Arc and BDNF mediated effects of hippocampal astrocytic glutamate uptake blockade on spatial memory stages.

Glutamate is involved in fundamental functions, including neuronal plasticity and memory. Astrocytes are integral elements involved in synaptic function, and the GLT-1 transporter possesses a critical role in glutamate uptake. Here, we study the role of GLT-1, specifically located in astrocytes, in the consolidation, expression, reconsolidation and persistence of spatial object recognition memory in rats. Administration of dihydrokainic acid (DHK), a selective GLT-1 inhibitor, into the dorsal hippocampus around a weak training which only induces short-term memory, promotes long-term memory formation. This promotion is prevented by hippocampal administration of protein-synthesis translation inhibitor, blockade of Activity-regulated cytoskeleton-associated protein (Arc) translation or Brain-Derived Neurotrophic Factor (BDNF) action, which are plasticity related proteins necessary for memory consolidation. However, DHK around a strong training, which induces long-term memory, does not affect memory consolidation. Administration of DHK before the test session impairs the expression of long-term memory, and this effect is dependent of Arc translation. Furthermore, DHK impairs reconsolidation if applied before a reactivation session, and this effect is independent of Arc translation. These findings reveal specific consequences on spatial memory stages developed under hippocampal GLT-1 blockade, shedding light on the intricate molecular mechanisms, governed in part for the action of glia.

Access to Diverse Glutamic Acid Dendrons and a Janus Peptide Dendrimer Using an Atypical Solid Phase Synthesis.

The negligible cytotoxicity of anion surface-linked dendrons makes glutamic acid-based dendrons a potential candidate for materials and biological applications. Despite the inherent drawbacks of the conventional solution phase synthesis of glutamic acid-based dendrons, there have been no advancements in these protocols. Herein, we demonstrate the first-ever convergent solid phase synthesis of dendrons, up to fourth generation, having glutamic acid branching points produced by preactivation of dicarboxylic acid groups with N-hydroxysuccinimide and simultaneous coupling with amine groups of two growing peptide chains, with excellent yields (30-70%). In addition to the general advantages, such as the easy workup, a final single purification step, and an overall short synthesis duration, the convergent solid phase synthesis allowed us to chemically synthesize glutamic acid branching-based dendrons that cannot be accessed by standard divergent solid phase synthesis. This method has also been validated for its application in synthesizing hard-to-achieve Janus peptide dendrimers in a single stretch on a solid support. Our work corroborates the efficacy of controlled -COOH activation to accomplish an atypical solid phase synthesis of diverse glutamic acid dendrons in a convergent fashion. This is the first example of a Janus peptide dendrimer being synthesized on a solid support, utilizing both convergent and divergent approaches simultaneously.

Isoliensinine activated the Nrf2/GPX4 pathway to inhibit glutamate-induced ferroptosis in HT-22 cells.

Isoliensinine (ISO), a natural compound, is a bibenzyl isoquinoline alkaloid monomer in lotus seed, which has strong antioxidant and free radical scavenging activities. The oxidative toxicity caused by glutamic acid overdose is one of the important mechanisms of nerve cell injury, and the oxidative toxicity caused by glutamic acid is related to ferroptosis. This study aims to establish a glutamate-induced injury model of mouse hippocampal neurons HT-22 cells, and investigate the protective effect of ISO on the neurotoxicity of glutamate-induced HT-22 cells. The results showed that ISO inhibited glutamate-induced ferroptosis of neuronal cells through nuclear factor E2-related factor 2/glutathione peroxidase 4 (Nrf2/GPX4) signaling pathway. Pretreatment of HT-22 cells with ISO significantly reduced glutamate-induced cell death. Ferroptosis inhibitors have the same effect. ISO inhibited the decrease of mitochondrial membrane potential detection and the increase of iron content induced by glutamate, the increase of malondialdehyde and reactive oxygen species in cytoplasm and lipid, and protected the activities of GPx and superoxide dismutase enzymes. In addition, WB showed that glutamic acid could induce the upregulated expression of long-chain esteryl coA synthase 4 (ACSL4) protein and the downregulated expression of SLC7A11 and GPX4 protein in HT-22 cells, while ISO could prevent the abnormal expression of these proteins induced by glutamic acid. The nuclear translocation of Nrf2 in HT-22 cells was increased, and the expression of downstream heme oxygenase-1 protein was upregulated. In summary, ISO protects HT-22 cells from glutamate-induced ferroptosis through a novel mechanism of the Nrf2/GPX4 signaling pathway.

