Ionotropic Glutamate Receptors Research Articles

Candidate membrane protein gene families related to chemoreception in a wood-boring beetle, Pharsalia antennata Gahan (Coleoptera: Cerambycidae)

The longhorned beetles are key players for the maintenance of biodiversity in the terrestrial ecosystem. As xylophagous cerambycid insects in Coleoptera, the beetles have evolved specialized olfactory and gustatory systems to recognize chemical cues in the surrounding habitats. Despite over 36,000 described species in the Cerambycidae family including a wood-boring pest Pharsalia antennata, only a limited number of them (<1 %) have been characterized regarding their chemical ecology at the molecular level. Here, we surveyed four membrane protein gene families in P. antennata related to chemoreception through transcriptomics, phylogenetics and expression profiling analyses. In total, 144 genes encoding 72 odorant receptors (ORs), 33 gustatory receptors (GRs), 23 ionotropic receptors (IRs), four sensory neuron membrane proteins (SNMPs) and 12 ionotropic glutamate receptors (iGluRs) were harvested from the transcriptome of multiple tissues including antennae and legs of both sexes. The lineage-specific expansion of PantORs possibly implied a diverse range of host plants in this beetle, supporting this correlation between the host range and olfactory receptor repertoire sizes across cerambycid species. Further phylogenetic analysis revealed that Group 2 was contributed mainly to the large OR gene repertoire in P. antennata, representing 18 genes in Group 2A and eight in Group 2B. On the other hand, some key chemosensory genes were identified by applying a phylogenetics approach, such as PantOR21 close to the 2-phenylethanol receptor in Megacyllene caryae, three carbon dioxide GRs and seven Antennal IRs (A-IRs) clades. We also determined sex- and tissue-specific expression profiles of 69 chemosensory genes, revealing the high expression of most PantORs in antennae. Noticeably, 10 sex-biased genes (six PantORs, three PantIRs and PantSNMP1a) were presented in antennae, five sex-biased PantGRs in legs and 39 sex-biased genes (15 PantORs, 13 PantGRs, eight PantIRs and three PantSNMPs) in abdomens. These findings have greatly enhanced our knowledge about the chemical ecology of P. antennata and identify candidate molecular targets for mediating smell and taste of this beetle.

Inhibitory Role of L-theanine, a Structural Analogue of Glutamate, Against GluR5 Kainate Receptor and its Prospective Utility Against Excitotoxicity.

Overactivation of receptors that respond to excitatory neurotransmitters can result in various harmful outcomes, such as the inability to properly modulate calcium levels, generation of free radicals, initiation of the mitochondrial permeability transition, and subsequent secondary damage caused by excitotoxicity. A non-proteinogenic amino acid of tea, L-theanine, is structurally related to glutamate, the major stimulatory neurotransmitter in the brain. Previous reports have emphasised its ability to bind with glutamate receptors. An in-depth understanding of the binding compatibility between ionotropic glutamate receptors and L-theanine is a compelling necessity. In this molecular docking study, the antagonistic effect of L-theanine and its possible therapeutic benefit in GluR5 kainate receptor inhibition has been evaluated and compared to the familiar AMPA and kainite receptor antagonists, cyanoquinoxaline (CNQX) and dinitroquinoxaline (DNQX), using Molegro Virtual Docker 7.0.0. The capacity of L-theanine to cohere with the GluR5 receptor was revealed to be higher than that of glutamate, although it could not surpass the high binding tendency of competitive antagonists CNQX and DNQX. Nonetheless, the drug-likeness score and the blood-brain barrier traversing potential of L-theanine were higher than CNQX and DNQX. The study provides an inference to the advantage of L-theanine, which can be a safe and effective alternative natural therapy for rescuing neuronal death due to excitotoxicity.

Two Signaling Modes Are Better than One: Flux-Independent Signaling by Ionotropic Glutamate Receptors Is Coming of Age.

