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Giniatullin AR, Mukhutdinova KA, Petrov AM. Mechanism of Purinergic Regulation of Neurotransmission in Mouse Neuromuscular Junction: The Role of Redox Signaling and Lipid Rafts. Neurochem Res 2024:10.1007/s11064-024-04153-5. [PMID: 38814360 DOI: 10.1007/s11064-024-04153-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 04/16/2024] [Accepted: 05/16/2024] [Indexed: 05/31/2024]
Abstract
Acetylcholine is the main neurotransmitter at the vertebrate neuromuscular junctions (NMJs). ACh exocytosis is precisely modulated by co-transmitter ATP and its metabolites. It is assumed that ATP/ADP effects on ACh release rely on activation of presynaptic Gi protein-coupled P2Y13 receptors. However, downstream signaling mechanism of ATP/ADP-mediated modulation of neuromuscular transmission remains elusive. Using microelectrode recording and fluorescent indicators, the mechanism underlying purinergic regulation was studied in the mouse diaphragm NMJs. Pharmacological stimulation of purinoceptors with ADP decreased synaptic vesicle exocytosis evoked by both low and higher frequency stimulation. This inhibitory action was suppressed by antagonists of P2Y13 receptors (MRS 2211), Ca2+ mobilization (TMB8), protein kinase C (chelerythrine) and NADPH oxidase (VAS2870) as well as antioxidants. This suggests the participation of Ca2+ and reactive oxygen species (ROS) in the ADP-triggered signaling. Indeed, ADP caused an increase in cytosolic Ca2+ with subsequent elevation of ROS levels. The elevation of [Ca2+]in was blocked by MRS 2211 and TMB8, whereas upregulation of ROS was prevented by pertussis toxin (inhibitor of Gi protein) and VAS2870. Targeting the main components of lipid rafts, cholesterol and sphingomyelin, suppressed P2Y13 receptor-dependent attenuation of exocytosis and ADP-induced enhancement of ROS production. Inhibition of P2Y13 receptors decreased ROS production and increased the rate of exocytosis during intense activity. Thus, suppression of neuromuscular transmission by exogenous ADP or endogenous ATP can rely on P2Y13 receptor/Gi protein/Ca2+/protein kinase C/NADPH oxidase/ROS signaling, which is coordinated in a lipid raft-dependent manner.
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Affiliation(s)
| | - Kamilla A Mukhutdinova
- Kazan State Medical University, 49 Butlerova St., Kazan, RT, Russia, 420012
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, 2/31 Lobachevsky St, Kazan, RT, Russia, 420111
| | - Alexey M Petrov
- Kazan State Medical University, 49 Butlerova St., Kazan, RT, Russia, 420012.
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, 2/31 Lobachevsky St, Kazan, RT, Russia, 420111.
- Kazan Federal University, 18 Kremlyovskaya Street, Kazan, Russia, 420008.
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Yamaguchi T, Kouzaki K, Sasaki K, Nakazato K. Alterations in neuromuscular junction morphology with ageing and endurance training modulate neuromuscular transmission and myofibre composition. J Physiol 2024. [PMID: 38173183 DOI: 10.1113/jp285143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Accepted: 12/12/2023] [Indexed: 01/05/2024] Open
Abstract
Both ageing and exercise training affect the neuromuscular junction (NMJ) structure. Morphological alterations in the NMJ have been considered to influence neuromuscular transmission and myofibre properties, but the direct link between the morphology and function has yet to be established. We measured the neuromuscular transmission, myofibre composition and NMJ structure of 5-month-old (young) and 24-month-old untrained (aged control) and trained (aged trained) mice. Aged trained mice were subjected to 2 months of endurance training before the measurement. Neuromuscular transmission was evaluated in vivo as the ratio of ankle plantar flexion torque evoked by the sciatic nerve stimulation to that by direct muscle stimulation. The torque ratio was significantly lower in aged mice than in young and aged trained mice at high-frequency stimulations, showing a significant positive correlation with voluntary grip strength. The degree of pre- to post-synaptic overlap of the NMJ was also significantly lower in aged mice and positively correlated with the torque ratio. We also found that the proportion of fast-twitch fibres in the soleus muscle decreased with age, and that age-related denervation occurred preferentially in fast-twitch fibres. Age-related denervation and a shift in myofibre composition were partially prevented by endurance training. These results suggest that age-related deterioration of the NMJ structure impairs neuromuscular transmission and alters myofibre composition, but these alterations can be prevented by structural amelioration of NMJ with endurance training. Our findings highlight the importance of the NMJ as a major determinant of age-related deterioration of skeletal muscles and the clinical significance of endurance training as a countermeasure. KEY POINTS: The neuromuscular junction (NMJ) plays an essential role in neuromuscular transmission and the maintenance of myofibre properties. We show that neuromuscular transmission is impaired with ageing but recovered by endurance training, which contributes to alterations in voluntary strength. Neuromuscular transmission is associated with the degree of pre- to post-synaptic overlap of the NMJ. Age-related denervation of fast-twitch fibres and a shift in myofibre composition toward a slower phenotype are partially prevented by endurance training. Our study provides substantial evidence that age-related and exercise-induced alterations in neuromuscular transmission and myofibre properties are associated with morphological changes in the NMJ.
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Affiliation(s)
- Tatsuhiro Yamaguchi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
- Japan Society for the Promotion of Science, Tokyo, Japan
| | - Karina Kouzaki
- Graduate School of Health and Sport Science, Nippon Sport Science University, Tokyo, Japan
| | - Kazushige Sasaki
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Koichi Nakazato
- Graduate School of Health and Sport Science, Nippon Sport Science University, Tokyo, Japan
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3
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Xia M, Chen C, Xu Y, Li Y, Sheng X, Ding H. Extracting Individual Muscle Drive and Activity From High-Density Surface Electromyography Signals Based on the Center of Gravity of Motor Unit. IEEE Trans Biomed Eng 2023; 70:2852-2862. [PMID: 37043313 DOI: 10.1109/tbme.2023.3266575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
Abstract
Neural interfacing has played an essential role in advancing our understanding of fundamental movement neurophysiology and the development of human-machine interface. However, direct neural interfaces from brain and nerve recording are currently limited in clinical areas for their invasiveness and high selectivity. Here, we applied the surface electromyogram (EMG) in studying the neural control of movement and proposed a new non-invasive way of extracting neural drive to individual muscles. Sixteen subjects performed isometric contractions to complete six hand tasks. High-density surface EMG signals (256 channels in total) recorded from the forearm muscles were decomposed into motor unit firing trains. The location of each decomposed motor unit was represented by its center of gravity and was put into clustering for distinct muscle regions. All the motor units in the same cluster served as a muscle-specific motor pool from which individual muscle drive could be extracted directly. Moreover, we cross-validated the self-clustered muscle regions by magnetic resonance imaging (MRI) recorded from the subjects' forearms. All motor units that fall within the MRI region are considered correctly clustered. We achieved a clustering accuracy of 95.72% ± 4.01% for all subjects. We provided a new framework for collecting experimental muscle-specific drives and generalized the way of surface electrode placement without prior knowledge of the targeting muscle architecture.
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Motamed C. Intraoperative Monitoring of Neuromuscular Blockade. Life (Basel) 2023; 13:life13051184. [PMID: 37240830 DOI: 10.3390/life13051184] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 05/10/2023] [Accepted: 05/13/2023] [Indexed: 05/28/2023] Open
Abstract
There is a global trend of new guidelines highly recommending quantitative neuromuscular monitoring in the operating room. In fact, it is almost certain that quantitatively monitoring the depth of intraoperative muscle paralysis may permit the rational use of muscle relaxants and avoid some of the major related complications, namely postoperative pulmonary complications. A specific culture related to this issue is necessary to integrate quantitative monitoring of muscle relaxants as part of a major monitoring entity in anesthetized patients. For this purpose, it is necessary to fully understand the physiology, pharmacology and concept of monitoring as well as the choice of pharmacological reversal, including the introduction of sugammadex a decade ago.
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Affiliation(s)
- Cyrus Motamed
- Institut de Cancérologie Gustave Roussy, 94080 Villejuif, France
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Tsentsevitsky AN, Gafurova CR, Mukhutdinova KA, Giniatullin AR, Fedorov NS, Malomouzh AI, Petrov AM. Sphingomyelinase modulates synaptic vesicle mobilization at the mice neuromuscular junctions. Life Sci 2023; 318:121507. [PMID: 36801470 DOI: 10.1016/j.lfs.2023.121507] [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: 12/26/2022] [Revised: 02/07/2023] [Accepted: 02/14/2023] [Indexed: 02/21/2023]
Abstract
AIMS Sphingomyelin is an abundant component of the presynaptic membrane and an organizer of lipid rafts. In several pathological conditions, sphingomyelin is hydrolyzed due to an upregulation and release of secretory sphingomyelinases (SMases). Herein, the effects of SMase on exocytotic neurotransmitter release were studied in the diaphragm neuromuscular junctions of mice. MAIN METHODS Microelectrode recordings of postsynaptic potentials and styryl (FM) dyes were used to estimate neuromuscular transmission. Membrane properties were assessed with fluorescent techniques. KEY FINDINGS Application of SMase at a low concentration (0.01 U ml-1) led to a disruption of lipid-packing in the synaptic membranes. Neither spontaneous exocytosis nor evoked neurotransmitter release (in response to single stimuli) were affected by SMase treatment. However, SMase significantly increased neurotransmitter release and the rate of fluorescent FM-dye loss from the synaptic vesicles at 10, 20 and 70 Hz stimulation of the motor nerve. In addition, SMase treatment prevented a shift of the exocytotic mode from "full-collapse" fusion to "kiss-and-run" during high-frequency (70 Hz) activity. The potentiating effects of SMase on neurotransmitter release and FM-dye unloading were suppressed when synaptic vesicle membranes were also exposed to this enzyme (i.e., stimulation occurred during SMase treatment). SIGNIFICANCE Thus, hydrolysis of the plasma membrane sphingomyelin can enhance mobilization of synaptic vesicles and facilitate full fusion mode of exocytosis, but SMase acting on vesicular membrane had a depressant effect on the neurotransmission. Partially, the effects of SMase can be related with the changes in synaptic membrane properties and intracellular signaling.
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Affiliation(s)
- Andrei N Tsentsevitsky
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky St, Box 30, Kazan, RT 420111, Russia
| | - Chulpan R Gafurova
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky St, Box 30, Kazan, RT 420111, Russia
| | - Kamilla A Mukhutdinova
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky St, Box 30, Kazan, RT 420111, Russia
| | - Arthur R Giniatullin
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky St, Box 30, Kazan, RT 420111, Russia; Kazan State Medial University, 49 Butlerova St., Kazan, RT 420012, Russia
| | - Nikita S Fedorov
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky St, Box 30, Kazan, RT 420111, Russia
| | - Artem I Malomouzh
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky St, Box 30, Kazan, RT 420111, Russia
| | - Alexey M Petrov
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky St, Box 30, Kazan, RT 420111, Russia; Kazan State Medial University, 49 Butlerova St., Kazan, RT 420012, Russia.
