1
|
Polishchuk A, Cilleros-Mañé V, Balanyà-Segura M, Just-Borràs L, Forniés-Mariné A, Silvera-Simón C, Tomàs M, Jami El Hirchi M, Hurtado E, Tomàs J, Lanuza MA. BDNF/TrkB signalling, in cooperation with muscarinic signalling, retrogradely regulates PKA pathway to phosphorylate SNAP-25 and Synapsin-1 at the neuromuscular junction. Cell Commun Signal 2024; 22:371. [PMID: 39044222 PMCID: PMC11265447 DOI: 10.1186/s12964-024-01735-2] [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: 05/07/2024] [Accepted: 07/04/2024] [Indexed: 07/25/2024] Open
Abstract
BACKGROUND Protein kinase A (PKA) enhances neurotransmission at the neuromuscular junction (NMJ), which is retrogradely regulated by nerve-induced muscle contraction to promote Acetylcholine (ACh) release through the phosphorylation of molecules involved in synaptic vesicle exocytosis (SNAP-25 and Synapsin-1). However, the molecular mechanism of the retrograde regulation of PKA subunits and its targets by BDNF/TrkB pathway and muscarinic signalling has not been demonstrated until now. At the NMJ, retrograde control is mainly associated with BDNF/TrkB signalling as muscle contraction enhances BDNF levels and controls specific kinases involved in the neurotransmission. Neurotransmission at the NMJ is also highly modulated by muscarinic receptors M1 and M2 (mAChRs), which are related to PKA and TrkB signallings. Here, we investigated the hypothesis that TrkB, in cooperation with mAChRs, regulates the activity-dependent dynamics of PKA subunits to phosphorylate SNAP-25 and Synapsin-1. METHODS To explore this, we stimulated the rat phrenic nerve at 1Hz (30 minutes), with or without subsequent contraction (abolished by µ-conotoxin GIIIB). Pharmacological treatments were conducted with the anti-TrkB antibody clone 47/TrkB for TrkB inhibition and exogenous h-BDNF; muscarinic inhibition with Pirenzepine-dihydrochloride and Methoctramine-tetrahydrochloride for M1 and M2 mAChRs, respectively. Diaphragm protein levels and phosphorylation' changes were detected by Western blotting. Location of the target proteins was demonstrated using immunohistochemistry. RESULTS While TrkB does not directly impact the levels of PKA catalytic subunits Cα and Cβ, it regulates PKA regulatory subunits RIα and RIIβ, facilitating the phosphorylation of critical exocytotic targets such as SNAP-25 and Synapsin-1. Furthermore, the muscarinic receptors pathway maintains a delicate balance in this regulatory process. These findings explain the dynamic interplay of PKA subunits influenced by BDNF/TrkB signalling, M1 and M2 mAChRs pathways, that are differently regulated by pre- and postsynaptic activity, demonstrating the specific roles of the BDNF/TrkB and muscarinic receptors pathway in retrograde regulation. CONCLUSION This complex molecular interplay has the relevance of interrelating two fundamental pathways in PKA-synaptic modulation: one retrograde (neurotrophic) and the other autocrine (muscarinic). This deepens the fundamental understanding of neuromuscular physiology of neurotransmission that gives plasticity to synapses and holds the potential for identifying therapeutic strategies in conditions characterized by impaired neuromuscular communication.
Collapse
Affiliation(s)
- Aleksandra Polishchuk
- Universitat Rovira i Virgili. Unitat d'Histologia i Neurobiologia (UHNeurob), Facultat de Medicina i Ciències de la Salut. c/ Sant Llorenç 21, Reus, 43201, Spain
- Unitat d'Histologia i Neurobiologia (UHNeurob), Institut d'Investigació Sanitària Pere Virgili (IISPV), Reus, Spain
| | - Víctor Cilleros-Mañé
- Universitat Rovira i Virgili. Unitat d'Histologia i Neurobiologia (UHNeurob), Facultat de Medicina i Ciències de la Salut. c/ Sant Llorenç 21, Reus, 43201, Spain
- Unitat d'Histologia i Neurobiologia (UHNeurob), Institut d'Investigació Sanitària Pere Virgili (IISPV), Reus, Spain
| | - Marta Balanyà-Segura
- Universitat Rovira i Virgili. Unitat d'Histologia i Neurobiologia (UHNeurob), Facultat de Medicina i Ciències de la Salut. c/ Sant Llorenç 21, Reus, 43201, Spain
- Unitat d'Histologia i Neurobiologia (UHNeurob), Institut d'Investigació Sanitària Pere Virgili (IISPV), Reus, Spain
| | - Laia Just-Borràs
- Universitat Rovira i Virgili. Unitat d'Histologia i Neurobiologia (UHNeurob), Facultat de Medicina i Ciències de la Salut. c/ Sant Llorenç 21, Reus, 43201, Spain
- Unitat d'Histologia i Neurobiologia (UHNeurob), Institut d'Investigació Sanitària Pere Virgili (IISPV), Reus, Spain
| | - Anton Forniés-Mariné
- Universitat Rovira i Virgili. Unitat d'Histologia i Neurobiologia (UHNeurob), Facultat de Medicina i Ciències de la Salut. c/ Sant Llorenç 21, Reus, 43201, Spain
| | - Carolina Silvera-Simón
- Universitat Rovira i Virgili. Unitat d'Histologia i Neurobiologia (UHNeurob), Facultat de Medicina i Ciències de la Salut. c/ Sant Llorenç 21, Reus, 43201, Spain
- Unitat d'Histologia i Neurobiologia (UHNeurob), Institut d'Investigació Sanitària Pere Virgili (IISPV), Reus, Spain
| | - Marta Tomàs
- Universitat Rovira i Virgili. Unitat d'Histologia i Neurobiologia (UHNeurob), Facultat de Medicina i Ciències de la Salut. c/ Sant Llorenç 21, Reus, 43201, Spain
- Unitat d'Histologia i Neurobiologia (UHNeurob), Institut d'Investigació Sanitària Pere Virgili (IISPV), Reus, Spain
| | - Meryem Jami El Hirchi
- Universitat Rovira i Virgili. Unitat d'Histologia i Neurobiologia (UHNeurob), Facultat de Medicina i Ciències de la Salut. c/ Sant Llorenç 21, Reus, 43201, Spain
- Unitat d'Histologia i Neurobiologia (UHNeurob), Institut d'Investigació Sanitària Pere Virgili (IISPV), Reus, Spain
| | - Erica Hurtado
- Universitat Rovira i Virgili. Unitat d'Histologia i Neurobiologia (UHNeurob), Facultat de Medicina i Ciències de la Salut. c/ Sant Llorenç 21, Reus, 43201, Spain
- Unitat d'Histologia i Neurobiologia (UHNeurob), Institut d'Investigació Sanitària Pere Virgili (IISPV), Reus, Spain
| | - Josep Tomàs
- Universitat Rovira i Virgili. Unitat d'Histologia i Neurobiologia (UHNeurob), Facultat de Medicina i Ciències de la Salut. c/ Sant Llorenç 21, Reus, 43201, Spain
- Unitat d'Histologia i Neurobiologia (UHNeurob), Institut d'Investigació Sanitària Pere Virgili (IISPV), Reus, Spain
| | - Maria A Lanuza
- Universitat Rovira i Virgili. Unitat d'Histologia i Neurobiologia (UHNeurob), Facultat de Medicina i Ciències de la Salut. c/ Sant Llorenç 21, Reus, 43201, Spain.
- Unitat d'Histologia i Neurobiologia (UHNeurob), Institut d'Investigació Sanitària Pere Virgili (IISPV), Reus, Spain.
| |
Collapse
|
2
|
Falcetta D, Quirim S, Cocchiararo I, Chabry F, Théodore M, Stiefvater A, Lin S, Tintignac L, Ivanek R, Kinter J, Rüegg MA, Sinnreich M, Castets P. CaMKIIβ deregulation contributes to neuromuscular junction destabilization in Myotonic Dystrophy type I. Skelet Muscle 2024; 14:11. [PMID: 38769542 PMCID: PMC11106974 DOI: 10.1186/s13395-024-00345-3] [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: 02/11/2024] [Accepted: 05/13/2024] [Indexed: 05/22/2024] Open
Abstract
BACKGROUND Myotonic Dystrophy type I (DM1) is the most common muscular dystrophy in adults. Previous reports have highlighted that neuromuscular junctions (NMJs) deteriorate in skeletal muscle from DM1 patients and mouse models thereof. However, the underlying pathomechanisms and their contribution to muscle dysfunction remain unknown. METHODS We compared changes in NMJs and activity-dependent signalling pathways in HSALR and Mbnl1ΔE3/ΔE3 mice, two established mouse models of DM1. RESULTS Muscle from DM1 mouse models showed major deregulation of calcium/calmodulin-dependent protein kinases II (CaMKIIs), which are key activity sensors regulating synaptic gene expression and acetylcholine receptor (AChR) recycling at the NMJ. Both mouse models exhibited increased fragmentation of the endplate, which preceded muscle degeneration. Endplate fragmentation was not accompanied by changes in AChR turnover at the NMJ. However, the expression of synaptic genes was up-regulated in mutant innervated muscle, together with an abnormal accumulation of histone deacetylase 4 (HDAC4), a known target of CaMKII. Interestingly, denervation-induced increase in synaptic gene expression and AChR turnover was hampered in DM1 muscle. Importantly, CaMKIIβ/βM overexpression normalized endplate fragmentation and synaptic gene expression in innervated Mbnl1ΔE3/ΔE3 muscle, but it did not restore denervation-induced synaptic gene up-regulation. CONCLUSIONS Our results indicate that CaMKIIβ-dependent and -independent mechanisms perturb synaptic gene regulation and muscle response to denervation in DM1 mouse models. Changes in these signalling pathways may contribute to NMJ destabilization and muscle dysfunction in DM1 patients.
