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Lundt S, Zhang N, Polo-Parada L, Wang X, Ding S. Dietary NMN supplementation enhances motor and NMJ function in ALS. Exp Neurol 2024; 374:114698. [PMID: 38266764 DOI: 10.1016/j.expneurol.2024.114698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 01/15/2024] [Accepted: 01/20/2024] [Indexed: 01/26/2024]
Abstract
Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disease that causes the degeneration of motor neurons in the motor cortex and spinal cord. Patients with ALS experience muscle weakness and atrophy in the limbs which eventually leads to paralysis and death. NAD+ is critical for energy metabolism, such as glycolysis and oxidative phosphorylation, but is also involved in non-metabolic cellular reactions. In the current study, we determined whether the supplementation of nicotinamide mononucleotide (NMN), an NAD+ precursor, in the diet had beneficial impacts on disease progression using a SOD1G93A mouse model of ALS. We found that the ALS mice fed with an NMN-supplemented diet (ALS+NMN mice) had modestly extended lifespan and exhibited delayed motor dysfunction. Using electrophysiology, we studied the effect of NMN on synaptic transmission at neuromuscular junctions (NMJs) in symptomatic of ALS mice (18 weeks old). ALS+NMN mice had larger end-plate potential (EPP) amplitudes and maintained better responses than ALS mice, and also had restored EPP facilitation. While quantal content was not affected by NMN, miniature EPP (mEPP) amplitude and frequency were elevated in ALS+NMN mice. NMN supplementation in diet also improved NMJ morphology, innervation, mitochondrial structure, and reduced reactive astrogliosis in the ventral horn of the lumbar spinal cord. Overall, our results indicate that dietary consumption of NMN can slow motor impairment, enhance NMJ function and improve healthspan of ALS mice.
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Affiliation(s)
- Samuel Lundt
- Interdisciplinary Neuroscience Program, University of Missouri, Columbia, MO 65211, United States of America; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, United States of America
| | - Nannan Zhang
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, United States of America
| | - Luis Polo-Parada
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, United States of America; Department of Medical, Physiology and Pharmacology, University of Missouri, Columbia, MO 65211, United States of America
| | - Xinglong Wang
- Department of Pharmacology & Toxicology, University of Arizona, Tucson, AZ 85721, United States of America
| | - Shinghua Ding
- Interdisciplinary Neuroscience Program, University of Missouri, Columbia, MO 65211, United States of America; Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65211, United States of America; Department of Chemical and Biomedical Engineering, University of Missouri, Columbia, MO 65211, United States of America.
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Rimbert S, Moreira JB, Xapelli S, Lévi S. Role of purines in brain development, from neuronal proliferation to synaptic refinement. Neuropharmacology 2023:109640. [PMID: 37348675 DOI: 10.1016/j.neuropharm.2023.109640] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 06/15/2023] [Accepted: 06/19/2023] [Indexed: 06/24/2023]
Abstract
The purinergic system includes P1 and P2 receptors, which are activated by ATP and its metabolites. They are expressed in adult neuronal and glial cells and are crucial in brain function, including neuromodulation and neuronal signaling. As P1 and P2 receptors are expressed throughout embryogenesis and development, purinergic signaling also has an important role in the development of the peripheral and central nervous system. In this review, we present the expression pattern and activity of purinergic receptors and of their signaling pathways during embryonic and postnatal development of the nervous system. In particular, we review the involvement of the purinergic signaling in all the crucial steps of brain development i.e. in neural stem cell proliferation, neuronal differentiation and migration as well as in astrogliogenesis and oligodendrogenesis. Then, we review data showing a crucial role of the ATP and adenosine signaling pathways in the formation of the peripheral neuromuscular junction and of central GABAergic and glutamatergic synapses. Finally, we examine the consequences of deregulation of the purinergic system during development and discuss the therapeutic potential of targeting it at adult stage in diseases with reactivation of the ATP and adenosine pathway.
