Aelfwin Stone, Oliver Cujic, Angel Rowlett, Sophia Aderhold, Emma Savage, Bruce Graham, Joern R Steinert
{"title":"Triose-phosphate isomerase deficiency is associated with a dysregulation of synaptic vesicle recycling in <i>Drosophila melanogaster</i>.","authors":"Aelfwin Stone, Oliver Cujic, Angel Rowlett, Sophia Aderhold, Emma Savage, Bruce Graham, Joern R Steinert","doi":"10.3389/fnsyn.2023.1124061","DOIUrl":"https://doi.org/10.3389/fnsyn.2023.1124061","url":null,"abstract":"<p><strong>Introduction: </strong>Numerous neurodegenerative diseases are associated with neuronal dysfunction caused by increased redox stress, often linked to aberrant production of redox-active molecules such as nitric oxide (NO) or oxygen free radicals. One such protein affected by redox-mediated changes is the glycolytic enzyme triose-phosphate isomerase (TPI), which has been shown to undergo 3-nitrotyrosination (a NO-mediated post-translational modification) rendering it inactive. The resulting neuronal changes caused by this modification are not well understood. However, associated glycation-induced cytotoxicity has been reported, thus potentially causing neuronal and synaptic dysfunction via compromising synaptic vesicle recycling.</p><p><strong>Methods: </strong>This work uses <i>Drosophila melanogaster</i> to identify the impacts of altered TPI activity on neuronal physiology, linking aberrant TPI function and redox stress to neuronal defects. We used <i>Drosophila</i> mutants expressing a missense allele of the TPI protein, M81T, identified in a previous screen and resulting in an inactive mutant of the TPI protein (<i>TPI<sup>M81T</sup></i> , wstd<sup>1</sup>). We assessed synaptic physiology at the glutamatergic <i>Drosophila</i> neuromuscular junction (NMJ), synapse morphology and behavioural phenotypes, as well as impacts on longevity.</p><p><strong>Results: </strong>Electrophysiological recordings of evoked and spontaneous excitatory junctional currents, alongside high frequency train stimulations and recovery protocols, were applied to investigate synaptic depletion and subsequent recovery. Single synaptic currents were unaltered in the presence of the wstd<sup>1</sup> mutation, but frequencies of spontaneous events were reduced. Wstd<sup>1</sup> larvae also showed enhanced vesicle depletion rates at higher frequency stimulation, and subsequent recovery times for evoked synaptic responses were prolonged. A computational model showed that TPI mutant larvae exhibited a significant decline in activity-dependent vesicle recycling, which manifests itself as increased recovery times for the readily-releasable vesicle pool. Confocal images of NMJs showed no morphological or developmental differences between wild-type and wstd<sup>1</sup> but TPI mutants exhibited learning impairments as assessed by olfactory associative learning assays.</p><p><strong>Discussion: </strong>Our data suggests that the wstd<sup>1</sup> phenotype is partially due to altered vesicle dynamics, involving a reduced vesicle pool replenishment, and altered endo/exocytosis processes. This may result in learning and memory impairments and neuronal dysfunction potentially also presenting a contributing factor to other reported neuronal phenotypes.</p>","PeriodicalId":12650,"journal":{"name":"Frontiers in Synaptic Neuroscience","volume":"15 ","pages":"1124061"},"PeriodicalIF":3.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10011161/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9131154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"GluN2B-NMDAR subunit contribution on synaptic plasticity: A phenomenological model for CA3-CA1 synapses.","authors":"Justinas J Dainauskas, Hélène Marie, Michele Migliore, Ausra Saudargiene","doi":"10.3389/fnsyn.2023.1113957","DOIUrl":"https://doi.org/10.3389/fnsyn.2023.1113957","url":null,"abstract":"<p><p>Synaptic plasticity is believed to be a key mechanism underlying learning and memory. We developed a phenomenological N-methyl-D-aspartate (NMDA) receptor-based voltage-dependent synaptic plasticity model for synaptic modifications at hippocampal CA3-CA1 synapses on a hippocampal CA1 pyramidal neuron. The model incorporates the GluN2A-NMDA and GluN2B-NMDA receptor subunit-based functions and accounts for the synaptic strength dependence on the postsynaptic NMDA receptor composition and functioning without explicitly modeling the NMDA receptor-mediated intracellular calcium, a local trigger of synaptic plasticity. We embedded the model into a two-compartmental model of a hippocampal CA1 pyramidal cell and validated it against experimental data of spike-timing-dependent synaptic plasticity (STDP), high and low-frequency stimulation. The developed model predicts altered learning rules in synapses formed on the apical dendrites of the detailed compartmental model of CA1 pyramidal neuron in the presence of the GluN2B-NMDA receptor hypofunction and can be used in hippocampal networks to model learning in health and disease.