to the cell surface via its interaction with AChRs. In contrast, the targeting of AChRs to the cell membrane does not require rapsyn. These results indicate that AChRs play a critical role in the insertion and/or association of rapsyn with the plasma membrane of synaptic sites.
Collapse
|
36
|
Muscle Yap Is a Regulator of Neuromuscular Junction Formation and Regeneration. J Neurosci 2017; 37:3465-3477. [PMID: 28213440 DOI: 10.1523/jneurosci.2934-16.2017] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 02/02/2017] [Accepted: 02/07/2017] [Indexed: 12/14/2022] Open
Abstract
Yes-associated protein (Yap) is a major effector of the Hippo pathway that regulates cell proliferation and differentiation during development and restricts tissue growth in adult animals. However, its role in synapse formation remains poorly understood. In this study, we characterized Yap's role in the formation of the neuromuscular junction (NMJ). In HSA-Yap-/- mice where Yap was mutated specifically in muscle cells, AChR clusters were smaller and were distributed in a broader region in the middle of muscle fibers, suggesting that muscle Yap is necessary for the size and location of AChR clusters. In addition, HSA-Yap-/- mice also exhibited remarkable presynaptic deficits. Many AChR clusters were not or less covered by nerve terminals; miniature endplate potential frequency was reduced, which was associated with an increase in paired-pulse facilitation, indicating structural and functional defects. In addition, muscle Yap mutation prevented reinnervation of denervated muscle fibers. Together, these observations indicate a role of muscle Yap in NMJ formation and regeneration. We found that β-catenin was reduced in the cytoplasm and nucleus of mutant muscles, suggesting compromised β-catenin signaling. Both NMJ formation and regeneration deficits of HSA-Yap-/- mice were ameliorated by inhibiting β-catenin degradation, further corroborating a role of β-catenin or Wnt-dependent signaling downstream of Yap to regulate NMJ formation and regeneration.SIGNIFICANCE STATEMENT This paper explored the role of Yes-associated protein (Yap) in neuromuscular junction (NMJ) formation and regeneration. Yap is a major effector of the Hippo pathway that regulates cell proliferation and differentiation during development and restricts tissue growth in adult animals. However, its role in synapse formation remains poorly understood. We provide evidence that muscle Yap mutation impairs both postsynaptic and presynaptic differentiation and function and inhibits NMJ regeneration after nerve injury, indicating a role of muscle Yap in these events. Further studies suggest compromised β-catenin signaling as a potential mechanism. Both NMJ formation and regeneration deficits of HSA-Yap-/- mice were ameliorated by inhibiting β-catenin degradation, corroborating a role of β-catenin or Wnt-dependent signaling downstream of Yap to regulate NMJ formation and regeneration.
Collapse
|
37
|
The origins of rimmed vacuoles and granulovacuolar degeneration bodies are associated with the Wnt signaling pathway. Neurosci Lett 2017; 638:55-59. [DOI: 10.1016/j.neulet.2016.12.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 11/29/2016] [Accepted: 12/06/2016] [Indexed: 01/07/2023]
|
38
|
Vezina-Audette R, Tremblay M, Carbonetto S. Laminin is instructive and calmodulin dependent kinase II is non-permissive for the formation of complex aggregates of acetylcholine receptors on myotubes in culture. Matrix Biol 2016; 57-58:106-123. [PMID: 27964993 DOI: 10.1016/j.matbio.2016.11.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 11/16/2016] [Indexed: 12/11/2022]
Abstract
Previous work has shown that myotubes cultured on laminin-coated substrates form complex aggregates of synaptic proteins that are similar in shape and composition to neuromuscular junctions (NMJs). Here we show that laminin instructs the location of complex aggregates which form only on the lower surface when laminin is coated onto culture dishes but over the entire cell when laminin is added in solution. Silencing of myotubes by agents that block electrical activity (tetrodotoxin, verapamil) or by inhibitors of calmodulin dependent kinase (CaMKII) render the myotube permissive for the formation of complex aggregates. Treatment with laminin alone will facilitate the formation of complex aggregates hours later when myotubes are made permissive by inhibiting CaMKII. The AChR agonist carbachol disperses pre formed aggregates suggesting that non-permissiveness may involve active dispersal of AChRs. The permissive period requires ongoing protein synthesis. The latter may reflect a requirement for rapsyn, which turns over rapidly, and is necessary for aggregation. Consistent with this geldanamycin, an agent that increases rapsyn turnover disrupts complex aggregates. Agrin is well known to induce small clusters of AChRs but does not induce complex aggregates even though aggregate formation requires MuSK, a receptor tyrosine kinase activated by agrin. Dystroglycan (DG) is the major laminin receptor mediating complex aggregate formation with some contribution from β1 integrins. In addition, there is a pool of CaMKII associated with DG. We discuss how these permissive and instructive mechanisms bear on NMJ formation in vivo.
