Glutamatergic Synapses Research Articles

A biallelic mutation in CACNA2D2 associated with developmental and epileptic encephalopathy affects calcium channel-dependent as well as synaptic functions of α2δ-2.

α2δ proteins serve as auxiliary subunits of voltage-gated calcium channels and regulate channel membrane expression and current properties. Besides their channel function, α2δ proteins regulate synapse formation, differentiation, and synaptic wiring. Considering these important functions, it is not surprising that CACNA2D1-4, the genes encoding for α2δ-1 to -4 isoforms, have been implicated in neurological, neurodevelopmental, and neuropsychiatric disorders. Mutations in CACNA2D2 have been associated with developmental and epileptic encephalopathy (DEE) and cerebellar atrophy. In our present study, we performed a detailed functional characterization of the p.R593P mutation in α2δ-2, a homozygous mutation previously identified in two siblings with DEE. Importantly, we analyzed both calcium channel-dependent as well as synaptic functions of α2δ-2. Our data show that the corresponding p.R596P mutation in mouse α2δ-2 drastically decreases membrane expression and synaptic targeting of α2δ-2. This defect correlates with altered biophysical properties of postsynaptic CaV1.3 channel but has no effect on presynaptic CaV2.1 channels upon heterologous expression in tsA201 cells. However, homologous expression of α2δ-2_R596P in primary cultures of hippocampal neurons affects the ability of α2δ-2 to induce a statistically significant increase in the presynaptic abundance of endogenous CaV2.1 channels and presynaptic calcium transients. Moreover, our data demonstrate that in addition to lowering membrane expression, the p.R596P mutation reduces the trans-synaptic recruitment of GABAA receptors and presynaptic synapsin clustering in glutamatergic synapses. Lastly, the α2δ-2_R596P reduces the amplitudes of glutamatergic miniature postsynaptic currents in transduced hippocampal neurons. Taken together, our data strongly link the human biallelic p.R593P mutation to the underlying severe neurodevelopmental disorder and highlight the importance of studying α2δ mutations not only in the context of channelopathies but also synaptopathies.

Aberrant generation of dentate gyrus granule cells is associated with epileptic susceptibility in p53 conditional knockout mice.

Neuronal apoptosis is a mechanism used to clear the cells of oxidative stress or DNA damage and refine the final number of neurons for a functional neuronal circuit. The tumor suppressor protein p53 is a key regulator of the cell cycle and serves as a checkpoint for eliminating neurons with high DNA damage, hyperproliferative signals or cellular stress. During development, p53 is largely expressed in progenitor cells. In the adult brain, p53 expression is restricted to the neurogenic niches where it regulates cell proliferation and self-renewal. To investigate the functional consequences of p53 deletion in the cortex and hippocampus, we generated a conditional mutant mouse (p53-cKO) in which p53 is deleted from pallial progenitors and their derivatives. Surprisingly, we did not find any significant change in the number of neurons in the mutant cortex or CA region of the hippocampus compared with control mice. However, p53-cKO mice exhibit more proliferative cells in the subgranular zone of the dentate gyrus and more granule cells in the granular cell layer. Glutamatergic synapses in the CA3 region are more numerous in p53-cKO mice compared with control littermates, which correlates with overexcitability and higher epileptic susceptibility in the mutant mice.

Glutamate, Gangliosides, and the Synapse: Electrostatics at Work in the Brain.

The synapse is a piece of information transfer machinery replacing the electrical conduction of nerve impulses at the end of the neuron. Like many biological mechanisms, its functioning is heavily affected by time constraints. The solution selected by evolution is based on chemical communication that, in theory, cannot compete with the speed of nerve conduction. Nevertheless, biochemical and biophysical compensation mechanisms mitigate this intrinsic weakness: (i) through the high concentrations of neurotransmitters inside the synaptic vesicles; (ii) through the concentration of neurotransmitter receptors in lipid rafts, which are signaling platforms; indeed, the presence of raft lipids, such as gangliosides and cholesterol, allows a fine tuning of synaptic receptors by these lipids; (iii) through the negative electrical charges of the gangliosides, which generate an attractive (for cationic neurotransmitters, such as serotonin) or repulsive (for anionic neurotransmitters, such as glutamate) electric field. This electric field controls the flow of glutamate in the tripartite synapse involving pre- and post-synaptic neurons and the astrocyte. Changes in the expression of brain gangliosides can disrupt the functioning of the glutamatergic synapse, causing fatal diseases, such as Rett syndrome. In this review, we propose an in-depth analysis of the role of gangliosides in the glutamatergic synapse, highlighting the primordial and generally overlooked role played by the electric field of synaptic gangliosides.