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Dmitrieva SA, Vologin SG, Tsentsevitsky AN, Arkhipov AY, Khuzakhmetova VF, Sibgatullina GV, Bukharaeva EA. Sympathetic Innervation and Endogenous Catecholamines in Neuromuscular Preparations of Muscles with Different Functional Profiles. BIOCHEMISTRY (MOSCOW) 2023; 88:364-373. [PMID: 37076283 DOI: 10.1134/s0006297923030069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/28/2023]
Abstract
Influence of the sympathetic nervous system on the work of skeletal muscles contractile apparatus is now beyond doubt. However, until recently there was no evidence that the endings of sympathetic nerves can be located in close proximity to the neuromuscular synapses, and there is also no reliable data on how much endogenous adrenaline and noradrenaline can be contained near the synaptic contact in skeletal muscles. In this research, using fluorescent analysis, immunohistochemical and enzyme immunoassays the isolated neuromuscular preparations of three skeletal muscles of different functional profiles and containing different types of muscle fibers were examined. Close contact between the sympathetic and motor cholinergic nerve endings and the presence of tyrosine hydroxylase in this area were demonstrated. Concentrations of endogenous adrenaline and noradrenaline in the solution perfusing the neuromuscular preparation were determined under different modes of its functioning. The effects of α and β adrenoreceptor blockers on the processes of acetylcholine quantal secretion from the motor nerve endings were compared. The data obtained provide evidence for the presence of endogenous catecholamines in the neuromuscular junction region and their role in modulation of the synaptic function.
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Affiliation(s)
- Svetlana A Dmitrieva
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Kazan, 420111, Russia
| | - Semyon G Vologin
- Tatar Research Institute of Agriculture, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Kazan, 420059, Russia
| | - Andrei N Tsentsevitsky
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Kazan, 420111, Russia
| | - Arsenii Yu Arkhipov
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Kazan, 420111, Russia
| | - Venera F Khuzakhmetova
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Kazan, 420111, Russia
| | - Guzel V Sibgatullina
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Kazan, 420111, Russia
| | - Ellya A Bukharaeva
- Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Kazan, 420111, Russia.
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7
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Gafurova CR, Tsentsevitsky AN, Petrov AM. Frequency-Dependent Engagement of Synaptic Vesicle Pools in the Mice Motor Nerve Terminals. Cell Mol Neurobiol 2023; 43:729-739. [PMID: 35113291 DOI: 10.1007/s10571-022-01202-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 01/28/2022] [Indexed: 01/01/2023]
Abstract
Nerve terminals contain numerous synaptic vesicles (SVs) whose exo-endocytic cycling maintains neurotransmitter release. SVs may have different properties, thereby constituting separate pools. However, behavior of SV pools remains elusive in many synapses. To fill this gap, we studied the functioning of SV pools at both low- and higher-frequency stimulations utilizing microelectrode recording and dual-labeling of SVs with FM-dyes at the mice motor nerve terminals. It was found that higher-frequency stimulation caused exocytosis of different kinds of SVs. One type of SVs contributed to exocytosis exclusively at intense activities and their exocytotic rate was depended on the order in which these SVs were recovered by endocytosis. Another type of SVs can sustain the release in response to both low- and higher-frequency stimulations, but increasing activity did not lead to enhanced exocytotic rate of these SVs. In addition, depression of neurotransmitter release induced by 20 Hz stimulation occurred independent on previous episode of 10 Hz activity. We suggest that during prolonged stimulation at least two SV pools can operate. One termed "house-keeping" that would be active at different frequencies and the other termed "plug-in" that would respond to increasing activity.
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Affiliation(s)
- Chulpan R Gafurova
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, Box 30, Kazan, Russia, 420111
| | - Andrei N Tsentsevitsky
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, Box 30, Kazan, Russia, 420111
| | - Alexey M Petrov
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, Box 30, Kazan, Russia, 420111. .,Kazan State Medial University, 49 Butlerova Street, Kazan, Russia, 420012.
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Cahalan SD, Boehm I, Jones RA, Piercy RJ. Recognising the potential of large animals for modelling neuromuscular junction physiology and disease. J Anat 2022; 241:1120-1132. [PMID: 36056593 PMCID: PMC9558152 DOI: 10.1111/joa.13749] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 08/05/2022] [Accepted: 08/08/2022] [Indexed: 12/28/2022] Open
Abstract
The aetiology and pathophysiology of many diseases of the motor unit remain poorly understood and the role of the neuromuscular junction (NMJ) in this group of disorders is particularly overlooked, especially in humans, when these diseases are comparatively rare. However, elucidating the development, function and degeneration of the NMJ is essential to uncover its contribution to neuromuscular disorders, and to explore potential therapeutic avenues to treat these devastating diseases. Until now, an understanding of the role of the NMJ in disease pathogenesis has been hindered by inherent differences between rodent and human NMJs: stark contrasts in body size and corresponding differences in associated axon length underpin some of the translational issues in animal models of neuromuscular disease. Comparative studies in large mammalian models, including examination of naturally occurring, highly prevalent animal diseases and evaluation of their treatment, might provide more relevant insights into the pathogenesis and therapy of equivalent human diseases. This review argues that large animal models offer great potential to enhance our understanding of the neuromuscular system in health and disease, and in particular, when dealing with diseases for which nerve length dependency might underly the pathogenesis.
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Affiliation(s)
- Stephen D Cahalan
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Science and Services, Royal Veterinary College, University of London, London, UK
| | - Ines Boehm
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK.,Biozentrum University of Basel, Basel, Switzerland
| | - Ross A Jones
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
| | - Richard J Piercy
- Comparative Neuromuscular Diseases Laboratory, Department of Clinical Science and Services, Royal Veterinary College, University of London, London, UK
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Davis LA, Fogarty MJ, Brown A, Sieck GC. Structure and Function of the Mammalian Neuromuscular Junction. Compr Physiol 2022; 12:3731-3766. [PMID: 35950651 PMCID: PMC10461538 DOI: 10.1002/cphy.c210022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The mammalian neuromuscular junction (NMJ) comprises a presynaptic terminal, a postsynaptic receptor region on the muscle fiber (endplate), and the perisynaptic (terminal) Schwann cell. As with any synapse, the purpose of the NMJ is to transmit signals from the nervous system to muscle fibers. This neural control of muscle fibers is organized as motor units, which display distinct structural and functional phenotypes including differences in pre- and postsynaptic elements of NMJs. Motor units vary considerably in the frequency of their activation (both motor neuron discharge rate and duration/duty cycle), force generation, and susceptibility to fatigue. For earlier and more frequently recruited motor units, the structure and function of the activated NMJs must have high fidelity to ensure consistent activation and continued contractile response to sustain vital motor behaviors (e.g., breathing and postural balance). Similarly, for higher force less frequent behaviors (e.g., coughing and jumping), the structure and function of recruited NMJs must ensure short-term reliable activation but not activation sustained for a prolonged period in which fatigue may occur. The NMJ is highly plastic, changing structurally and functionally throughout the life span from embryonic development to old age. The NMJ also changes under pathological conditions including acute and chronic disease. Such neuroplasticity often varies across motor unit types. © 2022 American Physiological Society. Compr Physiol 12:1-36, 2022.
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Affiliation(s)
- Leah A. Davis
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Matthew J. Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Alyssa Brown
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Gary C. Sieck
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
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Bermedo-García F, Zelada D, Martínez E, Tabares L, Henríquez JP. Functional regeneration of the murine neuromuscular synapse relies on long-lasting morphological adaptations. BMC Biol 2022; 20:158. [PMID: 35804361 PMCID: PMC9270767 DOI: 10.1186/s12915-022-01358-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 05/05/2022] [Indexed: 12/04/2022] Open
Abstract
Background In a broad variety of species, muscle contraction is controlled at the neuromuscular junction (NMJ), the peripheral synapse composed of a motor nerve terminal, a muscle specialization, and non-myelinating terminal Schwann cells. While peripheral nerve damage leads to successful NMJ reinnervation in animal models, muscle fiber reinnervation in human patients is largely inefficient. Interestingly, some hallmarks of NMJ denervation and early reinnervation in murine species, such as fragmentation and poly-innervation, are also phenotypes of aged NMJs or even of unaltered conditions in other species, including humans. We have reasoned that rather than features of NMJ decline, such cellular responses could represent synaptic adaptations to accomplish proper functional recovery. Here, we have experimentally tackled this idea through a detailed comparative study of the short- and long-term consequences of irreversible (chronic) and reversible (partial) NMJ denervation in the convenient cranial levator auris longus muscle. Results Our findings reveal that irreversible muscle denervation results in highly fragmented postsynaptic domains and marked ectopic acetylcholine receptor clustering along with significant terminal Schwann cells sprouting and progressive detachment from the NMJ. Remarkably, even though reversible nerve damage led to complete reinnervation after 11 days, we found that more than 30% of NMJs are poly-innervated and around 65% of postsynaptic domains are fragmented even 3 months after injury, whereas synaptic transmission is fully recovered two months after nerve injury. While postsynaptic stability was irreversibly decreased after chronic denervation, this parameter was only transiently affected by partial NMJ denervation. In addition, we found that a combination of morphometric analyses and postsynaptic stability determinations allows discriminating two distinct forms of NMJ fragmentation, stable-smooth and unstable-blurred, which correlate with their regeneration potential. Conclusions Together, our data unveil that reversible nerve damage imprints a long-lasting reminiscence in the NMJ that results in the rearrangement of its cellular components. Instead of being predictive of NMJ decline, these traits may represent an efficient adaptive response for proper functional recovery. As such, these features are relevant targets to be considered in strategies aimed to restore motor function in detrimental conditions for peripheral innervation. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-022-01358-4.
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Affiliation(s)
- Francisca Bermedo-García
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - Diego Zelada
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - Esperanza Martínez
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile
| | - Lucía Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, Universidad de Sevilla, Sevilla, Spain
| | - Juan Pablo Henríquez
- Laboratory of Neuromuscular Studies (NeSt Lab), Group for the Study of Developmental Processes (GDeP), Department of Cell Biology, Faculty of Biological Sciences, Universidad de Concepción, Concepción, Chile.
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11
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Szule JA. Hypothesis Relating the Structure, Biochemistry and Function of Active Zone Material Macromolecules at a Neuromuscular Junction. Front Synaptic Neurosci 2022; 13:798225. [PMID: 35069169 PMCID: PMC8766674 DOI: 10.3389/fnsyn.2021.798225] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 12/14/2021] [Indexed: 12/22/2022] Open
Abstract
This report integrates knowledge of in situ macromolecular structures and synaptic protein biochemistry to propose a unified hypothesis for the regulation of certain vesicle trafficking events (i.e., docking, priming, Ca2+-triggering, and membrane fusion) that lead to neurotransmitter secretion from specialized “active zones” of presynaptic axon terminals. Advancements in electron tomography, to image tissue sections in 3D at nanometer scale resolution, have led to structural characterizations of a network of different classes of macromolecules at the active zone, called “Active Zone Material’. At frog neuromuscular junctions, the classes of Active Zone Material macromolecules “top-masts”, “booms”, “spars”, “ribs” and “pins” direct synaptic vesicle docking while “pins”, “ribs” and “pegs” regulate priming to influence Ca2+-triggering and membrane fusion. Other classes, “beams”, “steps”, “masts”, and “synaptic vesicle luminal filaments’ likely help organize and maintain the structural integrity of active zones. Extensive studies on the biochemistry that regulates secretion have led to comprehensive characterizations of the many conserved proteins universally involved in these trafficking events. Here, a hypothesis including a partial proteomic atlas of Active Zone Material is presented which considers the common roles, binding partners, physical features/structure, and relative positioning in the axon terminal of both the proteins and classes of macromolecules involved in the vesicle trafficking events. The hypothesis designates voltage-gated Ca2+ channels and Ca2+-gated K+ channels to ribs and pegs that are connected to macromolecules that span the presynaptic membrane at the active zone. SNARE proteins (Syntaxin, SNAP25, and Synaptobrevin), SNARE-interacting proteins Synaptotagmin, Munc13, Munc18, Complexin, and NSF are designated to ribs and/or pins. Rab3A and Rabphillin-3A are designated to top-masts and/or booms and/or spars. RIM, Bassoon, and Piccolo are designated to beams, steps, masts, ribs, spars, booms, and top-masts. Spectrin is designated to beams. Lastly, the luminal portions of SV2 are thought to form the bulk of the observed synaptic vesicle luminal filaments. The goal here is to help direct future studies that aim to bridge Active Zone Material structure, biochemistry, and function to ultimately determine how it regulates the trafficking events in vivo that lead to neurotransmitter secretion.
