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Krakowian D, Lesiak M, Auguściak-Duma A, Witecka J, Kusz D, Sieroń AL, Gawron K. Analysis of the TID-I and TID-L Splice Variants' Expression Profile under In Vitro Differentiation of Human Mesenchymal Bone Marrow Cells into Osteoblasts. Cells 2024; 13:1021. [PMID: 38920651 PMCID: PMC11201664 DOI: 10.3390/cells13121021] [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: 05/19/2024] [Revised: 06/08/2024] [Accepted: 06/09/2024] [Indexed: 06/27/2024] Open
Abstract
Bone formation is a complex process regulated by a variety of pathways that are not yet fully understood. One of the proteins involved in multiple osteogenic pathways is TID (DNAJA3). The aim of this work was to study the association of TID with osteogenesis. Therefore, the expression profiles of the TID splice variants (TID-L, TID-I) and their protein products were analyzed during the proliferation and differentiation of bone marrow mesenchymal stromal cells (B-MSCs) into osteoblasts. As the reference, the hFOB1.19 cell line was used. The phenotype of B-MSCs was confirmed by the presence of CD73, CD90, and CD105 surface antigens on ~97% of cells. The osteoblast phenotype was confirmed by increased alkaline phosphatase activity, calcium deposition, and expression of ALPL and SPP1. The effect of silencing the TID gene on the expression of ALPL and SPP1 was also investigated. The TID proteins and the expression of TID splice variants were detected. After differentiation, the expression of TID-L and TID-I increased 5-fold and 3.7-fold, respectively, while their silencing resulted in increased expression of SPP1. Three days after transfection, the expression of SPP1 increased 7.6-fold and 5.6-fold in B-MSCs and differentiating cells, respectively. Our preliminary study demonstrated that the expression of TID-L and TID-I changes under differentiation of B-MSCs into osteoblasts and may influence the expression of SPP1. However, for better understanding the functional association of these results with the relevant osteogenic pathways, further studies are needed.
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Affiliation(s)
- Daniel Krakowian
- Department of Molecular Biology and Genetics, Faculty of Medical Sciences in Katowice, Medical University of Silesia, 40-055 Katowice, Poland
- Toxicology Research Group, Łukasiewicz Research Network—Institute of Industrial Organic Chemistry Branch Pszczyna, 43-200 Pszczyna, Poland
| | - Marta Lesiak
- Department of Molecular Biology and Genetics, Faculty of Medical Sciences in Katowice, Medical University of Silesia, 40-055 Katowice, Poland
| | - Aleksandra Auguściak-Duma
- Department of Molecular Biology and Genetics, Faculty of Medical Sciences in Katowice, Medical University of Silesia, 40-055 Katowice, Poland
| | - Joanna Witecka
- Department of Molecular Biology and Genetics, Faculty of Medical Sciences in Katowice, Medical University of Silesia, 40-055 Katowice, Poland
- Department of Parasitology, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia, 41-200 Sosnowiec, Poland
| | - Damian Kusz
- Department of Orthopaedics and Traumatology, Faculty of Medical Sciences in Katowice, Medical University of Silesia, 40-055 Katowice, Poland
| | - Aleksander L. Sieroń
- Department of Molecular Biology and Genetics, Faculty of Medical Sciences in Katowice, Medical University of Silesia, 40-055 Katowice, Poland
| | - Katarzyna Gawron
- Department of Molecular Biology and Genetics, Faculty of Medical Sciences in Katowice, Medical University of Silesia, 40-055 Katowice, Poland
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Dong YN, Ngaba LV, An J, Adeshina MW, Warren N, Wong J, Lynch DR. A peptide derived from TID1S rescues frataxin deficiency and mitochondrial defects in FRDA cellular models. Front Pharmacol 2024; 15:1352311. [PMID: 38495102 PMCID: PMC10940384 DOI: 10.3389/fphar.2024.1352311] [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: 12/07/2023] [Accepted: 02/02/2024] [Indexed: 03/19/2024] Open
Abstract
Friedreich's ataxia (FRDA), the most common recessive inherited ataxia, results from homozygous guanine-adenine-adenine (GAA) repeat expansions in intron 1 of the FXN gene, which leads to the deficiency of frataxin, a mitochondrial protein essential for iron-sulphur cluster synthesis. The study of frataxin protein regulation might yield new approaches for FRDA treatment. Here, we report tumorous imaginal disc 1 (TID1), a mitochondrial J-protein cochaperone, as a binding partner of frataxin that negatively controls frataxin protein levels. TID1 interacts with frataxin both in vivo in mouse cortex and in vitro in cortical neurons. Acute and subacute depletion of frataxin using RNA interference markedly increases TID1 protein levels in multiple cell types. In addition, TID1 overexpression significantly increases frataxin precursor but decreases intermediate and mature frataxin levels in HEK293 cells. In primary cultured human skin fibroblasts, overexpression of TID1S results in decreased levels of mature frataxin and increased fragmentation of mitochondria. This effect is mediated by the last 6 amino acids of TID1S as a peptide made from this sequence rescues frataxin deficiency and mitochondrial defects in FRDA patient-derived cells. Our findings show that TID1 negatively modulates frataxin levels, and thereby suggests a novel therapeutic target for treating FRDA.
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Affiliation(s)
- Yi Na Dong
- Department of Pediatrics and Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Lucie Vanessa Ngaba
- Department of Pediatrics and Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Jacob An
- Department of Pediatrics and Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Miniat W. Adeshina
- Department of Pediatrics and Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Nathan Warren
- Department of Pediatrics and Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - Johnathan Wong
- Department of Pediatrics and Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
| | - David R. Lynch
- Department of Pediatrics and Neurology, The Children’s Hospital of Philadelphia, Philadelphia, PA, United States
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
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Li G, Zhang C, Wang H, Xia W, Zhang X, Liu Z, Wang Y, Zhao H, Xu B. Characterisation of the heat shock protein Tid and its involvement in stress response regulation in Apis cerana. Front Physiol 2022; 13:1068873. [PMID: 36620206 PMCID: PMC9813389 DOI: 10.3389/fphys.2022.1068873] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 12/13/2022] [Indexed: 12/24/2022] Open
Abstract
Objective: The impact of various environmental stresses on native Apis cerana cerana fitness has attracted intense attention in China. However, the defence responses of A. cerana cerana to different stressors are poorly understood. Here, we aimed to elucidate the regulatory mechanism mediated by the tumorous imaginal discs (Tid) protein of A. cerana cerana (AccTid) in response to stressors. Methods: We used some bioinformatics softwares to analyse the characterisation of Tid. Then, qRT-PCR, RNA interference and heat resistance detection assays were used to explore the function of Tid in stress response in A. cerana cerana. Results: AccTid is a homologous gene of human Tid1 and Drosophila Tid56, contains a conserved J domain and belongs to the heat shock protein DnaJA subfamily. The level of AccTid induced expression was increased under temperature increases from 40°C to 43°C and 46°C, and AccTid knockdown decreased the heat resistance of A. cerana cerana, indicating that the upregulation of AccTid plays an important role when A. cerana cerana is exposed to heat stress. Interestingly, contrary to the results of heat stress treatment, the transcriptional level of AccTid was inhibited by cold, H2O2 and some agrochemical stresses and showed no significant change under ultraviolet ray and sodium arsenite stress. These results suggested that the requirement of A. cerana cerana for Tid differs markedly under different stress conditions. In addition, knockdown of AccTid increased the mRNA levels of some Hsps and antioxidant genes. The upregulation of these Hsps and antioxidant genes may be a functional complement of AccTid knockdown. Conclusion: AccTid plays a crucial role in A. cerana cerana stress responses and may mediate oxidative damage caused by various stresses. Our findings will offer fundamental knowledge for further investigations of the defence mechanism of A. cerana cerana against environmental stresses.
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Affiliation(s)
- Guilin Li
- College of Life Sciences, Qufu Normal University, Qufu, China
| | - Chenghao Zhang
- College of Life Sciences, Qufu Normal University, Qufu, China
| | - Hongfang Wang
- College of Animal Science and Technology, Shandong Agricultural University, Taian, Shandong, China
| | - Wenli Xia
- College of Life Sciences, Qufu Normal University, Qufu, China
| | - Xinyi Zhang
- College of Life Sciences, Qufu Normal University, Qufu, China
| | - Zhenguo Liu
- College of Animal Science and Technology, Shandong Agricultural University, Taian, Shandong, China
| | - Ying Wang
- College of Animal Science and Technology, Shandong Agricultural University, Taian, Shandong, China
| | - Hang Zhao
- College of Life Sciences, Qufu Normal University, Qufu, China,*Correspondence: Hang Zhao, ; Baohua Xu,
| | - Baohua Xu
- College of Animal Science and Technology, Shandong Agricultural University, Taian, Shandong, China,*Correspondence: Hang Zhao, ; Baohua Xu,
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Banerjee S, Chaturvedi R, Singh A, Kushwaha HR. Putting human Tid-1 in context: an insight into its role in the cell and in different disease states. Cell Commun Signal 2022; 20:109. [PMID: 35854300 PMCID: PMC9297570 DOI: 10.1186/s12964-022-00912-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 05/20/2022] [Indexed: 12/24/2022] Open
Abstract
Background Tumorous imaginal disc 1 (hTid-1) or DnaJ homolog subfamily A member 3 (DNAJA3), is a part of the heat shock protein (Hsp) 40 family and is predominantly found to reside in the mitochondria. hTid-1 has two mRNA splicing variants, hTid-1S and hTid-1L of 40 and 43 kDa respectively in the cytosol which are later processed upon import into the mitochondrial matrix. hTid-1 protein is a part of the DnaJ family of proteins which are co-chaperones and specificity factors for DnaK proteins of the Hsp70 family, and bind to Hsp70, thereby activating its ATPase activity. hTid-1 has been found to be critical for a lot of important cellular processes such as proliferation, differentiation, growth, survival, senescence, apoptosis, and movement and plays key roles in the embryo and skeletal muscle development.