Collapse
Affiliation(s)
- Denis Falcetta
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, 1 rue Michel Servet, Geneva, CH-1211, Switzerland
- Neuromuscular Research Group, Departments of Neurology and Biomedicine, University and University Hospital Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
- Biozentrum, University of Basel, Spitalstrasse 41, Basel, CH-4056, Switzerland
| | - Sandrine Quirim
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, 1 rue Michel Servet, Geneva, CH-1211, Switzerland
| | - Ilaria Cocchiararo
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, 1 rue Michel Servet, Geneva, CH-1211, Switzerland
| | - Florent Chabry
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, 1 rue Michel Servet, Geneva, CH-1211, Switzerland
| | - Marine Théodore
- Neuromuscular Research Group, Departments of Neurology and Biomedicine, University and University Hospital Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Adeline Stiefvater
- Neuromuscular Research Group, Departments of Neurology and Biomedicine, University and University Hospital Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Shuo Lin
- Biozentrum, University of Basel, Spitalstrasse 41, Basel, CH-4056, Switzerland
| | - Lionel Tintignac
- Neuromuscular Research Group, Departments of Neurology and Biomedicine, University and University Hospital Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Robert Ivanek
- Department of Biomedicine, University Hospital and University of Basel, Hebelstrasse 20, Basel, CH-4053, Switzerland
- Swiss Institute of Bioinformatics, Hebelstrasse 20, Basel, CH-4053, Switzerland
| | - Jochen Kinter
- Neuromuscular Research Group, Departments of Neurology and Biomedicine, University and University Hospital Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Markus A Rüegg
- Biozentrum, University of Basel, Spitalstrasse 41, Basel, CH-4056, Switzerland
| | - Michael Sinnreich
- Neuromuscular Research Group, Departments of Neurology and Biomedicine, University and University Hospital Basel, Klingelbergstrasse 50/70, Basel, CH-4056, Switzerland
| | - Perrine Castets
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, 1 rue Michel Servet, Geneva, CH-1211, Switzerland.
| |
Collapse
|
3
|
Polishchuk A, Cilleros-Mañé V, Just-Borràs L, Balanyà-Segura M, Vandellòs Pont G, Silvera Simón C, Tomàs M, Garcia N, Tomàs J, Lanuza MA. Synaptic retrograde regulation of the PKA-induced SNAP-25 and Synapsin-1 phosphorylation. Cell Mol Biol Lett 2023; 28:17. [PMID: 36869288 PMCID: PMC9985302 DOI: 10.1186/s11658-023-00431-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 02/09/2023] [Indexed: 03/05/2023] Open
Abstract
BACKGROUND Bidirectional communication between presynaptic and postsynaptic components contribute to the homeostasis of the synapse. In the neuromuscular synapse, the arrival of the nerve impulse at the presynaptic terminal triggers the molecular mechanisms associated with ACh release, which can be retrogradely regulated by the resulting muscle contraction. This retrograde regulation, however, has been poorly studied. At the neuromuscular junction (NMJ), protein kinase A (PKA) enhances neurotransmitter release, and the phosphorylation of the molecules of the release machinery including synaptosomal associated protein of 25 kDa (SNAP-25) and Synapsin-1 could be involved. METHODS Accordingly, to study the effect of synaptic retrograde regulation of the PKA subunits and its activity, we stimulated the rat phrenic nerve (1 Hz, 30 min) resulting or not in contraction (abolished by µ-conotoxin GIIIB). Changes in protein levels and phosphorylation were detected by western blotting and cytosol/membrane translocation by subcellular fractionation. Synapsin-1 was localized in the levator auris longus (LAL) muscle by immunohistochemistry. RESULTS Here we show that synaptic PKA Cβ subunit regulated by RIIβ or RIIα subunits controls activity-dependent phosphorylation of SNAP-25 and Synapsin-1, respectively. Muscle contraction retrogradely downregulates presynaptic activity-induced pSynapsin-1 S9 while that enhances pSNAP-25 T138. Both actions could coordinately contribute to decreasing the neurotransmitter release at the NMJ. CONCLUSION This provides a molecular mechanism of the bidirectional communication between nerve terminals and muscle cells to balance the accurate process of ACh release, which could be important to characterize molecules as a therapy for neuromuscular diseases in which neuromuscular crosstalk is impaired.
Collapse
Affiliation(s)
- Aleksandra Polishchuk
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Víctor Cilleros-Mañé
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Laia Just-Borràs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Marta Balanyà-Segura
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Genís Vandellòs Pont
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Carolina Silvera Simón
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Marta Tomàs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Neus Garcia
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain
| | - Josep Tomàs
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain.
| | - Maria A Lanuza
- Unitat d'Histologia i Neurobiologia (UHNEUROB), Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, c/ Sant Llorenç 21, 43201, Reus, Spain.
| |
Collapse
|
4
|
Ravaei A, Emanuele M, Nazzaro G, Fadiga L, Rubini M. Placental DNA methylation profile as predicting marker for autism spectrum disorder (ASD). Mol Med 2023; 29:8. [PMID: 36647002 PMCID: PMC9843962 DOI: 10.1186/s10020-022-00593-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 12/15/2022] [Indexed: 01/18/2023] Open
Abstract
Autism spectrum disorder (ASD) is a neurodevelopmental disorder that impairs normal brain development and socio-cognitive abilities. The pathogenesis of this condition points out the involvement of genetic and environmental factors during in-utero life. Placenta, as an interface tissue between mother and fetus, provides developing fetus requirements and exposes it to maternal environment as well. Therefore, the alteration of DNA methylation as epigenetic consequence of gene-environmental interaction in the placenta could shed light on ASD pathogenesis. In this study, we reviewed the current findings on placental methylation status and its association with ASD. Differentially methylated regions (DMRs) in ASD-developing placenta were found to be mainly enriched in ASD gene loci affecting synaptogenesis, microtubule dynamics, neurogenesis and neuritogenesis. In addition, non-genic DMRs in ASD-placenta proposes an alternative contributing mechanism for ASD development. Our study highlights the importance of placental DNA methylation signature as a biomarker for ASD prediction.
Collapse
Affiliation(s)
- Amin Ravaei
- grid.8484.00000 0004 1757 2064Medical Genetics Laboratory, Department of Neuroscience and Rehabilitation, University of Ferrara, Via Fossato di Mortara 74, 44121 Ferrara, Italy
| | - Marco Emanuele
- grid.8484.00000 0004 1757 2064Section of Physiology, Department of Neuroscience and Rehabilitation, University of Ferrara, Ferrara, Italy ,grid.25786.3e0000 0004 1764 2907IIT@UniFe Center for Translational Neurophysiology of Speech and Communication (CTNSC), Istituto Italiano di Tecnologia, Ferrara, Italy
| | - Giovanni Nazzaro
- grid.8484.00000 0004 1757 2064Section of Physiology, Department of Neuroscience and Rehabilitation, University of Ferrara, Ferrara, Italy ,grid.25786.3e0000 0004 1764 2907IIT@UniFe Center for Translational Neurophysiology of Speech and Communication (CTNSC), Istituto Italiano di Tecnologia, Ferrara, Italy
| | - Luciano Fadiga
- grid.8484.00000 0004 1757 2064Section of Physiology, Department of Neuroscience and Rehabilitation, University of Ferrara, Ferrara, Italy ,grid.25786.3e0000 0004 1764 2907IIT@UniFe Center for Translational Neurophysiology of Speech and Communication (CTNSC), Istituto Italiano di Tecnologia, Ferrara, Italy
| | - Michele Rubini
- grid.8484.00000 0004 1757 2064Medical Genetics Laboratory, Department of Neuroscience and Rehabilitation, University of Ferrara, Via Fossato di Mortara 74, 44121 Ferrara, Italy
| |
Collapse
|
5
|
A link between agrin signalling and Ca v3.2 at the neuromuscular junction in spinal muscular atrophy. Sci Rep 2022; 12:18960. [PMID: 36347955 PMCID: PMC9643518 DOI: 10.1038/s41598-022-23703-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 11/03/2022] [Indexed: 11/11/2022] Open
Abstract
SMN protein deficiency causes motoneuron disease spinal muscular atrophy (SMA). SMN-based therapies improve patient motor symptoms to variable degrees. An early hallmark of SMA is the perturbation of the neuromuscular junction (NMJ), a synapse between a motoneuron and muscle cell. NMJ formation depends on acetylcholine receptor (AChR) clustering triggered by agrin and its co-receptors lipoprotein receptor-related protein 4 (LRP4) and transmembrane muscle-specific kinase (MuSK) signalling pathway. We have previously shown that flunarizine improves NMJs in SMA model mice, but the mechanisms remain elusive. We show here that flunarizine promotes AChR clustering in cell-autonomous, dose- and agrin-dependent manners in C2C12 myotubes. This is associated with an increase in protein levels of LRP4, integrin-beta-1 and alpha-dystroglycan, three agrin co-receptors. Furthermore, flunarizine enhances MuSK interaction with integrin-beta-1 and phosphotyrosines. Moreover, the drug acts on the expression and splicing of Agrn and Cacna1h genes in a muscle-specific manner. We reveal that the Cacna1h encoded protein Cav3.2 closely associates in vitro with the agrin co-receptor LRP4. In vivo, it is enriched nearby NMJs during neonatal development and the drug increases this immunolabelling in SMA muscles. Thus, flunarizine modulates key players of the NMJ and identifies Cav3.2 as a new protein involved in the NMJ biology.
Collapse
|
6
|
Nhieu J, Lin YL, Wei LN. CRABP1 in Non-Canonical Activities of Retinoic Acid in Health and Diseases. Nutrients 2022; 14:nu14071528. [PMID: 35406141 PMCID: PMC9003107 DOI: 10.3390/nu14071528] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/01/2022] [Accepted: 04/03/2022] [Indexed: 12/30/2022] Open
Abstract
In this review, we discuss the emerging role of Cellular Retinoic Acid Binding Protein 1 (CRABP1) as a mediator of non-canonical activities of retinoic acid (RA) and relevance to human diseases. We first discuss the role of CRABP1 in regulating MAPK activities and its implication in stem cell proliferation, cancers, adipocyte health, and neuro-immune regulation. We then discuss an additional role of CRABP1 in regulating CaMKII activities, and its implication in heart and motor neuron diseases. Through molecular and genetic studies of Crabp1 knockout (CKO) mouse and culture models, it is established that CRABP1 forms complexes with specific signaling molecules to function as RA-regulated signalsomes in a cell context-dependent manner. Gene expression data and CRABP1 gene single nucleotide polymorphisms (SNPs) of human cancer, neurodegeneration, and immune disease patients implicate the potential association of abnormality in CRABP1 with human diseases. Finally, therapeutic strategies for managing certain human diseases by targeting CRABP1 are discussed.