Collapse
Affiliation(s)
- Raphael Vezina-Audette
- Centre for Research in Neuroscience, and Dept. of Neurology, McGill University Health Centre, 1650, Cedar Ave., Montreal, Quebec, H3G 1A4, Canada
| | - Mathieu Tremblay
- Centre for Research in Neuroscience, and Dept. of Neurology, McGill University Health Centre, 1650, Cedar Ave., Montreal, Quebec, H3G 1A4, Canada
| | - Salvatore Carbonetto
- Centre for Research in Neuroscience, and Dept. of Neurology, McGill University Health Centre, 1650, Cedar Ave., Montreal, Quebec, H3G 1A4, Canada.
| |
Collapse
|
39
|
Li L, Cao Y, Wu H, Ye X, Zhu Z, Xing G, Shen C, Barik A, Zhang B, Xie X, Zhi W, Gan L, Su H, Xiong WC, Mei L. Enzymatic Activity of the Scaffold Protein Rapsyn for Synapse Formation. Neuron 2016; 92:1007-1019. [PMID: 27839998 DOI: 10.1016/j.neuron.2016.10.023] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 07/21/2016] [Accepted: 10/07/2016] [Indexed: 12/22/2022]
Abstract
Neurotransmission is ensured by a high concentration of neurotransmitter receptors at the postsynaptic membrane. This is mediated by scaffold proteins that bridge the receptors with cytoskeleton. One such protein is rapsyn (receptor-associated protein at synapse), which is essential for acetylcholine receptor (AChR) clustering and NMJ (neuromuscular junction) formation. We show that the RING domain of rapsyn contains E3 ligase activity. Mutation of the RING domain that abolishes the enzyme activity inhibits rapsyn- as well as agrin-induced AChR clustering in heterologous and muscle cells. Further biological and genetic studies support a working model where rapsyn, a classic scaffold protein, serves as an E3 ligase to induce AChR clustering and NMJ formation, possibly by regulation of AChR neddylation. This study identifies a previously unappreciated enzymatic function of rapsyn and a role of neddylation in synapse formation, and reveals a potential target of therapeutic intervention for relevant neurological disorders.
Collapse
Affiliation(s)
- Lei Li
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Yu Cao
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Haitao Wu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Xinchun Ye
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Zhihui Zhu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Guanglin Xing
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Chengyong Shen
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Arnab Barik
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Bin Zhang
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Xiaoling Xie
- Department of Ophthalmology, University of Rochester, Rochester, NY 14642, USA
| | - Wenbo Zhi
- Center for Biotechnology and Genomic Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Lin Gan
- Department of Ophthalmology, University of Rochester, Rochester, NY 14642, USA
| | - Huabo Su
- Vascular Biology Center, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Wen-Cheng Xiong
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA; Department of Neurology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA; Charlie Norwood VA Medical Center, Augusta, GA 30912, USA
| | - Lin Mei
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA; Department of Neurology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA; Charlie Norwood VA Medical Center, Augusta, GA 30912, USA.