Mahuang Fuzi Xixin decoction: A potent analgesic for neuropathic pain targeting the NMDAR2B/CaMKIIα/ERK/CREB pathway

Neuropathic pain (NeP) is a condition charactesized by nervous system injury or dysfunction that affects a significant portion of the population. Current treatments are ineffective, highlighting the need for novel therapeutic approaches. Mahuang Fuzi Xixin decoction (MFXD) has shown promise for treating pain conditions in clinical practice; however, its potential against NeP and the underlying mechanisms remain unclear. This study identified 35 compounds in MFXD using ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS). The analgesic effects of MFXD on chronic constriction injury (CCI) rats were evaluated through the detection of mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL). The analgesic effects of MFXD in rats with chronic constriction injury (CCI) were evaluated by measuring the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL). Low-dose MFXD (L-MFXD) group (4.8 g/kg) and high-dose MFXD (H-MFXD) group (9.6 g/kg) exhibited significantly higher MWT and TWL values than the CCI group on days 11 and 15 post-CCI surgery, substantiating the remarkable analgesic efficacy of MFXD. Network pharmacology analysis identified 58 key targets enriched in pathways such as long-term potentiation (LTP) and glutamatergic synapse. The MCODE algorithm further identified core targets with significant enrichment in LTP. Molecular docking revealed that mesaconitine, rosmarinic acid, and delgrandine from MFXD exhibited high binding affinity with NMDAR2B (−11 kcal/mol), CaMKIIα (−14.3 kcal/mol), and ERK (−10.8 kcal/mol). Western blot and immunofluorescence confirmed that H-MFXD significantly suppressed the phosphorylation levels of NMDAR2B, CaMKIIα, ERK, and CREB in the spinal cord tissue of CCI rats. In conclusion, this study demonstrates that MFXD possesses potent analgesic effects on NeP by suppressing the NMDAR2B/CaMKIIα/ERK/CREB signalling pathway. This study unlocks a path toward potentially revolutionising NeP treatment with MFXD, encouraging further research and clinical development.

α-Bungarotoxin labelling of AMPA receptor-associated TARPs in living neurons

In mammalian central neurons AMPARs are clustered at glutamatergic synapses where they mediate fast excitatory transmission. In addition to four pore-forming subunits (GluA1-4), AMPARs contain auxiliary transmembrane AMPAR regulatory proteins (γ2, γ3, γ4, γ5, γ7 or γ8) whose incorporation can vary between neuron types, brain regions, and stages of development. As well as modulating the functional properties of AMPARs, these auxiliary subunits play a central role in AMPAR trafficking. Directly visualizing TARPs could therefore provide a valuable insight into mechanisms underlying these processes. Although antibodies are routinely used for the detection of surface proteins, our experience suggests anti-TARP antibodies are too bulky to access their target, possibly due to close interactions between the extracellular domains of TARP and AMPAR subunits. We therefore assessed the utility of a small monovalent probe – fluorescent α-bungarotoxin (α-Btx) – for TARP labelling in living neurons. We inserted the bungarotoxin binding site (BBS) within the extracellular domain of TARPs to enable their detection in cells exposed to fluorescent α-Btx. Focusing on the prototypical TARP γ2, we demonstrate that the small size of fluorescent α-Btx allows it to bind to the BBS-tagged TARP when associated with AMPARs. Importantly, labelled γ2 enhances AMPAR function in the same way as unmodified γ2. In living neurons, fluorescent α-Btx-labelled γ2 associates with AMPAR clusters at synapses. As a proof-of-principle, we employed our method to compare the surface trafficking of γ2 and γ7 in cerebellar stellate neurons. Our approach provides a simple way to visualize TARPs within AMPARs in living cells.

Scavenger Receptor Class B Type I Modulates Epileptic Seizures and Receptor α2δ-1 Expression.