D-Glutamate production by stressed Escherichia coli gives a clue for the hypothetical induction mechanism of the ALS disease.

In the search for the origin of Amyotrophic Lateral Sclerosis disease (ALS), we hypothesized earlier (Monselise, 2019) that D-amino acids produced by stressed microbiome may serve as inducers of the disease development. Many examples of D-amino acid accumulation under various stress conditions were demonstrated in prokaryotic and eukaryotic cells. In this work, wild-type Escherichia coli, members of the digestive system, were subjected to carbon and nitrogen starvation stress. Using NMR and LC-MS techniques, we found for the first time that D-glutamate accumulated in the stressed bacteria but not in control cells. These results together with the existing knowledge, allow us to suggest a new insight into the pathway of ALS development: D-glutamate, produced by the stressed microbiome, induces neurobiochemical miscommunication setting on C1q of the complement system. Proving this insight may have great importance in preventive medicine of such MND modern-age diseases as ALS, Alzheimer, and Parkinson.

Unveiling the shield: Troglitazone's impact on epilepsy-induced nerve injury through ferroptosis inhibition.

BACKGROUND: Epilepsy is a widespread central nervous system disorder with an estimated 50 million people affected globally. It is characterized by a bimodal incidence peak among infants and the elderly and is influenced by a variety of risk factors, including a significant genetic component. Despite the use of anti-epileptic drugs (AEDs), drug-refractory epilepsy develops in about one-third of patients, highlighting the need for alternative therapeutic approaches. AIMS: The primary aim of this study was to evaluate the neuroprotective effects of troglitazone (TGZ) in epilepsy and to explore the potential mechanisms underlying its action. METHODS: We employed both in vitro and in vivo models to assess TGZ's effects. The in vitro model involved glutamate-induced toxicity in HT22 mouse hippocampal neurons, while the in vivo model used kainic acid (KA) to induce epilepsy in mice. A range of methods, including Hoechst/PI staining, CCK-8 assay, flow cytometry, RT-PCR analysis, Nissl staining, scanning electron microscopy, and RNA sequencing, were utilized to assess various parameters such as cellular damage, viability, lipid-ROS levels, mitochondrial membrane potential, mRNA expression, seizure grade, and mitochondrial morphology. RESULTS: Our results indicate that TGZ, at doses of 5 or 20 mg/kg/day, significantly reduces KA-induced seizures and neuronal damage in mice by inhibiting the process of ferroptosis. Furthermore, TGZ was found to prevent changes in mitochondrial morphology. In the glutamate-induced HT22 cell damage model, 2.5 µM TGZ effectively suppressed neuronal ferroptosis, as shown by a reduction in lipid-ROS accumulation, a decrease in mitochondrial membrane potential, and an increase in PTGS2 expression. The anti-ferroptotic effect of TGZ was confirmed in an erastin-induced HT22 cell damage model as well. Additionally, TGZ reversed the upregulation of Plaur expression in HT22 cells treated with glutamate or erastin. The downregulation of Plaur expression was found to alleviate seizures and reduce neuronal damage in the mouse hippocampus. CONCLUSION: This study demonstrates that troglitazone has significant therapeutic potential in the treatment of epilepsy by reducing epileptic seizures and the associated brain damage through the inhibition of neuronal ferroptosis. The downregulation of Plaur expression plays a crucial role in TGZ's anti-ferroptotic effect, offering a promising avenue for the development of new epilepsy treatments.