Collapse
Affiliation(s)
| | | | - Li-Na Wei
- Correspondence: ; Tel.: +1-612-6259-402
| |
Collapse
|
7
|
Li DD, Deng J, Jin B, Han S, Gu XY, Zhou XF, Yin XF. Effects of delayed repair of peripheral nerve injury on the spatial distribution of motor endplates in target muscle. Neural Regen Res 2022; 17:459-464. [PMID: 34269223 PMCID: PMC8464005 DOI: 10.4103/1673-5374.317990] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Motor endplates (MEPs) are important sites of information exchange between motor neurons and skeletal muscle, and are distributed in an organized pattern of lamellae in the muscle. Delayed repair of peripheral nerve injury typically results in unsatisfactory functional recovery because of MEP degeneration. In this study, the mouse tibial nerve was transected and repaired with a biodegradable chitin conduit, immediately following or 1 or 3 months after the injury. Fluorescent α-bungarotoxin was injected to label MEPs. Tissue optical clearing combined with light-sheet microscopy revealed that MEPs were distributed in an organized pattern of lamellae in skeletal muscle after delayed repair for 1 and 3 months. However, the total number of MEPs, the number of MEPs per lamellar cluster, and the maturation of single MEPs in gastrocnemius muscle gradually decreased with increasing denervation time. These findings suggest that delayed repair can restore the spatial distribution of MEPs, but it has an adverse effect on the homogeneity of MEPs in the lamellar clusters and the total number of MEPs in the target muscle. The study procedures were approved by the Animal Ethics Committee of the Peking University People's Hospital (approval No. 2019PHC015) on April 8, 2019.
Collapse
Affiliation(s)
- Dong-Dong Li
- Department of Trauma and Orthopedics, Peking University People's Hospital; Department of Orthopedics, PLA Strategic Support Force Medical Center, Beijing, China
| | - Jin Deng
- Department of Trauma and Orthopedics, Peking University People's Hospital, Beijing, China
| | - Bo Jin
- Department of Trauma and Orthopedics, Peking University People's Hospital, Beijing, China
| | - Shuai Han
- Department of Trauma and Orthopedics, Peking University People's Hospital, Beijing, China
| | - Xin-Yi Gu
- Department of Trauma and Orthopedics, Peking University People's Hospital, Beijing, China
| | - Xue-Feng Zhou
- Department of Orthopedics, PLA Strategic Support Force Medical Center, Beijing, China
| | - Xiao-Feng Yin
- Department of Trauma and Orthopedics, Peking University People's Hospital, Beijing, China
| |
Collapse
|
8
|
Chang NC, Yeh CT, Lin YK, Kuo KT, Fong IH, Kounis NG, Hu P, Hung MY. Garcinol Attenuates Lipoprotein(a)-Induced Oxidative Stress and Inflammatory Cytokine Production in Ventricular Cardiomyocyte through α7-Nicotinic Acetylcholine Receptor-Mediated Inhibition of the p38 MAPK and NF-κB Signaling Pathways. Antioxidants (Basel) 2021; 10:antiox10030461. [PMID: 33809417 PMCID: PMC8000018 DOI: 10.3390/antiox10030461] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 02/27/2021] [Accepted: 03/10/2021] [Indexed: 12/12/2022] Open
Abstract
Garcinol, a nicotinic acetylcholine receptor (nAChR) antagonist, has recently been established as an anti-inflammation agent. However, the molecular mechanism by which garcinol suppresses inflammation in the context of acute myocardial infarction (AMI) remains unclear. Hypothesis: We hypothesized that the administration of physiological doses of garcinol in mice with isoproterenol-induced AMI decreased the effect of lipoprotein(a) (Lp(a))-induced inflammation both in vivo and in vitro via the α7-nAChRs mediated p38 mitogen-activated protein kinase (MAPK)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) signaling pathway. We analyzed altered reactive oxygen species (ROS) generation, the production of superoxide by mitochondria, cytokine expression patterns, and the role of the p38 MAPK/NF-κB signaling pathway after Lp(a)-stimulated human ventricular cardiomyocyte AC16 cells were treated with increasing doses of garcinol. C-reactive protein (CRP), interleukin (IL)-1β, IL-6, or tumor necrosis factor (TNF)-α production were detected by enzyme-linked immunosorbent assay. The Cell Counting Kit-8 assay was used to evaluate drug cytotoxicity. Western blots and confocal fluorescence microscopy were used to determine altered expression patterns of inflammatory biomarkers. We also examined whether the therapeutic effect of garcinol in AMI was mediated in part by α7-nAChR. Lp(a)-induced inflammatory cardiomyocytes had increased expression of membrane-bound α7-nAChRs in vitro and in vivo. Low-dose garcinol did not affect cardiomyocyte viability but significantly reduced mitochondrial ROS, CRP, IL-1β, IL-6, and TNF-α production in Lp(a)-stimulated cardiomyocytes (p < 0.05). The Lp(a)-induced phosphorylation of p38 MAPKs, CamKII, and NFκB, as well as NFκB-p65 nuclear translocation, was also suppressed (p < 0.05) by garcinol, while the inhibition of p38 MAPK by the inhibitor SB203580 decreased the phosphorylation of extracellular signal-regulated kinase (ERK) and p38 MAPK. Garcinol protected cardiomyocytes by inhibiting apoptosis and inflammation in mice with AMI. Furthermore, garcinol also enhanced the expression of microRNA-205 that suppressed the α7-nAChR-induced p38 MAPK/NF-κB signaling pathway. Garcinol suppresses Lp(a)-induced oxidative stress and inflammatory cytokines by α7-nAChR-mediated inhibition of p38 MAPK/NF-κB signaling in cardiomyocyte AC16 cells and isoproterenol-induced AMI mice.
Collapse
Affiliation(s)
- Nen-Chung Chang
- Division of Cardiology, Department of Internal Medicine, Taipei Medical University Hospital, Taipei 110, Taiwan
- Division of Cardiology, Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan;
- Taipei Heart Institute, Taipei Medical University, Taipei 110, Taiwan
| | - Chi-Tai Yeh
- Department of Medical Research and Education, Taipei Medical University—Shuang Ho Hospital, New Taipei City 23561, Taiwan; (C.-T.Y.); (I.-H.F.)
- Department of Medical Laboratory Science and Biotechnology, Yuanpei University of Medical Technology, Hsinchu City 30015, Taiwan
| | - Yen-Kuang Lin
- Biostatistics Center, Office of Data Science, Taipei Medical University, Taipei 110, Taiwan
- Graduate Institute of Data Science, Taipei Medical University, Taipei 110, Taiwan
- Research Center of Big Data, College of Management, Taipei Medical University, Taipei 110, Taiwan;
| | - Kuang-Tai Kuo
- Division of Thoracic Surgery, Department of Surgery, Shuang Ho Hospital, Taipei Medical University, New Taipei City 23561, Taiwan;
- Division of Thoracic Surgery, Department of Surgery, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan
| | - Iat-Hang Fong
- Department of Medical Research and Education, Taipei Medical University—Shuang Ho Hospital, New Taipei City 23561, Taiwan; (C.-T.Y.); (I.-H.F.)
- Department of Medical Laboratory Science and Biotechnology, Yuanpei University of Medical Technology, Hsinchu City 30015, Taiwan
| | - Nicholas G. Kounis
- Department of Internal Medicine, Division of Cardiology, University of Patras Medical School, 26221 Patras, Greece;
| | - Patrick Hu
- Department of Cardiology, University of California, Riverside, CA 92521, USA;
- Department of Cardiology, Riverside Medical Clinic, Riverside, CA 92506, USA
| | - Ming-Yow Hung
- Division of Cardiology, Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan;
- Taipei Heart Institute, Taipei Medical University, Taipei 110, Taiwan
- Division of Cardiology, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, New Taipei City 23561, Taiwan
- Correspondence: ; Tel.: +886-2-22490088
| |
Collapse
|
9
|
Martinez-Pena y Valenzuela I, Akaaboune M. The Metabolic Stability of the Nicotinic Acetylcholine Receptor at the Neuromuscular Junction. Cells 2021; 10:cells10020358. [PMID: 33572348 PMCID: PMC7916148 DOI: 10.3390/cells10020358] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 02/03/2021] [Accepted: 02/04/2021] [Indexed: 11/16/2022] Open
Abstract
The clustering and maintenance of nicotinic acetylcholine receptors (AChRs) at high density in the postsynaptic membrane is a hallmark of the mammalian neuromuscular junction (NMJ). The regulation of receptor density/turnover rate at synapses is one of the main thrusts of neurobiology because it plays an important role in synaptic development and synaptic plasticity. The state-of-the-art imaging revealed that AChRs are highly dynamic despite the overall structural stability of the NMJ over the lifetime of the animal. This review highlights the work on the metabolic stability of AChRs at developing and mature NMJs and discusses the role of synaptic activity and the regulatory signaling pathways involved in the dynamics of AChRs.
Collapse
Affiliation(s)
| | - Mohammed Akaaboune
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA;
- Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109, USA
- Correspondence: ; Tel.: +1-73-(46)-478512; Fax: +1-73-(46)-470884
| |
Collapse
|
10
|
Rodríguez Cruz PM, Cossins J, Beeson D, Vincent A. The Neuromuscular Junction in Health and Disease: Molecular Mechanisms Governing Synaptic Formation and Homeostasis. Front Mol Neurosci 2020; 13:610964. [PMID: 33343299 PMCID: PMC7744297 DOI: 10.3389/fnmol.2020.610964] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 10/30/2020] [Indexed: 12/28/2022] Open
Abstract
The neuromuscular junction (NMJ) is a highly specialized synapse between a motor neuron nerve terminal and its muscle fiber that are responsible for converting electrical impulses generated by the motor neuron into electrical activity in the muscle fibers. On arrival of the motor nerve action potential, calcium enters the presynaptic terminal, which leads to the release of the neurotransmitter acetylcholine (ACh). ACh crosses the synaptic gap and binds to ACh receptors (AChRs) tightly clustered on the surface of the muscle fiber; this leads to the endplate potential which initiates the muscle action potential that results in muscle contraction. This is a simplified version of the events in neuromuscular transmission that take place within milliseconds, and are dependent on a tiny but highly structured NMJ. Much of this review is devoted to describing in more detail the development, maturation, maintenance and regeneration of the NMJ, but first we describe briefly the most important molecules involved and the conditions that affect their numbers and function. Most important clinically worldwide, are myasthenia gravis (MG), the Lambert-Eaton myasthenic syndrome (LEMS) and congenital myasthenic syndromes (CMS), each of which causes specific molecular defects. In addition, we mention the neurotoxins from bacteria, snakes and many other species that interfere with neuromuscular transmission and cause potentially fatal diseases, but have also provided useful probes for investigating neuromuscular transmission. There are also changes in NMJ structure and function in motor neuron disease, spinal muscle atrophy and sarcopenia that are likely to be secondary but might provide treatment targets. The NMJ is one of the best studied and most disease-prone synapses in the nervous system and it is amenable to in vivo and ex vivo investigation and to systemic therapies that can help restore normal function.