Scavenger receptor class B type I (SR-BI) is abundant in adult mouse and human brains, but its function in the central nervous system (CNS) remains unclear. This study explored the role of SR-BI in epilepsy and its possible underlying mechanism. Expression patterns of SR-BI in the brains of mice with kainic acid (KA)-induced epilepsy were detected using immunofluorescence staining, quantitative real-time polymerase chain reaction (qPCR), and Western blotting(WB). Behavioral analysis was performed by 24-hour video monitoring and hippocampal local field potential (LFP) recordings were employed to verify the role of SR-BI in epileptogenesis. RNA sequencing (RNA-seq) was used to obtain biological information on SR-BI in the CNS. WB, qPCR, and co-immunoprecipitation (Co-IP) were performed to identify the relationship between SR-BI and the gabapentin receptor α2δ-1.The results showed that SR-BI was primarily co-localized with astrocytes and its expression was down-regulated in the hippocampus of KA mice. Notably, overexpressing SR-BI alleviated the epileptic behavioral phenotype in KA mice. Hippocampal transcriptomic analysis revealed 1043 differentially expressed genes (DEGs) in the SR-BI-overexpressing group. Most DEGs confirmed by RNA-seq analysis were associated with synapses, neuronal projections, neuron development, and ion binding. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis demonstrated that the DEGs were enriched in the glutamatergic synapse pathway. Furthermore, the gabapentin receptor α2δ-1 decreased with SR-BI overexpression in epileptic mice. Overall, these findings highlight the important role of SR-BI in regulating epileptogenesis and that the gabapentin receptor α2δ-1 is a potential downstream target of SR-BI.

RNA editing regulates glutamatergic synapses in the frontal cortex of a molecular subtype of Amyotrophic Lateral Sclerosis

BackgroundAmyotrophic Lateral Sclerosis (ALS) is a highly heterogenous neurodegenerative disorder that primarily affects upper and lower motor neurons, affecting additional cell types and brain regions. Underlying molecular mechanisms are still elusive, in part due to disease heterogeneity. Molecular disease subtyping through integrative analyses including RNA editing profiling is a novel approach for identification of molecular networks involved in pathogenesis.MethodsWe aimed to highlight the role of RNA editing in ALS, focusing on the frontal cortex and the prevalent molecular disease subtype (ALS-Ox), previously determined by transcriptomic profile stratification. We established global RNA editing (editome) and gene expression (transcriptome) profiles in control and ALS-Ox cases, utilizing publicly available RNA-seq data (GSE153960) and an in-house analysis pipeline. Functional annotation and pathway analyses identified molecular processes affected by RNA editing alterations. Pearson correlation analyses assessed RNA editing effects on expression. Similar analyses on additional ALS-Ox and control samples (GSE124439) were performed for verification. Targeted re-sequencing and qRT-PCR analysis targeting CACNA1C, were performed using frontal cortex tissue from ALS and control samples (n = 3 samples/group).ResultsWe identified reduced global RNA editing in the frontal cortex of ALS-Ox cases. Differentially edited transcripts are enriched in synapses, particularly in the glutamatergic synapse pathway. Bioinformatic analyses on additional ALS-Ox and control RNA-seq data verified these findings. We identified increased recoding at the Q621R site in the GRIK2 transcript and determined positive correlations between RNA editing and gene expression alterations in ionotropic receptor subunits GRIA2, GRIA3 and the CACNA1C transcript, which encodes the pore forming subunit of a post-synaptic L-type calcium channel. Experimental data verified RNA editing alterations and editing-expression correlation in CACNA1C, highlighting CACNA1C as a target for further study.ConclusionsWe provide evidence on the involvement of RNA editing in the frontal cortex of an ALS molecular subtype, highlighting a modulatory role mediated though recoding and gene expression regulation on glutamatergic synapse related transcripts. We report RNA editing effects in disease-related transcripts and validated editing alterations in CACNA1C. Our study provides targets for further functional studies that could shed light in underlying disease mechanisms enabling novel therapeutic approaches.

Decreased free D-aspartate levels in the blood serum of patients with schizophrenia.

