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Proceedings of the National Academy of... Apr 2024Stable matching of neurotransmitters with their receptors is fundamental to synapse function and reliable communication in neural circuits. Presynaptic neurotransmitters...
Stable matching of neurotransmitters with their receptors is fundamental to synapse function and reliable communication in neural circuits. Presynaptic neurotransmitters regulate the stabilization of postsynaptic transmitter receptors. Whether postsynaptic receptors regulate stabilization of presynaptic transmitters has received less attention. Here, we show that blockade of endogenous postsynaptic acetylcholine receptors (AChR) at the neuromuscular junction destabilizes the cholinergic phenotype in motor neurons and stabilizes an earlier, developmentally transient glutamatergic phenotype. Further, expression of exogenous postsynaptic gamma-aminobutyric acid type A receptors (GABA receptors) in muscle cells stabilizes an earlier, developmentally transient GABAergic motor neuron phenotype. Both AChR and GABA receptors are linked to presynaptic neurons through transsynaptic bridges. Knockdown of specific components of these transsynaptic bridges prevents stabilization of the cholinergic or GABAergic phenotypes. Bidirectional communication can enforce a match between transmitter and receptor and ensure the fidelity of synaptic transmission. Our findings suggest a potential role of dysfunctional transmitter receptors in neurological disorders that involve the loss of the presynaptic transmitter.
Topics: Synapses; Receptors, Cholinergic; Synaptic Transmission; Motor Neurons; Receptors, GABA-A; gamma-Aminobutyric Acid; Neurotransmitter Agents; Cholinergic Agents; Receptors, Presynaptic
PubMed: 38568976
DOI: 10.1073/pnas.2318041121 -
Cellular and Molecular Neurobiology Apr 2024The phenomenon of ischemic postconditioning (PostC) is known to be neuroprotective against ischemic reperfusion (I/R) injury. One of the key processes in PostC is the...
The phenomenon of ischemic postconditioning (PostC) is known to be neuroprotective against ischemic reperfusion (I/R) injury. One of the key processes in PostC is the opening of the mitochondrial ATP-dependent potassium (mito-K) channel and depolarization of the mitochondrial membrane, triggering the release of calcium ions from mitochondria through low-conductance opening of the mitochondrial permeability transition pore. Mitochondrial calcium uniporter (MCU) is known as a highly sensitive transporter for the uptake of Ca present on the inner mitochondrial membrane. The MCU has attracted attention as a new target for treatment in diseases, such as neurodegenerative diseases, cancer, and ischemic stroke. We considered that the MCU may be involved in PostC and trigger its mechanisms. This research used the whole-cell patch-clamp technique on hippocampal CA1 pyramidal cells from C57BL mice and measured changes in spontaneous excitatory post-synaptic currents (sEPSCs), intracellular Ca concentration, mitochondrial membrane potential, and N-methyl-D-aspartate receptor (NMDAR) currents under inhibition of MCU by ruthenium red 265 (Ru265) in PostC. Inhibition of MCU increased the occurrence of sEPSCs (p = 0.014), NMDAR currents (p < 0.001), intracellular Ca concentration (p < 0.001), and dead cells (p < 0.001) significantly after reperfusion, reflecting removal of the neuroprotective effects in PostC. Moreover, mitochondrial depolarization in PostC with Ru265 was weakened, compared to PostC (p = 0.004). These results suggest that MCU affects mitochondrial depolarization in PostC to suppress NMDAR over-activation and prevent elevation of intracellular Ca concentrations against I/R injury.
Topics: Animals; Mice; Mice, Inbred C57BL; Ischemic Postconditioning; Receptors, N-Methyl-D-Aspartate; Brain Injuries; Adenosine Triphosphate; Calcium Channels; Ruthenium Compounds
PubMed: 38568450
DOI: 10.1007/s10571-024-01464-7 -
BioRxiv : the Preprint Server For... Mar 2024WWC2 (WW and C2 domain-containing protein) is implicated in several neurological disorders, however its function in the brain has yet to be determined. Here, we...
WWC2 (WW and C2 domain-containing protein) is implicated in several neurological disorders, however its function in the brain has yet to be determined. Here, we demonstrate that WWC2 interacts with inhibitory but not excitatory postsynaptic scaffolds, consistent with prior proteomic identification of WWC2 as a putative component of the inhibitory postsynaptic density. Using mice lacking WWC2 expression in excitatory forebrain neurons, we show that WWC2 suppresses GABA R incorporation into the plasma membrane and regulates HAP1 and GRIP1, which form a complex promoting GABA R recycling to the membrane. Inhibitory synaptic transmission is dysregulated in CA1 pyramidal cells lacking WWC2. Furthermore, unlike the WWC2 homolog KIBRA (WWC1), a key regulator of AMPA receptor trafficking at excitatory synapses, deletion of WWC2 does not affect synaptic AMPAR expression. In contrast, loss of KIBRA does not affect GABA R membrane expression. These data reveal unique, synapse class-selective functions for WWC proteins as regulators of ionotropic neurotransmitter receptors and provide insight into mechanisms regulating GABA R membrane expression.