| |
Collapse
|
40
|
Axonal degeneration, distal collateral branching and neuromuscular junction architecture alterations occur prior to symptom onset in the SOD1G93A mouse model of amyotrophic lateral sclerosis. J Chem Neuroanat 2016; 76:35-47. [DOI: 10.1016/j.jchemneu.2016.03.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 01/29/2016] [Accepted: 03/19/2016] [Indexed: 12/11/2022]
|
41
|
Abstract
Myasthenia gravis is an autoimmune disease of the neuromuscular junction (NMJ) caused by antibodies that attack components of the postsynaptic membrane, impair neuromuscular transmission, and lead to weakness and fatigue of skeletal muscle. This can be generalised or localised to certain muscle groups, and involvement of the bulbar and respiratory muscles can be life threatening. The pathogenesis of myasthenia gravis depends upon the target and isotype of the autoantibodies. Most cases are caused by immunoglobulin (Ig)G1 and IgG3 antibodies to the acetylcholine receptor (AChR). They produce complement-mediated damage and increase the rate of AChR turnover, both mechanisms causing loss of AChR from the postsynaptic membrane. The thymus gland is involved in many patients, and there are experimental and genetic approaches to understand the failure of immune tolerance to the AChR. In a proportion of those patients without AChR antibodies, antibodies to muscle-specific kinase (MuSK), or related proteins such as agrin and low-density lipoprotein receptor-related protein 4 (LRP4), are present. MuSK antibodies are predominantly IgG4 and cause disassembly of the neuromuscular junction by disrupting the physiological function of MuSK in synapse maintenance and adaptation. Here we discuss how knowledge of neuromuscular junction structure and function has fed into understanding the mechanisms of AChR and MuSK antibodies. Myasthenia gravis remains a paradigm for autoantibody-mediated conditions and these observations show how much there is still to learn about synaptic function and pathological mechanisms.
Collapse
Affiliation(s)
- William D Phillips
- Physiology and Bosch Institute, University of Sydney, Anderson Stuart Bldg (F13), Sydney, 2006, Australia
| | - Angela Vincent
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK
| |
Collapse
|
42
|
Accumulation of human full-length tau induces degradation of nicotinic acetylcholine receptor α4 via activating calpain-2. Sci Rep 2016; 6:27283. [PMID: 27277673 PMCID: PMC4899694 DOI: 10.1038/srep27283] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Accepted: 05/13/2016] [Indexed: 01/07/2023] Open
Abstract
Cholinergic impairments and tau accumulation are hallmark pathologies in sporadic Alzheimer’s disease (AD), however, the intrinsic link between tau accumulation and cholinergic deficits is missing. Here, we found that overexpression of human wild-type full-length tau (termed hTau) induced a significant reduction of α4 subunit of nicotinic acetylcholine receptors (nAChRs) with an increased cleavage of the receptor producing a ~55kDa fragment in primary hippocampal neurons and in the rat brains, meanwhile, the α4 nAChR currents decreased. Further studies demonstrated that calpains, including calpain-1 and calpain-2, were remarkably activated with no change of caspase-3, while simultaneous suppression of calpain-2 by selective calpain-2 inhibitor but not calpain-1 attenuated the hTau-induced degradation of α4 nAChR. Finally, we demonstrated that hTau accumulation increased the basal intracellular calcium level in primary hippocampal neurons. We conclude that the hTau accumulation inhibits nAChRs α4 by activating calpain-2. To our best knowledge, this is the first evidence showing that the intracellular accumulation of tau causes cholinergic impairments.
Collapse
|
43
|
Vilmont V, Cadot B, Ouanounou G, Gomes ER. A system for studying mechanisms of neuromuscular junction development and maintenance. Development 2016; 143:2464-77. [PMID: 27226316 PMCID: PMC4958317 DOI: 10.1242/dev.130278] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 05/12/2016] [Indexed: 12/12/2022]
Abstract
The neuromuscular junction (NMJ), a cellular synapse between a motor neuron and a skeletal muscle fiber, enables the translation of chemical cues into physical activity. The development of this special structure has been subject to numerous investigations, but its complexity renders in vivo studies particularly difficult to perform. In vitro modeling of the neuromuscular junction represents a powerful tool to delineate fully the fine tuning of events that lead to subcellular specialization at the pre-synaptic and post-synaptic sites. Here, we describe a novel heterologous co-culture in vitro method using rat spinal cord explants with dorsal root ganglia and murine primary myoblasts to study neuromuscular junctions. This system allows the formation and long-term survival of highly differentiated myofibers, motor neurons, supporting glial cells and functional neuromuscular junctions with post-synaptic specialization. Therefore, fundamental aspects of NMJ formation and maintenance can be studied using the described system, which can be adapted to model multiple NMJ-associated disorders.