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Affiliation(s)
- Solen Rimbert
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, 75005, Paris, France
| | - João B Moreira
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, 75005, Paris, France; Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal; Instituto de Medicina Molecular - João Lobo Antunes (iMM - JLA), Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Sara Xapelli
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal; Instituto de Medicina Molecular - João Lobo Antunes (iMM - JLA), Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
| | - Sabine Lévi
- INSERM UMR-S 1270, Sorbonne Université, Institut du Fer à Moulin, 75005, Paris, France.
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Ohkawara B, Ito M, Ohno K. Secreted Signaling Molecules at the Neuromuscular Junction in Physiology and Pathology. Int J Mol Sci 2021; 22:ijms22052455. [PMID: 33671084 PMCID: PMC7957818 DOI: 10.3390/ijms22052455] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 02/22/2021] [Accepted: 02/25/2021] [Indexed: 02/08/2023] Open
Abstract
Signal transduction at the neuromuscular junction (NMJ) is affected in many human diseases, including congenital myasthenic syndromes (CMS), myasthenia gravis, Lambert–Eaton myasthenic syndrome, Isaacs’ syndrome, Schwartz–Jampel syndrome, Fukuyama-type congenital muscular dystrophy, amyotrophic lateral sclerosis, and sarcopenia. The NMJ is a prototypic cholinergic synapse between the motor neuron and the skeletal muscle. Synaptogenesis of the NMJ has been extensively studied, which has also been extrapolated to further understand synapse formation in the central nervous system. Studies of genetically engineered mice have disclosed crucial roles of secreted molecules in the development and maintenance of the NMJ. In this review, we focus on the secreted signaling molecules which regulate the clustering of acetylcholine receptors (AChRs) at the NMJ. We first discuss the signaling pathway comprised of neural agrin and its receptors, low-density lipoprotein receptor-related protein 4 (Lrp4) and muscle-specific receptor tyrosine kinase (MuSK). This pathway drives the clustering of acetylcholine receptors (AChRs) to ensure efficient signal transduction at the NMJ. We also discuss three secreted molecules (Rspo2, Fgf18, and connective tissue growth factor (Ctgf)) that we recently identified in the Wnt/β-catenin and fibroblast growth factors (FGF) signaling pathways. The three secreted molecules facilitate the clustering of AChRs by enhancing the agrin-Lrp4-MuSK signaling pathway.
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Affiliation(s)
- Bisei Ohkawara
- Correspondence: ; Tel.: +81-52-744-2447; Fax: +81-52-744-2449
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Abstract
Purinergic signaling involves extracellular purines and pyrimidines acting upon specific cell surface purinoceptors classified into the P1, P2X, and P2Y families for nucleosides and nucleotides. This widespread signaling mechanism is active in all major tissues and influences a range of functions in health and disease. Orthologs to all but one of the human purinoceptors have been found in mouse, making this laboratory animal a useful model to study their function. Indeed, analyses of purinoceptors via knock-in or knockout approaches to produce gain or loss of function phenotypes have revealed several important therapeutic targets. None of the homozygous purinoceptor knockouts proved to be developmentally lethal, which suggest that either these receptors are not involved in key developmental processes or that the large number of receptors in each family allowed for functional compensation. Different models for the same purinoceptor often show compatible phenotypes but there have been examples of significant discrepancies. These revealed unexpected differences in the structure of human and mouse genes and emphasized the importance of the genetic background of different mouse strains. In this chapter, we provide an overview of the current knowledge and new trends in the modifications of purinoceptor genes in vivo. We discuss the resulting phenotypes, their applications and relative merits and limitations of mouse models available to study purinoceptor subtypes.
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Affiliation(s)
- Robin M H Rumney
- School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK
| | - Dariusz C Górecki
- School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK.
- Military Institute of Hygiene and Epidemiology, Warsaw, Poland.