Main body hTid-1 participates in several protein–protein interactions in the cell, which mediate different processes such as proteasomal degradation and autophagy of the interacting protein partners. hTid-1 also functions as a co-chaperone and participates in interactions with several different viral oncoproteins. hTid-1 also plays a critical role in different human diseases such as different cancers, cardiomyopathies, and neurodegenerative disorders. Conclusion This review article is the first of its kind presenting consolidated information on the research findings of hTid-1 to date. This review suggests that the current knowledge of the role of hTid-1 in disorders like cancers, cardiomyopathies, and neurodegenerative diseases can be correlated with the findings of its protein–protein interactions that can provide a deep insight into the pathways by which hTid-1 affects disease pathogenesis and it can be stated that hTid-1 may serve as an important therapeutic target for these disorders. Graphical Abstract ![]()
Video Abstract
Supplementary Information The online version contains supplementary material available at 10.1186/s12964-022-00912-5.
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Affiliation(s)
- Sagarika Banerjee
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Rupesh Chaturvedi
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.,School of Biotechnology and Special Centre for Systems Medicine, Jawaharlal Nehru University, New Delhi, India
| | - Anu Singh
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.
| | - Hemant R Kushwaha
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India. .,School of Biotechnology and Special Centre for Systems Medicine, Jawaharlal Nehru University, New Delhi, India.
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Mitochondrial "dysmorphology" in variant classification. Hum Genet 2021; 141:55-64. [PMID: 34750646 DOI: 10.1007/s00439-021-02378-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 09/25/2021] [Indexed: 10/19/2022]
Abstract
Mitochondrial disorders are challenging to diagnose. Exome sequencing has greatly enhanced the diagnostic precision of these disorders although interpreting variants of uncertain significance (VUS) remains a formidable obstacle. Whether specific mitochondrial morphological changes can aid in the classification of these variants is unknown. Here, we describe two families (four patients), each with a VUS in a gene known to affect the morphology of mitochondria through a specific role in the fission-fusion balance. In the first, the missense variant in MFF, encoding a fission factor, was associated with impaired fission giving rise to a characteristically over-tubular appearance of mitochondria. In the second, the missense variant in DNAJA3, which has no listed OMIM phenotype, was associated with fragmented appearance of mitochondria consistent with its published deficiency states. In both instances, the highly specific phenotypes allowed us to upgrade the classification of the variants. Our results suggest that, in select cases, mitochondrial "dysmorphology" can be helpful in interpreting variants to reach a molecular diagnosis.
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Medina-Moreno A, Henríquez JP. Maturation of a postsynaptic domain: Role of small Rho GTPases in organising nicotinic acetylcholine receptor aggregates at the vertebrate neuromuscular junction. J Anat 2021; 241:1148-1156. [PMID: 34342888 DOI: 10.1111/joa.13526] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 07/15/2021] [Accepted: 07/20/2021] [Indexed: 12/13/2022] Open
Abstract
The neuromuscular junction (NMJ) is the peripheral synapse formed between a motor axon and a skeletal muscle fibre that allows muscle contraction and the coordinated movement in many species. A main hallmark of the mature NMJ is the assembly of nicotinic acetylcholine receptor (nAChR) aggregates in the muscle postsynaptic domain, that distributes in perfect apposition to presynaptic motor terminals. To assemble its unique functional architecture, initial embryonic NMJs undergo an early postnatal maturation process characterised by the transformation of homogenous nAChR-containing plaques to elaborate and branched pretzel-like structures. In spite of a detailed morphological characterisation, the molecular mechanisms controlling the intracellular scaffolding that organises a postsynaptic domain at the mature NMJ have not been fully elucidated. In this review, we integrate evidence of key processes and molecules that have shed light on our current understanding of the NMJ maturation process. On the one hand, we consider in vitro studies revealing the potential role of podosome-like structures to define discrete low nAChR-containing regions to consolidate a plaque-to-pretzel transition at the NMJ. On the other hand, we focus on in vitro and in vivo evidence demonstrating that members of the Ras homologous (Rho) protein family of small GTPases (small Rho GTPases) play indispensable roles on NMJ maturation by regulating the stability of nAChR aggregates. We combine this evidence to propose that small Rho GTPases are key players in the assembly of podosome-like structures that drive the postsynaptic maturation of vertebrate NMJs.
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Affiliation(s)
- Angelymar Medina-Moreno
- Laboratory of Neuromuscular Studies (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA BioBio), Universidad de Concepción, Concepción, Chile
| | - Juan Pablo Henríquez
- Laboratory of Neuromuscular Studies (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA BioBio), Universidad de Concepción, Concepción, Chile
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An Inside Job: Molecular Determinants for Postsynaptic Localization of Nicotinic Acetylcholine Receptors. Molecules 2021; 26:molecules26113065. [PMID: 34063759 PMCID: PMC8196675 DOI: 10.3390/molecules26113065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/13/2021] [Accepted: 05/15/2021] [Indexed: 11/29/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) mediate fast synaptic transmission at neuromuscular and autonomic ganglionic synapses in the peripheral nervous system. The postsynaptic localization of muscle ((α1)2β1γδ) and neuronal ((α3β4)2β4) nicotinic receptors at these synapses is mediated by interactions between the nAChR intracellular domains and cytoplasmic scaffolding proteins. Recent high resolution structures and functional studies provide new insights into the molecular determinants that mediate these interactions. Surprisingly, they reveal that the muscle nAChR binds 1–3 rapsyn scaffolding molecules, which dimerize and thereby form an interconnected lattice between receptors. Moreover, rapsyn binds two distinct sites on the nAChR subunit cytoplasmic loops; the MA-helix on one or more subunits and a motif specific to the β subunit. Binding at the latter site is regulated by agrin-induced phosphorylation of βY390, and increases the stoichiometry of rapsyn/AChR complexes. Similarly, the neuronal nAChR may be localized at ganglionic synapses by phosphorylation-dependent interactions with 14-3-3 adaptor proteins which bind specific motifs in each of the α3 subunit cytoplasmic loops. Thus, postsynaptic localization of nAChRs is mediated by regulated interactions with multiple scaffolding molecules, and the stoichiometry of these complexes likely helps regulate the number, density, and stability of receptors at the synapse.
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Gao Y, Han X, Wei L, Yuan Y, Zhao C, Zhang M, Wang Z, Li X, Xu W. Study on the differential proteomics of rat hippocampal mitochondria during deep hypothermic circulatory arrest. ANNALS OF TRANSLATIONAL MEDICINE 2021; 9:346. [PMID: 33708973 PMCID: PMC7944285 DOI: 10.21037/atm-21-95] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 02/10/2021] [Indexed: 11/06/2022]
Abstract
BACKGROUND This study aimed to investigate the effect of deep hypothermic circulatory arrest (DHCA) on rat hippocampal mitochondrial protein expression and its differential proteomics, and explore the potential mechanisms behind the effect. METHODS We used internal jugular vein reflux and tail artery perfusion methods to establish the rat cardiopulmonary bypass (CPB) model. Rats were dissected to obtain the hippocampus, and the hippocampal mitochondria were purified. The mitochondrial morphology and the mitochondrial marker cytochrome C oxidase (COX) qualitatively examined via transmission electron microscopy and western-blot analysis, respectively. The qualified samples were subjected to isobaric tags for relative and absolute quantification (iTRAQ); we then established the CPB model again to obtain the rat hippocampus for cryoultramicrotomy, and used immunofluorescent double staining technique to qualitatively and semi-quantitatively verify two representative differentially expressed proteins. RESULTS By searching the Mascot 2.2 database, 29 differentially expressed proteins were obtained with statistical significance, including 21 known proteins and 8 unknowns. The expression level of COX and monoacylglycerol lipase did not change significantly (P>0.05) during the hyperacute phase; however, their intracellular localizations were altered. CONCLUSIONS DHCA induced the differential expression of 29 rat hippocampal mitochondrial proteins, some of which had altered intracellular localization. We speculated that the localized alteration of these proteins is one of the neuroprotection mechanisms that occurs during DHCA.
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Affiliation(s)
- Yongjun Gao
- Department of Neurosurgery, Second Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Xiuli Han
- Department of Stomatology, Children’s Hospital Affiliated to Kunming Medical University, Kunming, China
| | - Liang Wei
- Department of Neurosurgery, East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yong Yuan
- Department of Neurosurgery, Second Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Chengbin Zhao
- Department of Neurosurgery, Second Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Ming Zhang
- Department of Neurosurgery, Second Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Zheng Wang
- Department of Neurosurgery, Second Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Xuhui Li
- Department of Neurosurgery, Second Affiliated Hospital of Kunming Medical University, Kunming, China
| | - Wei Xu
- Department of Neurosurgery, Second Affiliated Hospital of Kunming Medical University, Kunming, China
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Zelada D, Bermedo-García F, Collao N, Henríquez JP. Motor function recovery: deciphering a regenerative niche at the neuromuscular synapse. Biol Rev Camb Philos Soc 2020; 96:752-766. [PMID: 33336525 PMCID: PMC7986695 DOI: 10.1111/brv.12675] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 11/20/2020] [Accepted: 11/25/2020] [Indexed: 12/13/2022]
Abstract
The coordinated movement of many organisms relies on efficient nerve–muscle communication at the neuromuscular junction (NMJ), a peripheral synapse composed of a presynaptic motor axon terminal, a postsynaptic muscle specialization, and non‐myelinating terminal Schwann cells. NMJ dysfunctions are caused by traumatic spinal cord or peripheral nerve injuries as well as by severe motor pathologies. Compared to the central nervous system, the peripheral nervous system displays remarkable regenerating abilities; however, this capacity is limited by the denervation time frame and depends on the establishment of permissive regenerative niches. At the injury site, detailed information is available regarding the cells, molecules, and mechanisms involved in nerve regeneration and repair. However, a regenerative niche at the final functional step of peripheral motor innervation, i.e. at the mature neuromuscular synapse, has not been deciphered. In this review, we integrate classic and recent evidence describing the cells and molecules that could orchestrate a dynamic ecosystem to accomplish successful NMJ regeneration. We propose that such a regenerative niche must ensure at least two fundamental steps for successful NMJ regeneration: the proper arrival of incoming regenerating axons to denervated postsynaptic muscle domains, and the resilience of those postsynaptic domains, in morphological and functional terms. We here describe and combine the main cellular and molecular responses involved in each of these steps as potential targets to help successful NMJ regeneration.