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12
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Tks5 Regulates Synaptic Podosome Formation and Stabilization of the Postsynaptic Machinery at the Neuromuscular Junction. Int J Mol Sci 2021; 22:ijms222112051. [PMID: 34769479 PMCID: PMC8585010 DOI: 10.3390/ijms222112051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 11/03/2021] [Accepted: 11/04/2021] [Indexed: 11/16/2022] Open
Abstract
Currently, the etiology of many neuromuscular disorders remains unknown. Many of them are characterized by aberrations in the maturation of the neuromuscular junction (NMJ) postsynaptic machinery. Unfortunately, the molecular factors involved in this process are still largely unknown, which poses a great challenge for identifying potential therapeutic targets. Here, we identified Tks5 as a novel interactor of αdystrobrevin-1, which is a crucial component of the NMJ postsynaptic machinery. Tks5 has been previously shown in cancer cells to be an important regulator of actin-rich structures known as invadosomes. However, a role of this scaffold protein at a synapse has never been studied. We show that Tks5 is crucial for remodeling of the NMJ postsynaptic machinery by regulating the organization of structures similar to the invadosomes, known as synaptic podosomes. Additionally, it is involved in the maintenance of the integrity of acetylcholine receptor (AChR) clusters and regulation of their turnover. Lastly, our data indicate that these Tks5 functions may be mediated by its involvement in recruitment of actin filaments to the postsynaptic machinery. Collectively, we show for the first time that the Tks5 protein is involved in regulation of the postsynaptic machinery.
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13
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Camargo WL, Kushmerick C, Pinto E, Souza N, Cavalcante W, Souza-Neto FP, Guatimosim S, Prado M, Guatimosim C, Naves LA. Homeostatic plasticity induced by increased acetylcholine release at the mouse neuromuscular junction. Neurobiol Aging 2021; 110:13-26. [PMID: 34844076 DOI: 10.1016/j.neurobiolaging.2021.10.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 10/21/2021] [Accepted: 10/22/2021] [Indexed: 02/07/2023]
Abstract
At the neuromuscular junction (NMJ), changes to the size of the postsynaptic potential induce homeostatic compensation. At the Drosophila NMJ, increased glutamate release causes a compensatory decrease in quantal content, but it is unknown if this mechanism operates at the cholinergic mammalian NMJ. We addressed this question by recording endplate potentials (EPP) and muscle contraction in 3-month and 24-month ChAT-ChR2-EYFP mice that overexpress vesicular acetylcholine transporter and release more acetylcholine per vesicle. At 3 months, the quantal content of EPPs from ChAT-ChR2-EYFP mice were not different from WT controls, however tetanic depression was greater, and quantal size during high-frequency stimulation and the size of the readily releasable pool (RRP) were decreased. At 24 months of age, quantal content was reduced in ChAT-ChR2-EYFP mice, which normalized synaptic depression despite smaller RRP. The effect of pancuronium on indirect evoked muscle twitch was not different between groups. These results indicate that an increase in the amount of acetylcholine per vesicle induces two distinct age-dependent homeostatic mechanisms compensating excessive acetylcholine release.
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Affiliation(s)
| | | | | | | | | | | | | | - Mam Prado
- Robarts Research Institute and Department of Physiology and Pharmacology and Anatomy & Cell Biology, University of Western Ontario, London, ON, Canada
| | | | - L A Naves
- Departments of Physiology and biophysics
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14
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Duc P, Vignes M, Hugon G, Sebban A, Carnac G, Malyshev E, Charlot B, Rage F. Human neuromuscular junction on micro-structured microfluidic devices implemented with a custom micro electrode array (MEA). LAB ON A CHIP 2021; 21:4223-4236. [PMID: 34559171 DOI: 10.1039/d1lc00497b] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
In the neuromuscular system, signal transmission from motor neurons (MNs) to innervated muscle fibers is crucial for their synaptic function, viability, and maintenance. In order to better understand human neuromuscular junction (hNMJ) functionality, it is important to develop on-a-chip devices with human cells. To investigate this cell network, microfluidic platforms are useful to grow different cell types in isolated compartments. Such devices have already been developed to study in vitro neuronal circuitry. Here, we combined microfluidics with two techniques: soft lithography and custom microelectrodes array (MEA). Our goal was to create hNMJs on a specific pattern of electrodes to stimulate pre-synaptic axons and record post-synaptic muscle activity. Micromachining was used to create structurations to guide muscle growth above electrodes, without impairing axon propagation, therefore optimizing the effectiveness of activity recording. Electrodes were also arranged to be aligned with the microfluidic chambers in order to specifically stimulate axons that were growing between the two compartments. Isolation of the two cell types allows for the selective treatment of neurons or muscle fibers to assess NMJ functionality hallmarks. Altogether, this microfluidic/microstructured/MEA platform allowed mature and functional in vitro hNMJ modelling. We demonstrate that electrical activation of MNs can trigger recordable extracellular muscle action potentials. This study provides evidence for a physiologically relevant model to mimic a hNMJ that will in the future be a powerful tool, more sensitive than calcium imaging, to better understand and characterize NMJs and their disruption in neurodegenerative diseases.
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Affiliation(s)
- Pauline Duc
- IGMM, University of Montpellier, CNRS, Montpellier, France.
| | - Michel Vignes
- IBMM UMR5247, University of Montpellier, CNRS, Montpellier, France
| | - Gérald Hugon
- PhyMedExp, INSERM U1046, CNRS UMR9214, Université de Montpellier, Montpellier, France
| | - Audrey Sebban
- IES, CNRS University of Montpellier, Montpellier 34095, France
| | - Gilles Carnac
- PhyMedExp, INSERM U1046, CNRS UMR9214, Université de Montpellier, Montpellier, France
| | - Eugene Malyshev
- IES, CNRS University of Montpellier, Montpellier 34095, France
| | - Benoît Charlot
- IES, CNRS University of Montpellier, Montpellier 34095, France
| | - Florence Rage
- IGMM, University of Montpellier, CNRS, Montpellier, France.
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15
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Zakyrjanova GF, Tsentsevitsky AN, Kuznetsova EA, Petrov AM. Immune-related oxysterol modulates neuromuscular transmission via non-genomic liver X receptor-dependent mechanism. Free Radic Biol Med 2021; 174:121-134. [PMID: 34391813 DOI: 10.1016/j.freeradbiomed.2021.08.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Revised: 08/08/2021] [Accepted: 08/12/2021] [Indexed: 11/22/2022]
Abstract
Inflammatory reactions induce changes in the neuromuscular system. The mechanisms underlying this link are unclear. Besides cytokines and reactive oxygen species (ROS), production of an antiviral oxysterol 25-hydroxycholesterol (25HC) by immune cells is quickly increased in response to inflammation. Hypothetically, 25HC could contribute to regulation of neuromuscular activity as well as redox status. We found that 25HC (0.01-10 μM) can bidirectionally modulate neurotransmission in mice diaphragm, the main respiratory muscle. Low concentrations (≤0.1 μM) of 25HC reduced involvement of synaptic vesicles (SVs) into exocytosis during 20-Hz activity, whereas higher inflammatory-related concentrations (≥1 μM) had a profound potentiating effect on SV mobilization. The latter stimulatory action of 25HC was accompanied by increase in Ca2+ release from intracellular stores via IP3 receptors. Both increase in SV mobilization and [Ca2+]in were suppressed by a specific antagonist of liver X receptors (LXRs). These receptors formed clusters within the synaptic membranes in a lipid raft-dependent manner. Either raft disruption or intracellular Ca2+ chelation prevented 25HC-mediated acceleration of the exocytotic rate. The same action had inhibition of estrogen receptor α, Gi-protein, Gβγ, phospholipase C and protein kinase C. Additionally, 1 μM 25HC upregulated ROS production in a Ca2+-dependent way and an antioxidant partially decreased the exocytosis-promoting effect of 25HC. Thus, 25HC has prooxidant properties and it is a potent regulator of SV mobilization via activation of lipid raft-associated LXRs which can trigger signaling via estrogen receptor α - Gi-protein - Gβγ - phospholipase C - Ca2+ - protein kinase C pathway. 25HC-mediated increase in ROS may modulate this signaling.
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Affiliation(s)
- Guzel F Zakyrjanova
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, Box 30, Kazan, 420111, Russia; Department of Normal Physiology, Institute of Neuroscience, Kazan State Medial University, 49 Butlerova Street, Kazan, 420012, Russia
| | - Andrei N Tsentsevitsky
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, Box 30, Kazan, 420111, Russia
| | - Eva A Kuznetsova
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, Box 30, Kazan, 420111, Russia
| | - Alexey M Petrov
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, Box 30, Kazan, 420111, Russia; Department of Normal Physiology, Institute of Neuroscience, Kazan State Medial University, 49 Butlerova Street, Kazan, 420012, Russia.
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16
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Deschenes MR, Trebelhorn AM, High MC, Tufts HL, Oh J. Sensitivity of subcellular components of neuromuscular junctions to decreased neuromuscular activity. Synapse 2021; 75:e22220. [PMID: 34318955 DOI: 10.1002/syn.22220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 07/21/2021] [Accepted: 07/22/2021] [Indexed: 12/16/2022]
Abstract
Muscle unloading imparts subtotal disuse on the neuromuscular system resulting in reduced performance capacity. This loss of function, at least in part, can be attributed to disruptions at the neuromuscular junction (NMJ). However, research has failed to document morphological remodeling of the NMJ with short term muscle unloading. Here, rather than quantifying cellular components of the NMJ, we examined subcellular active zone responses to 2 weeks of unloading in male Wistar rats. It was revealed that in the plantaris, but not the soleus muscles, unloading elicited significant (P ≤ 0.05) decrements in active zone staining as measured by Bassoon, and calcium channel expression. It was also discovered that unloading decreased the area of calcium channels staining relative to active zone areas of staining suggesting potential interference in the ability of calcium influx to trigger the release of vesicles docked at the active zone. Post-synaptic adaptations of the motor endplate were not evident. This presynaptic subcellular size reduction was not associated with atrophy of the underlying plantaris muscle fibers, although atrophy of the weight-bearing soleus fibers, where no subcellular remodeling was evident, was noted. These results suggest that the active zone is highly sensitive to alterations in neuromuscular activity, and that morphological adaptation of excitatory and contractile components of the NMJ can occur independently of each other.