PubMed: 38559047
DOI: 10.1101/2024.03.11.584487 -
Journal of Personalized Medicine Feb 2024The thymus is a lymphoid organ involved in the differentiation of T cells, and has a central role in the physiopathogenesis of Myasthenia Gravis (MG). This connection is... (Review)
Review
The thymus is a lymphoid organ involved in the differentiation of T cells, and has a central role in the physiopathogenesis of Myasthenia Gravis (MG). This connection is proved by a series of changes in the level of neuromuscular junctions, which leads to a decrease in the amplitude of the action potential in the post-synaptic membrane. Because of this, the presence of anti-cholinergic receptor antibodies (AChR), characteristic of MG, is found, which causes the progressive regression of the effect of acetylcholine at the level of neuromuscular junctions, with the appearance of muscle weakness. The thymectomy is a surgical variant of drug therapy administered to patients with MG. In the case of patients with nonthymomatous MG, thymectomy has become a therapeutic standard, despite the fact that there is no solid scientific evidence to explain its positive effect. Videothoracoscopic surgery or robotic surgery led to a decrease in the length of hospital stay for these patients. This paper aims to synthesize the information presented in the literature in order to create a background for the perspectives of thymectomy.
PubMed: 38540983
DOI: 10.3390/jpm14030241 -
Nanoscale Horizons Apr 2024The behavior of polyelectrolytes in confined spaces has direct relevance to the protein mediated ion transport in living organisms. In this paper, we govern lithium...
The behavior of polyelectrolytes in confined spaces has direct relevance to the protein mediated ion transport in living organisms. In this paper, we govern lithium chloride transport by the interface provided by polyelectrolytes, polycation, poly(diallyldimethylammonium chloride) (PDDA) and, polyanion, double stranded deoxyribonucleic acid (dsDNA), in confined graphene oxide (GO) membranes. Polyelectrolyte-GO interfaces demonstrate neuromorphic functions that were successfully applied with nanochannel ion interactions contributed, resulting in ion memory effects. Excitatory and inhibitory post-synaptic currents were tuned continuously as the number of pulses applied increased accordingly, increasing decay times. Furthermore, we demonstrated the short-term memory of a trained vs untrained device in computation. On account of its simple and safe production along with its robustness and stability, we anticipate our device to be a low dimensional building block for arrays to embed artificial neural networks in hardware for neuromorphic computing. Additionally, incorporating such devices with sensing and actuating parts for a complete feedback loop produces robotics with its own ability to learn by modifying actuation based on sensing data.
Topics: Graphite; DNA; Quaternary Ammonium Compounds; Polyethylenes; Neural Networks, Computer; Membranes, Artificial; Oxides
PubMed: 38533738
DOI: 10.1039/d3nh00570d -
Cold Spring Harbor Protocols Mar 2024Chemical synaptic transmission is an important means of neuronal communication in the nervous system. Upon the arrival of an action potential, the nerve terminal...
Chemical synaptic transmission is an important means of neuronal communication in the nervous system. Upon the arrival of an action potential, the nerve terminal experiences an influx of calcium ions, which in turn trigger the exocytosis of synaptic vesicles (SVs) and the release of neurotransmitters into the synaptic cleft. Transmitters elicit synaptic responses in the postsynaptic cell by binding to and activating specific receptors. This is followed by the recycling of SVs at presynaptic terminals. The larval neuromuscular junction (NMJ) shares many structural and functional similarities to synapses in other animals, including humans. These include the basic features of synaptic transmission, as well as the molecular mechanisms regulating the SV cycle. Because of its large size, easy accessibility, and well-characterized genetics, the fly NMJ is an excellent model system for dissecting the cellular and molecular mechanisms of synaptic transmission. Here, we describe the theory and practice of electrophysiology as applied to the larval NMJ preparation. We introduce the basics of membrane potentials, with an emphasis on the resting potential and synaptic potential. We also describe the equipment and methods required to set up an electrophysiology rig.
PubMed: 38519095
DOI: 10.1101/pdb.top107820 -
Cold Spring Harbor Protocols Mar 2024Electrophysiological recording is a group of techniques used to record electrical field potentials generated by cells. These techniques rely on several types of...