Collapse
Affiliation(s)
- Pedro M. Rodríguez Cruz
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Judith Cossins
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, The John Radcliffe Hospital, Oxford, United Kingdom
| |
Collapse
|
11
|
Lee AM, Picciotto MR. Effects of nicotine on DARPP-32 and CaMKII signaling relevant to addiction. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2020; 90:89-115. [PMID: 33706940 PMCID: PMC8008986 DOI: 10.1016/bs.apha.2020.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
Paul Greengard brought to neuroscience the idea of, and evidence for, the role of second messenger systems in neuronal signaling. The fundamental nature of his contributions is evident in the far reach of his work, relevant to various subfields and topics in neuroscience. In this review, we discuss some of Greengard's work from the perspective of nicotinic acetylcholine receptors and their relevance to nicotine addiction. Specifically, we review the roles of dopamine- and cAMP-regulated phospho-protein of 32kDa (DARPP-32) and Ca2+/calmodulin-dependent kinase II (CaMKII) in nicotine-dependent behaviors. For each protein, we discuss the historical context of their discovery and initial characterization, focusing on the extensive biochemical and immunohistochemical work conducted by Greengard and colleagues. We then briefly summarize contemporary understanding of each protein in key intracellular signaling cascades and evidence for the role of each protein with respect to systems and behaviors relevant to nicotine addiction.
Collapse
Affiliation(s)
- Angela M Lee
- Department of Psychiatry, Yale University, New Haven, CT, United States; Yale Interdepartmental Neuroscience Program, New Haven, CT, United States
| | - Marina R Picciotto
- Department of Psychiatry, Yale University, New Haven, CT, United States; Yale Interdepartmental Neuroscience Program, New Haven, CT, United States.
| |
Collapse
|
12
|
Chen PJ, Zelada D, Belhasan DC, Akaaboune M. Phosphorylation of α-dystrobrevin is essential for αkap accumulation and acetylcholine receptor stability. J Biol Chem 2020; 295:10677-10688. [PMID: 32532815 DOI: 10.1074/jbc.ra120.013952] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 06/08/2020] [Indexed: 01/26/2023] Open
Abstract
The maintenance of a high density of the acetylcholine receptor (AChR) is the hallmark of the neuromuscular junction. Muscle-specific anchoring protein (αkap) encoded within the calcium/calmodulin-dependent protein kinase IIα (CAMK2A) gene is essential for the maintenance of AChR clusters both in vivo and in cultured muscle cells. The underlying mechanism by which αkap is maintained and regulated remains unknown. Here, using human cell lines, fluorescence microscopy, and pulldown and immunoblotting assays, we show that α-dystrobrevin (α-dbn), an intracellular component of the dystrophin glycoprotein complex, directly and robustly promotes the stability of αkap in a concentration-dependent manner. Mechanistically, we found that the phosphorylatable tyrosine residues of α-dbn are essential for the stability of α-dbn itself and its interaction with αkap, with substitution of three tyrosine residues in the α-dbn C terminus with phenylalanine compromising the αkap-α-dbn interaction and significantly reducing both αkap and α-dbn accumulation. Moreover, the αkap-α-dbn interaction was critical for αkap accumulation and stability. We also found that the absence of either αkap or α-dbn markedly reduces AChRα accumulation and that overexpression of α-dbn or αkap in cultured muscle cells promotes the formation of large agrin-induced AChR clusters. Collectively, these results indicate that the stability of αkap and α-dbn complex plays an important role in the maintenance of high-level expression of AChRs.
Collapse
Affiliation(s)
- Po-Ju Chen
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Diego Zelada
- Department of Cell Biology, Universidad de Concepción, Concepción, Chile
| | - Dina Cheryne Belhasan
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA
| | - Mohammed Akaaboune
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, USA .,Program in Neuroscience, University of Michigan, Ann Arbor, Michigan, USA
| |
Collapse
|
13
|
Rudolf R, Straka T. Nicotinic acetylcholine receptor at vertebrate motor endplates: Endocytosis, recycling, and degradation. Neurosci Lett 2019; 711:134434. [PMID: 31421156 DOI: 10.1016/j.neulet.2019.134434] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 08/08/2019] [Accepted: 08/14/2019] [Indexed: 12/31/2022]
Abstract
At vertebrate motor endplates, the conversion of nerve impulses into muscle contraction is initiated by binding of acetylcholine to its nicotinic receptor (nAChR) at the postsynapse. Efficiency and safety of this process are dependent on proper localization, density, and molecular composition of the receptors. To warrant this, intricate machineries regulating the turnover of nAChR are in place. They control and execute the processes of i) expression, ii) delivery to the postsynaptic membrane, iii) clustering at the plasma membrane, iv) endocytic retrieval, v) activity-dependent recycling, and vi) degradation of nAChR. Concentrating on aspects iv-vi, this review addresses the current status of techniques, concepts, and open questions on endocytosis, recycling, and degradation of nAChR. A picture is emerging, that shows connections between executing machineries and their regulators. The first group includes the actin cytoskeleton, myosin motor proteins, Rab G-proteins, and the autophagic cascade. The second group features protein kinases A and C, Cdk5, and CaMKII as well as other components like the E3-ligase MuRF1 and the membrane shaping regulator, SH3GLB1. Recent studies have started to shed light onto nerve inputs that appear to master the tuning of the postsynaptic protein trafficking apparatus and the expression of critical components for nAChR turnover.
Collapse
Affiliation(s)
- Rüdiger Rudolf
- Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, Mannheim, Germany; Interdisciplinary Center for Neurosciences, Heidelberg University, Heidelberg, Germany; Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany.
| | - Tatjana Straka
- Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences, Mannheim, Germany; Interdisciplinary Center for Neurosciences, Heidelberg University, Heidelberg, Germany; Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
| |
Collapse
|
14
|
Koppel N, Friese MB, Cardasis HL, Neubert TA, Burden SJ. Vezatin is required for the maturation of the neuromuscular synapse. Mol Biol Cell 2019; 30:2571-2583. [PMID: 31411944 PMCID: PMC6740198 DOI: 10.1091/mbc.e19-06-0313] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Key genes, such as Agrin, Lrp4, and MuSK, are required for the initial formation, subsequent maturation, and long-term stabilization of mammalian neuromuscular synapses. Additional molecules are thought to function selectively during the evolution and stabilization of these synapses, but these molecular players are largely unknown. Here, we used mass spectrometry to identify vezatin, a two-pass transmembrane protein, as an acetylcholine receptor (AChR)–associated protein, and we provide evidence that vezatin binds directly to AChRs. We show that vezatin is dispensable for the formation of synapses but plays a later role in the emergence of a topologically complex and branched shape of the synapse, as well as the stabilization of AChRs. In addition, neuromuscular synapses in vezatin mutant mice display premature signs of deterioration, normally found only during aging. Thus, vezatin has a selective role in the structural elaboration and postnatal maturation of murine neuromuscular synapses.
Collapse
Affiliation(s)
- Natasha Koppel
- Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| | - Matthew B Friese
- Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| | - Helene L Cardasis
- Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| | - Thomas A Neubert
- Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| | - Steven J Burden
- Helen L. and Martin S. Kimmel Center for Biology and Medicine, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016
| |
Collapse
|
15
|
Wang JS, Bojovic D, Chen Y, Lindgren CA. Homocysteine sensitizes the mouse neuromuscular junction to oxidative stress by nitric oxide. Neuroreport 2018; 29:1030-1035. [PMID: 29939872 PMCID: PMC6044473 DOI: 10.1097/wnr.0000000000001073] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Homocysteine (HCY), a redox-active metabolite of the methionine cycle, is of particular clinical interest because of its association with various neurodegenerative diseases including amyotrophic lateral sclerosis. It has been previously established that HCY exacerbates damage to motor neurons from reactive oxygen species (ROS) such as hydrogen peroxide. To assess the role of HCY at the mammalian neuromuscular junction, neurotransmission was monitored by electrophysiology at the mouse epitrochleoanconeus muscle. Preparations were preincubated in HCY before inducing ROS and recordings were taken before and after ROS treatment. In this study, HCY was observed to sensitize the neuromuscular junction to ROS-induced depression of spontaneous transmission frequency, an effect we found to be mediated by a N-methyl-D-aspartate receptor (NMDAR) and nitric oxide (NO). The NMDAR antagonist D, L-2-amino-5-phosphonopentanoic acid prevented the HCY-induced sensitization to oxidative stress. Disrupting NO activity with either the nitric oxide synthase I antagonist Nω-nitro-L-arginine methyl ester hydrochloride or the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide potassium salt also prevented sensitization. Moreover, replacing HCY with the exogenous NO donor Diethylamine NONOate diethylammonium was sufficient to reconstitute the effects of HCY-induced sensitization to ROS. Interestingly, a novel secondary effect was observed where HCY itself depresses quantal content, an effect found to be mediated by NMDARs independently of nitric oxide and ROS. Collectively, these data present a novel model of two distinct pathways through which HCY alters neurotransmission at the neuromuscular junction. Characterizing HCY's mechanism of action is of particular clinical relevance as many treatments for amyotrophic lateral sclerosis are centered on mitigating HCY-induced pathologies.