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Affiliation(s)
- Michael R Deschenes
- Department of Kinesiology & Health Sciences, College of William & Mary, Williamsburg, Virginia, USA.,Program in Neuroscience, College of William & Mary, Williamsburg, Virginia, USA
| | - Audrey M Trebelhorn
- Department of Kinesiology & Health Sciences, College of William & Mary, Williamsburg, Virginia, USA
| | - Madeline C High
- Department of Kinesiology & Health Sciences, College of William & Mary, Williamsburg, Virginia, USA
| | - Hannah L Tufts
- Program in Neuroscience, College of William & Mary, Williamsburg, Virginia, USA
| | - Jeongeun Oh
- Department of Kinesiology & Health Sciences, College of William & Mary, Williamsburg, Virginia, USA
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17
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Russo K, Wharton KA. BMP/TGF-β signaling as a modulator of neurodegeneration in ALS. Dev Dyn 2021; 251:10-25. [PMID: 33745185 DOI: 10.1002/dvdy.333] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 03/12/2021] [Accepted: 03/12/2021] [Indexed: 12/19/2022] Open
Abstract
This commentary focuses on the emerging intersection between BMP/TGF-β signaling roles in nervous system function and the amyotrophic lateral sclerosis (ALS) disease state. Future research is critical to elucidate the molecular underpinnings of this intersection of the cellular processes disrupted in ALS and those influenced by BMP/TGF-β signaling, including synapse structure, neurotransmission, plasticity, and neuroinflammation. Such knowledge promises to inform us of ideal entry points for the targeted modulation of dysfunctional cellular processes in an effort to abrogate ALS pathologies. It is likely that different interventions are required, either at discrete points in disease progression, or across multiple dysfunctional processes which together lead to motor neuron degeneration and death. We discuss the challenging, but intriguing idea that modulation of the pleiotropic nature of BMP/TGF-β signaling could be advantageous, as a way to simultaneously treat defects in more than one cell process across different forms of ALS.
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Affiliation(s)
- Kathryn Russo
- Department of Neuroscience, Brown University, Providence, Rhode Island, USA.,Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, USA
| | - Kristi A Wharton
- Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, USA.,Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, USA
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18
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Hoy KC, Strain MM, Turtle JD, Lee KH, Huie JR, Hartman JJ, Tarbet MM, Harlow ML, Magnuson DSK, Grau JW. Evidence That the Central Nervous System Can Induce a Modification at the Neuromuscular Junction That Contributes to the Maintenance of a Behavioral Response. J Neurosci 2020; 40:9186-9209. [PMID: 33097637 PMCID: PMC7687054 DOI: 10.1523/jneurosci.2683-19.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 10/13/2020] [Accepted: 10/14/2020] [Indexed: 11/21/2022] Open
Abstract
Neurons within the spinal cord are sensitive to environmental relations and can bring about a behavioral modification without input from the brain. For example, rats that have undergone a thoracic (T2) transection can learn to maintain a hind leg in a flexed position to minimize exposure to a noxious electrical stimulation (shock). Inactivating neurons within the spinal cord with lidocaine, or cutting communication between the spinal cord and the periphery (sciatic transection), eliminates the capacity to learn, which implies that it depends on spinal neurons. Here we show that these manipulations have no effect on the maintenance of the learned response, which implicates a peripheral process. EMG showed that learning augments the muscular response evoked by motoneuron output and that this effect survives a sciatic transection. Quantitative fluorescent imaging revealed that training brings about an increase in the area and intensity of ACh receptor labeling at the neuromuscular junction (NMJ). It is hypothesized that efferent motoneuron output, in conjunction with electrical stimulation of the tibialis anterior muscle, strengthens the connection at the NMJ in a Hebbian manner. Supporting this, paired stimulation of the efferent nerve and tibialis anterior generated an increase in flexion duration and augmented the evoked electrical response without input from the spinal cord. Evidence is presented that glutamatergic signaling contributes to plasticity at the NMJ. Labeling for vesicular glutamate transporter is evident at the motor endplate. Intramuscular application of an NMDAR antagonist blocked the acquisition/maintenance of the learned response and the strengthening of the evoked electrical response.SIGNIFICANCE STATEMENT The neuromuscular junction (NMJ) is designed to faithfully elicit a muscular contraction in response to neural input. From this perspective, encoding environmental relations (learning) and the maintenance of a behavioral modification over time (memory) are assumed to reflect only modifications upstream from the NMJ, within the CNS. The current results challenge this view. Rats were trained to maintain a hind leg in a flexed position to avoid noxious stimulation. As expected, treatments that inhibit activity within the CNS, or disrupt peripheral communication, prevented learning. These manipulations did not affect the maintenance of the acquired response. The results imply that a peripheral modification at the NMJ contributes to the maintenance of the learned response.
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Affiliation(s)
- Kevin C Hoy
- Case Comprehensive Cancer Center/Case Western Reserve School of Medicine, Cleveland, Ohio 44106
| | - Misty M Strain
- U.S. Army Institute of Surgical Research, JBSA Fort Sam Houston, Houston, Texas 78234
| | - Joel D Turtle
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - Kuan H Lee
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - J Russell Huie
- Department of Neuroscience, University of California San Francisco, San Francisco, California 94110
| | - John J Hartman
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - Megan M Tarbet
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
| | - Mark L Harlow
- Department of Biology, Texas A&M University, College Station, Texas 77843
| | - David S K Magnuson
- Department of Neurological Surgery, University of Louisville, Louisville, Kentucky 40202
| | - James W Grau
- Department of Psychological and Brain Sciences, Texas A&M University, College Station, Texas 77843
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19
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Badawi Y, Nishimune H. Impairment Mechanisms and Intervention Approaches for Aged Human Neuromuscular Junctions. Front Mol Neurosci 2020; 13:568426. [PMID: 33328881 PMCID: PMC7717980 DOI: 10.3389/fnmol.2020.568426] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 10/16/2020] [Indexed: 12/19/2022] Open
Abstract
The neuromuscular junction (NMJ) is a chemical synapse formed between a presynaptic motor neuron and a postsynaptic muscle cell. NMJs in most vertebrate species share many essential features; however, some differences distinguish human NMJs from others. This review will describe the pre- and postsynaptic structures of human NMJs and compare them to NMJs of laboratory animals. We will focus on age-dependent declines in function and changes in the structure of human NMJs. Furthermore, we will describe insights into the aging process revealed from mouse models of accelerated aging. In addition, we will compare aging phenotypes to other human pathologies that cause impairments of pre- and postsynaptic structures at NMJs. Finally, we will discuss potential intervention approaches for attenuating age-related NMJ dysfunction and sarcopenia in humans.
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Affiliation(s)
- Yomna Badawi
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, KS, United States
| | - Hiroshi Nishimune
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, KS, United States.,Neurobiology of Aging, Tokyo Metropolitan Institute of Gerontology, Itabashi, Japan
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20
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Lenina OA, Zueva IV, Zobov VV, Semenov VE, Masson P, Petrov KA. Slow-binding reversible inhibitor of acetylcholinesterase with long-lasting action for prophylaxis of organophosphate poisoning. Sci Rep 2020; 10:16611. [PMID: 33024231 PMCID: PMC7538863 DOI: 10.1038/s41598-020-73822-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 09/22/2020] [Indexed: 12/02/2022] Open
Abstract
Organophosphorus (OP) compounds represent a serious health hazard worldwide. The dominant mechanism of their action results from covalent inhibition of acetylcholinesterase (AChE). Standard therapy of acute OP poisoning is partially effective. However, prophylactic administration of reversible or pseudo-irreversible AChE inhibitors before OP exposure increases the efficiency of standard therapy. The purpose of the study was to test the duration of the protective effect of a slow-binding reversible AChE inhibitor (C547) in a mouse model against acute exposure to paraoxon (POX). It was shown that the rate of inhibition of AChE by POX in vitro after pre-inhibition with C547 was several times lower than without C547. Ex vivo pre-incubation of mouse diaphragm with C547 significantly prevented the POX-induced muscle weakness. Then it was shown that pre-treatment of mice with C547 at the dose of 0.01 mg/kg significantly increased survival after poisoning by 2xLD50 POX. The duration of the pre-treatment was effective up to 96 h, whereas currently used drug for pre-exposure treatment, pyridostigmine at a dose of 0.15 mg/kg was effective less than 24 h. Thus, long-lasting slow-binding reversible AChE inhibitors can be considered as new potential drugs to increase the duration of pre-exposure treatment of OP poisoning.
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Affiliation(s)
- Oksana A Lenina
- Arbuzov Institute of Organic and Physical Chemistry, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Arbuzov str., 8, Kazan, Russian Federation, 420088
| | - Irina V Zueva
- Arbuzov Institute of Organic and Physical Chemistry, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Arbuzov str., 8, Kazan, Russian Federation, 420088
| | - Vladimir V Zobov
- Arbuzov Institute of Organic and Physical Chemistry, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Arbuzov str., 8, Kazan, Russian Federation, 420088
- Kazan Federal University, 18 Kremlyovskaya str, Kazan, Russia, 420008
| | - Vyacheslav E Semenov
- Arbuzov Institute of Organic and Physical Chemistry, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Arbuzov str., 8, Kazan, Russian Federation, 420088
| | - Patrick Masson
- Kazan Federal University, 18 Kremlyovskaya str, Kazan, Russia, 420008
| | - Konstantin A Petrov
- Arbuzov Institute of Organic and Physical Chemistry, Federal Research Center "Kazan Scientific Center of the Russian Academy of Sciences", Arbuzov str., 8, Kazan, Russian Federation, 420088.
- Kazan Federal University, 18 Kremlyovskaya str, Kazan, Russia, 420008.
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21
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Modulatory Roles of ATP and Adenosine in Cholinergic Neuromuscular Transmission. Int J Mol Sci 2020; 21:ijms21176423. [PMID: 32899290 PMCID: PMC7503321 DOI: 10.3390/ijms21176423] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/29/2020] [Accepted: 09/01/2020] [Indexed: 12/23/2022] Open
Abstract
A review of the data on the modulatory action of adenosine 5’-triphosphate (ATP), the main co-transmitter with acetylcholine, and adenosine, the final ATP metabolite in the synaptic cleft, on neuromuscular transmission is presented. The effects of these endogenous modulators on pre- and post-synaptic processes are discussed. The contribution of purines to the processes of quantal and non-quantal secretion of acetylcholine into the synaptic cleft, as well as the influence of the postsynaptic effects of ATP and adenosine on the functioning of cholinergic receptors, are evaluated. As usual, the P2-receptor-mediated influence is minimal under physiological conditions, but it becomes very important in some pathophysiological situations such as hypothermia, stress, or ischemia. There are some data demonstrating the same in neuromuscular transmission. It is suggested that the role of endogenous purines is primarily to provide a safety factor for the efficiency of cholinergic neuromuscular transmission.
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22
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Boehm I, Alhindi A, Leite AS, Logie C, Gibbs A, Murray O, Farrukh R, Pirie R, Proudfoot C, Clutton R, Wishart TM, Jones RA, Gillingwater TH. Comparative anatomy of the mammalian neuromuscular junction. J Anat 2020; 237:827-836. [PMID: 32573802 PMCID: PMC7542190 DOI: 10.1111/joa.13260] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 05/28/2020] [Accepted: 05/28/2020] [Indexed: 12/11/2022] Open
Abstract
The neuromuscular junction (NMJ)—a synapse formed between lower motor neuron and skeletal muscle fibre—represents a major focus of both basic neuroscience research and clinical neuroscience research. Although the NMJ is known to play an important role in many neurodegenerative conditions affecting humans, the vast majority of anatomical and physiological data concerning the NMJ come from lower mammalian (e.g. rodent) animal models. However, recent findings have demonstrated major differences between the cellular anatomy and molecular anatomy of human and rodent NMJs. Therefore, we undertook a comparative morphometric analysis of the NMJ across several larger mammalian species in order to generate baseline inter‐species anatomical reference data for the NMJ and to identify animal models that better represent the morphology of the human NMJ in vivo. Using a standardized morphometric platform (‘NMJ‐morph’), we analysed 5,385 individual NMJs from lower/pelvic limb muscles (EDL, soleus and peronei) of 6 mammalian species (mouse, cat, dog, sheep, pig and human). There was marked heterogeneity of NMJ morphology both within and between species, with no overall relationship found between NMJ morphology and muscle fibre diameter or body size. Mice had the largest NMJs on the smallest muscle fibres; cats had the smallest NMJs on the largest muscle fibres. Of all the species examined, the sheep NMJ had the most closely matched morphology to that found in humans. Taken together, we present a series of comprehensive baseline morphometric data for the mammalian NMJ and suggest that ovine models are likely to best represent the human NMJ in health and disease.