Neuronal and non-neuronal functions of the synaptic cell adhesion molecule neurexin in Nematostella vectensis.

The evolutionary transition from diffusion-mediated cell-cell communication to faster, targeted synaptic signaling in animal nervous systems is still unclear. Genome sequencing analyses have revealed a widespread distribution of synapse-related genes among early-diverging metazoans, but how synaptic machinery evolved remains largely unknown. Here, we examine the function of neurexins (Nrxns), a family of presynaptic cell adhesion molecules with critical roles in bilaterian chemical synapses, using the cnidarian model, Nematostella vectensis. Delta-Nrxns are expressed mainly in neuronal cell clusters that exhibit both peptidergic and classical neurotransmitter signaling. Knockdown of δ-Nrxn reduces spontaneous peristalsis of N. vectensis polyps. Interestingly, gene knockdown and pharmacological studies suggest that δ-Nrxn is involved in glutamate- and glycine-mediated signaling rather than peptidergic signaling. Knockdown of the epithelial α-Nrxn reveals a major role in cell adhesion between ectodermal and endodermal epithelia. Overall, this study provides molecular, functional, and cellular insights into the pre-neural function of Nrxns, as well as key information for understanding how and why they were recruited to the synaptic machinery.

Orofacial antinociceptive activity of codeine-associated geraniol in mice: a controlled triple-blind study.

This is a nonclinical, controlled, and triple-blind study to investigate the effects of codeine-associated geraniol on the modulation of orofacial nociception and its potential central nervous system depressing effect in an animal model. The orofacial antinociceptive activity of geraniol in combination with codeine was assessed through the following tests: (i) formalin-induced pain, (ii) glutamate-induced pain, and (iii) capsaicin-induced pain. Six animals were equally distributed into six groups and received the following treatments, given intraperitoneally (i.p.) 30 minutes before the experiments: a) geraniol/codeine 50/30 mg/kg; b) geraniol/codeine 50/15 mg/kg; c) geraniol/codeine 50/7.5 mg/kg; d) geraniol 50 mg/kg; e) codeine 30 mg/kg (positive control); or f) 0.9% sodium chloride (negative control). We performed pain behavior analysis after the injection of formalin (20 µL, 20%), glutamate (20 µL, 25 µM), and capsaicin (20 µL, 2.5 µg) into the paranasal region. Rubbing time of the paranasal region by the hind or front paw was used as a parameter. In the neurogenic phase of the formalin test, the geraniol/codeine at 50/7.5 mg/kg was able to promote the maximum antinociceptive effect, reducing nociception by 71.9% (p < 0.0001). In the inflammatory phase of the formalin test, geraniol/codeine at 50/30 mg/kg significantly reduced orofacial nociception (p < 0.005). In the glutamate test, geraniol/codeine at 50/30 mg/kg reduced the rubbing time by 54.2% and reduced nociception in the capsaicin test by 66.7% (p < 0.005). Geraniol alone or in combination does not promote nonspecific depressing effects on the central nervous system. Based on our findings, we suggest the possible synergy between geraniol and codeine in the modulation of orofacial pain.

Development of a dual-template molecularly imprinted electrochemical sensor for the simultaneous detection of depression markers 5-HT and Glu.