</p>","PeriodicalId":12650,"journal":{"name":"Frontiers in Synaptic Neuroscience","volume":"15 ","pages":"1113957"},"PeriodicalIF":3.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10050887/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9296614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Réka Bod, Kinga Tóth, Nour Essam, Estilla Zsófia Tóth, Loránd Erõss, László Entz, Attila G Bagó, Dániel Fabó, István Ulbert, Lucia Wittner
{"title":"Synaptic alterations and neuronal firing in human epileptic neocortical excitatory networks.","authors":"Réka Bod, Kinga Tóth, Nour Essam, Estilla Zsófia Tóth, Loránd Erõss, László Entz, Attila G Bagó, Dániel Fabó, István Ulbert, Lucia Wittner","doi":"10.3389/fnsyn.2023.1233569","DOIUrl":"https://doi.org/10.3389/fnsyn.2023.1233569","url":null,"abstract":"<p><p>Epilepsy is a prevalent neurological condition, with underlying neuronal mechanisms involving hyperexcitability and hypersynchrony. Imbalance between excitatory and inhibitory circuits, as well as histological reorganization are relatively well-documented in animal models or even in the human hippocampus, but less is known about human neocortical epileptic activity. Our knowledge about changes in the excitatory signaling is especially scarce, compared to that about the inhibitory cell population. This study investigated the firing properties of single neurons in the human neocortex <i>in vitro</i>, during pharmacological blockade of glutamate receptors, and additionally evaluated anatomical changes in the excitatory circuit in tissue samples from epileptic and non-epileptic patients. Both epileptic and non-epileptic tissues exhibited spontaneous population activity (SPA), NMDA receptor antagonization reduced SPA recurrence only in epileptic tissue, whereas further blockade of AMPA/kainate receptors reversibly abolished SPA emergence regardless of epilepsy. Firing rates did not significantly change in excitatory principal cells and inhibitory interneurons during pharmacological experiments. Granular layer (L4) neurons showed an increased firing rate in epileptic compared to non-epileptic tissue. The burstiness of neurons remained unchanged, except for that of inhibitory cells in epileptic recordings, which decreased during blockade of glutamate receptors. Crosscorrelograms computed from single neuron discharge revealed both mono- and polysynaptic connections, particularly involving intrinsically bursting principal cells. Histological investigations found similar densities of SMI-32-immunopositive long-range projecting pyramidal cells in both groups, and shorter excitatory synaptic active zones with a higher proportion of perforated synapses in the epileptic group. These findings provide insights into epileptic modifications from the perspective of the excitatory system and highlight discrete alterations in firing patterns and synaptic structure. Our data suggest that NMDA-dependent glutamatergic signaling, as well as the excitatory synaptic machinery are perturbed in epilepsy, which might contribute to epileptic activity in the human neocortex.</p>","PeriodicalId":12650,"journal":{"name":"Frontiers in Synaptic Neuroscience","volume":"15 ","pages":"1233569"},"PeriodicalIF":3.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10450510/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10105808","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Julianna Goenaga, Alfonso Araque, Paulo Kofuji, Daniela Herrera Moro Chao
{"title":"Calcium signaling in astrocytes and gliotransmitter release.","authors":"Julianna Goenaga, Alfonso Araque, Paulo Kofuji, Daniela Herrera Moro Chao","doi":"10.3389/fnsyn.2023.1138577","DOIUrl":"https://doi.org/10.3389/fnsyn.2023.1138577","url":null,"abstract":"<p><p>Glia are as numerous in the brain as neurons and widely known to serve supportive roles such as structural scaffolding, extracellular ionic and neurotransmitter homeostasis, and metabolic support. However, over the past two decades, several lines of evidence indicate that astrocytes, which are a type of glia, play active roles in neural information processing. Astrocytes, although not electrically active, can exhibit a form of excitability by dynamic changes in intracellular calcium levels. They sense synaptic activity and release neuroactive substances, named gliotransmitters, that modulate neuronal activity and synaptic transmission in several brain areas, thus impacting animal behavior. This \"dialogue\" between astrocytes and neurons is embodied in the concept of the tripartite synapse that includes astrocytes as integral elements of synaptic function. Here, we review the recent work and discuss how astrocytes <i>via</i> calcium-mediated excitability modulate synaptic information processing at various spatial and time scales.