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Affiliation(s)
- Diego Zelada
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
| | - Francisca Bermedo-García
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
| | - Nicolás Collao
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
| | - Juan P Henríquez
- Neuromuscular Studies Laboratory (NeSt Lab), Department of Cell Biology, Faculty of Biological Sciences, Center for Advanced Microscopy (CMA Bio-Bio), Universidad de Concepción, Casilla 160-C, Concepción, Chile
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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.
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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
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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.
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Gupta S, Gangenahalli G. Analysis of molecular switch between leukocyte and substrate adhesion in bone marrow endothelial cells. Life Sci 2019; 238:116981. [DOI: 10.1016/j.lfs.2019.116981] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 10/03/2019] [Accepted: 10/16/2019] [Indexed: 01/26/2023]
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13
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Bai Y, Guo D, Sun X, Tang G, Liao T, Peng Y, Xu J, Shi L. Balanced Rac1 activity controls formation and maintenance of neuromuscular acetylcholine receptor clusters. J Cell Sci 2018; 131:jcs.215251. [PMID: 30012833 DOI: 10.1242/jcs.215251] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 07/02/2018] [Indexed: 11/20/2022] Open
Abstract
Rac1, an important Rho GTPase that regulates the actin cytoskeleton, has long been suggested to participate in acetylcholine receptor (AChR) clustering at the postsynaptic neuromuscular junction. However, how Rac1 is regulated and how it influences AChR clusters have remained unexplored. This study shows that breaking the balance of Rac1 regulation, by either increasing or decreasing its activity, led to impaired formation and maintenance of AChR clusters. By manipulating Rac1 activity at different stages of AChR clustering in cultured myotubes, we show that Rac1 activation was required for the initial formation of AChR clusters, but its persistent activation led to AChR destabilization, and uncontrolled hyperactivation of Rac1 even caused excessive myotube fusion. Both AChR dispersal and myotube fusion induced by Rac1 were dependent on its downstream effector Pak1. Two Rac1 GAPs and six Rac1 GEFs were screened and found to be important for normal AChR clustering. This study reveals that, although general Rac1 activity remains at low levels during terminal differentiation of myotubes and AChR cluster maintenance, tightly regulated Rac1 activity controls normal AChR clustering.
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Affiliation(s)
- Yanyang Bai
- JNU-HKUST Joint Laboratory for Neuroscience and Innovative Drug Research, College of Pharmacy, Jinan University, Guangzhou 510632, Guangdong, China
| | - Daji Guo
- JNU-HKUST Joint Laboratory for Neuroscience and Innovative Drug Research, College of Pharmacy, Jinan University, Guangzhou 510632, Guangdong, China
| | - Xiaoyu Sun
- JNU-HKUST Joint Laboratory for Neuroscience and Innovative Drug Research, College of Pharmacy, Jinan University, Guangzhou 510632, Guangdong, China
| | - Genyun Tang
- Department of Medical Genetics, Hunan Provincial Key Laboratory of Dong Medicine, Hunan University of Medicine, Huaihua 418000, Hunan, China
| | - Tailin Liao
- Department of Neurobiology, Key Laboratory of Medical Neurobiology of Ministry of Health, Zhejiang Province Key Laboratory of Neurobiology, Zhejiang University School of Medicine, Hangzhou 310058, Zhejiang, China
| | - Yinghui Peng
- JNU-HKUST Joint Laboratory for Neuroscience and Innovative Drug Research, College of Pharmacy, Jinan University, Guangzhou 510632, Guangdong, China
| | - Junyu Xu
- Department of Neurobiology, Key Laboratory of Medical Neurobiology of Ministry of Health, Zhejiang Province Key Laboratory of Neurobiology, Zhejiang University School of Medicine, Hangzhou 310058, Zhejiang, China
| | - Lei Shi
- JNU-HKUST Joint Laboratory for Neuroscience and Innovative Drug Research, College of Pharmacy, Jinan University, Guangzhou 510632, Guangdong, China
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Roy JP, Halford MM, Stacker SA. The biochemistry, signalling and disease relevance of RYK and other WNT-binding receptor tyrosine kinases. Growth Factors 2018; 36:15-40. [PMID: 29806777 DOI: 10.1080/08977194.2018.1472089] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The receptor tyrosine kinases (RTKs) are a well-characterized family of growth factor receptors that have central roles in human disease and are frequently therapeutically targeted. The RYK, ROR, PTK7 and MuSK subfamilies make up an understudied subset of WNT-binding RTKs. Numerous developmental, stem cell and pathological roles of WNTs, in particular WNT5A, involve signalling via these WNT receptors. The WNT-binding RTKs have highly context-dependent signalling outputs and stimulate the β-catenin-dependent, planar cell polarity and/or WNT/Ca2+ pathways. RYK, ROR and PTK7 members have a pseudokinase domain in their intracellular regions. Alternative signalling mechanisms, including proteolytic cleavage and protein scaffolding functions, have been identified for these receptors. This review explores the structure, signalling, physiological and pathological roles of RYK, with particular attention paid to cancer and the possibility of therapeutically targeting RYK. The other WNT-binding RTKs are compared with RYK throughout to highlight the similarities and differences within this subset of WNT receptors.
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Affiliation(s)
- James P Roy
- a Tumour Angiogenesis and Microenvironment Program , Peter MacCallum Cancer Centre , Melbourne , Australia
- b Sir Peter MacCallum Department of Oncology , The University of Melbourne , Parkville , Australia
| | - Michael M Halford
- a Tumour Angiogenesis and Microenvironment Program , Peter MacCallum Cancer Centre , Melbourne , Australia
| | - Steven A Stacker
- a Tumour Angiogenesis and Microenvironment Program , Peter MacCallum Cancer Centre , Melbourne , Australia
- b Sir Peter MacCallum Department of Oncology , The University of Melbourne , Parkville , Australia
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15
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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
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16
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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.
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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
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17
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Takamori M. Synaptic Homeostasis and Its Immunological Disturbance in Neuromuscular Junction Disorders. Int J Mol Sci 2017; 18:ijms18040896. [PMID: 28441759 PMCID: PMC5412475 DOI: 10.3390/ijms18040896] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 04/04/2017] [Accepted: 04/19/2017] [Indexed: 12/14/2022] Open
Abstract
In the neuromuscular junction, postsynaptic nicotinic acetylcholine receptor (nAChR) clustering, trans-synaptic communication and synaptic stabilization are modulated by the molecular mechanisms underlying synaptic plasticity. The synaptic functions are based presynaptically on the active zone architecture, synaptic vesicle proteins, Ca2+ channels and synaptic vesicle recycling. Postsynaptically, they are based on rapsyn-anchored nAChR clusters, localized sensitivity to ACh, and synaptic stabilization via linkage to the extracellular matrix so as to be precisely opposed to the nerve terminal. Focusing on neural agrin, Wnts, muscle-specific tyrosine kinase (a mediator of agrin and Wnts signalings and regulator of trans-synaptic communication), low-density lipoprotein receptor-related protein 4 (the receptor of agrin and Wnts and participant in retrograde signaling), laminin-network (including muscle-derived agrin), extracellular matrix proteins (participating in the synaptic stabilization) and presynaptic receptors (including muscarinic and adenosine receptors), we review the functional structures of the synapse by making reference to immunological pathogenecities in postsynaptic disease, myasthenia gravis. The synapse-related proteins including cortactin, coronin-6, caveolin-3, doublecortin, R-spondin 2, amyloid precursor family proteins, glia cell-derived neurotrophic factor and neurexins are also discussed in terms of their possible contribution to efficient synaptic transmission at the neuromuscular junction.
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Affiliation(s)
- Masaharu Takamori
- Neurological Center, Kanazawa-Nishi Hospital, Kanazawa, Ishikawa 920-0025, Japan.
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18
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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]
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19
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Cheng LH, Hung KF, Lee TC, Huang CY, Chiu WT, Lo JF, Huang TF. Mitochondrial co-chaperone protein Tid1 is required for energy homeostasis during skeletal myogenesis. Stem Cell Res Ther 2016; 7:185. [PMID: 27927223 PMCID: PMC5143475 DOI: 10.1186/s13287-016-0443-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 11/01/2016] [Accepted: 11/17/2016] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Tid1 is a mitochondrial co-chaperone protein and its transcript is abundantly expressed in skeletal muscle tissues. However, the physiological function of Tid1 during skeletal myogenesis remains unclear. METHODS In vitro induced differentiation assay of mouse myoblast C2C12 cells was applied to examine the physiological role of Tid1 during skeletal myogenesis. In addition, transgenic mice with muscle specific (HSA-Cre) Tid1 deletion were established and examined to determine the physiological function of Tid1 during skeletal muscle development in vivo. RESULTS Expression of Tid1 protein was upregulated in the differentiated C2C12 cells, and the HSA-Tid1f/f mice displayed muscular dystrophic phenotype. The expression of myosin heavy chain (MyHC), the protein served as the muscular development marker, was reduced in HSA-Tid1f/f mice at postnatal day (P)5 and P8. The protein levels of ATP sensor (p-AMPK) and mitochondrial biogenesis protein (PGC-1α) were also significantly reduced in HSA-Tid1f/f mice. Moreover, Tid1 deficiency induced apoptotic marker Caspase-3 in muscle tissues of HSA-Tid1f/f mice. Consistent with the in vivo finding, we observed that downregulation of Tid1 not only reduced the ATP production but also abolished the differentiation ability of C2C12 cells by impairing the mitochondrial activity. CONCLUSION Together, our results suggest that Tid1 deficiency reduces ATP production and abolishes mitochondrial activity, resulting in energy imbalance and promoting apoptosis of muscle cells during myogenesis. It will be of importance to understand the function of Tid1 during human muscular dystrophy in the future.