Collapse
Affiliation(s)
- John S Wang
- Department of Biology, Grinnell College, Grinnell, Iowa, USA
| | | | | | | |
Collapse
|
16
|
|
17
|
Martin AA, Richmond JE. The sarco(endo)plasmic reticulum calcium ATPase SCA-1 regulates the Caenorhabditis elegans nicotinic acetylcholine receptor ACR-16. Cell Calcium 2018; 72:104-115. [PMID: 29748129 DOI: 10.1016/j.ceca.2018.02.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 02/22/2018] [Accepted: 02/22/2018] [Indexed: 12/26/2022]
Abstract
Nicotinic acetylcholine receptors (nAChR) are present in many excitable tissues and are found both pre and post-synaptically. Through their non-specific cationic permeability, these nAChRs have excitatory roles in neurotransmission, neuromodulation, synaptic plasticity, and neuroprotection. Thus, nAChR mislocalization or functional deficits are associated with many neurological disease states. Therefore identifying the mechanisms that regulate nAChR expression and function will inform our understanding of normal as well as pathological physiological conditions and offer avenues for potential therapeutic advances. Taking advantage of the genetic tractability of the soil nematode Caenorhabditis elegans, a forward genetic screen was performed to isolate regulators of the vertebrate α7 nAChR homologue ACR-16. From this screen a novel regulator of the ACR-16 receptor was identified, the sarco(endo)plasmic reticulum calcium ATPase sca-1. The sca-1 mutant affects ACR-16 receptor level at the NMJ, receptor functionality, and synaptic transmission. Responses to pressure-ejected nicotine in sca-1 mutants are indistinguishable from wild type, which implies the ACR-16 receptors are mislocalized at the NMJ. Changes in cytosolic baseline calcium levels in sca-1 and other mutants indicates a calcium-driven regulation mechanism of the α7-like NAChR ACR-16.
Collapse
Affiliation(s)
- Ashley A Martin
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, United States.
| | - Janet E Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, United States
| |
Collapse
|
18
|
Parallel epigenetic modifications induced by hatchery rearing in a Pacific salmon. Proc Natl Acad Sci U S A 2017; 114:12964-12969. [PMID: 29162695 DOI: 10.1073/pnas.1711229114] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Wild stocks of Pacific salmonids have experienced sharp declines in abundance over the past century. Consequently, billions of fish are released each year for enhancing abundance and sustaining fisheries. However, the beneficial role of this widely used management practice is highly debated since fitness decrease of hatchery-origin fish in the wild has been documented. Artificial selection in hatcheries has often been invoked as the most likely explanation for reduced fitness, and most studies to date have focused on finding signatures of hatchery-induced selection at the DNA level. We tested an alternative hypothesis, that captive rearing induces epigenetic reprogramming, by comparing genome-wide patterns of methylation and variation at the DNA level in hatchery-reared coho salmon (Oncorhynchus kisutch) with those of their wild counterparts in two geographically distant rivers. We found a highly significant proportion of epigenetic variation explained by the rearing environment that was as high as the one explained by the river of origin. The differentially methylated regions show enrichment for biological functions that may affect the capacity of hatchery-born smolts to migrate successfully in the ocean. Shared epigenetic variation between hatchery-reared salmon provides evidence for parallel epigenetic modifications induced by hatchery rearing in the absence of genetic differentiation between hatchery and natural-origin fish for each river. This study highlights epigenetic modifications induced by captive rearing as a potential explanatory mechanism for reduced fitness in hatchery-reared salmon.
Collapse
|
19
|
Gawor M, Prószyński TJ. The molecular cross talk of the dystrophin-glycoprotein complex. Ann N Y Acad Sci 2017; 1412:62-72. [DOI: 10.1111/nyas.13500] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 08/29/2017] [Accepted: 09/04/2017] [Indexed: 12/25/2022]
Affiliation(s)
- Marta Gawor
- Laboratory of Synaptogenesis; Nencki Institute of Experimental Biology; Polish Academy of Sciences Warsaw Poland
| | - Tomasz J. Prószyński
- Laboratory of Synaptogenesis; Nencki Institute of Experimental Biology; Polish Academy of Sciences Warsaw Poland
| |
Collapse
|
20
|
Bernadzki KM, Gawor M, Pęziński M, Mazurek P, Niewiadomski P, Rędowicz MJ, Prószyński TJ. Liprin-α-1 is a novel component of the murine neuromuscular junction and is involved in the organization of the postsynaptic machinery. Sci Rep 2017; 7:9116. [PMID: 28831123 PMCID: PMC5567263 DOI: 10.1038/s41598-017-09590-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Accepted: 07/25/2017] [Indexed: 01/26/2023] Open
Abstract
Neuromuscular junctions (NMJs) are specialized synapses that connect motor neurons to skeletal muscle fibers and orchestrate proper signal transmission from the nervous system to muscles. The efficient formation and maintenance of the postsynaptic machinery that contains acetylcholine receptors (AChR) are indispensable for proper NMJ function. Abnormalities in the organization of synaptic components often cause severe neuromuscular disorders, such as muscular dystrophy. The dystrophin-associated glycoprotein complex (DGC) was shown to play an important role in NMJ development. We recently identified liprin-α-1 as a novel binding partner for one of the cytoplasmic DGC components, α-dystrobrevin-1. In the present study, we performed a detailed analysis of localization and function of liprin-α-1 at the murine NMJ. We showed that liprin-α-1 localizes to both pre- and postsynaptic compartments at the NMJ, and its synaptic enrichment depends on the presence of the nerve. Using cultured muscle cells, we found that liprin-α-1 plays an important role in AChR clustering and the organization of cortical microtubules. Our studies provide novel insights into the function of liprin-α-1 at vertebrate neuromuscular synapses.
Collapse
Affiliation(s)
- Krzysztof M Bernadzki
- Laboratory of Synaptogenesis, Polish Academy of Sciences, 3 Pasteura Street, Warsaw, 02-093, Poland
| | - Marta Gawor
- Laboratory of Synaptogenesis, Polish Academy of Sciences, 3 Pasteura Street, Warsaw, 02-093, Poland
| | - Marcin Pęziński
- Laboratory of Synaptogenesis, Polish Academy of Sciences, 3 Pasteura Street, Warsaw, 02-093, Poland
| | - Paula Mazurek
- Laboratory of Synaptogenesis, Polish Academy of Sciences, 3 Pasteura Street, Warsaw, 02-093, Poland
| | - Paweł Niewiadomski
- Laboratory of Synaptogenesis, Polish Academy of Sciences, 3 Pasteura Street, Warsaw, 02-093, Poland
| | - Maria J Rędowicz
- Laboratory of Molecular Basis of Cell Motility, Nencki Institute of Experimental Biology, Polish Academy of Sciences, 3 Pasteura Street, Warsaw, 02-093, Poland
| | - Tomasz J Prószyński
- Laboratory of Synaptogenesis, Polish Academy of Sciences, 3 Pasteura Street, Warsaw, 02-093, Poland.
| |
Collapse
|
21
|
Wild F, Khan MM, Rudolf R. Evidence for the subsynaptic zone as a preferential site for CHRN recycling at neuromuscular junctions. Small GTPases 2017; 10:395-402. [PMID: 28489965 DOI: 10.1080/21541248.2017.1324939] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Vertebrate skeletal muscle contraction is mediated by nicotinic acetylcholine receptors (CHRN). Endocytosis and recycling of CHRN regulate their proper abundance at nerve-muscle synapses, i.e. neuromuscular junctions. Recent work showed that RAB5 is essential for CHRN endocytosis. Here, using in vivo-imaging of endocytosed CHRN and RAB-GFP fusion proteins, we deliver evidence for differential effects of RAB5-GFP, RAB4-GFP, and RAB11-GFP on CHRN endocytosis. Furthermore, while newly endocytosed CHRN colocalized with RAB5-GFP over large stretches of muscle fibers, RAB4-GFP and RAB11-GFP colocalized with endocytosed CHRN almost exclusively at neuromuscular junctions. In agreement with previous findings, this data suggests the existence of a specialized subsynaptic zone that is particularly relevant for CHRN recycling.
Collapse
Affiliation(s)
- Franziska Wild
- a Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences , Mannheim , Germany.,b Interdisciplinary Center for Neurosciences, Heidelberg University , Heidelberg , Germany.,c Institute of Toxicology and Genetics, Karlsruhe Institute of Technology , Eggenstein-Leopoldshafen , Germany
| | - Muzamil Majid Khan
- a Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences , Mannheim , Germany.,b Interdisciplinary Center for Neurosciences, Heidelberg University , Heidelberg , Germany.,c Institute of Toxicology and Genetics, Karlsruhe Institute of Technology , Eggenstein-Leopoldshafen , Germany
| | - Rüdiger Rudolf
- a Institute of Molecular and Cell Biology, Mannheim University of Applied Sciences , Mannheim , Germany.,b Interdisciplinary Center for Neurosciences, Heidelberg University , Heidelberg , Germany.,c Institute of Toxicology and Genetics, Karlsruhe Institute of Technology , Eggenstein-Leopoldshafen , Germany
| |
Collapse
|
22
|
Aittaleb M, Martinez-Pena Y Valenzuela I, Akaaboune M. Spatial distribution and molecular dynamics of dystrophin glycoprotein components at the neuromuscular junction in vivo. J Cell Sci 2017; 130:1752-1759. [PMID: 28364093 DOI: 10.1242/jcs.198358] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 03/29/2017] [Indexed: 11/20/2022] Open
Abstract
A bimolecular fluorescence complementation (BiFC) approach was used to study the molecular interactions between different components of the postsynaptic protein complex at the neuromuscular junction of living mice. We show that rapsyn forms complex with both α-dystrobrevin and α-syntrophin at the crests of junctional folds. The linkage of rapsyn to α-syntrophin and/or α-dystrobrevin is mediated by utrophin, a protein localized at acetylcholine receptor (AChR)-rich domains. In mice deficient in α-syntrophin, in which utrophin is no longer present at the synapse, rapsyn interaction with α-dystrobrevin was completely abolished. This interaction was completely restored when either utrophin or α-syntrophin was introduced into muscles deficient in α-syntrophin. However, in neuromuscular junctions deficient in α-dystrobrevin, in which utrophin is retained, complex formation between rapsyn and α-syntrophin was unaffected. Using fluorescence recovery after photobleaching, we found that α-syntrophin turnover is 5-7 times faster than that of AChRs, and loss of α-dystrobrevin has no effect on rapsyn and α-syntrophin half-life, whereas the half-life of AChR was significantly altered. Altogether, these results provide new insights into the spatial distribution of dystrophin glycoprotein components and their dynamics in living mice.