Glutamate is the major excitatory neurotransmitter in the central nervous system. Glutamatergic transmission can be mediated by ionotropic glutamate receptors (iGluRs), which mediate rapid synaptic depolarization that can be associated with Ca2+ entry and activity-dependent change in the strength of synaptic transmission, as well as by metabotropic glutamate receptors (mGluRs), which mediate slower postsynaptic responses through the recruitment of second messenger systems. A wealth of evidence reported over the last three decades has shown that this dogmatic subdivision between iGluRs and mGluRs may not reflect the actual physiological signaling mode of the iGluRs, i.e., α-amino-3-hydroxy-5-methyl-4-isoxasolepropionic acid (AMPA) receptors (AMPAR), kainate receptors (KARs), and N-methyl-D-aspartate (NMDA) receptors (NMDARs). Herein, we review the evidence available supporting the notion that the canonical iGluRs can recruit flux-independent signaling pathways not only in neurons, but also in brain astrocytes and cerebrovascular endothelial cells. Understanding the signaling versatility of iGluRs can exert a profound impact on our understanding of glutamatergic synapses. Furthermore, it may shed light on novel neuroprotective strategies against brain disorders.

Structure and function of GluN1-3A NMDA receptor excitatory glycine receptor channel.

N-methyl-d-aspartate receptors (NMDARs) and other ionotropic glutamate receptors (iGluRs) mediate most of the excitatory signaling in the mammalian brains in response to the neurotransmitter glutamate. Uniquely, NMDARs composed of GluN1 and GluN3 are activated exclusively by glycine, the neurotransmitter conventionally mediating inhibitory signaling when it binds to pentameric glycine receptors. The GluN1-3 NMDARs are vital for regulating neuronal excitability, circuit function, and specific behaviors, yet our understanding of their functional mechanism at the molecular level has remained limited. Here, we present cryo-electron microscopy structures of GluN1-3A NMDARs bound to an antagonist, CNQX, and an agonist, glycine. The structures show a 1-3-1-3 subunit heterotetrameric arrangement and an unprecedented pattern of GluN3A subunit orientation shift between the glycine-bound and CNQX-bound structures. Site-directed disruption of the unique subunit interface in the glycine-bound structure mitigated desensitization. Our study provides a foundation for understanding the distinct structural dynamics of GluN3 that are linked to the unique function of GluN1-3 NMDARs.

Constitutive activity of ionotropic glutamate receptors via hydrophobic substitutions in the ligand-binding domain.

Neurotransmitter ligands electrically excite neurons by activating ionotropic glutamate receptor (iGluR) ion channels. Knowledge of the iGluR amino acid residues that dominate ligand-induced activation would enable the prediction of function from sequence. We therefore explored the molecular determinants of activity in rat N-methyl-D-aspartate (NMDA)-type iGluRs (NMDA receptors), complex heteromeric iGluRs comprising two glycine-binding GluN1 and two glutamate-binding GluN2 subunits, using amino acid sequence analysis, mutagenesis, and electrophysiology. We find that a broadly conserved aspartate residue controls both ligand potency and channel activity, to the extent that certain substitutions at this position bypass the need for ligand binding in GluN1 subunits, generating NMDA receptors activated solely by glutamate. Furthermore, we identify a homomeric iGluR from the placozoan Trichoplax adhaerens that has utilized native mutations of this crucial residue to evolve into a leak channel that is inhibited by neurotransmitter binding, pointing to a dominant role of this residue throughout the iGluR superfamily.

Association of rs11081062 polymorphism of DLGAP1 gene and levels of SLC1A1 protein with obsessive-compulsive disorder

Glutamate is an important neurotransmitter known to be effective in obsessive-compulsive disorder (OCD). The aim of this study is to investigate the relationship between the DLGAP1 gene encoding the scaffold protein of ionotropic glutamate receptors and the SLC1A1 gene encoding the glutamate transporter protein with OCD. Study groups consisted of 95 patients with OCD and 100 healthy controls. The severity of OCD in the patient group was determined by using the Y-BOCS. Single nucleotide polymorphisms of rs11081062 (C/T) in DLGAP1 and rs587777696 (C/T) in SLC1A1 were analyzed by real-time PCR. Levels of SLC1A1 protein were determined by ELISA. A significant difference was found between genotype distributions of rs11081062 in DLGAP1 in study groups (p < 0.001). No significant association was found rs587777696 in SLC1A1 in OCD patients and controls. SLC1A1 protein levels were found to be lower in OCD patients compared to controls (p = 0.005). According to OCD risk estimates for genotypes distributions of rs11081062 in DLGAP1, having CT + TT genotypes was associated with the occurrence of sexual and religious obsessions and counting compulsions (p = 0.038, OR = 2.98; p = 0.033, OR = 3.43; p = 0.035, OR = 2.66, respectively). CT genotype in DLGAP1 rs11081062 polymorphism was found to increase the risk of OCD in the female gender (p = 0.042, OR = 3.01). This study suggests that rs11081062 in DLGAP1 may be associated with OCD and that SLC1A1 protein levels may be involved in the occurrence of OCD. We believe that our research can contribute to the understanding of the importance of glutamate in OCD.