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Affiliation(s)
- Li-Hao Cheng
- Institute of Oral Biology, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Kai-Feng Hung
- Department of Dentistry, School of Dentistry, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Te-Chang Lee
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, Republic of China
| | - Chih-Yang Huang
- Graduate Institute of Chinese Medical Science and Institute of Medical Science, China Medical University, Taichung, Taiwan, Republic of China.,Institute of Basic Medical Science, China Medical University, Taichung, Taiwan, Republic of China.,Department of Health and Nutrition Biotechnology, Asia University, Taichung, Taiwan, Republic of China
| | - Wen-Ting Chiu
- Institute of Oral Biology, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Jeng-Fan Lo
- Institute of Oral Biology, National Yang-Ming University, Taipei, Taiwan, Republic of China. .,Department of Dentistry, School of Dentistry, National Yang-Ming University, Taipei, Taiwan, Republic of China. .,Graduate Institute of Chinese Medical Science and Institute of Medical Science, China Medical University, Taichung, Taiwan, Republic of China. .,Department of Dentistry, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China. .,Genome Research Center, National Yang-Ming University, Taipei, Taiwan, Republic of China. .,National Yang-Ming University VGH Genome Research Center, Taipei, Taiwan, Republic of China.
| | - Tung-Fu Huang
- School of Medicine, National Yang-Ming University, Taipei, Taiwan, Republic of China. .,Department of Orthopedics and Traumatology, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China.
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20
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Neuregulin1 displayed on motor axons regulates terminal Schwann cell-mediated synapse elimination at developing neuromuscular junctions. Proc Natl Acad Sci U S A 2016; 113:E479-87. [PMID: 26755586 DOI: 10.1073/pnas.1519156113] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Synaptic connections in the nervous system are rearranged during development and in adulthood as a feature of growth, plasticity, aging, and disease. Glia are implicated as active participants in these changes. Here we investigated a signal that controls the participation of peripheral glia, the terminal Schwann cells (SCs), at the neuromuscular junction (NMJ) in mice. Transgenic manipulation of the levels of membrane-tethered neuregulin1 (NRG1-III), a potent activator of SCs normally presented on motor axons, alters the rate of loss of motor inputs at NMJs during developmental synapse elimination. In addition, NMJs of adult transgenic mice that expressed excess axonal NRG1-III exhibited continued remodeling, in contrast to the more stable morphologies of controls. In fact, synaptic SCs of these adult mice with NRG1-III overexpression exhibited behaviors evident in wild type neonates during synapse elimination, including an affinity for the postsynaptic myofiber surface and phagocytosis of nerve terminals. Given that levels of NRG1-III expression normally peak during the period of synapse elimination, our findings identify axon-tethered NRG1 as a molecular determinant for SC-driven neuromuscular synaptic plasticity.
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21
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Niu G, Zhang H, Liu D, Chen L, Belani C, Wang HG, Cheng H. Tid1, the Mammalian Homologue of Drosophila Tumor Suppressor Tid56, Mediates Macroautophagy by Interacting with Beclin1-containing Autophagy Protein Complex. J Biol Chem 2015; 290:18102-18110. [PMID: 26055714 DOI: 10.1074/jbc.m115.665950] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Indexed: 12/19/2022] Open
Abstract
One of the fundamental functions of molecular chaperone proteins is to selectively conjugate cellular proteins, targeting them directly to lysosome. Some of chaperones, such as the stress-induced Hsp70, also play important roles in autophagosome-forming macroautophagy under various stress conditions. However, the role of their co-chaperones in autophagy regulation has not been well defined. We here show that Tid1, a DnaJ co-chaperone for Hsp70 and the mammalian homologue of the Drosophila tumor suppressor Tid56, is a key mediator of macroautophagy pathway. Ectopic expression of Tid1 induces autophagy by forming LC3+ autophagosome foci, whereas silencing Tid1 leads to drastic impairment of autophagy as induced by nutrient deprivation or rapamycin. In contrast, Hsp70 is dispensable for a role in nutrient deprivation-induced autophagy. The murine Tid1 can be replaced with human Tid1 in murine fibroblast cells for induction of autophagy. We further show that Tid1 increases autophagy flux by interacting with the Beclin1-PI3 kinase class III protein complex in response to autophagy inducing signal and that Tid1 is an essential mediator that connects IκB kinases to the Beclin1-containing autophagy protein complex. Together, these results reveal a crucial role of Tid1 as an evolutionarily conserved and essential mediator of canonical macroautophagy.
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Affiliation(s)
- Ge Niu
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Huan Zhang
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Dan Liu
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Li Chen
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland 21201
| | - Chandra Belani
- Penn State Hershey Cancer Institute, Penn State University College of Medicine, Hershey, Pennsylvania 17033
| | - Hong-Gang Wang
- Penn State Hershey Cancer Institute, Penn State University College of Medicine, Hershey, Pennsylvania 17033
| | - Hua Cheng
- Institute of Human Virology, University of Maryland School of Medicine, Baltimore, Maryland 21201; Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland 21201; Departments of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201; Departments of Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201.
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22
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Evoli A, Iorio R. Characteristics of myasthenia gravis with antibodies to muscle-specific kinase and low-density lipoprotein-related receptor protein 4. ACTA ACUST UNITED AC 2015. [DOI: 10.1111/cen3.12173] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Amelia Evoli
- Institute of Neurology; Catholic University; Roma Italy
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23
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Essential role of TID1 in maintaining mitochondrial membrane potential homogeneity and mitochondrial DNA integrity. Mol Cell Biol 2014; 34:1427-37. [PMID: 24492964 DOI: 10.1128/mcb.01021-13] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The tumorous imaginal disc 1 (TID1) protein localizes mainly to the mitochondrial compartment, wherein its function remains largely unknown. Here we report that TID1 regulates the steady-state homogeneity of the mitochondrial membrane potential (Δψ) and maintains the integrity of mitochondrial DNA (mtDNA). Silencing of TID1 with RNA interference leads to changes in the distribution of Δψ along the mitochondrial network, characterized by an increase in Δψ in focal regions. This effect can be rescued by ectopic expression of a TID1 construct with an intact J domain. Chronic treatment with a low dose of oligomycin, an inhibitor of F1Fo ATP synthase, decreases the cellular ATP content and phenocopies TID1 loss of function, indicating a connection between the disruption of mitochondrial bioenergetics and hyperpolarization. Prolonged silencing of TID1 or low-dose oligomycin treatment leads to the loss of mtDNA and the consequent inhibition of oxygen consumption. Biochemical and colocalization data indicate that complex I aggregation underlies the focal accumulation of Δψ in TID1-silenced cells. Given that TID1 is proposed to function as a cochaperone, these data show that TID1 prevents complex I aggregation and support the existence of a TID1-mediated stress response to ATP synthase inhibition.
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24
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Wnt signaling in skeletal muscle dynamics: myogenesis, neuromuscular synapse and fibrosis. Mol Neurobiol 2013; 49:574-89. [PMID: 24014138 DOI: 10.1007/s12035-013-8540-5] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 08/15/2013] [Indexed: 12/21/2022]
Abstract
The signaling pathways activated by Wnt ligands are related to a wide range of critical cell functions, such as cell division, migration, and synaptogenesis. Here, we summarize compelling evidence on the role of Wnt signaling on several features of skeletal muscle physiology. We briefly review the role of Wnt pathways on the formation of muscle fibers during prenatal and postnatal myogenesis, highlighting its role on the activation of stem cells of the adult muscles. We also discuss how Wnt signaling regulates the precise formation of neuromuscular synapses, by modulating the differentiation of presynaptic and postsynaptic components, particularly regarding the clustering of acetylcholine receptors on the muscle membrane. In addition, based on previous evidence showing that Wnt pathways are linked to several diseases, such as Alzheimer's and cancer, we address recent studies indicating that Wnt signaling plays a key role in skeletal muscle fibrosis, a disease characterized by an increase in the extracellular matrix components leading to failure in muscle regeneration, tissue disorganization and loss of muscle activity. In this context, we also discuss the possible cross-talk between the Wnt/β-catenin pathway with two other critical profibrotic pathways, transforming growth factor β and connective tissue growth factor, which are potent stimulators of the accumulation of connective tissue, an effect characteristic of the fibrotic condition. As it has emerged in other pathological conditions, we suggests that muscle fibrosis may be a consequence of alterations of Wnt signaling activity.
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Takamori M. Structure of the neuromuscular junction: function and cooperative mechanisms in the synapse. Ann N Y Acad Sci 2013; 1274:14-23. [PMID: 23252893 DOI: 10.1111/j.1749-6632.2012.06784.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
As an overview of the structure of the neuromuscular junction, three items are described focusing on cooperative mechanisms involving the synapse and leading to muscle contraction: (1) presynaptic acetylcholine release regulated by vesicle cycling (exocytosis and endocytosis); the fast-mode of endocytosis requires a large influx of external Ca(2+) and is promoted by the activation of G protein-coupled receptors and receptor tyrosine kinases; (2) postsynaptic acetylcholine receptor clustering mediated by the muscle-specific, Dok7-stimulated tyrosine kinase (MuSK) through two signaling mechanisms: one via agrin-Lrp4-MuSK (Ig1/2 domains) and the second via Wnt-MuSK (Frizzled-like cysteine-rich domain)-adaptor Dishevelled; Wnts/MuSK and Lrp4 direct a retrograde signal to presynaptic differentiation; (3) muscle contractile machinery regulated by Ca(2+) -release and Ca(2+) -influx channels, including the depolarization-activated ryanodine receptor-1 and the receptor- and/or store-operated transient receptor potential canonical. The first mechanism is dysfunctional in Lambert-Eaton myasthenic syndrome, the second in anti-acetylcholine receptor-negative myasthenia gravis (MG), and the third in thymoma-associated MG.