Electrophysiological recording is a group of techniques used to record electrical field potentials generated by cells. These techniques rely on several types of electrodes, which can be manufactured in the laboratory. In intracellular recording, glass microelectrodes are used to pierce the cell membrane, and then to measure the electrical potential difference between the inside and the outside of the cell. Another technique, called loose patch or focal recording, is similar to intracellular recording but the electrode tip does not pierce into the cell membrane. Rather, the electrode tip is placed near a nerve or the postsynaptic side of the neuromuscular junction (NMJ) to record extracellular changes in local potentials. A third technique involves a suction electrode, which is used to draw part of the motor nerve into the electrode so that electrical pulses can be applied to elicit action potentials of the nerve. Suction electrodes are specifically used to evoke synaptic potentials at the larval NMJ. This protocol details some basic methods for manufacturing microelectrodes used for intracellular recording and two-electrode voltage-clamp and loose patch electrodes used for focal recording. In addition, a method is provided for manufacturing homemade suction electrodes used for nerve stimulation.
PubMed: 38519091
DOI: 10.1101/pdb.prot108134 -
PloS One 2024Chromodomain helicase DNA binding domain (CHD) proteins, including CHD7 and CHD8, remodel chromatin to enable transcriptional programs. Both proteins are important for...
Chromodomain helicase DNA binding domain (CHD) proteins, including CHD7 and CHD8, remodel chromatin to enable transcriptional programs. Both proteins are important for proper neural development as heterozygous mutations in Chd7 and Chd8 are causative for CHARGE syndrome and correlated with autism spectrum disorders, respectively. Their roles in mature neurons are poorly understood despite influencing the expression of genes required for cell adhesion, neurotransmission, and synaptic plasticity. The Drosophila homolog of CHD7 and CHD8, Kismet (Kis), promotes neurotransmission, endocytosis, and larval locomotion. Endocytosis is essential in neurons for replenishing synaptic vesicles, maintaining protein localization, and preserving the size and composition of the presynaptic membrane. Several forms of endocytosis have been identified including clathrin-mediated endocytosis, which is coupled with neural activity and is the most prevalent form of synaptic endocytosis, and activity-dependent bulk endocytosis, which occurs during periods of intense stimulation. Kis modulates the expression of gene products involved in endocytosis including promoting shaggy/GSK3β expression while restricting PI3K92E. kis mutants electrophysiologically phenocopy a liquid facets mutant in response to paradigms that induce clathrin-mediated endocytosis and activity-dependent bulk endocytosis. Further, kis mutants do not show further reductions in endocytosis when activity-dependent bulk endocytosis or clathrin-mediated endocytosis are pharmacologically inhibited. We find that Kis is important in postsynaptic muscle for proper endocytosis but the ATPase domain of Kis is dispensable for endocytosis. Collectively, our data indicate that Kis promotes both clathrin-mediated endocytosis and activity-dependent bulk endocytosis possibly by promoting transcription of several endocytic genes and maintaining the size of the synaptic vesicle pool.
Topics: Animals; Clathrin; Chromatin; Chromatin Assembly and Disassembly; Synaptic Transmission; Drosophila; Endocytosis; DNA Helicases
PubMed: 38512854
DOI: 10.1371/journal.pone.0300255 -
The European Journal of Neuroscience May 2024Ca-dependent K (BK) channels at varicosities in Xenopus nerve-muscle cell cultures were used to quantify experimentally the instantaneous active zone [Ca] resulting from...
Ca-dependent K (BK) channels at varicosities in Xenopus nerve-muscle cell cultures were used to quantify experimentally the instantaneous active zone [Ca] resulting from different rates and durations of Ca entry in the absence of extrinsic buffers and correlate this with neurotransmitter release. Ca tail currents produce mean peak [Ca] ~ 30 μM; with continued influx, [Ca] reaches ~45-60 μM at different rates depending on Ca driving force and duration of influx. Both I and release are dependent on Ca microdomains composed of both N- and L-type Ca channels. Domains collapse with a time constant of ~0.6 ms. We have constructed an active zone (AZ) model that approximately fits this data, and depends on incorporation of the high-capacity, low-affinity fixed buffer represented by phospholipid charges in the plasma membrane. Our observations suggest that in this preparation, (1) some BK channels, but few if any of the Ca sensors that trigger release, are located within Ca nanodomains while a large fraction of both are located far enough from Ca channels to be blockable by EGTA, (2) the I is more sensitive than the excitatory postsynaptic current (EPSC) to [Ca] (K-26 μM vs. ~36 μM [Ca]); (3) with increasing [Ca], the I grows with a Hill coefficient of 2.5, the EPSC with a coefficient of 3.9; (4) release is dependent on the highest [Ca] achieved, independent of the time to reach it; (5) the varicosity synapses differ from mature frog nmjs in significant ways; and (6) BK channels are useful reporters of local [Ca].
Topics: Animals; Calcium; Neurotransmitter Agents; Cells, Cultured; Large-Conductance Calcium-Activated Potassium Channels; Neurons; Xenopus laevis; Muscle Cells; Synaptic Transmission; Synapses
PubMed: 38483240
DOI: 10.1111/ejn.16289