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Proceedings of the National Academy of... Jun 2024Ca/calmodulin (CaM)-dependent kinase II (CaMKII) plays a critical role in long-term potentiation (LTP), a well-established model for learning and memory through the...
Ca/calmodulin (CaM)-dependent kinase II (CaMKII) plays a critical role in long-term potentiation (LTP), a well-established model for learning and memory through the enhancement of synaptic transmission. Biochemical studies indicate that CaMKII catalyzes a phosphotransferase (kinase) reaction of both itself (autophosphorylation) and of multiple downstream target proteins. However, whether either type of phosphorylation plays any role in the synaptic enhancing action of CaMKII remains hotly contested. We have designed a series of experiments to define the minimal requirements for the synaptic enhancement by CaMKII. We find that autophosphorylation of T286 and further binding of CaMKII to the GluN2B subunit are required both for initiating LTP and for its maintenance (synaptic memory). Once bound to the NMDA receptor, the synaptic action of CaMKII occurs in the absence of target protein phosphorylation. Thus, autophosphorylation and binding to the GluN2B subunit are the only two requirements for CaMKII in synaptic memory.
Topics: Calcium-Calmodulin-Dependent Protein Kinase Type 2; Phosphorylation; Animals; Receptors, N-Methyl-D-Aspartate; Long-Term Potentiation; Memory; Synapses; Rats; Mice
PubMed: 38889145
DOI: 10.1073/pnas.2402783121 -
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 -
Acta Neuropathologica Jun 2024Myasthenia gravis is a chronic antibody-mediated autoimmune disease disrupting neuromuscular synaptic transmission. Informative biomarkers remain an unmet need to...
Myasthenia gravis is a chronic antibody-mediated autoimmune disease disrupting neuromuscular synaptic transmission. Informative biomarkers remain an unmet need to stratify patients with active disease requiring intensified monitoring and therapy; their identification is the primary objective of this study. We applied mass spectrometry-based proteomic serum profiling for biomarker discovery. We studied an exploration and a prospective validation cohort consisting of 114 and 140 anti-acetylcholine receptor antibody (AChR-Ab)-positive myasthenia gravis patients, respectively. For downstream analysis, we applied a machine learning approach. Protein expression levels were confirmed by ELISA and compared to other myasthenic cohorts, in addition to myositis and neuropathy patients. Anti-AChR-Ab levels were determined by a radio receptor assay. Immunohistochemistry and immunofluorescence of intercostal muscle biopsies were employed for validation in addition to interactome studies of inter-alpha-trypsin inhibitor heavy chain H3 (ITIH3). Machine learning identified ITIH3 as potential serum biomarker reflective of disease activity. Serum levels correlated with disease activity scores in the exploration and validation cohort and were confirmed by ELISA. Lack of correlation between anti-AChR-Ab levels and clinical scores underlined the need for biomarkers. In a subgroup analysis, ITIH3 was indicative of treatment responses. Immunostaining of muscle specimens from these patients demonstrated ITIH3 localization at the neuromuscular endplates in myasthenia gravis but not in controls, thus providing a structural equivalent for our serological findings. Immunoprecipitation of ITIH3 and subsequent proteomics lead to identification of its interaction partners playing crucial roles in neuromuscular transmission. This study provides data on ITIH3 as a potential pathophysiological-relevant biomarker of disease activity in myasthenia gravis. Future studies are required to facilitate translation into clinical practice.
Topics: Humans; Myasthenia Gravis; Biomarkers; Male; Female; Middle Aged; Adult; Aged; Autoantibodies; Receptors, Cholinergic; Proteomics; Cohort Studies; Young Adult; Proteinase Inhibitory Proteins, Secretory; Machine Learning
PubMed: 38888758
DOI: 10.1007/s00401-024-02754-6 -
Brain Pathology (Zurich, Switzerland) Jun 2024Voltage-gated Ca2.1 (P/Q-type) Ca channels play a crucial role in regulating neurotransmitter release, thus contributing to synaptic plasticity and to processes such as...