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Affiliation(s)
- Ines Boehm
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
| | - Abrar Alhindi
- School of Medicine, UNESP-São Paulo State University, Botucatu, Sao Paulo, Brazil.,Faculty of Medicine, Department of Anatomy, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Ana S Leite
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK.,School of Medicine, UNESP-São Paulo State University, Botucatu, Sao Paulo, Brazil
| | - Chandra Logie
- The Roslin Institute and R(D)SVS, University of Edinburgh, Edinburgh, UK
| | - Alyssa Gibbs
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
| | - Olivia Murray
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
| | - Rizwan Farrukh
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
| | - Robert Pirie
- The Roslin Institute and R(D)SVS, University of Edinburgh, Edinburgh, UK
| | | | - Richard Clutton
- The Roslin Institute and R(D)SVS, University of Edinburgh, Edinburgh, UK
| | - Thomas M Wishart
- The Roslin Institute and R(D)SVS, University of Edinburgh, Edinburgh, UK
| | - Ross A Jones
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
| | - Thomas H Gillingwater
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.,Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
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23
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Belotti E, Schaeffer L. Regulation of Gene expression at the neuromuscular Junction. Neurosci Lett 2020; 735:135163. [PMID: 32553805 DOI: 10.1016/j.neulet.2020.135163] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Revised: 06/11/2020] [Accepted: 06/14/2020] [Indexed: 01/08/2023]
Abstract
Gene expression in skeletal muscle is profoundly changed upon innervation. 50 years of research on the neuromuscular system have greatly increased our understanding of the mechanisms underlying these changes. By controlling the expression and the activity of key transcription factors, nerve-evoked electrical activity in the muscle fiber positively and negatively regulates the expression of hundreds of genes. Innervation also compartmentalizes gene expression into synaptic and extra-synaptic regions of muscle fibers. In addition, electrically-evoked, release of several factors (e.g. Agrin, Neuregulin, Wnt ligands) induce the clustering of synaptic proteins and of a few muscle nuclei. The sub-synaptic nuclei acquire a particular chromatin organization and develop a specific gene expression program dedicated to building and maintaining a functional neuromuscular synapse. Deciphering synapse-specific, transcriptional regulation started with the identification of the N-box, a six base pair element present in the promoters of the acetylcholine δ and ε subunits. Most genes with synapse-specific expression turned out to contain at least one N-box in their promoters. The N-box is a response element for the synaptic signals Agrin and Neuregulins as well as a binding site for transcription factors of the Ets family. The Ets transcription factors GABP and Erm are implicated in the activation of post-synaptic genes via the N-box. In muscle fibers, Erm expression is restricted to the NMJ whereas GABP is expressed in all muscle nuclei but phosphorylated and activated by the JNK and ERK signaling pathways in response to Agrin and Neuregulins. Post-synaptic gene expression also correlates with chromatin modifications at the genomic level as evidenced by the strong enrichment of decondensed chromatin and acetylated histones in sub-synaptic nuclei. Here we discuss these transcriptional pathways for synaptic specialization at NMJs.
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Affiliation(s)
- Edwige Belotti
- INMG, Inserm U1217, CNRS UMR5310, Université Lyon 1, Université De Lyon, Lyon, France
| | - Laurent Schaeffer
- INMG, Inserm U1217, CNRS UMR5310, Université Lyon 1, Université De Lyon, Lyon, France; Centre De Biotechnologie Cellulaire, Hospices Civils De Lyon, Lyon, France.
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Ge D, Noakes PG, Lavidis NA. What are Neurotransmitter Release Sites and Do They Interact? Neuroscience 2020; 425:157-168. [DOI: 10.1016/j.neuroscience.2019.11.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2019] [Revised: 11/10/2019] [Accepted: 11/11/2019] [Indexed: 12/22/2022]
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Brehm P, Wen H. Zebrafish neuromuscular junction: The power of N. Neurosci Lett 2019; 713:134503. [PMID: 31557523 DOI: 10.1016/j.neulet.2019.134503] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 09/11/2019] [Accepted: 09/16/2019] [Indexed: 11/26/2022]
Abstract
In the early 1950s, Katz and his colleagues capitalized on the newly developed intracellular microelectrode recording technique to investigate synaptic transmission. For study they chose frog neuromuscular junction (NMJ), which was ideally suited due to the accessibility and large size of the muscle cells. Paradoxically, the large size precluded the use of next generation patch clamp technology. Consequently, electrophysiological study of synaptic function shifted to small central synapses made amenable by patch clamp. Recently, however, the unique features offered by zebrafish have rekindled interest in the NMJ as a model for electrophysiological study of synaptic transmission. The small muscle size and synaptic simplicity provide the singular opportunity to perform in vivo spinal motoneuron-target muscle patch clamp recordings. Additional incentive is provided by zebrafish lines harboring mutations in key synaptic proteins, many of which are embryonic lethal in mammals, but all of which are able to survive well past synapse maturation in zebrafish. This mini-review will highlight features that set zebrafish NMJs apart from traditional NMJs. We also draw into focus findings that offer the promise of identifying features that define release sites, which serve to set the upper limit of transmitter release. Since its conception several candidates representing release sites have been proposed, most of which are based on distinctions among vesicle pools in their state of readiness for release. However, models based on distinctions among vesicles have become enormously complicated and none adequately account for setting an upper limit for exocytosis in response to an action potential (AP). Specifically, findings from zebrafish NMJ point to an alternative model, positing that elements other than vesicles per se set the upper limits of release.
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Affiliation(s)
- Paul Brehm
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR, USA.
| | - Hua Wen
- Vollum Institute, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR, USA
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Glutamate at the Vertebrate Neuromuscular Junction: From Modulation to Neurotransmission. Cells 2019; 8:cells8090996. [PMID: 31466388 PMCID: PMC6770210 DOI: 10.3390/cells8090996] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 08/21/2019] [Accepted: 08/27/2019] [Indexed: 12/23/2022] Open
Abstract
Although acetylcholine is the major neurotransmitter operating at the skeletal neuromuscular junction of many invertebrates and of vertebrates, glutamate participates in modulating cholinergic transmission and plastic changes in the last. Presynaptic terminals of neuromuscular junctions contain and release glutamate that contribute to the regulation of synaptic neurotransmission through its interaction with pre- and post-synaptic receptors activating downstream signaling pathways that tune synaptic efficacy and plasticity. During vertebrate development, the chemical nature of the neurotransmitter at the vertebrate neuromuscular junction can be experimentally shifted from acetylcholine to other mediators (including glutamate) through the modulation of calcium dynamics in motoneurons and, when the neurotransmitter changes, the muscle fiber expresses and assembles new receptors to match the nature of the new mediator. Finally, in adult rodents, by diverting descending spinal glutamatergic axons to a denervated muscle, a functional reinnervation can be achieved with the formation of new neuromuscular junctions that use glutamate as neurotransmitter and express ionotropic glutamate receptors and other markers of central glutamatergic synapses. Here, we summarize the past and recent experimental evidences in support of a role of glutamate as a mediator at the synapse between the motor nerve ending and the skeletal muscle fiber, focusing on the molecules and signaling pathways that are present and activated by glutamate at the vertebrate neuromuscular junction.
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Nicole S, Azuma Y, Bauché S, Eymard B, Lochmüller H, Slater C. Congenital Myasthenic Syndromes or Inherited Disorders of Neuromuscular Transmission: Recent Discoveries and Open Questions. J Neuromuscul Dis 2019; 4:269-284. [PMID: 29125502 PMCID: PMC5701762 DOI: 10.3233/jnd-170257] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Congenital myasthenic syndromes (CMS) form a heterogeneous group of rare diseases characterized by fatigable muscle weakness. They are genetically-inherited and caused by defective synaptic transmission at the cholinergic neuromuscular junction (NMJ). The number of genes known to cause CMS when mutated is currently 30, and the relationship between fatigable muscle weakness and defective functions is quite well-understood for many of them. However, some of the most recent discoveries in individuals with CMS challenge our knowledge of the NMJ, where the basis of the pathology has mostly been investigated in animal models. Frontier forms between CMS and congenital myopathy, which have been genetically and clinically identified, underline the poorly understood interplay between the synaptic and extrasynaptic molecules in the neuromuscular system. In addition, precise electrophysiological and histopathological investigations of individuals with CMS suggest an important role of NMJ plasticity in the response to CMS pathogenesis. While efficient drug-based treatments are already available to improve neuromuscular transmission for most forms of CMS, others, as well as neurological and muscular comorbidities, remain resistant. Taken together, the available pathological data point to physiological issues which remain to be understood in order to achieve precision medicine with efficient therapeutics for all individuals suffering from CMS.
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Affiliation(s)
- Sophie Nicole
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, 75013 Paris, France
| | - Yoshiteru Azuma
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
| | - Stéphanie Bauché
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, 75013 Paris, France
| | - Bruno Eymard
- Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, 75013 Paris, France.,AP-HP, Hôpital Pitié-Salpétrière, 75013 Paris, France
| | - Hanns Lochmüller
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
| | - Clarke Slater
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
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Slater CR. 'Fragmentation' of NMJs: a sign of degeneration or regeneration? A long journey with many junctions. Neuroscience 2019; 439:28-40. [PMID: 31129203 DOI: 10.1016/j.neuroscience.2019.05.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 05/07/2019] [Accepted: 05/07/2019] [Indexed: 12/13/2022]
Abstract
Mammalian neuromuscular junctions (NMJs) often consist of curved bands of synaptic contact, about 3-6 μm wide, which resemble pretzels. This contrasts with the NMJs of most animal species which consist of a cluster of separate synaptic spots, each of which is also about 3-6 μm across. In a number of situations, including a variety of disease states as well as normal ageing, mammalian NMJs acquire a more 'fragmented' appearance that resembles somewhat that of other species. This 'fragmentation' of the NMJ has sometimes been interpreted as a 'disintegration' or 'degeneration', with the suggestion that it might be associated with impaired neuromuscular transmission. An alternative view is that NMJ fragmentation is the outcome of a normal process by which the NMJ is maintained in an effective state. In this highly personal commentary, I cite a number of examples of this and point out that although the 'pretzel' form arises during normal development as a result of the sculpting of an immature synaptic 'plaque', in virtually all situations where new synaptic contact is established in adult mammals this occurs by the addition of new synaptic 'spots' rather than by the extension, or neoformation, of 'pretzels'. Further, where appropriate studies have been performed, no evidence of a correlation between the degree of fragmentation and the efficacy of transmission has emerged. It may therefore be more appropriate to consider NMJ 'fragmentation' as a form of regeneration, rather than of degeneration. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.