Targeting N-Methyl-d-Aspartate Receptors in Neurodegenerative Diseases.

N-methyl-d-aspartate receptors (NMDARs) are the main class of ionotropic receptors for the excitatory neurotransmitter glutamate. They play a crucial role in the permeability of Ca2+ ions and excitatory neurotransmission in the brain. Being heteromeric receptors, they are composed of several subunits, including two obligatory GluN1 subunits (eight splice variants) and regulatory GluN2 (GluN2A~D) or GluN3 (GluN3A~B) subunits. Widely distributed in the brain, they regulate other neurotransmission systems and are therefore involved in essential functions such as synaptic transmission, learning and memory, plasticity, and excitotoxicity. The present review will detail the structure, composition, and localization of NMDARs, their role and regulation at the glutamatergic synapse, and their impact on cognitive processes and in neurodegenerative diseases (Alzheimer's, Huntington's, and Parkinson's disease). The pharmacology of different NMDAR antagonists and their therapeutic potentialities will be presented. In particular, a focus will be given on fluoroethylnormemantine (FENM), an investigational drug with very promising development as a neuroprotective agent in Alzheimer's disease, in complement to its reported efficacy as a tomography radiotracer for NMDARs and an anxiolytic drug in post-traumatic stress disorder.

Effect of the General Anaesthetic Ketamine on Electrical and Ca2+ Signal Propagation in Arabidopsis thaliana

The systemic electrical signal propagation in plants (i.e., from leaf to leaf) is dependent on GLUTAMATE RECEPTOR-LIKE proteins (GLRs). The GLR receptors are the homologous proteins to the animal ionotropic glutamate receptors (iGluRs) which are ligand-gated non-selective cation channels that mediate neurotransmission in the animal’s nervous system. In this study, we investigated the effect of the general anaesthetic ketamine, a well-known non-competitive channel blocker of human iGluRs, on systemic electrical signal propagation in Arabidopsis thaliana. We monitored the electrical signal propagation, intracellular calcium level [Ca2+]cyt and expression of jasmonate (JA)-responsive genes in response to heat wounding. Although ketamine affected the shape and the parameters of the electrical signals (amplitude and half-time, t1/2) mainly in systemic leaves, it was not able to block a systemic response. Increased [Ca2+]cyt and the expression of jasmonate-responsive genes were detected in local as well as in systemic leaves in response to heat wounding in ketamine-treated plants. This is in contrast with the effect of the volatile general anaesthetic diethyl ether which completely blocked the systemic response. This low potency of ketamine in plants is probably caused by the fact that the critical amino acid residues needed for ketamine binding in human iGluRs are not conserved in plants’ GLRs.

Isradipine, an L-type calcium channel blocker, attenuates cocaine effects in mice by reducing central glutamate release

Substance abuse disorder is a chronic condition for which pharmacological treatment options remain limited. L-type calcium channels (LTCC) have been implicated in drug-related plasticity and behavior. Specifically, dopaminergic neurons in the mesocorticolimbic pathway express Cav1.2 and Cav1.3 channels, which may regulate dopaminergic activity associated with reward behavior. Therefore, this study aimed to investigate the hypothesis that pre-administration of the LTCC blocker, isradipine can mitigate the effects of cocaine by modulating central glutamatergic transmission. For that, we administered isradipine at varying concentrations (1, 7.5, and 15 μg/μL) via intracerebroventricular injection in male Swiss mice. This pretreatment was carried out prior to subjecting animals to behavioral assessments to evaluate cocaine-induced locomotor sensitization and conditioned place preference (CPP). The results revealed that isradipine administered at a concentration of 1 μg/μL effectively attenuated both the sensitization and CPP induced by cocaine (15 mg/kg, via i. p.). Moreover, mice treated with 1 μg/μL of isradipine showed decreased presynaptic levels of glutamate and calcium in the cortex and hippocampus as compared to control mice following cocaine exposure. Notably, the gene expression of ionotropic glutamate receptors, AMPA, and NMDA, remained unchanged, as did the expression of Cav1.2 and Cav1.3 channels. Importantly, these findings suggest that LTCC blockage may inhibit behavioral responses to cocaine, most likely by decreasing glutamatergic input in areas related to addiction.

