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International Journal of Molecular... Aug 2023Proton-gated channels of the ASIC family are widely distributed in central neurons, suggesting their role in common neurophysiological functions. They are involved in...
Proton-gated channels of the ASIC family are widely distributed in central neurons, suggesting their role in common neurophysiological functions. They are involved in glutamatergic neurotransmission and synaptic plasticity; however, the exact function of these channels remains unclear. One problem is that acidification of the synaptic cleft due to the acidic content of synaptic vesicles has opposite effects on ionotropic glutamate receptors and ASICs. Thus, the pH values required to activate ASICs strongly inhibit AMPA receptors and almost completely inhibit NMDA receptors. This, in turn, suggests that ASICs can provide compensation for post-synaptic responses in the case of significant acidifications. We tested this hypothesis by patch-clamp recordings of rat brain neuron responses to acidifications and glutamate receptor agonists at different pH values. Hippocampal pyramidal neurons have much lower ASICs than glutamate receptor responses, whereas striatal interneurons show the opposite ratio. Cortical pyramidal neurons and hippocampal interneurons show similar amplitudes in their responses to acidification and glutamate. Consequently, the total response to glutamate agonists at different pH levels remains rather stable up to pH 6.2. Besides these pH effects, the relationship between the responses mediated by glutamate receptors and ASICs depends on the presence of Mg and the membrane voltage. Together, these factors create a complex picture that provides a framework for understanding the role of ASICs in synaptic transmission and synaptic plasticity.
Topics: Animals; Rats; Synapses; Synaptic Vesicles; Synaptic Transmission; Corpus Striatum; Excitatory Amino Acid Agonists; Glutamic Acid
PubMed: 37629153
DOI: 10.3390/ijms241612974 -
Cold Spring Harbor Perspectives in... Apr 2024The synapse is the communication unit of the brain, linking billions of neurons through trillions of synaptic connections. The lipid landscape of the synaptic membrane... (Review)
Review
The synapse is the communication unit of the brain, linking billions of neurons through trillions of synaptic connections. The lipid landscape of the synaptic membrane underpins neurotransmitter release through the exocytic fusion of neurotransmitter-containing vesicles, endocytic recycling of these synaptic vesicles, and the postsynaptic response following binding of the neurotransmitter to specialized receptors. How the connected brain can learn and acquire memories through synaptic plasticity is unresolved. Phospholipases, and especially the phospholipase A1 isoform DDHD2, have recently been shown to play a critical role in memory acquisition through the generation of saturated free fatty acids such as myristic and palmitic acids. This emerging synaptic plasticity pathway suggests that phospholipases cannot only respond to synaptic activity by altering the phospholipid landscape but also contribute to the establishment of long-term memories in our brain.
Topics: Synaptic Membranes; Phospholipases; Synapses; Synaptic Transmission; Neurotransmitter Agents; Neuronal Plasticity
PubMed: 38151329
DOI: 10.1101/cshperspect.a041405 -
Journal of Neurochemistry Apr 2024Skeletal muscle fiber is a large syncytium with multiple and evenly distributed nuclei. Adult subsynaptic myonuclei beneath the neuromuscular junction (NMJ) express...
Skeletal muscle fiber is a large syncytium with multiple and evenly distributed nuclei. Adult subsynaptic myonuclei beneath the neuromuscular junction (NMJ) express specific genes, the products of which coordinately function in the maintenance of the pre- and post-synaptic regions. However, the gene expression profiles that promote the NMJ formation during embryogenesis remain largely unexplored. We performed single-nucleus RNA sequencing (snRNA-seq) analysis of embryonic and neonatal mouse diaphragms, and found that each myonucleus had a distinct transcriptome pattern during the NMJ formation. Among the previously reported NMJ-constituting genes, Dok7, Chrna1, and Chrnd are specifically expressed in subsynaptic myonuclei at E18.5. In the E18.5 diaphragm, ca. 10.7% of the myonuclei express genes for the NMJ formation (Dok7, Chrna1, and Chrnd) together with four representative β-catenin regulators (Amotl2, Ptprk, Fam53b, and Tcf7l2). Additionally, the temporal gene expression patterns of these seven genes are synchronized in differentiating C2C12 myoblasts. Amotl2 and Ptprk are expressed in the sarcoplasm, where β-catenin serves as a structural protein to organize the membrane-anchored NMJ structure. In contrast, Fam53b and Tcf7l2 are expressed in the myonucleus, where β-catenin serves as a transcriptional coactivator in Wnt/β-catenin signaling at the NMJ. In C2C12 myotubes, knockdown of Amotl2 or Ptprk markedly, and that of Fam53b and Tcf7l2 less efficiently, impair the clustering of acetylcholine receptors. In contrast, knockdown of Fam53b and Tcf7l2, but not of Amotl2 or Ptprk, impairs the gene expression of Slit2 encoding an axonal attractant for motor neurons, which is required for the maturation of motor nerve terminal. Thus, Amotl2 and Ptprk exert different roles at the NM compared to Fam53b and Tcf7l2. Additionally, Wnt ligands originating from the spinal motor neurons and the perichondrium/chondrocyte are likely to work remotely on the subsynaptic nuclei and the myotendinous junctional nuclei, respectively. We conclude that snRNA-seq analysis of embryonic/neonatal diaphragms reveal a novel coordinated expression profile especially in the Wnt/β-catenin signaling that regulate the formation of the embryonic NMJ.