A dual-template molecularly imprinted electrochemical sensor was developed for the simultaneous detection of serotonin (5-HT) and glutamate (Glu). First, amino-functionalized reduced graphene oxide (NRGO) was used as the modification material of a GCE to increase its electrical conductivity and specific surface area, using Glu and 5-HT as dual-template molecules and o-phenylenediamine (OPD) with self-polymerization ability as functional monomers. Through self-assembly and electropolymerization, dual-template molecularly imprinted polymers were formed on the electrode. After removing the templates, the specific recognition binding sites were exposed. The amount of NRGO, polymerization parameters, and elution parameters were further optimized to construct a dual-template molecularly imprinted electrochemical sensor, which can specifically recognize double-target molecules Glu and 5-HT. The differential pulse voltammetry (DPV) technique was used to achieve simultaneous detection of Glu and 5-HT based on their distinct electrochemical activities under specific conditions. The sensor showed a good linear relationship for Glu and 5-HT in the range 1 ~ 100 µM, and the detection limits were 0.067 µM and 0.047 µM (S/N = 3), respectively. The sensor has good reproducibility, repeatability, and selectivity. It was successfully utilized to simultaneously detect Glu and 5-HT in mouse serum, offering a more dependable foundation for objectively diagnosing and early warning of depression. Additionally, the double signal sensing strategy also provides a new approach for the simultaneous detection of both electroactive and non-electroactive substances.

Substitution of acidic residues near the catalytic Glu131 leads to human HYAL1 activity at neutral pH via charge-charge interactions.

Human hyaluronidase 1 (HYAL1) and PH20 play vital roles in degrading hyaluronic acids through the substrate-assisted double displacement mechanism. While HYAL1, a lysosomal enzyme, functions optimally under acidic conditions, PH20, a sperm surface hyaluronidase, displays a broader pH range, from acidic to neutral. Our objective was to extend HYAL1's pH range towards neutral pH by introducing repulsive charge-charge interactions involving the catalytic Glu131, increasing its pKa as the proton donor. Substituting individual acidic residues in the ß3-loop (S77D), ß3'-ß3″ hairpin (T86D and P87E), and at Ala132 (A132D and A132E) enabled HYAL1 to demonstrate enzyme activity at pH 7, with the mutants S77D, P87E, and A132E showing the highest activity in the substrate gel assay. However, double and triple substitutions, including S77D/T86D/A132E as found in the PH20 configuration, did not result in enhanced activity compared to single substitutions. Conversely, PH20 mutants with non-acidic substitutions, such as D94S in the ß3-loop and D103T in the ß3'-ß3″ hairpin, significantly reduced activity within the pH range of 4 to 7. However, the PH20 mutant E149A, reciprocally substituted compared to A132E in HYAL1, exhibited activity similar to PH20 wild-type (WT) at pH 7. In a turbidimetric assay, HYAL1 mutants with single acidic substitutions exhibited activity similar to that of PH20 WT at pH 7. These results suggest that substituting acidic residues near Glu131 results in HYAL1 activity at neutral pH through electrostatic repulsion. This study highlights the significance of charge-charge interactions in both HYAL1 and PH20 in regulating the pH-dependent activity of hyaluronidases.

Circulating glutamine/glutamate ratio is closely associated with type 2 diabetes and its associated complications.

Objective: This study aims to conduct a comprehensive investigation of the serum amino acid profiles of individuals with type 2 diabetes (T2D) and its related complications. Methods: Patients with T2D were enrolled in this study. Sixteen kinds of common amino acids in the fasting circulating were assessed through liquid chromatography-mass spectrometry (LC-MS). Subsequently, correlation, regression analyses, and receiver operating characteristic (ROC) curves were conducted to assess the associations between amino acids and clinical indicators. Results: Thirteen different kinds of amino acids were identified in diabetic patients, as compared with normal controls. The Glutamine/Glutamate (Gln/Glu) ratio was negatively correlated with BMI, HbA1c, serum uric acid, and the triglyceride-glucose (TyG) index, while it was positively correlated with HDL-C. Logistic regression analyses indicated that Gln/Glu was a consistent protective factor for both T2D (OR = 0.65, 95% CI 0.50-0.86) and obesity (OR = 0.79, 95% CI 0.66-0.96). The ROC curves demonstrated that Gln/Glu, proline, valine, and leucine provided effective predictions for diabetes risk, with Gln/Glu exhibiting the highest AUC [0.767 (0.678-0.856)]. In patients with T2D, Gln was the only amino acid that displayed a negative correlation with HbA1c (r = -0.228, p = 0.017). Furthermore, HOMA-ß exhibited a negative correlation with Glu (r = -0.301, p = 0.003) but a positive correlation with Gln/Glu (r = 0.245, p = 0.017). Notably, logistic regression analyses revealed an inverse correlation of Gln/Glu with the risk of diabetic kidney disease (OR = 0.74, 95% CI 0.55-0.98) and a positive association with the risk of diabetic retinopathy (OR = 1.53, 95% CI 1.08-2.15). Conclusion: The Gln/Glu ratio exhibited a significant association with diabetes, common metabolic parameters, and diabetic complications. These findings shed light on the pivotal role of Gln metabolism in T2D and its associated complications.