Schizophrenia (SCZ) and autism spectrum disorder (ASD) are neurodevelopmental diseases characterized by different psychopathological manifestations and divergent clinical trajectories. Various alterations at glutamatergic synapses have been reported in both disorders, including abnormal NMDA and metabotropic receptor signaling. We conducted a bicentric study to assess the blood serum levels of NMDA receptors-related glutamatergic amino acids and their precursors, including L-glutamate, L-glutamine, D-aspartate, L-aspartate, L-asparagine, D-serine, L-serine and glycine, in ASD, SCZ patients and their respective control subjects. Specifically, the SCZ patients were subdivided into treatment-resistant and non-treatment-resistant SCZ patients, based on their responsivity to conventional antipsychotics. D-serine and D-aspartate serum reductions were found in SCZ patients compared to controls. Conversely, no significant differences between cases and controls were found in amino acid concentrations in the two ASD cohorts analyzed. This result further encourages future research to evaluate the predictive role of selected D-amino acids as peripheral markers for SCZ pathophysiology and diagnosis.

Parkinson’s-linked LRRK2-G2019S derails AMPAR trafficking, mobility, and composition in striatum with cell-type and subunit specificity

Parkinson's disease (PD) is a multifactorial disease that affects multiple brain systems and circuits. While defined by motor symptoms caused by degeneration of brainstem dopamine neurons, debilitating non-motor abnormalities in fronto-striatal-based cognitive function are common, appear early, and are initially independent of dopamine. Young adult mice expressing the PD-associated G2019S missense mutation in Lrrk2 also exhibit deficits in fronto-striatal-based cognitive tasks. In mice and humans, cognitive functions require dynamic adjustments in glutamatergic synapse strength through cell-surface trafficking of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors (AMPARs), but it is unknown how LRRK2 mutation impacts dynamic features of AMPAR trafficking in striatal projection neurons (SPNs). Here, we used Lrrk2G2019S knockin mice to show that surface AMPAR subunit stoichiometry is altered biochemically and functionally in mutant SPNs in dorsomedial striatum to favor the incorporation of GluA1 over GluA2. GluA1-containing AMPARs were resistant to internalization from the cell surface, leaving an excessive accumulation of GluA1 on the surface within and outside synapses. This negatively impacted trafficking dynamics that normally support synapse strengthening, as GluA1-containing AMPARs failed to increase at synapses in response to a potentiating stimulus and showed significantly reduced surface mobility. Surface GluA2-containing AMPARs were expressed at normal levels in synapses, indicating subunit-selective impairment. Abnormal surface accumulation of GluA1 was independent of PKA activity and was limited to D1R SPNs. Since LRRK2 mutation is thought to be part of a common PD pathogenic pathway, our data suggest that sustained, striatal cell-type specific changes in AMPAR composition and trafficking contribute to cognitive or other impairments associated with PD.

Severe Developmental Delay and Behavior Abnormalities in a Patient with De Novo CAMK2B Mutation: A Case Report and Literature Review.

The calcium/calmodulin-dependent protein kinase II-beta ( CAMK2B ) gene is important for calcium signaling and glutamatergic synapses, which impacts neuroplasticity and learning. Mutations in the CAMK2B gene, which cause autosomal dominant mental retardation 54 (Online Mendelian Inheritance in Man # 617799), can have multisystemic clinical impact. Due to the rarity of CAMK2B mutations at present, case reports about patients with CAMK2B mutations are limited. The present case report describes a patient with CAMK2B -related disorder confirmed by whole exome sequencing and adds to the current information in the literature. We review three case reports in literature with detailed descriptions of patients presenting with mutations in the CAMK2B gene. While there is a broad spectrum of phenotypic presentations, there appears to be an emerging neurobehavioral phenotype. Optimal management of patients will require attention to behavioral issues as well as involvement of neuropsychiatric expertise along with other supports for development and vision abnormalities.

RhoGEF Tiam2 Regulates Glutamatergic Synaptic Transmission in Hippocampal CA1 Pyramidal Neurons.

Glutamatergic synapses exhibit significant molecular diversity, but circuit-specific mechanisms that underlie synaptic regulation are not well characterized. Prior reports show that Rho-guanine nucleotide exchange factor (RhoGEF) Tiam1 regulates perforant path→dentate gyrus granule neuron synapses. In the present study, we report Tiam1's homolog Tiam2 is implicated in glutamatergic neurotransmission in CA1 pyramidal neurons. We find that Tiam2 regulates evoked excitatory glutamatergic currents via a postsynaptic mechanism mediated by the catalytic Dbl-homology domain. Overall, we present evidence for RhoGEF Tiam2's role in glutamatergic synapse function at Schaffer collateral→CA1 pyramidal neuron synapses.