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Abstract
Extracellular purines and pyrimidines play major roles during embryogenesis, organogenesis, postnatal development and ageing in vertebrates, including humans. Pluripotent stem cells can differentiate into three primary germ layers of the embryo but may also be involved in plasticity and repair of the adult brain. These cells express the molecular components necessary for purinergic signalling, and their developmental fates can be manipulated via this signalling pathway. Functional P1, P2Y and P2X receptor subtypes and ectonucleotidases are involved in the development of different organ systems, including heart, blood vessels, skeletal muscle, urinary bladder, central and peripheral neurons, retina, inner ear, gut, lung and vas deferens. The importance of purinergic signalling in the ageing process is suggested by changes in expression of A1 and A2 receptors in old rat brains and reduction of P2X receptor expression in ageing mouse brain. By contrast, in the periphery, increases in expression of P2X3 and P2X4 receptors are seen in bladder and pancreas.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF, UK,
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Abstract
It is now widely recognised that extracellular nucleotides, signalling via purinergic receptors, participate in numerous biological processes in most tissues. It has become evident that extracellular nucleotides have significant regulatory effects in the musculoskeletal system. In early development, ATP released from motor nerves along with acetylcholine acts as a cotransmitter in neuromuscular transmission; in mature animals, ATP functions as a neuromodulator. Purinergic receptors expressed by skeletal muscle and satellite cells play important pathophysiological roles in their development or repair. In many cell types, expression of purinergic receptors is often dependent on differentiation. For example, sequential expression of P2X5, P2Y1 and P2X2 receptors occurs during muscle regeneration in the mdx model of muscular dystrophy. In bone and cartilage cells, the functional effects of purinergic signalling appear to be largely negative. ATP stimulates the formation and activation of osteoclasts, the bone-destroying cells. Another role appears to be as a potent local inhibitor of mineralisation. In osteoblasts, the bone-forming cells, ATP acts via P2 receptors to limit bone mineralisation by inhibiting alkaline phosphatase expression and activity. Extracellular ATP additionally exerts significant effects on mineralisation via its hydrolysis product, pyrophosphate. Evidence now suggests that purinergic signalling is potentially important in several bone and joint disorders including osteoporosis, rheumatoid arthritis and cancers. Strategies for future musculoskeletal therapies might involve modulation of purinergic receptor function or of the ecto-nucleotidases responsible for ATP breakdown or ATP transport inhibitors.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF, UK,
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Affiliation(s)
| | - Anthony Sinadinos
- School of Pharmacy and Biomedical Sciences; University of Portsmouth; Portsmouth PO1 2DT UK
| | - Dariusz C. Gorecki
- School of Pharmacy and Biomedical Sciences; University of Portsmouth; Portsmouth PO1 2DT UK
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Young CNJ, Brutkowski W, Lien CF, Arkle S, Lochmüller H, Zabłocki K, Górecki DC. P2X7 purinoceptor alterations in dystrophic mdx mouse muscles: relationship to pathology and potential target for treatment. J Cell Mol Med 2012; 16:1026-37. [PMID: 21794079 PMCID: PMC4365874 DOI: 10.1111/j.1582-4934.2011.01397.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is a lethal inherited muscle disorder. Pathological characteristics of DMD skeletal muscles include, among others, abnormal Ca(2+) homeostasis and cell signalling. Here, in the mdx mouse model of DMD, we demonstrate significant P2X7 receptor abnormalities in isolated primary muscle cells and cell lines and in dystrophic muscles in vivo. P2X7 mRNA expression in dystrophic muscles was significantly up-regulated but without alterations of specific splice variant patterns. P2X7 protein was also up-regulated and this was associated with altered function of P2X7 receptors producing increased responsiveness of cytoplasmic Ca(2+) and extracellular signal-regulated kinase (ERK) phosphorylation to purinergic stimulation and altered sensitivity to NAD. Ca(2+) influx and ERK signalling were stimulated by ATP and BzATP, inhibited by specific P2X7 antagonists and insensitive to ivermectin, confirming P2X7 receptor involvement. Despite the presence of pannexin-1, prolonged P2X7 activation did not trigger cell permeabilization to propidium iodide or Lucifer yellow. In dystrophic mice, in vivo treatment with the P2X7 antagonist Coomassie Brilliant Blue reduced the number of degeneration-regeneration cycles in mdx skeletal muscles. Altered P2X7 expression and function is thus an important feature in dystrophic mdx muscle and treatments aiming to inhibit P2X7 receptor might slow the progression of this disease.