(S)-3-(3,4-Dihydroxybenzyl) piperazine-2,5-dione (cyclo-Gly-L-DOPA or CG-Nio-CGLD) peptide loaded in Chitosan Glutamate-Coated Niosomes as anti-Colorectal cancer activity.

BACKGROUND: Colorectal cancer (CRC), now the second most prevalent malignant tumor worldwide, is more prevalent in young adults. In recent decades, there has been progress in creating anti-colorectal cancer medications, including cytotoxic compounds. OBJECTIVES: Novel anticancer drugs are needed to surmount existing obstacles. A recent study investigated the effectiveness of novel formulations in preventing colorectal cancer. METHODS: During this study, we assessed a new kind of niosome called cyclo-Gly-L-DOPA (CG-Nio-CGLD) made from chitosan glutamate. We evaluated the anti-colorectal cancer properties of CG-Nio-CGLD utilizing CCK-8, invasion assay, MTT assay, flow cytometry, and cell cycle analysis. The transcription of genes associated with apoptosis was analyzed using quantitative real-time PCR. At the same time, the cytotoxicity of nanomaterials on both cancer and normal cell lines was assessed using MTT assays. Novel anticancer drugs are needed to surmount existing obstacles. A recent study investigated the effectiveness of newly developed formulations in preventing colorectal cancer. RESULTS: The Nio-CGLD and CG-Nio-CGLD were spherical mean diameters of 169.12 ± 1.87 and 179.26 ± 2.17 nm, respectively. Entrapment efficiency (EE%) measurements of the Nio-CGLD and CG-Nio-CGLD were 63.12 ± 0.51 and 76.43 ± 0.34%, respectively. In the CG-Nio-CGLD group, the percentages of early, late, necrotic, and viable CL40 cells were 341.93%, 23.27%, 9.32%, and 25.48%. The transcription of the genes PP53, cas3, and cas8 was noticeably higher in the treatment group compared to the control group (P > 0.001). Additionally, the treatment group had lower BCL2 and survivin gene expression levels than the control group (P < 0.01). Additionally, CG-Nio-CGLD formulations demonstrated a biocompatible nanoscale delivery mechanism and displayed little cytotoxicity toward the CCD 841 CoN reference cell line. CONCLUSION: These findings indicate that chitosan-based noisome encapsulation may enhance the effectiveness of CG-Nio-CGLD formulations in fighting cancer.

The human VGLUT3-pT8I mutation elicits uneven striatal DA signaling, food or drug maladaptive consumption in male mice.

Cholinergic striatal interneurons (ChIs) express the vesicular glutamate transporter 3 (VGLUT3) which allows them to regulate the striatal network with glutamate and acetylcholine (ACh). In addition, VGLUT3-dependent glutamate increases ACh vesicular stores through vesicular synergy. A missense polymorphism, VGLUT3-p.T8I, was identified in patients with substance use disorders (SUDs) and eating disorders (EDs). A mouse line was generated to understand the neurochemical and behavioral impact of the p.T8I variant. In VGLUT3T8I/T8I male mice, glutamate signaling was unchanged but vesicular synergy and ACh release were blunted. Mutant male mice exhibited a reduced DA release in the dorsomedial striatum but not in the dorsolateral striatum, facilitating habit formation and exacerbating maladaptive use of drug or food. Increasing ACh tone with donepezil reversed the self-starvation phenotype observed in VGLUT3T8I/T8I male mice. Our study suggests that unbalanced dopaminergic transmission in the dorsal striatum could be a common mechanism between SUDs and EDs.