Collapse
Affiliation(s)
- Mohamed Aittaleb
- Department of Molecular, Cellular, and Developmental Biology, and Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109, USA
| | - Isabel Martinez-Pena Y Valenzuela
- Department of Molecular, Cellular, and Developmental Biology, and Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109, USA
| | - Mohammed Akaaboune
- Department of Molecular, Cellular, and Developmental Biology, and Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109, USA .,College of Sciences and Engineering, Life Science Division, Hamad Bin Khalifa University, Doha, Qatar
| |
Collapse
|
23
|
Xenopus Nerve-Muscle Cultures: a Novel Cell-Based Assay for Serological Diagnosis and Pathological Research of Myasthenia Gravis. CURRENT PATHOBIOLOGY REPORTS 2017. [DOI: 10.1007/s40139-017-0126-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
|
24
|
Vezina-Audette R, Tremblay M, Carbonetto S. Laminin is instructive and calmodulin dependent kinase II is non-permissive for the formation of complex aggregates of acetylcholine receptors on myotubes in culture. Matrix Biol 2016; 57-58:106-123. [PMID: 27964993 DOI: 10.1016/j.matbio.2016.11.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 11/16/2016] [Indexed: 12/11/2022]
Abstract
Previous work has shown that myotubes cultured on laminin-coated substrates form complex aggregates of synaptic proteins that are similar in shape and composition to neuromuscular junctions (NMJs). Here we show that laminin instructs the location of complex aggregates which form only on the lower surface when laminin is coated onto culture dishes but over the entire cell when laminin is added in solution. Silencing of myotubes by agents that block electrical activity (tetrodotoxin, verapamil) or by inhibitors of calmodulin dependent kinase (CaMKII) render the myotube permissive for the formation of complex aggregates. Treatment with laminin alone will facilitate the formation of complex aggregates hours later when myotubes are made permissive by inhibiting CaMKII. The AChR agonist carbachol disperses pre formed aggregates suggesting that non-permissiveness may involve active dispersal of AChRs. The permissive period requires ongoing protein synthesis. The latter may reflect a requirement for rapsyn, which turns over rapidly, and is necessary for aggregation. Consistent with this geldanamycin, an agent that increases rapsyn turnover disrupts complex aggregates. Agrin is well known to induce small clusters of AChRs but does not induce complex aggregates even though aggregate formation requires MuSK, a receptor tyrosine kinase activated by agrin. Dystroglycan (DG) is the major laminin receptor mediating complex aggregate formation with some contribution from β1 integrins. In addition, there is a pool of CaMKII associated with DG. We discuss how these permissive and instructive mechanisms bear on NMJ formation in vivo.
Collapse
Affiliation(s)
- Raphael Vezina-Audette
- Centre for Research in Neuroscience, and Dept. of Neurology, McGill University Health Centre, 1650, Cedar Ave., Montreal, Quebec, H3G 1A4, Canada
| | - Mathieu Tremblay
- Centre for Research in Neuroscience, and Dept. of Neurology, McGill University Health Centre, 1650, Cedar Ave., Montreal, Quebec, H3G 1A4, Canada
| | - Salvatore Carbonetto
- Centre for Research in Neuroscience, and Dept. of Neurology, McGill University Health Centre, 1650, Cedar Ave., Montreal, Quebec, H3G 1A4, Canada.
| |
Collapse
|
25
|
Pirkmajer S, Chibalin AV. Na,K-ATPase regulation in skeletal muscle. Am J Physiol Endocrinol Metab 2016; 311:E1-E31. [PMID: 27166285 DOI: 10.1152/ajpendo.00539.2015] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 05/02/2016] [Indexed: 12/17/2022]
Abstract
Skeletal muscle contains one of the largest and the most dynamic pools of Na,K-ATPase (NKA) in the body. Under resting conditions, NKA in skeletal muscle operates at only a fraction of maximal pumping capacity, but it can be markedly activated when demands for ion transport increase, such as during exercise or following food intake. Given the size, capacity, and dynamic range of the NKA pool in skeletal muscle, its tight regulation is essential to maintain whole body homeostasis as well as muscle function. To reconcile functional needs of systemic homeostasis with those of skeletal muscle, NKA is regulated in a coordinated manner by extrinsic stimuli, such as hormones and nerve-derived factors, as well as by local stimuli arising in skeletal muscle fibers, such as contractions and muscle energy status. These stimuli regulate NKA acutely by controlling its enzymatic activity and/or its distribution between the plasma membrane and the intracellular storage compartment. They also regulate NKA chronically by controlling NKA gene expression, thus determining total NKA content in skeletal muscle and its maximal pumping capacity. This review focuses on molecular mechanisms that underlie regulation of NKA in skeletal muscle by major extrinsic and local stimuli. Special emphasis is given to stimuli and mechanisms linking regulation of NKA and energy metabolism in skeletal muscle, such as insulin and the energy-sensing AMP-activated protein kinase. Finally, the recently uncovered roles for glutathionylation, nitric oxide, and extracellular K(+) in the regulation of NKA in skeletal muscle are highlighted.
Collapse
Affiliation(s)
- Sergej Pirkmajer
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; and
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| |
Collapse
|
26
|
Kamerbeek CB, Mateos MV, Vallés AS, Pediconi MF, Barrantes FJ, Borroni V. Diacylglycerol levels modulate the cellular distribution of the nicotinic acetylcholine receptor. Int J Biochem Cell Biol 2016; 74:1-11. [PMID: 26898898 DOI: 10.1016/j.biocel.2016.02.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Revised: 02/03/2016] [Accepted: 02/15/2016] [Indexed: 10/22/2022]
Abstract
Diacylglycerol (DAG), a second messenger involved in different cell signaling cascades, activates protein kinase C (PKC) and D (PKD), among other kinases. The present work analyzes the effects resulting from the alteration of DAG levels on neuronal and muscle nicotinic acetylcholine receptor (AChR) distribution. We employ CHO-K1/A5 cells, expressing adult muscle-type AChR in a stable manner, and hippocampal neurons, which endogenously express various subtypes of neuronal AChR. CHO-K1/A5 cells treated with dioctanoylglycerol (DOG) for different periods showed augmented AChR cell surface levels at short incubation times (30min-4h) whereas at longer times (18h) the AChR was shifted to intracellular compartments. Similarly, in cultured hippocampal neurons surface AChR levels increased as a result of DOG incubation for 4h. Inhibition of endogenous DAG catabolism produced changes in AChR distribution similar to those induced by DOG treatment. Specific enzyme inhibitors and Western blot assays revealed that DAGs exert their effect on AChR distribution through the modulation of the activity of classical PKC (cPKC), novel PKC (nPKC) and PKD activity.
Collapse
Affiliation(s)
- Constanza B Kamerbeek
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga km 7, 8000 Bahía Blanca, Argentina
| | - Melina V Mateos
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga km 7, 8000 Bahía Blanca, Argentina
| | - Ana S Vallés
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga km 7, 8000 Bahía Blanca, Argentina
| | - María F Pediconi
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga km 7, 8000 Bahía Blanca, Argentina
| | - Francisco J Barrantes
- Laboratory of Molecular Neurobiology, Institute for Biomedical Research UCA-CONICET, Faculty of Medical Sciences, Av. Alicia Moreau de Justo 1600, C1107AFF Buenos Aires, Argentina
| | - Virginia Borroni
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga km 7, 8000 Bahía Blanca, Argentina.
| |
Collapse
|
27
|
Lindskog C, Linné J, Fagerberg L, Hallström BM, Sundberg CJ, Lindholm M, Huss M, Kampf C, Choi H, Liem DA, Ping P, Väremo L, Mardinoglu A, Nielsen J, Larsson E, Pontén F, Uhlén M. The human cardiac and skeletal muscle proteomes defined by transcriptomics and antibody-based profiling. BMC Genomics 2015; 16:475. [PMID: 26109061 PMCID: PMC4479346 DOI: 10.1186/s12864-015-1686-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 06/05/2015] [Indexed: 11/29/2022] Open
Abstract
Background To understand cardiac and skeletal muscle function, it is important to define and explore their molecular constituents and also to identify similarities and differences in the gene expression in these two different striated muscle tissues. Here, we have investigated the genes and proteins with elevated expression in cardiac and skeletal muscle in relation to all other major human tissues and organs using a global transcriptomics analysis complemented with antibody-based profiling to localize the corresponding proteins on a single cell level. Results Our study identified a comprehensive list of genes expressed in cardiac and skeletal muscle. The genes with elevated expression were further stratified according to their global expression pattern across the human body as well as their precise localization in the muscle tissues. The functions of the proteins encoded by the elevated genes are well in line with the physiological functions of cardiac and skeletal muscle, such as contraction, ion transport, regulation of membrane potential and actomyosin structure organization. A large fraction of the transcripts in both cardiac and skeletal muscle correspond to mitochondrial proteins involved in energy metabolism, which demonstrates the extreme specialization of these muscle tissues to provide energy for contraction. Conclusions Our results provide a comprehensive list of genes and proteins elevated in striated muscles. A number of proteins not previously characterized in cardiac and skeletal muscle were identified and localized to specific cellular subcompartments. These proteins represent an interesting starting point for further functional analysis of their role in muscle biology and disease. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1686-y) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Cecilia Lindskog
- Science for Life Laboratory, Dept of Immunology Genetics and Pathology, Uppsala University, SE-751 85, Uppsala, Sweden.
| | - Jerker Linné
- Science for Life Laboratory, Dept of Immunology Genetics and Pathology, Uppsala University, SE-751 85, Uppsala, Sweden.
| | - Linn Fagerberg
- Science for Life Laboratory, KTH - Royal Institute of Technology, AlbaNova University Center, SE-171 21, Stockholm, Sweden.
| | - Björn M Hallström
- Science for Life Laboratory, KTH - Royal Institute of Technology, AlbaNova University Center, SE-171 21, Stockholm, Sweden.
| | - Carl Johan Sundberg
- Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77, Stockholm, Sweden.
| | - Malene Lindholm
- Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77, Stockholm, Sweden.