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Affiliation(s)
- Christopher N J Young
- School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, UK
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Shi L, Fu AK, Ip NY. 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] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 04/09/2012] [Accepted: 04/15/2012] [Indexed: 01/22/2023]
Abstract
The vertebrate neuromuscular junction (NMJ), a peripheral synapse formed between motoneuron and skeletal muscle, is characterized by a protracted postnatal period of maturation and life-long maintenance. In neuromuscular disorders such as congenital myasthenic syndromes (CMSs), disruptions of NMJ maturation and/or maintenance are frequently observed. In particular, defective neuromuscular transmission associated with structural and molecular abnormalities at the pre- and postsynaptic membranes, as well as at the synaptic cleft, has been reported in these patients. Here, we review recent advances in the understanding of molecular and cellular events that mediate NMJ maturation and maintenance. The underlying regulatory mechanisms, including key molecular regulators at the presynaptic nerve terminal, synaptic cleft, and postsynaptic muscle membrane, are discussed.
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Kaczmarek-Hájek K, Lörinczi E, Hausmann R, Nicke A. Molecular and functional properties of P2X receptors--recent progress and persisting challenges. Purinergic Signal 2012; 8:375-417. [PMID: 22547202 PMCID: PMC3360091 DOI: 10.1007/s11302-012-9314-7] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 10/18/2011] [Indexed: 12/16/2022] Open
Abstract
ATP-gated P2X receptors are trimeric ion channels that assemble as homo- or heteromers from seven cloned subunits. Transcripts and/or proteins of P2X subunits have been found in most, if not all, mammalian tissues and are being discovered in an increasing number of non-vertebrates. Both the first crystal structure of a P2X receptor and the generation of knockout (KO) mice for five of the seven cloned subtypes greatly advanced our understanding of their molecular and physiological function and their validation as drug targets. This review summarizes the current understanding of the structure and function of P2X receptors and gives an update on recent developments in the search for P2X subtype-selective ligands. It also provides an overview about the current knowledge of the regulation and modulation of P2X receptors on the cellular level and finally on their physiological roles as inferred from studies on KO mice.
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Affiliation(s)
- Karina Kaczmarek-Hájek
- Max Planck Institute for Experimental Medicine, Hermann Rein Str. 3, 37075, Göttingen, Germany
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Nasiripourdori A, Taly V, Grutter T, Taly A. From toxins targeting ligand gated ion channels to therapeutic molecules. Toxins (Basel) 2011; 3:260-93. [PMID: 22069709 PMCID: PMC3202823 DOI: 10.3390/toxins3030260] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 02/01/2011] [Accepted: 03/16/2011] [Indexed: 11/21/2022] Open
Abstract
Ligand-gated ion channels (LGIC) play a central role in inter-cellular communication. This key function has two consequences: (i) these receptor channels are major targets for drug discovery because of their potential involvement in numerous human brain diseases; (ii) they are often found to be the target of plant and animal toxins. Together this makes toxin/receptor interactions important to drug discovery projects. Therefore, toxins acting on LGIC are presented and their current/potential therapeutic uses highlighted.