Metabolomics-based search for lung cancer markers among patients with different smoking status.

Tobacco smoking is the main etiological factor of lung cancer (LC), which can also cause metabolome disruption. This study aimed to investigate whether the observed metabolic shift in LC patients was also associated with their smoking status. Untargeted metabolomics profiling was applied for the initial screening of changes in serum metabolic profile between LC and chronic obstructive pulmonary disease (COPD) patients, selected as a non-cancer group. Differences in metabolite profiles between current and former smokers were also tested. Then, targeted metabolomics methods were applied to verify and validate the proposed LC biomarkers. For untargeted metabolomics, a single extraction-dual separation workflow was applied. The samples were analyzed using a liquid chromatograph-high resolution quadrupole time-of-flight mass spectrometer. Next, the selected metabolites were quantified using liquid chromatography-triple-quadrupole mass spectrometry. The acquired data confirmed that patients' stratification based on smoking status impacted the discriminating ability of the identified LC marker candidates. Analyzing a validation set of samples enabled us to determine if the putative LC markers were truly robust. It demonstrated significant differences in the case of four metabolites: allantoin, glutamic acid, succinic acid, and sphingosine-1-phosphate. Our research showed that studying the influence of strong environmental factors, such as tobacco smoking, should be considered in cancer marker research since it reduces the risk of false positives and improves understanding of the metabolite shifts in cancer patients.

Polycomb repressive complex 2 is critical for mouse cortical glutamatergic neuron development.

The Polycomb Repressive Complex 2 (PRC2) regulates corticogenesis, yet the consequences of mutations to this epigenetic modifier in the mature brain are poorly defined. Importantly, PRC2 core genes are haploinsufficient and causative of several human neurodevelopmental disorders. To address the role of PRC2 in mature cortical structure and function, we conditionally deleted the PRC2 gene Eed from the developing mouse dorsal telencephalon. Adult homozygotes displayed smaller forebrain structures. Single-nucleus transcriptomics revealed that glutamatergic neurons were particularly affected, exhibiting dysregulated gene expression profiles, accompanied by aberrations in neuronal morphology and connectivity. Remarkably, homozygous mice performed well on challenging cognitive tasks. In contrast, while heterozygous mice did not exhibit clear anatomical or behavioral differences, they displayed dysregulation of neuronal genes and altered neuronal morphology that was strikingly different from homozygous phenotypes. Collectively, these data reveal how alterations to PRC2 function shape the mature brain and reveal a dose-specific role for PRC2 in determining glutamatergic neuron identity.

Genome-scale metabolic network of human carotid plaque reveals the pivotal role of glutamine/glutamate metabolism in macrophage modulating plaque inflammation and vulnerability.

BACKGROUND: Metabolism is increasingly recognized as a key regulator of the function and phenotype of the primary cellular constituents of the atherosclerotic vascular wall, including endothelial cells, smooth muscle cells, and inflammatory cells. However, a comprehensive analysis of metabolic changes associated with the transition of plaque from a stable to a hemorrhaged phenotype is lacking. METHODS: In this study, we integrated two large mRNA expression and protein abundance datasets (BIKE, n = 126; MaasHPS, n = 43) from human atherosclerotic carotid artery plaque to reconstruct a genome-scale metabolic network (GEM). Next, the GEM findings were linked to metabolomics data from MaasHPS, providing a comprehensive overview of metabolic changes in human plaque. RESULTS: Our study identified significant changes in lipid, cholesterol, and inositol metabolism, along with altered lysosomal lytic activity and increased inflammatory activity, in unstable plaques with intraplaque hemorrhage (IPH+) compared to non-hemorrhaged (IPH-) plaques. Moreover, topological analysis of this network model revealed that the conversion of glutamine to glutamate and their flux between the cytoplasm and mitochondria were notably compromised in hemorrhaged plaques, with a significant reduction in overall glutamate levels in IPH+ plaques. Additionally, reduced glutamate availability was associated with an increased presence of macrophages and a pro-inflammatory phenotype in IPH+ plaques, suggesting an inflammation-prone microenvironment. CONCLUSIONS: This study is the first to establish a robust and comprehensive GEM for atherosclerotic plaque, providing a valuable resource for understanding plaque metabolism. The utility of this GEM was illustrated by its ability to reliably predict dysregulation in the cholesterol hydroxylation, inositol metabolism, and the glutamine/glutamate pathway in rupture-prone hemorrhaged plaques, a finding that may pave the way to new diagnostic or therapeutic measures.