Topics: Mice; Animals; Transcriptome; beta Catenin; Neuromuscular Junction; Wnt Signaling Pathway; RNA, Small Nuclear; Embryonic Development; Muscle, Skeletal; Receptors, Cholinergic
PubMed: 37994470
DOI: 10.1111/jnc.16013 -
The Journal of Pharmacology and... Sep 2023The effects of a general anesthetic xenon (Xe) on spontaneous, miniature, electrically evoked synaptic transmissions were examined using the "synapse bouton...
The effects of a general anesthetic xenon (Xe) on spontaneous, miniature, electrically evoked synaptic transmissions were examined using the "synapse bouton preparation," with which we can clearly evaluate pure synaptic responses and accurately quantify pre- and postsynaptic transmissions. Glycinergic and glutamatergic transmissions were investigated in rat spinal sacral dorsal commissural nucleus and hippocampal CA3 neurons, respectively. Xe presynaptically inhibited spontaneous glycinergic transmission, the effect of which was resistant to tetrodotoxin, Cd, extracellular Ca, thapsigargin (a selective sarcoplasmic/endoplasmic reticulum Ca-ATPase inhibitor), SQ22536 (an adenylate cyclase inhibitor), 8-Br-cAMP (membrane-permeable cAMP analog), ZD7288 (an hyperpolarization-activated cyclic nucleotide-gated channel blocker), chelerythrine (a PKC inhibitor), and KN-93 (a CaMKII inhibitor) while being sensitive to PKA inhibitors (H-89, KT5720, and Rp-cAMPS). Moreover, Xe inhibited evoked glycinergic transmission, which was canceled by KT5720. Like glycinergic transmission, spontaneous and evoked glutamatergic transmissions were also inhibited by Xe in a KT5720-sensitive manner. Our results suggest that Xe decreases glycinergic and glutamatergic spontaneous and evoked transmissions at the presynaptic level in a PKA-dependent manner. These presynaptic responses are independent of Ca dynamics. We conclude that PKA can be the main molecular target of Xe in the inhibitory effects on both inhibitory and excitatory neurotransmitter release. SIGNIFICANCE STATEMENT: Spontaneous and evoked glycinergic and glutamatergic transmissions were investigated using the whole-cell patch clamp technique in rat spinal sacral dorsal commissural nucleus and hippocampal CA3 neurons, respectively. Xenon (Xe) significantly inhibited glycinergic and glutamatergic transmission presynaptically. As a signaling mechanism, protein kinase A was responsible for the inhibitory effects of Xe on both glycine and glutamate release. These results may help understand how Xe modulates neurotransmitter release and exerts its excellent anesthetic properties.
Topics: Rats; Animals; Rats, Wistar; Xenon; Cyclic AMP-Dependent Protein Kinases; Neurons; Synaptic Transmission; Presynaptic Terminals; Hippocampus; Spinal Cord; Neurotransmitter Agents
PubMed: 37391223
DOI: 10.1124/jpet.123.001599 -
Proceedings of the National Academy of... Jun 2024Synapses containing γ-aminobutyric acid (GABA) constitute the primary centers for inhibitory neurotransmission in our nervous system. It is unclear how these synaptic...