</p>","PeriodicalId":12650,"journal":{"name":"Frontiers in Synaptic Neuroscience","volume":"15 ","pages":"1138577"},"PeriodicalIF":3.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10017551/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9518873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rodrigo Del Rio, Rosa G Serrano, Eric Gomez, Joshua C Martinez, Marina A Edward, Rommel A Santos, Kenneth S Diaz, Susana Cohen-Cory
{"title":"Cell-autonomous and differential endocannabinoid signaling impacts the development of presynaptic retinal ganglion cell axon connectivity <i>in vivo</i>.","authors":"Rodrigo Del Rio, Rosa G Serrano, Eric Gomez, Joshua C Martinez, Marina A Edward, Rommel A Santos, Kenneth S Diaz, Susana Cohen-Cory","doi":"10.3389/fnsyn.2023.1176864","DOIUrl":"https://doi.org/10.3389/fnsyn.2023.1176864","url":null,"abstract":"<p><p>Cannabis exposure during gestation evokes significant molecular modifications to neurodevelopmental programs leading to neurophysiological and behavioral abnormalities in humans. The main neuronal receptor for Δ<sup>9</sup>-tetrahydrocannabinol (THC) is the type-1 cannabinoid receptor CB<sub>1</sub>R, one of the most abundant G-protein-coupled receptors in the nervous system. While THC is the major psychoactive phytocannabinoid, endocannabinoids (eCBs) are the endogenous ligands of CB<sub>1</sub>R and are known to act as retrograde messengers to modulate synaptic plasticity at different time scales in the adult brain. Accumulating evidence indicates that eCB signaling through activation of CB<sub>1</sub>R plays a central role in neural development. During development, most CB<sub>1</sub>R localized to axons of projection neurons, and in mice eCB signaling impacts axon fasciculation. Understanding of eCB-mediated structural plasticity during development, however, requires the identification of the precise spatial and temporal dynamics of CB<sub>1</sub>R-mediated modifications at the level of individual neurons in the intact brain. Here, the cell-autonomous role of CB<sub>1</sub>R and the effects of CB<sub>1</sub>R-mediated eCB signaling were investigated using targeted single-cell knockdown and pharmacologic treatments in <i>Xenopus</i>. We imaged axonal arbors of retinal ganglion cells (RGCs) in real time following downregulation of CB<sub>1</sub>R <i>via</i> morpholino (MO) knockdown. We also analyzed RGC axons with altered eCB signaling following treatment with URB597, a selective inhibitor of the enzyme that degrades Anandamide (AEA), or JZL184, an inhibitor of the enzyme that blocks 2-Arachidonoylglycerol (2-AG) hydrolysis, at two distinct stages of retinotectal development. Our results demonstrate that CB<sub>1</sub>R knockdown impacts RGC axon branching at their target and that differential 2-AG and AEA-mediated eCB signaling contributes to presynaptic structural connectivity at the time that axons terminate and when retinotectal synaptic connections are made. Altering CB<sub>1</sub>R levels through CB<sub>1</sub>R MO knockdown similarly impacted dendritic morphology of tectal neurons, thus supporting both pre- and postsynaptic cell-autonomous roles for CB<sub>1</sub>R-mediated eCB signaling.</p>","PeriodicalId":12650,"journal":{"name":"Frontiers in Synaptic Neuroscience","volume":"15 ","pages":"1176864"},"PeriodicalIF":3.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10213524/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9918573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Graham M Pitcher, Livia Garzia, A Sorana Morrissy, Michael D Taylor, Michael W Salter
{"title":"Synapse-specific diversity of distinct postsynaptic GluN2 subtypes defines transmission strength in spinal lamina I.","authors":"Graham M Pitcher, Livia Garzia, A Sorana Morrissy, Michael D Taylor, Michael W Salter","doi":"10.3389/fnsyn.2023.1197174","DOIUrl":"https://doi.org/10.3389/fnsyn.2023.1197174","url":null,"abstract":"<p><p>The unitary postsynaptic response to presynaptic quantal glutamate release is the fundamental basis of excitatory information transfer between neurons. The view, however, of individual glutamatergic synaptic connections in a population as homogenous, fixed-strength units of neural communication is becoming increasingly scrutinized. Here, we used minimal stimulation of individual glutamatergic afferent axons to evoke single