Collapse
Affiliation(s)
- Valérie Vilmont
- Myology Research Center, UM76-INSERM U974-CNRS FRE 3617 Sorbonne Universités, UPMC Université Paris 06, Paris, France
| | - Bruno Cadot
- Myology Research Center, UM76-INSERM U974-CNRS FRE 3617 Sorbonne Universités, UPMC Université Paris 06, Paris, France
| | - Gilles Ouanounou
- FRE CNRS 3693 (U.N.I.C), Unité de Neuroscience, Information et Complexité CNRS, Bât. 33, 1 Ave de la Terasse, Gif sur Yvette 91198, France
| | - Edgar R Gomes
- Myology Research Center, UM76-INSERM U974-CNRS FRE 3617 Sorbonne Universités, UPMC Université Paris 06, Paris, France Instituto de Medicina Molecular, Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal
| |
Collapse
|
44
|
Ghazanfari N, Linsao ELTB, Trajanovska S, Morsch M, Gregorevic P, Liang SX, Reddel SW, Phillips WD. Forced expression of muscle specific kinase slows postsynaptic acetylcholine receptor loss in a mouse model of MuSK myasthenia gravis. Physiol Rep 2015; 3:3/12/e12658. [PMID: 26702075 PMCID: PMC4760443 DOI: 10.14814/phy2.12658] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2015] [Accepted: 11/20/2015] [Indexed: 12/12/2022] Open
Abstract
We investigated the influence of postsynaptic tyrosine kinase signaling in a mouse model of muscle‐specific kinase (MuSK) myasthenia gravis (MG). Mice administered repeated daily injections of IgG from MuSK MG patients developed impaired neuromuscular transmission due to progressive loss of acetylcholine receptor (AChR) from the postsynaptic membrane of the neuromuscular junction. In this model, anti‐MuSK‐positive IgG caused a reduction in motor endplate immunolabeling for phosphorylated Src‐Y418 and AChR β‐subunit‐Y390 before any detectable loss of MuSK or AChR from the endplate. Adeno‐associated viral vector (rAAV) encoding MuSK fused to enhanced green fluorescent protein (MuSK‐EGFP) was injected into the tibialis anterior muscle to increase MuSK synthesis. When mice were subsequently challenged with 11 daily injections of IgG from MuSK MG patients, endplates expressing MuSK‐EGFP retained more MuSK and AChR than endplates of contralateral muscles administered empty vector. Recordings of compound muscle action potentials from myasthenic mice revealed less impairment of neuromuscular transmission in muscles that had been injected with rAAV‐MuSK‐EGFP than contralateral muscles (empty rAAV controls). In contrast to the effects of MuSK‐EGFP, forced expression of rapsyn‐EGFP provided no such protection to endplate AChR when mice were subsequently challenged with MuSK MG IgG. In summary, the immediate in vivo effect of MuSK autoantibodies was to suppress MuSK‐dependent tyrosine phosphorylation of proteins in the postsynaptic membrane, while increased MuSK synthesis protected endplates against AChR loss. These results support the hypothesis that reduced MuSK kinase signaling initiates the progressive disassembly of the postsynaptic membrane scaffold in this mouse model of MuSK MG.
Collapse
Affiliation(s)
- Nazanin Ghazanfari
- Physiology and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia
| | - Erna L T B Linsao
- Physiology and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia
| | - Sofie Trajanovska
- Physiology and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia
| | - Marco Morsch
- Physiology and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia Department of Biomedical Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Paul Gregorevic
- Baker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
| | - Simon X Liang
- Department of Biochemistry and Molecular Biology, College of Basic Medical Sciences, Liaoning Medical University, Liaoning, China
| | - Stephen W Reddel
- Department of Molecular Medicine, Concord Hospital, Sydney, New South Wales, Australia
| | - William D Phillips
- Physiology and Bosch Institute, University of Sydney, Sydney, New South Wales, Australia
| |
Collapse
|
45
|
Clinical and scientific aspects of muscle-specific tyrosine kinase-related myasthenia gravis. Curr Opin Neurol 2014; 27:558-65. [DOI: 10.1097/wco.0000000000000136] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
46
|
Non-apoptotic role of caspase-3 in synapse refinement. Neurosci Bull 2014; 30:667-70. [PMID: 25027781 DOI: 10.1007/s12264-014-1454-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 07/04/2014] [Indexed: 01/19/2023] Open
Abstract
Caspases, a family of cysteine proteases, mediate programmed cell death during early neural development and neurodegeneration, as well as following neurotoxic insults. Notably, accumulating lines of evidence have shown non-apoptotic roles of caspases in the structural and functional plasticity of neuronal circuits under physiological conditions, such as growth-cone dynamics and axonal/dendritic pruning, as well as neuronal excitability and plasticity. Here, we summarize recent progress on the roles of caspases in synaptic refinement.