Ligand-gated ion channels as potential biomarkers for ADT-mediated cognitive decline in prostate cancer patients.

Men with prostate cancer are at increased risk of developing cognitive decline by the use of second-generation androgen signaling inhibitors. To date, reliable and sensitive biomarkers that could distinguish men at high risk of cognitive dysfunction under androgen deprivation therapy (ADT) have not been characterized. We used high-throughput transcriptional profiling utilizing human prostate cancer cell culture models mimicking ADT, biomarker selection using minimal common oncology data elements-cytoscape, and bioinformatic analyses employing Advaita® iPathwayGuide and DisGeNET for identification of disease-related gene associations. Validation analysis of genes was performed on brain neuronal and glial cells by quantitative real-time polymerase chain reaction assay. Our systematic analysis of androgen deprivation-associated genes involved multiple biological processes, including neuroactive ligand-receptor interaction, axon guidance, cytokine-cytokine receptor interaction, and metabolic and cancer signaling pathways. Genes associated with neuroreceptor ligand interaction, including gamma-aminobutyric acid (GABA) A and B receptors and nuclear core proteins, were identified as top upstream regulators. Functional enrichment and protein-protein interaction network analysis highlighted the role of ligand-gated ion channels (LGICs) and their receptors in cognitive dysfunction. Gene-disease association assigned forgetfulness, intellectual disability, visuospatial deficit, bipolar disorder, and other neurocognitive impairment with upregulation of type-1 angiotensin II receptor, brain-derived neurotrophic factor, GABA type B receptor subunit 2 (GABBR2), GABRA3, GABRA5, GABRB1, glycine receptor beta, glutamate ionotropic receptor N-methyl-D-aspartate receptor (NMDA) type subunit 1, glutamate ionotropic receptor NMDA type subunit 2D, 5-hydroxytryptamine receptor 1D, interferon beta 1, and nuclear receptor subfamily 3 group C member 1 as top differentially expressed genes. Validation studies of brain glial cells, neurons, and patients on ADT demonstrated the association of these genes with cognitive decline. Our findings highlight LGICs as potential biomarkers for ADT-mediated cognitive decline. Further validation of these biomarkers may lead to future practical clinical use.

Neurodevelopmental Disorders Caused by Genetic Defects in Structure of Glutamatergic Receptors

Background: the role of glutamate receptor dysfunction in mental disorders, neurological, autoimmune, and oncological pathology has been intensively investigated in the past decade. The development of drugs that target glutamatergic receptors has also been a focus of research.The aim was to describe modern concepts of neurodevelopmental disorders (according to the International Classification of Diseases 11th revision, L1-6A0) that are associated with genetically induced alterations of the structure of glutamatergic receptors.Material and method: a search for descriptions of cases with impaired neuropsychiatric development associated with genetic defects of ionotropic and metabotropic glutamate receptor subunits was performed in the MEDLINE/Gene database, MEDLINE/PubMed scientific library, Online Mendelian Inheritance in Man (OMIM), UniProt, ClinGen and eLibrary. Genetically induced structural abnormalities of most known ionotropic (GluA, GluN, GluK, GluD) and a number of metabotropic glutamate receptors (mGluR1, 5, 7) are associated with severe variants of neuropsychiatric disorders that manifest in infancy and early childhood.Conclusion: the considerable variation in the clinical presentation of these cases demands a transnosological approach to diagnosis and management of patients, under cooperation of specialists in pediatrics, child psychiatry, neurology, genetics, and medical and social rehabilitation.