synapse resolution postsynaptic responses from central sensory lamina I neurons in an <i>ex vivo</i> adult rat spinal slice preparation. We detected unitary events exhibiting a NMDA receptor component with distinct kinetic properties across synapses conferred by specific GluN2 subunit composition, indicative of GluN2 subtype-based postsynaptic heterogeneity. GluN2A, 2A and 2B, or 2B and 2D synaptic predominance functioned on distinct lamina I neuron types to narrowly, intermediately, or widely tune, respectively, the duration of evoked unitary depolarization events from resting membrane potential, which enabled individual synapses to grade differentially depolarizing steps during temporally patterned afferent input. Our results lead to a model wherein a core locus of proteomic complexity prevails at this central glutamatergic sensory synapse that involves distinct GluN2 subtype configurations. These findings have major implications for subthreshold integrative capacity and transmission strength in spinal lamina I and other CNS regions.</p>","PeriodicalId":12650,"journal":{"name":"Frontiers in Synaptic Neuroscience","volume":"15 ","pages":"1197174"},"PeriodicalIF":3.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10368998/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9942067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Timo Ueberbach, Clara A Simacek, Irmgard Tegeder, Sergei Kirischuk, Thomas Mittmann
{"title":"Tonic activation of GABA<sub>B</sub> receptors via GAT-3 mediated GABA release reduces network activity in the developing somatosensory cortex in GAD67-GFP mice.","authors":"Timo Ueberbach, Clara A Simacek, Irmgard Tegeder, Sergei Kirischuk, Thomas Mittmann","doi":"10.3389/fnsyn.2023.1198159","DOIUrl":"https://doi.org/10.3389/fnsyn.2023.1198159","url":null,"abstract":"<p><p>The efficiency of neocortical information processing critically depends on the balance between the glutamatergic (excitatory, E) and GABAergic (inhibitory, I) synaptic transmission. A transient imbalance of the E/I-ratio during early development might lead to neuropsychiatric disorders later in life. The transgenic glutamic acid decarboxylase 67-green fluorescent protein (GAD67-GFP) mouse line (KI) was developed to selectively visualize GABAergic interneurons in the CNS. However, haplodeficiency of the GAD67 enzyme, the main GABA synthetizing enzyme in the brain, temporarily leads to a low GABA level in the developing brain of these animals. However, KI mice did not demonstrate any epileptic activity and only few and mild behavioral deficits. In the present study we investigated how the developing somatosensory cortex of KI-mice compensates the reduced GABA level to prevent brain hyperexcitability. Whole-cell patch clamp recordings from layer 2/3 pyramidal neurons at P14 and at P21 revealed a reduced frequency of miniature inhibitory postsynaptic currents (mIPSCs) in KI mice without any change in amplitude or kinetics. Interestingly, mEPSC frequencies were also decreased, while the E/I-ratio was nevertheless shifted toward excitation. Surprisingly, multi-electrode-recordings (MEA) from acute slices revealed a decreased spontaneous neuronal network activity in KI mice compared to wild-type (WT) littermates, pointing to a compensatory mechanism that prevents hyperexcitability. Blockade of GABA<sub>B</sub> receptors (GABA<sub>B</sub>Rs) with CGP55845 strongly increased the frequency of mEPSCs in KI, but failed to affect mIPSCs in any genotype or age. It also induced a membrane depolarization in P14 KI, but not in P21 KI or WT mice. MEA recordings in presence of CGP55845 revealed comparable levels of network activity in both genotypes, indicating that tonically activated GABA<sub>B</sub>Rs balance neuronal activity in P14 KI cortex despite the reduced GABA levels. Blockade of GABA transporter 3 (GAT-3) reproduced the CGP55845 effects suggesting that tonic activation of GABA<sub>B</sub>Rs is mediated by ambient GABA released via GAT-3 operating in reverse mode. We conclude that GAT-3-mediated GABA release leads to tonic activation of both pre- and postsynaptic GABA<sub>B</sub>Rs and restricts neuronal excitability in the developing cortex to compensate for reduced neuronal GABA synthesis. Since GAT-3 is predominantly located in astrocytes, GAD67 haplodeficiency may potentially stimulate astrocytic GABA synthesis through GAD67-independent pathways.</p>","PeriodicalId":12650,"journal":{"name":"Frontiers in Synaptic Neuroscience","volume":"15 ","pages":"1198159"},"PeriodicalIF":3.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10267986/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9657825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}