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26
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Rudell JB, Ferns MJ. Regulation of muscle acetylcholine receptor turnover by β subunit tyrosine phosphorylation. Dev Neurobiol 2013; 73:399-410. [PMID: 23325468 DOI: 10.1002/dneu.22070] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 11/17/2012] [Accepted: 12/29/2012] [Indexed: 12/21/2022]
Abstract
At the neuromuscular junction (NMJ), the postsynaptic localization of muscle acetylcholine receptor (AChR) is regulated by neural signals and occurs via several processes including metabolic stabilization of the receptor. However, the molecular mechanisms that influence receptor stability remain poorly defined. Here, we show that neural agrin and the tyrosine phosphatase inhibitor, pervanadate slow the degradation of surface receptor in cultured muscle cells. Their action is mediated by tyrosine phosphorylation of the AChR β subunit, as agrin and pervandate had no effect on receptor half-life in AChR-β(3F/3F) muscle cells, which have targeted mutations of the β subunit cytoplasmic tyrosines. Moreover, in wild type AChR-β(3Y) muscle cells, we found a linear relationship between average receptor half-life and the percentage of AChR with phosphorylated β subunit, with half-lives of 12.7 and 23 h for nonphosphorylated and phosphorylated receptor, respectively. Surprisingly, pervanadate increased receptor half-life in AChR-β(3Y) myotubes in the absence of clustering, and agrin failed to increase receptor half-life in AChR-β(3F/3F) myotubes even in the presence of clustering. The metabolic stabilization of the AChR was mediated specifically by phosphorylation of βY390 as mutation of this residue abolished β subunit phosphorylation but did not affect δ subunit phosphorylation. Receptor stabilization also led to higher receptor levels, as agrin increased surface AChR by 30% in AChR-β(3Y) but not AChR-β(3F/3F) myotubes. Together, these findings identify an unexpected role for agrin-induced phosphorylation of β(Y390) in downregulating AChR turnover. This likely stabilizes AChR at developing synapses, and contributes to the extended half-life of AChR at adult NMJs.
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Affiliation(s)
- John B Rudell
- Department of Physiology and Membrane Biology, University of California Davis, Davis, CA, USA
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27
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Zong Y, Jin R. Structural mechanisms of the agrin-LRP4-MuSK signaling pathway in neuromuscular junction differentiation. Cell Mol Life Sci 2012. [PMID: 23178848 DOI: 10.1007/s00018-012-1209-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The neuromuscular junction (NMJ) is the most extensively studied model of neuronal synaptogenesis. Acetylcholine receptor (AChR) clustering on the postsynaptic membrane is a cardinal event in the differentiation of NMJs. AChR clustering and postsynaptic differentiation is orchestrated by sophisticated interactions among three proteins: the neuron-secreted proteoglycan agrin, the co-receptor LRP4, and the muscle-specific receptor tyrosine kinase MuSK. LRP4 and MuSK act as scaffolds for multiple binding partners, resulting in a complex and dynamic network of interacting proteins that is required for AChR clustering. In this review, we discuss the structural basis for NMJ postsynaptic differentiation mediated by the agrin-LRP4-MuSK signaling pathway.
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Affiliation(s)
- Yinong Zong
- Center for Neuroscience, Aging, and Stem Cell Research, Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA, 92037, USA
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28
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Singhal N, Martin PT. Role of extracellular matrix proteins and their receptors in the development of the vertebrate neuromuscular junction. Dev Neurobiol 2012; 71:982-1005. [PMID: 21766463 DOI: 10.1002/dneu.20953] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The vertebrate neuromuscular junction (NMJ) remains the best-studied model for understanding the mechanisms involved in synaptogenesis, due to its relatively large size, its simplicity of patterning, and its unparalleled experimental accessibility. During neuromuscular development, each skeletal myofiber secretes and deposits around its extracellular surface an assemblage of extracellular matrix (ECM) proteins that ultimately form a basal lamina. This is also the case at the NMJ, where the motor nerve contributes additional factors. Before most of the current molecular components were known, it was clear that the synaptic ECM of adult skeletal muscles was unique in composition and contained factors sufficient to induce the differentiation of both pre- and postsynaptic membranes. Biochemical, genetic, and microscopy studies have confirmed that agrin, laminin (221, 421, and 521), collagen IV (α3-α6), collagen XIII, perlecan, and the ColQ-bound form of acetylcholinesterase are all synaptic ECM proteins with important roles in neuromuscular development. The roles of their many potential receptors and/or binding proteins have been more difficult to assess at the genetic level due to the complexity of membrane interactions with these large proteins, but roles for MuSK-LRP4 in agrin signaling and for integrins, dystroglycan, and voltage-gated calcium channels in laminin-dependent phenotypes have been identified. Synaptic ECM proteins and their receptors are involved in almost all aspects of synaptic development, including synaptic initiation, topography, ultrastructure, maturation, stability, and transmission.
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Affiliation(s)
- Neha Singhal
- Center for Gene Therapy, The Research Institute at Nationwide Children's Hospital, Department of Pediatrics, Ohio State University College of Medicine, Columbus, Ohio 43205, USA
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29
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Molecular mechanisms underlying maturation and maintenance of the vertebrate neuromuscular junction. Trends Neurosci 2012; 35:441-53. [PMID: 22633140 DOI: 10.1016/j.tins.2012.04.005] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 04/09/2012] [Accepted: 04/15/2012] [Indexed: 01/22/2023]
Abstract
The vertebrate neuromuscular junction (NMJ), a peripheral synapse formed between motoneuron and skeletal muscle, is characterized by a protracted postnatal period of maturation and life-long maintenance. In neuromuscular disorders such as congenital myasthenic syndromes (CMSs), disruptions of NMJ maturation and/or maintenance are frequently observed. In particular, defective neuromuscular transmission associated with structural and molecular abnormalities at the pre- and postsynaptic membranes, as well as at the synaptic cleft, has been reported in these patients. Here, we review recent advances in the understanding of molecular and cellular events that mediate NMJ maturation and maintenance. The underlying regulatory mechanisms, including key molecular regulators at the presynaptic nerve terminal, synaptic cleft, and postsynaptic muscle membrane, are discussed.
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Barik A, Xiong WC, Mei L. MuSK: A Kinase Critical for the Formation and Maintenance of the Neuromuscular Junction. ACTA ACUST UNITED AC 2012. [DOI: 10.1007/978-1-61779-824-5_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
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31
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Klooster R, Plomp JJ, Huijbers MG, Niks EH, Straasheijm KR, Detmers FJ, Hermans PW, Sleijpen K, Verrips A, Losen M, Martinez-Martinez P, De Baets MH, van der Maarel SM, Verschuuren JJ. Muscle-specific kinase myasthenia gravis IgG4 autoantibodies cause severe neuromuscular junction dysfunction in mice. Brain 2012; 135:1081-101. [DOI: 10.1093/brain/aws025] [Citation(s) in RCA: 158] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Abstract
Congenital myasthenic syndromes (CMS) represent a heterogeneous group of disorders in which the safety margin of neuromuscular transmission is compromised by one or more specific mechanisms. Clinical, electrophysiologic, and morphologic studies have paved the way for detecting CMS-related mutations in proteins residing in the nerve terminal, the synaptic basal lamina, or in the postsynaptic region of the motor endplate. The disease proteins identified to date include the acetylcholine receptor, acetylcholinesterase, choline acetyltransferase, rapsyn, and Na(v)1.4, muscle-specific kinase, agrin, β2-laminin, downstream of tyrosine kinase 7, and glutamine-fructose-6-phosphate transaminase 1. Analysis of electrophysiologic and biochemical properties of mutant proteins expressed in heterologous systems have contributed crucially to defining the molecular consequences of the observed mutations and have resulted in improved therapy of most CMS.
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Affiliation(s)
- Andrew G Engel
- Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA.
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Henríquez JP, Krull CE, Osses N. The Wnt and BMP families of signaling morphogens at the vertebrate neuromuscular junction. Int J Mol Sci 2011; 12:8924-46. [PMID: 22272112 PMCID: PMC3257109 DOI: 10.3390/ijms12128924] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Revised: 11/18/2011] [Accepted: 11/22/2011] [Indexed: 11/16/2022] Open
Abstract
The neuromuscular junction has been extensively employed in order to identify crucial determinants of synaptogenesis. At the vertebrate neuromuscular synapse, extracellular matrix and signaling proteins play stimulatory and inhibitory roles on the assembly of functional synapses. Studies in invertebrate species have revealed crucial functions of early morphogens during the assembly and maturation of the neuromuscular junction. Here, we discuss growing evidence addressing the function of Wnt and Bone morphogenetic protein (BMP) signaling pathways at the vertebrate neuromuscular synapse. We focus on the emerging role of Wnt proteins as positive and negative regulators of postsynaptic differentiation. We also address the possible involvement of BMP pathways on motor neuron behavior for the assembly and/or regeneration of the neuromuscular junction.