Computational Investigation of BMAA and Its Carbamate Adducts as Potential GluR2 Modulators.

Beta-N-methylamino-l-alanine (BMAA) is a potential neurotoxic nonprotein amino acid, which can reach the human body through the food chain. When BMAA interacts with bicarbonate in the human body, carbamate adducts are produced, which share a high structural similarity with the neurotransmitter glutamate. It is believed that BMAA and its l-carbamate adducts bind in the glutamate binding site of ionotropic glutamate receptor 2 (GluR2). Chronic exposure to BMAA and its adducts could cause neurological illness such as neurodegenerative diseases. However, the mechanism of BMAA action and its carbamate adducts bound to GluR2 has not yet been elucidated. Here, we investigate the binding modes and the affinity of BMAA and its carbamate adducts to GluR2 in comparison to the natural agonist, glutamate, to understand whether these can act as GluR2 modulators. Initially, we perform molecular dynamics simulations of BMAA and its carbamate adducts bound to GluR2 to examine the stability of the ligands in the S1/S2 ligand-binding core of the receptor. In addition, we utilize alchemical free energy calculations to compute the difference in the free energy of binding of the beta-carbamate adduct of BMAA to GluR2 compared to that of glutamate. Our findings indicate that carbamate adducts of BMAA and glutamate remain stable in the binding site of the GluR2 compared to BMAA. Additionally, alchemical free energy results reveal that glutamate and the beta-carbamate adduct of BMAA have comparable binding affinity to the GluR2. These results provide a rationale that BMAA carbamate adducts may be, in fact, the modulators of GluR2 and not BMAA itself.

Nitrate promotes the growth and the production of short-chain fatty acids and tryptophan from commensal anaerobe Veillonella dispar in the lactate-deficient environment by facilitating the catabolism of glutamate and aspartate.

Veillonella spp. are nitrate-reducing bacteria with anaerobic respiratory activity that reduce nitrate to nitrite. They are obligate anaerobic, Gram-negative cocci that ferment lactate as the main carbon source and produce short-chain fatty acids (SCFAs). Commensal Veillonella reside in the human body site where lactate level is, however, limited for Veillonella growth. In this study, nitrate was shown to promote the anaerobic growth of Veillonella in the lactate-deficient media. We aimed to investigate the underlying mechanisms and the metabolism involved in nitrate respiration. Nitrate (15 mM) was demonstrated to promote Veillonella dispar growth and viability in the tryptone-yeast extract medium containing 0.5 mM L-lactate. Metabolite and transcriptomic analyses revealed nitrate enabled V. dispar to actively utilize glutamate and aspartate from the medium and secrete tryptophan. Glutamate or aspartate was further supplemented to a medium to investigate individual catabolism during nitrate respiration. Notably, nitrate was demonstrated to elevate SCFA production in the glutamate-supplemented medium, and further increase tryptophan production in the aspartate-supplemented medium. We proposed that the increased consumption of glutamate provided reducing power for nitrate respiration and aspartate served as a substrate for fumarate formation. Both glutamate and aspartate were incorporated into the central metabolic pathways via reverse tricarboxylic acid cycle and were linked with the increased production of acetate, propionate, and tryptophan. This study provides further understanding of the promoted growth and metabolic mechanisms by commensal V. dispar utilizing nitrate and specific amino acids to adapt to the lactate-deficient environment.IMPORTANCENitrate is a pivotal ecological factor influencing microbial community and metabolism. Dietary nitrate provides health benefits including anti-diabetic and anti-hypertensive effects via microbial-derived metabolites such as nitrite. Unraveling the impacts of nitrate on the growth and metabolism of human commensal bacteria is imperative to comprehend the intricate roles of nitrate in regulating microbial metabolism, community, and human health. Veillonella are lactate-utilizing, nitrate-reducing bacteria that are frequently found in the human body site where lactate levels are low and nitrate is at millimolar levels. Here, we comprehensively described the metabolic strategies employed by V. dispar to thrive in the lactate-deficient environment using nitrate respiration and catabolism of specific amino acids. The elevated production of SCFAs and tryptophan from amino acids during nitrate respiration of V. dispar further suggested the potential roles of nitrate and Veillonella in the promotion of human health.