Genetic mutation profiling reveals biomarkers for targeted therapy efficacy and prognosis in non-small cell lung cancer

IntroductionThe genetic heterogeneity of non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations may affect clinical responses and outcomes to EGFR tyrosine kinase inhibitors (EGFR-TKIs). This study aims to investigate the genomic factors that influence the efficacy and clinical outcomes of first-line, second-line and third-line treatments in NSCLC and explore the heterogeneity of resistance mechanisms. Materials and methodsThis real-world study comprised 65 patients with EGFR mutant NSCLC. Molecular alterations were detected using a customized DNA panel before and after administering targeted therapy. The efficacy and prognosis of each treatment line were evaluated. ResultsIn first-generation EGFR-TKIs treatment, gefitinib showed favorable efficacy compared to icotinib and erlotinib, particularly in patients with EGFR L858R mutations. The resistance mechanisms to first-generation EGFR-TKIs varied among different EGFR mutation cohorts and different first-generation EGFR-TKIs. In second-line EGFR-TKIs treatment, EPH receptor A3 (EPHA3), IKAROS family zinc finger 1 (IKZF1), p21 (RAC1) activated kinase 5 (PAK5), DNA polymerase epsilon, catalytic subunit (POLE), RAD21 cohesin complex component (RAD21) and RNA binding motif protein 10 (RBM10) mutations were markedly associated with poorer progression-free survival (PFS). Notably, EPHA3, IKZF1 and RBM10 were identified as independent predictors of PFS. The mechanisms of osimertinib resistance exhibited heterogeneity, with a higher proportion of non-EGFR-dependent resistant mutations. In third-line treatments, the combination of osimertinib and anlotinib demonstrated superior efficacy compared to other regimens. Glutamate ionotropic receptor NMDA type subunit 2A (GRIN2A) mutation was an independent risk indicator of shorter OS following third-line treatments. ConclusionsComprehending the tumor evolution in NSCLC is advantageous for assessing the efficacy and prognosis at each stage of treatment, providing valuable insights to guide personalized treatment decisions for patients.

N-methyl-d-aspartate receptors: Structure, function, and role in organophosphorus compound poisoning.

Acute organophosphorus compound (OP) poisoning induces symptoms of the cholinergic crises with the occurrence of severe epileptic seizures. Seizures are induced by hyperstimulation of the cholinergic system, but are enhanced by hyperactivation of the glutamatergic system. Overstimulation of muscarinic cholinergic receptors by the elevated acetylcholine causes glutamatergic hyperexcitation and an increased influx of Ca2+ into neurons through a type of ionotropic glutamate receptors, N-methyl-d-aspartate (NMDA) receptors (NMDAR). These excitotoxic signaling processes generate reactive oxygen species, oxidative stress, and activation of the neuroinflammatory response, which can lead to recurrent epileptic seizures, neuronal cell death, and long-term neurological damage. In this review, we illustrate the NMDAR structure, complexity of subunit composition, and the various receptor properties that change accordingly. Although NMDARs are in normal physiological conditions important for controlling synaptic plasticity and mediating learning and memory functions, we elaborate the detrimental role NMDARs play in neurotoxicity of OPs and focus on the central role NMDAR inhibition plays in suppressing neurotoxicity and modulating the inflammatory response. The limited efficacy of current medical therapies for OP poisoning concerning the development of pharmacoresistance and mitigating proinflammatory response highlights the importance of NMDAR inhibitors in preventing neurotoxic processes and points to new avenues for exploring therapeutics for OP poisoning.

The anterior retrosplenial cortex is required for short-term object in place recognition memory retrieval: Role of ionotropic glutamate receptors in male and female Long-Evans rats.