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Affiliation(s)
| | - Valérie Taly
- Laboratory of Chemical Biology, Institut de Science et d'Ingénierie Supramoléculaires; ISIS/Université de Strasbourg, CNRS-UMR 7006, 8, allée Gaspard Monge, BP 70028, F-67083, Strasbourg Cedex, France;
| | - Thomas Grutter
- Laboratoire de Biophysicochimie des Récepteurs Canaux, UMR 7199 “Conception et Application de Molécules Bioactives” CNRS-Université de Strasbourg, 74 Route du Rhin-BP 60024, 67401 Illkirch Cedex, France;
| | - Antoine Taly
- Laboratoire de Biophysicochimie des Récepteurs Canaux, UMR 7199 “Conception et Application de Molécules Bioactives” CNRS-Université de Strasbourg, 74 Route du Rhin-BP 60024, 67401 Illkirch Cedex, France;
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Martinello T, Baldoin MC, Morbiato L, Paganin M, Tarricone E, Schiavo G, Bianchini E, Sandonà D, Betto R. Extracellular ATP signaling during differentiation of C2C12 skeletal muscle cells: role in proliferation. Mol Cell Biochem 2011; 351:183-96. [PMID: 21308481 DOI: 10.1007/s11010-011-0726-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Accepted: 01/05/2011] [Indexed: 02/06/2023]
Abstract
Evidence shows that extracellular ATP signals influence myogenesis, regeneration and physiology of skeletal muscle. Present work was aimed at characterizing the extracellular ATP signaling system of skeletal muscle C2C12 cells during differentiation. We show that mechanical and electrical stimulation produces substantial release of ATP from differentiated myotubes, but not from proliferating myoblasts. Extracellular ATP-hydrolyzing activity is low in myoblasts and high in myotubes, consistent with the increased expression of extracellular enzymes during differentiation. Stimulation of cells with extracellular nucleotides produces substantial Ca(2+) transients, whose amplitude and shape changed during differentiation. Consistently, C2C12 cells express several P2X and P2Y receptors, whose level changes along with maturation stages. Supplementation with either ATP or UTP stimulates proliferation of C2C12 myoblasts, whereas excessive doses were cytotoxic. The data indicate that skeletal muscle development is accompanied by major functional changes in extracellular ATP signaling.
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Affiliation(s)
- Tiziana Martinello
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy
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Burnstock G, Ulrich H. Purinergic signaling in embryonic and stem cell development. Cell Mol Life Sci 2011; 68:1369-94. [PMID: 21222015 DOI: 10.1007/s00018-010-0614-1] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 12/07/2010] [Accepted: 12/10/2010] [Indexed: 01/23/2023]
Abstract
Nucleotides are of crucial importance as carriers of energy in all organisms. However, the concept that in addition to their intracellular roles, nucleotides act as extracellular ligands specifically on receptors of the plasma membrane took longer to be accepted. Purinergic signaling exerted by purines and pyrimidines, principally ATP and adenosine, occurs throughout embryologic development in a wide variety of organisms, including amphibians, birds, and mammals. Cellular signaling, mediated by ATP, is present in development at very early stages, e.g., gastrulation of Xenopus and germ layer definition of chick embryo cells. Purinergic receptor expression and functions have been studied in the development of many organs, including the heart, eye, skeletal muscle and the nervous system. In vitro studies with stem cells revealed that purinergic receptors are involved in the processes of proliferation, differentiation, and phenotype determination of differentiated cells. Thus, nucleotides are able to induce various intracellular signaling pathways via crosstalk with other bioactive molecules acting on growth factor and neurotransmitter receptors. Since normal development is disturbed by dysfunction of purinergic signaling in animal models, further studies are needed to elucidate the functions of purinoceptor subtypes in developmental processes.
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Low SE, Kuwada JY, Hume RI. Amino acid variations resulting in functional and nonfunctional zebrafish P2X(1) and P2X (5.1) receptors. Purinergic Signal 2008; 4:383-92. [PMID: 18850305 PMCID: PMC2583207 DOI: 10.1007/s11302-008-9124-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2008] [Accepted: 09/11/2008] [Indexed: 11/24/2022] Open
Abstract
Several zebrafish P2X receptors (zP2X(1), zP2X(2), and zP2X(5.1)) have been reported to produce little or no current although their mammalian orthologs produce functional homomeric receptors. We isolated new cDNA clones for these P2X receptors that revealed sequence variations in each. The new variants of zP2X(1) and zP2X(5.1) produced substantial currents when expressed by Xenopus oocytes, however the new variant of zP2X(2) was still nonfunctional. zP2X(2) lacks two lysine residues essential for ATP responsiveness in other P2X receptors; however introduction of these two lysines was insufficient to allow this receptor to function as a homotrimer. We also tested whether P2X signaling is required for myogenesis or synaptic communication at the zebrafish neuromuscular junction. We found that embryonic skeletal muscle expressed only one P2X receptor, P2X(5.1). Antisense knockdown of P2X(5.1) eliminated skeletal muscle responsiveness to ATP but did not prevent myogenesis or behaviors that require functional transmission at the neuromuscular junction.