| | - Mikael Huss
- Science for Life Laboratory, Dept of Biochemistry and Biophysics, Stockholm University, Box 1031, SE-17121, Solna, Sweden.
| | - Caroline Kampf
- Science for Life Laboratory, Dept of Immunology Genetics and Pathology, Uppsala University, SE-751 85, Uppsala, Sweden.
| | - Howard Choi
- NHLBI Proteomics Center at UCLA, Departments of Physiology and Medicine, Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
| | - David A Liem
- NHLBI Proteomics Center at UCLA, Departments of Physiology and Medicine, Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
| | - Peipei Ping
- NHLBI Proteomics Center at UCLA, Departments of Physiology and Medicine, Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
| | - Leif Väremo
- Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 58, Gothenburg, Sweden.
| | - Adil Mardinoglu
- Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 58, Gothenburg, Sweden.
| | - Jens Nielsen
- Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 58, Gothenburg, Sweden.
| | - Erik Larsson
- Department of Immunology, Genetics and Pathology, Rudbeck Laboratory, Uppsala University, SE-751 85, Uppsala, Sweden.
| | - Fredrik Pontén
- Science for Life Laboratory, Dept of Immunology Genetics and Pathology, Uppsala University, SE-751 85, Uppsala, Sweden.
| | - Mathias Uhlén
- Science for Life Laboratory, KTH - Royal Institute of Technology, AlbaNova University Center, SE-171 21, Stockholm, Sweden. .,NHLBI Proteomics Center at UCLA, Departments of Physiology and Medicine, Division of Cardiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
| |
Collapse
|
28
|
The knockdown of αkap alters the postsynaptic apparatus of neuromuscular junctions in living mice. J Neurosci 2015; 35:5118-27. [PMID: 25834039 DOI: 10.1523/jneurosci.3951-14.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A muscle-specific nonkinase anchoring protein (αkap), encoded within the calcium/calmodulin kinase II (camk2) α gene, was recently found to control the stability of acetylcholine receptor (AChR) clusters on the surface of cultured myotubes. However, it remains unknown whether this protein has any effect on receptor stability and the maintenance of the structural integrity of neuromuscular synapses in vivo. By knocking down the endogenous expression of αkap in mouse sternomastoid muscles with shRNA, we found that the postsynaptic receptor density was dramatically reduced, the turnover rate of receptors at synaptic sites was significantly increased, and the insertion rates of both newly synthesized and recycled receptors into the postsynaptic membrane were depressed. Moreover, we found that αkap shRNA knockdown impaired synaptic structure as postsynaptic AChR clusters and their associated postsynaptic scaffold proteins within the neuromuscular junction were completely eliminated. These results provide new mechanistic insight into the role of αkap in regulating the stability of the postsynaptic apparatus of neuromuscular synapses.
Collapse
|
29
|
Brenner HR, Akaaboune M. Recycling of acetylcholine receptors at ectopic postsynaptic clusters induced by exogenous agrin in living rats. Dev Biol 2014; 394:122-8. [PMID: 25093969 DOI: 10.1016/j.ydbio.2014.07.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Revised: 06/16/2014] [Accepted: 07/18/2014] [Indexed: 10/24/2022]
Abstract
During the development of the neuromuscular junction, motor axons induce the clustering of acetylcholine receptors (AChRs) and increase their metabolic stability in the muscle membrane. Here, we asked whether the synaptic organizer agrin might regulate the metabolic stability and density of AChRs by promoting the recycling of internalized AChRs, which would otherwise be destined for degradation, into synaptic sites. We show that at nerve-free AChR clusters induced by agrin in extrasynaptic membrane, internalized AChRs are driven back into the ectopic synaptic clusters where they intermingle with pre-existing and new receptors. The extent of AChR recycling depended on the strength of the agrin stimulus, but not on the development of junctional folds, another hallmark of mature postsynaptic membranes. In chronically denervated muscles, in which both AChR stability and recycling are significantly decreased by muscle inactivity, agrin maintained the amount of recycled AChRs at agrin-induced clusters at a level similar to that at denervated original endplates. In contrast, AChRs did not recycle at agrin-induced clusters in C2C12 or primary myotubes. Thus, in muscles in vivo, but not in cultured myotubes, neural agrin promotes the recycling of AChRs and thereby increases their metabolic stability.
Collapse
Affiliation(s)
- Hans Rudolf Brenner
- Department of Biomedicine, University of Basel, Pharmazentrum, Klingelbergstrasse 50, CH-4056 Basel, Switzerland.
| | - Mohammed Akaaboune
- Department of Molecular, Cellular, and Developmental Biology and Program in Neuroscience, University of Michigan, Ann Arbor, MI 48109, USA.
| |
Collapse
|
30
|
Rudolf R, Khan MM, Labeit S, Deschenes MR. Degeneration of neuromuscular junction in age and dystrophy. Front Aging Neurosci 2014; 6:99. [PMID: 24904412 PMCID: PMC4033055 DOI: 10.3389/fnagi.2014.00099] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 05/08/2014] [Indexed: 12/27/2022] Open
Abstract
Functional denervation is a hallmark of aging sarcopenia as well as of muscular dystrophy. It is thought to be a major factor reducing skeletal muscle mass, particularly in the case of sarcopenia. Neuromuscular junctions (NMJs) serve as the interface between the nervous and skeletal muscular systems, and thus they may receive pathophysiological input of both pre- and post-synaptic origin. Consequently, NMJs are good indicators of motor health on a systemic level. Indeed, upon sarcopenia and dystrophy, NMJs morphologically deteriorate and exhibit altered characteristics of primary signaling molecules, such as nicotinic acetylcholine receptor and agrin. Since a remarkable reversibility of these changes can be observed by exercise, there is significant interest in understanding the molecular mechanisms underlying synaptic deterioration upon aging and dystrophy and how synapses are reset by the aforementioned treatments. Here, we review the literature that describes the phenomena observed at the NMJ in sarcopenic and dystrophic muscle as well as to how these alterations can be reversed and to what extent. In a second part, the current information about molecular machineries underlying these processes is reported.
Collapse
Affiliation(s)
- Rüdiger Rudolf
- Institute of Molecular and Cell Biology, University of Applied Sciences Mannheim , Mannheim , Germany ; Institute of Medical Technology, University of Heidelberg and University of Applied Sciences Mannheim , Mannheim , Germany ; Institute of Toxicology and Genetics, Karlsruhe Institute of Technology , Eggenstein-Leopoldshafen , Germany
| | - Muzamil Majid Khan
- Institute of Molecular and Cell Biology, University of Applied Sciences Mannheim , Mannheim , Germany ; Institute of Toxicology and Genetics, Karlsruhe Institute of Technology , Eggenstein-Leopoldshafen , Germany
| | - Siegfried Labeit
- Institute of Integrative Pathophysiology, University Medical Centre Mannheim , Mannheim , Germany
| | - Michael R Deschenes
- Department of Kinesiology and Health Sciences, The College of William and Mary , Williamsburg, VA , USA
| |
Collapse
|
31
|
Martinez-Pena y Valenzuela I, Pires-Oliveira M, Akaaboune M. PKC and PKA regulate AChR dynamics at the neuromuscular junction of living mice. PLoS One 2013; 8:e81311. [PMID: 24260568 PMCID: PMC3829966 DOI: 10.1371/journal.pone.0081311] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 10/14/2013] [Indexed: 11/19/2022] Open
Abstract
The steady state of the acetylcholine receptor (AChR) density at the neuromuscular junction (NMJ) is critical for efficient and reliable synaptic transmission. However, little is known about signaling molecules involved in regulating the equilibrium between the removal and insertion of AChRs that establishes a stable postsynaptic receptor density over time. In this work, we tested the effect of activities of two serine/threonine kinases, PKC and PKA, on the removal rate of AChRs from and the re-insertion rate of internalized recycled AChRs into synaptic sites of innervated and denervated NMJs of living mice. Using an in vivo time-lapse imaging approach and various pharmacological agents, we showed that PKC and PKA activities have antagonistic effects on the removal and recycling of AChRs. Inhibition of PKC activity or activation of PKA largely prevents the removal of pre-existing AChRs and promotes the recycling of internalized AChRs into the postsynaptic membrane. In contrast, stimulation of PKC or inactivation of PKA significantly accelerates the removal of postsynaptic AChRs and depresses AChR recycling. These results indicate that a balance between PKA and PKC activities may be critical for the maintenance of the postsynaptic receptor density.
Collapse
Affiliation(s)
| | - Marcelo Pires-Oliveira
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Mohammed Akaaboune
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
- Program in Neuroscience, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
| |
Collapse
|
32
|
McClure-Begley TD, Stone KL, Marks MJ, Grady SR, Colangelo CM, Lindstrom JM, Picciotto MR. Exploring the nicotinic acetylcholine receptor-associated proteome with iTRAQ and transgenic mice. GENOMICS, PROTEOMICS & BIOINFORMATICS 2013; 11:207-18. [PMID: 23891776 PMCID: PMC3806329 DOI: 10.1016/j.gpb.2013.05.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 05/01/2013] [Accepted: 05/19/2013] [Indexed: 11/24/2022]
Abstract
Neuronal nicotinic acetylcholine receptors (nAChRs) containing α4 and β2 subunits are the principal receptors in the mammalian central nervous system that bind nicotine with high affinity. These nAChRs are involved in nicotine dependence, mood disorders, neurodegeneration and neuroprotection. However, our understanding of the interactions between α4β2-containing (α4β2(∗)) nAChRs and other proteins remains limited. In this study, we identified proteins that interact with α4β2(∗) nAChRs in a genedose dependent pattern by immunopurifying β2(∗) nAChRs from mice that differ in α4 and β2 subunit expression and performing proteomic analysis using isobaric tags for relative and absolute quantitation (iTRAQ). Reduced expression of either the α4 or the β2 subunit results in a correlated decline in the expression of a number of putative interacting proteins. We identified 208 proteins co-immunoprecipitated with these nAChRs. Furthermore, stratified linear regression analysis indicated that levels of 17 proteins was correlated significantly with expression of α4β2 nAChRs, including proteins involved in cytoskeletal rearrangement and calcium signaling. These findings represent the first application of quantitative proteomics to produce a β2(∗) nAChR interactome and describe a novel technique used to discover potential targets for pharmacological manipulation of α4β2 nAChRs and their downstream signaling mechanisms.