The anterior retrosplenial cortex (aRSC) integrates multimodal sensory information into cohesive associative recognition memories. Little is known about how information is integrated during different learning phases (i.e., encoding and retrieval). Additionally, sex differences are observed in performance of some visuospatial memory tasks; however, inconsistent findings warrant more research. We conducted three experiments using the 1-h delay object-in-place (1-h OiP) test to assess recognition memory retrieval in male and female Long-Evans rats. (i) We found both sexes performed equally in three repeated 1-h OiP test sessions. (ii) We showed infusions of a mixture of muscimol/baclofen (GABAA/B receptor agonists) into the aRSC ~15-min prior to the test phase disrupted 1-h OiP in both sexes. (iii) We assessed the role of aRSC ionotropic glutamate receptors in 1-h OiP retrieval using another squad of cannulated rats and confirmed that infusions of either the competitive AMPA/Kainate receptor antagonist CNQX (3 mM) or competitive NMDA receptor antagonist AP-5 (30 mM) (volumes = 0.50 uL/side) significantly impaired 1-h OiP retrieval in both sexes compared to controls. Taken together, findings challenge reported sex differences and clearly establish a role for aRSC ionotropic glutamate receptors in short-term visuospatial recognition memory retrieval. Thus, modulating neural activity in the aRSC may alleviate some memory processing impairments in related disorders.

Behavioral analysis of kainate receptor KO mice and the role of GluK3 subunit in anxiety

Kainate receptors (KARs) are one of the ionotropic glutamate receptors in the central nervous system (CNS) comprised of five subunits, GluK1-GluK5. There is a growing interest in the association between KARs and psychiatric disorders, and there have been several studies investigating the behavioral phenotypes of KAR deficient mice, however, the difference in the genetic background has been found to affect phenotype in multiple mouse models of human diseases. Here, we examined GluK1-5 single KO mice in a pure C57BL/6N background and identified that GluK3 KO mice specifically express anxiolytic-like behavior with an alteration in dopamine D2 receptor (D2R)-induced anxiety, and reduced D2R expression in the striatum. Biochemical studies in the mouse cortex confirmed that GluK3 subunits do not assemble with GluK4 and GluK5 subunits, that can be activated by lower concentration of agonists. Overall, we found that GluK3-containing KARs function to express anxiety, which may represent promising anti-anxiety medication targets.

Small-molecule positive allosteric modulation of homomeric kainate receptors GluK1-3: development of screening assays and insight into GluK3 structure.

The kainate receptors GluK1-3 (glutamate receptor ionotropic, kainate receptors 1-3) belong to the family of ionotropic glutamate receptors and are essential for fast excitatory neurotransmission in the brain, and are associated with neurological and psychiatric diseases. How these receptors can be modulated by small-molecule agents is not well understood, especially for GluK3. We show that the positive allosteric modulator BPAM344 can be used to establish robust calcium-sensitive fluorescence-based assays to test agonists, antagonists, and positive allosteric modulators of GluK1-3. The half-maximal effective concentration (EC50) of BPAM344 for potentiating the response of 100 μm kainate was determined to be 26.3 μm for GluK1, 75.4 μm for GluK2, and 639 μm for GluK3. Domoate was found to be a potent agonist for GluK1 and GluK2, with an EC50 of 0.77 and 1.33 μm, respectively, upon co-application of 150 μm BPAM344. At GluK3, domoate acts as a very weak agonist or antagonist with a half-maximal inhibitory concentration (IC50) of 14.5 μm, in presence of 500 μm BPAM344 and 100 μm kainate for competition binding. Using H523A-mutated GluK3, we determined the first dimeric structure of the ligand-binding domain by X-ray crystallography, allowing location of BPAM344, as well as zinc-, sodium-, and chloride-ion binding sites at the dimer interface. Molecular dynamics simulations support the stability of the ion sites as well as the involvement of Asp761, Asp790, and Glu797 in the binding of zinc ions. Using electron microscopy, we show that, in presence of glutamate and BPAM344, full-length GluK3 adopts a dimer-of-dimers arrangement.

Voltage tunes mGlu5 receptor function, impacting synaptic transmission.

Voltage sensitivity is a common feature of many membrane proteins, including some G-protein coupled receptors (GPCRs). However, the functional consequences of voltage sensitivity in GPCRs are not well understood. In this study, we investigated the voltage sensitivity of the post-synaptic metabotropic glutamate receptor mGlu5 and its impact on synaptic transmission. Using biosensors and electrophysiological recordings in non-excitable HEK293T cells or neurons. We found that mGlu5 receptor function is optimal at resting membrane potentials. We observed that membrane depolarization significantly reduced mGlu5 receptor activation, Gq-PLC/PKC stimulation, Ca2+ release and mGlu5 receptor-gated currents through transient receptor potential canonical, TRPC6, channels or glutamate ionotropic NMDA receptors. Notably, we report a previously unknown activity of the NMDA receptor at the resting potential of neurons, enabled by mGlu5. Our findings suggest that mGlu5 receptor activity is directly regulated by membrane voltage which may have a significant impact on synaptic processes and pathophysiological functions.