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Affiliation(s)
- Clarke R Slater
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.
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Ivanovski T, Miralles F. Lambert-Eaton Myasthenic syndrome: early diagnosis is key. Degener Neurol Neuromuscul Dis 2019; 9:27-37. [PMID: 31191084 PMCID: PMC6524763 DOI: 10.2147/dnnd.s192588] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 03/18/2019] [Indexed: 12/12/2022] Open
Abstract
Lambert-Eaton myasthenic syndrome (LEMS) is an uncommon disorder of neuromuscular transmission with distinctive pathophysiological, clinical, electrophysiological and laboratory features. There are two forms of LEMS. The paraneoplastic (P-LEMS) form is associated with a malignant tumor that is most frequently a small cell lung carcinoma (SCLC), and the autoimmune (A-LEMS) form is often related to other dysimmune diseases. Approximately 90% of LEMS patients present antibodies against presynaptic membrane P/Q-type voltage-gated calcium channels (VGCC). These antibodies are directly implicated in the pathophysiology of the disorder, provoke reduced acetylcholine (ACh) at the nerve terminal and consequently lead to muscle weakness. LEMS is clinically characterized by proximal muscle weakness, autonomic dysfunction and areflexia. In clinically suspected cases, diagnoses are confirmed by serological and electrodiagnostic tests. The detection of P/Q-type VGCC antibodies is supportive when there is clinical suspicion but should be carefully interpreted in the absence of characteristic clinical or electrodiagnostic features. Typical electrodiagnostic findings (ie, reduced compound motor action potentials (CMAPs), significant decrements in the responses to low frequency stimulation and incremental responses after brief exercise or high-frequency stimulation) reflect the existence of a presynaptic transmission defect and are key confirmatory criteria. Diagnosis requires a high level of awareness and necessitates the initiation of a prompt screening and surveillance process to detect and treat malignant tumors. In clinically affected patients without cancer and after cancer treatment, symptomatic treatment with 3,4-diaminopyridine or immunosuppressive agents can significantly improve neurologic symptoms and the quality of life. We present a detailed review of LEMS with special emphasis on the pathophysiological mechanisms, clinical manifestation and diagnostic procedure.
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Affiliation(s)
- Trajche Ivanovski
- Neurology Department, Hospital Universitari Son Llatzer, Palma de Mallorca, Balearic Islands, Spain
| | - Francesc Miralles
- Neurology Department, Hospital Universitari Son Espases, Palma de Mallorca, Balearic Islands, Spain
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30
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Ge D, Noakes PG, Lavidis NA. Seasonal comparison of the neuromuscular junction morphology of Bufo marinus. J Comp Neurol 2019; 527:1931-1939. [PMID: 30737989 DOI: 10.1002/cne.24661] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 01/05/2019] [Accepted: 02/01/2019] [Indexed: 12/12/2022]
Abstract
At mammalian neuromuscular junctions (NMJs), prolonged inactivity leads to muscle denervation and atrophy. By contrast, amphibian NMJs do not show such degeneration even though they can remain in a state of drought-imposed dormancy (hibernation) for many years. We have previously reported that during the dry season, toad (Bufo marinus) NMJs display decreased sensitivity to extracellular calcium-dependent neurotransmitter release, which leads to minimal neuromuscular transmission. In the present study, we examined and compared NMJ morphology of toads obtained from the wild during the wet season (February-March) when these toads are active, to toads obtained from dry season (October-November) when toads are inactive. Iliofibularis muscles were isolated and prepared for immunostaining with anti-SV2, a monoclonal antibody that labels synaptic vesicle glycoprotein SV2. The corresponding postsynaptic acetylcholine receptors were stained using Alexa Fluro-555 conjugated α-bungarotoxin. Confocal microscopy and three-dimensional reconstructions were then used to examine the pre-and postsynaptic morphology of toads NMJs from the dry (inactive) and wet (active) seasons. Total axon branch number, the percentage of axon branches with discontinuous distributions of synaptic vesicles, and further the Pearson value of colocalization of pre and postsynaptic elements in each NMJs from both the dry and wet season were compared. While our previous studies on dry toads revealed a significant reduction in evoked neurotransmission, our present findings show that the structure of the NMJs suffered limited level of remodeling, suggesting a mechanism utilized by NMJs in dry season toads to support quick recover from their dormant state after the heavy rain in wet season.
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Affiliation(s)
- Dengyun Ge
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, Queensland, Australia
| | - Peter G Noakes
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, Queensland, Australia.,Queensland Brain Institute, The University of Queensland, Queensland, Australia
| | - Nickolas A Lavidis
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, Queensland, Australia
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31
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Raghavan M, Fee D, Barkhaus PE. Generation and propagation of the action potential. ACTA ACUST UNITED AC 2019; 160:3-22. [DOI: 10.1016/b978-0-444-64032-1.00001-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Giniatullin A, Petrov A, Giniatullin R. Action of Hydrogen Peroxide on Synaptic Transmission at the Mouse Neuromuscular Junction. Neuroscience 2018; 399:135-145. [PMID: 30593920 DOI: 10.1016/j.neuroscience.2018.12.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 11/30/2018] [Accepted: 12/17/2018] [Indexed: 12/15/2022]
Abstract
Hydrogen peroxide (H2O2) is one of the reactive oxygen species (ROS), endogenously produced during metabolism, which acts as a second messenger. In skeletal muscles, hypoxia- or hyperthermia-induced increase in H2O2 might affect synaptic transmission by targeting the most redox-sensitive presynaptic compartment (Giniatullin et al., 2006). However, the effects of H2O2 as a signal molecule have not previously been studied in different patterns of the synaptic activity. Here, using optical and microelectrode recording of synaptic vesicle exocytosis, we studied the use-dependent action of low concentrations of H2O2 and other oxidants in the mouse neuromuscular junction. We found that: (i) H2O2 at low micromole concentrations inhibited both spontaneous and evoked transmitter releases from the motor nerve terminals in a use-dependent manner, (ii) the antioxidant N-acetylcysteine (NAC) eliminated these depressant effects, (iii) the influence of H2O2 was not associated with lipid oxidation suggesting a pure signaling action, (iv) the intracellular oxidant Chloramine-T or (v) the glutathione depletion produced similar to H2O2 depressant effects. Taken together, our data revealed the effective inhibition of neurotransmitter release by ROS, which was proportional to the intensity of synaptic activity at the neuromuscular junction. The combination of various oxidants suggested an intracellular location for redox-sensitive sites responsible for modulation of the synaptic transmission in the skeletal muscle.
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Affiliation(s)
| | - Alexey Petrov
- Institute of Neuroscience, Kazan State Medial University, Kazan, Russia; Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Centre "Kazan Scientific Centre of RAS", Kazan, Russia
| | - Rashid Giniatullin
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia; A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
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Mechanism of P2X7 receptor-dependent enhancement of neuromuscular transmission in pannexin 1 knockout mice. Purinergic Signal 2018; 14:459-469. [PMID: 30362043 DOI: 10.1007/s11302-018-9630-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 10/02/2018] [Indexed: 01/15/2023] Open
Abstract
P2X7 receptors are present in presynaptic membranes of motor synapses, but their regulatory role in modulation of neurotransmitter release remains poorly understood. P2X7 receptors may interact with pannexin 1 channels to form a purinergic signaling unit. The potential mechanism of P2X7 receptor-dependent modulation of acetylcholine (ACh) release was investigated by recording miniature endplate potentials (MEPPs) and evoked endplate potentials (EPPs) in neuromuscular junctions of wild-type (WT) and pannexin 1 knockout (Panx1-/-) mice. Modulation of P2X7 receptors with the selective inhibitor A740003 or the selective agonist BzATP did not alter the parameters of either spontaneous or evoked ACh release in WT mice. In Panx1-/- mice, BzATP-induced activation of P2X7 receptors resulted in a uniformly increased quantal content of EPPs during a short stimulation train. This effect was accompanied by an increase in the size of the readily releasable pool, while the release probability did not change. Inhibition of calmodulin by W-7 or of calcium/calmodulin-dependent kinase II (CaMKII) by KN-93 completely prevented the potentiating effect of BzATP on the EPP quantal content. The blockade of L-type calcium channels also prevented BzATP action on evoked synaptic activity. Thus, the activation of presynaptic P2X7 receptors in mice lacking pannexin 1 resulted in enhanced evoked ACh release. Such enhanced release was provoked by triggering the calmodulin- and CaMKII-dependent signaling pathway, followed by activation of presynaptic L-type calcium channels. We suggest that in WT mice, this pathway is downregulated due to pannexin 1-dependent tonic activation of inhibitory presynaptic purinergic receptors, which overcomes P2X7-mediated effects.
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Ghelani T, Sigrist SJ. Coupling the Structural and Functional Assembly of Synaptic Release Sites. Front Neuroanat 2018; 12:81. [PMID: 30386217 PMCID: PMC6198076 DOI: 10.3389/fnana.2018.00081] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 09/18/2018] [Indexed: 01/04/2023] Open
Abstract
Information processing in our brains depends on the exact timing of calcium (Ca2+)-activated exocytosis of synaptic vesicles (SVs) from unique release sites embedded within the presynaptic active zones (AZs). While AZ scaffolding proteins obviously provide an efficient environment for release site function, the molecular design creating such release sites had remained unknown for a long time. Recent advances in visualizing the ultrastructure and topology of presynaptic protein architectures have started to elucidate how scaffold proteins establish “nanodomains” that connect voltage-gated Ca2+ channels (VGCCs) physically and functionally with release-ready SVs. Scaffold proteins here seem to operate as “molecular rulers or spacers,” regulating SV-VGCC physical distances within tens of nanometers and, thus, influence the probability and plasticity of SV release. A number of recent studies at Drosophila and mammalian synapses show that the stable positioning of discrete clusters of obligate release factor (M)Unc13 defines the position of SV release sites, and the differential expression of (M)Unc13 isoforms at synapses can regulate SV-VGCC coupling. We here review the organization of matured AZ scaffolds concerning their intrinsic organization and role for release site formation. Moreover, we also discuss insights into the developmental sequence of AZ assembly, which often entails a tightening between VGCCs and SV release sites. The findings discussed here are retrieved from vertebrate and invertebrate preparations and include a spectrum of methods ranging from cell biology, super-resolution light and electron microscopy to biophysical and electrophysiological analysis. Our understanding of how the structural and functional organization of presynaptic AZs are coupled has matured, as these processes are crucial for the understanding of synapse maturation and plasticity, and, thus, accurate information transfer and storage at chemical synapses.