Collapse
|
47
|
Abstract
Motor neurons regulate neuromuscular junction formation by using agrin to stimulate acetylcholine receptor clustering and using acetylcholine to disperse unnecessary receptor clusters on muscle fibers. Wang et al. (2014) now report in this issue of Developmental Cell a critical role for caspase-3 in intracellular mechanisms of acetylcholine-induced dispersal.
Collapse
Affiliation(s)
- Chengyong Shen
- Department of Neuroscience and Regenerative Medicine and Department of Neurology, Medical College of Georgia, Georgia Regents University, 1120 15(th) Street, Augusta, GA 30912, USA; Charlie Norwood VA Medical Center, Augusta, GA 30904, USA
| | - Wen C Xiong
- Department of Neuroscience and Regenerative Medicine and Department of Neurology, Medical College of Georgia, Georgia Regents University, 1120 15(th) Street, Augusta, GA 30912, USA; Charlie Norwood VA Medical Center, Augusta, GA 30904, USA
| | - Lin Mei
- Department of Neuroscience and Regenerative Medicine and Department of Neurology, Medical College of Georgia, Georgia Regents University, 1120 15(th) Street, Augusta, GA 30912, USA; Charlie Norwood VA Medical Center, Augusta, GA 30904, USA.
| |
Collapse
|
48
|
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.
Collapse
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
Collapse
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.
| |
Collapse
|
49
|
Fontenele M, Lim B, Oliveira D, Buffolo M, Perlman DH, Schupbach T, Araujo H. Calpain A modulates Toll responses by limited Cactus/IκB proteolysis. Mol Biol Cell 2013; 24:2966-80. [PMID: 23864715 PMCID: PMC3771957 DOI: 10.1091/mbc.e13-02-0113] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Calcium-dependent cysteine proteases of the calpain family are modulatory proteases that cleave their substrates in a limited manner. Among their substrates, calpains target vertebrate and invertebrate IκB proteins. Because proteolysis by calpains potentially generates novel protein functions, it is important to understand how this affects NFκB activity. We investigate the action of Calpain A (CalpA) on the Drosophila melanogaster IκB homologue Cactus in vivo. CalpA alters the absolute amounts of Cactus protein. Our data indicate, however, that CalpA uses additional mechanisms to regulate NFκB function. We provide evidence that CalpA interacts physically with Cactus, recognizing a Cactus pool that is not bound to Dorsal, a fly NFκB/Rel homologue. We show that proteolytic cleavage by CalpA generates Cactus fragments lacking an N-terminal region required for Toll responsiveness. These fragments are generated in vivo and display properties distinct from those of full-length Cactus. We propose that CalpA targets free Cactus, which is incorporated into and modulates Toll-responsive complexes in the embryo and immune system.
Collapse
Affiliation(s)
- Marcio Fontenele
- Institute for Biomedical Sciences, Federal University of Rio de Janeiro, CEP 21941-902 Rio de Janeiro, Brazil Chemistry Institute, Federal University of Rio de Janeiro, CEP 21941-902 Rio de Janeiro, Brazil Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, Brazil Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544 Princeton Collaborative Proteomics and Mass Spectrometry Center, Princeton University, Princeton, NJ 08544 Molecular Biology Department, Princeton University, Princeton, NJ 08544 Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | | | | | | | | | | | | |
Collapse
|
50
|
Skeletal muscle calpain acts through nitric oxide and neural miRNAs to regulate acetylcholine release in motor nerve terminals. J Neurosci 2013; 33:7308-7324. [PMID: 23616539 DOI: 10.1523/jneurosci.0224-13.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Cholinergic overactivity in diseases of neuromuscular transmission elicits a retrograde signal resembling homeostatic synaptic plasticity that downregulates transmitter release. Understanding this compensatory pathway could provide insights into novel therapeutic avenues and molecular mechanisms underlying learning and memory. Here we identify nitric oxide as a possible source of this signal in pathological human and mouse muscle samples and link this signaling pathway to changes in synaptic function in the neuromuscular junction. We further show that neuronal nitric oxide synthase is regulated by cholinergic excess through activation of skeletal muscle calpain and its effect on Cdk5 and CaMKII, leading to direct modulation of presynaptic function. Finally, we show that this signaling pathway acts through specific miRNA control of presynaptic vesicle protein expression. The control of presynaptic miRNA levels by postsynaptic activity represents a novel mechanism for the modulation of synaptic activity in normal or pathological conditions.
Collapse
|