The positive allosteric modulator BPAM344 and L-glutamate introduce an active-like structure of the ligand-binding domain of GluK2.

Kainate receptors belong to the family of ionotropic glutamate receptors and contribute to the majority of fast excitatory neurotransmission. Consequently, they also play a role in brain diseases. Therefore, understanding how these receptors can be modulated is of importance. Our study provides a crystal structure of the dimeric ligand-binding domain of the kainate receptor GluK2 in complex with L-glutamate and the small-molecule positive allosteric modulator, BPAM344, in an active-like conformation. The role of Thr535 and Gln786 in modulating GluK2 by BPAM344 was investigated using a calcium-sensitive fluorescence-based assay on transiently transfected cells expressing GluK2 and mutants hereof. This study may aid in the design of compounds targeting kainate receptors, expanding their potential as targets for the treatment of brain diseases.

Integrated UPLC/Q-TOF-MS/MS Analysis and Network Pharmacology to Reveal the Neuroprotective Mechanisms and Potential Pharmacological Ingredients of Aurantii Fructus Immaturus and Aurantii Fructus.

Aurantii Fructus (AF) and Aurantii Fructus Immaturus (AFI) have been used for thousands of years as traditional Chinese medicine (TCM) with sedative effects. Modern studies have shown that Citrus plants also have protective effects on the nervous system. However, the effective substances and mechanisms of action in Citrus TCMs still remain unclear. In order to explore the pharmacodynamic profiles of identified substances and the action mechanism of these herbs, a comprehensive approach combining ultra-high-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS/MS) analysis and network pharmacology was employed. Firstly, UNIFI 2.1.1 software was used to identify the chemical characteristics of AF and AFI. Secondly, the SwissTargetPrediction database was used to predict the targets of chemical components in AF and AFI. Targets for neuroprotection were also collected from GeneCards: The Human Gene Database (GeneCards-Human Genes|Gene Database|Gene Search). The networks between targets and compounds or diseases were then constructed using Cytoscape 3.9.1. Finally, the Annotation, Visualization and Integrated Discovery Database (DAVID) (DAVID Functional Annotation Bioinformatics Microarray Analysis) was used for GO and pathway enrichment analysis. The results showed that 50 of 188 compounds in AF and AFI may have neuroprotective biological activities. These activities are associated with the regulatory effects of related components on 146 important signaling pathways, derived from the KEGG (KEGG: Kyoto Encyclopedia of Genes and Genomes), such as neurodegeneration (hsa05022), the Alzheimer's disease pathway (hsa05010), the NF-kappa B signaling pathway (hsa04064), the hypoxia-inducible factor (HIF)-1 signaling pathway (hsa04066), apoptosis (hsa04210), the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor resistance signaling pathway (hsa01521), and others, by targeting 108 proteins, including xanthine dehydrogenase (XDH), glutamate ionotropic receptor NMDA type subunit 2B (GRIN2B), and glucose-6-phosphate dehydrogenase (G6PD), among others. These targets are thought to be related to inflammation, neural function and cell growth.

An AI-generated proteome-scale dataset of predicted protein structures for the ctenophore Mnemiopsis leidyi.

This Dataset Brief describes the computational prediction of protein structures for the ctenophore Mnemiopsis leidyi. Here, we report the proteome-scale generation of 15,333 protein structure predictions using AlphaFold, as well as an updated implementation of publicly available search, manipulation, and visualization tools for these protein structure predictions through the Mnemiopsis Genome Project Portal (https://research.nhgri.nih.gov/mnemiopsis). The utility of these predictions is demonstrated by highlighting comparisons to experimentally determined structures for the light-sensitive protein mnemiopsin 1 and the ionotropic glutamate receptor (iGluR). The application of these novel protein structure prediction methods will serve to further position non-bilaterian species such as Mnemiopsis as powerful model systems for the study of early animal evolution and human health.