Identification of homer protein homolog 3 as a prognostic marker of colon adenocarcinoma

BackgroundHomer protein homolog 3 (HOMER3), a factor implicated in both physiological and pathological processes, has been studied extensively to determine the relationship between its expression level and the prognosis of various malignancies. However, the significance and clinicopathological role of HOMER3 in colorectal adenocarcinoma remain unclear. MethodsIn this study, bioinformatics techniques were used to find the correlation between high HOMER3 expression levels and clinicopathological features of colorectal adenocarcinoma (COAD) patients. ResultsCellular experiments confirmed the differential expression of HOMER3 in tumor cells compared to normal cells. HOMER3 overexpression was significantly associated with COAD staging and carcinoembryonic antigen (CEA) levels. Patients with high HOMER3 expression levels have a poor prognosis. HOMER3 expression levels can be distinguished more accurately between tumor and non-tumor tissues (AUC = 0.634). The HOMER3 gene variation rate in COAD tissue was 0.7 %. Moreover, 16 of the 22 DNA methylation sites in HOMER3 were associated with COAD prognosis. Our findings confirmed that HOMER3 was positively correlated with immune cell infiltration and immune checkpoints (PD-1, CTLA-4, LMTK3, and LAG3) in COAD, Specifically, we will clearly state that while there is statistical significance, the actual strength of the correlations is weak. During KEGG enrichment analysis, HOMER3 was enriched along with DLG4 and SHANK1 in glutamatergic synapses. Additionally, upstream microRNAs that could bind to HOMER3 were predicted. These findings suggest that HOMER3 might be involved in COAD development and immune regulation. ConclusionsHOMER3 acts as a potential biomarker that can facilitate innovative developments in the diagnosis and prognostic assessment of COAD.

MDGAs perform activity-dependent synapse type-specific suppression via distinct extracellular mechanisms

MDGA (MAM domain containing glycosylphosphatidylinositol anchor) family proteins were previously identified as synaptic suppressive factors. However, various genetic manipulations have yielded often irreconcilable results, precluding precise evaluation of MDGA functions. Here, we found that, in cultured hippocampal neurons, conditional deletion of MDGA1 and MDGA2 causes specific alterations in synapse numbers, basal synaptic transmission, and synaptic strength at GABAergic and glutamatergic synapses, respectively. Moreover, MDGA2 deletion enhanced both N-methyl-D-aspartate (NMDA) receptor- and α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor-mediated postsynaptic responses. Strikingly, ablation of both MDGA1 and MDGA2 abolished the effect of deleting individual MDGAs that is abrogated by chronic blockade of synaptic activity. Molecular replacement experiments further showed that MDGA1 requires the meprin/A5 protein/PTPmu (MAM) domain, whereas MDGA2 acts via neuroligin-dependent and/or MAM domain-dependent pathways to regulate distinct postsynaptic properties. Together, our data demonstrate that MDGA paralogs act as unique negative regulators of activity-dependent postsynaptic organization at distinct synapse types, and cooperatively contribute to adjustment of excitation-inhibition balance.

Transcriptome analysis revealed the characteristics and functions of long non-coding RNAs in the hypothalamus during sexual maturation in goats

The hypothalamus is an essential neuroendocrine area in animals that regulates sexual development. Long non-coding RNAs (lncRNAs) are hypothesized to regulate physiological processes related to animal reproduction. However, the regulatory mechanism by which lncRNAs participate in sexual maturity in goats is poorly known, particularly from birth to sexual maturation. In this study, RNAseq analysis was conducted on the hypothalamus of four developmental stages (1day (D1, n = 5), 2 months (M2, n = 5), 4 months (M4, n = 5), and 6 months (M6, n = 5)) of Jining grey goats. The results showed that a total of 237 differentially expressed lncRNAs (DELs) were identified in the hypothalamus. Among these, 221 DELs exhibited cis-regulatory effects on 693 target genes, while 24 DELs demonstrated trans-regulatory effects on 63 target genes. The target genes of these DELs are mainly involved in biological processes related to energy metabolism, signal transduction and hormone secretion, such as sphingolipid signaling pathway, adipocytokine signaling pathway, neurotrophic signaling pathway, glutamatergic synapse, P53 signaling pathway and GnRH signaling pathway. In addition, XR_001918477.1, TCONS_00077463, XR_001918760.1, and TCONS_00029048 and their potential target genes may play a crucial role in the process of goat sexual maturation. This study advances our understanding of lncRNA in hypothalamic tissue during sexual maturation in goats and will give a theoretical foundation for improving goat reproductive features.