STING: Stay near to STIM(1) neuroprotection.

In a recent publication in Cell, Woo et al.1 report that stimulator of interferon genes (STING) links inflammation with glutamate-driven excitotoxicity to induce ferroptosis, identifying a mechanism of inflammation-induced neurodegeneration and also a novel candidate therapeutic target for multiple sclerosis.

Molecular mechanism of ligand gating and opening of NMDA receptor.

Glutamate transmission and activation of ionotropic glutamate receptors are the fundamental means by which neurons control their excitability and neuroplasticity1. The N-methyl-D-aspartate receptor (NMDAR) is unique among all ligand-gated channels, requiring two ligands-glutamate and glycine-for activation. These receptors function as heterotetrameric ion channels, with the channel opening dependent on the simultaneous binding of glycine and glutamate to the extracellular ligand-binding domains (LBDs) of the GluN1 and GluN2 subunits, respectively2,3. The exact molecular mechanism for channel gating by the two ligands has been unclear, particularly without structures representing the open channel and apo states. Here we show that the channel gate opening requires tension in the linker connecting the LBD and transmembrane domain (TMD) and rotation of the extracellular domain relative to the TMD. Using electron cryomicroscopy, we captured the structure of the GluN1-GluN2B (GluN1-2B) NMDAR in its open state bound to a positive allosteric modulator. This process rotates and bends the pore-forming helices in GluN1 and GluN2B, altering the symmetry of the TMD channel from pseudofourfold to twofold. Structures of GluN1-2B NMDAR in apo and single-liganded states showed that binding of either glycine or glutamate alone leads to distinct GluN1-2B dimer arrangements but insufficient tension in the LBD-TMD linker for channel opening. This mechanistic framework identifies a key determinant for channel gating and a potential pharmacological strategy for modulating NMDAR activity.

Alanine and glutamate catabolism collaborate to ensure the success of Bacillus subtilis sporulation.

Sporulation as a typical bacterial differentiation process has been studied for decades. However, two crucial aspects of sporulation, (i) the energy sources supporting the process, and (ii) the maintenance of spore dormancy throughout sporulation, are scarcely explored. Here, we reported the crucial role of RocG-mediated glutamate catabolism in regulating mother cell lysis, a critical step for sporulation completion of Bacillus subtilis, likely by providing energy metabolite ATP. Notably, rocG overexpression resulted in an excessive ATP accumulation in sporulating cells, leading to adverse effects on future spore properties, e.g. increased germination efficiency, reduced DPA content, and lowered heat resistance. Additionally, we revealed that Ald-mediated alanine metabolism was highly related to the inhibition of premature germination and the maintenance of spore dormancy during sporulation, which might be achieved by decreasing the typical germinant L-alanine concentration in sporulating environment. Our data inferred that sporulation of B. subtilis was a highly orchestrated biological process requiring a delicate balance in diverse metabolic pathways, hence ensuring both the completion of sporulation and production of high-quality spores.