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Affiliation(s)
- Tina Ghelani
- Faculty of Biology, Chemistry, Pharmacy, Freie Universität Berlin, Berlin, Germany
| | - Stephan J Sigrist
- Faculty of Biology, Chemistry, Pharmacy, Freie Universität Berlin, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Berlin, Germany
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35
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Ribchester RR, Slater CR. Rapid retrograde regulation of transmitter release at the NMJ. CURRENT OPINION IN PHYSIOLOGY 2018. [DOI: 10.1016/j.cophys.2018.06.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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36
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Petrov KA, Nikolsky EE, Masson P. Autoregulation of Acetylcholine Release and Micro-Pharmacodynamic Mechanisms at Neuromuscular Junction: Selective Acetylcholinesterase Inhibitors for Therapy of Myasthenic Syndromes. Front Pharmacol 2018; 9:766. [PMID: 30050445 PMCID: PMC6052098 DOI: 10.3389/fphar.2018.00766] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 06/25/2018] [Indexed: 12/22/2022] Open
Abstract
Neuromuscular junctions (NMJs) are directly involved into such indispensable to life processes as respiration and locomotion. However, motor nerve forms only one synaptic contact at each muscle fiber. This unique configuration requires specific properties and constrains to be effective. The very high density of acetylcholine receptors (AChRs) of muscle type in synaptic cleft and an excess of acetylcholine (ACh) released under physiological conditions make this synapse extremely reliable. Nevertheless, under pathological conditions such as myasthenia gravis and congenital myasthenic syndromes, the safety factor can be markedly reduced. Drugs used for short-term symptomatic therapy of these pathological states, cause partial inhibition of cholinesterases (ChEs). These enzymes catalyze the hydrolysis of ACh, thus terminate its action on AChRs. Extension of the lifetime of ACh molecules compensates muscular AChRs abnormalities and, consequently, rescues muscle contractions. In this mini review, we will first outline the functional organization of the NMJ, and then, consider the concept of the safety factor and how it may be changed. This will be followed by a look at autoregulation of ACh release that influences the safety factor of NMJs. Finally, we will consider the morphological features of NMJs as a putative reserve to increase effectiveness of pathological muscle weakness therapy by ChEs inhibitors due to opportunity to use micro-pharmacodynamic mechanisms.
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Affiliation(s)
- Konstantin A Petrov
- A.E. Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center of Russian Academy of Sciences, Kazan, Russia.,Neuropharmacology Lab, Kazan Federal University, Kazan, Russia
| | - Evgeny E Nikolsky
- Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of Russian Academy of Sciences, Kazan, Russia
| | - Patrick Masson
- Neuropharmacology Lab, Kazan Federal University, Kazan, Russia
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Cellular and Molecular Anatomy of the Human Neuromuscular Junction. Cell Rep 2018; 21:2348-2356. [PMID: 29186674 PMCID: PMC5723673 DOI: 10.1016/j.celrep.2017.11.008] [Citation(s) in RCA: 127] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 08/18/2017] [Accepted: 11/01/2017] [Indexed: 12/20/2022] Open
Abstract
The neuromuscular junction (NMJ) plays a fundamental role in transferring information from lower motor neuron to skeletal muscle to generate movement. It is also an experimentally accessible model synapse routinely studied in animal models to explore fundamental aspects of synaptic form and function. Here, we combined morphological techniques, super-resolution imaging, and proteomic profiling to reveal the detailed cellular and molecular architecture of the human NMJ. Human NMJs were significantly smaller, less complex, and more fragmented than mouse NMJs. In contrast to mice, human NMJs were also remarkably stable across the entire adult lifespan, showing no signs of age-related degeneration or remodeling. Super-resolution imaging and proteomic profiling revealed distinctive distribution of active zone proteins and differential expression of core synaptic proteins and molecular pathways at the human NMJ. Taken together, these findings reveal human-specific cellular and molecular features of the NMJ that distinguish them from comparable synapses in other mammalian species.
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24S-hydroxycholesterol suppresses neuromuscular transmission in SOD1(G93A) mice: A possible role of NO and lipid rafts. Mol Cell Neurosci 2018; 88:308-318. [PMID: 29550246 DOI: 10.1016/j.mcn.2018.03.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Revised: 02/08/2018] [Accepted: 03/12/2018] [Indexed: 12/12/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by the initial denervation of skeletal muscle and subsequent death of motor neurons. A dying-back pattern of ALS suggests a crucial role for neuromuscular junction dysfunction. In the present study, microelectrode recording of postsynaptic currents and optical detection of synaptic vesicle traffic (FM1-43 dye) and intracellular NO levels (DAF-FM DA) were used to examine the effect of the major brain-derived cholesterol metabolite 24S-hydroxycholesterol (24S-HC, 0.4 μM) on neuromuscular transmission in the diaphragm of transgenic mice carrying a mutant superoxide dismutase 1 (SODG93A). We found that 24S-HC suppressed spontaneous neurotransmitter release and neurotransmitter exocytosis during high-frequency stimulation. The latter was accompanied by a decrease in both the rate of synaptic vesicle recycling and activity-dependent enhancement of NO production. Inhibition of NO synthase with L-NAME also attenuated synaptic vesicle exocytosis during high-frequency stimulation and completely abolished the effect of 24S-HC itself. Of note, 24S-HC enhanced the labeling of synaptic membranes with B-subunit of cholera toxin, suggesting an increase in lipid ordering. Lipid raft-disrupting agents (methyl-β-cyclodextrin, sphingomyelinase) prevented the action of 24S-HC on both lipid raft marker labeling and NO synthesis. Together, these experiments indicate that 24S-HC is able to suppress the exocytotic release of neurotransmitter in response to intense activity via a NO/lipid raft-dependent pathway in the neuromuscular junctions of SODG93A mice.
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Willadt S, Nash M, Slater C. Age-related changes in the structure and function of mammalian neuromuscular junctions. Ann N Y Acad Sci 2017; 1412:41-53. [PMID: 29291259 DOI: 10.1111/nyas.13521] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 09/07/2017] [Accepted: 09/12/2017] [Indexed: 12/17/2022]
Abstract
As mammals age, their neuromuscular junctions (NMJs) change their form, with an increasingly complex system of axonal branches innervating increasingly fragmented regions of postsynaptic differentiation. It has been suggested that this remodeling is associated with impairment of neuromuscular transmission and that this contributes to age-related muscle weakness in mammals, including humans. Here, we review previous work on NMJ aging, most of which has focused on either structure or function, as well as a new study aimed at seeking correlation between the structure and function of individual NMJs. While it is clear that extensive structural changes occur as part of the aging process, it is much less certain how, if at all, these are correlated with an impairment of function. This leaves open the question of whether loss of NMJ function is a significant cause of age-related muscle weakness.
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Affiliation(s)
- Silvia Willadt
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Mark Nash
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Clarke Slater
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK
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40
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Badawi Y, Nishimune H. Presynaptic active zones of mammalian neuromuscular junctions: Nanoarchitecture and selective impairments in aging. Neurosci Res 2017; 127:78-88. [PMID: 29221906 DOI: 10.1016/j.neures.2017.11.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 11/17/2017] [Accepted: 11/27/2017] [Indexed: 12/16/2022]
Abstract
Neurotransmitter release occurs at active zones, which are specialized regions of the presynaptic membrane. A dense collection of proteins at the active zone provides a platform for molecular interactions that promote recruitment, docking, and priming of synaptic vesicles. At mammalian neuromuscular junctions (NMJs), muscle-derived laminin β2 interacts with presynaptic voltage-gated calcium channels to organize active zones. The molecular architecture of presynaptic active zones has been revealed using super-resolution microscopy techniques that combine nanoscale resolution and multiple molecular identification. Interestingly, the active zones of adult NMJs are not stable structures and thus become impaired during aging due to the selective degeneration of specific active zone proteins. This review will discuss recent progress in the understanding of active zone nanoarchitecture and the mechanisms underlying active zone organization in mammalian NMJs. Furthermore, we will summarize the age-related degeneration of active zones at NMJs, and the role of exercise in maintaining active zones.
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Affiliation(s)
- Yomna Badawi
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, KS, 66160, USA
| | - Hiroshi Nishimune
- Department of Anatomy and Cell Biology, University of Kansas School of Medicine, Kansas City, KS, 66160, USA.
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41
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Meriney SD, Tarr TB, Ojala KS, Wu M, Li Y, Lacomis D, Garcia-Ocaña A, Liang M, Valdomir G, Wipf P. Lambert-Eaton myasthenic syndrome: mouse passive-transfer model illuminates disease pathology and facilitates testing therapeutic leads. Ann N Y Acad Sci 2017; 1412:73-81. [PMID: 29125190 DOI: 10.1111/nyas.13512] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 08/31/2017] [Accepted: 09/09/2017] [Indexed: 11/29/2022]
Abstract
Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder caused by antibodies directed against the voltage-gated calcium channels that provide the calcium ion flux that triggers acetylcholine release at the neuromuscular junction. To study the pathophysiology of LEMS and test candidate therapeutic strategies, a passive-transfer animal model has been developed in mice, which can be created by daily intraperitoneal injections of LEMS patient serum or IgG into mice for 2-4 weeks. Results from studies of the mouse neuromuscular junction have revealed that each synapse has hundreds of transmitter release sites but that the probability for release at each one is likely to be low. LEMS further reduces this low probability such that transmission is no longer effective at triggering a muscle contraction. The LEMS-mediated attack reduces the number of presynaptic calcium channels, disorganizes transmitter release sites, and results in the homeostatic upregulation of other calcium channel types. Symptomatic treatment is focused on increasing the probability of release from dysfunctional release sites. Current treatment uses the potassium channel blocker 3,4-diaminopyridine (DAP) to broaden the presynaptic action potential, providing more time for calcium channels to open. Current research is focused on testing new calcium channel gating modifiers that work synergistically with DAP.
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Affiliation(s)
- Stephen D Meriney
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Tyler B Tarr
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Kristine S Ojala
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Man Wu
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Yizhi Li
- Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - David Lacomis
- Division of Neuromuscular Diseases, Departments of Neurology and Pathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
| | - Adolfo Garcia-Ocaña
- Diabetes, Obesity and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Mary Liang
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Guillermo Valdomir
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania
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42
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The Structure of Human Neuromuscular Junctions: Some Unanswered Molecular Questions. Int J Mol Sci 2017; 18:ijms18102183. [PMID: 29048368 PMCID: PMC5666864 DOI: 10.3390/ijms18102183] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 09/25/2017] [Accepted: 10/13/2017] [Indexed: 12/21/2022] Open
Abstract
The commands that control animal movement are transmitted from motor neurons to their target muscle cells at the neuromuscular junctions (NMJs). The NMJs contain many protein species whose role in transmission depends not only on their inherent properties, but also on how they are distributed within the complex structure of the motor nerve terminal and the postsynaptic muscle membrane. These molecules mediate evoked chemical transmitter release from the nerve and the action of that transmitter on the muscle. Human NMJs are among the smallest known and release the smallest number of transmitter "quanta". By contrast, they have the most deeply infolded postsynaptic membranes, which help to amplify transmitter action. The same structural features that distinguish human NMJs make them particularly susceptible to pathological processes. While much has been learned about the molecules which mediate transmitter release and action, little is known about the molecular processes that control the growth of the cellular and subcellular components of the NMJ so as to give rise to its mature form. A major challenge for molecular biologists is to understand the molecular basis for the development and maintenance of functionally important aspects of NMJ structure, and thereby to point to new directions for treatment of diseases in which neuromuscular transmission is impaired.
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Pulido C, Marty A. Quantal Fluctuations in Central Mammalian Synapses: Functional Role of Vesicular Docking Sites. Physiol Rev 2017; 97:1403-1430. [DOI: 10.1152/physrev.00032.2016] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 04/28/2017] [Accepted: 04/29/2017] [Indexed: 12/23/2022] Open
Abstract
Quantal fluctuations are an integral part of synaptic signaling. At the frog neuromuscular junction, Bernard Katz proposed that quantal fluctuations originate at “reactive sites” where specific structures of the presynaptic membrane interact with synaptic vesicles. However, the physical nature of reactive sites has remained unclear, both at the frog neuromuscular junction and at central synapses. Many central synapses, called simple synapses, are small structures containing a single presynaptic active zone and a single postsynaptic density of receptors. Several lines of evidence indicate that simple synapses may release several synaptic vesicles in response to a single action potential. However, in some synapses at least, each release event activates a significant fraction of the postsynaptic receptors, giving rise to a sublinear relation between vesicular release and postsynaptic current. Partial receptor saturation as well as synaptic jitter gives to simple synapse signaling the appearance of a binary process. Recent investigations of simple synapses indicate that the number of released vesicles follows binomial statistics, with a maximum reflecting the number of docking sites present in the active zone. These results suggest that at central synapses, vesicular docking sites represent the reactive sites proposed by Katz. The macromolecular architecture and molecular composition of docking sites are presently investigated with novel combinations of techniques. It is proposed that variations in docking site numbers are central in defining intersynaptic variability and that docking site occupancy is a key parameter regulating short-term synaptic plasticity.