Synapses containing γ-aminobutyric acid (GABA) constitute the primary centers for inhibitory neurotransmission in our nervous system. It is unclear how these synaptic structures form and align their postsynaptic machineries with presynaptic terminals. Here, we monitored the cellular distribution of several GABAergic postsynaptic proteins in a purely glutamatergic neuronal culture derived from human stem cells, which virtually lacks any vesicular GABA release. We found that several GABA receptor (GABAR) subunits, postsynaptic scaffolds, and major cell-adhesion molecules can reliably coaggregate and colocalize at even GABA-deficient subsynaptic domains, but remain physically segregated from glutamatergic counterparts. Genetic deletions of both Gephyrin and a Gephyrin-associated guanosine di- or triphosphate (GDP/GTP) exchange factor Collybistin severely disrupted the coassembly of these postsynaptic compositions and their proper apposition with presynaptic inputs. Gephyrin-GABAR clusters, developed in the absence of GABA transmission, could be subsequently activated and even potentiated by delayed supply of vesicular GABA. Thus, molecular organization of GABAergic postsynapses can initiate via a GABA-independent but Gephyrin-dependent intrinsic mechanism.
Topics: Humans; Membrane Proteins; gamma-Aminobutyric Acid; Receptors, GABA-A; Carrier Proteins; Presynaptic Terminals; Synapses; Synaptic Transmission; Rho Guanine Nucleotide Exchange Factors
PubMed: 38889143
DOI: 10.1073/pnas.2315100121 -
Developmental Dynamics : An Official... Aug 2023The local signaling mechanism which directly assembles and maintains glutamatergic synapses has not been well understood. Glutamatergic synapses are made of presynaptic... (Review)
Review
The local signaling mechanism which directly assembles and maintains glutamatergic synapses has not been well understood. Glutamatergic synapses are made of presynaptic and postsynaptic compartments with distinct sets of proteins. The planar cell polarity (PCP) pathway is highly conserved and responsible for establishing and maintaining the cell and tissue polarity along the tissue plane. The six core PCP proteins form antagonizing complexes within the cells and asymmetric intercellular complexes across neighboring cells which regulate cell-cell interactions during planar polarity signaling. Accumulating evidence suggests that the PCP proteins play essential roles in glutamatergic synapse assembly, maintenance and function in the brain. This review summarizes the key evidence that PCP proteins may be responsible for the formation and stability of the vast majority of the glutamatergic synapses in hippocampus and medial prefrontal cortex, the progress in understanding the mechanisms of how PCP proteins assemble and maintain glutamatergic synapses and initial insights on how disruption of the function of the PCP proteins can lead to neurodegenerative, neurodevelopmental and neuropsychiatric disorders. The PCP proteins may be the missing pieces of a long-standing puzzle and filling this gap of knowledge may provide the basis for understanding many unsolved questions in synapse biology.
Topics: Cell Polarity; Signal Transduction; Membrane Proteins; Synapses
PubMed: 36780134
DOI: 10.1002/dvdy.574 -
PLoS Biology Mar 2024Proteome analyses of the postsynaptic density (PSD), a proteinaceous specialization beneath the postsynaptic membrane of excitatory synapses, have identified several... (Meta-Analysis)
Meta-Analysis
Proteome analyses of the postsynaptic density (PSD), a proteinaceous specialization beneath the postsynaptic membrane of excitatory synapses, have identified several thousands of proteins. While proteins with predictable functions have been well studied, functionally uncharacterized proteins are mostly overlooked. In this study, we conducted a comprehensive meta-analysis of 35 PSD proteome datasets, encompassing a total of 5,869 proteins. Employing a ranking methodology, we identified 97 proteins that remain inadequately characterized. From this selection, we focused our detailed analysis on the highest-ranked protein, FAM81A. FAM81A interacts with PSD proteins, including PSD-95, SynGAP, and NMDA receptors, and promotes liquid-liquid phase separation of those proteins in cultured cells or in vitro. Down-regulation of FAM81A in cultured neurons causes a decrease in the size of PSD-95 puncta and the frequency of neuronal firing. Our findings suggest that FAM81A plays a crucial role in facilitating the interaction and assembly of proteins within the PSD, and its presence is important for maintaining normal synaptic function. Additionally, our methodology underscores the necessity for further characterization of numerous synaptic proteins that still lack comprehensive understanding.