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Affiliation(s)
- Juan P. Henríquez
- Laboratory of Developmental Neurobiology (LDNB), Department of Cell Biology, Faculty of Biological Sciences, University of Concepcion, and CMA Bio-Bio, Concepcion 4089100, Chile
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +56-41-220-4531; Fax: +56-41-224-5975
| | - Catherine E. Krull
- University of Michigan, 5211 Dental, Ann Arbor, Michigan, MI 48109, USA; E-Mail:
| | - Nelson Osses
- Institute of Chemistry, Faculty of Sciences, Pontificia Universidad Católica de Valparaíso, Valparaiso 2340025, Chile; E-Mail:
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Proft J, Faraji J, Robbins JC, Zucchi FCR, Zhao X, Metz GA, Braun JEA. Identification of bilateral changes in TID1 expression in the 6-OHDA rat model of Parkinson's disease. PLoS One 2011; 6:e26045. [PMID: 22016808 PMCID: PMC3189242 DOI: 10.1371/journal.pone.0026045] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Accepted: 09/16/2011] [Indexed: 01/06/2023] Open
Abstract
Parkinson's disease (PD) is a common neurodegenerative disease characterized by the loss of dopaminergic neurons in the substantia nigra and the aggregation of α-synuclein into Lewy bodies. Existing therapies address motor dysfunction but do not halt progression of the disease. A still unresolved question is the biochemical pathway that modulates the outcome of protein misfolding and aggregation processes in PD. The molecular chaperone network plays an important defensive role against cellular protein misfolding and has been identified as protective in experimental models of protein misfolding diseases like PD. Molecular mechanisms underlying chaperone-neuroprotection are actively under investigation. Current evidence implicates a number of molecular chaperones in PD including Hsp25, Hsp70 and Hsp90, however their precise involvement in the neurodegenerative cascade is unresolved. The J protein family (DnaJ or Hsp40 protein family) has long been known to be important in protein conformational processes.We assessed sensory and motor function of control and PD rats and then evaluated the brain region-specific expression levels of select J proteins by Western analysis. Surprisingly, we observed a widespread 26 kDa breakdown product of the J protein, TID1, (tumorous imaginal discs, mtHsp40 or DnaJ3) in a 6-hydroxydopamine (6-OHDA) rat model of PD in which food handling, gait symmetry and sensory performance were impaired. Greater behavioral deficits were associated with lower TID1 expression. Furthermore, direct application of either 6-OHDA or MPP+ (1-methyl-4-phenylpyridinum) to CAD (CNS-derived catecholinaminergic neuronal cell line) cell cultures, reduced TID1 expression levels.Our results suggest that changes in cellular TID1 are a factor in the pathogenesis of PD by impeding functional and structural compensation and exaggerating neurodegenerative processes. In contrast, no changes were observed in CSPα, Hsp40, Hsp70, Hsc70 and PrP(C) levels and no activation of caspase3 was observed. This study links TID1 to PD and provides a new target for therapeutics that halts the PD progression.
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Affiliation(s)
- Juliane Proft
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, Canada
| | - Jamshid Faraji
- Canadian Centre for Behavioural Neuroscience, University of Lethbridge, Lethbridge, Canada
- Neuroscience Research Centre, Golestan University of Medical Sciences, Gorgan, Islamic Republic of Iran
| | - Jerrah C. Robbins
- Canadian Centre for Behavioural Neuroscience, University of Lethbridge, Lethbridge, Canada
| | - Fabiola C. R. Zucchi
- Canadian Centre for Behavioural Neuroscience, University of Lethbridge, Lethbridge, Canada
| | - Xiaoxi Zhao
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, Canada
| | - Gerlinde A. Metz
- Canadian Centre for Behavioural Neuroscience, University of Lethbridge, Lethbridge, Canada
| | - Janice E. A. Braun
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, Canada
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Nestin negatively regulates postsynaptic differentiation of the neuromuscular synapse. Nat Neurosci 2011; 14:324-30. [PMID: 21278733 PMCID: PMC3069133 DOI: 10.1038/nn.2747] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Accepted: 12/22/2010] [Indexed: 01/14/2023]
Abstract
Positive and negative regulation of neurotransmitter receptor aggregation on the postsynaptic membrane is a critical event during synapse formation. Acetylcholine (ACh) and agrin are two opposing signals that regulate ACh receptor (AChR) clustering during neuromuscular junction (NMJ) development. ACh induces dispersion of AChR clusters that are not stabilized by agrin via a cyclin-dependent kinase 5 (Cdk5)-mediated mechanism, but regulation of Cdk5 activation is poorly understood. Here we show that the intermediate filament protein nestin physically interacts with Cdk5 and is required for ACh-induced association of p35, the co-activator of Cdk5, with the muscle membrane. Blockade of nestin-dependent signaling inhibits ACh-induced Cdk5 activation and the dispersion of AChR clusters in cultured myotubes. Similar to the effects of Cdk5 gene inactivation, knockdown of nestin in agrin-deficient embryos significantly restores AChR clusters. These results suggest that nestin is required for ACh-induced, Cdk5-dependent dispersion of AChR clusters during NMJ development.
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Hallock PT, Xu CF, Park TJ, Neubert TA, Curran T, Burden SJ. Dok-7 regulates neuromuscular synapse formation by recruiting Crk and Crk-L. Genes Dev 2011; 24:2451-61. [PMID: 21041412 DOI: 10.1101/gad.1977710] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Agrin, released by motor neurons, promotes neuromuscular synapse formation by stimulating MuSK, a receptor tyrosine kinase expressed in skeletal muscle. Phosphorylated MuSK recruits docking protein-7 (Dok-7), an adaptor protein that is expressed selectively in muscle. In the absence of Dok-7, neuromuscular synapses fail to form, and mutations that impair Dok-7 are a major cause of congenital myasthenia in humans. How Dok-7 stimulates synaptic differentiation is poorly understood. Once recruited to MuSK, Dok-7 directly stimulates MuSK kinase activity. This unusual activity of an adapter protein is mediated by the N-terminal region of Dok-7, whereas most mutations that cause congenital myasthenia truncate the C-terminal domain. Here, we demonstrate that Dok-7 also functions downstream from MuSK, and we identify the proteins that are recruited to the C-terminal domain of Dok-7. We show that Agrin stimulates phosphorylation of two tyrosine residues in the C-terminal domain of Dok-7, which leads to recruitment of two adapter proteins: Crk and Crk-L. Furthermore, we show that selective inactivation of Crk and Crk-L in skeletal muscle leads to severe defects in neuromuscular synapses in vivo, revealing a critical role for Crk and Crk-L downstream from Dok-7 in presynaptic and postsynaptic differentiation.
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Affiliation(s)
- Peter T Hallock
- Molecular Neurobiology Program, Skirball Institute of Biomolecular Medicine, New York University Medical School, New York, New York 10016, USA
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37
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Dityatev A, Seidenbecher CI, Schachner M. Compartmentalization from the outside: the extracellular matrix and functional microdomains in the brain. Trends Neurosci 2011; 33:503-12. [PMID: 20832873 DOI: 10.1016/j.tins.2010.08.003] [Citation(s) in RCA: 162] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 08/13/2010] [Accepted: 08/13/2010] [Indexed: 10/19/2022]
Abstract
The extracellular matrix (ECM) of the central nervous system is well recognized as a migration and diffusion barrier that allows for the trapping and presentation of growth factors to their receptors at the cell surface. Recent data highlight the importance of ECM molecules as synaptic and perisynaptic scaffolds that direct the clustering of neurotransmitter receptors in the postsynaptic compartment and that present barriers to reduce the lateral diffusion of membrane proteins away from synapses. The ECM also contributes to the migration and differentiation of stem cells in the neurogenic niche and organizes the polarized localization of ion channels and transporters at contacts between astrocytic processes and blood vessels. Thus, the ECM contributes to functional compartmentalization in the brain.
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Affiliation(s)
- Alexander Dityatev
- Department of Neuroscience and Brain Technologies, Italian Institute of Technology, via Morego 30, Genova, Italy.
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38
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Abstract
The c-Met receptor tyrosine kinase (MetR) is frequently overexpressed and constitutively phosphorylated in a number of human malignancies. Activation of the receptor by its ligand, hepatocyte growth factor (HGF), leads to increased cell proliferation, motility, survival and disruption of adherens junctions. In this study, we show that hTid-1, a DNAJ/Hsp40 chaperone, represents a novel modulator of the MetR signaling pathway. hTid-1 is a co-chaperone of the Hsp70 family of proteins, and has been shown to regulate a number of cellular signaling proteins including several involved in tumorigenic and apoptotic pathways. In this study we demonstrate that hTid-1 binds to unphosphorylated MetR and becomes dissociated from the receptor upon HGF stimulation. Overexpression of the short form of hTid-1 (hTid-1(S)) in 786-0 renal clear cell carcinomas (RCCs) enhances MetR kinase activity leading to an increase in HGF-mediated cell migration with no discernible effect on cell proliferation. By contrast, knockdown of hTid-1 markedly impairs both the onset and amplitude of MetR phosphorylation in response to HGF without altering receptor protein levels. hTid-1-depleted cells display defective migratory properties, coincident with inhibition of ERK/MAP kinase and STAT3 pathways. Taken together, our findings denote hTid-1(S) as an essential regulatory component of MetR signaling. We propose that the binding of hTid-1(S) to MetR may stabilize the receptor in a ligand-competent state and this stabilizing function may influence conformational changes that take place during the catalytic cycle that promote kinase activation. Given the prevalence of HGF/MetR pathway activation in human cancers, targeted inhibition of hTid-1 may be a useful therapeutic in the management of MetR-dependent malignancies.