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Affiliation(s)
- Camila Pulido
- Laboratory of Brain Physiology, CNRS UMR 8118, Paris Descartes University, Paris, France
| | - Alain Marty
- Laboratory of Brain Physiology, CNRS UMR 8118, Paris Descartes University, Paris, France
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44
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Ge D, Lavidis N. Seasonal factors influence quantal transmitter release and calcium dependence at amphibian neuromuscular junctions. Am J Physiol Regul Integr Comp Physiol 2017. [PMID: 28637657 DOI: 10.1152/ajpregu.00070.2017] [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: 11/22/2022]
Abstract
Amphibian neuromuscular junctions (NMJs) are composed of hundreds of neurotransmitter release sites that exhibit nonuniform transmitter release probabilities and demonstrated seasonal modulation. We examined whether recruitment of release sites is variable when the extracellular calcium concentration ([Ca2+]o) is increased in the wet and dry seasons. The amount of transmitter released from the entire nerve terminal increases by approximately the fourth power as [Ca2+]o is increased. Toad (Bufo marinus) NMJs were visualized using 3,3'-diethyloxardicarbocyanine iodide [DiOC2(5)] fluorescence, and focal loose patch extracellular recordings were used to record the end-plate currents (EPCs) from small groups of release sites. Quantal content (m̄e ), average probability of quantal release (pe ), and the number of active release sites (ne ) were determined for different [Ca2+]o Our results indicated that the recruitment of quantal release sites with increasing [Ca2+]o differs spatially (between different groups of release sites) and also temporally (in different seasons). These differences were reflected by the nonuniform alterations in pe and ne Most release site groups demonstrated an increase in both pe and ne when [Ca2+]o increased. In ~30% of release site groups examined, pe decreased while ne increased only during the active period (wet season). Although the dry season induced parallel right shift in the quantal release versus extracellular calcium concentration when compared with the wet season, the dependence of quantal content on [Ca2+]o was not changed. These results demonstrate the flexibility, reserve, and adaptive capacity of neuromuscular junctions in maintaining appropriate levels of neurotransmission.
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Affiliation(s)
- Dengyun Ge
- School of Biomedical Sciences, The University of Queensland, St. Lucia, Australia
| | - Nickolas Lavidis
- School of Biomedical Sciences, The University of Queensland, St. Lucia, Australia
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45
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Kasimov M, Fatkhrakhmanova M, Mukhutdinova K, Petrov A. 24S-Hydroxycholesterol enhances synaptic vesicle cycling in the mouse neuromuscular junction: Implication of glutamate NMDA receptors and nitric oxide. Neuropharmacology 2017; 117:61-73. [DOI: 10.1016/j.neuropharm.2017.01.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 01/24/2017] [Accepted: 01/27/2017] [Indexed: 12/29/2022]
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46
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Wang WC, Brehm P. A Gradient in Synaptic Strength and Plasticity among Motoneurons Provides a Peripheral Mechanism for Locomotor Control. Curr Biol 2017; 27:415-422. [PMID: 28111148 DOI: 10.1016/j.cub.2016.12.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 12/02/2016] [Accepted: 12/06/2016] [Indexed: 01/28/2023]
Abstract
The recruitment of motoneurons during force generation follows a general pattern that has been confirmed across diverse species [1-3]. Motoneurons are recruited systematically according to synaptic inputs and intrinsic cellular properties and corresponding to movements of different intensities. However, much less is known about the output properties of individual motoneurons and how they affect the translation of motoneuron recruitment to the strength of muscle contractions. In larval zebrafish, spinal motoneurons are recruited in a topographic gradient according to their input resistance (Rin) at different swimming strengths and speeds. Whereas dorsal, lower-Rin primary motoneurons (PMns) are only activated during behaviors that involve strong and fast body bends, more ventral, higher-Rin secondary motoneurons (SMns) are recruited during weaker and slower movements [4-6]. Here we perform in vivo paired recordings between identified spinal motoneurons and skeletal muscle cells in larval zebrafish. We characterize individual motoneuron outputs to single muscle cells and show that the strength and reliability of motoneuron outputs are inversely correlated with motoneuron Rin. During repetitive high-frequency motoneuron drive, PMn synapses undergo depression, whereas SMn synapses potentiate. We monitor muscle cell contractions elicited by single motoneurons and show that the pattern of motoneuron output strength and plasticity observed in electrophysiological recordings is reflected in muscle shortening. Our findings indicate a link between the recruitment pattern and output properties of spinal motoneurons that can together generate appropriate intensities for muscle contractions. We demonstrate that motoneuron output properties provide an additional peripheral mechanism for graded locomotor control at the neuromuscular junction.
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Affiliation(s)
- Wei-Chun Wang
- Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, USA.
| | - Paul Brehm
- Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, USA
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47
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Jones RA, Reich CD, Dissanayake KN, Kristmundsdottir F, Findlater GS, Ribchester RR, Simmen MW, Gillingwater TH. NMJ-morph reveals principal components of synaptic morphology influencing structure-function relationships at the neuromuscular junction. Open Biol 2016; 6:160240. [PMID: 27927794 PMCID: PMC5204123 DOI: 10.1098/rsob.160240] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 11/09/2016] [Indexed: 01/10/2023] Open
Abstract
The ability to form synapses is one of the fundamental properties required by the mammalian nervous system to generate network connectivity. Structural and functional diversity among synaptic populations is a key hallmark of network diversity, and yet we know comparatively little about the morphological principles that govern variability in the size, shape and strength of synapses. Using the mouse neuromuscular junction (NMJ) as an experimentally accessible model synapse, we report on the development of a robust, standardized methodology to facilitate comparative morphometric analysis of synapses ('NMJ-morph'). We used NMJ-morph to generate baseline morphological reference data for 21 separate pre- and post-synaptic variables from 2160 individual NMJs belonging to nine anatomically distinct populations of synapses, revealing systematic differences in NMJ morphology between defined synaptic populations. Principal components analysis revealed that overall NMJ size and the degree of synaptic fragmentation, alongside pre-synaptic axon diameter, were the most critical parameters in defining synaptic morphology. 'Average' synaptic morphology was remarkably conserved between comparable synapses from the left and right sides of the body. Systematic differences in synaptic morphology predicted corresponding differences in synaptic function that were supported by physiological recordings, confirming the robust relationship between synaptic size and strength.
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Affiliation(s)
- Ross A Jones
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
- Centre for Integrative Physiology, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
- Anatomy, Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
| | - Caitlan D Reich
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
- Centre for Integrative Physiology, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
- Anatomy, Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
| | - Kosala N Dissanayake
- Centre for Integrative Physiology, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
| | - Fanney Kristmundsdottir
- Anatomy, Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
| | - Gordon S Findlater
- Anatomy, Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
| | - Richard R Ribchester
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
- Centre for Integrative Physiology, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
| | - Martin W Simmen
- Centre for Integrative Physiology, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
| | - Thomas H Gillingwater
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
- Centre for Integrative Physiology, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
- Anatomy, Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK
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48
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Willadt S, Nash M, Slater CR. Age-related fragmentation of the motor endplate is not associated with impaired neuromuscular transmission in the mouse diaphragm. Sci Rep 2016; 6:24849. [PMID: 27094316 PMCID: PMC4837408 DOI: 10.1038/srep24849] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Accepted: 04/05/2016] [Indexed: 02/04/2023] Open
Abstract
As mammals age, their neuromuscular junctions (NMJs) gradually change their form, acquiring an increasingly fragmented appearance consisting of numerous isolated regions of synaptic differentiation. It has been suggested that this remodelling is associated with impairment of neuromuscular transmission, and that this contributes to age-related muscle weakness in mammals, including humans. The underlying hypothesis, that increasing NMJ fragmentation is associated with impaired transmission, has never been directly tested. Here, by comparing the structure and function of individual NMJs, we show that neuromuscular transmission at the most highly fragmented NMJs in the diaphragms of old (26-28 months) mice is, if anything, stronger than in middle-aged (12-14 months) mice. We suggest that NMJ fragmentation per se is not a reliable indicator of impaired neuromuscular transmission.
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Affiliation(s)
- Silvia Willadt
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Mark Nash
- Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Clarke R. Slater
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom
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49
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Kasimov MR, Zakyrjanova GF, Giniatullin AR, Zefirov AL, Petrov AM. Similar oxysterols may lead to opposite effects on synaptic transmission: Olesoxime versus 5α-cholestan-3-one at the frog neuromuscular junction. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:606-16. [PMID: 27102612 DOI: 10.1016/j.bbalip.2016.04.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 03/17/2016] [Accepted: 04/15/2016] [Indexed: 02/03/2023]
Abstract
Cholesterol oxidation products frequently have a high biological activity. In the present study, we have used microelectrode recording of end plate currents and FM-based optical detection of synaptic vesicle exo-endocytosis to investigate the effects of two structurally similar oxysterols, olesoxime (cholest-4-en-3-one, oxime) and 5ɑ-cholestan-3-one (5ɑCh3), on neurotransmission at the frog neuromuscular junction. Olesoxime is an exogenous, potentially neuroprotective, substance and 5ɑCh3 is an intermediate product in cholesterol metabolism, which is elevated in the case of cerebrotendinous xanthomatosis. We found that olesoxime slightly increased evoked neurotransmitter release in response to a single stimulus and significantly reduced synaptic depression during high frequency activity. The last effect was due to an increase in both the number of synaptic vesicles involved in exo-endocytosis and the rate of synaptic vesicle recycling. In contrast, 5ɑCh3 reduced evoked neurotransmitter release during the low- and high frequency synaptic activities. The depressant action of 5ɑCh3 was associated with a reduction in the number of synaptic vesicles participating in exo- and endocytosis during high frequency stimulation, without a change in rate of the synaptic vesicle recycling. Of note, olesoxime increased the staining of synaptic membranes with the B-subunit of cholera toxin and the formation of fluorescent ganglioside GM1 clusters, and decreased the fluorescence of 22-NBD-cholesterol, while 5ɑCh3 had the opposite effects, suggesting that the two oxysterols have different effects on lipid raft stability. Taken together, these data show that these two structurally similar oxysterols induce marked different changes in neuromuscular transmission which are related with the alteration in synaptic vesicle cycle.
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Affiliation(s)
- M R Kasimov
- Department of Normal Physiology, Kazan State Medical University, Kazan 420012, Russia
| | - G F Zakyrjanova
- Department of Normal Physiology, Kazan State Medical University, Kazan 420012, Russia
| | - A R Giniatullin
- Department of Normal Physiology, Kazan State Medical University, Kazan 420012, Russia
| | - A L Zefirov
- Department of Normal Physiology, Kazan State Medical University, Kazan 420012, Russia
| | - A M Petrov
- Department of Normal Physiology, Kazan State Medical University, Kazan 420012, Russia.
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