Voltage-gated Ca2.1 (P/Q-type) Ca channels play a crucial role in regulating neurotransmitter release, thus contributing to synaptic plasticity and to processes such as learning and memory. Despite their recognized importance in neural function, there is limited information on their potential involvement in neurodegenerative conditions such as Alzheimer's disease (AD). Here, we aimed to explore the impact of AD pathology on the density and nanoscale compartmentalization of Ca2.1 channels in the hippocampus in association with GABA receptors. Histoblotting experiments showed that the density of Ca2.1 channel was significantly reduced in the hippocampus of APP/PS1 mice in a laminar-dependent manner. Ca2.1 channel was enriched in the active zone of the axon terminals and was present at a very low density over the surface of dendritic tree of the CA1 pyramidal cells, as shown by quantitative SDS-digested freeze-fracture replica labelling (SDS-FRL). In APP/PS1 mice, the density of Ca2.1 channel in the active zone was significantly reduced in the strata radiatum and lacunosum-moleculare, while it remained unaltered in the stratum oriens. The decline in Cav2.1 channel density was found to be associated with a corresponding impairment in the GABAergic synaptic function, as evidenced by electrophysiological experiments carried out in the hippocampus of APP/PS1 mice. Remarkably, double SDS-FRL showed a co-clustering of Ca2.1 channel and GABA receptor in nanodomains (~40-50 nm) in wild type mice, while in APP/PS1 mice this nanoarchitecture was absent. Together, these findings suggest that the AD pathology-induced reduction in Ca2.1 channel density and Ca2.1-GABA de-clustering may play a role in the synaptic transmission alterations shown in the AD hippocampus. Therefore, uncovering these layer-dependent changes in P/Q calcium currents associated with AD pathology can benefit the development of future strategies for AD management.
PubMed: 38887180
DOI: 10.1111/bpa.13279 -
Molecular Brain Jun 2024Areca nut, the seed of Areca catechu L., is one of the most widely consumed addictive substances in the world after nicotine, ethanol, and caffeine. The major effective...
Areca nut, the seed of Areca catechu L., is one of the most widely consumed addictive substances in the world after nicotine, ethanol, and caffeine. The major effective constituent of A. catechu, arecoline, has been reported to affect the central nervous system. Less is known if it may affect pain and its related emotional responses. In this study, we found that oral application of arecoline alleviated the inflammatory pain and its induced anxiolytic and anti-depressive-like behavior. Arecoline also increased the mechanical nociceptive threshold and alleviated depression-like behavior in naïve mice. In the anterior cingulate cortex (ACC), which acts as a hinge of nociception and its related anxiety and depression, by using the multi-electrode field potential recording and whole-cell patch-clamp recording, we found that the evoked postsynaptic transmission in the ACC of adult mice has been inhibited by the application of arecoline. The muscarinic receptor is the major receptor of the arecoline in the ACC. Our results suggest that arecoline alleviates pain, anxiety, and depression-like behavior in both physiological and pathological conditions, and this new mechanism may help to treat patients with chronic pain and its related anxiety and disorder in the future.
Topics: Animals; Synaptic Transmission; Anxiety; Arecoline; Male; Depression; Behavior, Animal; Nociception; Mice, Inbred C57BL; Gyrus Cinguli; Mice; Cerebral Cortex
PubMed: 38886822
DOI: 10.1186/s13041-024-01106-5 -
The Journal of Pain Jun 2024While early-life adversity has been associated with a higher risk of developing chronic pain in adulthood, the cellular and molecular mechanisms by which chronic stress...