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Gomez AM, Van Den Broeck J, Vrolix K, Janssen SP, Lemmens MAM, Van Der Esch E, Duimel H, Frederik P, Molenaar PC, Martínez-Martínez P, De Baets MH, Losen M. Antibody effector mechanisms in myasthenia gravis-pathogenesis at the neuromuscular junction. Autoimmunity 2010; 43:353-70. [PMID: 20380584 DOI: 10.3109/08916930903555943] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Myasthenia gravis (MG) is an autoimmune disorder caused by autoantibodies that are either directed to the muscle nicotinic acetylcholine receptor (AChR) or to the muscle-specific tyrosine kinase (MuSK). These autoantibodies define two distinct subforms of the disease-AChR-MG and MuSK-MG. Both AChR and MuSK are expressed on the postsynaptic membrane of the neuromuscular junction (NMJ), which is a highly specialized region of the muscle dedicated to receive and process signals from the motor nerve. Autoantibody binding to proteins of the postsynaptic membrane leads to impaired neuromuscular transmission and muscle weakness. Pro-inflammatory antibodies of the human IgG1 and IgG3 subclass modulate the AChR, cause complement activation, and attract lymphocytes; together acting to decrease levels of the AChR and AChR-associated proteins and to reduce postsynaptic folding. In patients with anti-MuSK antibodies, there is no evidence of loss of junctional folds and no apparent loss of AChR density. Anti-MuSK antibodies are predominantly of the IgG4 isotype, which functionally differs from other IgG subclasses in its anti-inflammatory activity. Moreover, IgG4 undergoes a posttranslational modification termed Fab arm exchange that prevents cross-linking of antigens. These findings suggest that MuSK-MG may be different in etiological and pathological mechanisms from AChR-MG. The effector functions of IgG subclasses on synapse structure and function are discussed in this review.
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Affiliation(s)
- Alejandro M Gomez
- Neuroimmunology Group, Department of Neuroscience, School of Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
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Ghazanfari N, Fernandez KJ, Murata Y, Morsch M, Ngo ST, Reddel SW, Noakes PG, Phillips WD. Muscle specific kinase: organiser of synaptic membrane domains. Int J Biochem Cell Biol 2010; 43:295-8. [PMID: 20974278 DOI: 10.1016/j.biocel.2010.10.008] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Revised: 10/15/2010] [Accepted: 10/15/2010] [Indexed: 11/19/2022]
Abstract
Muscle Specific Kinase (MuSK) is a transmembrane tyrosine kinase vital for forming and maintaining the mammalian neuromuscular junction (NMJ: the synapse between motor nerve and skeletal muscle). MuSK expression switches on during skeletal muscle differentiation. MuSK then becomes restricted to the postsynaptic membrane of the NMJ, where it functions to cluster acetylcholine receptors (AChRs). The expression, activation and turnover of MuSK are each regulated by signals from the motor nerve terminal. MuSK forms the core of an emerging signalling complex that can be acutely activated by neural agrin (N-agrin), a heparin sulfate proteoglycan secreted from the nerve terminal. MuSK activation initiates complex intracellular signalling events that coordinate the local synthesis and assembly of synaptic proteins. The importance of MuSK as a synapse organiser is highlighted by cases of autoimmune myasthenia gravis in which MuSK autoantibodies can deplete MuSK from the postsynaptic membrane, leading to complete disassembly of the adult NMJ.
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Affiliation(s)
- Nazanin Ghazanfari
- Physiology and Bosch Institute, Anderson Stuart Bldg (F13), The University of Sydney, Sydney, NSW 2006, Australia.
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41
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Cole RN, Ghazanfari N, Ngo ST, Gervásio OL, Reddel SW, Phillips WD. Patient autoantibodies deplete postsynaptic muscle-specific kinase leading to disassembly of the ACh receptor scaffold and myasthenia gravis in mice. J Physiol 2010; 588:3217-29. [PMID: 20603331 PMCID: PMC2976017 DOI: 10.1113/jphysiol.2010.190298] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2010] [Accepted: 07/02/2010] [Indexed: 01/14/2023] Open
Abstract
The postsynaptic muscle-specific kinase (MuSK) coordinates formation of the neuromuscular junction (NMJ) during embryonic development. Here we have studied the effects of MuSK autoantibodies upon the NMJ in adult mice. Daily injections of IgG from four MuSK autoantibody-positive myasthenia gravis patients (MuSK IgG; 45 mg day(1)i.p. for 14 days) caused reductions in postsynaptic ACh receptor (AChR) packing as assessed by fluorescence resonance energy transfer (FRET). IgG from the patients with the highest titres of MuSK autoantibodies caused large (51-73%) reductions in postsynaptic MuSK staining (cf. control mice; P < 0.01) and muscle weakness. Among mice injected for 14 days with control and MuSK patient IgGs, the residual level of MuSK correlated with the degree of impairment of postsynaptic AChR packing. However, the loss of postsynaptic MuSK preceded this impairment of postsynaptic AChR. When added to cultured C2 muscle cells the MuSK autoantibodies caused tyrosine phosphorylation of MuSK and the AChR beta-subunit, and internalization of MuSK from the plasma membrane. The results suggest a pathogenic mechanism in which MuSK autoantibodies rapidly deplete MuSK from the postsynaptic membrane leading to progressive dispersal of postsynaptic AChRs. Moreover, maintenance of postsynaptic AChR packing at the adult NMJ would appear to depend upon physical engagement of MuSK with the AChR scaffold, notwithstanding activation of the MuSK-rapsyn system of AChR clustering.
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Affiliation(s)
- R N Cole
- Physiology, Anderson Stuart Bldg (F13), University of Sydney, NSW 2006 Australia
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42
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Wang J, Fu XQ, Lei WL, Wang T, Sheng AL, Luo ZG. Nuclear factor kappaB controls acetylcholine receptor clustering at the neuromuscular junction. J Neurosci 2010; 30:11104-13. [PMID: 20720118 PMCID: PMC6633475 DOI: 10.1523/jneurosci.2118-10.2010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Revised: 06/29/2010] [Accepted: 07/02/2010] [Indexed: 11/21/2022] Open
Abstract
At the vertebrate neuromuscular junction (NMJ), acetylcholine receptor (AChR) clustering is stimulated by motor neuron-derived glycoprotein Agrin and requires a number of intracellular signal or structural proteins, including AChR-associated scaffold protein Rapsyn. Here, we report a role of nuclear factor kappaB (NF-kappaB), a well known transcription factor involved in a variety of immune responses, in regulating AChR clustering at the NMJ. We found that downregulating the expression of RelA/p65 subunit of NF-kappaB or inhibiting NF-kappaB activity by overexpression of mutated form of IkappaB (inhibitor kappaB), which is resistant to proteolytic degradation and thus constitutively keeps NF-kappaB inactive in the cytoplasma, impeded the formation of AChR clusters in cultured C2C12 muscle cells stimulated by Agrin. In contrast, overexpression of RelA/p65 promoted AChR clustering. Furthermore, we investigated the mechanism by which NF-kappaB regulates AChR clustering. Interestingly, we found that downregulating the expression of RelA/p65 caused a marked reduction in the protein and mRNA level of Rapsyn and upregulation of RelA/p65 enhanced Rapsyn promoter activity. Mutation of NF-kappaB binding site on Rapsyn promoter prevented responsiveness to RelA/p65 regulation. Moreover, forced expression of Rapsyn in RelA/p65 downregulated muscle cells partially rescued AChR clusters, suggesting that NF-kappaB regulates AChR clustering, at least partially through the transcriptional regulation of Rapsyn. In line with this notion, genetic ablation of RelA/p65 selectively in the skeletal muscle caused a reduction of AChR density at the NMJ and a decrease in the level of Rapsyn. Thus, NF-kappaB signaling controls AChR clustering through transcriptional regulation of synaptic protein Rapsyn.
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Affiliation(s)
- Jia Wang
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Xiu-Qing Fu
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Wen-Liang Lei
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Tong Wang
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Ai-Li Sheng
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
| | - Zhen-Ge Luo
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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43
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Niks EH, Kuks JBM, Wokke JHJ, Veldman H, Bakker E, Verschuuren JJGM, Plomp JJ. Pre- and postsynaptic neuromuscular junction abnormalities in musk myasthenia. Muscle Nerve 2010; 42:283-8. [PMID: 20544919 DOI: 10.1002/mus.21642] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Autoantibodies to muscle-specific kinase (MuSK) can cause myasthenia gravis (MG). The pathophysiological mechanism remains unknown. We report in vitro electrophysiological and histological studies of the neuromuscular junction in a MuSK MG patient. Low levels of presynaptic acetylcholine release and small miniature endplate potentials were found. This combination of pre- and postsynaptic abnormalities was supported by histology, revealing partially denervated postsynaptic areas, and some degeneration of postsynaptic folds. Results suggest that anti-MuSK antibodies reduce the stability of muscle-nerve contact.
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Affiliation(s)
- Erik H Niks
- Department of Neurology, Leiden University Medical Center, K5Q-114, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
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44
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Abstract
A critical step in synaptic development is the differentiation of presynaptic and postsynaptic compartments. This complex process is regulated by a variety of secreted factors that serve as synaptic organizers. Specifically, fibroblast growth factors, Wnts, neurotrophic factors and various other intercellular signaling molecules are proposed to regulate presynaptic and/or postsynaptic differentiation. Many of these factors appear to function at both the neuromuscular junction and in the central nervous system, although the specific function of the molecules differs between the two. Here we review secreted molecules that organize the synaptic compartments and discuss how these molecules shape synaptic development, focusing on mammalian in vivo systems. Their critical role in shaping a functional neural circuit is underscored by their possible link to a wide range of neurological and psychiatric disorders both in animal models and by mutations identified in human patients.