Collapse
Affiliation(s)
- Tristan D. McClure-Begley
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06508, USA
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80303, USA
| | - Kathy L. Stone
- W.M. Keck Biotechnology Resource Laboratory, Yale University School Medicine, New Haven, CT 06509, USA
| | - Michael J. Marks
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80303, USA
- Department of Psychology and Neuroscience, University of Colorado, Boulder, CO 80309, USA
| | - Sharon R. Grady
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80303, USA
| | - Christopher M. Colangelo
- W.M. Keck Biotechnology Resource Laboratory, Yale University School Medicine, New Haven, CT 06509, USA
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Jon M. Lindstrom
- Department of Neuroscience, Medical School of the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Marina R. Picciotto
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06508, USA
| |
Collapse
|
33
|
Skeletal muscle calpain acts through nitric oxide and neural miRNAs to regulate acetylcholine release in motor nerve terminals. J Neurosci 2013; 33:7308-7324. [PMID: 23616539 DOI: 10.1523/jneurosci.0224-13.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Cholinergic overactivity in diseases of neuromuscular transmission elicits a retrograde signal resembling homeostatic synaptic plasticity that downregulates transmitter release. Understanding this compensatory pathway could provide insights into novel therapeutic avenues and molecular mechanisms underlying learning and memory. Here we identify nitric oxide as a possible source of this signal in pathological human and mouse muscle samples and link this signaling pathway to changes in synaptic function in the neuromuscular junction. We further show that neuronal nitric oxide synthase is regulated by cholinergic excess through activation of skeletal muscle calpain and its effect on Cdk5 and CaMKII, leading to direct modulation of presynaptic function. Finally, we show that this signaling pathway acts through specific miRNA control of presynaptic vesicle protein expression. The control of presynaptic miRNA levels by postsynaptic activity represents a novel mechanism for the modulation of synaptic activity in normal or pathological conditions.
Collapse
|
34
|
Electrical stimulation accelerates neuromuscular junction formation through ADAM19/neuregulin/ErbB signaling in vitro. Neurosci Lett 2013; 545:29-34. [DOI: 10.1016/j.neulet.2013.04.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 03/05/2013] [Accepted: 04/01/2013] [Indexed: 11/27/2022]
|
35
|
Arora K, Alfulaij N, Higa JK, Panee J, Nichols RA. Impact of sustained exposure to β-amyloid on calcium homeostasis and neuronal integrity in model nerve cell system expressing α4β2 nicotinic acetylcholine receptors. J Biol Chem 2013; 288:11175-90. [PMID: 23479730 DOI: 10.1074/jbc.m113.453746] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Although the interaction between β-amyloid (Aβ) and nicotinic acetylcholine receptors has been widely studied, the impact of prolonged exposure to Aβ on nAChR expression and signaling is not known. In this study, we employed a neuronal culture model to better understand the impact of sustained exposure of Aβ on the regulation of cellular and synaptic function. The differentiated rodent neuroblastoma cell line NG108-15 expressing exogenous high-affinity α4β2 nAChRs was exposed to soluble oligomeric Aβ for several days. Ca(2+) responses, expression levels of α4β2 nAChRs, rate of mitochondrial movement, mitochondrial fission, levels of reactive oxygen species, and nuclear integrity were compared between Aβ-treated and untreated cells, transfected or not (mock-transfected) with α4β2 nAChRs. Sustained exposure of Aβ(1-42) to α4β2 nAChR-transfected cells for several days led to increased Ca(2+) responses on subsequent acute stimulation with Aβ(1-42) or nicotine, paralleled by increased expression levels of α4β2 nAChRs, likely the result of enhanced receptor recycling. The rate of mitochondrial movement was sharply reduced, whereas the mitochondrial fission protein pDrp-1 was increased in α4β2 nAChR-transfected cells treated with Aβ(1-42). In addition, the presence of α4β2 nAChRs dramatically enhanced Aβ(1-42)-mediated increases in reactive oxygen species and nuclear fragmentation, eventually leading to apoptosis. Our data thus show disturbed calcium homeostasis coupled with mitochondrial dysfunction and loss of neuronal integrity on prolonged exposure of Aβ in cells transfected with α4β2 nAChRs. Together, the results suggest that the presence of nAChRs sensitizes neurons to the toxic actions of soluble oligomeric Aβ, perhaps contributing to the cholinergic deficit in Alzheimer disease.
Collapse
Affiliation(s)
- Komal Arora
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813, USA
| | | | | | | | | |
Collapse
|
36
|
A role for the calmodulin kinase II-related anchoring protein (αkap) in maintaining the stability of nicotinic acetylcholine receptors. J Neurosci 2012; 32:5177-85. [PMID: 22496563 DOI: 10.1523/jneurosci.6477-11.2012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
αkap, a muscle specific anchoring protein encoded within the Camk2a gene, is thought to play a role in targeting multiple calcium/calmodulin kinase II isoforms to specific subcellular locations. Here we demonstrate a novel function of αkap in stabilizing nicotinic acetylcholine receptors (AChRs). Knockdown of αkap expression with shRNA significantly enhanced the degradation of AChR α-subunits (AChRα), leading to fewer and smaller AChR clusters on the surface of differentiated C2C12 myotubes. Mutagenesis and biochemical studies in HEK293T cells revealed that αkap promoted AChRα stability by a ubiquitin-dependent mechanism. In the absence of αkap, AChRα was heavily ubiquitinated, and the number of AChRα was increased by proteasome inhibitors. However, in the presence of αkap, AChRα was less ubiquitinated and proteasome inhibitors had almost no effect on AChRα accumulation. The major sites of AChRα ubiquitination reside within the large intracellular loop and mutations of critical lysine residues in this loop to arginine increased AChRα stability in the absence of αkap. These results provide an unexpected mechanism by which αkap controls receptor trafficking onto the surface of muscle cells and thus the maintenance of postsynaptic receptor density and synaptic function.
Collapse
|
37
|
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.
Collapse
|
38
|
Gordon LR, Gribble KD, Syrett CM, Granato M. Initiation of synapse formation by Wnt-induced MuSK endocytosis. Development 2012; 139:1023-33. [PMID: 22318632 DOI: 10.1242/dev.071555] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In zebrafish, the MuSK receptor initiates neuromuscular synapse formation by restricting presynaptic growth cones and postsynaptic acetylcholine receptors (AChRs) to the center of skeletal muscle cells. Increasing evidence suggests a role for Wnts in this process, yet how muscle cells respond to Wnt signals is unclear. Here, we show that in vivo, wnt11r and wnt4a initiate MuSK translocation from muscle membranes to recycling endosomes and that this transition is crucial for AChR accumulation at future synaptic sites. Moreover, we demonstrate that components of the planar cell polarity pathway colocalize to recycling endosomes and that this localization is MuSK dependent. Knockdown of several core components disrupts MuSK translocation to endosomes, AChR localization and axonal guidance. We propose that Wnt-induced trafficking of the MuSK receptor to endosomes initiates a signaling cascade to align pre- with postsynaptic elements. Collectively, these findings suggest a general mechanism by which Wnt signals shape synaptic connectivity through localized receptor endocytosis.
Collapse
Affiliation(s)
- Laura R Gordon
- Department of Cell and Developmental Biology, University of Pennsylvania. Philadelphia, PA 19104-6058, USA
| | | | | | | |
Collapse
|
39
|
Donepezil attenuates hippocampal neuronal damage and cognitive deficits after global cerebral ischemia in gerbils. Neurosci Lett 2012; 510:29-33. [PMID: 22240104 DOI: 10.1016/j.neulet.2011.12.064] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Revised: 12/12/2011] [Accepted: 12/28/2011] [Indexed: 01/25/2023]
Abstract
Decreased cerebral blood flow causes cognitive impairments and neuronal injury in vascular dementia. In the present study, we reported that donepezil, a cholinesterase inhibitor, improved transient global cerebral ischemia-induced spatial memory impairment in gerbils. Treatment with 5mg/kg of donepezil for 21 consecutive days following a 10-min period of ischemia significantly inhibited delayed neuronal death in the hippocampal CA1 region. In Morris water maze test, memory impairment was significantly improved by donepezil treatment. Western blot analysis showed that donepezil treatment prevented reductions in p-CaMKII and p-CREB protein levels in the hippocampus. These results suggest that donepezil attenuates the memory deficit induced by transient global cerebral ischemia and this neuroprotection may be associated with the phosphorylation of CaMKII and CERB in the hippocampus.
Collapse
|
40
|
Nicotinic acetylcholine receptor stability at the NMJ deficient in α-syntrophin in vivo. J Neurosci 2011; 31:15586-96. [PMID: 22031904 DOI: 10.1523/jneurosci.4038-11.2011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
α-Syntrophin (α-syn), a scaffold protein, links signaling molecules to the dystrophin-glycoprotein complex. Absence of α-syn from the DGC is known to lead to structurally aberrant neuromuscular junctions (NMJs) with few acetylcholine receptors (AChRs) clustered at synaptic sites. Using α-syn knock-out mice, we show that during the first postnatal week, α-syn is not required for synapse formation. However, at postnatal day 6 (P6)-P7, the structural integrity of the postsynaptic apparatus is altered, the turnover rate of AChRs increases significantly, and the number/density of AChRs is impaired. At the adult α-syn(-/-) NMJ, the turnover rate of AChRs is ∼ 4 times faster than wild-type synapses, and most removed receptors are targeted to degradation as few AChRs recycled to synaptic sites. Biochemical analyses show that in muscle cells of adult knock-out α-syn mice, total AChRs and scaffold protein rapsyn are significantly reduced, the 89 kDa and 75 kDa isoforms of tyrosine phosphorylated α-dystrobrevin (α-dbn) 1 (which are required for the maintenance and stability of AChR in α-dbn(-/-) synapses) are barely detectable. Electroporation of GFP-α-dbn1 in α-syn(-/-) muscle cells partially restored receptor density, turnover rate, and the structural integrity of the postsynaptic apparatus, whereas expression of rapsyn-GFP failed to rescue the α-syn(-/-) synaptic phenotype. These results demonstrate that α-syn is required for the maturation and stability of the postsynaptic apparatus and suggest that α-syn may act via α-dbn1.
Collapse
|