While early-life adversity has been associated with a higher risk of developing chronic pain in adulthood, the cellular and molecular mechanisms by which chronic stress during the neonatal period can persistently sensitize developing nociceptive circuits remain poorly understood. Here, we investigate the effects of early-life stress (ELS) on synaptic integration and intrinsic excitability in dynorphin-lineage (DYN) interneurons within the adult mouse superficial dorsal horn (SDH), which are important for inhibiting mechanical pain and itch. The administration of neonatal limited bedding between postnatal days (P)2 and P9 evoked sex-dependent effects on spontaneous glutamatergic signaling, as female SDH neurons exhibited a higher amplitude of miniature excitatory postsynaptic currents (mEPSCs) after ELS, while mEPSC frequency was reduced in DYN neurons of the male SDH. Furthermore, ELS decreased the frequency of miniature inhibitory postsynaptic currents selectively in female DYN neurons. As a result, ELS increased the balance of spontaneous excitation versus inhibition (E:I ratio) in mature DYN neurons of the female, but not male, SDH network. Nonetheless, ELS weakened the total primary afferent-evoked glutamatergic drive onto adult DYN neurons selectively in females, without modifying afferent-evoked inhibitory signaling onto the DYN population. Finally, ELS failed to significantly change the intrinsic membrane excitability of mature DYN neurons in either males or females. Collectively, these data suggest that ELS exerts a long-term influence on the properties of synaptic transmission onto DYN neurons within the adult SDH, which includes a reduction in the overall strength of sensory input onto this important subset of inhibitory interneurons. PERSPECTIVE: This study suggests that chronic stress during the neonatal period influences synaptic function within adult spinal nociceptive circuits in a sex-dependent manner. These findings yield new insight into the potential mechanisms by which early-life adversity might shape the maturation of pain pathways in the central nervous system (CNS).
PubMed: 38885917
DOI: 10.1016/j.jpain.2024.104609 -
Phytomedicine : International Journal... Jun 2024Dysfunction of dopamine homeostasis (DAH), which is regulated by vesicular monoamine transporter 2 (VMAT2), is a vital cause of dopamine (DA) neurotoxicity and motor...
BACKGROUND
Dysfunction of dopamine homeostasis (DAH), which is regulated by vesicular monoamine transporter 2 (VMAT2), is a vital cause of dopamine (DA) neurotoxicity and motor deficits in Parkinson's disease (PD). Gastrodin (4-hydroxybenzyl alcohol 4-O-β-D-glucoside; GTD), a natural active compound derived from Gastrodia elata Blume, can be used to treat multiple neurological disorders, including PD. However, whether GTD regulates VMAT2-mediated DAH dysfunction in PD models remains unclear.
PURPOSE
To explore whether GTD confers dopaminergic neuroprotection by facilitating DA vesicle storage and maintaining DAH in PD models.
METHODS
Mice were treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and PC12 cells with 1-methyl-4-phenyl-pyridinium (MPP) to induce PD characteristics. Multiple behavioural tests were performed to evaluate the motor functions of the mice. HPLC was used to measure DA and 3,4-dihydroxyphenylacetic acid (DOPAC) levels. Transmission electron microscopy was used to observe synaptic vesicles. Molecular docking and molecular dynamics were used to determine the binding affinity of GTD to the target protein. Reserpine (Res, a VMAT2 inhibitor) and PD0325901 (901, a MEK inhibitor) were employed to investigate the mechanism of GTD. Western blotting and immunohistochemistry were used to assess the expression of the target proteins.
RESULTS
GTD attenuated motor deficits and dopaminergic neuronal injury, reversed the imbalance of DAH, and increased VMAT2 levels and vesicle volume in MPTP-induced mice. GTD ameliorated cell damage, ROS release, and dysfunction of DAH in MPP-induced PC12 cells. Moreover, the neuroprotective effects of GTD were reversed by Res in vitro and in vivo. Furthermore, GTD can activate the MEK/ERK/CREB pathway to upregulate VMAT2 in vitro and in vivo. Interestingly, 901 reversed the effects of GTD on VMAT2 and dopaminergic neuronal impairment.
CONCLUSION
GTD relieved PD-related motor deficits and dopaminergic neuronal impairment by facilitating MEK-depended VMAT2 to regulate DAH, which offers new insights into its therapeutic potential.