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Affiliation(s)
- Erin M Johnson-Venkatesh
- Molecular & Behavioral Neuroscience Institute, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA
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45
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Stetler RA, Gan Y, Zhang W, Liou AK, Gao Y, Cao G, Chen J. Heat shock proteins: cellular and molecular mechanisms in the central nervous system. Prog Neurobiol 2010; 92:184-211. [PMID: 20685377 DOI: 10.1016/j.pneurobio.2010.05.002] [Citation(s) in RCA: 199] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Revised: 05/23/2010] [Accepted: 05/27/2010] [Indexed: 12/30/2022]
Abstract
Emerging evidence indicates that heat shock proteins (HSPs) are critical regulators in normal neural physiological function as well as in cell stress responses. The functions of HSPs represent an enormous and diverse range of cellular activities, far beyond the originally identified roles in protein folding and chaperoning. HSPs are now understood to be involved in processes such as synaptic transmission, autophagy, ER stress response, protein kinase and cell death signaling. In addition, manipulation of HSPs has robust effects on the fate of cells in neurological injury and disease states. The ongoing exploration of multiple HSP superfamilies has underscored the pluripotent nature of HSPs in the cellular context, and has demanded the recent revamping of the nomenclature referring to these families to reflect a re-organization based on structure and function. In keeping with this re-organization, we first discuss the HSP superfamilies in terms of protein structure, regulation, expression and distribution in the brain. We then explore major cellular functions of HSPs that are relevant to neural physiological states, and from there we discuss known and proposed HSP impacts on major neurological disease states. This review article presents a three-part discussion on the array of HSP families relevant to neuronal tissue, their cellular functions, and the exploration of therapeutic targets of these proteins in the context of neurological diseases.
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Affiliation(s)
- R Anne Stetler
- Geriatric Research, Educational and Clinical Center, Veterans Affairs Pittsburgh Health Care System, Pittsburgh, PA 15261, United States.
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46
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Wu H, Xiong WC, Mei L. To build a synapse: signaling pathways in neuromuscular junction assembly. Development 2010; 137:1017-33. [PMID: 20215342 DOI: 10.1242/dev.038711] [Citation(s) in RCA: 379] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Synapses, as fundamental units of the neural circuitry, enable complex behaviors. The neuromuscular junction (NMJ) is a synapse type that forms between motoneurons and skeletal muscle fibers and that exhibits a high degree of subcellular specialization. Aided by genetic techniques and suitable animal models, studies in the past decade have brought significant progress in identifying NMJ components and assembly mechanisms. This review highlights recent advances in the study of NMJ development, focusing on signaling pathways that are activated by diffusible cues, which shed light on synaptogenesis in the brain and contribute to a better understanding of muscular dystrophy.
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Affiliation(s)
- Haitao Wu
- Program of Developmental Neurobiology, Institute of Molecular Medicine and Genetics, Department of Neurology, Medical College of Georgia, Augusta, GA 30912, USA
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47
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Maselli RA, Arredondo J, Cagney O, Ng JJ, Anderson JA, Williams C, Gerke BJ, Soliven B, Wollmann RL. Mutations in MUSK causing congenital myasthenic syndrome impair MuSK-Dok-7 interaction. Hum Mol Genet 2010; 19:2370-9. [PMID: 20371544 PMCID: PMC2876883 DOI: 10.1093/hmg/ddq110] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We describe a severe congenital myasthenic syndrome (CMS) caused by two missense mutations in the gene encoding the muscle specific receptor tyrosine kinase (MUSK). The identified MUSK mutations M605I and A727V are both located in the kinase domain of MuSK. Intracellular microelectrode recordings and microscopy studies of the neuromuscular junction conducted in an anconeus muscle biopsy revealed decreased miniature endplate potential amplitudes, reduced endplate size and simplification of secondary synaptic folds, which were consistent with postsynaptic deficit. The study also showed a striking reduction of the endplate potential quantal content, consistent with additional presynaptic failure. Expression studies in MuSK deficient myotubes revealed that A727V, which is located within the catalytic loop of the enzyme, caused severe impairment of agrin-dependent MuSK phosphorylation, aggregation of acetylcholine receptors (AChRs) and interaction of MuSK with Dok-7, an essential intracellular binding protein of MuSK. In contrast, M605I, resulted in only moderate impairment of agrin-dependent MuSK phosphorylation, aggregation of AChRs and interaction of MuSK with Dok-7. There was no impairment of interaction of mutants with either the low-density lipoprotein receptor-related protein, Lrp4 (a co-receptor of agrin) or with the mammalian homolog of the Drosophila tumorous imaginal discs (Tid1). Our findings demonstrate that missense mutations in MUSK can result in a severe form of CMS and indicate that the inability of MuSK mutants to interact with Dok-7, but not with Lrp4 or Tid1, is a major determinant of the pathogenesis of the CMS caused by MUSK mutations.
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Affiliation(s)
- Ricardo A Maselli
- Department of Neurology, School of Veterinary Medicine, University of California Davis, Davis, CA 95618, USA.
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Shi L, Butt B, Ip FCF, Dai Y, Jiang L, Yung WH, Greenberg ME, Fu AKY, Ip NY. Ephexin1 is required for structural maturation and neurotransmission at the neuromuscular junction. Neuron 2010; 65:204-16. [PMID: 20152127 DOI: 10.1016/j.neuron.2010.01.012] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/24/2009] [Indexed: 12/24/2022]
Abstract
The maturation of neuromuscular junctions (NMJs) requires the topological transformation of postsynaptic acetylcholine receptor (AChR)-containing structures from a simple plaque to an elaborate structure composed of pretzel-like branches. This maturation process results in the precise apposition of the presynaptic and postsynaptic specializations. However, little is known about the molecular mechanisms underlying the plaque-to-pretzel transition of AChR clusters. In this study, we identify an essential role for the RhoGEF ephexin1 in the maturation of AChR clusters. Adult ephexin1(-/-) mice exhibit severe muscle weakness and impaired synaptic transmission at the NMJ. Intriguingly, when ephexin1 expression is deficient in vivo, the NMJ fails to mature into the pretzel-like shape, and such abnormalities can be rescued by re-expression of ephexin1. We further demonstrate that ephexin1 regulates the stability of AChR clusters in a RhoA-dependent manner. Taken together, our findings reveal an indispensible role for ephexin1 in regulating the structural maturation and neurotransmission of NMJs.
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Affiliation(s)
- Lei Shi
- Department of Biochemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China
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Madhavan R, Gong ZL, Ma JJ, Chan AWS, Peng HB. The function of cortactin in the clustering of acetylcholine receptors at the vertebrate neuromuscular junction. PLoS One 2009; 4:e8478. [PMID: 20041195 PMCID: PMC2793544 DOI: 10.1371/journal.pone.0008478] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Accepted: 12/03/2009] [Indexed: 11/18/2022] Open
Abstract
Background Postsynaptic enrichment of acetylcholine receptors (AChRs) at the vertebrate neuromuscular junction (NMJ) depends on the activation of the muscle receptor tyrosine MuSK by neural agrin. Agrin-stimulation of MuSK is known to initiate an intracellular signaling cascade that leads to the clustering of AChRs in an actin polymerization-dependent manner, but the molecular steps which link MuSK activation to AChR aggregation remain incompletely defined. Methodology/Principal Findings In this study we used biochemical, cell biological and molecular assays to investigate a possible role in AChR clustering of cortactin, a protein which is a tyrosine kinase substrate and a regulator of F-actin assembly and which has also been previously localized at AChR clustering sites. We report that cortactin was co-enriched at AChR clusters in situ with its target the Arp2/3 complex, which is a key stimulator of actin polymerization in cells. Cortactin was further preferentially tyrosine phosphorylated at AChR clustering sites and treatment of myotubes with agrin significantly enhanced the tyrosine phosphorylation of cortactin. Importantly, forced expression in myotubes of a tyrosine phosphorylation-defective cortactin mutant (but not wild-type cortactin) suppressed agrin-dependent AChR clustering, as did the reduction of endogenous cortactin levels using RNA interference, and introduction of the mutant cortactin into muscle cells potently inhibited synaptic AChR aggregation in response to innervation. Conclusion Our results suggest a novel function of phosphorylation-dependent cortactin signaling downstream from agrin/MuSK in facilitating AChR clustering at the developing NMJ.
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Affiliation(s)
- Raghavan Madhavan
- Department of Biology, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
| | - Zhuolin L. Gong
- Department of Biology, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
| | - Jin Jin Ma
- Department of Biology, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
| | - Ariel W. S. Chan
- Department of Biology, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
| | - H. Benjamin Peng
- Department of Biology, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China
- * E-mail:
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Pilgram GSK, Potikanond S, Baines RA, Fradkin LG, Noordermeer JN. The roles of the dystrophin-associated glycoprotein complex at the synapse. Mol Neurobiol 2009; 41:1-21. [PMID: 19899002 PMCID: PMC2840664 DOI: 10.1007/s12035-009-8089-5] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2009] [Accepted: 10/15/2009] [Indexed: 12/30/2022]
Abstract
Duchenne muscular dystrophy is caused by mutations in the dystrophin gene and is characterized by progressive muscle wasting. A number of Duchenne patients also present with mental retardation. The dystrophin protein is part of the highly conserved dystrophin-associated glycoprotein complex (DGC) which accumulates at the neuromuscular junction (NMJ) and at a variety of synapses in the peripheral and central nervous systems. Many years of research into the roles of the DGC in muscle have revealed its structural function in stabilizing the sarcolemma. In addition, the DGC also acts as a scaffold for various signaling pathways. Here, we discuss recent advances in understanding DGC roles in the nervous system, gained from studies in both vertebrate and invertebrate model systems. From these studies, it has become clear that the DGC is important for the maturation of neurotransmitter receptor complexes and for the regulation of neurotransmitter release at the NMJ and central synapses. Furthermore, roles for the DGC have been established in consolidation of long-term spatial and recognition memory. The challenges ahead include the integration of the behavioral and mechanistic studies and the use of this information to identify therapeutic targets.
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Affiliation(s)
- Gonneke S K Pilgram
- Department of Molecular and Cell Biology, Leiden University Medical Center, The Netherlands
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