Deciphering novel molecular gene expression signatures and pathways in cystic fibrosis through integrative bioinformatics strategies

Cystic fibrosis (CF), a fatal autosomal recessive disorder, is triggered by a genetic alteration of the CF transmembrane conductance regulator (CFTR) gene. On a global scale, around one in 3000 live births are affected with CF annually. While diagnosis and therapy are available for CF patients with non-specific and rare mutations, the current research is dedicated to exploring customized biomarkers, genes, signaling networks, and therapy for improving the management of CF. Although still in the early stages of development and validation, mRNA and gene-based treatment strategies are aimed to target patients who are resistant to CFTR gene restoration therapies. In this study, we utilized the systems biology approaches integrated with gene expression analysis to identify novel biomarkers and pathways for CF treatment. At first, out of 54,676 differentially expressed genes, we identified 104 upregulated and 107 downregulated genes. The upregulated genes were largely concentrated on Glutamatergic synapses, and the downregulated genes were enriched in ubiquitin-mediated proteolysis. Utilizing the enrichment analysis, we explored deeper into the pathways linked to these genes, with emphasis on relevant pathways involving bronchial epithelial cells. Following the enrichment analysis, we identified six essential genes: WWP2, RNASEL, CUL1, CDC42, HDAC4, and UBA2. Furthermore, the discovered genes were evaluated using expression profile analysis. Finally, our data indicate that the WWP2 gene has a critical role in CF management. The current findings provide a coherent theoretical foundation for future experiments to further explore the WWP2 gene as a unique and prognostic target for developing an effective CF therapeutic approach.

Bone marrow-derived myeloid cells transiently colonize the brain during postnatal development and interact with glutamatergic synapses

Although the roles of embryonic yolk sac-derived, resident microglia in neurodevelopment were extensively studied, the possible involvement of bone marrow-derived cells remains elusive. In this work, we used a fate-mapping strategy to selectively label bone marrow-derived cells and their progeny in the brain (FLT3+IBA1+). FLT3+IBA1+ cells were confirmed to be transiently present in the healthy brain during early postnatal development. FLT3+IBA1+ cells have a distinct morphology index at postnatal day(P)0, P7, and P14 compared with neighboring microglia. FLT3+IBA1+ cells also express the microglial markers P2RY12 and TMEM119 and interact with VGLUT1 synapses at P14. Scanning electron microscopy indeed showed that FLT3+ cells contact and engulf pre-synaptic elements. Our findings suggest FLT3+IBA1+ cells might assist microglia in their physiological functions in the developing brain including synaptic pruning which is performed using their purinergic sensors. Our findings stimulate further investigation on the involvement of peripheral macrophages during homeostatic and pathological development.

Ventral tegmental area dopamine projections to the hippocampus trigger long-term potentiation and contextual learning

In most models of neuronal plasticity and memory, dopamine is thought to promote the long-term maintenance of Long-Term Potentiation (LTP) underlying memory processes, but not the initiation of plasticity or new information storage. Here, we used optogenetic manipulation of midbrain dopamine neurons in male DAT::Cre mice, and discovered that stimulating the Schaffer collaterals – the glutamatergic axons connecting CA3 and CA1 regions - of the dorsal hippocampus concomitantly with midbrain dopamine terminals within a 200 millisecond time-window triggers LTP at glutamatergic synapses. Moreover, we showed that the stimulation of this dopaminergic pathway facilitates contextual learning in awake behaving mice, while its inhibition hinders it. Thus, activation of midbrain dopamine can operate as a teaching signal that triggers NeoHebbian LTP and promotes supervised learning.