PubMed: 38885579
DOI: 10.1016/j.phymed.2024.155819 -
Journal of Pharmacy & Bioallied Sciences Apr 2024The synaptic contacts play an important role in central nervous system (CNS) functioning. Ultrastructural features of synapses in CNS are not studied in naphthalene...
INTRODUCTION
The synaptic contacts play an important role in central nervous system (CNS) functioning. Ultrastructural features of synapses in CNS are not studied in naphthalene neurotoxicity model.
MATERIALS AND METHODOLOGY
In the present work, transmission electron microscopy was used for studying the ultrastructural features of synapses in the hippocampus of Sprague Dawley rat brain, on subsequent exposure to naphthalene balls. The ultrastructural changes were observed for naphthalene low dose (200 mg), high dose (400 mg) after the treatment for 28 days, and post-delayed toxicity phase after 14 days in Sprague Dawley rats.
RESULTS
In comparison with different groups of naphthalene exposure including control and satellite, axon degeneration, axonal demyelination and abnormal synapses was observed in high dose naphthalene administration group. In the post-delayed naphthalene toxicity group, degeneration of synaptic contacts was observed.
CONCLUSIONS
This exploration of ultrastructural variations in the synapses of Hippocampus gives information that will be valued in naphthalene neurotoxicological research.
PubMed: 38882886
DOI: 10.4103/jpbs.jpbs_1184_23 -
Brain Research Jun 2024Epilepsy is a prevalent neurological illness which is linked with high worldwide burdens. Oxidative stress (OS) is recognized to be among the contributors that trigger... (Review)
Review
Epilepsy is a prevalent neurological illness which is linked with high worldwide burdens. Oxidative stress (OS) is recognized to be among the contributors that trigger the advancement of epilepsy, affecting neuronal excitability and synaptic transmission. Various types of non-coding RNAs (ncRNAs) are known to serve vital functions in many disease mechanisms, including epilepsy. The current review sought to understand better the mechanisms through which these ncRNAs regulate epilepsy's OS-related pathways. We investigated the functions of microRNAs in controlling gene expression at the post-translatory stage and their involvement in OS and neuroinflammation. We also looked at the different regulatory roles of long ncRNAs, including molecular scaffolding, enhancer, and transcriptional activator, during OS. Circular RNAs and their capability to act as miRNA decoys and their consequential impact on epilepsy development were also explored. Our review aimed to improve the current understanding of novel therapies for epilepsy based on the role of ncRNAs in OS pathways. We also demonstrated the roles of ncRNAs in epilepsy treatment and diagnosis, explaining that these molecules play vital roles that could be used in therapy as biomarkers.
PubMed: 38880410
DOI: 10.1016/j.brainres.2024.149089 -
Neuron Jun 2024NMDA receptors (NMDARs) are ionotropic receptors crucial for brain information processing. Yet, evidence also supports an ion-flux-independent signaling mode mediating...
NMDA receptors (NMDARs) are ionotropic receptors crucial for brain information processing. Yet, evidence also supports an ion-flux-independent signaling mode mediating synaptic long-term depression (LTD) and spine shrinkage. Here, we identify AETA (Aη), an amyloid-β precursor protein (APP) cleavage product, as an NMDAR modulator with the unique dual regulatory capacity to impact both signaling modes. AETA inhibits ionotropic NMDAR activity by competing with the co-agonist and induces an intracellular conformational modification of GluN1 subunits. This favors non-ionotropic NMDAR signaling leading to enhanced LTD and favors spine shrinkage. Endogenously, AETA production is increased by in vivo chemogenetically induced neuronal activity. Genetic deletion of AETA production alters NMDAR transmission and prevents LTD, phenotypes rescued by acute exogenous AETA application. This genetic deletion also impairs contextual fear memory. Our findings demonstrate AETA-dependent NMDAR activation (ADNA), characterizing AETA as a unique type of endogenous NMDAR modulator that exerts bidirectional control over NMDAR signaling and associated information processing.
PubMed: 38878768
DOI: 10.1016/j.neuron.2024.05.027