Topics: Proteome; Phase Separation; Disks Large Homolog 4 Protein; Synapses; Synaptic Membranes
PubMed: 38452102
DOI: 10.1371/journal.pbio.3002006 -
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 -
Microsystems & Nanoengineering 2023Spiking neural networks (SNNs) have immense potential due to their utilization of synaptic plasticity and ability to take advantage of temporal correlation and low power...
Synaptic transistor with multiple biological functions based on metal-organic frameworks combined with the LIF model of a spiking neural network to recognize temporal information.
Spiking neural networks (SNNs) have immense potential due to their utilization of synaptic plasticity and ability to take advantage of temporal correlation and low power consumption. The leaky integration and firing (LIF) model and spike-timing-dependent plasticity (STDP) are the fundamental components of SNNs. Here, a neural device is first demonstrated by zeolitic imidazolate frameworks (ZIFs) as an essential part of the synaptic transistor to simulate SNNs. Significantly, three kinds of typical functions between neurons, the memory function achieved through the hippocampus, synaptic weight regulation and membrane potential triggered by ion migration, are effectively described through short-term memory/long-term memory (STM/LTM), long-term depression/long-term potentiation (LTD/LTP) and LIF, respectively. Furthermore, the update rule of iteration weight in the backpropagation based on the time interval between presynaptic and postsynaptic pulses is extracted and fitted from the STDP. In addition, the postsynaptic currents of the channel directly connect to the very large scale integration (VLSI) implementation of the LIF mode that can convert high-frequency information into spare pulses based on the threshold of membrane potential. The leaky integrator block, firing/detector block and frequency adaptation block instantaneously release the accumulated voltage to form pulses. Finally, we recode the steady-state visual evoked potentials (SSVEPs) belonging to the electroencephalogram (EEG) with filter characteristics of LIF. SNNs deeply fused by synaptic transistors are designed to recognize the 40 different frequencies of EEG and improve accuracy to 95.1%. This work represents an advanced contribution to brain-like chips and promotes the systematization and diversification of artificial intelligence.
PubMed: 37484501
DOI: 10.1038/s41378-023-00566-4 -
Biological Psychiatry Nov 2023Loss-of-function mutations in the contactin-associated protein-like 2 (CNTNAP2) gene are causal for neurodevelopmental disorders, including autism, schizophrenia,...
BACKGROUND
Loss-of-function mutations in the contactin-associated protein-like 2 (CNTNAP2) gene are causal for neurodevelopmental disorders, including autism, schizophrenia, epilepsy, and intellectual disability. CNTNAP2 encodes CASPR2, a single-pass transmembrane protein that belongs to the neurexin family of cell adhesion molecules. These proteins have a variety of functions in developing neurons, including connecting presynaptic and postsynaptic neurons, and mediating signaling across the synapse.
METHODS
To study the effect of loss of CNTNAP2 function on human cerebral cortex development, and how this contributes to the pathogenesis of neurodevelopmental disorders, we generated human induced pluripotent stem cells from one neurotypical control donor null for full-length CNTNAP2, modeling cortical development from neurogenesis through to neural network formation in vitro.
RESULTS
CNTNAP2 is particularly highly expressed in the first two populations of early-born excitatory cortical neurons, and loss of CNTNAP2 shifted the relative proportions of these two neuronal types. Live imaging of excitatory neuronal growth showed that loss of CNTNAP2 reduced neurite branching and overall neuronal complexity. At the network level, developing cortical excitatory networks null for CNTNAP2 had complex changes in activity compared with isogenic controls: an initial period of relatively reduced activity compared with isogenic controls, followed by a lengthy period of hyperexcitability, and then a further switch to reduced activity.
CONCLUSIONS
Complete loss of CNTNAP2 contributes to the pathogenesis of neurodevelopmental disorders through complex changes in several aspects of human cerebral cortex excitatory neuron development that culminate in aberrant neural network formation and function.
Topics: Humans; Autistic Disorder; Cerebral Cortex; Induced Pluripotent Stem Cells; Loss of Function Mutation; Membrane Proteins; Nerve Net; Nerve Tissue Proteins; Neurodevelopmental Disorders; Neurogenesis; Neurons; Schizophrenia
PubMed: 37001843
DOI: 10.1016/j.biopsych.2023.03.014