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Affiliation(s)
- Sean E. Low
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N. University Ave, Ann Arbor, MI 48109-1048 USA
| | - John Y. Kuwada
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N. University Ave, Ann Arbor, MI 48109-1048 USA
| | - Richard I. Hume
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N. University Ave, Ann Arbor, MI 48109-1048 USA
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Bettini NL, Moores TS, Baxter B, Deuchars J, Parson SH. Dynamic remodelling of synapses can occur in the absence of the parent cell body. BMC Neurosci 2007; 8:79. [PMID: 17897464 PMCID: PMC2048966 DOI: 10.1186/1471-2202-8-79] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Accepted: 09/26/2007] [Indexed: 02/03/2023] Open
Abstract
Background Retraction of nerve terminals is a characteristic feature of development, injury and insult and may herald many neurodegenerative diseases. Although morphological events have been well characterized, we know relatively little about the nature of the underlying cellular machinery. Evidence suggests a strong local component in determining which neuronal branches and synapses are lost, but a greater understanding of this basic neurological process is required. Here we test the hypothesis that nerve terminals are semi-autonomous and able to rapidly respond to local stimuli in the absence of communication with their parent cell body. Results We used an isolated preparation consisting of distal peripheral nerve stumps, associated nerve terminals and post-synaptic muscle fibres, maintained in-vitro for up to 3 hrs. In this system synapses are intact but the presynaptic nerve terminal is disconnected from its cell soma. In control preparations synapses were stable for extended periods and did not undergo Wallerian degneration. In contrast, addition of purines triggers rapid changes at synapses. Using fluorescence and electron microscopy we observe ultrastructural and gross morphological events consistent with nerve terminal retraction. We find no evidence of Wallerian or Wallerian-like degeneration in these preparations. Pharmacological experiments implicate pre-synaptic P2X7 receptor subunits as key mediators of these events. Conclusion The data presented suggest; first that isolated nerve terminals are able to regulate connectivity independent of signals from the cell body, second that synapses exist in a dynamic state, poised to shift from stability to loss by activating intrinsic mechanisms and molecules, and third that local purines acting at purinergic receptors can trigger these events. A role for ATP receptors in this is not surprising since they are frequently activated during cellular injury, when adenosine tri-phosphate is released from damaged cells. Local control demands that the elements necessary to drive retraction are constitutively present. We hypothesize that pre-existing scaffolds of molecular motors and cytoskeletal proteins could provide the dynamism required to drive such structural changes in nerve terminals in the absence of the cell body.
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Affiliation(s)
- Natalia L Bettini
- University of Leeds, Institute of Membrane and Systems Biology, Faculty of Biological Sciences, Garstang Building, LS2 9JT, UK
- University of Sussex, Sussex Centre for Neuroscience, School of Life Sciences, Falmer, Brighton, BN1 9QG
| | - Thomas S Moores
- University of Leeds, Institute of Membrane and Systems Biology, Faculty of Biological Sciences, Garstang Building, LS2 9JT, UK
| | - Becki Baxter
- University of Leeds, Institute of Membrane and Systems Biology, Faculty of Biological Sciences, Garstang Building, LS2 9JT, UK
- University of Edinburgh, Section of Anatomy, Centre for Integrative Physiology, Old Medical School, Edinburgh, EH8 9AG, UK
| | - Jim Deuchars
- University of Leeds, Institute of Membrane and Systems Biology, Faculty of Biological Sciences, Garstang Building, LS2 9JT, UK
| | - Simon H Parson
- University of Leeds, Institute of Membrane and Systems Biology, Faculty of Biological Sciences, Garstang Building, LS2 9JT, UK
- University of Edinburgh, Section of Anatomy, Centre for Integrative Physiology, Old Medical School, Edinburgh, EH8 9AG, UK
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