Synapse-Specific Trapping of SNARE Machinery Proteins in the Anesthetized Drosophila Brain.

General anesthetics disrupt brain network dynamics through multiple pathways, in part through postsynaptic potentiation of inhibitory ion channels as well as presynaptic inhibition of neuroexocytosis. Common clinical general anesthetic drugs, such as propofol and isoflurane, have been shown to interact and interfere with core components of the exocytic release machinery to cause impaired neurotransmitter release. Recent studies however suggest that these drugs do not affect all synapse subtypes equally. We investigated the role of the presynaptic release machinery in multiple neurotransmitter systems under isoflurane general anesthesia in the adult female Drosophila brain using live-cell super-resolution microscopy and optogenetic readouts of exocytosis and neural excitability. We activated neurotransmitter-specific mushroom body output neurons and imaged presynaptic function under isoflurane anesthesia. We found that isoflurane impaired synaptic release and presynaptic protein dynamics in excitatory cholinergic synapses. In contrast, isoflurane had little to no effect on inhibitory GABAergic or glutamatergic synapses. These results present a distinct inhibitory mechanism for general anesthesia, whereby neuroexocytosis is selectively impaired at excitatory synapses, while inhibitory synapses remain functional. This suggests a presynaptic inhibitory mechanism that complements the other inhibitory effects of these drugs.

Neto proteins differentially modulate the gating properties of Drosophila NMJ glutamate receptors.

The formation of functional synapses requires co-assembly of ion channels with their accessory proteins which controls where, when, and how neurotransmitter receptors function. The auxiliary protein Neto modulates the function of kainate-type glutamate receptors in vertebrates as well as at the Drosophila neuromuscular junction (NMJ), a glutamatergic synapse widely used for genetic studies on synapse development. We previously reported that Neto is essential for the synaptic recruitment and function of glutamate receptors. Here, using outside-out patch-clamp recordings and fast ligand application, we examine for the first time the biophysical properties of recombinant Drosophila NMJ receptors expressed in HEK293T cells and compare them with native receptor complexes of genetically controlled composition. The two Neto isoforms, Neto-α and Neto-β, differentially modulate the gating properties of NMJ receptors. Surprisingly, we found that deactivation is extremely fast and that the decay of synaptic currents resembles the rate of iGluR desensitization. The functional analyses of recombinant iGluRs that we report here should greatly facilitate the interpretation of compound in vivo phenotypes of mutant animals.

Vagus nerve stimulation enhances remyelination and decreases innate neuroinflammation in lysolecithin-induced demyelination

BackgroundCurrent treatments for Multiple Sclerosis (MS) poorly address chronic innate neuroinflammation nor do they offer effective remyelination. The vagus nerve has a strong regulatory role in inflammation and Vagus Nerve Stimulation (VNS) has potential to affect both neuroinflammation and remyelination in MS. ObjectiveThis study investigated the effects of VNS on demyelination and innate neuroinflammation in a validated MS rodent model. MethodsLysolecithin (LPC) was injected in the corpus callosum (CC) of 46 Lewis rats, inducing a demyelinated lesion. 33/46 rats received continuously-cycled VNS (cVNS) or one-minute per day VNS (1minVNS) or sham VNS from 2 days before LPC-injection until perfusion at 3 days post-injection (dpi) (corresponding with a demyelinated lesion with peak inflammation). 13/46 rats received cVNS or sham from 2 days before LPC-injection until perfusion at 11 dpi (corresponding with a partial remyelinated lesion). Immunohistochemistry and proteomics analyses were performed to investigate the extend of demyelination and inflammation. ResultsImmunohistochemistry showed that cVNS significantly reduced microglial and astrocytic activation in the lesion and lesion border, and significantly reduced the Olig2+ cell count at 3 dpi. Furthermore, cVNS significantly improved remyelination with 57.4 % versus sham at 11 dpi. Proteomic gene set enrichment analyses showed increased activation of (glutamatergic) synapse pathways in cVNS versus sham, most pronounced at 3 dpi. ConclusioncVNS improved remyelination of an LPC-induced lesion. Possible mechanisms might include modulation of microglia and astrocyte activity, increased (glutamatergic) synapses and enhanced oligodendrocyte clearance after initial injury.